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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Precise leveling, space geodesy and geodynamics

The implications of currently available leveling data on understanding the crustal dynamics of the continental United States are investigated. Neotectonic deformation, near surface movements, systematic errors in releveling measurements, and the implications of this information for earthquake prediction are described. Vertical crustal movements in the vicinity of the 1931 Valentine, Texas, earthquake which may represent coseismic deformation are investigated. The detection of vertical fault displacements by precise leveling in western Kentucky is reported. An empirical basis for defining releveling anomalies and its implications for crustal deformation in southern California is presented. Releveling measurements in the eastern United States and their meaning in the context of possible crustal deformation, including uplift of the Appalachian Mountains, eastward tilting of the Atlantic Coastal Plain, and apparent movements associated with a number of structural features along the east coast, are reported.

Reilinger, R.↗
NASA NTRS1981

Precise time technology for selected Air Force systems: Present status and future requirements

Precise time and time interval (PTTI) technology is becoming increasingly significant to Air Force operations as digital techniques find expanded utility in military missions. Timing has a key role in the function as well as in navigation. A survey of the PTTI needs of several Air Force systems is presented. Current technology supporting these needs was reviewed and new requirements are emphasized for systems as they transfer from initial development to final operational deployment.

Yannoni, N. F.↗
NASA NTRS1981

Feasibility of collision warning, precision approach and landing using GPS, volume 1

The use of GPS, with an appropriately configured data link, to enhance general aviation avionic functions encountered in the terminal area and on approach was investigated with emphasis on approach and landing guidance and collision warning. The feasibility of using differential GPS to obtain the precision navigation solutions required for landing was studied. Results show that the concept is sound. An experimental program was developed to demonstrate this concept. The collision avoidance/warning concept was examined through the development of a functional system specification.

Ruedger, W. H.↗
NASA NTRS1981

Gamma ray bursts: A review of recent high-precision measurements

Recent measurements and discoveries in gamma ray bursts and transients are reviewed including observations of the red shifted annihilation line in two kinds of slow transients (in 'classical' gamma ray bursts and in the unique 1979 March 5th event); of red shifted nuclear lines in a slow transient and in one gamma ray burst; and of the positions of precise source locations of gamma ray bursts and of the March 5th event, within the supernova remnant N49 in the Large Magellanic Cloud.

Cline, T. L.↗
NASA NTRS1980

The Magsat precision vector magnetometer

This paper examines the Magsat precision vector magnetometer which is designed to measure projections of the ambient field in three orthogonal directions. The system contains a highly stable and linear triaxial fluxgate magnetometer with a dynamic range of + or - 2000 nT (1 nT = 10 to the -9 weber per sq m). The magnetometer electronics, analog-to-digital converter, and digitally controlled current sources are implemented with redundant designs to avoid a loss of data in case of failures. Measurements are carried out with an accuracy of + or - 1 part in 64,000 in magnitude and 5 arcsec in orientation (1 arcsec = 0.00028 deg).

Acuna, M. H.↗
NASA NTRS1981

Geometric dilution of precision in Global Positioning System navigation

The evaluation of the GPS navigation performance is essentially equivalent to the computation of the diagonal terms of the geometric dilution of precision (GDOP) matrix. Certain theoretical results concerning the general properties of the GDOP matrix are obtained. An efficient algorithm for the computation of the GDOP matrix and the navigation performance index is given; and applications of the results are illustrated by numerical examples.

Fang, B. T.↗
NASA NTRS1980

Precision orbit determination software validation experiment

This paper presents the results of an experiment which was designed to ascertain the level of agreement between GEODYN and UTOPIA, two completely independent computer programs used for precision orbit determination, and to identify the sources which limit the agreement. For a limited set of models and a seven-day data set arc length, the altitude components of the ephemeris obtained by the two programs agree at the sub-centimeter level throughout the arc.

Schutz, B. E.↗
NASA NTRS1981

Precision flux density measurements of the giant planets at 8420 MHz

Precision measurements of the 3.56 cm flux densities of Jupiter, Saturn, Uranus, and Neptune are reported. The results are compared with previously published measurements as a means of: (1) remotely sensing long-term changes in the microwave emission from the atmospheres of these planets; (2) measuring the effects of Saturn's rings on the disk temperature as observed from earth at different ring inclination angles.

Turegano, J. A.↗
NASA NTRS1980

Design of a high precision microwave reflector

Development of a high accuracy spherical microwave reflector to support contour RMS and pointing requirements for a new series of space instruments is reported. The reflector system is composed of precision machined aluminum tile reflectors supported from a eutectic coated graphite epoxy structure by flexures. Several basic technologies have been integrated into a manufacturing process that accommodates fabrication techniques of both optical and composite constraints. The optical figure and its change due to thermal gradient was measured in a thermal vacuum environment with a Ronchi system. The radiometer system is in support of the Microwave Limb Sounder, an experiment to measure emissions from earth's atmospheric limb thus obtaining wind, temperature, pressure and chemical composition measurements.

Noller, E. W.↗
NASA NTRS1982

Precise Sealing of Fused-Quartz Ampoules

New technique rapidly evacuates and seals fused-quartz ampoule with precise clearance over contents without appreciably thinning ampoule walls. Quartz plug is lowered into working section of ampoule after ampoule has been evacuated. Plug is then fused to ampoule walls, forming vacuum seal. New technique maintains wall strength and pumping speed.

Debnan, W. J. J.↗
NASA NTRS1983

Formulas for Precise Transverse Mercator Projection

Transverse mercator projection, surface of Earth or other spheroid is mapped onto cylinder tangent at meridian of longitude. New method performs mapping by means of mathematical series in which higher order terms correct for deviation from exact sphericity. New method yields precise geodetic maps.

Wallis, D. E.↗
NASA NTRS1981

Techniques for increasing the efficiency of Earth gravity calculations for precision orbit determination

Two techniques were analyzed. The first is a representation using Chebyshev expansions in three-dimensional cells. The second technique employs a temporary file for storing the components of the nonspherical gravity force. Computer storage requirements and relative CPU time requirements are presented. The Chebyshev gravity representation can provide a significant reduction in CPU time in precision orbit calculations, but at the cost of a large amount of direct-access storage space, which is required for a global model.

Smith, R. L.↗
NASA NTRS1982

Proceedings of the Thirteenth Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting

Proceedings of an annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting are summarized. A transparent view of the state-of-the-art, an opportunity to express needs, a view of important future trends, and a review of relevant past accomplishments were considered for PTTI managers, systems engineers, and program planner. Specific aims were: to provide PTTI users with new and useful applications, procedures, and techniques; to allow the PTTI researcher to better assess fruitful directions for research efforts.

Wardrip, S. C.↗
NASA NTRS1982

Precise time and time interval users, requirements and specifications

The functional areas of application of Precise Time and Time Interval (PTTI) were considered and expanded. A comprehensive overview of the PTTI requirements and applications would provide an opportunity for individuals working in a specific functional area. Mutual problems, requirements, applications or successes shared by those in other functional areas were studied. Based upon the results of a two year study a compendium of PTTI requirements, applications and the means of meeting the requirements among Department of Defense components, other government agencies and major commercial users was compiled and is presented. It was found that the planning process for PTTI support for new acquisitions or new programs was less than a well defined, coordinated process. The processes are described in general terms and a generic model for requirements determination and subsequent coordination which may enhance the planning process and introduce cost benefits to the program is also presented.

Bowser, J. R.↗
NASA NTRS1982

Precision of spiral-bevel gears

The kinematic errors in spiral bevel gear trains caused by the generation of nonconjugate surfaces, by axial displacements of the gears during assembly, and by eccentricity of the assembled gears were determined. One mathematical model corresponds to the motion of the contact ellipse across the tooth surface, (geometry I) and the other along the tooth surface (geometry II). The following results were obtained: (1) kinematic errors induced by errors of manufacture may be minimized by applying special machine settings, the original error may be reduced by order of magnitude, the procedure is most effective for geometry 2 gears, (2) when trying to adjust the bearing contact pattern between the gear teeth for geometry 1 gears, it is more desirable to shim the gear axially; for geometry II gears, shim the pinion axially; (3) the kinematic accuracy of spiral bevel drives are most sensitive to eccentricities of the gear and less sensitive to eccentricities of the pinion. The precision of mounting accuracy and manufacture are most crucial for the gear, and less so for the pinion.

Litvin, F. L.↗
NASA NTRS1982

Evaluation of SMART sensor displays for multidimensional precision control of Space Shuttle remote manipulator

An enhanced proximity sensor and display system was developed at the Jet Propulsion Laboratory (JPL) and tested on the full scale Space Shuttle Remote Manipulator at the Johnson Space Center (JSC) Manipulator Development Facility (MDF). The sensor system, integrated with a four-claw end effector, measures range error up to 6 inches, and pitch and yaw alignment errors within + or 15 deg., and displays error data on both graphic and numeric displays. The errors are referenced to the end effector control axes through appropriate data processing by a dedicated microcomputer acting on the sensor data in real time. Both display boxes contain a green lamp which indicates whether the combination of range, pitch and yaw errors will assure a successful grapple. More than 200 test runs were completed in early 1980 by three operators at JSC for grasping static and capturing slowly moving targets. The tests have indicated that the use of graphic/numeric displays of proximity sensor information improves precision control of grasp/capture range by more than a factor of two for both static and dynamic grapple conditions.

Bejczy, A. K.↗
NASA NTRS1981

Precision flux density measurements of the giant planets at 8420 MHz

Precision measurements of the 3.56 cm flux densities of Jupiter, Saturn, Uranus, and Neptune are reported. The results are compared with previously published measurements as a means of: remotely sensing long-term changes in the microwave emission from the atmospheres of these planets and measuring the effects of Saturn's rings on the disk temperature as observed from earth at different ring inclination angles.

Turegano, J. A.↗