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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

An XPS study of the adherence of refractory carbide, silicide, and boride RF-sputtered wear-resistant coatings

Radio frequency sputtering was used to deposit refractory carbide, silicide, and boride coatings on 440-C steel substrates. Both sputter etched and pre-oxidized substrates were used and the films were deposited with and without a substrate bias. The composition of the coatings was determined as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. Friction and wear tests were conducted to evaluate coating adherence. In the interfacial region there was evidence that bias may produce a graded interface for some compounds. Biasing, while generally improving bulk film stoichiometry, can adversely affect adherence by removing interfacial oxide layers. Oxides of all film constituents except carbon and iron were present in all cases but the iron oxide coverage was only complete on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 films. In the case of mixed oxides, preoxidation enhanced film adherence. In the layered case it did not.

Brainard, W. A.↗
NASA NTRS1978

A fracture specimen for high-temperature testing

A wedge-loaded tapered DCB specimen is proposed for fracture toughness and stable crack growth measurements of ceramic materials at elevated temperatures. The specimen is wedge-loaded by a compression pin seated in the starter notch. By appropriate selection of the specimen's taper and starter notch angle, the stress intensity factor is maintained relatively constant through 50 percent of the test section. Room temperature fracture toughness testings of commercial grade polycrystalline alumina specimens indicate that the crack will run straight for approximately 50 percent of the length of the test section without side grooving. A moderate 10 percent side grooving was sufficient to maintain straight crack extension throughout the entire specimen length.

Kobayashi, A. S.↗
NASA NTRS1978

Microcrater and solar-flare track maturation of the lunar regolith

The microcrater, pancake and cosmic ray track record in the 100-200 microns feldspar fraction of a variety of surface soils and Apollo and Luna 16-24 cores have been studied. In Luna 24, a study of the glassy agglutinates plus breccias in 9 levels revealed this core was deposited as discrete layers, most of which are immature. Luna 16 and 20 cores were found respectively mature and immature. Glassy agglutinates and impact microcraters, absent to rare in immature soils such as 12033 and 14141, are present in similar abundances on crystals from submature to mature soils. In submature and mature soils, pancakes are present on 60 to 100 percent of crystals and craters on 50 to 70 percent. Microcrater, track and solar wind gas data suggest feldspar crystals in the size range considered reach an equilibrium maturity grade faster than bulk soils. This is interpreted as due to the limited lifetime of these crystals in the lunar regolith.

Poupeau, G.↗
NASA NTRS1979

Sweating responses during heat acclimation and moderate conditioning

Experiments were conducted on ten young male subjects to determine sweating onset, distribution, and patterns as well as the relationships of these responses to body temperature during heat acclimation and moderate conditioning performed in temperate (24 C) conditions. The subjects are randomly assigned to two groups of five subjects each. The experimental period consisted of eight successive days of either graded exercise to exhaustion on a bicycle ergometer in heat (acclimation group) or in a temperate environment (control group). Major conclusions are that (1) acclimation and conditioning result in relatively more sweat rate on the limbs than on the torso, but that these changes are less related to body temperature than torso sweat rate; and (2) sweating sensitivity increases during acclimation and conditioning, but its contribution to heat acclimation is minor.

Shvartz, E.↗
NASA NTRS1979

Surface accuracy measurement system deployable reflector antennas

Conceptual optical sensor configurations for measuring the surface deformations of large, deployable space antennas are described. These antennas include precision deployable reflectors up to 30 meters diameter and 1000 GHz frequency and mesh deployable reflectors up to 100 meters diameter and 30 GHz frequency. For each representative antenna configuration, the surface deformation sensor provides continuous, real-time measurements at a sufficient number of sample points to be compatible with active surface control. Moreover, the sensor system does not interfere with the mechanical or microwave characteristics of either the antenna surface or the feed. For the applications considered, the sensor system consists of a central receiver ring containing six to ten long focal length, angle measuring instruments, each viewing a dedicated set of bright point targets at the antenna. The targets, either light emitting diodes or illuminated retroreflectors, are modulated to eliminate errors from spurious backgrounds. Very preliminary performance estimates indicate that the sensor system, using commerical grade components, can produce a 20th to a 30th wavelength accuracy (3 sigma).

Neiswander, R. S.↗
NASA NTRS1978

Excess fission xenon at Apollo 16

Results are reported of stepwise heating analyses of Xe and Kr in four Apollo 16 low-grade breccias: 60019, 60225, 60275, and 67455. All four samples contain significant amounts of solar wind gases and at least three contain excess fission Xe. This observation indicates that the excess fission Xe effect is global rather than local, i.e., results from moon-wide redistribution of fission Xe rather than local redistribution in KREEP-rich Apollo 14 material. It is suggested that the excess fission Xe phenomenon represents a temporal variation in the amount of fission Xe available for redistribution, that it is prominent in samples from both highland sites simply because they are older than mare sites, and that samples from these sites had experienced at least some of their surface exposure at an early epoch.

Bernatowicz, T. J.↗
NASA NTRS1978

Development of a process for high capacity-arc heater production of silicon

The realization of low cost, electric power from large-area silicon, photovoltaic arrays will depend on the development of new methods for large capacity production of solar grade (SG) silicon with a cost of less than $10 per kilogram by 1986 (established Department of Energy goal). The objective of the program is to develop a method to produce SG silicon in large quantities based on the high temperature-sodium reduction of silicon tetrachloride (SiCl4) to yield molten silicon and the coproduct salt vapor (NaCl). Commercial ac electric arc heaters will be utilized to provide a hyper-heated mixture of argon and hydrogen which will furnish the required process energy. The reactor is designed for a nominal silicon flow rate of 45 kg/hr. Analyses and designs have been conducted to evaluate the process and complete the initial design of the experimental verification unit.

Reed, W. H.↗
NASA NTRS1979

Computer design synthesis of a below knee-Syme prosthesis

A detailed design synthesis analysis of the BK Syme prosthesis is provided, to determine the socket's cutout orientation size and shape, cutout fillet shape, socket wall thickness distribution and the reinforced fiber distribution in the socket wall, for a minimally stressed structurally safe lightweight prosthesis. For analysis purposes, the most adverse socket loading is obtained at the push-off stage of gait; this loading is idealized as an axial in-plane loading on the bottom edge of the circular cylindrical socket shell whose top edge is considered fixed. Finite element stress analysis of the socket shell (with uniform and graded wall thickness) are performed for various orientations of the cutout and for various types of corner fillets. A lateral cutout with a streamline fillet is recommended. The wall material (i.e., thickness) distribution is determined so as to minimize the stresses, while ensuring that the wall material's stress limits are not exceeded. For such a maximally stressed lightweight socket shell, the panels in the neighborhood of the cutout are checked to ensure that they do not buckle under their acquired stresses. A fiber-reinforced laminated composite socket shell is also analyzed in order to recommend optimum variables in orientations and densities of reinforcing fibers.

Elangovan, P. T.↗
NASA NTRS1980

Corrosion-resistant ceramic thermal barrier coating

Two-layer thermal barrier coating, consisting of metal-CrA1Y bond coating and calcium silicate ceramic outer layer, greatly improves resistance of turbine parts to hot corrosion from fuel and air impurities. Both layers can be plasma sprayed, and ceramic layer may be polished to reduce frictional losses. Ceramic provides thermal barrier, so parts operate cooler metal temperatures, coolant flow can be reduced, or gas temperatures increased. Lower grade fuels also can be used.

Hodge, P. E.↗
NASA NTRS1980

Temperature controller for hyperthermia devices

Temperature controller monitors and controls temperature in local region of tumor. Medical grade thermocouples are inserted in or near tumor, controller pulse modulates radio frequency diathermy power source to maintain temperature within 0.2 C. System may be extended to control diathermy of more than one tumor or patient.

Couch, R. H.↗
NASA NTRS1981

Automatic chemical vapor deposition

Report reviews chemical vapor deposition (CVD) for processing integrated circuits and describes fully automatic machine for CVD. CVD proceeds at relatively low temperature, allows wide choice of film compositions (including graded or abruptly changing compositions), and deposits uniform films of controllable thickness at fairly high growth rate. Report gives overview of hardware, reactants, and temperature ranges used with CVD machine.

Kennedy, B. W.↗
NASA NTRS1981

Pulse-shaping circuit for laser excitation

Narrower, impedence-matched pulses initiate stabler electric discharges for gas lasers. Discharges are more efficient, more compact, capable of high repetition rate, and less expensive than conventional electron-beam apparatus, but gas tends to break down and form localized arcs. Pulse-shaping circuit compresses width of high-voltage pulses from relatively-slow rise-time voltage generator and gradually grades circuit impedance from inherent high impedance of generator to low impedence of gas.

Laudenslager, J. B.↗
NASA NTRS1981

Applying the helium ionization detector in chromatography

High noise levels and oversensitivity of helium detector make flame-ionization and thermal-conductivity detectors more suitable for chromotography. Deficiencies are eliminated by modifying helium device to operate in saturation rather than multiplication mode. Result is low background current, low noise, high stability, and high sensitivity. Detector analyzes halocarbons, hydrocarbons, hydrogen cyanide, ammonia, and inorganics without requiring expensive research-grade helium.

Gibson, E. K.↗
NASA NTRS1981

Producing silicon continuously

Fluid-bed vaporization followed by chemical vapor deposition generates large, semiconductor-grade silicon particles. Method is economical, high-volume alternative to conventional batch-processing methods. Harvested chunks, extracted in cyclone separator, are about 0.5 to 1.3 centimeters in diameter. Process is not limited to polymer feedstock; it utilizes any halosilane intermediate used in silicon production.

Ingle, W. M.↗
NASA NTRS1979

The 30/20 GHz mixed user architecture development study: Executive summary

The baseline 30/30 GHz satellite communication system, designed for cost-effective communications in the years 1990 to 2000, incorporates on-board satellite demodulation and routing of individual 64 kbps digital voice-grade circuits. This level of routing flexibility is necessary to provide efficient communications to the large number of direct-to-user terminals (DTU) projected. The circuit interfacing hardware is distributed among all the DTU and master control stations. The switching circuitry which provides full interconnectivity between 30 to 45 thousand circuits is in the satellite. The DTU terminal cost, perhaps the largest element in the system cost, represents the largest economic value element of the system because it avoids using terrestrial signal distribution and routing and the charges associated with these functions. Satellite baseline design and power requirements for the system are examined.

Source record↗
NASA NTRS1979

Sodium storage and injection system

A sodium storage and injection system for delivering atomized liquid sodium to a chemical reactor employed in the production of solar grade silicon is disclosed. The system is adapted to accommodate start-up, shut-down, normal and emergency operations, and is characterized by (1) a jacketed injection nozzle adapted to atomize liquefied sodium and (2) a supply circuit connected to the nozzle for delivering the liquefied sodium. The supply circuit is comprised of a plurality of replaceable sodium containment vessels, a pump interposed between the vessels and the nozzle, and a pressurizing circuit including a source of inert gas connected with the vessels for maintaining the sodium under pressure.

Keeton, A. R.↗
NASA NTRS1979

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulants

The reformulation of a commercial grade of ethylene/vinyl acetate copolymer for use as a pottant in solar cell module manufacture was investigated. Potentially successful formulations were prepared by compounding the raw polymer with antioxidants, ultraviolet absorbers and crosslinking agents to yield stabilized and curable compositions. The resulting elastomer was found to offer low cost (approximately $0.80/lb.), low temperature processability, high transparency (91% transmission), and low modulus. Cured specimens of the final formulation endured 4000 hours of fluorescent sunlamp radiation without change which indicates excellent stability.

Willis, P. B.↗