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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Transfer of pulsation-relation wave activity across the magnetopause: Observations of corresponding spectra by ISEE-1 and ISEE-2

Comparison of power spectra of magnetic field data from ISEE-1 and -2 recorded simultaneously on both sides of the magnetopause showed that power level inside the magnetosphere varied with power level outside in the magnetosheath and suggested that the same frequencies were enhanced on the two sides of the boundary. Power levels were two to three orders of magnitude lower inside than outside the magnetosphere, indicating that wave energy was transmitted inside from the sheath.

Greenstadt, E. W.↗
NASA NTRS1983

Numerical simulation of a disk-shaped electron accelerating electrostatic probe

This paper presents a method utilizing the numerical plasma simulation particle-in-cell technique for studying electron accelerating probe characteristics. A probe configuration other than the commonly used plane, cylindrical, or spherical case will be studied; the probe configuration used is that of a disk. Cylindrical geometry is used in the simulation model. One of the advantages of a numerical simulation is the ease with which the details of the system can be examined. Therefore, in addition to the current-voltage characteristics of the static probe, other results are presented such as the time evolution of the plasma properties and studies of the sheath region surrounding the probe.

Nonnast, J. H.↗
NASA NTRS1983

Accretion onto magnetized neutron stars - X-ray pulsars with intermediate rotation rates

Assuming that the accreting material originates in a wind or envelope and therefore carried no net angular momentum, the Kevin-Helmholtz instability is applied to the transport of accreting plasma across the magnetopause of a rotating and magnetized neutron star for the case in which this surface is interchange-stable. Magnetopause location is determined, and the blackbody emission temperature is estimated. A possible period-dependence is noted in the X-ray temperature data which is in approximate agreement with the present model calculations. The magnetopause is found to be insufficiently stable to support an optically thick sheath of plasma surrounding the source, so that neither shrouding of the X-ray source nor significant reprocessing of the radiation field is possible in the model presented. It is concluded that while the flow structure at the magnetopause can control accretion column geometry, the emerging pulse profile and spectra are only indirectly altered, through a dynamical influence on emission region geometry.

Burnard, D. J.↗
NASA NTRS1982

Micromechanical predictions of crack initiation, propagation and crack growth resistance in boron/aluminum composites

An elastoplastic, axisymmetric finite element model has been used to predict the initiation and propagation of a crack in a composite model consisting of a single broken boron fiber embedded in an annular sheath of aluminum matrix. The accuracy of the axisymmetric finite element model for crack problems has been established by solving the classical problem of a penny-shaped crack in a thick cylindrical rod under axial tension. Also, the stress intensity factors predicted by the present numerical model are compared with continuum results. A constant displacement boundary condition applied during an increment of crack growth permits a substantial amount of stable crack growth in the matrix material. The concept of Crack Growth Resistance Curves (KR-curves) has been used to determine the point of crack instability

Mahishi, J. M.↗
NASA NTRS1983

A model for the formation of spokes in Saturn's rings

Evidence is mounting which implies that the generation, evolution, and motion of spokes require a dense plasma near the Saturn ring plane. It is presently suggested that spokes consist of charged, micron-sized dust particles which are elevated from the rings by radially moving, dense plasma columns due to meteor impacts on the ring. Electrostatic wall sheaths at the ring, and ring charging by electric fields sufficiently strong to overcome the gravitational force on small dust particles, arise from the dense plasma, which also increases the probability of dust particle excess electronic charge. The radial motion of the plasma column is due to an azimuthal polarization electric field due to the relative motion between the corotating plasma and the negatively charged dust particles moving at Keplerian speeds.

Goertz, C. K.↗
NASA NTRS1983

Numerically simulated two-dimensional auroral double layers

A magnetized 2 1/2-dimensional particle-in-cell system which is periodic in one direction and bounded by reservoirs of Maxwellian plasma in the other is used to numerically simulate electrostatic plasma double layers. For the cases of both oblique and two-dimensional double layers, the present results indicate periodic instability, Debye length rather than gyroradii scaling, and low frequency electrostatic turbulence together with electron beam-excited electrostatatic electron-cyclotron waves. Estimates are given for the thickness of auroral doule layers, as well as the separations within multiple auroral arcs. Attention is given to the temporal modulation of accelerated beams, and the possibilities for ion precipitation and ion conic production by the double layer are hypothesized. Simulations which include the atmospheric backscattering of electrons imply the action of an ionospheric sheath which accelerates ionospheric ions upward.

Borovsky, J. E.↗
NASA NTRS1982

The NASA Space Environment Simulation Laboratory

The NASA Space Environment Simulation Laboratory (SESL) features a chamber for studying specific space plasma physics phenomena. The test chamber, an upright domed cylinder having a 17 m diam and a 27 m height for an inner working volume, is lined with magnetic field generator coils. The chamber pressure is nominally 1/1,000,000th torr. Equipment positioning is carried out by remote control from outside guided by a closed circuit television system. Plasma is generated in the chamber by means of a 30 cm Kaufman thruster which produces ion densities of 100,000-1,000,000/cu cm. The ion bulk flow energy is in the range of 20-50 eV and a charge exchange with the ambient gas produces a cold isotropic ion component. Langmuir probes provide measurements of the electron temperature and density, and the composition and pressure are monitored by mass spectrometry and ion gages. Experiments have been performed on electron beam-plasma interactions, VLF antenna impedance measurements, and high voltage plasma sheaths which may be encountered by spacecraft.

Jost, R. J.↗
NASA NTRS1983

Transfer of pulsation-related wave activity across the magnetopause - Observations of corresponding spectra by ISEE-1 and ISEE-2

Comparison of power spectra of magnetic field data from ISEE-1 and -2 recorded simultaneously on both sides of the magnetopause showed that power level inside the magnetosphere varied with power level outside in the magnetosheath and suggested that the same frequencies were enhanced on the two sides of the boundary. Power levels were two to three orders of magnitude lower inside than outside the magnetosphere, indicating that wave energy was transmitted inside from the sheath, through a locally stable magnetopause.

Greenstadt, E. W.↗
NASA NTRS1983

Preliminary scramjet design for hypersonic airbreathing missile application

A conceptual design study of a scramjet engine was conducted for a hypersonic surface to air missile (HYSAM). The definition of the engine was based upon the requirements of accelerating the HYSAM from Mach 4 at 20,000 feet to Mach 6 at 100,000 feet and the cruise conditions at Mach 6. The resulting external and internal environmental conditions were used by various engineering disciplines performing design, stress and heat transfer analysis. A detailed structural analysis was conducted along with an indepth thermal analysis. Structurally all the components within the system exhibit positive margins of safety. A feasible concept was defined which uses state-of-the-art materials and existing TMC technology. The engine basically consists of a three dimensional carbon/carbon combustor/nozzle secured to an FS-85 columbium inlet. The carbon/carbon liner is sheathed with carbon felt insulation to thermally protect the FS-85 structure and skin. The thermal analysis of the engine indicates that a thermally viable configuration exists.

Carlson, C. H.↗
NASA NTRS1984

Mechanisms of graviperception and response in pea seedlings

A new method for the mass isolation and purification of multigranular amyloplasts from the bundle sheath parenchyma of etiolated pa epicotyls was presented. These bodies, which displace within 2+3 minutes of exposure to 1 x g, are probably the gravity receptors (statoliths) in this plant. These amyloplasts were characterized as having a doublemembrane with a surface-localized ATPase, a high calcium content, and their own genomic DNA. These amyloplasts are investigated as to (a) the reasons for their especially high density, probable related to their starch content, (b) the possible identity of their DNA with the DNA of chloroplasts and unigranular amyloplasts, and (c) possible importance of their high calcium content.

Galston, A. W.↗
NASA NTRS1984

The role of gravity in leaf blade curvatures

In the past year we have gained useful information on several aspects of leaf blade growth. The most important observations are as follows: The C(14)-1AA moves preferentially in a gravipositive dorsiventral direction through the blade. This movement is inhibited by inversion of the blade. The responding cells in leaf blade hyponasty are in the lower epidermis and bundle sheath cells. Two additional responses in the leaf were characterized. In addition to blade curvature, the leaf shows petiole curvature and changes in the liminal angle subtended by the pulvinus. Ethylene production was studied under a number of conditions. The blade, rather than the petiole or pulvinus, is the principal site of auxin-promoted ethylene synthesis. The effects of a variety of agents on the blade, including gibberellic acid, abscisic acid, vanadate, low pH buffers, and blue light were reviewed.

Hayes, A. B.↗
NASA NTRS1984

Plasma and magnetospheric research

Research developments in the following areas are discussed: (1) an ion trajectory computer code which plots the paths of ions ejected from the polar cusp ionosphere; (2) the response of plasmaspheric ion temperatures to geomagnetic activity; (3) spacecraft sheath effects; (4) plasma flow; (5) neutral gas temperatures; and (6) instrument fabrication, modification, and maintenance.

Comfort, R. H.↗
NASA NTRS1984

Experimental observations of self-similar plasma expansion

The present investigation is concerned with measurements of the plasma potential profile of an expanding plasma, taking into account the demonstration of the self-similar behavior of such a plasma. The obtained experimental results are consistent with self-similar solutions reported by Crow et al. (1975). It is found that the quasi-neutrality condition breaks down early during the experiment. A consideration of the effect of charge separation is, therefore, required. Attention is given to the evolution of the potential profiles of the expanding plasma as a function of time, the accelerated ion fronts, and the sheath formation of the expanding plasma into a floating boundary.

Chan, C.↗
NASA NTRS1982

The design and development of a rectangular, shingle-type photovoltaic module

A shingle-type photovoltaic module has been designed and developed to meet the requirements of specifications for residential applications. The module is ideally suited for installation directly to the sheathing of a sloping, south-facing roof of a residential, industrial, or commercial building. The design requirements are examined, taking into account also module safety requirements. Aspects of module design and analysis are discussed, giving attention to installation details, solar cells and electrical circuit design, the encapsulation system, substrate lamination, and the module-to-module interconnecting cable. Details of module assembly experience and test and outdoor exposure experience are also considered.

Shepard, N. F., Jr.↗
NASA NTRS1984

Thermoelectric and Thermionic Conversion Technology

Applied research and technology efforts in thermoelectric and thermionic programs were recommended that will enable space power systems for the nation's future space missions. Specifically it was argued that the effort in thermoelectric materials technology be broadened with the objective of obtaining a material with a Figure of Merit greater than 1.0 x 10(-3)/K for hot junction temperatures of 1100 to 1500 K. The recommended effort in thermionics is to pursue technology programs that will result in an understanding and lifetime prediction methodologies for fuel-emitter and sheath-insulator behavior as a function of operating time and temperature. Also it is recommended that an effort be initiated that combines the thermoelectric, thermionic and power electronic technologies into a program to develop the technology for high temperature, high radiation resistant, and high current electronic switches.

Mondt, J. F.↗
NASA NTRS1985

Plasma and magnetospheric research

Analysis techniques and software development; data analysis and modeling; spacecraft sheath effects; laboratory plasma flow studies; and instrument development are described.

Comfort, R. H.↗
NASA NTRS1985

Plasma and magnetospheric research

Research and development in plasmas and magnetospheric environments is reported. Topics discussed include: analysis and techniques of software development; data analysis and modeling; spacecraft sheath effects; laboratory plasma flow studies; instrument development.

Comfort, R. H.↗