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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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Expendable evaporant heat sink design concepts - optimization of wick-type boiler and porous plate sublimator heat sink modules, and thermal conditioning panel design
Subliming ablation effects on boundary layer transition for cones in hypersonic flow, discussing Reynolds numbers measured in wind tunnel tests
Granular ammonium perchlorate thermal decomposition analyzed by cinemicrography, discussing sublimation role
Computer program solves combined problem of heat transfer and material response for the stagnation region of blunt bodies experiencing melting and vaporizing or subliming ablation. Program contains formulas for the transitional regime to bridge between the free-molecule and continuum regimes.
Thermodynamics and kinetics of sublimation, catalytic, and oxidation reactions
Ammonium perchlorate decomposition, deflagration, sublimation, crystal growth and surface properties, using scanning electron microscope
High temperature cobalt-base alloy resistant to corrosion by liquid metals and to sublimation in vacuum environment
A rather general computer code has been developed for the numerical solution of the laminar boundary layer and thin shock layer (stagnation point only) equations for a multi-component gas mixture with finite reaction rates. The purpose of this paper is to indicate the capabilities of this computer program by presenting solutions for pure air flows and flows with carbon ablation. At the body surface the effects of oxidation and sublimation of carbon are taken into account with the following species included in the gas model: 0 2 , N 2 , O, N, NO, NO + , C 1 , C 2 , C 3 , CN, CO, and CO 2 . Results for the boundary layer along a 10° half-angle hyperboloid with ablation of carbon are compared to pure air results. Shock layer results for several wall temperatures and altitudes are presented and compared to pure air results. Other types of problems that can be solved with this computer code are indicated.
Crosshatched wave patterns in liquid films, discussing supersonic wind tunnel experiments aimed at elimination of sublimation or vaporization as pattern generating mechanisms
Jupiter atmosphere entry probes graphite ablative heat shields performance, indicating convective and radiative blockage and graphite sublimation processes in surface heat balance
A functional description of the environmental control subsystem is presented. Development, tests, checkout, and flight experiences of the subsystem are discussed; and the design fabrication, and operational difficulties associated with the various components and subassemblies are recorded. Detailed information is related concerning design changes made to, and problems encountered with, the various elements of the subsystem, such as the thermal control water sublimator, the carbon dioxide sensing and control units, and the water section. The problems associated with water sterilization, water/glycol formulation, and materials compatibility are discussed. The corrective actions taken are described with the expection that this information may be of value for future subsystems. Although the main experiences described are problem oriented, the subsystem has generally performed satisfactorily in flight.
A literature survey was conducted to collect material properties data on all advanced high temperature materials. Three of these, Y2O3-stabilized ZrO2, ThO2, and ZrB2 with additives of C and SiC were selected for further study. Stabilized ZrO2 and ThO2 were found to have higher temperature oxidation resistance than any metal and great potential for use in advanced biowaste resistojets. ZrO2 has a lower electrical resistivity and sublimation and a higher creep endurance strength. ZrO2 and ThO2 tubular heat exchangers, electrically heated indirectly, were evaluated in short tests to about 1900 K in flowing CO2. ZrO2 was subjected to N2, H2, H2O and vacuum as well. X-ray diffraction and fluorescence analyses were made. The metal-to-ceramic seal technology for ZrO2 and ThO2 was developed using chemical vapor deposition of tantalum for metallizing and 82 Au - 18 Ni filler braze.
An overview of research on radio and radar meteors accomplished during the past decade is presented, and the work of the past year is highlighted. Velocity distribution and mass flux data are obtained for meteors in the range 10 to 0.0001 g, the size believed to be the principal hazard to space missions. The physical characteristics of mass, structure and density, luminosity, and ablation are briefly described, and the formulation of a theory for interactions of ionization and excitation during collision of atomic particles is mentioned. Five classes of meteoroids are identified, including the two of iron and stone meteorites. Stream meteors associated with known comets are Classes A or C, and parent comets of Class B streams are not observed. Class A meteoroids are identified with the core of a cometary nucleus, Class C with less dense surface of the nucleus after sublimation of ices, and Class B with less dense cores of smaller cometary nuclei. Atmospheric meteor phenomena associated with winds and gravity waves, density and temperature, atomic oxygen, and meteor rate changes are mentioned.
Heat shielding for planetary entry probes of future Jovian and Venusian missions will encounter heating levels well beyond those previously experienced. These entries are typically dominated by radiative heating from the shock layer. This paper demonstrates the potential of reflecting this incident radiation diffusely from an ablating material. This technique contrasts with the absorption experienced by char-forming or graphitic ablators. Two dielectric materials, Teflon (polytetra-fluoroethylene) and boron nitride, are examined for their ablative performance, including reflection, in a combined convective- and radiative-heating environment. For Teflon, at the conditions obtained, superimposition of radiative heating upon a convective stream causes no additional increase in surface recession over the convective only results. For boron nitride, an excellent room-temperature reflector in the visible spectrum, a decrease in reflectivity from 90 to 55 percent is experienced when the surface undergoes sublimation at high temperatures. The process of reflection in each of these materials is described in terms of backscattering from crystals. The significance of a sizable reflection as a mode of energy accommodation is demonstrated for Venusian entries as a potential reduction in mass loss due to ablation.
Comparison of graphite ablation experiment results in the diffusion-controlled oxidation and sublimation regimes with results of an equilibrium chemistry, film coefficient ablation analysis. Mass transfer and energy transfer effects are considered. Tests were conducted in an arcjet facility at convective heating rates of 600 to 800 W/sq cm, radiative heating rates up to 2900 W/sq cm, with test specimen surface pressures of 0.06, 0.1, and 0.3 atm in an air stream. The experimental and analytical mass loss and surface temperature results agreed well when the carbon vapor thermodynamic properties from the JANAF tables are used in the analysis.
An f/2 objective-grating spectrograph aboard an Aerobee rocket recorded a faint image of Comet Tago-Sato-Kosaka (1969g) in L-alpha emission. Some sharpening of the image and reduction of film grain noise was accomplished by multiplying the picture's Fourier transform by an optimum filter function. After this processing, which was carried out digitally, the L-alpha comet image appeared as a nearly circularly symmetric diffuse glow approximately 800,000 km in diameter. There was also the suggestion of a faintly visible core of emission whose dimensions are less than 100,000 km. The sublimation of ice in the nucleus of the comet and the subsequent dissociation of the free water molecules by sunlight could produce a large cloud of hydrogen atoms around the comet. Resonant reradiation of solar L-alpha emission by this cloud is probably responsible for the most of the observed emission.
Economical technique has been developed for manufacturing air-cooled turbine blades and vanes for gas turbine engines. Process uses tungsten inserts to form coolant passages. After casting, inserts are reduced to tungsten oxide during sublimation with oxygen at elevated temperature. Tungsten oxide is leached out of coolant passages with a molten salt solution.
An analysis is presented that shows the desirability and feasibility of using a xenon fill in the initial stages of operation of a silicon-germanium radioisotope thermoelectric generator to be used in outer-planetary exploration. The xenon cover gas offers protection against oxidation and against material sublimation, and allows the generator to deliver required power throughout the prelaunch and launch phases. The protective mechanisms afforded by the xenon cover gas and the mechanization of a xenon supply system are also discussed.