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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Wave-particle interactions on the FAST satellite

NASA's Fast Auroral Snapshot, or 'FAST' satellite, scheduled for launch in 1993, will investigate the plasma physics of the low altitude auroral zone from a 3500-km apogee polar orbit. FAST will give attention to wave, double-layer, and soliton production processes due to electrons and ions, as well as to wave-wave interactions, and the acceleration of electrons and ions by waves and electric fields. FAST will employ an intelligent data-handling system capacle of data acquisition at rates of up to 1 Mb/sec, in addition to a 1-Gbit solid-state memory. The data need be gathered for only a few minutes during passes through the auroral zone, since the most interesting auroral phenomena occur in such narrow regions as auroral arcs, electrostatic shocks, and superthermal electron bursts.

Temerin, M. A.↗
NASA NTRS1981

One-dimensional models of quasi-neutral parallel electric fields

Parallel electric fields can exist in the magnetic mirror geometry of auroral field lines if they conform to the quasineutral equilibrium solutions. Results on quasi-neutral equilibria and on double layer discontinuities were reviewed and the effects on such equilibria due to non-unique solutions, potential barriers and field aligned current flows using as inputs monoenergetic isotropic distribution functions were examined.

Stern, D. P.↗
NASA NTRS1986

Effects of impurities on silicon solar-cell performance

Model analyses indicate that sophisticated solar cell designs (back surface fields, optical reflectors, surface passivation, and double layer antireflective coatings) can produce devices with conversion efficiencies above 20%. To realize this potential, the quality of the silicon from which the cells are made must be improved; and these excellent electrical properties must be maintained during device processing. As the cell efficiency rises, the sensitivity to trace contaminants also increases. For example, the threshold Ti impurity concentraion at which cell performance degrades is more than an order of magnitude lower for an 18% cell than for a 16% cell. Similar behavior occurs for numerous other metal species which introduce deep level traps that stimulate the recombination of photogenerated carriers in silicon. Purification via crystal growth in conjunction with gettering steps to preserve the large diffusion length of the as grown material can lead to the production of devices with efficiencies above 18%, as verified experimentally.

Hopkins, R. H.↗
NASA NTRS1991

Earth's core-mantle boundary - Results of experiments at high pressures and temperatures

Laboratory experiments document that liquid iron reacts chemically with silicates at high pressures (above 2.4 x 10 to the 10th Pa) and temperatures. In particular, (Mg,Fe)SiO3 perovskite, the most abundant mineral of earth's lower mantle, is expected to react with liquid iron to produce metallic alloys (FeO and FeSi) and nonmetallic silicates (SiO2 stishovite and MgSiO3 perovskite) at the pressures of the core-mantle boundary, 14 x 10 to the 10th Pa. The experimental observations, in conjunction with seismological data, suggest that the lowermost 200 to 300 km of earth's mantle, the D-double-prime layer, may be an extremely heterogeneous region as a result of chemical reactions between the silicate mantle and the liquid iron alloy of earth's core. The combined thermal-chemical-electrical boundary layer resulting from such reactions offers a plausible explanation for the complex behavior of seismic waves near the core-mantle boundary and could influence earth's magnetic field observed at the surface.

Knittle, Elise↗
NASA NTRS2014

Graphene-Based Ultra-Light Batteries for Aircraft

Develop a graphene‐based ultracapacitor prototype that is flexible, thin, lightweight, durable, low cost, and safe and that will demonstrate the feasibility for use in aircraft center dot These graphene‐based devices store charge on graphene sheets and take advantage of the large accessible surface area of graphene (2,600 m2/g) to increase the electrical energy that can be stored. center dot The proposed devices should have the electrical storage capacity of thin‐film‐ion batteries but with much shorter charge/discharge cycle times as well as longer lives center dot The proposed devices will be carbon‐based and so will not have the same issues with flammability or toxicity as the standard lithium‐based storage cells There are two main established methods for the storage and delivery of electrical energy: center dot Batteries - Store energy with electrochemical reactions - High energy densities - Slow charge/discharge cycles - Used in applications requiring large amounts of energy  aircraft center dot Electrochemical capacitors - Store energy in electrochemical double layers - Fast charge/discharge cycles - Low energy densities - Used in electronics devices - Large capacitors are used in truck engine cranking

Graphene↗
NASA NTRS1986

Impurity effects in silicon for high efficiency solar cells

Model analyses indicate that sophisticated solar cell designs including, e.g., back surface fields, optical reflectors, surface passivation, and double layer antireflective coatings can produce devices with conversion efficiencies above 20 percent (AM1). To realize this potential, the quality of the silicon from which the cells are made must be improved; and these excellent electrical properties must be maintained during device processing. As the cell efficiency rises, the sensitivity to trace contaminants also increases. For example, the threshold Ti impurity concentration at which cell performance degrades is more than an order of magnitude lower for an 18-percent cell. Similar behavior occurs for numerous other metal species which introduce deep level traps that stimulate the recombination of photogenerated carriers in silicon. Purification via crystal growth in conjunction with gettering steps to preserve the large diffusion length of the as-grown material can lead to the production of devices with efficiencies aboved 18 percent, as has been verified experimentally.

Hopkins, R. H.↗
NASA NTRS1999

TAL Performance and Mission Analysis in a CDL Capacitor Powered Direct-Drive Configuration

The goals of this research are (1) to prove the concept feasibility of a direct-drive electric propulsion system, and (2) to evaluate the performance and characteristics of a Russian TAL (Thruster with Anode Layer) operating in a long-pulse mode, powered by a capacitor-based power source developed at Space Power Institute. The TAL, designated D-55, is characterized by an external acceleration zone and is powered by a unique chemical double layer (CDL) capacitor bank with a capacitance of 4 F at a charge voltage of 400 V. Performance testing of this power supply on the TAL was conducted at NASA Lewis Research Center in Cleveland, OH. Direct thrust measurements of the TAL were obtained at CDL power levels ranging from 450 to 1750 W. The specific impulse encompassed a range from 1150 s to 2200 s, yielding thruster system efficiencies between 50 and 60%. Preliminary mission analysis of the CDL direct-drive concept and other electric propulsion options was performed for the ORACLE spacecraft in 6am/6pm and 12am/12pm, 300 km sun-synchronous orbits. The direct-drive option was competitive with the other systems by increasing available net mass between 5 and 42% and reducing two-year system wet mass between 18 and 63%. Overall, the electric propulsion power requirements for the satellite solar array were reduced between 57 and 91% depending oil the orbit evaluated The direct-drive, CDL capacitor-based concept in electric propulsion thus promises to be a highly-efficient, viable alternative for satellite operations in specific near-Earth missions.

Hrbud, Ivana↗
NASA NTRS2005

Comparison of Electric Fields and Density structures Seen in Simulations and Satellite Observations

There are now clear observations of large parallel electric fields (E(sub ||)) from Polar and FAST in the auroral upward-current region (UCR). Such fields are associated with large perpendicular electric fields (E(sub perpendicular) and density cavities. The observed features of the fields and density are found to be compatible with their spatial structures seen in a simulated U-shaped potential structure (USPS), consisting of double layers (DL) with obliqueness ranging from zero to 90 degrees from the magnetic field. The spatial and temporal evolution of the USPS, its up and down motions and its striations into thin long potential structures, suggest a variety of signatures in the satellite detection of E(sub ||) and E(sub perpendicular)

Singh, Nagendra↗
NASA NTRS1990

Kinetic equilibria of plasma shear layers

The analysis of plasma beam and shear problems in magnetic fields is usually based on a hydromagnetic fluid model. In a low-density collisionless plasma, however, the kinetic effects of the plasma, such as finite Larmor radius effects, are not yet clearly understood. In this paper, the kinetic equilibria of plasma shears in a uniform and fixed magnetic field, with full ion motion, are discussed by solving the Vlasov equation with a given electric field and drift velocity. In this model, the ion density profile through the plasma shear layer is quite different from the one predicted by a hydromagnetic model. As a result of a complicated ion gyromotion through the shear layer, single- and double-humped ion density profiles are obtained. The dependence on the temperature and the strength of the shear will be discussed. The results show a significant difference between positive and negative shears.

Cai, D.↗
NASA NTRS1981

Measurement of volt/meter vertical electric fields in the middle atmosphere

A test flight for a series of middle atmosphere electrodynamics rockets was launched from Wallops Island, Virginia, at 7:18 EST on July 31, 1980. The mother-daughter configuration contained a three axis symmetric double probe electric field instrument and a blunt probe on the daughter payload, and a Gerdien condenser and a single axis (vertical) asymmetric double probe electric field instrument on the mother payload. The payloads reached an apogee of 111 km, and data were gathered from all instruments on the downleg. A downward vertical electric field with a maximum amplitude of about 4 V/m was observed in a layer between about 57 and 67 km. The integrated potential across this layer was approximately 20 kV. Conductivity measurements indicated that free electrons were absent from the region of large electric fields; however, the decrease in conductivity was insufficient to maintain vertical current continuity through the layer. These results establish the existence of large mesospheric electric fields, supporting previous results from single axis measurements.

Maynard, N. C.↗
NASA NTRS1983

The plasmaspheric electric field as measured by ISEE 1

The electrodynamics of the plasmasphere has been a topic of considerable interest. Models predict a space charge buildup, or Alfven layer, at the inner edge of the ring current which opposes the dawn-dusk convection electric field in the magnetosphere and thus shields the plasmasphere from the convection electric field. The current study has the objective to present data from the ISEE 1 double cylindrical probe instrument. All measurements reported were made in the plasmasphere with electron densities of the order of 30-50 or greater per cu cm. The average electric field pattern for quiet conditions is found to be qualitatively consistent with previous average results from whistler measurements and radar backscattering measurements. The magnitudes and gross patterns are in qualitative agreement with representative ionospheric dynamo models. The basic convective flow vectors from the penetration of the magnetospheric electric field tend to follow contours which are parallel to those of the average plasmapause boundary on the nightside.

Maynard, N. C.↗
NASA NTRS2005

Energetic ion production and electrode erosion in hollow cathode discharges

Ions with energies significantly in excess of the discharge voltage have been reported in high current hollow cathode discharges. Models of DC potential hills downstream of the cathode and ion acoustic instabilities in a double layer postulated in the cathode orifice have been proposed to explain these energetic ions, but have not been substantiated in experiments.

ion thruster↗
NASA NTRS1981

Physics of auroral arc formation; Proceedings of the Chapman Conference on Formation of Auroral Arcs, Fairbanks, AK, July 21-25, 1980

The results of satellite, balloon-borne, and ground-based observations of auroral phenomena are discussed in terms of the morphology of auroral arcs and the behavior and characteristics of auroral electrons and ions. Further attention is given to auroral electric fields and field aligned currents, and to the development of models of auroral potential structures and energization of auroral particles. A simulation of space plasma phenomena is presented, along with numerical simulations of auroral potential structures and related phenomena, including the V-potential double layers and auroral arc deformations, and a simulation of auroral arcs. Plasma waves observed on auroral field lines and in laboratory conditions are reported, and theoretical studies of waves and turbulence in auroral plasmas are described.

Akasofu, S.-I.↗
NASA NTRS1992

The growth and characterization of Al(x)Ga(1-x)As/Ge heterostructures

The effects of the growth temperature and the Al(x)Ga(1-x)As layer thickness on the structural, optical, and electrical properties of Al(x)Ga(1-x)As/Ge heterostructures grown for photovoltaic applications were investigated using different-thickness (between 1 micron and 5 microns) Al(x)Ga(1-x)As layers grown by MOCVD in the temperature range between 660 and 780 C. Results obtained from double-crystal X-ray rocking curve measurements, electron beam induced current, cross-sectional TEM, Raman spectroscopy, SIMS, and steady-state and time-resolved photoluminescence measurements are presented. It was found that the highest minority carrier lifetime, 2.41 ns, was obtained for T(G) = 780 C, but the lowest interfacial recombination velocity, 1.6 x 10 exp 4, was obtained at 660 C.

Choi, S. W.↗
NASA NTRS2016

Magnetospheric Multiscale Satellites Observations of Parallel Electric Fields Associated with Magnetic Reconnection

We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E (sub parallel)) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E (sub parallel) events near the electron diffusion region have amplitudes on the order of 100 millivolts per meter, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E (sub parallel) events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E (sub parallel) events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

Ergun, R. E.↗
NASA NTRS1991

Thermal performance of a liquid hydrogen tank multilayer insulation system at warm boundary temperatures of 630, 530, and 152 R

The results are presented of a study conducted to obtain experimental heat transfer data on a liquid hydrogen tank insulated with 34 layers of MLI (multilayer insulation) for warm side boundary temperatures of 630, 530, and 150 R. The MLI system consisted of two blankets, each blanket made up of alternate layers of double silk net (16 layers) and double aluminized Mylar radiation shields (15 layers) contained between two cover sheets of Dacron scrim reinforced Mylar. The insulation system was designed for and installed on a 87.6 in diameter liquid hydrogen tank. Nominal layer density of the insulation blankets is 45 layers/in. The insulation system contained penetrations for structural support, plumbing, and electrical wiring that would be representative of a cryogenic spacecraft. The total steady state heat transfer rates into the test tank for shroud temperatures of 630, 530, 152 R were 164.4, 95.8, and 15.9 BTU/hr respectively. The noninsulation heat leaks into the tank (12 fiberglass support struts, tank plumbing, and instrumentation lines) represent between 13 to 17 pct. of the total heat input. The heat input values would translate to liquid H2 losses of 2.3, 1.3, and 0.2 pct/day, with the tank held at atmospheric pressure.

Stochl, Robert J.↗
NASA NTRS1991

Thermal performance of a liquid hydrogen tank multilayer insulation system at warm boundary temperatures of 630, 530, and 152 R

The results are presented of a study conducted to obtain experimental heat transfer data on a liquid hydrogen tank insulated with 34 layers of MLI (multilayer insulation) for warm side boundary temperatures of 630, 530, and 150 R. The MLI system consisted of two blankets, each blanket made up of alternate layers of double silk net (16 layers) and double aluminized Mylar radiation shields (15 layers) contained between two cover sheets of Dacron scrim reinforced Mylar. The insulation system was designed for and installed on an 87.6 in. diameter liquid hydrogen tank. Nominal layer density of the insulation blankets is 45 layers/in. The insulation system contained penetrations for structural support, plumbing, and electrical wiring that would be representative of a cryogenic spacecraft. The total steady state heat transfer rates into the test tank for shroud temperatures of 630, 530, 152 R were 164.4, 95.8, and 15.9 BTU/hr, respectively. The noninsulation heat leaks into the tank (12 fiberglass support struts, tank plumbing, and instrumentation lines) represent between 13 to 17 pct. of the total heat input. The heat input values would translate to liquid H2 losses of 2.3, 1.3, and 0.2 pct/day, with the tank held at atmospheric pressure.

Stochl, Robert J.↗
NASA NTRS1991

Current collection by conducting bodies in the low earth orbit

Collection of electrons by a conducting cylinder in a flowing magnetized plasma is studied by means of numerical simulations. Transport of electrons across magnetic field lines in regions of large electric fields in the sheath structure of the cylinder is demonstrated. The potential structures, current flow in the plasma and plasma distributions around the cylinder are presented with and without a release of a neutral gas plume near the cylinder. The simulation with the plume shows current enhancement and formation of a double layer, which is found to be highly dynamic. The simulation with the neutral gas plume simulates the plasma processes occurring in a plasma contactor.

Singh, Nagendra↗