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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Highly force-free relativistic electron beam equilibrium.

A non-hollowed-out relativistic electron beam model is considered in which the axial current well exceeds the Alfven limit when the field-configuration of the beam is highly force free. In this model, the current has an axial as well as an azimuthal component. For a given ratio of these two current components, a family of solutions is obtained in which there is an upper limit on beam radius. Over a large range of the beam radius, the axial current in our model is large compared with the current carried by a beam of the same radius in Hammer and Rostoker's model.

Kan, J. R.↗
NASA NTRS1974

Insulation of nonlinear and random vibrations in the mining industry

The insulation of nonlinear and random vibrations is considered for some ore preparing and sorting implements: rotary crushers, resonance screens, hammer mills, etc. The appearance of subharmonic vibrations is analyzed, and the conditions for their appearance are determined. A method is given for calculating the insulation of these vibrations by means of elastic elements made of rubber. The insulation of the random vibrations produced by Symons crushers is calculated by determining the transmissability and deformation of the insulation system for a narrow band random response.

Zeveleanu, C.↗
NASA NTRS1973

Measurement of vibration rate of manually operated percussion machines

A special apparatus for measurement of accelerations of between 1 and 5000 g and shock stress pulses from 20 kg/cu cm up, with durations of 50.1 million sec and higher was designed and built. The amplitudes and shapes of the peak vibroshock pulses, arising during operation of a hammer, are obtained; the recording time of the continuous process is determined by the time of one revolution of the drum of a specially made mechanical photo attachment.

Aleksandrov, Y. V.↗
NASA NTRS1974

Study of cryogenic propellant systems for loading the space shuttle

Computer programs were written to model the liquid oxygen loading system for the space shuttle. The programs allow selection of input data through graphic displays which schematically depict the part of the system being modeled. The computed output is also displayed in the form of graphs and printed messages. Any one of six computation options may be selected. The first four of these pertain to thermal stresses, pressure surges, cooldown times, flow rates and pressures during cooldown. Options five and six deal with possible water hammer effects due to closing of valves, steady flow and transient response to changes in operating conditions after cooldown. Procedures are given for operation of the graphic display unit and minicomputer.

Voth, R. O.↗
NASA NTRS1973

Delta's inexpensive, reliable, and versatile third generation upper stage

The need for larger diameter fairings to encapsulate spacecraft designed to use Delta's increased lifting capabilities resulted in hammer-head design configurations that would have unaccepably degraded vehicle flight characteristics. This situation led to the development of the Straight Eight configuration. The towed mode arrangement for the second stage negated the requirement for the engine compartment structure, thus establishing the potential for an improved packaging of the hydraulic and pneumatic systems. Therefore, with cost reduction and reliability improvement objectives, a second stage propulsion system improvement program was initiated. The paper will describe these improvements and their system benefits.

Bonnett, E. W.↗
NASA NTRS1977

Low cost silicon solar array project silicon materials task: Establishment of the feasibility of a process capable of low-cost, high volume production of silane (step 1) and the pyrolysis of silane to semiconductor-grade silicon (step 2)

A quartz fluid bed reactor capable of operating at temperatures of up to 1000 C was designed, constructed, and successfully operated. During a 30 minute experiment, silane was decomposed within the reactor with no pyrolysis occurring on the reactor wall or on the gas injection system. A hammer mill/roller-crusher system appeared to be the most practical method for producing seed material from bulk silicon. No measurable impurities were detected in the silicon powder produced by the free space reactor, using the cathode layer emission spectroscopic technique. Impurity concentration followed by emission spectroscopic examination of the residue indicated a total impurity level of 2 micrograms/gram. A pellet cast from this powder had an electrical resistivity of 35 to 45 ohm-cm and P-type conductivity.

Breneman, W. C.↗
NASA NTRS1981

Cleaving machine for hard crystals

Hard crystalline materials such as lithium fluoride (LiF) are cleaved in thin sections by semiautomatic machine. Yield of undistorted LiF crystals is almost 100 percent, even when cleaved section is only 1/32 inch thick. Machine contains spring-activated hammer that limits penetration of blade and controls shock that cleaves crystal. Fixture with spring-loaded clamps precisely locates and holds crystal, restraining it in ideal position for cleaving. Crystal then splays apart.

Benedicto, J. S. J.↗
NASA NTRS1979

High G pyrotechnic shock simulation using metal-to-metal impact

A technique for simulating high g level pyrotechnic shocks is described and the results of applying the technique to obtain the MIL-STD-1540A shock spectrum with a maximum acceleration of 18,000g at 2,000 Hz are presented. Designing the resonant beam and plate on which the test unit is mounted, and generating a proper impulsive load on them, were the essentials of the technique. One dimensional stress wave and Euler equations were employed in the design. A metal pendulum hammer was used to generate the impulsive load.

Bai, M.↗
NASA NTRS1982

The dynamic flexural response of propeller blades

The determination of the torsional constants of three blade models having NACA four-digit symmetrical airfoil cross sections is presented. Values were obtained for these models analytically and experimentally. Results were also obtained for three other models having rectangular, elliptical, and parabolic cross sections. Complete modal analyses were performed for five blade models. The identification of modal parameters was done for cases when the blades were modeled as either undamped or damped multi-degree-of-freedom systems. For the experimental phase of this study, the modal testing was performed using a Dual Channel FFT analyzer and an impact hammer (which produced an impulsive excitation). The natural frequency and damping of each mode in the frequency range up to 2 kHz were measured. A small computer code was developed to calculate the dynamic response of the blade models for comparison with the experimental results. A comparison of the undamped and damped cases was made for all five blade models at the instant of maximum excitation force. The program was capable of handling models where the excitation forces were distributed arbitrarily along the length of the blade.

Djordjevic, S. Z.↗
NASA NTRS1982

Crystal cleaving machine

A machine is disclosed for cleaving hard crystals. A typical example of which is lithium fluoride, with prcision and uniformity and includes vertical axis positioning control means for an adjustable spring tension guided hammer mechanism employed to strike an anvil. A crystal cleaving shock wave transmitted to a cleaving blade is generated having an angulated cleaving edge in contact with one corner of the crystal. Connection between the anvil and the blade is by means of a pair of vertical shafts held in substantially friction free engagement by two pairs of adjustable linear bearings. An underlying crystal holding fixture with horizontal position control means includes a zero reference stop face for the crystal and opposing spring-loaded clamping and vertical positioning elements which are precisely guided.

Hallberg, F. C.↗
NASA NTRS1985

Stepped-Pin Clevis Resists Jamming

Pin modification allows pyrotechnic release devices to operate more smoothly. New clevis pin has stepped diameters to prevent bending as it exits yoke. In contrast, conventional unstepped clevis pin bends and jams as it is withdrawn. Stepped pin design suitable for explosive and possible hammer driven pin sullers.

Killgrove, T. O.↗
NASA NTRS1983

Application of image processing technology to problems in manuscript encapsulation

The long term effects of encapsulation individual sheets of the Codex Hammer were investigated. The manuscript was simulated with similar sheets of paper which were photographed under repeatable raking light conditions to enhance their surface texture, encapsulated in plexiglas, cycled in an environmental test chamber, and rephotographed at selected intervals. The film images were digitized, contrast enhanced, geometrically registered, and apodized. An FFT analysis of a control sheet and two experimental sheets indicates no micro-burnishing, but reveals that the ""mesoscale'' deformations with sizes 8mm are degrading monotonically, which is of no concern. Difference image analysis indicates that the sheets were increasingly stressed with time and that the plexiglas did not provide a sufficient environmental barrier under the simulation conditions. The relationship of these results to the Codex itself is to be determined.

Glackin, D. L.↗
NASA NTRS1984

Advanced powder metallurgy aluminum alloys via rapid solidification technology

Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

Ray, R.↗
NASA NTRS1985

Improved Highway Pads for Tracked Vehicles

New pads attach faster and hold more securely than conventional pads. Rubber pad held on tread by bent locking tab and by lip that engages recess in tread. Tab hammered in during installation and pried out during removal. New designs ease installation of rubber pads on treads of tracked vehicles to prevent damage to highways. Designs apply to bulldozers, cranes, and excavating machines.

Collins, Earl R., Jr.↗
NASA NTRS1986

Damage-Free Relief-Valve Disassembly

Tool safely disassembles relief valves without damage to sensitive parts. Relief-valve disassembly tool used to extract valve nozzle from its housing. Holding device on tool grops nozzle. When user strikes hammer against impact disk, holding device pulls nozzle from press fit. Previously, nozzle dislodged by striking spindle above it, but practice often damaged retaining screw. New tool removes nozzle directly. With minor modifications, tool adapted to valves from different manufacturers.

Haselmaier, H.↗
NASA NTRS1985

Self-locking mechanical center joint

A device for connecting, rotating and locking together a pair of structural half columns is described. The device is composed of an identical pair of cylindrical hub assemblies connected at their inner faces by a spring loaded hinge; each hub assembly having a structural half column attached to its outer end. Each hub assembly has a spring loading locking ring member movably attached adjacent to its inner face and includes a latch member for holding the locking ring in a rotated position subject to the force of its spring. Each hub assembly also has a hammer member for releasing the latch on the opposing hub assembly when the hub assemblies are rotated together. The spring loaded hinge connecting the hub assemblies rotates the hub assemblies and attached structural half columns together bringing the inner faces of the opposing hub assemblies into contact with one another.

Bush, H. G.↗
NASA NTRS1984

Dynamic response and acoustic fatigue of stiffened composite structure

The results of acoustic fatigue and dynamic response tests performed on L-1011 graphite-epoxy (GrE) aileron and panel components are reported. The aileron featured glass microballoons between the GrE skins. Tests yielded random fatigue data from double and single cantilever coupons and modal data from impedance hammer and loudspeaker impulses. Numerical and sample test data were obtained on combined acoustic and shear loads, acoustic and thermal loads, random fatigue and damping of the integrally stiffened and secondary bonded panels. The fatigue data indicate a fatigue life beyond 10 million cycles. The acoustic data suggested that noise transmission could be enhanced in the integrally stiffened panels, which were more acoustic-fatigue resistant than were the secondary bonded panels.

Soovere, J.↗
NASA NTRS1986

Portable Hydraulic Powerpack

Rechargeable hydraulic powerpack functions as lightweight, compact source of mechanical energy. Self-contained hydraulic powerpack derives energy from solid chemical charge. Combustion of charge initiated by small hammer, and revolving feeder replaces charges expended. Combustion gases cool during expansion in turbine and not too hot for release to atmosphere. Unit has applications driving wheelchairs and operating drills, winches, and other equipment in remote areas. Also replaces electric motors and internal-combustion engines as source of power in explosive atmospheres.

Anderson, L. A.↗