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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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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Atmospheric and cloud structures of the Jovian planets

Wet adiabatic atmospheric models are computed for the four Jovian planets. Possible cloud-forming condensates considered are H2O ice, aqueous NH3 solution, NH4SH, and solid NH3, CH4, and Ar. Some techniques for computer calculation of condensation in a multiphase system of variable composition are discussed. Nominal models are computed for all four planets, and the effects of variations in composition and different pressure-temperature regimes are investigated in detail for Jupiter. The meaning of the calculated closed densities and their relation to the actual densities are discussed. The computed atmospheric profiles represent average conditions, subject to considerable local variations.

Weidenschilling, S. J.↗
NASA NTRS1974

Geothermal reservoir simulation

The prediction of long-term geothermal reservoir performance and the environmental impact of exploiting this resource are two important problems associated with the utilization of geothermal energy for power production. Our research effort addresses these problems through numerical simulation. Computer codes based on the solution of partial-differential equations using finite-element techniques are being prepared to simulate multiphase energy transport, energy transport in fractured porous reservoirs, well bore phenomena, and subsidence.

Mercer, J. W., Jr.↗
NASA NTRS1976

Non-equilibrium radiation from viscous chemically reacting two-phase exhaust plumes

A knowledge of the structure of the rocket exhaust plumes is necessary to solve problems involving plume signatures, base heating, plume/surface interactions, etc. An algorithm is presented which treats the viscous flow of multiphase chemically reacting fluids in a two-dimensional or axisymmetric supersonic flow field. The gas-particle flow solution is fully coupled with the chemical kinetics calculated using an implicit scheme to calculate chemical production rates. Viscous effects include chemical species diffusion with the viscosity coefficient calculated using a two-equation turbulent kinetic energy model.

Penny, M. M.↗
NASA NTRS1977

Monotectic and syntectic alloys. Experiment MA-044

The flight test furnace run of the monotectic and syntectic alloys experiment was successfully performed during the Apollo-Soyuz Test Project mission in July 1975. Examination of the returned sample cartridges and the formal comparative characterization of the low-g and one-g processed samples of lead-zinc and aluminum antimonide were completed. The results for aluminum antimonide show that polycrystalline and multiphased material can be homogenize in space under low-g conditions. Microstructural study on the lead-zinc flight samples shows that complete interdiffusion of lead and zinc had not been achieved, even though the flight data indicated a soak temperature in the miscible region that was 40 K above the published consolute temperature.

Lacy, L. L.↗
NASA NTRS1975

Annual health examination program, Ames Research Center

A cost analysis of a low-volume multiphasic health testing program is presented. The results indicate that unit costs are similar to those of high-volume automated programs. The comparability in unit cost appears to result from the savings in personnel and space requirements of the smaller program as compared with the larger ones.

Hughes, L.↗
NASA NTRS1977

An inventory of irrigated lands for selected counties within the state of California based on LANDSAT and supporting aircraft data

The author has identified the following significant results: (1) Goals of the irrigated lands project were addressed by the design and implementation of a multiphase sampling scheme that was founded on the utilization of a LANDSAT-based remote sensing system. (2) The synoptic coverage of LANDSAT and the eighteen day orbit cycle allowed the project to study agricultural test sites in a variety of environmental regions and monitor the development of crops throughout the major growing season. (3) The capability to utilize multidate imagery is crucial to the reliable estimation of irrigated acreage in California where multiple cropping is widespread and current estimation systems must rely on single data survey techniques. (4) In addition, the magnitude of agricultural acreage in California makes estimation by conventional methods impossible.

Colwell, R. N.↗
NASA NTRS1976

Diffusive isothermal partitioning in a layered medium with geologic applications

The diffusive isothermal partitioning of solute in a layered two-phase material has been analyzed to help elucidate the phenomenon of solute partitioning in multiphase lunar and terrestrial materials and to estimate the cooling history of samples. After reviewing the physical chemistry of partitioning and the case of an infinite one-dimensional diffusion couple, we solve in analytic form the case of a finite one-dimensional couple. The solution can be used to estimate cooling histories or to interpret laboratory experiments on partitioning. A sample calculation is included.

Hopper, R. W.↗
NASA NTRS1976

Annual review of materials science in space

The weightlessness of objects in free fall permits numerous novel manipulations of multiphase systems and suppresses buoyancy and convection in liquids and gases. In the present paper, the prospects for materials science in space are examined on the basis of the materials experiments performed on Skylab, including biological preparations and crystal growth. Plans for technology-oriented research on Spacelab are reviewed.

Bredt, J. H.↗
NASA NTRS1976

Texture and compositions of metal particles in Apollo 17, Station 6 boulder samples

Eighteen sections representing five matrix samples - 76015, 76215, 76275, 76295, and 76315 - from the Station 6 boulder were examined with emphasis on the textures and compositions of their native FeNi metal particles. It is found that many of the complex multiphase structures of the metal particles observed in the study cannot be explained by a continuous two-stage cooling of the impact-melt sheet. It is suggested that at least locally the boulder samples must have experienced multistage cooling and heating.

Misra, K. C.↗
NASA NTRS1979

Simple digital pulse-programing circuit

Pulse-sequencing circuit uses only shift register and Exclusive-OR gates. Circuit also serves as date-transition edge detector (for rising or falling edges). It is used in sample-and-hold, analog-to-digital conversion sequence control, multiphase clock logic, precise delay control computer control logic, edge detectors, other timing applications, and provides simple means to generate timing and control signals for data transfer, addressing, or mode control in microprocessors and minicomputers.

Langston, J. L.↗
NASA NTRS1978

The study of surface acoustic wave charge transfer device

A surface acoustic wave-charge transfer device, consisting of an n-type silicon substrate, a thermally grown silicon dioxide layer, and a sputtered film of piezoelectric zinc oxide is proposed as a means of circumventing problems associated with charge-coupled device (CCD) applications in memory, signal processing, and imaging. The proposed device creates traveling longitudinal electric fields in the silicon and replaces the multiphase clocks in CCD's. The traveling electric fields create potential wells which carry along charges stored there. These charges may be injected into the wells by light or by using a p-n junction as in conventional CCD's.

Papanicolaou, N.↗
NASA NTRS1978

Reaction diffusion in the NiCrAl and CoCrAl systems

The paper assesses the effect of overlay coating and substrate composition on the kinetics of coating depletion by interdiffusion. This is accomplished by examining the constitution, kinetics and activation energies for a series of diffusion couples primarily of the NiCrAl/Ni-10Cr or CoCrAl/Ni-10Cr type annealed at temperatures in the range 1000-1205 C for times up to 500 hr. A general procedure is developed for analyzing diffusion in multicomponent multiphase systems. It is shown that by introducing the concept of beta-source strength, which can be determined from appropriate phase diagrams, the Wagner solution for consumption of a second phase in a semiinfinite couple is successfully applied to the analysis of MCrAl couples. Thus, correlation of beta-recession rate constants with couple composition, total and diffusional activation energies, and interdiffusion coefficients are determined.

Levine, S. R.↗
NASA NTRS1980

Single-, two-, and three-phase binary-alloy systems

Series of three computer programs solves one-dimensional transient diffusion problems in single-and multiphase binary-alloy systems. Accurate understanding of diffusion process in binary-alloy system is important for development of metal matrix composites, some protective coatings, and thin-film technology.

Tenney, D. R.↗
NASA NTRS1979

The analysis and design of transonic two-element airfoil systems

The multiphase effort in the development of tools for the analysis and design of two-element airfoil systems, that is, airfoils with a slat or a flap at transonic speeds is described. The first phase involved the development of a method to compute the inviscid flow over such configurations. In the second phase the inviscid code was coupled to a boundary layer calculation program in order to compute the loss in performance due to viscous effects. An inverse code that constructs the airfoil system corresponding to a desired pressure distribution is described.

Volpe, G.↗
NASA NTRS1979

Lean, premixed, prevaporized combustion for aircraft gas turbine engines

The application of lean, premixed, prevaporized combustion to aircraft turbine engine systems can result in benefits in terms of superior combustion performance, improved combustor and turbine durability, and environmentally acceptable pollutant emissions. Lean, premixed prevaporized combustion is particularly attractive for reducing the oxides of nitrogen emissions during high altitude cruise. The NASA stratospheric cruise emission reduction program will evolve and demonstrate lean, premixed, prevaporized combustion technology for aircraft engines. This multiphased program is described. In addition, the various elements of the fundamental studies phase of the program are reviewed, and results to date of many of these studies are summarized.

Mularz, E. J.↗
NASA NTRS1979

Program for plasma-sprayed self-lubricating coatings

A method for preparing composite powders of the three coating components was developed and a procedure that can be used in applying uniform coatings of the composite powders was demonstrated. Composite powders were prepared by adjusting particle sizes of the components and employing a small amount of monoaluminum phosphate as an inorganic binder. Quantitative microscopy (image analysis) was found to be a convenient method of characterizing the composition of the multiphase plasma-sprayed coatings. Area percentages and distribution of the components were readily obtained by this method. The adhesive strength of the coating to a nickel-chromium alloy substrate was increased by about 40 percent by a heat treatment of 20 hours at 650 C.

Walther, G. C.↗
NASA NTRS1979

Environmental effects on advanced composites

The development of titanium matrix composites for elevated temperature applications was investigated. General solutions for treating diffusion in multiphase multicomponent systems were studied. Graphite polyimide composites were characterized with respect to mechanical property degradation by moisture.

Unnam, J.↗
NASA NTRS1979

Gravitational influences on the liquid-state homogenization and solidification of aluminum antimonide

Typical commercial or laboratory-prepared samples of polycrystalline AlSb contain microstructural inhomogeneities of Al- or Sb-rich phases in addition to the primary AlSb grains. The paper reports on gravitational influences, such as density-driven convection or sedimentation, that cause microscopic phase separation and nonequilibrium conditions to exist in earth-based melts of AlSb. A triple-cavity electric furnace is used to homogenize the multiphase AlSb samples in space and on earth. A comparative characterization of identically processed low- and one-gravity samples of commercial AlSb reveals major improvements in the homogeneity of the low-gravity homogenized material.

Ang, C.-Y.↗