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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Arc-driven rail gun research

The equations describing the performance of an inductively-driven rail gun are analyzed numerically. Friction between the projectile and rails is included through an empirical formulation. The equations are applied to the experiment of Rashleigh and Marshall to obtain an estimate of energy distribution in rail guns as a function of time. The effect of frictional heat dissipation on the bore of the gun is calculated. The mechanism of plasma and projectile acceleration in a dc rail gun is described from a microscopic point of view through the establishment of the Hall field. The plasma conductivity is shown to be a tensor indicating that there is a small component of current parallel to the direction of acceleration. The plasma characteristics are evaluated as a function of plasma mass through a simple fluid mechanical analysis of the plasma. By equating the energy dissipated in the plasma with the radiation heat loss, the properties of the plasma are determined.

Ray, P. K.↗
NASA NTRS1985

Energy spectrum of cosmic-ray iron nucleus observed with emulsion chamber

Energy spectrum of cosmic-ray Fe-nucleus has been measured from 4 GeV per nucleon to beyond 100 GeV per nucleon. The data were obtained using emulsion chambers on a balloon from Sanriku, Japan. The energies were estimated by the opening angle method after calibrated using 1.88 GeV per nucleon Fe collisions. The spectrum of Fe is approximately E-2.5 in the range from 10 to 200 GeV per nucleon. This result is in good agreement with those of other experiments.

Sato, Y.↗
NASA NTRS1985

Experiment Pamir-4: Analysis of superfamily with halo of electromagnetic nature detected in deep XEC

The family Pb2-11 was detected in the multilayer lead XEC with total thickness of 100 c.u. exposed at the Pamirs. Each lead layer was 1 cm thick, the first registering layer being located under 2 cm of Pb(= 4 c.u.). The family comprised a narrow group of gamma-rays which near the maximum of cascade development (= 14 c.u.) produced a dark spot of optical density D approx. .4 over area S = 25 sq.mm. The narrow group of gamma-rays was traced up to 14th layer corresponding to 30 c.u. Deeper in the chamber, for the space of 70 c.u. no hadron cascade was observed. Thus, the pure electromagnetic halo could be assumed. Preliminary results of the analysis of the family Pb2-11 was presented. The methods of estimation of energy of primary particle and height of nuclear interaction responsible for the observed halo are considered in more detail.

Zatsepin, G. T.↗
NASA NTRS1985

Correlation of high energy muons with primary composition in extensive air shower

An experimental investigation of high energy muons above 200 GeV in extensive air showers has been made for studying high energy interaction and primary composition of cosmic rays of energies in the range 10 to the 14th power approx. 10 to the 15th power eV. The muon energies are estimated from the burst sizes initiated by the muons in the rock, which are measured by four layers of proportional counters, each of area 5 x 2.6 sq m, placed at 30 m.w.e. deep, Funasaka tunnel vertically below the air shower array. These results are compared with Monte Carlo simulations based on the scaling model and the fireball model for two primary compositions, all proton and mixed.

Chou, C.↗
NASA NTRS1984

Lightning - Estimates of the rates of energy dissipation and nitrogen fixation

The nitrogen needed by plants can normally not be directly obtained from the nitrogen present in molecular form in the atmosphere. The reason for this situation is related to the great energy required to break the N-N bond. Only a few organisms, such as algae and certain bacteria, can 'fix' nitrogen. An abiological process for breaking the N-N bond is provided by lightning. The present investigation is concerned with this possibility. It is found that lightning produces approximately 2.6 x 10 to the 9th kg N per year. There are, however, uncertainties, which are mainly related to the energy of a lightning flash.

Borucki, W. J.↗
NASA NTRS1984

A detailed X-ray and radio comparison of Kepler's supernova remnant

High-resolution radio images of Kepler's SNR (SNR (SN 1604) at 6 and 21 cm have been obtained using the VLA. The orientation of linear polarization in the SNR implies a substantial nonrandom radial component for the magnetic field of the remnant. Based on a new X-ray picture of the SNR, obtained using the Einstein Observatory, a detailed comparison of the X-ray and radio morphology is carried out. There is a good correlation between rotation measure, obtained from the radio maps, and emission measure, an X-ray-derived quantity in the SNR shell. From the mean electron density value infered from an analysis of X-ray fluxes, a mean radial magnetic field of 14 micro G and a total magnetic field of 70 microG are estimated. The energy density of relativistic electrons in Kepler's SNR in the shell comparable to the energy density in the magnetic field; the relativistic electron-pressure is 2 percent of the thermal gas pressure. The strong correlation between radio emissivity and X-ray emissivity found over the SNR in somewhat large scale can be ascribed to acceleration of thermal electrons at the shock wave and insignificant diffusion of resultant relativistic electrons.

Matsui, Y.↗
NASA NTRS1985

Interpretation of F-106B in-flight lightning signatures

Various characteristics of the electromagnetic data obtained on a NASA F-106B aircraft during direct lightning strikes are presented. Time scales of interest range from 10 ns to 400 microsecond. The following topics are discussed: (1) Lightning current, I, measured directly versus I obtained from computer integration of measured I-dot; (2) A method of compensation for the low frequency cutoff of the current transformer used to measure I; (3) Properties of fast pulses observed in the lightning time-derivative waveforms; (4) The characteristic D-dot signature of the F-106B aircraft; (5) An RC-discharge interpretation for some lightning waveforms; (6) A method for inferring the locations of lightning channel attachment points on the aircraft by using B-dot data; (7) Simple, approximate relationships between D-dot and I-dot and between B and I; and (8) Estimates of energy, charge, voltage, and resistance for a particular lightning event.

Trost, T. F.↗
NASA NTRS1985

Analysis of vibronic transitions in titanium doped sapphire using the temperature of the fluorescence spectra

An analysis of the fluorescence spectra of titanium-doped sapphire crystals for temperatures ranging from 13 to 578 K is made. Zero- and multiphoton assisted electronic transitions are observed at temperatures below 125 K. Zero-phonon transition energies agree with previously reported measured and predicted values. Photon-assisted transitions suggest that two principle modes of lattice vibrations with energies of 220 and 260/cm are coupled to the electronic 2T2g state. A single phonon energy of 173/cm is observed to couple to the 2Eg electronic state. Crossover energy is estimated to be about 11,800/cm using a simple harmonic approximation. Lineshape analysis is performed. The fluorescence lifetime as measured to be a constant 3.9 microsec below 150 k decreasing to 2.9 microsec at 300 K.

Byvik, C. E.↗
NASA NTRS1986

A statistical model to estimate refractivity turbulence structure constant C sub n sup 2 in the free atmosphere

A computer program has been tested and documented (Warnock and VanZandt, 1985) that estimates mean values of the refractivity turbulence structure constant in the stable free atmosphere from standard National Weather Service balloon data or an equivalent data set. The program is based on the statistical model for the occurrence of turbulence developed by VanZandt et al. (1981). Height profiles of the estimated refractivity turbulence structure constant agree well with profiles measured by the Sunset radar with a height resolution of about 1 km. The program also estimates the energy dissipation rate (epsilon), but because of the lack of suitable observations of epsilon, the model for epsilon has not yet been evaluated sufficiently to be used in routine applications. Vertical profiles of the refractivity turbulence structure constant were compared with profiles measured by both radar and optical remote sensors and good agreement was found. However, at times the scintillometer measurements were less than both the radar and model values.

Warnock, J. M.↗
NASA NTRS1987

Measuring ocean waves from space; Proceedings of the Symposium, Johns Hopkins University, Laurel, MD, Apr. 15-17, 1986

Papers are presented on ocean-wave prediction; the quasi-universal form of the spectra of wind-generated gravity waves at different stages of their development; the limitations of the spectral measurements and observations of the group structure of surface waves; the effect of swell on the growth of wind wave; operational wave forecasting; ocean-wave models, and seakeeping using directional wave spectra. Consideration is given to microwave measurements of the ocean-wave directional spectra; SIR research; estimating wave energy spectra from SAR imagery, with the radar ocean-wave spectrometer, and SIR-B; the wave-measurement capabilities of the surface contour radar and the airborne oceanographic lidar; and SIR-B ocean-wave enhancement with fast-Fourier transform techniques. Topics discussed include wave-current interaction; the design and applicability of Spectrasat; the need for a global wave monitoring system; the age and source of ocean swell observed in Hurricane Josephine; and the use of satellite technology for insulin treatment.

Beal, Robert C.↗
NASA NTRS1989

Measurements of short-term thermal responses of coniferous forest canopies using thermal scanner data

Thermal Infrared Multispectral Scanner (TIMS) data were collected over a coniferous forest in western Oregon. Concurrent radiosonde measurements of atmospheric profiles of air temperature and moisture provided inputs to LOWTRAN6 for atmospheric radiance corrections of the TIMS data. Surface temperature differences measured by the TIMS over time between flight lines were combined with surface radiative energy balance estimates to develop thermal response numbers (TRN). These numbers characterized the thermal response of the diffent surface types. Barren surfaces had the lowest TRN, whereas the forested surfaces had the highest.

Luvall, J. C.↗
NASA NTRS1990

A Monte Carlo simulation technique for low-altitude, wind-shear turbulence

A case is made for including anisotropy in a Monte Carlo flight simulation scheme of low-altitude wind-shear turbulence by means of power spectral density. This study attempts to eliminate all flight simulation-induced deficiencies in the basic turbulence model. A full-scale low-altitude wind-shear turbulence simulation scheme is proposed with particular emphasis on low cost and practicality for near-ground flight. The power spectral density statistic is used to highlight the need for realistic estimates of energy transfer associated with low-altitude wind-shear turbulence. The simulation of a particular anisotropic turbulence model is shown to be a relatively simple extension from that of traditional isotropic (Dryden) turbulence.

Bowles, Roland L.↗
NASA NTRS1990

Target earth - It will happen

Cosmic impacts of the earth by asteroiods and comets are examined. The impact history of the moon is discussed and compared with that of the earth. Theoretical and laboratory simulation experiments to evaluate the consequences of a collision between the earth and an asteroid or comet are reviewed. Earth crossing asteroids are listed and the probability of impacts with various equivalent energies is estimated.

Morrison, David↗
NASA NTRS1989

Wave evolution in the marginal ice zone - Model predictions and comparisons with on-site and remote data

The ocean-wave dispersion relation and viscous attenuation by a sea ice cover were studied for waves in the marginal ice zone (MIZ). The Labrador ice margin experiment (Limex), conducted off the east coast of Newfoundland, Canada in March 1987, provided aircraft SAR, wave buoy, and ice property data. Based on the wave number spectrum from SAR data, the concurrent wave frequency spectrum from ocean buoy data, and accelerometer data on the ice during Limex '87, the dispersion relation has been derived and compared with the model. Accelerometers were deployed at the ice edge and into the ice pack. Data from the accelerometers were used to estimate wave energy attenuation rates and compared with the model. The model-data comparisons are reasonably good for the ice conditions observed during Limex' 87.

Liu, A. K.↗
NASA NTRS1993

The influence of the hydrologic cycle on the extent of sea ice with climatic implications

Multi-temporal satellite images, field observations, and field measurements were used to investigate the mechanisms by which sea ice melts offshore from the Mackenzie River delta. Advanced Very High Resolution Radiometer (AVHRR) satellite data recorded in 1986 were analyzed. The satellite data were geometrically corrected and radiometrically calibrated so that albedo and temperature values could be extracted. The investigation revealed that sea ice melted approximately 2 weeks earlier offshore from the Mackenzie River delta than along coasts where river discharge is minimal or non-existent. There is significant intra-delta variability in the timing and patterns of ice melt. An estimation of energy flux indicates that 30 percent more of the visible wavelength energy and 25 percent more of the near-infrared wavelength energy is absorbed by water offshore of the delta compared to coastal areas with minimal river discharge. The analysis also revealed that the removal of sea ice involves the following: over-ice-flooding along the coast offshore from river delta channels; under-ice flow of 'warm' river water; melting and calving of the fast ice; and, the formation of a bight in the pack ice edge. Two stages in the melting of sea ice were identified: (1) an early stage where heat is supplied to overflows largely by solar radiation, and (2) a later stage where heat is supplied by river discharge in addition to solar radiation. A simple thermodynamic model of the thaw process in the fast ice zone was developed and parameterized based on events recorded by the satellite images. The model treats river discharge as the source of sensible heat at the base of the ice cover. The results of a series of sensitivity tests to assess the influence of river discharge on the near shore ice are presented.

Dean, Kenneson G.↗
NASA NTRS1992

Simulated O VI Doppler dimming measurements of coronal outflow velocities

The possibility of determining O(5+) outflow velocities by using a Doppler dimming analysis of the resonantly scattered intensities of O VI lambda 1031.9 and lambda 1037.6 is addressed. The technique is sensitive to outflow velocities, W, in the range W greater than 30 and less than 250 km/s and can be used for probing regions of the inner solar corona, where significant coronal heating and solar wind acceleration may be occurring. These velocity measurements, when combined with measurements of other plasma parameters (temperatures and densities of ions and electrons) can be used to estimate the energy and mass flux of O(5+). In particular, it may be possible to locate where the flow changes from subsonic to supersonic and to identify source regions for the high and low speed solar wind. The velocity diagnostic technique is discussed with emphasis placed on the requirements needed for accurate outflow velocity determinations. Model determinations of outflow velocities based on simulated Doppler observations are presented.

Strachan, Leonard↗
NASA NTRS1992

An infrared supershell surrounding the Cygnus OB1 association

New studies are reported of a large, 2 x 5 deg peanut-shaped cavity in the far-infrared emission seen using IRAS data for the Cygnus X region. A more complete and better defined infrared supershell than reported by Lozinskaya and Repin (1990) is found and connected to the Cyg OB1 association. It is shown that the cavity represents the early stages of a superbubble produced by the winds and possible SNe from 10 to 20 massive stars. The locations and properties of these stars are used to estimate the energy deposition rate and to understand the manner in which supershells form and propagate. In Cyg OB1, spatially distributed subclustering appears to have played an important role in determining the nonspherical morphology of the superbubble.

Saken, Jon M.↗