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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 NTRS1980

VLBI measurements of radio source positions at the Jet Propulsion Laboratory

The results of approximately 1300 observations of 67 radio sources are presented. Most of the measurements were made at the stations of the Deep Space Network in California, Spain, and Australia at wavelengths of 13.1 and 3.6 cm, between 1971 and 1978. The formal errors in the derived source positions are generally in the neighborhood of 0.01 seconds of arc and the positions agree fairly well with those previously published.

Purcell, G. H., Jr.↗
NASA NTRS1979

Submilliarcsecond astrometry via VLBI. I - Relative position of the radio sources 3C 345 and NRAO 512

The relative position and relative proper motion of the radio sources 3C 345 and NRAO 512 are estimated from four sets of VLBI observations spread out over the period from October 1971 to May 1974. The use of phase-connection techniques yields the separation, in 1950.0 coordinates, of the centers of brightness of the compact components of the two sources. An upper bound of 0.0005 arcsec/yr is placed on the relative proper motion (70% estimated confidence limits). Bounds that can be placed on the distances to the two sources are considered, prospects for improvement in the determination of relative position and proper motion of these sources are discussed, and other possible applications of the basic technique are described.

Shapiro, I. I.↗
NASA NTRS1979

Positions and identifications of galactic X-ray sources

A catalog of compact Galactic X-ray sources with precise positions is presented together with a large bibliography. The catalog provides available X-ray, optical, and radio data for the 96 compact Galactic sources that have been identified and contains the most precise of the available optical, X-ray, or radio positions, the maximum and minimum published intensities, references to finding charts, and a comprehensive referenced list of X-ray, optical, and radio characteristics. The catalog also includes X-ray sources in the Magellanic clouds as well as all unidentified hard (greater than 2 keV) compact sources with an error radius of less than 60 arcsec and a Galactic latitude of less than 10 deg (absolute value). The sources list includes 14 X-ray Doppler or eclipsing binaries, seven or eight other X-ray pulsators, 23 transients or X-ray novae, 15 persistent bright bulge sources, seven X-ray sources associated with globular clusters, nine bursters, seven Galactic Center sources, and 18 other identified sources.

Bradt, H. V.↗
NASA NTRS1979

Position and shape of the Venus bow shock - Pioneer Venus Orbiter observations

Magnetometer data from the Pioneer Venus Orbiter is used to examine the position and shape of this planet's bow shock. Utilizing crossings identified on 86 occasions during the first 65 orbits a mean shock surface is defined for sun-Venus-satellite angles of 60-110 deg. Both the shock shape and variance in location are found to be very similar to the terrestrial case for the range in SVS angle considered. However, while the spread in shock positions at the earth is due predominantly to the magnetopause location varying in response to solar wind dynamic pressure, ionopause altitude variations can have little effect on total obstacle radius. Thus, the Cytherean shock is sometimes observed much closer to or farther from the planet than previously predicted by gasdynamic theory applied to the deflection of flow about a blunt body which acts neither as source nor sink for any portion of the flow.

Slavin, J. A.↗
NASA NTRS1980

The position and polarization of Type III solar bursts

The position and polarization of Type III solar bursts in the range of 24-220 MHz are studied, with emphasis on the bursts continuing to frequencies lower than 24 MHz. Consideration is given to the statistics of burst polarization, the relation between polarization and source position, and brightness temperature, flux densities, and source sizes.

Dulk, G. A.↗
NASA NTRS1980

The position and polarization of Type V solar bursts

Observations of the position and polarization of Type V solar radio bursts and their preceding Type III bursts are presented. The polarization, frequency range, source position, source movement, source size and brightness temperature of the bursts were measured using a 24-220 MHz spectropolarimeter, an 8-8000 MHz spectrograph and a three-frequency radioheliograph. Type V radiation is frequently found to have the opposite sense of circular polarization from that of the preceding Type III burst, with a degree of polarization similar to that of harmonic Type III radiation. A reversal of polarization is not observed when the accompanying Type III burst has no fundamental-harmonic structure, or when the Type V radiation is poorly developed. Possible mechanisms for the reversal are examined, including opposite magnetic field directions in Type III and V bursts, changes in mode coupling and a change in the mode of emission from o-mode for Type III to x-mode for Type V, and conditions needed for the mode change which is considered the most likely mechanism, are determined.

Dulk, G. A.↗
NASA NTRS1980

Experimental analysis of the boundary layer transition with zero and positive pressure gradient

The influence of a positive pressure gradient on the boundary layer transition is studied. The mean velocity and turbulence profiles of four cases are examined. As the intensity of the pressure gradient is increased, the Reynolds number of the transition onset and the length of the transition region are reduced. The Tollmein-Schlichting waves disturb the laminar regime; the amplification of these waves is in good agreement with the stability theory. The three dimensional deformation of the waves leads finally to the appearance of turbulence. In the case of zero pressure gradient, the properties of the turbulent spots are studied by conditional sampling of the hot-wire signal; in the case of positive pressure gradient, the turbulence appears in a progressive manner and the turbulent spots are much more difficult to characterize.

Arnal, D.↗
NASA NTRS1980

State of gas exchange in recumbent and orthostatic positions and under physical load in healthy persons of varying age, sex and body build

Age effect on gas exchange was studied in the recumbent and orthostatic positions and under physical load. In the case of the older age group and for normal as compared with hypersthenic persons, oxygen consumption during rest and during moderate physical overload diminishes. When the vertical position is assumed oxygen consumption in persons of various age groups is distinctly increased, particularly in the elderly group. There is a reduction in the amount of oxygen consumption, oxygen pulse, recovery coefficient, and work efficiency under moderate overload. In persons over 50, physical labor induces a large oxygen requirement and a sharp rise in the level of lactic acid and the blood's lactate/pyruvate ratio. No distinct difference was noted in the amount of oxygen consumed during rest and during physical overload in men and women of the same physical development and age.

Glezer, G. A.↗
NASA NTRS1972

X-ray position detector

An X-ray position detector for real time operation is described. A set of proportional counters is arranged into an array which can detect and indicate the position of an X-ray interaction within the array, in the X Y plane.

Garmire, G.↗
NASA NTRS1981

Loran-C plotting program for plotting lines of position on standard charts

A set of programs used to plot Loran C lines of position on any common map or standard aviation sectional chart are given. The Loran C plotting program JRPLOT FORTRAN uses a standard Calcomp compatible plotting subroutine package for the Hewlett-Packard 7203A graphic plotter. The programs are designed to be run on an IBM System 370 computer. A simple add subtract method is used to calculate the lines of position. A description of how to use the program and some methods of operation are given.

Roman, J. P.↗
NASA NTRS1980

The position angle of Jupiter's linearly polarized synchrotron emission Observations extending over 16 years

Parkes, Owens Valley and Goldstone measurements are presented, showing the variation with central meridian longitude of the position angle of Jupiter's linearly polarized synchrotron emission at wavelengths of 21, 13, 11 and 6 cm; the observations span a total time interval greater than one Jovian orbital period. The form of the position angle versus longitude curve shows a slight dependence on wavelength and epoch. The epoch dependence appears to reflect Jupiter's changing aspect with respect to the earth. The observations yield a Jovian rotation period agreeing to within about 0.02 s with that derived from the decametric burst measurements, implying a highly stable inner magnetic field configuration.

Komesaroff, M. M.↗
NASA NTRS1980

A comparative analysis of GPS range, Doppler and interferometric observations for geodetic positioning

Geodetic positioning accuracies obtained from range, integrated Doppler and double differenced interferometric phase observations from a constellation of twenty-four Global Positioning System satellites are presented. It is demonstrated the GPS range and Doppler observations will provide sufficient accuracy for the estimation of geodetic coordinates. However the instability of the receiver atomic oscillator will limit the usefulness of these observations in providing rapid first-order baseline determination. Interferometric phase measurements twice differenced to eliminate clock error appear as an alternate procedure for providing such accuracies.

Fell, P. J.↗
NASA NTRS1980

Brightness and polarization of the zodiacal light - Results of fixed-position observations from Skylab

A method is outlined for evaluating discrete and background starlight at the Skylab wavelengths so as to derive the total brightness of zodiacal light at five sky positions. These sky positions are north celestial pole, south ecliptic pole, vernal equinox and two places near the north galactic pole. Pioneer 10/11 imaging photopolarimeters were used to periodically measure sky brightness and polarization in the blue and red at heliocentric distances beyond 1.002 AU. Mean zodiacal light, which is assumed to be also solar color in total light, is then estimated by applying the method to all fixed-point observations.

Weinberg, J. L.↗
NASA NTRS1981

Wedge-and-strip anodes for centroid-finding position-sensitive photon and particle detectors

The paper examines geometries employing position-dependent charge partitioning to obtain a two-dimensional position signal from each detected photon or particle. Requiring three or four anode electrodes and signal paths, images have little distortion and resolution is not limited by thermal noise. An analysis of the geometrical image nonlinearity between event centroid location and the charge partition ratios is presented. In addition, fabrication and testing of two wedge-and-strip anode systems are discussed. Images obtained with EUV radiation and microchannel plates verify the predicted performance, with further resolution improvements achieved by adopting low noise signal circuitry. Also discussed are the designs of practical X-ray, EUV, and charged particle image systems.

Martin, C.↗
NASA NTRS1983

Variable-Position Acoustic Levitation

Method of acoustic levitation supports objects at positions other than acoustic nodes. Acoustic force is varied so it balances gravitational (or other) force, thereby maintaining object at any position within equilibrium range. Levitation method applicable to containerless processing. Such objects as table-tennis balls, hollow plastic spheres, and balsa-wood spheres levitated in laboratory by new method.

Barmatz, M. B.↗
NASA NTRS1981

Effect of positive pulse charge waveforms on the energy efficiency of lead-acid traction cells

The effects of four different charge methods on the energy conversion efficiency of 300 ampere hour lead acid traction cells were investigated. Three of the methods were positive pulse charge waveforms; the fourth, a constant current method, was used as a baseline of comparison. The positive pulse charge waveforms were: 120 Hz full wave rectified sinusoidal; 120 Hz silicon controlled rectified; and 1 kHz square wave. The constant current charger was set at the time average pulse current of each pulse waveform, which was 150 amps. The energy efficiency does not include charger losses. The lead acid traction cells were charged to 70 percent of rated ampere hour capacity in each case. The results of charging the cells using the three different pulse charge waveforms indicate there was no significant difference in energy conversion efficiency when compared to constant current charging at the time average pulse current value.

Smithrick, J. J.↗
NASA NTRS1982

Spatial, High-Accuracy, Positioning-Encoding Sensor (SHAPES) for large space system control applications

The Spatial, High-Accuracy, Position-Encoding Sensor is a controls sensor suitable for the determination of the static shape and vibrational motion of large space structures and similar systems and for the determination of position and velocity in rendezvous and docking. It uses a combination of electro-optical techniques to measure the three-dimensional coordinates distributed over the structure at reading rates high compared to the rates at which the coordinates are changing. The technical approach is that of measuring the distance to and the direction of points on the structure from a single sensor head. Many points can be measured simultaneously from a single head without significantly increasing the complexity of the system.

Mclauchlan, J. M.↗
NASA NTRS1982

Case-positive versus case-negative designs for low-rate lithium thionyl chloride cells

Case polarity design choices are discussed. Two examples of case-negative designs are presented. One battery is thionyl chloride limited and the other is lithium limited. The case-positive design is thionyl chloride limited. It is found that the case-positive/case-negative design consideration does not seem to have much bearing on storage. However, during low rate discharge, the case-negative cells show a steadily decreasing capacity as you go to lower and lower rates.

Mahy, T. X.↗