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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The sputter-generation of planetary coronae - Galilean satellites of Jupiter

The structure and mechanisms of the sputter-induced coronae surrounding the Galilean satellites of Jupiter are considered. Calculations are presented of the particle flux distributions expected in sputtering by collisional cascade and thermal spike mechanisms, and the coronae produced by the two mechanisms are examined. Consideration is then given to the coronal structures generated by sputtering of the surface of Io by corotating sulphur and oxygen plasma, and the sputtering of ice on the surfaces of the outer Galilean satellites as represented by Europa.

Watson, C. C.↗
NASA NTRS1984

Modeling Io volcanism: Maximum volcanic temperatures, depths of melting and magma composition

Interim results of thermal and structural modeling of volcanism on Io were presented. The final results of the modeling are summarized. The basic analysis is an evaluation of the magma trigger mechanism for initiating and maintaining eruptions. Secondary aspects include models of the mechanical mode of magma emplacement, interactions with a sulphur-rich upper crust, and more speculative implications for Io's volcanism.

Crumpler, L. S.↗
NASA NTRS1983

Application of the Parker flash method to high temperature thermoelectrics

Mathematical aspects of thermal diffusivity measurements are reviewed and applied to develop an experimental setup at JPL. Certain approximations commonly appearing in the literature are examined in some detail and rejected based upon sensitive slope variations having significant impact on the results. The final mathematical formulation used was one developed by Parker et al. (1961), which evaluated the diffusivity in a way that could be simply evaluated by examining an oscilloscope trace. A computer algorithm was written to examine solution sensitivity to the number of terms taken in the infinite series. The mathematical technique is being used at JPL to evaluate diffusivities of graphite, Boron Carbon and Lanthanum Sulphur compounds in the temperature range of 300 K to 1200 K.

Noon, E. L.↗
NASA NTRS1984

Atmospheric transport of pollutants from North America to the North Atlantic Ocean

Ground-based measurements strongly support the hypothesis that pollutant materials of anthropogenic origin are being transported over long distances in the midtroposphere and are a significant source of acid rain, acid snow, trace metal deposition, ozone and visibility-reducing aerosols in remote oceanic and polar regions of the Norhern Hemisphere. Atmospheric sulphur budget calculations and studies of acid rain on Bermuda indicate that a large fraction of pollutant materials emitted into the atmosphere in eastern North America are advected eastwards over the North Atlantic Ocean. The first direct airborne measurements of the vertical distribution of tropospheric aerosols over the western North Atlantic is reported here. A newly developed airborne differential adsorption lidar system was used to obtain continuous, remotely sensed aerosol distributions along its flight path. The data document two episodes of long-distance transport of pollutant materials from North America over the North Atlantic Ocean.

Harriss, R. C.↗
NASA NTRS1984

First estimate of annual mercury flux at the Kilauea main vent

Mercury and sulphur dioxide analyses were conducted from 1971 to 1980 on air samples collected immediately downwind of Halemaumau, the Kilauea main vent, in Hawaii. On the basis of these measurements, an Hg/SO2 ratio of 0.00051 has been derived which, when applied to the recently determined SO2 mass output of Halemaumau, yields a calculated Hg flux of 2.6 x 10 to the 8th g annually. This rate is consistent with Varekamp and Busek's (1981) evidence suggesting that volcanogenic Hg significantly contributes to the atmospheric total.

Siegel, S. M.↗
NASA NTRS1985

Post-carboniferous tectonics in the Anadarko Basin, Oklahoma: Evidence from side-looking radar imagery

The Anadarko Basin of western Oklahoma is a WNW-ESE elongated trough filled with of Paleozoic sediments. Most models call for tectonic activity to end in Pennsylvanian times. NASA Shuttle Imaging Radar revealed a distinctive and very straight lineament set extending virtually the entire length of the Anadarko Basin. The lineaments cut across the relatively flat-lying Permian units exposed at the surface. The character of these lineaments is seen most obviously as a tonal variation. Major streams, including the Washita and Little Washita rivers, appear to be controlled by the location of the lineaments. Subsurface data indicate the lineaments may be the updip expression of a buried major fault system, the Mountain View fault. Two principal conclusions arise from this analysis: (1) the complex Mountain View Fault system appears to extend southeast to join the Reagan, Sulphur, and/or Mill Creek faults of the Arbuckle Mountains, and (2) this fault system has been reactivated in Permian or younger times.

Nielsen, K. C.↗
NASA NTRS1984

Ratioed scatter diagrams - An erotetic method for phase identification on complex surfaces using scanning Auger microscopy

By ratioing multiple Auger intensities and plotting a two-dimensional occupational scatter diagram while digitally scanning across an area, the number and elemental association of surface phases can be determined. This can prove a useful tool in scanning Auger microscopic analysis of complex materials. The technique is illustrated by results from an anomalous region on the reaction zone of a SiC/Ti-6Al-4V metal matrix composite material. The anomalous region is shown to be a single phase associated with sulphur and phosphorus impurities. Imaging of a selected phase from the ratioed scatter diagram is possible and may be a useful technique for presenting multiple scanning Auger images.

Browning, R.↗
NASA NTRS1985

Rocket spectrogram of a solar flare in the 10-100 A region

The soft (10-100 A) X-ray spectrum of an M-class solar flare was observed with a high-resolution (0.02 A) rocket-borne spectrograph on 1982 July 13. The spectrum samples an area of 600/sq arcsec on the sun, centered on or near the brightest X-ray feature of the flare. Several hundred emission lines characteristic of temperatures from about 0.5 to 7 x 10 to the 6th K have been photographically recorded. All but three of the stronger lines have been identified. It is argued that previous identification of the line at 17.62 A as iron Ly-alpha is incorrect. Spectral lines from nickel, iron, chromium, calcium, sulphur, silicon, aluminium, magnesium, neon, oxygen, nitrogen, and carbon are tabulated and discussed with extensive reference to earlier work. Absolute line intensities are given and the calibration of the telescope-spectrograph is discussed.

Acton, L. W.↗
NASA NTRS1985

Explanation of the inward displacement of Io's hot plasma torus and consequences for sputtering sources

Radial profiles of the ion density and flux-tube content in the Io torus have peak values inside Io's orbit, even though Io is the effective source of these ions. Formation of an inward peak constrains either the velocity distributions or source regions of sputtered neutrals. A further constraint is that the ionization of neutrals on trapped trajectories that return to Io's surface must be limited. A dominant sulphur source is most easily reconciled with these constraints.

Linker, J. A.↗
NASA NTRS1986

Halos around planetary nebulae

Preliminary results of a CCD survey designed to detect and investigate faint halos around planetary nebulae are reported. A TI 800 x 800 pixel CCD was used to take deep exposures of 44 planetary nebulae. The exposures were obtained through an H-alpha filter at the Cassegrain focus of the Palomar 1.5 m telescope. Spatial resolutions of 1 to 2 arcsec were obtained across 400 arcsec wide fields. The images, which are in many cases considerably deeper than any previously taken, reveal numerous planetary nebula halos. About two-thirds of the studied nebulae possess extensive outer halos, here defined as any extended emission beyond the 10 percent isophote. Ionized sulphur electron density measurements show that in some nebulae, the mass in the halo is comparable to the mass contained in the primary H II region. The data have been used to place constraints on the mode of origin of the halos. It is likely that the halos originate either by dynamical separation of a single ejected shell of gas or by the ejection of two or more such shells from the central star. It is possible but less likely that the halos are caused by excitation of the preplanetary stellar wind and improbable that the halos represent reflection nebulae.

Jewitt, D. C.↗
NASA NTRS1986

Mass spectra of heavy ions near comet Halley

The heavy-ion analyzer, RPA2-PICCA, aboard the Giotto spacecraft, detected the first cometary ions at a distance of about 1.05 million km from the nucleus of comet Halley. In the inner coma the major ions identified are associated with the H2O, CO and CO2 groups. Ions of larger atomic mass unit are also present, corresponding possibly to various hydrocarbons, heavy metals of the iron-group or to sulphur compounds.

Korth, A.↗
NASA NTRS1986

On the effect of the Fe(2+)/Fe(3+) redox couple on oxidation of carbon in hot H3PO4

Oxidation studies of graphite:glassy carbon composites have been carried out at 1 and 4.7 atm. pressures in conc. H3PO4 in the presence and absence of iron ions. The concentration of the acid was varied over 85-100 wt pct, and of the iron ions over 30-300 ppm; the temperature varied over 190-210 C. Unlike the effect of Fe, which has been observed to increase the corrosion of carbon in sulphuric acid, the corrosion in phosphoric acid was observed to be slightly decreased or not at all affected. This result arises because of the catalytic reduction of the oxidized surface groups of carbon by Fe(2+) ions. The catalytic reduction is possible because under the experimental conditions the redox potential of the Fe(2+)/Fe(3+) couple is lower than the open-circuit voltage of carbon.

Dhar, H. P.↗
NASA NTRS1987

The composition and radial dependence of cometary ions in the coma of comet P/Halley

The heavy ion analyzer, RPA2-PICCA, on board the Giotto spacecraft detected an increase in the densities of cometary ions within a cometocentric distance of 150,000 km. The composition of cometary ions changed dramatically as the comet's nucleus was approached, but it was clearly dominated by the water group. The second and third most abundant ions identified were associated with the CO- or S-group and the CO2-group, respectively. Ions of larger atomic mass units were also present closer to the comet, and they possibly correspond to sulphur compounds and/or various hydrocarbons. Radial profiles of various groups of heavy ions and certain abundance ratios are presented. The peak density for all mass groups was detected at a cometocentric distance of about 11,000 km. A distinct boundary, where the ion velocity and temperature dropped significantly, was identified at about 27,000 km.

Korth, A.↗
NASA NTRS1988

Multi-property modeling of ocean basin carbon fluxes

The objectives of this project were to elucidate the causal mechanisms in some of the most important features of the global ocean/atomsphere carbon system. These included the interaction of physical and biological processes in the seasonal cycle of surface water pCo2, and links between productivity, surface chlorophyll, and the carbon cycle that would aid global modeling efforts. In addition, several other areas of critical scientific interest involving links between the marine biosphere and the global carbon cycle were successfully pursued; specifically, a possible relation between phytoplankton emitted DMS and climate, and a relation between the location of calcium carbonate burial in the ocean and metamorphic source fluxes of CO2 to the atmosphere. Six published papers covering the following topics are summarized: (1) Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary; (2) Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial; (3) Controls on CO2 sources and sinks in the earthscale surface ocean; (4) pre-anthropogenic, earthscale patterns of delta pCO2 between ocean and atmosphere; (5) Effect on atmospheric CO2 from seasonal variations in the high latitude ocean; and (6) Limitations or relating ocean surface chlorophyll to productivity.

Volk, Tyler↗
NASA NTRS1989

Fast molecular shocks. I - Reformation of molecules behind a dissociative shock

The physical and chemical processes that operate in the cooling gas behind a fast, dissociative, single-fluid shock propagating in a dense interstellar cloud are discussed. The treatment extends previous theoretical work on fast molecular shocks by including the effects of the conversion of Ly-alpha photons into radiation of the two-photon continuum and into H2 Lyman band emission lines, the effects of CO photodissociation following line absorption, and the formation and destruction of molecules containing the elements nitrogen, silicon, and sulphur, and of the complex hydrocarbons. Abundance profiles for the molecular species of interest are presented. After molecular hydrogen begins to reform, by means of gas phase and grain surface processes, the neutral species OH, H2O, O2, CO, CN, HCN, N2, NO, SO, and SiO reach substantial abundances. The molecular ions HeH(+), OH(+), SO(+), CH(+), H2(+), and H3(+), are produced while the gas is still hot and partially ionized. Emissions from them provide a possible diagnostic probe of fast molecular shocks.

Neufeld, David A.↗
NASA NTRS1990

Electrochemical incineration of wastes

The novel technology of waste removal in space vehicles by electrochemical methods is presented to convert wastes into chemicals that can be eventually recycled. The important consideration for waste oxidation is to select a right kind of electrode (anode) material that should be stable under anodic conditions and also a poor electrocatalyst for oxygen and chlorine evolution. On the basis of long term electrolysis experiments on seven different electrodes and on the basis of total organic carbon reduced, two best electrodes were identified. The effect of redox ions on the electrolyte was studied. Though most of the experiments were done in mixtures of urine and waste, the experiments with redox couples involved 2.5 M sulfuric acid in order to avoid the precipitation of redox ions by urea. Two methods for long term electrolysis of waste were investigated: (1) the oxidation on Pt and lead dioxide electrodes using the galvanostatic methods; and (2) potentiostatic method on other electrodes. The advantage of the first method is the faster rate of oxidation. The chlorine evolution in the second method is ten times less then in the first. The accomplished research has shown that urine/feces mixtures can be oxidized to carbon dioxide and water, but current densities are low and must be improved. The perovskite and Ti4O7 coated with RuO2 are the best electrode materials found. Recent experiment with the redox agent improves the current density, however, sulphuric acid is required to keep the redox agent in solution to enhance oxidation effectively. It is desirable to reduce the use of acid and/or find substitutes.

Bhardwaj, R. C.↗
NASA NTRS1989

Gas-phase formation of silicon carbides, oxides, and sulphides from atomic silicon ions

A systematic experimental study of the kinetics and mechanisms of the chemical reactions in the gas phase between ground-state Si(+)2p and a variety of astrophysical molecules. The aim of this study is to identify the reactions which trigger the formation of chemical bonds between silicon and carbon, oxygen and sulphur, and the chemical pathways which lead to further molecular growth. Such knowledge is valuable in the identification of new extraterrestrial silicon-bearing molecules and for an assessment of the gas-phase transition from atomic silicon to silicon carbide and silicate grain particles in carbon-rich and oxygen-rich astrophysical environments.

Bohme, Diethard K.↗
NASA NTRS1992

Southern Hemisphere Lidar Measurements of the Aerosol Clouds from Mt. Pinatubo and Mt. Hudson

On 19 Jul., 1991, during tests to determine the ability of the newly-modified CSIRO Ns:YAG lidar to measure signals from the stratosphere before the arrival of dust from the eruption of Mt. Pinatubo, a strongly scattering layer was detected at an altitude of 2 km. That evening, the spectacular sunset and twilight were typical of volcanically disturbed conditions. Lidar measurements at 532 nm were made between 1400 and 1500 EST (0400-0500 UT) on 19 Jul. through broken cloud. Approximately 3800 laser firings were averaged in 256 shot blocks. These and subsequent data have been analyzed to produce profiles of aerosol volume backscatter function and scattering ratio. Clouds again prevented a clear view of the twilights on the next two nights, although there was some evidence for an enhanced glow. The evidence suggested that the aerosol layer had disappeared. An explanation for this disappearance and the earlier than expected arrival of the layer over Melbourne was required. Nimbus 7 TOMS data for 23 Jun. showed that the SO2 from the eruption had extended at least 11000 km to the west and that the southern boundary of the cloud had reached 15 degrees S just 8 days after the climactic eruption. It can be assumed that this cloud also contained dust and sulphuric acid aerosol. It was proposed that a section had then been broken away from the main cloud and carried south by a large scale eddy between the low latitude easterlies and the strong mid-latitude westerlies which finally carried the aerosol cloud over southern Australia. Accompanying 30 mb wind data showed a counter clockwise circulation, responsible for the transport, located in the South Atlantic Ocean.

Young, Stuart A.↗