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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Two dimensional turbulence in inviscid fluids or guiding center plasmas

Analytic theory for two-dimensional turbulent equilibria for the inviscid Navier-Stokes equations is examined mathematically. Application of the technique to electrostatic guiding center plasma is discussed. A good fit is demonstrated for the approach to a predicted energy per Fourier mode obtained from a two-temperature canonical ensemble. Negative as well as positive temperature regimes are explored. Fluctuations about the mean energy per mode also compare well with theory. In the regime of alpha less than zero, beta greater than zero, with the minimum value of alpha plus beta times k squared near zero, contour plots of the stream function reveal macroscopic vortex structures similar to those seen previously in discrete vortex simulations. Eulerian direct interaction equations, which can be used to follow the approach to inviscid equilibrium, are derived.

Seyler, C. E., Jr.↗
NASA NTRS1974

Physical properties of giant planets

The chemical identification and physical nature of giant planets are discussed. The phase equilibria of H2-He mixture is briefly described for these large planets.

Wildt, R.↗
NASA NTRS1974

Modeling the evolution of Sm and Eu abundances during lunar igneous differentiation

The current work presents models for the evolution of europium and samarium abundances during lunar igneous processes. The effect of probable variations in lunar temperature and oxygen fugacity, mineral-liquid distribution coefficients, and the crystallization or melting progression are considered in the model calculations. Changes in the proportions of crystallizing phases strongly influence the evolution of trace element abundances during fractional crystallization, and models must include realistic estimates of the major phase equilibria during crystallization. The results are applied to evaluating the possibility of generating KREEP-rich materials by lunar igneous processes.

Weill, D. F.↗
NASA NTRS1975

Petrogenesis of KREEP

Solid/liquid distribution coefficients (weight basis) were experimentally determined for a number of trace elements for olivine, orthopyroxene, plagioclase and ilmenite. Values of distribution coefficients were measured at 1200 C and a f sub O2 of 10 to the -13.0 power for liquids similar in composition to the olivine-opx-plagioclase peritectic in the pseudoternary system (Fe,Mg)2SiO4-CaAl2Si2O8-SiO2. Values were also measured at 1140 C and a f sub O2 of 10 to the -12.8 power for liquids similar in composition to high-Ti mare basalts. Major and trace element partitioning and relevant phase equilibria were used to investigate possible parent-daughter relationships between a number of highland samples and highly evolved KREEP-rich materials. Out of about 80 highlands samples tested, 33 were found to be possible parents to the KREEP-rich materials. The average composition of these samples is very similar to that of the Low-K Fra Mauro basalt (LKFM). A model is proposed to explain the production of LKFM-type material and more evolved members of the KREEP suite.

Mckay, G. A.↗
NASA NTRS1976

Can enstatite meteorites form from a nebula of solar composition

Doubts have been expressed as to whether solar matter is sufficiently reducing to explain the minerals occurring in the enstatite chondrites and in the enstatite achondrites. Thermodynamic calculations on the stabilities of TiN, Si2N2O, CaS and silicon-bearing iron metal show that these substances can form under equilibrium conditions from a nebula of solar composition provided that the total pressure exceeds about 1 atm and that thermodynamic equilibria are frozen in at near-formation temperatures.

Herndon, J. M.↗
NASA NTRS1976

Evolution of major mineral compositions and trace element abundances during fractional crystallization of a model lunar composition

The evolution of major mineral compositions and trace element abundances during perfect fractional crystallization of a model lunar magma ocean was calculated. The minerals in the model lunar composition were olivine, orthopyroxene, clinopyroxene, and plagioclase. Lunar bulk composition data, major mineral/melt equilibria data, and trace element partition data were taken from published sources. The results show olivine beginning to crystallize at 1380 C. Approximately 50% of the system crystallizes as olivine. From 50 to 60% solidification, orthopyroxene crystallizes alone. During the final 40% solidification, Ca-rich clinopyroxene and plagioclase crystallize together. Various changes in composition of all these minerals are also noted during the process. Concomitant evolution of major element abundances in the melt is followed along with that of trace element abundances. Consequences of the results for constraints on some aspects of the composition of the lunar magma ocean and of the primitive moon are discussed.

Drake, M. J.↗
NASA NTRS1976

Mare basalt petrogenesis - A review of experimental studies

Experimental results relevant to the fundamental question of the origin of mare basalts are examined with particular reference to guidelines for an appropriate evaluation of experiments. The petrogenesis of mare basalts remains a controversial subject as no petrogenetic scenario has yet been able to satisfy all the geochemical and geophysical constraints. Several generalizations hold true if one accepts that high-pressure equilibria provide some useful but limited information on mare source regions in the lunar interior. Petrogenesis of lowand high-Ti suites is identified. If assimilative processes are involved in the petrogenesis of the high-Ti suite, the high-pressure experiments on the resultant hybrid liquids have little bearing on their origins.

Kesson, S. E.↗
NASA NTRS1976

Superalloy eutectic composites with the VI A refractory elements - Cr, Mo and W

The paper discusses the phase equilibria for the ternary systems NiAlCr, NiAlMo, and NiAlW, with emphasis on reactions from the liquid state, although some of the solid state reactions are mentioned. It is shown that eutectics in the Ni-Al-refractory element (Cr, Mo, W) systems offer the potential for high-temperature turbine blade and vane applications. In particular, it is shown that the phase diagrams of these ternary systems can be manipulated to alter the eutectic phases and morphologies by simple quaternary alloying modifications. The resultant combination of chemistry and structure can be controlled to ensure a behavior that is well-matched to hot section component materials requirements.

Jackson, M. R.↗
NASA NTRS1976

Petrogenesis of KREEP

Solid/liquid distribution coefficients were experimentally determined for a number of trace elements for olivine, orthopyroxene, plagioclase and ilmenite. Major- and trace-element partitioning and relevant phase equilibria are used to study possible parent-daughter relationships between a number of highland samples and highly evolved KREEP-rich materials. A model is proposed in which low-K Fra Mauro basalt type material was produced by fractionation of large amounts of olivine and lesser amounts of plagioclase from undifferentiated lunar material at about 4.4 AE.

Mckay, G. A.↗
NASA NTRS1977

Measured oxygen fugacities of the Angra dos Reis achondrite as a function of temperature

Measurements of the oxygen fugacity, f(O2), as a function of temperature, T, were made on an interior bulk sample of the cumulate achondrite, Angra dos Reis. Data clustered between the f(O2)-T relationship of the iron-wustite assemblage and 1.2 log atm units above iron-wustite. Interpretation of the data indicates that, throughout most of the cooling history of the meteorite, f(O2) values were defined by equilibria involving iron-bearing species at values close to the f(O2) of the assemblage iron-wustite. Measured f(O2) data are compatible with crystallization and cooling at pressures greater than 50 bars.

Brett, R.↗
NASA NTRS1977

Detection of interstellar DNC - Difficulties of chemical equilibrium hypothesis for enrichment

The J = 1-0 transition of DNC at 76.3058 GHz has been observed in emission in NGC 2264. Comparison with previous observations of HN(C-13) indicates that deuterium is enriched in DNC similarly to the enrichment reported for DCO(+) in this source. The DNC/HNC ratio is estimated to be about 1/24. The results cannot readily be interpreted in terms of chemical equilibria relating to the formation of DNC. It is suggested that the explanation must be sought in isotope effects on rates of formation of interstellar molecules.

Godfrey, P. D.↗
NASA NTRS1976

Computer Program for Calculation of Complex Chemical Equilibrium Compositions, Rocket Performance, Incident and Reflected Shocks, and Chapman-Jouguet Detonations. Interim Revision, March 1976

A detailed description of the equations and computer program for computations involving chemical equilibria in complex systems is given. A free-energy minimization technique is used. The program permits calculations such as (1) chemical equilibrium for assigned thermodynamic states (T,P), (H,P), (S,P), (T,V), (U,V), or (S,V), (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. The program considers condensed species as well as gaseous species.

Sanford Gordon↗
NASA NTRS1977

Copernicus studies of interstellar material in the Perseus II complex. III - The line of sight to Zeta Persei

Ultraviolet spectrophotometric data obtained with Copernicus are used to analyze the distribution, composition, density, temperature, and kinematics of the interstellar material along the line of sight to Zeta Persei. The far-UV extinction curve for the star is evaluated along with the kinematics of the interstellar gas, observations of atomic and molecular hydrogen, curves of growth for neutral and ionized species, atomic abundances and depletions, ionization equilibria, and observations of CO and OH lines. The results show that there are apparently three clouds along the line of sight to Zeta Persei: a main cloud at approximately +13 km/s which contains most of the material and forms all the neutral and molecular lines as well as most of the ionic lines, a second component at +22 km/s which must contribute to the strong UV lines of most ions, and a third component at roughly +2 km/s which gives rise to a strong Si III line at 1206 A. It is also found that the UV extinction curve has a somewhat steep far-UV rise, indicating the presence of a substantial number of small grains, and that about 30% of the hydrogen nuclei over the entire line of sight are in molecular form.

Snow, T. P., Jr.↗
NASA NTRS1975

Lunar anorthosite paradox - An alternative explanation

In most lunar terrae samples a trend of decreasing Ab-content of plagioclase with increasing Fa-content of olivine is observed. This covariance of composition is the opposite of the trend observed in terrestrial layered intrusions, and contradicts Bowen's reaction series. The 'anomalous' trend is considered in terms of olivine-melt and plagioclase-melt equilibria. The composition of plagioclase crystallizing from a melt depends directly upon the activity of silica in the melt, while the composition of olivine does not. It is proposed that the inverse correlation of plagioclase and olivine compositions in most lunar terrae rocks is a predictable consequence of crystallization from a lunar bulk composition which is poorer in silica than the bulk compositions of terrestrial layered intrusions. The data of Roedder and Weiblen (1974) lend support to this hypothesis.

Drake, M. J.↗
NASA NTRS1975

Mare basalts - Melting experiments and petrogenetic interpretations

Equilibrium crystallization sequences are determined in melting experiments in vacuum at Fe saturation on synthetic mare basalt compositions 70215 and 15318 Red Glass (both high-Ti) as well as 15555-15016 (low-Ti). The experiments confirm that much of the chemical variation within both the high- and low-Ti suites is controlled by near-surface fractionation processes, although the two suites cannot be related by such mechanisms. The components and crystallization products of the liquidus at various temperatures and pressures are reported. Mare basalt petrogenesis is interpreted in terms of high-pressure equilibria at Fe saturation; it is suggested that low-Ti basalts represent partial melts of a differentiated olivine-pyroxenite lunar mantle at 240 km or deeper, while cumulus clinopyroxene in the source is responsible for their REE characteristics. The formation of high-Ti basalts is considered.

Kesson, S. E.↗
NASA NTRS1975

The system anorthite-forsterite-fayalite-silica to 2 kbar with lunar petrologic applications

Near-liquidus phase relations in the magnesium-rich portion of the system anorthite-forsterite-fayalite-silica have been determined from synthesis experiments at 1 atm and 2 kbar at oxygen fugacities near the iron-wuestite buffer. The major-element chemistries of KREEP basalts are similar to peritectic liquids, L/ol,px,an/, produced experimentally. The reaction L/ol,px,an/ is well-located at low pressures. It intersects the join anorthite-enstatite-ferrosilite at Fe/(Fe+Mg) equals 0.45 (atomic ratio), and is peritectic only for Fe/(Fe+Mg) not greater than 0.45. Although positions of the equilibria, L/an,ol/ and L/ol,px/, differ significantly at 1 atm from their positions at 2 kbar, the position of the piercing point, L/ol,px,an/, on the anorthite-enstatite-ferrosilite join is not sensitive to pressure. The composition of liquids produced by partial melting of troctolites and pyroxenites in the lunar crustal environment will be affected by pressure, whereas liquids derived from gabbroic assemblages will not.

Merrill, R. B.↗
NASA NTRS1978

Metallurgical analysis of skylab M552 and M557 samples

The anomalous microstructures on the basis of phase equilibria, liquid/liquid phase separation, and liquid/solid segregation for the Skylab M557 and M552 flight samples were studied. All of the unknown diffraction spectra have been identified. The previously unknown crystal structure of the Zn3Sb2 phase the M577B Experiment was determined. Previously unreported effects due to the near-absence of the hydrostatic pressure head are documented for the M557C samples.

Larson, D. J., Jr.↗
NASA NTRS1978

Crystallization of a lunar magma ocean

The results of applying the presently most detailed thermal model to the cooling, crystallization and differentiation of a lunar magma ocean are used to delineate its general features, i.e., those features that are model independent within reasonable variations in ocean characteristics. Two primitive lunar compositions are used to illustrate the effect of different compositions and phase equilibria on the solidification time and mineralogy of magma oceans. The magma ocean thermal model led to some inferences about the thermal evolution of the outer portion of the moon modeled as isolated magma pods rather than as a magma ocean.

Minear, J. W.↗