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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Sulphur flows on Io

Flows of liquid sulfur are discussed as the sources of the variegated color patterns observed on Io. The variation of the viscosity of liquid sulfur as it cools from black to red to orange to yellow are shown to explain the black and red-black colors of the calderas, where molten sulfur reaches the surface, the red sinuous deposits presumably formed by high-viscosity laminar flows, and the yellow and orange-yellow plains, a product of rapid, turbulent flows. The sulfur allotropes responsible for these colors are preserved in the rapid quenching of molten sulfur, with a characteristic decay time under Ionian conditions estimated to be greater than the lifetime of Io. Observations of an atmospheric pressure of 10 to the -6th bar indicate that only a small fraction of Io is molten at any one time, however the entire surface is renewed in color and albedo by sulfur flows every thousand years.

Sagan, C.↗
NASA NTRS1979

Discontinuities in Jovian sulphur plasma

The radial distribution of the Jovian sulfur plasma is discussed. Spectra of the ionized sulfur in the Jovian magnetosphere indicate a sharp discontinuity in visible sulfur emission at a radial distance of six Jupiter radii (Io orbit), outside of which emission is greatly reduced and the plasma is observed not to be in corotation with the planet. Possible explanations of this phenomenon include an effect of Io on the electron temperature outside its orbit, leading to the suppression of S II emission by second ionization, and a current system in Jupiter's ionosphere which prevents plasma from diffusing outward and decouples it from the corotation field. This discontinuity also requires reconciliation with Pioneer observations of the radial and pitch-angle diffusion of energetic charged particles.

Mekler, Y.↗
NASA NTRS1982

Oscillator strengths and collision strengths for some ions of oxygen and sulphur

Collision strengths for electron impact excitation of the O II, O III, S II and S III for some transitions in the ultraviolet of the type ns(sup 2) np(sup q) yields ns np(sup q +1), ns(sup 2) np(sup q) yields ns(sup 2) np(sup q-1) (n+1)s and 3s2 3p(sup q) yields 352 3p(sup q -1) 3d are calculated in a close coupling approximation for an energy rate up to one million K. Configuration interaction target wave functions which give oscillator strengths accurate to 10% for O II and O III, and 20-30% for S II and S III, are used in the expansion. Accurate knowledge of the electron impact excitation cross sections is particularly significant for a proper interpretation of the combined ultraviolet observations of the Voyager UVS and IUE results on properties of the Io plasma torus.

Ho, Y. K.↗
NASA NTRS1983

Detection of sulphur in the galactic center

A strong detection at the (SIII) 18.71 micron line is reported for the Galactic Center region, Sgr A West. A line flux of 1.7 + or - 0.2x10 to the -17th power W cm(-2) is found for a 20-arc second beam-size measurement centered on IRS 1. A preliminary analysis indicates that the SIII abundance relative to hydrogen is consistent with the cosmic abundance of sulfur, 1.6x10 to the -5th power, if a filling factor of unity within the known clumps is assumed. However, the sulfur abundance in the Galactic Center may be as much as a factor of 3 overabundant if a filling factor of 0.03 is adopted, a value found to hold for some galactic HII regions.

Herter, T.↗
NASA NTRS1983

Stabilized lanthanum sulphur compounds

Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500 C to 1500 C by adding to it small amounts of calcium, barium, or strontium. This compound is an excellent thermoelectric material.

Reynolds, G. H.↗
NASA NTRS1983

Sulphur isotopic compositions of deep-sea hydrothermal vent animals

The S-34/S-32 ratios of tissues from vestimentiferan worms, brachyuran crabs, and giant clams living around deep hydrothermal vents are reported. Clean tissues were dried, ground, suspended in 0.1 M LiCl, shaken twice at 37 C to remove seawater sulfates, dried at 60 C, combusted in O2 in a Parr bomb. Sulfur was recovered as BaSO4, and the isotopic abundances in SO2 generated by thermal decomposition of 5-30-mg samples were determined using an isotope-ratio mass spectrometer. The results are expressed as delta S-34 and compared with values measured in seawater sulfates and in normal marine fauna. The values ranged from -4.7 to 4.7 per thousand, comparable to vent sulfide minerals (1.3-4.1 per thousand) and distinct from seawater sulfates (20.1 per thousand) and normal marine fauna (about 13-20 per thousand). These results indicate that vent sulfur rather than seawater sulfur is utilized by these animals, a process probably mediated by chemoautotrophic bacteria which can use inorganic sulfur compounds as energy sources.

Fry, B.↗
NASA NTRS1984

Study of the sulphur-containing molecules in the EUV region. IV - The dissociation processes of SO2 in the 760 A region

The fluoresence throughout the VUV and violet regions has been observed from photoexcitation of SO2, and the absolute fluorescence cross sections of the VUV emissions have been measured at selected atomic emission lines and in the synchrotron radiation continuum from 550 to 760 A. Emissions from the O I 1304 A and several S I lines account for the fluorescence observed in the VUV region, while the fluorescence observed in the UV and violet regions is due to excited SO and, also, possibly to excited SO2(+) and SO(+). Structure in the VUV fluorescence excitation function is attributed to predissociation of Rydberg states. The VUV fluorescence resulting from an O2 elimination process, SO2 + h times nu yielding metastable S + O2, has been observed in the present work although the threshold for this process has not been determined. The threshold corresponding to the total dissociation process, SO2 + h times nu yielding metastable S + 2O, has been measured and found to agree reasonably with the expected value calculated from thermochemical data. The processes for the formation of S(+) are also discussed.

Wu, C. Y. R.↗
NASA NTRS1984

Sulphur-rich volcanic eruptions and stratospheric aerosols

Data from direct measurements of stratospheric optical depth, Greenland ice-core acidity, and volcanological studies are compared, and it is shown that relatively small but sulfur-rich volcanic eruptions can have atmospheric effects equal to or even greater than much larger sulfur-poor eruptions. These small eruptions are probably the most frequent cause of increased stratospheric aerosols. The possible sources of the excess sulfur released in these eruptions are discussed.

Rampino, M. R.↗
NASA NTRS1988

Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary

The possible climatic effects of a drastic decrease in cloud condensation nuclei (CCN) associated with a severe reduction in the global marine phytoplankton abundance are investigated. Calculations suggest that a reduction in CCN of more than 80 percent and the resulting decrease in marine cloud albedo could have produced a rapid global warming of 6 C or more. Oxygen isotope analyses of marine sediments from many parts of the world have been interpreted as indicating a marked warming coincident with the demise of calcareous nannoplankton at the K/T boundary. Decreased marine cloud albedo and resulting high sea surface temperatures could have been a factor in the maintenance of low productivity in the 'Strangelove Ocean' period following the K/T extinctions.

Rampino, Michael R.↗
NASA NTRS1988

Resonance fluorescence calculations for some sulphur diatomics in comets

Statistical equilibrium calculations have been carried out for S2 which was detected in Comet IRAS-Araki-Alcock and for SO, SH and CS+ which are likely to be present in the cometary comas. In all cases, a pattern of features of similar intensity is predicted - so that identifications are possible even when signal : noise is poor and other emissions interfere. These results can guide searches and help confirm the presence of these features in cometary spectra.

Krishna Swamy, K. S.↗
NASA NTRS1989

Encapsulated diffusion of sulphur into InP

This talk outlines a simple process for the fabrication of n(+)-p solar cells in indium phosphide. Large area cells (greater than 0.25 sq cm) have been made by this process, with a photovoltaic conversion efficiency of 15.21 percent under AM0 conditions of illumination. An ideality factor of 1.1 and a saturation current density of 8 x 10 to the minus 15th power A/sq cm have been observed for these cells. The technique for cell fabrication involves the diffusion of sulfur into InP by an open tube process, and gives highly reproducible results from run to run. A vacuum-deposited layer of gallium sulphide (Ga2S3) was used as the source for sulfur diffusion, with a chemically vapor deposited SiO2 cap layer to prevent decomposition of the InP surface during heat treatment. Diffusions were carried out in a flowing nitrogen ambient at 585 to 708 C, and characterized by their surface carrier concentration and the diffusion constant. The diffusion profile for sulfur in InP is estimated to be of the complementary error function type. The activation energy of the diffusion was estimated to be 1.94 eV. The technique described here is ideally suited for the fabrication of shallow n(+)-p junctions in InP, and has been used for space-borne solar cells.

Parat, K. K.↗
NASA NTRS1995

Temperature structure of active regions deduced from helium-like sulphur lines

Solar active-region temperatures have been determined from the full-Sun spectra of helium-like sulfur (S XV) observed by the Bragg Crystal Spectrometer on Board the Yohkoh satellite. The average temperature deduced from S XV is demonstrated to vary with the solar activity level: A temperature of 2.5 x 10(exp 6) K is derived from the spectra taken during low solar activity, similar to the general corona, while 4 x 10(exp 6) K is obtained during a higher activity phase. For the latter, the high- temperature tail of the differential emission measure of active regions is found most likely due to the superposition of numerous flare-like events (micro/nano-flares).

Watanabe, Tetsuya↗
NASA NTRS2003

Solar Flare Abundances of Potassium, Argon, and Sulphur

The absolute coronal abundances of potassium has been determined for the first time from X-ray solar flare line and continuous spectra together with absolute and relative abundances of Ar and S. Potassium is of importance in the continuing debate concerning the nature of the coronal/photospheric element abundance ratios which are widely considered to depend on first ionization potential since it has the lowest FIP of any common element in the Sun. The measurements were obtained with the RESIK crystal spectrometer on the Coronas-F spacecraft. A differential emission measure DEM = const. x exp (-(beta)T(sub e) was found to be the most consistent with the data out of three models considered. We find that the coronal ratio [K/H] = 3.7 x 10(exp - 7), a factor 3 times photospheric, in agreement with other observations using line-to-line ratios. Our measured value for the coronal ratio [Ar/H] = 1.5 x 10(exp -6) is significantly less than photospheric, indicating that there is a slight depletion of this high-FIP element in the corona. For S (an intermediate-FIP element) we obtained [S/H] = 2.2 x 10(exp - 5), approximately the same as in previous work.

Oegerle, William↗
NASA NTRS1996

Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies

The evolution of non-photosynthetic sulphide-oxidizing bacteria was contemporaneous with a large shift in the isotopic composition of biogenic sedimentary sulphides between 0.64 and 1.05 billion years ago. Both events were probably driven by a rise in atmospheric oxygen concentrations to greater than 5-18% of present levels--a change that may also have triggered the evolution of animals.

Non-NASA Center↗
NASA NTRS2004

History of Sulphur Content Effects on the Thermal Stability of RP-1 under Heated Conditions

As technologies advance in the aerospace industry, a strong desire has emerged to design more efficient, longer life, reusable liquid hydrocarbon fueled rocket engines. To achieve this goal, a more complete understanding of the thermal stability and chemical makeup of the hydrocarbon propellant is needed. Since the main fuel used in modern liquid hydrocarbon systems is RP-1, there is concern that Standard Grade RP-1 may not be a suitable propellant for future-generation rocket engines due to concern over the outdated Mil-Specification for the fuel. This current specification allows high valued limits on contaminants such as sulfur compounds, and also lacks specification of required thermal stability qualifications for the fuel. Previous studies have highlighted the detrimental effect of high levels of mercaptan sulfur content (^50 ppm) on copper rocket engine materials, but the fuel itself has not been studied. While the role of sulfur in other fuels (e.g., aviation, diesel, and automotive fuels) has been extensively studied, little has been reported on the effects of sulfur levels in rocket fuels. Lower RP-1 sulfur concentrations need to be evaluated and an acceptable sulfur limit established before RP-1 can be recommended for use as the propellant for future launch vehicles. (5 tables, 8 figures, 9 refs.)

ASTM METHOD D-5623↗
NASA NTRS2014

Sulphur-bearing Compounds Detected by MSL SAM Evolved Gas Analysis of Materials from Yellowknife Bay, Gale Crater, Mars

The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) analysed several subsamples of sample fines (<150 μm) from three sites in Yellowknife Bay, an aeolian bedform termed Rocknest (hereafter "RN") and two samples drilled from the Sheepbed mudstone at sites named John Klein ("JK") and Cumberland ("CB"). SAM's evolved gas analysis (EGA) mass spectrometry detected H2O, CO2, O2, H2, SO2, H2S, HCl, NO, OCS, CS2 and other trace gases. The identity of evolved gases and temperature (T) of evolution can support mineral detection by CheMin and place constraints on trace volatile-bearing phases present below the CheMin detection limit or difficult to characterize with XRD (e.g., X-ray amorphous phases). Here, we focus on potential constraints on phases that evolved SO2, H2S, OCS, and CS2 during thermal analysis.

McAdam, A. C.↗
NASA NTRS1985

Stabilized Lanthanum Sulphur Compounds

Lanthanum sulfide is maintained in the stable cubic phase form over a temperature range of from 500 C to 1500 C by adding to it small amounts of calcium, barium. or strontium. This novel compound is an excellent thermoelectric material.

Reynolds, George H.↗