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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Evolution, calibration, and operational characteristics of the two-dimensional test section of the Langley 0.3-meter transonic cryogenic tunnel

Presented is a review of the development of the world's first cryogenic pressure tunnel, the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT). Descriptions of the instrumentation, data acquisition systems, and physical features of the two-dimensional 8- by 24-in, (20.32 by 60.96 cm) and advanced 13- by 13-in (33.02 by 33.02 cm) adaptive-wall test-section inserts of the 0.3-m TCT are included. Basic tunnel-empty Mach number distributions, stagnation temperature distributions, and power requirements are included. The Mach number capability of the facility is from about 0.20 to 0.90. Stagnation pressure can be varied from about 80 to 327 K.

Ladson, Charles L.↗
NASA NTRS1987

Calculated 70-meter antenna performance for offset L-band and C-band feeds

A series of calculations that were carried out in order to determine the performance of the new dual-shaped 70 meter antenna for feeds that are displaced from the focal ring are summarized. Calculations were carried out at 1.68 GHz (L-band) and 5.0 GHz (C-band) for a number of feed/subreflector configurations. The effects of feed displacement, feed pointing angle, subreflector tilt, and lateral subreflector movement are summarized. Of specific interest are gain, beam squint, and spillover noise temperature for each of the feed/subreflector configurations described above.

Hoppe, D.↗
NASA NTRS1987

Compound-taper feedhorn for the DSN 70-meter antennas

A novel X-band feedhorn was designed for the Deep Space Network (DSN) 70-meter antennas. The feedhorn is a compound-taper structure consisting of a corrugated flared section and a corrugated straight section. This feedhorn is designed to closely initiate the characteristics of the standard feedhorn, while providing the proper phase center location, without adding any significant loss to the system. The use of the existing feedhorn and the ease of manufacturing the corrugated straight section have resulted in major overall cost savings.

Manshadi, F.↗
NASA NTRS1987

A new linear quadratic optimal controller for the 34-meter high efficiency antenna position loop

The design of a new position loop controller for the 34-meter High Efficiency Deep Space antennas using linear quadratic (LQ) optimal control techniques is discussed. The LQ optimal control theory is reviewed, and model development and verification are discussed. Families of optimal gain vectors are generated by varying weight parameters. Performance specifications were used to select a final gain vector. Estimator dynamics were selected and the corresponding gain vectors were computed. Final estimator selection was based on position, commanded rate, and estimator error responses.

Nickerson, J. A.↗
NASA NTRS1986

Microstructures of niobium-germanium alloys processed in inert gas in the 100 meter drop tube

The 100 meter drop tube at NASA's Marshall Space Flight Center has been used for a series of experiments with niobium-germanium alloys. These experiments were conducted with electromagnetic levitation melting in a 200 torr helium environment. Liquid alloys experienced large degrees of undercooling prior to solidification in the drop tube. Several interesting metastable structures were observed. However, the recalescence event prevented extended solid solubility of germanium in the A-15 beta phase. Liquids of eutectic composition were found to undercool in the presence of solid alpha and solid Nb5Ge3.

Bayuzick, R. J.↗
NASA NTRS1986

The laser interferometer skin-friction meter - A numerical and experimental study

Limits to the applicability of thin-film lubrication theory are established. The following two problems are considered: (1) the response of the oil film to a time-varying skin friction such as is encountered in turbulent boundary layers, and (2) a 'surface-wave instability' encountered at high skin-friction levels. Results corresponding to the first problem reveal that the laser interferometer skin-friction meter may, in principle, be applied to the measurement of instantaneous skin friction. In addressing the second problem, it is shown that the observed surface waves are not the result of a hydrodynamic instability.

Murphy, J. D.↗
NASA NTRS1987

A transition detection study using a cryogenic hot film system in the Langley 0.3-meter transonic cryogenic tunnel

A transition detection study was conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT) using a specialized hot film system designed specifically for use in cryogenic wind tunnels. The quantitative transition location data obtained at near cryogenic conditions, 360 deg R (200K) represents the first definitive transition Reynolds numbers obtained in a cryogenic wind tunnel. The model was tested at both adiabatic and nonadiabatic wall conditions with a wall-to-total temperature ratio as low as 0.47. The test results indicated an improved technique for hot-film installation and a modified data acquisition system would allow the on-line determination of the location of boundary layer transition in cryogenic wind tunnels, such as the U.S. National Transonic Facility.

Johnson, C. B.↗
NASA NTRS1986

A summary of Reynolds number effects on some recent tests in the Langley 0.3-meter transonic cryogenic tunnel

Reynolds number effects noted from selected test programs conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (0.3-m TCT) are discussed. The tests, which cover a unit Reynolds number range from about 2.0 to 80.0 million per foot, summarize effects of Reynolds number on: (1) aerodynamic data from a supercritical airfoil, (2) results from several wall interference correction techniques, and (3) results obtained from advanced, cryogenic tests techniques. The test techniques include: (1) use of a cryogenic sidewall boundary layer removal system, (2) detailed pressure and hot wire measurements to determine test section flow quality, and (3) use of a new hot film system suitable for transition detection in a cryogenic wind tunnel. The results indicate that Reynolds number effects appear most significant when boundary layer transition effects are present and at high lift conditions when boundary layer separation exists on both the model and the tunnel sidewall.

Johnson, C. B.↗
NASA NTRS1986

A summary of the effects of Reynolds number on drag divergence for airfoils tested in the Langley 0.3-meter transonic cryogenic tunnel

The direct first order effect of Reynolds number on the determination of drag-divergence conditions is summarized for six airfoils which were tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. A second order effect, derived through the effect of Reynolds number on the sidewall boundary layer, is included. In addition, a comparison of how the drag divergence condition is affected on going from one class of airfoil to another is presented. The drag-divergence condition is affected first order by Reynolds number for each of the six airfoils and of course all data are affected second order, since the presence of the boundary layer necessitates a sidewall correction.

Jenkins, Renaldo V.↗
NASA NTRS1987

Quasi-static shape adjustment of a 15 meter diameter space antenna

A 15 meter diameter Hoop-Column antenna has been analyzed and tested to study shape adjustment of the reflector surface. The Hoop-Column antenna concept employs pretensioned cables and mesh to produce a paraboloidal reflector surface. Fabrication errors and thermal distortions may significantly reduce surface accuracy and consequently degrade electromagnetic performance. Thus, the ability to adjust the surface shape is desirable. The shape adjustment algorithm consisted of finite element and least squares error analyses to minimize the surface distortions. Experimental results verified the analysis. Application of the procedure resulted in a reduction of surface error by 38 percent. Quasi-static shape adjustment has the potential for on-orbit compensation for a variety of surface shape distortions.

Belvin, W. Keith↗
NASA NTRS1986

Diffraction-limited 10 microns imaging with 3 meter telescopes

An IR imaging system that achieves diffraction-limited spatial resolution (about 0.8 arcsec) at 10 microns on 3-meter ground-based telescopes. The system uses a linear array of sensitive HgCdTe photodiodes, scanned in the direction perpendicular to the array axis, to form two-dimensional images. Scans are completed rapidly enough to freeze atmospheric fluctuations. Individual detectors are small compared to the diameter of the Airy disk, and images are oversampled heavily in the scan direction. This method has a number of advantages for studying small fields with very high spatial resolution, and has been applied successfully to the problem of directly imaging faint circumstellar dust shells.

Bloemhof, E. E.↗
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.↗