Lithium peroxide test program Final report
Effects of chemical catalysts, bed cooling, chemical manufacturing techniques, operating conditions, and chemical handling procedures on lithium peroxide
Willis, L. A.↗
SEARCH · Search NASA
Results for “CHEMICAL EFFECT”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Effects of surface crossing in chemical reactions - The H3/plus/ system
Potential energy surfaces for singlet states of H3/plus/
Preston, R. K.↗
Magnetic head/tape interface study for satellite tape recorders. Volume 3: Test methods and procedures
Test methods and procedures for determining effect of chemical and physical forces at magnetic head/tape interface of satellite tape recorders
Owen, R. J.↗
Hypervelocity heat protection - A review of laboratory experiments
Test streams and chemical composition effects on ablative composites for hypervelocity heat protection of manned atmospheric entry vehicles
Vojvodich, N. S.↗
Theoretical model of vertical distributions of CO and CH4 in the mesosphere and upper stratosphere.
Carbon compounds (CO and CO2) and methane are added to an existing computer program (Shimazaki and Laird, 1970, 1972), which calculates diurnal variations in density distributions of pure oxygen compounds, hydrogen compounds, and nitrogen compounds. For the present model calculations, the original program was modified to calculate the steady-state profiles for all constituents, and then these solutions were used as the initial condition for solving the time-dependent equations. The effects of chemical reactions and vertical eddy diffusion transport on the CH4 and CO concentrations above 40 km, where one-dimensional treatment may not be too inappropriate, are discussed. Some of the 15 constituents included in the computer program interact with CO and CH4 chemically, and CH4 is more sensitive to the eddy diffusion coefficient than any other constituent. Therefore it is easier to determine the most appropriate profile of the eddy diffusion coefficient by comparing the model profile with the observations for CH4.
Shimazaki, T.↗
Effects of precursor heating on chemical and radiative nonequilibrium viscous flow around a Jovian entry body
The influence of precursor heating on viscous chemical nonequilibrium radiating flow around a Jovian entry body is investigated. Results obtained for a 45 deg hyperboloid blunt body entering the Jupiter's nominal atmosphere at zero angle of attack indicate that the nonequilibrium radiative heating rate is significantly higher than the corresponding equilibrium heating. The precursors heating, in general, increases the radiative and convective heating to the body and this increase is slightly higher for the nonequilibrium conditions.
Tiwari, S. N.↗
Effects of precursor heating on chemical and radiation nonequilibrium viscous flow around a Jovian entry body
The influence of precursor heating on viscous chemical nonequilibrium radiating flow around a Jovian entry body is investigated. Results obtained for a 45-degree hyperboloid blunt body entering Jupiter's nominal atmosphere at zero angle of attack indicate that the nonequilibrium radiative heating rate is significantly higher than the corresponding equilibrium heating. The precursor heating, in general, increases the radiative and convective heating to the body, and this increase is slightly higher for the nonequilibrium conditions.
Tiwari, S. N.↗
Dynamic tensile strength of lunar rock types
The dynamic tensile strength of four rocks are determined. A flat plate impact experiment is employed to generate approximately one-microsecond-duration tensile stress pulses in rock samples by superposing rarefaction waves to induce fracture. It is noted that the effect of chemical weathering and other factors has not been explicitly studied. The given tensile strengths are based on a series of experiments on each rock where determination of incipient spallation is made by terminal microscopic examination. The data are generally consistent with previous determinations, at least one of which was for a significantly chemically altered but physically coherent rock.
Cohn, S. N.↗
Surface diffusion activation energy determination using ion beam microtexturing
The activation energy for impurity atom (adatom) surface diffusion can be determined from the temperature dependence of the spacing of sputter cones. These cones are formed on the surface during sputtering while simultaneously adding impurities. The impurities form clusters by means of surface diffusion, and these clusters in turn initiate cone formation. Values are given for the surface diffusion activation energies for various materials on polycrystalline Cu, Al, Pb, Au, and Ni. The values for different impurity species on each of these substrates are approximately independent of impurity species within the experimental uncertainty, suggesting the absence of strong chemical bonding effects on the diffusion.
Rossnagel, S. M.↗
Morphology of volcanoes
The effects of chemical composition of the lava, physical processes of volcanic formation, and lava flow lengths on the morphology of Earth volcanoes were investigated. Difficulties in investigating volcanic morphology are discussed.
Schuver, H. J.↗
Numerical solution of the problem of flame propagation by the use of the random element method
A numerical, grid-free algorithm is presented for one-dimensional reaction-diffusion model of laminar flame propagation in premixed gases. It is based on the random element method we developed for the analysis of diffusional processes. The effect of combustion is taken into account by applying the principle of fractional steps to separate the process of diffusion, modeled by the random walk of computational elements, from the exothermic effects of chemical reaction, monitoring their strength. The validity of the algorithm is demonstrated by application to flame propagation problems for which exact solutions exist. The flame speed evaluated by its use oscillates around the exact value at a relatively small amplitude, while the temperature and species concentration profiles are self-correcting in their convergence to the exact solution. A satisfactory resolution is obtained by the use of quite a small number of computational elements which automatically adjust their distribution of fit sharp gradients.
Ghoniem, A. F.↗
Sintering, properties and fabrication of Si3N4 + Y2O3 based ceramics
Pure silicon nitride shows a remarkable resistance to sintering without the use of densification additives. The present investigation is concerned with results which show the effect of chemical content on sinterability, taking into account the composition, raw material impurities, and processing contaminants. Aspects of sintering are discussed along with strength characteristics, and oxidation relations. Attention is given to phase field I and II materials, phase field III and IV materials, tungsten carbide and oxidation at 600 C, and studies involving shape fabrication by injection molding. It was found that in sintering Si3N4 + Y2O3 an increase in the amount of Y2O3 and, in particular, the addition of Al2O3 enhances the fluidity of the liquid phase.
Quackenbush, C. L.↗
Effects of dust formation on chemical abundances
Gas-phase abundances of C, Mg, Si, Ca, and Fe have been measured for a number of planetary nebulae on the basis of optical, ultraviolet, and infrared emission-line intensities. The abundances of Si, Ca, and Fe show characteristic depletions of one to two orders-of-magnitude as a result of grain formation. Magnesium shows a similar depletion in the outer parts of several planetary nebulae, but it is undepleted in their inner parts. Carbon is not detectably depleted by grain formation. Efficient condensation of refractory elements can easily occur during the early stages of formation of a planetary nebula; but the observed, residual gas-phase abundances are not understood. Observations of molecules in the envelopes of late-type stars may provide useful clues.
Shields, G. A.↗
A model for reaction rates in turbulent reacting flows
To account for the turbulent temperature and species-concentration fluctuations, a model is presented on the effects of chemical reaction rates in computer analyses of turbulent reacting flows. The model results in two parameters which multiply the terms in the reaction-rate equations. For these two parameters, graphs are presented as functions of the mean values and intensity of the turbulent fluctuations of the temperature and species concentrations. These graphs will facilitate incorporation of the model into existing computer programs which describe turbulent reacting flows. When the model was used in a two-dimensional parabolic-flow computer code to predict the behavior of an experimental, supersonic hydrogen jet burning in air, some improvement in agreement with the experimental data was obtained in the far field in the region near the jet centerline. Recommendations are included for further improvement of the model and for additional comparisons with experimental data.
Chinitz, W.↗
Direct simulation of transitional flow for hypersonic reentry conditions
This paper presents results of flowfield calculations for typical hypersonic reentry conditions encountered by the nose region of the Space Shuttle Orbiter. Most of the transitional flow regime is covered by the altitude range of 150 to 92 km. Calculations were made with the Direct Simulation Monte Carlo (DSMC) method that accounts for translational, rotational, vibrational, and chemical nonequilibrium effects. Comparison of the DSMC heating results with both Shuttle flight data and continuum predictions showed good agreement at the lowest altitude considered. However, as the altitude increased, the continuum predictions, which did not include slip effects, departed rapidly from the DSMC results by overpredicting both heating and drag. The results demonstrate the effects of rarefaction on the shock and the shock layer, along with the extent of the slip and temperature jump at the surface. Also, the sensitivity of the flow structure to the gas-surface interaction model, thermal accommodation, and surface catalysis are studied.
Moss, J. N.↗
Convective and radiative heating of a Saturn entry probe
The extent of convective and radiative heating for a Saturn entry probe is investigated in the absence and presence of ablation mass injection. The flow in the shock layer is assumed to be axisymmetric, viscous and in local thermodynamic equilibrium. The importance of chemical nonequilibrium effects for both the radiative and convective nonblowing surface heating rates is demonstrated for prescribed entry conditions. Results indicate that the nonequilibrium chemistry can significantly influence the rate of radiative heating to the entry probes. With coupled carbon-phenolic ablation injection, the convective heating rates are reduced substantially. Turbulence has little effect on radiative heating but it increases the convective heating considerably.
Tiwari, S. N.↗
The rheology of icy satellites
High-temperature creep in orthoenstatite under conditions of controlled oxygen fugacity was studied. It was found that creep was conttrolled by the extremely thin layer of SiO2 which wetted the grain boundaries. Slight reduction of the (Mg, Fe)SiO3 enstatite during hot pressing produced microscopic particles of Fe and the thin film of intergranular SiO2. This result highlights another complication in determining the flow properties of iron bearing silicates which constitute the bulk of terrestrial planets and moons. The Phenomenon may be important in the ductile formation of any extraterrestrial body which is formed in a reducing environment. The rheology of dirty ice was studied. This involves micromechanical modeling of hardening phenomena due to contamination by a cosmic distribution of silicate particles. The larger particles are modeled by suspension theory. In order to handle the distribution of particles sizes, the hardening is readed as a critical phenomenon, and real space renormalization group techniques are used. Smaller particles interact directly with the dislocations. The particulate hardening effect was studied in metals. The magnitude of such hardening in ice and the defect chemistry of ice are studied to assess the effects of chemical contamination by methane, ammonia, or other likely contaminants.
Sammis, C. G.↗
Effect of processing treatments on strength of silica thread for quilted ceramic insulation on Space Shuttle
The effects of chemical, mechanical, and thermal processing treatments on the preflight strength properties of a silica sewing thread used to fabricate an external flexible Thermal Protection System (TPS) for the Space Shuttle vehicle are discussed. Below 540 C, loss of strength was observed for all treatments studied, but above conditioning temperatures of 540 C little change in strength properties was measured, indicating no appreciable mechanical damage to the yarn as a consequence of these processing treatments.
Sawko, P. M.↗