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Sample records for reaction control thruster

  1. Acoustic Resonance Reaction Control Thruster (ARCTIC) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ORBITEC proposes to develop and demonstrate the innovative Acoustic Resonance Reaction Control Thruster (ARCTIC) to provide rapid and reliable in-space impulse...

  2. Space Shuttle reaction control system thruster metal nitrate removal and characterization

    Science.gov (United States)

    Saulsberry, R. L.; Mccartney, P. A.

    1993-01-01

    The Space Shuttle hypergolic primary reaction control system (PRCS) thrusters continue to fail-leak or fail-off at a rate of approximately 1.5 per flight, attributed primarily to metal nitrate formation in the nitrogen tetroxide (N2O4) pilot operated valves (POV's). The failures have continued despite ground support equipment (GSE) and subsystem operational improvements. As a result, the Johnson Space Center (JSC) White Sands Test Facility (WSTF) performed a study to characterize the contamination in the N204 valves. This study prompted the development and implementation of a highly successful flushing technique using deionized (DI) water and gaseous nitrogen (GN2) to remove the contamination while minimizing Teflon seat damage. Following flushing a comprehensive acceptance test is performed before the thruster is deemed recovered. Between the time WSTF was certified to process flight thrusters (March 1992) and September 1993, a 68 percent thruster recovery rate was achieved. The contamination flushed from these thrusters was analyzed and has provided insight into the corrosion process, which is reported in this publication. Additionally, the long-term performance of 24 flushed thrusters installed in the WSTF Fleet Leader Shuttle reaction control subsystem (RCS) test articles is being assessed. WSTF continues to flush flight and test article thrusters and compile data to investigate metal nitrate formation characteristics in leaking and nonleaking valves.

  3. A Tool Measuring Remaining Thickness of Notched Acoustic Cavities in Primary Reaction Control Thruster NDI Standards

    Science.gov (United States)

    Sun, Yushi; Sun, Changhong; Zhu, Harry; Wincheski, Buzz

    2006-01-01

    Stress corrosion cracking in the relief radius area of a space shuttle primary reaction control thruster is an issue of concern. The current approach for monitoring of potential crack growth is nondestructive inspection (NDI) of remaining thickness (RT) to the acoustic cavities using an eddy current or remote field eddy current probe. EDM manufacturers have difficulty in providing accurate RT calibration standards. Significant error in the RT values of NDI calibration standards could lead to a mistaken judgment of cracking condition of a thruster under inspection. A tool based on eddy current principle has been developed to measure the RT at each acoustic cavity of a calibration standard in order to validate that the standard meets the sample design criteria.

  4. Failure Investigation of an Intra-Manifold Explosion in a Horizontally-Mounted 870 lbf Reaction Control Thruster

    Science.gov (United States)

    Durning, Joseph G., III; Westover, Shayne C.; Cone, Darren M.

    2011-01-01

    In June 2010, an 870 lbf Space Shuttle Orbiter Reaction Control System Primary Thruster experienced an unintended shutdown during a test being performed at the NASA White Sands Test Facility. Subsequent removal and inspection of the thruster revealed permanent deformation and misalignment of the thruster valve mounting plate. Destructive evaluation determined that after three nominal firing sequences, the thruster had experienced an energetic event within the fuel (monomethylhydrazine) manifold at the start of the fourth firing sequence. The current understanding of the phenomenon of intra-manifold explosions in hypergolic bipropellant thrusters is documented in literature where it is colloquially referred to as a ZOT. The typical ZOT scenario involves operation of a thruster in a gravitational field with environmental pressures above the triple point pressure of the propellants. Post-firing, when the thruster valves are commanded closed, there remains a residual quantity of propellant in both the fuel and oxidizer (nitrogen tetroxide) injector manifolds known as the "dribble volume". In an ambient ground test configuration, these propellant volumes will drain from the injector manifolds but are impeded by the local atmospheric pressure. The evacuation of propellants from the thruster injector manifolds relies on the fluids vapor pressure to expel the liquid. The higher vapor pressure oxidizer will evacuate from the manifold before the lower vapor pressure fuel. The localized cooling resulting from the oxidizer boiling during manifold draining can result in fuel vapor migration and condensation in the oxidizer passage. The liquid fuel will then react with the oxidizer that enters the manifold during the next firing and may produce a localized high pressure reaction or explosion within the confines of the oxidizer injector manifold. The typical ZOT scenario was considered during this failure investigation, but was ultimately ruled out as a cause of the explosion

  5. Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters

    Science.gov (United States)

    Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith

    2016-01-01

    NASA is providing preliminary design and requirements for the Space Launch System Exploration Upper Stage (EUS). The EUS will provide upper stage capability for vehicle ascent as well as on-orbit control capability. Requirements include performance of on-orbit burn to provide Orion vehicle with escape velocity. On-orbit attitude control is accommodated by a on-off Reaction Control System (RCS). Paper provides overview of approaches for design and stability of an attitude control system using a RCS.

  6. Feasibility Study of Two Candidate Reaction Wheel/thruster Hybrid Control Architecture Designs for the Cassini Spacecraft

    Science.gov (United States)

    Macala, Glenn A.; Lee, Allan Y.; Wang, Eric K.

    2012-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. Cassini carries a set of three "fixed" reaction wheels and a backup reaction wheel (reaction wheel #4) is mounted on top of an articulable platform. If necessary, this platform could be articulated to orient the backup reaction wheel with the degraded wheel. The reaction wheels are used primarily for attitude control when precise and stable pointing of a science instrument such as the narrow angle camera is required. In 2001-02, reaction wheel #3 exhibited signs of bearing cage instability. As a result, reaction wheel #4 was articulated to align with reaction wheel #3. Beginning in July 2003, Cassini was controlled using wheel #1, #2, and #4. From their first use in the spring of 2000 until today, reaction wheels #1 and #2 have accumulated more than3.5 billions revolutions each. As such, in spite of very carefully management of the wheel spin rates by the mission operation team, there are some observed increases in the drag torque of the wheels' bearings. Hence, the mission operations team must prepare for the contingency scenario in which the reaction wheel #1 (in addition to wheel #3) had degraded. In this hypothetical fault scenario, the two remaining reaction wheels (#2 and #4) will not be able to provide precise and stable three-axis control of the spacecraft. In this study, we evaluate the feasibility of controlling Cassini using the two remaining reaction wheels and four thrusters to meet the science pointing requirements for two key science operational modes: the Optical Remote Sensing and Downlink, Fields, Particles, & Waves operation modes. The performance (e.g., pointing control error, pointing stability, hydrazine consumption rate, etc.) of the hybrid controllers in both operations scenarios will be compared with those achieved

  7. Feasibility Study of Two Candidate Reaction Wheel/thruster Hybrid Control Architecture Designs for the Cassini Spacecraft

    Science.gov (United States)

    Macala, Glenn A.; Lee, Allan Y.; Wang, Eric K.

    2012-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. Cassini carries a set of three "fixed" reaction wheels and a backup reaction wheel (reaction wheel #4) is mounted on top of an articulable platform. If necessary, this platform could be articulated to orient the backup reaction wheel with the degraded wheel. The reaction wheels are used primarily for attitude control when precise and stable pointing of a science instrument such as the narrow angle camera is required. In 2001-02, reaction wheel #3 exhibited signs of bearing cage instability. As a result, reaction wheel #4 was articulated to align with reaction wheel #3. Beginning in July 2003, Cassini was controlled using wheel #1, #2, and #4. From their first use in the spring of 2000 until today, reaction wheels #1 and #2 have accumulated more than3.5 billions revolutions each. As such, in spite of very carefully management of the wheel spin rates by the mission operation team, there are some observed increases in the drag torque of the wheels' bearings. Hence, the mission operations team must prepare for the contingency scenario in which the reaction wheel #1 (in addition to wheel #3) had degraded. In this hypothetical fault scenario, the two remaining reaction wheels (#2 and #4) will not be able to provide precise and stable three-axis control of the spacecraft. In this study, we evaluate the feasibility of controlling Cassini using the two remaining reaction wheels and four thrusters to meet the science pointing requirements for two key science operational modes: the Optical Remote Sensing and Downlink, Fields, Particles, & Waves operation modes. The performance (e.g., pointing control error, pointing stability, hydrazine consumption rate, etc.) of the hybrid controllers in both operations scenarios will be compared with those achieved

  8. Cassini Thruster Calibration Algorithm Using Reaction Wheel Biasing Data

    Science.gov (United States)

    Rizvi, Farheen

    2012-01-01

    Thrust force estimates for the reaction control thrusters on-board Cassini spacecraft are presented in this paper. Cassini consists of two thruster branches (A and B) each with eight thrusters. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. It is important to track the thrust force estimates in order to detect any thruster degradation and for supporting various activities in spacecraft operations (Titan flyby, spacecraft maneuvers). The Euler equation, which describes the rotational motion of the spacecraft during a reaction wheel bias event, is used to develop the algorithm. The thrust estimates are obtained from the pseudo inverse solution using flight telemetry during the bias. Results show that the A-branch Z3A and Z4A thrusters exhibited degraded thrust in November 2008. Due to the degraded thrust performance of Z3A and Z4A, A-branch usage was discontinued and prime branch was swapped to B-branch in March 2009. The thrust estimates from the B-branch do not show any degradation to date. The algorithm is used to trend the B-branch thrust force estimates as the mission continues.

  9. The Effect of Reaction Control System Thruster Plume Impingement on Orion Service Module Solar Array Power Production

    Science.gov (United States)

    Bury, Kristen M.; Kerslake, Thomas W.

    2008-01-01

    NASA's new Orion Crew Exploration Vehicle has geometry that orients the reaction control system (RCS) thrusters such that they can impinge upon the surface of Orion's solar array wings (SAW). Plume impingement can cause Paschen discharge, chemical contamination, thermal loading, erosion, and force loading on the SAW surface, especially when the SAWs are in a worst-case orientation (pointed 45 towards the aft end of the vehicle). Preliminary plume impingement assessment methods were needed to determine whether in-depth, timeconsuming calculations were required to assess power loss. Simple methods for assessing power loss as a result of these anomalies were developed to determine whether plume impingement induced power losses were below the assumed contamination loss budget of 2 percent. This paper details the methods that were developed and applies them to Orion's worst-case orientation.

  10. Pulsed Electrogasdynamic Thruster for Attitude Control and Orbit Maneuver Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A new pulsed electric thruster, named "pulsed electrogasdynamic thruster," for attitude control and orbit maneuver is proposed. In this thruster, propellant gas is...

  11. Control capability analysis for complex spacecraft thruster configurations

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The set of forces and moments that can be generated by thrusters of a spacecraft is called the"control capability"with respect to the thruster configuration.If the control capability of a thruster configuration is adequate to fulfill a given space mission,we say this configuration is a feasible one with respect to the task.This study proposed a new way to analyze the control capability of the complex thruster configuration.Precise mathematical definitions of feasibility were proposed,based on which a criterion to judge the feasibility of the thruster configuration was presented through calculating the shortest distance to the boundary of the controllable region as a function of the thruster configuration.Finally,control capability analysis for the complex thruster configuration based on its feasibility with respect to the space mission was given followed by a 2-D thruster configuration example to demonstrate its validity.

  12. Digital computer control of a 30-cm mercury ion thruster

    Science.gov (United States)

    Low, C. A., Jr.

    1975-01-01

    The major objective was to define the exact role of an onboard spacecraft computer in the control of ion thrusters. An initial computer control system with accurate high speed capability was designed, programmed, and tested with the computer as the sole control element for an operating ion thruster. The command functions and a code format for a spacecraft digital control system were established. A second computer control system was constructed to operate with these functions and format. A throttle program sequence was established and tested. A two thruster array was tested with these computer control systems and the results reported.

  13. Pulsed Electrogasdynamic Thruster for Attitude Control and Orbit Maneuver Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In the Phase I program we successfully demonstrated the feasibility of the Pulsed ElectroGasdynamic (PEG) thruster for attitude control and orbital maneuvering. In...

  14. Advanced Development of a Compact 5-15 lbf Lox/Methane Thruster for an Integrated Reaction Control and Main Engine Propulsion System

    Science.gov (United States)

    Hurlbert, Eric A.; McManamen, John Patrick; Sooknanen, Josh; Studak, Joseph W.

    2011-01-01

    This paper describes the advanced development and testing of a compact 5 to 15 lbf LOX/LCH4 thruster for a pressure-fed integrated main engine and RCS propulsion system to be used on a spacecraft "vertical" test bed (VTB). The ability of the RCS thruster and the main engine to operate off the same propellant supply in zero-g reduces mass and improves mission flexibility. This compact RCS engine incorporates several features to dramatically reduce mass and parts count, to ease manufacturing, and to maintain acceptable performance given that specific impulse (Isp) is not the driver. For example, radial injection holes placed on the chamber body for easier drilling, and high temperature Haynes 230 were selected for the chamber over other more expensive options. The valve inlets are rotatable before welding allowing different orientations for vehicle integration. In addition, the engine design effort selected a coil-on-plug ignition system which integrates a relay and coil with the plug electrode, and moves some exciter electronics to avionics driver board. The engine injector design has small dribble volumes to target minimum pulse widths of 20 msec. and an efficient minimum impulse bit of less than 0.05 lbf-sec. The propellants, oxygen and methane, were chosen because together they are a non-toxic, Mars-forward, high density, space storable, and high performance propellant combination that is capable of pressure-fed and pump-fed configurations and integration with life support and power subsystems. This paper will present the results of the advanced development testing to date of the RCS thruster and the integration with a vehicle propulsion system.

  15. Thruster direction controlling of assembled spacecraft based on gimbal suspension

    Institute of Scientific and Technical Information of China (English)

    Hongliang Xu; Hai Huang

    2016-01-01

    The attitude control system design and its control effect are affected considerably by the mass-property pa-rameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass wil be changed in certain axe; conse-quently, some thrusters' directions are deviated from the center of mass (CM) in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters’ directions is proposed. By using the gimbal instaled at the end of the boom, the angle of the thruster is controled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finaly, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.

  16. Controllability of an underactuated spacecraft with one thruster under disturbance

    Institute of Scientific and Technical Information of China (English)

    Dong-Xia Wang; Ying-Hong Jia; Lei Jin; Hai-Chao Gui; Shi-Jie Xu

    2012-01-01

    For an underactuated spacecraft using only one thruster,the attitude controllability with respect to the orbit frame is studied in the presence of periodical oscillation disturbance,which provides a preconditional guide on designing control law for underactuated attitude control system.Firstly,attitude dynamic model was established for an underactuated spacecraft,and attitude motion was described using the special orthogonal group (SO (3)).Secondly,Liouville theorem was used to confirm that the flow generated by the drift vector of the underactuated attitude control system is volume-preserving.Furthermore,according to Poincaré's recurrence theorem,we draw conclusions that this drift field is weakly positively poisson stable (WPPS).Thirdly,the sufficient and necessary condition of controllability was obtained on the basis of lie algebra rank condition (LARC).Finally,the controllable conditions were analyzed and simulated in different cases of inertia matrix with the installed position of thruster.

  17. Cassini Spacecraft In-Flight Swap to Backup Attitude Control Thrusters

    Science.gov (United States)

    Bates, David M.

    2010-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 and arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. In order to meet the challenging attitude control and navigation requirements of the orbit profile at Saturn, Cassini is equipped with a monopropellant thruster based Reaction Control System (RCS), a bipropellant Main Engine Assembly (MEA) and a Reaction Wheel Assembly (RWA). In 2008, after 11 years of reliable service, several RCS thrusters began to show signs of end of life degradation, which led the operations team to successfully perform the swap to the backup RCS system, the details and challenges of which are described in this paper. With some modifications, it is hoped that similar techniques and design strategies could be used to benefit other spacecraft.

  18. Cassini Spacecraft In-Flight Swap to Backup Attitude Control Thrusters

    Science.gov (United States)

    Bates, David M.

    2010-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 and arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. In order to meet the challenging attitude control and navigation requirements of the orbit profile at Saturn, Cassini is equipped with a monopropellant thruster based Reaction Control System (RCS), a bipropellant Main Engine Assembly (MEA) and a Reaction Wheel Assembly (RWA). In 2008, after 11 years of reliable service, several RCS thrusters began to show signs of end of life degradation, which led the operations team to successfully perform the swap to the backup RCS system, the details and challenges of which are described in this paper. With some modifications, it is hoped that similar techniques and design strategies could be used to benefit other spacecraft.

  19. Fault-Tolerant Region-Based Control of an Underwater Vehicle with Kinematically Redundant Thrusters

    Directory of Open Access Journals (Sweden)

    Zool H. Ismail

    2014-01-01

    Full Text Available This paper presents a new control approach for an underwater vehicle with a kinematically redundant thruster system. This control scheme is derived based on a fault-tolerant decomposition for thruster force allocation and a region control scheme for the tracking objective. Given a redundant thruster system, that is, six or more pairs of thrusters are used, the proposed redundancy resolution and region control scheme determine the number of thruster faults, as well as providing the reference thruster forces in order to keep the underwater vehicle within the desired region. The stability of the presented control law is proven in the sense of a Lyapunov function. Numerical simulations are performed with an omnidirectional underwater vehicle and the results of the proposed scheme illustrate the effectiveness in terms of optimizing the thruster forces.

  20. Colloid Thruster for Attitude Control Systems (ACS) and Tip-off Control Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop and test key technologies needed for an integrated, high thrust colloid thruster system with no moving parts, for spacecraft attitude control...

  1. DESIGN AND DEVELOPMENT OF AUTO DEPTH CONTROL OF REMOTELY OPERATED VEHICLE USING THRUSTER SYSTEM

    Directory of Open Access Journals (Sweden)

    F.A. Ali

    2014-12-01

    Full Text Available Remotely Operated Vehicles are underwater robots designed specifically for surveillance, monitoring and collecting data for underwater activities. In the underwater vehicle industries, the thruster is an important part in controlling the direction, depth and speed of the ROV. However, there are some ROVs that cannot be maintained at the specified depth for a long time because of disturbance. This paper proposes an auto depth control using a thruster system. A prototype of a thruster with an auto depth control is developed and attached to the previously fabricated UTeM ROV. This paper presents the operation of auto depth control as well as thrusters for submerging and emerging purposes and maintaining the specified depth. The thruster system utilizes a microcontroller as its brain, a piezoresistive strain gauge pressure sensor and a DC brushless motor to run the propeller. Performance analysis of the auto depth control system is conducted to identify the sensitivity of the pressure sensor, and the accuracy and stability of the system. The results show that the thruster system performs well in maintaining a specified depth as well as stabilizing itself when a disturbanceoccurs even with a simple proportional controller used to control the thruster, where the thruster is an important component of the ROV.

  2. Control Valve for Miniature Xenon Ion Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA is continuing its development of electric propulsion engines for various applications. Efforts have been directed toward both large and small thrusters,...

  3. ISS Contingency Attitude Control Recovery Method for Loss of Automatic Thruster Control

    Science.gov (United States)

    Bedrossian, Nazareth; Bhatt, Sagar; Alaniz, Abran; McCants, Edward; Nguyen, Louis; Chamitoff, Greg

    2008-01-01

    In this paper, the attitude control issues associated with International Space Station (ISS) loss of automatic thruster control capability are discussed and methods for attitude control recovery are presented. This scenario was experienced recently during Shuttle mission STS-117 and ISS Stage 13A in June 2007 when the Russian GN&C computers, which command the ISS thrusters, failed. Without automatic propulsive attitude control, the ISS would not be able to regain attitude control after the Orbiter undocked. The core issues associated with recovering long-term attitude control using CMGs are described as well as the systems engineering analysis to identify recovery options. It is shown that the recovery method can be separated into a procedure for rate damping to a safe harbor gravity gradient stable orientation and a capability to maneuver the vehicle to the necessary initial conditions for long term attitude hold. A manual control option using Soyuz and Progress vehicle thrusters is investigated for rate damping and maneuvers. The issues with implementing such an option are presented and the key issue of closed-loop stability is addressed. A new non-propulsive alternative to thruster control, Zero Propellant Maneuver (ZPM) attitude control method is introduced and its rate damping and maneuver performance evaluated. It is shown that ZPM can meet the tight attitude and rate error tolerances needed for long term attitude control. A combination of manual thruster rate damping to a safe harbor attitude followed by a ZPM to Stage long term attitude control orientation was selected by the Anomaly Resolution Team as the alternate attitude control method for such a contingency.

  4. Reducing Pointing Errors During Cassini Reaction Control System Orbit Trim Maneuvers

    Science.gov (United States)

    Rizvi, Farheen

    2013-01-01

    The effect of altering a gain parameter in the Cassini reaction control system (RCS) delta-V controller on the maneuver execution errors during orbit trim maneuvers (OTMs) is explored. Cassini consists of two reaction control thruster branches (A & B) each with eight thrusters. Currently, the B-branch is operational while the A-branch serves as a back-up. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. During an OTM, the Z-thrusters fire to maintain the X and Y-axes pointing within an attitude control dead-zone (-10 to 10 milliradians). The errors do not remain at zero due to pointing error sources such as spacecraft center of mass offset from the geometric center of the Z-facing thrusters, and variability in the thruster forces due to the thruster hardware differences. The delta-V reaction control system (RCS) controller ensures that the attitude error remains within this dead-zone. Gain parameters within the RCS delta-V controller affect the maneuver execution errors. Different parameter values are used to explore effect on these errors. It is found that pointing error decreases and magnitude error increases rapidly for gain parameters 10 times greater than the current parameter values used in the flight software.

  5. Micropulsed Plasma Thrusters for Attitude Control of a Low-Earth-Orbiting CubeSat

    Science.gov (United States)

    Gatsonis, Nikolaos A.; Lu, Ye; Blandino, John; Demetriou, Michael A.; Paschalidis, Nicholas

    2016-01-01

    This study presents a 3-Unit CubeSat design with commercial-off-the-shelf hardware, Teflon-fueled micropulsed plasma thrusters, and an attitude determination and control approach. The micropulsed plasma thruster is sized by the impulse bit and pulse frequency required for continuous compensation of expected maximum disturbance torques at altitudes between 400 and 1000 km, as well as to perform stabilization of up to 20 deg /s and slew maneuvers of up to 180 deg. The study involves realistic power constraints anticipated on the 3-Unit CubeSat. Attitude estimation is implemented using the q method for static attitude determination of the quaternion using pairs of the spacecraft-sun and magnetic-field vectors. The quaternion estimate and the gyroscope measurements are used with an extended Kalman filter to obtain the attitude estimates. Proportional-derivative control algorithms use the static attitude estimates in order to calculate the torque required to compensate for the disturbance torques and to achieve specified stabilization and slewing maneuvers or combinations. The controller includes a thruster-allocation method, which determines the optimal utilization of the available thrusters and introduces redundancy in case of failure. Simulation results are presented for a 3-Unit CubeSat under detumbling, pointing, and pointing and spinning scenarios, as well as comparisons between the thruster-allocation and the paired-firing methods under thruster failure.

  6. Propulsion and control propellers with thruster nozzles primarily for aircraft applications

    Science.gov (United States)

    Pabst, W.

    1986-01-01

    A propulsion and control propeller with thruster nozzles, primarily for aircraft application is described. Adjustability of rotor blades at the hub and pressurized gas expulsion combined with an air propeller increase power. Both characteristics are combined in one simple device, and, furthermore, incorporate overall aircraft control so that mechanisms which govern lateral and horizontal movement become superfluous.

  7. Diagnosis and Fault-Tolerant Control for Thruster-Assisted Position Mooring System

    DEFF Research Database (Denmark)

    Nguyen, Trong Dong; Blanke, Mogens; Sørensen, Asgeir

    2007-01-01

    Development of fault-tolerant control systems is crucial to maintain safe operation of o®shore installations. The objective of this paper is to develop a fault- tolerant control for thruster-assisted position mooring (PM) system with faults occurring in the mooring lines. Faults in line...

  8. TRMM Re-Entry Planning: Attitude Determination and Control During Thruster Modes

    Science.gov (United States)

    DeWeese, Keith

    2005-01-01

    The Tropical Rainfall Measuring Mission (TRMM) spacecraft has been undergoing design for a controlled re-entry to Earth. During simulation of the re-entry plan, there was evidence of errors in the attitude determination algorithms during thruster modes. These errors affected the bum efficiency, and thus planning, during re-entry. During thruster modes, the spacecraft attitude is controlled off of integrated Gyro Error Angles that were designed to closely follow the nominal spacecraft pointing frame (Tip Frame). These angles, however, were not exactly mapped to the Tip Frame from the Body Frame. Additionally, in the initial formulation of the thruster mode attitude determination algorithms, several assumptions and approximations were made to conserve processor speed. These errors became noticeable and significant when simulating bums of much longer duration (-10 times) than had been produced in flight. A solution is proposed that uses attitude determination information from a propagated extended Kalman filter that already exists in the TRMM thruster modes. This attitude information is then used to rotate the Gyro Error Angles into the Tip Frame. An error analysis is presented that compares the two formulations. The new algorithm is tested using the TRMM High-Fidelity Simulator and verified with the TRMM Software Testing and Training Facility. Simulation results for both configurations are also presented.

  9. Electrospray Thrusters for Attitude Control of a 1-U CubeSat

    Science.gov (United States)

    Timilsina, Navin

    With a rapid increase in the interest in use of nanosatellites in the past decade, finding a precise and low-power-consuming attitude control system for these satellites has been a real challenge. In this thesis, it is intended to design and test an electrospray thruster system that could perform the attitude control of a 1-unit CubeSat. Firstly, an experimental setup is built to calculate the conductivity of different liquids that could be used as propellants for the CubeSat. Secondly, a Time-Of-Flight experiment is performed to find out the thrust and specific impulse given by these liquids and hence selecting the optimum propellant. On the other hand, a colloidal thruster system for a 1-U CubeSat is designed in Solidworks and fabricated using Lathe and CNC Milling Machine. Afterwards, passive propellant feeding is tested in this thruster system. Finally, the electronic circuit and wireless control system necessary to remotely control the CubeSat is designed and the final testing is performed. Among the propellants studied, Ethyl ammonium nitrate (EAN) was selected as the best propellant for the CubeSat. Theoretical design and fabrication of the thruster system was performed successfully and so was the passive propellant feeding test. The satellite was assembled for the final experiment but unfortunately the microcontroller broke down during the first test and no promising results were found out. However, after proving that one thruster works with passive feeding, it could be said that the ACS testing would have worked if we had performed vacuum compatibility tests for other components beforehand.

  10. Dawn Spacecraft Reaction Control System Flight Experience

    Science.gov (United States)

    Mizukami, Masashi; Nakazono, Barry

    2014-01-01

    The NASA Dawn spacecraft mission is studying conditions and processes of the solar system's earliest epoch by investigating two protoplanets remaining intact since their formations, Ceres and Vesta. Launch was in 2007. Ion propulsion is used to fly to and enter orbit around Vesta, depart Vesta and fly to Ceres, and enter orbit around Ceres. A conventional blowdown hydrazine reaction control system (RCS) is used to provide external torques for attitude control. Reaction wheel assemblies were intended to provide attitude control in most cases. However, the spacecraft experienced one, then two apparent failures of reaction wheels. Also, similar thrusters experienced degradation in a long life application on another spacecraft. Those factors led to RCS being operated in ways completely different than anticipated prior to launch. Numerous mitigations and developments needed to be implemented. The Vesta mission was fully successful. Even with the compromises necessary due to those anomalies, the Ceres mission is also projected to be feasible.

  11. Development of a Hardware-in-the-loop Simulator for Spacecraft Attitude Control Using Thrusters

    Science.gov (United States)

    Koh, Dong-Wook; Park, Sang-Young; Kim, Do-Hee; Choi, Kyu-Hong

    2009-03-01

    In this study, a Hardware-In-the-Loop (HIL) simulator using thrusters is developed to validate the spacecraft attitude system. To control the attitude of the simulator, eight cold gas thrusters are aligned with roll, pitch and yaw axis. Also linear actuators are applied to the HIL simulator for automatic mass balancing to compensate the center of mass offset from the center of rotation. The HIL simulator consists of an embedded computer (Onboard PC) for simulator system control, a wireless adapter for wireless network, a rate gyro sensor to measure 3-axis attitude of the simulator, an inclinometer to measure horizontal attitude, and a battery set to supply power for the simulator independently. For the performance test of the HIL simulator, a bang-bang controller and Pulse-Width Pulse-Frequency (PWPF) modulator are evaluated successfully. The maneuver of 68 deg. in yaw axis is tested for the comparison of the both controllers. The settling time of the bang-bang controller is faster than that of the PWPF modulator by six seconds in the experiment. The required fuel of the PWPF modulator is used as much as 51% of bang-bang controller in the experiment. Overall, the HIL simulator is appropriately developed to validate the control algorithms using thrusters.

  12. Thrust vector control of upper stage with a gimbaled thruster during orbit transfer

    Science.gov (United States)

    Wang, Zhaohui; Jia, Yinghong; Jin, Lei; Duan, Jiajia

    2016-10-01

    In launching Multi-Satellite with One-Vehicle, the main thruster provided by the upper stage is mounted on a two-axis gimbal. During orbit transfer, the thrust vector of this gimbaled thruster (GT) should theoretically pass through the mass center of the upper stage and align with the command direction to provide orbit transfer impetus. However, it is hard to be implemented from the viewpoint of the engineering mission. The deviations of the thrust vector from the command direction would result in large velocity errors. Moreover, the deviations of the thrust vector from the upper stage mass center would produce large disturbance torques. This paper discusses the thrust vector control (TVC) of the upper stage during its orbit transfer. Firstly, the accurate nonlinear coupled kinematic and dynamic equations of the upper stage body, the two-axis gimbal and the GT are derived by taking the upper stage as a multi-body system. Then, a thrust vector control system consisting of the special attitude control of the upper stage and the gimbal rotation of the gimbaled thruster is proposed. The special attitude control defined by the desired attitude that draws the thrust vector to align with the command direction when the gimbal control makes the thrust vector passes through the upper stage mass center. Finally, the validity of the proposed method is verified through numerical simulations.

  13. Colloid Thruster for Attitude Control Systems (ACS) and Tip-off Control Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop and deliver a complete engineering model colloid thruster system, capable of thrust levels and lifetimes required for spacecraft...

  14. Thruster Module

    Science.gov (United States)

    Andersson, G.

    2015-09-01

    The thruster module described in this paper provides a low but controlled acceleration in a mission which would normally be labelled “microgravity”. The first mission was Cryofenix, where tanks containing liquid hydrogen were used in the experiment. The experiment utilizing the low acceleration is using liquids and requires a precise acceleration profile throughout the mission. Acceleration obtained by payload rotation is not feasible due to that the transversal forces required to change the acceleration will cause undesired liquid turbulence. In order to satisfy the experiment requirements a thruster module was developed by SSC for the Cryofenix mission funded by CNES. The Cryofenix mission had a payload weight of 380 kg and an apogee of about 260 km. The module produces a controlled thrust in flight direction by means of a cold gas system.

  15. Performance and Qualification of the Power Supply and Control Unit for the HEMP Thruster

    Science.gov (United States)

    Brag, R.; Herty, F.

    2014-08-01

    In 2013, Astrium GmbH delivered several flight model electronics for Electric Propulsion (EP) systems or corresponding components. One of the elements is a Power Supply and Control Unit (PSCU) for the Thales development "High Efficiency Multistage Plasma Thruster" (HEMP-T) (see Figure 1). This paper presents the PSCU specification and results of the qualification and acceptance phase of the EQM and the PFM.

  16. Ionization and Charge Exchange Reactions in Neutral Entrainment of a Field Reversed Configuration Thruster

    Science.gov (United States)

    2012-07-16

    non - Maxwellian . This indicates that a kinetic approach has to be used to model neutral entrainment in FRC thrusters. Strong impact of electron...radiative cooling can be problematic for high-Z plasma (due to a Z2 dependence) and in radiative non -equilibrium conditions (volumetric emission).1...dg, (1) where g is the relative collision velocity and fe is the Maxwellian distribution function. 2. Single charge exchange (SCX, A+ +A → A+A+) For

  17. Analysis of Effectiveness of Phoenix Entry Reaction Control System

    Science.gov (United States)

    Dyakonov, Artem A.; Glass, Christopher E.; Desai, Prasun, N.; VanNorman, John W.

    2008-01-01

    Interaction between the external flowfield and the reaction control system (RCS) thruster plumes of the Phoenix capsule during entry has been investigated. The analysis covered rarefied, transitional, hypersonic and supersonic flight regimes. Performance of pitch, yaw and roll control authority channels was evaluated, with specific emphasis on the yaw channel due to its low nominal yaw control authority. Because Phoenix had already been constructed and its RCS could not be modified before flight, an assessment of RCS efficacy along the trajectory was needed to determine possible issues and to make necessary software changes. Effectiveness of the system at various regimes was evaluated using a hybrid DSMC-CFD technique, based on DSMC Analysis Code (DAC) code and General Aerodynamic Simulation Program (GASP), the LAURA (Langley Aerothermal Upwind Relaxation Algorithm) code, and the FUN3D (Fully Unstructured 3D) code. Results of the analysis at hypersonic and supersonic conditions suggest a significant aero-RCS interference which reduced the efficacy of the thrusters and could likely produce control reversal. Very little aero-RCS interference was predicted in rarefied and transitional regimes. A recommendation was made to the project to widen controller system deadbands to minimize (if not eliminate) the use of RCS thrusters through hypersonic and supersonic flight regimes, where their performance would be uncertain.

  18. Lifetime Improvement of Large Scale Green Monopropellant Thrusters via Novel, Long-Life Catalysts Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop a high performance, non-toxic storable, "green" monopropellant thruster suitable for in-space reaction control propulsion. The engine will...

  19. Closed Loop solar array-ion thruster system with power control circuitry

    Science.gov (United States)

    Gruber, R. P. (Inventor)

    1979-01-01

    A power control circuit connected between a solar array and an ion thruster receives voltage and current signals from the solar array. The control circuit multiplies the voltage and current signals together to produce a power signal which is differentiated with respect to time. The differentiator output is detected by a zero crossing detector and, after suitable shaping, the detector output is phase compared with a clock in a phase demodulator. An integrator receives no output from the phase demodulator when the operating point is at the maximum power but is driven toward the maximum power point for non-optimum operation. A ramp generator provides minor variations in the beam current reference signal produced by the integrator in order to obtain the first derivative of power.

  20. NASA Ares I Launch Vehicle Roll and Reaction Control Systems Design Status

    Science.gov (United States)

    Butt, Adam; Popp, Chris G.; Pitts, Hank M.; Sharp, David J.

    2009-01-01

    This paper provides an update of design status following the preliminary design review of NASA s Ares I first stage roll and upper stage reaction control systems. The Ares I launch vehicle has been chosen to return humans to the moon, mars, and beyond. It consists of a first stage five segment solid rocket booster and an upper stage liquid bi-propellant J-2X engine. Similar to many launch vehicles, the Ares I has reaction control systems used to provide the vehicle with three degrees of freedom stabilization during the mission. During launch, the first stage roll control system will provide the Ares I with the ability to counteract induced roll torque. After first stage booster separation, the upper stage reaction control system will provide the upper stage element with three degrees of freedom control as needed. Trade studies and design assessments conducted on the roll and reaction control systems include: propellant selection, thruster arrangement, pressurization system configuration, and system component trades. Since successful completion of the preliminary design review, work has progressed towards the critical design review with accomplishments made in the following areas: pressurant / propellant tank, thruster assembly, and other component configurations, as well as thruster module design, and waterhammer mitigation approach. Also, results from early development testing are discussed along with plans for upcoming system testing. This paper concludes by summarizing the process of down selecting to the current baseline configuration for the Ares I roll and reaction control systems.

  1. NASA Ares I Launch Vehicle Roll and Reaction Control Systems Overview

    Science.gov (United States)

    Popp, Chris; Butt, Adam; Sharp, David; Pitts, Hank

    2008-01-01

    NASA's Ares I launch vehicle, consisting of a five segment solid rocket booster first stage and a liquid bi-propellant J-2X engine upper stage, is the vehicle that's been chosen to return humans to the moon, mars, and beyond. This paper provides an overview of the work that has taken place on the Ares I launch vehicle roll and reaction control systems. Reaction control systems are found on many launch vehicles and provide a vehicle with a three degree of freedom stabilization during the mission. The Ares I baseline configuration currently consists of a first stage roll control system that will provide the vehicle with a method of counteracting the roll torque that is expected during launch. An upper stage reaction control system will allow the upper stage three degrees of freedom control as needed. Design assessments and trade studies are being conducted on the roll and reaction control systems including: propellant selection, thruster arrangement, pressurization system configuration, and system component trades. Other vehicle considerations and issues include thruster plume impingement, thruster module aerothermal and aerodynamic effects, and system integration. This paper concludes by summarizing the process of down selecting to the current baseline configuration for the Ares I roll and reaction control systems.

  2. Solid State Digital Propulsion "Cluster Thrusters" For Small Satellites Using High Performance Electrically Controlled Extinguishable Solid Propellants (ECESP)

    Science.gov (United States)

    Sawka, Wayne N.; Katzakian, Arthur; Grix, Charles

    2005-01-01

    Electrically controlled extinguishable solid propellants (ESCSP) are capable of multiple ignitions, extinguishments and throttle control by the application of electrical power. Both core and end burning no moving parts ECESP grains/motors to three inches in diameter have now been tested. Ongoing research has led to a newer family of even higher performance ECESP providing up to 10% higher performance, manufacturing ease, and significantly higher electrical conduction. The high conductivity was not found to be desirable for larger motors; however it is ideal for downward scaling to micro and pico- propulsion applications with a web thickness of less than 0.125 inch/ diameter. As a solid solution propellant, this ECESP is molecularly uniform, having no granular structure. Because of this homogeneity and workable viscosity it can be directly cast into thin layers or vacuum cast into complex geometries. Both coaxial and grain stacks have been demonstrated. Combining individual propellant coaxial grains and/or grain stacks together form three-dimensional arrays yield modular cluster thrusters. Adoption of fabless manufacturing methods and standards from the electronics industry will provide custom, highly reproducible micro-propulsion arrays and clusters at low costs. These stack and cluster thruster designs provide a small footprint saving spacecraft surface area for solar panels and/or experiments. The simplicity of these thrusters will enable their broad use on micro-pico satellites for primary propulsion, ACS and formation flying applications. Larger spacecraft may find uses for ECESP thrusters on extended booms, on-orbit refueling, pneumatic actuators, and gas generators.

  3. Attitude Model of a Reaction Wheel/Fixed Thruster Based Satellite Using Telemetry Data

    Science.gov (United States)

    2005-03-01

    with an in-depth discussion on the model that provides satellite orientation from received telemetry data. 3.1 Hardware This first section talks about... satellite orientation from 5-1 attitude controllers, but a lot of work remains to be done in improving the fidelity of the model in order to achieve more

  4. Magnesium Hall Thruster

    Science.gov (United States)

    Szabo, James J.

    2015-01-01

    This Phase II project is developing a magnesium (Mg) Hall effect thruster system that would open the door for in situ resource utilization (ISRU)-based solar system exploration. Magnesium is light and easy to ionize. For a Mars- Earth transfer, the propellant mass savings with respect to a xenon Hall effect thruster (HET) system are enormous. Magnesium also can be combusted in a rocket with carbon dioxide (CO2) or water (H2O), enabling a multimode propulsion system with propellant sharing and ISRU. In the near term, CO2 and H2O would be collected in situ on Mars or the moon. In the far term, Mg itself would be collected from Martian and lunar regolith. In Phase I, an integrated, medium-power (1- to 3-kW) Mg HET system was developed and tested. Controlled, steady operation at constant voltage and power was demonstrated. Preliminary measurements indicate a specific impulse (Isp) greater than 4,000 s was achieved at a discharge potential of 400 V. The feasibility of delivering fluidized Mg powder to a medium- or high-power thruster also was demonstrated. Phase II of the project evaluated the performance of an integrated, highpower Mg Hall thruster system in a relevant space environment. Researchers improved the medium power thruster system and characterized it in detail. Researchers also designed and built a high-power (8- to 20-kW) Mg HET. A fluidized powder feed system supporting the high-power thruster was built and delivered to Busek Company, Inc.

  5. NASA Marshall Space Flight Center Tri-gas Thruster Performance Characterization

    Science.gov (United States)

    Dorado, Vanessa; Grunder, Zachary; Schaefer, Bryce; Sung, Meagan; Pedersen, Kevin

    2013-01-01

    Historically, spacecraft reaction control systems have primarily utilized cold gas thrusters because of their inherent simplicity and reliability. However, cold gas thrusters typically have a low specific impulse. It has been determined that a higher specific impulse can be achieved by passing a monopropellant fluid mixture through a catalyst bed prior to expulsion through the thruster nozzle. This research analyzes the potential efficiency improvements from using tri-gas, a mixture of hydrogen, oxygen, and an inert gas, which in this case is helium. Passing tri-gas through a catalyst causes the hydrogen and oxygen to react and form water vapor, ultimately heating the exiting fluid and generating a higher specific impulse. The goal of this project was to optimize the thruster performance by characterizing the effects of varying several system components including catalyst types, catalyst lengths, and initial catalyst temperatures.

  6. Optical properties of thermal control coating contaminated by MMH/N2O4 5-pound thruster in a vacuum environment with solar simulation

    Science.gov (United States)

    Sommers, R. D.; Raquet, C. A.; Cassidy, J. F.

    1972-01-01

    Cat-a-lac Black, and S13G thermal control coatings were exposed to the exhaust of a thruster in a simulated space environment. Vacuum was maintained at less than 10 to the minus 5th power torr during thruster firing in the liquid helium cooled facility. The thruster was fired in a 50-millisecond pulse mode and the accumulated firing time was 224 seconds. Solar absorptance (alpha sub s) and thermal emittance (sigma) of the coatings were measured in-situ at intervals of 300 pulses. A calorimetric technique was used to measure alpha sub s and sigma. The tests, technique, and test results are presented. The Cat-a-lac Black coatings showed no change in alpha sub s or sigma. The S13G showed up to 25 percent increase in alpha sub s but no change in sigma.

  7. Waterhammer Modeling for the Ares I Upper Stage Reaction Control System Cold Flow Development Test Article

    Science.gov (United States)

    Williams, Jonathan H.

    2010-01-01

    The Upper Stage Reaction Control System provides three-axis attitude control for the Ares I launch vehicle during active Upper Stage flight. The system design must accommodate rapid thruster firing to maintain the proper launch trajectory and thus allow for the possibility to pulse multiple thrusters simultaneously. Rapid thruster valve closure creates an increase in static pressure, known as waterhammer, which propagates throughout the propellant system at pressures exceeding nominal design values. A series of development tests conducted in the fall of 2009 at Marshall Space Flight Center were performed using a water-flow test article to better understand fluid performance characteristics of the Upper Stage Reaction Control System. A subset of the tests examined waterhammer along with the subsequent pressure and frequency response in the flight-representative system and provided data to anchor numerical models. This thesis presents a comparison of waterhammer test results with numerical model and analytical results. An overview of the flight system, test article, modeling and analysis are also provided.

  8. On-Line, Gyro-Based, Mass-Property Identification for Thruster-Controlled Spacecraft Using Recursive Least Squares

    Science.gov (United States)

    Wilson, Edward; Lages, Chris; Mah, Robert; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Spacecraft control, state estimation, and fault-detection-and-isolation systems are affected by unknown v aerations in the vehicle mass properties. It is often difficult to accurately measure inertia terms on the ground, and mass properties can change on-orbit as fuel is expended, the configuration changes, or payloads are added or removed. Recursive least squares -based algorithms that use gyro signals to identify the center of mass and inverse inertia matrix are presented. They are applied in simulation to 3 thruster-controlled vehicles: the X-38 and Mini-AERCam under development at NASA-JSC, and the SAM, an air-bearing spacecraft simulator at the NASA-Ames Smart Systems Research Lab (SSRL).

  9. A mechanical, thermal and electrical packaging design for a prototype power management and control system for the 30 cm mercury ion thruster

    Science.gov (United States)

    Sharp, G. R.; Gedeon, L.; Oglebay, J. C.; Shaker, F. S.; Siegert, C. E.

    1978-01-01

    A prototype Electric Power Management and Thruster Control System for a 30 cm ion thruster has been built and is ready to support a first mission application. The system meets all of the requirements necessary to operate a thruster in a fully automatic mode. Power input to the system can vary over a full two to one dynamic range (200 to 400 V) for the solar array or other power source. The Power Management and Control system is designed to protect the thruster, the flight system and itself from arcs and is fully compatible with standard spacecraft electronics. The system is designed to be easily integrated into flight systems which can operate over a thermal environment ranging from 0.3 to 5 AU. The complete Power Management and Control system measures 45.7 cm x 15.2 cm x 114.8 cm and weighs 36.2 kg. At full power the overall efficiency of the system is estimated to be 87.4 percent. Three systems are currently being built and a full schedule of environmental and electrical testing is planned.

  10. A mechanical, thermal and electrical packaging design for a prototype power management and control system for the 30 cm mercury ion thruster

    Science.gov (United States)

    Sharp, G. R.; Gedeon, L.; Oglebay, J. C.; Shaker, F. S.; Siegert, C. E.

    1978-01-01

    A prototype electric power management and thruster control system for a 30 cm ion thruster is described. The system meets all of the requirements necessary to operate a thruster in a fully automatic mode. Power input to the system can vary over a full two to one dynamic range (200 to 400 V) for the solar array or other power source. The power management and control system is designed to protect the thruster, the flight system and itself from arcs and is fully compatible with standard spacecraft electronics. The system is easily integrated into flight systems which can operate over a thermal environment ranging from 0.3 to 5 AU. The complete power management and control system measures 45.7 cm (18 in.) x 15.2 cm (6 in.) x 114.8 cm (45.2 in.) and weighs 36.2 kg (79.7 lb). At full power the overall efficiency of the system is estimated to be 87.4 percent. Three systems are currently being built and a full schedule of environmental and electrical testing is planned.

  11. Experimental investigation of the catalytic decomposition and combustion characteristics of a non-toxic ammonium dinitramide (ADN)-based monopropellant thruster

    Science.gov (United States)

    Chen, Jun; Li, Guoxiu; Zhang, Tao; Wang, Meng; Yu, Yusong

    2016-12-01

    Low toxicity ammonium dinitramide (ADN)-based aerospace propulsion systems currently show promise with regard to applications such as controlling satellite attitude. In the present work, the decomposition and combustion processes of an ADN-based monopropellant thruster were systematically studied, using a thermally stable catalyst to promote the decomposition reaction. The performance of the ADN propulsion system was investigated using a ground test system under vacuum, and the physical properties of the ADN-based propellant were also examined. Using this system, the effects of the preheating temperature and feed pressure on the combustion characteristics and thruster performance during steady state operation were observed. The results indicate that the propellant and catalyst employed during this work, as well as the design and manufacture of the thruster, met performance requirements. Moreover, the 1 N ADN thruster generated a specific impulse of 223 s, demonstrating the efficacy of the new catalyst. The thruster operational parameters (specifically, the preheating temperature and feed pressure) were found to have a significant effect on the decomposition and combustion processes within the thruster, and the performance of the thruster was demonstrated to improve at higher feed pressures and elevated preheating temperatures. A lower temperature of 140 °C was determined to activate the catalytic decomposition and combustion processes more effectively compared with the results obtained using other conditions. The data obtained in this study should be beneficial to future systematic and in-depth investigations of the combustion mechanism and characteristics within an ADN thruster.

  12. Small Body GN&C Research Report: A Guidance and Control Technique for Small-Body Proximity Operations with Guaranteed Guidance Resolvability and Required Thruster Silent Time

    Science.gov (United States)

    Carson, John M., III; Ackmese, A. Behcet

    2005-01-01

    The guidance and control (G&C) algorithms for enabling small-body proximity operations are developed by using a model predictive control approach along with a convexification of the governing dynamics, control constraints, and trajectory/state constraints. The open-loop guidance is solved ahead of time or in a resolvable, real-time manner through the use of PWG (Pseudo Way-point Generation), a technique developed in this research. The PWG scheme ensures required thruster silent times during trajectory maneuvers. The feedback control is implemented to track the PWG trajectories in a manner that guarantees the resolvability for the open-loop problem, enabling the ability to update the G&C in a model-predictive manner. The schemes incorporate gravity models and thruster ring times into discrete dynamics that are solved as a optimal control problem to minimize fuel consumption or thruster energy expenditure. The optimal control problem is cast as an LMI (Linear Matrix Inequality) and then solved through Semi-Definite Programming techniques in a computationally efficient manner that provides convergence and constraint guarantees.

  13. Bi-directional thruster development and test report

    Science.gov (United States)

    Jacot, A. D.; Bushnell, G. S.; Anderson, T. M.

    1990-01-01

    The design, calibration and testing of a cold gas, bi-directional throttlable thruster are discussed. The thruster consists of an electro-pneumatic servovalve exhausting through opposite nozzles with a high gain pressure feedback loop to optimize performance. The thruster force was measured to determine hysteresis and linearity. Integral gain was used to maximize performance for linearity, hysteresis, and minimum thrust requirements. Proportional gain provided high dynamic response (bandwidth and phase lag). Thruster performance is very important since the thrusters are intended to be used for active control.

  14. Improvement of the Power Control Unit for Ion Thruster to Cope with Milli-Newton Range RIT

    Science.gov (United States)

    Ceruti, Luca; Polli, Aldo; Galantini, Paolo

    2014-08-01

    The recent development and testing activities of a miniaturized Radio-Frequency Ion Thruster, with relevant ancillary elements, in the range of 10 to 100 micro-Newtons, joined with past flight heritage in the milli-Newton range (RIT-10 for Artemis), shows an appealing capability of such an electrical propulsion technology to support thrust in a wide range of space applications from very fine attitude control up to deorbiting of small-medium satellites. As expectable, this implies that the mentioned ancillary elements (mainly Radio-Frequency Generator and Power Control Unit) require adaptation to the different requirements imposed to different missions and thrust ranges. Regarding the Power Control Unit different power levels, both the controllability requirements and the spacecraft interfaces impose non negligible adaptation leading to significant increase of development activities and associated cost (nonrecurring) increase. From that and with the main purpose to minimize such impacts and provide reliable equipments, Selex ES since a few years is devoting maximum attention in the incremental innovation of the existing design in order to maximize their reuse.

  15. Control Electronics For Reaction Wheel

    Science.gov (United States)

    Chamberlin, Keith

    1995-01-01

    Bidirectional operation achieved with single-polarity main power supply. Control circuitry generates pulse-width-modulated 800-Hz waveforms to drive two-phase ac motor and reaction wheel. Operates partly in response to digital magnitude-and-direction torque command generated by external control subsystem and partly in response to tachometric feedback in form of two once-per-revolution sinusoids with amplitudes proportional to speed. Operation in either of two modes called "normal" and "safehold." In normal mode, drive pulses timed so that, on average over one or few cycles, motor applies commanded torque. In safehold mode, pulses timed to keep motor running at set speed in one direction.

  16. Additive Manufacturing of Ion Thruster Optics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Plasma Controls will manufacture and test a set of ion optics for electric propulsion ion thrusters using additive manufacturing technology, also known as 3D...

  17. Cylindrical geometry hall thruster

    Science.gov (United States)

    Raitses, Yevgeny; Fisch, Nathaniel J.

    2002-01-01

    An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, wherein ions are accelerated in substantially the axial direction. The apparatus is suitable for operation at low power. It employs small size thruster components, including a ceramic channel, with the center pole piece of the conventional annular design thruster eliminated or greatly reduced. Efficient operation is accomplished through magnetic fields with a substantial radial component. The propellant gas is ionized at an optimal location in the thruster. A further improvement is accomplished by segmented electrodes, which produce localized voltage drops within the thruster at optimally prescribed locations. The apparatus differs from a conventional Hall thruster, which has an annular geometry, not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume.

  18. Conducting Wall Hall Thrusters

    Science.gov (United States)

    Goebel, Dan M.; Hofer, Richard R.; Mikellides, Ioannis G.; Katz, Ira; Polk, James E.; Dotson, Brandon

    2013-01-01

    A unique configuration of the magnetic field near the wall of Hall thrusters, called Magnetic Shielding, has recently demonstrated the ability to significantly reduce the erosion of the boron nitride (BN) walls and extend the life of Hall thrusters by orders of magnitude. The ability of magnetic shielding to minimize interactions between the plasma and the discharge chamber walls has for the first time enabled the replacement of insulating walls with conducting materials without loss in thruster performance. The boron nitride rings in the 6 kW H6 Hall thruster were replaced with graphite that self-biased to near the anode potential. The thruster efficiency remained over 60% (within two percent of the baseline BN configuration) with a small decrease in thrust and increase in Isp typical of magnetically shielded Hall thrusters. The graphite wall temperatures decreased significantly compared to both shielded and unshielded BN configurations, leading to the potential for higher power operation. Eliminating ceramic walls makes it simpler and less expensive to fabricate a thruster to survive launch loads, and the graphite discharge chamber radiates more efficiently which increases the power capability of the thruster compared to conventional Hall thruster designs.

  19. Oxygen-Methane Thruster

    Science.gov (United States)

    Pickens, Tim

    2012-01-01

    An oxygen-methane thruster was conceived with integrated igniter/injector capable of nominal operation on either gaseous or liquid propellants. The thruster was designed to develop 100 lbf (approximately 445 N) thrust at vacuum conditions and use oxygen and methane as propellants. This continued development included refining the design of the thruster to minimize part count and manufacturing difficulties/cost, refining the modeling tools and capabilities that support system design and analysis, demonstrating the performance of the igniter and full thruster assembly with both gaseous and liquid propellants, and acquiring data from this testing in order to verify the design and operational parameters of the thruster. Thruster testing was conducted with gaseous propellants used for the igniter and thruster. The thruster was demonstrated to work with all types of propellant conditions, and provided the desired performance. Both the thruster and igniter were tested, as well as gaseous propellants, and found to provide the desired performance using the various propellant conditions. The engine also served as an injector testbed for MSFC-designed refractory combustion chambers made of rhenium.

  20. Thermo-mechanical design aspects of mercury bombardment ion thrusters.

    Science.gov (United States)

    Schnelker, D. E.; Kami, S.

    1972-01-01

    The mechanical design criteria are presented as background considerations for solving problems associated with the thermomechanical design of mercury ion bombardment thrusters. Various analytical procedures are used to aid in the development of thruster subassemblies and components in the fields of heat transfer, vibration, and stress analysis. Examples of these techniques which provide computer solutions to predict and control stress levels encountered during launch and operation of thruster systems are discussed. Computer models of specific examples are presented.

  1. Solid State MEMS Thrusters Using Electrically Controlled Extinguishable Solid Propellant Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ET Materials, LLC developed the first ever electrically controlled extinguishable solid propellant (ECESP). The original propellant developed under Air Force SBIR...

  2. Plasma Diagnostic and Performance of a Permanent Magnet Hall Thruster

    CERN Document Server

    Ferreira, J L; Rego, I D S; Ferreira, I S; Ferreira, Jose Leonardo; Souza, Joao Henrique Campos De; Rego, Israel Da Silveira; Ferreira, Ivan Soares

    2004-01-01

    Electric propulsion is now a sucessfull method for primary propulsion of deep space long duration missions and for geosyncronous satellite attitude control. Closed Drift Plasma Thruster, so called Hall Thruster or SPT (stationary plasma thruster) were primarily conceived in USSR (the ancient Soviet Union) and now it is been developed by space agencies, space research institutes and industries in several countries such as France, USA, Israel, Russian Federation and Brazil. In this work, we show plasma characteristics and performance of a Hall Thruster designed with an innovative concept which uses an array of permanent magnets, instead of an eletromagnet, to produce a radial magnetic field inside its cylindrical plasma drift channel. Within this new concept, we expect to develop a Hall Thruster within power consuption that will scale up to small and medium size satellites. A plasma density and temperature space profiles inside and outside the thruster channel will be shown. Space plasma potential, ion temperat...

  3. Femtosecond laser control of chemical reactions

    CSIR Research Space (South Africa)

    Du Plessis, A

    2010-08-31

    Full Text Available Femtosecond laser control of chemical reactions is made possible through the use of pulse-shaping techniques coupled to a learning algorithm feedback loop – teaching the laser pulse to control the chemical reaction. This can result in controllable...

  4. Estimating Thruster Impulses From IMU and Doppler Data

    Science.gov (United States)

    Lisano, Michael E.; Kruizinga, Gerhard L.

    2009-01-01

    A computer program implements a thrust impulse measurement (TIM) filter, which processes data on changes in velocity and attitude of a spacecraft to estimate the small impulsive forces and torques exerted by the thrusters of the spacecraft reaction control system (RCS). The velocity-change data are obtained from line-of-sight-velocity data from Doppler measurements made from the Earth. The attitude-change data are the telemetered from an inertial measurement unit (IMU) aboard the spacecraft. The TIM filter estimates the threeaxis thrust vector for each RCS thruster, thereby enabling reduction of cumulative navigation error attributable to inaccurate prediction of thrust vectors. The filter has been augmented with a simple mathematical model to compensate for large temperature fluctuations in the spacecraft thruster catalyst bed in order to estimate thrust more accurately at deadbanding cold-firing levels. Also, rigorous consider-covariance estimation is applied in the TIM to account for the expected uncertainty in the moment of inertia and the location of the center of gravity of the spacecraft. The TIM filter was built with, and depends upon, a sigma-point consider-filter algorithm implemented in a Python-language computer program.

  5. Controlling chemical reactions of a single particle

    CERN Document Server

    Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2012-01-01

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achi...

  6. Capillary Discharge Thruster Experiments and Modeling (Briefing Charts)

    Science.gov (United States)

    2016-06-01

    PROPULSION MODELS & EXPERIMENTS Spacecraft Propulsion Relevant Plasma: From hall thrusters to plumes and fluxes on components Complex reaction physics i.e...PROPULSION MODELS & EXPERIMENTS Spacecraft Propulsion Relevant Plasma: From hall thrusters to plumes and fluxes on components Complex reaction ...Conductivity h is the Enthalpy Cs is the Sound Speed Θ is the Wall Energy Flux Pekker, 40th AIAA Plasmadynamics and Laser Conference, 2009. R.S. MARTIN (ERC INC

  7. Preventing Corrosion by Controlling Cathodic Reaction Kinetics

    Science.gov (United States)

    2016-03-25

    Preventing corrosion by controlling cathodic reaction kinetics Progress Report for Period: 1 SEP 2015-31 MAR 2016 John Keith Department of...25 March 2016 Preventing corrosion by controlling cathodic reaction kinetics Annual Summary Report: FY16 PI: John Keith, 412-624-7016,jakeith...dominate the metal’s cathodic behavior. Within an alkaline environment, we expect the following reduction reactions to be catalyzed on the oxide

  8. Chemical potential and reaction electronic flux in symmetry controlled reactions.

    Science.gov (United States)

    Vogt-Geisse, Stefan; Toro-Labbé, Alejandro

    2016-07-15

    In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc.

  9. Oxygen-Methane Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Orion Propulsion, Inc. proposes to develop an Oxygen and Methane RCS Thruster to advance the technology of alternate fuels. A successful Oxygen/CH4 RCS Thruster will...

  10. Iodine Hall Thruster

    Science.gov (United States)

    Szabo, James

    2015-01-01

    Iodine enables dramatic mass and cost savings for lunar and Mars cargo missions, including Earth escape and near-Earth space maneuvers. The demonstrated throttling ability of iodine is important for a singular thruster that might be called upon to propel a spacecraft from Earth to Mars or Venus. The ability to throttle efficiently is even more important for missions beyond Mars. In the Phase I project, Busek Company, Inc., tested an existing Hall thruster, the BHT-8000, on iodine propellant. The thruster was fed by a high-flow iodine feed system and supported by an existing Busek hollow cathode flowing xenon gas. The Phase I propellant feed system was evolved from a previously demonstrated laboratory feed system. Throttling of the thruster between 2 and 11 kW at 200 to 600 V was demonstrated. Testing showed that the efficiency of iodine fueled BHT-8000 is the same as with xenon, with iodine delivering a slightly higher thrust-to-power (T/P) ratio. In Phase II, a complete iodine-fueled system was developed, including the thruster, hollow cathode, and iodine propellant feed system. The nominal power of the Phase II system is 8 kW; however, it can be deeply throttled as well as clustered to much higher power levels. The technology also can be scaled to greater than 100 kW per thruster to support megawatt-class missions. The target thruster efficiency for the full-scale system is 65 percent at high specific impulse (Isp) (approximately 3,000 s) and 60 percent at high thrust (Isp approximately 2,000 s).

  11. Design and model experiments on thruster assisted mooring system; Futaishiki kaiyo kozobutsu no thruster ni yoru choshuki doyo seigyo

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, M.; Koterayama, W. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Kajiwara, H. [Kyushu Institute of Technology, Kitakyushu (Japan). Faculty of Computer Science and System Engineering; Hyakudome, T. [Kyushu University, Fukuoka (Japan)

    1996-12-31

    Described herein are dynamics and model experiments of the system in which positioning of a floating marine structure by mooring is combined with thruster-controlled positioning. Coefficients of dynamic forces acting on a floating structure model are determined experimentally and by the three-dimensional singularity distribution method, and the controller is designed by the PID, LQI and H{infinity} control theories. A model having a scale ratio of 1/100 was used for the experiments, where 2 thrusters were arranged in a diagonal line, one on the X-axis. It is found that the LQI and H{infinity} controllers of the thruster can control long-cycle rolling of the floating structure. They allow thruster control which is insensitive to wave cycle motion, and efficiently reduce positioning energy. The H{infinity} control regulates frequency characteristics of a closed loop more finely than the LQI control, and exhibits better controllability. 25 refs., 25 figs.

  12. Design and model experiments on thruster assisted mooring system; Futaishiki kaiyo kozobutsu no thruster ni yoru choshuki doyo seigyo

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, M.; Koterayama, W. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Kajiwara, H. [Kyushu Institute of Technology, Kitakyushu (Japan). Faculty of Computer Science and System Engineering; Hyakudome, T. [Kyushu University, Fukuoka (Japan)

    1996-12-31

    Described herein are dynamics and model experiments of the system in which positioning of a floating marine structure by mooring is combined with thruster-controlled positioning. Coefficients of dynamic forces acting on a floating structure model are determined experimentally and by the three-dimensional singularity distribution method, and the controller is designed by the PID, LQI and H{infinity} control theories. A model having a scale ratio of 1/100 was used for the experiments, where 2 thrusters were arranged in a diagonal line, one on the X-axis. It is found that the LQI and H{infinity} controllers of the thruster can control long-cycle rolling of the floating structure. They allow thruster control which is insensitive to wave cycle motion, and efficiently reduce positioning energy. The H{infinity} control regulates frequency characteristics of a closed loop more finely than the LQI control, and exhibits better controllability. 25 refs., 25 figs.

  13. Diagnostics Systems for Permanent Hall Thrusters Development

    Science.gov (United States)

    Ferreira, Jose Leonardo; Soares Ferreira, Ivan; Santos, Jean; Miranda, Rodrigo; Possa, M. Gabriela

    -Effect Thruster (PMHET), developed at the Plasma Physics Laboratory of UnB. The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magnetic field inside the cylindrical plasma drift channel of the thruster is very attractive, especially because of the possibility of developing a HET with power consumption low enough to be used in small satellites or medium-size satellites with low on board power. Hall-Effect Thrusters are now a very good option for spacecraft primary propulsion and also for station-keeping of medium and large satellites. This is because of their high specific impulse, efficient use of propellant mass and combined low and precise thrust capabilities, which are related to an economy in terms of propellant mass utilization , longer satellite lifetime and easier spacecraft maneuvering in microgravity environment. The first HETs were developed in the mid 1950’s, and they were first called Closed Drift Thrusters. Today, the successful use of electric thrusters for attitude control and orbit modification on hundreds of satellites shows the advanced stage of development of this technology. In addition to this, after the success of space missions such as Deep Space One and Dawn (NASA), Hayabusa (JAXA) and Smart-1 (ESA), the employment of electric thrusters is also consolidated for the primary propulsion of spacecraft. This success is mainly due to three factors: reliability of this technology; efficiency of propellant utilization, and therefore reduction of the initial mass of the ship; possibility of operation over long time intervals, with practically unlimited cycling and restarts. This thrusting system is designed to be used in satellite attitude control and long term space missions. One of the greatest advantage of this kind of thruster is the production of a steady state magnetic field by permanent magnets providing electron trapping and Hall current generation within a significant decrease on the electric energy supply

  14. Nonlinear control of the Salnikov model reaction

    DEFF Research Database (Denmark)

    Recke, Bodil; Jørgensen, Sten Bay

    1999-01-01

    This paper explores different nonlinear control schemes, applied to a simple model reaction. The model is the Salnikov model, consisting of two ordinary differential equations. The control strategies investigated are I/O-linearisation, Exact linearisation, exact linearisation combined with LQR...... and Control Lyapunov Functions (CLF's). The results show that based on the lowest possible cost function and shortest settling time, the exact linearisation performs marginally better than the other methods....

  15. Space Shuttle vernier thruster long-life chamber development

    Science.gov (United States)

    Krohn, Douglas D.

    1990-01-01

    The Space Shuttle Reaction Control Subsystem (RCS) vernier thruster is a pressure fed engine that utilizes storable propellants to provide precise attitude control for the Orbiter. The current vernier thruster is life limited due to its chamber material. By developing an iridium-lined rhenium chamber for the vernier, substantial gains could be achieved in the operational life of the chamber. The present RCS vernier, its requirements, operating characteristics, and life limitations are described. The current technology status of iridium-lined rhenium is presented along with a description of the operational life capabilities to be gained from implementing this material into the design of a long life vernier chamber. Discussion of the proposed demonstration program to be performed by the NASA Lyndon B. Johnson Space Center to attain additional insight into the application of this technology to the RCS vernier, includes the technical objectives, approach, and program schedule. The plans for further development and integration with the Orbiter and the Shuttle system are also presented.

  16. Finite-time sliding mode attitude control for a reentry vehicle with blended aerodynamic surfaces and a reaction control system

    Directory of Open Access Journals (Sweden)

    Geng Jie

    2014-08-01

    Full Text Available This paper proposes a finite-time robust flight controller, targeting for a reentry vehicle with blended aerodynamic surfaces and a reaction control system (RCS. Firstly, a novel finite-time attitude controller is pointed out with the introduction of a nonsingular finite-time sliding mode manifold. The attitude tracking errors are mathematically proved to converge to zero within finite time which can be estimated. In order to improve the performance, a second-order finite-time sliding mode controller is further developed to effectively alleviate chattering without any deterioration of robustness and accuracy. Moreover, an optimization control allocation algorithm, using linear programming and a pulse-width pulse-frequency (PWPF modulator, is designed to allocate torque commands for all the aerodynamic surface deflections and on–off switching-states of RCS thrusters. Simulations are provided for the reentry vehicle considering uncertain parameters and external disturbances for practical purposes, and the results demonstrate the effectiveness and robustness of the attitude control system.

  17. Finite-time sliding mode attitude control for a reentry vehicle with blended aerodynamic surfaces and a reaction control system

    Institute of Scientific and Technical Information of China (English)

    Geng Jie; Sheng Yongzhi; Liu Xiangdong

    2014-01-01

    This paper proposes a finite-time robust flight controller, targeting for a reentry vehicle with blended aerodynamic surfaces and a reaction control system (RCS). Firstly, a novel finite-time attitude controller is pointed out with the introduction of a nonsingular finite-time sliding mode manifold. The attitude tracking errors are mathematically proved to converge to zero within finite time which can be estimated. In order to improve the performance, a second-order finite-time slid-ing mode controller is further developed to effectively alleviate chattering without any deterioration of robustness and accuracy. Moreover, an optimization control allocation algorithm, using linear programming and a pulse-width pulse-frequency (PWPF) modulator, is designed to allocate torque commands for all the aerodynamic surface deflections and on-off switching-states of RCS thrusters. Simulations are provided for the reentry vehicle considering uncertain parameters and external disturbances for practical purposes, and the results demonstrate the effectiveness and robustness of the attitude control system.

  18. Liquid micro pulsed plasma thruster

    Directory of Open Access Journals (Sweden)

    Szelecka Agnieszka

    2015-06-01

    Full Text Available A new type of pulsed plasma thruster (PPT for small satellite propulsion is investigated, of which the most innovative aspect is the use of a non-volatile liquid propellant. The thruster is based on an open capillary design. The thruster achieved a thrust-to-power ratio above 45 μN/W, which constitutes a 5-fold improvement over the water-propelled pulsed plasma thruster, and which is also slightly above the performance of a similarly sized PPT with a solid propellant.

  19. Monopropellant Thruster Development Using a Family of Micro Reactors

    Science.gov (United States)

    2017-02-17

    SCALE IN MILES HWY 395 ROSAMOND BLVD...AVENUE E H IG H W AY 1 4 LA N C A S TE R B LV D . 14 0t h S TR E E T E A S T RESERVATION BOUNDARY 0 5 10 SCALE IN MILES HWY 395 ROSAMOND BLVD...Monopropellant Thrusters Physical Description • Small (~1-22N) Thrusters Used for Attitude Control and Maneuvering of Small Spacecraft. AF-M315E

  20. Helical plasma thruster

    Energy Technology Data Exchange (ETDEWEB)

    Beklemishev, A. D., E-mail: bekl@bk.ru [Budker Institute of Nuclear Physics SB RAS, Novosibirsk (Russian Federation)

    2015-10-15

    A new scheme of plasma thruster is proposed. It is based on axial acceleration of rotating magnetized plasmas in magnetic field with helical corrugation. The idea is that the propellant ionization zone can be placed into the local magnetic well, so that initially the ions are trapped. The E × B rotation is provided by an applied radial electric field that makes the setup similar to a magnetron discharge. Then, from the rotating plasma viewpoint, the magnetic wells of the helically corrugated field look like axially moving mirror traps. Specific shaping of the corrugation can allow continuous acceleration of trapped plasma ions along the magnetic field by diamagnetic forces. The accelerated propellant is expelled through the expanding field of magnetic nozzle. By features of the acceleration principle, the helical plasma thruster may operate at high energy densities but requires a rather high axial magnetic field, which places it in the same class as the VASIMR{sup ®} rocket engine.

  1. Characterization of a Pressure-Fed LOX/LCH4 Reaction Control System Under Simulated Altitude and Thermal Vacuum Conditions

    Science.gov (United States)

    Atwell, Matthew J.; Melcher, John C.; Hurlbert, Eric A.; Morehead, Robert L.

    2017-01-01

    A liquid oxygen, liquid methane (LOX/LCH4) reaction control system (RCS) was tested at NASA Glenn Research Center's Plum Brook Station in the Spacecraft Propulsion Research Facility (B-2) under simulated altitude and thermal vacuum conditions. The RCS is a subsystem of the Integrated Cryogenic Propulsion Test Article (ICPTA) and was initially developed under Project Morpheus. Composed of two 28 lbf-thrust and two 7 lbf-thrust engines, the RCS is fed in parallel with the ICPTA main engine from four propellant tanks. 40 tests consisting of 1,010 individual thruster pulses were performed across 6 different test days. Major test objectives were focused on system dynamics, and included characterization of fluid transients, manifold priming, manifold thermal conditioning, thermodynamic vent system (TVS) performance, and main engine/RCS interaction. Peak surge pressures from valve opening and closing events were examined. It was determined that these events were impacted significantly by vapor cavity formation and collapse. In most cases the valve opening transient was more severe than the valve closing. Under thermal vacuum conditions it was shown that TVS operation is unnecessary to maintain liquid conditions at the thruster inlets. However, under higher heat leak environments the RCS can still be operated in a self-conditioning mode without overboard TVS venting, contingent upon the engines managing a range of potentially severe thermal transients. Lastly, during testing under cold thermal conditions the engines experienced significant ignition problems. Only after warming the thruster bodies with a gaseous nitrogen purge to an intermediate temperature was successful ignition demonstrated.

  2. Arcjet space thrusters

    Science.gov (United States)

    Keefer, Dennis; Rhodes, Robert

    1993-01-01

    Electrically powered arc jets which produce thrust at high specific impulse could provide a substantial cost reduction for orbital transfer and station keeping missions. There is currently a limited understanding of the complex, nonlinear interactions in the plasma propellant which has hindered the development of high efficiency arc jet thrusters by making it difficult to predict the effect of design changes and to interpret experimental results. A computational model developed at the University of Tennessee Space Institute (UTSI) to study laser powered thrusters and radio frequency gas heaters has been adapted to provide a tool to help understand the physical processes in arc jet thrusters. The approach is to include in the model those physical and chemical processes which appear to be important, and then to evaluate our judgement by the comparison of numerical simulations with experimental data. The results of this study have been presented at four technical conferences. The details of the work accomplished in this project are covered in the individual papers included in the appendix of this report. We present a brief description of the model covering its most important features followed by a summary of the effort.

  3. Continuous Wheel Momentum Dumping Using Magnetic Torquers and Thrusters

    Science.gov (United States)

    Oh, Hwa-Suk; Choi, Wan-Sik; Eun, Jong-Won

    1996-12-01

    Two momentum management schemes using magnetic torquers and thrusters are sug-gested. The stability of the momentum dumping logic is proved at a general attitude equilibrium. Both momentum dumping control laws are implemented with Pulse-Width- Pulse-Frequency Modulated on-off control, and shown working equally well with the original continuous and variable strength control law. Thrusters are assummed to be asymmetrically configured as a contingency case. Each thruster is fired following separated control laws rather than paired thrusting. Null torque thrusting control is added on the thrust control calculated from the momentum control law for the gener-ation of positive thrusting force. Both magnetic and thrusting control laws guarantee the momentum dumping, however, the wheel inner loop control is needed for the "wheel speed" dumping, The control laws are simulated on the KOrea Multi-Purpose SATellite (KOMPSAT) model.

  4. Thruster Modelling for Underwater Vehicle Using System Identification Method

    Directory of Open Access Journals (Sweden)

    Mohd Shahrieel Mohd Aras

    2013-05-01

    Full Text Available This paper describes a study of thruster modelling for a remotely operated underwater vehicle (ROV by system identification using Microbox 2000/2000C. Microbox 2000/2000C is an XPC target machine device to interface between an ROV thruster with the MATLAB 2009 software. In this project, a model of the thruster will be developed first so that the system identification toolbox in MATLAB can be used. This project also presents a comparison of mathematical and empirical modelling. The experiments were carried out by using a mini compressor as a dummy depth pressure applied to a pressure sensor. The thruster model will thrust and submerge until it reaches a set point and maintain the set point depth. The depth was based on pressure sensor measurement. A conventional proportional controller was used in this project and the results gathered justified its selection.

  5. Thruster Modelling for Underwater Vehicle Using System Identification Method

    Directory of Open Access Journals (Sweden)

    Mohd Shahrieel Mohd Aras

    2013-05-01

    Full Text Available Abstract This paper describes a study of thruster modelling for a remotely operated underwater vehicle (ROV by system identification using Microbox 2000/2000C. Microbox 2000/2000C is an XPC target machine device to interface between an ROV thruster with the MATLAB 2009 software. In this project, a model of the thruster will be developed first so that the system identification toolbox in MATLAB can be used. This project also presents a comparison of mathematical and empirical modelling. The experiments were carried out by using a mini compressor as a dummy depth pressure applied to a pressure sensor. The thruster model will thrust and submerge until it reaches a set point and maintain the set point depth. The depth was based on pressure sensor measurement. A conventional proportional controller was used in this project and the results gathered justified its selection.

  6. Thermal-environmental testing of a 30-cm engineering model thruster

    Science.gov (United States)

    Mirtich, M. J.

    1976-01-01

    An experimental test program was carried out to document all 30-cm electron bombardment Hg ion bombardment thruster functions and characteristics over the thermal environment of several proposed missions. An engineering model thruster was placed in a thermal test facility equipped with -196 C walls and solar simulation. The thruster was cold soaked and exposed to simulated eclipses lasting in duration from 17 to 72 minutes. The thruster was operated at quarter, to full beam power in various thermal configurations which simulated multiple thruster operation, and was also exposed to 1 and 2 suns solar simulation. Thruster control characteristics and constraints; performance, including thrust magnitude and direction; and structural integrity were evaluated over the range of thermal environments tested.

  7. Thermal-environment testing of a 30-cm engineering model thruster

    Science.gov (United States)

    Mirtich, M. J.

    1976-01-01

    An experimental test program was carried out to document all 30-cm electron bombardment Hg ion bombardment thruster functions and characteristics over the thermal environment of several proposed missions. An engineering model thruster was placed in a thermal test facility equipped with -196 C walls and solar simulation. The thruster was cold soaked and exposed to simulated eclipses lasting in duration from 17 to 72 minutes. The thruster was operated at quarter, to full beam power in various thermal configurations which simulated multiple thruster operation, and was also exposed to 1 and 2 suns solar simulation. Thruster control characteristics and constraints; performance, including thrust magnitude and direction; and structural integrity were evaluated over the range of thermal environments tested.

  8. Thermal Modeling for Pulsed Inductive FRC Plasmoid Thrusters

    Science.gov (United States)

    Pfaff, Michael

    Due to the rising importance of space based infrastructure, long-range robotic space missions, and the need for active attitude control for spacecraft, research into Electric Propulsion is becoming increasingly important. Electric Propulsion (EP) systems utilize electric power to accelerate ions in order to produce thrust. Unlike traditional chemical propulsion, this means that thrust levels are relatively low. The trade-off is that EP thrusters have very high specific impulses (Isp), and can therefore make do with far less onboard propellant than cold gas, monopropellant, or bipropellant engines. As a consequence of the high power levels used to accelerate the ionized propellant, there is a mass and cost penalty in terms of solar panels and a power processing unit. Due to the large power consumption (and waste heat) from electric propulsion thrusters, accurate measurements and predictions of thermal losses are needed. Excessive heating in sensitive locations within a thruster may lead to premature failure of vital components. Between the fixed cost required to purchase these components, as well as the man-hours needed to assemble (or replace) them, attempting to build a high-power thruster without reliable thermal modeling can be expensive. This paper will explain the usage of FEM modeling and experimental tests in characterizing the ElectroMagnetic Plasmoid Thruster (EMPT) and the Electrodeless Lorentz Force (ELF) thruster at the MSNW LLC facility in Redmond, Washington. The EMPT thruster model is validated using an experimental setup, and steady state temperatures are predicted for vacuum conditions. Preliminary analysis of the ELF thruster indicates possible material failure in absence of an active cooling system for driving electronics and for certain power levels.

  9. A Robust Digital Autopilot for Spacecraft Equipped with Pulse-Operated Thrusters

    Science.gov (United States)

    Thurman, S. W.; Flashner, H.

    1996-01-01

    The analysis and design of attitude control systems for spacecraft employing pulse-operated (on-off) thrusters is usually accomplished through a combination of modeling approximations and empirical techniques. In this paper a new thruster pulse-modulation scheme for pointing and tracking applications is developed from nonlinear control theory.

  10. Design and development of the Army KE ASAT ACS thruster

    Science.gov (United States)

    Craddock, Jeff; Janeski, Bruce

    1993-06-01

    Increasingly ambitious missions for advanced kinetic energy (KE) weapons have necessitated the development of a lightweight storable-propellant attitude control system (ACS) thruster capable of very fast response and long duration firings. This paper summarizes the results of a ACS thruster design and development test effort, performed for the U.S. Army Space and Strategic Defense Command (USASSDC) on the KE Anti Satellite (KE ASAT) weapon system program. Design approaches used to achieve long-duration continuous firing with a composite combustion chamber are detailed. This design effort culminated in a 6.7 lbf. thruster assembly weighing less than 0.2 pounds, approximately one-sixth that of a conventional satellite ACS thruster. Results of tests of flightweight engines with nitrogen tetroxide and monomethyl hydrazine hypergolic propellants are included. The test series culminated in what is believed to be the industry's longest continuous firing of a composite combustion chamber. This thruster will be integrated into the KE ASAT kinetic vehicle for its first free-flight hover test in early FY94. The demonstrated fast response, high pulse performance, and long-duration capabilities of this engine suggest that this thruster can significantly increase the capability of other spacecraft.

  11. Thermodynamic Vent System for an On-Orbit Cryogenic Reaction Control Engine

    Science.gov (United States)

    Hurlbert, Eric A.; Romig, Kris A.; Jimenez, Rafael; Flores, Sam

    2012-01-01

    A report discusses a cryogenic reaction control system (RCS) that integrates a Joule-Thompson (JT) device (expansion valve) and thermodynamic vent system (TVS) with a cryogenic distribution system to allow fine control of the propellant quality (subcooled liquid) during operation of the device. It enables zero-venting when coupled with an RCS engine. The proper attachment locations and sizing of the orifice are required with the propellant distribution line to facilitate line conditioning. During operations, system instrumentation was strategically installed along the distribution/TVS line assembly, and temperature control bands were identified. A sub-scale run tank, full-scale distribution line, open-loop TVS, and a combination of procured and custom-fabricated cryogenic components were used in the cryogenic RCS build-up. Simulated on-orbit activation and thruster firing profiles were performed to quantify system heat gain and evaluate the TVS s capability to maintain the required propellant conditions at the inlet to the engine valves. Test data determined that a small control valve, such as a piezoelectric, is optimal to provide continuously the required thermal control. The data obtained from testing has also assisted with the development of fluid and thermal models of an RCS to refine integrated cryogenic propulsion system designs. This system allows a liquid oxygenbased main propulsion and reaction control system for a spacecraft, which improves performance, safety, and cost over conventional hypergolic systems due to higher performance, use of nontoxic propellants, potential for integration with life support and power subsystems, and compatibility with in-situ produced propellants.

  12. Artificial Neural Network Test Support Development for the Space Shuttle PRCS Thrusters

    Science.gov (United States)

    Lehr, Mark E.

    2005-01-01

    A significant anomaly, Fuel Valve Pilot Seal Extrusion, is affecting the Shuttle Primary Reaction Control System (PRCS) Thrusters, and has caused 79 to fail. To help address this problem, a Shuttle PRCS Thruster Process Evaluation Team (TPET) was formed. The White Sands Test Facility (WSTF) and Boeing members of the TPET have identified many discrete valve current trace characteristics that are predictive of the problem. However, these are difficult and time consuming to identify and trend by manual analysis. Based on this exhaustive analysis over months, 22 thrusters previously delivered by the Depot were identified as high risk for flight failures. Although these had only recently been installed, they had to be removed from Shuttles OV103 and OV104 for reprocessing, by directive of the Shuttle Project Office. The resulting impact of the thruster removal, replacement, and valve replacement was significant (months of work and hundreds of thousands of dollars). Much of this could have been saved had the proposed Neural Network (NN) tool described in this paper been in place. In addition to the significant benefits to the Shuttle indicated above, the development and implementation of this type of testing will be the genesis for potential Quality improvements across many areas of WSTF test data analysis and will be shared with other NASA centers. Future tests can be designed to incorporate engineering experience via Artificial Neural Nets (ANN) into depot level acceptance of hardware. Additionally, results were shared with a NASA Engineering and Safety Center (NESC) Super Problem Response Team (SPRT). There was extensive interest voiced among many different personnel from several centers. There are potential spin-offs of this effort that can be directly applied to other data acquisition systems as well as vehicle health management for current and future flight vehicles.

  13. Temperature Gradient in Hall Thrusters

    Energy Technology Data Exchange (ETDEWEB)

    D. Staack; Y. Raitses; N.J. Fisch

    2003-11-24

    Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons.

  14. High-Pressure Lightweight Thrusters

    Science.gov (United States)

    Holmes, Richard; McKechnie, Timothy; Shchetkovskiy, Anatoliy; Smirnov, Alexander

    2013-01-01

    Returning samples of Martian soil and rock to Earth is of great interest to scientists. There were numerous studies to evaluate Mars Sample Return (MSR) mission architectures, technology needs, development plans, and requirements. The largest propulsion risk element of the MSR mission is the Mars Ascent Vehicle (MAV). Along with the baseline solid-propellant vehicle, liquid propellants have been considered. Similar requirements apply to other lander ascent engines and reaction control systems. The performance of current state-ofthe- art liquid propellant engines can be significantly improved by increasing both combustion temperature and pressure. Pump-fed propulsion is suggested for a single-stage bipropellant MAV. Achieving a 90-percent stage propellant fraction is thought to be possible on a 100-kg scale, including sufficient thrust for lifting off Mars. To increase the performance of storable bipropellant rocket engines, a high-pressure, lightweight combustion chamber was designed. Iridium liner electrodeposition was investigated on complex-shaped thrust chamber mandrels. Dense, uniform iridium liners were produced on chamber and cylindrical mandrels. Carbon/carbon composite (C/C) structures were braided over iridium-lined mandrels and densified by chemical vapor infiltration. Niobium deposition was evaluated for forming a metallic attachment flange on the carbon/ carbon structure. The new thrust chamber was designed to exceed state-of-the-art performance, and was manufactured with an 83-percent weight savings. High-performance C/Cs possess a unique set of properties that make them desirable materials for high-temperature structures used in rocket propulsion components, hypersonic vehicles, and aircraft brakes. In particular, more attention is focused on 3D braided C/Cs due to their mesh-work structure. Research on the properties of C/Cs has shown that the strength of composites is strongly affected by the fiber-matrix interfacial bonding, and that weakening

  15. NEXT Ion Thruster Performance Dispersion Analyses

    Science.gov (United States)

    Soulas, George C.; Patterson, Michael J.

    2008-01-01

    The NEXT ion thruster is a low specific mass, high performance thruster with a nominal throttling range of 0.5 to 7 kW. Numerous engineering model and one prototype model thrusters have been manufactured and tested. Of significant importance to propulsion system performance is thruster-to-thruster performance dispersions. This type of information can provide a bandwidth of expected performance variations both on a thruster and a component level. Knowledge of these dispersions can be used to more conservatively predict thruster service life capability and thruster performance for mission planning, facilitate future thruster performance comparisons, and verify power processor capabilities are compatible with the thruster design. This study compiles the test results of five engineering model thrusters and one flight-like thruster to determine unit-to-unit dispersions in thruster performance. Component level performance dispersion analyses will include discharge chamber voltages, currents, and losses; accelerator currents, electron backstreaming limits, and perveance limits; and neutralizer keeper and coupling voltages and the spot-to-plume mode transition flow rates. Thruster level performance dispersion analyses will include thrust efficiency.

  16. Shared Magnetics Hall Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In the proposed Phase II program, Busek Co. will demonstrate an innovative methodology for clustering Hall thrusters into a high performance, very high power...

  17. Oxygen-Methane Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Two main innovations will be developed in the Phase II effort that are fundamentally associated with our gaseous oxygen/gaseous methane RCS thruster. The first...

  18. Shared Magnetics Hall Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In the proposed Phase I program, Busek Co. will demonstrate an innovative methodology for clustering Hall thrusters into a high performance, very high power...

  19. Use of microgravity sensors for quantification of space shuttle orbiter vernier reaction control system induced environments

    Science.gov (United States)

    Friend, Robert B.

    1998-01-01

    In the modeling of spacecraft dynamics it is important to accurately characterize the environment in which the vehicle operates, including the environments induced by the vehicle itself. On the Space Shuttle these induced environmental factors include reaction control system plume. Knowledge of these environments is necessary for performance of control systems and loads analyses, estimation of disturbances due to thruster firings, and accurate state vector propagation. During the STS-71 mission, while the Orbiter was performing attitude control for the mated Orbiter/Mir stack, it was noted that the autopilot was limit cycling at a rate higher than expected from pre-flight simulations. Investigations during the mission resulted in the conjecture that an unmodelled plume impingement force was acting upon the orbiter elevons. The in-flight investigations were not successful in determining the actual magnitude of the impingement, resulting in several sequential post-flight investigations. Efforts performed to better quantify the vernier reaction control system induced plume impingement environment of the Space Shuttle orbiter are described in this paper, and background detailing circumstances which required the more detailed knowledge of the RCS self impingement forces, as well as a description of the resulting investigations and their results is presented. The investigations described in this paper applied microgravity acceleration data from two shuttle borne microgravity experiments, SAMS and OARE, to the solution of this particular problem. This solution, now used by shuttle analysts and mission planners, results in more accurate propellant consumption and attitude limit cycle estimates in preflight analyses, which are critical for pending International Space Station missions.

  20. Iodine Hall Thruster for Space Exploration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In the Phase I program, Busek Co. Inc. tested an existing Hall thruster, the BHT-8000, on iodine propellant. The thruster was fed by a high flow iodine feed system,...

  1. The electrodeless Lorentz force (ELF) thruster experimental facility

    Science.gov (United States)

    Weber, T. E.; Slough, J. T.; Kirtley, D.

    2012-11-01

    An innovative facility for testing high-power, pulsed plasmoid thrusters has been constructed to develop the electrodeless Lorentz force (ELF) thruster concept. It is equipped with a suite of diagnostics optimized to study the physical processes taking place within ELF and evaluate its propulsive utility including magnetic field, neutral gas, and plasma flux diagnostics, a method to determine energy flow into the plasma from the pulsed power systems, and a new type of ballistic pendulum, which enables thrust to be measured without the need for installing the entire propulsion system on a thrust stand. Variable magnetic fields allow controlled studies of plume expansion in a small-scale experiment and dielectric chamber walls reduce electromagnetic influences on plasma behavior and thruster operation. The unique capabilities of this facility enable novel concept development to take place at greatly reduced cost and increased accessibility compared to testing at large user-facilities.

  2. Implementing Nonlinear Feedback Controllers Using DNA Strand Displacement Reactions.

    Science.gov (United States)

    Sawlekar, Rucha; Montefusco, Francesco; Kulkarni, Vishwesh V; Bates, Declan G

    2016-07-01

    We show how an important class of nonlinear feedback controllers can be designed using idealized abstract chemical reactions and implemented via DNA strand displacement (DSD) reactions. Exploiting chemical reaction networks (CRNs) as a programming language for the design of complex circuits and networks, we show how a set of unimolecular and bimolecular reactions can be used to realize input-output dynamics that produce a nonlinear quasi sliding mode (QSM) feedback controller. The kinetics of the required chemical reactions can then be implemented as enzyme-free, enthalpy/entropy driven DNA reactions using a toehold mediated strand displacement mechanism via Watson-Crick base pairing and branch migration. We demonstrate that the closed loop response of the nonlinear QSM controller outperforms a traditional linear controller by facilitating much faster tracking response dynamics without introducing overshoots in the transient response. The resulting controller is highly modular and is less affected by retroactivity effects than standard linear designs.

  3. Helicon plasma thruster discharge model

    Energy Technology Data Exchange (ETDEWEB)

    Lafleur, T., E-mail: trevor.lafleur@lpp.polytechnique.fr [Laboratoire de Physique des Plasmas, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ Paris-Sud, Ecole Polytechnique, 91128 Palaiseau, France and ONERA - The French Aerospace Lab, 91120 Palaiseau (France)

    2014-04-15

    By considering particle, momentum, and energy balance equations, we develop a semi-empirical quasi one-dimensional analytical discharge model of radio-frequency and helicon plasma thrusters. The model, which includes both the upstream plasma source region as well as the downstream diverging magnetic nozzle region, is compared with experimental measurements and confirms current performance levels. Analysis of the discharge model identifies plasma power losses on the radial and back wall of the thruster as the major performance reduction factors. These losses serve as sinks for the input power which do not contribute to the thrust, and which reduce the maximum plasma density and hence propellant utilization. With significant radial plasma losses eliminated, the discharge model (with argon) predicts specific impulses in excess of 3000 s, propellant utilizations above 90%, and thruster efficiencies of about 30%.

  4. Electron dynamics in Hall thruster

    Science.gov (United States)

    Marini, Samuel; Pakter, Renato

    2015-11-01

    Hall thrusters are plasma engines those use an electromagnetic fields combination to confine electrons, generate and accelerate ions. Widely used by aerospace industries those thrusters stand out for its simple geometry, high specific impulse and low demand for electric power. Propulsion generated by those systems is due to acceleration of ions produced in an acceleration channel. The ions are generated by collision of electrons with propellant gas atoms. In this context, we can realize how important is characterizing the electronic dynamics. Using Hamiltonian formalism, we derive the electron motion equation in a simplified electromagnetic fields configuration observed in hall thrusters. We found conditions those must be satisfied by electromagnetic fields to have electronic confinement in acceleration channel. We present configurations of electromagnetic fields those maximize propellant gas ionization and thus make propulsion more efficient. This work was supported by CNPq.

  5. Analysis of polymer molecules including reaction monitoring and control

    NARCIS (Netherlands)

    Schoenmakers, P.; van Herk, A.M.

    2013-01-01

    To monitor, control, and optimize emulsion polymerisations, there is a need to perform a variety of different measurements. The monomer conversion is a key parameter to monitor and control the reaction. A rapid response is required for real-time reaction monitoring. This chapter considers on-line an

  6. Power Electronics Development for the SPT-100 Thruster

    Science.gov (United States)

    Hamley, John A.; Hill, Gerald M.; Sankovic, John M.

    1994-01-01

    Russian electric propulsion technologies have recently become available on the world market. Of significant interest is the Stationary Plasma Thruster (SPT) which has a significant flight heritage in the former Soviet space program. The SPT has performance levels of up to 1600 seconds of specific impulse at a thrust efficiency of 0.50. Studies have shown that this level of performance is well suited for stationkeeping applications, and the SPT-100, with a 1.35 kW input power level, is presently being evaluated for use on Western commercial satellites. Under a program sponsored by the Innovative Science and Technology Division of the Ballistic Missile Defense Organization, a team of U.S. electric propulsion specialists observed the operation of the SPT-100 in Russia. Under this same program, power electronics were developed to operate the SPT-100 to characterize thruster performance and operation in the U.S. The power electronics consisted of a discharge, cathode heater, and pulse igniter power supplies to operate the thruster with manual flow control. A Russian designed matching network was incorporated in the discharge supply to ensure proper operation with the thruster. The cathode heater power supply and igniter were derived from ongoing development projects. No attempts were made to augment thruster electromagnet current in this effort. The power electronics successfully started and operated the SPT-100 thruster in performance tests at NASA Lewis, with minimal oscillations in the discharge current. The efficiency of the main discharge supply was measured at 0.92, and straightforward modifications were identified which could increase the efficiency to 0.94.

  7. Communication: Control of chemical reactions using electric field gradients.

    Science.gov (United States)

    Deshmukh, Shivaraj D; Tsori, Yoav

    2016-05-21

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts.

  8. Communication: Control of chemical reactions using electric field gradients

    Science.gov (United States)

    Deshmukh, Shivaraj D.; Tsori, Yoav

    2016-05-01

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts.

  9. Low Cost Refractory Matrix Composite Thruster for Mars Ascent Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The long-term goal for this effort is to develop a low-cost, high-temperature thruster. Within the attitude control propulsion community, many efforts have focused...

  10. Vacuum arc plasma thrusters with inductive energy storage driver

    Science.gov (United States)

    Krishnan, Mahadevan (Inventor)

    2009-01-01

    A plasma thruster with a cylindrical inner and cylindrical outer electrode generates plasma particles from the application of energy stored in an inductor to a surface suitable for the formation of a plasma and expansion of plasma particles. The plasma production results in the generation of charged particles suitable for generating a reaction force, and the charged particles are guided by a magnetic field produced by the same inductor used to store the energy used to form the plasma.

  11. Pulsed Plasma Thruster plume analysis

    Energy Technology Data Exchange (ETDEWEB)

    Parker, K. [Washington Univ., Aerospace and Energetics Research Program, Seattle, WA (United States)

    2003-11-01

    Micro-Pulsed Plasma Thrusters ({mu}PPTs) are a promising method for precision attitude control for small spacecraft in formation flying. They create an ionized plasma plume, which may interfere with other spacecraft in the formation. To characterize the ions in the plume, a diagnostic has been built that couples a drift tube with an energy analyzer. The drift tube provides time of flight measurements to determine the exhaust velocity, and the energy analyzer discriminates the ion energies. The energy analyzer measures the current on a collector plate downstream of four grids that repel electrons and ions below a specified energy. The first grid lowers the density of the plasma, therefore increasing Debye length. The second and fourth grids have a negative potential applied to them so they repel the electrons, while the third grid's voltage can be varied to repel lower energy ions. The ion energies can be computed by differentiating the data. Combining the information of the ion energies and their velocities identifies the ion masses in the PPT plume. The PPT used for this diagnostic is the micro-PPT developed for the Dawgstar satellite. This PPT uses 5.2 Joules per pulse and has a 2.3 cm{sup 2} propellant area, a 1.3 cm electrode length, and an estimated thrust of 85 {mu}N [C. Rayburn et al., AIAA-2000-3256]. This paper will describe the development and design of the time of flight/gridded energy analyzer diagnostic and present recent experimental results. (Author)

  12. Miniature Bipolar Electrostatic Ion Thruster

    Science.gov (United States)

    Hartley, Frank T.

    2006-01-01

    The figure presents a concept of a bipolar miniature electrostatic ion thruster for maneuvering a small spacecraft. The ionization device in the proposed thruster would be a 0.1-micron-thick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several mega-volts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes. In a thruster-based on this concept, one or more propellant gases would be introduced into such a membrane ionizer. Unlike in larger prior ion thrusters, all of the propellant molecules would be ionized. This thruster would be capable of bipolar operation. There would be two accelerator grids - one located forward and one located aft of the membrane ionizer. In one mode of operation, which one could denote the forward mode, positive ions leaving the ionizer on the backside would be accelerated to high momentum by an electric field between the ionizer and an accelerator grid. Electrons leaving the ionizer on the front side would be ejected into free space by a smaller accelerating field. The equality of the ion and electron currents would eliminate the need for an additional electron- or ion-emitting device to keep the spacecraft charge-neutral. In another mode of operation, which could denote the reverse mode, the polarities of the voltages applied to the accelerator grids and to the electrodes of the membrane ionizer would be the reverse of those of the forward mode. The reversal of electric fields would cause the ion and electrons to be ejected in the reverse of their forward mode directions, thereby giving rise to thrust in the direction opposite that of the forward mode.

  13. Experimental results of an iodine plasma in PEGASES gridded thruster

    Science.gov (United States)

    Grondein, Pascaline; Aanesland, Ane

    2015-09-01

    In the electric gridded thruster PEGASES, both positive and negative ions are expelled after extraction from an ion-ion plasma. This ion-ion plasma is formed downstream a localized magnetic field placed a few centimeters from the ionization region, trapping and cooling down the electron to allow a better attachment to an electronegative gas. For this thruster concept, iodine has emerged as the most attractive option. Heavy, under diatomic form and therefore good for high thrust, its low ionization threshold and high electronegativity lead to high ion-ion densities and low RF power. After the proof-of-concept of PEGASES using SF6 as propellant, we present here experimental results of an iodine plasma studied inside PEGASES thruster. At solid state at standard temperature and pressure, iodine is heated to sublimate, then injected inside the chamber where the neutral gas is heated and ionized. The whole injection system is heated to avoid deposition on surfaces and a mass flow controller allows a fine control on the neutral gas mass flow. A 3D translation stage inside the vacuum chamber allows volumetric plasma studies using electrostatic probes. The results are also compared with the global model dedicated to iodine as propellant for electric gridded thrusters. This work has been done within the LABEX Plas@par project, and received financial state aid managed by the Agence Nationale de la Recherche, as part of the programme ``Investissements d'avenir.''

  14. Design of a cusped field thruster for drag-free flight

    Science.gov (United States)

    Liu, H.; Chen, P. B.; Sun, Q. Q.; Hu, P.; Meng, Y. C.; Mao, W.; Yu, D. R.

    2016-09-01

    Drag-free flight has played a more and more important role in many space missions. The thrust control system is the key unit to achieve drag-free flight by providing a precise compensation for the disturbing force except gravity. The cusped field thruster has shown a significant potential to be capable of the function due to its long life, high efficiency, and simplicity. This paper demonstrates a cusped field thruster's feasibility in drag-free flight based on its instinctive characteristics and describes a detailed design of a cusped field thruster made by Harbin Institute of Technology (HIT). Furthermore, the performance test is conducted, which shows that the cusped field thruster can achieve a continuously variable thrust from 1 to 20 mN with a low noise and high resolution below 650 W, and the specific impulse can achieve 1800 s under a thrust of 18 mN and discharge voltage of 1000 V. The thruster's overall performance indicates that the cusped field thruster is quite capable of achieving drag-free flight. With the further optimization, the cusped field thruster will exhibit a more extensive application value.

  15. Concept Study of Radio Frequency (RF Plasma Thruster for Space Propulsion

    Directory of Open Access Journals (Sweden)

    Anna-Maria Theodora ANDREESCU

    2016-12-01

    Full Text Available Electric thrusters are capable of accelerating ions to speeds that are impossible to reach using chemical reaction. Recent advances in plasma-based concepts have led to the identification of electromagnetic (RF generation and acceleration systems as able to provide not only continuous thrust, but also highly controllable and wide-range exhaust velocities. For Future Space Propulsion there is a pressing need for low pressure, high mass flow rate and controlled ion energies. This paper explores the potential of using RF heated plasmas for space propulsion in order to mitigate the electric propulsion problems caused by erosion and gain flexibility in plasma manipulation. The main key components of RF thruster architecture are: a feeding system able to provide the required neutral gas flow, plasma source chamber, antenna/electrodes wrapped around the discharge tube and optimized electromagnetic field coils for plasma confinement. A preliminary analysis of system performance (thrust, specific impulse, efficiency is performed along with future plans of Space Propulsion based on this new concept of plasma mechanism.

  16. Coupled simulation of mixture plume for attitude-control satellite thruster%卫星姿控发动机混合物羽流场分区耦合计算研究

    Institute of Scientific and Technical Information of China (English)

    李志辉; 李中华; 杨东升; 毕林; 张顺玉

    2012-01-01

    研究求解喷管内流场N-S方程数值计算方法,发展基于N-S方程物面边界滑移流理论计算技术.提出求解羽流核心区轴对称DSMC模拟方法与远场三维DSMC仿真方案,发展多组元混合物羽流DSMC仿真方法.研究求解卫星姿控发动机内外近场、远场、倒流区和物面相互作用影响区多流域流场分区耦合计算技术,建立了一套用于求解混合物燃气羽流及对太阳电池帆板与卫星体表面撞击污染影响数值模拟方法.通过对分别安装于某在轨卫星不同位置两个典型姿控发动机燃气五组元混合物羽流计算研究及相关结果对比分析,证实本文数值方法可靠性.%The numerical method for the steady Navier-Stokes equations is studied to solve the inner flow field of the nozzle. The N-S computing technique with the slip-boundary theory is developed for the near-continuum slip flow near the nozzle exit. The DSMC method for the flow of axial symmetry is studied to simulate the core plume?the DSMC scheme for the simulation of three-dimensional far-field plume flow is developed, and the DSMC method is studied for multi-species mixture plume. Then, the multiregion decomposing and coupling technique is developed to solve the inside and outside flow of the thruster including the near-field, far-field, backflow and gas-surface infected regions. As a result, the numerical simulation method has been presented to compute the gas-fired mixture plume from the attitude-control thruster of the satellite and the impinging contamination on the surface of the solar array panel and satellite. To study the contamination effects produced by the five-species mixture plume from two representative attitude-control thrusters installed in different locations of the satellite in orbit, the present method is adopted to simulate the nozzle inflow, tremendous plume flowfield of five-species mixture including the impinging contamination of the particles from the gas

  17. Modeling of Reaction Processes Controlled by Diffusion

    CERN Document Server

    Revelli, J

    2003-01-01

    Stochastic modeling is quite powerful in science and technology.The technics derived from this process have been used with great success in laser theory, biological systems and chemical reactions.Besides, they provide a theoretical framework for the analysis of experimental results on the field of particle's diffusion in ordered and disordered materials.In this work we analyze transport processes in one-dimensional fluctuating media, which are media that change their state in time.This fact induces changes in the movements of the particles giving rise to different phenomena and dynamics that will be described and analyzed in this work.We present some random walk models to describe these fluctuating media.These models include state transitions governed by different dynamical processes.We also analyze the trapping problem in a lattice by means of a simple model which predicts a resonance-like phenomenon.Also we study effective diffusion processes over surfaces due to random walks in the bulk.We consider differe...

  18. A Microwave Thruster for Spacecraft Propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Chiravalle, Vincent P [Los Alamos National Laboratory

    2012-07-23

    This presentation describes how a microwave thruster can be used for spacecraft propulsion. A microwave thruster is part of a larger class of electric propulsion devices that have higher specific impulse and lower thrust than conventional chemical rocket engines. Examples of electric propulsion devices are given in this presentation and it is shown how these devices have been used to accomplish two recent space missions. The microwave thruster is then described and it is explained how the thrust and specific impulse of the thruster can be measured. Calculations of the gas temperature and plasma properties in the microwave thruster are discussed. In addition a potential mission for the microwave thruster involving the orbit raising of a space station is explored.

  19. J series thruster thermal test results

    Science.gov (United States)

    Bechtel, R. T.; Dulgeroff, C. R.

    1982-01-01

    Test experience with J series ion thrusters have indicated that the present thruster design may result in excessive temperatures in areas which utilize organic materials such as wire insulation, with the resultant outgassing and potential contamination of insulating materials. Further, it appears that thermal data obtained with earlier thruster designs, such as the 700 series thruster, may not be directly applicable to the J series design. Two J series thrusters were fitted with thermocouples and critical temperatures measured for a variety of configurations and operating parameters. Completely enclosing the thruster to reduce facility contamination significantly increased temperatures prompting the selection of a compromise geometry for life testing. The operating parameter having the largest effect on temperatures was discharge power, while beam power affected little else than extraction system temperatures. Several off-normal operating modes were also investigated. Data believed to be sufficient to effectively modify existing thermal models were obtained from the tests.

  20. Low Mass Electromagnetic Plasmoid Thruster with Integrated PPU Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Electromagnetic Plasmoid Thruster (EMPT) is a revolutionary electric propulsion thruster and power processing (PPU) system that will allow a dramatic decrease...

  1. Electron-wall Interaction in Hall Thrusters

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses; D. Staack; M. Keidar; N.J. Fisch

    2005-02-11

    Electron-wall interaction effects in Hall thrusters are studied through measurements of the plasma response to variations of the thruster channel width and the discharge voltage. The discharge voltage threshold is shown to separate two thruster regimes. Below this threshold, the electron energy gain is constant in the acceleration region and therefore, secondary electron emission (SEE) from the channel walls is insufficient to enhance electron energy losses at the channel walls. Above this voltage threshold, the maximum electron temperature saturates.

  2. Low-Voltage Hall Thruster Mode Transitions

    Science.gov (United States)

    2014-06-01

    Technical Paper 3. DATES COVERED (From - To) June 2014- July 2014 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER In-House Low-Voltage Hall Thruster Mode...ABSTRACT Past investigations of the 6kW-class H6 Hall thruster during low-voltage operation revealed two operating modes, corresponding to the...topologies were characterized for the H6 Hall thruster from 100V to 200V discharge, with variation in cathode flow fraction, cathode position inside and

  3. Mechanisms for control of biological electron transfer reactions.

    Science.gov (United States)

    Williamson, Heather R; Dow, Brian A; Davidson, Victor L

    2014-12-01

    Electron transfer (ET) through and between proteins is a fundamental biological process. The rates and mechanisms of these ET reactions are controlled by the proteins in which the redox centers that donate and accept electrons reside. The protein influences the magnitudes of the ET parameters, the electronic coupling and reorganization energy that are associated with the ET reaction. The protein can regulate the rates of the ET reaction by requiring reaction steps to optimize the system for ET, leading to kinetic mechanisms of gated or coupled ET. Amino acid residues in the segment of the protein through which long range ET occurs can also modulate the ET rate by serving as staging points for hopping mechanisms of ET. Specific examples are presented to illustrate these mechanisms by which proteins control rates of ET reactions. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Advanced Microwave Electrothermal Thruster (AMET) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Orbital Technologies Corporation (ORBITEC) and the University of Alabama at Huntsville (UAH) propose to develop the Advanced Microwave Electrothermal Thruster...

  5. Electrodeless plasma thrusters for spacecraft: A review

    Science.gov (United States)

    Bathgate, S. N.; Bilek, M. M. M.; McKenzie, D. R.

    2017-08-01

    The physics of electrodeless electric thrusters that use directed plasma to propel spacecraft without employing electrodes subject to plasma erosion is reviewed. Electrodeless plasma thrusters are potentially more durable than presently deployed thrusters that use electrodes such as gridded ion, Hall thrusters, arcjets and resistojets. Like other plasma thrusters, electrodeless thrusters have the advantage of reduced fuel mass compared to chemical thrusters that produce the same thrust. The status of electrodeless plasma thrusters that could be used in communications satellites and in spacecraft for interplanetary missions is examined. Electrodeless thrusters under development or planned for deployment include devices that use a rotating magnetic field; devices that use a rotating electric field; pulsed inductive devices that exploit the Lorentz force on an induced current loop in a plasma; devices that use radiofrequency fields to heat plasmas and have magnetic nozzles to accelerate the hot plasma and other devices that exploit the Lorentz force. Using metrics of specific impulse and thrust efficiency, we find that the most promising designs are those that use Lorentz forces directly to expel plasma and those that use magnetic nozzles to accelerate plasma.

  6. Energy diffusion controlled reaction rate in dissipative Hamiltonian systems

    Institute of Scientific and Technical Information of China (English)

    Deng Mao-Lin; Zhu Wei-Qiu

    2007-01-01

    In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean first-passage time (MFPT) of averaged system is formulated and the energy diffusion controlled reaction rate is obtained as the inverse of MFPT. The energy diffusion controlled reaction rate in the classical Kramers bistable potential and in a two-dimensional bistable potential with a heat bath are obtained by using the proposed approach respectively. The obtained results are then compared with those from Monte Carlo simulation of original systems and from the classical Kramers theory. It is shown that the reaction rate obtained by using the proposed approach agrees well with that from Monte Carlo simulation and is more accurate than the classical Kramers rate.

  7. Vacuum Plasma Spray (VPS) Material Applications for Thruster Components

    Science.gov (United States)

    Elam, Sandra; Holmes, Richard; Hickman, Robert

    2006-01-01

    A variety of vacuum plasma spray (VPS) material systems have been successfully applied to injector and thrust chamber components. VPS offers a versatile fabrication process with relatively low costs to produce near net shape parts. The materials available with VPS increase operating margins and improve component life by providing superior thermal and oxidation protection in specific engine environments. Functional gradient materials (FGM) formed with VPS allow thrust chamber liners to be fabricated with GRCop-84 (an alloy of copper, chrome, and niobium) and a protective layer of NiCrAlY on the hot wall. A variety of thrust chamber liner designs have been fabricated to demonstrate the versatility of the process. Hot-fire test results have confined the improved durability and high temperature performance of the material systems for thrust chamber liners. Similar FGM s have been applied to provide superior thermal protection on injector faceplates with NiCrAlY and zirconia coatings. The durability of the applied materials has been demonstrated with hot-fire cycle testing on injector faceplates in high temperature environments. The material systems can benefit the components used in booster and main engine propulsion systems. More recent VPS efforts are focused on producing rhenium based material systems for high temperature applications to benefit in-space engines like reaction control system (RCS) thrusters.

  8. Molecular controls of the oxygenation and redox reactions of hemoglobin.

    Science.gov (United States)

    Bonaventura, Celia; Henkens, Robert; Alayash, Abdu I; Banerjee, Sambuddha; Crumbliss, Alvin L

    2013-06-10

    The broad classes of O(2)-binding proteins known as hemoglobins (Hbs) carry out oxygenation and redox functions that allow organisms with significantly different physiological demands to exist in a wide range of environments. This is aided by allosteric controls that modulate the protein's redox reactions as well as its O(2)-binding functions. The controls of Hb's redox reactions can differ appreciably from the molecular controls for Hb oxygenation and come into play in elegant mechanisms for dealing with nitrosative stress, in the malarial resistance conferred by sickle cell Hb, and in the as-yet unsuccessful designs for safe and effective blood substitutes. An important basic principle in consideration of Hb's redox reactions is the distinction between kinetic and thermodynamic reaction control. Clarification of these modes of control is critical to gaining an increased understanding of Hb-mediated oxidative processes and oxidative toxicity in vivo. This review addresses emerging concepts and some unresolved questions regarding the interplay between the oxygenation and oxidation reactions of structurally diverse Hbs, both within red blood cells and under acellular conditions. Developing methods that control Hb-mediated oxidative toxicity will be critical to the future development of Hb-based blood substitutes.

  9. Modelling and Simulation of Variable Speed Thruster Drives with Full-Scale Verification

    Directory of Open Access Journals (Sweden)

    Jan F. Hansen

    2001-10-01

    Full Text Available In this paper considerations about modelling and simulation of variable speed thruster drives are made with comparison to full scale measurements from Varg FPSO. For special purpose vessels with electric propulsion operating in DP (Dynamic Positioning mode the thruster drives are essential for the vessel operation. Different model strategies of thruster drives are discussed. An advanced thruster drive model with a dynamic motor model and field vector control principle is shown. Simulations are performed with both the advanced model and a simplified model. These are compared with full-scale measurements from Varg FPSO. The simulation results correspond well with the measurements, for both the simplified model and the advanced model.

  10. Synthesis of porous gold nanoshells by controlled transmetallation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Pattabi, Manjunatha, E-mail: manjupattabi@yahoo.com; M, Krishnaprabha [Department of Materials Science, Mangalore University, Mangalagangothri-574199 (India)

    2015-06-24

    Aqueous synthesis of porous gold nanoshells in one step is carried out through controlled transmetallation (TM) reaction using a naturally available egg shell membrane (ESM) as a barrier between the sacrificial silver particles (AgNPs) and the gold precursor solution (HAuCl{sub 4}). The formation of porous gold nanoshells via TM reaction is inferred from UV-Vis spectroscopy and the scanning electron microscopic (SEM) studies.

  11. Controllability of Degenerating Reaction-Diffusion System in Electrocardiology

    CERN Document Server

    Bendahmane, Mostafa

    2011-01-01

    This paper is devoted to analyze the null controllability of a nonlinear reaction-diffusion system approximating a parabolic-elliptic system modeling electrical activity in the heart. The uniform, with respect to the degenerating parameter, null controllability of the approximating system by a single control force acting on a subdomain is shown. The proof needs a precisely estimate with respect to the degenerating parameter and it is done combining Carleman estimates and energy inequalities.

  12. Development of ion thruster IT-500

    Science.gov (United States)

    Koroteev, Anatoly S.; Lovtsov, Alexander S.; Muravlev, Vyacheslav A.; Selivanov, Mikhail Y.; Shagayda, Andrey A.

    2017-05-01

    A high-power ion thruster IT-500 was designed, manufactured and tested at Keldysh Research Center within a transport-power module project. This module is being designed to perform near-Earth space and interplanetary transport missions. In its nominal operation mode, IT-500 provides thrust in the range from 375 to 750 mN at specific impulse of 70 000 m/s and thrust efficiency of 0.75. Due to a high cost of the experimental testing of a large thruster, the emphasis was placed on the numerical optimization of the thruster design. The thruster completed performance tests and a 300 h wear test. The output characteristics of the thruster, obtained during the tests, confirmed the correctness of the provisional numerical optimization. IT-500 design, performance, and validation of the design approaches are discussed in this paper. Contribution to the Topical Issue: "Physics of Ion Beam Sources", edited by Holger Kersten and Horst Neumann.

  13. Performance of a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    Science.gov (United States)

    Polzin, Kurt A.; Raitses, Yevgeny; Fisch, Nathaniel J.

    2008-01-01

    While Hall thrusters can operate at high efficiency at kW power levels, it is difficult to construct one that operates over a broad envelope down to 100W while maintaining an efficiency of 45- 55%. Scaling to low power while holding the main dimensionless parameters constant requires a decrease in the thruster channel size and an increase in the magnetic field strength. Increasing the magnetic field becomes technically challenging since the field can saturate the miniaturized inner components of the magnetic circuit and scaling down the magnetic circuit leaves very little room for magnetic pole pieces and heat shields. An alternative approach is to employ a cylindrical Hall thruster (CHT) geometry. Laboratory model CHTs have operated at power levels ranging from the order of 50 Watts up to 1 kW. These thrusters exhibit performance characteristics which are comparable to conventional, annular Hall thrusters of similar size. Compared to the annular Hall thruster, the CHT has a lower insulator surface area to discharge chamber volume ratio. Consequently, there is the potential for reduced wall losses in the channel of a CHT, and any reduction in wall losses should translate into lower channel heating rates and reduced erosion. This makes the CHT geometry promising for low-power applications. Recently, a CHT that uses permanent magnets to produce the magnetic field topology was tested. This thruster has the promise of reduced power consumption over previous CHT iterations that employed electromagnets. Data are presented for two purposes: to expose the effect different controllable parameters have on the discharge and to summarize performance measurements (thrust, Isp, efficiency) obtained using a thrust stand. These data are used to gain insight into the thruster's operation and to allow for quantitative comparisons between the permanent magnet CHT and the electromagnet CHT.

  14. Review of reaction spheres for spacecraft attitude control

    Science.gov (United States)

    Zhu, Linyu; Guo, Jian; Gill, Eberhard

    2017-05-01

    With respect to spacecraft attitude control, reaction spheres are promising alternatives to conventional momentum exchange devices for the benefits brought by their 4π rotation. Many design concepts of reaction spheres have been proposed in the past decades, however, developments of the driving unit and the bearing, as well as their combination remain great challenges. To facilitate research and push developments in this field, this paper provides a comprehensive review of reaction spheres. To some extent, an in-depth survey of multi-DOF (degree of freedom) spherical motors and possible bearings is provided, along with their advantages and weaknesses addressed. Some multi-DOF actuators for different applications, such as robotic joints, are investigated since they share many similar challenges and techniques with reaction spheres. The experimental performances of realized reaction spheres are listed and compared. Limits of current designs are identified and their causes are analyzed and discussed. Compared with existing summaries on multi-DOF actuators and some surveys done for specific reaction spheres' design, this paper provides the first thorough review on reaction spheres, considering approaches to excite and support the free 4π rotation.

  15. Design of automatic thruster assisted mooring systems for ships

    Directory of Open Access Journals (Sweden)

    Jan P. Strand

    1998-04-01

    Full Text Available This paper addresses the mathematical modelling and controller design of an automatic thruster assisted position mooring system. Such control systems are applied to anchored floating production offloading and storage vessels and semi-subs. The controller is designed using model based control with a LQG feedback controller in conjunction with a Kalman filter. The controller design is in addition to the environmental loads accounting for the mooring forces acting on the vessel. This is reflected in the model structure and in the inclusion of new functionality.

  16. Coil system for plasmoid thruster

    Science.gov (United States)

    Eskridge, Richard H. (Inventor); Lee, Michael H. (Inventor); Martin, Adam K. (Inventor); Fimognari, Peter J. (Inventor)

    2010-01-01

    A coil system for a plasmoid thruster includes a bias coil, a drive coil and field coils. The bias and drive coils are interleaved with one another as they are helically wound about a conical region. A first field coil defines a first passage at one end of the conical region, and is connected in series with the bias coil. A second field coil defines a second passage at an opposing end of the conical region, and is connected in series with the bias coil.

  17. Non-Toxic Orbiter Maneuvering System (OMS) and Reaction Control System

    Science.gov (United States)

    Hurlbert, Eric A.; Nicholson, Leonard S. (Technical Monitor)

    1999-01-01

    NASA is pursuing the technology and advanced development of a non-toxic (NT) orbital maneuvering system (OMS) and reaction control system (RCS) for shuttle upgrades, RLV, and reusable first stages. The primary objectives of the shuttle upgrades program are improved safety, improved reliability, reduced operations time and cost, improved performance or capabilities, and commonality with future space exploration needs. Non-Toxic OMS/RCS offers advantages in each of these categories. A non-toxic OMS/RCS eliminates the ground hazards and the flight safety hazards of the toxic and corrosive propellants. The cost savings for ground operations are over $24M per year for 7 flights, and the savings increase with increasing flight rate up to $44M per year. The OMS/RCS serial processing time is reduced from 65 days to 13 days. The payload capability can be increased up to 5100 Ibms. The non-toxic OMS/RCS also provides improved space station reboost capability up to 20 nautical miles over the current toxic system of 14 nautical miles. A NT OMS/RCS represents a clear advancement in the SOA over MMH/NTO. Liquid oxygen and ethanol are clean burning, high-density propellants that provide a high degree of commonality with other spacecraft subsystems including life support, power, and thermal control, and with future human exploration and development of space missions. The simple and reliable pressure-fed design uses sub-cooled liquid oxygen at 250 to 350 psia, which allows a propellant to remain cryogenic for longer periods of time. The key technologies are thermal insulation and conditioning techniques are used to maintain the sub-cooling. Phase I successfully defined the system architecture, designed an integrated OMS/RCS propellant tank, analyzed the feed system, built and tested the 870 lbf RCS thrusters, and tested the 6000 lbf OMS engine. Phase 11 is currently being planned for the development and test of full-scale prototype of the system in 1999 and 2000

  18. Directional sensitivity of "first trial" reactions in human balance control.

    NARCIS (Netherlands)

    Oude Nijhuis, L.B.; Allum, J.H.J.; Borm, G.F.; Honegger, F.; Overeem, S.; Bloem, B.R.

    2009-01-01

    Support-surface movements are commonly used to examine balance control. Subjects typically receive a series of identical or randomly interspersed multidirectional balance perturbations and the atypical "first trial reaction" (evoked by the first perturbation) is often excluded from further analysis.

  19. Cathode-less gridded ion thrusters for small satellites

    Science.gov (United States)

    Aanesland, Ane

    2016-10-01

    Electric space propulsion is now a mature technology for commercial satellites and space missions that requires thrust in the order of hundreds of mN, and with available electric power in the order of kW. Developing electric propulsion for SmallSats (1 to 500 kg satellites) are challenging due to the small space and limited available electric power (in the worst case close to 10 W). One of the challenges in downscaling ion and Hall thrusters is the need to neutralize the positive ion beam to prevent beam stalling. This neutralization is achieved by feeding electrons into the downstream space. In most cases hollow cathodes are used for this purpose, but they are fragile and difficult to implement, and in particular for small systems they are difficult to downscale, both in size and electron current. We describe here a new alternative ion thruster that can provide thrust and specific impulse suitable for mission control of satellites as small as 3 kg. The originality of our thruster lies in the acceleration principles and propellant handling. Continuous ion acceleration is achieved by biasing a set of grids with Radio Frequency voltages (RF) via a blocking capacitor. Due to the different mobility of ions and electrons, the blocking capacitor charges up and rectifies the RF voltage. Thus, the ions are accelerated by the self-bias DC voltage. Moreover, due to the RF oscillations, the electrons escape the thruster across the grids during brief instants in the RF period ensuring a full space charge neutralization of the positive ion beam. Due to the RF nature of this system, the space charge limited current increases by almost a factor of 2 compared to classical DC biased grids, which translates into a specific thrust two times higher than for a similar DC system. This new thruster is called Neptune and operates with only one RF power supply for plasma generation, ion acceleration and electron neutralization. We will present the downscaling of this thruster to a 3cm

  20. Reaction parameters for controlled sonosynthesis of gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez M, A. L. [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Paseo Colon esq. Paseo Tollocan s/n, 50120 Toluca, Estado de Mexico (Mexico); Cabrera L, L. I. [UNAM-UAEM, Centro Conjunto de Investigacion en Quimica Sustentable, Km 14.5 Carretera Toluca-Atlacomulco, 50200 San Cayetano-Toluca, Estado de Mexico (Mexico)

    2015-07-01

    The synthesis of gold nanoparticles by sonochemical technique has been previously performed with excellent results. The synthesis has been carried out in the presence of citric acid, a strong reducing agent, which allows the nucleation and growth of gold nanoparticles, at the same time that controls particle size. In this work we report the use of sodium tartrate as a mild reducing agent that allows a better understanding of the effect of the reaction parameters during gold nanoparticle synthesis. A conventional sonication bath (37 k Hz) was used for the sonochemical synthesis. This work focuses on the reaction temperature effect and the effect of sodium tartrate concentration. It was confirmed that particle size, and particle morphology is dependent of these two reaction parameters. Equally, colloidal stabilization was related to reaction temperature and sodium tartrate concentration. It was also determined that Ostwald ripening takes place during sonochemical reaction under our conditions, allowing to understand the mechanism that takes place during synthesis. Gold nanoparticles with main particle size of 17 nm were achieved by this method. Characterization techniques used: Fourier transform infrared spectra (Ftir), X-ray diffraction and Atomic Force Microscope was used in order to determine particle size of the synthetic product of reaction M10c by tapping mode. (Author)

  1. Geometrical characterization and performance optimization of monopropellant thruster injector

    Directory of Open Access Journals (Sweden)

    T.R. Nada

    2012-12-01

    Full Text Available The function of the injector in a monopropellant thruster is to atomize the liquid hydrazine and to distribute it over the catalyst bed as uniformly as possible. A second objective is to place the maximum amount of catalyst in contact with the propellant in as short time as possible to minimize the starting transient time. Coverage by the spray is controlled mainly by cone angle and diameter of the catalyst bed, while atomization quality is measured by the Sauter Mean Diameter, SMD. These parameters are evaluated using empirical formulae. In this paper, two main types of injectors are investigated; plain orifice and full cone pressure swirl injectors. The performance of these two types is examined for use with blow down monopropellant propulsion system. A comprehensive characterization is given and design charts are introduced to facilitate optimizing the performance of the injector. Full-cone injector is a more suitable choice for monopropellant thruster and it might be available commercially.

  2. Mechanical design of SERT 2 thruster system

    Science.gov (United States)

    Zavesky, R. J.; Hurst, E. B.

    1972-01-01

    The mechanical design of the mercury bombardment thruster that was tested on SERT is described. The report shows how the structural, thermal, electrical, material compatibility, and neutral mercury coating considerations affected the design and integration of the subsystems and components. The SERT 2 spacecraft with two thrusters was launched on February 3, 1970. One thruster operated for 3782 hours and the other for 2011 hours. A high voltage short resulting from buildup of loose eroded material was believed to be the cause of failure.

  3. Iodine Hall Thruster Propellant Feed System for a CubeSat

    Science.gov (United States)

    Polzin, Kurt A.

    2014-01-01

    There has been significant work recently in the development of iodine-fed Hall thrusters for in-space propulsion applications.1 The use of iodine as a propellant provides many advantages over present xenon-gas-fed Hall thruster systems. Iodine is a solid at ambient temperature (no pressurization required) and has no special handling requirements, making it safe for secondary flight opportunities. It has exceptionally high ?I sp (density times specific impulse), making it an enabling technology for small satellite near-term applications and providing system level advantages over mid-term high power electric propulsion options. Iodine provides thrust and efficiency that are comparable to xenonfed Hall thrusters while operating in the same discharge current and voltage regime, making it possible to leverage the development of flight-qualified xenon Hall thruster power processing units for the iodine application. Work at MSFC is presently aimed at designing, integrating, and demonstrating a flight-like iodine feed system suitable for the Hall thruster application. This effort represents a significant advancement in state-of-the-art. Though Iodine thrusters have demonstrated high performance with mission enabling potential, a flight-like feed system has never been demonstrated and iodine compatible components do not yet exist. Presented in this paper is the end-to-end integrated feed system demonstration. The system includes a propellant tank with active feedback-control heating, fill and drain interfaces, latching and proportional flow control valves (PFCV), flow resistors, and flight-like CubeSat power and control electronics. Hardware is integrated into a CubeSat-sized structure, calibrated and tested under vacuum conditions, and operated under under hot-fire conditions using a Busek BHT-200 thruster designed for iodine. Performance of the system is evaluated thorugh accurate measurement of thrust and a calibrated of mass flow rate measurement, which is a function of

  4. Light Metal Propellant Hall Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop light metal Hall Effect thrusters that will help reduce the travel time, mass, and cost of SMD spacecraft. Busek has identified three...

  5. Precision Electrospray Thruster Assembly (PETA) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — New low cost, low volume, low power, rugged electrospray thrusters will be ideal as actuators for precision thrusting, if provided with precision high voltage power...

  6. T6 Ion Thruster Technology Development Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Provide discharge chamber and grid modeling for the new T6 based on JPL expertise on ion thruster performance and life; Enable/guide the T6 upgrade development to...

  7. Dual Mode Low Power Hall Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Sample and return missions desire and missions like Saturn Observer require a low power Hall thruster that can operate at high thrust to power as well as high...

  8. Q-thruster Breadboard Campaign Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Q-thruster technology is a mission enabling form of electric propulsion and is already being traded by NASA's Concept Architecture Team (CAT) & Human Space...

  9. Iodine Hall Thruster for Space Exploration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek Co. Inc. proposes to develop a high power (high thrust) electric propulsion system featuring an iodine fueled Hall Effect Thruster (HET). The system to be...

  10. High Thrust Efficiency MPD Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Magnetoplasmadynamic (MPD) thrusters can provide the high-specific impulse, high-power propulsion required to support human and robotic exploration missions to the...

  11. Optimized Magnetic Nozzles for MPD Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Magnetoplasmadynamic (MPD) thrusters can provide the high-specific impulse, high-power propulsion required to enable ambitious human and robotic exploration missions...

  12. Advanced High Efficiency Durable DACS Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Systima is developing a high performance 25 lbf DACS thruster that operates with a novel non-toxic monopropellant. The monopropellant has a 30% higher...

  13. Multiscale Modeling of Hall Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — New multiscale modeling capability for analyzing advanced Hall thrusters is proposed. This technology offers NASA the ability to reduce development effort of new...

  14. Reaction weakening and emplacement of crystalline thrusts: Diffusion control on reaction rate and strain rate

    Science.gov (United States)

    O'Hara, Kieran

    2007-08-01

    In the southern Appalachians, the Blue Ridge-Piedmont crystalline thrust sheet was emplaced onto low-grade Late Precambrian and Paleozoic sedimentary rocks in the footwall along a basal detachment consisting of phyllosilicate-rich mylonites (phyllonites). The phyllonites developed first by mechanical breakdown of feldspar followed by chemical breakdown to white mica in the presence of a pore fluid. Diffusion of solute in the pore fluid is the rate limiting step in controlling reaction rate and also the strain rate. Assuming solute diffusion follows the Stokes-Einstein equation, the shear strain rate is given by ⅆγ/ⅆt=2ωkT/5ηrx for shear stress ≥20 MPa, where n is a constant, ω is a geometric factor, k is Boltzmann's constant, T is absolute temperature, η is water viscosity, r is the atomic radius of the diffusing species, and x is the diffusion distance. A bulk diffusion coefficient in the range of ˜10 -10 to 10 -12 m 2/s over distances of 10-100 m results in strain rates of 10 -14 to 10 -13 s -1 in the temperature range 200-400 °C. It is concluded that greenschist grade crystalline thrust sheets develop on pre-existing basement faults that become weak during reaction softening and localize into high strain phyllonite zones in which pore fluid diffusion controls reaction rate and strain rate.

  15. MPD thruster research issues, activities, strategies

    Science.gov (United States)

    1991-01-01

    The following activities and plans in the MPD thruster development are summarized: (1) experimental and theoretical research (magnetic nozzles at present and high power levels, MPD thrusters with applied fields extending into the thrust chamber, and improved electrode performance); and (2) tools (MACH2 code for MPD and nozzle flow calculation, laser diagnostics and spectroscopy for non-intrusive measurements of flow conditions, and extension to higher power). National strategies are also outlined.

  16. Colloid Thrusters, Physics, Fabrication and Performance

    Science.gov (United States)

    2005-11-17

    response, including the time for reviewing in. tata needed, and completing and reviewing this collection of information. Send comments regarding this...a discussion with colleagues during the 2nd Colloid Thruster/ Nano Electrojet Workshop (MIT, April 14- 15, 2005, Ref. [11]) an agreement was reached...23 Jul 2003. 11. Second Colloid Thruster/ Nano Electrojet Workshop, CD with a collection of presentations by attendees to this Workshop. MIT, April 14

  17. Orthogonal Enzymatic Reactions to Control Supramolecular Hydrogelations%Orthogonal Enzymatic Reactions to Control Supramolecular Hydrogelations

    Institute of Scientific and Technical Information of China (English)

    陈国钦; 任春华; 王玲; 徐兵; 杨志谋

    2012-01-01

    Enzyme-responsive hydrogels have great potential in applications of controlled drug release, tissue engineering, etc. In this study, we reported on a supramolecular hydrogel that showed responses to two enzymes, phosphatase which was used to form the hydrogels and esterase which could trigger gelsol phase transitions. The gelation process and visco-elasticity property of the resulting gel, morphology of the nanostructures in hydrogel, and peptide conformation in the self-assembled nanostructure were characterized by theology, transmission electron microscope (TEM), and circular dichroism (CD), respectively. Potential application of the enzyme-responsive hydrogel in drug release was also demonstrated in this study. Though only one potential application of drug release was proved in this study, the responsive hydrogel system in this study might have potentials for the applications in fields of cell culture, controlled-drug release, etc.

  18. Hybrid multiscale simulation of a mixing-controlled reaction

    Energy Technology Data Exchange (ETDEWEB)

    Scheibe, Timothy D.; Schuchardt, Karen L.; Agarwal, Khushbu; Chase, Jared M.; Yang, Xiaofan; Palmer, Bruce J.; Tartakovsky, Alexandre M.; Elsethagen, Todd O.; Redden, George D.

    2015-09-01

    Continuum-scale models have been used to study subsurface flow, transport, and reactions for many years but lack the capability to resolve fine-grained processes. Recently, pore-scale models, which operate at scales of individual soil grains, have been developed to more accurately model and study pore-scale phenomena, such as mineral precipitation and dissolution reactions, microbially-mediated surface reactions, and other complex processes. However, these highly-resolved models are prohibitively expensive for modeling domains of sizes relevant to practical problems. To broaden the utility of pore-scale models for larger domains, we developed a hybrid multiscale model that initially simulates the full domain at the continuum scale and applies a pore-scale model only to areas of high reactivity. Since the location and number of pore-scale model regions in the model varies as the reactions proceed, an adaptive script defines the number and location of pore regions within each continuum iteration and initializes pore-scale simulations from macroscale information. Another script communicates information from the pore-scale simulation results back to the continuum scale. These components provide loose coupling between the pore- and continuum-scale codes into a single hybrid multiscale model implemented within the SWIFT workflow environment. In this paper, we consider an irreversible homogenous bimolecular reaction (two solutes reacting to form a third solute) in a 2D test problem. This paper is focused on the approach used for multiscale coupling between pore- and continuum-scale models, application to a realistic test problem, and implications of the results for predictive simulation of mixing-controlled reactions in porous media. Our results and analysis demonstrate that loose coupling provides a feasible, efficient and scalable approach for multiscale subsurface simulations.

  19. Space Technology: Game Changing Development Deep Space Engine (DSE) 100 lbf and 5 lbf Thruster Development and Qualification

    Science.gov (United States)

    Barnett, Gregory

    2017-01-01

    Science mission studies require spacecraft propulsion systems that are high-performance, lightweight, and compact. Highly matured technology and low-cost, short development time of the propulsion system are also very desirable. The Deep Space Engine (DSE) 100-lbf thruster is being developed to meet these needs. The overall goal of this game changing technology project is to qualify the DSE thrusters along with 5-lbf attitude control thrusters for space flight and for inclusion in science and exploration missions. The aim is to perform qualification tests representative of mission duty cycles. Most exploration missions are constrained by mass, power and cost. As major propulsion components, thrusters are identified as high-risk, long-lead development items. NASA spacecraft primarily rely on 1960s' heritage in-space thruster designs and opportunities exist for reducing size, weight, power, and cost through the utilization of modern materials and advanced manufacturing techniques. Advancements in MON-25/MMH hypergolic bipropellant thrusters represent a promising avenue for addressing these deficiencies with tremendous mission enhancing benefits. DSE is much lighter and costs less than currently available thrusters in comparable thrust classes. Because MON-25 propellants operate at lower temperatures, less power is needed for propellant conditioning for in-space propulsion applications, especially long duration and/or deep-space missions. Reduced power results in reduced mass for batteries and solar panels. DSE is capable of operating at a wide propellant temperature range (between -22 F and 122 F) while a similar existing thruster operates between 45 F and 70 F. Such a capability offers robust propulsion operation as well as flexibility in design. NASA's Marshall Space Flight Center evaluated available operational Missile Defense Agency heritage thrusters suitable for the science and lunar lander propulsion systems.

  20. New Possibilities for Magnetic Control of Chemical and Biochemical Reactions.

    Science.gov (United States)

    Buchachenko, Anatoly; Lawler, Ronald G

    2017-04-18

    Chemistry is controlled by Coulomb energy; magnetic energy is lower by many orders of magnitude and may be confidently ignored in the energy balance of chemical reactions. The situation becomes less clear, however, when reaction rates are considered. In this case, magnetic perturbations of nearly degenerate energy surface crossings may produce observable, and sometimes even dramatic, effects on reactions rates, product yields, and spectroscopic transitions. A case in point that has been studied for nearly five decades is electron spin-selective chemistry via the intermediacy of radical pairs. Magnetic fields, external (permanent or oscillating) and the internal magnetic fields of magnetic nuclei, have been shown to overcome electron spin selection rules for pairs of reactive paramagnetic intermediates, catalyzing or inhibiting chemical reaction pathways. The accelerating effects of magnetic stimulation may therefore be considered to be magnetic catalysis. This type of catalysis is most commonly observed for reactions of a relatively long-lived radical pair containing two weakly interacting electron spins formed by dissociation of molecules or by electron transfer. The pair may exist in singlet (total electron spin is zero) or triplet (total spin is unity) spin states. In virtually all cases, only the singlet state yields stable reaction products. Magnetic interactions with nuclear spins or applied fields may therefore affect the reactivity of radical pairs by changing the angular momentum of the pairs. Magnetic catalysis, first detected via its effect on spin state populations in nuclear and electron spin resonance, has been shown to function in a great variety of well-characterized reactions of organic free radicals. Considerably less well studied are examples suggesting that the basic mechanism may also explain magnetic effects that stimulate ATP synthesis, eliminating ATP deficiency in cardiac diseases, control cell proliferation, killing cancer cells, and

  1. Controlled Fluoroalkylation Reactions by Visible-Light Photoredox Catalysis.

    Science.gov (United States)

    Chatterjee, Tanmay; Iqbal, Naeem; You, Youngmin; Cho, Eun Jin

    2016-10-18

    base for dehydrohalogenation of the intermediate, and also a Brønsted base for deprotonation. In the same context, the selection of solvent is also critical since it affects the rate and selectivity of reactions depending upon its polarity and reagent solubilizing ability and plays additional roles in the process, for example, as a hydrogen atom source. By clearly understanding the roles of additives and solvent, we designed several controlled fluoroalkylation reactions where different products were formed selectively from the same starting substrates. In addition, we could exploit one of the most important advantages of radical reactions, that is, the use of unactivated π-systems such as alkenes, alkynes, arenes, and heteroarenes as radical acceptors without prefunctionalization. Furthermore, fluoroalkylation processes under mild room-temperature reaction conditions tolerate various functional groups and are therefore easily applicable to late-stage modifications of highly functionalized advanced intermediates.

  2. Integration Tests of the 4 kW-Class High Voltage Hall Accelerator Power Processing Unit with the HiVHAc and the SPT-140 Hall Effect Thrusters

    Science.gov (United States)

    Kamhawi, Hani; Pinero, Luis; Haag, Thomas; Huang, Wensheng; Ahern, Drew; Liang, Ray; Shilo, Vlad

    2016-01-01

    NASA's Science Mission Directorate is sponsoring the development of a 4 kW-class Hall propulsion system for implementation in NASA science and exploration missions. The main components of the system include the High Voltage Hall Accelerator (HiVHAc), an engineering model power processing unit (PPU) developed by Colorado Power Electronics, and a xenon flow control module (XFCM) developed by VACCO Industries. NASA Glenn Research Center is performing integrated tests of the Hall thruster propulsion system. This paper presents results from integrated tests of the PPU and XFCM with the HiVHAc engineering development thruster and a SPT-140 thruster provided by Space System Loral. The results presented in this paper demonstrate thruster discharge initiation along with open-loop and closed-loop control of the discharge current with anode flow for both the HiVHAc and the SPT-140 thrusters. Integrated tests with the SPT-140 thruster indicated that the PPU was able to repeatedly initiate the thruster's discharge, achieve steady state operation, and successfully throttle the thruster between 1.5 and 4.5 kW. The measured SPT-140 performance was identical to levels reported by Space Systems Loral.

  3. Control of serpentinisation rate by reaction-induced cracking

    Science.gov (United States)

    Malvoisin, Benjamin; Brantut, Nicolas; Kaczmarek, Mary-Alix

    2017-10-01

    Serpentinisation of mantle rocks requires the generation and maintenance of transport pathways for water. The solid volume increase during serpentinisation can lead to stress build-up and trigger cracking, which ease fluid penetration into the rock. The quantitative effect of this reaction-induced cracking mechanism on reactive surface generation is poorly constrained, thus hampering our ability to predict serpentinisation rate in geological environments. Here we use a combined approach with numerical modelling and observations in natural samples to provide estimates of serpentinisation rate at mid-ocean ridges. We develop a micromechanical model to quantify the propagation of serpentinisation-induced cracks in olivine. The maximum crystallisation pressure deduced from thermodynamic calculations reaches several hundreds of megapascals but does not necessary lead to crack propagation if the olivine grain is subjected to high compressive stresses. The micromechanical model is then coupled to a simple geometrical model to predict reactive surface area formation during grain splitting, and thus bulk reaction rate. Our model reproduces quantitatively experimental kinetic data and the typical mesh texture formed during serpentinisation. We also compare the model results with olivine grain size distribution data obtained on natural serpentinised peridotites from the Marum ophiolite and the Papuan ultramafic belt (Papua New Guinea). The natural serpentinised peridotites show an increase of the number of olivine grains for a decrease of the mean grain size by one order of magnitude as reaction progresses from 5 to 40%. These results are in agreement with our model predictions, suggesting that reaction-induced cracking controls the serpentinisation rate. We use our model to estimate that, at mid-ocean ridges, serpentinisation occurs up to 12 km depth and reaction-induced cracking reduces the characteristic time of serpentinisation by one order of magnitude, down to values

  4. Diffusion Controlled Reactions, Fluctuation Dominated Kinetics, and Living Cell Biochemistry

    CERN Document Server

    Konkoli, Zoran

    2009-01-01

    In recent years considerable portion of the computer science community has focused its attention on understanding living cell biochemistry and efforts to understand such complication reaction environment have spread over wide front, ranging from systems biology approaches, through network analysis (motif identification) towards developing language and simulators for low level biochemical processes. Apart from simulation work, much of the efforts are directed to using mean field equations (equivalent to the equations of classical chemical kinetics) to address various problems (stability, robustness, sensitivity analysis, etc.). Rarely is the use of mean field equations questioned. This review will provide a brief overview of the situations when mean field equations fail and should not be used. These equations can be derived from the theory of diffusion controlled reactions, and emerge when assumption of perfect mixing is used.

  5. Description of the Prometheus Program Alternator/Thruster Integration Laboratory (ATIL)

    Science.gov (United States)

    Baez, Anastacio N.; Birchenough, Arthur G.; Lebron-Velilla, Ramon C.; Gonzalez, Marcelo C.

    2005-01-01

    The Project Prometheus Alternator Electric Thruster Integration Laboratory's (ATIL) primary two objectives are to obtain test data to influence the power conversion and electric propulsion systems design, and to assist in developing the primary power quality specifications prior to system Preliminary Design Review (PDR). ATIL is being developed in stages or configurations of increasing fidelity and complexity in order to support the various phases of the Prometheus program. ATIL provides a timely insight of the electrical interactions between a representative Permanent Magnet Generator, its associated control schemes, realistic electric system loads, and an operating electric propulsion thruster. The ATIL main elements are an electrically driven 100 kWe Alternator Test Unit (ATU), an alternator controller using parasitic loads, and a thruster Power Processing Unit (PPU) breadboard. This paper describes the ATIL components, its development approach, preliminary integration test results, and current status.

  6. Low Mass Electromagnetic Plasmoid Thruster with Integrated PPU Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Electromagnetic Plasmoid Thruster (EMPT) is a revolutionary electric propulsion thruster and power processing (PPU) system that will allow a dramatic decrease in...

  7. Development of a Micro-Thruster Test Facility which fulfils the LISA requirements

    Science.gov (United States)

    Hey, Franz Georg; Keller, A.; Johann, U.; Braxmaier, C.; Tajmar, M.; Fitzsimons, E.; Weise, D.

    2015-05-01

    In the context of investigations for a sufficient attitude control thruster for LISA, we have developed a thruster test facility which consists of a highly precise thrust balance coupled with plasma diagnostics. In parallel to the test facility development, investigations to downscale a High Efficiency Multistage Plasma Thruster (HEMP-T) are also being carried out. The thruster has been used to demonstrate the measurement capabilities of the facility. The setup allows a parallel operation of all instruments and can also be used for other types of μN propulsion systems including cold gas thrusters. The thrust balance consists of two pendulums. As read out a heterodyne laser interferometer is used. Differential wave front sensing (DWS) enables the measurement of the pendulum tilt which, via suitable calibration using an electrostatic comb, can be converted to a thrust. The whole setup is a symmetric configuration enabling a common-mode rejection of the dominant noise sources (e.g. seismic noise etc.). The thrust balance has a demonstrated precision of 0.1 μN. Based on our unique design, this precision can be attained down to 10-3 Hz. Thus, the measurement setup is especially suitable for characterising the thrust noise of potential eLISA propulsion candidates. We give an overview of the design, the present performance and the future plans.

  8. Performance Characterization of a Three-Axis Hall Effect Thruster

    Science.gov (United States)

    2010-12-01

    here represents the first efforts to operate and quantify the performance of a three-axis Hall effect thruster. This thruster is based on the Busek BHT ...thruster were developed and thrust and current density measurements were performed and compared with the baseline BHT -200. The three-axis thruster was...efficiencies than the BHT -200. Beam current density measurements conducted using a guarded Faraday probe showed significant differences in plume divergence

  9. Design and operations of Hall thruster with segmented electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, N.J.; Raitses, Y.; Dorf, L.A.; Litvak, A.A.

    1999-12-10

    Principles of the Hall thruster with segmented electrodes are explored. A suitable vacuum facility was put into service. For purposes of comparison between segmented and conventional thruster approaches, a modular laboratory prototype thruster was designed and built. Under conventional operation, the thruster achieves state-of-the-art efficiencies (56% at 300 V and 890 W). Very preliminary results under operation with segmented electrodes are also described.

  10. Design and Operation of Hall Thruster with Segmented Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    A.A. Litvak; L.A. Dorf; N.J. Fisch; Y. Raitses

    1999-07-01

    Principles of the Hall thruster with segmented electrodes are explored. A suitable vacuum facility was put into service. For purposes of comparison between segmented and conventional thruster approaches, a modular laboratory prototype thruster was designed and built. Under conventional operation, the thruster achieves state-of-the-art efficiencies (56% at 300 V and 890 W). Very preliminary results under operation with segmented electrodes are also described.

  11. Investigations of Probe Induced Perturbations in a Hall Thruster

    Energy Technology Data Exchange (ETDEWEB)

    D. Staack; Y. Raitses; N.J. Fisch

    2002-08-12

    An electrostatic probe used to measure spatial plasma parameters in a Hall thruster generates perturbations of the plasma. These perturbations are examined by varying the probe material, penetration distance, residence time, and the nominal thruster conditions. The study leads us to recommendations for probe design and thruster operating conditions to reduce discharge perturbations, including metal shielding of the probe insulator and operation of the thruster at lower densities.

  12. Coaxial plasma thrusters for high specific impulse propulsion

    Science.gov (United States)

    Schoenberg, Kurt F.; Gerwin, Richard A.; Barnes, Cris W.; Henins, Ivars; Mayo, Robert; Moses, Ronald, Jr.; Scarberry, Richard; Wurden, Glen

    1991-01-01

    A fundamental basis for coaxial plasma thruster performance is presented and the steady-state, ideal MHD properties of a coaxial thruster using an annular magnetic nozzle are discussed. Formulas for power usage, thrust, mass flow rate, and specific impulse are acquired and employed to assess thruster performance. The performance estimates are compared with the observed properties of an unoptimized coaxial plasma gun. These comparisons support the hypothesis that ideal MHD has an important role in coaxial plasma thruster dynamics.

  13. A New Reaction-controlled Phase-transfer Catalyst System

    Institute of Scientific and Technical Information of China (English)

    Ming Qiang LI; Xi Gao JIAN; Gui Mei WANG; Yan YU

    2004-01-01

    A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.

  14. Performance of a Cylindrical Hall-Effect Thruster Using Permanent Magnets

    Science.gov (United States)

    Polzin, Kurt A.; Raitses, Y.; Merino, E.; Fisch, N. J.

    2009-01-01

    electromagnets. Data are presented to expose the effect different controllable parameters have on the discharge and to summarize performance measurements (thrust, Isp, efficiency) obtained using a thrust stand. In addition, beam current data are presented to show the effect of the magnetic field topology on the plume profile and current utilization and to gain insight into the thruster s operation. These data extend and improve upon the results previously presented by the authors in Ref. [1].

  15. Targeted Control of Permeability Using Carbonate Dissolution/Precipitation Reactions

    Science.gov (United States)

    Clarens, A. F.; Tao, Z.; Plattenberger, D.

    2016-12-01

    Targeted mineral precipitation reactions are a promising approach for controlling fluid flow in the deep subsurface. Here we studied the potential to use calcium and magnesium bearing silicates as cation donors that would react with aqueous phase CO2 under reservoir conditions to form solid carbonate precipitates. Preliminary experiments in high pressure and temperature columns suggest that these reactions can effectively lower the permeability of a porous media. Wollastonite (CaSiO3) was used as the model silicate, injected as solid particles into the pore space of a packed column, which was then subsequently flooded with CO2(aq). The reactions occur spontaneously, leveraging the favorable kinetics that occur at the high temperature and pressure conditions characteristic of the deep subsurface, to form solid phase calcium carbonate (CaCO3) and amorphous silica (SiO2) within the pore space. Both x-ray tomography imaging of reacted columns and electron microscopy imaging of thin sections were used to characterize where dissolution/precipitation occurred within the porous media. The spatial distribution of the products was closely tied to the flow rate and the duration of the experiment. The SiO2 product precipitated in close spatial proximity to the CaSiO3 reactant. The CaCO3 product, which is sensitive to the low pH and high pCO2 brine, precipitated out of solution further down the column as Ca2+ ions moved with the brine. The permeability of the columns decreased by several orders of magnitude after injecting the CaSiO3 particles. Following carbonation, the permeability decreased even further as precipitates filled flow paths within the pore network. A pore network model was developed to help understand the interplay between precipitation kinetics and flow in altering the permeability of the porous media. The effect of particle concentration and size, pore size, reaction time, and pCO2, are explored on pore/fracture aperture and reaction extent. To provide better

  16. Parametric Investigations of Non-Conventional Hall Thruster

    Energy Technology Data Exchange (ETDEWEB)

    Raitses, Y.; Fisch, N.J.

    2001-01-12

    Hall thrusters might better scale to low power with non-conventional geometry. A 9 cm cylindrical, ceramic-channel, Hall thruster with a cusp-type magnetic field distribution has been investigated. It exhibits discharge characteristics similar to conventional coaxial Hall thrusters, but does not expose as much channel surface. Significantly, its operation is not accompanied by large amplitude discharge low frequency oscillations.

  17. OL-AC Phillips Laboratory MPD thruster research program

    Science.gov (United States)

    Tilley, Dennis L.

    1992-01-01

    The topics are presented in viewgraph form and include the following: facility construction; quadruple langmuir probe measurements; hollow/porous anode magnetoplasmadynamic (MPD) thruster; the measurement of the ionization fraction inside of the MPD thruster; and the experimental investigation of the effects of microturbulence on MPD thruster performance.

  18. Pattern Recognition Control Design

    Science.gov (United States)

    Gambone, Elisabeth A.

    2018-01-01

    Spacecraft control algorithms must know the expected vehicle response to any command to the available control effectors, such as reaction thrusters or torque devices. Spacecraft control system design approaches have traditionally relied on the estimated vehicle mass properties to determine the desired force and moment, as well as knowledge of the effector performance to efficiently control the spacecraft. A pattern recognition approach was used to investigate the relationship between the control effector commands and spacecraft responses. Instead of supplying the approximated vehicle properties and the thruster performance characteristics, a database of information relating the thruster ring commands and the desired vehicle response was used for closed-loop control. A Monte Carlo simulation data set of the spacecraft dynamic response to effector commands was analyzed to establish the influence a command has on the behavior of the spacecraft. A tool developed at NASA Johnson Space Center to analyze flight dynamics Monte Carlo data sets through pattern recognition methods was used to perform this analysis. Once a comprehensive data set relating spacecraft responses with commands was established, it was used in place of traditional control methods and gains set. This pattern recognition approach was compared with traditional control algorithms to determine the potential benefits and uses.

  19. Electrostatic ion thrusters - towards predictive modeling

    Energy Technology Data Exchange (ETDEWEB)

    Kalentev, O.; Matyash, K.; Duras, J.; Lueskow, K.F.; Schneider, R. [Ernst-Moritz-Arndt Universitaet Greifswald, D-17489 (Germany); Koch, N. [Technische Hochschule Nuernberg Georg Simon Ohm, Kesslerplatz 12, D-90489 Nuernberg (Germany); Schirra, M. [Thales Electronic Systems GmbH, Soeflinger Strasse 100, D-89077 Ulm (Germany)

    2014-02-15

    The development of electrostatic ion thrusters so far has mainly been based on empirical and qualitative know-how, and on evolutionary iteration steps. This resulted in considerable effort regarding prototype design, construction and testing and therefore in significant development and qualification costs and high time demands. For future developments it is anticipated to implement simulation tools which allow for quantitative prediction of ion thruster performance, long-term behavior and space craft interaction prior to hardware design and construction. Based on integrated numerical models combining self-consistent kinetic plasma models with plasma-wall interaction modules a new quality in the description of electrostatic thrusters can be reached. These open the perspective for predictive modeling in this field. This paper reviews the application of a set of predictive numerical modeling tools on an ion thruster model of the HEMP-T (High Efficiency Multi-stage Plasma Thruster) type patented by Thales Electron Devices GmbH. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Chaos control by electric current in an enzymatic reaction.

    Science.gov (United States)

    Lekebusch, A; Förster, A; Schneider, F W

    1996-09-01

    We apply the continuous delayed feedback method of Pyragas to control chaos in the enzymatic Peroxidase-Oxidase (PO) reaction, using the electric current as the control parameter. At each data point in the time series, a time delayed feedback function applies a small amplitude perturbation to inert platinum electrodes, which causes redox processes on the surface of the electrodes. These perturbations are calculated as the difference between the previous (time delayed) signal and the actual signal. Unstable periodic P1, 1(1), and 1(2) orbits (UPOs) were stabilized in the CSTR (continuous stirred tank reactor) experiments. The stabilization is demonstrated by at least three conditions: A minimum in the experimental dispersion function, the equality of the delay time with the period of the stabilized attractor and the embedment of the stabilized periodic attractor in the chaotic attractor.

  1. Control of DNA replication by anomalous reaction-diffusion kinetics

    Science.gov (United States)

    Bechhoefer, John; Gauthier, Michel

    2010-03-01

    DNA replication requires two distinct processes: the initiation of pre-licensed replication origins and the propagation of replication forks away from the fired origins. Experiments indicate that these origins are triggered over the whole genome at a rate I(t) (the number of initiations per unreplicated length per time) that increases throughout most of the synthesis (S) phase, before rapidly decreasing to zero at the end of the replication process. We propose a simple model for the control of DNA replication in which the rate of initiation of replication origins is controlled by protein-DNA interactions. Analyzing recent data from Xenopus frog embryos, we find that the initiation rate is reaction limited until nearly the end of replication, when it becomes diffusion limited. Initiation of origins is suppressed when the diffusion-limited search time dominates. To fit the experimental data, we find that the interaction between DNA and the rate-limiting protein must be subdiffusive.

  2. Directional sensitivity of "first trial" reactions in human balance control.

    Science.gov (United States)

    Oude Nijhuis, Lars B; Allum, John H J; Borm, George F; Honegger, Flurin; Overeem, Sebastiaan; Bloem, Bastiaan R

    2009-06-01

    Support-surface movements are commonly used to examine balance control. Subjects typically receive a series of identical or randomly interspersed multidirectional balance perturbations and the atypical "first trial reaction" (evoked by the first perturbation) is often excluded from further analysis. However, this procedure may obscure vital information about neurophysiological mechanisms associated with the first perturbation and, by analogy, fully unexpected falls. We studied first trial reactions, aiming to clarify their directional impact on postural control and to characterize the underlying neurophysiological substrate. We instructed 36 subjects to maintain balance following support-surface rotations in six different directions. Perturbations in each direction were delivered in blocks, consisting of 10 serial stimuli. Full body kinematics, surface reactive forces, and electromyographic (EMG) responses were recorded. Regardless of direction, for the very first rotation, displacement of the center of mass was 15% larger compared with the ensuing nine identical rotations (P postural instability, mainly due to increased response amplitudes. Although rapid habituation occurs following presentation of identical stimuli, subjects immediately become unstable again when the perturbation direction suddenly changes. Excessive responses due to a failure to combine proprioceptive and vestibular cues effectively may explain this instability seen with first trials, particularly when falling backward.

  3. Experimental study of a low-thrust measurement system for thruster ground tests.

    Science.gov (United States)

    Gong, Jingsong; Hou, Lingyun; Zhao, Wenhua

    2014-03-01

    The development of thrusters used for the control of position and orbit of micro-satellites requires thrust stands that can measure low thrust. A new method to measure low thrust is presented, and the measuring device is described. The test results show that the thrust range is up to 1000 mN, the measurement error of the device is lower than ±1% of full scale, and the drift of the zero offset is less than ±1% of full scale. Its response rise time is less than 15 ms. It is employed to measure the working process of a model chemical thruster with repeatability.

  4. Mode Transitions in Hall Effect Thrusters

    Science.gov (United States)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Brown, Daniel L.; Hofer, Richard R.; Polk, James E.

    2013-01-01

    Mode transitions have been commonly observed in Hall Effect Thruster (HET) operation where a small change in a thruster operating parameter such as discharge voltage, magnetic field or mass flow rate causes the thruster discharge current mean value and oscillation amplitude to increase significantly. Mode transitions in a 6-kW-class HET called the H6 are induced by varying the magnetic field intensity while holding all other operating parameters constant and measurements are acquired with ion saturation probes and ultra-fast imaging. Global and local oscillation modes are identified. In the global mode, the entire discharge channel oscillates in unison and azimuthal perturbations (spokes) are either absent or negligible. Downstream azimuthally spaced probes show no signal delay between each other and are very well correlated to the discharge current signal. In the local mode, signals from the azimuthally spaced probes exhibit a clear delay indicating the passage of "spokes" and are not well correlated to the discharge current. These spokes are localized oscillations propagating in the ExB direction that are typically 10-20% of the mean value. In contrast, the oscillations in the global mode can be 100% of the mean value. The transition between global and local modes occurs at higher relative magnetic field strengths for higher mass flow rates or higher discharge voltages. The thrust is constant through mode transition but the thrust-to-power decreased by 25% due to increasing discharge current. The plume shows significant differences between modes with the global mode significantly brighter in the channel and the near-field plasma plume as well as exhibiting a luminous spike on thruster centerline. Mode transitions provide valuable insight to thruster operation and suggest improved methods for thruster performance characterization.

  5. A comparing design of satellite attitude control system based on reaction wheel

    Institute of Scientific and Technical Information of China (English)

    CHENG Hao; GE Sheng-min; SHEN Yi

    2008-01-01

    The disturbance caused by the reaction wheel with a current controller greatly influences the accuracy and stability of the satellite attitude control system.To solve this problem,the idea of speed feedback compensation control reaction wheel is put forward.This paper introduces the comparison on design and performance of two satellite attitude control systems,which are separately based on the current control reaction wheel and the speed feedback compensation control reaction wheel.Analysis shows that the speed feedback compensation control flywheel system may effectively suppress the torque fluctuation.Simulation results indicate that the satellite attitude control system with the speed feedback compensation control flywheel has improved performance.

  6. Measurements of Plasma Potential Distribution in Segmented Electrode Hall Thruster

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses; D. Staack; N.J. Fisch

    2001-10-16

    Use of a segmented electrode placed at the Hall thruster exit can substantially reduce the voltage potential drop in the fringing magnetic field outside the thruster channel. In this paper, we investigate the dependence of this effect on thruster operating conditions and segmented electrode configuration. A fast movable emissive probe is used to measure plasma potential in a 1 kW laboratory Hall thruster with semented electrodes made of a graphite material. Relatively small probe-induced perturbations of the thruster discharge in the vicinity of the thruster exit allow a reasonable comparison of the measured results for different thruster configurations. It is shown that the plasma potential distribution is almost not sensitive to changes of the electrode potential, but depends on the magnetic field distribution and the electrode placement.

  7. A Numerical Study on Hydrodynamic Interactions between Dynamic Positioning Thrusters

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Doo Hwa; Lee, Sang Wook [University of Ulsan, Ulsan (Korea, Republic of)

    2017-06-15

    In this study, we conducted computational fluid dynamics (CFD) simulations for the unsteady hydrodynamic interaction of multiple thrusters by solving Reynolds averaged Navier-Stokes equations. A commercial CFD software, STAR-CCM+ was used for all simulations by employing a ducted thruster model with combination of a propeller and No. 19a duct. A sliding mesh technique was used to treat dynamic motion of propeller rotation and non-conformal hexahedral grid system was considered. Four different combinations in tilting and azimuth angles of the thrusters were considered to investigate the effects on the propulsion performance. We could find that thruster-hull and thruster-thruster interactions has significant effect on propulsion performance and further study will be required for the optimal configurations with the best tilting and relative azimuth angle between thrusters.

  8. Advanced laboratory for testing plasma thrusters and Hall thruster measurement campaign

    Directory of Open Access Journals (Sweden)

    Szelecka Agnieszka

    2016-06-01

    Full Text Available Plasma engines are used for space propulsion as an alternative to chemical thrusters. Due to the high exhaust velocity of the propellant, they are more efficient for long-distance interplanetary space missions than their conventional counterparts. An advanced laboratory of plasma space propulsion (PlaNS at the Institute of Plasma Physics and Laser Microfusion (IPPLM specializes in designing and testing various electric propulsion devices. Inside of a special vacuum chamber with three performance pumps, an environment similar to the one that prevails in space is created. An innovative Micro Pulsed Plasma Thruster (LμPPT with liquid propellant was built at the laboratory. Now it is used to test the second prototype of Hall effect thruster (HET operating on krypton propellant. Meantime, an improved prototype of krypton Hall thruster is constructed.

  9. Pulsed Plasma Thruster (PPT) Technology: Earth Observing-1 PPT Operational and Advanced Components Being Developed

    Science.gov (United States)

    Pencil, Eric J.; Benson, Scott W.; Arrington, Lynn A.; Frus, John; Hoskins, W. Andrew; Burton, Rodney

    2003-01-01

    In 2002 the pulsed plasma thruster (PPT) mounted on the Earth Observing-1 spacecraft was operated successfully in orbit. The two-axis thruster system is fully incorporated in the attitude determination and control system and is being used to automatically counteract disturbances in the pitch axis of the spacecraft. The first tests conducted in space demonstrated the full range of PPT operation, followed by calibration of control torques from the PPT in the attitude control system. Then the spacecraft was placed in PPT control mode. To date, it has operated for about 30 hr. The PPT successfully controlled pitch momentum during wheel de-spin, solar array acceleration and deceleration during array rewind, and environmental torques in nominal operating conditions. Images collected with the Advanced Landsat Imager during PPT operation have demonstrated that there was no degradation in comparison to full momentum wheel control. In addition, other experiments have been performed to interrogate the effects of PPT operation on communication packages and light reflection from spacecraft surfaces. Future experiments will investigate the possibility of orbit-raising maneuvers, spacecraft roll, and concurrent operation with the Hyperion imager. Future applications envisioned for pulsed plasma thrusters include longer life, higher precision, multiaxis thruster configurations for three-axis attitude control systems or high-precision, formationflying systems. Advanced components, such as a "dry" mica-foil capacitor, a wear-resistant spark plug, and a multichannel power processing unit have been developed under contract with Unison Industries, General Dynamics, and C.U. Aerospace. Over the last year, evaluation tests have been conducted to determine power processing unit efficiency, atmospheric functionality, vacuum functionality, thruster performance evaluation, thermal performance, and component life.

  10. Algorithm of Attitude Control and Its Simulation of Free-Flying Space Robot

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Reaction wheel or reaction thruster is employed to maintain the attitude of the base of space robot fixed in attitude control of free-flying space robot.However, in this method, a large amount of fuel will be consumed, and it will shorten the on-orbit life span of space robot, it also vibrate the system and make the system unsteady.The restricted minimum disturbance map (RMDM) based algorithm of attitude control is presented to keep the attitude of the base fixed during the movement of the manipulator.In this method it is realized by planning motion trajectory of the end-effector of manipulator without using reaction wheel or reaction thruster.In order to verify the feasibility and effectiveness of the algorithm attitude control presented in this paper, computer simulation experiments have been made and the experimental results demonstrate that this algorithm is feasible.

  11. The electrodeless Lorentz force thruster experiment

    Science.gov (United States)

    Weber, Thomas E.

    The Electrodeless Lorentz Force (ELF) thruster is a novel type of plasma thruster, which utilizes Rotating Magnetic Field current drive within a diverging magnetic field to form, accelerate, and eject a Field Reversed Configuration plasmoid. The ELF program is a result of a Small Business Technology Transfer grant awarded to MSNW LLC by the Air Force Office of Scientific Research for the research of the revolutionary space propulsion concept represented by ELF. These grants are awarded to small businesses working in collaboration with a university, in this case, the University of Washington. The program was split into two concurrent research efforts; a numerical modeling study undertaken at the UW branch of the Plasma Science and Innovation Center, and an experimental effort taking place at the UW Plasma Dynamics Laboratory with additional support from MSNW (the latter being the subject of this dissertation). It is the aim of this dissertation is to present to the reader the necessary background information needed to understand the operation of the ELF thruster, an overview of the experimental setup, a review of the significant experimental findings, and a discussion regarding the operation and performance of the thruster.

  12. Hall Effect Thruster Ground Testing Challenges

    Science.gov (United States)

    2009-08-18

    conditional stability of the inverted pendulum thrust stand provides improved measurement sensitivity.5 With the displacement of the inverted pendulum...July 2005. 12Samiento, C., “RHETT2/ EPDM Hall Thruster Propulsion System Electromagnetic Compatability Evaluation,” Proceed- ings of the 25th

  13. Optical properties of thermal control coatings contaminated by MMH/N2O4 5-pound thruster in a vacuum environment with solar simulation.

    Science.gov (United States)

    Sommers, R. D.; Raquet, C. A.; Cassidy, J. F.

    1972-01-01

    Cat-a-lac Black and S13G thermal control coatings were exposed to the exhaust of a thrustor in a simulated space environment. Vacuum was maintained at less than 10 microtorr during thrustor firing in the liquid helium cooled facility. The thrustor was fired in a 50-millisecond pulse mode, and the accumulated firing time was 224 seconds. Solar absorptance and thermal emittance of the coatings were measured in-situ at intervals of 300 pulses, using a calorimetric technique. The Cat-a-lac Black coatings showed no change in solar absorptance or thermal emittance. The S13G showed up to 25% increase in solar absorptance but no change in thermal emittance.

  14. Microdischarge plasma thrusters for small satellite propulsion

    Science.gov (United States)

    Raja, Laxminarayan

    2009-10-01

    Small satellites weighing less than 100 kg are gaining importance in the defense and commercial satellite community owing to advantages of low costs to build and operate, simplicity of design, rapid integration and testing, formation flying, and multi-vehicle operations. The principal challenge in the design and development of small satellite subsystems is the severe mass, volume, and power constraints posed by the overall size of the satellite. The propulsion system in particular is hard to down scale and as such poses a major stumbling block for small satellite technology. Microdischarge-based miniaturized plasma thrusters are potentially a novel solution to this problem. In its most basic form a microdischarge plasma thruster is a simple extension of a cold gas micronozzle propulsion device, where a direct or alternating current microdischarge is used to preheat the gas stream to improve to specific impulse of the device. We study a prototypical thruster device using a detailed, self-consistent coupled plasma and fluid flow computational model. The model describes the microdischarge power deposition, plasma dynamics, gas-phase chemical kinetics, coupling of the plasma phenomena with high-speed flow, and overall propulsion system performance. Unique computational challenges associated with microdischarge modeling in the presence of high-speed flows are addressed. Compared to a cold gas micronozzle, a significant increase in specific impulse (50 to 100 %) is obtained from the power deposition in the diverging supersonic section of the thruster nozzle. The microdischarge remains mostly confined inside the micronozzle and operates in an abnormal glow discharge regime. Gas heating, primarily due to ion Joule heating, is found to have a strong influence on the overall discharge behavior. The study provides a validation of the concept as simple and effective approach to realizing a relatively high-specific impulse thruster device at small geometric scales.

  15. Dual control cell reaction ensemble molecular dynamics: A method for simulations of reactions and adsorption in porous materials

    Science.gov (United States)

    Lísal, Martin; Brennan, John K.; Smith, William R.; Siperstein, Flor R.

    2004-09-01

    We present a simulation tool to study fluid mixtures that are simultaneously chemically reacting and adsorbing in a porous material. The method is a combination of the reaction ensemble Monte Carlo method and the dual control volume grand canonical molecular dynamics technique. The method, termed the dual control cell reaction ensemble molecular dynamics method, allows for the calculation of both equilibrium and nonequilibrium transport properties in porous materials such as diffusion coefficients, permeability, and mass flux. Control cells, which are in direct physical contact with the porous solid, are used to maintain the desired reaction and flow conditions for the system. The simulation setup closely mimics an actual experimental system in which the thermodynamic and flow parameters are precisely controlled. We present an application of the method to the dry reforming of methane reaction within a nanoscale reactor model in the presence of a semipermeable membrane that was modeled as a porous material similar to silicalite. We studied the effects of the membrane structure and porosity on the reaction species permeability by considering three different membrane models. We also studied the effects of an imposed pressure gradient across the membrane on the mass flux of the reaction species. Conversion of syngas (H2/CO) increased significantly in all the nanoscale membrane reactor models considered. A brief discussion of further potential applications is also presented.

  16. Chemical Characterization and Reactivity of Fuel-Oxidizer Reaction Product

    Science.gov (United States)

    David, Dennis D.; Dee, Louis A.; Beeson, Harold D.

    1997-01-01

    Fuel-oxidizer reaction product (FORP), the product of incomplete reaction of monomethylhydrazine and nitrogen tetroxide propellants prepared under laboratory conditions and from firings of Shuttle Reaction Control System thrusters, has been characterized by chemical and thermal analysis. The composition of FORP is variable but falls within a limited range of compositions that depend on three factors: the fuel-oxidizer ratio at the time of formation; whether the composition of the post-formation atmosphere is reducing or oxidizing; and the reaction or post-reaction temperature. A typical composition contains methylhydrazinium nitrate, ammonium nitrate, methylammonium nitrate, and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. Thermal decomposition reactions of the FORP compositions used in this study were unremarkable. Neither the various compositions of FORP, the pure major components of FORP, nor mixtures of FORP with propellant system corrosion products showed any unusual thermal activity when decomposed under laboratory conditions. Off-limit thruster operations were simulated by rapid mixing of liquid monomethylhydrazine and liquid nitrogen tetroxide in a confined space. These tests demonstrated that monomethylhydrazine, methylhydrazinium nitrate, ammonium nitrate, or Inconel corrosion products can induce a mixture of monomethylhydrazine and nitrogen tetroxide to produce component-damaging energies. Damaging events required FORP or metal salts to be present at the initial mixing of monomethylhydrazine and nitrogen tetroxide.

  17. Fluorescence-based temperature control for polymerase chain reaction.

    Science.gov (United States)

    Sanford, Lindsay N; Wittwer, Carl T

    2014-03-01

    The ability to accurately monitor solution temperature is important for the polymerase chain reaction (PCR). Robust amplification during PCR is contingent on the solution reaching denaturation and annealing temperatures. By correlating temperature to the fluorescence of a passive dye, noninvasive monitoring of solution temperatures is possible. The temperature sensitivity of 22 fluorescent dyes was assessed. Emission spectra were monitored and the change in fluorescence between 45 and 95°C was quantified. Seven dyes decreased in intensity as the temperature increased, and 15 were variable depending on the excitation wavelength. Sulforhodamine B (monosodium salt) exhibited a fold change in fluorescence of 2.85. Faster PCR minimizes cycling times and improves turnaround time, throughput, and specificity. If temperature measurements are accurate, no holding period is required even at rapid speeds. A custom instrument using fluorescence-based temperature monitoring with dynamic feedback control for temperature cycling amplified a fragment surrounding rs917118 from genomic DNA in 3min and 45s using 35 cycles, allowing subsequent genotyping by high-resolution melting analysis. Gold-standard thermocouple readings and fluorescence-based temperature differences were 0.29±0.17 and 0.96±0.26°C at annealing and denaturation, respectively. This new method for temperature cycling may allow faster speeds for PCR than currently considered possible.

  18. MEMS-Based Solid Propellant Rocket Array Thruster

    Science.gov (United States)

    Tanaka, Shuji; Hosokawa, Ryuichiro; Tokudome, Shin-Ichiro; Hori, Keiichi; Saito, Hirobumi; Watanabe, Masashi; Esashi, Masayoshi

    The prototype of a solid propellant rocket array thruster for simple attitude control of a 10 kg class micro-spacecraft was completed and tested. The prototype has 10×10 φ0.8 mm solid propellant micro-rockets arrayed at a pitch of 1.2 mm on a 20×22 mm substrate. To realize such a dense array of micro-rockets, each ignition heater is powered from the backside of the thruster through an electrical feedthrough which passes along a propellant cylinder wall. Boron/potassium nitrate propellant (NAB) is used with/without lead rhodanide/potassium chlorate/nitrocellulose ignition aid (RK). Impulse thrust was measured by a pendulum method in air. Ignition required electric power of at least 3 4 W with RK and 4 6 W without RK. Measured impulse thrusts were from 2×10-5 Ns to 3×10-4 Ns after the calculation of compensation for air dumping.

  19. Los Alamos NEP research in advanced plasma thrusters

    Science.gov (United States)

    Schoenberg, Kurt; Gerwin, Richard

    1991-01-01

    Research was initiated in advanced plasma thrusters that capitalizes on lab capabilities in plasma science and technology. The goal of the program was to examine the scaling issues of magnetoplasmadynamic (MPD) thruster performance in support of NASA's MPD thruster development program. The objective was to address multi-megawatt, large scale, quasi-steady state MPD thruster performance. Results to date include a new quasi-steady state operating regime which was obtained at space exploration initiative relevant power levels, that enables direct coaxial gun-MPD comparisons of thruster physics and performance. The radiative losses are neglible. Operation with an applied axial magnetic field shows the same operational stability and exhaust plume uniformity benefits seen in MPD thrusters. Observed gun impedance is in close agreement with the magnetic Bernoulli model predictions. Spatial and temporal measurements of magnetic field, electric field, plasma density, electron temperature, and ion/neutral energy distribution are underway. Model applications to advanced mission logistics are also underway.

  20. Numerical investigation of two interacting parallel thruster-plumes and comparison to experiment

    Science.gov (United States)

    Grabe, Martin; Holz, André; Ziegenhagen, Stefan; Hannemann, Klaus

    2014-12-01

    Clusters of orbital thrusters are an attractive option to achieve graduated thrust levels and increased redundancy with available hardware, but the heavily under-expanded plumes of chemical attitude control thrusters placed in close proximity will interact, leading to a local amplification of downstream fluxes and of back-flow onto the spacecraft. The interaction of two similar, parallel, axi-symmetric cold-gas model thrusters has recently been studied in the DLR High-Vacuum Plume Test Facility STG under space-like vacuum conditions, employing a Patterson-type impact pressure probe with slot orifice. We reproduce a selection of these experiments numerically, and emphasise that a comparison of numerical results to the measured data is not straight-forward. The signal of the probe used in the experiments must be interpreted according to the degree of rarefaction and local flow Mach number, and both vary dramatically thoughout the flow-field. We present a procedure to reconstruct the probe signal by post-processing the numerically obtained flow-field data and show that agreement to the experimental results is then improved. Features of the investigated cold-gas thruster plume interaction are discussed on the basis of the numerical results.

  1. Power electronics for a 1-kilowatt arcjet thruster

    Science.gov (United States)

    Gruber, R. P.

    1986-01-01

    After more than two decades, new space mission requirements have revived interest in arcjet systems. The preliminary development and demonstration of new, high efficiency, power electronic concepts for start up and steady state control of dc arcjets is reported. The design comprises a pulse width modulated power converter which is closed loop configured to give fast current control. An inductor, in series with the arcjet, serves the dual role of providing instantaneous current control, as well as a high voltage arc ignition pulse. Benchmark efficiency, transient response, regulation, and ripple data are presented. Tests with arcjets demonstrate that the power electronics breadboard can start thrusters consistently with no apparent damage and transfer reliably to the nondestructive high voltage arc mode in less than a second.

  2. Carbon Nanotube Based Electric Propulsion Thruster with Low Power Consumption Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR project is to develop field emission electric propulsion (FEEP) thruster using carbon nanotubes (CNT) integrated anode. FEEP thrusters have gained...

  3. Pseudospectral Model for Hybrid PIC Hall-effect Thruster Simulation

    Science.gov (United States)

    2015-07-01

    1149. 8Goebel, D. M. and Katz, I., Fundamentals of Electric Propulsion : Ion and Hall Thrusters, John Wiley & Sons, Inc., 2008. 9Martin, R., J.W., K...Bilyeu, D., and Tran, J., “Dynamic Particle Weight Remapping in Hybrid PIC Hall -effect Thruster Simulation,” 34th Int. Electric Propulsion Conf...Paper 3. DATES COVERED (From - To) July 2015-July 2015 4. TITLE AND SUBTITLE Pseudospectral model for hybrid PIC Hall -effect thruster simulationect

  4. Micro Cathode Arc Thruster for PhoneSat: Development and Potential Applications

    Science.gov (United States)

    Gazulla, Oriol Tintore; Perez, Andres Dono; Agasid, Elwood; Uribe, Eddie; Trinh, Greenfield; Keidar, Michael; Teel, George; Haque, Samudra; Lukas, Joseph; Salas, Alberto Guillen; hide

    2014-01-01

    NASA Ames Research Center and the George Washington University are developing an electric propulsion subsystem that will be integrated into the PhoneSat bus. Experimental tests have shown a reliable performance by firing three different thrusters at various frequencies in vacuum conditions. The interface consists of a microcontroller that sends a trigger pulse to the Pulsed Plasma Unit that is responsible for the thruster operation. A Smartphone is utilized as the main user interface for the selection of commands that control the entire system. The propellant, which is the cathode itself, is a solid cylinder made of Titanium. This simplicity in the design avoids miniaturization and manufacturing problems. The characteristics of this thruster allow an array of µCATs to perform attitude control and orbital correction maneuvers that will open the door for the implementation of an extensive collection of new mission concepts and space applications for CubeSats. NASA Ames is currently working on the integration of the system to fit the thrusters and the PPU inside a 1.5U CubeSat together with the PhoneSat bus. This satellite is intended to be deployed from the ISS in 2015 and test the functionality of the thrusters by spinning the satellite around its long axis and measure the rotational speed with the phone gyros. This test flight will raise the TRL of the propulsion system from 5 to 7 and will be a first test for further CubeSats with propulsion systems, a key subsystem for long duration or interplanetary small satellite missions.

  5. Thermal Management of Superconducting Electromagnets in VASIMR Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future manned space exploration missions will require high power electric propulsion. VASIMR thrusters are the most attractive option because they offer short...

  6. High Throughput 600 Watt Hall Effect Thruster for Space Exploration

    Science.gov (United States)

    Szabo, James; Pote, Bruce; Tedrake, Rachel; Paintal, Surjeet; Byrne, Lawrence; Hruby, Vlad; Kamhawi, Hani; Smith, Tim

    2016-01-01

    A nominal 600-Watt Hall Effect Thruster was developed to propel unmanned space vehicles. Both xenon and iodine compatible versions were demonstrated. With xenon, peak measured thruster efficiency is 46-48% at 600-W, with specific impulse from 1400 s to 1700 s. Evolution of the thruster channel due to ion erosion was predicted through numerical models and calibrated with experimental measurements. Estimated xenon throughput is greater than 100 kg. The thruster is well sized for satellite station keeping and orbit maneuvering, either by itself or within a cluster.

  7. High Efficiency Hall Thruster Discharge Power Converter Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek leveraged previous, internally sponsored, high power, Hall thruster discharge converter development which allowed it to design, build, and test new printed...

  8. NASA HERMeS Hall Thruster Electrical Configuration Characterization

    Science.gov (United States)

    Peterson, Peter Y.; Kamhawi, Hani; Huang, Wensheng; Yim, John; Herman, Daniel; Williams, George; Gilland, James; Hofer, Richard

    2015-01-01

    The NASA Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight ready propulsion system. Part of the technology maturation was to test the TDU-1 thruster in several ground based electrical configurations to assess the thruster robustness and suitability to successful in-space operation. The ground based electrical configuration testing has recently been demonstrated as an important step in understanding and assessing how a Hall thruster may operate differently in-space compared to ground based testing, and to determine the best configuration to conduct development and qualification testing. This paper describes the electrical configuration testing of the HERMeS TDU-1 Hall thruster in NASA Glenn Research Center's Vacuum Facility 5. The three electrical configurations examined were 1) thruster body tied to facility ground, 2) thruster floating, and 3) thruster body electrically tied to cathode common. The HERMeS TDU-1 Hall thruster was also configured with two different exit plane boundary conditions, dielectric and conducting, to examine the influence on the electrical configuration characterization.

  9. Studies of Non-Conventional Configuration Closed Electron Drift Thrusters

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses; D. Staack; A. Smirnov; A.A. Litvak; L.A. Dorf; T. Graves; and N.J. Fisch

    2001-09-10

    In this paper, we review recent results obtained for segmented electrode and cylindrical Hall thrusters. A low sputtering graphite segmented electrode, placed at the exit of the annular thruster, is shown to affect the plasma potential distribution in the ceramic channel. This effect appears to be correlated with an observed plume reduction compared to a conventional, nonsegmented thruster. In preliminary experiments a 3-cm thruster was operated in the 50-200 W power range. Two operating regimes, stable and oscillating, were observed and investigated.

  10. Conducting wall Hall thrusters in magnetic shielding and standard configurations

    Science.gov (United States)

    Grimaud, Lou; Mazouffre, Stéphane

    2017-07-01

    Traditional Hall thrusters are fitted with boron nitride dielectric discharge channels that confine the plasma discharge. Wall properties have significant effects on the performances and stability of the thrusters. In magnetically shielded thrusters, interactions between the plasma and the walls are greatly reduced, and the potential drop responsible for ion acceleration is situated outside the channel. This opens the way to the utilization of alternative materials for the discharge channel. In this work, graphite walls are compared to BN-SiO2 walls in the 200 W magnetically shielded ISCT200-MS and the unshielded ISCT200-US Hall thrusters. The magnetically shielded thruster shows no significant change in the discharge current mean value and oscillations, while the unshielded thruster's discharge current increases by 25% and becomes noticeably less stable. The electric field profile is also investigated through laser spectroscopy, and no significant difference is recorded between the ceramic and graphite cases for the shielded thruster. The unshielded thruster, on the other hand, has its acceleration region shifted 15% of the channel length downstream. Lastly, the plume profile is measured with planar probes fitted with guard rings. Once again the material wall has little influence on the plume characteristics in the shielded thruster, while the unshielded one is significantly affected.

  11. Femtosecond laser control of chemical reaction of carbon monoxide and hydrogen

    CSIR Research Space (South Africa)

    Du Plessis, A

    2010-09-01

    Full Text Available Femtosecond laser control of chemical reactions is made possible through the use of pulse-shaping techniques coupled to a learning algorithm feedback loop – teaching the laser pulse to control the chemical reaction. This can result in controllable...

  12. A Reaction Sphere for High Performance Attitude Control Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Our innovative reaction sphere (Doty pending patent application serial number 61/164,868) has the potential to provide much higher performance than a conventional...

  13. Quantum-State Controlled Chemical Reactions of Ultracold KRb Molecules

    CERN Document Server

    Ospelkaus, S; Wang, D; de Miranda, M H G; Neyenhuis, B; Quéméner, G; Julienne, P S; Bohn, J L; Jin, D S; Ye, J

    2009-01-01

    How does a chemical reaction proceed at ultralow temperatures? Can simple quantum mechanical rules such as quantum statistics, single scattering partial waves, and quantum threshold laws provide a clear understanding for the molecular reactivity under a vanishing collision energy? Starting with an optically trapped near quantum degenerate gas of polar $^{40}$K$^{87}$Rb molecules prepared in their absolute ground state, we report experimental evidence for exothermic atom-exchange chemical reactions. When these fermionic molecules are prepared in a single quantum state at a temperature of a few hundreds of nanoKelvins, we observe p-wave-dominated quantum threshold collisions arising from tunneling through an angular momentum barrier followed by a near-unity probability short-range chemical reaction. When these molecules are prepared in two different internal states or when molecules and atoms are brought together, the reaction rates are enhanced by a factor of 10 to 100 due to s-wave scattering, which does not ...

  14. Miniature Reaction Wheel for Small Satellite Control Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall goal of this project is to design, develop, demonstrate, and deliver a miniature, high torque, low-vibration reaction wheel for use on small satellites....

  15. Sample controlled reaction temperature (SCRT): Controlling the phase composition of silicon nitride obtained by carbothermal reduction

    Energy Technology Data Exchange (ETDEWEB)

    Alcala, M.D.; Criado, J.M.; Real, C. [Instituto de Ciencia de Materiales de Sevilla, c/Americo Vespucio s/n; Isla de La Cartuja, 41092 Sevilla (Spain)

    2002-07-01

    Carbothermal reduction of silica is one of the most common methods of producing Si{sub 3}N{sub 4} powders. The experimental conditions have an important influence on the structure of the final product, especially the balance of {alpha}- to {beta}- Si{sub 3}N{sub 4}. The Sample Controlled Reaction Temperature method describes here has permitted to conclude that the phase composition of the silicon nitride is governed by the partial pressure of CO in the close vicinity of the sample. Moreover, the control of this parameter has an important influence on particle size and morphology of the final product. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  16. Fuel Oxidizer Reaction Products (FORP) Contamination of Service Module (SM) and Release of N-nitrosodimethylamine(NDMA)in a Humid Environment from Crew EVA Suits Contaminated with FORP

    Science.gov (United States)

    Schmidl, William; Mikatarian, Ron; Lam, Chiu-Wing; West, Bil; Buchanan, Vanessa; Dee, Louis; Baker, David; Koontz, Steve

    2004-01-01

    The Service Module (SM) is an element of the Russian Segment of the International Space Station (ISS). One of the functions of the SM is to provide attitude control for the ISS using thrusters when the U.S. Control Moment Gyros (CMG's) must be desaturated. Prior to an Extravehicular Activity (EVA) on the Russian Segment, the Docking Compartment (DC1) is depressurized, as it is used as an airlock. When the DC1 is depressurized, the CMG's margin of momentum is insufficient and the SM attitude control thrusters need to fire to desaturate the CMG's. SM roll thruster firings induce contamination onto adjacent surfaces with Fuel Oxidizer Reaction Products (FORP). FORP is composed of both volatile and non-volatile components. One of the components of FORP is the potent carcinogen N-nitrosdimethylamine (NDMA). Since the EVA crewmembers often enter the area surrounding the thrusters for tasks on the aft end of the SM and when translating to other areas of the Russian Segment, the presence of FORP is a concern. This paper will discuss FORP contamination of the SM surfaces, the release of NDMA in a humid environment from crew EVA suits, if they happen to be contaminated with FORP, and the toxicological risk associated with the NDMA release.

  17. Spatially parallel control of DNA reactions in optically manipulated microdroplets

    Science.gov (United States)

    Ogura, Yusuke; Nishimura, Takahiro; Tanida, Jun

    2011-01-01

    In order to show the potential of photonic techniques for realizing nanoscale computing, we examined the operation of DNA reactions by optical manipulation of microdroplets that contain DNA. The processing procedures are reconfigurable owing to flexibility in manipulating the microdroplets. The method is effective in, for example, implementing DNA computations in limited-volumes at multiple positions in parallel, enhancing an operation rate, and decreasing sample consumption, and it can be a promising technique applicable to photonic DNA computing. A reaction scheme using a pair of hairpin DNA and linear DNA was examined to confirm the method. The reaction scheme provides exchange of the sequence of a sticky-end of a DNA conformation, and it is usable for DNA computation. Microdroplets that contain DNA components were contacted to each other to start the reaction. By observing fluorescence intensity, we confirmed the reaction of sequence-change in the optically manipulated microdroplet. The experimental result also showed that different reactions are implemented at separate positions simultaneously.

  18. A collisionless plasma thruster plume expansion model

    Science.gov (United States)

    Merino, Mario; Cichocki, Filippo; Ahedo, Eduardo

    2015-06-01

    A two-fluid model of the unmagnetized, collisionless far region expansion of the plasma plume for gridded ion thrusters and Hall effect thrusters is presented. The model is integrated into two semi-analytical solutions valid in the hypersonic case. These solutions are discussed and compared against the results from the (exact) method of characteristics; the relative errors in density and velocity increase slowly axially and radially and are of the order of 10-2-10-3 in the cases studied. The plasma density, ion flux and ambipolar electric field are investigated. A sensitivity analysis of the problem parameters and initial conditions is carried out in order to characterize the far plume divergence angle in the range of interest for space electric propulsion. A qualitative discussion of the physics of the secondary plasma plume is also provided.

  19. Iodine Hall Thruster Propellant Feed System for a CubeSat

    Science.gov (United States)

    Polzin, Kurt A.; Peeples, Steven

    2014-01-01

    The components required for an in-space iodine vapor-fed Hall effect thruster propellant management system are described. A laboratory apparatus was assembled and used to produce iodine vapor and control the flow through the application of heating to the propellant reservoir and through the adjustment of the opening in a proportional flow control valve. Changing of the reservoir temperature altered the flowrate on the timescale of minutes while adjustment of the proportional flow control valve changed the flowrate immediately without an overshoot or undershoot in flowrate with the requisite recovery time associated with thermal control systems. The flowrates tested spanned a range from 0-1.5 mg/s of iodine, which is sufficient to feed a 200-W Hall effect thruster.

  20. Thermal Characterization of a Hall Effect Thruster

    Science.gov (United States)

    2008-03-01

    Material Curie Temperature Iron 770 °C Nickel 358 °C Cobalt 1130 °C Gadolinium 20 °C Terfenol 380-430 °C Alnico 850 °C Hard Ferrites 400-700...C Barium Ferrite 450 °C Hall Effect thrusters generally use iron magnets with a Curie temperature of 770 °C. Decreasing the magnetic strength

  1. ELECTROSTATIC ION THRUSTERS - TOWARDS PREDICTIVE MODELING

    Directory of Open Access Journals (Sweden)

    Julia Duras

    2015-02-01

    Full Text Available For satellite missions, thrusters have to be qualified in large vacuum vessels to simulate space environment. One caveat of these experiments is the possible  modification of the beam properties due to the interaction of the energetic ions with the  vessel walls. Impinging ions can produce sputtered impurities or secondary  electrons from the wall. These can stream back into the acceleration channel of the  thruster and produce co-deposited layers. Over the long operation time of thousands  of hours, such layers can modify the optimized geometry and induce changes of the ion beam properties, e.g. broadening of the angular distribution and thrust reduction. To study such effects, a Monte Carlo code for the simulation of the interaction of ion thruster beams with vessel  walls was developed. Strategies to overcome sputter limitations by additional baffles are  studied with the help of this Monte-Carlo erosion code.

  2. Multi-Scale Modeling of Plasma Thrusters

    Science.gov (United States)

    Batishchev, Oleg

    2004-11-01

    Plasma thrusters are characterized with multiple spatial and temporal scales, which are due to the intrinsic physical processes such as gas ionization, wall effects and plasma acceleration. Characteristic times for hot plasma and cold gas are differing by 6-7 orders of magnitude. The typical collisional mean-free-paths vary by 3-5 orders along the devices. These make questionable a true self-consistent modeling of the thrusters. The latter is vital to the understanding of complex physics, non-linear dynamics and optimization of the performance. To overcome this problem we propose the following approach. All processes are divided into two groups: fast and slow. The slow ones include gas evolution with known sources and ionization sink. The ionization rate, transport coefficients, energy sources are defined during "fast step". Both processes are linked through external iterations. Multiple spatial scales are handled using moving adaptive mesh. Development and application of this method to the VASIMR helicon plasma source and other thrusters will be discussed. Supported by NASA.

  3. Plume Comparisons between Segmented Channel Hall Thrusters

    Science.gov (United States)

    Niemack, Michael; Staack, David; Raitses, Yevgeny; Fisch, Nathaniel

    2001-10-01

    Angular ion flux plume measurements were taken in several configurations of segmented channel Hall thrusters. The configurations differed by the placement of relatively short rings made from materials with different conductive and secondary electron emission properties along the boron nitride ceramic channel of the thrusters (these have been shown to affect the plume [1]). The ion fluxes are compared with ion trajectory simulations based on plasma potential data acquired with a high speed emissive probe [2]. Preliminary results indicate that in addition to the physical properties of the segments, the plume angle can be strongly affected by the placement of segmented rings relative to the external and internal walls of the channel. [1] Y. Raitses, L. Dorf, A. Litvak and N. J. Fisch, Journal of Applied Physics 88, 1263, 2000 [2] D. Staack, Y. Raitses, N. J. Fisch, Parametric Investigations of Langmuir Probe Induced Perturbations in a Hall Thruster, DPP01 Poster Presentation This work was supported by the U.S. DOE Contract No. DE-ACO2-76-CHO3073.

  4. Adaptive control of ROVs with actuator dynamics and saturation

    Directory of Open Access Journals (Sweden)

    Ola-Erik Fjellstad

    1992-07-01

    Full Text Available A direct model reference adaptive controller (MRAC is derived for an underwater vehicle with significant thruster dynamics and limited thruster power. The reference model decomposition (RMD technique is used to compensate for the thruster dynamics. A reference model adjustment (RMA technique modifying the reference model acceleration is used to avoid thruster saturation. The design methods are simulated for the yawing motion of an underwater vehicle.

  5. Ultrafast Coherent Control and Characterization of Surface Reactions using FELs

    Energy Technology Data Exchange (ETDEWEB)

    Ogasawara, Hirohito; Nordlund, Dennis a Nilsson, Anders; /SLAC, SSRL

    2005-09-30

    The microscopic understanding of reactions at surfaces requires an in-depth knowledge of the dynamics of elementary processes on an ultrafast timescale. This can be accomplished using an ultrafast excitation to initiate a chemical reaction and then probe the progression of the reaction with an ultrashort x-ray pulse from the FEL. There is a great potential to use atom-specific spectroscopy involving core levels to probe the chemical nature, structure and bonding of species on surfaces. The ultrashort electron pulse obtained in the linear accelerator to feed the X-ray FEL can also be used for generation of coherent synchrotron radiation in the low energy THz regime to be used as a pump. This radiation has an energy close to the thermal excitations of low-energy vibrational modes of molecules on surfaces and phonons in substrates. The coherent THz radiation will be an electric field pulse with a certain direction that can collectively manipulate atoms or molecules on surfaces. In this respect a chemical reaction can be initiated by collective atomic motion along a specific reaction coordinate. If the coherent THz radiation is generated from the same source as the X-ray FEL radiation, full-time synchronization for pump-probe experiments will be possible. The combination of THz and X-ray spectroscopy could be a unique opportunity for FEL facilities to conduct ultrafast chemistry studies at surfaces.

  6. STM CONTROL OF CHEMICAL REACTIONS: Single-Molecule Synthesis

    Science.gov (United States)

    Hla, Saw-Wai; Rieder, Karl-Heinz

    2003-10-01

    The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope (STM) tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. Owing to these advances, it has become possible for the basic chemical reaction steps, such as dissociation, diffusion, adsorption, readsorption, and bond-formation processes, to be performed by using the STM tip. Complete sequences of chemical reactions are able to induce at a single-molecule level. New molecules can be constructed from the basic molecular building blocks on a one-molecule-at-a-time basis by using a variety of STM manipulation schemes in a systematic step-by-step manner. These achievements open up entirely new opportunities in nanochemistry and nanochemical technology. In this review, various STM manipulation techniques useful in the single-molecule reaction process are reviewed, and their impact on the future of nanoscience and technology are discussed.

  7. Laser controlled charge-transfer reaction at low temperatures

    CERN Document Server

    Petrov, Alexander; Kotochigova, Svetlana

    2016-01-01

    We study the low-temperature charge transfer reaction between a neutral atom and an ion under the influence of near-resonant laser light. By setting up a multi-channel model with field-dressed states we demonstrate that the reaction rate coefficient can be enhanced by several orders of magnitude with laser intensities of $10^6$ W/cm$^2$ or larger. In addition, depending on laser frequency one can induce a significant enhancement or suppression of the charge-exchange rate coefficient. For our intensities multi-photon processes are not important.

  8. Flex Dynamics Avoidance Control of the NEA Scout Solar Sail Spacecraft's Reaction Control System

    Science.gov (United States)

    Heaton Andrew; Stiltner, Brandon; Diedrich, Benjamin; Becker, Christopher; Orphee, Juan

    2017-01-01

    The Attitude Control System (ACS) is developed for a Near Earth Asteroid (NEA) Scout mission using a solar sail. The NEA-Scout spacecraft is a 6U cubesat with an 86 square-meter solar sail. NEA Scout will launch on Space Launch System (SLS) Exploration Mission 1 (EM-1), currently scheduled to launch in 2018. The spacecraft will rendezvous with a target asteroid after a two year journey, and will conduct science imagery. The solar sail spacecraft ACS consists of three major actuating subsystems: a Reaction Wheel (RW) control system, a Reaction Control System (RCS), and an Adjustable Mass Translator (AMT) system. The three subsystems allow for a wide range of spacecraft attitude control capabilities, needed for the different phases of the NEA-Scout mission. Because the sail is a flexible structure, care must be taken in designing a control system to avoid exciting the structural modes of the sail. This is especially true for the RCS, which uses pulse actuated, cold-gas jets to control the spacecraft's attitude. While the reaction wheels can be commanded smoothly, the RCS jets are simple on-off actuators. Long duration firing of the RCS jets - firings greater than one second - can be thought of as step inputs to the spacecraft's torque. On the other hand, short duration firings - pulses on the order of 0.1 seconds - can be thought of as impulses in the spacecraft's torque. These types of inputs will excite the structural modes of the spacecraft, causing the sail to oscillate. Sail oscillations are undesirable for many reasons. Mainly, these oscillations will feed into the spacecraft attitude sensors and pointing accuracy, and long term oscillations may be undesirable over the lifetime of the solar sail. In order to limit the sail oscillations, an RCS control scheme is being developed to minimize sail excitations. Specifically, an input shaping scheme similar to the method described in Reference 1 will be employed. A detailed description of the RCS control scheme will

  9. Haemostatic effect and tissue reactions of methods and agents used for haemorrhage control in apical surgery

    DEFF Research Database (Denmark)

    Jensen, Simon Storgaard; Yazdi, P M; Hjørting-Hansen, Erik

    2010-01-01

    To compare the haemostatic effect and tissue reactions of different agents and methods used for haemorrhage control in apical surgery.......To compare the haemostatic effect and tissue reactions of different agents and methods used for haemorrhage control in apical surgery....

  10. A high power ion thruster for deep space missions

    Science.gov (United States)

    Polk, James E.; Goebel, Dan M.; Snyder, John S.; Schneider, Analyn C.; Johnson, Lee K.; Sengupta, Anita

    2012-07-01

    The Nuclear Electric Xenon Ion System ion thruster was developed for potential outer planet robotic missions using nuclear electric propulsion (NEP). This engine was designed to operate at power levels ranging from 13 to 28 kW at specific impulses of 6000-8500 s and for burn times of up to 10 years. State-of-the-art performance and life assessment tools were used to design the thruster, which featured 57-cm-diameter carbon-carbon composite grids operating at voltages of 3.5-6.5 kV. Preliminary validation of the thruster performance was accomplished with a laboratory model thruster, while in parallel, a flight-like development model (DM) thruster was completed and two DM thrusters fabricated. The first thruster completed full performance testing and a 2000-h wear test. The second successfully completed vibration tests at the full protoflight levels defined for this NEP program and then passed performance validation testing. The thruster design, performance, and the experimental validation of the design tools are discussed in this paper.

  11. An Investigation into the Spectral Imaging of Hall Thruster Plumes

    Science.gov (United States)

    2015-07-01

    zone shifting to a more upstream location in the discharge channel as observed in Ref. 14 for the BHT -600 thruster likely due to increased electron...to a more upstream location in the discharge channel as observed in Ref. 14 for the BHT -600 thruster likely due to increased electron mobility from

  12. NASA HERMeS Hall Thruster Electrical Configuration Characterization

    Science.gov (United States)

    Peterson, Peter; Kamhawi, Hani; Huang, Wensheng; Yim, John; Herman, Daniel; Williams, George; Gilland, James; Hofer, Richard

    2016-01-01

    NASAs Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) Hall thruster has been the subject of extensive technology maturation in preparation for development into a flight ready propulsion system. Part of the technology maturation was to test the TDU-1 thruster in several ground based electrical configurations to assess the thruster robustness and suitability to successful in-space operation. The ground based electrical configuration testing has recently been demonstrated as an important step in understanding and assessing how a Hall thruster may operate differently in space compared to ground based testing, and to determine the best configuration to conduct development and qualification testing. This presentation will cover the electrical configuration testing of the TDU-1 HERMeS Hall thruster in NASA Glenn Research Centers Vacuum Facility 5. The three electrical configurations examined are the thruster body tied to facility ground, thruster floating, and finally the thruster body electrically tied to cathode common. The TDU-1 HERMeS was configured with two different exit plane boundary conditions, dielectric and conducting, to examine the influence on the electrical configuration characterization.

  13. Ultrafast Coherent Control and Characterization of Surface Reactions using FELs

    CERN Document Server

    Ogasawara, Hirohito; Nordlund, Dennis

    2005-01-01

    The microscopic understanding of surface chemistry requires a detailed understanding of the dynamics of elementary processes at surfaces. The ultrashort electron pulse obtained in the linear accelerator to feed the FEL can be used for generation of coherent synchrotron radiation in the low energy THz regime. With the current parameters for LCLS this corresponds to radiation with energy corresponding to excitations of low-energy vibrational modes of molecules on surfaces or phonons in substrates. The coherent radiation can coherently manipulate atoms or molecules on surfaces. In this respect a chemical reaction can be initiated by coherent atomic motion along a specific reaction coordinate. Since the THz radiation is generated from the same source as the FEL radiation full-time synchronization for pump-probe experiments will be possible. The possibility to perform time-resolved X-ray Emission Spectroscopy (XES) and X-ray Photoelectron Spectroscopy (XPS) measurements as a probe of chemical dynamics is an exciti...

  14. Increasing Slew Performance of Reaction Wheel Attitude Control Systems

    Science.gov (United States)

    2013-09-01

    based software package for solving optimal control problems [21]. A huge advantage of DIDO is that the optimal control problem from Equation (153...Beginner’s Guide to DIDO: A MATLAB Application Package for Solving Optimal Control Problems .” V7.3, Doc. TR-711, Monterey, CA: Elissar, 2007. [22] N. S

  15. Lipase-catalyzed ester exchange reactions in organic media with controlled humidity.

    Science.gov (United States)

    Goderis, H L; Ampe, G; Feyten, M P; Fouwé, B L; Guffens, W M; Van Cauwenbergh, S M; Tobback, P P

    1987-08-05

    Immobilized lipase activity is studied in organic solvent systems of controlled water content under the influence of a variety of reaction parameters, such as temperature, relative humidity, substrate concentrations, and type of fatty acid used. Control of the amount of water in the reaction system was found to be a valuable tool for the orientation of the reaction process and for the determination of the final reaction products. The properties of the immobilized lipase were studied using the interesterification of triolein and palmitic acid as the model system.

  16. Experimental Study of the Plume Characteristics of an Aged Monopropellant Hydrazine Thruster

    Science.gov (United States)

    1979-04-01

    surfaces such as solar panels, thermal control coatings , and optical surfaces can degrade satellite performance. Experimental studies with regard... coated , fused silica lens onto the thruster axial centerline. The port through which the beam passed into the chamber was also made of fused silica. As...copper alone, beeswax melted onto the copper, and SEM quality Microstick ® glue dripped onto the copper and spread by moving the disks to and fro

  17. Azimuthal Spoke Propagation in Hall Effect Thrusters

    Science.gov (United States)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Brown, Daniel L.; Hofer, Richard R.; Polk, James E.

    2013-01-01

    Spokes are azimuthally propagating perturbations in the plasma discharge of Hall Effect Thrusters (HETs) that travel in the E x B direction and have been observed in many different systems. The propagation of azimuthal spokes are investigated in a 6 kW HET known as the H6 using ultra-fast imaging and azimuthally spaced probes. A spoke surface is a 2-D plot of azimuthal light intensity evolution over time calculated from 87,500 frames/s videos. The spoke velocity has been determined using three methods with similar results: manual fitting of diagonal lines on the spoke surface, linear cross-correlation between azimuthal locations and an approximated dispersion relation. The spoke velocity for three discharge voltages (300, 400 and 450 V) and three anode mass flow rates (14.7, 19.5 and 25.2 mg/s) yielded spoke velocities between 1500 and 2200 m/s across a range of normalized magnetic field settings. The spoke velocity was inversely dependent on magnetic field strength for low B-field settings and asymptoted at B-field higher values. The velocities and frequencies are compared to standard drifts and plasma waves such as E x B drift, electrostatic ion cyclotron, magnetosonic and various drift waves. The empirically approximated dispersion relation yielded a characteristic velocity that matched the ion acoustic speed for 5 eV electrons that exist in the near-anode and near-field plume regions of the discharge channel based on internal measurements. Thruster performance has been linked to operating mode where thrust-to-power is maximized when azimuthal spokes are present so investigating the underlying mechanism of spokes will benefit thruster operation.

  18. Marzipan: polymerase chain reaction-driven methods for authenticity control.

    Science.gov (United States)

    Brüning, Philipp; Haase, Ilka; Matissek, Reinhard; Fischer, Markus

    2011-11-23

    According to German food guidelines, almonds are the only oilseed ingredient allowed for the production of marzipan. Persipan is a marzipan surrogate in which the almonds are replaced by apricot or peach kernels. Cross-contamination of marzipan products with persipan may occur if both products are produced using the same production line. Adulterations or dilutions, respectively, of marzipan with other plant-derived products, for example, lupine or pea, have also been found. Almond and apricot plants are closely related. Consequently, classical analytical methods for the identification/differentiation often fail or are not sensitive enough to quantify apricot concentrations below 1%. Polymerase chain reaction (PCR)-based methods have been shown to enable the differentiation of closely related plant species in the past. These methods are characterized by high specificity and low detection limits. Isolation methods were developed and evaluated especially with respect to the matrix marzipan in terms of yield, purity, integrity, and amplificability of the isolated DNA. For the reliable detection of apricot, peach, pea, bean, lupine, soy, cashew, pistachio, and chickpea, qualitative standard and duplex PCR methods were developed and established. The applicability of these methods was tested by cross-reaction studies and analysis of spiked raw pastes. Contaminations at the level of 0.1% could be detected.

  19. Geochemical controls on shale groundwaters: Results of reaction path modeling

    Energy Technology Data Exchange (ETDEWEB)

    Von Damm, K.L.; VandenBrook, A.J.

    1989-03-01

    The EQ3NR/EQ6 geochemical modeling code was used to simulate the reaction of several shale mineralogies with different groundwater compositions in order to elucidate changes that may occur in both the groundwater compositions, and rock mineralogies and compositions under conditions which may be encountered in a high-level radioactive waste repository. Shales with primarily illitic or smectitic compositions were the focus of this study. The reactions were run at the ambient temperatures of the groundwaters and to temperatures as high as 250/degree/C, the approximate temperature maximum expected in a repository. All modeling assumed that equilibrium was achieved and treated the rock and water assemblage as a closed system. Graphite was used as a proxy mineral for organic matter in the shales. The results show that the presence of even a very small amount of reducing mineral has a large influence on the redox state of the groundwaters, and that either pyrite or graphite provides essentially the same results, with slight differences in dissolved C, Fe and S concentrations. The thermodynamic data base is inadequate at the present time to fully evaluate the speciation of dissolved carbon, due to the paucity of thermodynamic data for organic compounds. In the illitic cases the groundwaters resulting from interaction at elevated temperatures are acid, while the smectitic cases remain alkaline, although the final equilibrium mineral assemblages are quite similar. 10 refs., 8 figs., 15 tabs.

  20. Micro-Discharge Micro-Thruster

    Science.gov (United States)

    2005-06-01

    breakdown at the maximum applied voltage (900 V) in Argon. The back side of the Paschen curve for Ar occurs at a pressure-length (P·d) product of less than...significant capacitance to ground from either lead (~ 100 nF). As small as this is, it had a profound effect on the discharge (see next section). A more space... effect in most thrusters even in the 100 Watt class. For a micro-discharge, even a stray coupling capacitance 50 pF observed for the power leads

  1. [Software and hardware design for the temperature control system of quantitative polymerase chain reaction].

    Science.gov (United States)

    Qiu, Xian-bo; Yuan, Jing-qi; Li, Qi

    2005-07-01

    A temperature control system for quantitive polymerase chain reaction (PCR) is presented in the paper with both software and hardware configuration. The performance of the control system has been improved by optimizing the software and hardware design according to the system's properties. The control system has been proven to have a good repeatability and reliability as well as high control precision.

  2. Temperature Control System for Biochemical Reactions in Microchip-Based Devices

    Institute of Scientific and Technical Information of China (English)

    荆高山; 张坚; 朱小山; 冯继宏; 谭智敏; 刘理天; 程京

    2001-01-01

    A silicon-glass chip based microreactor has been designed and fabricated for biochemical reactions such as polymerase chain reactions (PCR). The chip based microreactor has integrated resistive heating elements. The computer-controlled temperature control system is highly reliable with precise temperature control, excellent temperature uniformity, and rapid heating and cooling capabilities. The development of the microreaction system is an important step towards the construction of a lab-on-a-chip system.

  3. Heterogeneous nucleation - current transients under chemical reaction control

    CERN Document Server

    D'Ajello-Tettamanzy, P C; Kipervaser, Z G S

    2002-01-01

    Heterogeneous nucleation on catalytic surfaces plunged into a fluid is described through a stochastic model. To generate this non-equilibrium process we assume that the turn on of a electrostatic potential triggers a complex dynamics that includes a free Brownian motion, a reaction kinetic and a stimulated migration before the final adhesion of ions on the surface (electrode). At, when the potential is switched on, the spatial symmetry is broken and a two-stage process is developed. First the ion undergoes a change in its electrochemical character (at some region of the space) and then reacts at some specific points to stick together on the surface. The continuous addition of ions develops a material deposit connected to the current transient signals measured in electrochemical deposition processes. Unlike current models found in the literature, this procedure avoids the computation of the area covered by the diffusion zones, allowing a formalism skill to describe equally well the absorption of ions by channe...

  4. Impact of Excitation and Reaction Processes on FRC Thruster Efficiency

    Science.gov (United States)

    2013-06-01

    bimodality essentially disappears after about 50 µs, but the ion distribution function is still visibly non - Maxwellian even after 1 ms. The neutral atom...manifested in differences in their translational temperatures as well as in non - Maxwellian distribution functions. The elector and ion velocity...electron, and neutral temperatures strongly differ, and the ion and neutral gas distribution function is strongly non - Maxwellian . The electron velocity

  5. Social Reactions to Sexual Assault Disclosure and Problem Drinking: Mediating Effects of Perceived Control and PTSD

    OpenAIRE

    Peter-Hagene, Liana C.; Ullman, Sarah E.

    2013-01-01

    Sexual assault survivors receive various positive and negative social reactions to assault disclosures, yet little is known about mechanisms linking these social reactions to posttraumatic stress disorder (PTSD) symptoms and problem drinking. Data from a large, diverse sample of women who had experienced adult sexual assault was analyzed with structural equation modeling to test a theoretical model of the relationships between specific negative social reactions (e.g., controlling, infantilizi...

  6. Controlling the redox reaction at the interface between sealing glasses and Cr-containing interconnect: Effect of competitive reaction

    Science.gov (United States)

    Chen, Shunrun; Lin, Jianxin; Yang, Hsiwen; Tang, Dian; Zhang, Teng

    2014-12-01

    In this paper, MnO2 is added to CaO-SrO-B2O3-SiO2 sealing system to control the redox glass/metal interfacial reaction in Solid Oxide Fuel Cells. The effect of MnO2 dopant on the valance states of Mn ions in glasses, the glass structure and glass/metal interfacial reaction is systematically investigated. The quenched glasses contain Mn2+ ion only; whereas, the Mn3+ content in glasses, held at 600 °C for 9 h, increases with increasing MnO2 dopant. The good bondage can be observed at the interfaces between Crofer 22APU and glass containing 6 mol % MnO2, held at 700 °C for 500 h. The competitive reaction reduces the redox chromate formation by consuming the oxygen at the glass/metal interface. In addition, the competitive reaction results in the formation of a continuous Mn-Cr oxide scale at the glass/metal interface, which is helpful for reducing the further diffusion of Cr from metallic interconnect to glass.

  7. Controlled state-to-state atom-exchange reaction in an ultracold atom-dimer mixture

    CERN Document Server

    Rui, Jun; Liu, Lan; Zhang, De-Chao; Liu, Ya-Xiong; Nan, Jue; Zhao, Bo; Pan, Jian-Wei

    2016-01-01

    Ultracold molecules offer remarkable opportunities to study chemical reactions at nearly zero temperature. Although significant progresses have been achieved in exploring ultracold bimolecular reactions, the investigations are usually limited to measurements of the overall loss rates of the reactants. Detection of the reaction products will shed new light on understanding the reaction mechanism and provide a unique opportunity to study the state-to-state reaction dynamics. Here we report on the direct observation of an exoergic atom-exchange reaction in an ultracold atom-dimer mixture. Both the atom and molecule products are observed and the quantum states are characterized. By changing the magnetic field, the reaction can be switched on or off, and the reaction rate can be controlled. The reaction is efficient and we have measured a state-to-state reaction rate of up to $1.1(3)\\times10^{-9}$cm$^{3}/$s from the time evolution of the reactants and products. Our work represents the realization of a controlled q...

  8. Global model of an iodine gridded plasma thruster

    Science.gov (United States)

    Grondein, P.; Lafleur, T.; Chabert, P.; Aanesland, A.

    2016-03-01

    Most state-of-the-art electric space propulsion systems such as gridded and Hall effect thrusters use xenon as the propellant gas. However, xenon is very rare, expensive to produce, and used in a number of competing industrial applications. Alternatives to xenon are currently being investigated, and iodine has emerged as a potential candidate. Its lower cost and larger availability, its solid state at standard temperature and pressure, its low vapour pressure and its low ionization potential make it an attractive option. In this work, we compare the performances of a gridded ion thruster operating separately with iodine and xenon, under otherwise identical conditions using a global model. The thruster discharge properties such as neutral, ion, and electron densities and electron temperature are calculated, as well as the thruster performance parameters such as thrust, specific impulse, and system efficiencies. For similar operating conditions, representative of realistic thrusters, the model predicts similar thrust levels and performances for both iodine and xenon. The thruster efficiency is however slightly higher for iodine compared with xenon, due to its lower ionization potential. This demonstrates that iodine could be a viable alternative propellant for gridded plasma thrusters.

  9. High-Power, High-Thrust Ion Thruster (HPHTion)

    Science.gov (United States)

    Peterson, Peter Y.

    2015-01-01

    Advances in high-power photovoltaic technology have enabled the possibility of reasonably sized, high-specific power solar arrays. At high specific powers, power levels ranging from 50 to several hundred kilowatts are feasible. Ion thrusters offer long life and overall high efficiency (typically greater than 70 percent efficiency). In Phase I, the team at ElectroDynamic Applications, Inc., built a 25-kW, 50-cm ion thruster discharge chamber and fabricated a laboratory model. This was in response to the need for a single, high-powered engine to fill the gulf between the 7-kW NASA's Evolutionary Xenon Thruster (NEXT) system and a notional 25-kW engine. The Phase II project matured the laboratory model into a protoengineering model ion thruster. This involved the evolution of the discharge chamber to a high-performance thruster by performance testing and characterization via simulated and full beam extraction testing. Through such testing, the team optimized the design and built a protoengineering model thruster. Coupled with gridded ion thruster technology, this technology can enable a wide range of missions, including ambitious near-Earth NASA missions, Department of Defense missions, and commercial satellite activities.

  10. NASA's Evolutionary Xenon Thruster: The NEXT Ion Propulsion System for Solar System Exploration

    Science.gov (United States)

    Pencil, Eric J.; Benson, Scott W.

    2008-01-01

    This viewgraph presentation reviews NASA s Evolutionary Xenon Thruster (NEXT) Ion Propulsion system. The NEXT project is developing a solar electric ion propulsion system. The NEXT project is advancing the capability of ion propulsion to meet NASA robotic science mission needs. The NEXT system is planned to significantly improve performance over the state of the art electric propulsion systems, such as NASA Solar Electric Propulsion Technology Application Readiness (NSTAR). The status of NEXT development is reviewed, including information on the NEXT Thruster, the power processing unit, the propellant management system (PMS), the digital control interface unit, and the gimbal. Block diagrams NEXT system are presented. Also a review of the lessons learned from the Dawn and NSTAR systems is provided. In summary the NEXT project activities through 2007 have brought next-generation ion propulsion technology to a sufficient maturity level.

  11. Study of monopropellants for electrothermal thrusters. Evaluation test program task summary report

    Science.gov (United States)

    Kuenzly, J. D.

    1974-01-01

    An electrothermal thruster designed for operation with MIL-grade hydrazine is suitable for operation with propellants having lower freezing points. These propellants are 76% hydrazine - 24% hydrazine azide, Aerozine-50, 50% hydrazine - 50% monomethylydrazine, and a TRW-formulated mixture of 35% hydrazine - 50% monomethylhydrane - 15% ammonia. A steady-state specific impulse of 200 sec was exceeded by all propellants. A pulse-mode value of 175 sec specific impulse was exceeded by the azide blend for pulse widths greater than 50 ms and was met by the carbonaceous propellants for pulse widths greater than 100 ms. Longer residence times were required for the carbonaceous propellants; the original thruster design was modified by increasing the characteristic chamber length and density of screen packing. A substantial amount of thermal energy must be supplied to initiate decomposition of propellants containing unsymmetrical-dimethylhydrazine and monomethylhydrazine. The rate controlling factor appeared to be the endothermic removal of methyl radicals.

  12. Fixed Point Transformations Based Iterative Control of a Polymerization Reaction

    Science.gov (United States)

    Tar, József K.; Rudas, Imre J.

    As a paradigm of strongly coupled non-linear multi-variable dynamic systems the mathematical model of the free-radical polymerization of methyl-metachrylate with azobis (isobutyro-nitrile) as an initiator and toluene as a solvent taking place in a jacketed Continuous Stirred Tank Reactor (CSTR) is considered. In the adaptive control of this system only a single input variable is used as the control signal (the process input, i.e. dimensionless volumetric flow rate of the initiator), and a single output variable is observed (the process output, i.e. the number-average molecular weight of the polymer). Simulation examples illustrate that on the basis of a very rough and primitive model consisting of two scalar variables various fixed-point transformations based convergent iterations result in a novel, sophisticated adaptive control.

  13. Performance and flow characteristics of MHD seawater thruster

    Energy Technology Data Exchange (ETDEWEB)

    Doss, E.D.

    1990-01-01

    The main goal of the research is to investigate the effects of strong magnetic fields on the electrical and flow fields inside MHD thrusters. The results of this study is important in the assessment of the feasibility of MHD seawater propulsion for the Navy. To accomplish this goal a three-dimensional fluid flow computer model has been developed and applied to study the concept of MHD seawater propulsion. The effects of strong magnetic fields on the current and electric fields inside the MHD thruster and their interaction with the flow fields, particularly those in the boundary layers, have been investigated. The results of the three-dimensional computations indicate that the velocity profiles are flatter over the sidewalls of the thruster walls in comparison to the velocity profiles over the electrode walls. These nonuniformities in the flow fields give rise to nonuniform distribution of the skin friction along the walls of the thrusters, where higher values are predicted over the sidewalls relative to those over the electrode walls. Also, a parametric study has been performed using the three-dimensional MHD flow model to analyze the performance of continuous electrode seawater thrusters under different operating parameters. The effects of these parameters on the fluid flow characteristics, and on the thruster efficiency have been investigated. Those parameters include the magnetic field (10--20 T), thruster diameter, surface roughness, flow velocity, and the electric load factor. The results show also that the thruster performance improves with the strength of the magnetic field and thruster diameter, and the efficiency decreases with the flow velocity and surface roughness.

  14. Femtosecond laser induced and controlled chemical reaction of carbon monoxide and hydrogen

    CSIR Research Space (South Africa)

    Du Plessis, A

    2011-07-01

    Full Text Available Results from experiments aimed at bimolecular chemical reaction control of CO and H2 at room temperature and pressure, without any catalyst, using shaped femtosecond laser pulses are presented. A stable reaction product (CO2) was measured after...

  15. Transient tests on an MHD thruster

    Energy Technology Data Exchange (ETDEWEB)

    Pierson, E.S. (Purdue Univ., Hammond, IN (United States). Dept. of Engineering); Libera, J.; Petrick, M. (Argonne National Lab., IL (United States). Energy Systems Div.)

    1993-01-01

    Three different types of transient tests were made -- coast downs to zero voltage and current under open circuit and short circuit conditions, reverses where the applied voltage was reversed to the same or a different value, and jumps where the voltage applied to the thruster was increased without a change in polarity. Most except the coast downs were dons both quickly (voltage changes as fast as possible) and slowly (6 s to complete the voltage change). A few slower (12 s) transients were done. Transient runs were made for water conductivities of 16.2 and 5.09 S/m. In all cases steady-state conditions were established and several seconds of data taken before initiating the transients. Data were measured every 0.75 to 1 .5 second over the time interval of interest. Particular attention was paid to looking for evidence of gas bubbles, and to the chance of the voltage profiles between the electrodes. The data are interpreted based on the behavior of the power supply and the thruster.

  16. Optimisation of a quantum pair space thruster

    Directory of Open Access Journals (Sweden)

    Valeriu DRAGAN

    2012-06-01

    Full Text Available The paper addresses the problem of propulsion for long term space missions. Traditionally a space propulsion unit has a propellant mass which is ejected trough a nozzle to generate thrust; this is also the case with inert gases energized by an on-board power unit. Unconventional methods for propulsion include high energy LASERs that rely on the momentum of photons to generate thrust. Anti-matter has also been proposed for energy storage. Although the momentum of ejected gas is significantly higher, the LASER propulsion offers the perspective of unlimited operational time – provided there is a power source. The paper will propose the use of the quantum pair formation for generating a working mass, this is different than conventional anti-matter thrusters since the material particles generated are used as propellant not as energy storage.Two methods will be compared: LASER and positron-electron, quantum pair formation. The latter will be shown to offer better momentum above certain energy levels.For the demonstrations an analytical solution is obtained and provided in the form of various coefficients. The implications are, for now, theoretical however the practicality of an optimized thruster using such particles is not to be neglected for long term space missions.

  17. Adaptive variable structure control based on backstepping for spacecraft with reaction wheels during attitude maneuver

    Institute of Scientific and Technical Information of China (English)

    SONG Bin; MA Guang-fu; LI Chuan-jiang

    2009-01-01

    An adaptive variable structure control method based on backstepping is proposed for the attitude maneuver problem of rigid spacecraft with reaction wheel dynamics in the presence of uncertain inertia matrix and external disturbances. The proposed control approach is a combination of the backstepping and the adaptive variable structure control. The cascaded structure of the attitude maneuver control system with reaction wheel dynamics gives the advantage for applying the backstepping method to construct Lyapunov functions. The robust stability to external disturbances and parametric uncertainty is guaranteed by the adaptive variable structure control. To validate the proposed control algorithm, numerical simulations using the proposed approach are performed for the attitude maneuver mission of rigid spacecraft with a configuration consisting of four reaction wheels for actuator and three magnetorquers for momentum unloading. Simulation results verify the effectiveness of the proposed control algorithm.

  18. Method of controlled reduction of nitroaromatics by enzymatic reaction with oxygen sensitive nitroreductase enzymes

    Science.gov (United States)

    Shah, Manish M.; Campbell, James A.

    1998-01-01

    A method for the controlled reduction of nitroaromatic compounds such as nitrobenzene and 2,4,6-trinitrotoluene by enzymatic reaction with oxygen sensitive nitroreductase enzymes, such as ferredoxin NADP oxidoreductase.

  19. Self consistent kinetic simulations of SPT and HEMP thrusters including the near-field plume region

    CERN Document Server

    Matyash, K; Mutzke, A; Kalentev, O; Taccogna, F; Koch, N; Schirra, M

    2009-01-01

    The Particle-in-Cell (PIC) method was used to study two different ion thruster concepts - Stationary Plasma Thrusters (SPT) and High Efficiency Multistage Plasma Thrusters (HEMP-T), in particular the plasma properties in the discharge chamber due to the different magnetic field configurations. Special attention was paid to the simulation of plasma particle fluxes on the thrusters channel surfaces. In both cases, PIC proved itself as a powerful tool, delivering important insight into the basic physics of the different thruster concepts. The simulations demonstrated that the new HEMP thruster concept allows for a high thermal efficiency due to both minimal energy dissipation and high acceleration efficiency. In the HEMP thruster the plasma contact to the wall is limited only to very small areas of the magnetic field cusps, which results in much smaller ion energy flux to the thruster channel surface as compared to SPT. The erosion yields for dielectric discharge channel walls of SPT and HEMP thrusters were calc...

  20. Experimental Investigation of a Direct-drive Hall Thruster and Solar Array System at Power Levels up to 10 kW

    Science.gov (United States)

    Snyder, John S.; Brophy, John R.; Hofer, Richard R.; Goebel, Dan M.; Katz, Ira

    2012-01-01

    As NASA considers future exploration missions, high-power solar-electric propulsion (SEP) plays a prominent role in achieving many mission goals. Studies of high-power SEP systems (i.e. tens to hundreds of kilowatts) suggest that significant mass savings may be realized by implementing a direct-drive power system, so NASA recently established the National Direct-Drive Testbed to examine technical issues identified by previous investigations. The testbed includes a 12-kW solar array and power control station designed to power single and multiple Hall thrusters over a wide range of voltages and currents. In this paper, single Hall thruster operation directly from solar array output at discharge voltages of 200 to 450 V and discharge powers of 1 to 10 kW is reported. Hall thruster control and operation is shown to be simple and no different than for operation on conventional power supplies. Thruster and power system electrical oscillations were investigated over a large range of operating conditions and with different filter capacitances. Thruster oscillations were the same as for conventional power supplies, did not adversely affect solar array operation, and were independent of filter capacitance from 8 to 80 ?F. Solar array current and voltage oscillations were very small compared to their mean values and showed a modest dependence on capacitor size. No instabilities or anomalous behavior were observed in the thruster or power system at any operating condition investigated, including near and at the array peak power point. Thruster startup using the anode propellant flow as the power 'switch' was shown to be simple and reliable with system transients mitigated by the proper selection of filter capacitance size. Shutdown via cutoff of propellant flow was also demonstrated. A simple electrical circuit model was developed and is shown to have good agreement with the experimental data.

  1. General Attitude Control Algorithm for Spacecraft Equipped with Star Camera and Reaction Wheels

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    A configuration consisting of a star camera, four reaction wheels and magnetorquers for momentum unloading has become standard for many spacecraft missions. This popularity has motivated numerous agencies and private companies to initiate work on the design of an imbedded attitude control system...... realized on an integrated circuit. This paper considers two issues: slew maneuver with a feature of avoiding direct exposure of the camera's CCD chip to the Sun %, three-axis attitude control and optimal control torque distribution in a reaction wheel assembly. The attitude controller is synthesized...

  2. Controlled Reactions between Ultracold Alkali and Metastable Helium Atoms

    CERN Document Server

    Flores, Adonis Silva; Knoop, Steven

    2016-01-01

    In an ultracold, optically trapped mixture of $^{87}$Rb and metastable triplet $^4$He atoms we have studied trap loss for different spin-state combinations, for which interspecies Penning ionization is the main two-body loss process. We observe long trapping lifetimes for the purely quartet spin-state combination, indicating strong suppression of Penning ionization loss by at least two orders of magnitude. For the other spin-mixtures we observe short lifetimes that depend linearly on the doublet character of the entrance channel. We compare the extracted loss rate coefficient with recent predictions of multichannel quantum-defect theory for reactive collisions involving a strong exothermic loss channel and find near-universal loss for doublet scattering. Our work demonstrates control of reactive collisions by internal atomic state preparation, which also implies magnetic field tunability.

  3. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    Science.gov (United States)

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  4. Impact of nozzle separation on the plumes of two parallel thrusters

    Science.gov (United States)

    Grabe, Martin; Dettleff, Georg; Hannemann, Klaus

    2016-11-01

    Two identical, interacting plumes emanating from model thrusters with parallel axes separated from 50 to 150 throat diameters are studied numerically. The nozzle throat Reynolds number is set to nearly 15, 000 to match that of a small bi-propellant attitude control thruster, but the simulated gas is nitrogen with a stagnation temperature of 300 K. The near-isentropic, dense plume core is computed with the DLR Navier-Stokes solver TAU and the conditions at a suitably defined interface are then used on the inflow boundary of a separately conducted direct simulation Monte Carlo (DSMC) simulation. The results are shown to agree favorably with particle flux measurements performed in the DLR high-vacuum plume test facility for chemical thrusters (STG-CT). Varying the nozzle separation distance alters the degree of rarefaction in the interaction plane, and by tagging DSMC particles according to their origin, the effect on the individual plume may be investigated. The impact of nozzle axis separation on mass flux along the line formed by the intersecting planes of symmetry is compared to the case of two equal superposed (i. e. non-interfering) plumes.

  5. A cavity ring-down spectroscopy sensor for real-time Hall thruster erosion measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lee, B. C. [Physics Department, Colorado State University, Fort Collins, Colorado 80521 (United States); Huang, W. [NASA Glenn Research Center, 2100 Brookpark Rd., Cleveland, Ohio 44135 (United States); Tao, L.; Yamamoto, N.; Yalin, A. P., E-mail: ayalin@engr.colostate.edu [Mechanical Engineering Department, Colorado State University, Fort Collins, Colorado 80521 (United States); Gallimore, A. D. [Aerospace Engineering Department, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2014-05-15

    A continuous-wave cavity ring-down spectroscopy sensor for real-time measurements of sputtered boron from Hall thrusters has been developed. The sensor uses a continuous-wave frequency-quadrupled diode laser at 250 nm to probe ground state atomic boron sputtered from the boron nitride insulating channel. Validation results from a controlled setup using an ion beam and target showed good agreement with a simple finite-element model. Application of the sensor for measurements of two Hall thrusters, the H6 and SPT-70, is described. The H6 was tested at power levels ranging from 1.5 to 10 kW. Peak boron densities of 10 ± 2 × 10{sup 14} m{sup −3} were measured in the thruster plume, and the estimated eroded channel volume agreed within a factor of 2 of profilometry. The SPT-70 was tested at 600 and 660 W, yielding peak boron densities of 7.2 ± 1.1 × 10{sup 14} m{sup −3}, and the estimated erosion rate agreed within ∼20% of profilometry. Technical challenges associated with operating a high-finesse cavity in the presence of energetic plasma are also discussed.

  6. Development Status of Power Processing Unit for 250mN-Class Hall Thruster

    Science.gov (United States)

    Osuga, H.; Suzuki, K.; Ozaki, T.; Nakagawa, T.; Suga, I.; Tamida, T.; Akuzawa, Y.; Suzuki, H.; Soga, Y.; Furuichi, T.; Maki, S.; Matui, K.

    2008-09-01

    Institute for Unmanned Space Experiment Free Flyer (USEF) and Mitsubishi Electric Corporation (MELCO) are developing the next generation ion engine system under the sponsorship of Ministry of Economy, Trade and Industry (METI) within six years. The system requirement specifications are a thrust level of over 250mN and specific impulse of over 1500 sec with a less than 5kW electric power supply, and a lifetime of over 3,000 hours. These target specifications required the development of both a Hall Thruster and a Power Processing Unit (PPU). In the 2007 fiscal year, the PPU called Second Engineering Model (EM2) consist of all power supplies was a model for the Hall Thruster system. The EM2 PPU showed the discharge efficiency was over 96.2% for 250V and 350V at output power between 1.8kW to 4.5kW. And also the Hall Thruster could start up quickly and smoothly to control the discharge voltage, the inner magnet current, the outer magnet current and the xenon flow rate. This paper reports on the design and test results of the EM2 PPU.

  7. 20mN, Variable Specific Impulse Colloid Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — During Phase I, Busek designed and manufactured an electrospray emitter capable of generating 20 mN in a 7" x 7" x 1.7" package. The thruster consists of nine...

  8. 20mN, Variable Specific Impulse Colloid Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Colloid thrusters have long been known for their exceptional thrust efficiency and ability to operate over a range of specific impulse due to easily variable...

  9. A High Performance Cathode Heater for Hall Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High current hollow cathodes are the baseline electron source for next generation high power Hall thrusters. Currently for electron sources providing current levels...

  10. High Throughput Hall Thruster for Small Spacecraft Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek Co. Inc. proposes to develop a high throughput, nominal 100 W Hall Effect Thruster (HET). This HET will be sized for small spacecraft (< 180 kg), including...

  11. Magnesium Hall Thruster for Solar System Exploration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovation being developed in this program is a Mg Hall Effect Thruster system that would open the door for In-Situ Resource Utilization based solar system...

  12. Plume Characterization of Busek 600W Hall Thruster

    Science.gov (United States)

    2012-03-09

    Dr. William A. Hargus Jr. (Member) Date iv Abstract The BHT -600W thruster has a high potential to place on various commercial and...Thrust Measurement ........................................................................................71 A. BHT -200W...71 B. BHT -600W’s Performance

  13. Radio Frequency Micro Ion Thruster for Precision Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop radio frequency discharge, gridded micro-ion thruster that produces sub-mN thrust precisely adjustable over a wide dynamic thrust range....

  14. Radio Frequency Micro Ion Thruster for Precision Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to continue development of an engineering model radio frequency discharge, gridded micro ion thruster that produces sub-mN to mN thrust precisely...

  15. High Input Voltage Hall Thruster Discharge Converter Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall scope of this Phase I/II effort is the development of a high efficiency 15kW (nominal) Hall thruster discharge converter. In Phase I, Busek Co. Inc. will...

  16. High Throughput Hall Thruster for Small Spacecraft Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek is developing a high throughput nominal 100-W Hall Effect Thruster. This device is well sized for spacecraft ranging in size from several tens of kilograms to...

  17. Modeling Common Cause Failures of Thrusters on ISS Visiting Vehicles

    Science.gov (United States)

    Haught, Megan

    2014-01-01

    This paper discusses the methodology used to model common cause failures of thrusters on the International Space Station (ISS) Visiting Vehicles. The ISS Visiting Vehicles each have as many as 32 thrusters, whose redundancy makes them susceptible to common cause failures. The Global Alpha Model (as described in NUREG/CR-5485) can be used to represent the system common cause contribution, but NUREG/CR-5496 supplies global alpha parameters for groups only up to size six. Because of the large number of redundant thrusters on each vehicle, regression is used to determine parameter values for groups of size larger than six. An additional challenge is that Visiting Vehicle thruster failures must occur in specific combinations in order to fail the propulsion system; not all failure groups of a certain size are critical.

  18. Three Phase Resonant DC Power Converter for Ion Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The new generation of, high performance electric propulsion missions will require high mass throughput and most likely the use of grided ion thruster equipped with...

  19. Magnesium Hall Thruster for Solar System Exploration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to prove the feasibility of a Mg Hall effect thruster system that would open the door for In-Situ Resource Utilization (ISRU) based solar system...

  20. Long Life Cold Cathodes for Hall effect Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An electron source incorporating long life, high current density cold cathodes inside a microchannel plate for use with ion thrusters is proposed. Cathode lifetime...

  1. Near-Term Laser Launch Capability: The Heat Exchanger Thruster

    Science.gov (United States)

    Kare, Jordin T.

    2003-05-01

    The heat exchanger (HX) thruster concept uses a lightweight (up to 1 MW/kg) flat-plate heat exchanger to couple laser energy into flowing hydrogen. Hot gas is exhausted via a conventional nozzle to generate thrust. The HX thruster has several advantages over ablative thrusters, including high efficiency, design flexibility, and operation with any type of laser. Operating the heat exchanger at a modest exhaust temperature, nominally 1000 C, allows it to be fabricated cheaply, while providing sufficient specific impulse (~600 seconds) for a single-stage vehicle to reach orbit with a useful payload; a nominal vehicle design is described. The HX thruster is also comparatively easy to develop and test, and offers an extremely promising route to near-term demonstration of laser launch.

  2. Four Thruster Microfluidic Electrospray Propulsion (MEP) Cubesat Board Demonstration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Cubesat Microfluidic Electrospray Propulsion (MEP) system module prototype will be designed, built and tested to demonstrate that a four MEP thruster system can...

  3. Energetics and control of ultracold isotope-exchange reactions between heteronuclear dimers in external fields

    CERN Document Server

    Tomza, Michał

    2015-01-01

    We show that isotope-exchange reactions between ground-state alkali-metal, alkaline-earth-metal, and lanthanide heteronuclear dimers consisting of two isotopes of the same atom are exothermic with an energy change in the range of 1-8000$\\,$MHz thus resulting in cold or ultracold products. For these chemical reactions there are only one rovibrational and at most several hyperfine possible product states. The number and energetics of open and closed reactive channels can be controlled by the laser and magnetic fields. The exothermic isotope-exchange reactions can be tuned to become endothermic by employing a laser-induced state-selective Stark shift control thus providing a ground for testing models of the chemical reactivity. The present proposal opens the way for studying the state-to-state dynamics of ultracold chemical reactions beyond the universal limit with a meaningful control over quantum states of both reactants and products.

  4. Energetics and Control of Ultracold Isotope-Exchange Reactions between Heteronuclear Dimers in External Fields

    Science.gov (United States)

    Tomza, Michał

    2015-08-01

    We show that isotope-exchange reactions between ground-state alkali-metal, alkaline-earth-metal, and lanthanide heteronuclear dimers consisting of two isotopes of the same atom are exothermic with an energy change in the range of 1-8000 MHz, thus resulting in cold or ultracold products. For these chemical reactions, there are only one rovibrational and at most several hyperfine possible product states. The number and energetics of open and closed reactive channels can be controlled by the laser and magnetic fields. We suggest a laser-induced isotope- and state-selective Stark shift control to tune the exothermic isotope-exchange reactions to become endothermic, thus providing the ground for testing models of the chemical reactivity. The present proposal opens the way for studying the state-to-state dynamics of ultracold chemical reactions beyond the universal limit with a meaningful control over the quantum states of both reactants and products.

  5. Preliminary Results of Plasma Flow Measurements in a 2 KW Segmented Hall Thruster

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses; D. Staack; A. Dunaevsky; L. Dorf; N.J. Fisch

    2003-03-01

    A 2-kW Hall thruster was developed, built, and operated in an upgraded vacuum facility. The thruster performance and parameters of the plasma flow were measured by new diagnostics for plume measurements and plasma measurements inside the thruster channel. The thruster demonstrated efficient operation in terms of propellant and current utilization efficiencies in the input power range of 0.5-3.5 kW. Preliminary measurements of the ion energy spectra from the thruster axis region and the distribution of plasma parameters in the vicinity of the thruster exit are reported.

  6. Laser-Driven Mini-Thrusters

    Science.gov (United States)

    Sterling, Enrique; Lin, Jun; Sinko, John; Kodgis, Lisa; Porter, Simon; Pakhomov, Andrew V.; Larson, C. William; Mead, Franklin B.

    2006-05-01

    Laser-driven mini-thrusters were studied using Delrin® and PVC (Delrin® is a registered trademark of DuPont) as propellants. TEA CO2 laser (λ = 10.6 μm) was used as a driving laser. Coupling coefficients were deduced from two independent techniques: force-time curves measured with a piezoelectric sensor and ballistic pendulum. Time-resolved ICCD images of the expanding plasma and combustion products were analyzed in order to determine the main process that generates the thrust. The measurements were also performed in a nitrogen atmosphere in order to test the combustion effects on thrust. A pinhole transmission experiment was performed for the study of the cut-off time when the ablation/air breakdown plasma becomes opaque to the incoming laser pulse.

  7. Low-Mass, Low-Power Hall Thruster System

    Science.gov (United States)

    Pote, Bruce

    2015-01-01

    NASA is developing an electric propulsion system capable of producing 20 mN thrust with input power up to 1,000 W and specific impulse ranging from 1,600 to 3,500 seconds. The key technical challenge is the target mass of 1 kg for the thruster and 2 kg for the power processing unit (PPU). In Phase I, Busek Company, Inc., developed an overall subsystem design for the thruster/cathode, PPU, and xenon feed system. This project demonstrated the feasibility of a low-mass power processing architecture that replaces four of the DC-DC converters of a typical PPU with a single multifunctional converter and a low-mass Hall thruster design employing permanent magnets. In Phase II, the team developed an engineering prototype model of its low-mass BHT-600 Hall thruster system, with the primary focus on the low-mass PPU and thruster. The goal was to develop an electric propulsion thruster with the appropriate specific impulse and propellant throughput to enable radioisotope electric propulsion (REP). This is important because REP offers the benefits of nuclear electric propulsion without the need for an excessively large spacecraft and power system.

  8. Performance Evaluation of the Prototype Model NEXT Ion Thruster

    Science.gov (United States)

    Herman, Daniel A.; Soulas, George C.; Patterson, Michael J.

    2008-01-01

    The performance testing results of the first prototype model NEXT ion engine, PM1, are presented. The NEXT program has developed the next generation ion propulsion system to enhance and enable Discovery, New Frontiers, and Flagship-type NASA missions. The PM1 thruster exhibits operational behavior consistent with its predecessors, the engineering model thrusters, with substantial mass savings, enhanced thermal margins, and design improvements for environmental testing compliance. The dry mass of PM1 is 12.7 kg. Modifications made in the thruster design have resulted in improved performance and operating margins, as anticipated. PM1 beginning-of-life performance satisfies all of the electric propulsion thruster mission-derived technical requirements. It demonstrates a wide range of throttleability by processing input power levels from 0.5 to 6.9 kW. At 6.9 kW, the PM1 thruster demonstrates specific impulse of 4190 s, 237 mN of thrust, and a thrust efficiency of 0.71. The flat beam profile, flatness parameters vary from 0.66 at low-power to 0.88 at full-power, and advanced ion optics reduce localized accelerator grid erosion and increases margins for electron backstreaming, impingement-limited voltage, and screen grid ion transparency. The thruster throughput capability is predicted to exceed 750 kg of xenon, an equivalent of 36,500 hr of continuous operation at the full-power operating condition.

  9. Thrust Stand Measurements of a Conical Inductive Pulsed Plasma Thruster

    Science.gov (United States)

    Hallock, Ashley K.; Polzin, Kurt A.

    2013-01-01

    Inductive Pulsed Plasma Thrusters (iPPT) spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current Propellant is accelerated and expelled at a high exhaust velocity (O(10 -- 100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. A conical coil geometry may offer higher propellant utilization efficiency over that of a at inductive coil, however an increase in propellant utilization may be met with a decrease in axial electromagnetic acceleration, and in turn, a decrease in the total axially-directed kinetic energy imparted to the propellant.

  10. NASA Brief: Q-Thruster Physics

    Science.gov (United States)

    White, Harold

    2013-01-01

    Q-thrusters are a low-TRL form of electric propulsion that operates on the principle of pushing off of the quantum vacuum. A terrestrial analog to this is to consider how a submarine uses its propeller to push a column of water in one direction, while the sub recoils in the other to conserve momentum -the submarine does not carry a "tank" of sea water to be used as propellant. In our case, we use the tools of Magnetohydrodynamics (MHD) to show how the thruster pushes off of the quantum vacuum which can be thought of as a sea of virtual particles -principally electrons and positrons that pop into and out of existence, and where fields are stronger, there are more virtual particles. The idea of pushing off the quantum vacuum has been in the technical literature for a few decades, but to date, the obstacle has been the magnitude of the predicted thrust which has been derived analytically to be very small, and therefore not likely to be useful for human spaceflight. Our recent theoretical model development and test data suggests that we can greatly increase the magnitude of the negative pressure of the quantum vacuum and generate a specific force such that technology based on this approach can be competitive for in-space propulsion approx. 0.1N/kW), and possibly for terrestrial applications (approx. 10N/kW). As an additional validation of the approach, the theory allows calculation of physics constants from first principles: Gravitational constant, Planck constant, Bohr radius, dark energy fraction, electron mass.

  11. Reaction rate estimation of controlled-release antifouling paint binders: Rosin-based systems

    DEFF Research Database (Denmark)

    Meseguer Yebra, Diego; Kiil, Søren; Dam-Johansen, Kim

    2005-01-01

    at product optimisation and innovation (e.g. incorporation of natural active agents). This study seeks to attain scientifically founded knowledge of the reaction mechanisms and the rate of reaction with sea water of a Zn-carboxylate of a synthetic rosin compound. The kinetic expression attained can be used...... have shown that mathematical coating models based on a fundamental knowledge of the underlying mechanisms of A/F paints is a promising tool for accelerated product testing at different operational conditions of a sailing ship or a paint rotor. Such models can also be used for generation of ideas aiming...... rather than pointing at a certain diffusion control in the reaction rate experiments. The reverse reaction is found not to affect the hydrolysis rate within the pores, of antifouling paints significantly. It is concluded, from the reaction mechanism proposed, that the observed partial exchange of Zn2...

  12. Synchronization criteria for generalized reaction-diffusion neural networks via periodically intermittent control.

    Science.gov (United States)

    Gan, Qintao; Lv, Tianshi; Fu, Zhenhua

    2016-04-01

    In this paper, the synchronization problem for a class of generalized neural networks with time-varying delays and reaction-diffusion terms is investigated concerning Neumann boundary conditions in terms of p-norm. The proposed generalized neural networks model includes reaction-diffusion local field neural networks and reaction-diffusion static neural networks as its special cases. By establishing a new inequality, some simple and useful conditions are obtained analytically to guarantee the global exponential synchronization of the addressed neural networks under the periodically intermittent control. According to the theoretical results, the influences of diffusion coefficients, diffusion space, and control rate on synchronization are analyzed. Finally, the feasibility and effectiveness of the proposed methods are shown by simulation examples, and by choosing different diffusion coefficients, diffusion spaces, and control rates, different controlled synchronization states can be obtained.

  13. Modeling and Fuzzy Logic Control of an Active Reaction Compensating Platform System

    Directory of Open Access Journals (Sweden)

    Y.J. Lin

    1995-01-01

    Full Text Available This article presents the application of the fuzzy logic (FL concept to the active control of a multiple degree of freedom reaction compensating platform system that is designed and used for isolating vibratory disturbances of space-based devices. The physical model used is a scaled down two-plate platform system. In this work, simulation is performed and presented. According to the desired performance specifications, a full range of investigation regarding the development of an FL stabilization controller for the system is conducted. Specifically, the study includes four stages: comprehensive dynamic modeling of the reaction compensating system; analysis of the dynamic responses of the platform system when it is subjected to various disturbances; design of an FL controller capable of filtering the vibratory disturbances transmitted to the bottom plate of the platform system; performance evaluation of the developed FL controller through computer simulations. To simplify the simulation work, the system model is linearized and the system component parameter variations are not considered. The performance of the FL controller is tested by exciting the system with an impulsive force applied at an arbitrarily chosen point on the top plate. It is shown that the proposed FL controller is robust in that the resultant active system is well stabilized when subjected to a random external disturbance. The comparative study of the performances of the FL controlled active reaction and passive reaction compensating systems also reveals that the FL controlled system achieves significant improvements in reducing vibratory accelerations over passive systems.

  14. Initial Thrust Measurements of Marshall's Ion-ioN Thruster

    Science.gov (United States)

    Caruso, Natalie R. S.; Scogin, Tyler; Liu, Thomas M.; Walker, Mitchell L. R.; Polzin, Kurt A.; Dankanich, John W.

    2015-01-01

    Electronegative ion thrusters are a variation of traditional gridded ion thruster technology differentiated by the production and acceleration of both positive and negative ions. Benefits of electronegative ion thrusters include the elimination of lifetime-limiting cathodes from the thruster architecture and the ability to generate appreciable thrust from both charge species. While much progress has been made in the development of electronegative ion thruster technology, direct thrust measurements are required to unambiguously demonstrate the efficacy of the concept and support continued development. In the present work, direct thrust measurements of the thrust produced by the MINT (Marshall's Ion-ioN Thruster) are performed using an inverted-pendulum thrust stand in the High-Power Electric Propulsion Laboratory's Vacuum Test Facility-1 at the Georgia Institute of Technology with operating pressures ranging from 4.8 x 10(exp -5) and 5.7 x 10(exp -5) torr. Thrust is recorded while operating with a propellant volumetric mixture ratio of 5:1 argon to nitrogen with total volumetric flow rates of 6, 12, and 24 sccm (0.17, 0.34, and 0.68 mg/s). Plasma is generated using a helical antenna at 13.56 MHz and radio frequency (RF) power levels of 150 and 350 W. The acceleration grid assembly is operated using both sinusoidal and square waveform biases of +/-350 V at frequencies of 4, 10, 25, 125, and 225 kHz. Thrust is recorded for two separate thruster configurations: with and without the magnetic filter. No thrust is discernable during thruster operation without the magnetic filter for any volumetric flow rate, RF forward Power level, or acceleration grid biasing scheme. For the full thruster configuration, with the magnetic filter installed, a brief burst of thrust of approximately 3.75 mN +/- 3 mN of error is observed at the start of grid operation for a volumetric flow rate of 24 sccm at 350 W RF power using a sinusoidal waveform grid bias at 125 kHz and +/- 350 V

  15. Adaptive FTC based on Control Allocation and Fault Accommodation for Satellite Reaction Wheels

    OpenAIRE

    Baldi, P.; Blanke, Mogens; P. Castaldi; Mimmo, N.; S. Simani

    2016-01-01

    This paper proposes an active fault tolerant control scheme to cope with faults or failures affecting the flywheel spin rate sensors or satellite reaction wheel motors. The active fault tolerant control system consists of a fault detection and diagnosis module along with a control allocationand fault accommodation module directly exploiting the on-line fault estimates. The use of the nonlinear geometric approach and radial basis function neural networks allows to obtain a precise fault isolat...

  16. High Performance Plasma Channel Insulators for High Power Hall Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA missions for planetary exploration require high power, long-life Hall thrusters. However, thruster power and lifetime are limited by the erosion of plasma...

  17. Micro Pulsed Inductive Thruster with Solid Fuel Option (uPIT_SF) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Micro Pulsed Inductive Thruster with Solid Fuel Option (5PIT_SF) is a high-precision impulse bit electromagnetic plasma micro-thruster. The 5PIT prototype is a...

  18. Hall Effect Thruster for High Power Solar Electric Propulsion Technology Demonstration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop a flight version of a high power Hall Effect thruster. While numerous high power Hall Effect thrusters have been demonstrated in the...

  19. Lifetime Improvement of Large Scale Green Monopropellant Thrusters via Novel, Long-Life Catalysts Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop and life-test a flight-weight, 5N class green monopropellant thruster in Phase II. The most important feature that sets this thruster apart...

  20. High Performance Plasma Channel Insulators for High Power Hall Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA missions for planetary exploration require high power, long-life Hall thrusters. However, thruster power and lifetime are limited by the erosion of plasma...

  1. Thruster-Assisted Position Mooring of C/S Inocean Cat I Drillship

    OpenAIRE

    Bjørnø, Jon

    2016-01-01

    This thesis presents the development of a new research foundation into the Marine Cybernetic Laboratory, the C/S Inocean Cat I Drillship. This is a 1:90 scaled model of an Arctic drillship design by Inocean for Statoil. The C/S Inocean Cat I Drillship model is equipped with six Aero-naut Precision Schottel azimuth thrusters which are driven by six O.S. OMA-2820-950 motors and six Dynamixel MX-106R servo motors. To control the model a real time controller, CompactRIO, from National Instrum...

  2. Controlling the emotional heart: heart rate biofeedback improves cardiac control during emotional reactions.

    Science.gov (United States)

    Peira, Nathalie; Fredrikson, Mats; Pourtois, Gilles

    2014-03-01

    When regulating negative emotional reactions, one goal is to reduce physiological reactions. However, not all regulation strategies succeed in doing that. We tested whether heart rate biofeedback helped participants reduce physiological reactions in response to negative and neutral pictures. When viewing neutral pictures, participants could regulate their heart rate whether the heart rate feedback was real or not. In contrast, when viewing negative pictures, participants could regulate heart rate only when feedback was real. Ratings of task success paralleled heart rate. Participants' general level of anxiety, emotion awareness, or cognitive emotion regulation strategies did not influence the results. Our findings show that accurate online heart rate biofeedback provides an efficient way to down-regulate autonomic physiological reactions when encountering negative stimuli.

  3. Controlled trifluoromethylation reactions of alkynes through visible-light photoredox catalysis.

    Science.gov (United States)

    Iqbal, Naeem; Jung, Jaehun; Park, Sehyun; Cho, Eun Jin

    2014-01-07

    The control of a reaction that can form multiple products is a highly attractive and challenging concept in synthetic chemistry. A set of valuable CF3 -containing molecules, namely trifluoromethylated alkenyl iodides, alkenes, and alkynes, were selectively generated from alkynes and CF3 I by environmentally benign and efficient visible-light photoredox catalysis. Subtle differences in the combination of catalyst, base, and solvent enabled the control of reactivity and selectivity for the reaction between an alkyne and CF3 I. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Adaptive FTC based on Control Allocation and Fault Accommodation for Satellite Reaction Wheels

    DEFF Research Database (Denmark)

    Baldi, P.; Blanke, Mogens; Castaldi, P.;

    2016-01-01

    This paper proposes an active fault tolerant control scheme to cope with faults or failures affecting the flywheel spin rate sensors or satellite reaction wheel motors. The active fault tolerant control system consists of a fault detection and diagnosis module along with a control allocation...... estimation filters, which do not need a priori information about the internal model of the signal to be estimated. The adaptive control allocation and sensor fault accommodation can handle both temporal faults and failures. Simulation results illustrate the convincing fault correction and attitude control...

  5. Reaction Wheel Installation Deviation Compensation for Overactuated Spacecraft with Finite-Time Attitude Control

    Directory of Open Access Journals (Sweden)

    Aihua Zhang

    2013-01-01

    Full Text Available A novel attitude tracking control scheme is presented for overactuated spacecraft to address the attitude stabilization problem in presence of reaction wheel installation deviation, external disturbance and uncertain mass of moment inertia. An adaptive sliding mode control technique is proposed to track the uncertainty. A Lyapunov-based analysis shows that the compensation control law can guarantee that the desired attitude trajectories are followed in finite-time. The key feature of the proposed control strategy is that it globally asymptotically stabilizes the system, even in the presence of reaction wheel installation deviation, external disturbances, and uncertain mass of moment inertia. The attitude track performance using the proposed finite-time compensation control is evaluated through a numerical example.

  6. In-Flight Position Calibration of the Cassini Articulated Reaction Wheel Assembly

    Science.gov (United States)

    Brown, Todd S.

    2012-01-01

    NASA's long-lived Cassini-Huygens spacecraft is currently in its 14th year of flight and in the midst of its second, and final, extended mission. Cassini is a massive interplanetary spacecraft that is three axis stabilized and can maintain attitude control using either its reaction control system thrusters or using reaction wheel control. Cassini has four identical reaction wheels, of which three are mutually orthogonal and have a fixed orientation. The fourth reaction wheel has an articulation motor that allows this reaction wheel to be aligned with the momentum direction of any of the other three fixed reaction wheels. The articulation motor allows this reaction wheel to be used as a replacement for any of the other three wheels without any performance degradation. However, due to limitations in the design of this backup system, there are few telemetric indications of the orientation of this reaction wheel following an articulation. This investigation serves to outline the procedures that have been developed by the Cassini Attitude and Articulation Control Subsystem to calibrate the position of the articulated reaction wheel assembly in the event that the momentum direction of this reaction wheel must be reoriented.

  7. Thermally activated reaction–diffusion-controlled chemical bulk reactions of gases and solids

    Directory of Open Access Journals (Sweden)

    S. Möller

    2015-01-01

    Full Text Available The chemical kinetics of the reaction of thin films with reactive gases is investigated. The removal of thin films using thermally activated solid–gas to gas reactions is a method to in-situ control deposition inventory in vacuum and plasma vessels. Significant scatter of experimental deposit removal rates at apparently similar conditions was observed in the past, highlighting the need for understanding the underlying processes. A model based on the presence of reactive gas in the films bulk and chemical kinetics is presented. The model describes the diffusion of reactive gas into the film and its chemical interaction with film constituents in the bulk using a stationary reaction–diffusion equation. This yields the reactive gas concentration and reaction rates. Diffusion and reaction rate limitations are depicted in parameter studies. Comparison with literature data on tokamak co-deposit removal results in good agreement of removal rates as a function of pressure, film thickness and temperature.

  8. Sliding mode control of reaction flywheel-based brushless DC motor with buck converter

    Institute of Scientific and Technical Information of China (English)

    Liu Gang; Zhang Cong

    2013-01-01

    Reaction flywheel is a significant actuator for satellites' attitude control.To improve out-put torque and rotational speed accuracy for reaction flywheel,this paper reviews the modeling and control approaches of DC-DC converters and presents an application of the variable structure system theory with associated sliding regimes.Firstly,the topology of reaction flywheel is constructed.The small signal linearization process for a buck converter is illustrated.Then,based on the state averaging models and reaching qualification expressed by the Lee derivative,the general results of the sliding mode control (SMC) are analyzed.The analytical equivalent control laws for reaction flywheel are deduced detailedly by selecting various sliding surfaces at electromotion,energy consumption braking,reverse connection braking stages.Finally,numerical and experimental examples are presented for illustrative purposes.The results demonstrate that favorable agreement is established between the simulations and experiments.The proposed control strategy achieves preferable rotational speed regulation,strong rejection of modest disturbances,and high-precision output torque and rotational speed tracking abilities.

  9. Global Linear Stability Analysis of the Spoke Oscillation in Hall Effect Thrusters

    Science.gov (United States)

    2014-07-15

    characterize the spoke in a wide range of HETs, including both conventional and non-conventional designs (the H6 thruster, the NASA 173Mv1, the Busek BHT -600...near plume of the thruster[126]. Similarly, Liu [127, 128] also finds azimuthal oscillations in the BHT -200 and BHT -600 thrusters via high speed-imaging

  10. Genetic control of the angular leaf spot reaction in common bean leaves and pods

    Directory of Open Access Journals (Sweden)

    Jerônimo Constantino Borel

    2011-12-01

    Full Text Available Information about genetic control of plant reaction to pathogens is essential in plant breeding programs focusing resistance. This study aimed to obtain information about genetic control of the angular leaf spot reaction in leaves and pods from common bean (Phaseolus vulgaris L. line ESAL 686. This line was crossed with cultivars Jalo EEP 558 (resistant, Cornell 49-242 (resistant and Carioca MG (susceptible. Generations F1, F2 and backcrosses (BC11 and BC21 were obtained. In the dry season (2009, parents and respective populations were evaluated for angular leaf spot reaction under field conditions. Disease severity was evaluated on leaves and pods using diagrammatic scales. Severity scores were obtained and mean and variance genetic components were estimated for both. Segregation of F2 generation was analyzed for some crosses. Different genes control angular leaf spot reaction in leaves and pods. Mean and variance components showed predominance of additive effects. Heritability was high, however, was greater on pods than on leaves which indicated that leaf reaction is more influenced by the environment.

  11. The Maillard reaction and its control during food processing. The potential of emerging technologies.

    Science.gov (United States)

    Jaeger, H; Janositz, A; Knorr, D

    2010-06-01

    The Maillard reaction between reducing sugars and amino acids is a common reaction in foods which undergo thermal processing. Desired consequences like the formation of flavor and brown color of some cooked foods but also the destruction of essential amino acids and the production of anti-nutritive compounds require the consideration of the Maillard reaction and relevant mechanisms for its control. This paper aims to exemplify the recent advances in food processing with regard to the controllability of heat-induced changes in the food quality. Firstly, improved thermal technologies, such as ohmic heating, which allows direct heating of the product and overcoming the heat transfer limitations of conventional thermal processing are presented in terms of their applicability to reduce the thermal exposure during food preservation. Secondly, non-thermal technologies such as high hydrostatic pressure and pulsed electric fields and their ability to extend the shelf life of food products without the application of heat, thus also preserving the quality attributes of the food, will be discussed. Finally, an innovative method for the removal of Maillard reaction substrates in food raw materials by the application of pulsed electric field cell disintegration and extraction as well as enzymatic conversion is presented in order to demonstrate the potential of the combination of processes to control the occurrence of the Maillard reaction in food processing.

  12. Kinetics and corrosion products of aqueous nitrate reduction by iron powder without reaction conditions control

    Institute of Scientific and Technical Information of China (English)

    FAN Xiaomeng; GUAN Xiaohong; MA Jun; AI Hengyu

    2009-01-01

    Although considerable research has been conducted on nitrate reduction by zero-valent iron powder (Fe0), these studies were mostly operated under anaerobic and invariable pH conditions that was unsuitable for practical application.Without reaction conditions (dissolved oxygen or reaction pH) control, this study aimed at subjecting the kinetics of denitrification by microscale Fe0 (160-200 mesh) to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface.Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant.Additional test results showed that the reduction rate of nitrate increased with increasing Fe0 dosage.The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe0 dosage.Experimental results also suggested that nitrate reduction by microscale Fe0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration.X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO(OH), was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5.The proportion of FeO(OH) increased as reaction time went on, whereas the proportion of Fe3O4 decreased.

  13. Magnetic Field Tailored Annular Hall Thruster with Anode Layer

    Science.gov (United States)

    Lee, Seunghun; Kim, Holak; Kim, Junbum; Lim, Youbong; Choe, Wonho; Korea Institute of Materials Science Collaboration

    2016-09-01

    Plasma propulsion system is one of the key components for advanced missions of satellites as well as deep space exploration. A typical plasma propulsion system is Hall effect thruster that uses crossed electric and magnetic fields to ionize a propellant gas and to accelerate the ionized gas to generate momentum. In Hall thruster plasmas, magnetic field configuration is important due to the fact that electron confinement in the electromagnetic fields affects both plasma and ion beam characteristics as well as thruster performance parameters including thrust, specific impulse, power efficiency, and life time. In this work, development of an anode layer Hall thruster (TAL) with magnetic field tailoring has been attempted. The TAL is possible to keep discharge in 1 to 2 kilovolts of anode voltage, which is useful to obtain high specific impulse. The magnetic field tailoring is used to minimize undesirable heat dissipation and secondary electron emission from the wall surrounding the plasma. We will report 3 W and 200 W thrusters performances measured by a pendulum thrust stand according to the magnetic field configuration. Also, the measured result will be compared with the plasma diagnostics conducted by an angular Faraday probe, a retarding potential analyzer, and a ExB probe.

  14. 20-mN Variable Specific Impulse (Isp) Colloid Thruster

    Science.gov (United States)

    Demmons, Nathaniel

    2015-01-01

    Busek Company, Inc., has designed and manufactured an electrospray emitter capable of generating 20 mN in a compact package (7x7x1.7 in). The thruster consists of nine porous-surface emitters operating in parallel from a common propellant supply. Each emitter is capable of supporting over 70,000 electrospray emission sites with the plume from each emitter being accelerated through a single aperture, eliminating the need for individual emission site alignment to an extraction grid. The total number of emission sites during operation is expected to approach 700,000. This Phase II project optimized and characterized the thruster fabricated during the Phase I effort. Additional porous emitters also were fabricated for full-scale testing. Propellant is supplied to the thruster via existing feed-system and microvalve technology previously developed by Busek, under the NASA Space Technology 7's Disturbance Reduction System (ST7-DRS) mission and via follow-on electric propulsion programs. This project investigated methods for extending thruster life beyond the previously demonstrated 450 hours. The life-extending capabilities will be demonstrated on a subscale version of the thruster.

  15. Evaluation of externally heated pulsed MPD thruster cathodes

    Science.gov (United States)

    Myers, Roger M.; Domonkos, Matthew; Gallimore, Alec D.

    1993-01-01

    Recent interest in solar electric orbit transfer vehicles (SEOTV's) has prompted a reevaluation of pulsed magnetoplasmadynamic (MPD) thruster systems due to their ease of power scaling and reduced test facility requirements. In this work the use of externally heated cathodes was examined in order to extend the lifetime of these thrusters to the 1000 to 3000 hours required for SEOTV missions. A pulsed MPD thruster test facility was assembled, including a pulse-forming network (PFN), ignitor supply and propellant feed system. Results of cold cathode tests used to validate the facility, PFN, and propellant feed system design are presented, as well as a preliminary evaluation of externally heated impregnated tungsten cathodes. The cold cathode thruster was operated on both argon and nitrogen propellants at peak discharge power levels up to 300 kW. The results confirmed proper operation of the pulsed thruster test facility, and indicated that large amounts of gas were evolved from the BaO-CaO-Al2O3 cathodes during activation. Comparison of the expected space charge limited current with the measured vacuum current when using the heated cathode indicate that either that a large temperature difference existed between the heater and the cathode or that the surface work function was higher than expected.

  16. Thrust Stand Measurements of a Conical Pulsed Inductive Plasma Thruster

    Science.gov (United States)

    Hallock, Ashley K.; Polzin, Kurt A.; Emsellem, Gregory D.

    2012-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters can su er from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA)[4], shown in Fig. 1 is a pulsed inductive plasma thruster that is able to operate at lower pulse energies by partially ionizing propellant with an electron cyclotron resonance (ECR) discharge inside a conical inductive coil whose geometry serves to potentially increase propellant and plasma plume containment relative to at coil geometries. The ECR plasma is created with the use of permanent mag- nets arranged to produce a thin resonance region along the inner surface of the coil, restricting plasma formation and, in turn, current sheet formation to areas of high magnetic coupling to the driving coil.

  17. A Template-Controlled Solid-State Reaction for the Organic Chemistry Laboratory

    Science.gov (United States)

    Friscic, Tomislav; Hamilton, Tamara D.; Papaefstathiou, Giannis S.; MacGillivray, Leonard R.

    2005-01-01

    An experiment for the organic chemistry laboratory that involves a template-controlled solid-state reaction is described. The experiment utilizes a template to direct the assembly of an olefin in the solid state that undergoes a [2 + 2] photodimerization.

  18. Low quality of reporting adverse drug reactions in paediatric randomised controlled trials

    NARCIS (Netherlands)

    de Vries, Tjalling W; van Roon, Eric N

    2010-01-01

    OBJECTIVE: Randomised controlled trials (RCT) offer an opportunity to learn about frequency and character of adverse drug reactions. To improve the quality of reporting adverse effects, the Consort group published recommendations. The authors studied the application of these recommendations in RCTs

  19. The method of conducting of the controlled thermonuclear reaction; Sposob prowadzenia kontrolowanej reakcji termojadrowej

    Energy Technology Data Exchange (ETDEWEB)

    Chmielewski, A.G.; Smulek, W.; Dembinski, W.; Fuks, L. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland)

    1992-07-31

    The method of conducting the controlled thermonuclear reaction has been patented. The method consists in diffusion of reacting gases (deuterium or tritium) through palladium or palladium alloys membrane. The membrane divides two chambers. The first chamber has been kept under the elevated pressure of a substrate gases, the second one under the vacuum conditions. The process has been running in elevated temperature. 1 fig.

  20. Slew Maneuver Control for Spacecraft Equipped with Star Camera and Reaction Wheels

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Kulczycki, P.

    2005-01-01

    A configuration consisting of a star camera, four reaction wheels and magnetorquers for momentum unloading has become standard for many spacecraft missions. This popularity has motivated numerous agencies and private companies to initiate work on the design of an imbedded attitude control system...... realized on an integrated circuit. This paper provides an easily implementable control algorithm for this type of configuration. The paper considers two issues: slew maneuver with a feature of avoiding direct exposure of the camera's CCD chip to the Sun %, three-axis attitude control and optimal control...

  1. On the perturbation solution of interface-reaction controlled diffusion in solids

    Institute of Scientific and Technical Information of China (English)

    Zhi-Wei Cui; Feng Gao; Jian-Min Qu

    2012-01-01

    Insertion of species A into species B forms a product P through two kinetic processes,namely,(1) the chemical reaction between A and B that occurs at the B-P interface,and (2) the diffusion of species A in product P.These two processes are symbiotic in that the chemical reaction provides the driving force for the diffusion,while the diffusion sustains the chemical reaction by providing sufficient reactant to the reactive interface.In this paper,a mathematical framework is developed for the coupled reactiondiffusion processes.The resulting system of boundary and initial value problem is solved analytically for the case of interface-reaction controlled diffusion,i.e.,the rate of diffusion is much faster than the rate of chemical reaction at the interface so that the final kinetics are limited by the interface chemical reaction.Asymptotic expressions are given for the velocity of the reactive interface and the concentration of diffusing species under two different boundary conditions.

  2. Multifaceted and route-controlled "click" reactions based on vapor-deposited coatings.

    Science.gov (United States)

    Sun, Ting-Pi; Tai, Ching-Heng; Wu, Jyun-Ting; Wu, Chih-Yu; Liang, Wei-Chieh; Chen, Hsien-Yeh

    2016-02-01

    "Click" reactions provide precise and reliable chemical transformations for the preparation of functional architectures for biomaterials and biointerfaces. The emergence of a multiple-click reaction strategy has paved the way for a multifunctional microenvironment with orthogonality and precise multitasking that mimics nature. We demonstrate a multifaceted and route-controlled click interface using vapor-deposited functionalized poly-para-xylylenes. Distinctly clickable moieties of ethynyl and maleimide were introduced into poly-para-xylylenes in one step via a chemical vapor deposition (CVD) copolymerization process. The advanced interface coating allows for a double-click route with concurrent copper(i)-catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) and the thiol-maleimide click reaction. Additionally, double-click reactions can also be performed in a cascade manner by controlling the initiation route to enable the CuAAC and/or thiol-yne reaction using a mono-functional alkyne-functionalized poly-para-xylylene. The use of multifaceted coatings to create straightforward and orthogonal interface properties with respect to protein adsorption and cell attachment is demonstrated and characterized.

  3. Thermal Environmental Testing of NSTAR Engineering Model Ion Thrusters

    Science.gov (United States)

    Rawlin, Vincent K.; Patterson, Michael J.; Becker, Raymond A.

    1999-01-01

    NASA's New Millenium program will fly a xenon ion propulsion system on the Deep Space 1 Mission. Tests were conducted under NASA's Solar Electric Propulsion Technology Applications Readiness (NSTAR) Program with 3 different engineering model ion thrusters to determine thruster thermal characteristics over the NSTAR operating range in a variety of thermal environments. A liquid nitrogen-cooled shroud was used to cold-soak the thruster to -120 C. Initial tests were performed prior to a mature spacecraft design. Those results and the final, severe, requirements mandated by the spacecraft led to several changes to the basic thermal design. These changes were incorporated into a final design and tested over a wide range of environmental conditions.

  4. 2-D Magnetohydrodynamic Modeling of A Pulsed Plasma Thruster

    Science.gov (United States)

    Thio, Y. C. Francis; Cassibry, J. T.; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)

    2002-01-01

    Experiments are being performed on the NASA Marshall Space Flight Center (MSFC) MK-1 pulsed plasma thruster. Data produced from the experiments provide an opportunity to further understand the plasma dynamics in these thrusters via detailed computational modeling. The detailed and accurate understanding of the plasma dynamics in these devices holds the key towards extending their capabilities in a number of applications, including their applications as high power (greater than 1 MW) thrusters, and their use for producing high-velocity, uniform plasma jets for experimental purposes. For this study, the 2-D MHD modeling code, MACH2, is used to provide detailed interpretation of the experimental data. At the same time, a 0-D physics model of the plasma initial phase is developed to guide our 2-D modeling studies.

  5. Neural Network Control of CSTR for Reversible Reaction Using Reverence Model Approach

    Directory of Open Access Journals (Sweden)

    Duncan ALOKO

    2007-01-01

    Full Text Available In this work, non-linear control of CSTR for reversible reaction is carried out using Neural Network as design tool. The Model Reverence approach in used to design ANN controller. The idea is to have a control system that will be able to achieve improvement in the level of conversion and to be able to track set point change and reject load disturbance. We use PID control scheme as benchmark to study the performance of the controller. The comparison shows that ANN controller out perform PID in the extreme range of non-linearity.This paper represents a preliminary effort to design a simplified neutral network control scheme for a class of non-linear process. Future works will involve further investigation of the effectiveness of thin approach for the real industrial chemical process

  6. Experimental characterization of radio frequency microthermal thruster performance

    Science.gov (United States)

    Williams, Shae E.

    Microsatellite (cold gas thrusters. Design constraints rule out much of traditional propulsion, requiring new and nonobvious technologies to advance the state of the art and enable longer and more flexible missions. The radio frequency microthermal thruster is shown to be worth thorough study for this application. A basic analytical model is constructed to look at expected performance, and the theory behind that model is explained. Calibration and the challenges in working with extremely low forces and displacements are also examined. The results of extensive testing on this thruster type are presented. Important trends are confirmed and validated, such as a linearity of specific impulse with power, and consistent nonlinearities with frequency and mass flow rate. Additionally, tests indicate a nonlinear relationship between applied frequency and thruster internal geometry that can more than triple the heating occurring in the thruster. Further tests focus on this relationship, and find more information about how these parameters couple are found to be primarily due to induced inefficiencies in stochastic heating and the inability of a vibrating voltage sheath to transfer energy into the flow. Additionally, first steps towards optimizing a design for performance are taken, such as analyzing the effect of adding a converging/diverging nozzle and finding an optimal length of inner electrode to be exposed to plasma. Overall, specific impulses of up to 85 seconds are found with argon as the propellant, doubling cold gas specific impulse, and an error on specific impulse is calculated to be less than 3% in either direction. These results after only slight efforts at design optimization indicate much more improvement is possible with this technology that would make an RF microthermal thruster viable as a commercial product.

  7. Unexpected Control Structure Interaction on International Space Station

    Science.gov (United States)

    Gomez, Susan F.; Platonov, Valery; Medina, Elizabeth A.; Borisenko, Alexander; Bogachev, Alexey

    2017-01-01

    On June 23, 2011, the International Space Station (ISS) was performing a routine 180 degree yaw maneuver in support of a Russian vehicle docking when the on board Russian Segment (RS) software unexpectedly declared two attitude thrusters failed and switched thruster configurations in response to unanticipated ISS dynamic motion. Flight data analysis after the maneuver indicated that higher than predicted structural loads had been induced at various locations on the United States (U.S.) segment of the ISS. Further analysis revealed that the attitude control system was firing thrusters in response to both structural flex and rigid body rates, which resonated the structure and caused high loads and fatigue cycles. It was later determined that the thruster themselves were healthy. The RS software logic, which was intended to react to thruster failures, had instead been heavily influenced by interaction between the control system and structural flex. This paper will discuss the technical aspects of the control structure interaction problem that led to the RS control system firing thrusters in response to structural flex, the factors that led to insufficient preflight analysis of the thruster firings, and the ramifications the event had on the ISS. An immediate consequence included limiting which thrusters could be used for attitude control. This complicated the planning of on-orbit thruster events and necessitated the use of suboptimal thruster configurations that increased propellant usage and caused thruster lifetime usage concerns. In addition to the technical aspects of the problem, the team dynamics and communication shortcomings that led to such an event happening in an environment where extensive analysis is performed in support of human space flight will also be examined. Finally, the technical solution will be presented, which required a multidisciplinary effort between the U.S. and Russian control system engineers and loads and dynamics structural engineers to

  8. Lacunary Keggin Polyoxotungstate as Reaction-controlled Phasetransfer Catalyst for Catalytic Epoxidation of Olefins

    Institute of Scientific and Technical Information of China (English)

    LI,Ming-Qiang(李明强); JIAN,Xi-Gao(蹇锡高); YANG,Yong-Qiang(杨永强)

    2004-01-01

    A new reaction-controlled phase-transfer catalyst system, lacunary Keggin polyoxotungstate [C7H7N(CH3)3]9PW9O34 has been synthesized and used for catalytic epoxidation of olefins with H2O2 as the oxidant.Infrared spectra were used to analyze the behavior of the phase transfer of catalyst. In this system, the catalyst not only can act as homogeneous catalyst but also as heterogeneous catalyst to be easily filtered and reused. The epoxidation reaction is clean and exhibits high conversion and selectivity as well as excellent catalyst stability.

  9. Multicomponent reactions for synthesis of bioactive polyheterocyclic ring systems under controlled microwave irradiation

    Directory of Open Access Journals (Sweden)

    Eman M.H. Abbas

    2014-11-01

    Full Text Available The multi-component reaction of 1-benzothiopyran-4-ones with heterocyclic amines and dimethylformamide-dimethylacetal (DMFDMA in DMF at 150 °C under controlled microwave heating afforded novel poly-heterocyclic ring systems. Also, reaction of 3-dimethylaminomethylene-1-benzothiopyran-4-one with activemethylene derivatives was investigated. The structure of all products was established on the bases of spectral data and elemental analyses and alternative synthesis if possible. The prepared compounds were screened for their antitumor activity against HCT-116 “colon” cancer cell line and some derivatives showed promising activity.

  10. Proton mediated control of biochemical reactions with bioelectronic pH modulation

    Science.gov (United States)

    Deng, Yingxin; Miyake, Takeo; Keene, Scott; Josberger, Erik E.; Rolandi, Marco

    2016-04-01

    In Nature, protons (H+) can mediate metabolic process through enzymatic reactions. Examples include glucose oxidation with glucose dehydrogenase to regulate blood glucose level, alcohol dissolution into carboxylic acid through alcohol dehydrogenase, and voltage-regulated H+ channels activating bioluminescence in firefly and jellyfish. Artificial devices that control H+ currents and H+ concentration (pH) are able to actively influence biochemical processes. Here, we demonstrate a biotransducer that monitors and actively regulates pH-responsive enzymatic reactions by monitoring and controlling the flow of H+ between PdHx contacts and solution. The present transducer records bistable pH modulation from an “enzymatic flip-flop” circuit that comprises glucose dehydrogenase and alcohol dehydrogenase. The transducer also controls bioluminescence from firefly luciferase by affecting solution pH.

  11. Plasma Thruster Development: Magnetoplasmadynamic Propulsion, Status and Basic Problems.

    Science.gov (United States)

    1986-02-01

    Closed Drift Hall-Ion Thruster Flown on the Russian Satellite Meteor I, 1971, from Reference 13 12 4 Flat Coil Induction Thruster Schematic from...the Russian Satellite Meteor 1, 1971. from Ref. 1-3. 13 COIL Br PLASMA SWITCH0 0 FZ jeBr 0 CAPACITOR 0 Fig.- 4:Fa olInuto huse ceai fromRef-22 40 14 is...minute crater (on the order of 10- 4 cm diameter). High pressures, on the order of 100 bar, and vaporization rates in these craters have been

  12. An approach to the parametric design of ion thrusters

    Science.gov (United States)

    Wilbur, Paul J.; Beattie, John R.; Hyman, Jay, Jr.

    1988-01-01

    A methodology that can be used to determine which of several physical constraints can limit ion thruster power and thrust, under various design and operating conditions, is presented. The methodology is exercised to demonstrate typical limitations imposed by grid system span-to-gap ratio, intragrid electric field, discharge chamber power per unit beam area, screen grid lifetime and accelerator grid lifetime constraints. Limitations on power and thrust for a thruster defined by typical discharge chamber and grid system parameters when it is operated at maximum thrust-to-power are discussed.

  13. Physics and Dynamics of Current Sheets in Pulsed Plasma Thrusters

    Science.gov (United States)

    2007-11-02

    pulsed plasma thruster. A simple experiment would involve measuring the impulse bit of a coaxial gas-fed pulsed plasma thruster operated in both positive...Princeton, NJ, 2002. [2] J. Marshal. Performance of a hydromagnetic plasma gun . The Physics of Fluids, 3(1):134–135, January-February 1960. [3] R.G. Jahn...Jahn and K.E. Clark. A large dielecteic vacuum facility. AIAA Jour- nal, 1966. [16] L.C. Burkhardt and R.H. Lovberg. Current sheet in a coaxial plasma

  14. Optimization of a coaxial electron cyclotron resonance plasma thruster with an analytical model

    Science.gov (United States)

    Cannat, F.; Lafleur, T.; Jarrige, J.; Chabert, P.; Elias, P.-Q.; Packan, D.

    2015-05-01

    A new cathodeless plasma thruster currently under development at Onera is presented and characterized experimentally and analytically. The coaxial thruster consists of a microwave antenna immersed in a magnetic field, which allows electron heating via cyclotron resonance. The magnetic field diverges at the thruster exit and forms a nozzle that accelerates the quasi-neutral plasma to generate a thrust. Different thruster configurations are tested, and in particular, the influence of the source diameter on the thruster performance is investigated. At microwave powers of about 30 W and a xenon flow rate of 0.1 mg/s (1 SCCM), a mass utilization of 60% and a thrust of 1 mN are estimated based on angular electrostatic probe measurements performed downstream of the thruster in the exhaust plume. Results are found to be in fair agreement with a recent analytical helicon thruster model that has been adapted for the coaxial geometry used here.

  15. Optimization of a coaxial electron cyclotron resonance plasma thruster with an analytical model

    Energy Technology Data Exchange (ETDEWEB)

    Cannat, F., E-mail: felix.cannat@onera.fr, E-mail: felix.cannat@gmail.com; Lafleur, T. [Physics and Instrumentation Department, Onera -The French Aerospace Lab, Palaiseau, Cedex 91123 (France); Laboratoire de Physique des Plasmas, CNRS, Sorbonne Universites, UPMC Univ Paris 06, Univ Paris-Sud, Ecole Polytechnique, 91128 Palaiseau (France); Jarrige, J.; Elias, P.-Q.; Packan, D. [Physics and Instrumentation Department, Onera -The French Aerospace Lab, Palaiseau, Cedex 91123 (France); Chabert, P. [Laboratoire de Physique des Plasmas, CNRS, Sorbonne Universites, UPMC Univ Paris 06, Univ Paris-Sud, Ecole Polytechnique, 91128 Palaiseau (France)

    2015-05-15

    A new cathodeless plasma thruster currently under development at Onera is presented and characterized experimentally and analytically. The coaxial thruster consists of a microwave antenna immersed in a magnetic field, which allows electron heating via cyclotron resonance. The magnetic field diverges at the thruster exit and forms a nozzle that accelerates the quasi-neutral plasma to generate a thrust. Different thruster configurations are tested, and in particular, the influence of the source diameter on the thruster performance is investigated. At microwave powers of about 30 W and a xenon flow rate of 0.1 mg/s (1 SCCM), a mass utilization of 60% and a thrust of 1 mN are estimated based on angular electrostatic probe measurements performed downstream of the thruster in the exhaust plume. Results are found to be in fair agreement with a recent analytical helicon thruster model that has been adapted for the coaxial geometry used here.

  16. Reaction temperature sensing (RTS)-based control for Li-ion battery safety

    OpenAIRE

    Guangsheng Zhang; Lei Cao; Shanhai Ge; Chao-Yang Wang; Shaffer, Christian E.; Christopher D. Rahn

    2015-01-01

    We report reaction temperature sensing (RTS)-based control to fundamentally enhance Li-ion battery safety. RTS placed at the electrochemical interface inside a Li-ion cell is shown to detect temperature rise much faster and more accurately than external measurement of cell surface temperature. We demonstrate, for the first time, that RTS-based control shuts down a dangerous short-circuit event 3 times earlier than surface temperature- based control and prevents cell overheating by 50 °C and t...

  17. Optimal control of the initiation of a pericyclic reaction in the electronic ground state

    Indian Academy of Sciences (India)

    Timm Bredtmann; Jörn Manz

    2012-01-01

    Pericyclic reactions in the electronic ground state may be initiated by down-chirped pump-dump sub-pulses of an optimal laser pulse, in the ultraviolet (UV) frequency and sub-10 femtosecond (fs) time domain. This is demonstrated by means of a quantum dynamics model simulation of the Cope rearrangement of Semibullvalene. The laser pulse is designed by means of optimal control theory, with detailed analysis of the mechanism. The theoretical results support the recent experimental initiation of a pericyclic reaction. The present approach provides an important step towards monitoring asynchronous electronic fluxes during synchronous nuclear pericyclic reaction dynamics, with femto-to-attosecond time resolution, as motivated by the recent prediction of our group.

  18. Control of rare events in reaction and population systems by deterministically imposed transitions.

    Science.gov (United States)

    Khasin, M; Dykman, M I

    2011-03-01

    We consider control of reaction and population systems by imposing transitions between states with different numbers of particles or individuals. The transitions take place at predetermined instants of time. Even where they are significantly less frequent than spontaneous transitions, they can exponentially strongly modify the rates of rare events, including switching between metastable states or population extinction. We also study optimal control of rare events. Specifically, we are interested in the optimal control of disease extinction for a limited vaccine supply. A comparison is made with control of rare events by modulating the rates of elementary transitions rather than imposing transitions deterministically. It is found that, unexpectedly, for the same mean control parameters, controlling the transitions rates can be more efficient.

  19. Coaxial microwave electrothermal thruster performance in hydrogen

    Science.gov (United States)

    Richardson, W.; Asmussen, J.; Hawley, M.

    1994-01-01

    The microwave electro thermal thruster (MET) is an electric propulsion concept that offers the promise of high performance combined with a long lifetime. A unique feature of this electric propulsion concept is its ability to create a microwave plasma discharge separated or floating away from any electrodes or enclosing walls. This allows propellant temperatures that are higher than those in resistojets and reduces electrode and wall erosion. It has been demonstrated that microwave energy is coupled into discharges very efficiently at high input power levels. As a result of these advantages, the MET concept has been identified as a future high power electric propulsion possibility. Recently, two additional improvements have been made to the coaxial MET. The first was concerned with improving the microwave matching. Previous experiments were conducted with 10-30 percent reflected power when incident power was in excess of 600 W(exp 6). Power was reflected back to the generator because the impedance of the MET did not match the 50 ohm impedance of the microwave circuit. To solve this problem, a double stub tuning system has been inserted between the MET and the microwave power supply. The addition of the double stub tuners reduces the reflected power below 1 percent. The other improvement has prepared the coaxial MET for hydrogen experiments. To operate with hydrogen, the vacuum window which separates the coaxial line from the discharge chamber has been changed from teflon to boron nitride. All the microwave energy delivered to the plasma discharge passes through this vacuum window. This material change had caused problems in the past because of the increased microwave reflection coefficients associated with the electrical properties of boron nitride. However, by making the boron nitride window electrically one-half of a wavelength long, power reflection in the window has been eliminated. This technical note summarizes the experimental performance of the improved

  20. Initial Investigation of Reaction Control System Design on Spacecraft Handling Qualities for Earth Orbit Docking

    Science.gov (United States)

    Bailey, Randall E.; Jackson, E. Bruce; Goodrich, Kenneth H.; Ragsdale, W. Al; Neuhaus, Jason; Barnes, Jim

    2008-01-01

    A program of research, development, test, and evaluation is planned for the development of Spacecraft Handling Qualities guidelines. In this first experiment, the effects of Reaction Control System design characteristics and rotational control laws were evaluated during simulated proximity operations and docking. Also, the influence of piloting demands resulting from varying closure rates was assessed. The pilot-in-the-loop simulation results showed that significantly different spacecraft handling qualities result from the design of the Reaction Control System. In particular, cross-coupling between translational and rotational motions significantly affected handling qualities as reflected by Cooper-Harper pilot ratings and pilot workload, as reflected by Task-Load Index ratings. This influence is masked but only slightly by the rotational control system mode. While rotational control augmentation using Rate Command Attitude Hold can reduce the workload (principally, physical workload) created by cross-coupling, the handling qualities are not significantly improved. The attitude and rate deadbands of the RCAH introduced significant mental workload and control compensation to evaluate when deadband firings would occur, assess their impact on docking performance, and apply control inputs to mitigate that impact.

  1. Global control of reaction wheel pendulum through energy regulation and extended linearization of the state variables

    Directory of Open Access Journals (Sweden)

    Oscar D. Montoya-Giraldo

    2014-01-01

    Full Text Available This paper presents the design and simulation of a global controller for the Reaction Wheel Pendulum system using energy regulation and extended linearization methods for the state feedback. The proposed energy regulation is based on the gradual reduction of the energy of the system to reach the unstable equilibrium point. The signal input for this task is obtained from the Lyapunov stability theory. The extended state feedback controller design is used to get a smooth nonlinear function that extends the region of operation to a bigger range, in contrast with the static linear state feedback obtained through the method of approximate linearization around an operating point. The general designed controller operates with a switching between the two control signals depending upon the region of operation; perturbations are applied in the control signal and the (simulated measured variables to verify the robustness and efficiency of the controller. Finally, simulations and tests using the model of the reaction wheel pendulum system, allow to observe the versatility and functionality of the proposed controller in the entire operation region of the pendulum.

  2. Vibrational control of electron-transfer reactions: a feasibility study for the fast coherent transfer regime.

    Science.gov (United States)

    Antoniou, P; Ma, Z; Zhang, P; Beratan, D N; Skourtis, S S

    2015-12-14

    Molecular vibrations and electron-vibrational interactions are central to the control of biomolecular electron and energy-transfer rates. The vibrational control of molecular electron-transfer reactions by infrared pulses may enable the precise probing of electronic-vibrational interactions and of their roles in determining electron-transfer mechanisms. This type of electron-transfer rate control is advantageous because it does not alter the electronic state of the molecular electron-transfer system or irreversibly change its molecular structure. For bridge-mediated electron-transfer reactions, infrared (vibrational) excitation of the bridge linking the electron donor to the electron acceptor was suggested as being capable of influencing the electron-transfer rate by modulating the bridge-mediated donor-to-acceptor electronic coupling. This kind of electron-transfer experiment has been realized, demonstrating that bridge-mediated electron-transfer rates can be changed by exciting vibrational modes of the bridge. Here, we use simple models and ab initio computations to explore the physical constraints on one's ability to vibrationally perturb electron-transfer rates using infrared excitation. These constraints stem from the nature of molecular vibrational spectra, the strengths of the electron-vibrational coupling, and the interaction between molecular vibrations and infrared radiation. With these constraints in mind, we suggest parameter regimes and molecular architectures that may enhance the vibrational control of electron transfer for fast coherent electron-transfer reactions.

  3. Pinning Control Strategies for Synchronization of Linearly Coupled Neural Networks With Reaction-Diffusion Terms.

    Science.gov (United States)

    Wang, Jin-Liang; Wu, Huai-Ning; Huang, Tingwen; Ren, Shun-Yan

    2016-04-01

    Two types of coupled neural networks with reaction-diffusion terms are considered in this paper. In the first one, the nodes are coupled through their states. In the second one, the nodes are coupled through the spatial diffusion terms. For the former, utilizing Lyapunov functional method and pinning control technique, we obtain some sufficient conditions to guarantee that network can realize synchronization. In addition, considering that the theoretical coupling strength required for synchronization may be much larger than the needed value, we propose an adaptive strategy to adjust the coupling strength for achieving a suitable value. For the latter, we establish a criterion for synchronization using the designed pinning controllers. It is found that the coupled reaction-diffusion neural networks with state coupling under the given linear feedback pinning controllers can realize synchronization when the coupling strength is very large, which is contrary to the coupled reaction-diffusion neural networks with spatial diffusion coupling. Moreover, a general criterion for ensuring network synchronization is derived by pinning a small fraction of nodes with adaptive feedback controllers. Finally, two examples with numerical simulations are provided to demonstrate the effectiveness of the theoretical results.

  4. Structural and dynamical control of the reaction rate in protein electron transfer

    Science.gov (United States)

    Balabin, Ilya A.

    Electron transfer (ET) reactions in proteins are key steps in many vital bioenergetic processes, and the reaction rate is known to be highly sensitive to the protein structure in some cases. For most bioenergetic reactions, as described by the Fermi Golden rule, the rate is proportional to a product of the average square of the effective electronic donor to acceptor coupling and a Franck-Condon factor, which accounts for the nuclear control of the energy gap. The nuclear factor is reasonably well described in Marcus theory and its modifications, and this work is focused on the mechanisms that control the effective coupling. About ten years ago, the Pathways model described for the first time how protein environment may control the effective coupling. In this work, a novel theoretical approach is developed to explore the mechanisms of structural and dynamical control beyond the qualitative level of the Pathways model. In Chapter 1, the assumptions of the Pathways model, its limitations and effects of the structure and the electronic Hamiltonian are investigated for model chain-like bridges using the Dyson's equations. In Chapter II, the framework to explore the sensitivity of the effective coupling to quality of the electronic Hamiltonian, the interference among the dominant pathways and the bridge dynamics is presented. This analysis employs the Green's function technique and includes combined molecular dynamics and electronic structure calculations. Finally, in Chapter III, this framework is tested on the bacterial photosynthetic reaction center, and the mechanisms of the structural and dynamical control for different ET steps are discussed.

  5. Inductive Pulsed Plasma Thruster Development and Testing at NASA-MSFC

    Science.gov (United States)

    Polzin, Kurt A.

    2013-01-01

    THE inductive pulsed plasma thruster (IPPT) is an electrodeless space propulsion device where a capacitor is charged to an initial voltage and then discharged producing a high current pulse through a coil. The field produced by this pulse ionizes propellant, inductively driving current in a plasma located near the face of the coil. Once the plasma is formed it can be accelerated and expelled at a high exhaust velocity by the electromagnetic Lorentz body force arising from the interaction of the induced plasma current and the magnetic field produced by the current in the coil. In the present work, we present a summary of the IPPT research and development conducted at NASA's Marshall Space Flight Center (MSFC). As a higher-power, still relatively low readiness level system, there are many issues associated with the eventual deployment and use of the IPPT as a primary propulsion system on spacecraft that remain to be addressed. The present program aimed to fabricate and test hardware to explore how these issues could be addressed. The following specific areas were addressed within the program and will be discussed within this paper. a) Conical theta-pinch IPPT geometry thruster configuration. b) Repetition-rate multi-kW thruster pulsing. c) Long-lifetime pulsed gas valve. d) Fast pulsed gas valve driver and controller. e) High-voltage, repetitive capacitor charging power processing unit. During the course of testing, a number of specific tests were conducted, including several that, to our knowledge, have either never been previously conducted (such as multi-KW repetition-rate operation) or have not been performed since the early 1990s (direct IPPT thrust measurements).2 Conical theta-pinch IPPT thrust stand measurements are presented in Fig. 1 while various time-integrated and time

  6. Dynamic Neural Network-Based Pulsed Plasma Thruster (PPT) Fault Detection and Isolation for Formation Flying of Satellites

    Science.gov (United States)

    Valdes, A.; Khorasani, K.

    The main objective of this paper is to develop a dynamic neural network-based fault detection and isolation (FDI) scheme for the Pulsed Plasma Thrusters (PPTs) that are used in the Attitude Control Subsystem (ACS) of satellites that are tasked to perform a formation flying mission. By using data collected from the relative attitudes of the formation flying satellites our proposed "High Level" FDI scheme can detect the pair of thrusters which is faulty, however fault isolation cannot be accomplished. Based on the "High Level" FDI scheme and the DNN-based "Low Level" FDI scheme developed earlier by the authors, an "Integrated" DNN-based FDI scheme is then proposed. To demonstrate the FDI capabilities of the proposed schemes various fault scenarios are simulated.

  7. Preliminary input to the space shuttle reaction control subsystem failure detection and identification software requirements (uncontrolled)

    Science.gov (United States)

    Bergmann, E.

    1976-01-01

    The current baseline method and software implementation of the space shuttle reaction control subsystem failure detection and identification (RCS FDI) system is presented. This algorithm is recommended for conclusion in the redundancy management (RM) module of the space shuttle guidance, navigation, and control system. Supporting software is presented, and recommended for inclusion in the system management (SM) and display and control (D&C) systems. RCS FDI uses data from sensors in the jets, in the manifold isolation valves, and in the RCS fuel and oxidizer storage tanks. A list of jet failures and fuel imbalance warnings is generated for use by the jet selection algorithm of the on-orbit and entry flight control systems, and to inform the crew and ground controllers of RCS failure status. Manifold isolation valve close commands are generated in the event of failed on or leaking jets to prevent loss of large quantities of RCS fuel.

  8. Controlling the ambiphilic nature of σ-arylpalladium intermediates in intramolecular cyclization reactions.

    Science.gov (United States)

    Solé, Daniel; Fernández, Israel

    2014-01-21

    The reactivity of main group organometallics, such as organolithium compounds (RLi) and Grignard reagents (RMgX), is quite straightforward. In these species the R group usually exhibits nucleophilic reactivity without any possibility of inducing electrophilic character. In contrast, in organopalladium complexes, researchers can switch the reactivity from electrophilic to nucleophilic relatively simply. Although σ-aryl and σ-vinylpalladium complexes are commonly used as electrophiles in C-C bond-forming reactions, recent research has demonstrated that they can also react with carbon-heteroatom multiple bonds in a nucleophilic manner. Nevertheless, researchers have completely ignored the issue of controlling the ambiphilic nature of such species. This Account describes our efforts toward selectively promoting the same starting materials toward either electrophilic α-arylation or nucleophilic addition reactions to different carbonyl groups. We could tune the properties of the σ-arylpalladium intermediates derived from amino-tethered aryl halides and carbonyl compounds to achieve chemoselective transformations. Therefore, chemists can control the ambiphilic nature of such intermediates and, consequently, the competition between the alternative reaction pathways by the adequate selection of the reaction conditions and additives (base, presence/absence of phenol, bidentate phosphines). The nature of the carbonyl group (aldehydes, ketones, esters, and amides) and the length of the tether connecting it to the aniline moiety also play an important role in the outcome of these processes. Our joint computational and experimental efforts to elucidate the reaction mechanism of these palladium-catalyzed transformations suggest that beyond the formation of the four-membered azapalladacycle, two major factors help to control the dual character of the palladium(II) intermediates derived from 2-haloanilines. First, their high nucleophilicity strongly modifies the interaction of

  9. Employee reactions to the use of management control systems in hospitals: motivation vs. threat.

    Science.gov (United States)

    Lopez-Valeiras, Ernesto; Gomez-Conde, Jacobo; Lunkes, Rogerio Joao

    2017-02-10

    Management control systems (such as budgets or balanced scorecards) are formal procedures used by managers to promote employee behavior aligned with organisational objectives. Employees may react to these control systems by either becoming more motivated or perceiving them as a threat. The aim of this paper is to determine the extent to which hospital ownership (public or private), professional group (physician, nurse, pharmacist or administrative employee), type of contract (fixed or temporary), gender and tenure can condition employee reaction to management control systems. We conducted the study in the three largest hospitals in the State of Santa Catarina (Brazil), two public (federal and state-owned) and one private (non-profit organisation). Physicians, nurses, pharmacists and administrative employees received a questionnaire between October 2013 and January 2014 concerning their current perceptions. We obtained 100 valid responses and conducted an ANOVA variance analysis. Our results show that the effect of management control systems on employees differs according to hospital ownership, professional group and type of contract. However, no significant evidence was found concerning gender or tenure. The results obtained contribute to creating specific knowledge on the reactions of employees to the use of management control systems in hospitals. This information may be important in adapting management control systems to the characteristics of the hospital and its employees, which may in turn contribute to reducing dysfunctional worker behavior. Copyright © 2017 SESPAS. Publicado por Elsevier España, S.L.U. All rights reserved.

  10. Size-controlled synthesis of Cu2O nanoparticles via reaction-diffusion

    Science.gov (United States)

    Badr, Layla; Epstein, Irving R.

    2017-02-01

    Copper (I) oxide nanoparticles are synthesized by a simple reaction-diffusion process involving Cu+ ions and sodium hydroxide in gelatin. The mean diameter and the size dispersion of the nanoparticles can be controlled by two experimental parameters, the percent of gelatin in the medium and the hydroxide ion concentration. UV-visible spectroscopy, transmission electron microscopy and X-ray diffraction are used to analyze the size, morphology, and chemical composition of the nanoparticles generated.

  11. KINETIC MODEL FOR DIFFUSION-CONTROLLED INTERMOLECULAR REACTION OF HOMOGENOUS POLYMER UNDER STEADY SHEAR

    Institute of Scientific and Technical Information of China (English)

    Meng-ge Liu; Wei Yu; Chi-xing Zhou

    2006-01-01

    The kinetic model for diffusion-controlled intermolecular reaction of homogenous polymer under steady shear was theoretically studied. The classic formalism and the concept of conformation ellipsoids were integrated to get a new equation, which directly correlates the rate constant with shear rate. It was found that the rate constant is not monotonic with shear rate. The scale of rate constant is N-1.5 (N is the length of chains), which is in consistent with de Gennes's result.

  12. Flow field description of the Space Shuttle Vernier reaction control system exhaust plumes

    Science.gov (United States)

    Cerimele, Mary P.; Alred, John W.

    1987-01-01

    The flow field for the Vernier Reaction Control System (VRCS) jets of the Space Shuttle Orbiter has been calculated from the nozzle throat to the far-field region. The calculations involved the use of recently improved rocket engine nozzle/plume codes. The flow field is discussed, and a brief overview of the calculation techniques is presented. In addition, a proposed on-orbit plume measurement experiment, designed to improve future estimations of the Vernier flow field, is addressed.

  13. Orbiter subsystem hardware/software interaction analysis. Volume 8: AFT reaction control system, part 2

    Science.gov (United States)

    Becker, D. D.

    1980-01-01

    The orbiter subsystems and interfacing program elements which interact with the orbiter computer flight software are analyzed. The failure modes identified in the subsystem/element failure mode and effects analysis are examined. Potential interaction with the software is examined through an evaluation of the software requirements. The analysis is restricted to flight software requirements and excludes utility/checkout software. The results of the hardware/software interaction analysis for the forward reaction control system are presented.

  14. Orbiter subsystem hardware/software interaction analysis. Volume 8: Forward reaction control system

    Science.gov (United States)

    Becker, D. D.

    1980-01-01

    The results of the orbiter hardware/software interaction analysis for the AFT reaction control system are presented. The interaction between hardware failure modes and software are examined in order to identify associated issues and risks. All orbiter subsystems and interfacing program elements which interact with the orbiter computer flight software are analyzed. The failure modes identified in the subsystem/element failure mode and effects analysis are discussed.

  15. Optimal Attitude Control of Agile Spacecraft Using Combined Reaction Wheel and Control Moment Gyroscope Arrays

    Science.gov (United States)

    2015-12-01

    Finally, research objectives and an overview of the entire document are given. 1.1 Motivation: Satellite Tracking Mission The satellite imagery business ...has been booming and shows no trend of decline [15– 19]. As seen from the recent search for missing Malaysia Airlines Flight 370, significant amounts...to achieve the pointing accuracy and completion time in the family of the other controllers. In fact, the PID controller completes the mission 7

  16. NASA's Evolutionary Xenon Thruster (NEXT) Ion Propulsion System Information Summary

    Science.gov (United States)

    Pencil, Eirc S.; Benson, Scott W.

    2008-01-01

    This document is a guide to New Frontiers mission proposal teams. The document describes the development and status of the NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system (IPS) technology, its application to planetary missions, and the process anticipated to transition NEXT to the first flight mission.

  17. Mission and System Advantages of Iodine Hall Thrusters

    Science.gov (United States)

    Dankanich, John W.; Szabo, James; Pote, Bruce; Oleson, Steve; Kamhawi, Hani

    2014-01-01

    The exploration of alternative propellants for Hall thrusters continues to be of interest to the community. Investments have been made and continue for the maturation of iodine based Hall thrusters. Iodine testing has shown comparable performance to xenon. However, iodine has a higher storage density and resulting higher ?V capability for volume constrained systems. Iodine's vapor pressure is low enough to permit low-pressure storage, but high enough to minimize potential adverse spacecraft-thruster interactions. The low vapor pressure also means that iodine does not condense inside the thruster at ordinary operating temperatures. Iodine is safe, it stores at sub-atmospheric pressure, and can be stored unregulated for years on end; whether on the ground or on orbit. Iodine fills a niche for both low power (10kW) electric propulsion regimes. A range of missions have been evaluated for direct comparison of Iodine and Xenon options. The results show advantages of iodine Hall systems for both small and microsatellite application and for very large exploration class missions.

  18. Rapid evaluation of ion thruster lifetime using optical emission spectroscopy

    Science.gov (United States)

    Rock, B. A.; Parsons, M. L.; Mantenieks, M. A.

    1985-01-01

    A major life-limiting phenomenon of electric thrusters is the sputter erosion of discharge chamber components. Thrusters for space propulsion are required to operate for extended periods of time, usually in excess of 10,000 hr. Lengthy and very costly life-tests in high-vacuum facilities have been required in the past to determine the erosion rates of thruster components. Alternative methods for determining erosion rates which can be performed in relatively short periods of time at considerably lower costs are studied. An attempt to relate optical emission intensity from an ion bombarded surface (screen grid) to the sputtering rate of that surface is made. The model used a kinetic steady-state (KSS) approach, balancing the rates of population and depopulation of ten low-lying excited states of the sputtered molybdenum atom (MoI) with those of the ground state to relate the spectral intensities of the various transitions of the MoI to the population densities. Once this is accomplished, the population density can be related to the sputting rate of the target. Radiative and collisional modes of excitation and decay are considered. Since actual data has not been published for MoI excitation rate and decay constants, semiempirical equations are used. The calculated sputtering rate and intensity is compared to the measured intensity and sputtering rates of the 8 and 30 cm ion thrusters.

  19. Mode Transitions in Magnetically Shielded Hall Effect Thrusters

    Science.gov (United States)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Huang, Wensheng; Kamhawi, Hani; Hofer, Richard R.; Jorns, Benjamin A.; Polk, James E.

    2014-01-01

    A mode transition study is conducted in magnetically shielded thrusters where the magnetic field magnitude is varied to induce mode transitions. Three different oscillatory modes are identified with the 20-kW NASA-300MS-2 and the 6-kW H6MS: Mode 1) global mode similar to unshielded thrusters at low magnetic fields, Mode 2) cathode oscillations at nominal magnetic fields, and Mode 3) combined spoke, cathode and breathing mode oscillations at high magnetic fields. Mode 1 exhibits large amplitude, low frequency (1-10 kHz), breathing mode type oscillations where discharge current mean value and oscillation amplitude peak. The mean discharge current is minimized while thrust-to-power and anode efficiency are maximized in Mode 2, where higher frequency (50-90 kHz), low amplitude, cathode oscillations dominate. Thrust is maximized in Mode 3 and decreases by 5-6% with decreasing magnetic field strength. The presence or absence of spokes and strong cathode oscillations do not affect each other or discharge current. Similar to unshielded thrusters, mode transitions and plasma oscillations affect magnetically shielded thruster performance and should be characterized during system development.

  20. STS-39: OMS Pod Thruster Removal/Replace

    Science.gov (United States)

    1991-01-01

    Shown is the removal and replacement of the Discovery's orbital maneuvering systems (OMS) pod thruster. The OMS engine will be used to propel Discovery north, off of its previous orbital groundtrack, without changing the spacecraft's altitude. A burn with this lateral effect is known as "out-of-plane."

  1. Thermal stability of the krypton Hall effect thruster

    Directory of Open Access Journals (Sweden)

    Szelecka Agnieszka

    2017-03-01

    Full Text Available The Krypton Large IMpulse Thruster (KLIMT ESA/PECS project, which has been implemented in the Institute of Plasma Physics and Laser Microfusion (IPPLM and now is approaching its final phase, was aimed at incremental development of a ~500 W class Hall effect thruster (HET. Xenon, predominantly used as a propellant in the state-of-the-art HETs, is extremely expensive. Krypton has been considered as a cheaper alternative since more than fifteen years; however, to the best knowledge of the authors, there has not been a HET model especially designed for this noble gas. To address this issue, KLIMT has been geared towards operation primarily with krypton. During the project, three subsequent prototype versions of the thruster were designed, manufactured and tested, aimed at gradual improvement of each next exemplar. In the current paper, the heat loads in new engine have been discussed. It has been shown that thermal equilibrium of the thruster is gained within the safety limits of the materials used. Extensive testing with both gases was performed to compare KLIMT’s thermal behaviour when supplied with krypton and xenon propellants.

  2. Simulations of a Plasma Thruster Utilizing the FRC Configuration

    Energy Technology Data Exchange (ETDEWEB)

    Rognlien, T. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Cohen, B. I. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-10-10

    This report describes work performed by LLNL to model the behavior and performance of a reverse-field configuration (FRC) type of plasma device as a plasma thruster as summarized by Razin et al. [1], which also describes the MNX device at PPPL used to study this concept.

  3. Hardware in the Loop Testing of an Iodine-Fed Hall Thruster

    Science.gov (United States)

    Polzin, Kurt A.; Peeples, Steven R.; Cecil, Jim; Lewis, Brandon L.; Molina Fraticelli, Jose C.; Clark, James P.

    2015-01-01

    chamber (it is under 10(exp -6) torr at -75 C), making it possible to 'cryopump' the propellant with lower-cost recirculating refrigerant-based systems as opposed to using liquid nitrogen or low temperature gaseous helium cryopanels. In the present paper, we describe testing performed using an iodine-fed 200 W Hall thruster mounted to a thrust stand and operated in conjunction with MSFCs Small Projects Rapid Integration and Test Environment (SPRITE) Portable Hardware In the Loop (PHIL) hardware. This work is performed in support of the iodine satellite (iSAT) project, which aims to fly a 200-W iodine-fed thruster on a 12-U CubeSat. The SPRITE PHIL hardware allows a given vehicle to do a checkout of its avionics algorithm by allowing it to monitor and feed data to simulated sensors and effectors in a digital environment. These data are then used to determine the attitude of the vehicle and a separate computer is used to interpret the data set and visualize it using a 3D graphical interface. The PHIL hardware allows the testing of the vehicles bus by providing 'real' hardware interfaces (in the case of this test a real RS422 bus) and specific components can be modeled to show their interactions with the avionics algorithm (e.g. a thruster model). For the iSAT project the PHIL is used to visualize the operating cycle of the thruster and the subsequent effect this thrusting has on the attitude of the satellite over a given period of time. The test is controlled using software running on an Andrews Space Cortex 160 flight computer. This computer is the current baseline for a full iSAT mission. While the test could be conducted with a lab computer and software, the team chose to exercise the propulsion system with a representative CubeSat-class computer. For purposes of this test, the "flight" software monitored the propulsion and PPU systems, controlled operation of the thruster, and provided thruster state data to the PHIL simulation. Commands to operate the thruster were

  4. Results of the qualification test campaign of a Pulsed Plasma Thruster for Cubesat Propulsion (PPTCUP)

    Science.gov (United States)

    Ciaralli, S.; Coletti, M.; Gabriel, S. B.

    2016-04-01

    Pulsed Plasma Thruster for Cubesat Propulsion (PPTCUP) is an ablative pulsed plasma thruster designed with the aim of providing translational and orbital control to Cubesat platforms. The qualification model presented in this paper has been developed by Mars Space Ltd, Clyde Space Ltd and the University of Southampton to produce a versatile "stand-alone" module that can be bolted on the Cubesat structure, allowing the orbital control along the X or Y-axis of the satellite. An extensive and complete test campaign to qualify the unit for space flight, which includes electromagnetic compatibility (EMC) characterization, thermal cycling and mechanical tests, has been performed according to the NASA GEVS procedures. PPTCUP is characterized by an averaged specific impulse of 655±58 s and a deliverable total impulse of 48.2±4.2 Ns. Finally, it has been found that the unit is compliant with the EMC requirements and can successfully withstand the thermal and mechanical loads typical of a Cubesat space mission.

  5. Supramolecular photocatalysis: combining confinement and non-covalent interactions to control light initiated reactions.

    Science.gov (United States)

    Vallavoju, Nandini; Sivaguru, J

    2014-06-21

    Using non-bonding interactions to control photochemical reactions requires an understanding of not only thermodynamics and kinetics of ground state and excited state processes but also the intricate interactions that dictate the dynamics within the system of interest. This review is geared towards a conceptual understanding of how one can control the reactivity and selectivity in the excited state by employing confinement and non-covalent interactions. Photochemical reactivity of organic molecules within confined containers and organized assemblies as well as organic templates that interact through H-bonding and/or cation-carbonyl/cation-π interactions is reviewed with an eye towards understanding supramolecular effects and photocatalysis.

  6. Magnetoplasmadynamic electric propulsion thruster behavior at the hundred megawatt level

    Science.gov (United States)

    Marriott, Darin William

    Characteristic measurements were made of a hundred megawatt modified helium inverse pinch switch and compared against numerical modeling and theoretically expected behavior. Thruster voltage was measured for currents between three and three hundred kilo amps and for mass flow rates between 0.96 and 40 grams per second. From that, characteristic voltage, power, and resistance curves were generated. Electron temperature measurements made inside the plasma flow using triple Langmuir probes were found to be between three and thirty electron volts. General expected MPD thruster behavior, such as decreasing resistance with increasing mass flow rate, were confirmed. The quasi steady assumption was studied between 1.5 and 1.7 milliseconds and found to be appropriate. A theoretical model, based on integrating the magnetic field to determine thrust, as for an MPD thruster, was used to estimate fall voltages, pumping coefficients, and specific impulse. An empirical model for thruster voltage was then created to estimate the behavior of voltage as a function of the similarity parameter. The two models were then put together and found to be self consistent with the experimental data. Three sources of power loss were estimated given the experimental and theoretical model. The power lost due to fall voltage mechanisms was calculated from the theoretical model and the input current as a function of time. The ionization losses were estimated using a worst case scenario of complete double ionization of the input helium mass flow rate as a function of time. Thermal losses were calculated from the electron temperature and the input mass flow rate. Total temperature, specific impulse, and efficiency measurements were all presented as a function of a similarity parameter in line with MPD theory. Basic MPD thruster behavior was confirmed. Suggestions were made for future continuation of the project.

  7. Carbon Back Sputter Modeling for Hall Thruster Testing

    Science.gov (United States)

    Gilland, James H.; Williams, George J.; Burt, Jonathan M.; Yim, John Tamin

    2016-01-01

    Lifetime requirements for electric propulsion devices, including Hall Effect thrusters, are continually increasing, driven in part by NASA's inclusion of this technology in it's exploration architecture. NASA will demonstrate high-power electric propulsion system on the Solar Electric Propulsion Technology Demonstration Mission (SEP TDM). The Asteroid Redirect Robotic mission is one candidate SEP TDM, which is projected to require tens of thousands of thruster life. As thruster life is increased, for example through the use of improved magnetic field designs, the relative influence of facility effects increases. One such effect is the sputtering and redeposition, or back sputter, of facility materials by the high energy thruster plumes. In support of wear testing for the Hall Effect Rocket with Magnetic Shielding (HERMeS) project, the back sputter from a Hall effect thruster plume has been modeled for the NASA Glenn Research Center's Vacuum Facility 5. The predicted wear at a near-worst case condition of 600 V, 12.5 kW was found to be on the order of 1 micron/kh in a fully carbon-lined chamber. A more detailed numerical Monte Carlo code was also modified to estimate back sputter for a detailed facility and pumping configuration. This code demonstrated similar back sputter rate distributions, but is not yet accurately modeling the magnitudes. The modeling has been benchmarked to recent HERMeS wear testing, using multiple microbalance measurements. These recent measurements have yielded values on the order of 1.5 - 2 micron/kh at 600 V and 12.5 kW.

  8. Comparisons in Performance of Electromagnet and Permanent-Magnet Cylindrical Hall-Effect Thrusters

    Science.gov (United States)

    Polzin, K. A.; Raitses, Y.; Gayoso, J. C.; Fisch, N. J.

    2010-01-01

    Three different low-power cylindrical Hall thrusters, which more readily lend themselves to miniaturization and low-power operation than a conventional (annular) Hall thruster, are compared to evaluate the propulsive performance of each. One thruster uses electromagnet coils to produce the magnetic field within the discharge channel while the others use permanent magnets, promising power reduction relative to the electromagnet thruster. A magnetic screen is added to the permanent magnet thruster to improve performance by keeping the magnetic field from expanding into space beyond the exit of the thruster. The combined dataset spans a power range from 50-350 W. The thrust levels over this range were 1.3-7.3 mN, with thruster efficiencies and specific impulses spanning 3.5-28.7% and 400-1940 s, respectively. The efficiency is generally higher for the permanent magnet thruster with the magnetic screen, while That thruster s specific impulse as a function of discharge voltage is comparable to the electromagnet thruster.

  9. Pump-shaped dump optimal control reveals the nuclear reaction pathway of isomerization of a photoexcited cyanine dye.

    Science.gov (United States)

    Dietzek, Benjamin; Brüggemann, Ben; Pascher, Torbjörn; Yartsev, Arkady

    2007-10-31

    Using optimal control as a spectroscopic tool we decipher the details of the molecular dynamics of the essential multidimensional excited-state photoisomerization - a fundamental chemical reaction of key importance in biology. Two distinct nuclear motions are identified in addition to the overall bond-twisting motion: Initially, the reaction is dominated by motion perpendicular to the torsion coordinate. At later times, a second optically active vibration drives the system along the reaction path to the bottom of the excited-state potential. The time scales of the wavepacket motion on a different part of the excited-state potential are detailed by pump-shaped dump optimal control. This technique offers new means to control a chemical reaction far from the Franck-Condon point of absorption and to map details of excited-state reaction pathways revealing unique insights into the underlying reaction mechanism.

  10. Attitude Control of a Satellite Simulator Using Reaction Wheels and a PID Controller

    Science.gov (United States)

    2010-03-01

    Rohe, and Welty in the development of AFIT’s second- generation satellite simulator, SimSat II [40]. Instead of building another dumbbell-style spherical...Nathan F. Welty . A Systems Engineering Approach to the Design of a Spacecraft Dynamics and Control Testbed. MS thesis, Air Force Institute of

  11. Isolating Reactions at the Picoliter Scale: Parallel Control of Reaction Kinetics at the Liquid-Liquid Interface.

    Science.gov (United States)

    Phan-Quang, Gia Chuong; Lee, Hiang Kwee; Ling, Xing Yi

    2016-07-11

    Miniaturized liquid-liquid interfacial reactors offer enhanced surface area and rapid confinement of compounds of opposite solubility, yet they are unable to provide in situ reaction monitoring at a molecular level at the interface. A picoreactor operative at the liquid-liquid interface is described, comprising plasmonic colloidosomes containing Ag octahedra strategically assembled at the water-in-decane emulsion interface. The plasmonic colloidosomes isolate ultrasmall amounts of solutions (<200 pL), allowing parallel monitoring of multiple reactions simultaneously. Using the surface-enhanced Raman spectroscopy (SERS) technique, in situ monitoring of the interfacial protonation of dimethyl yellow (p-dimethylaminoazobenzene (DY)) is performed, revealing an apparent rate constant of 0.09 min(-1) for the first-order reaction. The presence of isomeric products with similar physical properties is resolved, which would otherwise be indiscernible by other analytical methods.

  12. A general strategy for nanohybrids synthesis via coupled competitive reactions controlled in a hybrid process.

    Science.gov (United States)

    Wang, Rongming; Yang, Wantai; Song, Yuanjun; Shen, Xiaomiao; Wang, Junmei; Zhong, Xiaodi; Li, Shuai; Song, Yujun

    2015-01-01

    A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission).

  13. Biophysical assay for tethered signaling reactions reveals tether-controlled activity for the phosphatase SHP-1

    Science.gov (United States)

    Goyette, Jesse; Salas, Citlali Solis; Coker-Gordon, Nicola; Bridge, Marcus; Isaacson, Samuel A.; Allard, Jun; Dushek, Omer

    2017-01-01

    Tethered enzymatic reactions are ubiquitous in signaling networks but are poorly understood. A previously unreported mathematical analysis is established for tethered signaling reactions in surface plasmon resonance (SPR). Applying the method to the phosphatase SHP-1 interacting with a phosphorylated tether corresponding to an immune receptor cytoplasmic tail provides five biophysical/biochemical constants from a single SPR experiment: two binding rates, two catalytic rates, and a reach parameter. Tether binding increases the activity of SHP-1 by 900-fold through a binding-induced allosteric activation (20-fold) and a more significant increase in local substrate concentration (45-fold). The reach parameter indicates that this local substrate concentration is exquisitely sensitive to receptor clustering. We further show that truncation of the tether leads not only to a lower reach but also to lower binding and catalysis. This work establishes a new framework for studying tethered signaling processes and highlights the tether as a control parameter in clustered receptor signaling.

  14. Control analysis of systems with reaction blocks that 'cross-talk'.

    Science.gov (United States)

    Ainscow, E K; Brand, M D

    1998-09-01

    Practical application of metabolic control analysis has been facilitated by use of the top-down approach, which divides a metabolic system into a small number of reaction blocks, linked by a few key intermediates. Previous papers have stressed that communication between blocks should be only through the explicit intermediates, 'cross-talk' between reaction blocks invalidated the approach. Here we show how the restriction is a result of the use of inhibitors of the blocks, and can be overcome if other system modulations are used. We also show a way to treat the related problem of enzymes that appear in more than one block such as the analysis of glycolytic substrate cycles into ATP consuming and net flux activities.

  15. Study and Developement of Compact Permanent Magnet Hall Thrusters for Future Brazillian Space Missions

    Science.gov (United States)

    Ferreira, Jose Leonardo; Martins, Alexandre; Cerda, Rodrigo

    2016-07-01

    The Plasma Physics Laboratory of UnB has been developing a Permanent Magnet Hall Thruster (PHALL) for the UNIESPAÇO program, part of the Space Activities Program conducted by AEB- The Brazillian Space Agency since 2004. Electric propulsion is now a very successful method for primary and secondary propulsion systems. It is essential for several existing geostationary satellite station keeping systems and for deep space long duration solar system missions, where the thrusting system can be designed to be used on orbit transfer maneuvering and/or for satellite attitude control in long term space missions. Applications of compact versions of Permanent Magnet Hall Thrusters on future brazillian space missions are needed and foreseen for the coming years beginning with the use of small divergent cusp field (DCFH) Hall Thrusters type on CUBESATS ( 5-10 kg , 1W-5 W power consumption) and on Micro satellites ( 50- 100 kg, 10W-100W). Brazillian (AEB) and German (DLR) space agencies and research institutions are developing a new rocket dedicated to small satellite launching. The VLM- Microsatellite Launch Vehicle. The development of PHALL compact versions can also be important for the recently proposed SBG system, a future brazillian geostationary satellite system that is already been developed by an international consortium of brazillian and foreign space industries. The exploration of small bodies in the Solar System with spacecraft has been done by several countries with increasing frequency in these past twenty five years. Since their historical beginning on the sixties, most of the Solar System missions were based on gravity assisted trajectories very much depended on planet orbit positioning relative to the Sun and the Earth. The consequence was always the narrowing of the mission launch window. Today, the need for Solar System icy bodies in situ exploration requires less dependence on gravity assisted maneuvering and new high precision low thrust navigation methods

  16. The Development of Plasma Thrusters and Its Importance for Space Technology and Science Education at University of Brasilia

    Science.gov (United States)

    Ferreira, Jose Leonardo; Calvoso, Lui; Gessini, Paolo; Ferreira, Ivan

    Since 2004 The Plasma Physics Laboratory of University of Brasilia (Brazil) is developing Hall Plasma Thurusters for Satellite station keeping and orbit control. The project is supported by CNPq, CAPES, FAP DF and from The Brazillian Space Agency-AEB. The project is part of The UNIESPAÇO Program for Space Activities Development in Brazillian Universities. In this work we are going to present the highlights of this project together with its vital contribution to include University of Brasilia in the Brazillian Space Program. Electric propulsion has already shown, over the years, its great advantages in being used as main and secondary thruster system of several space mission types. Between the many thruster concepts, one that has more tradition in flying real spacecraft is the Hall Effect Thruster (HET). These thrusters, first developed by the USSR in the 1960s, uses, in the traditional design, the radial magnetic field and axial electric field to trap electrons, ionize the gas and accelerate the plasma to therefore generate thrust. In contrast to the usual solution of using electromagnets to generate the magnetic field, the research group of the Plasma Physics Laboratory of University of Brasília has been working to develop new models of HETs that uses combined permanent magnets to generate the necessary magnetic field, with the main objective of saving electric power in the final system design. Since the beginning of this research line it was developed and implemented two prototypes of the Permanent Magnet Hall Thruster (PMHT). The first prototype, called P-HALL1, was successfully tested with the using of many diagnostics instruments, including, RF probe, Langmuir probe, Ion collector and Ion energy analyzer. The second prototype, P-HALL2, is currently under testing, and it’s planned the increasing of the plasma diagnostics and technology analysis, with the inclusion of a thrust balance, mass spectroscopy and Doppler broadening. We are also developing an

  17. Pickup ion processes associated with spacecraft thrusters: Implications for solar probe plus

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Adam, E-mail: a.j.clemens@qmul.ac.uk; Burgess, David [School of Physics and Astronomy, Queen Mary University of London, London (United Kingdom)

    2016-03-15

    Chemical thrusters are widely used in spacecraft for attitude control and orbital manoeuvres. They create an exhaust plume of neutral gas which produces ions via photoionization and charge exchange. Measurements of local plasma properties will be affected by perturbations caused by the coupling between the newborn ions and the plasma. A model of neutral expansion has been used in conjunction with a fully three-dimensional hybrid code to study the evolution and ionization over time of the neutral cloud produced by the firing of a mono-propellant hydrazine thruster as well as the interactions of the resulting ion cloud with the ambient solar wind. Results are presented which show that the plasma in the region near to the spacecraft will be perturbed for an extended period of time with the formation of an interaction region around the spacecraft, a moderate amplitude density bow wave bounding the interaction region and evidence of an instability at the forefront of the interaction region which causes clumps of ions to be ejected from the main ion cloud quasi-periodically.

  18. Pickup ion processes associated with spacecraft thrusters: Implications for solar probe plus

    Science.gov (United States)

    Clemens, Adam; Burgess, David

    2016-03-01

    Chemical thrusters are widely used in spacecraft for attitude control and orbital manoeuvres. They create an exhaust plume of neutral gas which produces ions via photoionization and charge exchange. Measurements of local plasma properties will be affected by perturbations caused by the coupling between the newborn ions and the plasma. A model of neutral expansion has been used in conjunction with a fully three-dimensional hybrid code to study the evolution and ionization over time of the neutral cloud produced by the firing of a mono-propellant hydrazine thruster as well as the interactions of the resulting ion cloud with the ambient solar wind. Results are presented which show that the plasma in the region near to the spacecraft will be perturbed for an extended period of time with the formation of an interaction region around the spacecraft, a moderate amplitude density bow wave bounding the interaction region and evidence of an instability at the forefront of the interaction region which causes clumps of ions to be ejected from the main ion cloud quasi-periodically.

  19. Controlling an electron-transfer reaction at a metal surface by manipulating reactant motion and orientation.

    Science.gov (United States)

    Bartels, Nils; Krüger, Bastian C; Auerbach, Daniel J; Wodtke, Alec M; Schäfer, Tim

    2014-12-08

    The loss or gain of vibrational energy in collisions of an NO molecule with the surface of a gold single crystal proceeds by electron transfer. With the advent of new optical pumping and orientation methods, we can now control all molecular degrees of freedom important to this electron-transfer-mediated process, providing the most detailed look yet into the inner workings of an electron-transfer reaction and showing how to control its outcome. We find the probability of electron transfer increases with increasing translational and vibrational energy as well as with proper orientation of the reactant. However, as the vibrational energy increases, translational excitation becomes unimportant and proper orientation becomes less critical. One can understand the interplay of all three control parameters from simple model potentials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Metabolic control analysis of biochemical pathways based on a thermokinetic description of reaction rates

    DEFF Research Database (Denmark)

    Nielsen, Jens Bredal

    1997-01-01

    Metabolic control analysis is a powerful technique for the evaluation of flux control within biochemical pathways. Its foundation is the elasticity coefficients and the flux control coefficients (FCCs). On the basis of a thermokinetic description of reaction rates it is here shown...... affinity. This parameter can often be determined from experiments in vitro. The methodology is applicable only to the analysis of simple two-step pathways, but in many cases larger pathways can be lumped into two overall conversions. In cases where this cannot be done it is necessary to apply an extension...... be much more widely applied, although it was originally based on linearized kinetics. The methodology of determining elasticity coefficients directly from pool levels is illustrated with an analysis of the first two steps of the biosynthetic pathway of penicillin. The results compare well with previous...

  1. Microwave ECR Ion Thruster Development Activities at NASA Glenn Research Center

    Science.gov (United States)

    Foster, John E.; Patterson, Michael J.

    2002-01-01

    Outer solar system missions will have propulsion system lifetime requirements well in excess of that which can be satisfied by ion thrusters utilizing conventional hollow cathode technology. To satisfy such mission requirements, other technologies must be investigated. One possible approach is to utilize electrodeless plasma production schemes. Such an approach has seen low power application less than 1 kW on earth-space spacecraft such as ARTEMIS which uses the rf thruster the RIT 10 and deep space missions such as MUSES-C which will use a microwave ion thruster. Microwave and rf thruster technologies are compared. A microwave-based ion thruster is investigated for potential high power ion thruster systems requiring very long lifetimes.

  2. Performance Characterization of a Novel Plasma Thruster to Provide a Revolutionary Operationally Responsive Space Capability with Micro- and Nano-Satellites

    Science.gov (United States)

    2011-03-24

    controllers. ............ 33 Figure 15. BPU -600 Host Simulator software interface. ................................................. 34 Figure 16...Figure 14. Xenon and krypton bottle and battery of four mass flow controllers. Power for the thruster and cathode were provided by a Busek BPU -600...supply, which was capable of 0-55 V and 0-55 A. Control of the PPU was achieved using Busek‘s BPU -600 Host Simulator, which was a LabView

  3. Test stand for precise measurement of impulse and thrust vector of small attitude control jets

    Science.gov (United States)

    Woodruff, J. R.; Chisel, D. M.

    1973-01-01

    A test stand which accurately measures the impulse bit and thrust vector of reaction jet thrusters used in the attitude control system of space vehicles has been developed. It can be used to measure, in a vacuum or ambient environment, both impulse and thrust vector of reaction jet thrusters using hydrazine or inert gas propellants. The ballistic pendulum configuration was selected because of its accuracy, simplicity, and versatility. The pendulum is mounted on flexure pivots rotating about a vertical axis at the center of its mass. The test stand has the following measurement capabilities: impulse of 0.00004 to 4.4 N-sec (0.00001 to 1.0 lb-sec) with a pulse duration of 0.5 msec to 1 sec; static thrust of 0.22 to 22 N (0.05 to 5 lb) with a 5 percent resolution; and thrust angle alinement of 0.22 to 22 N (0.05 to 5 lb) thrusters with 0.01 deg accuracy.

  4. Reaction-Multi Diffusion Model for Nutrient Release and Autocatalytic Degradation of PLA-Coated Controlled-Release Fertilizer

    Directory of Open Access Journals (Sweden)

    Sayed Ameenuddin Irfan

    2017-03-01

    Full Text Available A mathematical model for the reaction-diffusion equation is developed to describe the nutrient release profiles and degradation of poly(lactic acid (PLA-coated controlled-release fertilizer. A multi-diffusion model that consists of coupled partial differential equations is used to study the diffusion and chemical reaction (autocatalytic degradation simultaneously. The model is solved using an analytical-numerical method. Firstly, the model equation is transformed using the Laplace transformation as the Laplace transform cannot be inverted analytically. Numerical inversion of the Laplace transform is used by employing the Zakian method. The solution is useful in predicting the nutrient release profiles at various diffusivity, concentration of extraction medium, and reaction rates. It also helps in explaining the transformation of autocatalytic concentration in the coating material for various reaction rates, times of reaction, and reaction-multi diffusion. The solution is also applicable to the other biodegradable polymer-coated controlled-release fertilizers.

  5. How does practise of internal Chinese martial arts influence postural reaction control?

    Science.gov (United States)

    Gorgy, Olivier; Vercher, Jean-Louis; Coyle, Thelma

    2008-04-01

    The aim of this study was to determine the effects of Chinese martial arts practice on postural reaction control after perturbation. Participants standing in Romberg tandem posture were subjected to an unexpected lateral platform translation with the eyes open or closed at two translation amplitudes. The peak displacement of the centre of pressure and of the centre of mass, and the onset latency of muscular activity (tibialis anterior, gastrocnemius, lumbodorsal muscular group, and rectus abdominis), were evaluated for martial arts practitioners and for sport and non-sport participants. Compared with the sport and non-sport participants, the martial arts group showed lower maximal centre of pressure and centre of mass peak displacements in both the lateral and anterior - posterior directions, but no difference was found in the onset of muscular responses. We conclude that martial arts practice influences postural reaction control during a fixed-support strategy in a tandem task. The martial arts group used the ankle joint more frequently than the sport and non-sport participants, especially in the eyes-closed conditions. Our results suggest that the better balance recovery in the martial arts group is a consequence of better control of biomechanical properties of the lower limbs (e.g. through muscular response by co-contraction), not a change in the neuromuscular temporal pattern.

  6. Ex vivo engineered immune organoids for controlled germinal center reactions.

    Science.gov (United States)

    Purwada, Alberto; Jaiswal, Manish K; Ahn, Haelee; Nojima, Takuya; Kitamura, Daisuke; Gaharwar, Akhilesh K; Cerchietti, Leandro; Singh, Ankur

    2015-09-01

    Ex vivo engineered three-dimensional organotypic cultures have enabled the real-time study and control of biological functioning of mammalian tissues. Organs of broad interest where its architectural, cellular, and molecular complexity has prevented progress in ex vivo engineering are the secondary immune organs. Ex vivo immune organs can enable mechanistic understanding of the immune system and more importantly, accelerate the translation of immunotherapies as well as a deeper understanding of the mechanisms that lead to their malignant transformation into a variety of B and T cell malignancies. However, till date, no modular ex vivo immune organ has been developed with an ability to control the rate of immune reaction through tunable design parameter. Here we describe a B cell follicle organoid made of nanocomposite biomaterials, which recapitulates the anatomical microenvironment of a lymphoid tissue that provides the basis to induce an accelerated germinal center (GC) reaction by continuously providing extracellular matrix (ECM) and cell-cell signals to naïve B cells. Compared to existing co-cultures, immune organoids provide a control over primary B cell proliferation with ∼100-fold higher and rapid differentiation to the GC phenotype with robust antibody class switching.

  7. Development, Vibration, and Thermal Characterization of a Steady Operating Pulsed Power System for FRC Thrusters

    Science.gov (United States)

    2015-04-01

    Field (RMF) to produce large plasma currents inside a conical thruster creating a field-reversed configuration (FRC) plasmoid that is magnetically...in turn charges a high-Q capacitor. Connected in series with the thruster antenna, the resonant RLC circuit oscillates at high frequency with a...Field (RMF) to produce large plasma currents inside a conical thruster creating a field-reversed configuration (FRC) plasmoid that is magnetically

  8. Attitude Control Synthesis for Small Satellites Using Gradient Method. Part II Linear Equations, Synthesis

    Directory of Open Access Journals (Sweden)

    Adrian CHELARU

    2013-03-01

    Full Text Available In order to continue paper [5] which presented the nonlinear equations of the movement for small satellite, this paper presents some aspects regarding the synthesis of the attitude control. Afterthe movement equation linearization, the stability and command matrixes will be established and by using the gradient methods controller we will obtain them. Two attitude control cases will beanalysed: the reaction wheels and the micro thrusters. The results will be used in the project European Space Moon Orbit - ESMO, founded by the European Space Agency in which the POLITEHNICA University of Bucharest is involved.

  9. Comparison of Mars Science Laboratory Reaction Control System Jet Computations With Flow Visualization and Velocimetry

    Science.gov (United States)

    Bathel, Brett F.; Danehy, Paul M.; Johansen, Craig T.; Ashcraft, Scott W.; Novak, Luke A.

    2013-01-01

    Numerical predictions of the Mars Science Laboratory reaction control system jets interacting with a Mach 10 hypersonic flow are compared to experimental nitric oxide planar laser-induced fluorescence data. The steady Reynolds Averaged Navier Stokes equations using the Baldwin-Barth one-equation turbulence model were solved using the OVERFLOW code. The experimental fluorescence data used for comparison consists of qualitative two-dimensional visualization images, qualitative reconstructed three-dimensional flow structures, and quantitative two-dimensional distributions of streamwise velocity. Through modeling of the fluorescence signal equation, computational flow images were produced and directly compared to the qualitative fluorescence data.

  10. Efficient oxidation of benzyl alcohol with heteropolytungstate as reaction-controlled phase-transfer catalyst

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of heteropolytungstates has been synthesized and utilized as catalysts to catalyze oxidation of benzyl alcohol with aqueous hydrogen peroxide. The results indicated that three of these catalysts showed the properties of reaction-controlled phasetransfer catalysis, and they had excellent catalytic ability to the oxidation of benzyl alcohol. No other by-products were detected by gas chromatography. Once the hydrogen peroxide was consumed completely, the catalyst precipitated from solvent, and the results of the catalyst recycle showed that the catalyst had high stability.

  11. Controllable Chemoselectivity in Visible-Light Photoredox Catalysis: Four Diverse Aerobic Radical Cascade Reactions.

    Science.gov (United States)

    Liu, Xinfei; Ye, Xinyi; Bureš, Filip; Liu, Hongjun; Jiang, Zhiyong

    2015-09-21

    Reported is the controllable selectivity syntheses of four distinct products from the same starting materials by visible-light photoredox catalysis. By employing a dicyanopyrazine-derived chromophore (DPZ) as photoredox catalyst, an aerobic radical mechanism has been developed, and allows the reactions of N-tetrahydroisoquinolines (THIQs) with N-itaconimides to through four different pathways, including addition-cyclization, addition-elimination, addition-coupling, and addition-protonation, with satisfactory chemoselectivity. The current strategy provide straightforward access to four different but valuable N-heterocyclic adducts in moderate to excellent yields. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Progress and prospects in nanoscale dry processes: How can we control atomic layer reactions?

    Science.gov (United States)

    Ishikawa, Kenji; Karahashi, Kazuhiro; Ichiki, Takanori; Chang, Jane P.; George, Steven M.; Kessels, W. M. M.; Lee, Hae June; Tinck, Stefan; Um, Jung Hwan; Kinoshita, Keizo

    2017-06-01

    In this review, we discuss the progress of emerging dry processes for nanoscale fabrication. Experts in the fields of plasma processing have contributed to addressing the increasingly challenging demands in achieving atomic-level control of material selectivity and physicochemical reactions involving ion bombardment. The discussion encompasses major challenges shared across the plasma science and technology community. Focus is placed on advances in the development of fabrication technologies for emerging materials, especially metallic and intermetallic compounds and multiferroic, and two-dimensional (2D) materials, as well as state-of-the-art techniques used in nanoscale semiconductor manufacturing with a brief summary of future challenges.

  13. Control of photoassociation reaction F+H→HF with ultrashort laser pulse

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The laser-induced vibrational state-selectivity of product HF in photoassociation reaction H+F→HF is theoretically investigated by using the time-dependent quantum wave packet method. The population transfer process from the continuum state down to the bound vibrational states can be controlled by the driving laser. The effects of laser pulse parameters and the initial momentum of the two collision atoms on the vibrational population of the product HF are discussed in detail. Photodissociation accompanied with the photoassociation process is also described.

  14. Theory of Solvation-Controlled Reactions in Stimuli-Responsive Nanoreactors

    CERN Document Server

    Angioletti-Uberti, Stefano; Ballauff, Matthias; Dzubiella, Joachim

    2015-01-01

    Metallic nanoparticles embedded in stimuli-responsive polymers can be regarded as nanoreactors since their catalytic activity can be changed within wide limits: the physicochemical properties of the polymer network can be tuned and switched by external parameters, e.g. temperature or pH, and thus allows a selective control of reactant mobility and concentration close to the reaction site. Based on a combination of Debye's model of diffusion through an energy landscape and a two-state model for the polymer, here we develop an analytical expression for the observed reaction rate constant $k_{\\rm obs}$. Our formula shows an exponential dependence of this rate on the solvation free enthalpy change $\\Delta \\bar{G}_{\\rm sol}$, a quantity which describes the partitioning of the reactant in the network versus bulk. Thus, changes in $\\Delta \\bar{G}_{\\rm sol}$, and not in the diffusion coefficient, will be the decisive factor affecting the reaction rate in most cases. A comparison with recent experimental data on switc...

  15. A novel control of enzymatic enantioselectivity through the racemic temperature influenced by reaction media.

    Science.gov (United States)

    Jin, Xin; Liu, Bokai; Ni, Zhong; Wu, Qi; Lin, Xianfu

    2011-05-06

    The influence of reaction media on the racemic temperature (T(r)) in the lipase-catalyzed resolution of ketoprofen vinyl ester was investigated. An effective approach to the control of the enzymatic enantioselectivity and the prediction of the increasing tendency was developed based on the T(r) influenced by reaction media. The T(r) for the resolution catalyzed by Candida rugosa lipase (CRL) was found at 29 °C in aqueous and S-ketoprofen was obtained predominantly at 40 °C. However, CRL showed R-selectivity at 40 °C in diisopropyl ether because the T(r) was changed to 56 °C. CRL, lipase from AYS Amano(®) and Mucor javanicus lipase were further applied for the investigation of the enzymatic enantioselectivity in dioxane, DIPE, isooctane and their mixed media with water. The effects of the reaction medium on T(r) could be related to the solvent hydrophobicity, the lipase conformational flexibility and the interaction between the enantiomers and the lipase.

  16. Engineering Model Propellant Feed System Development for an Iodine Hall Thruster Demonstration Mission

    Science.gov (United States)

    Polzin, Kurt A.

    2016-01-01

    chamber (it is under 10(exp -6) torr at -75 C), making it possible to 'cryopump' the propellant with lower-cost recirculating refrigerant-based systems as opposed to using liquid nitrogen or low temperature gaseous helium cryopanels. In the present paper, we describe the design and testing of the engineering model propellant feed system for iSAT (see Fig. 1). The feed system is based around an iodine propellant reservoir and two proportional control valves (PFCVs) that meter the iodine flow to the cathode and anode. The flow is split upstream of the PFCVs to both components can be fed from a common reservoir. Testing of the reservoir is reported to demonstrate that the design is capable of delivering the required propellant flow rates to operate the thruster. The tubing and reservoir are fabricated from hastelloy to resist corrosion by the heated gaseous iodine propellant. The reservoir, tubing, and PFCVs are heated to ensure the sublimed propellant will not re-deposit within the feed system. Heating is accomplished through a number of individual zones to control the overall power expended on heating the system and insulation is employed to minimize the amount of power used to heat the system prior to thruster operation.

  17. Low-Cost High-Performance Hall Thruster Support System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Colorado Power Electronics (CPE) has built an innovative modular power processing unit (PPU) for Hall Thrusters, including discharge, magnet, heater and keeper...

  18. Carbon Nanotube Based Electric Propulsion Thruster with Low Power Consumption Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Field emission electric propulsion (FEEP) thrusters have gained considerable attention for spacecrafts disturbance compensation because of excellent characteristics....

  19. Plasma Characterization of Hall Thruster with Active and Passive Segmented Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Raitses, Y.; Staack, D.; Fisch, N.J.

    2002-09-04

    Non-emissive electrodes and ceramic spacers placed along the Hall thruster channel are shown to affect the plasma potential distribution and the thruster operation. These effects are associated with physical properties of the electrode material and depend on the electrode configuration, geometry and the magnetic field distribution. An emissive segmented electrode was able to maintain thruster operation by supplying an additional electron flux to sustain the plasma discharge between the anode and cathode neutralizer. These results indicate the possibility of new configurations for segmented electrode Hall thruster.

  20. Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster

    Science.gov (United States)

    Jorns, Benjamin A.; Hofery, Richard R.

    2013-01-01

    The oscillations from 0-100 kHz in a 6-kW magnetically shielded thruster are experimen- tally characterized. Changes in plasma parameters that result from the magnetic shielding of Hall thrusters have the potential to significantly alter thruster transients. A detailed investigation of the resulting oscillations is necessary both for the purpose of determin- ing the underlying physical processes governing time-dependent behavior in magnetically shielded thrusters as well as for improving thruster models. In this investigation, a high speed camera and a translating ion saturation probe are employed to examine the spatial extent and nature of oscillations from 0-100 kHz in the H6MS thruster. Two modes are identified at 8 kHz and 75-90 kHz. The low frequency mode is azimuthally uniform across the thruster face while the high frequency oscillation is concentrated close to the thruster centerline with an m = 1 azimuthal dependence. These experimental results are discussed in the context of wave theory as well as published observations from an unshielded variant of the H6MS thruster.

  1. Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase I: Numerical Simulations

    Science.gov (United States)

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.

    2011-01-01

    In a proof-of-principle effort to demonstrate the feasibility of magnetically shielded (MS) Hall thrusters, an existing laboratory thruster has been modified with the guidance of physics-based numerical simulation. When operated at a discharge power of 6-kilowatts the modified thruster has been designed to reduce the total energy and flux of ions to the channel insulators by greater than 1 and greater than 3 orders of magnitude, respectively. The erosion rates in this MS thruster configuration are predicted to be at least 2-4 orders of magnitude lower than those in the baseline (BL) configuration. At such rates no detectable erosion is expected to occur.

  2. pH-Controlled Oxidation of an Aromatic Ketone: Structural Elucidation of the Products of Two Green Chemical Reactions

    Science.gov (United States)

    Ballard, C. Eric

    2010-01-01

    A laboratory experiment emphasizing the structural elucidation of organic compounds has been developed as a discovery exercise. The "unknown" compounds are the products of the pH-controlled oxidation of 4'-methoxyacetophenone with bleach. The chemoselectivity of this reaction is highly dependent on the pH of the reaction media: under basic…

  3. pH-Controlled Oxidation of an Aromatic Ketone: Structural Elucidation of the Products of Two Green Chemical Reactions

    Science.gov (United States)

    Ballard, C. Eric

    2010-01-01

    A laboratory experiment emphasizing the structural elucidation of organic compounds has been developed as a discovery exercise. The "unknown" compounds are the products of the pH-controlled oxidation of 4'-methoxyacetophenone with bleach. The chemoselectivity of this reaction is highly dependent on the pH of the reaction media: under basic…

  4. Convective heat flux in a laser-heated thruster

    Science.gov (United States)

    Wu, P. K. S.

    1978-01-01

    An analysis is performed to estimate the convective heating to the wall in a laser-heated thruster on the basis of a solution of the laminar boundary-layer equations with variable transport properties. A local similiarity approximation is used, and it is assumed that the gas phase is in equilibrium. For the thruster described by Wu (1976), the temperature and pressure distributions along the nozzle are obtained from the core calculation. The similarity solutions and heat flux are obtained from the freestream conditions of the boundary layer, in order to determine if it is necessary to couple the boundary losses directly to the core calculation. In addition, the effects of mass injection on the convective heat transfer across the boundary layer with large density-viscosity product gradient are examined.

  5. The BMDO Thruster-on-a-Pallet Program

    Science.gov (United States)

    Caveny, Leonard H.; Curran, Francis M.; Sankovic, John M.; Allen, Douglas M.; Brophy, John R.; Garner, Charles

    1995-01-01

    The Ballistic Missile Defense Organization sponsors an aggressive program to develop and demonstrate electric propulsion and space power technologies for future missions. This program supports a focused effort to design, fabricate, and space qualify a Russian Hall thruster system-on-a-pallet ready to take advantage of a near-term flight opportunity. The Russian Hall Effect Thruster Technology (RHETT) program will demonstrate an integrated pallet design in late FY95. The program also includes a parallel effort to develop advanced Solar Concentrator Arrays with Refractive Linear Element Technology (SCARLET). This synergistic technology will be demonstrated in a flight experiment this summer on the Comet satellite. This paper provides an overview of the RHETT and SCARLET programs with an emphasis on electric propulsion, recent progress, and near-term program plans.

  6. Development of Velocity Guidance Assistance System by Haptic Accelerator Pedal Reaction Force Control

    Science.gov (United States)

    Yin, Feilong; Hayashi, Ryuzo; Raksincharoensak, Pongsathorn; Nagai, Masao

    This research proposes a haptic velocity guidance assistance system for realizing eco-driving as well as enhancing traffic capacity by cooperating with ITS (Intelligent Transportation Systems). The proposed guidance system generates the desired accelerator pedal (abbreviated as pedal) stroke with respect to the desired velocity obtained from ITS considering vehicle dynamics, and provides the desired pedal stroke to the driver via a haptic pedal whose reaction force is controllable and guides the driver in order to trace the desired velocity in real time. The main purpose of this paper is to discuss the feasibility of the haptic velocity guidance. A haptic velocity guidance system for research is developed on the Driving Simulator of TUAT (DS), by attaching a low-inertia, low-friction motor to the pedal, which does not change the original characteristics of the original pedal when it is not operated, implementing an algorithm regarding the desired pedal stroke calculation and the reaction force controller. The haptic guidance maneuver is designed based on human pedal stepping experiments. A simple velocity profile with acceleration, deceleration and cruising is synthesized according to naturalistic driving for testing the proposed system. The experiment result of 9 drivers shows that the haptic guidance provides high accuracy and quick response in velocity tracking. These results prove that the haptic guidance is a promising velocity guidance method from the viewpoint of HMI (Human Machine Interface).

  7. Orion Service Module Reaction Control System Plume Impingement Analysis Using PLIMP/RAMP2

    Science.gov (United States)

    Wang, Xiao-Yen; Lumpkin, Forrest E., III; Gati, Frank; Yuko, James R.; Motil, Brian J.

    2009-01-01

    The Orion Crew Exploration Vehicle Service Module Reaction Control System engine plume impingement was computed using the plume impingement program (PLIMP). PLIMP uses the plume solution from RAMP2, which is the refined version of the reacting and multiphase program (RAMP) code. The heating rate and pressure (force and moment) on surfaces or components of the Service Module were computed. The RAMP2 solution of the flow field inside the engine and the plume was compared with those computed using GASP, a computational fluid dynamics code, showing reasonable agreement. The computed heating rate and pressure using PLIMP were compared with the Reaction Control System plume model (RPM) solution and the plume impingement dynamics (PIDYN) solution. RPM uses the GASP-based plume solution, whereas PIDYN uses the SCARF plume solution. Three sets of the heating rate and pressure solutions agree well. Further thermal analysis on the avionic ring of the Service Module was performed using MSC Patran/Pthermal. The obtained temperature results showed that thermal protection is necessary because of significant heating from the plume.

  8. Thrusters Pairing Guidelines for Trajectory Corrections of Projectiles

    Science.gov (United States)

    2011-01-12

    Gill, J., “Experimental Investigation of Super- and Hypersonic Jet Interaction on Missile Configurations,” Journal of Spacecraft and Rockets, Vol. 35...Thrusters Pairing Guidelines for Trajectory Corrections of Projectiles Daniel Corriveau∗ Canadian Department of National Defence , Quebec City, Quebec...course correction process for a 30-mm fin-stabilized air- defense projectile and a standard 105-mm spin-stabilized artillery shell are presented

  9. Investigation of Hall Effect Thruster Channel Wall Erosion Mechanisms

    Science.gov (United States)

    2016-08-01

    mentorship, humor, and amazing barbecue parties. I would also like to thank my thesis committee, Dr. Yim, Prof Simon, and Dr. Ready for taking the...indicate that BN is depleted relative to silica in the highly eroded region of the thruster. This surprising result mirrors that obtained by Garnier...predict the decrease in BN in the HE region. Grain ejection provides a plausible mechanism that could explain this surprising observation. 3.6. Summary

  10. Hall Effect Thruster Plume Contamination and Erosion Study

    Science.gov (United States)

    Jaworske, Donald A.

    2000-01-01

    The objective of the Hall effect thruster plume contamination and erosion study was to evaluate the impact of a xenon ion plume on various samples placed in the vicinity of a Hall effect thruster for a continuous 100 hour exposure. NASA Glenn Research Center was responsible for the pre- and post-test evaluation of three sample types placed around the thruster: solar cell cover glass, RTV silicone, and Kapton(R). Mass and profilometer), were used to identify the degree of deposition and/or erosion on the solar cell cover glass, RTV silicone, and Kapton@ samples. Transmittance, reflectance, solar absorptance, and room temperature emittance were used to identify the degree of performance degradation of the solar cell cover glass samples alone. Auger spectroscopy was used to identify the chemical constituents found on the surface of the exposed solar cell cover glass samples. Chemical analysis indicated some boron nitride contamination on the samples, from boron nitride insulators used in the body of the thruster. However, erosion outweighted contamination. All samples exhibited some degree of erosion. with the most erosion occurring near the centerline of the plume and the least occurring at the +/- 90 deg positions. For the solar cell cover glass samples, erosion progressed through the antireflective coating and into the microsheet glass itself. Erosion occurred in the solar cell cover glass, RTV silicone and Kapton(R) at different rates. All optical properties changed with the degree of erosion, with solar absorptance and room temperature emittance increasing with erosion. The transmittance of some samples decreased while the reflectance of some samples increased and others decreased. All results are consistent with an energetic plume of xenon ions serving as a source for erosion.

  11. Iodine Plasma Species Measurements in a Hall Effect Thruster Plume

    Science.gov (United States)

    2013-05-01

    60 90 0 2 4 6 8 Current (mA/cm^2) A n g l e ( d e g ) Xenon Iodine 500 V, 2 A, I2 Presented at 2012 JPC 33 Distribution A: Approved for public...Over 1 hour of operation on iodine – Additional 1/2 hour with thruster flowing Xe – Current up to ~50 A into anode Presented at 2012 JPC

  12. Computational molecular technology towards macroscopic chemical phenomena-molecular control of complex chemical reactions, stereospecificity and aggregate structures

    Energy Technology Data Exchange (ETDEWEB)

    Nagaoka, Masataka [Graduate School of Information Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Honmachi, Kawaguchi 332-0012 (Japan); ESICB, Kyoto University, Kyodai Katsura, Nishikyo-ku, Kyoto 615-8520 (Japan)

    2015-12-31

    A new efficient hybrid Monte Carlo (MC)/molecular dynamics (MD) reaction method with a rare event-driving mechanism is introduced as a practical ‘atomistic’ molecular simulation of large-scale chemically reactive systems. Starting its demonstrative application to the racemization reaction of (R)-2-chlorobutane in N,N-dimethylformamide solution, several other applications are shown from the practical viewpoint of molecular controlling of complex chemical reactions, stereochemistry and aggregate structures. Finally, I would like to mention the future applications of the hybrid MC/MD reaction method.

  13. Performance characterization of a permanent-magnet helicon plasma thruster

    Science.gov (United States)

    Takahashi, Kazunori; Charles, Christine; Boswell, Rod

    2012-10-01

    Helicon plasma thrusters operated at a few kWs of rf power is an active area of an international research. Recent experiments have clarified part of the thrust-generation mechanisms. Thrust components which have been identified include an electron pressure inside the source region and a Lorentz force due to an electron diamagnetic drift current and a radial component of the applied magnetic field. The use of permanent magnets (PMs) instead of solenoids is one of the solutions for improving the thruster efficiency because it does not require electricity for the magnetic nozzle formation. Here the thrust imparted from a permanent-magnet helicon plasma thruster is directly measured using a pendulum thrust balance. The source consists of permanent magnet (PM) arrays, a double turn rf loop antenna powered by a 13.56 MHz rf generator and a glass source tube. The PM arrays provide a magnetic nozzle near the open exit of the source and two configurations, which have maximum field strengths of about 100 and 270 G, are tested. A thrust of 15 mN, specific impulse of 2000 sec and a thrust efficiency of 8 percent are presently obtained for 2 kW of input power, 24 sccm flow rate of argon and the stronger magnetic field configuration.

  14. Two-dimensional model of stationary plasma thruster

    Energy Technology Data Exchange (ETDEWEB)

    Pitchford, L.C.; Boeuf, J.P. [Universite Paul Sabatier, Toulouse (France)

    1995-12-31

    A stationary plasma thruster, SPT, (also called closed-drift thrusters or Hall thrusters) is an electromagnetic propulseur design which has been developed over the past thirty years in the former USSR. SPT`s are small devices with a thrust greater than 1000 s{sup -1}, and a lifetime of several 1000 hours or more. These properties make the SPT of interest for applications such as satellite station-keeping or orbit transfer. The geometry of the SPT is shown; it consists of a hollow, cylindrical dielectric (typically of several centimeters length and diameter) with a central dielectric rod. A voltage on the order of several 100`s of V is applied at the anode (at one end of the cylinder). The cathode is an externally powered hollow cathode or a hot filament positioned slightly past the exit of the dielectric cylinder. Gas, typically xenon, flows in from around the anode and is ionized by the electrons which are emitted from the cathode. A magnetic field is applied which is mainly in the radial direction. The magnetic strength is such that the electrons tend to be trapped along the magnetic field lines, but the ion trajectories are not significantly influenced by the magnetic field. For these conditions, the current at the anode is several amps. At the exit plane, the xenon is almost fully ionized. The ion flux at the exhaust provides the thrust.

  15. High-Efficiency Hall Thruster Discharge Power Converter

    Science.gov (United States)

    Jaquish, Thomas

    2015-01-01

    Busek Company, Inc., is designing, building, and testing a new printed circuit board converter. The new converter consists of two series or parallel boards (slices) intended to power a high-voltage Hall accelerator (HiVHAC) thruster or other similarly sized electric propulsion devices. The converter accepts 80- to 160-V input and generates 200- to 700-V isolated output while delivering continually adjustable 300-W to 3.5-kW power. Busek built and demonstrated one board that achieved nearly 94 percent efficiency the first time it was turned on, with projected efficiency exceeding 97 percent following timing software optimization. The board has a projected specific mass of 1.2 kg/kW, achieved through high-frequency switching. In Phase II, Busek optimized to exceed 97 percent efficiency and built a second prototype in a form factor more appropriate for flight. This converter then was integrated with a set of upgraded existing boards for powering magnets and the cathode. The program culminated with integrating the entire power processing unit and testing it on a Busek thruster and on NASA's HiVHAC thruster.

  16. A novel laser ablation plasma thruster with electromagnetic acceleration

    Science.gov (United States)

    Zhang, Yu; Zhang, Daixian; Wu, Jianjun; He, Zhen; Zhang, Hua

    2016-10-01

    A novel laser ablation plasma thruster accelerated by electromagnetic means was proposed and investigated. The discharge characteristics and thrust performance were tested with different charged energy, structural parameters and propellants. The thrust performance was proven to be improved by electromagnetic acceleration. In contrast with the pure laser propulsion mode, the thrust performance in electromagnetic acceleration modes was much better. The effects of electrodes distance and the off-axis distance between ceramic tube and cathode were tested, and it's found that there were optimal structural parameters for achieving optimal thrust performance. It's indicated that the impulse bit and specific impulse increased with increasing charged energy. In our experiments, the thrust performance of the thruster was optimal in large charged energy modes. With the charged energy 25 J and the use of metal aluminum, a maximal impulse bit of 600 μNs, a specific impulse of approximate 8000 s and thrust efficiency of about 90% were obtained. For the PTFE propellant, a maximal impulse bit of about 350 μNs, a specific impulse of about 2400 s, and thrust efficiency of about 16% were obtained. Besides, the metal aluminum was proven to be the better propellant than PTFE for the thruster.

  17. Experimental studies of anode sheath phenomena in a hall thruster.

    Energy Technology Data Exchange (ETDEWEB)

    Dorf, L. A. (Leonid A.); Fisch, N. J.; Raitses, Yevgeny F.

    2004-01-01

    Both electron-repelling (negative anode fall) and electron-attracting (positive anode fall) anode sheaths in a Hall thruster were identified experimentally by performing accurate, non-disturbing near-anode measurements with biased and emissive probes. An interesting new phenomenon revealed by the probe measurements is that the anode fall changes from positive to negative upon removal of the dielectric coating, which appears on the anode surface during the course of Hall thruster operation. Probe measurements in a Hall thruster with three different magnetic field configurations show that an anode fall at the clean anode is a function of the radial magnetic field profile inside the channel. A positive anode fall formation mechanism suggested in this work is that: (1) when the anode front surface is coated with dielectric, a discharge current closes to the anode at the surfaces that remain conductive, (2) a total thermal electron current toward the conductive area is significantly smaller than the discharge current, therefore an additional electron flux needs to be attracted toward the conductive surfaces by the electronattracting sheath that appears at these surfaces.

  18. A kinetic study of the reactions between H2O2 and Cu,Zn superoxide dismutase; evidence for an electrostatic control of the reaction rate.

    Science.gov (United States)

    Viglino, P; Scarpa, M; Rotilio, G; Rigo, A

    1988-01-04

    H2O2 was shown to reduce the copper ion of native bovine Cu,Zn superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) (ECu2+) and to oxidize the reduced enzyme (ECu+). The time-course of these processes was monitored by NMR measurement of the longitudinal relaxation rate of the water protons. A steady-state characterized by the same ratio [ECu2+]/[( EC2+] + [ECu+]) was obtained either by starting from the oxidized or the reduced enzyme. The kinetics of these processes appear to be quite complex, since different reactions between H2O2, or its reaction products, and the enzyme-bound copper control the reaction rate. The solution of the differential equations describing the kinetic processes showed that the oxidation and the reduction of the copper ion by H2O2 are first-order with respect to the copper ion itself only when these processes approach the steady-state. The rate constants of the reduction and oxidation reactions were calculated according to these equations and were found to have comparable values which are in the range 5-80 and 5-45 M-1.min-1, respectively, changing the pH from 5.6 to 7 at 0.21 M ionic strength. This result, together with the dependence of the reaction rates on pH and ionic strength, points to HO2- as the reactive species in both processes, and indicates that the electrostatic control of the access of the peroxide to the active site is the rate-determining step of the two redox reactions.

  19. Dynamic reaction design of enzymic biotransformations in organic media: equilibrium-controlled synthesis of antibiotics by penicillin G acylase.

    Science.gov (United States)

    Fernandez-Lafuente, R; Rosell, C M; Guisan, J M

    1996-10-01

    Parameters relevant to the thermodynamically controlled synthesis of cephalothin utilizing highly active stabilized penicillin G acylase derivatives were studied. These included solubility/stability of substrates, enzyme derivative activity/stability, reaction course and synthetic yields. These parameters were altered by varying the pH, dimethylformamide concentration and temperature. Simultaneous optimization of the selected parameters could not be achieved with a single set of conditions. However, continuous adjustment of conditions throughout the reaction course allowed each parameter to be optimized (dynamic reaction design). This strategy works by optimizing those parameters that are critical to the overall reaction at a given point, whilst leaving others sub-optimal when their contribution to the total is minimal. This strategy has achieved a 90% transformation of antibiotic nucleus to cephalothin at a final concentration of 20 g/l, high enzyme and reactant stability, with a reaction period of 3 h (using 1 ml of derivative/40 ml of reaction solution).

  20. Design of a high density cold gas attitude control system

    Science.gov (United States)

    Hall, Sarah E.; Lewis, Mark J.; Akin, David L.

    1993-01-01

    A comparison of the experimental results of a nitrous oxide cold gas thruster with the predicted performance from a numerical simulation of nozzle operations is discussed. Tests were conducted in a vacuum chamber to verify analytical predictions of both nitrogen and nitrous oxide. Preliminary results indicate an Isp for N2O of 61, and an Isp of 69 for N2. Based on the results of this research, parameters are presented for a nitrous oxide-based reaction control system for a small spacecraft currently under development.

  1. Oral stereognostic ability among tongue thrusters with interdental lisp, tongue thrusters without interdental lisp and normal children.

    Science.gov (United States)

    Colletti, E A; Geffner, D; Schlanger, P

    1976-02-01

    30 children, i.e., 10 children per group, 8 yr. of age, were given an oral stereognostic test. This test of 10 geometric forms varying in shape were developed by NIDR. 47 stimuli pairs were used and 10 pairs were repeated to measure test reliability. Subjects were blindfolded and asked to respond whether Items 1 and 2, presented consecutively, were the same or different. Results indicated that both groups of tongue thrusters with and without interdental lisp scored significantly more poorly than did normal children (t = 4.68, P less than .001; t = 5.00, P less than .001), respectively. There were no significant differences, however, between tongue thrusters with and without interdental lisp (t = .33, P greater than .05). Observations indicated that normal children used the tongue tip more frequently and accurately when discriminating the geometric forms than did the other groups.

  2. Independent control of the shape and composition of ionic nanocrystals through sequential cation exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Luther, Joseph Matthew; Zheng, Haimei; Sadtler, Bryce; Alivisatos, A. Paul

    2009-07-06

    Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

  3. Bifurcation analysis of a delay reaction-diffusion malware propagation model with feedback control

    Science.gov (United States)

    Zhu, Linhe; Zhao, Hongyong; Wang, Xiaoming

    2015-05-01

    With the rapid development of network information technology, information networks security has become a very critical issue in our work and daily life. This paper attempts to develop a delay reaction-diffusion model with a state feedback controller to describe the process of malware propagation in mobile wireless sensor networks (MWSNs). By analyzing the stability and Hopf bifurcation, we show that the state feedback method can successfully be used to control unstable steady states or periodic oscillations. Moreover, formulas for determining the properties of the bifurcating periodic oscillations are derived by applying the normal form method and center manifold theorem. Finally, we conduct extensive simulations on large-scale MWSNs to evaluate the proposed model. Numerical evidences show that the linear term of the controller is enough to delay the onset of the Hopf bifurcation and the properties of the bifurcation can be regulated to achieve some desirable behaviors by choosing the appropriate higher terms of the controller. Furthermore, we obtain that the spatial-temporal dynamic characteristics of malware propagation are closely related to the rate constant for nodes leaving the infective class for recovered class and the mobile behavior of nodes.

  4. Control and Automation of Fluid Flow, Mass Transfer and Chemical Reactions in Microscale Segmented Flow

    Science.gov (United States)

    Abolhasani, Milad

    Flowing trains of uniformly sized bubbles/droplets (i.e., segmented flows) and the associated mass transfer enhancement over their single-phase counterparts have been studied extensively during the past fifty years. Although the scaling behaviour of segmented flow formation is increasingly well understood, the predictive adjustment of the desired flow characteristics that influence the mixing and residence times, remains a challenge. Currently, a time consuming, slow and often inconsistent manual manipulation of experimental conditions is required to address this task. In my thesis, I have overcome the above-mentioned challenges and developed an experimental strategy that for the first time provided predictive control over segmented flows in a hands-off manner. A computer-controlled platform that consisted of a real-time image processing module within an integral controller, a silicon-based microreactor and automated fluid delivery technique was designed, implemented and validated. In a first part of my thesis I utilized this approach for the automated screening of physical mass transfer and solubility characteristics of carbon dioxide (CO2) in a physical solvent at a well-defined temperature and pressure and a throughput of 12 conditions per hour. Second, by applying the segmented flow approach to a recently discovered CO2 chemical absorbent, frustrated Lewis pairs (FLPs), I determined the thermodynamic characteristics of the CO2-FLP reaction. Finally, the segmented flow approach was employed for characterization and investigation of CO2-governed liquid-liquid phase separation process. The second part of my thesis utilized the segmented flow platform for the preparation and shape control of high quality colloidal nanomaterials (e.g., CdSe/CdS) via the automated control of residence times up to approximately 5 minutes. By introducing a novel oscillatory segmented flow concept, I was able to further extend the residence time limitation to 24 hours. A case study of a

  5. A Simple and Inexpensive Device for Slow, Controlled Addition of a Solution to a Reaction Mixture

    Science.gov (United States)

    Osvath, Peter

    1995-07-01

    A number of reactions require the slow and controlled addition of a solution containing one reagent to another. Attempting to control the flow rate over a number of hours using a conventional constant pressure addition funnel is a frustrating exercise; commercially available constant volume addition funnels are expensive and must be adjusted by trial and error each time a reaction is carried out. The use of an (expensive) peristaltic pump or syringe pump overcomes these problems but can introduce other complications. We have recently had occasion to carry out the synthesis of thioether macrocycles and cages requiring the slow and controlled addition of DMF solutions of (offensively odoriferous) thiols or (air-sensitive) thiolates to a reactant solution under nitrogen(1), Although the use of a syringe pump was called for, there are obvious difficulties associated with purging the solution and assembling such an apparatus under nitrogen, and we report a simple and inexpensive solution. A Male Luer Lock tip (recovered from a broken syringe) was sweated onto the flattened tip of a pressure-equalizing addition funnel and a syringe needle was attached. Judicious selection of needle length, bore size, and reactant volume can be used to control the addition time simply and reproducibly. With a 250-mL funnel, the flow rate changes by <25% from the beginning to the end of the addition. (In fact, a reduction in the rate of addition may even be advantageous as the reaction proceeds, the reagent in the receiving flask is consumed, its concentration drops, and the rate of reaction will decrease). A piece of fine Teflon tubing of appropriate length attached to the needle can be used to reduce the flow rate even further, but this is only necessary for very slow rates of addition. For example, the time of addition of 200 mL, of an ethanolic solution could be varied from approximately 5 minutes (150mm/17 gauge) to approximately 5 h (200mm/22 gauge), and once the addition time for a

  6. Multidisciplinary approach to materials selection for bipropellant thrusters using ablative and radiative cooling

    Indian Academy of Sciences (India)

    A Adami; M Mortazavi; M Nosratollahi

    2016-01-01

    Reduction of costs is a main consideration in every space mission, and propulsion system is an important subsystem of those missions where orbital maneuvers are considered. Lighter propulsions with higher performance are necessary to reduce the mission costs. Bipropellant propulsions have been widely used in launch vehicles and upper-stages as well as deorbit modules because of better performances in comparison with other propulsion systems. Unfortunately heat transfer and thermal control limit bipropellant propulsion performance and maximum performance cannot be achieved. Well-known cooling methods such as regenerative and film cooling increase the cost using extra equipment and high temperature materials. In this paper, a new approach for cooling is presented based on combined ablative and radiative cooling. Governing equations are derived for two or three layers of thermal protection system (TPS) to optimize the TPS mass. The first layer is used as an ablative layer to control the temperature where the second and third layers are used as an insulator to control the heat fluxes. Proposed cooling method has been applied for two real bipropellant thrusters. According to the results, the presented algorithm can suitably predict the heat fluxes and satisfy the wall temperature constraint. Then, the algorithm has been used to minimize the wall temperatures as low as possible and replace high temperature materials (platinum alloy) with common materials (composite or steel). It is shown that selection of TPS materials affects the TPS mass and Isp simultaneously, but conversely. Best solution should be derived by trading off between structure temperature (cost), Isp (performance), and TPS thicknesses (geometry). Multidisciplinary approach to TPS and structure material selection of a bipropellant thruster is presented for a case study. It has been shown that mass and performance penalties of using TPS are acceptable, considering the advantages of using steel alloy instead

  7. A single residue controls electron transfer gating in photosynthetic reaction centers

    Science.gov (United States)

    Shlyk, Oksana; Samish, Ilan; Matěnová, Martina; Dulebo, Alexander; Poláková, Helena; Kaftan, David; Scherz, Avigdor

    2017-03-01

    Interquinone QA- → QB electron-transfer (ET) in isolated photosystem II reaction centers (PSII-RC) is protein-gated. The temperature-dependent gating frequency “k” is described by the Eyring equation till levelling off at T ≥ 240 °K. Although central to photosynthesis, the gating mechanism has not been resolved and due to experimental limitations, could not be explored in vivo. Here we mimic the temperature dependency of “k” by enlarging VD1-208, the volume of a single residue at the crossing point of the D1 and D2 PSII-RC subunits in Synechocystis 6803 whole cells. By controlling the interactions of the D1/D2 subunits, VD1-208 (or 1/T) determines the frequency of attaining an ET-active conformation. Decelerated ET, impaired photosynthesis, D1 repair rate and overall cell physiology upon increasing VD1-208 to above 130 Å3, rationalize the >99% conservation of small residues at D1-208 and its homologous motif in non-oxygenic bacteria. The experimental means and resolved mechanism are relevant for numerous transmembrane protein-gated reactions.

  8. A single residue controls electron transfer gating in photosynthetic reaction centers

    Science.gov (United States)

    Shlyk, Oksana; Samish, Ilan; Matěnová, Martina; Dulebo, Alexander; Poláková, Helena; Kaftan, David; Scherz, Avigdor

    2017-01-01

    Interquinone QA− → QB electron-transfer (ET) in isolated photosystem II reaction centers (PSII-RC) is protein-gated. The temperature-dependent gating frequency “k” is described by the Eyring equation till levelling off at T ≥ 240 °K. Although central to photosynthesis, the gating mechanism has not been resolved and due to experimental limitations, could not be explored in vivo. Here we mimic the temperature dependency of “k” by enlarging VD1-208, the volume of a single residue at the crossing point of the D1 and D2 PSII-RC subunits in Synechocystis 6803 whole cells. By controlling the interactions of the D1/D2 subunits, VD1-208 (or 1/T) determines the frequency of attaining an ET-active conformation. Decelerated ET, impaired photosynthesis, D1 repair rate and overall cell physiology upon increasing VD1-208 to above 130 Å3, rationalize the >99% conservation of small residues at D1-208 and its homologous motif in non-oxygenic bacteria. The experimental means and resolved mechanism are relevant for numerous transmembrane protein-gated reactions. PMID:28300167

  9. A reaction-diffusion-based coding rate control mechanism for camera sensor networks.

    Science.gov (United States)

    Yamamoto, Hiroshi; Hyodo, Katsuya; Wakamiya, Naoki; Murata, Masayuki

    2010-01-01

    A wireless camera sensor network is useful for surveillance and monitoring for its visibility and easy deployment. However, it suffers from the limited capacity of wireless communication and a network is easily overflown with a considerable amount of video traffic. In this paper, we propose an autonomous video coding rate control mechanism where each camera sensor node can autonomously determine its coding rate in accordance with the location and velocity of target objects. For this purpose, we adopted a biological model, i.e., reaction-diffusion model, inspired by the similarity of biological spatial patterns and the spatial distribution of video coding rate. Through simulation and practical experiments, we verify the effectiveness of our proposal.

  10. Interior Controllability of a 2×2 Reaction-Diffusion System with Cross-Diffusion Matrix

    Directory of Open Access Journals (Sweden)

    Hugo Leiva

    2009-01-01

    Full Text Available We prove the interior approximate controllability for the following 2×2 reaction-diffusion system with cross-diffusion matrix ut=aΔu−β(−Δ1/2u+bΔv+1ωf1(t,x in (0,τ×Ω, vt=cΔu−dΔv−β(−Δ1/2v+1ωf2(t,x in (0,τ×Ω, u=v=0, on (0,T×∂Ω, u(0,x=u0(x, v(0,x=v0(x, x∈Ω, where Ω is a bounded domain in ℝN (N≥1, u0,v0∈L2(Ω, the 2×2 diffusion matrix D=[abcd] has semisimple and positive eigenvalues 0<ρ1≤ρ2, β is an arbitrary constant, ω is an open nonempty subset of Ω, 1ω denotes the characteristic function of the set ω, and the distributed controls f1,f2∈L2([0,τ];L2(Ω. Specifically, we prove the following statement: if λ11/2ρ1+β>0 (where λ1 is the first eigenvalue of −Δ, then for all τ>0 and all open nonempty subset ω of Ω the system is approximately controllable on [0,τ].

  11. Performance of a Permanent-Magnet Cylindrical Hall-Effect Thruster

    Science.gov (United States)

    Polzin, K. A.; Sooby, E. S.; Kimberlin, A. C.; Raites, Y.; Merino, E.; Fisch, N. J.

    2009-01-01

    The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic topologies. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying higher thrust efficiency. Thruster performance measurements on this configuration were obtained over a power range of 70-350 W and with the cathode orifice located at three different axial positions relative to the thruster exit plane. The thrust levels over this power range were 1.25-6.5 mN, with anode efficiencies and specific impulses spanning 4-21% and 400-1950 s, respectively. The anode efficiency of the permanent-magnet thruster compares favorable with the efficiency of the electromagnet thruster when the power consumed by the electromagnets is taken into account.

  12. Investigation of Low Discharge Voltage Hall Thruster Operating Modes and Ionization Processes

    Science.gov (United States)

    2009-08-14

    a null-type, inverted pendulum thrust stand based on the NASA GRC design.11 The thruster is shown mounted to the thrust stand in Figure 3... cloud of neutral propellant. This thruster operation was studied in detail using the far-field diagnostics and characterized with variations in

  13. Ion behavior in low-power magnetically shielded and unshielded Hall thrusters

    Science.gov (United States)

    Grimaud, L.; Mazouffre, S.

    2017-05-01

    Magnetically shielded Hall thrusters achieve a longer lifespan than traditional Hall thrusters by reducing wall erosion. The lower erosion rate is attributed to a reduction of the high energy ion population impacting the walls. To investigate this phenomenon, the ion velocity distribution functions are measured with laser induced fluorescence at several points of interest in the magnetically shielded ISCT200-MS and the unshielded ISCT200-US Hall thrusters. The center of the discharge channel is probed to highlight the difference in plasma positioning between the shielded and unshielded thrusters. Erosion phenomena are investigated by taking measurements of the ion velocity distribution near the inner and outer wall as well as above the magnetic poles where some erosion is observed. The resulting distribution functions show a displacement of the acceleration region from inside the channel in the unshielded thruster to downstream of the exit plane in the ISCT200-MS. Near the walls, the unshielded thruster displays both a higher relative ion density as well as a significant fraction of the ions with velocities toward the walls compared to the shielded thruster. Higher proportions of high velocity ions are also observed. Those results are in accordance with the reduced erosion observed. Both shielded and unshielded thrusters have large populations of ions impacting the magnetic poles. The mechanism through which those ions are accelerated toward the magnetic poles has so far not been explained.

  14. Thrust Measurement of Laser Detonation Thruster with a Pulsed Glass Laser

    Science.gov (United States)

    Wang, Bin; Han, Taro; Michigami, Keisuke; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2011-11-01

    Experimental studies were carried out for measuring the laser propulsion thrust with using of a Q-switched Nd:Glass laser. In the tests, a laser beam with 33 ns FWHM pulse width was focused to generate breakdown in the cone-shaped nozzle of aluminum thrusters which were fixed at the end of a ballistic pendulum. The pulse energy used was 1.0 J and the focusing number is 6.27, which gave the highest energy conversion efficiency from laser energy to that of induced blast wave as found in previous research. The momentum coupling coefficient Cm dependency on nozzle apex angles, 30°, 45° and 60°, were investigated with carefully controlling of the laser ignition positions. Results show that, solid-state laser could be a candidate to suffice laser propulsion missions in term of Cm it can achieve.

  15. Operation of a Segmented Hall Thruster with Low-sputtering Carbon-velvet Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Raitses, Y.; Staack, D.; Dunaevsky, A.; Fisch, N.J.

    2005-12-01

    Carbon fiber velvet material provides exceptional sputtering resistance properties exceeding those for graphite and carbon composite materials. A 2 kW Hall thruster with segmented electrodes made of this material was operated in the discharge voltage range of 200–700 V. The arcing between the floating velvet electrodes and the plasma was visually observed, especially, during the initial conditioning time, which lasted for about 1 h. The comparison of voltage versus current and plume characteristics of the Hall thruster with and without segmented electrodes indicates that the magnetic insulation of the segmented thruster improves with the discharge voltage at a fixed magnetic field. The observations reported here also extend the regimes wherein the segmented Hall thruster can have a narrower plume than that of the conventional nonsegmented thruster.

  16. Electron Cross-field Transport in a Low Power Cylindrical Hall Thruster

    Energy Technology Data Exchange (ETDEWEB)

    A. Smirnov; Y. Raitses; N.J. Fisch

    2004-06-24

    Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. We show that in order to explain the observed discharge current, the electron anomalous collision frequency {nu}{sub B} has to be on the order of the Bohm value, {nu}{sub B} {approx} {omega}{sub c}/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant.

  17. Performance Evaluation of an Expanded Range XIPS Ion Thruster System for NASA Science Missions

    Science.gov (United States)

    Oh, David Y.; Goebel, Dan M.

    2006-01-01

    This paper examines the benefit that a solar electric propulsion (SEP) system based on the 5 kW Xenon Ion Propulsion System (XIPS) could have for NASA's Discovery class deep space missions. The relative cost and performance of the commercial heritage XIPS system is compared to NSTAR ion thruster based systems on three Discovery class reference missions: 1) a Near Earth Asteroid Sample Return, 2) a Comet Rendezvous and 3) a Main Belt Asteroid Rendezvous. It is found that systems utilizing a single operating XIPS thruster provides significant performance advantages over a single operating NSTAR thruster. In fact, XIPS performs as well as systems utilizing two operating NSTAR thrusters, and still costs less than the NSTAR system with a single operating thruster. This makes XIPS based SEP a competitive and attractive candidate for Discovery class science missions.

  18. MarsCAT: Mars Array of ionospheric Research Satellites using the CubeSat Ambipolar Thruster

    Science.gov (United States)

    Bering, E. A., III; Pinsky, L.; Li, L.; Jackson, D. R.; Chen, J.; Reed, H.; Moldwin, M.; Kasper, J. C.; Sheehan, J. P.; Forbes, J.; Heine, T.; Case, A. W.; Stevens, M. L.; Sibeck, D. G.

    2015-12-01

    The MarsCAT (Mars Array of ionospheric Research Satellites using the CubeSat Ambipolar Thruster) Mission is a two 6U CubeSat mission to study the ionosphere of Mars proposed for the NASA SIMPLeX opportunity. The mission will investigate the plasma and magnetic structure of the Martian ionosphere, including transient plasma structures, magnetic field structure and dynamics, and energetic particle activity. The transit plan calls for a piggy back ride with Mars 2020 using a CAT burn for MOI, the first demonstration of CubeSat propulsion for interplanetary travel. MarsCAT will make correlated multipoint studies of the ionosphere and magnetic field of Mars. Specifically, the two spacecraft will make in situ observations of the plasma density, temperature, and convection in the ionosphere of Mars. They will also make total electron content measurements along the line of sight between the two spacecraft and simultaneous 3-axis local magnetic field measurements in two locations. Additionally, MarsCAT will demonstrate the performance of new CubeSat telemetry antennas designed at the University of Houston that are designed to be low profile, rugged, and with a higher gain than conventional monopole (whip) antennas. The two MarsCAT CubeSats will have five science instruments: a 3-axis DC magnetometer, adouble-Langmuir probe, a Faraday cup, a solid state energetic particle detector (Science Enhancement Option), and interspacecraft total electron content radio occulation experiment. The MarsCAT spacecraft will be solar powered and equipped with a CAT thruster that can provide up to 4.8 km/s of delta-V, which is sufficient to achieve Mars orbit using the Mars 2020 piggyback. They have an active attitude control system, using a sun sensor and flight-proven star tracker for determination, and momentum wheels for 3-axis attitude control.

  19. Computer-controlled system for the study of oxidase reactions: application to the peroxidase-oxidase oscillator.

    Science.gov (United States)

    McDonald, Andrew G; Tipton, Keith F

    2010-12-16

    An apparatus for the study of bisubstrate oxidase reactions at maintained steady-state substrate concentrations is described, and its specific application to the peroxidase-oxidase biochemical oscillator is reported. Instrument control and data acquisition are provided by custom software written in LabVIEW. The software allows measurement, recording, and control of dissolved oxygen through a Clark-type oxygen electrode, reaction monitoring by a UV/vis spectrophotometer, and controlled substrate delivery by a syringe infusion pump. For peroxidase from horseradish, the optimal pH for oscillatory behavior was found to be in the range 4.5-5.5.

  20. False-Positive Clostridium difficile in Negative-Control Reactions Peak and Then Decrease with Repetitive Refrigeration of Immunoassay.

    Science.gov (United States)

    Rodriguez-Palacios, Alexander; Stämpfli, Henry R; Chang, Yung-Fu

    2014-01-01

    Aberrant false-positive reactions in negative-controls during ELISA testing for Clostridium difficile indicated the potential for false-diagnoses. Experiments with 96-well products showed a maximum peak of false-positive immunoassay reactions with the provided negative-control reagents after 5 refrigeration-to-room temperature cycles (P refrigeration cycles. Because repetitive refrigeration causes a peak of false-positives, the use of single negative-controls per ELISA run might be insufficient to monitor aberrant preanalytical false-positives if immunoassays are subject to repetitive refrigeration.

  1. Power to the People: Using Learner Control to Improve Trainee Reactions and Learning in Web-Based Instructional Environments

    Science.gov (United States)

    Orvis, Karin A.; Fisher, Sandra L.; Wasserman, Michael E.

    2009-01-01

    This experimental study investigated the mechanisms by which learner control influences learning in an e-learning environment. The authors hypothesized that learner control would enhance learning indirectly through its effect on trainee reactions and learner engagement (in particular, off-task attention), such that learners who were more satisfied…

  2. Sputtering of ZnO by a modified radio-frequency ion thruster (RIT) as ion-beam-sputter-source

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Martin; Polity, Angelika; Feili, Davar; Meyer, Bruno K. [I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)

    2011-07-01

    Radio-Frequency-Ion-Thrusters, as designed for propulsion systems (ion extraction and grid system), are also qualified for thin film deposition and surface etching, because they can be used with different gases (inert and reactive) and extraction voltages. ZnO thin films were deposited on float glass using a 4 inch ceramic ZnO target. The deposition temperature was varied using a heated substrate holder, as well as additional oxygen flow was provided to control the stoichiometry of the films. First investigations on this thin films will be presented.

  3. Cation coordination reactions on nanocrystals: surface/interface, doping control and advanced photocatalysis applications (Conference Presentation)

    Science.gov (United States)

    Zhang, Jiatao

    2016-10-01

    Abstract: Including the shape and size effect, the controllable doping, hetero-composite and surface/interface are the prerequisite of colloidal nanocrystals for exploring their optoelectronic properties, such as fluorescence, plasmon-exciton coupling, efficient electron/hole separation, and enhanced photocatalysis applications. By controlling soft acid-base coordination reactions between cation molecular complexes and colloidal nanocrystals, we showed that chemical thermodynamics could drive nanoscale monocrystalline growth of the semiconductor shell on metal nano-substrates and the substitutional heterovalent doping in semiconductor nanocrystals. We have demonstrated evolution of relative position of Au and II-VI semiconductor in Au-Semi from symmetric to asymmetric configuration, different phosphines initiated morphology engineering, oriented attachment of quantum dots into micrometer nanosheets with synergistic control of surface/interface and doing, which can further lead to fine tuning of plasmon-exciton coupling. Therefore, different hydrogen photocatalytic performance, Plasmon enhanced photocatalysis properties have been achieved further which lead to the fine tuning of plasmon-exciton coupling. Substitutional heterovalent doping here enables the tailoring of optical, electronic properties and photocatalysis applications of semiconductor nanocrystals because of electronic impurities (p-, n-type doping) control. References: (1) J. Gui, J. Zhang*, et al. Angew. Chem. Int. Ed. 2015, 54, 3683. (2) Q. Zhao, J. Zhang*, etc., Adv. Mater. 2014, 26, 1387. (3) J. Liu, Q. Zhao, S. G. Wang*, J. Zhang*, etc., Adv. Mater. 2015, 27-2753-2761. (4) H. Qian, J. Zhang*, etc., NPG Asia Mater. (2015) 7, e152. (5) M. Ji, M. Xu, etc., J. Zhang*, Adv. Mater. 2016, in proof. (6) S. Yu, J. T. Zhang, Y. Tang, M. Ouyang*, Nano Lett. 2015, 15, 6282-6288. (7) J. Zhang, Y. Tang, K. Lee and M. Ouyang*, Science 2010, 327, 1634. (8) J. Zhang, Y. Tang, K. Lee, M. Ouyang*, Nature 2010, 466

  4. Apparent Rate Constant for Diffusion-Controlled Three molecular (catalytic) reaction

    OpenAIRE

    Burlatsky, S. F.; Moreau, M

    1996-01-01

    We present simple explicit estimates for the apparent reaction rate constant for three molecular reactions, which are important in catalysis. For small concentrations and $d> 1$, the apparent reaction rate constant depends only on the diffusion coefficients and sizes of the particles. For small concentrations and $d\\le 1$, it is also time -- dependent. For large concentrations, it gains the dependence on concentrations.

  5. Summary of Altitude Pulse Testing of a 100-lbf L02/LCH4 Reaction Control Engine

    Science.gov (United States)

    Marshall, William M.; Kleinhenz, Julie E.

    2011-01-01

    Recently, liquid oxygen-liquid methane (LO2/LCH4) has been considered as a potential "green" propellant alternative for future exploration missions. The Propulsion and Cryogenic Advanced Development (PCAD) project has been tasked by NASA to develop this propulsion combination to enable safe and cost effective exploration missions. To date, limited experience with such combinations exist, and as a result a comprehensive test program is critical to demonstrating the viability of implementing such a system. The NASA Glenn Research Center has conducted a test program of a 100-lbf (445-N) reaction control engine (RCE) at the center s Altitude Combustion Stand (ACS), focusing on altitude testing over a wide variety of operational conditions. The ACS facility includes a unique propellant conditioning feed system (PCFS) which allows precise control of propellant inlet conditions to the engine. Engine performance as a result of these inlet conditions was examined extensively during the test program. This paper is a companion to the previous specific impulse testing paper, and discusses the pulsed mode operation portion of testing, with a focus on minimum impulse bit (I-bit) and repeatable pulse performance. The engine successfully demonstrated target minimum impulse bit performance at all conditions, as well as successful demonstration of repeatable pulse widths. Some anomalous conditions experienced during testing are also discussed, including a double pulse phenomenon which was not noted in previous test programs for this engine.

  6. Remote-controlling chemical reactions by light: towards chemistry with high spatio-temporal resolution.

    Science.gov (United States)

    Göstl, Robert; Senf, Antti; Hecht, Stefan

    2014-03-21

    The foundation of the chemical enterprise has always been the creation of new molecular entities, such as pharmaceuticals or polymeric materials. Over the past decades, this continuing effort of designing compounds with improved properties has been complemented by a strong effort to render their preparation (more) sustainable by implementing atom as well as energy economic strategies. Therefore, synthetic chemistry is typically concerned with making specific bonds and connections in a highly selective and efficient manner. However, to increase the degree of sophistication and expand the scope of our work, we argue that the modern aspiring chemist should in addition be concerned with attaining (better) control over when and where chemical bonds are being made or broken. For this purpose, photoswitchable molecular systems, which allow for external modulation of chemical reactions by light, are being developed and in this review we are covering the current state of the art of this exciting new field. These "remote-controlled synthetic tools" provide a remarkable opportunity to perform chemical transformations with high spatial and temporal resolution and should therefore allow regulating biological processes as well as material and device performance.

  7. The interplay between transport and reaction rates as controls on nitrate attenuation in permeable, streambed sediments

    Science.gov (United States)

    Lansdown, K.; Heppell, C. M.; Trimmer, M.; Binley, A.; Heathwaite, A. L.; Byrne, P.; Zhang, H.

    2015-06-01

    Anthropogenic nitrogen fixation and subsequent use of this nitrogen as fertilizer have greatly disturbed the global nitrogen cycle. Rivers are recognized hot spots of nitrogen removal in the landscape as interaction between surface water and sediments creates heterogeneous redox environments conducive for nitrogen transformations. Our understanding of riverbed nitrogen dynamics to date comes mainly from shallow sediments or hyporheic exchange flow pathways with comparatively little attention paid to groundwater-fed, gaining reaches. We have used 15N techniques to quantify in situ rates of nitrate removal to 1 m depth within a groundwater-fed riverbed where subsurface hydrology ranged from strong upwelling to predominantly horizontal water fluxes. We combine these rates with detailed hydrologic measurements to investigate the interplay between biogeochemical activity and water transport in controlling nitrogen attenuation along upwelling flow pathways. Nitrate attenuation occurred via denitrification rather than dissimilatory nitrate reduction to ammonium or anammox (range = 12 to >17,000 nmol 15N L-1 h-1). Overall, nitrate removal within the upwelling groundwater was controlled by water flux rather than reaction rate (i.e., Damköhler numbers rates of denitrification and short water residence time close to the riverbed surface balanced by slower rates of denitrification and water flux at depth. Within this permeable riverbed >80% of nitrate removal occurs within sediments not exposed to hyporheic exchange flows under base flow conditions, illustrating the importance of deep sediments as nitrate sinks in upwelling systems.

  8. Human Outer Solar System Exploration via Q-Thruster Technology

    Science.gov (United States)

    Joosten, B. Kent; White, Harold G.

    2014-01-01

    Propulsion technology development efforts at the NASA Johnson Space Center continue to advance the understanding of the quantum vacuum plasma thruster (QThruster), a form of electric propulsion. Through the use of electric and magnetic fields, a Q-thruster pushes quantum particles (electrons/positrons) in one direction, while the Qthruster recoils to conserve momentum. This principle is similar to how a submarine uses its propeller to push water in one direction, while the submarine recoils to conserve momentum. Based on laboratory results, it appears that continuous specific thrust levels of 0.4 - 4.0 N/kWe are achievable with essentially no onboard propellant consumption. To evaluate the potential of this technology, a mission analysis tool was developed utilizing the Generalized Reduced Gradient non-linear parameter optimization engine contained in the Microsoft Excel® platform. This tool allowed very rapid assessments of "Q-Ship" minimum time transfers from earth to the outer planets and back utilizing parametric variations in thrust acceleration while enforcing constraints on planetary phase angles and minimum heliocentric distances. A conservative Q-Thruster specific thrust assumption (0.4 N/kWe) combined with "moderate" levels of space nuclear power (1 - 2 MWe) and vehicle specific mass (45 - 55 kg/kWe) results in continuous milli-g thrust acceleration, opening up realms of human spaceflight performance completely unattainable by any current systems or near-term proposed technologies. Minimum flight times to Mars are predicted to be as low as 75 days, but perhaps more importantly new "retro-phase" and "gravity-augmented" trajectory shaping techniques were revealed which overcome adverse planetary phasing and allow virtually unrestricted departure and return opportunities. Even more impressively, the Jovian and Saturnian systems would be opened up to human exploration with round-trip times of 21 and 32 months respectively including 6 to 12 months of

  9. Background Pressure Effects on Krypton Hall Effect Thruster Internal Acceleration

    Science.gov (United States)

    2013-08-01

    krypton operation of the BHT -600 at the conditions in Table 2 yields a thrust of 22.4 mN corresponding to an anode efficiency of approximately 31...measurement volume is ap- proximately 500 µm diameter by 1 mm length.   Measurement Domain Figure 3 shows a cross-section of the BHT -600 Hall effect...of the BHT -600 Hall effect thruster with measurement volume shown in red. All dimensions are given in mm.     tion of the transition

  10. Optimal control of a Cope rearrangement by coupling the reaction path to a dissipative bath or a second active mode

    Energy Technology Data Exchange (ETDEWEB)

    Chenel, A. [Laboratoire de Chimie Physique, UMR 8000 and CNRS, Université Paris-Sud, F-91405 Orsay (France); Meier, C. [Laboratoire Collisions, Agrégats, Réactivité, UMR 5589, IRSAMC, Université Paul Sabatier, F-31062 Toulouse (France); Dive, G. [Centre d’Ingéniérie des Protéines, Université de Liège, Sart Tilman, B6, B-4000 Liège (Belgium); Desouter-Lecomte, M. [Laboratoire de Chimie Physique, UMR 8000 and CNRS, Université Paris-Sud, F-91405 Orsay (France); Département de Chimie, Université de Liège, Bât B6c, Sart Tilman, B4000 Liège (Belgium)

    2015-01-14

    We compare the strategy found by the optimal control theory in a complex molecular system according to the active subspace coupled to the field. The model is the isomerization during a Cope rearrangement of Thiele’s ester that is the most stable dimer obtained by the dimerization of methyl-cyclopentadienenylcarboxylate. The crudest partitioning consists in retaining in the active space only the reaction coordinate, coupled to a dissipative bath of harmonic oscillators which are not coupled to the field. The control then fights against dissipation by accelerating the passage across the transition region which is very wide and flat in a Cope reaction. This mechanism has been observed in our previous simulations [Chenel et al., J. Phys. Chem. A 116, 11273 (2012)]. We compare here, the response of the control field when the reaction path is coupled to a second active mode. Constraints on the integrated intensity and on the maximum amplitude of the fields are imposed limiting the control landscape. Then, optimum field from one-dimensional simulation cannot provide a very high yield. Better guess fields based on the two-dimensional model allow the control to exploit different mechanisms providing a high control yield. By coupling the reaction surface to a bath, we confirm the link between the robustness of the field against dissipation and the time spent in the delocalized states above the transition barrier.

  11. Propellantless Attitude Control of Solar Sail Technology Utilizing Reflective Control Devices

    Science.gov (United States)

    Munday, Jeremy

    2016-01-01

    Solar sails offer an opportunity for a CubeSatscale, propellant-free spacecraft technology that enables long-term and long-distance missions not possible with traditional methods. Solar sails operate using the transfer of linear momentum from photons of sunlight reflected from the surface of the sail. To propel the spacecraft, no mechanically moving parts, thrusters, or propellant are needed. However, attitude control, or orientation, is still performed using traditional methods involving reaction wheels and propellant ejection, which severely limit mission lifetime. For example, the current state of the art solutions employed by upcoming missions couple solar sails with a state of the art propellant ejection gas system. Here, the use of the gas thruster has limited the lifetime of the mission. To solve the limited mission lifetime problem, the Propellantless Attitude Control of Solar Sail Technology Utilizing Reflective Control Devices project team is working on propellantless attitude control using thin layers of material, an optical film, electrically switchable from transparent to reflective. The technology is based on a polymer-dispersed liquid crystal (PDLC), which allows this switch upon application of a voltage. This technology removes the need for propellant, which reduces weight and cost while improving performance and lifetime.

  12. Quantum-limited biochemical magnetometers designed using the Fisher information and quantum reaction control

    CERN Document Server

    Vitalis, K M

    2016-01-01

    Radical-ion pairs and their reactions have triggered the study of quantum effects in biological systems. This is because they exhibit a number of effects best understood within quantum information science, and at the same time are central in understanding the avian magnetic compass and the spin transport dynamics in photosynthetic reaction centers. Here we address radical-pair reactions from the perspective of quantum metrology. Since the coherent spin motion of radical-pairs is effected by an external magnetic field, these spin-dependent reactions essentially realize a biochemical magnetometer. Using the quantum Fisher information, we find the fundamental quantum limits to the magnetic sensitivity of radical-pair magnetometers. We then explore how well the usual measurement scheme considered in radical-pair reactions, the measurement of reaction yields, approaches the fundamental limits. In doing so, we find the optimal hyperfine interaction Hamiltonian that leads to the best magnetic sensitivity as obtained...

  13. Chemical Characterization and Reactivity Testing of Fuel-Oxidizer Reaction Product (Test Report)

    Science.gov (United States)

    1996-01-01

    The product of incomplete reaction of monomethylhydrazine (MMH) and nitrogen tetroxide (NTO) propellants, or fuel-oxidizer reaction product (FORP), has been hypothesized as a contributory cause of an anomaly which occurred in the chamber pressure (PC) transducer tube on the Reaction Control Subsystem (RCS) aft thruster 467 on flight STS-51. A small hole was found in the titanium-alloy PC tube at the first bend below the pressure transducer. It was surmised that the hole may have been caused by heat and pressure resulting from ignition of FORP. The NASA Johnson Space Center (JSC) White Sands Test Facility (WSTF) was requested to define the chemical characteristics of FORP, characterize its reactivity, and simulate the events in a controlled environment which may have lead to the Pc-tube failure. Samples of FORP were obtained from the gas-phase reaction of MMH with NTO under laboratory conditions, the pulsed firings of RCS thrusters with modified PC tubes using varied oxidizer or fuel lead times, and the nominal RCS thruster firings at WSTF and Kaiser-Marquardt. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), ion chromatography (IC), inductively coupled plasma (ICP) spectrometry, thermogravimetric analysis (TGA) coupled to FTIR (TGA/FTIR), and mechanical impact testing were used to qualitatively and quantitatively characterize the chemical, thermal, and ignition properties of FORP. These studies showed that the composition of FORP is variable but falls within a limited range of compositions that depends on the fuel loxidizer ratio at the time of formation, composition of the post-formation atmosphere (reducing or oxidizing), and reaction or postreaction temperature. A typical composition contains methylhydrazinium nitrate (MMHN), ammonium nitrate (AN), methylammonium nitrate (MAN), and trace amounts of hydrazinium nitrate and 1,1-dimethylhydrazinium nitrate. The thermal decomposition

  14. Quantum-limited biochemical magnetometers designed using the Fisher information and quantum reaction control

    OpenAIRE

    Vitalis, K. M.; Kominis, I. K.

    2016-01-01

    Radical-ion pairs and their reactions have triggered the study of quantum effects in biological systems. This is because they exhibit a number of effects best understood within quantum information science, and at the same time are central in understanding the avian magnetic compass and the spin transport dynamics in photosynthetic reaction centers. Here we address radical-pair reactions from the perspective of quantum metrology. Since the coherent spin motion of radical-pairs is effected by a...

  15. Reaction Mechanism and Control of Selectivity in Catalysis by Oxides: Some Challenges and Open Questions

    Directory of Open Access Journals (Sweden)

    Siglinda Perathoner

    2001-11-01

    Full Text Available Some aspects of the reaction mechanisms in multistep selective (ammoxidation reactions over oxide surfaces are discussed evidencing some of the challenges for surface science and theory in describing these reactions, and for applied catalysis in order to have a more in deep identification of the key factors governing surface reactivity and which may be used to improve catalytic performances. In particular, the role of chemisorbed species in the modification of the surface reactivity and the presence of multiple pathways of reaction are evidenced by comparing the behavior of V-based catalysts in C3-C4 alkanes and alkene oxidation.

  16. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    Science.gov (United States)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  17. Enceladus Plume Density Modeling and Reconstruction for Cassini Attitude Control System

    Science.gov (United States)

    Sarani, Siamak

    2010-01-01

    In 2005, Cassini detected jets composed mostly of water, spouting from a set of nearly parallel rifts in the crust of Enceladus, an icy moon of Saturn. During an Enceladus flyby, either reaction wheels or attitude control thrusters on the Cassini spacecraft are used to overcome the external torque imparted on Cassini due to Enceladus plume or jets, as well as to slew the spacecraft in order to meet the pointing needs of the on-board science instruments. If the estimated imparted torque is larger than it can be controlled by the reaction wheel control system, thrusters are used to control the spacecraft. Having an engineering model that can predict and simulate the external torque imparted on Cassini spacecraft due to the plume density during all projected low-altitude Enceladus flybys is important. Equally important is being able to reconstruct the plume density after each flyby in order to calibrate the model. This paper describes an engineering model of the Enceladus plume density, as a function of the flyby altitude, developed for the Cassini Attitude and Articulation Control Subsystem, and novel methodologies that use guidance, navigation, and control data to estimate the external torque imparted on the spacecraft due to the Enceladus plume and jets. The plume density is determined accordingly. The methodologies described have already been used to reconstruct the plume density for three low-altitude Enceladus flybys of Cassini in 2008 and will continue to be used on all remaining low-altitude Enceladus flybys in Cassini's extended missions.

  18. Development and Control of the Naval Postgraduate School Planar Autonomous Docking Simulator (NPADS)

    Science.gov (United States)

    Porter, Robert D.

    2002-09-01

    The objective of this thesis was to design, construct and develop the initial autonomous control algorithm for the NPS Planar Autonomous Docking Simulator (NPADS) The effort included hardware design, fabrication, installation and integration; mass property determination; and the development and testing of control laws utilizing MATLAB and Simulink for modeling and LabView for NPADS control, The NPADS vehicle uses air pads and a granite table to simulate a 2-D, drag-free, zero-g space environment, It is a completely self-contained vehicle equipped with eight cold-gas, bang-bang type thrusters and a reaction wheel for motion control, A 'star sensor' CCD camera locates the vehicle on the table while a color CCD docking camera and two robotic arms will locate and dock with a target vehicle, The on-board computer system leverages PXI technology and a single source, simplifying systems integration, The vehicle is powered by two lead-acid batteries for completely autonomous operation, A graphical user interface and wireless Ethernet enable the user to command and monitor the vehicle from a remote command and data acquisition computer. Two control algorithms were developed and allow the user to either control the thrusters and reaction wheel manually or simply specify a desired location and rotation angle,

  19. Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

    Science.gov (United States)

    Hallock, Ashley K.; Polzin, Kurt A.; Kimberlin, Adam C.; Perdue, Kevin A.

    2012-01-01

    Operational characteristics of two separate inductive thrusters with conical theta pinch coils of different cone angles are explored through thrust stand measurements and time- integrated, unfiltered photography. Trends in impulse bit measurements indicate that, in the present experimental configuration, the thruster with the inductive coil possessing a smaller cone angle produced larger values of thrust, in apparent contradiction to results of a previous thruster acceleration model. Areas of greater light intensity in photographs of thruster operation are assumed to qualitatively represent locations of increased current density. Light intensity is generally greater in images of the thruster with the smaller cone angle when compared to those of the thruster with the larger half cone angle for the same operating conditions. The intensity generally decreases in both thrusters for decreasing mass flow rate and capacitor voltage. The location of brightest light intensity shifts upstream for decreasing mass flow rate of propellant and downstream for decreasing applied voltage. Recognizing that there typically exists an optimum ratio of applied electric field to gas pressure with respect to breakdown efficiency, this result may indicate that the optimum ratio was not achieved uniformly over the coil face, leading to non-uniform and incomplete current sheet formation in violation of the model assumption of immediate formation where all the injected propellant is contained in a magnetically-impermeable current sheet.

  20. Elementary scaling laws for the design of low and high power hall effect thrusters

    Science.gov (United States)

    Dannenmayer, K.; Mazouffre, S.

    2011-10-01

    An advanced set of scaling laws for Hall effect thrusters running with Xenon as propellant is established on the basis of the existence of an optimum atom number density that warrants a high efficiency thruster operation. A set of general relationships between macroscopic quantities, like thrust and input power, dimensions, including the channel length, the channel width and the channel mean diameter, and magnetic field strength are inferred from the main physical processes at work in a Hall thruster discharge. The "atom density constraint" of which the nature is here critically interpreted allows simplifying those relationships as it leads to a linear dependency between the channel length and mean diameter. Scaling laws which represent an essential tool for sizing up and down Hall thrusters are eventually obtained after proportionnality coefficients are determined. This last step is realized by means of a vast database that presently encompasses 33 single-stage Hall thrusters. In order to illustrate the usefulness of this new set of scaling laws, two practical applications are given and discussed. The scaling laws are first employed to calculate the dimensions and the operating parameters for a 20-kilowatt Hall thruster capable of producing 1 N of thrust. Such an electrical engine would permit orbit transfer of large communication satellites. Finally, the geometry of a Hall thruster is determined for tolerating 100 kW, an interesting power level for interplanetary trips.

  1. Orion Exploration Flight Test Reaction Control System Jet Interaction Heating Environment from Flight Data

    Science.gov (United States)

    White, Molly E.; Hyatt, Andrew J.

    2016-01-01

    The Orion Multi-Purpose Crew Vehicle (MPCV) Reaction Control System (RCS) is critical to guide the vehicle along the desired trajectory during re-­-entry. However, this system has a significant impact on the convective heating environment to the spacecraft. Heating augmentation from the jet interaction (JI) drives thermal protection system (TPS) material selection and thickness requirements for the spacecraft. This paper describes the heating environment from the RCS on the afterbody of the Orion MPCV during Orion's first flight test, Exploration Flight Test 1 (EFT-1). These jet plumes interact with the wake of the crew capsule and cause an increase in the convective heating environment. Not only is there widespread influence from the jet banks, there may also be very localized effects. The firing history during EFT-1 will be summarized to assess which jet bank interaction was measured during flight. Heating augmentation factors derived from the reconstructed flight data will be presented. Furthermore, flight instrumentation across the afterbody provides the highest spatial resolution of the region of influence of the individual jet banks of any spacecraft yet flown. This distribution of heating augmentation across the afterbody will be derived from the flight data. Additionally, trends with possible correlating parameters will be investigated to assist future designs and ground testing programs. Finally, the challenges of measuring JI, applying this data to future flights and lessons learned will be discussed.

  2. Non-Toxic Reaction Control System for the Reusable First Stage Vehicle

    Science.gov (United States)

    Keith, E. L.; Rothschild, W. J.

    1999-01-01

    This paper presents the Boeing Reusable Space Systems vision of a Reaction Control System (RCS) for the Reusable First Stage (RFS) being considered as a replacement for the Solid Rocket Booster for the Space Shuttle. The requirement is to achieve reliable vehicle control during the upper atmospheric portion of the RFS trajectory while enabling more efficient ground operations, unhindered by constraints caused by operating with highly toxic RCS propellants. Boeing's objective for this effort is to develop a safer, more efficient and environmentally friendly RCS design approach that is suitable for the RFS concept of operations, including a low cost, efficient turnaround cycle. The Boeing RCS concept utilizes ethanol and liquid oxygen in place of the highly toxic, suspected carcinogen, ozone-depleting mono-methyl-hydrazine and highly toxic nitrogen tetroxide. The Space Shuttle Upgrade program, under the leadership of the NASA Johnson Space Flight Center, is currently developing liquid oxygen and ethanol (ethyl alcohol) technology for use as non-toxic orbital maneuvering system (OMS) and RCS. The development of this liquid oxygen and ethanol technology for the Space Shuttle offers a significant leverage to select much of the same technology for the RFS program. There are significant design and development issues involved with bringing this liquid oxygen and ethanol technology to a state of maturity suitable for an operational RCS. The risks associated with a new LOX and Ethanol RCS are mitigated by maintaining kerosene and hydrogen peroxide RCS technology as an alternative. These issues, presented within this paper, include managing the oxygen supply and achieving reliable ignition in the short pulse mode of engine operation. Performance, reliability and operations requirements are presented along with a specific RCS design concept to satisfying these requirements. The work reported in this paper was performed under NASA Marshall Space Flight Center Contract Number

  3. ACTIVE MODEL ROCKET STABILIZATION VIA COLD GAS THRUSTERS

    OpenAIRE

    Malyuta, Danylo; Collaud, Xavier; Martins Gaspar, Mikael; Rouaze, Gautier Marie Pierre; Pictet, Raimondo; Ivanov, Anton; Mullin, Nickolay

    2015-01-01

    This paper describes the development and testing of a reaction control system (RCS) for a model rocket named FALCO-4. The rocket uses cold gas jets to keep itself perfectly vertical at low speeds. We first describe the mechanical layout of FALCO-4 and the characteristics of the cold gas propulsion system. We then propose a dynamical model of the rocket and a control scheme based on decoupled PID regulators for roll, pitch and yaw. The control scheme is then evaluated based on MATLAB simulatio...

  4. Ion angular distribution simulation of the HEMP Thruster

    Science.gov (United States)

    Duras, Julia; Koch, Norbert; Kahnfeld, Daniel; Bandelow, Gunnar; Matthias, Paul; Lüskow, Karl Felix; Schneider, Ralf; Kemnitz, Stefan

    2016-10-01

    Ion angular current and energy distributions are important parameters for ion thrusters, which are typically measured at a few tens of centimetres to a few meters distance from thruster exit. However, fully kinetic Particle-in-Cell simulations are not able to simulate such domain sizes, due to high computational costs. Therefore, a parallelisation strategy of the code is presented to reduce computational time. To map diagnostics information from the domain boundary of the calculational domain to the positions of experimental diagnostics the concept of transfer functions is introduced. The calculated ion beam angular distributions in the plume region are quite sensitive to boundary conditions of the potential, possible additional source contributions, e.g. from secondary electron emission at vessel walls, and charge exchange collisions. This work was supported by the Bavarian State Ministry of Education Science and the Arts and the German Space Agency DLR. We also like to thank R. Heidemann from THALES Electron Devices GmbH, for interesting and stimulating discussions.

  5. Assessment of Pole Erosion in a Magnetically Shielded Hall Thruster

    Science.gov (United States)

    Mikellides, Ioannis G.; Ortega, Alejandro L.

    2014-01-01

    Numerical simulations of a 6-kW laboratory Hall thruster called H6 have been performed to quantify the erosion rate at the inner pole. The assessments have been made in two versions of the thruster, namely the unshielded (H6US) and magnetically shielded (H6MS) configurations. The simulations have been performed with the 2-D axisymmetric code Hall2De which employs a new multi-fluid ion algorithm to capture the presence of low-energy ions in the vicinity of the poles. It is found that the maximum computed erosion rate at the inner pole of the H6MS exceeds the measured rate of back-sputtered deposits by 4.5 times. This explains only part of the surface roughening that was observed after a 150-h wear test, which covered most of the pole area exposed to the plasma. For the majority of the pole surface the computed erosion rates are found to be below the back-sputter rate and comparable to those in the H6US which exhibited little to no sputtering in previous tests. Possible explanations for the discrepancy are discussed.

  6. Engineering Risk Assessment of Space Thruster Challenge Problem

    Science.gov (United States)

    Mathias, Donovan L.; Mattenberger, Christopher J.; Go, Susie

    2014-01-01

    The Engineering Risk Assessment (ERA) team at NASA Ames Research Center utilizes dynamic models with linked physics-of-failure analyses to produce quantitative risk assessments of space exploration missions. This paper applies the ERA approach to the baseline and extended versions of the PSAM Space Thruster Challenge Problem, which investigates mission risk for a deep space ion propulsion system with time-varying thruster requirements and operations schedules. The dynamic mission is modeled using a combination of discrete and continuous-time reliability elements within the commercially available GoldSim software. Loss-of-mission (LOM) probability results are generated via Monte Carlo sampling performed by the integrated model. Model convergence studies are presented to illustrate the sensitivity of integrated LOM results to the number of Monte Carlo trials. A deterministic risk model was also built for the three baseline and extended missions using the Ames Reliability Tool (ART), and results are compared to the simulation results to evaluate the relative importance of mission dynamics. The ART model did a reasonable job of matching the simulation models for the baseline case, while a hybrid approach using offline dynamic models was required for the extended missions. This study highlighted that state-of-the-art techniques can adequately adapt to a range of dynamic problems.

  7. Experimental Study of the Microdischarge Plasma Thruster (MDPT)

    Science.gov (United States)

    Kc, Utsav; Varghese, Philip; Raja, Laxminarayan

    2008-10-01

    Small satellite propulsion requirements dictate the need for a scaled down propulsion device capable of providing low thrust with small impulse bits. We have designed and studied a simple miniaturized thruster called Microdischarge Plasma Thruster (MDPT). It comprises a tri-layer sandwich structure with a dielectric layer sandwiched between two electrode layers, and a contoured through hollow drilled into the structure. Each layer is 100's microns in thickness and the hole diameter of the same order. Argon is used as the propellant gas with flow rates of ˜ 1 SCCM. The pressure is adequate to produce a stable microdischarge between the electrodes even with modest voltages (˜1000 V). The microdischarge adds heat to the supersonic portion of the flowing gas which is shown to produce additional thrust over the baseline cold gas flow. The studies have also demonstrated that the MDPT exhaust plume is composed of ions albeit at low concentrations, suggesting possibility of MDPT to be operated in a mixed electrothermal/electrostatic mode. We present discussion of multiple discharge operating modes and electrical characteristics of the MDPT. Spectral measurements of the plume are used to determine its composition and calculate its temperature. The momentum thrust of the MDPT is measured with a torsion balance.

  8. Assessment of Pole Erosion in a Magnetically Shielded Hall Thruster

    Science.gov (United States)

    Mikellides, Ioannis G.; Ortega, Alejandro L.

    2014-01-01

    Numerical simulations of a 6-kW laboratory Hall thruster called H6 have been performed to quantify the erosion rate at the inner pole. The assessments have been made in two versions of the thruster, namely the unshielded (H6US) and magnetically shielded (H6MS) configurations. The simulations have been performed with the 2-D axisymmetric code Hall2De which employs a new multi-fluid ion algorithm to capture the presence of low-energy ions in the vicinity of the poles. It is found that the maximum computed erosion rate at the inner pole of the H6MS exceeds the measured rate of back-sputtered deposits by 4.5 times. This explains only part of the surface roughening that was observed after a 150-h wear test, which covered most of the pole area exposed to the plasma. For the majority of the pole surface the computed erosion rates are found to be below the back-sputter rate and comparable to those in the H6US which exhibited little to no sputtering in previous tests. Possible explanations for the discrepancy are discussed.

  9. Optimization of energy transfer in microwave electrothermal thrusters

    Science.gov (United States)

    Sullivan, D. J.; Micci, M. M.

    1993-01-01

    Results are presented from preliminary tests conducted to evaluate the performance of a prototype microwave electrothermal thruster. The primary component of the device is a microwave resonant cavity. The device produces stable axial plasmas within a pressurized section of the cavity with the plasma positioned in the inlet region of the nozzle. Plasma stability is enhanced by axial power coupling, an optimal distribution of electric power density within the cavity, and a propellant gas flow which has a large vortical velocity component. The thruster has been operated with a number of propellant gases: helium, nitrogen, ammonia, and hydrogen. Plasmas can be formed in a reliable manner at cavity pressures of 1 kPa and incident power levels ranging from 50 W to 350 W, depending on the gas used, and can be operated at pressures up to 300 kPa at power levels up to 2200 W. Ideal performance results of vacuum Isp and thermal efficiency vs. specific power are presented for each gas. Representative results of this preliminary work are: He - Isp = 625 s, eta-thermal = 90 percent; N2 - Isp = 270 s, eta-thermal = 41 percent; NH3 - Isp = 475 s, eta-thermal= 55 percent; H2 - Isp = 1040 s, eta-thermal = 53 percent.

  10. Suicide Survivors' Mental Health and Grief Reactions: A Systematic Review of Controlled Studies

    Science.gov (United States)

    Sveen, Carl-Aksel; Walby, Fredrik A.

    2008-01-01

    There has been a debate over several decades whether suicide survivors experience more severe mental health consequences and grief reactions than those who have been bereaved through other causes of death. This is the first systematic review of suicide survivors' reactions compared with survivors after other modes of death. Studies were identified…

  11. Erosion Measurements in a Diverging Cusped-Field Thruster (Pre Print)

    Science.gov (United States)

    2012-02-01

    3,000 3,000∗ BHT -200 [15] 200 43.5% 1,287-1,519 >1,700 HT-100 [16] 175 25% [4] 300 [17] 1,500 [17]∗∗ SPT-30 [18] 150 26% [19] 600∗ - SPT-20M [20] ...provide longer lifetimes to low-power thrusters with performance capabilities similar to Hall thrusters. Performance similar to the BHT -200, a...only the DCF and BHT -200 thrusters have the reported capability of operating past 1000 h without exposing components of their magnetic circuit. The

  12. Comparison of Numerical and Experimental Time-Resolved Near-Field Hall Thruster Plasma Properties

    Science.gov (United States)

    2014-03-06

    RESOLVED NEAR-FIELD HALL THRUSTER PLASMA PROPERTIES 807 TABLE I BHT -600 HALL THRUSTER AT NOMINAL XENON OPERATING CONDITIONS AND PERFORMANCE [21] 1.2-m...is a 600 W BHT -600 with a 3.2-mm hollow cathode manufactured by the Busek Company (Natick, MA). This thruster has been studied previously using both...electrostatic probes and various opti- cal diagnostics [17]–[20]. The BHT -600 has an acceleration channel outer radius of 32 mm, inner radius of 24 mm

  13. Effects of Anode Temperature on Working Characteristics and Performance of a Low Power Arcjet Thruster

    Institute of Scientific and Technical Information of China (English)

    PAN Wen-Xia; LI Teng; WU Cheng-Kang

    2009-01-01

    An arc-heated thruster of 130-800 W input power is tested in a vacuum chamber at pressures lower than 20 Pa with argon or H_2-N_2 gas mixture as propellant.The time-dependent arc voltage-current curve,outside-surface temperature of the anode nozzle and the produced thrust of the firing arcjet thruster are measured in situ simultaneously,in order to analyze and evaluate the dependence of thruster working characteristics and output properties,such as specific impulse and thrust efficiency,on nozzle temperature.

  14. Satellite Microwave Communication Signal Degradation Due To Hall Thruster Plasma Plumes

    Science.gov (United States)

    Wiley, J. C.; Hallock, G. A.; Spencer, E. A.; Meyer, J. W.; Loane, J. T.

    2001-10-01

    We have developed a geometric optics vector ray-tracing code, BeamServer, for analyzing the effects of Hall thruster plasma plumes on satellite microwave communication signals. The possible effects include main beam attenuation and squinting, side lobe degradation, and induced cross-polarization. We report on a study of Hall current thruster (HCT) mounting positions on a realistic satellite configuration and a study with a highly shaped reflector. Results indicate HCT signal degradation can occur and should be considered in the satellite design process. Initial results of antenna pattern perturbations due to low frequency plume oscillations driven by thruster instabilities are also given.

  15. Influence of Triply-Charged Ions and Ionization Cross-Sections in a Hybrid-PIC Model of a Hall Thruster Discharge

    Science.gov (United States)

    Smith, Brandon D.; Boyd, Iain D.; Kamhawi, Hani

    2014-01-01

    The sensitivity of xenon ionization rates to collision cross-sections is studied within the framework of a hybrid-PIC model of a Hall thruster discharge. A revised curve fit based on the Drawin form is proposed and is shown to better reproduce the measured crosssections at high electron energies, with differences in the integrated rate coefficients being on the order of 10% for electron temperatures between 20 eV and 30 eV. The revised fit is implemented into HPHall and the updated model is used to simulate NASA's HiVHAc EDU2 Hall thruster at discharge voltages of 300, 400, and 500 V. For all three operating points, the revised cross-sections result in an increase in the predicted thrust and anode efficiency, reducing the error relative to experimental performance measurements. Electron temperature and ionization reaction rates are shown to follow the trends expected based on the integrated rate coefficients. The effects of triply-charged xenon are also assessed. The predicted thruster performance is found to have little or no dependence on the presence of triply-charged ions. The fraction of ion current carried by triply-charged ions is found to be on the order of 1% and increases slightly with increasing discharge voltage. The reaction rates for the 0?III, I?III, and II?III ionization reactions are found to be of similar order of magnitude and are about one order of magnitude smaller than the rate of 0?II ionization in the discharge channel.

  16. Two-Pulse Atomic Coherent Control (2PACC) Spectroscopy of Eley-Rideal Reactions. An Application of an Atom Laser

    CERN Document Server

    Jorgensen, S F; Jorgensen, Solvejg; Kosloff, Ronnie

    2003-01-01

    A spectroscopic application of the atom laser is suggested. The spectroscopy termed 2PACC employs the coherent properties of matter-waves from a two pulse atom laser. These waves are employed to control a gas-surface chemical recombination reaction. The method is demonstrated for an Eley-Rideal reaction of a hydrogen or alkali atom-laser pulse where the surface target is an adsorbed hydrogen atom. The reaction yields either a hydrogen or alkali hydride molecule. The desorbed gas phase molecular yield and its internal state is shown to be controlled by the time and phase delay between two atom-laser pulses. The calculation is based on solving the time-dependent Schrodinger equation in a diabatic framework. The probability of desorption which is the predicted 2PACC signal has been calculated as a function of the pulse parameters.

  17. Longitudinal relations among parents' reactions to children's negative emotions, effortful control, and math achievement in early elementary school.

    Science.gov (United States)

    Swanson, Jodi; Valiente, Carlos; Lemery-Chalfant, Kathryn; Bradley, Robert H; Eggum-Wilkens, Natalie D

    2014-01-01

    Panel mediation models and fixed-effects models were used to explore longitudinal relations among parents' reactions to children's displays of negative emotions, children's effortful control (EC), and children's math achievement (N = 291; M age in fall of kindergarten = 5.66 years, SD = .39 year) across kindergarten through second grade. Parents reported their reactions and children's EC. Math achievement was assessed with a standardized achievement test. First-grade EC mediated the relation between parents' reactions at kindergarten and second-grade math achievement, beyond stability in constructs across study years. Panel mediation model results suggested that socialization of EC may be one method of promoting math achievement in early school; however, when all omitted time-invariant covariates of EC and math achievement were controlled, first-grade EC no longer predicted second-grade math achievement. © 2014 The Authors. Child Development © 2014 Society for Research in Child Development, Inc.

  18. Controlled growth of gold nanoparticles in zeolite L via ion-exchange reactions and thermal reduction processes

    KAUST Repository

    Zeng, Shangjing

    2014-09-01

    The growth of gold nanoparticles in zeolite can be controlled using ion-exchange reactions and thermal reduction processes. We produce a number of different sizes of the gold nanoparticles with the particle size increasing with increased temperature of the final heat treatment. © 2014 Elsevier B.V.

  19. Quantum Diffusion-Controlled Chemistry: Reactions of Atomic Hydrogen with Nitric Oxide in Solid Parahydrogen.

    Science.gov (United States)

    Ruzi, Mahmut; Anderson, David T

    2015-12-17

    Our group has been working to develop parahydrogen (pH2) matrix isolation spectroscopy as a method to study low-temperature condensed-phase reactions of atomic hydrogen with various reaction partners. Guided by the well-defined studies of cold atom chemistry in rare-gas solids, the special properties of quantum hosts such as solid pH2 afford new opportunities to study the analogous chemical reactions under quantum diffusion conditions in hopes of discovering new types of chemical reaction mechanisms. In this study, we present Fourier transform infrared spectroscopic studies of the 193 nm photoinduced chemistry of nitric oxide (NO) isolated in solid pH2 over the 1.8 to 4.3 K temperature range. Upon short-term in situ irradiation the NO readily undergoes photolysis to yield HNO, NOH, NH, NH3, H2O, and H atoms. We map the postphotolysis reactions of mobile H atoms with NO and document first-order growth in HNO and NOH reaction products for up to 5 h after photolysis. We perform three experiments at 4.3 K and one at 1.8 K to permit the temperature dependence of the reaction kinetics to be quantified. We observe Arrhenius-type behavior with a pre-exponential factor of A = 0.036(2) min(-1) and Ea = 2.39(1) cm(-1). This is in sharp contrast to previous H atom reactions we have studied in solid pH2 that display definitively non-Arrhenius behavior. The contrasting temperature dependence measured for the H + NO reaction is likely related to the details of H atom quantum diffusion in solid pH2 and deserves further study.

  20. A chemical reaction controlled mechanochemical route to construction of CuO nanoribbons for high performance lithium-ion batteries.

    Science.gov (United States)

    Chen, Kunfeng; Xue, Dongfeng

    2013-12-07

    We reported a chemical reaction controlled mechanochemical route to synthesize mass CuO nanosheets by manual grinding in a mortar and pestle, which does not require any solvent, complex apparatus and techniques. The activation of chemical reactions by milling reactants was thus proved, and the energy from mechanical grinding promotes the fast formation of CuO nanoribbons. The resultant materials have preferential nanoscale ribbon-like morphology that can show large capacity and high cycle performance as lithium-ion battery anodes. After 50 cycles, the discharge capacity of CuO nanoribbon electrodes is 614.0 mA h g(-1), with 93% retention of the reversible capacity. The thermodynamic reactions of the CuO battery showed size-dependent characterization. The microstructures of CuO nanosheets and reaction routes can be controlled by the ratio of NaOH/CuAc2 according to the chemical reactions involved. The intact nanoribbon structure, thin-layer, and hierarchical structures endow present CuO materials with high reversible capacity and excellent cycling performances. The simple, economical, and environmentally friendly mechanochemical route is of great interest in modern synthetic chemistry.

  1. Exposures and reactions to allergens among hairdressing apprentices and matched controls

    DEFF Research Database (Denmark)

    Bregnhøj, Anne; Søsted, Heidi; Menné, Torkil;

    2011-01-01

    Early and extensive exposures to chemical substances such as are found in hair dyes, perfumes and nickel are known risk factors for allergic reactions. Hairdressing apprentices belong to a high-risk group, as they are exposed both occupationally and personally.......Early and extensive exposures to chemical substances such as are found in hair dyes, perfumes and nickel are known risk factors for allergic reactions. Hairdressing apprentices belong to a high-risk group, as they are exposed both occupationally and personally....

  2. Kinetic and thermodynamic control in β-phenylethylamines reaction with isatin

    Science.gov (United States)

    Vélez, Yormari; Díaz-Oviedo, Christian; Quevedo, Rodolfo

    2017-04-01

    In this work it was established that dopamine's reaction with isatin produces the respective spiroisoquinoline through a Pictet-Spengler reaction whilst phenylethylamines, having less activated aromatic rings (tyramine and phenylethylamine), produce the respective imine as a mixture of stereoisomers E and Z. This article analyses the spectroscopic and structural patterns of the stereoisomers (E/Z) obtained and proposes the experimental conditions necessary for obtaining each of them as major products.

  3. Design and Testing of a Small Inductive Pulsed Plasma Thruster

    Science.gov (United States)

    Martin, Adam K.; Eskridge, Richard H.; Dominguez, Alexandra; Polzin, Kurt A.; Riley, Daniel P.; Kimberlin, Adam C.

    2015-01-01

    The design and testing of a small inductive pulsed plasma thruster (IPPT), shown in Fig. 1 with all the major subsystems required for a thruster of this kind are described. Thrust measurements and imaging of the device operated in rep-rated mode are presented to quantify the performance envelope of the device. The small IPPT described in this paper was designed to serve as a test-bed for the pulsed gas-valves and solid-state switches required for a IPPTs. A modular design approach was used to permit future modifications and upgrades. The thruster consists of the following sub-systems: a) a multi-turn, spiral-wound acceleration coil (27 cm o.d., 10 cm i.d.) driven by a 10 microFarad capacitor and switched with a high-voltage thyristor, b) a fast pulsed gas-valve, and c.) a glow-discharge pre-ionizer (PI) circuit. The acceleration-coil circuit may be operated at voltages up to 4 kV (the thyristor limit is 4.5 kV). The device may be operated at rep-rates up to 30 Hz with the present gas-valve. Thrust measurements and imaging of the device operated in rep-rated mode will be presented. The pre-ionizer consists of a 0.3 microFarad capacitor charged to 4 kV and connected to two annular stainless-steel electrodes bounding the area of the coil-face. The 4 kV potential is held across them and when the gas is puffed in over the coil, the PI circuit is completed, and a plasma is formed. Even at the less than optimal base-pressure in the chamber (approximately 5 × 10(exp -4) torr), the PI held-off the applied voltage, and only discharged upon command. For a capacitor charge of 2 kV the peak coil current is 4.1 kA, and during this pulse a very bright discharge (much brighter than from the PI alone) was observed (see Fig. 2). Interestingly, for discharges at this charge voltage the PI was not required as the current rise rate, dI/dt, of the coil itself was sufficient to ionize the gas.

  4. Heteropolymolybdate as a New Reaction-controlled Phase-transfer Catalyst for Efficient Alcohol Oxidation with Hydrogen Peroxide

    Institute of Scientific and Technical Information of China (English)

    Zhi Huan WENG; Jin Yan WANG; Xi Gao JIAN

    2006-01-01

    A new catalytic process for the synthesis of aldehyde from alcohol by oxidation with H2O2 with high selectivity was studied. In this system, heteropolymolybdate [C7H7N(CH3)3]3{PO4[MoO(O2)2]4} was utilized as the reaction-controlled phase-transfer catalyst to catalyze oxidation of benzyl and aliphatic alcohols. The molar ratio of H2O2 and alcohol was 0.75, no other by-products were detected by gas chromatography, the results of oxidation reaction indicated that the catalyst has high activity and stability.

  5. HIGH ENERGY REPLACEMENT FOR TEFLON PROPELLANT IN PULSED PLASMA THRUSTERS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This program will utilize a well-characterized Pulsed Plasma Thruster (PPT) to test experimental high-energy extinguishable solid propellants (HE), instead of...

  6. Feasibility of a 5mN Laser-Driven Mini-Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We have developed a next-generation thruster under a Phase II SBIR which we believe can meet NASA requirements after some modifications and improvements. It is the...

  7. Kinetic Molecular Dynamic Model of Hall Thruster Channel Wall Erosion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Hall thrusters are being considered for many space missions because their high specific impulse delivers a larger payload mass fraction than chemical rockets. With a...

  8. On the microscopic mechanism of ion-extraction of a gridded ion propulsion thruster

    CERN Document Server

    Kirmse, Danny

    2013-01-01

    The following paper includes a physical microscopic particle-description of the phenomena and mechanisms that lead to the extraction of ions with the aim to generate thrust. This theoretical treatise arose from the intention to visualize the behavior of the involved particles under effect of the involved electrical fields. By this way, an underlying basis for experimental investigations of the work of an ion thruster should be formed. So a foundation was created, which explains the ion extracting and so thrust generating function of an ion thruster. The theoretical work was related to the Radio-frequency Ion Thruster (RIT). But the model worked out can be generalized for all thruster types that use electrostatic fields to extract positively charged ions.

  9. Hall Effect Thruster for High Power Solar Electric Propulsion Technology Demonstration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In Phase I Busek matured the design of an existing 15-kW laboratory thruster. Magnetic modeling was performed to generate a circuit incorporating magnetic shielding....

  10. Simulation of a Cold Gas Thruster System and Test Data Correlation

    Science.gov (United States)

    Hauser, Daniel M.; Quinn, Frank D.

    2012-01-01

    During developmental testing of the Ascent Abort 1 (AA-1) cold gas thruster system, unexpected behavior was detected. Upon further review the design as it existed may not have met the requirements. To determine the best approach for modifying the design, the system was modeled with a dynamic fluid analysis tool (EASY5). The system model consisted of the nitrogen storage tank, pressure regulator, thruster valve, nozzle, and the associated interconnecting line lengths. The regulator and thruster valves were modeled using a combination of the fluid and mechanical modules available in EASY5. The simulation results were then compared against actual system test data. The simulation results exhibited behaviors similar to the test results, such as the pressure regulators response to thruster firings. Potential design solutions were investigated using the analytical model parameters, including increasing the volume downstream of the regulator and increasing the orifice area. Both were shown to improve the regulator response.

  11. Effect of Ambipolar Potential on the Propulsive Performance of the GDM Plasma Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The gasdynamic mirror (GDM) plasma thruster has the ability to confine high-density plasma for the length of time required to heat it to the temperatures...

  12. Effect of Ambipolar Potential on the Propulsive Performance of the GDM Plasma Thruster Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Gasdynamic Mirror (GDM) thruster is an electric propulsion device, without electrodes, that will magnetically confine a plasma with such density and temperature...

  13. Wide Throttling, High Throughput Hall Thruster for Science and Exploration Missions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In response to Topic S3.04 "Propulsion Systems," Busek Co. Inc. will develop a high throughput Hall effect thruster with a nominal peak power of 1-kW and wide...

  14. Wide Throttling, High Throughput Hall Thruster for Science and Exploration Missions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In response to Topic S3-04 "Propulsion Systems," Busek proposes to develop a high throughput Hall effect thruster with a nominal peak power of 1-kW and wide...

  15. Propellantless Spacecraft Formation-Flying and Maneuvering with Photonic Laser Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Until the former NIAC was closed, we had investigated a nano-meter accuracy formation flight method based on photon thrusters and tethers, Photon Tether Formation...

  16. Hot-Fire Testing of a 1N AF-M315E Thruster

    Science.gov (United States)

    Burnside, Christopher G.; Pedersen, Kevin; Pierce, Charles W.

    2015-01-01

    This hot-fire test continues NASA investigation of green propellant technologies for future missions. To show the potential for green propellants to replace some hydrazine systems in future spacecraft, NASA Marshall Space Flight Center (MSFC) is continuing to embark on hot-fire test campaigns with various green propellant blends. NASA completed a hot-fire test of a 1N AF-M315E monopropellant thruster at the Marshall Space Flight Center in the small altitude test stand located in building 4205. The thruster is a ground test article used for basic performance determination and catalyst studies. The purpose of the hot-fire testing was for performance determination of a 1N size thruster and form a baseline from which to study catalyst performance and life with follow-on testing to be conducted at a later date. The thruster performed as expected. The result of the hot-fire testing are presented in this paper and presentation.

  17. Effects of regular Tai Chi practice and jogging on neuromuscular reaction during lateral postural control in older people.

    Science.gov (United States)

    Wang, Shao-Jun; Xu, Dong-Qing; Li, Jing-Xian

    2017-01-01

    This study examined the effects of regular Tai Chi practice and jogging on the neuromuscular activity of the trunk, hip, and ankle joint muscles of older people during lateral postural perturbation. A total of 42 older people participated in the study and formed the Tai Chi, jogging, and sedentary control groups. Electromyography signals were collected from the peroneus longus, anterior tibialis, gluteus medius, and erector spinae during unpredictable mediolateral perturbation. The Tai Chi group exhibited significantly faster latencies of the tibialis anterior and erector spinae than the control group. The jogging group showed a significantly shorter neuromuscular reaction time of the erector spinae than the control group. No significant difference was observed between the Tai Chi and jogging groups. Long-term regular Tai Chi practice enhanced the neuromuscular reaction of the erector spinae and tibialis anterior to lateral perturbation and will help timely posture correction when lateral postural distributions occur.

  18. Assessment of the ribose-induced Maillard reaction as a means of gelatine powder identification and quality control.

    Science.gov (United States)

    Tan, Thuan-Chew; AlKarkhi, Abbas F M; Easa, Azhar Mat

    2012-10-15

    The addition of ribose to bovine or porcine gelatine solutions followed by heating at 95 °C yielded brown solutions with different pH, colour (CIE L(*) and b(*)) and absorbance (A(420*) values. These differences were used for gelatine powder identification, differentiation and quality control. Differentiation analysis of the Maillard reaction parameters was conducted using cluster analysis (CA) and confidence intervals (CI). The potential use of the method as a quality control procedure was evaluated by using statistical process control (SPC). CA revealed that the two types of gelatine could be classified into two different groups. CI (95% confidence) revealed that the absorbance and colour values could be used as indicators for differentiation between the two types of gelatine because the intervals between the Maillard reaction parameters of the samples were far apart. The methodology demonstrated good reproducibility because it behaved predictably based on the X¯-S charts generated from the SPC charts.

  19. Simulations on the influence of the spatial distribution of source electrons on the plasma in a cusped-field thruster

    Science.gov (United States)

    Brandt, Tim; Trottenberg, Thomas; Groll, Rodion; Jansen, Frank; Hey, Franz Georg; Johann, Ulrich; Kersten, Holger; Braxmaier, Claus

    2015-06-01

    We present results from simulations on the influence of source electrons on the plasma properties in a magnetic cusps environment. Our simulations are based on the VSim/Vorpal particle-in-cell plasma simulation package. Magnetic cusps are a typical feature of High Efficiency Multistage Plasma Thrusters (HEMPTs). This research is part of an effort to downscale a HEMPT to thrust levels in the μN and sub- μN regime. The aim is to fulfill the requirements of upcoming formation flight satellites and probes. Those missions demand very precise attitude control. In order to get the necessary insight, the plasma of a section of the HEMPT discharge chamber is simulated with idealized boundary conditions. The results for such a section at two different distributions of source electrons are shown. A significant increase of the overall ion number is recognized for one of the distributions. Comparisons with published similar simulations are made. Factors that should be important for improvements of this thruster type are highlighted.

  20. Overview of NASA GRCs Green Propellant Infusion Mission Thruster Testing and Plume Diagnostics

    Science.gov (United States)

    Deans, Matthew C.; Reed, Brian D.; Yim, John T.; Arrington, Lynn A.; Williams, George J.; Kojima, Jun J.; McLean, Christopher H.

    2014-01-01

    The Green Propellant Infusion Mission (GPIM) is sponsored by NASA's Space Technology Mission Directorate (STMD) Technology Demonstration Mission (TDM) office. The goal of GPIM is to advance the technology readiness level of a green propulsion system, specifically, one using the monopropellant, AF-M315E, by demonstrating ground handling, spacecraft processing, and on-orbit operations. One of the risks identified for GPIM is potential contamination of sensitive spacecraft surfaces from the effluents in the plumes of AF-M315E thrusters. NASA Glenn Research Center (GRC) is conducting activities to characterize the effects of AF-M315E plume impingement and deposition. GRC has established individual plume models of the 22-N and 1-N thrusters that will be used on the GPIM spacecraft. The models describe the pressure, temperature, density, Mach number, and species concentration of the AF-M315E thruster exhaust plumes. The models are being used to assess the impingement effects of the AF-M315E thrusters on the GPIM spacecraft. The model simulations will be correlated with plume measurement data from Laboratory and Engineering Model 22-N, AF-M315E thrusters. The thrusters will be tested in a small rocket, altitude facility at NASA GRC. The GRC thruster testing will be conducted at duty cycles representatives of the planned GPIM maneuvers. A suite of laser-based diagnostics, including Raman spectroscopy, Rayleigh spectroscopy, Schlieren imaging, and physical probes will be used to acquire plume measurements of AFM315E thrusters. Plume data will include temperature, velocity, relative density, and species concentration. The plume measurement data will be compared to the corresponding simulations of the plume model. The GRC effort will establish a data set of AF-M315E plume measurements and a plume model that can be used for future AF-M315E applications.