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1

Lateral dampers for thrust bearings  

Science.gov (United States)

The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

Hibner, D. H.; Szafir, D. R.

1985-01-01

2

Fatigue Life Analysis of Thrust Ball Bearing Using ANSYS  

Directory of Open Access Journals (Sweden)

Full Text Available This paper compares the total deformation of thrust ball bearing & contact stress b/w ball & raceways & its effect on fatigue life of thrust ball bearing. The 3-Dimensional Modeling has been done through modeling software Pro-e wildfire-5.0. The parts assembly is also done in Pro-e wildfire-5.0 & analysis has been done through ANSYS- 14. An analylitical method is good, less expensive and gives the best results. Analytical results give good agreement with the experimental data. The thrust ball bearings are subjected to various, thrust & dynamic loads, which simulated easily through Pro-E software & analysis because experimentally calculation is very complicated. The general theory used for calculating the Fatigue life of Bearing is basic life rating theory. The material taken for the Bearing is AISI8720H. In this study we have used various analysis codes and got a good result through these codes.

Prabhat Singh*1

2014-01-01

3

Research on Service Life Prediction Model of Thrust Needle Bearing  

Directory of Open Access Journals (Sweden)

Full Text Available Needle roller thrust bear is small in size and of high ability in load bearing, therefore it is widely used in fields of aviation and automobile etc.  But the relation between their service life and pre-tightening torque is not very clear, so the using design of the bear depends mainly on experience of engineer, because of lack of references. In the paper, the theoretical analysis on relation between torque and load is done, special wearing test instrument is developed and wearing test of thrust needle bear is conducted. Based on the results of the test, mathematical model of relation between the losing amount of pre-tightening torque and the pre-tightening torque is built, based on which use of the bear in engineering will be more reasonable, and their pre-tightening torque will be given more accurately.

Li Wei

2012-11-01

4

Advanced Active-Magnetic-Bearing Thrust-Measurement System  

Science.gov (United States)

An advanced thrust-measurement system utilizes active magnetic bearings to both (1) levitate a floating frame in all six degrees of freedom and (2) measure the levitation forces between the floating frame and a grounded frame. This system was developed for original use in measuring the thrust exerted by a rocket engine mounted on the floating frame, but can just as well be used in other force-measurement applications. This system offers several advantages over prior thrust-measurement systems based on mechanical support by flexures and/or load cells: The system includes multiple active magnetic bearings for each degree of freedom, so that by selective use of one, some, or all of these bearings, it is possible to test a given article over a wide force range in the same fixture, eliminating the need to transfer the article to different test fixtures to obtain the benefit of full-scale accuracy of different force-measurement devices for different force ranges. Like other active magnetic bearings, the active magnetic bearings of this system include closed-loop control subsystems, through which the stiffness and damping characteristics of the magnetic bearings can be modified electronically. The design of the system minimizes or eliminates cross-axis force-measurement errors. The active magnetic bearings are configured to provide support against movement along all three orthogonal Cartesian axes, and such that the support along a given axis does not produce force along any other axis. Moreover, by eliminating the need for such mechanical connections as flexures used in prior thrust-measurement systems, magnetic levitation of the floating frame eliminates what would otherwise be major sources of cross-axis forces and the associated measurement errors. Overall, relative to prior mechanical-support thrust-measurement systems, this system offers greater versatility for adaptation to a variety of test conditions and requirements. The basic idea of most prior active-magnetic-bearing force-measurement systems is to calculate levitation forces on the basis of simple proportionalities between changes in those forces and changes in feedback-controlled currents applied to levitating electromagnetic coils. In the prior systems, the effects of gap lengths on fringing magnetic fields and the concomitant effects on magnetic forces were neglected. In the present system, the control subsystems of the active magnetic bearings are coupled with a computer-based automatic calibration system running special-purpose software wherein gap-length-dependent fringing factors are applied to current and magnetic-flux-based force equations and combined with a multipoint calibration method to obtain greater accuracy.

Imlach, Joseph; Kasarda, Mary; Blumber, Eric

2008-01-01

5

On the Design of Tilting-Pad Thrust Bearings  

DEFF Research Database (Denmark)

Pockets are often machined in the surfaces of tilting-pad thrust bearings to allow for hydrostatic jacking in the start-up phase. Pockets and other recesses in the surfaces of bearing pads influence the pressure distribution and thereby the position of the pivot resulting in the most advantageous pad convergence ratio. In this thesis, a theoretical approach is applied in the attempt to quantify the influence of recesses in the pad surfaces. The recesses may be relatively deep and enclosed as is the case with pockets designed for hydrostatic jacking. Such recesses are characterized by low friction and a small pressure build-up. As in parallel-step bearings the recesses may also have a depth of the same order of magnitude as the oil film thickness. Such recesses are characterized by a strong pressure build-up caused by the reduction of the flow area at the end of the recess. Numerical models based on the Reynolds equation are used. They include the effects of variations of viscosity with temperature and the deformation of the bearing pads due to pressure and thermal gradients. The models are validated using measurements. Tilting-pad bearings of standard design are studied and the influences of the bearing length-to-width ratio, pad deformation and injection pocket size are quantified. Suggestions for the design of energy efficient bearings are given. The results show that correctly dimensioned, bearings with oil injection pockets have smaller friction coefficients than bearings with plain pads. Placing the pockets in the high-pressure zones close to the trailing edges of the bearing pads causes a substantial reduction in the friction coefficient. The design of the recess sizes and positions leading to the largest improvements is studied and design suggestions for various pad geometries are given. Parallel-step bearings theoretically have smaller friction coefficients than tilting-pad bearings. A design of a tilting-pad bearing is suggested which combines the benefits of the two types of bearings in a tilting-pad bearing with inlet pockets. This design results in a substantial reduction of the friction loss. Both this bearing and the bearing design with enclosed recesses in the high-pressure regions of the pads suffer from a higher sensitivity to the position of the pivot. The design of such bearing is therefore no trivial task.

Heinrichson, Niels

2007-01-01

6

An Experimental Study of Lubrication at Thrust Slide-Bearing of Scroll Compressors  

Science.gov (United States)

The previous studies have revealed that the wedge formation at the periphery of the thrust plate, caused by the elastic deformation due to pressure difference across the orbiting thrust plate, is a significant key factor to keep and improve the high performance in lubrication of the thrust-slide bearing. The present study focuses on the effect of the thickness and inner form of the thrust plate upon the lubrication features. A simplified model of cylindrical thrust slide-bearing with thinner thrust plate submerged in a refrigerant oil VG-56 was operated under pressurized conditions using R-22 as the pressurizing gas, where the pressure difference was adjusted from 0 to 1.0 MPa and the friction force and coefficient of friction were measured over a wide range of orbiting speeds, first. The wedge angle by elastic deformation is naturally increased with decreasing the thrust plate thickness, thus resulting in a clear improvement in lubrication at the thrust slide-bearing. On the contrast, secondly, the similar lubrication tests were conducted for the thrust plate with a real inner form, as complicated as in the real scroll compressors, where the thickness of the thrust plate was kept as in the original tests. As a result, no significant change in lubrication features, from those for the simplified cylindrical model, was not addressed, thus confirming that the test results addressed from the simplified cylindrical model tests can be effectively used to examine the basic characteristics in lubrication of thrust slide bearing of scroll compressors.

Ishii, Noriaki; Oku, Tatsuya; Anami, Keiko; Tsuji, Takuma; Ozasa, Toshihiro; Sawai, Kiyoshi; Morimoto, Takashi; Iida, Noboru

7

Note: Radial-thrust combo metal mesh foil bearing for microturbomachinery  

Science.gov (United States)

This Note proposes a novel radial-thrust combo metal mesh foil bearing (MMFB). Although MMFBs have advantages such as higher stiffness and damping over conventional air foil bearings, studies related to MMFBs have been limited to radial MMFBs. The novel combo MMFB is composed of a radial top foil, thrust top foils, and a ring-shaped metal mesh damper—fabricated by compressing a copper wire mesh—with metal mesh thrust pads for the thrust bearing at both side faces. In this study, the combo MMFB was fabricated in half-split type to support the rotor for a micro gas turbine generator. The manufacture and assembly process for the half-split-type combo MMFB is presented. In addition, to verify the proposed combo MMFB, motoring test results up to 250 000 rpm and axial displacements as a function of rotational speed are presented.

Park, Cheol Hoon; Choi, Sang Kyu; Hong, Doo Euy; Yoon, Tae Gwang; Lee, Sung Hwi

2013-10-01

8

Ontario Hydro`s Sir Adam Beck Pump Generating Station : thrust bearing and runner servomotor rehabilitation  

Energy Technology Data Exchange (ETDEWEB)

A study was conducted to examine the reasons for the recurring failure of generator thrust bearings at Ontario Hydro`s Sir Adam Beck Pump Generating Station (Niagara Falls) comprised of six 25 MW Deriaz turbines. The possible causes for the thrust bearing failures were listed and commented upon. The suspected causes include: (1) marginal bearing capacity, (2) shoes not flat, (3) sub standard oil, (4) dirt in bearing, (5) bearing cooling problems. To solve the problem, extra precaution was taken in the assembly of the bearing parts and extra capacity was added to the oil lift system. Following implementation of these measures, the unit has been operating smoothly for 3 years. 3 tabs., 4 figs.

Barbour, J.; Garro, A. [Ontario Hydro, Toronto, ON (Canada)

1998-12-01

9

Analysis of a Thrust Bearing with Flexible Pads and Flexible Supports  

DEFF Research Database (Denmark)

A theoretical analysis of a hydrodynamic thrust bearing is presented. The bearing investigated is used in an ndustrial product. The lubricant is water, but the results are valid also for other lubricants.At first the results from a 1-dimensional model for the fluid film forces and the associated deformation of the bearing geometry is presented. This model enlightens the influence of pad flexibility and support location and flexibility. Subsequently results from a 2-dimensional model of the bearing is presented. The model is used to carry out an optimization of the bearing design, and the obtained improvements in load carrying capacity is presented.

Klit, Peder

2007-01-01

10

High-Temperature (1000 F) Magnetic Thrust Bearing Test Rig Completed and Operational  

Science.gov (United States)

Large axial loads are induced on the rolling element bearings of a gas turbine. To extend bearing life, designers use pneumatic balance pistons to reduce the axial load on the bearings. A magnetic thrust bearing could replace the balance pistons to further reduce the axial load. To investigate this option, the U.S. Army Research Laboratory, the NASA Glenn Research Center, and Texas A&M University designed and fabricated a 7-in.- diameter magnetic thrust bearing to operate at 1000 F and 30,000 rpm, with a 1000-lb load capacity. This research was funded through a NASA Space Technology Transfer Act with Allison Advance Development Company under the Ultra-Efficient Engine Technology (UEET) Intelligent Propulsion Systems Foundation Technology project.

Montague, Gerald T.

2005-01-01

11

Design and analysis of hybrid thrust magnetic bearing for magnetically suspended reaction wheel  

Science.gov (United States)

Introduced the structure of a magnetic bearing reaction wheel for stabilization of spacecraft attitude, its rotation speed is from -5000rpm to 5000rpm (rating angular momentum is 20Nms). The main scope of this paper is to calculate and analyze the performance and parameters of the hybrid thrust magnetic bearing with permanent magnet bias for the magnetic bearing momentum wheel. Its magnetic force, current stiffness, and position stiffness are derived by using the equivalent magnetic circuit and their non-linearity are shown by the curves of force-current-position characteristic. The ranges of bearing capacity is obtained.

Han, Bangcheng

2008-10-01

12

A rotary microactuator supported on encapsulated microball bearings using an electro-pneumatic thrust balance  

International Nuclear Information System (INIS)

The development of a rotary microactuator supported on encapsulated microball bearings and driven by electro-pneumatic actuation is reported. The encapsulated bearing provides full support to an encased rotor, while an electro-pneumatic thrust balance is used to minimize rotor normal load. By minimizing normal load, bearing friction is reduced leading to increased speed and performance. Experimental results show that the microactuator is capable of repeatable operation and continuous 360° motion at speeds of 5–2000 rpm. This is the first demonstration of a ball bearing supported electrostatic microactuator with a fully encased rotor, capable of direct mechanical attachment or reliable interaction with external media

13

The Chevron Foil Thrust Bearing: Improved Performance Through Passive Thermal Management and Effective Lubricant Mixing  

Science.gov (United States)

An improved foil thrust bearing is described that eliminates or reduces the need for forced cooling of the bearing foils while at the same time improves the load capacity of the bearing, enhances damping, provides overload tolerance, and eliminates the high speed load capacity drop-off that plagues the current state of the art. The performance improvement demonstrated by the chevron foil thrust bearing stems from a novel trailing edge shape that splays the hot lubricant in the thin film radially, thus preventing hot lubricant carry-over into the ensuing bearing sector. Additionally, the chevron shaped trailing edge induces vortical mixing of the hot lubricant with the gas that is naturally resident within the inter-pad region of a foil thrust bearing. The elimination of hot gas carry-over in combination with the enhanced mixing has enabled a completely passive thermally managed foil bearing design. Laboratory testing at NASA has confirmed the original analysis and reduced this concept to practice.

Bruckner, Robert

2013-01-01

14

Bulk-Flow Analysis of Hybrid Thrust Bearings for Advanced Cryogenic Turbopumps  

Science.gov (United States)

A bulk-flow analysis and computer program for prediction of the static load performance and dynamic force coefficients of angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings have been completed. The product of the research is an efficient computational tool for the design of high-speed thrust bearings for cryogenic fluid turbopumps. The study addresses the needs of a growing technology that requires of reliable fluid film bearings to provide the maximum operating life with optimum controllable rotordynamic characteristics at the lowest cost. The motion of a cryogenic fluid on the thin film lands of a thrust bearing is governed by a set of bulk-flow mass and momentum conservation and energy transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. The bulk-flow model includes flow turbulence with fluid inertia advection, Coriolis and centrifugal acceleration effects on the bearing recesses and film lands. The cryogenic fluid properties are obtained from realistic thermophysical equations of state. Turbulent bulk-flow shear parameters are based on Hirs' model with Moody's friction factor equations allowing a simple simulation for machined bearing surface roughness. A perturbation analysis leads to zeroth-order nonlinear equations governing the fluid flow for the thrust bearing operating at a static equilibrium position, and first-order linear equations describing the perturbed fluid flow for small amplitude shaft motions in the axial direction. Numerical solution to the zeroth-order flow field equations renders the bearing flow rate, thrust load, drag torque and power dissipation. Solution to the first-order equations determines the axial stiffness, damping and inertia force coefficients. The computational method uses well established algorithms and generic subprograms available from prior developments. The Fortran9O computer program hydrothrust runs on a Windows 95/NT personal computer. The program, help files and examples are licensed by Texas A&M University Technology License Office. The study of the static and dynamic performance of two hydrostatic/hydrodynamic bearings demonstrates the importance of centrifugal and advection fluid inertia effects for operation at high rotational speeds. The first example considers a conceptual hydrostatic thrust bearing for an advanced liquid hydrogen turbopump operating at 170,000 rpm. The large axial stiffness and damping coefficients of the bearing should provide accurate control and axial positioning of the turbopump and also allow for unshrouded impellers, therefore increasing the overall pump efficiency. The second bearing uses a refrigerant R134a, and its application in oil-free air conditioning compressors is of great technological importance and commercial value. The computed predictions reveal that the LH2 bearing load capacity and flow rate increase with the recess pressure (i.e. increasing orifice diameters). The bearing axial stiffness has a maximum for a recess pressure rati of approx. 0.55. while the axial damping coefficient decreases as the recess pressure ratio increases. The computer results from three flow models are compared. These models are a) inertialess, b) fluid inertia at recess edges only, and c) full fluid inertia at both recess edges and film lands. The full inertia model shows the lowest flow rates, axial load capacity and stiffness coefficient but on the other hand renders the largest damping coefficients and inertia coefficients. The most important findings are related to the reduction of the outflow through the inner radius and the appearance of subambient pressures. The performance of the refrigerant hybrid thrust bearing is evaluated at two operating speeds and pressure drops. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The a

SanAndres, Luis

1998-01-01

15

Experimental equipment for measuring physical properties of the annular hydrostatic thrust bearing  

Science.gov (United States)

The hydraulic circuit, through which the mineral oil is brought, is an important part of hydrostatic bearings. The annular hydrostatic thrust bearing consists of two sliding plates divided by a layer of mineral oil. In the lower plate, there are oil grooves which distribute the liquid between the sliding areas. The hydraulic circuit is made of two basic parts: the energy source and the controlling part. The hydraulic pump, which brings the liquid into the sliding bearing, is the source of the pressure energy. The sliding bearing is weighted down by axial force, which can be changed during the process. That's why in front of the particular oil grooves control components adjusting pressure and flow size are located. This paper deals with a project of a hydraulic circuit for regulation of fluid layer in the annular hydrostatic thrust bearing and the testing equipment for measuring its physical properties. It will include the issue of measuring loading capacity and height of the fluid layer in the annular hydrostatic thrust bearing.

Kozdera, Michal; Drábková, Sylva; Bojko, Marian

2014-03-01

16

Development of the water-lubricated thrust bearing of the hydraulic turbine generator  

International Nuclear Information System (INIS)

In hydropower plant, a large quantities of turbine oil is used as machine control pressure oil and lubricating oil. If the oil leak out from hydropower plant, it flows into a river. And such oil spill has an adverse effect on natural environment because the oil does not degrade easily. Therefore the KANSAI and Hitachi Mitsubishi Hydro developed the water-lubricated thrust bearing for vertical type hydraulic turbine generator. The water-lubricated bearing has advantages in risk avoidance of river pollution because it does not need oil. For proceeding the development of the water-lubricated thrust bearing, we studied following items. The first is the examination of the trial products of water lubricating liquid. The second is the study of bearing structure which can satisfy bearing performance such as temperature characteristic and so on. The third is the mock-up testing for actual application in the future. As a result, it was found that the water-lubricated thrust bearing was technically applicable to actual equipments.

17

Investigation of the performance of high-speed thrust hydrostatic bearings with a jet compensation  

International Nuclear Information System (INIS)

The characteristics of hydrostatic thrust bearings (HB) for footstep bearings with circular centre chambers of various width, various dam lengths and gaps have been investigated. During the experiments, average pressures have been measured in the chamber and on the footstep dams which enable the effect of centrifugal forces on the bearing load carrying capacity to be estimated according to pressure fields. Evaluated are an effect of the chamber width and, cosequently, that of the dam width at the same total bearing width (b=26 mm) on the bearing load carrying capacity, and the working liquid flow rate as well as an effect of the rotation rate on the above-mentioned characteristics. Water with low viscosity has been used as a working fluid

18

Demonstration, Testing and Qualification of a High Temperature, High Speed Magnetic Thrust Bearing  

Science.gov (United States)

The gas turbine industry has a continued interest in improving engine performance and reducing net operating and maintenance costs. These goals are being realized because of advancements in aeroelasticity, materials, and computational tools such as CFD and engine simulations. These advancements aid in increasing engine thrust-to-weight ratios, specific fuel consumption, pressure ratios, and overall reliability through higher speed, higher temperature, and more efficient engine operation. Currently, rolling element bearing and squeeze film dampers are used to support rotors in gas turbine engines. Present ball bearing configurations are limited in speed (bearings require extensive preventative maintenance in order to assure their safe operation. Since these bearings are at their operational limits, new technologies must be found in order to take advantage of other advances. Magnetic bearings are well suited to operate at extreme temperatures and higher rotational speeds and are a promising solution to the problems that conventional rolling element bearings present. Magnetic bearing technology is being developed worldwide and is considered an enabling technology for new engine designs. Using magnetic bearings, turbine and compressor spools can be radically redesigned to be significantly larger and stiffer with better damping and higher rotational speeds. These advances, a direct result of magnetic bearing technology, will allow significant increases in engine power and efficiency. Also, magnetic bearings allow for real-time, in-situ health monitoring of the system, lower maintenance costs and down time.

DeWitt, Kenneth

2005-01-01

19

Design and evaluation of a 3 million DN series-hybrid thrust bearing  

Science.gov (United States)

The design and experimental evaluation of a series-hybrid thrust bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, is presented. Tests were conducted up to 16,000 rpm and at this speed an axial load of 15,600 N (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. A speed reduction of this magnitude would result in a tenfold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system produced a flawless return to the original mode of hybrid operation.

Scibbe, H. W.; Winn, L. W.; Eusepi, M.

1976-01-01

20

The performance of solid lubricated ball bearings operated in a vacuum under a high thrust load  

Science.gov (United States)

The performance of solid lubricated ball bearings was examined under a high thrust load, up to 3 kN, in a vacuum. Tested bearings were (1) angular contact ball bearings with a sputtered molybdenum disulfide (MoS2) film on balls and races, and with a PTFE based composite cage, and (2) angular contact full complement type ball bearings with an electro-plated lead(Pb) film on balls and races. Low frictional torque of about 1.5 N cm at a load of 3 kN, and a long life of 3 x 10(exp 7) revolutions were obtained with the bearings with a sputtered MoS2 film. However, torque spikes with a duration of about ten seconds and with an interval of several hundred hours were observed. The peak value was as high as 30 times of that in well lubricated state. An electro-plated Pb film also successfully lubricated a bearing for over 6 x 10(exp 6) revolutions under a load of 3 kN, although the frictional torque was about 10 times higher than that obtained with the MoS2 lubricated bearings.

Suzuki, Mineo; Nishimura, Makoto

 
 
 
 
21

Start-stop testing of two self-acting air-lubricated spiral groove thrust bearing coatings  

Science.gov (United States)

Start-stop tests were conducted on air-lubricated spiral-groove thrust bearings. Application of a matrix-bonded molybdenum disulfide (MoS2) coating over a porous chrome oxide coating resulted in significantly lower friction, compared to bearings coated with chrome oxide only. The MoS2 coated bearing sustained 15,000 start-stop cycles at a maximum of 3600 rpm. Each cycle was 15 seconds on, 30 seconds off. The chrome oxide coated bearing failed by local welding after 2030 cycles. Both types of coatings exhibited early failures under higher thrust loads when operating films were insufficient to sustain the load without overheating.

Dunfee, J. D.; Shapiro, W.

1974-01-01

22

Laminar Motion of the Incompressible Fluids in Self-Acting Thrust Bearings with Spiral Grooves  

Science.gov (United States)

We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the “pumping” direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime. PMID:24526896

Velescu, Cornel; Popa, Nicolae Calin

2014-01-01

23

Analytic Modeling of the Hydrodynamic, Thermal, and Structural Behavior of Foil Thrust Bearings  

Science.gov (United States)

A simulation and modeling effort is conducted on gas foil thrust bearings. A foil bearing is a self acting hydrodynamic device capable of separating stationary and rotating components of rotating machinery by a film of air or other gaseous lubricant. Although simple in appearance these bearings have proven to be complicated devices in analysis. They are sensitive to fluid structure interaction, use a compressible gas as a lubricant, may not be in the fully continuum range of fluid mechanics, and operate in the range where viscous heat generation is significant. These factors provide a challenge to the simulation and modeling task. The Reynolds equation with the addition of Knudsen number effects due to thin film thicknesses is used to simulate the hydrodynamics. The energy equation is manipulated to simulate the temperature field of the lubricant film and combined with the ideal gas relationship, provides density field input to the Reynolds equation. Heat transfer between the lubricant and the surroundings is also modeled. The structural deformations of the bearing are modeled with a single partial differential equation. The equation models the top foil as a thin, bending dominated membrane whose deflections are governed by the biharmonic equation. A linear superposition of hydrodynamic load and compliant foundation reaction is included. The stiffness of the compliant foundation is modeled as a distributed stiffness that supports the top foil. The system of governing equations is solved numerically by a computer program written in the Mathematica computing environment. Representative calculations and comparisons with experimental results are included for a generation I gas foil thrust bearing.

Bruckner, Robert J.; DellaCorte, Christopher; Prahl, Joseph M.

2005-01-01

24

A low-friction high-load thrust bearing and the human hip joint.  

Science.gov (United States)

A hydrostatic thrust bearing operating at a pressure of 130 MPa and with a coefficient of friction rising to 0.004 in 6 days is described. It consists of interleaved oil-coated Mylar and brass sheets, each 0.1 mm thick. At this pressure, the Mylar deforms to reveal a pool of lubricant bounded by contacting layers at its edges where the pressure tapers off to zero. Thus, most of the load is borne by the oil so its effective Coulomb (slip-stick) friction is very low. Expressions for the effective coefficient of friction, the area of the solid-to-solid contact and the torque needed to rotate the bearing are given in terms of its geometry, the viscosity of the lubricant and elapsed time. The mechanism of a bearing with similar geometry and properties, the human hip joint, is compared with this plastic bearing. While their low friction properties arise from the same basic cause, the different natures of their soft deformable materials lead to the hip joint having a much wider range of action. This work is an example of new engineering leading to a fresh insight into an action of Nature, which in turn suggests an improvement in engineering. PMID:20498516

McIlraith, A H

2010-06-01

25

A low-friction high-load thrust bearing and the human hip joint  

International Nuclear Information System (INIS)

A hydrostatic thrust bearing operating at a pressure of 130 MPa and with a coefficient of friction rising to 0.004 in 6 days is described. It consists of interleaved oil-coated Mylar and brass sheets, each 0.1 mm thick. At this pressure, the Mylar deforms to reveal a pool of lubricant bounded by contacting layers at its edges where the pressure tapers off to zero. Thus, most of the load is borne by the oil so its effective Coulomb (slip-stick) friction is very low. Expressions for the effective coefficient of friction, the area of the solid-to-solid contact and the torque needed to rotate the bearing are given in terms of its geometry, the viscosity of the lubricant and elapsed time. The mechanism of a bearing with similar geometry and properties, the human hip joint, is compared with this plastic bearing. While their low friction properties arise from the same basic cause, the different natures of their soft deformable materials lead to the hip joint having a much wider range of action. This work is an example of new engineering leading to a fresh insight into an action of Nature, which in turn suggests an improvement in engineering.

26

Rheodynamic Lubrication of an Externally Pressured Thrust Bearing Using Herschel-Bulkley Fluid with Sinusoidal Injection  

Directory of Open Access Journals (Sweden)

Full Text Available Lubricants with variable viscosity are assuming greater importance for its application in polymer industry, thermal reactors and in biomechanics. With the bearing operations in machines being subject to high speeds, loads, increasing mechanical shearing forces and continually increasing pressure, there has been an increasing interest to use non-Newtonian fluids characterized by a yield value. Some of them, which fit into this class, are Bingham, Casson and Herchel-Bulkley models. In the present work, the problem of an externally pressurized thrust bearing lubricated with Herschel-Bulkley fluid under the sinusoidal flow rate has been investigated. Herschel-Bulkley fluids are characterized by a yield value, which leads to the formation of rigid core in the flow region. The shape and extent of the core has been determined numerically for various values of the Herschel-Bulkley number, power-law index, amplitude of sinusoidal fluid film and time. Numerical solutions have been obtained for the bearing performances such as pressure distribution and load capacity for different values of the Herschel-Bulkley number, power-law index, amplitude of sinusoidal fluid film and time. The effects of sinusoidal injection of the lubricant and the non-Newtonian characteristics on the bearing performances have been discussed.

I.J. Amalraj

2012-01-01

27

Experimental Investigation of Friction Effect on Liner Model Rolling Bearings for Large Diameter Thrust Bearing Design  

Directory of Open Access Journals (Sweden)

Full Text Available Studying friction coefficient has significant importance, especially when dealing with high load and temperature applications that have frequent starting and stopping points. Towards that, two sets of angular contact Linear Model Mockup Bearings (LMMB were designed and fabricated. This linear model assembly was made up of high precision, grounded raceways (AISI 4140 and commercially purchased balls (AISI 52100. The experimental studies were carried out by placing different number of balls between the raceways under different loads at dry lubricating condition. The static friction coefficients were measured using two different experiments: viz gravitation-based experiment and direct linear force measurement experiment. And Digital Image Correlation (DIC technique was used to find the stiffness of LMMB set.

S. Babu

2012-12-01

28

Optimal design of Tilting-Pad Thrust Bearings with High Pressure Injection Pockets  

DEFF Research Database (Denmark)

A thermo-elasto-hydrodynamic(TEHD) model based on the Reynolds equation has been used to study the effect of oil injection pockets on the performance of tilting pad thrust bearings. The optimal position of the pivot both with respect to load carrying capacity and minimal power consumption is seen to move towards the leading edge of the pads as the pocket size is increased. A large pocket is seen to negatively influence the performance with respect to friction loss at most operating conditions while at some operating conditions it has a small positive influence. The small pocket has a slight positive influence on the friction loss at most operating conditions. Moderate thermal crowning is shown to have a positive effect on performance, reducing friction loss.

Heinrichson, Niels; Santos, Ilmar

2006-01-01

29

Inertia Effects in Rheodynamic Lubrication of an Externally Pressurized Thrust Bearing Using Bingham Lubricant with Sinusoidal Injection  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the present theoretical investigation, the combined effects of fluid inertia forces and sinusoidal injection of the Bingham lubricant, on the performance of an externally pressurized thrust bearing with circular geometry are studied. Using the conventional two-constant Bingham model and by adopting the method of averaging inertia terms, the reduced Navier-Stokes equations are modified and numerical solutions have been obtained for the bearing performances such as the pressure distribution ...

Amalraj, I. J.; Narasimman, S.; Kandasamy, A.

2013-01-01

30

Design and evaluation of a 3 million DN series-hybrid thrust bearing. [stability tests and fatigue tests  

Science.gov (United States)

The bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, was fatigue tested. Test conditions were representative of a mainshaft ball bearing in a gas turbine engine operating at maximum thrust load to simulate aircraft takeoff conditions. Tests were conducted up to 16000 rpm and at this speed an axial load of 15568 newtons (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. It was concluded that a speed reduction of this magnitude results in a ten-fold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system resulted in a flawless return to the original mode of hybrid operation.

Scibbe, H. W.; Winn, L. W.; Eusepi, M.

1976-01-01

31

Inertia Effects in Rheodynamic Lubrication of an Externally Pressurized Thrust Bearing Using Bingham Lubricant with Sinusoidal Injection  

Directory of Open Access Journals (Sweden)

Full Text Available In the present theoretical investigation, the combined effects of fluid inertia forces and sinusoidal injection of the Bingham lubricant, on the performance of an externally pressurized thrust bearing with circular geometry are studied. Using the conventional two-constant Bingham model and by adopting the method of averaging inertia terms, the reduced Navier-Stokes equations are modified and numerical solutions have been obtained for the bearing performances such as the pressure distribution and the load carrying capacity for different values of Bingham number, Reynolds number, time and amplitude. The effects of fluid inertia forces and the non-Newtonian characteristics of the Bingham lubricant on the bearing performances for different sinusoidal conditions are discussed.

I.J. Amalraj

2013-01-01

32

Robust Optimum Design of Thrust Hydrodynamic Bearings for Hard Disk Drives  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the robust optimum design which combines the geometrical optimization method proposed by Hashimoto and statistical method. Recently, 2.5? hard disk drives (HDDs are widely used for mobile devices such as laptops, video cameras and car navigation systems. In mobile applications, high durability towards external vibrations and shocks are essentials to the bearings of HDD spindle motor. In addition, the bearing characteristics are influenced by manufacturing error because of small size of the bearings of HDD. In this paper, the geometrical optimization is carried out to maximize the bearing stiffness using sequential quadratic programming to improve vibration characteristics. Additionally, the bearing stiffness is analyzed considering dimensional tolerance of the bearing using statistical method. The dimensional tolerance is assumed to distribute according to the Gaussian distribution, and then the bearing stiffness is estimated by combining the expectation and standard deviation. As a result, in the robust optimum design, new groove geometry of bearing can be obtained in which the bearing stiffness is four times higher than the stiffness of conventional spiral groove bearing. Moreover, the bearing has lower variability compared with the result of optimum design neglecting dimensional tolerance.

Hiromu Hashimoto

2012-10-01

33

A superconducting thrust-bearing system for an energy storage flywheel  

International Nuclear Information System (INIS)

We have constructed a bearing system for an energy storage flywheel. This bearing system uses a combination of permanent magnets and superconductors in an arrangement commonly termed as an Evershed bearing. In an Evershed system there are in fact two bearings which act in concert. In our system we have one bearing constructed entirely out of permanent magnets acting in attraction. This system bears the weight of the flywheel (43.6 kg) but would not, on its own, be stable. Stability is provided by a superconducting bearing which is formed by the interaction between the magnetic field of a permanent magnet sited on the rotor and superconductors on the stator. This overall arrangement is stable over a range of levitation heights and has been tested at rotation speeds of up to around 12 Hz (the maximum speed is dictated by the drive system not the bearing system). There is a sharp resonance peaking at between 2 and 3 Hz and spin down tests indicate that the equivalent coefficient of friction is of the order of 10-5. The rate of change of velocity is, however, not constant so the drag is clearly not solely frictional. The position of the resonance is dictated by the stiffness of the bearing relative to the mass of the flywheel but the amplitude of the resonance is dictated by the variation in magnitude of the magnetic field of the permanent magnets. Large magnets are (at present) fabricated in sections and this leads to a highly inhomogeneous field. The field has been smoothed by using a combination of iron which acts passively and copper which provides magnetic shielding due to the generation of eddy currents and therefore acts as an 'active' component. Calculations based on the spin down tests indicate that the resultant variation in field is of the order of 3% and measurements are being carried out to confirm this. (author)

34

Comparison of Models for the Steady-State Analysis of Tilting-Pad Thrust Bearings  

DEFF Research Database (Denmark)

Prediction of the minimum oil film thickness and the maximum temperature on the surface of the bearing pad is crucial in the design and dimensioning of bearings. Friction loss, oil bath temperature and pad deflection are other parameters of interest. Depending on the desired information a numerical model requires different levels of detail. The two dimensional Reynolds equation for pressure in the oil film can be solved isothermally or considering viscosity variations in two or three dimensions, requiring solution of the equations for thermal equilibrium in oil and pad. Knowing the temperature distribution the deflection of the pad due to pressure and thermal bending can be calculated using a flat plate approximation. At the five free sides of the pad heat transfer can be modelled. The temperature distribution at the inlet to the pad can be calculated through equilibrium of thermal energy for the groove between pads and the oil bath temperature from energy equilibrium for the entire bearing. The main theoretical contribution of this paper is the elaboration and comparison of 7 different mathematical models of increasing complexity. The results are compared to experimental data for steady-state operation of a 228 mm outer diameter bearing. It is found that for the given bearing a two dimensional model is sufficient to estimate the minimum oil film thickness and the maximum temperature on the pad surface. Three dimensional modelling does not improve the quality of the results.

Heinrichson, Niels; Santos, Ilmar

2005-01-01

35

Large motion tracking control for thrust magnetic bearings with fuzzy logic, sliding mode, and direct linearization  

Science.gov (United States)

Conventional use of magnetic bearings relies on a zero reference to keep the rotor centered in the radial and axial axes. This paper compares different control methods developed for the alternate control task of tracking an axial dynamic target. Controllers based on fuzzy logic, sliding mode, and direct linearization were designed to meet this task. Performance criteria, such as maximum axial displacement, minimum phase lag and I2R power losses were compared for each controller. The large motion, tracking problem for a rotor has utility in applications where dynamic seal clearances are required. This has a variety of potential applications in turbo-machinery, such as active stall control.

Minihan, T. P.; Lei, S.; Sun, G.; Palazzolo, A.; Kascak, A. F.; Calvert, T.

2003-06-01

36

Numerical simulation of flow in thrust bearing rotor-stator wheel space  

International Nuclear Information System (INIS)

The paper describes the use of a computational fluid dyanamics code for solving the navier-stokes equations for the flow of air in a sealed rotor-stator cavity having a tight clearance. Presented also is a description of the computational code which uses a calculation procedure that solves the govering differential equations by a finite-voume method, and simulates the turbulent streesses by a mixing length turbulence model. The code is validated for a static case with experimental data. Results are presented and discussed for static and rotaing test cases showing the influence of various individual parameters (mass flow, seal clearance, and rotor speeds) on the fluid danamics of the rotor-stator cavity. The numerical results of the static test cases have indicated that the cavity pressure varies nontinearly with a variable seal clearance at a fixed mass flow rate resulting in a nonlinear bearing stiffness. Moreover, the cavity radial pressure distribution is not constant in the rotational test cases, especially at high rotational reynolds numbers. (author). 23 refs., 13 figs., 1 table

37

2D THD and 3D TEHD analysis of large spindle supported thrust bearings with pins and double layer system used in the three gorges hydroelectric generators  

International Nuclear Information System (INIS)

A 2D THD model and a 3DTEHD model for large spindle supported thrust bearings were set up and used to analyze the lubrication performance of the Three Gorges test thrust beating withpins and double layer system developed by Alstom Power. The finite difference method was employed to solve the THD model, and the thermal-elasticdeformations in the pad and runner were obtained by the finite element software ANSYS11.0. The data transfer between the THD model and ANSYS11.0 was carried out automatically by an interface program.A detailed comparison between the experimental results and numerical predictions by the two different modelsset up in this paper was carried out. Poor agreement has been found between the theoretical results obtained by 2D THD model and experimental data, while 3D TEHD provides fairly good agreement, confirming the importance of thermal effects and thermal-elastic deformations in both pad and runner.

38

2D THD and 3D TEHD analysis of large spindle supported thrust bearings with pins and double layer system used in the three gorges hydroelectric generators  

Science.gov (United States)

A 2D THD model and a 3DTEHD model for large spindle supported thrust bearings were set up and used to analyze the lubrication performance of the Three Gorges test thrust beating withpins and double layer system developed by Alstom Power. The finite difference method was employed to solve the THD model, and the thermal-elasticdeformations in the pad and runner were obtained by the finite element software ANSYS11.0. The data transfer between the THD model and ANSYS11.0 was carried out automatically by an interface program.A detailed comparison between the experimental results and numerical predictions by the two different modelsset up in this paper was carried out. Poor agreement has been found between the theoretical results obtained by 2D THD model and experimental data, while 3D TEHD provides fairly good agreement, confirming the importance of thermal effects and thermal-elastic deformations in both pad and runner.

Huang, B.; Wu, Z. D.; Wu, J. L.; Wang, L. Q.

2012-11-01

39

Bears  

Science.gov (United States)

What are the characteristics of grizzly/brown bears and black bears? As you view the websites, please use this chart to record what you are learning about grizzly bears and black bears. For each bear, you should list 5 characteristics. Grizzly Bear and Black Bear Chart We will first begin by learning about black bears. Please go to these websites to learn some important facts about black bears. Black Bears Facts and Image Black Bear Facts for Kids Now that you have learned ...

Bledsoe, Miss

2011-04-07

40

The influence of Injection Pockets on the Performance of Tilting-Pad Thrust Bearings: Part II - Comparison Between Theory and Experiment  

DEFF Research Database (Denmark)

This is Part II of a two-part series of papers describing the effects of high pressure injection pockets on the operating conditions of tilting-pad thrust bearings. Measurements of the distribution of pressure and oil film thickness are presented for tilting-pad thrust bearing pads of approximately 100 cm2 surface area. Two pads are measured in a laboratory test-rig at loads of approximately 0.5, 1.5 and 4.0 MPa and velocities of up to 33 m/s. One pad has a plain surface. The other pad has a conical injection pocket at the pivot point and a leading edge taper. The measurements are compared to theoretical values obtained using a three dimensional thermo-elasto-hydrodynamic (TEHD) numerical model. At low and intermediate loads the theoretical pressure distribution corresponds well to the measured values for both pads although the influence of the pocket is slightly underestimated. At high loads large discrepancies exist for the pad with an injection pocket. It is argued that this is likely to be due to the unevenness of the collar surface. The measured and theoretical values of oil film thickness compare well at low loads. At high loads discrepancies grow to up to 25 %. It is argued that this is due to the accuracy of the measurements.

Heinrichson, Niels; Santos, Ilmar

2006-01-01

 
 
 
 
41

Bears, Bears, Bears!  

Science.gov (United States)

What are some things you learned about bears? Use these websites to find out about bears: Parts of a Bear Polar Bears Real Story of the Three Bears The truth about bears Brown Bears Now fill in your chart! Bear Fact Sheet Listen to your teacher for further instruction on completing a book about bears! ...

Ms.beason

2011-04-16

42

Magnetic Bearing  

Directory of Open Access Journals (Sweden)

Full Text Available The use of bearings is essential to all types of machines, especially in marine aspects they provide the function of supporting heavier component in a desired position. These bearings have contact with the rotating part and causes surface wear which can be controlled by lubrication. Researches have raised the standards of performance for rotating equipment by providing robust, cost effective, easy to implement magnetic bearing solutions. Use of magnetic bearings in ships can be more advantageous because it is contact –free resulting in no surface wear and hence no need for lubricant, no servicing and can work in clean environment. It has several other benefits like high reliability, clean environments, high speed applications, position and vibration control and can withstand in extreme conditions. Magnetic bearing will also restrict the translational sliding, which is merely a linear case of supporting a rotating object thus use of thrust block also eliminated. Magnetic bearing technology has become viable because of advances in micro-processing controllers that allows for confident and robust active control. This paper discusses more about the construction, principle and working of magnetic bearing in detail.

Anbuselvan. T

2013-06-01

43

PPT thrust stand  

Science.gov (United States)

A torsional-type thrust stand has been designed and built to test Pulsed Plasma Thrusters (PPT's) in both single shot and repetitive operating modes. Using this stand, momentum per pulse was determined strictly as a function of thrust stand deflection, spring constant, and natural frequency. No empirical corrections were required. The accuracy of the method was verified using a swinging impact pendulum. Momentum transfer data between the thrust stand and the pendulum were consistent to within 1%. Following initial calibrations, the stand was used to test a Lincoln Experimental Satellite (LES-8/9) thruster. The LES-8/9 system had a mass of approximately 7.5 kg, with a nominal thrust to weight ratio of 1.3 x 10(exp -5). A total of 34 single shot thruster pulses were individually measured. The average impulse bit per pulse was 266 microN-s, which was slightly less than the value of 300 microN-s published in previous reports on this device. Repetitive pulse measurements were performed similar to ordinary steady-state thrust measurements. The thruster was operated for 30 minutes at a repetition rate of 132 pulses per minute and yielded an average thrust of 573 microN. Using average thrust, the average impulse bit per pulse was estimated to be 260 microN-s, which was in agreement with the single shot data. Zero drift during the repetitive pulse test was found to be approximately 1% of the measured thrust.

Haag, Thomas W.

1995-11-01

44

PPT Thrust Stand  

Science.gov (United States)

A torsional-type thrust stand has been designed and built to test Pulsed Plasma Thrusters (PPT's) in both single shot and repetitive operating modes. Using this stand, momentum per pulse was determined strictly as a function of thrust stand deflection, spring constant, and natural frequency. No empirical corrections were required. The accuracy of the method was verified using a swinging impact pendulum. Momentum transfer data between the thrust stand and the pendulum were consistent to within 1%. Following initial calibrations, the stand was used to test a Lincoln Experimental Satellite (LES-8/9) thruster. The LES-8/9 system had a mass of approximately 7.5 kg, with a nominal thrust to weight ratio of 1.3 x 10(exp -5). A total of 34 single shot thruster pulses were individually measured. The average impulse bit per pulse was 266 microN-s, which was slightly less than the value of 300 microN-s published in previous reports on this device. Repetitive pulse measurements were performed similar to ordinary steady-state thrust measurements. The thruster was operated for 30 minutes at a repetition rate of 132 pulses per minute and yielded an average thrust of 573 microN. Using average thrust, the average impulse bit per pulse was estimated to be 260 microN-s, which was in agreement with the single shot data. Zero drift during the repetitive pulse test was found to be approximately 1% of the measured thrust.

Haag, Thomas W.

1995-01-01

45

Thrust stand for low-thrust liquid pulsed rocket engines  

Science.gov (United States)

A thrust stand is developed for measuring the pulsed thrust generated by low-thrust liquid pulsed rocket engines. It mainly consists of a thrust dynamometer, a base frame, a connecting frame, and a data acquisition and processing system. The thrust dynamometer assembled with shear mode piezoelectric quartz sensors is developed as the core component of the thrust stand. It adopts integral shell structure. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. The thrust is transferred to the sensors by means of static friction forces of fitting surfaces. The sensors could produce an amount of charges which are proportional to the thrust to be measured. The thrust stand is calibrated both statically and dynamically. The in situ static calibration is performed using a standard force sensor. The dynamic calibration is carried out using pendulum-typed steel ball impact technique. Typical thrust pulse is simulated by a trapezoidal impulse force. The results show that the thrust stand has a sensitivity of 25.832 mV/N, a linearity error of 0.24% FSO, and a repeatability error of 0.23% FSO. The first natural frequency of the thrust stand is 1245 Hz. The thrust stand can accurately measure thrust waveform of each firing, which is used for fine control of on-orbit vehicles in the thrust range of 5-20 N with pulse frequency of 50 Hz.

Xing, Qin; Zhang, Jun; Qian, Min; Jia, Zhen-yuan; Sun, Bao-yuan

2010-09-01

46

Thrust stand for low-thrust liquid pulsed rocket engines.  

Science.gov (United States)

A thrust stand is developed for measuring the pulsed thrust generated by low-thrust liquid pulsed rocket engines. It mainly consists of a thrust dynamometer, a base frame, a connecting frame, and a data acquisition and processing system. The thrust dynamometer assembled with shear mode piezoelectric quartz sensors is developed as the core component of the thrust stand. It adopts integral shell structure. The sensors are inserted into unique double-elastic-half-ring grooves with an interference fit. The thrust is transferred to the sensors by means of static friction forces of fitting surfaces. The sensors could produce an amount of charges which are proportional to the thrust to be measured. The thrust stand is calibrated both statically and dynamically. The in situ static calibration is performed using a standard force sensor. The dynamic calibration is carried out using pendulum-typed steel ball impact technique. Typical thrust pulse is simulated by a trapezoidal impulse force. The results show that the thrust stand has a sensitivity of 25.832 mV/N, a linearity error of 0.24% FSO, and a repeatability error of 0.23% FSO. The first natural frequency of the thrust stand is 1245 Hz. The thrust stand can accurately measure thrust waveform of each firing, which is used for fine control of on-orbit vehicles in the thrust range of 5-20 N with pulse frequency of 50 Hz. PMID:20887003

Xing, Qin; Zhang, Jun; Qian, Min; Jia, Zhen-yuan; Sun, Bao-yuan

2010-09-01

47

A MICRO TURBINE DEVICE WITH ENHANCED MICRO AIR-BEARINGS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As part of progress in developing a micro gas turbine engine, this paper presents the design, fabrication and testing of a silicon-based micro turbine device, which is driven by compressed air. To improve its rotational speed and stability, the turbine device has enhanced journal air bearing and thrust air bearings. The thrust air bearings are utilized for supporting the rotor from both its top- and bottom- sides. The top thrust air bearing employs pump-in type spiral grooves, and the bottom ...

Shan, X. -c; Zhang, Qide; Sun, Y. F.; Maeda, R.

2006-01-01

48

Bearing construction for refrigeration compresssor  

Science.gov (United States)

A hermetic refrigeration compressor has a cylinder block and a crankshaft rotatable about a vertical axis to reciprocate a piston in a cylinder on the cylinder block. A separate bearing housing is secured to the central portion of the cylinder block and extends vertically along the crankshaft, where it carries a pair of roller bearings to journal the crankshaft. The crankshaft has a radially extending flange which is journaled by a thrust-type roller bearing above the bearing housing to absorb the vertical forces on the crankshaft so that all three of the roller bearings are between the crankshaft and the bearing housing to maintain and control the close tolerances required by such bearings.

Middleton, Marc G. (Wyoming, MI); Nelson, Richard T. (Worthington, OH)

1988-01-01

49

Numerical and experimental investigations of micro air bearings for micro systems  

International Nuclear Information System (INIS)

The paper investigated performance of air bearing system in a micro device. A parametric study is carried out. The dynamic performance of a very short journal bearing (L/D < 0.1) and thrust bearing is studied. The parameters that affect the performance of the air bearing are discussed. The optimum values of the important parameters are explored, and the stability of the thrust bearing is discussed. The prototype and test result are presented

50

Fluidic thrust vector control  

Science.gov (United States)

The design and testing of a fluidic control nozzle for tactical missile thrust vector control (TVC) are discussed. Attention is given to a nozzle with a circular cross section up to the point of flow separation, two control ports that alternately open and close, and a nozzle extension downstream of the control ports being a two-dimensional rectangular slot. Design of the TVC system involved characterizing the flow and the sensitivity parameters, the dynamic response, and the performance of hot-gas firings. The test firings verified the feasibility of a nozzle that could withstand 5000 F, the use of thrust vector angles of over 20 deg. A dynamic model test demonstrated a repeatable performance with pressures up to 2000 psia, driving frequencies up to 50 Hz, and a response of 10-15 msec. Adjustment of the chamber pressures permitted equivalent performance using with different heat ratios during cold dynamic tests with CH4.

Haloulakos, V. E.

51

Thrust vector control for the Space Shuttle Solid Rocket Motor  

Science.gov (United States)

Thrust vector control (TVC) for the Space Shuttle Solid Rocket Motor (SRM) is obtained by omniaxis vectoring of the nozzle. The development and integration of the system are under the cognizance of Marshall Space Flight Center (MSFC). The nozzle and flexible bearing have been designed and will be built by Thiokol Corporation/Wasatch Division. The vector requirements of the system, the impact of multiple reuse on the components, and the unique problems associated with a large flexible bearing are discussed. The design details of each of the major TVC subcomponents are delineated. The subscale bearing development program and the overall development schedule also are presented.

Counter, D. N.; Brinton, B. C.

1975-01-01

52

Load responsive hydrodynamic bearing  

Science.gov (United States)

A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)

2002-01-01

53

Thrust modeling for hypersonic engines  

Science.gov (United States)

Expressions for the thrust losses of a scramjet engine are developed in terms of irreversible entropy increases and the degree of incomplete combustion. A method is developed which allows the calculation of the lost vehicle thrust due to different loss mechanisms within a given flow-field. This analysis demonstrates clearly the trade-off between mixing enhancement and resultant increased flow losses in scramjet combustors. An engine effectiveness parameter is defined in terms of thrust loss. Exergy and the thrust-potential method are related and compared.

Riggins, D. W.; Mcclinton, C. R.

1995-01-01

54

Polar Bear Polar Bear  

Science.gov (United States)

In this lesson, students will listen for key details in a nonfiction text about polar bears. They will work at completing a graphic organizer with the teacher to help organize their thinking and understanding of key details about a text. They will also complete an independent assignment where they will draw or write two things that they learned about the topic.

Burgess, Kelly

2012-09-11

55

Low-thrust rocket trajectories  

Energy Technology Data Exchange (ETDEWEB)

The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report.

Keaton, P.W.

1987-03-01

56

Low-thrust rocket trajectories  

Energy Technology Data Exchange (ETDEWEB)

The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report. 57 refs., 10 figs.

Keaton, P.W.

1986-01-01

57

Micro thrust and heat generator  

Science.gov (United States)

A micro thrust and heat generator have a means for providing a combustion fuel source to an ignition chamber of the micro thrust and heat generator. The fuel is ignited by a ignition means within the micro thrust and heat generator`s ignition chamber where it burns and creates a pressure. A nozzle formed from the combustion chamber extends outward from the combustion chamber and tappers down to a narrow diameter and then opens into a wider diameter where the nozzle then terminates outside of said combustion chamber. The pressure created within the combustion chamber accelerates as it leaves the chamber through the nozzle resulting in pressure and heat escaping from the nozzle to the atmosphere outside the micro thrust and heat generator. The micro thrust and heat generator can be microfabricated from a variety of materials, e.g., of polysilicon, on one wafer using surface micromachining batch fabrication techniques or high aspect ratio micromachining techniques (LIGA). 30 figs.

Garcia, E.J.

1998-11-17

58

Solid rocket thrust vector control  

Science.gov (United States)

Thrust vector control systems that superimpose a side force on the motor thrust, steering being achieved by the side force causing a moment about the vehicle center of gravity are described. A brief review of thrust vector control systems is presented, and two systems, flexible joint and liquid injection, are treated in detail. Treatment of the flexible-joint thrust vector control system is limited to the design of the flexible joint and its insulation against hot motor gases. Treatment of the liquid injection thrust vector control system is limited to discussion of the injectant, valves, piping, storage tanks, and pressurization system; no evaluation is presented of the nozzle except for (1) the effect of the injectant and erosion at the injection port and (2) the effect of injection on pressure distribution within the nozzle.

1974-01-01

59

Development of a high speed parallel hybrid boost bearing  

Science.gov (United States)

The analysis, design, and testing of the hybrid boost bearing are discussed. The hybrid boost bearing consists of a fluid film bearing coupled in parallel with a rolling element bearing. This coupling arrangement makes use of the inherent advantages of both the fluid film and rolling element bearing and at the same time minimizes their disadvantages and limitations. The analytical optimization studies that lead to the final fluid film bearing design are reported. The bearing consisted of a centrifugally-pressurized planar fluid film thrust bearing with oil feed through the shaft center. An analysis of the test ball bearing is also presented. The experimental determination of the hybrid bearing characteristics obtained on the basis of individual bearing component tests and a combined hybrid bearing assembly is discussed and compared to the analytically determined performance characteristics.

Winn, L. W.; Eusepi, M. W.

1973-01-01

60

Lubricants | Special Issue : Friction and Lubrication of Bearings  

...all Addendum Article Book Review Case Report Comment Commentary Communication Concept Paper Correction Creative Discussion Editorial Essay Letter New Book Received Opinion Project Report ...fr Phone: +33 549 496 543 Fax: +33 549 496 504 Interests: thermal effects in hydrodynamic journal and thrust bearings; non-laminar regime; transient effects; risk of bearing seizure; ...surfaces and wear of hydrodynamic bearings; PTFE and PEEK layered journal and thrust tilting pad bearings; theoretical analyses and numerical simulations under THD ... English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted ...

 
 
 
 
61

Army (MANTECH) thrust area concept: Optics thrust area  

Science.gov (United States)

With the shrinking of the U.S. Army's material needs and the compression of defense requirements, the Army Manufacturing Technology (MANTECH) Program has the opportunity to advance the manufacturing state-of-the-art and solve near term production problems of the U.S. industrial base. To exploit this opportunity, the Army restructured its MANTECH efforts in FY 90 based on a thrust area concept. Each of the ten current thrusts, directed by a thrust area manager, has a broad technical objective selected to improve specific manufacturing processes. The manager is charged with setting objectives, selecting tasks, monitoring execution, leveraging external resources, and establishing microfactories to promote technology transfer. The Optics Manufacturing Thrust is an example of the concept. It is currently directed at revitalizing the domestic precision optics manufacturing base, now characterized by high labor costs and 1940's technology, through introduction of revolutionary machines, new processes, and Computer Integrated Manufacturing (CIM) principles. Leveraging of MANTECH dollars with those of industry, academia, and state governments led to the establishment of the center for Optics Manufacturing and plans for regional centers. Recognition of the U.S. as a world leader in precision optics manufacturing and a dramatic reduction of both manufacturing time and cost should accrue from thrust area efforts.

Kopacz, Stanley P.

1992-04-01

62

Magnetic bearings  

International Nuclear Information System (INIS)

Active magnetic bearings have been selected for the main and shutdown circulators of the Modular High Temperature Gas-Cooled Reactor (MHTGR). This paper describes the active magnetic bearing system, its development status and its advantages and disadvantages. The reasons for selecting active magnetic bearings for the MHTGR are discussed together with the development status. Finally, the generic applicability of magnetic bearings to the power industry is reviewed

63

Superconducting bearings  

International Nuclear Information System (INIS)

The physics and technology of superconducting bearings is reviewed. Particular attention is given to the use of high-temperature superconductors (HTSs) in rotating bearings. The basic phenomenology of levitational forces is presented, followed by a brief discussion of the theoretical models that can be used for conceptual understanding and calculations. The merits of various HTS bearing designs are presented, and the behaviour of HTS bearings in typical situations is discussed. The article concludes with a brief survey of various proposed applications for HTS bearings. (author)

64

The R and D D's bearing test benches  

International Nuclear Information System (INIS)

In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author)

65

A feasibility study on the use of foil bearings in cryogenic turbopumps  

Science.gov (United States)

The feasibility of using foil bearings in future earth-to-orbit rocket engines is studied. A design parameter of a LOX pump of the SSME was selected as a prototype for this study. It was found that three-pad journal bearings and eight-pad thrust bearings met the operating requirements of the LOX turbopump.

Heshmat, Hooshang

1991-01-01

66

Thrust-Vector-Control System  

Science.gov (United States)

Control gains computed via matrix Riccati equation. Software-based system controlling aim of gimbaled rocket motor on spacecraft adaptive and optimal in sense it adjusts control gains in response to feedback, according to optimizing algorithm based on cost function. Underlying control concept also applicable, with modifications, to thrust-vector control on vertical-takeoff-and-landing airplanes, control of orientations of scientific instruments, and robotic control systems.

Murray, Jonathan

1992-01-01

67

Failure of GIMBAL bearing in directional GYRO  

International Nuclear Information System (INIS)

This paper relates to the directional gyro of a sensing device used in indigenously developed surface-to-surface missile. The assembling of more than one thousand components in the form of several sub assemblies including hundreds of silver solders of this device was done in the hundred-thousands-class clean room according to assembly procedure. Whereas more than twenty bearings including gimbals bearings were assembled in the ten-thousands-class clean room after inspection/ testing them on beating testing system as per routine. The device was entered in testing and adjustment phase after successful completion of assembly work. The directional gyro qualified all the tests except the most critical one, the drift-rate. The drift-rate of outer gimbal was 60% more than permissible limit whereas drift-rate of inner gimbal was found O.K. It was diagnosed that at least one inner gimbal bearing out of two had some problem. The results were same after rebalancing of gimbals three times. The directional gyro was disassembled in clean room and the radial-thrust-bearing was recovered and flange bearing which are inner gimbal bearings. They were checked on bearing testing system and it was found that flange-bearing had more friction than permissible limit and hence rejected but radial thrust bearing were declared O.K. The gyro was reassembled with new O.K. flange bearing and the assembly work was completed in all respects. The sensing device qualified all the tests including the drift-rate. This case study is being presented to emphasize the importance of careful assembly of gyro in clean environment. (author)

68

Oh! Bear  

Digital Repository Infrastructure Vision for European Research (DRIVER)

"Oh! Bear!" is a song of Mudugar inviting bears in the forest to dance with the people. The collection is a result of the WOLP funding that Dr Rayson K Alex received in 2011. The project was to collect the oral literature of an indigenous community called Mudugar. Mudugar live in the mountainous land of Attapady, Palakkad District, Kerala State, South India. The photographs, video-documentaries, audio files and translated interviews are materials collected over a period of two years. Mudugar ...

Alex, Rayson K.

2013-01-01

69

Multiplicity with a thrust cut  

International Nuclear Information System (INIS)

We evaluate the multiplicity of hadrons in the e+e--annihilation at a given thrust T in the modified leading-log approximation, including O(??s) corrections. The calculation is done at a large value of ?=1-T by the use of the factorisation which takes place in the one-particle-inclusive cross section at a given ?. At a small ?, a different type of factorisation takes place, which also enable us to evaluate the multiplicity. Two approaches are compares numerically. Measuring this quantity near ?=1/3, we can determine the multiplicity ratio between a gluon-jet and a quark-jet. (orig.)

70

Multiplicity with a thrust cut  

CERN Document Server

We evaluate the multiplicity of hadrons in the e+e- annihilation at a given thrust $T$ in the modified leading-log approximation, including $O(\\sqrt{\\alpha_s})$ corrections. The calculation is done at a large value of $\\tau =1-T$ by the use of the factorisation which takes place in the one-particle-inclusive cross section at a given $\\tau$. At a small $\\tau$, a different type of factorisation takes place, which also enable us to evaluate the multiplicity. Two approaches are compared numerically. Measuring this quantity near $\\tau =1/3$, we can determine the multiplicity ratio between a gluon-jet and a quark-jet.

Kimura, K

1993-01-01

71

Cave Bear  

Science.gov (United States)

Decoding an ancient cave bear. A two-ton, thirteen-foot cave bear, extinct for ten thousand years, has just experienced a rebirth of sorts. From a tooth and a bone, scientists have recovered its entire genetic code.Eddy Rubin, director of the Department of Energy's Joint Genome Institute, says finding genuine cave bear DNA was like looking for a needle in a haystack. The haystack were all the other organisms that were living in the bones and in the tooth of this ancient creature. And the needle was the little bit of the ancient creature's genome DNA, or genes.They used state-of-the-art computer technology to separate the bear genes from the clutter. Jurassic Park fans should note that they can't clone a new cave bear, nor can they recover DNA from creatures as old as the dinosaurs. But they do hope to reconstruct the genetic code of Neanderthals, our closest non-human relatives, to better understand how our own species evolved. This resource contains detailed text description of the research as well as likes for further inquiry.

American Association for the Advancement of Science (;)

2005-08-15

72

Low Thrust Orbital Maneuvers Using Ion Propulsion  

Science.gov (United States)

Low-thrust maneuver options, such as electric propulsion, offer specific challenges within mission-level Modeling, Simulation, and Analysis (MS&A) tools. This project seeks to transition techniques for simulating low-thrust maneuvers from detailed engineering level simulations such as AGI's Satellite ToolKit (STK) Astrogator to mission level simulations such as the System Effectiveness Analysis Simulation (SEAS). Our project goals are as follows: A) Assess different low-thrust options to achieve various orbital changes; B) Compare such approaches to more conventional, high-thrust profiles; C) Compare computational cost and accuracy of various approaches to calculate and simulate low-thrust maneuvers; D) Recommend methods for implementing low-thrust maneuvers in high-level mission simulations; E) prototype recommended solutions.

Ramesh, Eric

2011-10-01

73

MPD thrust chamber flow dynamics  

Science.gov (United States)

Flow within the thrust chamber of a Magnetoplasmadynamic (MPD) arcjet is examined experimentally and modeled with a 2-D magnetohydrodynamic code. Two quasi-steady MPD thrusters are considered under the same input conditions of current (21 kA) and total mass flow rate (0.006 kg/s, argon + 1.5 percent hydrogen). The arcjets have the same basic design, consisting of a central cathode, 3.8 cm diameter and 5 cm long, separated from a coaxial anode of equal length by a uniform gap of 2.3 cm. Two different mass injection arrangements are used (100 percent at mid-radius, and 50 percent at the cathode base, with the remainder at mid-radius). A new spectroscopic analysis procedure is developed that allows distributions of radial speed, heavy particle temperature and turbulent speed to be extracted from chordal measurements of light emission by the two species in the plasma flow. Good qualitative (and reasonable quantitative) agreement exists with distributions calculated by the MHD code, indicating that flow within the thrust chamber expands from an electromagnetically pumped plasma base (vs a pumped jet off the cathode tip). The significant variation of internal flow dynamics with mass injector arrangement implies the need for extensive experimentally validated code modeling in order to evaluate the potential performance of MPD thrusters.

1990-08-01

74

Static Load Distribution in Ball Bearings  

Science.gov (United States)

A numerical procedure for computing the internal loading distribution in statically loaded, single-row, angular-contact ball bearings when subjected to a known combined radial and thrust load is presented. The combined radial and thrust load must be applied in order to avoid tilting between inner and outer rings. The numerical procedure requires the iterative solution of Z + 2 simultaneous nonlinear equations - where Z is the number of the balls - to yield an exact solution for axial and radial deflections, and contact angles. Numerical results for a 218 angular-contact ball bearing have been compared with those from the literature and show significant differences in the magnitudes of the ball loads, contact angles, and the extent of the loading zone.

Ricci, Mario

2010-01-01

75

Nonlinear dynamics of a vectored thrust aircraft  

DEFF Research Database (Denmark)

With realistic relations for the aerodynamic coefficients, numerical simulations are applied to study the longitudional dynamics of a thrust vectored aircraft. As function of the thrust magnitude and the thrust vectoring angle the equilibrium state exhibits two saddle-node bifurcations and three Hopf bifurcations. Even when the equilibrium state is stable, weakly damped oscillations occur with a period of 1 min. If, in an attempt to compensate for these oscillations, the thrust deflection is periodically adjusted, a complicated structure of overlapping torus, saddle-node and period-doubling bifurcations arises. This structure is investigated by combining brute force bifurcation diagrams with one- and two-dimensional continuation analyses.

Mosekilde, Erik

1996-01-01

76

Design and evaluation of thrust vectored nozzles using a multicomponent thrust stand  

Science.gov (United States)

Future aircraft with the capability of short takeoff and landing, and improved maneuverability especially in the post-stall flight regime will incorporate exhaust nozzles which can be thrust vectored. In order to conduct thrust vector research in the Mechanical Engineering Department at Cal Poly, a program was planned with two objectives; design and construct a multicomponent thrust stand for the specific purpose of measuring nozzle thrust vectors; and to provide quality low moisture air to the thrust stand for cold flow nozzle tests. The design and fabrication of the six-component thrust stand was completed. Detailed evaluation tests of the thrust stand will continue upon the receipt of one signal conditioning option (-702) for the Fluke Data Acquisition System. Preliminary design of thrust nozzles with air supply plenums were completed. The air supply was analyzed with regard to head loss. Initial flow visualization tests were conducted using dual water jets.

Carpenter, Thomas W.; Blattner, Ernest W.; Stagner, Robert E.; Contreras, Juanita; Lencioni, Dennis; Mcintosh, Greg

1990-01-01

77

Hydrodynamic bearings  

CERN Document Server

This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

Bonneau, Dominique; Souchet, Dominique

2014-01-01

78

Computer-aided selection of materials for cryogenic turbopump bearings  

Science.gov (United States)

The life requirement for the angular contact ball bearings in the Space Shuttle Main Engine (SSME) high-pressure-oxygen turbopump (HPOTP) is 7.5 hours. In actual operation, significantly shorter service life has been experienced. The objective of this current program is to identify bearing materials and/or materials processing techniques offering significant potential for extending HPOTP bearing performance life. A thermomechanical analysis of the HPOTP shaft/bearing system was performed with the SHABERTH (SHaft-BEaring-THermal) computer program. Bearing fatigue life, ball-race contact stress, heat generation rate, bulk ring temperatures, and circumferential stress in the inner rings were quantified as functions of radial load, thrust load, and ball-race contact friction. The analysis results were used to formulate criteria that are being used for the selection of special materials for future turbopump bearings.

Maurer, R. E.; Pallini, R. A.

1985-01-01

79

Operation and design selection of high temperature superconducting magnetic bearings  

International Nuclear Information System (INIS)

Axial and radial high temperature superconducting (HTS) magnetic bearings are evaluated by their parameters. Journal bearings possess advantages over thrust bearings. High magnetic gradients in a multi-pole permanent magnet (PM) configuration, the surrounding melt textured YBCO stator and adequate designs are the key features for increasing the overall bearing stiffness. The gap distance between rotor and stator determines the specific forces and has a strong impact on the PM rotor design. We report on the designing, building and measuring of a 200 mm prototype 100 kg HTS bearing with an encapsulated and thermally insulated melt textured YBCO ring stator. The encapsulation requires a magnetically large-gap (4-5 mm) operation but reduces the cryogenic effort substantially. The bearing requires 3 l of LN2 for cooling down, and about 0.2 l LN2 h-1 under operation. This is a dramatic improvement of the efficiency and in the practical usage of HTS magnetic bearings

80

Weakening inside incipient thrust fault  

Science.gov (United States)

In fold-and-thrust belts, shortening is mainly accommodated by thrust faults that nucleate along décollement levels. Geological and geophysical evidence suggests that these faults might be weak because of a combination of processes such as pressure-solution, phyllosilicates reorientation and delamination, and fluid pressurization. In this study we aim to decipher the processes and the kinetics responsible for weakening of tectonic décollements. We studied the Millaris thrust (Southern Pyrenees): a fault representative of a décollement in its incipient stage. This fault accommodated a total shortening of about 30 meters and is constituted by a 10m thick, intensively foliated phyllonite developed inside a homogeneous marly unit. Detailed chemical and mineralogical analyses have been carried out to characterize the mineralogical change, the chemical transfers and volume change in the fault zone compared to non-deformed parent sediments. We also carried out microstructural analysis on natural and experimentally deformed rocks. Illite and chlorite are the main hydrous minerals. Inside fault zone, illite minerals are oriented along the schistosity whereas chlorite coats the shear surfaces. Mass balance calculations demonstrated a volume loss of up to 50% for calcite inside fault zone (and therefore a relative increase of phyllosilicates contents) because of calcite pressure solution mechanisms. We performed friction experiments in a biaxial deformation apparatus using intact rocks sheared in the in-situ geometry from the Millaris fault and its host sediments. We imposed a range of normal stresses (10 to 50 MPa), sliding velocity steps (3-100 ?m/s) and slide-hold slide sequences (3 to 1000 s hold) under saturated conditions. Mechanical results demonstrate that both fault rocks and parent sediments are weaker than average geological materials (friction ?velocity-strengthening behavior because of the presence of phyllosilicate horizons. Fault rocks are remarkably weaker (? 0.35). Additionally, fault zone rocks do not show frictional healing, further supporting a non-seismic behavior and prolonged weakness. This study quantitatively demonstrates how tectonic detachments localize in incompetent formations and become readily weak, even after experiencing very small displacements.

Lacroix, B.; Tesei, T.; Collettini, C.; Oliot, E.

2013-12-01

 
 
 
 
81

Lightweight Chambers for Thrust Assemblies  

Science.gov (United States)

The Marshall Space Flight Center (MSFC) of the National Aeronautics and Space Administration (NASA) has successfully applied new materials and fabrication techniques to create actively cooled thrust chambers that operate 200-400 degrees hotter and weigh 50% lighter than conventional designs. In some vehicles, thrust assemblies account for as much as 20% of the engine weight. So, reducing the weight of these components and increasing their operating range will benefit many engines and vehicle designs, including Reusable Launch Vehicle (RLV) concepts. Obviously, copper and steel alloys have been used successfully for many years in the chamber components of thrust assemblies. Yet, by replacing the steel alloys with Polymer Matrix Composite (PMC) and/or Metal Matrix Composite (MMC) materials, design weights can be drastically reduced. In addition, replacing the traditional copper alloys with a Ceramic Matrix Composite (CMC) or an advanced copper alloy (Cu-8Cr-4Nb, also known as GRCop-84) significantly increases allowable operating temperatures. Several small MMC and PMC demonstration chambers have recently been fabricated with promising results. Each of these designs included GRCop-84 for the cooled chamber liner. These units successfully verified that designs over 50% lighter are feasible. New fabrication processes, including advanced casting technology and a low cost vacuum plasma spray (VPS) process, were also demonstrated with these units. Hot-fire testing at MSFC is currently being conducted on the chambers to verify increased operating temperatures available with the GRCop-84 liner. Unique CMC chamber liners were also successfully fabricated and prepared for hot-fire testing. Yet, early results indicate these CMC liners need significantly more development in order to use them in required chamber designs. Based on the successful efforts with the MMC and PMC concepts, two full size "lightweight" chambers are currently being designed and fabricated for hot-fire testing at MSFC in 2001. These "full size" chambers will be similar in size to those used on the X33 engine (RS2200). One will be fabricated with a MMC structural jacket, while the other uses a PMC jacket. Each will be designed for thrust levels of 15,000 pounds in an oxygen/hydrogen environment with liquid hydrogen coolant. Both chambers will use GRCop-84 for its channel wall liner. Each unit is expected to be at least 60% lighter than a conventional design with traditional materials. Hot-fire testing on the full size units in late 2001 will directly compare performance results between a conventional chamber design and these "lightweight" alternatives. The technology developed and demonstrated by this effort will not only benefit next generation RLV programs, but it can be applied to other existing and future engine programs, as well. Efforts were sponsored by the Advanced Space Transportation Program for RLV Focused Technologies. The task team was led by MSFC with additional members from NASA-Glenn Research Center and the Rocketdyne Division of The Boeing Company. Specific materials development and fabrication processes were provided by Aerojet, Lockheed Martin Astronautics, Composite Optics, Inc., Hyper-Therm, Ceramic Composites, Inc., MSE Technology Applications, and Plasma Processes, Inc.

Elam, Sandra K.; Lee, Jonathan; Holmes, Richard; Zimmerman, Frank; Effinger, Mike; Turner, James E. (Technical Monitor)

2001-01-01

82

Thrust Characterization for Vortex Ring Thrusters  

Science.gov (United States)

Synthetic jets are zero net mass pulsatile jets that are commonly used in flow control applications in air. In these cases the natural resonant frequency of the actuators plays an important role. In this work we will present thrust characterization of vortex ring thrusters (VRTs) in liquid (equivalent of synthetic jets in liquid medium). VRTs design are motivated by pulsatile jet propulsion in squid and jellyfish. A prototype jet thruster was designed and build for this investigation. The effect of the actuation frequency and stroke ratio on the thrust level was experimentally studied. A simplified slug model was defined which predicted the thrust according to the momentum transfer. According to the model the thrust values for various frequencies converges to a single non-dimensionalized thrust, which is only a function of the stroke ratio. The accuracy of the model was defined in terms of a coefficient ? which related predicted thrust values to those measured experimentally. This coefficient was observed to be nearly unity for stroke ratios below the formation number of the jet, and for frequencies below critical cavitation frequencies. ? was seen to decrease (measured thrust drops below predicted thrust) with increasing frequency for all jets with stroke ratios above the formation number. The feasibility of using such a device in typical marine vehicles was tested by implementing the thruster in an unmanned underwater vehicle. The vehicle test-bed was operated in various dynamic maneuvers, including a simulated parallel park.

Krieg, Mike; Mohseni, Kamran

2007-11-01

83

AXIAL THRUST IN THE IMPELLER PUMPS  

Directory of Open Access Journals (Sweden)

Full Text Available The system of forces acting at the pump rotors and also the influence of the working conditions on the dimensions and distribution of the axial thrust are presented.The essential formulas, for the calculation of the axial thrust value are given on the basis of the most recent research.

Zbigniew Jankowski

1972-01-01

84

Thrust: Productivity-Oriented Library for CUDA  

Science.gov (United States)

Thrust is a parallel algorithms library which resembles the C++ Standard Template Library (STL). Thrust's high-level interface greatly enhances programmer productivity while enabling performance portability between GPUs and multicore CPUs. Interoperability with established technologies (such as CUDA, TBB, and OpenMP) facilitates integration with existing software.

Bell, Nathan; Hoberock, Jared

2012-12-01

85

Advances In Magnetic Bearings  

Science.gov (United States)

NASA technical memorandum reviews state of technology of magnetic bearings, focusing mainly on attractive bearings rather than repulsive, eddy-current, or Lorentz bearings. Attractive bearings offer greater load capacities and preferred for aerospace machinery.

Fleming, David P.

1994-01-01

86

Low thrust chemical rocket technology  

Science.gov (United States)

An on-going technology program to improve the performance of low thrust chemical rockets for spacecraft on-board propulsion applications is reviewed. Improved performance and lifetime is sought by the development of new predictive tools to understand the combustion and flow physics, introduction of high temperature materials and improved component designs to optimize performance, and use of higher performance propellants. Improved predictive technology is sought through the comparison of both local and global predictions with experimental data. Predictions are based on both the RPLUS Navier-Stokes code with finite rate kinetics and the JANNAF methodology. Data were obtained with laser-based diagnostics along with global performance measurements. Results indicate that the modeling of the injector and the combustion process needs improvement in these codes and flow visualization with a technique such as 2-D laser induced fluorescence (LIF) would aid in resolving issues of flow symmetry and shear layer combustion processes. High temperature material fabrication processes are under development and small rockets are being designed, fabricated, and tested using these new materials. Rhenium coated with iridium for oxidation protection was produced by the Chemical Vapor Deposition (CVD) process and enabled an 800 K increase in rocket operating temperature. Performance gains with this material in rockets using Earth storable propellants (nitrogen tetroxide and monomethylhydrazine or hydrazine) were obtained through component redesign to eliminate fuel film cooling and its associated combustion inefficiency while managing head end thermal soakback. Material interdiffusion and oxidation characteristics indicated that the requisite lifetimes of tens of hours were available for thruster applications. Rockets were designed, fabricated, and tested with thrusts of 22, 62, 440 and 550 N. Performance improvements of 10 to 20 seconds specific impulse were demonstrated. Higher performance propellants were evaluated: Space storable propellants, including liquid oxygen (LOX) as the oxidizer with nitrogen hydrides or hydrocarbon as fuels. Specifically, a LOX/hydrazine engine was designed, fabricated, and shown to have a 95 pct theoretical c-star which translates into a projected vacuum specific impulse of 345 seconds at an area ratio of 204:1. Further performance improvment can be obtained by the use of LOX/hydrogen propellants, especially for manned spacecraft applications, and specific designs must be developed and advanced through flight qualification.

Schneider, Steven J.

1992-11-01

87

Polar Bear  

Science.gov (United States)

In this episode of the Podcast of Life, host Ari Daniel Shapiro relates two close calls with polar bears. Listen as Heather Cray recalls how, dumped by a storm on a small Arctic island without a shotgun, she got an unexpected wake-up call. And when researcher Steve Amstrup accidentally crashed through the roof of a polar bearâs den, no one could predict what happened next. Also included is a Learn More section that provides background information on the scientists recorded in the podcast, lessons, images, and cool facts.

2009-01-01

88

Collar nut and thrust ring  

Science.gov (United States)

A collar nut comprises a hollow cylinder having fine interior threads at one end for threadably engaging a pump mechanical seal assembly and an inwardly depending flange at the other end. The flange has an enlarged portion with a groove for receiving an O-ring for sealing against the intrusion of pumpage from the exterior. The enlarged portion engages a thrust ring about the pump shaft for crushing a hard O-ring, such as a graphite O-ring. The hard O-ring seals the interior of the mechanical seal assembly and pump housing against the loss of lubricants or leakage of pumpage. The fine threads of the hollow cylinder provide the mechanical advantage for crushing the hard O-ring evenly and easily with a hand tool from the side of the collar nut rather than by tightening a plurality of bolts from the end and streamlines the exterior surface of the mechanical seal. The collar nut avoids the spatial requirements of bolt heads at the end of a seal and associated bolt head turbulence.

Lowery, Guy B. (Aiken, SC)

1991-01-01

89

Fuel Optimal Thrust Allocation In Dynamic Positioning  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis gives a short introduction to the Dynamic Positioning(DP) domain and focuses on developing a fuel optimal thrust allocation algorithm for marine DP vessels with a diesel electric power plant. Obtained data is used to develop a static model for the fuel consumption of a diesel generator, as a function of its produced power. This model is used to formulate a convex Quadratic Programming(QP)-problem that finds fuel optimal solutions to the thrust allocation problem. This is possible ...

Rindarøy, Martin

2013-01-01

90

Cryogenic turbopump bearing materials  

Science.gov (United States)

Materials used for modern cryogenic turbopump bearings must withstand extreme conditions of loads and speeds under marginal lubrication. Naturally, these extreme conditions tend to limit the bearing life. It is possible to significantly improve the life of these bearings, however, by improving the fatigue and wear resistance of bearing alloys, and improving the strength, liquid oxygen compatibility and lubricating ability of the bearing cage materials. Improved cooling will also help to keep the bearing temperatures low and hence prolong the bearing life.

Bhat, Biliyar N.

1989-01-01

91

FROM STUDIES ON THE THRUST IN SWIMMING  

Directory of Open Access Journals (Sweden)

Full Text Available Swimming speed is determined by many factors, including weight preparation of the swimmer which is one of the most important ones. This power is directly related to the speed a swimmer can reach in water, that is the value of thrust. The aim of the study was to establish the level of thrust and swimming speed of the 2nd year students (n=20 of the University School of Physical Education (USPE in Pozna? and to compare them with the results of study from 1983 in which the 4th year students (n=20 of the USPE in Pozna? were studied. The current study was carried out in the context of the long-term changes in swimming technique. Research methods: measurement of thrust in real conditions was performed using a prototype device for the measurement of thrust of a swimmer which makes it possible to register the force in the water environment; swimming speed was established on the basis of the time needed to cover the distance of 25 metres, according to the regulations of the Polish Swimming Association. Conclusions: the students taking part in the 1983 study had higher values of thrust, but a lower speed than the students taking part in the 2006 study, which suggests that apart from the thrust the technique of swimming has a important influence of the swimming speed.

Strzelczyk, R.

2008-07-01

92

Misalignment in Gas Foil Journal Bearings: An Experimental Study  

Science.gov (United States)

As gas foil journal bearings become more prevalent in production machines, such as small gas turbine propulsion systems and microturbines, system-level performance issues must be identified and quantified in order to provide for successful design practices. Several examples of system-level design parameters that are not fully understood in foil bearing systems are thermal management schemes, alignment requirements, balance requirements, thrust load balancing, and others. In order to address some of these deficiencies and begin to develop guidelines, this paper presents a preliminary experimental investigation of the misalignment tolerance of gas foil journal bearing systems. Using a notional gas foil bearing supported rotor and a laser-based shaft alignment system, increasing levels of misalignment are imparted to the bearing supports while monitoring temperature at the bearing edges. The amount of misalignment that induces bearing failure is identified and compared to other conventional bearing types such as cylindrical roller bearings and angular contact ball bearings. Additionally, the dynamic response of the rotor indicates that the gas foil bearing force coefficients may be affected by misalignment.

Howard, Samuel A.

2008-01-01

93

Effect of blade outlet angle on radial thrust of single-blade centrifugal pump  

Science.gov (United States)

Single-blade centrifugal pumps are widely used as sewage pumps. However, a large radial thrust acts on a single blade during pump operation because of the geometrical axial asymmetry of the impeller. This radial thrust causes vibrations of the pump shaft, reducing the service life of bearings and shaft seal devices. Therefore, to ensure pump reliability, it is necessary to quantitatively understand the radial thrust and clarify the behavior and generation mechanism. This study investigated the radial thrust acting on two kinds of single-blade centrifugal impellers having different blade outlet angles by experiments and computational fluid dynamics (CFD) analysis. Furthermore, the radial thrust was modeled by a combination of three components, inertia, momentum, and pressure, by applying an unsteady conservation of momentum to this impeller. As a result, the effects of the blade outlet angle on both the radial thrust and the modeled components were clarified. The total head of the impeller with a blade outlet angle of 16 degrees increases more than the impeller with a blade outlet angle of 8 degrees at a large flow rate. In this case, since the static pressure of the circumference of the impeller increases uniformly, the time-averaged value of the radial thrust of both impellers does not change at every flow rate. On the other hand, since the impeller blade loading becomes large, the fluctuation component of the radial thrust of the impeller with the blade outlet angle of 16 degrees increases. If the blade outlet angle increases, the fluctuation component of the inertia component will increase, but the time-averaged value of the inertia component is located near the origin despite changes in the flow rate. The fluctuation component of the momentum component becomes large at all flow rates. Furthermore, although the time-averaged value of the pressure component is almost constant, the fluctuation component of the pressure component becomes large at a large flow rate. In addition to the increase of the fluctuation component of this pressure component, because the fluctuation component of the inertia and momentum components becomes large (as mentioned above), the radial thrust increases at a large flow rate, as is the case for the impeller with a large blade outlet angle.

Nishi, Y.; Fukutomi, J.; Fujiwara, R.

2012-11-01

94

Effect of blade outlet angle on radial thrust of single-blade centrifugal pump  

International Nuclear Information System (INIS)

Single-blade centrifugal pumps are widely used as sewage pumps. However, a large radial thrust acts on a single blade during pump operation because of the geometrical axial asymmetry of the impeller. This radial thrust causes vibrations of the pump shaft, reducing the service life of bearings and shaft seal devices. Therefore, to ensure pump reliability, it is necessary to quantitatively understand the radial thrust and clarify the behavior and generation mechanism. This study investigated the radial thrust acting on two kinds of single-blade centrifugal impellers having different blade outlet angles by experiments and computational fluid dynamics (CFD) analysis. Furthermore, the radial thrust was modeled by a combination of three components, inertia, momentum, and pressure, by applying an unsteady conservation of momentum to this impeller. As a result, the effects of the blade outlet angle on both the radial thrust and the modeled components were clarified. The total head of the impeller with a blade outlet angle of 16 degrees increases more than the impeller with a blade outlet angle of 8 degrees at a large flow rate. In this case, since the static pressure of the circumference of the impeller increases uniformly, the time-averaged value of the radial thrust of both impellers does not change at every flow rate. On the other hand, since the impeller blade loading becomes large, the fluctuation component of the radial thrust of the impeller with the blade outlet anglef the impeller with the blade outlet angle of 16 degrees increases. If the blade outlet angle increases, the fluctuation component of the inertia component will increase, but the time-averaged value of the inertia component is located near the origin despite changes in the flow rate. The fluctuation component of the momentum component becomes large at all flow rates. Furthermore, although the time-averaged value of the pressure component is almost constant, the fluctuation component of the pressure component becomes large at a large flow rate. In addition to the increase of the fluctuation component of this pressure component, because the fluctuation component of the inertia and momentum components becomes large (as mentioned above), the radial thrust increases at a large flow rate, as is the case for the impeller with a large blade outlet angle.

95

Restoring thrusting in the East Greenland Caledonides  

Science.gov (United States)

Three principal lithostructural domains are recognized within the southern part (70° 76°N) of the East Greenland Caledonides. At the deepest structural levels, within foreland windows, a thin Neoproterozoic lower Paleozoic succession unconformably overlies older basement. The foreland is overridden by two major thrust sheets, a lower and an upper thrust sheet. Each of these comprise Paleoproterozoic or older crystalline basement rocks and their metasedimentary cover, and preserve evidence of both a pre-Caledonian (ca. 930 Ma) thermal event and the superimposed Caledonian orogenesis. Transport directions on major thrusts are top-to-the-west-northwest, and restoration of displacements with respect to the foreland windows permits reconstruction of a 500 700-km-wide sector of the pre-Caledonian Laurentian margin. One implication of the reconstruction is that the 18.5-km-thick Neoproterozoic lower Paleozoic succession preserved in the upper thrust sheet accumulated in a basin that was at least 200 km east of the foreland where the equivalent succession totals only 250 400 m. Scandian (ca. 430 Ma) thrusting resulted in 40% 60% shortening to produce the present ˜300-km-wide orogenic belt in East Greenland.

Higgins, A. K.; Leslie, A. G.

2000-11-01

96

Fluid Film Bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A hydrodynamic fluid film bearing in which a plurality of circumferentially spaced bearing elements are provided, defining areas of support for the rotating part of the bearing. At least some of the bearing elements are adjustable during operation to vary lubrication conditions in the fluid film. The bearing elements are of sufficiently high stiffness that the position of the entire bearing surface of each element is essentially independent of the pressure in the fluid film encountered during...

Martin, James Keith; Parkins, David Walter

1995-01-01

97

Bearing endurance tests in vacuum for sputtered molybdenum disulfide films  

Science.gov (United States)

Angular-contact, 440C stainless steel, ball bearings with sputtered MoS2 films 0.0000006 x 10-7m (6000 A) thick were evaluated in a vacuum bearing chamber (1750 rpm, 137.9-N- (31-lbf-) thrust load) for endurance. Two types of sputtered films were evaluated: (1) MOS2 sputtered directly onto bearing components, and (2) a thin 0.0000001 x 10-7m (1000 A) underlayer of Cr3Si2 subsequently sputtered with MoS2. Bearing test evaluations in vacuum showed that endurance lives of more than 1000 hours (105,000,000 cycles) were obtained with bearings (cage, races, and balls) directly sputtered with MoS2. The same endurance lives were also obtained when only the races and cage were sputtered with an underlayer of Cr3Si2 and subsequently with MoS2.

Spalvins, T.

1975-01-01

98

Hanging wall deformation of a seismogenic megasplay fault in an accretionary prism: The Nobeoka Thrust in southwestern Japan  

Science.gov (United States)

The structure and occurrence of deformation within the hanging wall of the Nobeoka Thrust in Kyushu, Japan, was investigated to understand the dynamic aspects of splay faulting in relation to seismic events. From field observations, hanging wall is suggested to have undergone four phases of deformation. The first phase involved horizontal shortening, as documented by folding and thrusting, followed by a phase of vertical loading shown by the development of horizontal slaty cleavages, pressure solution, and cleavage-parallel mineral vein precipitation. A third phase involved shearing, and deformation along cleavage restricted to near the Nobeoka Thrust, while the fourth phase produced widespread, brittle fracturing associated with the development of pseudotachylyte-bearing faults and tension crack filling veins high angle to cleavage. These four phases can be explained as follows. During the inter-seismic period, an extensionally stable taper was maintained in the inner wedge of the accretionary prism by dominant vertical loading (?1), in combination with a lesser amount of horizontal compression (?2) related to the locking of the mega-thrust. Elastic strain energy in the hanging wall of the inner wedge was co-seismically released by slip on the mega-thrust and horizontal shortening in the outer wedge associated with dynamic ductile weakening of the fault plane. This sudden release of elastic strain caused brittle fracturing with ?1 at a high angle to the shear surface of the Nobeoka Thrust, most of the displacement resulting from deformation of the footwall.

Kimura, Gaku; Hamahashi, Mari; Okamoto, Shin'ya; Yamaguchi, Asuka; Kameda, Jun; Raimbourg, Hugues; Hamada, Yohei; Yamaguchi, Haruka; Shibata, Tadahiro

2013-07-01

99

Pulsed thrust measurements using electromagnetic calibration techniques  

International Nuclear Information System (INIS)

A thrust stand for accurately measuring impulse bits, which ranged from 10-1000 ?N s using a noncontact electromagnetic calibration technique is described. In particular, a permanent magnet structure was designed to produce a uniform magnetic field, and a multiturn coil was made to produce a calibration force less than 10 mN. The electromagnetic calibration force for pulsed thrust measurements was linear to the coil current and changed less than 2.5% when the distance between the coil and magnet changed 6 mm. A pulsed plasma thruster was first tested on the thrust stand, and afterward five single impulse bits were measured to give a 310 ?N s average impulse bit. Uncertainty of the measured impulse bit was analyzed to evaluate the quality of the measurement and was found to be 10 ?N s with 95% credibility.

100

Thrust Vector Control using movable probes  

Science.gov (United States)

A study was undertaken to determine if movable probes or struts positioned in the nozzle can be used to provide Thrust Vector Control of the Space Shuttle Solid Rocket Booster. The study employed CFD to determine estimates of the shock standoff distance from the probe. An empirical correlation was used to construct the shock shape and the pressure distribution generated by the probe. The TVC performance for a single and multiple number of probes was then used to determine requirements for a maximum thrust angle offset of 7.5 degrees. Consideration was given to what materials would be suitable for the probe and if active cooling is required. Based on the performance analysis and thermal requirements, a Probe Thrust Vector Control (PTVC) system was sized. Indications are that a PTVC system weight is in the 1500 1bm weight range, compared to the existing weight of 7500 1bm for the SRB nozzle gimble system.

Cavalleri, Robert; Tiarn, Weihnurng; Readey, Harvey

1990-01-01

 
 
 
 
101

Spiral Groove Aerodynamic Bearings  

Directory of Open Access Journals (Sweden)

Full Text Available In order to research the conical spiral groove aerodynamic bearings, the bearing's lubrication analysis mathematical model is established. The Reynolds equation of the laminar flow condition is used to calculate the 3D pressure distribution by the locally finite difference method. The influence law of the gas film pressure distribution on the bearing performance is revealed by researching the nonlinear dynamic characteristic of gas film. It reveals the laws that the effect of the bearing structural parameters on the gas film pressure distribution and the bearing capacity. The results show that the spiral groove change the gas film thickness distribution and the gas film pressure distribution and achieve good bearing dynamic pressure effect, which improve the bearing performance and the bearing stability; The structure parameters affect the gas film pressure distribution and the static characteristics. Therefore, a reasonable choice of bearing structural parameters contributes to improve the bearing's static characteristics and bearing capacity.

Jia Chen-Hui

2013-01-01

102

A six degree-of-freedom thrust sensor for a labscale hybrid rocket  

Science.gov (United States)

A six degree-of-freedom thrust sensor was designed, constructed, calibrated, and tested using the labscale hybrid rocket at the University of Arkansas at Little Rock. The system consisted of six independent legs: one parallel to the axis of symmetry of the rocket for main thrust measurement, two vertical legs near the nozzle end of the rocket, one vertical leg near the oxygen input end of the rocket, and two separated horizontal legs near the nozzle end. Each leg was composed of a rotational bearing, a load cell, and a universal joint above and below the load cell. The leg was designed to create point contact along only one direction and minimize the non-axial forces applied to the load cell. With this system, force in each direction and moments for roll, pitch, and yaw can be measured. The system was calibrated and tested using a labscale hybrid rocket using gaseous oxygen and hydroxyl-terminated polybutadiene solid fuel. The thrust stand proved to be stable during calibration tests. Thrust force vector components and roll, pitch, and yaw moments were calculated for test firings with an oxygen mass flow rate range of 0.0174-0.0348 kg s-1.

Wright, Ann M.; Wright, Andrew B.; Born, Traig; Strickland, Ryan

2013-12-01

103

A microNewton thrust stand for average thrust measurement of pulsed microthruster  

Science.gov (United States)

A torsional thrust stand has been developed for the study of the average thrust for microNewton pulsed thrusters. The main body of the thrust stand mainly consists of a torsional balance, a pair of flexural pivots, a capacitive displacement sensor, a calibration assembly, and an eddy current damper. The behavior of the stand was thoroughly studied. The principle of thrust measurement was analyzed. The average thrust is determined as a function of the average equilibrium angle displacement of the balance and the spring stiffness. The thrust stand has a load capacity up to 10 kg, and it can theoretically measure the force up to 609.6 ?N with a resolution of 24.4 nN. The static calibrations were performed based on the calibration assembly composed of the multiturn coil and the permanent magnet. The calibration results demonstrated good repeatability (less than 0.68% FSO) and good linearity (less than 0.88% FSO). The assembly of the multiturn coil and the permanent magnet was also used as an exciter to simulate the microthruster to further research the performance of the thrust stand. Three sets of force pulses at 17, 33.5, and 55 Hz with the same amplitude and pulse width were tested. The repeatability error at each frequency was 7.04%, 1.78%, and 5.08%, respectively.

Zhou, Wei-Jing; Hong, Yan-Ji; Chang, Hao

2013-12-01

104

Thrust Characteristics of High-Thrust Spiral Motor Using FEM Analysis  

Science.gov (United States)

We propose a spiral-type motor that has high thrust characteristics as a linear actuator. This motor generates torque around the axis and thrust in the axial direction only by electromagnetic force. It has little friction because no additional hardware is required for straight-line movement. This paper presents the concept of the spiral motor. The finite-element method (FEM) analysis certifies that this motor has high motor constant as same as High Density Linear Motor (HDL). We also study a method to compensate the thrust fluctuation of 5-pitch-stator 6-pitch-mover model

Kwon, Hyuk-Jin; Fujimoto, Yasutaka

105

Bearings for Your Whirligig  

Science.gov (United States)

Experiment with friction and make bearings for a whirligig! This activity is a nice introduction to friction and bearings and demonstrates why bearings are useful for spinning. A related video show Vollis Simpson, an artist who creates kinetic sculptures and whirligigs, explain how he uses bearings in all of his spinning pieces so that they move smoothly.

Minnesota, Science M.

1995-01-01

106

Passive magnetic bearing configurations  

Science.gov (United States)

A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

Post, Richard F. (Walnut Creek, CA)

2011-01-25

107

Cryogenic foil bearing turbopumps  

Science.gov (United States)

Cryogenic foil bearing turbopumps offer high reliability and low cost. The fundamental cryogenic foil bearing technology has been validated in both liquid hydrogen and liquid oxygen. High load capacity, excellent rotor dynamics, and negligible bearing wear after over 100 starts and stops, and over many hours of testing, were observed in both fluids. An experimental liquid hydrogen foil bearing turbopump was also successfully demonstrated. The results indicate excellent stability, high reliability, wide throttle-ability, low bearing cooling flow, and two-phase bearing operability. A liquid oxygen foil bearing turbopump has been built and is being tested at NASA MSFC.

Gu, Alston L.

1993-01-01

108

Introduction to ball bearings  

Science.gov (United States)

The purpose of a ball bearing is to provide a relative positioning and rotational freedom while transmitting a load between two structures, usually a shaft and a housing. For high rotational speeds (e.g., in gyroscope ball bearings) the purpose can be expanded to include rotational freedom with practically no wear in the bearing. This condition can be achieved by separating the bearing parts with a coherent film of fluid known as an elastohydrodynamic film. This film can be maintained not only when the bearing carries the load on a shaft, but also when the bearing is preloaded to position the shaft to within micro- or nano-inch accuracy and stability. Background information on ball bearings is provided, different types of ball bearings and their geometry and kinematics are defined, bearing materials, manufacturing processes, and separators are discussed. It is assumed, for the purposes of analysis, that the bearing carries no load.

Hamrock, B. J.; Dowson, D.

1981-01-01

109

Recent research and development of bearings for helium circulator  

International Nuclear Information System (INIS)

This paper mainly describes recent studies and successful applications of water lubricated bearing and gas lubricated bearing. Both types of bearing seem to be suitable for a turbo machine installed in an atomic energy plant - such as the helium circulator of a HTGR - not to be affected by radioactivity, so we have been attracted by them for about 10 years. The former was investigated theoretically taking account of turbulent flow due to the low viscosity of water, and compared with the experimental data. Good agreement was obtained, and a successful example applied to a small-sized high speed air compressor is shown. The latter was investigated using a large-sized bearing test rig simulated to an actual machine. The tilting pad journal bearing and the tilting pad thrust bearing were taken and improved for some aspects. These bearings have been taken into service on an actual circulator and are now operating successfully. Currently, a magnetic bearing is being studied to pay special attention to endurance for an earthquake and catcher bearing system. We would like to have an opportunity to present these results in the near future. (author). 5 refs, 15 figs, 2 tabs

110

Ascent thrust vector control system test  

Science.gov (United States)

Testing of the Ascent Thrust Vector Control System in support of the Ares 1-X program at the Marshall Space Flight Center in Huntsville, Alabama. This image is extracted from a high definition video file and is the highest resolution available

2008-01-01

111

Conical Magnetic Bearings Developed for Active Stall Control in Gas Turbine Engines  

Science.gov (United States)

Active stall control is a current research area at the NASA Glenn Research Center that offers a great benefit in specific fuel consumption by allowing the gas turbine to operate beyond the onset of stall. Magnetic bearings are being investigated as a new method to perform active stall control. This enabling global aviation safety technology would result in improved fuel efficiency and decreased carbon dioxide emissions, as well as improve safety and reliability by eliminating oil-related delays and failures of engine components, which account for 40 percent of the commercial aircraft departure delays. Active stall control works by perturbing the flow in front of the compressor stage such that it cancels the pressure wave, which causes the compressor to go into stall. Radial magnetic bearings are able to whirl the shaft so that variations in blade tip leakage would flow upstream causing a perturbation wave that could cancel the rotating stall cell. Axial or thrust magnetic bearings cannot be used to cancel the surge mode in the compressor because they have a very low bandwidth and thus cannot modulate at a high enough frequency. Frequency response is limited because the thrust runner cannot be laminated. To improve the bandwidth of magnetic thrust bearings, researchers must use laminations to suppress the eddy currents. A conical magnetic bearing can be laminated, resulting in increased bandwidth in the axial direction. In addition, this design can produce both radial and thrust force in a single bearing, simplifying the installation. The proposed solution combines the radial and thrust bearing into one design that can be laminated--a conical magnetic bearing. The new conical magnetic bearing test rig, funded by a Glenn fiscal year 2002 Director's Discretionary Fund, was needed because none of the existing rigs has an axial degree of freedom. The rotor bearing configuration will simulate that of the main shaft on a gas turbine engine. One conical magnetic bearing replaces the ball bearing in front of the compressor, and the second replaces the roller bearing behind the burner. The rig was made operational to 10,000 rpm under Smart Efficient Components funding, and both position and current adaptive vibration control have been demonstrated. Upon program completion, recommendations will be made as to the efficacy of the conical magnetic bearing for active stall control.

Trudell, Jeffrey J.; Kascak, Albert F.; Provenza, Andrew J.; Buccieri, Carl J.

2004-01-01

112

Conditions for thrust faulting in a glacier  

Science.gov (United States)

Dipping, arcuate bands of debris-rich ice outcropping near the margins of glaciers are often interpreted as thrust faults, assumed to originate in zones of longitudinal compression. Identification of thrusts is typically based either on the geometry and sedimentology of the debris bands or on the crystal fabric of surrounding ice, but the physical processes necessary to generate thrusts are rarely evaluated. Herein, we combine a numerical model of compressive ice flow near a glacier margin with theoretical stress and strain rate criteria for ice fracture and stress criteria for frictional slip to determine the conditions necessary for thrust faulting in glaciers. This model is applied to two different glaciological settings where longitudinal compression has been documented: (1) the transition between warm-based and cold-based ice near the terminus of Storglaciären, Sweden, and (2) the downglacier extent of the 1983 surge front of Variegated Glacier where surging ice encountered stagnant ice. Simulations representing the margin of Storglaciären indicate that peak compressive strain rates are six orders of magnitude too small to induce fracture, whereas at Variegated Glacier, strain rates were an order of magnitude too small for compressive fracture. In both groups of simulations, preexisting fractures governed by Coulomb friction are susceptible to slip if they span the ice thickness, are oriented close to the optimal fracture angle, and, in the case of Storglaciären, are subject to water pressures that are a large fraction of ice overburden pressure. Variations about the optimal fracture orientation, low or zero water pressure, high sliding friction coefficient, and limited vertical or lateral fracture extent each tend to suppress thrusting.

Moore, Peter L.; Iverson, Neal R.; Cohen, Denis

2010-06-01

113

Structural geology and regional tectonic significance of the Ramgarh thrust, Himalayan fold-thrust belt of Nepal  

Science.gov (United States)

The Ramgarh thrust is one of the major fault systems of the Himalayan thrust belt in Nepal and northern India. The Ramgarh thrust sheet is ˜0.2-2.0 km thick and can be traced along strike the entire length of the Himalaya in Nepal. The fault generally places the oldest Paleoproterozoic rocks in the Lesser Himalayan series upon younger Lesser Himalayan rocks or lower Miocene foreland basin deposits. Regional balanced cross sections suggest that the Ramgarh thrust had at least ˜120 km of initial south vergent displacement. Subsequently, the frontal part of the thrust experienced further slip as the roof thrust for a large duplex in underlying Lesser Himalayan rocks. Ramgarh hanging wall strata are greenschist-grade phyllite, quartzite, and augen gneiss, all of which locally exhibit phyllonitic and mylonitic fabrics that indicate a top-to-the-south sense of shear. Structural fabrics in the Ramgarh thrust sheet are generally parallel to the fabrics in rocks above and below the thrust sheet. Regional and local mapping of the Ramgarh thrust in Nepal demonstrates that the fault always places a hanging wall flat upon a footwall flat, except where local lateral ramps complicate its geometry. Similarly, the structurally overlying Main Central thrust always places a hanging wall flat in Greater Himalayan series rocks upon the regionally flat Ramgarh thrust sheet. These geometric relationships preclude kinematic and thermal models that elevate Greater Himalayan and lower Lesser Himalayan rocks along high-angle thrust ramps in the vicinity of the present traces of the Ramgarh and Main Central thrust faults. Instead, the corresponding footwall ramps for these thrusts must be located more than 100 km north of the current trace of the Main Central thrust. The present steep dips of the Ramgarh and Main Central thrust sheets can be attributed to tilting during emplacement of structurally lower thrust sheets within a large antiformal duplex that occupies most of the Lesser Himalayan zone. The Ramgarh thrust sheet overlaps a bed length of at least 100 km in lower Miocene foreland basin deposits, indicating that a significant amount of displacement on the thrust must have occurred after ˜15 Ma. Growth of the Lesser Himalayan duplex and additional slip on the frontal part of the Ramgarh thrust occurred from ˜12 to 5 Ma. The presence of a major greenschist-grade metasedimentary thrust sheet composed of Lesser Himalayan rocks directly below the Main Central thrust suggests that the famous "inverted metamorphism" in this region is a result of structural inversion. Similarly, the concept of a broad zone of intense shear strain related exclusively to emplacement of the Main Central thrust sheet is probably invalid in Nepal.

Pearson, Ofori N.; Decelles, Peter G.

2005-08-01

114

Thrusting and gravel progradation in foreland basins: A test of post-thrusting gravel dispersal  

Science.gov (United States)

The use of gravels as syntectonic indicators of thrusting has recently been questioned by foreland-basin models that assign gravels to a post-thrusting interval of progradation, except in very proximal areas. On the basis of precise temporal control provided by magnetostratigraphically dated sections, the history of gravel progradation after a major thrusting and uplift event in the northwestern Himalaya is shown to be a virtually syntectonic phenomenon. Despite considerable crustal subsidence driven by a thick-skinned thrust, gravels prograded ˜70 km during a 1.5-m.y.-long thrusting event. By 3 m.y. after the start off thrusting, gravels extended more than 110 km into the basin. Although delayed gravel progradation appears appropriate for many Rocky Mountain foreland basins, it is clearly not valid for the Himalaya. We attribute the difference in depositional response between these basins to differences in the quantity of sediment supplied to them (sediment starved vs. overfilled), the availability of resistates in the source area, and the size of the antecedent drainage.

Burbank, D. W.; Beck, R. A.; Raynolds, R. G. H.; Hobbs, R.; Tahirkheli, R. A. K.

1988-12-01

115

Space Shuttle Main Engine Turbopump Bearing Testing at Marshall Space Flight Center  

Science.gov (United States)

The Space Shuttle has three main engines that are used for lift off into orbit. These engines are fed propellants by low and high pressure turbopumps on each engine. A main element of the pumps are the bearings supporting the main shaft that spins the turbine and pumps. These bearings must spin at high speeds, support the radial and axial thrust loads, and have high wear resistance without the benefit of lubrication. This paper describes the bearing testing that was done at the Marshall Space Flight Center and the results that were obtained to provide the best bearing design possible for safe and reliable engine performance.

Gibson, Howard; Thom, Robert; Moore, Chip

2010-01-01

116

Thrust and Propulsive Efficiency from an Instructive Viewpoint  

Science.gov (United States)

In a typical engineering or physics curriculum, the momentum equation is used for the determination of jet engine thrust. Even a simple thrust analysis requires a heavy emphasis on mathematics that can cause students and engineers to lose a physical perspective on thrust. This article provides for this physical understanding using only static…

Kaufman, Richard D.

2010-01-01

117

Latest Cretaceous-Paleogene basin development and resultant sedimentation patterns in the thrust belt and broken foreland of central Utah  

Energy Technology Data Exchange (ETDEWEB)

Latest Cretaceous tectonism in central and east-central Utah formed several intermontane basins both atop thrust sheets and between the thrust front and basement-involved uplifts in the former foreland basin. The upper Campanian Castlegate Sandstone and its inferred western equivalents were the last strata deposited prior to segmentation of the foreland basin. Thereafter, eastward transport of the thrust allochthon uplifted the most proximal part of the Castlegate depositional wedge. West of the thrust front, small intermontane basins formed on the allochthon. Sediment was transported into these basins from both eastern and western sources. In each basin, facies grade from basin-margin conglomeratic alluvial fan deposits to basin-interior flood-plain and lacustrine deposits within a few kilometers. These intermontane basins existed from latest Campanian through the late Paleocene, and may have been transported a short distance eastward as they formed. East of the thrust front in the latest Campanian and contemporaneous with basin formation on the allochthon, a northward-northeastward-flowing big river system transported sediment into the foreland basin from feldspar-rich source areas southwest of the study area. Subsequently, major movement of the San Rafael uplift in the very late Campanian or early Maastrichtian gave rise to an intermontane basin between the thrust front and the San Rafael uplift. Northwestward-flowing, pebble-bearing braided rivers deposited the oldest sediments in this basin prior to an influx from the south and southwest of sediment that formed a thick Maastrichtian clastic sequence. In contrast to deposition in basins on the allochthon, deposition east of the thrust front in the Paleocene was intermittent and restricted to rapidly shifting centers of basin subsidence.

Lawton, T.F. (New Mexico State Univ., Las Cruces (USA)); Franczyk, K.J.; Pitman, J.K. (Geological Survey, Denver, CO (USA))

1990-05-01

118

Development and Testing of an Axial Halbach Magnetic Bearing  

Science.gov (United States)

The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2006-01-01

119

NATURAL BARRIERS TARGETED THRUST FY 2004 PROJECTS  

Energy Technology Data Exchange (ETDEWEB)

This booklet contains project descriptions of work performed by the Department of Energy (DOE), Office of Civilian Radioactive Waste Management (OCRWM), Office of Science and Technology and International's (OST&I) Natural Barriers Targeted Thrust during Fiscal Year (FY) 2004. The Natural Barriers Targeted Thrust is part of OST&I's Science and Technology Program which supports the OCRWM mission to manage and dispose of high-level radioactive waste and spent nuclear fuel in a manner that protects health, safety, and the environment; enhances national and energy security; and merits public confidence. In general, the projects described will continue beyond FY 2004 assuming that the technical work remains relevant to the proposed Yucca Mountain Repository and sufficient funding is made available to the Science and Technology Program.

NA

2005-07-27

120

MATERIALS PERFORMANCE TARGETED THRUST FY 2004 PROJECTS  

International Nuclear Information System (INIS)

The Yucca Mountain site was recommended by the President to be a geological repository for commercial spent nuclear fuel and high-level radioactive waste. The multi-barrier approach was adopted for assessing and predicting system behavior, including both natural barriers and engineered barriers. A major component of the long-term strategy for safe disposal of nuclear waste is first to completely isolate the radionuclides in waste packages for long times and then to greatly retard the egress and transport of radionuclides from penetrated packages. The goal of the Materials Performance Targeted Thrust program is to further enhance the understanding of the role of engineered barriers in waste isolation. In addition, the Thrust will explore technical enhancements and seek to offer improvements in materials costs and reliability

 
 
 
 
121

MATERIALS PERFORMANCE TARGETED THRUST FY 2004 PROJECTS  

Energy Technology Data Exchange (ETDEWEB)

The Yucca Mountain site was recommended by the President to be a geological repository for commercial spent nuclear fuel and high-level radioactive waste. The multi-barrier approach was adopted for assessing and predicting system behavior, including both natural barriers and engineered barriers. A major component of the long-term strategy for safe disposal of nuclear waste is first to completely isolate the radionuclides in waste packages for long times and then to greatly retard the egress and transport of radionuclides from penetrated packages. The goal of the Materials Performance Targeted Thrust program is to further enhance the understanding of the role of engineered barriers in waste isolation. In addition, the Thrust will explore technical enhancements and seek to offer improvements in materials costs and reliability.

DOE

2005-09-13

122

High temperature thrust chamber for spacecraft  

Science.gov (United States)

A high temperature thrust chamber for spacecraft (20) is provided herein. The high temperature thrust chamber comprises a hollow body member (12) having an outer surface and an internal surface (16) defining the high temperature chamber (10). The body member (12) is made substantially of rhenium. An alloy (18) consisting of iridium and at least alloying metal selected of the group consisting of rhodium, platinum and palladium is deposited on at least a portion of the internal surface (16) of the body member (12). The iridium and the alloying metal are electrodeposited onto the body member (12). A HIP cycle is performed upon the body member (12) to cause the coating of iridium and the alloying metal to form the alloy (18) which protects the body member (12) from oxidation.

Chazen, Melvin L. (Inventor); Mueller, Thomas J. (Inventor); Kruse, William D. (Inventor)

1998-01-01

123

Solar electric propulsion thrust subsystem development  

Science.gov (United States)

The Solar Electric Propulsion System developed under this program was designed to demonstrate all the thrust subsystem functions needed on an unmanned planetary vehicle. The demonstration included operation of the basic elements, power matching input and output voltage regulation, three-axis thrust vector control, subsystem automatic control including failure detection and correction capability (using a PDP-11 computer), operation of critical elements in thermal-vacuum-, zero-gravity-type propellant storage, and data outputs from all subsystem elements. The subsystem elements, functions, unique features, and test setup are described. General features and capabilities of the test-support data system are also presented. The test program culminated in a 1500-h computer-controlled, system-functional demonstration. This included simultaneous operation of two thruster/power conditioner sets. The results of this testing phase satisfied all the program goals.

Masek, T. D.

1973-01-01

124

Low-thrust control of orbital elements  

Science.gov (United States)

This dissertation presents a method for controlling the orbital elements of a spacecraft using continuous low-thrust systems. The method involves the use of a general performance index, which is designed to minimize the difference between the instantaneous orbital elements of a spacecraft and some desired set of orbital elements. Due to the generality of the controller design, the resultant controller can be applied to a wide variety of scenarios about various bodies in space. To minimize the designed performance index, a shooting method and a Sequential Quadratic Programming algorithm are utilized and compared. The primary application of the general controller design in this study is the problem of generating and maintaining low-altitude, polar, Sun-synchronous orbits about the Moon. Such orbits are useful for lunar mapping missions, such as with NASA's Lunar Reconnaissance Orbiter (LRO) mission which began in June of 2009. While Sun-synchronous orbits are known to exist naturally about Earth, lunar Sun-synchronous orbits do not exist naturally and instead require a set of continuous low-thrust control actions for stationkeeping. In this dissertation, it is shown that Sun-synchronous orbits can be maintained for extended periods of time using low out-of-plane thrust levels. The steering profiles necessary for stationkeeping these orbits are shown to follow simple periodic profiles. From a literature search, this is the first known work which has studied the techniques required for maintaining Sun-synchronous orbits about the Moon. In order to demonstrate the effectiveness of the general controller design, it is also applied to two additional astronautical problems of interest. In particular, the controller design is applied to the problem of an orbit transfer between two inclined geosynchronous orbits about Earth and the problem of low-thrust asteroid deflection.

Harl, Nathan Robert

125

Analysis of thrust/torque signature of MOV  

International Nuclear Information System (INIS)

For the evaluation of operability of MOV(Motor Operated Valve), the precision prediction of thrust/torque acting on the valve is important. In this paper, the analytical prediction method of thrust/torque was proposed. The design basis stem thrust calculation typically considers the followings: packing thrust, stem rejection load, design basis differential pressure load. In general, test results show that temperature, pressure, fluid type, and differential pressure, independently and combination, all have an effect on the friction factor. The prediction results of thrust/torque are well agreement with dynamic test results

126

Thrust Vector Control for Nuclear Thermal Rockets  

Science.gov (United States)

Future space missions may use Nuclear Thermal Rocket (NTR) stages for human and cargo missions to Mars and other destinations. The vehicles are likely to require engine thrust vector control (TVC) to maintain desired flight trajectories. This paper explores requirements and concepts for TVC systems for representative NTR missions. Requirements for TVC systems were derived using 6 degree-of-freedom models of NTR vehicles. Various flight scenarios were evaluated to determine vehicle attitude control needs and to determine the applicability of TVC. Outputs from the models yielded key characteristics including engine gimbal angles, gimbal rates and gimbal actuator power. Additional factors such as engine thrust variability and engine thrust alignment errors were examined for impacts to gimbal requirements. Various technologies are surveyed for TVC systems for the NTR applications. A key factor in technology selection is the unique radiation environment present in NTR stages. Other considerations including mission duration and thermal environments influence the selection of optimal TVC technologies. Candidate technologies are compared to see which technologies, or combinations of technologies best fit the requirements for selected NTR missions. Representative TVC systems are proposed and key properties such as mass and power requirements are defined. The outputs from this effort can be used to refine NTR system sizing models, providing higher fidelity definition for TVC systems for future studies.

Ensworth, Clinton B. F.

2013-01-01

127

Axial Halbach Magnetic Bearings  

Science.gov (United States)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

128

Vacuum Thrust Optimised Expansion Deflection Nozzles  

Science.gov (United States)

ED nozzles have long been considered for launch vehicle applications, due to their postulated twin benefits of reduced length and altitude compensating capability. However, the difficulties involved in modelling the inviscid/viscous jet boundaries and associated flow phenomena during wake closure, have prevented the creation of a reliable method for the prediction of the performance characteristics of the type through atmospheric flight. However, if the operating regime of the nozzle is restricted to vacuum conditions (e.g. upper stages, and OTVs, etc), the wake region of the ED nozzle is permanently closed. Under these circumstances, the prediction of the pressure distribution along the viscous/inviscid flow boundary, and the complex interaction of the fluid flows during wake closure, becomes unnecessary. Therefore thrust calculation may be accomplished by conventional techniques, provided reliable methods are available for the prediction of the flow in the throat region (which may be arbitrarily displaced and inclined to the axis of revolution), and estimation of the pressure acting on the base of the central pintle. Prediction of ED nozzle throat flows has been accomplished by the use of CFD techniques, described in a previous paper. The analysis in this paper has been extended to complete nozzles by including a conventional method of characteristics based optimisation routine for the outer shroud contour, and a semi-empirical method for prediction of pintle base pressures. A brief parametric study is presented, outlining the effects of throat configuration (including throat wall radii, and radial displacement and inclination) on the performance of axisymmetric and planar ED nozzles under vacuum conditions. Whilst the method used for base pressure prediction requires several simplifying assumptions which affect the accuracy, results from an ongoing experimental program are reducing this uncertainty. Further as nozzles designed for vacuum operation are likely to have extremely high area ratios to maximise thrust coefficient, the relative magnitude of the pintle base pressure is small compared to the forces generated on the shroud, reducing the sensitivity of overall thrust calculations to errors in base pressure prediction. A comparison of thrust performance of bell and ED nozzles reveals that considerable reductions in length are possible, in the region of 30%. By implication this should result in a significant lowering of system mass. This conclusion is further supported by consideration of the unrealistic worst case scenario, which is the assumption of zero thrust contribution from the pintle. This analysis still produces length savings of over 20% when compared to conventional optimised bell nozzles.

Taylor, N. V.; Hempsell, C. M.

2002-01-01

129

Paleostress analysis of the Osning Thrust, Germany  

Science.gov (United States)

The Osning Thrust is a 100 km-scale NW-SE fault separating the Lower Saxony Basin to the NE from the Münsterland Basin to the SE. The fault has accommodated a polyphase deformation that started at least when it acted as one of the normal border faults of the Jurassic Lower Saxony Basin. Tectonic inversion of the basin in Late Cretaceous-Early Paleocene times led to the development of the SE-vergent Osning Thrust and to folding of rocks. A paleostress analysis was carried out in order to decipher the polyphase kinematics of the Osning Thrust. The fault slip data were collected in the folded Albian to Turonian stratigraphic units of the Münsterland basin, in the SE vicinity of a 20 km-long steep segment of the Osning Thrust. Fault slip data in sufficient amount to perform paleostress inversion were collected in 10 sites among 23 visited outcrops. Abundant minor faults trend sub-parallel to the NW-SE steep segment of the Osning Thrust but, surprisingly, they are dextral (and not reverse) in type. Another major set of E-W striking minor faults is remarkable. It corresponds to conjugate systems of either reverse or normal faults and to oblique- to strike-slip faults in a less extent. The paleostress tensors reveal a ca. N-S compression recorded in 5 locations under which the NW-SE steep faults were dextral and the E-W striking S- and N- dipping faults were reverse. Six stress tensors fit with a ca. N-S extension. They are calculated from E-W striking S- and N- dipping normal to oblique normal faults. The same N-S trend of minimum stress axis is also recorded with NNE-SSW dextral and E-W sinistral faults. We propose that along the studied segment of the Osning Thrust a N-S compressional stress field led to the inversion of the Lower Saxony Basin and that slip along the Osning Thrust was oblique reverse. At two locations, the N-S compressive stress states affected the rock prior to tilting of the beds (herein, due to folding) and at one site, the normal faults of the N-S extension clearly cut across reverse faults of the N-S compression. These two observations allow to propose a chronology between the reconstructed stress fields. While the N-S compression is presumably linked to the Late Cretaceous-Early Palaeocene inversion of the Lower Saxony Basin, the successive E-W extension is not constrained in age. However, it is known that tensional stresses have largely affected the west European platform in Oligocene times and this N-S extension revealed by the present study might be related to this tectonic event.

Saintot, Aline; Kozakovski, Anna; Pascal, Christophe

2013-04-01

130

Thrust evaluation of magneto plasma sail that obtains an electromagnetic thrust from the solar wind  

International Nuclear Information System (INIS)

Magneto Plasma Sail (MPS) is a propulsion system used in space, which generates its force by the interaction between the solar wind and an inflated magnetic field via a plasma injection. The quantitative evaluation of the thrust increment generated by injecting a plasma jet with a ?in less than unity was conducted by three-dimensional hybrid particle-in-cell (PIC) simulations in an ion inertia scale. The injected plasma ?in is 0.02 and the ratio of Larmor radius of injected ion to the representative length of the magnetic field is 0.5 at the injection point. In this situation, the obtained thrust of the MPS is 1.6 mN compared with the 0.2 mN of the thrust obtained by the pure magnetic sail since the induced current region on magnetosphere expanded by the magnetic inflation. (author)

131

Cryogenic Hybrid Magnetic Bearing  

Science.gov (United States)

Cryogenic hybrid magnetic bearing is example of class of magnetic bearings in which permanent magnets and electromagnets used to suspend shafts. Electromagnets provide active control of position of shaft. Bearing operates at temperatures from -320 degrees F (-196 degrees C) to 650 degrees F (343 degrees C); designed for possible use in rocket-engine turbopumps, where effects of cryogenic environment and fluid severely limit lubrication of conventional ball bearings. This and similar bearings also suitable for terrestrial rotating machinery; for example, gas-turbine engines, high-vacuum pumps, canned pumps, precise gimbals that suspend sensors, and pumps that handle corrosive or gritty fluids.

Meeks, Crawford R.; Dirusso, Eliseo; Brown, Gerald V.

1994-01-01

132

Stress, strain, and fault behavior at a thrust ramp: Insights from the Naukluft thrust, Namibia  

Science.gov (United States)

We report observations from a kilometer-scale thrust ramp on the Naukluft thrust, Namibia. The Naukluft thrust is a low angle thrust that was active at subgreenschist facies conditions and accommodated several tens of kilometers of displacement at the base of the Naukluft Nappe Complex in the Pan-African Damara Orogeny. The fault zone is generally planar and a few meters thick, comprising predominantly a dolomite-rich cataclasite. At the ramp, the fault-rock assemblage increases in thickness, and the hanging-wall, which elsewhere is relatively intact, contains a high density network of inclined quartz veins, subvertical dolomite and calcite veins, breccia zones, as well as injectites of cataclastic fault rock emanating from the fault surface. The geometry of the hanging-wall structures indicates local subhorizontal extension. Local tensile stress can be explained by bending in the hanging-wall as it deformed to slide above the ramp structure. High fluid pressures created dynamically during fast slip by decarbonation of carbonate fault rock, and by dewatering of the footwall under an impermeable fault during interseismic periods, led to additional reduction in local effective compressive stresses. In this location, the ramp is more optimally oriented for slip in the inferred regional stress field, and therefore likely to fail before the contiguous thrust flats that are subparallel to the maximum principal stress. As such, the ramp represents the likely location for nucleation of fault slip, which could both trigger dynamic failure of the adjacent thrust faults, and produce hanging-wall extensional structures.

Fagereng, Åke; Smith, Zach; Rowe, Christie D.; Makhubu, Bandile; Sylvester, Fernando Y. G.

2014-01-01

133

Teddy Bear Stories  

DEFF Research Database (Denmark)

This paper presents a semiotic analysis of a key cultural artefact, the teddy bear. After introducing the iconography of the teddy bear, it analyses different kinds of stories to show how teddy bears are endowed with meaning in everyday life: stories from children's books, reminiscenses by adults about their childhood teddy bears, and children's accounts of what they do with teddy bears, both written for school and told 'out of school', The chapter sees teddy bears as artefacts that provide a cultural channeling for the child's need of a transitional object and argues that the meanings of teddy bears have traditionally centred on interpersonal relations within the nuclear family, but have recently been institutionalized and commercialized.

van Leeuwen, Theo; Caldas-Coulthardt, Carmen

2014-01-01

134

Comparison of experimental and predicted performance of 150-millimeter-bore solid and drilled ball bearings to 3 million DN  

Science.gov (United States)

Seven 150-millimeter-bore ball bearings were run under 8900-newton (2000-lbf) thrust load at speeds from 6670 to 20,000 rpm (1 million to 3 million DN). Four of the bearings had conventional solid balls, and three bearings had drilled (cylindrically hollow) balls with 50-percent mass reduction. The bearings were under-race cooled and slot lubricated with a type 2 ester oil at flow rates from 4.35 x 0.001 to 5.94 x 0.001 cubic meter/min (1.15 to 1.57 gal/min). Friction torque and temperature were measured on all bearings. While there was considerable spread in the temperature data, the drilled ball bearings tended to run slightly cooler than the solid ball bearings at higher speeds. No significant difference in torque was noted, however, between the solid and drilled ball bearings. One bearing of each type was rerun at 17,800-newton (4000-lbf) thrust load. The solid ball bearings performed satisfactorily at 3 million DN. However, at about 2 million DN the drilled ball bearing experienced a broken ball, and cracks appeared in other balls as a result of flexure fatigue. Metallurgical examination of the cracked balls indicated a brittle structure in the bore of the drilled balls.

Scibbe, H. W.; Munson, H. E.

1974-01-01

135

Flexible joints for thrust vector control  

Science.gov (United States)

Flexible joints have been used to achieve thrust vector control over a wide range of sizes of nozzles and have been demonstrated successfully in bench tests and static firings, and are operational on two motors. From these many joints the problems of flexible joints have been defined as establishment of the movable nozzle envelope, definition of the actuation power requirements, definition of the mechanical properties of joint materials, adhesive bonding, test methods, and quality control. These data and problem solutions are contained in a large number of reports. Data relating to joint configuration, design requirements, materials selection, joint design, structural analysis, manufacture, and testing are summarized.

Woodberry, R. F. H.

1975-01-01

136

Thrust in e+e--annihilation  

International Nuclear Information System (INIS)

The thrust distribution in e+e--annihilation is analysed in perturbative QCD. Proper account is taken of multiple emission of gluons. Scaling holds for this quantity in the sense that its energy dependence comes only through the change in the QCD effective coupling. It thus provides an ideal means to determine the value of the QCD mass scale ? experimentally. From the data at W=91 GeV by the ALEPH collaboration at LEP, we obtain ? (5)sub(anti Manti S) =230-60+40 MeV. (orig.)

137

The technology of the bearings used in the nuclear power generation system turbine generator units  

International Nuclear Information System (INIS)

A bearing consists of all the stationary part which allow the relative motion in rotation or in translation, of a shaft line. Inside the bearing there is a journal bearing with a metallic anti-friction coating (the babbitt metal). The high power turbine generator unit rotors are supported by smooth transversal journal bearings fed with oil which fills the empty space and runs along the shaft. The technologies used for the bearings and the thrust bearings of the turbine generator units and the various shaft lines of the French CP0/CP1- and CP2/1300 MW-type nuclear power plants are described. The experience feedback is then discussed in terms of the dynamics of the shaft line, i.e. vibrational problems, the influence of the alignment and the babbitt metal incidents. (author)

138

The experimental study on efficiency improvement of turbo machinery supported with magnetic bearings  

International Nuclear Information System (INIS)

To implement a conventional electromagnetic bearing in small turbo machinery, it has problems such as load capacity and size. Therefore, in this paper, these problems are resolved by using a permanent magnet biased electromagnetic bearing as a thrust bearing of small turbo machinery. Because the flux path of the bearing is designed by reluctance path modulation using an electromagnet and a permanent magnet, the bearing improves upon non-linearity, power consumption, size and load capacity of a conventional electromagnetic bearing. Test rotating the shaft over 500,000DN were carried out to verify the performance of the proposed small turbo machinery. In addition, the relationships between mass flow rate and pressure rise were measured as changing the tip clearance to verify the feasibility of efficiency improvement and active surge control and these results were compared with theoretical results

139

Quadratic Programming Thrust Allocation and Management for Dynamic Positioning Ships  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To solve the complex thrust allocation problems of dynamic positioning ship with azimuth thrusters, the quadratic programming thrust allocation and management system was built. The power optimal thrust allocation was formulated as a quadratic programming problem by the linear treatments of inequality constraints and the optimal solution could be found in a finite amount of time. And some influence factors of thruster allocation were separated from algorithms and treated as a superstratum m...

Yushi Wei; Mingyu Fu; Jipeng Ning; Xingyan Sun

2013-01-01

140

Bearing Rigidity and Almost Global Bearing-Only Formation Stabilization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper studies the distributed control of bearing-constrained multi-agent formations using bearing-only measurements. In order to analyze bearing-constrained formations, we first present a bearing rigidity theory that is applicable to arbitrary dimensions. Based on the proposed bearing rigidity theory, we analyze two bearing-only formation control problems. In the first, each agent can measure the relative bearings to their neighbors in a global reference frame, while in...

Zhao, Shiyu; Zelazo, Daniel

2014-01-01

 
 
 
 
141

OMV/VTE variable thrust engine analysis  

Science.gov (United States)

The objective of the present work is to develop a predictive CFD based analytical tool for the Variable Thrust Engine (VTE) in the Orbital Maneuvering Vehicle (OMV). This objective is being accomplished within the framework of the Los Alamos KIVA computer code for chemically reactive flows with sprays. For the OMV application, the main structure of KIVA is to be retained while reformulating many of the phenomenological submodels, enhancing some of the numerics, and adding more features. The analytical model consists of the general conservation equations for two-phase reactive flows and of submodels for turbulence, chemical reactions, and bipropellant sprays. Tailoring this model to the OMV engine brings about the added complexities of combustion and flow processes that occur in a liquid hypergolic propellant rocket chamber. This report exposes the foundation upon which the analytical tool is being constructed and developed. Results from a cursory computational exercise involving the simulation of the flow and combustion processes in a hypothetical N2H4/N204 rocket engine thrust chamber is presented and discussed.

Larosillere, L.; Litchford, R.; Jeng, S. M.

1995-01-01

142

Emergency Control Aircraft System Using Thrust Modulation  

Science.gov (United States)

A digital longitudinal Aircraft Propulsion Control (APC system of a multiengine aircraft is provided by engine thrust modulation in response to comparing an input flightpath angle signal (gamma)c from a pilot thumbwheel. or an ILS system with a sensed flightpath angle y to produce an error signal (gamma)e that is then integrated (with reasonable limits) to generate a drift correction signal to be added to the error signal (gamma)e after first subtracting a lowpass filtered velocity signal Vel(sub f) for phugoid damping. The output error signal is multiplied by a constant to produce an aircraft thrust control signal ATC of suitable amplitude to drive a throttle servo for all engines. each of which includes its own full-authority digital engine control (FADEC) computer. An alternative APC system omits sensed flightpath angle feedback and instead controls the flightpath angle by feedback of the lowpass filtered velocity signal Vel(sub f) which also inherently provides phugoid damping. The feature of drift compensation is retained.

Burken, John J. (Inventor); Burcham, Frank W., Jr. (Inventor)

2000-01-01

143

Bearings: Technology and needs  

Science.gov (United States)

A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

Anderson, W. J.

1982-01-01

144

Kinematic modeling of folding above listric propagating thrusts  

Science.gov (United States)

We describe a kinematic approach to simulate folds above listric propagating thrusts. The model is based on a pre-defined circular thrust geometry with a maximum central angle beyond which the thrust is planar, inclined shear above the circular thrust, and trishear in front of the thrust. Provided the trajectory of thrust propagation is established, the model can be run forward and backwards. We use this last feature to implement a global simulated annealing, inverse modeling strategy. This inverse modeling strategy is applied to synthetic folds as well as two real examples in offshore Venezuela and the Niger Delta toe-thrust system. These three examples illustrate the benefits of the algorithm, particularly in predicting the possible range of models that can fit the structures. Thrust geometry, depth to detachment level, and backlimb geometry have high impact in model parameters such as backlimb shear angle and fault slip; while forelimb geometry is critical to constrain parameters such as fault propagation to fault slip ratio and trishear angle. Steep to overturned beds in forelimb areas are often not imaged by seismic, so in the absence of additional well data, considering all possible thrust-fold geometries is critical for the modeling and whatever prediction (e.g. hydrocarbon trap integrity) is made from it.

Cardozo, Nestor; Brandenburg, J. P.

2014-03-01

145

Thrust vector control by liquid injection for solid propellant rockets  

Science.gov (United States)

In liquid injection thrust vector control, a rocket jet is deflected for steering purposed by injecting a liquid into the nozzle exit cone. The liquid is preferably both dense and reactive so that it adds mass and energy and generates shocks in the supersonic exhaust. This behavior increases thrust in the affected part of the jet producing not only a side force for steering but an addition to axial thrust. This paper presents a summary of current liquid injection thrust vector control technology, including procedures for design, development, analysis, testing and evaluation, together with supporting data and references.

Zeamer, R. J.

1975-01-01

146

Unsteady thrust measurement techniques for pulse detonation engines  

Science.gov (United States)

Thrust is a critical performance parameter and its correct determination is necessary to characterize an engine. Many conventional thrust measurement techniques prevail. However, further developments are required for correct measurement of thrust in the case of a pulse detonation engine (PDE), since the entire thrust generation process is intermittent. The significant effect of system dynamics in the form of inertial forces, stress wave propagation and reflections initiated in the structure due to detonations and pulse-to-pulse interaction in a fast operating PDE further complicate the thrust measurement process. These complications call for a further, detailed study of the unsteady thrust characteristics. A general approach was first developed to recover actual thrust from the measured thrust generated by the PDE. The developed approach consisted of two steps. The first step incorporated a deconvolution procedure using a pre-established system transfer function and measured input to reconstruct the output yielding the deconvolved thrust. The second step accounted for inertial forces through an acceleration compensation procedure. These two steps allowed the actual thrust to be determined. A small scale PDE operating at 10 and 20 Hz with varied filling fractions and mixture equivalence ratios was used for the experimental application of the general approach. The analytical study of gas dynamics in the PDE while in operation and the measured pressure histories at the exit of the engine allowed the generated thrust during a cycle to be determined semi-empirically. The thrust values determined semi-empirically were compared against the experimental results. A dynamical model of the PDE was created for the study of the unsteady thrust characteristics using finite element analysis. The results from finite element analysis were compared against semi-empirical and experimental results. In addition, finite element analysis also facilitated to numerically determine the unsteady thrust generated by the PDE at higher operating frequencies of 50 and 100 Hz. The actual thrust estimated experimentally, semi-empirically and numerically were expressed in the form of specific impulse for comparison. The results obtained via semi-empirical method and finite element analysis were found to be in good agreement with each other. However, the results obtained experimentally were slightly lower than the other two. Finally, the results obtained in this research work were also compared against the findings reported in literature. The comparison gave satisfying results. The developed general approach used to recover actual thrust generated by a PDE was also used to recover actual aerodynamic drag experienced by a blunt nose cone model in a nominal Mach 8-9 flow. The limited validation against modified Newtonian theory was provided as the results obtained after applying the developed approach matched the predicted values.

Joshi, Dibesh Dhoj

147

Bear Spray Safety Program  

Science.gov (United States)

A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.

Blome, C.D.; Kuzniar, R.L.

2009-01-01

148

The Incredible Water Bear  

Science.gov (United States)

This image-rich Micscape Magazine article explores how water bears can be found almost everywhere yet are still unknown to almost everybody, why there are relatively few light microscope photographs of water bears in the literature and on the Web, and how light microscopy can outperform scanning electron microscopy when viewing these animals. It includes a list of historical references, early sketches, and colorful images of water bears, also known as tardigrades.

Mach, Martin; Magazine, Micscape

149

Radial thrust of low-head cross-flow water turbine; Teirakusa kanryu suisha no radial thrust  

Energy Technology Data Exchange (ETDEWEB)

In a cross-flow water turbine, water crosses the runner vertically into the shaft. Therefore, large radial thrust acts on the runner in spite of the small output. The runner blades of the cross-flow turbine are thin, and repeated stress of this thrust acts on the shaft and the blades. It is important in the turbine design to estimate the value of radial thrust accurately. In this work, the quantity and the direction of radial thrust worked on the runner are measured experimentally using a non contact displacement probe, when the effective head, the rotating speed, and the guide vane opening are changed. Moreover, the calculating method of radial thrust at the point of maximum efficiency is proposed. It is confirmed to be able to forecast the radial thrust, by comparison with the experimental result. 4 refs., 14 figs.

Kitahora, T.; Kurokawa, J. [Yokohama National Univ., Yokohama (Japan). Faculty of Engineering; Toyokura, T. [Shonan Institute of Technology, Kanagawa (Japan)

1995-08-25

150

Bearing restoration by grinding  

Science.gov (United States)

A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.

Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.

1976-01-01

151

Fault interaction along the Central Andean thrust front: The Las Peñas thrust, Cerro Salinas thrust and the Montecito Anticline  

Science.gov (United States)

The region in west-central Argentina between the thin-skinned Precordillera and the thick-skinned Sierras Pampeanas structural domain is among the most active zones of thrust tectonics in the world. We quantify the rates of deformation on the east-vergent Las Peñas thrust (LPT), and the west-vergent Cerro Salinas thrust (CST). The Montecito anticline (MA) is located at their intersection. We mapped three key locations, collected stratigraphic logs from the MA, dated three ashes using U-Pb in zircon and dated 10 terraces using cosmogenic Be-10 depth profiles. Five terrace levels are present where the Rio Las Peñas crosses the LPT, up to 45 m above the modern river. Cosmogenic dating of the uppermost terrace (T1) yields and age of 123.8 +26.5/-12.3 ka. A reconstruction of this surface using a blind thrust rupture scenario indicates 73 +/- 7 m horizontal shortening and 34 +/- 3 m vertical displacement. Shortening across the structure is therefore 0.59 +0.10/-0.13 mm/yr with a vertical uplift rate of 0.27 +0.05/-0.06 mm/a. Previous work indicates higher rates to the south on the order of 2 mm/yr (Schmidt et al., 2011). Lower terraces give ages of 38.0 +11/-6.2 ka (T2) and 1.5 +5.0/-0.6 ka (T4). Three terrace levels are preserved near the center of the CST. The middle surface (T2) is folded across the axis of the structure and yields an age of 112.5 +33/-14.4 ka. Given 22.9 m surface uplift, this indicates a vertical uplift rate of 0.20 +0.05/-0.06 mm/yr, similar to the rate on the LPT. The upper terrace (T1) yields a younger age (97.1 +29.8/-12.4 ka); the T1 and T2 ages overlap within uncertainty, indicating rapid river incision at the time of their formation. An intercalated ash within the Neogene strata gives an age of 16.2 +/- 0.2. Previous work indicates long-term shortening rates of 0.8 mm/yr (Verges et al., 2007) and that the CST initiated after 8.5 Ma. The lowermost unit exposed in the MA is the Los Pozos Fm., with no indication of syn-depositional deformation. An intercalated ash from the top of this formation yields an age of 5.76 +/- 0.09 Ma. Internal unconformities are present within the overlying transitional unit and the Mogotes Fm., indicating deformation post-dates 5.8 Ma in the MA. An ash within the Mogotes Fm. is 1.52 +/- 0.06 Ma. Slip is modeled as 3.5 km reverse slip across an east-dipping dislocation with a 45 degree dip. This suggests horizontal shortening and vertical uplift of 0.42 mm/yr since the onset of deformation. Uplifted terraces near the center of the MA are 4.7 +0.8/-0.3 ka (T2) and 1.9 +3.4/-1.9 ka (T3), 6 and 4.6 m above the modern river, respectively. This suggests recent vertical uplift or incision rates of 1.3-2.4 mm/yr. These data suggest that deformation in the MA is comparable to that at the LPT and CST. Deformation in the MA could be accelerating, but alternatively, river incision could be accelerating due to climate change.

Schoenbohm, L. M.; Costa, C. H.; Brooks, B. A.; Bohon, W.; Gardini, C.; Cisneros, H.

2013-12-01

152

Development of a large support surface for an air-bearing type zero-gravity simulator  

Science.gov (United States)

The methods used in producing a large, flat surface to serve as the supporting surface for an air-bearing type zero-gravity simulator using low clearance, thrust-pad type air bearings are described. Major problems encountered in the use of self-leveled epoxy coatings in this surface are discussed and techniques are recommended which proved effective in overcoming these problems. Performance requirements of the zero-gravity simulator vehicle which were pertinent to the specification of the air-bearing support surface are also discussed.

Glover, K. E.

1976-01-01

153

A six degree-of-freedom magnetic bearing for microgravity vibration isolation  

Science.gov (United States)

A design for a magnetic bearing, proposed as the fine stage of a coarse-fine actuator for microgravity vibration isolation, is presented. The bearing is novel in that it uses a geometry that has just three independent flux path systems. This contrasts the twelve flux path systems (six bidirectional thrust bearings) used in conventional designs. The design results in compactness, light weight, and high performance when compared with the published designs. A control system is proposed to reject disturbances caused by an umbilical connection to the experiment.

Allan, A. Peter; Knospe, Carl R.

1992-05-01

154

Time to reconcile thermal inversion models around thrusts  

Science.gov (United States)

Inversion of metamorphic thermal isograds is commonly observed around mega-thrusts, particularly in close association with major thrusts in collision belts. However, the processes leading to such thermal inversion still constitute an open issue. Various models have already addressed their possible syn-deformational origin during thrusting. However, because they concentrated on specific contexts and processes, none of these models has achieved a general consensus. Hence, in order to reconcile these different models of syn-deformational thermal inversion, it becomes crucial to find a way allowing to determine the key process controlling the thermal evolution for any thrust zone. Here, we present a dimensional analysis allowing to quantify the relative control of heat diffusion, advection and shear heating on the thermal evolution around thrusts. Our analytical solution invokes parameters that can define any thrust scenario in terms of kinematics, rheological strength and thermal context. Our study focuses mainly on the role of the thrust thickness, h, the shear zone dip angle, ?, the convergence velocity, V, and the effective viscosity, ?, of the shear zone. Our dimensional analysis shows that for typical values applicable to intracontinental thrusts (h = 1-5 km, ? = 15-45°, V = 1-3 cm/yr, ? = 1e19-1e21 Pa.s) heat diffusion as well as advection as well as shear heating can be the dominant process controlling the thermal evolution around thrusts. This result explains the difficulty of finding a unique model for inverted metamorphism. From this, we first validate our dimensional analysis with two-dimensional thermo- kinematical models: for typical values and scenarios applicable to different thrusts, our numerical results show specific thermal evolutions. Then, we apply our first-order coupled analytical-numerical method to natural occurrences of inverted zonation of metamorphic peak temperatures. In this way, our analysis suggests that the inverted metamorphism associated to the Main Central Thrust in the Himalayas, for instance, can be mainly a result of shear heating.

Duprat-Oualid, Sylvia; Yamato, Philippe; Schmalholz, Stefan M.

2014-05-01

155

OTV Bearing Deflection Investigation.  

Science.gov (United States)

The primary goal of the Bearing Deflectometer Investigation was to gain experience in the use of fiber optic displacement probe technology for bearing health monitoring in a liquid hydrogen turbo pump. The work specified in this Task Order was conducted i...

B. L. Reimer, R. T. Diepenbrock, M. G. Millis

1993-01-01

156

Linear kinematic air bearing  

Science.gov (United States)

Bearing provides continuous, smooth movement of the cat's-eye mirror, eliminating wear and deterioration of bearing surface and resulting oscillation effects in servo system. Design features self-aligning configuration; single-point, pivotal pad mounting, having air passage through it; and design of pads that allows for precise control of discharge path of air from pads.

Mayall, S. D.

1974-01-01

157

Initiation system for low thrust motor igniter  

Science.gov (United States)

A test program was carried out to demonstrate an igniter motor initiation system utilizing the bimetallic material Pyrofuze for a solid propellant rocket with controlled low rate of thrust buildup. The program consisted of a series of vacuum ignition tests using a slab burning window motor that simulated the principal initial ballistic parameters of the full scale igniter motor. A Pyrofuze/pyrotechnic igniter system was demonstrated that uses a relatively low electrical current level for initiation and that eliminates the necessity of a pyrotechnic squib, with its accompanying accidental firing hazards and the typical basket of pyrotechnic pellets. The Pyrofuze ignition system does require an initial constraining of the igniter motor nozzle flow, and at the low initiating electrical current level the ignition delay time of this system was found to be quite sensitive to factors affecting local heat generation or loss rates.

Strand, L. D.; Davis, D. P.; Shafer, J. I.

1972-01-01

158

Temporary tongue thrust: failure during orthodontic treatment.  

Science.gov (United States)

This report presents the case of a 25-year-old male patient who sought orthodontic treatment. Oral examination revealed an Angle Class I relation, with a bimaxillary dento-alveolar protrusion, evidence of anterior crowding, and a large overbite and overjet. Radiographic examination revealed a skeletal Class I occlusion. During the distal movement of the canines, occlusal interferences between the canines occurred and the commencement of a tongue thrust was observed. After correction of the applied forces, the canine movement was completed and the habit was no longer detectable. The incident indicates that an unusual oral habit suspiciously occurring during treatment should lead to an immediate reconsideration of the orthodontic treatment strategy. PMID:12502128

Piyapattamin, Thosapol; Soma, Kunimichi; Hisano, Masataka

2002-03-01

159

Transient analysis of blowdown thrust force under PWR LOCA  

International Nuclear Information System (INIS)

The analytical results of blowdown characteristics and thrust forces were compared with the experiments, which were performed as pipe whip and jet discharge tests under the PWR LOCA conditions. The blowdown thrust forces obtained by Navier-Stokes momentum equation about a single-phase, homogeneous and separated two-phase flow, assuming critical pressure at the exit if a critical flow condition was satisfied. The following results are obtained. (1) The node-junction method is useful for both the analyses of the blowdown thrust force and of the water hammer phenomena. (2) The Henry-Fauske model for subcooled critical flow is effective for the analysis of the maximum thrust force under the PWR LOCA conditions. The jet thrust parameter of the analysis and experiment is equal to 1.08. (3) The thrust parameter of saturated blowdown has the same one with the value under pressurized condition when the stagnant pressure is chosen as the saturated one. (4) The dominant terms of the blowdown thrust force in the momentum equation are the pressure and momentum terms except that the acceleration term has large contribution only just after the break. (5) The blowdown thrust force in the analysis greatly depends on the selection of the exit pressure. (author)

160

Electronics Engineering Department Thrust Area report FY'84  

International Nuclear Information System (INIS)

This report describes the work of the Electronics Engineering Department Thrust Areas for FY'84: diagnostics and microelectronic engineering; signal and control engineering; microwave and pulsed power engineering; computer-aided engineering; engineering modeling and simulation; and systems engineering. For each Thrust Area, an overview and a description of the goals and achievements of each project is provided

 
 
 
 
161

Tongue-thrust and the stability of overjet correction.  

Science.gov (United States)

Long-term study of incidence of tongue-thrust from age 4 to 18 finds the dysfunction disappearing in some individuals and appearing in others. A small study of the effect of tongue-thrust therapy on stability of overjet correction suggests a beneficial effect. PMID:3473948

Andrianopoulos, M V; Hanson, M L

1987-04-01

162

Second-order QCD corrections to the thrust distribution  

CERN Document Server

We compute the next-to-next-to-leading order (NNLO) QCD corrections to the thrust distribution in electron-positron annihilation. The corrections turn out to be sizable, enhancing the previously known next-to-leading order prediction by about 15%. Inclusion of the NNLO corrections significantly reduces the theoretical renormalisation scale uncertainty on the prediction of the thrust distribution.

Ridder, A Gehrmann-De; Glover, E W N; Marlen-Heinrich, G

2007-01-01

163

Thrust Measurements for a Pulse Detonation Engine Driven Ejector  

Science.gov (United States)

Results of an experimental effort on pulse detonation driven ejectors aimed at probing different aspects of PDE ejector processes, are presented and discussed. The PDE was operated using ethylene as the fuel and an equimolar oxygen/nitrogen mixture as the oxidizer at an equivalence ratio of one. The thrust measurements for the PDE alone are in excellent agreement with experimental and modeling results reported in the literature and serve as a Baseline for the ejector studies. These thrust measurements were then used as a basis for quantifying thrust augmentation for various PDE/ejector setups using constant diameter ejector tubes and various detonation tube/ejector tube overlap distances. The results show that for the geometries studied here, a maximum thrust augmentation of 24% is achieved. The thrust augmentation results are complemented by shadowgraph imaging of the flowfield in the ejector tube inlet area and high frequency pressure transducer measurements along the length of the ejector tube.

Santoro, Robert J.; Pak, Sibtosh; Shehadeh, R.; Saretto, S. R.; Lee, S.-Y.

2005-01-01

164

Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum  

Science.gov (United States)

This paper describes the test campaigns designed to investigate and demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma. This paper will not address the physics of the quantum vacuum plasma thruster (QVPT), but instead will describe the recent test campaign. In addition, it contains a brief description of the supporting radio frequency (RF) field analysis, lessons learned, and potential applications of the technology to space exploration missions. During the first (Cannae) portion of the campaign, approximately 40 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 935 megahertz and 28 watts. During the subsequent (tapered cavity) portion of the campaign, approximately 91 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 1933 megahertz and 17 watts. Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level. Test campaign results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.

Brady, David A.; White, Harold G.; March, Paul; Lawrence, James T.; Davies, Frank J.

2014-01-01

165

Experimental evaluation of 150-millimeter bore ball bearing to 3 million DN using either solid or drilled balls  

Science.gov (United States)

Seven 150-mm bore ball bearings were run under 8900 Newton (2000 lb) thrust load at speeds from 6670 to 20,000 rpm (1 to 3 million DN). Four of the bearings had conventional solid balls and three bearing had drilled (cylindrically hollow) balls with 50 percent mass reduction. The bearings were under-race cooled and slot-lubricated with Type 2 ester oil at flow rates from 4.35 to 5.80 liters per minute (1.15 to 1.57 gal min). Friction torque and temperatures were measured on all bearings. No significant difference in torque was noted, between the solid and drilled ball bearings. One bearing of each type was rerun at 17,800 Newtons (4000 lb) thrust load. The solid ball bearings performed satisfactorily at 3 million DN. However, at about 2 million DN the drilled ball bearing experienced a broken ball and cracks appeared in two other balls as the result of flexure fatigue. Metallurgical examination of the cracked balls indicated a brittle structure in the bore of the drilled balls.

Scibbe, H. W.; Munson, H. E.

1973-01-01

166

HTS magnetic bearings  

Science.gov (United States)

Radial HTS magnetic bearings (SMB) up to 200 mm size are developed and tested in prototype fast rotating machines to demonstrate the potential to replace conventional bearings. The individual rotational bearing components HTS and PM, their physical interaction and technology is reviewed. Characterisation experiments are conducted to understand the rotor dynamic behaviour. In terms of unbalance and critical speeds the suspended wheels and rotors compare favourably with conventional bearing devices. The rationale of our present bearing technology lies in the assembling of both low-speed magnetic bearings for centrifugal and wafer processing units up to 20,000 rpm as well as a high-speed optical mirror accelerated to rim speed of more than 500 m/s (174,000 rpm) confirming stable low-drag and low energy operation. Two new-type U shaped semicircle HTS bearings coupled each with a 6 W/80 K cryocooler of the Stirling type allow the contact-free operation of a Si wafer carrier in semiconductor wet processes.

Werfel, Frank N.; Flögel-Delor, Uta; Rothfeld, Rolf; Wippich, Dieter; Riedel, Thomas

2002-08-01

167

14 CFR Appendix I to Part 25 - Installation of an Automatic Takeoff Thrust Control System (ATTCS)  

Science.gov (United States)

... Installation of an Automatic Takeoff Thrust Control System (ATTCS) I...Installation of an Automatic Takeoff Thrust Control System (ATTCS) I25...2Definitions. (a) Automatic Takeoff Thrust Control System (ATTCS)....

2010-01-01

168

Thrust Stand Characterization of the NASA Evolutionary Xenon Thruster (NEXT)  

Science.gov (United States)

Direct thrust measurements have been made on the NASA Evolutionary Xenon Thruster (NEXT) ion engine using a standard pendulum style thrust stand constructed specifically for this application. Values have been obtained for the full 40-level throttle table, as well as for a few off-nominal operating conditions. Measurements differ from the nominal NASA throttle table 10 (TT10) values by 3.1 percent at most, while at 30 throttle levels (TLs) the difference is less than 2.0 percent. When measurements are compared to TT10 values that have been corrected using ion beam current density and charge state data obtained at The Aerospace Corporation, they differ by 1.2 percent at most, and by 1.0 percent or less at 37 TLs. Thrust correction factors calculated from direct thrust measurements and from The Aerospace Corporation s plume data agree to within measurement error for all but one TL. Thrust due to cold flow and "discharge only" operation has been measured, and analytical expressions are presented which accurately predict thrust based on thermal thrust generation mechanisms.

Diamant, Kevin D.; Pollard, James E.; Crofton, Mark W.; Patterson, Michael J.; Soulas, George C.

2010-01-01

169

Thrusting Evolution in the Southern Cordillera Oriental (Northern Argentine Andes)  

Science.gov (United States)

Growth strata and unconformities observed in the Neogene-Quaternary synorogenic sediments in the southern Cordillera Oriental of northern Argentine Andes demonstrate that deformation migrated eastwards from the Puna to the Santa Bárbara system, as it is accepted and well documented. However, the newly described growth sequences and unconformities allow us to unravel a more precise timing of the structures and determining the partitioning of the deformation through time into the thrust and fold wedge. Thrust evolution was mostly controlled by the reactivation of earlier extensional faults of the Salta Rift Basin. The geometry of the inverted structures combined with the general forward migration of the deformation, resulted in different thrust sequences. The foreland dipping imbricate stack of the western Cordillera Oriental developed forwards during Middle-Upper Miocene, giving rise to a break back thrusting sequence. Thrust propagation rate increased at Upper Miocene- Lower Pliocene times when the eastern part of the Cordillera Oriental developed. At that time a widespread deformation and synchronous thrusting occurred in the Cordillera Oriental. Afterwards, deformation was mostly restricted in the eastern part of the Cordillera Oriental. Finally, during the Quaternary deformation involved a wider zone, including all the Cordillera Oriental and the Santa Barbara System, leading to the reactivation of previously developed thrusts.

Carrera, N.; Munoz, J.

2007-05-01

170

Artificial halo orbits for low-thrust propulsion spacecraft  

Science.gov (United States)

We consider periodic halo orbits about artificial equilibrium points (AEP) near to the Lagrange points L 1 and L 2 in the circular restricted three body problem, where the third body is a low-thrust propulsion spacecraft in the Sun-Earth system. Although such halo orbits about artificial equilibrium points can be generated using a solar sail, there are points inside L 1 and beyond L 2 where a solar sail cannot be placed, so low-thrust, such as solar electric propulsion, is the only option to generate artificial halo orbits around points inaccessible to a solar sail. Analytical and numerical halo orbits for such low-thrust propulsion systems are obtained by using the Lindstedt Poincaré and differential corrector method respectively. Both the period and minimum amplitude of halo orbits about artificial equilibrium points inside L 1 decreases with an increase in low-thrust acceleration. The halo orbits about artificial equilibrium points beyond L 2 in contrast show an increase in period with an increase in low-thrust acceleration. However, the minimum amplitude first increases and then decreases after the thrust acceleration exceeds 0.415 mm/s2. Using a continuation method, we also find stable artificial halo orbits which can be sustained for long integration times and require a reasonably small low-thrust acceleration 0.0593 mm/s2.

Baig, Shahid; McInnes, Colin R.

2009-08-01

171

PCs and Polar Bears  

Science.gov (United States)

This article looks at the growing energy consumption from consumer electronics and the increases it may cause in greenhouse gases and global warming. The article appears in the free, online magazine Beyond Penguins and Polar Bears.

Fries-Gaither, Jessica

2011-01-01

172

Optimal synchronizability of bearings  

CERN Document Server

Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with asymmetrically weighted couplings. Accordingly, these networks can exhibit optimal synchronization properties through fine tuning of the local interaction strength as a function of node degree [Motter, Zhou, and Kurths, Phys. Rev. E 71, 016116 (2005)]. We show that, in analogy, the synchronizability of bearings can be maximized by counterbalancing the number of contacts and the inertia of their constituting rotor disks through the mass-radius relation, $m\\sim r^{\\alpha}$, with an optimal exponent $\\alpha=\\alpha_{\\times}$ which converges to unity for a large number of rotors. Under this condition, and regardless of the presence of a long-tailed distribution of disk radii composing the mechanical system, the average participation per disk is maximized and the energy dissipation rate is homogeneo...

Araújo, N A M; Baram, R M; Herrmann, H J; Andrade, J S

2013-01-01

173

Powered Descent Guidance with General Thrust-Pointing Constraints  

Science.gov (United States)

The Powered Descent Guidance (PDG) algorithm and software for generating Mars pinpoint or precision landing guidance profiles has been enhanced to incorporate thrust-pointing constraints. Pointing constraints would typically be needed for onboard sensor and navigation systems that have specific field-of-view requirements to generate valid ground proximity and terrain-relative state measurements. The original PDG algorithm was designed to enforce both control and state constraints, including maximum and minimum thrust bounds, avoidance of the ground or descent within a glide slope cone, and maximum speed limits. The thrust-bound and thrust-pointing constraints within PDG are non-convex, which in general requires nonlinear optimization methods to generate solutions. The short duration of Mars powered descent requires guaranteed PDG convergence to a solution within a finite time; however, nonlinear optimization methods have no guarantees of convergence to the global optimal or convergence within finite computation time. A lossless convexification developed for the original PDG algorithm relaxed the non-convex thrust bound constraints. This relaxation was theoretically proven to provide valid and optimal solutions for the original, non-convex problem within a convex framework. As with the thrust bound constraint, a relaxation of the thrust-pointing constraint also provides a lossless convexification that ensures the enhanced relaxed PDG algorithm remains convex and retains validity for the original nonconvex problem. The enhanced PDG algorithm provides guidance profiles for pinpoint and precision landing that minimize fuel usage, minimize landing error to the target, and ensure satisfaction of all position and control constraints, including thrust bounds and now thrust-pointing constraints.

Carson, John M., III; Acikmese, Behcet; Blackmore, Lars

2013-01-01

174

High efficiency thrust vector control allocation  

Science.gov (United States)

The design of control mixing algorithms for launch vehicles with multiple vectoring engines yields competing objectives for which no straightforward solution approach exists. The designer seeks to optimally allocate the effector degrees of freedom such that maneuvering capability is maximized subject to constraints on available control authority. In the present application, such algorithms are generally restricted to linear transformations so as to minimize adverse control-structure interaction and maintain compatibility with industry-standard methods for control gain design and stability analysis. Based on the application of the theory of ellipsoids, a complete, scalable, and extensible framework is developed to effect rapid analysis of launch vehicle capability. Furthermore, a control allocation scheme is proposed that simultaneously balances attainment of the maximum maneuvering capability with rejection of internal loads and performance losses resulting from thrust vectoring in the null region of the admissible controls. This novel approach leverages an optimal parametrization of the weighted least squares generalized inverse and exploits the analytic properties of the constraint geometry so as to enable recovery of more than ninety percent of the theoretical capability while maintaining linearity over the majority of the attainable set.

Orr, Jeb S.

175

Electromechanical actuation for thrust vector control applications  

Science.gov (United States)

The advanced launch system (ALS), is a launch vehicle that is designed to be cost-effective, highly reliable, and operationally efficient with a goal of reducing the cost per pound to orbit. An electromechanical actuation (EMA) system is being developed as an attractive alternative to the hydraulic systems. The controller will integrate 20 kHz resonant link power management and distribution (PMAD) technology and pulse population modulation (PPM) techniques to implement field-oriented vector control (FOVC) of a new advanced induction motor. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a built-in test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance, and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA thrust vector control (TVC) system. The EMA system and work proposed for the future are discussed.

Roth, Mary Ellen

1990-01-01

176

Correlate Life Predictions and Condition Indicators in Helicopter Tail Gearbox Bearings  

Science.gov (United States)

Research to correlate bearing remaining useful life (RUL) predictions with Helicopter Health Usage Monitoring Systems (HUMS) condition indicators (CI) to indicate the damage state of a transmission component has been developed. Condition indicators were monitored and recorded on UH-60M (Black Hawk) tail gearbox output shaft thrust bearings, which had been removed from helicopters and installed in a bearing spall propagation test rig. Condition indicators monitoring the tail gearbox output shaft thrust bearings in UH-60M helicopters were also recorded from an on-board HUMS. The spal-lpropagation data collected in the test rig was used to generate condition indicators for bearing fault detection. A damage progression model was also developed from this data. Determining the RUL of this component in a helicopter requires the CI response to be mapped to the damage state. The data from helicopters and a test rig were analyzed to determine if bearing remaining useful life predictions could be correlated with HUMS condition indicators (CI). Results indicate data fusion analysis techniques can be used to map the CI response to the damage levels.

Dempsey, Paula J.; Bolander, Nathan; Haynes, Chris; Branning, Jeremy; Wade, Daniel R.

2010-01-01

177

Compound Actuator for Linear Piezoelectric Motor having High Thrust Force.  

Science.gov (United States)

In order to excite an effective vibration in the piezoelectric linear actuator we proposed the compound piezoelectric linear actuator for high thrust force based on 'shaking beam'. The compound actuator consists of two shaking beams and is rigidly fastene...

S. Yoon, S. Bordinas, S. Kim, D. K. Lee, S. Nahm

2003-01-01

178

Quadratic Programming Thrust Allocation and Management for Dynamic Positioning Ships  

Directory of Open Access Journals (Sweden)

Full Text Available To solve the complex thrust allocation problems of dynamic positioning ship with azimuth thrusters, the quadratic programming thrust allocation and management system was built. The power optimal thrust allocation was formulated as a quadratic programming problem by the linear treatments of inequality constraints and the optimal solution could be found in a finite amount of time. And some influence factors of thruster allocation were separated from algorithms and treated as a superstratum management module. In this system, online adjustment of input constraints and singularity avoidance could be realized, and the reliability and adaptability of thrust allocation were improved consequently. Finally, the validity and excellent performance of this method was proved by the simulation.

Yushi Wei

2013-01-01

179

Rapid prototype fabrication processes for high-performance thrust cells  

Science.gov (United States)

The Thrust Cell Technologies Program (Air Force Phillips Laboratory Contract No. F04611-92-C-0050) is currently being performed by Rocketdyne to demonstrate advanced materials and fabrication technologies which can be utilized to produce low-cost, high-performance thrust cells for launch and space transportation rocket engines. Under Phase 2 of the Thrust Cell Technologies Program (TCTP), rapid prototyping and investment casting techniques are being employed to fabricate a 12,000-lbf thrust class combustion chamber for delivery and hot-fire testing at Phillips Lab. The integrated process of investment casting directly from rapid prototype patterns dramatically reduces design-to-delivery cycle time, and greatly enhances design flexibility over conventionally processed cast or machined parts.

Hunt, K.; Chwiedor, T.; Diab, J.; Williams, R.

1994-01-01

180

Application of in-flight thrust determination uncertainty  

Science.gov (United States)

A numerical example is given of a previously proposed methodology for the evaluation of in-flight thrust measurement uncertainty, using data extracted from a performance report comparing two different missile prototypes under a variety of flight conditions. Attention is given to the data for the AGM-68B Air Launched Cruise Missile, which is powered by the F107 dual-spool, mixed flow turbofan engine. Assessments are made of the definition of the measurement process, instrumentation error estimation, the propagation of errors to thrust calculation, mathematical model errors, the in-flight thrust error component, and correction to standard conditions. It is concluded that in-flight thrust measurement uncertainty limits can be evaluated from measurement system error analysis results and test data for the missile evaluation process presently described.

Adams, G. R.; Thompson, J. W., Jr.; Abernethy, R. B.; Biesiadny, T.; Havey, C. T.; Steurer, J. W.; Ascough, J. C.; Williams, D. D.

1983-01-01

 
 
 
 
181

An Assessment of Gas Foil Bearing Scalability and the Potential Benefits to Civilian Turbofan Engines  

Science.gov (United States)

Over the past several years the term oil-free turbomachinery has been used to describe a rotor support system for high speed turbomachinery that does not require oil for lubrication, damping, or cooling. The foundation technology for oil-free turbomachinery is the compliant foil bearing. This technology can replace the conventional rolling element bearings found in current engines. Two major benefits are realized with this technology. The primary benefit is the elimination of the oil lubrication system, accessory gearbox, tower shaft, and one turbine frame. These components account for 8 to 13 percent of the turbofan engine weight. The second benefit that compliant foil bearings offer to turbofan engines is the capability to operate at higher rotational speeds and shaft diameters. While traditional rolling element bearings have diminished life, reliability, and load capacity with increasing speeds, the foil bearing has a load capacity proportional to speed. The traditional applications for foil bearings have been in small, lightweight machines. However, recent advancements in the design and manufacturing of foil bearings have increased their potential size. An analysis, grounded in experimentally proven operation, is performed to assess the scalability of the modern foil bearing. This analysis was coupled to the requirements of civilian turbofan engines. The application of the foil bearing to larger, high bypass ratio engines nominally at the 120 kN (approx.25000 lb) thrust class has been examined. The application of this advanced technology to this system was found to reduce mission fuel burn by 3.05 percent.

Bruckner, Robert J.

2010-01-01

182

Correlating the Ultrasonic Thrust Force with Acoustic Streaming Velocity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The UltraSonic Thruster (UST) is an actuator which employs a piezoelectric transducer to generate a highly directive ultrasonic wave so as to produce bulk fluid movement. This streaming phenomenon can be utilized underwater for thrusting or maneuvering purposes in marine applications, and particularly at very small scale. We make a new connection between fluid flow and forces, establishing a specific formula for estimating overall thrust from the velocity field. Using Par...

Tan, Alfred C. H.; Hover, Franz S.

2009-01-01

183

Fracturing stages in foreland fold and thrust belts  

Science.gov (United States)

Many of the most prolific hydrocarbon systems of the world are hosted in foreland fold and thrust belts, where oil migration is frequently ensured by the sub-seismic fracture network and oil accumulation occurs in km-scale anticlines associated with major thrust-faults. The existence of this well known hydrocarbon play, were oil fields development requires reconstructing the deformation pattern at depth, is one of the reasons that have promoted an impressive number of meso-structural studies in foreland fold and thrust belts and in the adjacent foreland basins since the late 60's. These works point out that thrust-related anticlines are characterised by almost unique deformation patterns out of which a common deformation pathway can be identified. In particular, in most thrust belts developing above subducting forelands, five stages of deformation can be recorded by meso-structures affecting pre- and syn-kinematic sedimentary rocks. These stages are: (i) foreland flexuring, taking place in the peripheral bulge and in the outermost sectors of the foredeep; (ii) along-strike stretching, occurring in the foredeep; (iii) layer-parallel shortening, which may occur both in the innermost sectors of the foredeep and in the thrust-and fold belt during the first stages of fold growth (pre to early-folding); (iv) syn-folding sensu-stricto fracturing, occurring during the growth of thrust-related anticlines; (v) unloading-related fracturing, which affects mostly mountain front anticlines during their later exhumation stage. In this work we provide a review of the typical meso-structural assemblages occurring during the above mentioned deformation stages, with the purpose of placing constraints to stress and strain fields evolution before and during thrusting, and consider the behaviour of each developed meso-structural assemblage during the subsequent deformation stages.

Tavani, Stefano; Storti, Fabrizio; Lacombe, Olivier; Corradetti, Amerigo; Muñoz, Josep; Mazzoli, Stefano

2014-05-01

184

Exploring fold and thrust belts in Google Earth  

Science.gov (United States)

Google Earth enhances traditional geologic maps by allowing the viewer to explore three-dimensional map patterns and the interaction between structure and topography in dictating those map patterns. This activity overlays 4, 7.5' USGS quadrangles on Google Earth terrain and imagery data and encourages students to investigate common features of fold-and-thrust belts. Keywords: Google Earth, fold-and-thrust belt, visualization

Loveless, Jack

185

Lower extremity thrust and non-thrust joint mobilization for patellofemoral pain syndrome: a case report.  

Science.gov (United States)

A 40-year old female presented to physical therapy with a one-year history of insidious right anteromedial and anterolateral knee pain. Additionally, the patient had a history of multiple lateral ankle sprains bilaterally, the last sprain occurring on the right ankle 1 year prior to the onset of knee pain. The patient was evaluated and given a physical therapy diagnosis of patellofemoral pain syndrome (PFPS), with associated talocrural and tibiofemoral joint hypomobility limiting ankle dorsiflexion and knee extension, respectively. Treatment included a high-velocity low amplitude thrust manipulation to the talocrural joint, which helped restore normal ankle dorsiflexion range of motion. The patient also received tibiofemoral joint non-thrust manual therapy to regain normal knee extension mobility prior to implementing further functional progression exercises to her home program (HEP). This case report highlights the importance of a detailed evaluation of knee and ankle joint mobility in patients presenting with anterior knee pain. Further, manual physical therapy to the lower extremity was found to be successful in restoring normal movement patterns and pain-free function in a patient with chronic anterior knee pain. PMID:24976753

Simpson, Brad G; Simon, Corey B

2014-05-01

186

A double pendulum plasma thrust balance and thrust measurement at a tandem mirror exhaust  

International Nuclear Information System (INIS)

For the purpose of measuring the plasma momentum flux in a plasma system, a highly sensitive and precision balance has been developed. It can measure a force, an impulse, or thrust as low as 0.1 mN free of mechanical noise, electrical and magnetic pickups. The double pendulum system consists of two parallel conducting plates. One or both of the plates can be suspended by needles. The needle suspended plate (or plates) can swing freely with negligible friction because of the sharp points of the needles. When one of the plates is impacted by an impulse it will swing relatively to the fixed plate or other movable plate. The capacitance between the plates changes as a result of such a motion. The change of capacitance as a function of time is recorded as an oscillating voltage signal. The amplitude of such a voltage signal is proportional to the impacting force or impulse. The proportional factor can be calibrated. The forces can thus be read out from the recorded value of the voltage. The equation of motion for the pendulum system has been solved analytically. The circuit equation for the electronic measurement system has been formulated and solved numerically. Using this balance the thrust at the exhaust of a Tandem Mirror plasma thruster has been measured. The analytical solution of the overall characteristics agrees greatly with the measurement. copyright 1995 American Institute of Physics

187

A double pendulum plasma thrust balance and thrust measurement at a tandem mirror exhaust  

Science.gov (United States)

For the purpose of measuring the plasma momentum flux in a plasma system, a highly sensitive and precision balance has been developed. It can measure a force, an impulse, or thrust as low as 0.1 mN free of mechanical noise, electrical and magnetic pickups. The double pendulum system consists of two parallel conducting plates. One or both of the plates can be suspended by needles. The needle suspended plate (or plates) can swing freely with negligible friction because of the sharp points of the needles. When one of the plates is impacted by an impulse it will swing relatively to the fixed plate or other movable plate. The capacitance between the plates changes as a result of such a motion. The change of capacitance as a function of time is recorded as an oscillating voltage signal. The amplitude of such a voltage signal is proportional to the impacting force or impulse. The proportional factor can be calibrated. The forces can thus be read out from the recorded value of the voltage. The equation of motion for the pendulum system has been solved analytically. The circuit equation for the electronic measurement system has been formulated and solved numerically. Using this balance the thrust at the exhaust of a Tandem Mirror plasma thruster has been measured. The analytical solution of the overall characteristics agrees greatly with the measurement.

Yang, T. F.; Liu, Ping; Chang-Díaz, F. R.; Lander, Harvey; Childs, R. A.; Becker, H. D.; Fairfax, S. A.

1995-09-01

188

Caledonian shortening by combined folding and thrusting in the immediate footwall of the Caledonian sole thrust: The example of the Repparfjord Tectonic Window, northern Norway.  

Science.gov (United States)

The Repparfjord Tectonic Window (RTW) is a window through the Caledonian nappes in northern Norway that exposes a package of greenschist facies metasedimentary and metavolcanic rocks of Paleoproterozoic age. These were deformed and metamorphosed during the Svecofennian orogeny producing km-wavelength upright NE-SW folds. Pervasive effects of a later Caledonian overprint, caused by the emplacement of the Kalak Nappe Complex during the Silurian, are limited and confined to the northwestern edge of the window, where NW-SE-shortening caused the development of a compressional imbricate stack. Individual imbricates exploit preexisting, progressively tightening upright to overturned folds and are bound by generally very steep to sub-vertical discrete faults. One of these structures, the Skinnfjellet Fault Zone (SFZ), truncates the large doloarenite-hosted Nussir Cu deposit and has a present-day orientation that makes reverse displacement mechanically difficult. This study aims at a better understanding of the mechanical and temporal evolution of these steep thrusts. The SFZ strikes roughly NS, is sub-vertical and bears dip-slip lineations. It separates greenstones in the west from arcosic sandstones, conglomerates and the Nussir Cu deposit in the east. Kinematic indicators give east block up. Faulting occurred mostly under brittle conditions producing an approximately eight meter thick damage zone and a 40 cm thick fault gouge core. A second prominent fault is the Nussirjavrri Fault Zone (NFZ). The main fault plane dips moderately toward the NNE, bears a NW plunging lineation and a number of kinematic indicators indicate top-to-the-SSE thrusting. The fault trace is mappable for c. one km, but high-resolution geophysics indicates an ENE-WSW continuation. Mapping shows that the fault zone is folded openly with a fold axis trending NNE/SSW, consistent with the geometry of a subregional folding phase of inferred Caledonian age. The fault affects greenstones, graphitic slates and dolomites. The mylonitic thrust core thickness varies from 10 to 40 cm and is composed by alternating dark and light bands of chlorite, muscovite and graphite, together with quartz and carbonates. Interspersed within the foliation are interstitial euhedral pyrite and cm to dm scale dolomite clasts. Dolomite decarbonation is locally observed. Synkinematic quartz veins occur subparallel to the tectonic foliation. Quartz is dynamically recrystallized by SGRR and has an average grain size of c. 35µm. Thin sections show two distinct and strong LPO's. One is preserved within the core grains whereas the other is found within arrays of the recrystallized subgrains, whose distribution appears to be controlled by healed brittle fractures. Mapping indicates that the NFZ is cut by the SFZ and its overall transport direction to the SSE, in addition to its structural location at the front of the imbricate, strengthen its interpretation as a Caledonian structure (also consistent with dated and similarly oriented faults from the RTW). We suggest that the SFZ formed as an antithetic back thrust within the Caledonian imbricate stack, possibly exploiting the limbs of a preexisting large-scale antiform. During Caledonian shortening this Paleoproterozoic megafold was tightened, leading to a progressive steepening of the fold limbs and of the SFZ, while NFZ was progressively folded around the fold hinge.

Jørgen Kjøll, Hans; Torgersen, Espen; Viola, Giulio

2014-05-01

189

Tribology of alternative bearings.  

Science.gov (United States)

The tribological performance and biological activity of the wear debris produced has been compared for highly cross-linked polyethylene, ceramic-on-ceramic, metal-on-metal, and modified metal bearings in a series of in vitro studies from a single laboratory. The functional lifetime demand of young and active patients is 10-fold greater than the estimated functional lifetime of traditional polyethylene. There is considerable interest in using larger diameter heads in these high demand patients. Highly cross-linked polyethylene show a four-fold reduction in functional biological activity. Ceramic-on-ceramic bearings have the lowest wear rates and least reactive wear debris. The functional biological activity is 20-fold lower than with highly cross-linked polyethylene. Hence, ceramic-on-ceramic bearings address the tribological lifetime demand of highly active patients. Metal-on-metal bearings have substantially lower wear rates than highly cross-linked polyethylene and wear decreases with head diameter. Bedding in wear is also lower with reduced radial clearance. Differential hardness ceramic-on-metal bearings and the application of ceramic-like coatings reduce metal wear and ion levels. PMID:17016223

Fisher, John; Jin, Zhongmin; Tipper, Joanne; Stone, Martin; Ingham, Eileen

2006-12-01

190

Gas Foil Bearing Misalignment and Unbalance Effects  

Science.gov (United States)

The effects of misalignment and unbalance on gas foil bearings are presented. The future of U.S. space exploration includes plans to conduct science missions aboard space vehicles, return humans to the Moon, and place humans on Mars. All of these endeavors are of long duration, and require high amounts of electrical power for propulsion, life support, mission operations, etc. One potential source of electrical power of sufficient magnitude and duration is a nuclear-fission-based system. The system architecture would consist of a nuclear reactor heat source with the resulting thermal energy converted to electrical energy through a dynamic power conversion and heat rejection system. Various types of power conversion systems can be utilized, but the Closed Brayton Cycle (CBC) turboalternator is one of the leading candidates. In the CBC, an inert gas heated by the reactor drives a turboalternator, rejects excess heat to space through a heat exchanger, and returns to the reactor in a closed loop configuration. The use of the CBC for space power and propulsion is described in more detail in the literature (Mason, 2003). In the CBC system just described, the process fluid is a high pressure inert gas such as argon, krypton, or a helium-xenon mixture. Due to the closed loop nature of the system and the associated potential for damage to components in the system, contamination of the working fluid is intolerable. Since a potential source of contamination is the lubricant used in conventional turbomachinery bearings, Gas Foil Bearings (GFB) have high potential for the rotor support system. GFBs are compliant, hydrodynamic journal and thrust bearings that use a gas, such as the CBC working fluid, as their lubricant. Thus, GFBs eliminate the possibility of contamination due to lubricant leaks into the closed loop system. Gas foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Aircraft Air Cycle Machines (ACMs) and ground-based microturbines have demonstrated histories of successful long-term operation using GFBs (Heshmat et al., 2000). Small aircraft propulsion engines, helicopter gas turbines, and high-speed electric motors are potential future applications.

Howard, Samuel A.

2008-01-01

191

Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum  

Science.gov (United States)

This paper describes the eight-day August 2013 test campaign designed to investigate and demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma. This paper will not address the physics of the quantum vacuum plasma thruster, but instead will describe the test integration, test operations, and the results obtained from the test campaign. Approximately 30-50 micro-Newtons of thrust were recorded from an electric propulsion test article consisting primarily of a radio frequency (RF) resonant cavity excited at approximately 935 megahertz. Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure. Several different test configurations were used, including two different test articles as well as a reversal of the test article orientation. In addition, the test article was replaced by an RF load to verify that the force was not being generated by effects not associated with the test article. The two test articles were designed by Cannae LLC of Doylestown, Pennsylvania. The torsion pendulum was designed, built, and operated by Eagleworks Laboratories at the NASA Johnson Space Center of Houston, Texas. Approximately six days of test integration were required, followed by two days of test operations, during which, technical issues were discovered and resolved. Integration of the two test articles and their supporting equipment was performed in an iterative fashion between the test bench and the vacuum chamber. In other words, the test article was tested on the bench, then moved to the chamber, then moved back as needed to resolve issues. Manual frequency control was required throughout the test. Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article). Test data gathered includes torsion pendulum displacement measurements which are used to calculate generated force, still imagery in the visible spectrum to document the physical configuration, still imagery in the infrared spectrum to characterize the thermal environment, and video imagery. Post-test data includes static and animated graphics produced during RF resonant cavity characterization using the COMSOL Multiphysics® software application. Excerpts from all of the above are included and discussed in this paper. Lessons learned from test integration and operations include identification of the need to replace manual control of the resonant cavity target frequency with an automated frequency control capability. Future test plans include the development of an automatic frequency control circuit. Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma. Future test plans include independent verification and validation at other test facilities.

Brady, David; White, Harold G.; March, Paul; Lawrence, James T.; Davies, Frank J.

2014-01-01

192

Analytic partial derivatives for estimating low-thrust parameters.  

Science.gov (United States)

Analytic partial derivatives for estimating orbital low-thrust parameters via differential correction are developed and compared with two different numerical methods. The formulation is independent of the particular thrust model used and is applicable to all physically possible elliptic orbits. The starting point for the development is the set of variational equations of the elliptic orbital elements in the form due to Lagrange. The first time derivatives of the elements are transformed to derivatives with respect to the space variable, true anomaly, and integrated to first order in closed form in a straightforward general perturbations approach, with one exception: particular attention is given to the mean anomaly as influenced by thrust perturbations in the semimajor axis so that the complete first-order effect is included. The partials of the elements are then taken with respect to any given thrust parameter. Two comparisons are made with numerical methods for computing these thrust partials: numerical quotients and numerical integration of the variational equations for thrust.

Cunningham, G. W.

1972-01-01

193

Radial Halbach Magnetic Bearings  

Science.gov (United States)

Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while minimizing it on the opposite side. The advantage of this configuration is that it makes it possible to approach the theoretical maximum force per unit area that could be exerted by a given amount of permanent-magnet material. The configuration is named after physicist Klaus Halbach, who conceived it for use in particle accelerators. Halbach arrays have also been studied for use in magnetic-levitation ("maglev") railroad trains. In a radial Halbach magnetic bearing, the basic Halbach arrangement is modified into a symmetrical arrangement of sector-shaped permanent magnets mounted on the outer cylindrical surface of a drum rotor (see Figure 2). The magnets are oriented to concentrate the magnetic field on their radially outermost surface. The stator coils are mounted in a stator shell surrounding the rotor.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2009-01-01

194

Modular gear bearings  

Science.gov (United States)

A gearing system using modular gear bearing components. Each component is composed of a core, one or more modules attached to the core and two or more fastening modules rigidly attaching the modules to the core. The modules, which are attached to the core, may consist of gears, rollers or gear bearing components. The core orientation affects the orientation of the modules attached to the core. This is achieved via the keying arrangement of the core and the component modules that attach to the core. Such an arrangement will also facilitate the phase tuning of gear modules with respect to the core and other gear modules attached to the core.

Vranish, John M. (Inventor)

2009-01-01

195

Electromechanical actuation for thrust vector control applications  

Science.gov (United States)

At present, actuation systems for the Thrust Vector Control (TVC) for launch vehicles are hydraulic systems. The Advanced Launch System (ALS), a joint initiative between NASA and the Air Force, is a launch vehicle that is designed to be cost effective, highly reliable and operationally efficient with a goal of reducing the cost per pound to orbit. As part of this initiative, an electromechanical actuation system is being developed as an attractive alternative to the hydraulic systems used today. NASA-Lewis is developing and demonstrating an Induction Motor Controller Actuation System with a 40 hp peak rating. The controller will integrate 20 kHz resonant link Power Management and Distribution (PMAD) technology and Pulse Population Modulation (PPM) techniques to implement Field Oriented Vector Control (FOVC) of a new advanced induction motor. Through PPM, multiphase variable frequency, variable voltage waveforms can be synthesized from the 20 kHz source. FOVC shows that varying both the voltage and frequency and their ratio (V/F), permits independent control of both torque and speed while operating at maximum efficiency at any point on the torque-speed curve. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a Built-in Test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA TVC system. The design and fabrication of the motor controller is being done by General Dynamics Space Systems Division. The University of Wisconsin-Madison will assist in the design of the advanced induction motor and in the implementation of the FOVC theory. A 75 hp electronically controlled dynamometer will be used to test the motor controller in all four quadrants of operation using flight type control algorithms. Integrated testing of the controller and actuator will be conducted at a facility yet to be named. The EMA system described above is discussed in detail.

Roth, Mary Ellen

196

Study of superconducting magnetic bearing applicable to the flywheel energy storage system that consist of HTS-bulks and superconducting-coils  

International Nuclear Information System (INIS)

The Railway Technical Research Institute conducted a study to develop a superconducting magnetic bearing applicable to the flywheel energy-storage system for railways. In the first step of the study, the thrust rolling bearing was selected for application, and adopted liquid-nitrogen-cooled HTS-bulk as a rotor, and adopted superconducting coil as a stator for the superconducting magnetic bearing. Load capacity of superconducting magnetic bearing was verified up to 10 kN in the static load test. After that, rotation test of that approximately 5 kN thrust load added was performed with maximum rotation of 3000rpm. In the results of bearing rotation test, it was confirmed that position in levitation is able to maintain with stability during the rotation. Heat transfer properties by radiation in vacuum and conductivity by tenuous gas were basically studied by experiment by the reason of confirmation of rotor cooling method. The experimental result demonstrates that the optimal gas pressure is able to obtain without generating windage drag. In the second stage of the development, thrust load capacity of the bearing will be improved aiming at the achievement of the energy capacity of a practical scale. In the static load test of the new superconducting magnetic bearing, stable 20kN-levitation force was obtained.

197

Rotordynamics of Automotive Turbochargers Linear and Nonlinear Rotordynamics – Bearing Design – Rotor Balancing  

CERN Document Server

This book deals with rotordynamics of automotive turbochargers while encompassing the analysis of the dynamics of rotating machines at very high rotor speeds of 300,000 rpm and above. This interdisciplinary field involves 1. thermodynamics and turbo-matching knowledge to compute working conditions of turbochargers, 2. fluid and bearing dynamics to calculate various operating thrust loads and to design the rotating floating ring bearings (two-oil-film bearings), and 3. tribology to improve the rotor stability and to reduce the bearing friction. Mathematical background in modeling and simulation methods is necessary; however, the prerequisites have been kept to a minimum. The book addresses both practitioners working in the field of rotordynamics of automotive turbochargers and graduate students in mechanical engineering.

Nguyen-Schäfer, Hung

2012-01-01

198

Rotordynamics of automotive turbochargers. Linear and nonlinear rotordynamics - Bearing design - Rotor balancing  

Energy Technology Data Exchange (ETDEWEB)

Describes the rotordynamics of automotive turbochargers. Requires only a minimum of mathematical background. Written by an R and D expert from industry. This book deals with rotordynamics of automotive turbochargers while encompassing the analysis of the dynamics of rotating machines at very high rotor speeds of 300,000 rpm and above. This interdisciplinary field involves 1. thermodynamics and turbo-matching knowledge to compute working conditions of turbochargers, 2. fluid and bearing dynamics to calculate various operating thrust loads and to design the rotating floating ring bearings (two-oil-film bearings), and 3. tribology to improve the rotor stability and to reduce the bearing friction. Mathematical background in modeling and simulation methods is necessary; however, the prerequisites have been kept to a minimum. The book addresses both practitioners working in the field of rotordynamics of automotive turbochargers and graduate students in mechanical engineering.

Nguyen-Schaefer, Hung [Bosch Mahle Turbo Systems GmbH und Co. KG, Stuttgart (Germany)

2012-11-01

199

Kinematics of thrust belt development in the external Dinarides, Croatia  

Science.gov (United States)

Many compressional orogenic systems include foreland fold-and-thrust belts, but the relationship between foreland thrust belt kinematics and hinterland crustal thickening, and their dependence on numerous additional factors such as variable accretionary flux, fault friction, surface processes, crustal flow, and pre-existing structure remains controversial. The Dinaric orogen may provide an important opportunity to isolate the relative importance of some of these factors. The external Dinarides are composed primarily of carbonate strata. Their insensitivity to climatic variability may potentially mitigate this important source of uncertainty relative to many other fold and thrust belts. As a first step toward understanding the kinematics of the external Dinarides, we measured present-day crustal velocity along a N13°E profile across the southern Adria microplate and external Dinarides collision zone. We used these data to develop an elastic dislocation model representing contemporary fold and thrust belt kinematics and decollement geometry. At the latitude of the Dalmatian Islands, the model fault plane reaches the surface some 80~km seaward of mapped SW-verging thrusts of Eocene and perhaps Neogene age along the coastal areas, consistent with SW-migrating deformation in an active fold and thrust belt. South of the Dalmatian Islands, however, the modern deformation front appears to be located within about 1~km of the older mapped faults. The largest known earthquakes in the system (~M7) are associated with this southern stationary-width part of the system. Possible explanations for along-strike variability in thrust belt kinematics include along-strike changes in decollement friction, clastic sediment availability and drainage network connectivity, accretionary flux associated with variable Adria carbonate platform thickness, retroarc exhumation, and subaerial distribution of pro-wedge carbonates.

Bennett, R. A.; Hreinsdottir, S.; Buble, G.; Fay, N. P.; Casale, G.; Gendaszek, A.; Cowan, D.; Basic, T.; Bacic, Z.; Marjanovic, M.

2007-12-01

200

Magnetic bearings for cryogenic turbomachines  

Science.gov (United States)

Magnetic bearings offer a number of advantages over gas bearings for the support of rotors in cryogenic turboexpanders and compressors. Their performance is relatively independent of the temperature or pressure of the process gas for a large range of conditions. Active magnetic bearing systems that use capacitive sensors have been developed for high speed compressors for use in cryogenic refrigerators. Here, the development of a magnetic bearing system for a miniature ultra high speed compressor is discussed. The magnetic bearing has demonstrated stability at rotational speeds exceeding 250,000 rpm. This paper describes the important features of the magnetic bearing and presents test results demonstrating its performance characteristics.

Iannello, Victor; Sixsmith, Herbert

1991-01-01

 
 
 
 
201

Bear vs Bee  

Science.gov (United States)

This interactive Java applet is a game that challenges a student to solve problems by using logic and rudimentary engineering skills. The goal in each case is to create a conveyance that gets the bear to the pot of honey, avoiding the bees. The game has 32 stages of increasing complexity.

2012-01-01

202

Development of Flexible Bearing  

Directory of Open Access Journals (Sweden)

Full Text Available Elastomeric base isolation systems are proven to be effective in reducing seismic forces transmitted to buildings. However, due to their cost, the use of these devices is currently limited to large and expensive buildings. A fiber reinforced elastomeric isolator utilizes fiber fabric, such as carbon fiber, glass fibre, and etc. as the reinforcement material instead of solid steel plates. The fibre fabric reinforcement is extensible in tension and has no flexural rigidity. Elastomers normally used in the isolator are natural rubber; neoprene, butyl rubber and nit rile rubber etc. These devices were fabricated by binding alternating layers of rubber and fibre mesh. The fibre mesh is used to increase the vertical stiffness of the bearings while maintaining low lateral stiffness. Characterizing the behaviour of a fibre reinforced bearing “shape factor” of the bearing, Poisson’s ratio of the elastomeric material and flexibility of the reinforcing sheets and investigate the effect of reinforcement flexibility on compressive behaviour of elastomeric bearings with different geometrical and material properties. Bonding with fibre reinforcements can increase the stiffness of elastic layers only when the elastic layer is compressed.

K.S.Mohanraj

2014-06-01

203

Tardigrada (Water Bears)  

Science.gov (United States)

This reference page offers a brief description of Tardigrades, also known as water bears. It includes information about their physical appearance, an explanation of their name, likely habitats, internal organs and other distinguishing features, and a few images. A diagram of a common tardigrade, Macrobiotus macronyx, is also provided via an internal link.

Micrographia

204

Magnetically leviated superconducting bearing  

Science.gov (United States)

A magnetically levitated superconducting bearing includes a magnet (2) mounted on a shaft (12) that is rotatable around an axis of rotation and a Type II superconductor (6) supported on a stator (14) in proximity to the magnet (2). The superconductor (6) is positioned so that when it is cooled to its superconducting state in the presence of a magnetic field, it interacts with the magnet (2) to produce an attractive force that levitates the magnet (2) and supports a load on the shaft (12). The interaction between the superconductor (6) and magnet(2) also produces surface screening currents (8) that generate a repulsive force perpendicular to the load. The bearing also has means for maintaining the superconductor at a temperature below its critical temperature (16, 18). The bearing could also be constructed so the magnet (2) is supported on the stator (14) and the superconductor (6) is mounted on the shaft (12). The bearing can be operated by cooling the superconductor (6) to its superconducting state in the presence of a magnetic field.

Weinberger, Bernard R. (Avon, CT); Lynds, Jr., Lahmer (Glastonbury, CT)

1993-01-01

205

From thrusting to transpressional tectonics in the Aghdarband Basin (NE Iran): evidence for Cimmerian oblique convergence  

Science.gov (United States)

The Aghdarband Basin, consisting of a strongly deformed arc-related Triassic marine succession, is a key-area for the study of the Cimmerian events, as it is unconformably covered by mid-Jurassic gently folded sediments entirely sealing the Cimmerian compressive structures. The basin developed during part of the Triassic in a highly mobile tectonic context suggested by abrupt facies variations and local unconformities. In addition, syn-sedimentary tectonic activity is testified by the occurrence of carbonate olistholiths in the deepest parts of the basin. The marine succession, spanning from Olenekian to lowermost Carnian, shows at the base continental conglomerates andsandstones, as well as basaltic lava flows, possibly of Early Triassic age. They are followed by the shallow water Sefid Kuh Limestone, in which an intraformational unconformity has been now identified. This unit is locally covered by deep-water limestones of the Nazarkardeh Fm. which interfinger with slope facies of the Sefid Kuh Limestone. The volcaniclastic sandstone layers of the Sina Fm follow up-section with a deep unconformity, marked in several places by deep erosion and tilting of the underlying units. The Sina Fm. is in turn unconformably covered by the coal bearing shales of the Miankhui Fm., with a Norian-Rhaetian age testified by plant megafossils, marking the end of marine sedimentation and of volcanic-arc activity. The Triassic units are overthrusted to the south by Upper Palaeozoic siliciclastic successions showing in some cases a LG metamorphic imprint. They largely include the Qara Geithan Fm. consisting of granitic rocks, acidic to basic volcanics, and locally also large blocks of Permian bioclastic limestones derived from the erosion of the Palaeotethys accretionary wedge, exposed south of Aghdarband. The whole succession of the Aghdarband Basin, including the unconformable Miankhui Fm., is deeply involved in a north-verging thrust stack which interacts in the northern part of the area with an important strike-slip shear zone. Several tectonic units have been recognized within the Triassic succession, causing repetitions of the whole stratigraphic succession. Two main thrust sheets are exposed in the southern part of the basin under the Upper Palaeozoic thrust stack. Thrust faults and folds consistently show a N-directed tectonic transport, suggested by dip-slip motion along S-dipping reverse faults and axial plane geometry. Deformation occurred at shallow levels taking to the formation of cataclastic shear zones and to disjunctive and pencil cleavage in the shale layers of the succession. The thrust sheets comprise the Miankhui Fm. which shows a thick basal coal layer (up to 10 m) deeply excavated at the Aghdarband Mine. Nice examples of coal-related tectonics are exposed in open pits and tunnels of the mine. Intensive deformation of the coal, forming complex shear zones with s-c bands, causes the décollement of the Miankhui beds which show intensive tectonic thickening and repetitions mainly caused by polyphase thrust imbrications and disharmonic folding. The northernmost part of the Triassic basin shows a very complex setting, with traspressional structures given by vertical strike-slip faults and closed to tight folds with steeply plunging axes. According to our new data, up to four tectonic slices can be distinguished in this complex area. This structural zone is directly bounded to the north by severely deformed LG metamorphic rocks resulting from a volcaniclastic succession with Devonian and Carboniferous marble layers. Systematic asymmetry of major and parasitic folds, as well as rotation and torsion of axial surfaces indicate a general left-lateral transpressional regime, whereas kinematic indicators along the main fault planes show both left- and right-lateral motions. According to our relative chronology, dextral movements follow in time the sinistral ones reactivating previous Cimmerian structures and displacing also the surrounding Jurassic to Neogene succession of Kopeh Dagh in relatively recent times. Fold analyses along

Zanchi, Andrea; Balini, Marco; Ghassemi, Mohammad Reza; Zanchetta, Stefano

2010-05-01

206

Development of the Himalayan frontal thrust zone: Salt Range, Pakistan  

Science.gov (United States)

The Salt Range is the active frontal thrust zone of the Himalaya in Pakistan. Seismic reflection data show that a 1 km offset of the basement acted as a buttress that caused the central Salt Range-Potwar Plateau thrust sheet to ramp to the surface, exposing Mesozoic and Paleozoic strata. The frontal part of the thrust sheet was folded passively as it overrode the subthrust surface on a ductile layer of Eocambrian salt. Lack of internal deformation of the rear part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer. Early to middle Pliocene (˜4.5 Ma) conglomerate deposition in the southern Potwar Plateau, previously interpreted in terms of compressional deformation, may instead document uplift related to basement normal faulting. Stratigraphic evidence, paleomagnetic dating of unconformities, and sediment-accumulation rates suggest that the thrust sheet began to override the basement offset from 2.1 to 1.6 Ma. Cross-section balancing demonstrates at least 20 to 23 km of shortening across the ramp. The rate of Himalayan convergence that can be attributed to underthrusting of Indian basement beneath sediments in the Pakistan foreland is therefore at least 9-14 mm/yr, about 20%-35% of the total plate convergence rate.

Baker, Dan M.; Lillie, Robert J.; Yeats, Robert S.; Johnson, Gary D.; Yousuf, Mohammad; Zamin, Agha Sher Hamid

1988-01-01

207

Development of the Himalayan frontal thrust zone: Salt Range, Pakistan  

Energy Technology Data Exchange (ETDEWEB)

The Salt Range is the active frontal thrust zone of the Himalaya in Pakistan. Seismic reflection data show that a 1 km offset of the basement acted as a buttress that caused the central Salt Range-Potwar Plateau thrust sheet to ramp to the surface, exposing Mesozoic and Paleozoic strata. The frontal part of the thrust sheet was folded passively as it overrode the subthrust surface on a ductile layer of Eocambrian salt. Lack of internal deformation of the rear part of the thrust sheet is due to decoupling of sediments from the basement along this salt layer. Early to middle Pliocene (approx. 4.5 Ma) conglomerate deposition in the southern Potwar Plateau, previously interpreted in terms of compressional deformation, may instead document uplift related to basement normal faulting. Stratigraphic evidence, paleomagnetic dating of unconformities, and sediment-accumulation rates suggest that the thrust sheet began to override the basement offset from 2.1 to 1.6 Ma. Cross-section balancing demonstrates at least 20 to 23 km of shortening across the ramp. The rate of Himalayan convergence that can be attributed to underthrusting of Indian basement beneath sediments in the Pakistan foreland is therefore at least 9-14 mm/yr, about 20-35% of the total plate convergence rate.

Baker, D.M.; Lillie, R.J.; Yeats, R.S.; Johnson, G.D.; Yousuf, M.; Zamin, A.S.H.

1988-01-01

208

Thrust Augmentation Measurements Using a Pulse Detonation Engine Ejector  

Science.gov (United States)

Results of an experimental effort on pulse detonation driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE)/ejector setup that was specifically designed for the study and operated at frequencies up to 50 Hz. The results of various experiments designed to probe different aspects of the PDE/ejector setup are reported. The baseline PDE was operated using ethylene (C2H4) as the fuel and an oxygen/nitrogen O2 + N2) mixture at an equivalence ratio of one. The PDE only experiments included propellant mixture characterization using a laser absorption technique, high fidelity thrust measurements using an integrated spring-damper system, and shadowgraph imaging of the detonation/shock wave structure emanating from the tube. The baseline PDE thrust measurement results at each desired frequency agree with experimental and modeling results reported in the literature. These PDE setup results were then used as a basis for quantifying thrust augmentation for various PDE/ejector setups with constant diameter ejector tubes and various ejector lengths, the radius of curvature for the ejector inlets and various detonation tube/ejector tube overlap distances. For the studied experimental matrix, the results showed a maximum thrust augmentation of 106% at an operational frequency of 30 Hz. The thrust augmentation results are complemented by shadowgraph imaging of the flowfield in the ejector tube inlet area and high frequency pressure transducer measurements along the length of the ejector tube.

Santoro, Robert J.; Pal, Sibtosh

2005-01-01

209

Thrust Augmentation Measurements for a Pulse Detonation Engine Driven Ejector  

Science.gov (United States)

Thrust augmentation results of an ongoing study of pulse detonation engine driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE) setup with various ejector configurations. The PDE used in these experiments utilizes ethylene (C2H4) as the fuel, and an equi-molar mixture of oxygen and nitrogen as the oxidizer at an equivalence ratio of one. High fidelity thrust measurements were made using an integrated spring damper system. The baseline thrust of the PDE engine was first measured and agrees with experimental and modeling results found in the literature. Thrust augmentation measurements were then made for constant diameter ejectors. The parameter space for the study included ejector length, PDE tube exit to ejector tube inlet overlap distance, and straight versus rounded ejector inlets. The relationship between the thrust augmentation results and various physical phenomena is described. To further understand the flow dynamics, shadow graph images of the exiting shock wave front from the PDE were also made. For the studied parameter space, the results showed a maximum augmentation of 40%. Further increase in augmentation is possible if the geometry of the ejector is tailored, a topic currently studied by numerous groups in the field.

Pal, S.; Santoro, Robert J.; Shehadeh, R.; Saretto, S.; Lee, S.-Y.

2005-01-01

210

Effect of a bearing gap on hemolytic property in a hydrodynamically levitated centrifugal blood pump with a semi-open impeller.  

Science.gov (United States)

We have developed a hydrodynamically levitated centrifugal blood pump with a semi-open impeller for long-term circulatory assist. The pump uses hydrodynamic bearings to enhance durability and reliability without additional displacement-sensors or control circuits. However, a narrow bearing gap of the pump has a potential for hemolysis. The purpose of this study is to develop the hydrodynamically levitated centrifugal blood pump with a semi-open impeller, and to evaluate the effect of a bearing gap on hemolytic property. The impeller levitates using a spiral-groove type thrust bearing, and a herringbone-groove type radial bearing. The pump design was improved by adopting a step type thrust bearing and optimizing the pull-up magnetic force. The pump performance was evaluated by a levitation performance test, a hemolysis test and an animal experiment. In these tests, the bearing gap increased from 1 to 63 ?m. In addition, the normalized index of hemolysis (NIH) improved from 0.415 to 0.005 g/100 l, corresponding to the expansion of the bearing gap. In the animal experiment for 24 h, the plasma-free hemoglobin remained within normal ranges (<4.0 mg/dl). We confirmed that the hemolytic property of the pump was improved to the acceptable level by expanding the bearing gap greater than 60 ?m. PMID:23442235

Kosaka, Ryo; Nishida, Masahiro; Maruyama, Osamu; Yambe, Tomoyuki; Imachi, Kou; Yamane, Takashi

2013-01-01

211

Separability of drag and thrust in undulatory animals and machines  

CERN Document Server

For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal- istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation fram...

Bale, Rahul; Neveln, Izaak D; Bhalla, Amneet Pal Singh; MacIver, Malcolm A; Patankar, Neelesh A

2014-01-01

212

Optimization of Flapping Airfoils for Maximum Thrust and Propulsive Efficiency  

Directory of Open Access Journals (Sweden)

Full Text Available A numerical optimization algorithm based on the steepest decent along the variation of the optimization function is implemented for maximizing the thrust and/or propulsive efficiency of a single flapping airfoil. Unsteady, low speed laminar flows are computed using a Navier-Stokes solver on moving overset grids. The flapping motion of the airfoil is described by a combined sinusoidal plunge and pitching motion. Optimization parameters are taken to be the amplitudes of the plunge and pitching motions, and the phase shift between them. Computations are performed in parallel in a work station cluster. The numerical simulations show that high thrust values may be obtained at the expense of reduced efficiency. For high efficiency in thrust generation, the induced angle of attack of the airfoil is reduced and large scale vortex formations at the leading edge are prevented. 

I. H. Tuncer

2004-01-01

213

Dynamic Model for Thrust Generation of Marine Propellers  

DEFF Research Database (Denmark)

Mathematical models of propeller thrust and torque are traditionally based on steady state thrust and torque characteristics obtained in model basin or cavitation tunnel tests. Experimental results showed that these quasi steady state models do not accurately describe the transient phenomena in a thruster. A recently published dynamic model was based on the experimental observations. Describing zero advance speed conditions accurately, this model, however, does not work for a vessel at non- zero relative water speed. This paper derives a large signal dynamic model of propeller that includes the eects of transients in the ow over a wide range of operation. The results are essential for accurate thrust control in dynamic positioning and in underwater robotics.

Blanke, Mogens; Lindegaard, Karl-Petter

2000-01-01

214

Circle-to-circle constant-thrust orbit raising  

Science.gov (United States)

This paper provides simple graphical/analytical tools to determine the minimum elapsed time and associated fuel of a constant-thrust vehicle transferring between coplanar circular orbits. The rocket equation models the effects of continuous fuel expenditure while also serving to recast the solution in terms of accumulated velocity change. These orbit-raising solutions are globally mapped with no restrictions on initial thrust magnitude, intermediate eccentricity, or number of revolutions of the central body. Several examples are presented to verify the transfer charts/equations and familiarize the reader with their use. These are useful tools for mission planners and satellite designers to assess preliminary fuel requirements and transfer times for constant-thrust systems. They are also good for performing propulsion trade-off studies for various missions. A straight-edge and scientific calculator are the only tools needed.

Alfano, Salvatore; Thorne, James D.

1994-01-01

215

Subleading Corrections To Thrust Using Effective Field Theory  

CERN Document Server

We calculate the subleading corrections to the thrust rate using Soft-Collinear Effective Theory to factorize the rate and match onto jet and soft operators that describe the degrees of freedom of the relevant scales. We work in the perturbative regime where all the scales are well above \\Lambda_QCD. The thrust rate involves an incomplete sum over final states that is enforced by a measurement operator. Subleading corrections require matching onto not only the higher dimensional dijet operators, but also matching onto subleading measurement operators in the effective theory. We explicitly show how to factorize the O(\\alpha_s \\tau) thrust rate into a hard function multiplied by the convolution of the vacuum expectation value of jet and soft operators. Our approach can be generalized to other jet shapes and rates.

Freedman, Simon M

2013-01-01

216

Frictionless Bearing Uses Permanent Magnets  

Science.gov (United States)

The purpose of this innovation was to develop a frictionless bearing for high speed, light load applications. The device involves the incorporation of permanent magnets in the bearing design. The repulsion of like magnetic poles provides concentric support of the inner member so that no metallic contact occurs between the bearing surfaces.

1965-01-01

217

Centrifugally decoupling touchdown bearings  

Energy Technology Data Exchange (ETDEWEB)

Centrifugally decoupling mechanical bearing systems provide thin tensioned metallic ribbons contained in a support structure. This assembly rotates around a stationary shaft being centered at low speeds by the action of the metal ribbons. Tension springs are connected on one end to the ribbons and on the other end to the support structure. The ribbons pass through slots in the inner ring of the support structure. The spring preloading thus insures contact (or near-contact) between the ribbons and the shaft at rotation speeds below the transition speed. Above this speed, however, the centrifugal force on the ribbons produces a tensile force on them that exceeds the spring tensile force so that the ribbons curve outward, effectively decoupling them from mechanical contact with the shaft. They still remain, however, in position to act as a touchdown bearing in case of abnormally high transverse accelerations.

Post, Richard F

2014-06-24

218

Passive magnetic bearing system  

Energy Technology Data Exchange (ETDEWEB)

An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.

Post, Richard F.

2014-09-02

219

The Polar Bear Game  

Science.gov (United States)

In this game, which is similar to Petals Around the Rose (cataloged separately), a player rolls 5 dice and asks the participants, âHow many polar bears are around the ice holes?â The participants try to figure out the riddle (rules of the game) by studying the dice arrangements and the answers that correspond. This webpage extends the game to have players also determine the number of fish and plankton.

2010-10-24

220

Radium bearing waste disposal  

International Nuclear Information System (INIS)

Fernald radium bearing ore residue waste, stored within Silos 1 and 2 (K-65) and Silo 3, will be vitrified for disposal at the Nevada Test Site (NTS). A comprehensive, parametric evaluation of waste form, packaging, and transportation alternatives was completed to identify the most cost-effective approach. The impacts of waste loading, waste form, regulatory requirements, NTS waste acceptance criteria, as-low-as-reasonably-achievable principles, and material handling costs were factored into the recommended approach

 
 
 
 
221

Magnetic translator bearings  

Science.gov (United States)

A magnetic bearing system for enabling translational motion includes a carriage and a shaft for movably supporting the carriage; a first magnetic bearing fixed to one of the carriage and shaft and slidably received in a first channel of the other of the carriage and shaft. The first channel is generally U shaped with two side walls and a back wall. The magnetic bearing includes a pair of spaced magnetic pole pieces, each pole piece having a pair of electromagnetic coils mounted on poles on opposite ends of the pole piece proximate the side walls, and a third electromagnetic coil mounted on a pole of the pole piece proximate the backwall; a motion sensor for sensing translational motion along two axes and rotationally about three axes of the carriage and shaft relative to each other; and a correction circuit responsive to the sensor for generating a correction signal to drive the coils to compensate for any misalignment sensed between the carriage and the shaft.

Hockney, Richard L. (Inventor); Downer, James R. (Inventor); Eisenhaure, David B. (Inventor); Hawkey, Timothy J. (Inventor); Johnson, Bruce G. (Inventor)

1990-01-01

222

Thermal subcoolers for low-thrust chemical orbital transfer vehicles  

Science.gov (United States)

A system alternative to pressurization for providing net positive suction pressure (NPSP) to the main engine of a low-thrust cryogenic stage has been conceptually designed and analyzed. Thermal subcoolers (heat exchangers) provide required NPSP levels by using throttled vent fluid to subcool propellant delivered to the engine. The study analyzed and sized subcoolers that provide NPSP levels of 0.5 to 12.0 psi for liquid oxygen, liquid hydrogen, and liquid methane propellants. The study was part of an overall investigation to compare pressurization and other methods of providing NPSP for low-thrust vehicles.

Pleasant, R. L.; Aydelott, J. C.

1981-01-01

223

Problems of millipound thrust measurement. The "Hansen Suspension"  

Energy Technology Data Exchange (ETDEWEB)

Considered in detail are problems which led to the need and use of the 'Hansen Suspension'. Also discussed are problems which are likely to be encountered in any low level thrust measuring system. The methods of calibration and the accuracies involved are given careful attention. With all parameters optimized and calibration techniques perfected, the system was found capable of a resolution of 10 {mu} lbs. A comparison of thrust measurements made by the 'Hansen Suspension' with measurements of a less sophisticated device leads to some surprising results.

Carta, David G.

2014-03-31

224

Automatic control of a primary electric thrust subsystem  

Science.gov (United States)

A concept for automatic control of the thrust subsystem has been developed by JPL and participating NASA Centers. This paper reports on progress in implementing the concept at JPL. Control of the Thrust Subsystem (TSS) is performed by the spacecraft computer command subsystem, and telemetry data is extracted by the spacecraft flight data subsystem. The Data and Control Interface Unit, an element of the TSS, provides the interface with the individual elements of the TSS. The control philosophy and implementation guidelines are presented. Control requirements are listed, and the control mechanism, including the serial digital data intercommunication system, is outlined. The paper summarizes progress to Fall 1974.

Macie, T. W.; Macmedan, M. L.

1975-01-01

225

A balanced cross section across the Himalayan frontal fold-thrust belt, Subathu area, Himachal Pradesh, India: thrust sequence, structural evolution and shortening  

Science.gov (United States)

The structural evolution of the frontal fold-thrust belt in the NW Himalayas has been deciphered through the construction of a balanced cross section, which incorporates all the Tertiary and the Precambrian sedimentary rock units belonging to the Sub-Himalaya Zone and the Lesser Himalaya Zone, respectively. Towards the foreland the structural geometry is rather simple with widely spaced thrust ramps and simple fault-bend folds in the hangingwall. In the central sector, the structural geometry seen at the surface is essentially controlled by a thrust system that can be approximately described as a buried hinterland-dipping duplex. The structural geometry becomes extremely complex in the northeastern sector (i.e. towards the hinterland) owing to out-of-sequence thrusting, low ramp spacing leading to dislocation of older thrusts and related structures by younger thrusts, folded thrusts, and breached horses. Stacked-up horses, occupied by Lesser Himalaya Zone formations, dominate the structural geometry in this sector. An in-sequence thrusting event followed by out-of-sequence thrusting in an approximately break-back style best describe the structural evolution of the fold-thrust belt in this area. A total slip of about 96 km occurred along the detachment and the shortening partitioned within the fold-thrust belt is about 72 km or about 71%.

Mukhopadhyay, Dilip K.; Mishra, Premanand

2005-08-01

226

Bearing for liquid metal pump  

Science.gov (United States)

A liquid metal pump bearing support comprises a series of tangentially oriented spokes that connect the bearing cylinder to the pump internals structure. The spokes may be arranged in a plurality of planes extending from the bearing cylinder to the pump internals with the spokes in one plane being arranged alternately with those in the next plane. The bearing support structure provides the pump with sufficient lateral support for the bearing structure together with the capability of accommodating differential thermal expansion without adversely affecting pump performance.

Dickinson, Robert J. (Shaler Township, Allegheny County, PA); Wasko, John (Plum Borough, PA); Pennell, William E. (Unity Township, Allegheny County, PA)

1984-01-01

227

The interaction between deepwater channel systems and growing thrusts and folds, toe-thrust region of the deepwater Niger Delta  

Science.gov (United States)

Gravity-driven seaward-verging thrusts, landward-verging back-thrusts and associated folds often characterize the slope and deepwater settings of passive margins. These structures, found in the "toe-thrust" region of the system, exert a significant control on sediment gravity flows because they create and determine the location and configuration of sediment depocentres and transport systems. However, to fully understand the interaction between sediment gravity flows and seabed topography we need to evaluate and quantify the geomorphic response of sub-marine channels to faulting in an area where the degree of tectonic shortening can be well constrained. This study exploits 3D seismic data in the outer toe-thrust region of the deepwater Niger Delta to analyze the interaction between Plio-Pleistocene channel systems and actively growing folds and thrusts. We first mapped folds and thrusts from the seismic data and we used this data to reconstruct the history of fold growth. We then used the sea-bed seismic horizon to build a 50 m resolution Digital Elevation Model (DEM) of the sea floor in Arc-GIS. From the DEM, we extracted channel long profiles across growing structures for both the current channel thalwegs and for the associated channel cut-and-fill sequences identified from the seismic data. We measured channel geometry at regular intervals along the channel length to evaluate system response to tectonic perturbation, and we used this data to help us approximate the down-system distribution of bed shear stress, and hence incision capacity. Initial results show that changes in submarine channel longitudinal profiles are directly correlated to underlying seabed thrusts and folds. Channels gradients are typically linear to slightly concave, and have an average gradient of 0.90. Actively growing thrusts are associated with a local steepening in channel gradient (up to 200% change), which typically extends 0.5 to 2 km upstream of the fault. Within these "knickzones", channel incision increases by approximately 50%, with a corresponding width decrease of approximately 25% or less. Our data demonstrate that submarine channel systems dynamically adjust their geometry and basal gradient in order to keep pace with the growth of tectonic structures and our results provide new data to test models of turbidite incision.

Jolly, B.; Lonergan, L.; Whittaker, A.

2012-04-01

228

High-Temperature Magnetic Bearings Being Developed for Gas Turbine Engines  

Science.gov (United States)

Magnetic bearings are the subject of a new NASA Lewis Research Center and U.S. Army thrust with significant industry participation, and cooperation with other Government agencies. The NASA/Army emphasis is on high-temperature applications for future gas turbine engines. Magnetic bearings could increase the reliability and reduce the weight of these engines by eliminating the lubrication system. They could also increase the DN (diameter of bearing times the rpm) limit on engine speed and allow active vibration cancellation systems to be used, resulting in a more efficient, "more electric" engine. Finally, the Integrated High Performance Turbine Engine Technology (IHPTET) program, a joint Department of Defense/industry program, identified a need for a high-temperature (1200 F) magnetic bearing that could be demonstrated in their Phase III engine. This magnetic bearing is similar to an electric motor. It has a laminated rotor and stator made of cobalt steel. Wound around the stator's circumference are a series of electrical wire coils which form a series of electric magnets that exert a force on the rotor. A probe senses the position of the rotor, and a feedback controller keeps it centered in the cavity. The engine rotor, bearings, and casing form a flexible structure with many modes. The bearing feedback controller, which could cause some of these modes to become unstable, could be adapted to varying flight conditions to minimize seal clearances and monitor the health of the system.

Kascak, Albert F.

1998-01-01

229

Integration of magnetic bearings in the design of advanced gas turbine engines  

Science.gov (United States)

Active magnetic bearings provide revolutionary advantages for gas turbine engine rotor support. These advantages include tremendously improved vibration and stability characteristics, reduced power loss, improved reliability, fault-tolerance, and greatly extended bearing service life. The marriage of these advantages with innovative structural network design and advanced materials utilization will permit major increases in thrust to weight performance and structural efficiency for future gas turbine engines. However, obtaining the maximum payoff requires two key ingredients. The first key ingredient is the use of modern magnetic bearing technologies such as innovative digital control techniques, high-density power electronics, high-density magnetic actuators, fault-tolerant system architecture, and electronic (sensorless) position estimation. This paper describes these technologies. The second key ingredient is to go beyond the simple replacement of rolling element bearings with magnetic bearings by incorporating magnetic bearings as an integral part of the overall engine design. This is analogous to the proper approach to designing with composites, whereby the designer tailors the geometry and load carrying function of the structural system or component for the composite instead of simply substituting composites in a design originally intended for metal material. This paper describes methodologies for the design integration of magnetic bearings in gas turbine engines.

Storace, Albert F.; Sood, Devendra K.; Lyons, James P.; Preston, Mark A.

1994-01-01

230

Cooling of rocket thrust chambers with liquid oxygen  

Science.gov (United States)

Rocket engines using high pressure liquid oxygen (LOX) and kerosene (RP-1) as the propellants have been considered for future launch vehicle propulsion. Generaly, in regeneratively cooled engines, thefuel is used to cool the combustion chamber. However, hydrocarbons such as RP-1 are limited in their cooling capability at high temperatures and pressures. Therefore, LOX is being considered as an alternative coolant. However, there has been concern as to the effect on the integrity of the chamber liner if oxygen leaks into the combustion zone through fatigue cracks that may develop between the cooling passages and the hot-gas side wall. To address this concern, an investigation was previously conducted with simulated fatigue cracks upstream of the thrust chamber throat. When these chambers were tested, an unexpected melting in the throat region developed which was not in line with the simulated fatigue cracks. The current experimental program was conducted in order to determine the cause for the failure in the earlier thrust chambers and to further investigate the effects of cracks in the thrust chamber liner upstream of the throat. The thrust chambers were tested at oxygen-to-fuel mixture ratios from 1.5 to 2.86 at a nominal chamber pressure of 8.6 MPa. As a result of the test series, the reason for the failure occurring in the earlier work was determined to be injector anomalies. The LOX leaking through the simulated fatigue cracks did not affect the integrity of the chambers.

Armstrong, Elizabeth S.; Schlumberger, Julie A.

1990-01-01

231

Investigation of thrust forces under NPP pipeline ruptures  

International Nuclear Information System (INIS)

Forces acting at a pipeline in the process of its depressurization and boiling water flow are investigated on the basis of experimental works by means of the BAGIRA program complex. Possibility of the BAGIRA complex application when investigating the thrust forces in cases of the NPP pipeline ruptures is shown

232

Thrust vector control for V/STOL aircraft  

Science.gov (United States)

To deflect exhaust of V/STOL aircraft fan deploy set of rectangular flaps so exhaust stream can be turned as required and then directed through exit nozzles which generate thrust in appropriate direction; lateral deflection of exhaust is provided by yaw vanes.

Toney, E. W.

1974-01-01

233

Solid rocket booster thrust vector control subsystem description  

Science.gov (United States)

Major Solid Rocket Booster-Thrust Vector Control (SRB-TVC) subsystem components and subcomponents used in the Space Transportation System (STS) are identified. Simplified schematics, detailed schematics, figures, photographs, and data are included to acquaint the reader with the operation, performance, and physical layout as well as the materials and instrumentation used.

Redmon, J., Jr. (compiler)

1983-01-01

234

Effect of quark masses on the perturbative thrust  

International Nuclear Information System (INIS)

We study the effect of quark masses on the thrust to O(?/sub s/) in QCD. We find the mass corrections to be significant and show that they reduce the estimated nonperturbative effects. They also allow realistic limits to be placed on the parameter ?

235

Precision thrust cumulant moments at N3LL  

Science.gov (United States)

We consider cumulant moments (cumulants) of the thrust distribution using predictions of the full spectrum for thrust including O(?s3) fixed order results, resummation of singular N3LL logarithmic contributions, and a class of leading power corrections in a renormalon-free scheme. From a global fit to the first thrust moment we extract the strong coupling and the leading power correction matrix element ?1. We obtain ?s(mZ)=0.1140±(0.0004)exp?±(0.0013)hadr±(0.0007)pert, where the 1-? uncertainties are experimental, from hadronization (related to ?1) and perturbative, respectively, and ?1=0.377±(0.044)exp?±(0.039)pertGeV. The nth thrust cumulants for n?2 are completely insensitive to ?1, and therefore a good instrument for extracting information on higher order power corrections, ?n'/Qn, from moment data. We find (?˜2')1/2=0.74±(0.11)exp?±(0.09)pertGeV.

Abbate, Riccardo; Fickinger, Michael; Hoang, André H.; Mateu, Vicent; Stewart, Iain W.

2012-11-01

236

Precision Thrust Cumulant Moments at N^3LL  

CERN Document Server

We consider cumulant moments (cumulants) of the thrust distribution using predictions of the full spectrum for thrust including O(alpha_s^3) fixed order results, resummation of singular N^3LL logarithmic contributions, and a class of leading power corrections in a renormalon-free scheme. From a global fit to the first thrust moment we extract the strong coupling and the leading power correction matrix element Omega_1. We obtain alpha_s(m_Z) = 0.1141 \\pm (0.0004)_exp \\pm (0.0014)_hadr \\pm (0.0007)_pert, where the 1-sigma uncertainties are experimental, from hadronization (related to Omega_1) and perturbative, respectively, and Omega_1 = 0.372 \\pm (0.044)_exp \\pm (0.039)_pert GeV. The n-th thrust cumulants for n > 1 are completely insensitive to Omega_1, and therefore a good instrument for extracting information on higher order power corrections, Omega'_n/Q^n, from moment data. We find (\\tilde Omega'_2)^(1/2) = 0.74 \\pm (0.11)_exp \\pm (0.09)_pert GeV.

Abbate, Riccardo; Hoang, Andre H; Mateu, Vicent; Stewart, Iain W

2012-01-01

237

On the thrust distribution in e+e- annihilation  

International Nuclear Information System (INIS)

The thrust distribution calculated in perturbative QCD through to O(?sub(s)2) is presented. The results, which come from an elaboration of previously published formulae, show that the O(?sub(s)2) correction at present energies is large and positive in agreement with the previously obtained results of many groups. (orig.)

238

Cooling of rocket thrust chambers with liquid oxygen  

Science.gov (United States)

Rocket engines using high pressure liquid oxygen (LOX) and kerosene (RP-1) as the propellants have been considered for future launch vehicle propulsion. Generally, in regeneratively cooled engines, the fuel is used to cool the combustion chamber. However, hydrocarbons such as RP-1 are limited in their cooling capability at high temperatures and pressures. Therefore, LOX is being considered as an alternative coolant. However, there has been concern as to the effect on the integrity of the chamber liner if oxygen leaks into the combustion zone through fatigue cracks that may develop between the cooling passages and the hot-gas side wall. To address this concern, an investigation was previously conducted with simulated fatigue cracks upstream of the thrust chamber throat. When these chambers were tested, an unexpected melting in the throat region developed which was not in line with the simulated fatigue cracks. The current experimental program was conducted in order to determine the cause for the failure in the earlier thrust chambers and to further investigate the effects of cracks in the thrust chamber liner upstream of the throat. The thrust chambers were tested at oxygen-to-fuel mixture ratios from 1.5 to 2.86 at a nominal chamber pressure of 8.6 MPa. As a result of the test series, the reason for the failure occurring in the earlier work was determined to be injector anomalies. The LOX leaking through the simulated fatigue cracks did not affect the integrity of the chambers.

Armstrong, Elizabeth S.; Schlumberger, Julie A.

1990-01-01

239

Engineering Research, Development and Technology, FY95: Thrust area report  

Energy Technology Data Exchange (ETDEWEB)

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the knowledge base, process technologies, specialized equipment, tools and facilities to support current and future LLNL programs. Engineering`s efforts are guided by a strategy that results in dual benefit: first, in support of Department of Energy missions, such as national security through nuclear deterrence; and second, in enhancing the nation`s economic competitiveness through their collaboration with US industry in pursuit of the most cost-effective engineering solutions to LLNL programs. To accomplish this mission, the Engineering Research, Development, and Technology Program has two important goals: (1) identify key technologies relevant to LLNL programs where they can establish unique competencies, and (2) conduct high-quality research and development to enhance their capabilities and establish themselves as the world leaders in these technologies. To focus Engineering`s efforts, technology thrust areas are identified and technical leaders are selected for each area. The thrust areas are comprised of integrated engineering activities, staffed by personnel from the nine electronics and mechanical engineering divisions, and from other LLNL organizations. This annual report, organized by thrust area, describes Engineering`s activities for fiscal year 1995. The report provides timely summaries of objectives methods, and key results from eight thrust areas: computational electronics and electromagnetics; computational mechanics; microtechnology; manufacturing technology; materials science and engineering; power conversion technologies; nondestructive evaluation; and information engineering.

NONE

1996-02-01

240

Aerospace applications of magnetic bearings  

Science.gov (United States)

Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advantages which must be traded off against increased weight, volume, electric power consumption, and system complexity. These perceptions have hampered the use of magnetic bearings in many aerospace applications because weight, volume, and power are almost always primary considerations. This paper will review progress on several active aerospace magnetic bearings programs at SatCon Technology Corporation. The magnetic bearing programs at SatCon cover a broad spectrum of applications including: a magnetically-suspended spacecraft integrated power and attitude control system (IPACS), a magnetically-suspended momentum wheel, magnetic bearings for the gas generator rotor of a turboshaft engine, a vibration-attenuating magnetic bearing system for an airborne telescope, and magnetic bearings for the compressor of a space-rated heat pump system. The emphasis of these programs is to develop magnetic bearing technologies to the point where magnetic bearings can be truly useful, reliable, and well tested components for the aerospace community.

Downer, James; Goldie, James; Gondhalekar, Vijay; Hockney, Richard

1994-05-01

 
 
 
 
241

Thrust Area Report, Engineering Research, Development and Technology  

Energy Technology Data Exchange (ETDEWEB)

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the knowledge base, process technologies, specialized equipment, tools and facilities to support current and future LLNL programs. Engineering`s efforts are guided by a strategy that results in dual benefit: first, in support of Department of Energy missions, such as national security through nuclear deterrence; and second, in enhancing the nation`s economic competitiveness through our collaboration with U.S. industry in pursuit of the most cost- effective engineering solutions to LLNL programs. To accomplish this mission, the Engineering Research, Development, and Technology Program has two important goals: (1) identify key technologies relevant to LLNL programs where we can establish unique competencies, and (2) conduct high-quality research and development to enhance our capabilities and establish ourselves as the world leaders in these technologies. To focus Engineering`s efforts technology {ital thrust areas} are identified and technical leaders are selected for each area. The thrust areas are comprised of integrated engineering activities, staffed by personnel from the nine electronics and mechanical engineering divisions, and from other LLNL organizations. This annual report, organized by thrust area, describes Engineering`s activities for fiscal year 1996. The report provides timely summaries of objectives, methods, and key results from eight thrust areas: Computational Electronics and Electromagnetics; Computational Mechanics; Microtechnology; Manufacturing Technology; Materials Science and Engineering; Power Conversion Technologies; Nondestructive Evaluation; and Information Engineering. Readers desiring more information are encouraged to contact the individual thrust area leaders or authors. 198 refs., 206 figs., 16 tabs.

Langland, R. T.

1997-02-01

242

14 CFR 25.904 - Automatic takeoff thrust control system (ATTCS).  

Science.gov (United States)

...2010-01-01 2010-01-01 false Automatic takeoff thrust control system (ATTCS). 25.904 Section 25...AIRPLANES Powerplant General § 25.904 Automatic takeoff thrust control system (ATTCS). Each applicant...

2010-01-01

243

Nanoprecipitation in bearing steels  

Energy Technology Data Exchange (ETDEWEB)

{theta}-phase is the main hardening species in bearing steels and appears in both martensitically and bainitically hardened microstructures. This work presents a survey of the microstrucural features accompanying nanoprecipitation in bearing steels. Nanoprecipitate structures formed in 1C-1.5Cr wt.% with additions of Cr, Mn, Mo, Si and Ni are studied. The work is combined with thermodynamic calculations and neural networks to predict the expected matrix composition, and whether this will transform martensitically or bainitically. Martensite tetragonality, composition and the amount of retained austenite are related to hardness and the type of nanoprecipitate structures in martensitic grades. The {theta}-phase volume fraction, the duration of the bainite to austenite transformation and the amount of retained austenite are related to hardness and a detailed quantitative description of the precipitate nanostructures. Such description includes compositional studies using energy-dispersive spectroscopy, which shows that nanoprecipitate formation takes place under paraequilibrium. Special attention is devoted to a novel two-step bainite tempering process which shows maximum hardness; we prove that this is the most effective process for incorporating solute into the precipitates, which are finer than those resulting from one-step banitic transformation processes.

Barrow, A.T.W. [SKF University Technology Centre, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Rivera-Diaz-del-Castillo, P.E.J., E-mail: pejr2@cam.ac.uk [SKF University Technology Centre, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom)

2011-11-15

244

Superconducting bearings in flywheels  

International Nuclear Information System (INIS)

Investigations are being carried out into the use of superconducting magnetic bearings to levitate energy storage flywheels. In a planned program of work, Cambridge University are aiming to produce a practical bearing system for Pirouette(TM). The Pirouette(TM) system is designed to provide 5 kWh of recoverable energy which is currently recoverable at a rate of 5 kW (future revisions will provide up to 50 kW). IES (a British Nuclear Fuels subsidiary) the owners of the Pirouette(TM) machine have supplied Cambridge with a flywheel. This flywheel weighs >40 kg and is being levitated using an Evershed-type arrangement in which the superconductor is being used to stabilize the interaction between two magnets. To date we have demonstrated stable levitation in static and low speed tests in a rig designed for low speeds of rotation in air. A second rig which is currently under construction at BNFL will run in vacuum at speeds of up to 50 (orig.)

245

Nanoprecipitation in bearing steels  

International Nuclear Information System (INIS)

?-phase is the main hardening species in bearing steels and appears in both martensitically and bainitically hardened microstructures. This work presents a survey of the microstrucural features accompanying nanoprecipitation in bearing steels. Nanoprecipitate structures formed in 1C-1.5Cr wt.% with additions of Cr, Mn, Mo, Si and Ni are studied. The work is combined with thermodynamic calculations and neural networks to predict the expected matrix composition, and whether this will transform martensitically or bainitically. Martensite tetragonality, composition and the amount of retained austenite are related to hardness and the type of nanoprecipitate structures in martensitic grades. The ?-phase volume fraction, the duration of the bainite to austenite transformation and the amount of retained austenite are related to hardness and a detailed quantitative description of the precipitate nanostructures. Such description includes compositional studies using energy-dispersive spectroscopy, which shows that nanoprecipitate formation takes place under paraequilibrium. Special attention is devoted to a novel two-step bainite tempering process which shows maximum hardness; we prove that this is the most effective process for incorporating solute into the precipitates, which are finer than those resulting from one-step banitic transformation processes.

246

Some tests on small-scale rectangular throat ejector. [thrust augmentation for V/STOL aircraft  

Science.gov (United States)

A small scale rectangular throat ejector with plane slot nozzles and a fixed throat area was tested to determine the effects of diffuser sidewall length, diffuser area ratio, and sidewall nozzle position on thrust and mass augmentation. The thrust augmentation ratio varied from approximately 0.9 to 1.1. Although the ejector did not have good thrust augmentation performance, the effects of the parameters studied are believed to indicate probable trends in thrust augmenting ejectors.

Dean, W. N., Jr.; Franke, M. E.

1979-01-01

247

Primarily Pro-bear-bility  

Science.gov (United States)

In this probability lesson plan students make predictions about the color of the bear they are likely to draw from a bag, and then draw and record the color of the bear they actually draw. Students complete this activity in cooperative learning groups and take turns removing a bear, without replacing it, and seeing if their predictions become more accurate. The lesson plan includes four student activity worksheets and extension questions and suggestions (PDF).

2006-01-01

248

A Comparison Study of Magnetic Bearing Controllers for a Fully Suspended Dynamic Spin Rig  

Science.gov (United States)

NASA Glenn Research Center (GRC) has developed a fully suspended magnetic bearing system for the Dynamic Spin Rig (DSR) that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteropolar radial magnetic bearings and a thrust bearing and the associated control system were integrated into the DSR to provide noncontact magnetic suspension and mechanical excitation of the 35 lb vertical rotor with blades to induce turbomachinery blade vibration. A simple proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked very well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, and energy savings for the system. The test results of a variety of controllers we demonstrated up to the rig's maximum allowable speed of 10,000 rpm are shown.

Choi, Benjamin; Johnson, Dexter; Morrison, Carlos; Mehmed, Oral; Huff, Dennis (Technical Monitor)

2002-01-01

249

YBCO texturation and applications of superconducting magnetic bearings in flywheels for energy storage  

International Nuclear Information System (INIS)

A thrust bearing has been built consisting of 6 melt-textured YBCO pellets (diameter 30 x 18 mm) and a Nd-Fe-B ring magnet. The maximum levitation force of the bearing was 65 N at zero gap. Vertical stiffness at 1 mm gap was 440 N/cm, lateral stiffness was 130 N/cm. The bearing has been integrated into a flywheel system rotating a 2.8 kg disk at speeds up to 15 000 rpm. The maximum energy capacity was 4.8 Wh. It can be expected that further refinement of this technology should allow the operation of superconducting flywheels in the kWh range. (orig.)

250

P and W Cryogenic Fluid-Film Bearing and Seal Technology Development and Implementation  

Science.gov (United States)

This presentation will summarize Pratt & Whitney's past, present, and future activities toward cryogenic fluid-film bearing and seal technology development and implementation. The three major areas of focus for this technology are analytical models and design tools, component testing, and technology implementation. The analytical models and design tools area will include a summary of current tools along with an overview of P&W's new full 3-D Navier-Stokes solution for hydrostatic bearings, HYDROB3D. P&W's comprehensive component test program, including teaming with the Air Force Phillips Laboratory, NASA's Marshall Space Flight Center, and Carrier Corporation, will be outlined. Component test programs consisting of material development and testing, surface patterns/roughness, pocket and orifice geometry variations, and static and dynamic performance of both journal and thrust bearings will be summarized. Finally, the technology implementation area will show the benefits and plans for P&W to incorporate this technology into products.

Pelfrey, Philip C.

1996-01-01

251

EVALUATION OF A LOW FRICTION - HIGH EFFICIENCY ROLLER BEARING ENGINE  

Energy Technology Data Exchange (ETDEWEB)

This Low Friction (High Efficiency Roller Bearing) Engine (LFE) report presents the work done by The Timken Company to conduct a technology demonstration of the benefits of replacing hydrodynamic bearings with roller bearings in the crankshaft and camshaft assemblies of an internal combustion engine for the purpose of collecting data sufficient to prove merit. The engines in the present study have been more extensively converted to roller bearings than any previous studies (40 needle roller bearings per engine) to gain understanding of the full potential of application of bearing technology. The project plan called for comparative testing of a production vehicle which was already respected for having demonstrated low engine friction levels with a rollerized version of that engine. Testing was to include industry standard tests for friction, emissions and fuel efficiency conducted on instrumented dynamometers. Additional tests for fuel efficiency, cold start resistance and other measures of performance were to be made in the actual vehicle. Comparative measurements of noise, vibration and harshness (NVH), were planned, although any work to mitigate the suspected higher NVH level in the rollerized engine was beyond the scope of this project. Timken selected the Toyota Avalon with a 3.5L V-6 engine as the test vehicle. In an attempt to minimize cost and fabrication time, a ‘made-from’ approach was proposed in which as many parts as possible would be used or modified from production parts to create the rollerized engine. Timken commissioned its test partner, FEV Engine Technology, to do a feasibility study in which they confirmed that using such an approach was possible to meet the required dimensional restrictions and tolerances. In designing the roller bearing systems for the crank and cam trains, Timken utilized as many production engine parts as possible. The crankshafts were produced from production line forgings, which use Timken steel, modified with special machining and heat treatment. Timken designed and manufactured all of the roller bearing related components such as the thrust bearing package. The production connecting rods and camshafts could not be used for the roller bearing engine, so new ones were produced according to the team’s designs using Timken steel. The remaining miscellaneous components were designed and procured by FEV. Timken prepared a display version of the crankshaft portion of the production engine without connecting rods which could be driven by a motor through a cogged-belt and electrically actuated clutch arrangement. A modified version was also made in which the engine was outfitted with roller bearings on the main bearing positions. Preliminary tests showed that the rollerized engine was running with 1/3 less friction than the standard display engine. Additional friction testing and noise characterization was cut short because of shipping damage to the rollerized engine display and because of other project priorities. The team did successfully demonstrate the ability to package roller bearings satisfactorily in numerous locations in a typical automotive engine. The scope of this project did not include durability demonstration and that subject would have to be addressed in any follow-on work. In the actual test phase, the rollerized engine did show significantly less friction in motored dynamometer tests compared to its production equivalent. The 5-10% improvement measured in this study was about half that seen in other studies. However, the fired test results did not show a reduction in friction which did not match prior experience or expectations. Subsequent teardown and inspection of the rollerized engine revealed potential sources of excessive friction in the experimental application. These features would be eliminated in a design not based on modification of production parts. The team is confident (based on experience) that friction reduction would be realized with proper modifications.

Kolarik, Robert V. II; Shattuck, Charles W.; Copper, Anthony P.

2009-06-30

252

Advances in Thrust-Based Emergency Control of an Airplane  

Science.gov (United States)

Engineers at NASA's Dryden Flight Research Center have received a patent on an emergency flight-control method implemented by a propulsion-controlled aircraft (PCA) system. Utilizing the preexisting auto-throttle and engine-pressure-ratio trim controls of the airplane, the PCA system provides pitch and roll control for landing an airplane safely without using aerodynamic control surfaces that have ceased to function because of a primary-flight-control-system failure. The installation of the PCA does not entail any changes in pre-existing engine hardware or software. [Aspects of the method and system at previous stages of development were reported in Thrust-Control System for Emergency Control of an Airplane (DRC-96-07), NASA Tech Briefs, Vol. 25, No. 3 (March 2001), page 68 and Emergency Landing Using Thrust Control and Shift of Weight (DRC-96-55), NASA Tech Briefs, Vol. 26, No. 5 (May 2002), page 58.]. Aircraft flight-control systems are designed with extensive redundancy to ensure low probabilities of failure. During recent years, however, several airplanes have exhibited major flight-control-system failures, leaving engine thrust as the last mode of flight control. In some of these emergency situations, engine thrusts were successfully modulated by the pilots to maintain flight paths or pitch angles, but in other situations, lateral control was also needed. In the majority of such control-system failures, crashes resulted and over 1,200 people died. The challenge lay in creating a means of sufficient degree of thrust-modulation control to safely fly and land a stricken airplane. A thrust-modulation control system designed for this purpose was flight-tested in a PCA an MD-11 airplane. The results of the flight test showed that without any operational control surfaces, a pilot can land a crippled airplane (U.S. Patent 5,330,131). The installation of the original PCA system entailed modifications not only of the flight-control computer (FCC) of the airplane but also of each engine-control computer. Inasmuch as engine-manufacturer warranties do not apply to modified engines, the challenge became one of creating a PCA system that does not entail modifications of the engine computers.

Creech, Gray; Burken, John J.; Burcham, Bill

2003-01-01

253

Design of Low-Thrust Gravity Assist Trajectories to Europa  

CERN Document Server

This paper presents the design of a mission to Europa using solar electric propulsion as main source of thrust. A direct transcription method based on Finite Elements in Time was used for the design and optimisation of the entire low-thrust gravity assist transfer from the Earth to Europa. Prior to that, a global search algorithm was used to generate a set of suitable first guess solutions for the transfer to Jupiter, and for the capture in the Jovian system. In particular, a fast deterministic search algorithm was developed to find the most promising set of swing-bys to reach Jupiter A second fast search algorithm was developed to find the best sequence of swing-bys of the Jovian moons. After introducing the global search algorithms and the direct transcription through Finite Elements in Time, the paper presents a number of first guess Solutions and a fully optimised transfer from the Earth to Europa.

Vasile, Massimiliano

2011-01-01

254

Low-thrust trajectory optimization in a full ephemeris model  

Science.gov (United States)

The low-thrust trajectory optimization with complicated constraints must be considered in practical engineering. In most literature, this problem is simplified into a two-body model in which the spacecraft is subject to the gravitational force at the center of mass and the spacecraft's own electric propulsion only, and the gravity assist (GA) is modeled as an instantaneous velocity increment. This paper presents a method to solve the fuel-optimal problem of low-thrust trajectory with complicated constraints in a full ephemeris model, which is closer to practical engineering conditions. First, it introduces various perturbations, including a third body's gravity, the nonspherical perturbation and the solar radiation pressure in a dynamic equation. Second, it builds two types of equivalent inner constraints to describe the GA. At the same time, the present paper applies a series of techniques, such as a homotopic approach, to enhance the possibility of convergence of the global optimal solution.

Cai, Xing-Shan; Chen, Yang; Li, Jun-Feng

2014-10-01

255

Engineering research, development and technology. Thrust area report, FY93  

Energy Technology Data Exchange (ETDEWEB)

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the technical staff, tools, and facilities needed to support current and future LLNL programs. The efforts are guided by a dual-benefit research and development strategy that supports Department of Energy missions, such as national security through nuclear deterrence and economic competitiveness through partnerships with U.S. industry. This annual report, organized by thrust area, describes the activities for the fiscal year 1993. The report provides timely summaries of objectives, methods, and results from nine thrust areas for this fiscal year: Computational Electronics and Electromagnetics; Computational Mechanics; Diagnostics and Microelectronics; Fabrication Technology; Materials Science and Engineering; Power Conversion Technologies; Nondestructive Evaluation; Remote Sensing, Imaging, and Signal Engineering; and Emerging Technologies. Separate abstracts were prepared for 47 papers in this report.

1994-05-01

256

Viking Orbiter 1975 thrust vector control system accuracy  

Science.gov (United States)

The thrust vector control (TVC) system of the Viking Orbiter 1975 is discussed. The purpose of the TVC system is to point the engine thrust at the vehicle center of mass and to maintain attitude stability during propulsive maneuvers. This is accomplished by mounting the engine in a two-axis gimbal system. The TVC system then controls the pointing of the engine by closed loop control of two linear actuators which extend or retract and rotate the engine in its gimbal system. The effect of the TVC on the velocity vector pointing error incurred during a propulsive maneuver is analyzed. Models for predicting the magnitude of the error for various propulsive maneuvers are developed.

Mcglinchey, L. F.

1974-01-01

257

Continuous low-thrust trajectory optimization: Techniques and applications  

Science.gov (United States)

Trajectory optimization is a powerful technique to analyze mission feasibility during mission design. High-thrust trajectory optimization problems are typically formulated as discrete optimization problems and are numerically well-behaved. Low-thrust systems, on the other hand, operate for significant periods of the mission time. As a result, the solution approach requires continuous optimization; the associated optimal control problems are in general numerically ill-conditioned. In addition, case studies comparing the performance of low-thrust technologies for space travel have not received adequate attention in the literature and are in most instances incomplete. The objective of this dissertation is therefore to design an efficient optimal control algorithm and to apply it to the minimum-time transfer problem of low-thrust spacecraft. We devise a cascaded computational scheme based on numerical and analytical methods. Whereas other conventional optimization packages rely on numerical solution approaches, we employ analytical and semi-analytical techniques such as symmetry and homotopy methods to assist in the solution-finding process. The first objective is to obtain a single optimized trajectory that satisfies some given boundary conditions. The initialization phase for this first trajectory includes a global, stochastic search based on Adaptive Simulated Annealing; the fine tuning of optimization parameters---the local search---is accomplished by Quasi-Newton and Newton methods. Once an optimized trajectory has been obtained, we use system symmetry and homotopy techniques to generate additional optimal control solutions efficiently. We obtain optimal trajectories for several interrelated problem families that are described as Multi-Point Boundary Value Problems. We present and prove two theorems describing system symmetries for solar sail spacecraft and discuss symmetry properties and symmetry breaking for electric spacecraft systems models. We demonstrate how these symmetry properties can be used to significantly simplify the solution-finding process.

Kim, Mischa

258

Energy from sea wave thrust and flow of water  

International Nuclear Information System (INIS)

The area adjacent to the tidal rivers, irrigational canal, drain and also the seashore may be energized harnessing the energy from the flow/wave thrust by simply converting it into unidirectional rotating force to drive the generator for power generation. The existing plants are big in size and also fixed in place. A plant which will be a small/portable type is described. 7 refs., figs

259

Thrust distribution resummation in e^{+}e^{-} collisions  

CERN Document Server

In this talk we report on the recent progresses on IR logarithms resummation for the Thrust distribution in e^{+}e^{-} collisions. Using renormalisation group (RG) evolution in Laplace space, the resummation of logarithmically enhanced corrections is performed to next-to-next-to-leading logarithmic (NNLL) accuracy. To combine the resummed expressions with the fixed-order results, we derive the log(R)-matching and R-matching of the NNLL approximation to the fixed-order NNLO distribution.

Monni, Pier Francesco

2012-01-01

260

Second order QCD contributions to thrust and spherocity  

International Nuclear Information System (INIS)

In e+e- annihilation there are regions of high spherocity S and low thrust T (S > 16/3?2 and T +e- ? q anti q GG and e+e- ? q anti q q anti q neglecting only cubic and higher order terms in ?sub(s). We give the corresponding QCD predictions which suggest that the calculable corrections to these variables may be slowly convergent. (orig.)

 
 
 
 
261

Second order QCD contributions to thrust and spherocity  

International Nuclear Information System (INIS)

In e+e- annihilation there are regions of high spherocity S and low thrust T(S > 16/3?2 and T +e- ? q anti qGG and e+e- ? q anti q q anti q neglecting only cubic and higher order terms in ?sub(s). We give the corresponding QCD predictions which suggest that the calculable corrections to these variables may be slowly convergent. (orig.)

262

Direct thrust measurement of a permanent magnet helicon double layer thruster  

Science.gov (United States)

Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.

Takahashi, K.; Lafleur, T.; Charles, C.; Alexander, P.; Boswell, R. W.; Perren, M.; Laine, R.; Pottinger, S.; Lappas, V.; Harle, T.; Lamprou, D.

2011-04-01

263

Direct thrust measurement of a permanent magnet helicon double layer thruster  

International Nuclear Information System (INIS)

Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.

264

Permanent-Magnet Meissner Bearing  

Science.gov (United States)

Permanent-magnet meissner bearing features inherently stable, self-centering conical configuration. Bearing made stiffer or less stiff by selection of magnets, springs, and spring adjustments. Cylindrical permanent magnets with axial magnetization stacked coaxially on rotor with alternating polarity. Typically, rare-earth magnets used. Magnets machined and fitted together to form conical outer surface.

Robertson, Glen A.

1994-01-01

265

Superconducting bearings for flywheel applications  

DEFF Research Database (Denmark)

A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings in flywheels.

Abrahamsen, A.B.

2001-01-01

266

The 7.5K lbf thrust engine preliminary design for Orbit Transfer Vehicle  

Science.gov (United States)

This document summarizes the preliminary design of the Aerojet version of the Orbit Transfer Vehicle main engine. The concept of a 7500 lbf thrust LO2/GH2 engine using the dual expander cycle for optimum efficiency is validated through power balance and thermal calculations. The engine is capable of 10:1 throttling from a nominal 2000 psia to a 200 psia chamber pressure. Reservations are detailed on the feasibility of a tank head start, but the design incorporates low speed turbopumps to mitigate the problem. The mechanically separate high speed turbopumps use hydrostatic bearings to meet engine life requirements, and operate at sub-critical speed for better throttling ability. All components were successfully packaged in the restricted envelope set by the clearances for the extendible/retractable nozzle. Gimbal design uses an innovative primary and engine out gimbal system to meet the +/- 20 deg gimbal requirement. The hydrogen regenerator and LOX/GH2 heat exchanger uses the Aerojet platelet structures approach for a highly compact component design. The extendible/retractable nozzle assembly uses an electric motor driven jack-screw design and a one segment carbon-carbon or silicide coated columbium nozzle with an area ratio, when extended, of 1430:1. A reliability analysis and risk assessment concludes the report.

Hayden, Warren R.; Sabiers, Ralph; Schneider, Judy

1994-01-01

267

Nanobalance: an automated interferometric balance for micro-thrust measurement.  

Science.gov (United States)

The paper is concerned with a new instrument, nanobalance, measuring thrust and noise of space micro-thrusters in the range 0-1 mN with submicronewton accuracy. Low-noise micro-thrusters will be essential for upcoming "drag-free" space missions like GOCE, SMART-2, LISA, and Darwin. Nanobalance departs from traditional thrust measuring concepts so as to exploit sensitivity of in-vacuum Fabry-Pérot interferometers to subnanometric displacements. That is achieved by an optical cavity embraced by two equal pendulums suspended at a constant distance, one of which carrying the micro-thruster under test. Any thrust, changing the optical path length of the injected laser beam, is detected as the frequency variation restoring a standing wave in the cavity. The paper presents the measurement principles, the error budget as derived from recent tests as well as instrument automation, which is essential for facilitating instrument setup and adaptation from measurement trial to trial. The authors are responsible for instrument automation and measurement processing. PMID:15098578

Canuto, Enrico; Rolino, Andrea

2004-04-01

268

CFD evaluation of an advanced thrust vector control concept  

Science.gov (United States)

A potential concept that can offer an alternate method for thrust vector control of the Space Shuttle Solid Rocket Booster is the use of a cylindrical probe that is inserted (on demand) through the wall of the rocket nozzle. This Probe Thrust Vector Control (PTVC) concept is an alternate to that of a gimbaled nozzle or a Liquid Injection Thrust Vector (LITVC) system. The viability of the PTVC concept can be assessed either experimentally and/or with the use of CFD. A purely experimental assessment can be time consuming and expensive, whereas a CFD assessment can be very time- and cost-effective. Two key requirements of the proposed concept are PTVC vectoring performance and the active cooling requirements for the probe to maintain its thermal and structural integrity. An active thermal cooling method is the injection of coolant around the pheriphery of the probe. How much coolant is required and how this coolant distributes itself in the flow field is of major concern. The objective of the work reported here is the use of CFD to answer these question and in the design of test hardware to substantiate the results of the CFD predictions.

Tiarn, Weihnurng; Cavalleri, Robert

1990-01-01

269

Electric sail control mode for amplified transverse thrust  

CERN Document Server

The electric solar wind sail produces thrust by centrifugally spanned high voltage tethers interacting with the solar wind protons. The sail attitude can be controlled and attitude maneuvers are possible by tether voltage modulation synchronous with the sail rotation. Especially, the sail can be inclined with respect to the solar wind direction to obtain transverse thrust to change the osculating orbit angular momentum. Such an inclination has to be maintained by a continual control voltage modulation. Consequently, the tether voltage available for the thrust is less than the maximum voltage provided by the power system. Using a spherical pendulum as a model for a single rotating tether, we derive analytical estimations for the control efficiency for two separate sail control modes. One is a continuous control modulation that corresponds to strictly planar tether tip motion. The other is an on-off modulation with the tether tip moving along a closed loop on a saddle surface. The novel on-off mode is introduce...

Toivanen, Petri; Envall, Jouni

2014-01-01

270

Flywheel Challenge: HTS Magnetic Bearing  

Energy Technology Data Exchange (ETDEWEB)

A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know.

Werfel, F N; Floegel-Delor, U; Riedel, T; Rothfeld, R; Wippich, D; Goebel, B [Adelwitz Technologiezentrum GmbH (ATZ), Rittergut Adelwitz, O4886 Arzberg (Germany)

2006-06-01

271

Flywheel Challenge: HTS Magnetic Bearing  

International Nuclear Information System (INIS)

A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know

272

Space Station alpha joint bearing  

Science.gov (United States)

Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.

Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.

1987-01-01

273

Geophagy by yellowstone grizzly bears  

Science.gov (United States)

We documented 12 sites in the Yellowstone ecosystem where grizzly bears (Ursus arctos horribilis) had purposefully consumed soil (an activity known as geophagy). We also documented soil in numerous grizzly bear feces. Geophagy primarily occurred at sites barren of vegetation where surficial geology had been modified by geothermal activity. There was no evidence of ungulate use at most sites. Purposeful consumption of soil by bears peaked first from March to May and again from August to October, synchronous with peaks in consumption of ungulate meat and mushrooms. Geophageous soils were distinguished from ungulate mineral licks and soils in general by exceptionally high concentrations of potassium (K) and high concentrations of magnesium (Mg) and sulphur (S). Our results do not support the hypotheses that bears were consuming soil to detoxify secondary compounds in grazed foliage, as postulated for primates, or to supplement dietary sodium, as known for ungulates. Our results suggest that grizzly bears could have been consuming soil as an anti-diarrheal.

Mattson, D.J.; Green, G.I.; Swalley, R.

1999-01-01

274

Bearing development program for a 25 kWe solar-powered organic Rankine-cycle engine  

Science.gov (United States)

The bearing development program is summarized for a 25-kWe power conversion subsystem (PCS) consisting of an organic Rankine-cycle engine, and permanent magnetic alternator (PMA) and rectifier to be used in a 100-kWe point-focusing distributed receiver solar power plant. The engine and alternator were hermetically sealed and used toluene as the working fluid. The turbine, alternator, and feed pump (TAP) were mounted on a single shaft operating at speeds up to 60,000 rev/min. Net thermal-to-electric efficiencies in the range of 21 to 23% were demonstrated at the maximum working fluid temperature of 400 C (750 F). A chronological summary of the bearing development program is presented. The primary causes of bearing wear problems were traced to a combination of rotordynamic instability and electrodynamic discharge across the bearing surfaces caused by recirculating currents from the PMA. These problems were resolved by implementing an externally supplied, flooded-bearing lubrication system and by electrically insulating all bearings from the TAP housing. This program resulted in the successful development of a stable, high-speed, toluene-lubricated five-pad tilting-pad journal bearing and Rayleigh step thrust bearing system capable of operating at all inclinations between horizontal and vertical.

Nesmith, B.

1985-01-01

275

Attitude Control for an Aero-Vehicle Using Vector Thrusting and Variable Speed Control Moment Gyros  

Science.gov (United States)

Stabilization of passively unstable thrust-levitated vehicles can require significant control inputs. Although thrust vectoring is a straightforward choice for realizing these inputs, this may lead to difficulties discussed in the paper. This paper examines supplementing thrust vectoring with Variable-Speed Control Moment Gyroscopes (VSCMGs). The paper describes how to allocate VSCMGs and the vectored thrust mechanism for attitude stabilization in frequency domain and also shows trade-off between vectored thrust and VSCMGs. Using an H2 control synthesis methodology in LMI optimization, a feedback control law is designed for a thrust-levitated research vehicle and is simulated with the full nonlinear model. It is demonstrated that VSCMGs can reduce the use of vectored thrust variation for stabilizing the hovering platform in the presence of strong wind gusts.

Shin, Jong-Yeob; Lim, K. B.; Moerder, D. D.

2005-01-01

276

Subduction mega-thrust beneath Mt. Fuji, central Japan  

Science.gov (United States)

The Philippine Sea plate (PHS) is being subducted beneath Honshu, associated with the buoyant subduction of the Izu-Bonin arc. Many scientists estimated the plate boundary along the northwestern part of the Izu collision zone, however, covered by volcanic products from Mt. Fuji and Hakone volcanoes, no active fault system is recognized. To reveal the location of plate boundary mega-trust and to evaluate the seismic hazards produced by these active faults, we performed deep and shallow high -resolution seismic reflection profiling across the flank of Mt. Fuji and Hakone volcanoes. Deep seismic data were acquired for 34-km-long seismic line, using four vibroseis trucks and explosives (IVI) and a 200 channels recording system. On the deep seismic section, westward dipping reflectors are dominant beneath the Hakone volcano on the PHS and extend to the west at the depth of 7 km beneath sub-horizontal reflectors. The top surface of the west dipping reflectors is interpreted as a plate boundary mega-thrust. The velocity profile obtained by refraction tomography suggests that the high velocity zone on the hanging wall and low velocity westward dipping layer in the footwall, which corresponds the volcanic products of Hakone volcano. The hanging-wall unit consists of the accreted arc crust from the Izu-Bonin arc, Quaternary coarse trough fill and Quaternary volcanic products. On the seismic section, the vertical offset of the top of Vp 5.4 km/sec zone is 2.5 km. Probable Quaternary coarse trough fill, deposited in the trough between the Izu-Bonin arc and Honshu arc, distributed on the mega-thrust forming wedge-shaped geometry. The high-resolution seismic section suggests that the plate boundary fault zone consists of several branching faults. The frontal thrust controlled the thickness of the deposits, probably younger than 300 ka, for 1-km-vertical offset, suggesting that the net slip rate of the major thrust is about 10 mm/y. Based on morphotectonic observation and high-resolution shallow seismic sections, it is highly probable that the thrust displaced the Gotemba debris avalanche deposits dated 2.9 ka (Miyachi et al., 2004). From the seismic hazard point of view, such large slip rate of this thrust indicates that the estimated magnitude of earthquake reaches to be M8-. As the seismogenic source fault is located beneath Mt. Fuji, strong ground motions produced by the movement of this fault, may cause the debris avalanche of the flank of Mt. Fuji and it has potential to produce devastative damage to the cities distributed on the flank of Mt. Fuji. Further research will be needed to obtain more precise estimate the seismic hazards produced by this mega-thrust.

Sato, H.; Ishiyama, T.; Iwasaki, T.; Abe, S.; Kato, N.; Imaizumi, T.; Hirata, N.

2012-12-01

277

Thermal barrier coatings (TBC's) for high heat flux thrust chambers  

Science.gov (United States)

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot-section components has become critical, but at the same time the service conditions have put our best alloy systems to their limits. As a result, implementation of cooling holes and thermal barrier coatings are new advances in hot-section technologies now looked at for modifications to reach higher temperature applications. Current thermal barrier coatings used in today's turbine applications is known as 8%yttria-stabilized zirconia (YSZ) and there are no coatings for current thrust chambers. Current research is looking at the applicability of 8%yttria-stabilized hafnia (YSH) for turbine applications and the implementation of 8%YSZ onto thrust chambers. This study intends to determine if the use of thermal barrier coatings are applicable for high heat flux thrust chambers using industrial YSZ will be advantageous for improvements in efficiency, thrust and longer service life by allowing the thrust chambers to be used more than once.

Bradley, Christopher M.

278

Alex the Bear Goes to Child Care  

Medline Plus

Full Text Available ... Guardians » Helpful Tools » Meet Alex the Bear Meet Alex the Bear, a new friend of Child Care ... a daunting experience for both children and parents. Alex the Bear, the newest friend of Child Care ...

279

Alex the Bear Goes to Child Care  

Science.gov (United States)

... Guardians » Helpful Tools » Meet Alex the Bear Meet Alex the Bear, a new friend of Child Care ... a daunting experience for both children and parents. Alex the Bear, the newest friend of Child Care ...

280

Alex the Bear Goes to Child Care  

Medline Plus

Full Text Available ... Tools » Meet Alex the Bear Meet Alex the Bear, a new friend of Child Care Aware® Going ... experience for both children and parents. Alex the Bear, the newest friend of Child Care Aware®, seeks ...

 
 
 
 
281

Bears, Big and Little. Young Discovery Library Series.  

Science.gov (United States)

This book is written for children 5 through 10. Part of a series designed to develop their curiosity, fascinate them and educate them, this volume describes: (1) the eight species of bears, including black bear, brown bear, grizzly bear, spectacled bear, sun bear, sloth bear, polar bear, and giant panda; (2) geographical habitats of bears; (3)…

Pfeffer, Pierre

282

Kinematics of thrust sheets within transverse zones: a structural and paleomagnetic investigation in the Appalachian thrust belt of Georgia and Alabama  

Science.gov (United States)

Deformation styles of orogenic belts change along strike across transverse zones (TZs); hence, the kinematics of TZs is indispensable for three-dimensional restoration of thrust belts. We investigate the causes of deviation in strike of fold axes and fault surfaces in two TZs of the southern Appalachians using structural cross-sections and paleomagnetism. In the Rising Fawn TZ of Georgia, hanging-wall lateral-ramp folds yield paleomagnetic rotations and variation in magnitude of thrust translation. Plunge of folds, differential slip, and rotations are associated with lateral-ramp geometry and along-strike variation in the rheology and thickness of units that host lower and upper detachment levels. In Alabama, the internal geometry, strike, and paleomagnetic rotations of the Helena thrust sheet change across the Anniston TZ. These differences resulted from movement of the Helena thrust sheet over different footwall blocks and sub-décollement basement graben structures, and from differential slip along an oblique ramp. Rotations of thrust sheets within TZs occur where a thrust sheet was translated over: (1) an oblique/lateral ramp with contrasting rock strengths at lower and upper detachment levels, (2) a transverse basement fault that separates contrasting basement structural domains, and (3) intersections between frontal ramps and transverse structures. Because of the local causes of rotations in lateral structures, paleomagnetic and structural analyses of TZs are necessary for understanding the kinematics and restoration of both single thrust sheets and large-scale curves in thrust belts.

Bayona, Germán; Thomas, William A.; Van der Voo, Rob

2003-08-01

283

Eastern slopes grizzly bear project  

Energy Technology Data Exchange (ETDEWEB)

The cumulative effects of human activities on the grizzly bears in the central Canadian Rockies are not well known. As a result, a project was initiated in 1994 to address the urgent requirement for accurate scientific information on the habitat and populations of grizzly bears in the area of the Banff National Park and Kananaskis Country. This area is probably the most heavily used and developed area where the grizzly still survives. The information gathered throughout the course of this study will be used to better protect and manage the bears and other sensitive carnivores in the region. Using telemetry, researchers are monitoring 25 grizzly bears which were radio-collared in a 22,000 square-kilometer area in the upper Bow Valley drainage of the eastern Alberta slopes. The researchers involved in the project are working with representatives from Husky Oil and Talisman Energy on the sound development of the Moose Mountain oil and gas field without adversely affecting the grizzly bear population. Information collected over seven years indicated that the grizzly bears have few and infrequent offspring. Using the information gathered so far, the location of the Moose Mountain to Jumping Pound pipeline was carefully selected, since the bears recover very slowly from high mortality, and also considering that the food and cover had already been compromised by the high number of roads, trails and other human activities in the area. The status of the population and habitat of the grizzly bear will be assessed upon the conclusion of the field research phase in 2001. Models will be updated using the data obtained during eight years and will assist in the understanding of complex variables that affect grizzly bears.

NONE

2001-01-01

284

Random bearings and their stability  

CERN Document Server

Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity are studied.

Baram, R M

2005-01-01

285

Paleogeographic inversion resulting from large out of sequence breaching thrusts: The León Fault (Cantabrian Zone, NW Iberia). A new picture of the external Variscan Thrust Belt in the Ibero-Armorican Arc  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Out of sequence breaching thrusts may give rise to duplication of a former thrust stack in map view in the same manner that stratigraphic units are repeated by initial thrusts. In this way, large breaching thrusts may put an inicial paleogeographic pattern out of order, producing apparent paleogeographic inversions at regional scale. The León Fault, an orogen-scale fault located in the Variscan foreland fold-thrust belt of the Iberian Peninsula, known as the Cantabrian Zone, has caused much ...

Alosno, J. L.

2009-01-01

286

Structural evidence for northeastward movement on the Chocolate Mountains thrust, southeasternmost Calfornia  

Energy Technology Data Exchange (ETDEWEB)

The Late Cretaceous Chocolate Mountains thrust of southeastern California and southwestern Arizona places a block of Proterozoic and Mesozoic continental crust over the late Mesozoic continental margin oceanic sedimentary and volcanic rocks of the regionally distinctive Orocopia Schist. The Chocolate Mountains thrust is interpreted as a thrust (burial, subduction) fault rather than a low-angle normal (exhumation, unroofing, uplift) fault. The Chocolate Mountains thrust zone contains sparse to locally abundant mesoscopic asymmetric folds. Fabric relations indicate that these folds are an integral part of and coeval with the thrust zone. On a lower hemisphere equal-area plot representing the orientation and sense of asymmetry of 80 thrust zone folds from 36 localities, spread over an area 60 by 10 km, Z folds plot northwest of and S folds plot southeast of a northeast-southwest striking vertical plane of overall monoclinic symmetry. The only sense of movement consistent with the collective asymmetry of the thrust zone folds is top to the northeast. Paleomagnetic data suggest that the original sense of thrusting, prior to Neogene vertical axis tectonic rotation related to the San Andreas fault system, was northward. The essential point is that movement of the upper plate of the Chocolate Mountains thrust evidently was continentward. Continentward thrusting suggests a tectonic scenario in which an insular or peninsular microcontinental fragment collided with mainland southern California. Alternative tectonic models involving subduction of the Orocopia Schist eastward beneath continental southern California circumvent the suture problem but are presently not supported by any direct structural evidence.

Dillon, J.T. (Alaska Div. of Geological and Geophysical Surveys, Fairbanks (USA)); Haxel, G.B. (Geological Survey, Flagstaff, AZ (USA)); Tosdal, R.M. (Geological Survey, Menlo Park, CA (USA))

1990-11-10

287

Emplacement history of a thrust sheet based on analysis of pressure solution cleavage and deformed fossils  

Energy Technology Data Exchange (ETDEWEB)

The emplacement history of a thrust sheet is recorded by the strain accumulated in its hanging wall and footwall. Detailed studies of second order structures and analysis of strain due to pressure solution and plastic deformation allow the authors to determine the deformation history of the Meade thrust in the Idaho - Wyoming thrust belt. Emplacement of the Meade thrust was accompanied by the formation of a series of second order in echelon folds in the footwall. Temporal relations based on detailed structural studies show that these folds, which are confined to the Jurassic Twin Creek Formation, formed progressively in front of the advancing Meade thrust and were successively truncated and overridden by footwall imbricates of the Meade thrust. The Twin Creek Formation in both the hanging wall and footwall of the Meade thrust is penetratively deformed, with a well developed pressure solution cleavage. In addition, plastic strain is recorded by deformed Pentacrinus within fossil hash layers in the Twin Creek. Much of this penetrative deformation took place early in the history of the thrust sheet as layer parallel shortening, and the cleavage and deformed fossils behaved passively during subsequent folding and faulting. The later stages of deformation may be sequentially removed through balancing techniques to track successive steps in the deformation. This strain history, which is typical of an internal thrust sheet, is partly controlled by the lithologies involved, timing between successive thrusts, and the amount of interaction between major faults.

Protzman, G.M.; Mitra, G.

1985-01-01

288

Gravity sliding, thrusting, and petroleum traps in the Magdalena Basins and Cordillera Orientale, Colombia  

Energy Technology Data Exchange (ETDEWEB)

Major gravity slides on flanks of mountain belts can be misinterpreted as tectonic thrusts. They occur as synclines ([open quotes]fauteuils glisses[close quotes]) striking sub-parallel to dip slopes of major uplifts, overlie low-angle listric thrusts which pass upslope into listric or bedding-parallel normal faults, and may be associated with gravity-driven buried thrust fronts. The Nuevo Mondo syncline, underlain by the La Salinas thrust, and similar synclines along the east side of the Magdalena valley are interpreted as [open quotes]fauteuils glisses[close quotes], whose occurrence at the edge of the Cordillera Orientale creates an illusion of westward thrusting. Minor faults, formerly interpreted as east-dipping reverse faults along the west edge of the Cordillera Orientale are too small to have uplifted the Cordillera or to be correlatable with the major thrusts beneath synclines. They are reinterpreted as major west-dipping parallel faults, pass downslope westward beneath the synclines and/or into blind imbricate thrust structures. The Magdalena basins contain attractive east-verging tectonic thrust traps for hydrocarbons, and less attractive post-tectonic west-verging thrust traps formed by sliding down the east flank of the basin. Interpretation of these structures as post-deformational features allows modeling of the Cordillera Orientale as an overthrust sheet about 10 km thick that moved over 160 km southeastward. Its ramp underlies the east flank of the Magdalena basins. Its buried thrust front marks the edge of the Llanos basin.

Jones, P.B. (International Tectonic Consultants Ltd., Calgary, Alberta (Canada))

1993-02-01

289

Preliminary Design of Low-Thrust Interplanetary Missions  

Science.gov (United States)

For interplanetary missions, highly efficient electric propulsion systems can be used to increase the mass delivered to the destination and/or reduce the trip time over typical chemical propulsion systems. This technology is being demonstrated on the Deep Space 1 mission - part of NASA's New Millennium Program validating technologies which can lower the cost and risk and enhance the performance of future missions. With the successful demonstration on Deep Space 1, future missions can consider electric propulsion as a viable propulsion option. Electric propulsion systems, while highly efficient, produce only a small amount of thrust. As a result, the engines operate during a significant fraction of the trajectory. This characteristic makes it much more difficult to find optimal trajectories. The methods for optimizing low-thrust trajectories are typically categorized as either indirect, or direct. Indirect methods are based on calculus of variations, resulting in a two-point boundary value problem that is solved by satisfying terminal constraints and targeting conditions. These methods are subject to extreme sensitivity to the initial guess of the variables - some of which are not physically intuitive. Adding a gravity assist to the trajectory compounds the sensitivity. Direct methods parameterize the problem and use nonlinear programming techniques to optimize an objective function by adjusting a set of variables. A variety of methods of this type have been examined with varying results. These methods are subject to the limitations of the nonlinear programming techniques. In this paper we present a direct method intended to be used primarily for preliminary design of low-thrust interplanetary trajectories, including those with multiple gravity assists. Preliminary design implies a willingness to accept limited accuracy to achieve an efficient algorithm that executes quickly.

Sims, Jon A.; Flanagan, Steve N.

1997-01-01

290

A Passive Magnetic Bearing Flywheel  

Science.gov (United States)

A 100 percent passive magnetic bearing flywheel rig employing no active control components was designed, constructed, and tested. The suspension clothe rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm, which is 65 percent above the first critical speed of 3336 rpm. Operation was not continued beyond this point because of the excessive noise generated by the air impeller and because of inadequate containment in case of failure. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.

Siebert, Mark; Ebihara, Ben; Jansen, Ralph; Fusaro, Robert L.; Morales, Wilfredo; Kascak, Albert; Kenny, Andrew

2002-01-01

291

Antiformal closure in ductile and brittle-ductile in fold-and-thrust belt tranverse zones, Moine Thrust Belt, NW Scotland  

Science.gov (United States)

Abrupt lateral changes in thrust geometry occur in many mountain-building fold-and-thrust belts. Such changes in architecture are referred to as so-called transverse zones, and are commonly thought to be related to kinematic responses to irregularities generated across pre-existing, sometimes re-activated, basement faults. In many cases however the causative structure is concealed, either by distal parts of the thrust belt or the foreland basin. Sharp lateral changes in the structural geometry of ductile thrust stacks are less widely studied and reported. In NW Scotland, the classic Caledonian WNW-vergent Moine Thrust Belt exposes excellent examples of the structural architecture in such transverse zones, both in kilometre-scale thick monolithic (meta-)sandstone packages subject to ductile deformation, and in much thinner heterolithic packages subject to brittle-ductile deformation. In both cases the amplitude of the antiformal disturbance associated with the transverse zone is much greater than amplitude of any irregularity identified in the basement below. In Neoproterozoic Moine rocks in the hanging wall of the Moine Thrust, a large-scale lateral culmination wall forms a component part of the Oykel Transverse Zone (OTZ), a kilometre-scale thick constrictional ductile shear zone striking sub-parallel to the WNW-directed thrust transport direction. The OTZ forms the SW limit of the Cassley Culmination. ESE-plunging mullions are an integral part of the fabric of the transverse zone and were generated by constriction sub-parallel to the WNW-directed thrust transport direction. Main folds and fabrics in the transverse zone hanging-wall are folded by main folds and fabrics in the footwall, demonstrating the overall foreland-propagating record of ductile deformation as the Cassley Culmination grew. Constriction and mullion development are attributed to differential, transtensional movement across the transverse zone during the later stages of culmination development. Subsequent formation of the classic Assynt Culmination below the Moine Thrust accentuated upwards-bulging of the Cassley Culmination above, amplifying the lateral change across the Oykel Tranverse Zone. The OTZ aligns with a pronounced gravity gradient; interpretive geophysical modelling relates this gradient to a buried basement ramp that possibly controlled the location of the transverse zone. Farther towards the foreland in the Assynt Culmination of the Moine Thrust Belt, the Traligill Transverse Zone also trends sub-parallel to the transport direction and is associated with an en echelon fault system cutting thrusts, with discontinuity of the thrust and thrust sheet architecture, and with oblique fold and thrust structures. This transverse zone is developed above a basement cross-fault which records repeated brittle reactivation of a Proterozoic shear zone. Thrusting thus deformed a sedimentary sequence that was already disrupted by faults aligned sub-parallel to the thrust transport direction. The amplitude of the anticlinal disturbance in the fold-and-thrust architecture along the Traligill Transverse Zone is much greater (c. 1000 m) than the vertical displacement (c. 100 m) determined along the fault; this is attributed to oblique transpressional thrust-stacking within the transverse zone, generated by the small angle between the thrust transport direction and the strike of the pre-existing fault.

Leslie, G.; Krabbendam, M.

2009-04-01

292

Experiments on heat transfer in a cryogenic engine thrust chamber  

Science.gov (United States)

Tests are conducted on a cryogenic engine using liquid oxygen as oxidizer and gaseous hydrogen as fuel with water as a coolant. The coolant flow passage of the thrust chamber is of milled channel configuration. Measured heat transfer results compare well with those predicted by a thermal analysis using the standard Bartz correlation and the Hess and Kunz correlation for hot gas side and coolant side heat transfer coefficients, respectively. This confirms the conclusions of a recent theoretical study by the authors in which a comparison of various heat transfer correlations was made.

Sugathan, N.; Srinivasan, K.; Srinivasa Murthy, S.

1993-04-01

293

Guidance Law for a Flight Vehicle after Thrust Cutoff  

Science.gov (United States)

This paper deals with a guidance law for a flight vehicle with varying velocity after thrust cutoff. This guidance law is mechanized by combining the proportional navigation and the pure pursuit navigation with the mixture ratio. Since the performance of the guidance law depends on the ratio, the discussion is focused on the determination of the ratio. Finally, the simulation results show that if the LOS angle noises are small, the proposed guidance law is effective even if the missile velocity decreases and has higher off-boresight ability than the proportional navigation.

Dohi, Naoto; Baba, Yoriaki; Takano, Hiroyuki

294

Pulsatory phenomenon in a thrust optimized contour nozzle  

Energy Technology Data Exchange (ETDEWEB)

A numerical study of the flow in an axisymmetric over-expanded thrust optimized contour nozzle is presented. The separation flow structures at different pressure ratios are investigated. The start-up process exhibits two different shock structures. For a range of pressure ratios, hysteresis phenomenon occurs between these two separation patterns. For a larger pressure ratio, where the principal separation point is always inside the nozzle, another phenomenon appears. This phenomenon results in an oscillatory longitudinal quasi periodic movement of the separation structure. The computed nozzle wall pressures show a correct agreement with the experimental measurements and the pulsations frequency of the oscillatory phenomenon is also well predicted. (authors)

Nebbache, A.; Pilinski, C. [Institut National de Recherches Agronomiques (INRA), CORIA-LMFN, UMR 6614, 76 - Rouen (France)

2006-05-15

295

Design of high power electromechanical actuator for thrust vector control  

Science.gov (United States)

NASA-Marshall has undertaken the development of electromechanical actuators (EMAs) for thrust vector control (TVC) augmentation system implementation. The TVC EMA presented has as its major components two three-phase brushless dc motors, a two-pass gear-reduction system, and a roller screw for rotary-to-linear motion conversion. System control is furnished by a solid-state electronic controller and power supply; a pair of resolvers deliver position feedback to the controller, such that precise positioning is achieved. Peformance comparisons have been conducted between the EMA and comparable-performance hydraulic systems applicable to TVCs.

Cowan, J. R.; Myers, W. N.

1991-01-01

296

Thrust vector control algorithm design for the Cassini spacecraft  

Science.gov (United States)

This paper describes a preliminary design of the thrust vector control algorithm for the interplanetary spacecraft, Cassini. Topics of discussion include flight software architecture, modeling of sensors, actuators, and vehicle dynamics, and controller design and analysis via classical methods. Special attention is paid to potential interactions with structural flexibilities and propellant dynamics. Controller performance is evaluated in a simulation environment built around a multi-body dynamics model, which contains nonlinear models of the relevant hardware and preliminary versions of supporting attitude determination and control functions.

Enright, Paul J.

1993-01-01

297

Variable thrust/specific-impulse of multiplexed electrospray microthrusters  

Science.gov (United States)

We report on the development of a single-propellant ElectroSpray (ES) microthruster able to: (a) cover a wide range of specific impulse (Isp) and thrust at high propulsion efficiency, and (b) provide macroscopic thrust via micro-fabricated emitter arrays. The electrospray is a mature technology for the emission of fast nanodroplets at a propulsive efficiency larger than 50% over the full Isp range. The size of the droplets depends on the propellant flow rate and the physical properties of the electrolyte, especially the electric conductivity. To achieve a useful thrust one needs to multiplex the ES by operating many in parallel, which we achieve via silicon microfabrication of arrays of multiple and identical nozzles. The Multiplexed Electrospray (MES) micro-thruster is composed mainly of two electrodes: a nozzle-array and an extractor electrode, between which the electric field needed to form the ES is established. We tested nozzle arrays with up to 37 capillaries, that are spaced 1mm apart, with ID/OD = 10/30? m. The capillaries are filled with 2.01? m silicon dioxide beads to increase the hydraulic impedance and ensure uniform flow rate through the different emitters. A third electrode (accelerator) is mounted downstream the extractor to accelerate the droplets, thereby increasing the microthruster performance. The system is packaged in an alumina casing for electrical insulation and propellant feed. Tests run in a vacuum chamber at a pressure ? 10-5 mbar demonstrated reliable operation for several hours with a relatively high beam energy of 7.56kV. The 37-nozzle MES device was tested with the ionic liquid ethylammonium nitrate (EAN), at estimated total flow rates between 1.2 and 14 ? L/h, emitted currents between 14.2 and 23.0 ? A, specific impulse ranging between 710 and 1930s, and thrust ranging between 7.5 and 33 ? N. EAN is well suited to cover a relatively broad range of charge/mass- at an average propulsion efficiency of 66%. With further scale-up to a 600-MES system, the device would be suitable for micro-satellites missions such as attitude control and station keeping.

Lenguito, G.; Fernandez de la Mora, J.; Gomez, A.

298

Light gluino effects in thrust at NNLL order  

International Nuclear Information System (INIS)

Recent progress in computations of event shape distributions have reduced uncertainties in the strong coupling from fits to available experimental data to the percent level. It is therefore reasonable to ask for possible effects of new physics. We consider the effects of light gluinos in the thrust distribution at the NNLL order level in the framework of Soft-Collinear-Effective-Theory (SCET). This involves modifications of the standard QCD renormalization group evolution and the computation of additional corrections to the hard, jet and soft functions that appear in the SCET factorization theorem.

299

FIDD bearing-only SLAM  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Simultaneous Localization and Mapping (SLAM) is perhaps the most fundamental problem to solve in robotics in order to build truly autonomous mobile robots. The sensors have a large impact on the algorithm used for SLAM. In this work a novel method, called Filtered Inverse Depth Delayed (FIDD) Initialization which is intended for initializing new features in Bearing-Only SLAM systems. Unlike range sensors which provide range and angular information, a bearing sensor (e.g. cameras) mea...

Mungui?a Alcala?, Rodrigo Francisco; Grau Saldes, Antoni

2010-01-01

300

Teddy Bear Line-Up  

Science.gov (United States)

This problem requires children to develop logical reasoning and promotes using visualization to plan ahead. Students are presented with a line of four blue, then four red followed by four yellow and finally four green bears and are asked to rearrange them using the least number of moves so that no two bears of the same color are next to each other. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, and an idea for support and extension.

2009-04-01

 
 
 
 
301

Failure analysis of superconducting bearings  

International Nuclear Information System (INIS)

The dynamics of superconductor bearings in a cryogenic failure scenario have been analyzed. As the superconductor warms up, the rotor goes through multiple resonance frequencies, begins to slow down and finally touches down when the superconductor goes through its transition temperature. The bearing can be modelled as a system of springs with axial, radial and cross stiffness. These springs go through various resonant modes as the temperature of the superconductor begins to rise. We have presented possible explanations for such behaviour

302

Designing Rolling-Element Bearings  

Science.gov (United States)

Bearing Analysis Tool (BAT) is a computer program for designing rolling-element bearings for cryogenic turbomachines. BAT provides a graphical user interface (GUI) that guides the entry of data to develop mathematical models of bearings. The GUI breaks model data into logical subsets that are entered through logic-driven input screens. The software generates a threedimensional graphical model of a bearing as the data are entered. Most dataentry errors become immediately obvious in the graphical model. BAT provides for storage of all the data on a shaft/bearing system, enabling the creation of a library of proven designs. Data from the library can be transferred to subsequent projects by use of simple cut-and-paste routines. BAT includes a library of temperature- dependent cryogenic bearing-material properties for use in the mathematical models. BAT implements algorithms that (1) enable the user to select combinations of design and/or operating-condition parameters, and then (2) automatically optimize the design by performing trade studies over all of the parameter combinations. This feature enables optimization over a large trade space in a fraction of the time taken when using prior bearingmodel software.

Moore, James D., Jr.

2007-01-01

303

Dynamic friction and wear in a planar-contact encapsulated microball bearing using an integrated microturbine  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The demonstration and characterization of a novel planar-contact encapsulated microball bearing using a radial in-flow microturbine are presented. Stable operation of the air-driven silicon microturbine is shown for over 1 000 000 revolutions at speeds, pressure drops, and flow rates of up to 10 000 r/min, 0.45 lbf/in2, and 3.5 slm, respectively. Incorporation of a gas thrust plenum using a novel packaging scheme has enabled comprehensive spin-down friction characterization of the encapsulate...

Mccarthy, Matthew; Waits, C. Mike; Ghodssi, Reza

2008-01-01

304

Improvement of hemolysis in a centrifugal blood pump with hydrodynamic bearings and semi-open impeller.  

Science.gov (United States)

We have developed a centrifugal blood pump with hydrodynamic bearings and semi-open impeller, and evaluated the levitation performance test and the hemolysis test. This pump is operated without any complicated control circuit and displacement-sensing module. The casing diameter is 74 mm and the height is 38 mm including flanges for volts. The weight is 251 g and the volume is 159 cm3. By changing the stator relative position against the rotor, the levitation characteristics of the impeller can be adjusted. The diameter of impeller is 36 mm and the height is 25 mm. The impeller is levitated by the thrust bearing of spiral groove type and a radial bearing of herringbone type. The pump performance was evaluated through the levitation performance test and the hemolysis test. As a result, the normalized index of hemolysis (NIH) was reduced from 0.72 g/100 L to 0.024 g/100 L corresponding to the changes of the groove direction of the hydrodynamic bearing and the expansion of the bearing gap. During these studies, we confirmed that the hemolytic property was improved by balancing the fluid dynamic force and the magnetic force. PMID:18002872

Kosaka, Ryo; Yamane, Takashi; Maruyama, Osamu; Nishida, Masahiro; Yada, Toru; Saito, Sakae; Hirai, Shusaku

2007-01-01

305

Thrust-breakthrough of asymmetric anticlines: Observational constraints from surveys in the Brooks Range, Alaska  

Science.gov (United States)

To gain insights into the processes governing the thrust-truncation of anticlines, we conducted a field study of the thrust-truncated folds in the remote Brooks Range of northern Alaska, where there is a transition in fold style from symmetric detachment folds to thrust-truncated asymmetric folds. In order to document the detailed geometry of the km-scale folds exposed in cliff-forming, largely inaccessible outcrops, a new surveying technique was developed that combines data from a theodolite and laser range finder. The field observations, survey profiles, and cross section reconstructions, indicate that late-stage thrust breakthrough of the anticlines within the mechanically competent Lisburne Group carbonates accommodated continued shortening when other mechanisms became unfeasible, including fold tightening, forelimb rotation, and parasitic folding in the anticline forelimbs. These results provide constraints on the processes that govern the transition from buckle folding to thrust truncation in fold-and-thrust belts worldwide.

Jadamec, Margarete A.; Wallace, Wesley K.

2014-05-01

306

Effect of Fuel Properties on the Specific Thrust of a Ramjet Engine  

Directory of Open Access Journals (Sweden)

Full Text Available Various aspects of specific thrust in ramjet propulsion have been considered. It is shown that while the peak specific impulse of ideal ramjet is theoretically obtained for fuel/air ratio f 0, the specific thrust which determines the thrust level of a given engine at certain operating conditions, increases with increasing fuel/air ratio up to (approximately the stoichiometric ratio. Furthermore, in general, the specific thrust is related to the heat release per unit mass of air fqR, where the theoretical maximum is approximately proportional to its square root in stoichiometric conditions, fstqR. This can be the basis for selecting an appropriate fuel according to its potential specific thrust. It should be noted that certain metals such as magnesium, aluminum, and zirconium can provide about three-times higher specific heat release than hydrocarbons or hydrogen. Thus, these may be the better candidates for missions requiring high specific thrusts.

Alon Gany

2006-07-01

307

"Null-E" magnetic bearings  

Science.gov (United States)

Using electromagnetic forces to suspend rotating objects (rotors) without mechanical contact is often an appealing technical solution. Magnetic suspensions are typically required to have adequate load capacity and stiffness, and low rotational loss. Other desired features include low price, high reliability and manufacturability. With recent advances in permanent-magnet materials, the required forces can often be obtained by simply using the interaction between permanent magnets. While a magnetic bearing based entirely on permanent magnets could be expected to be inexpensive, reliable and easy to manufacture, a fundamental physical principle known as Earnshaw's theorem maintains that this type of suspension cannot be statically stable. Therefore, some other physical mechanisms must be included. One such mechanism employs the interaction between a conductor and a nonuniform magnetic field in relative motion. Its advantages include simplicity, reliability, wide range of operating temperature and system autonomy (no external wiring and power supplies are required). The disadvantages of the earlier embodiments were high rotational loss, low stiffness and load capacity. This dissertation proposes a novel type of magnetic bearing stabilized by the field-conductor interaction. One of the advantages of this bearing is that no electric field, E, develops in the conductor during the rotor rotation when the system is in no-load equilibrium. Because of this we refer to it as the Null-E Bearing. Null-E Bearings have potential for lower rotational loss and higher load capacity and stiffness than other bearings utilizing the field-conductor interaction. Their performance is highly insensitive to manufacturing inaccuracies. The Null-E Bearing in its basic form can be augmented with supplementary electronics to improve its performance. Depending on the degree of the electronics involvement, a variety of magnetic bearings can be developed ranging from a completely passive to an active magnetic bearing of a novel type. This dissertation contains theoretical analysis of the Null-E Bearing operation, including derivation of the stability conditions and estimation of some of the rotational losses. The validity of the theoretical conclusions has been demonstrated by building and testing a prototype in which non-contact suspension of a 3.2-kg rotor is achieved at spin speeds above 18 Hz.

Filatov, Alexei Vladimirovich

2002-09-01

308

Saturn IB S-IB Stage Thrust Structure Assembly at Michoud Assembly Facility (MAF)  

Science.gov (United States)

In one of the initial assembly steps for the Saturn IB launch vehicle's S-IB (first) stage, workers at the Michoud Assembly Facility (MAF) near New Orleans, Louisiana, complete the thrust structure. Developed by the Marshall Space Flight Center and built by the Chrysler Corporation at Michoud Assembly Facility (MAF), the S-IB utilized eight H-1 engines and each produced 200,000 pounds of thrust, a combined thrust of 1,600,000 pounds.

1969-01-01

309

Research at IMU: achievements, thrust areas and future challenges  

Directory of Open Access Journals (Sweden)

Full Text Available There have been significant achievements inresearch at IMU as indicated by the increasing amountof external funds obtained, and number of publicationsand postgraduate students produced since it startedits research activities in the year 2000. However, it isa great challenge indeed to ensure sustainability ofour research, which is currently heavily dependent oninternal funding. There is a need to realign our strategiesto further enhance our competitiveness in securingexternal funding for research. In line with this, theInstitute for Research, Development and Innovation(IRDI was officially established on 18 September2012. The Institute will serve as a platform to supportall research activities at IMU. There are four Centresof Excellence based on the identified thrust areas underIRDI, namely 1 Centre for Bioactive Molecules andDrug Discovery; 2 Centre for Environmental andPopulation Health; 3 Centre for Cancer and StemCell Research, and 4 Centre for Health ProfessionalEducation Research. Major findings based on research inthese four thrust areas are reviewed in this paper. Withthe strategic planning and establishment of IRDI, it isour aspiration to bring research at IMU to a higher level.

Wan-Loy Chu

2013-04-01

310

Experimental performance of cascade thrust reversers at forward velocity  

Science.gov (United States)

A series of static and wind tunnel tests were performed on four cowl cascade thrust reverser configurations which had various reversed jet emission patterns applicable to an externally blown flap STOL aircraft. The work was performed using a model fan which was 14.0 cm in diameter and passed a fan mass flow of 2.49 kg/sec at an approximate fan pressure ratio of 1.22 and fan corrected rotational speed of 35,800 rpm. The tests demonstrated that the reingestion of fan flow significantly reduced the reverser efficiency and that the thrust reverser efficiency was improved by reducing the reversed jet azimuthal emmission angle. The reverser efficiency at STOL landing speeds was as high as 0.95; however, configurations with lateral emission were adversely affected by yawing the nacelle at forward velocity. Measurements of the internal static pressure at the stator exit showed significant increases in the local static pressure for configurations with reduced jet emission angles.

Dietrich, D. A.; Luidens, R. W.

1973-01-01

311

Precision electromagnetic calibration technique for micro-Newton thrust stands  

Science.gov (United States)

This paper introduces a new direct non-contact electromagnetic calibration technique for high precision measurements of micro-thrust and impulse. A ring-shaped electromagnet with an air gap is used in the calibration. The calibration force is produced by the interaction of a uniform magnetic field with a copper wire current in the air gap. This force depends linearly on this current as well as the steady angular displacement of the torsion arm of the thrust stand. The range of calibration force is very large and the calibration force is easy to generate and insensitive to the arm displacement. The calibration uncertainty for a 150-?N force is 4.17 ?N. The more influential factor on the calibration uncertainty is the magnetization of the electromagnet core due to the copper wire current. In the impulse calibration, the exerted impulse is linearly dependent on the maximal angular displacement of the torsion arm. The uncertainty in the impulse calibration is determined by uncertainties in both the force calibration and the pulse time.

He, Zhen; Wu, Jianjun; Zhang, Daixian; Lu, Gaofei; Liu, Zejun; Zhang, Rui

2013-05-01

312

Compact and High Thrust Air Turbo Ram Engine  

Science.gov (United States)

The Air Turbo Ramjet (ATR) is a combined cycle engine which performs like a turbojet engine at subsonic speeds and a ramjet at supersonic speeds and therefore the ATR is an attractive propulsion system for the wide operation range (e.g. Mach 0 to Mach 4). The ATR can provide a higher specific impulse than a solid fuel rocket engine and a higher thrust per frontal area than a turbojet engine. The major ATR components are the inlet, fan (compressor), turbine, gas generator, combustor and exhaust nozzle. In the ATR, the turbine drive gas is generated by a decomposed liquid or solid fuel gas generator. In order to carry heavier payloads and to attain shorter flight time, the compact and high thrust engine is required. In this study, the ram combustor with the double-staged flameholders and the fan with tandem blade were introduced to shorten the engine length and to increase the fan pressure ratio, respectively. Furthermore, the engine testing was carried out on sea level static condition to confirm the engine component integration technologies for the ATR propulsion system.

Hasegawa, Hiroaki; Kitahara, Kazuki; Inukai, Yasuo

313

Trajectory Optimization of Multi-Asteroids Exploration with Low Thrust  

Science.gov (United States)

Multi-asteroid tour missions require consideration of the visiting sequences and trajectory optimization for each leg, which is a typical global optimization problem. In this paper, the problem is divided into a multi-level optimization problem. Determination of the visiting sequence plays a key part for a tour mission. In this paper, the energy differences between different orbits and phase differences are used to estimate the energy required for a tour mission. First, this paper discusses the relation between fuel cost for transfer and classical orbit elements difference based on the energy relation of Keplerian orbits and the characteristics of low-thrust spacecraft. Second, the phase difference is combined with the energy difference to achieve the rendezvous energy. In addition, the lower and upper bounds of rendezvous time can be estimated by analyzing the phase difference. Very-low-thrust trajectory optimization problems have always been considered difficult problems due to the large time scales. In this paper, a hybrid algorithm of PSO (particle swarm optimization) and DE (differential evolution) is used to achieve a solution to the energy-optimal tour mission. Based on GTOC-3 (Global Trajectory Optimization Competition), this paper determines the exploration sequence and provides the optimal solution.

Zhu, Kaijian; Jiang, Fanghua; Li, Junfeng; Baoyin, Hexi

314

Design of Force Sensor Leg for a Rocket Thrust Detector  

Science.gov (United States)

A hybrid rocket is composed of a solid fuel and a separate liquid or gaseous oxidizer. These rockets may be throttled like liquid rockets, are safer than solid rockets, and are much less complex than liquid rockets. However, hybrid rockets produce thrust oscillations that are not practical for large scale use. A lab scale hybrid rocket at the University of Arkansas at Little Rock (UALR) Hybrid Rocket Facility is used to develop sensors to measure physical properties of hybrid rockets. Research is currently being conducted to design a six degree of freedom force sensor to measure the thrust and torque in all three spacial dimensions. The detector design uses six force sensor legs. Each leg utilizes strain gauges and a Wheatstone bridge to produce a voltage propotional to the force on the leg. The leg was designed using the CAD software ProEngineer and ProMechanica. Computer models of the strains on the single leg will be presented. A prototype leg was built and was tested in an INSTRON and results will be presented.

Woten, Douglas; McGehee, Tripp; Wright, Anne

2005-03-01

315

Design and test of electromechanical actuators for thrust vector control  

Science.gov (United States)

New control mechanisms technologies are currently being explored to provide alternatives to hydraulic thrust vector control (TVC) actuation systems. For many years engineers have been encouraging the investigation of electromechanical actuators (EMA) to take the place of hydraulics for spacecraft control/gimballing systems. The rationale is to deliver a lighter, cleaner, safer, more easily maintained, as well as energy efficient space vehicle. In light of this continued concern to improve the TVC system, the Propulsion Laboratory at the NASA George C. Marshall Space Flight Center (MSFC) is involved in a program to develop electromechanical actuators for the purpose of testing and TVC system implementation. Through this effort, an electromechanical thrust vector control actuator has been designed and assembled. The design consists of the following major components: Two three-phase brushless dc motors, a two pass gear reduction system, and a roller screw, which converts rotational input into linear output. System control is provided by a solid-state electronic controller and power supply. A pair of resolvers and associated electronics deliver position feedback to the controller such that precise positioning is achieved. Testing and evaluation is currently in progress. Goals focus on performance comparisons between EMA's and similar hydraulic systems.

Cowan, J. R.; Weir, Rae Ann

1993-01-01

316

Thrust and efficiency model for electron-driven magnetic nozzles  

International Nuclear Information System (INIS)

A performance model is presented for magnetic nozzle plasmas driven by electron thermal expansion to investigate how the thrust coefficient and beam divergence efficiency scale with the incoming plasma flow and magnetic field geometry. Using a transformation from cylindrical to magnetic coordinates, an approximate analytical solution is derived to the axisymmetric two-fluid equations for a collisionless plasma flow along an applied magnetic field. This solution yields an expression for the half-width at half-maximum of the plasma density profile in the far-downstream region, from which simple scaling relations for the thrust coefficient and beam divergence efficiency are derived. It is found that the beam divergence efficiency is most sensitive to the density profile of the flow into the nozzle throat, with the highest efficiencies occurring for plasmas concentrated along the nozzle axis. Increasing the expansion ratio of the magnetic field leads to efficiency improvements that are more pronounced for incoming plasmas that are not concentrated along the axis. This implies that the additional magnet required to increase the expansion ratio may be worth the added complexity for plasma sources that exhibit poor confinement

317

Thrust and efficiency model for electron-driven magnetic nozzles  

Energy Technology Data Exchange (ETDEWEB)

A performance model is presented for magnetic nozzle plasmas driven by electron thermal expansion to investigate how the thrust coefficient and beam divergence efficiency scale with the incoming plasma flow and magnetic field geometry. Using a transformation from cylindrical to magnetic coordinates, an approximate analytical solution is derived to the axisymmetric two-fluid equations for a collisionless plasma flow along an applied magnetic field. This solution yields an expression for the half-width at half-maximum of the plasma density profile in the far-downstream region, from which simple scaling relations for the thrust coefficient and beam divergence efficiency are derived. It is found that the beam divergence efficiency is most sensitive to the density profile of the flow into the nozzle throat, with the highest efficiencies occurring for plasmas concentrated along the nozzle axis. Increasing the expansion ratio of the magnetic field leads to efficiency improvements that are more pronounced for incoming plasmas that are not concentrated along the axis. This implies that the additional magnet required to increase the expansion ratio may be worth the added complexity for plasma sources that exhibit poor confinement.

Little, Justin M.; Choueiri, Edgar Y. [Electric Propulsion and Plasma Dynamics Laboratory, Princeton University, Princeton, New Jersey 08544 (United States)

2013-10-15

318

Thrust Ripples Reduction for a Vector Controlled Permanent Magnet Linear Synchronous Motor with IMC Controller  

Directory of Open Access Journals (Sweden)

Full Text Available The significant drawback of PMLSM is thrust ripples, which is mainly generated by the detent force caused by the interaction of the permanent magnet and iron core without input current in armature winding. It is the function of mover position relative to the stator. This will deteriorate the performance of the drive system in high precision applications. This paper focus on the thrust ripples reduction. To minimize the thrust ripples and realize the high-precision control, the components of thrust ripples are extracted first and then compensate with PI and IMC (Internal Model Control controller

RAMESH BABU.DEVA

2013-06-01

319

Static internal performance characteristics of two thrust reverser concepts for axisymmetric nozzles  

Science.gov (United States)

The statis performance of two axisymmetric nozzle thrust reverser concepts was investigated. A rotating vane thrust reverser represented a concept in which reversing is accomplished upstream of the nozzle throat, and a three door reverser concept provided reversing downstream of the nozzle throat. Nozzle pressure ratio was varied from 2.0 to approximately 6.0. The results of this investigation indicate that both the rotating vane and three door reverser concepts were effective static thrust spoilers with the landing approach nozzle geometry and were capable of providing at least a 50 percent reversal of static thrust when fully deployed with the ground roll nozzle geometry.

Leavitt, L. D.; Re, R. J.

1982-01-01

320

Seafloor expression and shallow structure of a fold-and-thrust system, Isfjorden, west Spitsbergen  

Directory of Open Access Journals (Sweden)

Full Text Available A detailed map of the structure of the west Spitsbergen fold-and-thrust belt in the Isfjorden area, Spitsbergen, is presented. The map was constructed from a dense grid of two-dimensional multichannel reflection seismic and bathymetric data. Joint interpretation of two data sets allowed a comparison of tectonic structures detected along the uppermost parts of the seismic sections and those reflected in the morphology of the seafloor. Three major, predominantly north-west–south-east striking faults were identified. The westernmost fault (T1 is a hinterland-directed (most likely out of sequence thrust, while the central and easternmost faults (T2 and T3 are foreland-directed (in-sequence thrusts. The thrusts divide Isfjorden into three subareas. Subarea 1 is bounded by thrust faults T1 and T2 and comprises Tertiary rocks surrounded by Jurassic–Cretaceous strata. The structural signature of Subarea 1 is that of a system of hinterland- and foreland-directed thrust faults, resulting in a seafloor relief characterized by parallel ridges and troughs. Subarea 2 is limited by thrust faults T2 and T3 and shows Jurassic–Cretaceous outcrops on the seafloor. Subarea 3 is situated east of the main thrust fault T3 and mainly involves outcrops of Triassic–Jurassic rocks. Together, Subareas 2 and 3 are dominated by foreland-directed, north-west–south-east and NNW–SSE-striking thrusts that are hardly detectable in bathymetric data.

Maria Blinova

2012-09-01

 
 
 
 
321

Sequence of thrusting and origin of culminations in the northern and central Oman Mountains  

Science.gov (United States)

Detailed mapping and structural analysis of three large-scale culminations (Sumeini and Asjudi half-windows and Haybi-Hawasina window) in the Oman Mountains shows a considerably more complex history of deformation than a simple foreland (or downward) sequence of thrust development. Early thrusting processes tended to create a regular stacking order of imbricate slices and major thrust sheets, complying with the "rules' of thrust propagation, assembled progressively downwards and forwards in the direction of translation. 'Out-of-sequence' thrusts can also be demonstrated in places by truncation of footwall structures (folds, imbricate slices, etc.), gross strain differences between thrust sheets, downward-facing structures in footwall units and elimination of thrust sheets beneath. Late stage thrusts frequently cut up-section through the previously assembled stack putting previously younger, lower thrust sheets over previously older, higher ones. Many of the culminations in the northern and central Oman Mountains were formed by ramping associated with this late-stage leap-frog rethrusting event.

Searle, M. P.

322

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

Science.gov (United States)

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.

Gong, Jingsong; Hou, Lingyun; Zhao, Wenhua

2014-03-01

323

Thrust initiation and its control on tectonic wedge geometry: An insight from physical and numerical models  

Science.gov (United States)

We performed a series of sandbox experiments to investigate the initiation of thrust ramping in tectonic wedges on a mechanically continuous basal decollement. The experiments show that the decollement slope (?) is the key factor in controlling the location of thrust initiation with respect to the backstop (i.e. tectonic suture line). For ? = 0, the ramping begins right at the backstop, followed by sequential thrusting in the frontal direction, leading to a typical mono-vergent wedge. In contrast, the ramp initiates away from the backstop as ? > 0. Under this boundary condition an event of sequential back thrusting takes place prior to the onset of frontal thrust progression. These two-coupled processes eventually give rise to a bi-vergent geometry of the thrust wedge. Using the Drucker-Prager failure criterion in finite element (FE) models, we show the location of stress intensification to render a mechanical basis for the thrust initiation away from the backstop if ? > 0. Our physical and FE model results explain why the Main Central Thrust (MCT) is located far away from the Indo-Tibetan plate contact (ITSZ) in the Himalayan fold-and-thrust belts.

Bose, Santanu; Mandal, Nibir; Saha, Puspendu; Sarkar, Shamik; Lithgow-Bertelloni, Carolina

2014-10-01

324

Development of porous ceramic air bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Porous air bearings enjoy some important advantages over conventional air bearing types such as increased load carrying capacity, higher stiffness and improved damping. However, these types of bearings have yet to find widespread acceptance due to problems with obtaining materials with consistent permeability, instability issues relating to the volume of gas trapped at the bearing surface in the pores, and manufacturing the bearing without altering the permeability. Using...

Roach, Christopher James

2001-01-01

325

Bearing damage versus central lubrication system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The examination paper which has been carried out at Stora Enso illustrates the difficulties around surveillance of bearing condition and the short length of bearing lives in the press section on the cardboard machines. This paper also illustrates if the short bearing lives are lubrication related, and how the lubrication funds affect the length of the bearing lives. There is a complication with finding bearing failures at the using vibration analysis on relatively low revolution machines, thi...

Egestrand, Jens

2012-01-01

326

Superconductor bearings, flywheels and transportation  

Science.gov (United States)

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

Werfel, F. N.; Floegel-Delor, U.; Rothfeld, R.; Riedel, T.; Goebel, B.; Wippich, D.; Schirrmeister, P.

2012-01-01

327

Superconductor bearings, flywheels and transportation  

International Nuclear Information System (INIS)

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

328

'Dodo' and 'Baby Bear' Trenches  

Science.gov (United States)

NASA's Phoenix Mars Lander's Surface Stereo Imager took this image on Sol 11 (June 5, 2008), the eleventh day after landing. It shows the trenches dug by Phoenix's Robotic Arm. The trench on the left is informally called 'Dodo' and was dug as a test. The trench on the right is informally called 'Baby Bear.' The sample dug from Baby Bear will be delivered to the Phoenix's Thermal and Evolved-Gas Analyzer, or TEGA. The Baby Bear trench is 9 centimeters (3.1 inches) wide and 4 centimeters (1.6 inches) deep. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

329

Air bearing vacuum seal assembly  

International Nuclear Information System (INIS)

An air bearing vacuum seal assembly is described that is capable of rotating at the speed of several thousand revolutions per minute using an air cushion to prevent the rotating and stationary parts from touching, and a two stage differential pumping arrangment to maintain the pressure gradient between the air cushion and the vacuum so that the leak rate into the vacuum is, for example, less than 1 x 10-4Pa m3/s. The air bearing vacuum seal has particular application for mounting rotating targets to an evacuated accelerator beam tube for bombardment of the targets with high-power charged particle beams in vacuum

330

Palinspastic reconstruction of the Alpine thrust belt at the Alpine-Carpathian transition - A geological Sudoku  

Science.gov (United States)

The palinspastic reconstruction of the Austroalpine thrust belt is part of the project Karpatian Tectonics, which is funded by OMV Austria. The objective is to reconstruct the evolution of the thrust belt through the Early to Middle Miocene in order to obtain information on the palaeogeographic position of the Northern Calcareous Alps (NCA) in the region of the present Vienna Basin. A particular goal of the study is to constrain the position of reservoir rocks within the Rhenodanubic Flysch units and the NCA with respect to the autochthonous Malmian source rocks overlying the European basement below the Alpine-Carpathian thrust wedge, and to constrain the burial history of these source rocks. Reconstruction uses regional 2D seismic lines crossing from the European foreland into the fold-thrust belt, 3D seismic data covering the external thrust sheets, and lithostratigraphic data from a total of 51 selected wells, which were drilled and provided by OMV Austria. The main criterion, whether a well was suitable for palinspastic reconstruction or not, was its penetration of Alpine thrust sheets down to the Autochthonous Molasse of the foreland. Additional wells, which do not penetrate the entire Alpine thrust complex but include the Allochthonous Molasse or the external Alpine-Carpathian nappes (Waschberg and Roseldorf thrust unit, Rhenodanubic Flysch nappes) in their well path, were also taken into account. The well data in particular comprise stratigraphic information on the youngest overthrust sediments of the different thrust units and the underlying Autochthonous foreland Molasse. These data allow constraining the timing of thrust events in the allochthonous thrust units and overthrusting of the Autochthonous Molasse. In the particular case of overthrust Autochthonous Molasse, additionally to the timing of overthrusting, which can be derived from the youngest overthrust sediments, the palaeogeographic position of the Alpine Carpathian thrust front could directly be inferred from well data for the specific time period. By further utilization of geological maps, geological cross sections and two regional c. 80 km long composite 2D seismic sections through the external Alpine thrusts, the positions of major thrusts could be approximated for five time slices. This procedure was applied for the front of the allochthonous Molasse units, the floor thrust of the Roseldorf thrust unit, the Waschberg thrust unit and the frontal thrusts of the Rhenodanubic Flysch and the NCA. In addition, several out-of-sequence thrusts within the Waschberg unit, the Molasse unit, the Rhenodanubic Flysch and the Calcareous Alps (floor thrust of the NCA and two internal thrusts) were taken into account. The reconstruction results in 5 palinspastic maps for the time slices early Egerian (25 Ma), early Eggenburgian (20 Ma), Ottnangian (17.5 Ma), Lower Karpatian (16.5 Ma) and the Karpatian/ Badenian stage boundary (16 Ma). Convergence rates, which were calculated for the four intervening time intervals, range from about 3 mm/yr to 5 mm/yr. These values compare well with estimated convergence rates reconstructed for the Miocene in the western Eastern Alps (Schmid et al., 1996), as well as with plate tectonic constraints on Tertiary convergence rates (Dewey et al., 1989). Dewey, J., Helman, M.L., Turco, E., Hutton, D.H.W.&Knott, S.D., 1989. Kinematics of the western Mediterranean, in: N.P. Coward, D. Dietrich & R.G. Park (eds.), Alpine Tectonics, Geol. Soc. Spec. Publ., 45: 265-283. Schmid, S.M., Pfiffner, O.A., Frotzheim, N., Schönborn, G. & Kissling, E., 1996. Geophysical-geological transect and tectonic evolution of the Swiss-Italian Alps. Tectonics, 15: 1036-1064.

Beidinger, A.; Decker, K.; Zamolyi, A.; Hölzel, M.; Hoprich, M.; Strauss, P.

2009-04-01

331

Minimum Thrust Load Control for Floating Wind Turbine  

DEFF Research Database (Denmark)

— Offshore wind energy capitalizes on the higher and less turbulent wind at sea. Shallow water sites are pro?table for deployment of monopile wind turbines at water depths of up to 30 meters. Beyond 30 meters, the wind is even stronger and less turbulent. At these depths, ?oating wind turbines become pro?table, capable of accessing unexploited wind resources while reaching regions of new consumers. However, ?oating wind turbines are subject to reduced structural stiffness which results in instabilities when standard wind turbine control systems are applied. Based on optimal control, this paper presents a new minimum thrust control strategy capable of stabilizing a ?oating wind turbine. The new control strategy explores the freedom of variable generator speed above rated wind speed. A comparison to the traditional constant speed strategy, shows improvements in structural fore-aft oscillations and power stability when using the new control strategy.

Christiansen, SØren; Bak, Thomas

2012-01-01

332

Solar electric low-thrust Mercury orbiter missions.  

Science.gov (United States)

Results of a preliminary study of unmanned Mercury orbiter missions which might be flown in the early 1980s. Five different levels of orbiter size and complexity are considered, ranging from a small orbiter carrying 22 kg of low data-rate instruments to a dual satellite mission employing 110 kg of science instruments emphasizing regional and local scale surface imagery. An Intermediate-20 class launch vehicle is required to deliver a minimal surface-imaging science package into Mercury orbit using a ballistic mission mode. Employment of a 15 kW solar electric low-thrust stage permits delivery of the more capable dual satellite package with a Titan IIID (5)/Centaur.

Klopp, D. A.; Wells, W. C.

1972-01-01

333

Mechanical properties of foliated cataclasites from the Nobeoka thrust  

Science.gov (United States)

Understanding the mechanics of plate boundary earthquakes requires a sound investigation of the deformation style and mechanical behavior not only within plate boundary faults but also in the surrounding rocks. It is critical to quantify the strain accumulation and accommodation in the entire subduction systems. Recent studies suggest that heterogeneous deformation and strain distribution in mélanges observed in many ancient accretionary prism outcrops are related to slow slip events and low frequency earthquakes [Fagereng and Sibson, 2010; Kitamura and Kimura, 2011]. However, there are few experimental studies to describe mechanical properties of mélanges and foliated cataclasites. Here, we report on triaxial deformation experiments on foliated cataclasites from the footwall of the Nobeoka thrust, Japan. The Nobeoka thrust, which is exhumated in Kyushu, southwest Japan, is considered as one of the ancient out-of-sequence faults. The Nobeoka thrust fault core, hanging wall, and foot wall rocks were recently cored and logged in a vertical borehole as a NOBELL project [Hamahashi et al., in press]. The Nobeoka thrust is recovered at 41.3 m from the ground. The hanging wall (0-41.3 m coring interval) is composed of the Kitagawa Group of phyllite of alternating beds of sandstone and shale, while the footwall (41.3-255 m) is composed of the Hyuga Group of foliated cataclasite consisting of scaly shale, tuffacious shale, sandstone, and acidic tuff. For deformation experiments, we used foliated catacalsite core samples, which are in better quality and less weathered than outcrop samples. Cylindrical samples with a diameter of 20 mm and a length of 30 mm were subsampled from the cores. The cylindrical specimen were deformed at an axial displacement rate of 0.05-0.5 ?m/s, corresponding to strain rates of 1.6 ×10-6-1.6 ×10-5 s-1, and at a temperature of 250 ° C and an effective pressure (Pe) of 120 MPa (confining pressure of 200 MPa and pore pressure of 80 MPa) or 20 MPa (confining pressure of 200 MPa and pore pressure of 180 MPa). The temperature was chosen based on the estimated temperature (250-300 ° C) at which the footwall foliated cataclasites were formed [Kondo et al., 2005]. The two different effective pressures of 120 MPa and 20 MPa correspond to the stress conditions at ~8 km (geothermal gradient of ~30 ° C/km) with hydrostatic pore pressure and lithostatic pore pressure, respectively. The preliminary results show that the foliated cataclasite samples, taken from the coring interval of 153 m, deform in a brittle manner at Pe = 20 MPa. The strengths reach at 80-90 MPa at peak following a strain weakening to residual strengths of 40-60 MPa. At Pe = 120 MPa, on the other hand, the foliated cataclasite deforms in a brittle-ductile transition manner and steady-state strength is ~ 300 MPa. We will present more experimental results and microstructure observations of the experimentally deformed samples.

Kitajima, Hiroko; Takahashi, Miki; Kimura, Gaku; Yamaguchi, Asuka; Saito, Saneatsu; Hamahashi, Mari; Fukuchi, Rina; Kameda, Jun; Hamada, Yohei; Fujimoto, Koichiro; Hashimoto, Yoshitaka; Kitamura, Yujin; Hina, Shoko; Eida, Mio

2014-05-01

334

Cooling of high pressure rocket thrust chambers with liquid oxygen  

Science.gov (United States)

An experimental program using hydrogen and oxygen as the propellants and supercritical liquid oxygen (LOX) as the coolant was conducted at 4.14 and 8.274 MN/sq m chamber pressure. It was aimed to demonstrate the effect of LOX leaking into the combustion region through small cracks in the chamber wall, and to verify the supercritical oxygen heat transfer correlation developed from heated tube experiments. Four thrust chambers with throat diameters of 0.066 m were tested; three of these were cyclically tested to 4.14 MM/sq m chamber pressure until a crack developed; the fourth chamber was operated at 8.274 MM/sq m pressure to obtain steady state heat transfer data. Wall temperature measurements confirmed the heat transfer correlation.

Price, H. G.

1980-01-01

335

Space Transportation System solid rocket booster thrust vector control system  

Science.gov (United States)

The Solid Rocket Booster, Thrust Vector Control (TVC) system was designed in accordance with the following requirements: self-contained power supply, failsafe operation, 20 flight uses after exposure to seawater landings, optimized cost, and component interchangeability. Trade studies were performed which led to the selection of a recirculating hydraulic system powered by Auxiliary Power Units (APU) which drive the hydraulic actuators and gimbal the solid rocket motor nozzle. Other approaches for the system design were studied in arriving at the recirculating hydraulic system powered by an APU. These systems must withstand the imposed environment and be usable for a minimum of 20 Space Transportation System flights with a minimum of refurbishment. The TVC system completed the required qualification and verification tests and is certified for the intended application. Substantiation data include analytical and test data.

Verble, A. J., Jr.; Mccool, A. A.; Potter, J. H.

1980-01-01

336

Power corrections and renormalon resummation for the average thrust  

International Nuclear Information System (INIS)

Infrared power corrections for the average thrust in e+e- annihilation are analyzed in the framework of renormalon resummation, motivated by analogy with the skeleton expansion in QED and the BLM approach. Performing the 'massive gluon' renormalon integral a renormalization scheme invariant result is obtained. We find that a major part of the discrepancy between the known next-to-leading order (NLO) calculation and experiment can be explained by resummation of higher order perturbative terms. This fact does not preclude the infrared finite coupling interpretation with a substantial 1/Q power term. Fitting the regularized perturbative sum plus a 1/Q term to experimental data yields ?sMS-bar (Mz) = 0.110 ± 0.006

337

Power corrections and renormalon resummation for the average thrust  

CERN Document Server

Infrared power corrections for the average thrust in e+e- annihilation are analyzed in the framework of renormalon resummation, motivated by analogy with the skeleton expansion in QED and the BLM approach. Performing the ``massive gluon'' renormalon integral a renormalization scheme invariant result is obtained. We find that a major part of the discrepancy between the known next-to-leading order (NLO) calculation and experiment can be explained by resummation of higher order perturbative terms. This fact does not preclude the infrared finite coupling interpretation with a substantial 1/Q power term. Fitting the regularized perturbative sum plus a 1/Q term to experimental data yields alpha_s^{MSbar}(M_Z)=0.110 \\pm 0.006.

Gardi, E; Gardi, Einan; Grunberg, Georges

2000-01-01

338

Analysis of Tank PMD Rewetting Following Thrust Resettling  

Science.gov (United States)

Recent investigations have successfully demonstrated closed-form analytical solutions of spontaneous capillary flows in idealized cylindrical containers with interior corners. In this report, the theory is extended and applied to complex containers modeling spacecraft fuel tanks employing propellant management devices (PMDs). The specific problem investigated is one of spontaneous rewetting of a typical partially filled liquid fuel/cryogen tank with PMD after thrust resettling. The transients of this flow impact the logistics of orbital maneuvers and potentially tank thermal control. The general procedure to compute the initial condition (mean radius of curvature for the interface) for the closed-form transient flows is first outlined then solved for several 'complex' cylindrical tanks exhibiting symmetry. The utility and limitations of the technique as a design tool are discussed in a summary, which also highlights comparisons with NASA flight data of a model propellant tank with PMD.

Weislogel, M. M.; Sala, M. A.; Collicott, S. H.

2002-10-01

339

Momentum Management Tool for Low-Thrust Missions  

Science.gov (United States)

A momentum management tool was designed for the Dawn low-thrust interplanetary spacecraft en route to the asteroids Vesta and Ceres, in an effort to better understand the early creation of the solar system. Momentum must be managed to ensure the spacecraft has enough control authority to perform necessary turns and hold a fixed inertial attitude against external torques. Along with torques from solar pressure and gravity-gradients, ion-propulsion engines produce a torque about the thrust axis that must be countered by the four reaction wheel assemblies (RWA). MomProf is a ground operations tool built to address these concerns. The momentum management tool was developed during initial checkout and early cruise, and has been refined to accommodate a wide range of momentum-management issues. With every activity or sequence, wheel speeds and momentum state must be checked to avoid undesirable conditions and use of consumables. MomProf was developed to operate in the MATLAB environment. All data are loaded into MATLAB as a structure to provide consistent access to all inputs by individual functions within the tool. Used in its most basic application, the Dawn momentum tool uses the basic principle of angular momentum conservation, computing momentum in the body frame, and RWA wheel speeds, for all given orientations in the input file. MomProf was designed specifically to be able to handle the changing external torques and frequent de - saturations. Incorporating significant external torques adds complexity since there are various external torques that act under different operational modes.

Swenka, Edward R.; Smith, Brett A.; Vanelli, Charles A.

2010-01-01

340

Tectonometamorphic evolution of the gneissic Kidal assemblage related to the Pan-African thrust tectonics (Adrar des Iforas, Mali)  

Science.gov (United States)

In the central part of the Adrar des Iforas (Mali), the 2 Ba Eburnean granulatic unit has been thrust above a high-grade gneissic unit, the so-called 'Kidal assemblage', during an early event of the Pan-African orogeny. The Kidal assemblage can be defined as a tectonic mixing of an Eburnean granulitic basement, its sedimentary cover of Middle to Upper Proterozoic age (quartzites, marbles, basalts and metavolcanics) and various pretectonic rocks: ultrabasic to basic rocks, diorites, tonalites. All these rocks have been deformed during at least four main events and metamorphosed together. Thrusting of the Iforas Granulitic Unit above the Kidal assemblage happened during the first event D1. The movement direction was roughly N-S, as shown by the stretching lineation. Some field criteria indicate a sense of displacement towards the north. The lattice preferred orientation of quartz c- and axes indicate that the slip was dominantly on prismatic and probably pyramidal planes along an direction; consequently D1 deformation was achieved at high temperature or low-strain rate. The quartz c- and axes do not show any constant asymmetry, so they do not indicate a sense of shear. Two metamorphic stages have been found in the Kidal assemblage: the first one is characterized by kyanite in aluminous metasediments and by the occurrence of garnet-clinopyroxene-bearing boundis of basic rocks. The P-T range of this event is located at 700 ± 50°C and around 10 Kb. The second event is a syntectonic high temperature (600-650°C) low pressure (3.5 Kb) stage accompanied by migmatization. Such a tangential deformation in barrowian-type metamorphic conditions and with N-S transport direction is known along the entire Trans-Saharan belt and cannot be related in a simple way to the collision between West African Craton and the mobile belt.

Champenois, M.; Boullier, A. M.; Sautter, V.; Wright, L. I.; Barbey, P.

 
 
 
 
341

Thermal ground water flow systems in the thrust zone in southeastern Idaho  

Energy Technology Data Exchange (ETDEWEB)

The results of a regional study of thermal and non-thermal ground water flow systems in the thrust zone of southern Idaho and western Wyoming are presented. The study involved hydrogeologic and hydrochemical data collection and interpretation. Particular emphasis was placed on analyzing the role that thrust zones play in controlling the movement of thermal and non-thermal fluids.

Ralston, D.R.

1983-05-01

342

Modeling two sequential coaxial phases of shortening in a foreland thrust belt  

Science.gov (United States)

Analog sandbox models are used to simulate two sequential coaxial phases of shortening in a foreland thrust belt. A sufficient hiatus is considered so that erosion and sedimentation after the first phase create an angular unconformity that is subsequently deformed. The effect of variation in thickness of post-erosional sediment package and presence of a weak layer at the unconformity level are analyzed. During the second phase, some first phase thrusts are reactivated and new thrusts are also initiated. Thrust reactivation results in a structure spacing that is smaller than the expected spacing for a thicker sediment package. Reactivation of pre-existing structures prevents the weak layer from acting as an intermediate décollement. An increase in thickness ratio tends to weaken reactivation of pre-existing thrusts. Model results also show that total displacement along individual reactivated thrusts generally increases downwards across the unconformity, which could be used to distinguish thrust reactivation in the field. Two regional examples from the northern Eastern Cordillera in Colombia and from the Variscan frontal zone in Western Europe, respectively, where multiphase coaxial shortening occurred, are compared with model results. Both natural cases show features, such as partially eroded first-generation folds and truncated first-generation thrusts that are indicators for two sequential phases of deformation as observed in the models.

Deng, Hongling; Koyi, Hemin A.; Froitzheim, Nikolaus

2014-09-01

343

Investigation of thrust effect on the vibrational characteristics of flexible guided missiles  

Science.gov (United States)

In this paper the effect of thrust on the bending behaviour of flexible missiles is investigated. For this purpose, the governing equations of motion of a flexible guided missile are derived following the Lagrangian approach. The missile is idealized as a non-uniform beam where the bending elastic deflections are modelled using the method of modal substitution. The vehicle (time varying) bending modeshapes and natural frequencies are determined by modelling variable mass and stiffness distributions with thrust and mass burning effects accounted for. To solve this problem the missile is divided into several segments of uniform stiffness, density and axial force distribution. This approach produces a non-linear transcendental equation, which requires an iterative scheme to numerically determine the magnitude of the eigenvalues. Since inertial measuring units (IMU) also sense the local body vibrations, the mass and stiffness non-uniformities plus the thrust action on elastic missiles can potentially influence their measurements and thus must be properly accounted for in an aeroelastic simulation. It is noted that the thrust force reduces the vehicle natural frequency while mass consumption increases it. Thus the modal natural frequencies can either decrease or increase in time. Also the critical buckling thrust, which dynamically causes a zero natural frequency, is obtained and therefore the thrust instability limitations are determined through simulation. With proper modelling of the IMU vibrations effects and engine/thrust fluctuations, the influence of body vibrations on the missile dynamics and controls are investigated with axial thrust effect.

Pourtakdoust, S. H.; Assadian, N.

2004-04-01

344

Static internal performance of single expansion-ramp nozzles with thrust vectoring and reversing  

Science.gov (United States)

The effects of geometric design parameters on the internal performance of nonaxisymmetric single expansion-ramp nozzles were investigated at nozzle pressure ratios up to approximately 10. Forward-flight (cruise), vectored-thrust, and reversed-thrust nozzle operating modes were investigated.

Re, R. J.; Berrier, B. L.

1982-01-01

345

Critical taper wedge mechanics of fold-and-thrust belts on Venus - Initial results from Magellan  

Science.gov (United States)

Examples of fold-and-thrust belts from a variety of tectonic settings on Venus are introduced. Predictions for the mechanics of fold-and-thrust belts on Venus are examined on the basis of wedge theory, rock mechanics data, and currently known conditions on Venus. The theoretical predictions are then compared with new Magellan data.

Suppe, John; Connors, Chris

1992-01-01

346

Second-Order QCD Corrections to the Thrust Distribution in Electron-Positron Annihilation  

International Nuclear Information System (INIS)

We compute the next-to-next-to-leading-order (NNLO) QCD corrections to the thrust distribution in electron-positron annihilation. The corrections turn out to be sizable, enhancing the previously known next-to-leading-order prediction by about 15%. Inclusion of the NNLO corrections significantly reduces the theoretical renormalization scale uncertainty on the prediction of the thrust distribution

347

Master ``blind'' thrust faults hidden under the Zagros folds: active basement tectonics and surface morphotectonics  

Science.gov (United States)

The basement-involved active fold-thrust belt of the Zagros in southwest Iran is underlain by numerous seismogenic blind basement thrust faults covered by the folded Phanerozoic sedimentary rocks. Meizoseismal regions of moderate- to large-magnitude earthquakes in the Zagros are localized and concentrated along particular structural-geomorphological features and topographic fronts at the surface. The study reveals at least four active SW-vergent segmented master blind thrusts in the Zagros collisional belt, along which different morphotectonic units are thrusting over the deforming regions. These boundary thrusts, which make contiguous frontal asymmetric anticlines, prominent escarpments and Quaternary deformation, mark topographic fronts at the surface, and have vertically displaced geologic marker beds for more than 6000 m, include: the High Zagros (with a maximum recorded historic earthquake of Ms = 6.0 at Daryan); the Mountain Front ( Ms = 7.0 at Khurgu); the Dezful Embayment ( Ms = 5.7); and the Foredeep ( Ms = 6.5 at Ahwaz) thrusts. Three other seismogenic blind thrusts responsible for the Qir ( Ms = 6.9), the Lar ( Ms = 6.5) and the Beriz-Dehkuyeh ( Ms = 5.7) earthquakes are also documented in this study. The master faults, as evidenced by deformation of the asymmetric anticlines in the hanging wall of the blind thrusts, are segmented and discontinuous, and are separated by gaps in faulting that have presumably controlled the extent of rupture and the magnitude of earthquakes. The master seismic thrusts are displaced right-laterally by deep-seated active transverse faults of Kazerun ( Io = VIII), Sarvestan ( Ms = 6.4?) and Sabz Pushan. The study shows that active deformation in the Zagros is dominated by: (1) prevalent subsurface blind thrusting; (2) occasional surface strike-slip faulting; (3) coseismic asymmetric folding and uplift of sedimentary cover; and (4) surface thrusting ramping up from at least two regional upper (Miocene Gachsaran) and lower (Lower Cambrian Hormoz) décollement detachments. The active master thrust faults have implications for seismic hazard assessment that were not previouly appreciated. The possibility of large compressive earthquakes ( Ms ˜ 7.0) along the introduced blind thrusts must be considered. Locations of other unknown segmented blind thrusts in the belt, which have distinct effects on the surface morphotectonics and topography, and on the structures at depth, could be easily based on meizoseismal maps of the earthquakes combined with active morphotectonic features, morphometric analyses and accurate aftershock sequence studies.

Berberian, Manuel

1995-01-01

348

Effects of vibration and shock on the performance of gas-bearing space-power Brayton cycle turbomachinery. 2: Sinusoidal and random vibration  

Science.gov (United States)

The vibration response of a gas-bearing rotor-support system was analyzed experimentally documented for sinusoidal and random vibration environments. The NASA Brayton Rotating Unit (BRU), 36,000 rpm; 10 KWe turbogenerator; was subjected in the laboratory to sinusoidal and random vibrations to evaluate the capability of the BRU to (1) survive the vibration levels expected to be encountered during periods of nonoperation and (2) operate satisfactorily (that is, without detrimental bearing surface contacts) at the vibration levels expected during normal BRU operation. Response power spectral density was calculated for specified input random excitation, with particular emphasis upon the dynamic motions of the thrust bearing runner and stator. A three-mass model with nonlinear representation of the engine isolator mounts was used to calculate axial rotor-bearing shock response.

Tessarzik, J. M.; Chiang, T.; Badgley, R. H.

1973-01-01

349

Intelligent Engine Systems: Bearing System  

Science.gov (United States)

The overall requirements necessary for sensing bearing distress and the related criteria to select a particular rotating sensor were established during the phase I. The current phase II efforts performed studies to evaluate the Robustness and Durability Enhancement of the rotating sensors, and to design, and develop the Built-in Telemetry System concepts for an aircraft engine differential sump. A generic test vehicle that can test the proposed bearing diagnostic system was designed, developed, and built. The Timken Company, who also assisted with testing the GE concept of using rotating sensors for the differential bearing diagnostics during previous phase, was selected as a subcontractor to assist General Electric (GE) for the design, and procurement of the test vehicle. A purchase order was prepared to define the different sub-tasks, and deliverables for this task. The University of Akron was selected to provide the necessary support for installing, and integrating the test vehicle with their newly designed test facility capable of simulating the operating environment for the planned testing. The planned testing with good and damaged bearings will be on hold pending further continuation of this effort during next phase.

Singh, Arnant P.

2008-01-01

350

Journal and Wave Bearing Impedance Calculation Software  

Science.gov (United States)

The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

Hanford, Amanda; Campbell, Robert

2012-01-01

351

Space Shuttle Main Engine structural analysis and data reduction/evaluation. Volume 2: High pressure oxidizer turbo-pump turbine end bearing analysis  

Science.gov (United States)

The high-pressure oxidizer turbopump (HPOTP) consists of two centrifugal pumps, on a common shaft, that are directly driven by a hot-gas turbine. Pump shaft axial thrust is balanced in that the double-entry main inducer/impeller is inherently balanced and the thrusts of the preburner pump and turbine are nearly equal but opposite. Residual shaft thrust is controlled by a self-compensating, non-rubbing, balance piston. Shaft hang-up must be avoided if the balance piston is to perform properly. One potential cause of shaft hang-up is contact between the Phase 2 bearing support and axial spring cartridge of the HPOTP main pump housing. The status of the bearing support/axial spring cartridge interface is investigated under current loading conditions. An ANSYS version 4.3, three-dimensional, finite element model was generated on Lockheed's VAX 11/785 computer. A nonlinear thermal analysis was then executed on the Marshall Space Flight Center Engineering Analysis Data System (EADS). These thermal results were then applied along with the interference fit and bolt preloads to the model as load conditions for a static analysis to determine the gap status of the bearing support/axial spring cartridge interface. For possible further analysis of the local regions of HPOTP main pump housing assembly, detailed ANSYS submodels were generated using I-DEAS Geomod and Supertab (Appendix A).

Sisk, Gregory A.

1989-01-01

352

Large-scale thrusting along the northern margin of the Tibetan Plateau and the southwest Tarim basin: 230 km long active Hotian thrust sheet  

Science.gov (United States)

We present the geometry, kinematics and mechanics of large-scale thrusting in the West Kunlun Shan and the southwest Tarim Basin, which is associated with the northward motion of Tibet. The great frontal structure is the ~230km long intact bedding parallel Hotian thrust sheet composed of strata of the Tarim Basin lying above a regional gypsum horizon at the base of the Cenozoic sequence. The toe of the Hotian thrust sheet steps steeply to the surface two thirds of the way across the basin forming the Selibuya-Mazartag hills in the sand desert. The Hotan thrust constitutes one of the longest active intact thrust sheets in the world, showing little internal deformation, however at its back it steps down to a Cambrian detachment at the base of the Paleozoic below a belt of complex high-amplitude anticlines near the front of the West Kunlun Shan, which display break-forward imbricate and wedge structure. More interior, steep reverse faults such as the Tieklik thrust bring older strata to the surface, including Paleozoic basement. The Cambrian detachment also extends northward under the Tarim basin with minor hanging-wall deformation that warps the Hotian Thrust sheet locally, causing the development of growth strata in the Hotian thrust sheet that providesa quantitative record of its motion over these warps. Seismic profiles in the southwest Tarim basin reveal widespread growth strata that record much of the structural history beginning in the early Pliocene Atushi Formation. Ages of seismic reflectors are calibrated to a surface magnetostratigraphic sequence(from Zheng et al., 2000)and traced throughout the seismic grid. The bottom of the growth strata is dated at 3.6 Ma indicating a Pliocene and younger age of thrusting and folding in the southwest Tarim Basin. Structural restoration suggests minimum shortening greater than 35km. The Tieklik thrust consumed at least 10 km in early Pliocene. The fold-and-thrust belts of the southwest Tarim basin shortened >25km in late Pliocene and Pleistocene. Some slip propagated northward into the inland of Tarim basin and developed the thrust surface rupture zone at Selibuya-Mazartag. The overall shortening rate is ~10 mm/yr in the fold-and-thrust belt of the southwest Tarim basin since Pliocene. The strength of the gypsum detachment of the 240 km long Hotian thrust sheet can be estimated from the tapered geometry. Using wedge theory (Suppe 2007) we find that the ratio of critical wedge strength W to detachment strength F is equal to the detachment dip in radians for a wedge of zero surface slope. The current dip of the Hotian detachment is 0.08° or 0.014. Typical wedge strengths are in the range 0.5-1, therefore based on the lack of internal deformation we estimate an upper bound on the strength of the gypsum detachment, expressed as an exceedingly weak effective friction coefficient of less than ~0.0005-0.0015.

Wang, Xin; Suppe, John; Liang, Hang; He, Dengfa

2014-05-01

353

Alex the Bear Goes to Child Care  

Medline Plus

Full Text Available ... Quality Child Care Videos Child Care Aware Public Service Announcements Meet Alex the Bear Resources Resources for ... Quality Child Care Videos Child Care Aware Public Service Announcements Meet Alex the Bear Child Care Aware ...

354

Hunting for 'bears' in the backyard  

Science.gov (United States)

This Micscape Magazine article offers practical hints about how to collect and study tardigrades, or water bears, from mosses in your backyard. It features a general introduction of water bears, a video, and a section of references for further reading.

Walker, Dave; Magazine, Micscape

355

Rolling Element Bearing Stiffness Matrix Determination (Presentation)  

Energy Technology Data Exchange (ETDEWEB)

Current theoretical bearing models differ in their stiffness estimates because of different model assumptions. In this study, a finite element/contact mechanics model is developed for rolling element bearings with the focus of obtaining accurate bearing stiffness for a wide range of bearing types and parameters. A combined surface integral and finite element method is used to solve for the contact mechanics between the rolling elements and races. This model captures the time-dependent characteristics of the bearing contact due to the orbital motion of the rolling elements. A numerical method is developed to determine the full bearing stiffness matrix corresponding to two radial, one axial, and two angular coordinates; the rotation about the shaft axis is free by design. This proposed stiffness determination method is validated against experiments in the literature and compared to existing analytical models and widely used advanced computational methods. The fully-populated stiffness matrix demonstrates the coupling between bearing radial, axial, and tilting bearing deflections.

Guo, Y.; Parker, R.

2014-01-01

356

Stable isotopes to detect food-conditioned bears and to evaluate human-bear management  

Science.gov (United States)

We used genetic and stable isotope analysis of hair from free-ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food-conditioned or non-food-conditioned and used these data to predict whether bears with an unknown management status were food-conditioned (FC) or non-food-conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population-level) and reactive (individual-level) human–bear management, and discussed new metrics to evaluate the overall human–bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food-conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001–2003 to 2005–2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human–bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human–bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population.

Hopkins, John B., III; Koch, Paul L.; Schwartz, Charles C.; Ferguson, Jake M.; Greenleaf, Schuyler S.; Kalinowski, Steven T.

2012-01-01

357

Theory of the Ultimate Bearing Capacity Calculation  

Directory of Open Access Journals (Sweden)

Full Text Available The traditional formula and calculation method for calculating the ultimate bearing capacity is not scientific. According to the research, the ultimate bearing capacity is equal to the real degree of the material and detection force product. Ultimate bearing capacity is not for the change of detecting the force. On the basis of this understanding, a new theory of the study bearing capacity of rock-soil and new methods is generated.

Chang Yi Wang

2012-01-01

358

Theory of the Ultimate Bearing Capacity Calculation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The traditional formula and calculation method for calculating the ultimate bearing capacity is not scientific. According to the research, the ultimate bearing capacity is equal to the real degree of the material and detection force product. Ultimate bearing capacity is not for the change of detecting the force. On the basis of this understanding, a new theory of the study bearing capacity of rock-soil and new methods is generated.

Chang Yi Wang; Ben Jun Wang; Shu Zun Jiang

2012-01-01

359

Technology development for indigenous water lubricated bearings  

International Nuclear Information System (INIS)

Water Lubricated Bearings (WLB) are used in various mechanisms of fuel handling systems of PHWRs and AHWR. Availability and random failures of these bearings was a major factor in refuelling operations. Indigenous development of these bearings was taken up and 7 types of antifriction bearings in various sizes (totaling 37 variants) for PHWR, AHWR and Dhruva applications were successfully developed. This paper deals with various aspects of WLB development. (author)

360

Journal bearing performance and metrology issues  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: In this paper, a radial clearance of a journal bearings and the metrology of the radial clearance measurement is described.Design/methodology/approach: In this experimental study out-of-roundness and radial clearance of journal bearings were measured with high precision and the impact of their metrology was examined on the specific oil film thickness of the bearing. Some metrological issues were emerged and these should be taken into account when bearings are designed.Findings: An in...

Sharma, S.; Hargreaves, D.; Scott, W.

2009-01-01

 
 
 
 
361

Did Tharsis have a detached cap? Insight gained from global thrust fault vergence frequencies.  

Science.gov (United States)

Current geophysical models of the mechanical structure of Tharsis can be delineated by the proposed strength of the base of the volcanic pile, at its interface with the Noachian crust. The 'welded base' class of models suggests that the base of the volcanic pile is brittle and effectively welded to the Noachian crust [e.g. Solomon and Head, 1982; Phillips et al., 2001]. Alternatively, a 'detached cap' model proposes that much of the base of Tharsis was ductile and slippery [e.g. Banerdt and Golombek, 1990; Tanaka et al., 1991]. In this abstract, we compare predicted thrust fault vergence frequencies for each class of models against a global set of MOLA-based thrust fault vergence frequencies. Determination of thrust fault vergence from topography is now possible (e.g. Okubo et al., 2001, 2002 fall AGU). Within a thrust fault-related fold (i.e. a wrinkle ridge or lobate scarp), the thrust verges from the shallowest sloping fold limb toward the steepest sloping fold limb. Using this relation, we extract thrust fault vergence directions along 36 evenly spaced topographic profiles constructed in 10° intervals radial to Tharsis. These topographic profiles are based on the MOLA Mission Experiment Gridded Data Records at 128 pixel/degree ( ˜455 m/pixel at the equator) resolution. Our results show that the percentage of thrusts that verge away from Tharsis (47.5% - 48.8%) is sub-equal with the percentage of thrusts that verge toward Tharsis for thrusts within 9000 km, 6000 km, and 4500 km of Tharsis. Based on mechanical analyses of a brittlely deforming plate [Davis and Engelder, 1985; Montési and Zuber, 2003], we infer that welded base models would produce sub-equal thrust fault vergence frequencies on all parts of Tharsis and in the surrounding Noachian crust. By comparison, in the detached cap model, if the base of the Tharsis load were sufficiently hot and weak in shear, we would predict sub-equal vergence frequencies above the central, ductile part of the base. This area would then be ringed by an annulus of outward-verging thrusts near the edge of the Tharsis load, where basal ductility decreases toward the colder, brittle periphery, causing shearing. Alternatively, if the base of the detached cap was stronger but still ductile, then we would again predict the formation of thrust faults that consistently verge away from the center of Tharsis but in a much larger annulus. In both detached cap scenarios, we would also predict sub-equal thrust fault vergence frequencies within the surrounding Noachian crust. Neither of the 'bull's eye' patterns of thrust fault vergence frequencies predicted for the detached cap model is observed in our profile results. Instead, we find that our observations of sub-equal thrust fault vergence frequencies support the welded base class of Tharsis models. Therefore, at the time when the thrust-related folds were forming (e.g. late Noachian to early Hesperian), lateral spreading of Tharsis would have occurred independent of regional shearing along mid-lithospheric ductile horizons. If shearing did occur along a detached Tharsis base, this process would have had to take place before the formation of the thrust-related folds (and evidence of this event would be buried by subsequent Tharsis volcanics). Further, episodes of widespread Tharsis-radial graben formation, which are contemporaneous with or post date thrust fold formation, must have also occurred in the absence of mid-lithospheric shear zones due either to a detached Tharsis base, or to shallow volatile-rich layers (e.g. Okubo and Schultz, in review, GSA Bulletin).

Okubo, C. H.; Schultz, R. A.

2003-12-01

362

Cool Polar Bears: Dabbing on the Texture  

Science.gov (United States)

In this article, the author describes how her second-graders created their cool polar bears. The students used the elements of shape and texture to create the bears. They used Monet's technique of dabbing paint so as to give the bear some texture on his fur.

O'Connell, Jean

2011-01-01

363

Bears and pipeline construction in Alaska  

Energy Technology Data Exchange (ETDEWEB)

Serious problems were encountered with bears during construction of the 1274-km trans-Alaska oil pipeline between Prudhoe Bay and Valdez. This multi-billion-dollar project traversed both black bear (Ursus americanus Pallas) and grizzly bear (U. arctos L.) habitat throughtout its entire length. Plans for dealing with anticipated problems with bears were often inadequate. Most (71%) problems occurred north of the Yukon River in a previously roadless wilderness where inadequate refuse disposal and widespread animal feeding created dangerous situations. Of the 192 officially reported bear problems associated with the Trans-Alaska Pipeline System (TAPS) (1971-1979), about 65% involved the presence of bears in camps or dumps, 13% the feeding of bears on garbage or handouts, 10% property damage or economic loss, 7% bears under and in buildings, and only 5% charges by bears. Remarkably, no bear-related injuries were reported, suggesting that bears became accustomed to people and did not regard them as a threat. Following construction of the TAPS there have been proposals for pipelines to transport natural gas from Prudhoe Bay to southern and Pacific-rim markets. Based on past experience, some animal control measures were developed during the planning phase for the authorized gas pipeline route in Alaska. Fences installed around 100-person survey camps were found to be effective in deterring bears in two traditionally troublesome areas. 16 refs., 7 figs., 1 tab.

Follmann, E.H.; Hechtel, J.L. (Univ. of Alaska Fairbanks, AK (USA))

1990-06-01

364

36 CFR 13.1236 - Bear orientation.  

Science.gov (United States)

...2010-07-01 2010-07-01 false Bear orientation. 13.1236 Section 13...Brooks Camp Developed Area § 13.1236 Bear orientation. All persons visiting the BCDA must receive an NPS-approved Bear Orientation. Failure to receive an...

2010-07-01

365

Dare to Care for a Grizzly Bear  

Science.gov (United States)

Using the Nature episode “The Good, The Bad and the Grizzly,” students will be able to articulate the complex and competing perspectives on how to best handle the growing bear population, and they will investigate the factors contributing to the destabilization of the bear’s Yellowstone ecosystem.

Wnet

2008-11-18

366

14 CFR 27.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 27.623 Section 27.623...Construction General § 27.623 Bearing factors. (a) Except as provided...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

367

14 CFR 29.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 29.623 Section 29.623...Construction General § 29.623 Bearing factors. (a) Except as provided...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

368

14 CFR 25.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 25.623 Section 25.623...Construction General § 25.623 Bearing factors. (a) Except as provided...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

369

14 CFR 23.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 23.623 Section 23.623...Design and Construction § 23.623 Bearing factors. (a) Each part that has...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

370

Analytical guidance for spacecraft relative motion under constant thrust using relative orbit elements  

Science.gov (United States)

Proximity control of modern nano-spacecraft often relies on low and discrete thrust engines that are characterized by low consumption, and generate on-off force profiles. New guidance solutions must take into account the nature of this type of orbital engines. This paper introduces novel analytical guidance solutions for spacecraft relative motion considering continuous, on-off thrust, and using relative orbit elements as a geometrical representation of the dynamics. The solutions provide the relative state vector at any given time, accommodating any thrust magnitude along the three directions of the relative frame, as well as generic activation times and durations. Relative orbit elements geometrically interpret key aspects of the relative motion, including for example, the relative ellipse size, and the evolution of its center in time. The new solutions provide the guidance designer with a direct visualization of the thrust effects on the relative motion geometry, offering new possibilities for analytical guidance in the presence of continuous thrust engines, such as low thrust engines on nano-spacecraft. The paper presents the analytical solutions, and tests their effectiveness using a sample thrust profile based on input-shaping, previously developed by one of the authors using classical Cartesian coordinates. The use of relative orbit elements shows substantial benefits and added simplicity with respect to Cartesian-based approaches, holding the promise for straightforward onboard spacecraft implementation. The software developed for this research will be available open source1

Bevilacqua, Riccardo; Lovell, Thomas Alan

2014-09-01

371

Identifying multiple detachment horizons and an evolving thrust history through cross-section restoration and appraisal in the Moine Thrust Belt, NW Scotland  

Science.gov (United States)

Many thrust systems, including parts of the Moine Thrust Belt, are commonly interpreted as rather simple imbricate fans, splaying from a master detachment (floor thrust) at depth. We use field observations and geological map data to construct cross-sections through the Achnashellach Culmination, southern Moine Thrust Belt, Northwest Scotland, to test this interpretation. Initially cross-sections are constructed by assuming a single lower detachment; line length imbalances and thrust trajectory mismatches between deformed and restored-state sections indicate an invalid model. Significant differences in horizon lengths between two rock units are seen, indicating the position of a second detachment which, when incorporated into the deformed-state cross-section creates a valid structural model. The presence of this second detachment accounts for complex geometries seen at outcrop, and indicates that the Achnashellach Culmination is likely to have formed by the sequential activation of two detachment horizons. This new structural model has been derived using an iterative workflow involving cross-section construction, section balancing and integration of field observations from across the study area, ensuring model validity in three dimensions. This workflow is applicable to other systems in general.

Watkins, Hannah; Bond, Clare E.; Butler, Robert W. H.

2014-09-01

372

Non-Contact Thrust Stand Calibration Method for Repetitively-Pulsed Electric Thrusters  

Science.gov (United States)

A thrust stand calibration technique for use in testing repetitively-pulsed electric thrusters for in-space propulsion has been developed and tested using a modified hanging pendulum thrust stand. In the implementation of this technique, current pulses are applied to a solenoidal coil to produce a pulsed magnetic field that acts against the magnetic field produced by a permanent magnet mounted to the thrust stand pendulum arm. The force on the magnet is applied in this non-contact manner, with the entire pulsed force transferred to the pendulum arm through a piezoelectric force transducer to provide a time-accurate force measurement. Modeling of the pendulum arm dynamics reveals that after an initial transient in thrust stand motion the quasisteady average deflection of the thrust stand arm away from the unforced or zero position can be related to the average applied force through a simple linear Hooke s law relationship. Modeling demonstrates that this technique is universally applicable except when the pulsing period is increased to the point where it approaches the period of natural thrust stand motion. Calibration data were obtained using a modified hanging pendulum thrust stand previously used for steady-state thrust measurements. Data were obtained for varying impulse bit at constant pulse frequency and for varying pulse frequency. The two data sets exhibit excellent quantitative agreement with each other as the constant relating average deflection and average thrust match within the errors on the linear regression curve fit of the data. Quantitatively, the error on the calibration coefficient is roughly 1% of the coefficient value.

Wong, Andrea R.; Toftul, Alexandra; Polzin, Kurt A.; Pearson, J. Boise

2011-01-01

373

Radiation effects in low-thrust orbit transfers  

International Nuclear Information System (INIS)

A low-thrust orbit transfer vehicle (OTV) and its payload must be designed to survive in the near-Earth radiation environment for a much longer duration than a conventional upper stage. This paper examines the effects of natural radiation on OTV's using data that have become available since 1991 from the CRRES and APEX satellites. Dose rates for microelectronics in LEO-to-GEO missions are calculated for spiral orbit raising and for multi-impulse transfers. Semiconductor devices that are shielded by less than 2.5 mm of aluminum (0.69 g/cm2) are inappropriate for spiral transfers, because they require hardness levels >100 krad (Si). Shield thicknesses of 6-12 mm reduce this requirement to about 10 krad (Si), which is still an order of magnitude higher than the radiation dose in a 10-year mission at GEO with similar shielding. The dose for a multi-impulse LEO-to-GEO transfer is about 10 times smaller than for a spiral transfer. Estimates of single event upset rates and photovoltaic array degradation are also provided

374

VPS Process for Copper Components in Thrust Chamber Assemblies  

Science.gov (United States)

For several years, NASA's Marshall Space Flight Center (MSFC) has been working with Plasma Processes, Inc., (PPI) to fabricate thrust chamber liners with GRCop-84. Using the vacuum plasma spray (VPS) process, chamber liners of a variety of shapes and sizes have been created. Each has been formed as a functional gradient material (FGM) that creates a unique protective layer of NiCrAlY on the GRCop-84 liner s hot wall surface. Hot-fire testing was successfully conducted on a subscale unit to demonstrate the liner's durability and performance. Similar VPS technology has also been applied to create functional gradient coatings (FGC) on copper injector faceplates. Protective layers of NiCrAlY and zirconia were applied to both coaxial and impinging faceplate designs. Hot-fire testing is planned for these coated injectors in April 2005. The resulting material systems for both copper alloy components allows them to operate at higher temperatures with improved durability and operating margins.

Elam, Sandra; Holmes, Richard; Hickman, Robert; McKechnie, Tim; Thom, George

2005-01-01

375

Microstructures and rheology of a calcite-shale thrust fault  

Science.gov (United States)

A thin (˜2 cm) layer of extensively sheared fault rock decorates the ˜15 km displacement Copper Creek thrust at an exposure near Knoxville, TN (USA). In these ultrafine-grained (shale clasts. One cm below the fault rock layer, sedimentary laminations in non-penetratively deformed footwall shale are cut by calcite veins, small faults, and stylolites. A 350 ?m thick calcite vein separates the fault rocks and footwall shale. The vein is composed of layers of (1) coarse calcite grains (>5 ?m) that exhibit a lattice preferred orientation (LPO) with pores at twin-twin and twin-grain boundary intersections, and (2) ultrafine-grained (0.3 ?m) calcite that exhibits interpenetrating grain boundaries, four-grain junctions and lacks a LPO. Coarse calcite layers crosscut ultrafine-grained layers indicating intermittent vein formation during shearing. Calcite in the fault rock layer is derived from vein calcite and grain-size reduction of calcite took place by plasticity-induced fracture. The ultrafine-grained calcite deformed primarily by diffusion-accommodated grain boundary sliding and formed an interconnected network around shale clasts within the shear zone. The interconnected network of ultrafine-grained calcite indicates that calcite, not shale, was the weak phase in this fault zone.

Wells, Rachel K.; Newman, Julie; Wojtal, Steven

2014-08-01

376

Low-thrust trajectories for human missions to Ceres  

Science.gov (United States)

A low-thrust trajectory design study is performed for a mission to send humans to Ceres and back. The flight times are constrained to 270 days for each leg, and a grid search is performed over propulsion system power, ranging from 6 to 14 MW, and departure V?, ranging from 0 to 3 km/s. A propulsion system specific mass of 5 kg/kW is assumed. Each mission delivers a 75 Mg payload to Ceres, not including propulsion system mass. An elliptical spiral method for transferring from low Earth orbit to an interplanetary trajectory is described and used for the mission design. A mission with a power of 11.7 MW and departure V? of 3 km/s is found to offer a minimum initial mass in low Earth orbit of 289 Mg. A preliminary supply mission delivering 80 Mg of supplies to Ceres is also designed with an initial mass in low Earth orbit of 127 Mg. Based on these results, it appears that a human mission to Ceres is not significantly more difficult than current plans to send humans to Mars.

Laipert, Frank E.; Longuski, James M.

2014-02-01

377

Variable Flavor Number Scheme for Final State Jets in Thrust  

CERN Document Server

We present results for mass effects coming from secondary radiation of heavy quark pairs related to gluon splitting in the thrust distribution for e+e- collisions. The results are given in the dijet limit where the hard interaction scale and the scales related to collinear and soft radiation are widely separated. We account for the corresponding fixed-order corrections at O(alpha_s^2) and the summation of all logarithmic terms related to the hard, collinear and soft scales as well as the quark mass at N3LL order. We also remove the O(Lambda_QCD) renormalon in the partonic soft function leading to an infrared evolution equation with a matching condition related to the massive quark threshold. The quark mass can be arbitrary, ranging from the infinitely heavy case, where decoupling takes place, down to the massless limit where the results smoothly merge into the well known predictions for massless quarks. Our results are formulated in the framework of factorization theorems for e+e- dijet production and provide...

Pietrulewicz, Piotr; Hoang, Andre H; Jemos, Ilaria; Mateu, Vicent

2014-01-01

378

Fault Tolerant Homopolar Magnetic Bearings  

Science.gov (United States)

Magnetic suspensions (MS) satisfy the long life and low loss conditions demanded by satellite and ISS based flywheels used for Energy Storage and Attitude Control (ACESE) service. This paper summarizes the development of a novel MS that improves reliability via fault tolerant operation. Specifically, flux coupling between poles of a homopolar magnetic bearing is shown to deliver desired forces even after termination of coil currents to a subset of failed poles . Linear, coordinate decoupled force-voltage relations are also maintained before and after failure by bias linearization. Current distribution matrices (CDM) which adjust the currents and fluxes following a pole set failure are determined for many faulted pole combinations. The CDM s and the system responses are obtained utilizing 1D magnetic circuit models with fringe and leakage factors derived from detailed, 3D, finite element field models. Reliability results are presented vs. detection/correction delay time and individual power amplifier reliability for 4, 6, and 7 pole configurations. Reliability is shown for two success criteria, i.e. (a) no catcher bearing contact following pole failures and (b) re-levitation off of the catcher bearings following pole failures. An advantage of the method presented over other redundant operation approaches is a significantly reduced requirement for backup hardware such as additional actuators or power amplifiers.

Li, Ming-Hsiu; Palazzolo, Alan; Kenny, Andrew; Provenza, Andrew; Beach, Raymond; Kascak, Albert

2003-01-01

379

Bearing strength of lunar soil.  

Science.gov (United States)

Bearing load vs penetration curves have been measured on a 1.3 g sample of lunar soil from the scoop of the Surveyor 3 soil mechanics surface sampler, using a circular indentor 2 mm in diameter. Measurements were made in an Earth laboratory, in air. This sample provided a unique opportunity to evaluate earlier, remotely controlled, in-situ measurements of lunar surface bearing properties. Bearing capacity, measured at a penetration equal to the indentor diameter, varied from 0.02-0.04 N/sq cm at bulk densities of 1.15 g/cu cm to 30-100 N/sq cm at 1.9 g/cu cm. Deformation was by compression directly below the indentor at bulk densities below 1.61 g/cu cm, by outward displacement at bulk densities over 1.62 g/cu cm. Preliminary comparison of in-situ remote measurements with those on returned material indicates good agreement if the lunar regolith at Surveyor 3 has a bulk density of 1.6 g/cu cm at 2.5 cm depth.

Jaffe, L. D.

1971-01-01

380

Technical assessment of Engineering`s Manufacturing Technology Thrust Area at Lawrence Livermore National Laboratory  

Energy Technology Data Exchange (ETDEWEB)

This document investigates the connection between the Manufacturing Technology Thrust Area and its market and concludes that the connection should include the programs internal to LLNL and customers outside of LLNL. The thrust area`s existing mission is reviewed and while it remains relevant to the future, it is too broad for the assigned resources. The scope of the thrust area`s mission is therefore narrowed to more specifically address precision in manufacturing. The course to pursue the new focus is plotted, and the projects for FY95 are briefly discussed.

Blaedel, K.L.

1995-07-27

 
 
 
 
381

Sensor-based control of rocket thrust chamber feature location for automated braze paste dispensing  

Science.gov (United States)

A sensor-based control system has been developed for locating key features on rocket thrust chamber assemblies for automated braze paste dispensing. The system uses a non-contact Multi-Axis Seam Tracking (MAST) sensor to locate these features. The MAST sensor measures capacitance variations between the sensor and thrust chamber surface to produce four varying voltages for control purposes. The sensor information is used to locate the thrust chamber surface and to guide the robotic paste dispensing equipment along the seams in real-time. Experiments demonstrate that seams can be tracked at 50 mm/sec within the accuracy required for braze paste dispensing.

Schmitt, Dan J.; Novak, Jim L.; Maslakowski, John E.; Starr, Gregory P.

382

Tongue strength: its relationship to tongue thrusting, open-bite, and articulatory proficiency.  

Science.gov (United States)

Maximum protrusive tongue strength was measured for two experimental groups of 35 normal speaking children and 21 children with frontal lisping, anterior tongue thrusting during swallow, and open-bite malocclusion, and a control group of 85 children with normal speech and occlusion who did not thrust their tongues during swallow. No significant differences in tongue strength were found among these groups. The findings were interpreted to support the view that tongue strengthening exercises recommended by some authors for the correction of tongue thrusting or associated frontal lisping may be superfluous. PMID:7442160

Dworkin, J P; Culatta, R A

1980-05-01

383

Tethered towing using open-loop input-shaping and discrete thrust levels  

Science.gov (United States)

Asteroid retrieval, satellite servicing, and debris removal concepts often rely on a thrusting vehicle to redirect and steer a passive object. One effective way to tow the object is through a tether. This study employs a discretized tether model attached to six degree-of-freedom end bodies. To reduce the risk of a post-burn collision between the end bodies, discrete thrust input shaping profiles are considered including a Posicast input and a bang-off-bang thrust profile. These input shaping techniques attain desirable collision avoidance performance by inducing a tumbling or gravity gradient motion of the tethered formation. Their performance is compared to an earlier frequency notched thruster profile.

Jasper, Lee; Schaub, Hanspeter

2014-12-01

384

Valve assembly having remotely replaceable bearings  

International Nuclear Information System (INIS)

A valve assembly having remotely replaceable bearings is disclosed wherein a valve disc is supported within a flow duct for rotation about a pair of axially aligned bearings, one of which is carried by a spindle received within a diametral bore in the valve disc, and the other of which is carried by a bearing support block releasably mounted on the duct circumferentially of an annular collar on the valve disc coaxial with its diametrical bore. The spindle and bearing support block are adapted for remote removal to facilitate servicing or replacement of the valve disc support bearings

385

A motor with superconducting magnetic bearings  

International Nuclear Information System (INIS)

Superconducting bearings may be one of the most promising near term applications of HTSC. For use at liquid nitrogen temperature and below, they offer the advantage of lower energy consumption and higher reliability. Different bearing configurations have been proposed. But in order to substitute for conventional bearings a further increase in the critical current density of the superconductor and improved bearing concepts are necessary. For this it is necessary to take into account the peculiarities of the interaction between permanent magnets and bulk superconductors. As a contribution to this programme we present the model of a motor with superconducting magnetic bearings. (orig.)

386

Pratt and Whitney cryogenic turbopump bearing experience  

Science.gov (United States)

Successful, reusable bearings require lubrication, traditionally, a transfer film from sacrificial cage wear. Early testing included materials screening programs to identify suitable cryogenic cage materials. A specially developed element tester that simulated the function of a ball bearing cage was used. Suitable materials must provide lubrication with an acceptably low wear rate, without abrading contacting surfaces. The most promising materials were tested in full scale bearings at speeds up to 4 MDN. Teflon, filled with 40 percent bronze powder, was the best performing material. A variety of bearings were designed and successfully tested in LH2 and LOX. Bearings with bronze filled Teflon cages were successfully tested for 150 hrs. In overload tests, the same design was tested for 5 hrs at maximum Hertz stresses above 450 ksi and an additional 5 hrs with a maximum Hertz stress exceeding 500 ksi. Four bearings were tested in LOX for 25 hrs, with a maximum time per bearing of 10 hrs.

Poole, W. E.; Bursey, R. W., Jr.

1988-01-01

387

Chromatographic (TLC) differentiation of grizzly bear and black bear scats  

Science.gov (United States)

While past work concluded that thin-layer chromatography (TLC) was inadequate for the separation of grizzly (Ursus arctos horribilis) and black bear (U. americanus) scats, our study found differences adequate for species separation. A key was constructed using 19 of 40 data points recorded on each(N)=356 profiles of 178) know-species scat. Accuracy was best for late summer scats (94%). Methods for specimen preparation, analysis, and reading the TLC profiles are discussed. Factors involved in scat variation were tested.

Picton, Harold D.; Kendall, Katherine C.

1994-01-01

388

Hydrostatic bearings for a turbine fluid flow metering device  

Science.gov (United States)

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between bearing surfaces, thereby minimizing bearing wear and corrosion.

Fincke, J.R.

1980-05-02

389

Paleozoic structural controls on shortening transfer in the Subandean foreland thrust system, Ene and southern Ucayali basins, Peru  

Science.gov (United States)

The Neogene evolution of the Ene and southern Ucayali basins of the Subandes has been controlled by two stacked thrust wedges that differ in terms of tectonic styles. The lower thrust wedge is formed by deep-seated décollements within the basement related to thick-skinned foreland structures inherited from an Early Carboniferous thrust system. Seismic reflection data show that this Paleozoic compressional system has been eroded and unconformably covered by Late Carboniferous clastic sediments. It generated an irregular Paleozoic sedimentary architecture controlling the Neogene thrust propagation. The upper thin-skinned thrust wedge developed within this Paleozoic sedimentary series and constitutes the Subandean zone. Cross-section balancing shows an along-strike homogenous horizontal shortening of ˜56 km (˜30%) across the Ene-southern Ucayali thrust system. This amount of shortening was vertically partitioned onto the two stacked thrust wedges. The N-S thickness variations of the Paleozoic sedimentary prism controlled the eastward propagation of the upper thrust wedge. The southern thickening of the Paleozoic series generated major décollements and the shortening excess is of 7 km (16%) in comparison to the north. Consequently, the northern lack of shortening onto the upper thrust wedge was transferred to the Early Carboniferous compressional structures of the lower thrust wedge. We suggest that this vertical partitioning of the shortening was accommodated by a regional oblique ramp: the Tambo transfer zone. This geometrical analysis of the Ene-southern Ucayali thrust system provides new perspectives for future hydrocarbon exploration in this region.

Espurt, Nicolas; Brusset, StéPhane; Baby, Patrice; Hermoza, Wilber; BolañOs, Rolando; Uyen, Dennys; DéRamond, Joachim

2008-06-01

390

Deepwater fold and thrust belt SE Nansha Trough, the South China Sea  

Science.gov (United States)

The deepwater fold and thrust belt SE Nansha Trough, the South China Sea, hosting a significant number of proven hydrocarbon accumulations, is one of the most important areas of deepwater development and production. In the past two decades, there has been long-standing academic interest in the controlling mechanism of deepwater folding-and-thrusting. Two mechanisms have been discussed as primary controlling factors: 1) basement-driven crustal shortening and 2) gravity-related delta tectonics. In this study, based on reprocessed and post-stack depth-migrated regional 2D seismic profiles across the deepwater fold and thrust belt and previous research achievements, their geological structural interpretation reveal the features of compressional, syn-depositional deformation. Consequently, the dynamic mechanism and its evolution models for the deepwater fold and thrust tectonics are established.

Bing, Han; Benduo, Zhu; Ling, Wan

2014-05-01

391

Static Investigation of a Multiaxis Thrust-Vectoring Nozzle With Variable Internal Contouring Ability  

Science.gov (United States)

The thrust efficiency and vectoring performance of a convergent-divergent nozzle were investigated at static conditions in the model preparation area of the Langley 16-Foot Transonic Tunnel. The diamond-shaped nozzle was capable of varying the internal contour of each quadrant individually by using cam mechanisms and retractable drawers to produce pitch and yaw thrust vectoring. Pitch thrust vectoring was achieved by either retracting the lower drawers to incline the throat or varying the internal flow-path contours to incline the throat. Yaw thrust vectoring was achieved by reducing flow area left of the nozzle centerline and increasing flow area right of the nozzle centerline; a skewed throat deflected the flow in the lateral direction.

Wing, David J.; Mills, Charles T. L.; Mason, Mary L.

1997-01-01

392

Performance characterization of a helicon double layer thruster using direct thrust measurements  

Science.gov (United States)

The performance of a helicon double layer thruster (HDLT) has been characterized using a pendulum type thrust stand and retarding field energy analyser. Data recorded for a fixed propellant flow rate of 16 sccm of krypton and fixed magnetic field topology show that the thrust generated increases linearly with increasing radio frequency input power over a range 250-650 W. Over the power range investigated thrust levels of approximately 1-2.8 mN were achieved. A maximum effective specific impulse of 280 s was determined using the thrust data. Ion energy distribution functions indicate that increasing power corresponds to improved plasma generation processes as general trends show increasing plasma and beam currents with increasing power.

Pottinger, Sabrina; Lappas, Vaios; Charles, Christine; Boswell, Rod

2011-06-01

393

Performance characterization of a helicon double layer thruster using direct thrust measurements  

Energy Technology Data Exchange (ETDEWEB)

The performance of a helicon double layer thruster (HDLT) has been characterized using a pendulum type thrust stand and retarding field energy analyser. Data recorded for a fixed propellant flow rate of 16 sccm of krypton and fixed magnetic field topology show that the thrust generated increases linearly with increasing radio frequency input power over a range 250-650 W. Over the power range investigated thrust levels of approximately 1-2.8 mN were achieved. A maximum effective specific impulse of 280 s was determined using the thrust data. Ion energy distribution functions indicate that increasing power corresponds to improved plasma generation processes as general trends show increasing plasma and beam currents with increasing power.

Pottinger, Sabrina; Lappas, Vaios [Surrey Space Centre, University of Surrey, Guildford GU2 7XH (United Kingdom); Charles, Christine; Boswell, Rod [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2011-06-15

394

Performance characterization of a helicon double layer thruster using direct thrust measurements  

International Nuclear Information System (INIS)

The performance of a helicon double layer thruster (HDLT) has been characterized using a pendulum type thrust stand and retarding field energy analyser. Data recorded for a fixed propellant flow rate of 16 sccm of krypton and fixed magnetic field topology show that the thrust generated increases linearly with increasing radio frequency input power over a range 250-650 W. Over the power range investigated thrust levels of approximately 1-2.8 mN were achieved. A maximum effective specific impulse of 280 s was determined using the thrust data. Ion energy distribution functions indicate that increasing power corresponds to improved plasma generation processes as general trends show increasing plasma and beam currents with increasing power.

395

Experimental thrust performance of a high area-ratio rocket nozzle  

Science.gov (United States)

An experimental investigation was conducted to determine the thrust performance attainable from high-area-ratio rocket nozzles. A modified Rao-contoured nozzle with an expansion area of 1030 was test fired with hydrogen-oxygen propellants at altitude conditions. The nozzle was also tested as a truncated nozzle, at an expansion area ratio of 428. Thrust coefficient and thrust coefficient efficiency values are presented for each configuration at various propellant mixture ratios (oxygen/fuel). Several procedural techniques were developed permitting improved measurement of nozzle performance. The more significant of these were correcting the thrust for the aneroid effects, determining the effective chamber pressure, and referencing differential pressure transducers to a vacuum reference tank.

Pavli, A. J.; Kacynski, K. J.; Smith, T. A.

1986-01-01

396

Experimental thrust performance of a high-area-ratio rocket nozzle  

Science.gov (United States)

An experimental investigation was conducted to determine the thrust performance attainable from high-area-ratio rocket nozzles. A modified Rao-contoured nozzle with an expansion area of 1030 was test fired with hydrogen-oxygen propellants at altitude conditions. The nozzle was also tested as a truncated nozzle, at an expansion area ratio of 428. Thrust coefficient and thrust coefficient efficiency values are presented for each configuration at various propellant mixture ratios (oxygen/fuel). Several procedural techniques were developed permitting improved measurement of nozzle performance. The more significant of these were correcting the thrust for the aneroid effects, determining the effective chamber pressure, and referencing differential pressure transducers to a vacuum reference tank.

Pavli, Albert J.; Kacynski, Kenneth J.; Smith, Tamara A.

1987-01-01

397

Fail-Safe Operation of a High-Temperature Magnetic Bearing Investigated for Gas Turbine Engine Applications  

Science.gov (United States)

The Structural Mechanics and Dynamics Branch at the NASA Glenn Research Center has developed a three-axis high-temperature magnetic bearing suspension rig to enhance the safety of the bearing system up to 1000 F. This test rig can accommodate thrust and radial bearings up to a 22.84 cm (9 in.) diameter with a maximum axial loading of 22.25 kN (5000 lb) and a maximum radial loading up to 4.45 kN (1000 lb). The test facility was set up to test magnetic bearings under high-temperature (1100 F) and high-speed (20,000 rpm) conditions. The magnetic bearing is