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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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Liquid-level indicator, consisting of a diode heated by a resistor, allows simultaneous use of two or three of the liquids nitrogen, hydrogen, and helium. Operation depends on strong temperature-dependence of the forward resistance of a germanium diode and the difference between liquid and vapor in heat-transfer properties.
Testing technique permits accurate measurement of temperature-dependent thermal conductivity, by virtue of the small temperature differential required across a specimen. The permissible mean insulation temperature ranges from cryogenic to 10 degrees F for the insulation under test.
The results are presented of a study to determine the effect of in-situ proton irradiation upon low temperature, low intensity performance of several cell types. The cell types were selected in an attempt to distinguish variations in temperature-dependent radiation resistance which could be attributed to the n-p or p-n structure, diffused or implanted junctions, crucible grown or float-zone type base material, and high or low base resistivity. The results indicate that while expected variations of performance occur at room temperature, all cell types degrade more or less similarly at lower temperatures with normalized degradation becoming increasingly rapid as temperature is reduced. Recommendations for an optimized cell for Jupiter probe use are included along with a definition of the testing required on these cells to insure good performance characteristics.
A previous calculation of the thermodynamic properties of interstitial solid solutions based on the technique of Kirkwood expansions has been extended to include the effects of second nearest neighbor solute atom mutual interactions. The error inherent in the first order (or quasi-chemical) counting of the degeneracy of the solution crystal is avoided. It is shown that, at high temperatures, even strong second nearest neighbor solute mutual interactions have a negligible effect on the entropy of the solution and a small, temperature-dependent effect on the solute partial enthalpy.
Variations in oxygen isotopic abundances of meteoritic minerals, chondrules, whole meteorites, and planets are discussed in terms of a model involving isotopic exchange between primordial dust and a cooling solar nebular gas. From the temperature-dependence of the isotopic fractionation factors, temperatures have been assigned to the processes of initial condensation, chondrule formation, and planetary accretion. Separated phases from carbonaceous chondrites fall into three isotopic groups representing widely differing conditions of formation: (1) low-iron olivine and pyroxene, and calcium-aluminum silicates condensed at temperatures above 1000 K; (2) high-iron olivine and pyroxene melted to form chondrules after prior cooling and exchange to temperatures of 530-620 K; and (3) hydrous silicates condensed at temperatures below 400 K.
Experimental data are presented for heat transfer to the turbulent boundary layer subjected to transpiration and acceleration at constant values of the acceleration parameter K of approximately .00000145. This is a moderately strong acceleration, but not so strong as to result in laminarization of the boundary layer. The results for transpiration fractions F of -0.002, 0.0, and +0.0058 are presented in detail in tabular form, and in graphs of Stanton number versus enthalpy thickness Reynolds number. In addition, temperature profiles at several stations are presented. Stanton number results for F = -0.004, +0.002, and +0.004 are also presented, but in graphical form only. The data were obtained using air as both the free-stream and the transpired fluid, at relatively low velocities, and with temperature differences sufficiently low so that the influence of temperature-dependent fluid properties is minimal. All data were obtained with the surface maintained at a temperature invariant in the direction of flow.
The dissociation of molecular hydrogen by helium was studied at 5500 deg K using the quasiclassical approximation. The temperature-dependent reaction cross sections were very dependent on the initial quantum states of the molecule. A rate constant was estimated for the dissociation reaction, and agreement between theory and experiment was satisfactory.
Measurement of thermal diffusivity on Apollo 11 type A and type C samples in the temperature range between 150 and 440 K under atmospheric pressure. Thermal diffusivity of type C material is lower and less temperature-dependent than type A material. Both types of samples exhibit lower thermal diffusivities than nonporous terrestrial basalt. The rate of heat generation of Apollo 11 and 12 samples was calculated from the concentrations of radioactive elements: potassium, thorium, and uranium. Apollo 11 crystalline rocks show an average rate of heat generation which is not significantly different from terrestrial basalt. The Th/U ratio does not differ greatly from chondritic and terrestrial averages.
Aqueous formaldehyde is shown to exert both sporostatic and sporocidal effects on Bacillus subtilis spores. The sporostatic effect is a result of the reversible inhibition of spore germination occasioned by aqueous formaldehyde; the sporocidal effect is due to the temperature-dependent inactivation of these spores in aqueous formaldehyde. The physicochemical state of formaldehyde in solution provides a framework with which to interpret both the sporostatic and sporocidal properties of aqueous formaldehyde.
The BOPACE program (Boeing plastic analysis capability for engines) was developed to meet the need for an advanced thermal-elastic-plastic-creep structural analyzer by providing incremental relation between stresses and strains. The cumulative stress-strain relation, for temperature-dependent, or temperature independent elasticity is discussed along with the option for plane-stress analysis or plane-strain analysis. The BOPACE solution approach is summarized.
A thermoelastic stress analysis procedure is reported for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations. Results of the analysis indicate the optimum design configuration, with respect to compatible materials, effect of the solder coating, and effect of the interconnector geometry. Good agreement was found between results of the analysis and the test program.
Discussion of the various phenomena which affect the available output power of a typical radioisotope thermoelectric generator (RTG), including estimates of the magnitude of these effects. Power degradation, as well as the corresponding changes in operating temperature, are calculated by means of a computer code which systematically accounts for the time- and temperature-dependent variables. A model for predicting available output power of an RTG is developed which includes changes in performance due to fuel decay, alteration of bulk thermoelectric properties, changes in electrode contacts, geometry changes due to material sublimation, and degradation of the thermal insulation.
A temperature-dependent version of a combined hardening theory, including isotropic and kinematic hardening, is presented within the framework of recent plasticity formulations. This theory has been found to be especially useful in finite-element analysis of aerospace vehicle engines under conditions of large plastic strain and low-cycle fatigue.
Temperature-dependent studies of excitability and tension-production kinetics were made on isolated trabecular strips from hibernating hamsters (HH), nonhibernating hamsters (CH), and from rats (R). The strips were electrically driven and isometric tension along with its first time derivative (dP/dt) were recorded. Excitabilities of both hamster tissues were greater than that of rat tissue from 5 to 38 C with HH greater than CH. Peak tension production followed the order of HH greater than CH greater than R at all temperatures below 24 C. Rat preparations showed an optimum peak tension production at about 31 C while HH and CH showed optima between 17 and 24 C. Times to maximal rates of tension rise showed significant variation. In this respect, the order of sensitivity to decreasing temperature was HH greater than CH greater than R.
The viscosity of liquid anorthite has been determined over the temperature ranges between 1450 to 1620 C and 820 to 950 C. The high-temperature data agree well with previous experimental data and with predictions of the Bottinga and Weill model. The overall log (viscosity) versus 1/T relation exhibits pronounced and rather continuous curvature. The viscosity of anorthite is higher at any given temperature and more strongly temperature-dependent than that of the anorthite-rich lunar compositions 14259, 14310, and 15418. The room-temperature density of glassy anorthite (2.64 gm/cu cm) and the thermal expansion coefficients of glassy and liquid anorthite have also been determined. The volume expansion coefficient for the glass is about 0.000018 per deg C, and that for the liquid is about 0.000048 per deg C. These values are used to relate the high-temperature flow data to the predictions of free-volume theories.
Preparations of formaldehyde in various organic liquids - ethylene glycol, glycerol, and propylene glycol - serve as effective disinfectants towards microbial vegetative cells and spores. This disinfection is a temperature-dependent process and is manifest when these formaldehyde base disinfectants are dissolved in water. The irritating vapors associated with formaldehyde disinfection are not present in either of these new formaldehyde base disinfectants or in aqueous solutions of them.
New measurements of the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn at 3.1- and 8.6-mm wavelengths are given. The temperatures reported for the planets at 3.1-mm wavelength are higher than previous measurements in this wavelength range and change the interpretation of some planetary spectra. For Mercury, it is found that the mean brightness temperature is independent of wavelength and that a temperature-dependent thermal conductivity is not required to match the observations. In the case of Mars, the spectrum is shown to rise in the millimeter region, as simple models predict. For Jupiter, the need to recalculate the spectrum with recent models is demonstrated. The flux density scale proposed by Dent (1972) has been revised according to a more accurate determination of the millimeter brightness temperature of Jupiter.
The results of magnetization and Mossbauer experiments are described which give evidence for superparamagnetism in the quenched face-centered-cubic (gamma) phase of the ternary system Fe .34, C .52, V .14 (Vicalloy II). Magnetometer data are given which clearly show that splat-cooled Vicalloy II does not exhibit long-range magnetic order. These data together with the Mossbauer data indicate that short-range magnetic ordering occurs which is temperature-dependent with coalescence of magnetic clusters over a limited temperature range. The model presented reasonably accounts for the observed effects and indicates that this ternary system is superparamagnetic down to 4.2 K.