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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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A summary of the results of the 12 Marshall Space Flight Center science demonstrations performed on Skylab is presented. The demonstrations include diffusion in liquids, ice melting, liquid floating zone, gyroscope, liquid films, immiscible liquids, Rochelle salt growth, deposition of silver crystals, fluid mechanics, neutron environment, orbital mechanics, and charged particle mobility.
The NASA Space Power Research and Technology Program has the objective to provide the technological basis for satisfying the nation's future needs regarding electrical power in space. The development of power sources of low mass and increased environmental resistance is considered. Attention is given to advances in the area of photovoltaic energy conversion, improved Ni-Cd battery components, a nickel-hydrogen battery, remotely activated silver-zinc and lithium-water batteries, the technology of an advanced water electrolysis/regenerative fuel cell system, aspects of thermal-to-electric conversion, environmental interactions, multi-kW low cost systems, and high-performance systems.
High-pressure experiments in a piston-cylinder apparatus with silver-palladium containers were conducted to study the stability of synthetic armalcolite, (Fe,Mg)Ti2O5, as a function of pressures up to 15 kbar at 1000, 1100, and 1200 C. Three armalcolite compositions were used, each with an initial Fe/(Fe + Mg) ratio of 0.5. Composition I contained no zirconium, whereas compositions II and III were prepared with 4% and 10% by weight ZrO2. Difference in stability due to the presence or absence of Zr in these synthetic armalcolites is discussed. 4 wt% ZrO2 appears to saturate armalcolite at 1200 C and 1 atm. Zirconium is found to reduce armalcolite stability, but this effect is not great. The stability of armalcolite as a function of oxygen fugacity is determined thermogravimetrically at 1200 C and 1 atm. Knowledge of the range of oxygen fugacity at which armalcolite is stable and of the equilibrium oxide mineral assemblages outside this range provides important information about lunar cooling histories in terms of oxygen fugacity.
Thermionic converters using a variety of metal oxide collector surfaces have been fabricated and tested. Both work function and power output data are presented and evaluated. Oxides of barium, strontium, zinc, tungsten and titanium have been incorporated into a variable spacing converter. Tungsten oxide was found to give the highest converter performance and to furnish oxygen for the emitter at the same time. Oxygenated emitters operate at reduced cesium pressure with an increase in electrode spacing. Electron spectroscopy for chemical analysis (ESCA) performed on several tungsten oxide collectors showed cesium penetration of the oxide layer, possibly forming a cesium tungstate bronze. Titanium oxide showed high performance but did not furnish oxygen for the emitter; strontium oxide, in the form of a sprayed layer, appeared to dissociate in the presence of cesium. Sprayed coatings of barium and zinc oxides produced collector work functions of about 1.3 eV, but had excessive series resistance. Lanthanum hexaboride, in combination with oxygen introduced through a silver tube, and cesium produced a low work function collector and better than average performance.
Silver and gold were evaporated up to several monolayers in thickness onto W single-crystal surfaces of the 110 and 100 plane types in the temperature range between 300 and 1300 K. The mode of growth and the structure of the layers were studied by Auger electron spectroscopy and low-energy electron diffraction. The results are compared with thermal desorption spectroscopy data and work-function change measurements. They show certain similarities but also some striking differences between the two systems Ag/W and Au/W as well as a strong crystallographic anisotropy of adsorption and condensation.
Relatively discharge free vacuum feedthrough uses silver-plated copper conductor jacketed by carbon filled silicon semiconductor to reduce concentrated electric fields and minimize occurrence of partial discharge.
Vestibular neuron activity was examined by studying nerve stimulation and evoked response. A cooling element, applied to the nerve consisted of a silver hook through which a coolant fluid flowed. Temperature changes were recorded via microtermistors on an eight channel brush recorder, together with response. Diffusion of the cooling effect was measured, recovery time was assessed, and the nerve was then studied hystologically and ultrastructurally. Problems in frog preparation were discussed along with problems in maintaining healthy specimens and bacteria controlled aquaria.
Reduction in cell output was observed in N(+)/P cells upon exposure to illumination or upon the application of a sufficiently high forward bias. Conversely, an enhancement in output was observed when P(+)/N cells were illuminated. Investigations performed on N(+)/P cells indicated that a recombination center located at E sub c - 0.37 eV in the forbidden band was responsible for the loss in output. The center was electrically inactive in its ground state but was activated either by raising the minority carrier quasi-Fermi level sufficiently close to the latent center energy level in the band gap, or by direct excitation of electrons from the valence band to the latent center level. The center was identified as a complex of a lattice defect and a silver atom or cluster of atoms.
The efficiency for conversion of electromagnetic energy to chemical and electrical energy utilizing semiconductor single crystals as photoanodes in electrochemical cells was investigated. Efficiencies as high as 20 percent were achieved for the conversion of 330 nm radiation to chemical energy in the form of hydrogen by the photoelectrolysis of water in a SrTiO3 based cell. The SrTiO3 photoanodes were shown to be stable in 9.5 M NaOH solutions for periods up to 48 hours. Efficiencies of 9 percent were measured for the conversion of broadband visible radiation to hydrogen using n-type GaAs crystals as photoanodes. Crystals of GaAs coated with 500 nm of gold, silver, or tin for surface passivation show no significant change in efficiency. By suppressing the production of hydrogen in a CdSe-based photogalvanic cell, an efficiency of 9 percent was obtained in conversion of 633 nm light to electrical energy. A CdS-based photogalvanic cell produced a conversion efficiency of 5 percent for 500 nm radiation.
The effects of cathode material, cathode operating temperature, anode configuration, window materials, and hydrogen additives on laser lifetime are determined. Internally oxidized copper and silber-copper alloy cathodes were tested. The cathode operating temperature was raised in some tubes through the use of thermal insulation. Lasers incorporating thermally insulated silver copper oxide cathodes clearly yielded the longest lifetimes-typically in excess of 22,000 hours. The use of platinum sheet versus platinum pin anodes had no observable effect on laser lifetime. Similarly, the choice of germanium, cadmium telluride, or zinc selenide as the optical window material appears to have no impact on lifetime.
Material coatings for an air-lubricated, compliant journal bearing for an automotive gas turbine engine were exposed to service test temperatures of 540 C or 650 C for 300 hours, and to 10 temperature cycles from room temperatures to the service test temperatures. Selected coatings were then put on journal and partial-arc foils and tested in start-stop cycle tests at 14 kPa (2 psi) loading for 2000 cycles. Half of the test cycles were performed at a test chamber service temperature of 540 C (1000 F) or 650 C (1200 F); the other half were performed at room temperature. Based on test results, the following combinations and their service temperature limitations are recommended: HL-800 TM (CdO and graphite) on foil versus chrome carbide on journal up to 370 C (700 F); NASA PS 120 (Tribaloy 400, silver and CaF2 on journal versus uncoated foil up to 540 C (1000 F); and Kaman DES on journal and foil up to 640 C (1200 F). Kaman DES coating system was further tested successfully at 35 kPa (5 psi) loading for 2000 start-stop cycles.
The results are given of an advanced module development program with the objective of providing a low cost solar cell mechanical interconnect design. The design approach, which avoids soldering or welding operations, lends itself to automated assembly techniques thus supporting the Low-Cost Silicon Solar Array Project goals. The first group of six modules contained aluminum contact cells and the second group of six modules contained silver-titanium-palladium contact cells. Extensive component and environmental testing at the module level showed that reliable cell mechanical interconnection can be achieved when utilizing the proper electrical contact materials and pressures. A discussion is given of the module design, manufacturing procedure, test program, significant problem areas and solutions, and conclusions and recommendations as formulated and conducted by XEOS.
A program was developed to predict radiative exchange factors in three-dimensional configurations with curved, specularly-reflecting surfaces using the Monte Carlo method. It was shown that this can be done efficiently by using the normal Monte Carlo method for closed configurations and/or high surface emissivities, while Energy Partitioning should be used for open configurations and/or low surface emissivities. Comparison with experiments on the Space Shuttle radiator panels showed that the simple model of gray, diffuse emission is sufficient for the prediction of exchange factors between actual (silver-coated teflon) surfaces. For solar-irradiation exchange factors on the Space Shuttle, on the other hand, spectral and directional variations of surface properties must be taken into account.
The absolute intensities of the studied transitions of CO2 have been measured from spectra obtained under high resolution. Vibration-rotation line intensities and integrated band intensities are reported. The studied bands are characterized by origins at 7593.5 and 7584 cm to the minus 1. Spectra were obtained by an Ames' 25-m base path White-type absorption cell equipped with silver-coated mirrors together with a 5-m focal length Czerny-Turner scanning spectrometer. The procedures for calculating the widths and intensities are explained, and uncertainty limits of the reported values are considered.
Scanning electron microscopy (SEM) and Auger electron microscopy (AEM) were employed to observe elemental surface decomposition resulting from the brazing of a copper-treated steel. Two types of steel were used for the study, stainless steel (treated with a eutectic silver-copper alloy), and low-carbon steel (treated with pure copper). Attention is given to oxygen partial pressure during the processes; a low enough pressure (8 x 10 to the -5th torr) was found to totally inhibit the spreading of the filler material at a fixed heating cycle. With both types of steel, copper treatment enhanced even spreading at a decreased temperature.
The image of an 80 to 90 percent underexposed medical radiograph can be increased to readable density and contrast by autoradiographic image intensification. The technique consists of combining the image silver of the radiograph with a radioactive compound, thiourea labeled with sulfur-35, and then making an autoradiograph from the activated negative.
The data on the 1975 Lexan event are reexamined in a framework that does not depend on the details of a particular track model. Instead, visual measurements of two quantities, photographic evidence, and silver-grain densities measured with an automated microscopic-image dissector are cited. It is shown that throughout the detector stack the particle had a roughly constant value of absolute Z/beta of about 109-114 based on energy deposition at radial distance less than about 0.01 micron. Its energy deposition at radial distance greater than about 20 microns was incompatible with that expected from any known cosmic ray nucleus with Z/beta in this range. A monopole is ruled out, and the three candidates compatible with the data are: (1) a slow, supermassive particle with beta about 0.4, charge about 45e, and mass above 1000-10,000 amu; (2) a fast antinucleus with Z/beta about -109 to -114 and absolute Z between 76 and 96; and (3) a very fast nucleus with Z about 110-114 and beta above about 0.99.
Soldering procedure, successfully tested for attaching leads to silicon solar cells, cover-glasses, is simple, inexpensive, and very effective in forming stable connection. Procedure uses solder of indium alloyed with either silver or tin.