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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 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Docking simulation analysis of range data requirements for the orbital maneuvering vehicle

The results of an initial study are reported assess the controllability of the Orbital Maneuvering Vehicle (OMV) for terminal closure and docking are reported. The vehicle characteristics used in this study are those of the Marshall Space Flight Center (MSFC) baseline OMV which were published with the request for proposals for preliminary design of this vehicle. This simulation was conducted at MSFC using the Target Motion Simulator. The study focused on the OMV manual mode capability to accommodate both stabilized and tumbling target engagements with varying complements of range and range rate data displayed to the OMV operator. Four trained test subjects performed over 400 simulated orbital dockings during this study. A firm requirement for radar during the terminal closure and dock phase of the OMV mission was not established by these simulations. Fifteen pound thrusters recommended in the MSFC baseline design were found to be advantageous for initial rate matching maneuvers with unstabilized targets; however, lower thrust levels were desirable for making the final docking maneuvers.

Micheal, J. D.↗
NASA NTRS1985

Energy-range relations for hadrons in nuclear matter

Range-energy relations for hadrons in nuclear matter exist similarly to the range-energy relations for charged particles in materials. When hadrons of GeV kinetic energies collide with atomic nuclei massive enough, events occur in which incident hadron is stopped completely inside the target nucleus without causing particle production - without pion production in particular. The stoppings are always accompanied by intensive emission of nucleons with kinetic energy from about 20 up to about 400 MeV. It was shown experimentally that the mean number of the emitted nucleons is a measure of the mean path in nuclear matter in nucleons on which the incident hadrons are stopped.

Strugalski, Z.↗
NASA NTRS1985

Hadronic components of EAS by rigorous saddle point method in the energy range between 10(5) and 10(8) GeV

The study of hadronic components in the high energy range between 10 to the 5 and 10 to the 8 Gev exhibits by far the strongest mass sensitivity since the primary energy spectrum as discussed by Linsley and measured by many air shower experimental groups indicates a change of slope from -1.7 to 2.0 in this energy range. This change of slope may be due to several reasons such as a genuine spectral feature of astrophysical origin, a confinement effect of galactic component or a rather rapid change of mass, a problem which we have attempted to study here in detail.

Sinha, M.↗
NASA NTRS1985

Samarkand complex setup for investigation of cosmic ray variation in the energy range of 7 10 (9) - 10 (15) eV

The Samarkand complex setup is aimed at the study of cosmic ray variations in a wide energy range from 7 billion eV (which corresponds to the geomagnetic threshold in the region of Samarkand) up to approx 10 to the 15th power to 10 to the 16th power eV. The setup consists of four 6-counter sections of neutron supermonitor with counters SNM-15 and 48 scintillator detectors (1 sq m each) placed under and above the supermonitor. The effective area of the setup for recording neutrons and muons is 24 sq m. The setup can register time variations of the following cosmic ray components: (1) the total neutron counting rate, (2) counting rates for neutrons of different multiplicity, (3) soft-muon fluxes, (4) hard-muon fluxes at various zenith and azimuth angles, (5) electron-photon component, (6) extensive air showers (EAS) induced by primary particles in a wide energy range and accompanied or not accompanied by muons and neutrons.

Dorman, L. I.↗
NASA NTRS1985

Latitude variation of recurrent MeV-energy proton flux enhancements in the heliocentric radial range 11 to 20 AU and possible correlation with solar coronal hole dynamics

Recurrent low energy (not less than 0.5 MeV) proton flux enhancements, reliable indicators of corotating plasma interaction regions in interplanetary space, have been observed on the Voyager 1 and 2 and Pioneer 11 spacecraft in the heliographic latitude range 2 deg S to 23 deg N and the heliocentric radial range 11 to 20 AU. After a period of rather high correlation between fluxes at different latitudes in early 1983, distinct differences develop. The evolution of the fluxes appears to be related to the temporal and latitudinal dynamics of solar coronal holes, suggesting that information about the latitudinal structure of solar wind stream sources propagates to these distances.

Christon, S. P.↗
NASA NTRS1985

MLRS - A lunar/artificial satellite laser ranging facility at the McDonald Observatory

Experience from lunar and satellite laser ranging experiments carried out at McDonald Observatory has been used to design the McDonald Laser Ranging Station (MLRS). The MLRS is a dual-purpose installation designed to obtain observations from the LAGEOS satellite and lunar targets. The instruments used at the station include a telescope assembly 0.76 meters in diameter; a Q-switched doubled neodymium YAG laser with a pulse rate of three nanoseconds; and a GaAs photodetector with Fabry-Perot interferometric filter. A functional diagram of the system is provided. The operating parameters of the instruments are summarized in a table.

Shelus, P. J.↗
NASA NTRS1985

Satellite laser ranging - Current status and future prospects

The characteristics and capabilities of instruments and operational techniques in the field of satellite laser ranging (SLR) are discussed. Following a brief introduction to the basic concept of SLR, a developmental history of each of the major components of an SLR hardware is given, including the laser transmitter, photomultiplier, discriminator, and time interval unit. The sources of range error in each of the devices are examined, and techniques for reducing error are described. A description of current SLR hardware is summarized using samples of actual satellite data obtained in 1981, which show that orbital fits with a 1.5 single shot rms and normal point rms error of less than 3 mm with 1-6 percent data entering. The development of even more precise measurement techniques in the future with the advent of the Starlette and LAGEOS II SLR system is also discussed.

Degnan, J. J.↗
NASA NTRS1986

Field Funneling and Range Straggling in Silicon Detectors

Magnitudes of field funneling and range straggling determined in silicon-surface-barrier (Schottky-barrier) charged-particle detectors (SSBD's) through meaurement of charges collected from alpha-particle tracks. Method used extended to straightforward measurement of charge collection from heavy-ion tracks in these and other semiconductor devices. Such measurements used to assess single-event upsets in integratedcircuit chips, with view toward making them resistant to radiation. Field funneling and range straggling measured with electronic system in which charge collected from individual ions measured and recorded by multichannel analyzer.

Zoutendyk, J. A.↗
NASA NTRS1985

A First Look at Airborne Imaging Spectrometer (AIS) Data in an Area of Altered Volcanic Rocks and Carbonate Formations, Hot Creek Range, South Central Nevada

Three flight lines of Airborne Imaging Spectrometer (AIS) data were collected in 128 bands between 1.2 and 2.4 microns in the Hot Creek Range, Nevada on July 25, 1984. The flight lines are underlain by hydrothermally altered and unaltered Paleozoic carbonates and Tertiary rhyolitic to latitic volcanics in the Tybo mining district. The original project objectives were to discriminate carbonate rocks from other rock types, to distinguish limestone from dolomite, and to discriminate carbonate units from each other using AIS imagery. Because of high cloud cover over the prime carbonate flight line and because of the acquisition of another flight line in altered and unaltered volcanics, the study has been extended to the discrimination of alteration products. In an area of altered and unaltered rhyolites and latites in Red Rock Canyon, altered and unaltered rock could be discriminated from each other using spectral features in the 1.16 to 2.34 micron range. The altered spectral signatures resembled montmorillonite and kaolinite. Field samples were gathered and the presence of montmorillonite was confirmed by X-ray analysis.

Feldman, S. C.↗
NASA NTRS1985

Dislocation model for aseismic fault slip in the transverse ranges of Southern California

Geodetic data at a plate boundary can reveal the pattern of subsurface displacements that accompany plate motion. These displacements are modelled as the sum of rigid block motion and the elastic effects of frictional interaction between blocks. The frictional interactions are represented by uniform dislocation on each of several rectangular fault patches. The block velocities and fault parameters are then estimated from geodetic data. Bayesian inversion procedure employs prior estimates based on geological and seismological data. The method is applied to the Transverse Ranges, using prior geological and seismological data and geodetic data from the USGS trilateration networks. Geodetic data imply a displacement rate of about 20 mm/yr across the San Andreas Fault, while the geologic estimates exceed 30 mm/yr. The prior model and the final estimates both imply about 10 mm/yr crustal shortening normal to the trend of the San Andreas Fault. Aseismic fault motion is a major contributor to plate motion. The geodetic data can help to identify faults that are suffering rapid stress accumulation; in the Transverse Ranges those faults are the San Andreas and the Santa Susana.

Cheng, A.↗
NASA NTRS1985

Observing tectonic plate motions and deformations from satellite laser ranging

The scope of geodesy has been greatly affected by the advent of artificial near-earth satellites. The present paper provides a description of the results obtained from the reduction of data collected with the aid of satellite laser ranging. It is pointed out that dynamic reduction of satellite laser ranging (SLR) data provides very precise positions in three dimensions for the laser tracking network. The vertical components of the stations, through the tracking geometry provided by the global network and the accurate knowledge of orbital dynamics, are uniquely related to the center of mass of the earth. Attention is given to the observations, the methodologies for reducing satellite observations to estimate station positions, Lageos-observed tectonic plate motions, an improved temporal resolution of SLR plate motions, and the SLR vertical datum.

Christodoulidis, D. C.↗
NASA NTRS1985

A comparison between Lageos laser ranging and very long baseline interferometry determined baseline lengths

NASA's Crustal Dynamics Project (CDP) has the objective to improve the understanding of geodynamics by measuring crustal deformation, tectonic motion, and polar motion and earth rotation. Three different approaches are utilized for obtaining these measurements. One is based on satellite laser ranging (SLR), while another makes use of very long baseline interferometry (VLBI) which uses reception of radio signals from quasars. The third approach involves laser ranging to the moon. An important part of the CDP is to compare baselines periodically or the straight-line distance between two points on the earth's surface as determined by either SLR or VLBI. Attention is given to the SLR analysis, the VLBI analysis, a local survey, and error sources. A table is presented with the baselines between SLR survey markers as measured by VLBI and SLR.

Kolenkiewicz, R.↗
NASA NTRS1985

Precision geodesy and geodynamics using Starlette laser ranging

The French Starlette satellite, launched in February 1975, was the first satellite specifically designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. It has been found that Starlette represents a valuable complement to the U.S. geodetic satellites. In an analysis of Starlette laser ranging data conducted by Marsh and Williamson (1978), it was concluded that by tailoring a gravity model to a specific satellite and observation period, substantial improvements in data fits and, therefore, in orbit accuracy could be achieved. In the present analyses, a tailored gravity model has been derived for Starlette from the data acquired for the 4-year period, 1975-1978. Attention is given to the solution for geodetic and geodynamic parameters and polar motion.

Marsh, J. G.↗
NASA NTRS1986

High dynamic range VLBI observations of NGC 6251

The large radio galaxy NGC 6251 has been observed with an 11-telescope VLBI array, including the full VLA, at 18 cm. High-dynamic-range maps of both the VLBI-scale and VLA-scale radio structure from these observations, as well as hybrid maps from earlier VLBI experiments at 6 and 13 cm, are presented. The 18-cm VLBI hybrid map has an unusually high dynamic range of about 300 to 1 (ratio of the peak brightness to five times the rms noise level) and is limited by thermal noise rather than calibration errors. A lower limit of 80 to 1 for the ratio of jet/counterjet brightness at parsec scales can be set. This is the strongest such limit produced by VLBI observations of any source to date. If the absence of a detectable counterjet is caused by relativistic beaming, then the jet must be aligned within 45 deg of the line of sight. The VLA map shows a complex structure along the previously detected kiloparsec-scale counterjet. The physical conditions in the inner few parsecs of the NGC 6251 jet and their relation to the conditions in the extraordinarily long and well collimated kiloparsec-scale jets are discussed, and it is shown that both small-scale and large-scale morphology can be explained in terms of a simple model and relativistic beaming.

Jones, D. L.↗
NASA NTRS1984

Rotary balance data and analysis for the X-29A airplane for an angle-of-attack range of 0 deg to 90 deg

The rotational aerodynamic characteristics are discussed for a 1/8 scale model of the X-29A airplane. The effects of rotation on the aerodynamics of the basic model were determined, as well as the influence of airplane components, various control deflections, and several forebody modifications. These data were measured using a rotary balance, over an angle of attack range of 0 to 90 deg, for clockwise and counter clockwise rotations covering an omega b/2V range of 0 to 0.4.

Ralston, J. N.↗
NASA NTRS1986

A computational method to model radar return range in a polygonally based, computer-generated-imagery simulation

Described is a method for modeling a ground-mapping radar system for use in simulations where the terrain is in a polygonal form commonly used with computer generated imagery (CGI). The method employs a unique approach for rapidly rejecting polygons not visible to the radar to facilitate the real-time simulation of the radar return. This rapid rejection of the nonvisible polygons requires the precalculation and storage of a set of parameters that do not vary during the simulation. The calculation of a radar range as a function of the radar forward-looking angle to the CGI terrain is carried out only for the visible polygons. This method was used as part of a simulation for terrain-following helicopter operations on the vertical motion simulator at the NASA Ames Research Center. It proved to be an efficient means for returning real-time simulated radar range data.

Moran, F. J.↗
NASA NTRS1986

A Cassegrain reflector system for compact range applications

An integral part of a compact range is the means of providing a uniform plane wave. A Cassegrain reflector system is one alternative for achieving this goal. Theoretically, this system offers better performance than a simple reflector system. The longer pathlengths in the Cassegrain system lead to a more uniform field in the plane of interest. The addition of the subreflector creates several problems, though. System complexity is increased both in terms of construction and performance analysis. The subreflector also leads to aperture blockage and the orientation of the feed now results in spillover illuminating the target areas as well as the rest of the range. Finally, the addition of the subreflector leads to interaction between the two reflectors resulting in undesired field variations in the plane of interest. These difficulties are addressed and through the concept of blending the surfaces, a Cassegrain reflector system is developed that will provide a uniform plane wave that offers superior performance over large target areas for a given size reflector system. Design and analysis is implemented by considering the main reflector and subreflector separately. Then the system may be put together and the final design and system analysis completed.

Rader, Mark D.↗
NASA NTRS1987

Calibration of the EGRET high-energy gamma-ray telescope in the range 20-10,000 MeV with a tunable beam of quasi-monoenergetic gamma rays at SLAC

The EGRET telescope, one of the instruments to be carried on NASA's Gamma Ray Observatory, is designed to explore the high-energy portion (20-24,000 MeV) of the electromagnetic spectrum. A calibration source of gamma-rays over this wide energy range has been used together with an appropriate set of intensity-monitoring instruments, to conduct a calibration of the EGRET telescope over this energy range for the full telescope aperture. The calibration method and an overview of the results are described.

Thompson, D. J.↗