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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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Thermionic work function of refractory intermetallic compounds and their electronic and crystal structures
Growth parameters for refractory carbide single crystals
High temperature diffusion studies between uranium materials and refractory metals and alloys - thermionic emission properties
Irradiation of refractory uranium dioxide and uranium carbide fuels at high specific powers to high burnups
Extruded tungsten composites containing fibered or reacted additives examined, noting stress rupture life, temperature effect, creep properties, density, hardness, etc
Growth parameters for refractory carbide single crystals
Fusion temperature in refractory carbide systems
Refractory glass fibers composition, fiber forming characteristics, construction and operation
Testing machine for evaluating high temperature fabrics under dynamic loading and heating conditions
Apparatus for refractory single crystal fusion growth at high temperature using arc melting
Niobium and tantalum alloys compatibility with boiling potassium tested for applications to turboelectric space power system
Design and performance of space storable liquid FLOX methane thrustor of refractory composite materials
Silicon ribbon growth experiments were conducted using orifices (dies) fabricated from SiC-SiO2 mixtures, fused quartz, SiC, and fine-grained, high density graphite. The best results were obtained from graphite dies. A number of different approaches was tried in modifying the thermal gradient in the dies and in holding the dies. The best results here were obtained from a 0.25-in. thick Mo disc holding a graphite die directly and fitting the die quite closely. Ribbon growths as wide as 9 mm were obtained, while the longest ribbon was 450 x 3.5 x 0.5 mm. Resistivities of ribbons grown from graphite dies have been measured over the range of 0.03 to 1.6 ohm-cm. Some thoughts and literature findings are presented regarding refractory oxide materials as potential orifices.
The flow field characteristics within the discharge chamber and exhaust of a quasi-steady magnetoplasmadynamic (MPD) arcjet were examined to clarify the nature of the plasma acceleration process. The observation of discharge characteristics unperturbed by insulator ablation and terminal voltage fluctuations, first requires the satisfaction of three criteria: the use of refractory insulator materials; a mass injection geometry tailored to provide propellant to both electrode regions of the discharge; and a cathode of sufficient surface area to permit nominal MPD arcjet operation for given combinations of arc current and total mass flow. The axial velocity profile and electromagnetic discharge structure were measured for an arcjet configuration which functions nominally at 15.3 kA and 6 g/sec argon mass flow. An empirical two-flow plasma acceleration model is advanced which delineates inner and outer flow regions and accounts for the observed velocity profile and calculated thrust of the accelerator.
Chemical fractionation processes are investigated with emphasis on selective single isotope fractionation in polyisotopic systems, particularly in oxygen. The related temperature parameters of meteoritic condensates and of their source medium are investigated by a thermometric method that is independent of assumptions regarding temperatures and pressures in the solar nebula. The crucial nonlinear chemical fractionation of O-16 was demonstrated experimentally. The effect was achieved in condensed CO2 formed from CO with C-12 O-16 selectively excited by H Ly alpha. The effect was verified by mass spectrometric measurements. The meteorite paleotemperature estimates were advanced from defining only thermal exposure to evaluating time and temperature independently. Grain temperatures at condensation of refractory inclusion materials are indicated to be less than 900 K in agreement with radiation temperature considerations and observations in circumstellar dust shells.
Advances in the understanding of comet Halley's dust environment are highlighted. Spacecraft results on the dust composition, the detection of subfemtogram grains, and the particle-mass distribution; jets and the dust-emission pattern; the existence of discrete sources on the nucleus surface and the determination of their locations from day-to-day motions of coma features; CN jets; large-scale phenomena, including an antitail, streamers, and a sunward spike; infrared observations, such as the 3.4 microns emission feature, applications of array detectors, and rare far-infrared data; the chemical modification of low-temperature ices by UV and cosmic-ray irradiation processes, their laboratory simulations, and applications to the evolution of comets; the interstellar-connection models of comet origin; and the formation of a mantle made of refractory organic material on the nucleus surface.
Meteoroid ablation in the Neptune atmosphere can influence the chemistry of the upper atmosphere through the supply of oxygen, in the case of water-ice meteoroid ablation, which will eventually be converted to CO in the upper atmosphere, and through the ablation and recondensation of relatively refractory meteoroid material, which leads to the production of dust particles that can act as sites for lower-atmosphere condensation of hydrocarbons. An analysis is presently made of ablation rate calculation uncertainties. The ablation equations presented are applicable to other planets.
Bolts instrumented with strain gauges used to measure shear forces. Bolts installed in multiple-bolt lap joints to obtain data on distribution of stresses and deformations in and around joints. Strain gauges indicate share of applied load borne by each individual bolt. In original application, bolted panels made of advanced refractory composite materials designed to withstand use at temperatures up to 4,000 degrees F. Also applicable to other joint materials and measurement of shear loads in other connections such as, shear loads on shafts in pulleys or gears.