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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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Determining electron concentration in flowing plasma in presence of accelerating and evaporating water droplets
Developing empirical equation for calculating effects of container geometry on liquid lubricant evaporation in vacuum
Spatter proof evaporant source design for use in vacuum deposition of solid thin films on substrates
Improved microwave transmission by adding rapidly evaporating liquid droplets to plasma sheath to remove free electrons
Feasibility of spraying flash evaporator as heat rejection device for space shuttle environmental control system
Mathematical prediction of evaporating water droplet wetting dynamics on stainless steel, Lucite, Teflon, and copper surfaces
Liquid spray flash evaporator for space shuttle thermal control
Electron beam evaporation and recrystallization of InSb thin films yielding high Hall mobilities
Evaporated Rh films preparation at various substrate temperatures in vacuum UV, determining reflectance and optical constants
Floating times of liquid/solid sphere on evaporative fluid /liquid nitrogen/ in metastable Leidenfrost film boiling
Room temperature evaporating water drop shape history on cooper, lucite, stainless steel and Teflon, observing wetting dynamics effects
Field evaporation of solid metal electrodes has been proposed as an ion source for an electrostatic propulsion device. The chief advantage over existing ion sources is the prospect of 100 percent fuel utilization efficiency. This advantage arises as a result of the elimination of the need for a gaseous precursor state for propellant ionization. The attainment of required high surface field strengths is achieved through field-induced extrusion of the electrode geometry at elevated temperatures. Contributions of both surface and bulk transport mechanisms are taken into account.
A simple expression is obtained using a diffusion model for the effect of ambient pressure on the outgassing or evaporation rate of materials. The correctness of the expression is demonstrated by comparing the estimates from this expression with actual weight loss measurements. It is shown that the rate of mass loss is governed by the ratio of mean free path to the characteristic dimension of the surface in question.
An expression is presented which may be used to estimate changes in composition as a consequence of evaporation during the storage of liquid oxygen. The sensitivity of fuel-cell systems to such changes is discussed, and sample calculations are presented.
The influence of substrate imperfections on the nucleation and growth of fcc metals on alkali halides is discussed. Films deposited on well characterized substrated under well defined vacuum evaporation conditions are investigated. The experimental results of this work are correlated with similar work by other investigators. Models which have been proposed by various authors to explain experimental results are critically examined and areas of difficulty are pointed out. The influence of defects on nucleation rate and the orientation of the film is emphasized. Specific examples of impurity effects, irradiation effects and the influence of amorphous layers are discussed in detail. Evidence is shown that the formation of multiply twinned particles is a result of coalescence and growth. The only consistent model for the orienting influence of impurities is shown to be a chemical reaction effect. It is demonstrated that an alkali metal impurity is very likely responsible for the orienting influence of both water vapor exposure and irradiation. A negative result is found for the reported possibility of an orienting influence being transmitted through an amorphous layer.
The weight-loss rate in vacuum of 18 lubricating liquids and greases is reported for temperatures up to 120 C. Eleven types of 'medium-viscosity' (20 to 52 centistokes at 40 C) fluids were studied. In addition, a variety of perfluoro ether liquids having viscosities of 350 to 500 centistokes at 40 C were investigated, as were some commercial greases based on these liquids. The results showed that a methylchlorophenyl silicone, a high-viscosity-index perfluoro ether research fluid, and a polyoctene have suitably low outgassing properties for long-term space applicaitons requiring a medium-viscosity lubricant. Perfluoro ether greases also displayed low outgassing, but batch-to-batch variation was great. Mass spectrometer measurements indicated that the outgassed species were characterized by much lower molecular weights than that expected for the liquids. This suggests that lubricant transfer techniques which rely on evaporation from a reservoir may not be desirable for long-term space applications.
Determination of the sticking probability for hydrogen adsorption on clean Ni(111), Ni(100), polycrystalline nickel sheet, and polycrystalline evaporated nickel films, using a modification of the reflection detector technique of Horgan and King (1970) for metal films. The initial sticking probability for hydrogen adsorption on a nickel film at 300 K by the proposed method is found to be 0.25 in comparison to 0.35 for hydrogen adsorption on a nickel film using the reflection detector technique. Also, the sticking probabilities on smooth single-crystal (111) and (100) planes and polycrystalline sheets are found to be lower than those on the rougher polycrystalline nickel films.
Reexamination of a model originally suggested by Bates and Spitzer (1951) for interstellar molecule production by evaporation of grain mantles. It is shown that allowance for reactions involving CH(+), formerly ignored, remove the difficulties experienced by Bates and Spitzer. The essential features of CH and CH(+) observations in the directions of certain stars can be understood on the basis of this model.