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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

Roble, R. G.↗
NASA NTRS1979

Coupled generator and combustor performance calculations for potential early commercial MHD power plants

A parametric study of the performance of the MHD generator and combustor components of potential early commercial open-cycle MHD/steam power plants is presented. Consideration is given to the effects of air heater system concept, MHD combustor type, coal type, thermal input power, oxygen enrichment of the combustion, subsonic and supersonic generator flow and magnetic field strength on coupled generator and combustor performance. The best performance is found to be attained with a 3000 F, indirectly fired air heater, no oxygen enrichment, Illinois no. 6 coal, a two-stage cyclone combustor with 85% slag rejection, a subsonic generator, and a magnetic field configuration yielding a constant transverse electric field of 4 kV/m. Results indicate that optimum net MHD generator power is generally compressor-power-limited rather than electric-stress-limited, with optimum net power a relatively weak function of operating pressure.

Dellinger, T. C.↗
NASA NTRS1980

Relativistic K-LL Auger spectra in the intermediate-coupling scheme with configuration interaction

Theoretical K-LL Auger spectra from relativistic Dirac-Hartree-Slater calculations in intermediate coupling with configuration interaction (ICWCI) are considered. Calculated transition rates for 25 elements with Z between 18 and 96, inclusive, are listed and compare well with experimental data. Relativistic effects are found to be important above Z equal to about 35, and ICWCI is necessary to describe the spectra for Z less than about 60.

Chen, M. H.↗
NASA NTRS1980

Planetary wave coupling between the troposphere and the middle atmosphere as a possible sun-weather mechanism

The possibility of planetary wave coupling between the troposphere and solar-induced alterations in the upper atmosphere providing a viable mechanism for giving rise to sun-weather relationships is investigated. Some of the observational evidence for solar-activity-induced effects on levels of the upper atmosphere ranging from the thermosphere down to the lower stratosphere are reviewed. It is concluded that there is evidence for such effects extending down to the middle stratosphere and below. Evidence is also reviewed that these effects are due to changes in solar ultraviolet emission during disturbed solar conditions. A theoretical planetary wave model is then used to see at what levels in the upper atmosphere moderate changes in the mean zonal wind state would result in tropospheric changes. It is concluded that changes in the mean zonal flow of about 20% at levels in the vicinity of 35 km or below would give rise to changes in the tropospheric planetary wave pattern that are less than but on the same order as the observed interannual variability in the tropospheric wave pattern at middle and high latitudes.

Geller, M. A.↗
NASA NTRS1979

800 x 800 charge-coupled device /CCD/ camera for the Galileo Jupiter Orbiter mission

During January 1982 the NASA space transportation system will launch a Galileo spacecraft composed of an orbiting bus and an atmospheric entry probe to arrive at the planet Jupiter in July 1985. A prime element of the orbiter's scientific instrument payload will be a new generation slow-scan planetary imaging system based on a newly developed 800 x 800 charge-coupled device (CCD) image sensor. Following Jupiter orbit insertion, the single, narrow-angle, CCD camera, designated the Solid State Imaging (SSI) Subsystem, will operate for 20 months as the orbiter makes repeated encounters with Jupiter and its Galilean Satellites. During this period the SSI will acquire 40,000 images of Jupiter's atmosphere and the surfaces of the Galilean Satellites. This paper describes the SSI, its operational modes, and science objectives.

Clary, M. C.↗
NASA NTRS1979

Charge-coupled device /CCD/ trackers for high accuracy guidance applications

Recent advances in large area charge coupled device (CCD) imaging detectors and high speed microprocessors have prompted the development of a new class of electro-optical tracking instruments at the Jet Propulsion Laboratory (JPL). These instruments are designed for standardized NASA-wide usage and are characterized by their extremely high pointing accuracy and stability and performance capabilities which are largely software defined and thus easily adapted to a variety of mission requirements. This paper presents an examination of the methods by which CCD detectors are being incorporated in star tracker instruments and the performance capabilities that can be expected from currently available devices. The multi-function sensor concept, in which a single sensor can function in a variety of guidance applications, is described. Software algorithms designed to provide efficient extraction of guidance information from both point and extended images are also presented. CCD star tracker implementations currently underway at JPL are described, and performance data obtained during laboratory testing is presented and discussed.

Salomon, P. M.↗
NASA NTRS1980

Interplanetary optical navigation using Charge Coupled Devices

Charge Coupled Devices (CCD) will be used as optical navigation image detectors in space missions planned for the 1980's. This paper presents analyses directed at assessing the performance of an imaging system employing a CCD (i.e., a solid state imager (SSI)), for a Jovian satellite tour environment. CCD operating principles are summarized and methods of calculating theoretical dynamic range presented. Methods of analyzing the SSI's ability to perform the fundamental optical navigation function of imaging a target body and one or more stars, are presented. This capability is expressed as a function of SSI optical and electronic parameters and of astrophysical parameters. The influence of these factors and pointing control errors on navigation picture budgets is analyzed. The effect of the sun's glare is analyzed from the standpoint of its reduction of SSI dynamic range and increase of navigation picture budget. Radiation effects on SSI navigation imaging performance are discussed and a method of analyzing probabilities of distinguishing real from false stars presented.

Davis, R. P.↗
NASA NTRS1980

Vibration-rotation line shifts for 1 sigma g + H2/V,J/-1S/0/ He computed via close coupling - Temperature dependence

The density shifting of vibration-rotation transitions of H2 perturbed by He was computed (as a function of temperature) with no adjustable parameters. The calculation was carried out using the framework of the impact theory of Baranger with S-matrix elements obtained via close coupling calculations which incorporated the ab initio H2-H2 system potential of Tsapline et al.(1977). Vibrational and rotational inelasticity were neglected in the calculations; nevertheless good agreement with experimental data was obtained, up to moderate temperatures, for the density shift. A much poorer comparison was obtained for the density broadening.

Hahne, G. E.↗
NASA NTRS1982

Study of Two Digital Charge-Coupled Devices

Recent report describes reliability study of two charge-coupled-device (CCD) shift registers. Major objective of study was to establish methodology for selecting, testing, screening, derating and applying CCD's. Includes a discussion of CCD structures and operating principles. Characteristics of SCCD and BCCD types are compared.

Wilson, D. D.↗
NASA NTRS1980

Study of digital charge coupled devices

Charge coupled devices represent unique usage of the metal oxide semiconductor concept. These devices can sample an AC signal at the input, transfer charge proportional to this signal through the CCD shift register and then provide an output of the same frequency and shape as the input. The delay time between input and output is controlled by the CCD operating frequency and the number of stages in the shift resistor. This work is a reliability evaluation of the buried channel and surface channel CCD technologies. The constructions are analyzed, failure modes are described, and test results are reported.

Wilson, D. D.↗
NASA NTRS1981

Magnetosphere-Ionosphere coupling through the auroral acceleration region

An important form of coupling between the magnetosphere and the ionosphere occurs through acceleration mechanisms operative in the high altitude ionosphere on magnetic field lines connecting to the auroral zone. Energetic ion mass spectrometer data from within these auroral acceleration regions are presented to illustrate the characteristics of the mechanisms. Observations of ionospheric plasmas in the ring current, the distant plasma sheet, and the magnetotail lobes are shown illustrating the extent of their circulation and the importance of their contribution to the plasma in each regime. Finally the precipitating plasmas in the auroral region and the extent and peculiar effects of the 0(+) component of that precipitation on the ionosphere are illustrated.

Sharp, R. D.↗
NASA NTRS1981

Advanced InSb monolithic Charge Coupled Infrared Imaging Devices (CCIRID)

The continued development of monolithic InSb charge coupled infrared imaging devices (CCIRIDs) is discussed. The processing sequence and structural design of 20-element linear arrays are discussed. Also, results obtained from radiometric testing of the 20-element arrays using a clamped sample-and-hold output circuit are reported. The design and layout of a next-generation CCIRID chip are discussed. The major devices on this chip are a 20 by 16 time-delay-and-integration (TDI) area array and a 100-element linear imaging array. The development of a process for incorporating an ion implanted S(+) planar channel stop into the CCIRID structure and the development of a thin film transparent photogate are also addressed. The transparent photogates will increase quantum efficiency to greater than 70% across the 2.5 to 5.4 micrometer spectral region in future front-side illuminated CCIRIDs.

Koch, T. L.↗
NASA NTRS1980

Two-photon excitation cross section in light and intermediate atoms in frozen-core LS-coupling approximation

Using the method of explicit summation over the intermediate states two-photon absorption cross sections in light and intermediate atoms based on the simplistic frozen-core approximation and LS coupling have been formulated. Formulas for the cross section in terms of integrals over radial wave functions are given. Two selection rules, one exact and one approximate, valid within the stated approximations are derived. The formulas are applied to two-photon absorptions in nitrogen, oxygen, and chlorine. In evaluating the radial integrals, for low-lying levels, the Hartree-Fock wave functions, and for high-lying levels, hydrogenic wave functions obtained by the quantum-defect method have been used. A relationship between the cross section and the oscillator strengths is derived.

Omidvar, K.↗
NASA NTRS1980

Distributed parameter system coupled ARMA expansion identification and adaptive parallel IIR filtering - A unified problem statement

A novel interconnection of distributed parameter system (DPS) identification and adaptive filtering is presented, which culminates in a common statement of coupled autoregressive, moving-average expansion or parallel infinite impulse response configuration adaptive parameterization. The common restricted complexity filter objectives are seen as similar to the reduced-order requirements of the DPS expansion description. The interconnection presents the possibility of an exchange of problem formulations and solution approaches not yet easily addressed in the common finite dimensional lumped-parameter system context. It is concluded that the shared problems raised are nevertheless many and difficult.

Johnson, C. R., Jr.↗
NASA NTRS1981

Radiatively coupled thermionic power system concept

It is shown that thermionic converters at moderate emitter temperatures of about 1600 K can be designed for a radiatively coupled 100 kWe device. A nuclear reactor is a primary heat source, with heat pipes extracting heat from the reactor and distributing it over a large surface opposite an array of thermionic energy converters. The radiative heat transfer across the vacuum gap heats up the thermionic emitters, and excess heat from the converters is radiated from the collector electrodes to the vacuum of space; the heat transfer is controlled by the energy density to be transferred, and by the temperature differential between the heat source and the heat receiver. It is concluded that this system achieves isolation of power converter modules from the heat source, elimination of additional radiators, and reduction of converter dimensions.

Shimada, K.↗
NASA NTRS1981

The effect of microscopic turbulence on magnetosphere-ionosphere coupling

The effect of turbulence on the coupling of the magnetosphere and ionosphere has been investigated by including an effective collision frequency in the electron equation of motion. When this term is combined with the continuity equation, the ion equation of motion and Maxwell's equations, a dispersion relation for the kinetic Alfven wave including effective collisions is found. The wave-particle interaction leads to a strong damping of the wave. Inclusion of the effects of plasma sheet kinetics yields a scale size transverse to the magnetic field which corresponds to the size of visual auroral arcs.

Lysak, R. L.↗
NASA NTRS1980

Wind tunnel determination of dynamic cross-coupling derivatives - A new approach

The latest developments in the NAE ongoing dynamic stability research program are briefly summarized. Emphasis is placed on the recently developed wind-tunnel data reduction procedures used to obtain cross and cross-coupling derivatives due to an oscillatory motion. These procedures, which account for the dynamic behaviour of the model-balance subsystem, are described for the balance configurations currently in use. The principles on which they are based, however, are quite general and can therefore be applied to other balance configurations. Two full-model dynamic stability apparatuses are described and typical results, obtained from dynamic calibrations as well as from wind-tunnel experiments, are presented.

Hanff, E. S.↗
NASA NTRS1981

Effect of gravity on coupled convective and interfacial instabilities during directional solidification

Instabilities occurring during the directional constant-rate solidification of a dilute solution of tin in lead are investigated as a function of gravity with particular emphasis on small constant gravitational accelerations. Two types of instabilities have been identified: (1) convective type that corresponds to long wavelengths, and (2) morphological type that corresponds to short wavelengths. These instabilities are coupled but while the convective instabilities depend strongly on gravity, the morphological instabilities are practically independent of gravity. For low velocities, the convective instabilities occur at much lower solute concentrations than the morphological instabilities, whereas at high velocities the reverse is true.

Coriell, S. R.↗