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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 145 records · Page 8

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NASA NTRS1972

Design and test of porous-tungsten mercury vaporizers.

Future use of large size Kaufman thrusters and thruster arrays will impose new design requirements for porous plug type vaporizers. Larger flow rate coupled with smaller pores to prevent liquid intrusion will be desired. This paper presents the results of testing samples of porous tungsten for flow rate, liquid intrusion pressure level, and mechanical strength. Nitrogen gas was used in addition to mercury flow for approximate calibration. Liquid intrusion pressure levels will require that flight thruster systems with long feed lines have some way (a valve) to restrict dynamic line pressures during launch.

Kerslake, W. R.↗

NASA NTRS1973

Transparent polymeric laminates

Laminate prepared from epoxy-boroxine and phenolphthalein polycarbonate has high mechanical strength at elevated temperature and is resistant to impact, fire, and high-energy thermal radiation. Polycarbonate is prepared by reaction of phenolphthalein with phosgene in presence of amine catalyst and immiscible organic solvent phase.

Parker, J. A.↗

NASA NTRS1972

Design and development of polyphenylene oxide foam as a reusable internal insulation for LH2 tanks, phase 2

PPO form was tested for mechanical strength, for the effects of 100 thermal cycles from 450 K (359 F) to 21 K (-423 F) and for gas flow resistance characteristics. PPO foam panels were investigated for density variations, methods for joining panels were studied and panel joint thermal test specimens were fabricated. The range of foam panel thickness under investigation was extended to include 7 mm (0.3 in) and 70 mm (2.8 in) panels which also were tested for thermal performance.

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NASA NTRS1973

Development and Characterization of CPI Surface Insulation

A new type of reusable surface material that could find application as a component of the thermal protection system of the space shuttle orbiter is discussed. These materials consist of 20-30% dense closed cell high emittance glass ceramic foams formulated by sintering an intimate mixture of fly ash cenospheres with 4-12 wt % cobalt oxide. These unique ceramic foams exhibit: (1) High mechanical strengths; (2) no need for waterproof coating due to the non-interconnecting cell network; (3) high emissivities; (4) ability to withstand space shuttle thermal environments with no loss of reuse capability; and (5) a machinable ceramic with capability of maintaining the close tolerances required of an integrated heat shield system.

Tobin, A.↗

NASA NTRS1974

Design, development, fabrication and testing of high temperature Flat Conductor Cable (FCC)

The results are presented of a development program for a flat, 25-conductor signal cable and a flat, 3-conductor power cable. Flat cables employ conductors made of strips or flattened round copper conductors insulated with polyimide films. It is shown that conductor thickness ranges from 0.003 to 0.010 inch, and begins to soften and loose mechanical strength at temperatures above 200 C.

Rigling, W. S.↗

NASA NTRS1974

High temperature polyimide foams for shuttle upper surface thermal insulation

Polyimide foams developed by Monsanto Company were examined for use as upper surface space shuttle thermal insulation. It was found that postcured polyimide foams having a density of 64 kg/cu m (4 lb/cu ft) had acceptable physical properties up to and exceeding 700 K (800 F). Physical tests included cyclic heating and cooling in vacuum, weight and dimensional stability, mechanical strength and impact resistance, acoustic loading and thermal conductivity. Molding and newly developed postcuring procedures were defined.

Ball, G. L., III↗

NASA NTRS1975

Sinter of uniform, predictable, blemish-free nickel plaque for large aerospace nickel cadmium cells

A series of nickel slurry compositions were tested. Important slurry parameters were found to be the nature of the binder, a pore former and the method of mixing. A slow roll mixing which is non-turbulent successfully eliminated entrapped air so that bubbles and pockets were avoided in the sinter. A slurry applicator was developed which enabled an equal quantity of slurry to be applied to both sides of the grid. Sintering in a furnace having a graded atmosphere characteristic, ranging from oxidizing to strongly reducing, improved adhesion of porous sinter to grid and resulted in a uniform welding of nickel particles to each other throughout the plaque. Sintering was carried out in a horizontal furnace having three heating zones and 16 heating control circuits. Tests used for plaque evaluation include (1) appearance, (2) grid location and adhesion, (3) mechanical strength, (4) thickness, (5) weight per unit area, (6) void volume per unit area, (7) surface area and (8) electrical resistance. Plaque material was impregnated using Heliotek proprietary processes and 100 AH cells were fabricated.

Seiger, H. N.↗

NASA NTRS1975

Bonded electrodes for use on the external surface of spacecraft

A new bonding process is described which is suitable for applying electrodes to the external surfaces of spacecraft and sounding rockets. A polyimide material containing small, uniform glass spheres provides the necessary insulation and mechanical strength. The bonded electrodes are simple to construct and are shown to have good electrical, vacuum, and thermal properties.

Kendall, B. R. F.↗

NASA NTRS1975

Design and development of polyphenylene oxide foam as a reusable internal insulation for LH2 tanks

Material specification and fabrication process procedures for foam production are presented. The properties of mechanical strength, modulus of elasticity, density and thermal conductivity were measured and related to foam quality. Properties unique to the foam such as a gas layer insulation, density gradient parallel to the fiber direction, and gas flow conductance in both directions were correlated with foam quality. Inspection and quality control tests procedures are outlined and photographs of test equipment and test specimens are shown.

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NASA NTRS1977

Superconductivity in sputtered CuMO6S8

Samples were prepared by melting the metals, followed by annealing to various temperatures. The result was a structurally weak material. Sputtered films on sapphire substrates were prepared and studied. The substrates give the films mechanical strength and permit easy attachment of electrical leads. Materials were characterized by X-ray diffraction, electron microscopy, electrical resistance vs. temperature, and critical current measurements. Some of the results on CuMo6S8 are presented.

Alterovitz, S.↗

NASA NTRS1976

Recent advances in the development of composites based on the NCNS resins

The NCNS resins, a new class of addition polymerized polyaromatic melamines, have undergone further development in the past year. Pilot plant quantities of resin NCNS-12M have been made available for evaluation. High solids laminating varnishes were prepared in alcohol/ethyl acetate and alcohol/chlorinated solvent mixtures. The prepregs had sufficient room temperature stability after three month storage to retain good processing characteristics and good bonded mechanical properties. Laminates were fabricated by vacuum bag-autoclave processing and by 5 minute press molding cycles. These laminates had low flame spread and low smoke emitting properties and retained good elevated temperature properties upon long-term oxidative aging. Humidity aging studies were carried out for 30 days at 95% R.H., 120 F. on NCNS/graphite fiber laminates. Initial results indicate that the NCNS resins, particularly those prepared from polymethylene polyphenylamines, are resistant to environmental degradation of elevated temperature mechanical strength.

Kray, R. J.↗

NASA NTRS1977

Mechanical processess affecting differentiation of protolunar material

Mechanisms prior to lunar formation are sought to account for the loss of volatiles, the depletion of iron, and the enrichment of plagioclase. Some of the same mechanisms are necessary to account for achondritic, stony-iron, and iron meteorites. Collisions seem marginally capable of providing the heat to accomplish the differentiation into iron, magnesian silicates, and plagioclase. Once this differentiation is accomplished, the subsequent mechanical history should have been sufficient to sort material according to composition in the protolunar circumterrestrial cloud. Effects operating include the correlation of body size with mechanical strength; the lesser ability of the cloud to trap the larger, denser infalling bodies; the more rapid drawing into the Earth of the larger moonlets; and the higher energy orbits for dominantly plagioclase smaller pieces broken off by collision.

Kaula, W. M.↗

NASA NTRS1978

Fabrication of stainless steel clad tubing

The feasibility of producing stainless steel clad carbon steel tubing by a gas pressure bonding process was evaluated. Such a tube product could provide substantial chromium savings over monolithic stainless tubing in the event of a serious chromium shortage. The process consists of the initial assembly of three component tubesets from conventionally produced tubing, the formation of a strong metallurgical bond between the three components by gas pressure bonding, and conventional cold draw and anneal processing to final size. The quality of the tubes produced was excellent from the standpoint of bond strength, mechanical, and forming properties. The only significant quality problem encountered was carburization of the stainless clad by the carbon steel core which can be overcome by further refinement through at least three different approaches. The estimated cost of clad tubing produced by this process is greater than that for monolithic stainless tubing, but not so high as to make the process impractical as a chromium conservation method.

Kovach, C. W.↗

NASA NTRS1978

Quantitative Ultrasonic Evaluation of Mechanical Properties of Engineering Materials

Progress in the application of ultrasonic techniques to nondestructive measurement of mechanical strength of engineering materials is reviewed. A dormant concept in nondestructive evaluation (NDE) is invoked. The availability of ultrasonic methods that can be applied to actual parts to assess their potential susceptibility to failure under design conditions is discussed. It was shown that ultrasonic methods yield measurements of elastic moduli, microstructure, hardness, fracture toughness, tensile strength, yield strength, and shear strength for a wide range of materials (including many types of metals, ceramics, and fiber composites). It was also indicated that although most of these methods were shown feasible in laboratory studies, more work is needed before they can be used on actual parts in processing, assembly, inspection, and maintenance lines.

Vary, A.↗

NASA NTRS1978

Lightweight electrically-powered flexible thermal laminate

Cross-layered woven or unwoven yarns are used to provide an active thermal control mechanism for spacecraft use. One set of yarns is composed of flexible electrically conductive metal fibers which are capable of being resistance heated by the application of voltage. Another set of yarns, nonconductive and flexible, provides mechanical strength and precludes the passage of electrical current between the metal yarns by virtue of the spacing between them. A lightweight, electrically nonconductive film is bonded to the cross-layered yarns to protect the metal yarns from the elements (minimize electrical shorts from moisture such as rain), to provide additional strength to the fabric, and to prevent conductive loss of heat in nonvacuum applications. The nonconductive film is metalized on its obverse side to provide a more uniform heat load distribution.

Dawn, F. S.↗

NASA NTRS1979

Three methods for in situ cross-linking of polyvinyl alcohol films for application as ion-conducting membranes in potassium hydroxide electrolyte

Three methods of in situ cross-linking polyvinyl alcohol films are presented. They are: (1) acetalization with a dialdehyde such as glutaraldehyde, (2) acetalization with aldehyde groups formed by selective oxidative cleaving of the few percent of 1,2 diol units present in polyvinyl alcohol, and (3) cross-linking by hydrogen abstraction by reaction with hydrogen atoms and hydroxyl radicals from irradiated water. For the third method, improvement in film conductivity in KOH solution at the expense of mechanical strength is obtained by the presence of polyacrylic acid in the polyvinyl alcohol films. Resistivities in 45 percent KOH are given for in situ cross-linked films prepared by each of the three methods.

Philipp, W. H.↗

NASA NTRS1979

A review of issues and strategies in nondestructive evaluation of fiber reinforced structural composites

Techniques for quantitative assessment of the mechanical strength and integrity of fiber composites during manufacture and service and following repair operations are presented. Problems and approaches are discussed relative to acceptance criteria, calibrating standards, and methods for nondestructive evaluation of composites in strength-critical applications. Acousto-ultrasonic techniques provide the methods of choice in this area.

Vary, A.↗

NASA NTRS1979

Planetary rings

Two models of planetary ring formation are discussed: the break-up of a large body coming nearer to the planet than the Roche limit for the particular mechanical strength of the body would allow; and condensation of the protoplanetary nebula within a suitable Roche limit without formation of a large satellite. The location of the newly discovered Uranian rings has been interpreted in terms of three-body orbital resonance with satellites. A possible relationship between the origin and characteristics of the Uranian rings and the unusual tilt of the planetary axis is also discussed. In addition, attention is given to the polarization of light characteristic of planetary rings.

Smoluchowski, R.↗