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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Two dimensional imaging observations of meter-decameter bursts associated with the February 1986 flare activity

An analysis is presented of the two dimensional imaging observations of a flare observed on 3 Feb. l986 using the Clark Lake Multifrequency Radioheliograph. The flare produced almost all types of Meter-decimeter radio emission: enhanced storm radiation, type III/V bursts, II and IV and flare continuum. The flare continuum had early (FCE) and late (FC II) components and the type II occurred during the period between these two components. Comparing the source positions of type III/V and FCE it was found that these bursts must have occurred along adjacent open and closed field lines, respectively. The positional analysis of type II and FC II implies that the nonthermal electrons responsible for FC II need not be accelerated by type II shock and this conclusion is further supported by the close association of FC II with a microwave peak. Using the positional and temporal analysis of all these bursts and the associated hard X-ray and microwave emissions, a schematic model is developed for the magnetic field configuration in the flaring region in which the nonthermal particles responsible for these bursts are confined or along which they propagate.

Gopalswamy, N.↗
NASA NTRS1986

Balloon-borne three-meter telescope for far-infrared and submillimeter astronomy

The study and revision of the gimbal design of the Three-Meter Balloon Borne Telescope (TMBBT) is discussed. Efforts were made to eliminate the alignment and limited rotation problems inherent in the flex-pivot design. A new design using ball bearings to replace the flex-pivots was designed and its performance analyzed. An error analysis for the entire gondola pointing system was also prepared.

Fazio, Giovanni G.↗
NASA NTRS1987

Pressure distributions from high Reynolds number transonic tests of an NACA 0012 airfoil in the Langley 0.3-meter transonic cryogenic tunnel

Tests were conducted in the 2-D test section of the Langley 0.3-meter Transonic Cryogenic Tunnel on a NACA 0012 airfoil to obtain aerodynamic data as a part of the Advanced Technology Airfoil Test (ATAT) program. The test program covered a Mach number range of 0.30 to 0.82 and a Reynolds number range of 3.0 to 45.0 x 10 to the 6th power. The stagnation pressure was varied between 1.2 and 6.0 atmospheres and the stagnation temperature was varied between 300 K and 90 K to obtain these test conditions. Tabulated pressure distributions and integrated force and moment coefficients are presented as well as plots of the surface pressure distributions. The data are presented uncorrected for wall interference effects and without analysis.

Ladson, Charles L.↗
NASA NTRS1988

Optical links in the angle-data assembly of the 70-meter antennas

In the precision-pointing mode the 70 meter antennas utilize an optical link provided by an autocollimator. In an effort to improve reliability and performance, commercial instruments were evaluated as replacement candidates, and upgraded versions of the existing instruments were designed and tested. The latter were selected for the Neptune encounter, but commercial instruments with digital output show promise of significant performance improvement for the post-encounter period.

Nelson, M. D.↗
NASA NTRS1988

Seventy-meter antenna performance predictions: GTD analysis compared with traditional ray-tracing methods

A comparative analysis was performed, using both the Geometrical Theory of Diffraction (GTD) and traditional pathlength error analysis techniques, for predicting RF antenna gain performance and pointing corrections. The NASA/JPL 70 meter antenna with its shaped surface was analyzed for gravity loading over the range of elevation angles. Also analyzed were the effects of lateral and axial displacements of the subreflector. Significant differences were noted between the predictions of the two methods, in the effect of subreflector displacements, and in the optimal subreflector positions to focus a gravity-deformed main reflector. The results are of relevance to future design procedure.

Schredder, J. M.↗
NASA NTRS1986

High Reynolds number tests of a Douglas DLBA 032 airfoil in the Langley 0.3-meter transonic cryogenic tunnel

A wind-tunnel investigation of a Douglas advanced-technology airfoil was conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT). The temperature was varied from 227 K (409 R) to 100 K (180 R) at pressures ranging from about 159 kPa (1.57 atm) to about 514 kPa (5.07 atm). Mach number was varied from 0.50 to 0.78. These variables provided a Reynolds number range (based on airfoil chord) from 6.0 to 30.0 x 10 to the 6th power. This investigation was specifically designed to: (1) test a Douglas airfoil from moderately low to flight-equivalent Reynolds numbers, and (2) evaluate sidewall-boundary-layer effects on transonic airfoil performance characteristics by a systematic variation of Mach number, Reynolds number, and sidewall-boundary-layer removal. Data are included which demonstrate the effects of fixing transition, Mach number, Reynolds number, and sidewall-boundary-layer removal on the aerodynamic characteristics of the airfoil. Also included are remarks on model design and model structural integrity.

Johnson, Charles B.↗
NASA NTRS1988

Aerodynamic performance and pressure distributions for a NASA SC(2)-0714 airfoil tested in the Langley 0.3-meter transonic cryogenic tunnel

This report presents in graphic and tabular forms the aerodynamic coefficient and surface pressure distribution data for a NASA SC(2)-0714 airfoil tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. The test was another in a series of tests involved in the joint NASA/U.S. Industry Advanced Technology Airfoil Tests program. This 14% thick supercritical airfoil was tested at Mach numbers from 0.6 to 0.76 and angles of attack from -2.0 to 6.0 degrees. The test Reynolds numbers were 4 million, 6 million, 10 million, 15 million, 30 million, 40 million, and 45 million.

Jenkins, Renaldo V.↗
NASA NTRS1988

X-band noise temperature near the Sun at a 34-meter high efficiency antenna

The X-band system noise temperature near the Sun was measured at the DSS 15, a 34 meter high efficiency (HEF) antenna, in November 1987. Data was taken at angles off the center of the Sun from 0 to 4 degrees. At angles greater than 0.5 degree, the measured results agree with Voyager tracking data taken at solar conjunction in late December 1987. Within the solar disk, at angles lower than 0.27 degree, the temperature measured was lower than the prediction of a model by 30 percent, after adjusting for known receiver nonlinearities. The discrepancy in this extreme case is probably caused by unknown nonlinearities in the receiver, uncertainties in the model, or both. The measurement is nevertheless credible for practically all Sun-Earth-probe angles of interest to deep space missions.

Rebold, T. A.↗
NASA NTRS1986

Calibration of a 1 meter diameter normal incidence extreme ultraviolet telescope/spectrometer

A 1-meter normal incidence telescope, with a normal incidence concave diffraction grating spectrometer at its focus, has been developed. The instrument's spectral coverage is 350 to 1150A with a spectral resolution of 5A and a peak effective area of 6 sq cm at 500A. The instrument was launched on an Aries sounding rocket on November 27, 1983 in an effort to determine the hydrogen and helium abundance in the local interstellar medium. A description of this instrument, with the primary emphasis on the methods used to calibrate it, is presented.

Jelinsky, Patrick↗
NASA NTRS1987

Undercooling of bulk high temperature metals in the 100 meter drop tube

The 100-meter drop tube at NASA Marshall Space Flight Center provides an excellent opportunity to study the effects of containerless, microgravity processing in metals and alloys. In a series of experiments high melting temperature pure metals were melted in an electron beam furnace and dropped in vacuum. Sample sizes ranged from 0.175 to 1.2 grams. Large undercoolings on the order of 18 percent of the melting temperature were observed in Ti, Zr, Nb, Mo, Rh, Ta, and Pt. Undercoolings of 5 to 18 percent T(m) were observed in Ru and Ir. These undercooling results are consistent, repeatable, and occur in a high percentage of experiments. The experimental technique will be presented as well as the resultant microstructures of undercooled drops. The data will be discussed with respect to nucleation theory.

Hofmeister, William↗
NASA NTRS1987

Voyager-Neptune telemetry - The DSN 70 meter antenna upgrade

The Deep Space Network (DSN) is responsible for the acquisition of in-situ science and engineering measurements and navigation data from spacecraft exploring the Solar System. Key characteristics of the DSN design approach, the costs to upgrade performance over the past several decades, and some fundamental constraints on performance are discussed. The specific 70-meter upgrade task and the resulting overall benefits to Voyager-Neptune and the mission set are addressed.

Hall, Justin R.↗
NASA NTRS1987

Space ten-meter telescope (STMT) - Structural and thermal feasibility study of the primary mirror

The structural and thermal behavior of a ten-meter primary mirror for a space optical/near-IR telescope in geosynchronous orbit is studied. The glass-type lightweighted mirror is monolithic, of the double arch type, and is supported at only three points. The computer programs SSPTA (thermal), NASTRAN (finite element), and ACCOS V (optical) are used in sequence to determine the temperature, deformation, and optical performance of the mirror. A mirror temperature of 130 K or less appears to be obtainable by purely passive means. With a fused silica or standard Zerodur blank, thermally-induced deformation is unacceptable and cannot be fully corrected by an active secondary mirror over the desired field. Either active thermal control or a blank of lower thermal expansion coefficient would be required.

Bely, Pierre Y.↗
NASA NTRS1988

A simplified oil-film skin-friction meter

The oil-film method of skin friction measurement, which does not require calibration, nevertheless entails that interferometric measurements of the oil film be obtained. The oil-film method is presently simplified by eliminating interferometry and its requisite polished surface, by taking direct and dynamic measurements of the oil-film slope with a small position-sensing photodiode. This technique has undergone verification in incompressible turbulent and laminar flows in flat-plate boundary layers and pipe flows; the meter is judged to be inexpensive, simple, and robust.

Bandyopadhyay, P. R.↗
NASA NTRS1988

DSN 64-meter antenna L-band (1668-MHz) microwave system performance overview

In 1985, L-band (1668 MHz) receive-only feed systems were installed on the three Deep Space Network 64 meter antennas to provide tracking support for two non-NASA spacecraft. The specifications, design approach, and operational test results are presented. The L-band microwave system met all of its tracking goals and is currently being upgraded to include a C-band (5000 MHz) uplink.

Withington, J.↗
NASA NTRS1988

Sidewall boundary-layer measurements with upstream suction in the Langley 0.3-meter transonic cryogenic tunnel

The Langley 0.3 Meter Transonic Cryogenic Tunnel has provision for boundary removal from the sidewalls to reduce sidewall interference effects on the test data. The tests carried out to determine the change in the empty test section sidewall boundary layer thickness at the model station with upstream boundary layer mass removal are described. The boundary layer measurements showed that the upstream removal region is effective in reducing the boundary layer thickness at the model station. The boundary layer displacement thickness reduced from about 1.2 percent to about .4 percent of the test section width. The boundary layer velocity profiles followed a power law variation in the outer region and showed good correlation when plotted in terms of boundary layer momentum thickness.

Murthy, A. V.↗
NASA NTRS1988

Automatic inspection of analog and digital meters in a robot vision system

A critical limitation of most of the robots utilized in industrial environments arises due to their inability to utilize sensory feedback. This forces robot operation into totally preprogrammed or teleoperation modes. In order to endow the new generation of robots with higher levels of autonomy techniques for sensing of their work environments and for accurate and efficient analysis of the sensory data must be developed. In this paper detailed development of vision system modules for inspecting various types of meters, both analog and digital, encountered in a robotic inspection and manipulation tasks are described. These modules are tested using industrial robots having multisensory input capability.

Trivedi, Mohan M.↗
NASA NTRS1989

NASA SC(2)-0714 airfoil data corrected for sidewall boundary-layer effects in the Langley 0.3-meter transonic cryogenic tunnel

This report presents the corrected aerodynamic data for A NASA SC(2)-0714 airfoil tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. This test was another in the series of tests involved in the joint NASA/U.S. industry Advanced Technology Airfoil Tests program. This 14 percent thick critical airfoil was tested at Mach numbers from 0.6 to 0.76 and angles of attack from -2.0 to 6.0 deg. The test Reynolds numbers were 4 million, 6 million, 10 million, 15 million, 30 million, 40 million, and 45 million. Corrections for the effects of the sidewall boundary layer have been made. The uncorrected data were previously published in NASA Technical Memorandum 4044.

Jenkins, Renaldo V.↗
NASA NTRS1989

RF performance measurement of the DSS-14 70-meter antenna at C-band/L-band

The calibration of the 70-meter antenna at C-band (5.01 GHz) and L-band (1.668 GHz) is described. This calibration comes after a modification to an existing L-band feed to include the C-band frequencies. The test technique employs noise-adding radiometers and associated equipment running simultaneously at both frequencies. The test procedure is described including block diagrams, and results are presented for efficiency, system temperature, and pointing.

Gatti, M. S.↗