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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

EUV emission from Titan's upper atmosphere - Voyager 1 encounter

Most of the observed emission short of Lyman-alpha is shown to be accounted for by electron impact on N2 above 3600 km, in an analysis of Titan's EUV emission spectra obtained at the Voyager 1 encounter. It is determined that N2 is the major component of Titan's upper atmosphere, with 3900-km upper limit mixing ratios of NeI, ArI, CO, H2, and HI of 0.01, 0.06, 0.05, 0.06 and 0.1, respectively. Magnetospheric electron precipitation produces an average dayside electron density of about 3000/cu cm between 3600 and 4000 km, which is the region of bright limb emission, and magnetospheric electron impact dissociation of N2 generates an N atom escape rate of 3 x 10 to the 26th/sec from Titan's exosphere when Titan is within Saturn's magnetosphere.

Strobel, D. F.↗
NASA NTRS1981

The 1980 rocket coronagraph measurements of the solar wind acceleration region

Spectroscopic measurements of temperatures, densities and flow velocities in the solar wind acceleration region provide critical empirical constraints on solar stellar wind theory. Preliminary results of an analysis of H I Lyman-alpha and white light measurements made on 16 February 1980 in a polar coronal region are reported. The hydrogen kinetic temperatures in the observed region were found to be nearly constant with T sub HI approximately equals 10 degrees K at heliocentric distances between 1.5 and 4 solar radii. The outflow velocities were found to be subsonic indicating that the critical point in the observed region was located at r approximately greater than 4 solar radii.

Withbroe, G. L.↗
NASA NTRS1981

InSb heterodyne receivers for submillimeter astronomy

InSb hot electron bolometer mixer receivers have been developed for submillimeter line studies of the interstellar medium up to about 500 GHz. The receivers have been used aboard the NASA Kuiper Airborne Observatory which is transported to about 12,000 km by a C141 aircraft. Data have been obtained on new interstellar lines (such as the ground-state fine structure transition of atomic carbon at 492 GHz) and such molecular transitions as carbon monoxide and water. Other data were obtained at ground level using the 5-cm Hale telescope at Mount Palomar and the NASA Infrared Telescope facility at Mauna Kea, HI. The heterodyne bolometers have reached noise temperatures of less than 400 K at all frequencies to 500 GHz.

Phillips, T. G.↗
NASA NTRS1983

Aeroelastic considerations for continuous patrol/high altitude surveillance platforms

For the last several years, an investigation has been conducted regarding the feasibility of unmanned, airborne, High-Altitude Powered Platforms (HAPP), and High Surveillance Platforms for Over-the-Horizon Targeting (HI-SPOT). These airborne platforms have been proposed as a means of achieving a continuous regional communication-relay or for continuous regional surveillance for use in agricultural research or military applications, i.e., fleet support. These platforms would offer improvements over existing orbiting satellites. These improvements are related to better resolution and increased mission flexibility. The required mission endurance up to six months, would be obtained through the use of either solar power, a cryogenically fueled engine, or microwave-power. Attention is given to airborne platform configuration, structure, structural and aerodynamic modeling, modal analysis, and flutter analysis.

Turner, C. D.↗
NASA NTRS1982

Infrared observations of low-mass star formation in Orion - HH objects

The results of a preliminary analysis of IR data on Herbig-Haro objects in the Orion nebula are reported. The observations were made with the high angular resolution IR photometry equipment on the NASA Kuiper Airborne Observatory and the NASA facility on Mauna Kea, HI. Data were taken in the 1-200 microns region with 40, 6, and 8 arcsec resolution. Attention was focused on NGC 1999 (HH1-3) and M78 (HH24-25) and the determination of absolute luminosities of the exciting stars. Measurements were also made of the IR energy distribution in the thermally emitting dust clouds and the point sources. Herbig-Haro objects featured compact and far IR sizes and large visual extinction, in addition to a steeply rising energy distribution up to 50-100 microns, where the luminosity emitted was concentrated.

Harvey, P. M.↗
NASA NTRS1983

The ISPM experiment for spectral, composition and anistropy measurements of charged particles at low energie

The Heliosphere Instrument for Spectral, Composition, and Anisotropy at Low Energies (HI-SCALE) designed to measure interplanetary ions and electrons is described. Ions and electrons are detected by five separate solid-state detector telescopes oriented to give complete pitch angle coverage from the spinning spacecraft. Ion elemental abundances are determined by a telescope using a thin front detector element in a three-element telescope. Experiment operation is controlled by a microprocessor-based data system. Inflight calibration is provided by radioactive sources mounted on closable telescope covers. Ion and electron spectral information is determined using broad-energy-range rate channels, and a pulse-height analyzer for more detailed spectra. The instrument weighs 5.775 kg and uses 4.0 W power.

Lanzerotti, L. J.↗
NASA NTRS1984

Voltage controlling mechanisms in low resistivity silicon solar cells: A unified approach

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

Weizer, V. G.↗
NASA NTRS1984

Application of transonic codes to aeroelastic modeling of airfoils including active controls

A study is performed using aeroelastic modeling to investigate the stability behavior of airfoils in small-disturbance transonic flow. Two conventional airfoils, NACA 64.A006 and NACA 64A010, and a supercritical airfoil, MBB A-3, are considered. Three sets of unsteady aerodynamic data are computed using three different transonic codes (LTRAN2-NLR, LTRAN2-HI, and USTS) for comparison purposes. Stability results obtained using a constant matrix, state-space, aeroelastic model are presented in a root-locus format. Use of the state-space model is demonstrated through application to flutter suppression using active controls. Aeroelastic effects due to simple, constant gain, partial feedback, control laws that utilize displacement, velocity, and acceleration sensing are studied using a variety of control gains. Calculations are also performed using linear subsonic aerodynamic theory to reveal the differences between including and not including transonic effects in the aeroelastic model. Aeroelastic stability behavior of these airfoils is physically interpreted and discussed in detail.

Batina, J. T.↗
NASA NTRS1984

Cosmic ray propagation in the local superbubble

It is suggested that a ring of HI gas lying in the galactic plane is part of a supershell which formed some 3 x to the 7th power years ago. The consequences of a closed magnetic supershell for cosmic ray propagation are examined and it is concluded that there is no evidence which precludes the production and trapping of cosmic rays in such a region. A consequence of superbubble confinement is that the mean age of cosmic rays would be independent of energy. This can be tested by high energy observations of the isotopic composition of Be.

Steitmatter, R. E.↗
NASA NTRS1984

Preliminary investigation of labyrinth packing pressure drops at onset of swirl-induced rotor instability

Backward and forward subsynchronous instability was observed in a flexible model test rotor under the influence of swirl flow in a straight-through labyrinth packing. The packing pressure drop at the onset of instability was then measured for a range of operating speeds, clearances and inlet swirl conditions. The trend in these measurements for forward swirl and forward instability is generally consistent with the short packing rotor force formulations of Benchert and Wachter. Diverging clearances were also destabilizing and had a forward orbit with forward swirl and a backward orbit with reverse swirl. A larger, stiff rotor model system is now being assembled which will permit testing steam turbine-type straight-through and hi-lo labyrinth packings. With calibrated and adjustable bearings in this new apparatus, direct measure of the net destabilizing force generated by the packings can be made.

Miller, E. H.↗
NASA NTRS1984

Mg II Spectra of Late Type Stars Used to Probe the LISM

IUE spectra of Mg II h and k in late type dwarfs and giants were used to detect and measure absorption components due to the LISM. This technique gives a method of probing the awkward range from d = 3 pc to d = 80 pc from the Sun. In spite of interpretational uncertainties the HI component of the LISM can be plotted well enough to confirm it as a cloud some 20 to 30 pc in extent, peaking sharply in density towards l(II)-25 deg., moving towards the Sun from l(II)-25 deg, b(II) = + 10 deg., at 28 Km/sec. The hole towards l(II) = 150 deg is confirmed, suggesting a solar position close to the cloud's edge in this direction.

Beckman, J. E.↗
NASA NTRS1984

Voyager EUV and FUV Observations

The Voyager 1 and 2 ultraviolet spectrometers are sensitive over the wavelength range 500 to 1700 A. In the extreme ultraviolet (EUV), at wavelengths shortward of the Lyman limit (912 A), Voyager observations detected emission from three out of a sample of 11 nearly hot DA white dwarfs. These observations imply very low HI column densities in the directions of the three stars detected. In the far ultraviolet (FUV), at wavelengths between 912 and 1200 A, Voyager observations of O and B stars can be used to study interstellar reddening at the shortest wavelengths and to provide useful estimates of interstellar H2 column densities.

Holberg, J. B.↗
NASA NTRS1984

A Warm Magnetoactive Plasma in a Large Volume of Space

A diffuse ionized warm gas fills a large volume of space in the general direction of Radio Loop II. There are three types of observational evidence: Faraday rotation measures (RM's) of extragalactic sources; emission measures (EM's) derived from the H alpha emission line in the diffuse interstellar medium; and magnetic field strengths in HI clouds derived from Zeeman splitting observations.

Heiles, C.↗
NASA NTRS1982

An exploratory study of finite difference grids for transonic unsteady aerodynamics

Unsteady aerodynamic forces are calculated by the XTRAN2L finite difference program which solves the complete two dimensional unsteady transonic small perturbation equation. The unsteady forces are obtained using a pulse transfer function technique which assumes the flow field behaves in a locally linear fashion about a mean condition. Forces are calculated for a linear flat plate using the default grids from the LTRAN2-NLR, LTRAN2-HI, and XTRAN3S programs. The forces are compared to the exact theoretical values for flat plate, and grid generated boundary and internal numerical reflections are observed to cause significant errors in the unsteady airloads. Grids are presented that alleviate the reflections while reducing computational time up to fifty-three percent and program size up to twenty-eight percent. Forces are presented for a six percent thick parabolic arc airfoil which demonstrate that the transform technique may be successfully applied to nonlinear transonic flows.

Seidel, D. A.↗
NASA NTRS1984

The ultraviolet spectrum of periodic Comet Encke (1980 XI)

A comparison of the ultraviolet spectrum of periodic Comet Encke (1980 XI), recorded by the IUE between October 24, and November 5, 1980 with similar spectra, of short- and long-period comets, shows the gaseous composition of P/Encke to be nearly identical to that of the other comets observed by the IUE. If P/Encke is indeed the remains of a once-giant comet, this similarity implies a homogeneous radial structure for the cometary ice nucleus. The OH brightness distribution shows a spatial variation similar to the visible fan-shaped image of the comet, suggestive of a nonuniform distribution of volatile ices on the surface of the nucleus. The total derived water production rate appears to be a factor of 5 higher than that derived from HI Lyman-alpha observations made during the 1970 apparition, and shows a variation with heliocentric distance (r) as r to the -3.3 power over the range 0.81 to 1.02 AU.

Feldman, P. D.↗
NASA NTRS1985

Cosmic ray propagation in the local superbubble

It is suggested that a ring of HI gas lying in the galactic plane is part of a supershell which formed some 3 x 10 to the 7th power years ago. The consequences of a closed magnetic supershell for cosmic ray propagation are examined and it is concluded that there is no evidence which precludes the production and trapping of cosmic rays in such a region. A consequence of superbubble confinement is that the mean age of cosmic rays would be independent of energy. This can be tested by high energy observations of the isotopic composition of Be.

Streitmatter, R. E.↗
NASA NTRS1984

Voltage controlling mechanisms in low resistivity silicon solar cells - A unified approach

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

Weizer, V. G.↗
NASA NTRS1985

Thin film module development

The design of ARCO Solar, Inc.'s Genesis G100 photovoltaic module was driven by several criteria, including environmental stability (both electrical and mechanical), consumer aesthetics, low materials costs, and manufacturing ease. The module circuitry is designed as a 12 volt battery charger, using monolithic patterning techniques on a glass superstrate. This patterning and interconnect method proves amenable to high volume, low cost production throughput, and the use of glass serves the dual role of handling ease and availability. The mechanical design of the module centers on environmental stability. Packaging of the glass superstrate circuit must provide good resistance to thermal and humidity exposure along with hi-pot insulation and hailstone impact resistance. The options considered are given. Ethylene vinyl acetate (EVA) is chosen as the pottant material for its excellent weatherability.

Jester, T.↗