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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Side forces on a tangent ogive forebody with a fineness ratio of 3.5 at high angles of attack and Mach numbers from 0.1 to 0.7

An experimental investigation was conducted in the Ames 12-Foot Wind Tunnel to determine the subsonic aerodynamic characteristics, at high angles of attack, of a tangent ogive forebody with a fineness ratio of 3.5. The investigation included the effects of nose bluntness, nose strakes, nose booms, a simulated canopy, and boundary-layer trips. The forebody was also tested with a short afterbody attached. Static longitudinal and lateral-directional stability data were obtained at Reynolds numbers ranging from 0.3 mil. to 3.8 mil. (based on base diameter) at a Mach number of 0.25, and at a Reynolds number of 0.8 mil. at Mach numbers ranging from 0.1 to 0.7. Angle of attack was varied from 0 to 88 deg at zero sideslip, and the sideslip angle was varied from -10 to 30 deg at angles of attack of 40, 55, and 70 deg.

Keener, E. R.↗
NASA NTRS1976

Side forces on a tangent ogive forebody with a fineness ratio of 2.5 at high angles of attack and low speed

A wind tunnel study to determine the subsonic aerodynamic characteristics, at high angles of attack, of a tangent ogive forebody with a fineness ratio of 2.5, is reported. Static longitudinal and lateral-directional stability data were obtained at Reynolds numbers ranging from 0.4 x 1 million to 3.7 x 1 million (based on base diameter) at a Mach number of 0.25. Angle of attack was varied from 36 deg to 88 deg at zero sideslip. It was found that at low Reynolds numbers the forebody does not have a side force att high angles of attack; however, at Reynolds numbers above about 2 x 1 million, a side force occurs in the angle of attack range from 45 deg to 80 deg. The maximum side force is as large as the maximum normal force. The maximum normal force coefficient varies between 1.0 and 2.0 over the Reynolds number range tested and occurs at angles of attack near 65 deg.

Keener, E. R.↗
NASA NTRS1977

Glass fining experiments in zero gravity

Ground based experiments were conducted to demonstrate that thermal migration actually operated in glass melts. Thermal migration consistent with the theory was found in one experiment on a borax melt, i.e., there was an approximately linear relation between the bubble diameter and bubble velocity for a given temperature and temperature gradient. It also appeared that nearby bubbles were attracted to one another, which could greatly aid fining. Interpretation of these results was not possible because of complications arising from gravity, i.e., floating of the bubbles, circulation currents due to buoyancy-driven natural connection, and flow of the melt out from the cell.

Smith, H. D.↗
NASA NTRS1977

Detection of forbidden S III fine-structure emission in ionized nebulae

The 3P2-3P1 fine-structure line of doubly ionized sulfur has been detected at 534.41 + or - 0.03 kaysers in the spectra of NGC 7027, BD +30 deg 3639, and G333.6-0.2. The abundance of S(2+) and the electron density are discussed. The ionization of G333.6-0.2 is lower than expected from its luminosity.

Greenberg, L. T.↗
NASA NTRS1977

Fine energy resolution survey of the sky with a germanium gamma-ray spectrometer

A fine-energy-resolution survey (38 to 2700 keV) of the sky has been performed from a spinning polar-orbiting satellite with a cooled germanium spectrometer. The measurements, performed with a fast time resolution (32 ms), permit one to analyze the energy spectra from repeated noon-midnight orbits in selected portions of the local daytime or nighttime sky. During the initial period of the experiment, the sky was surveyed in two broad intervals spanning the galactic plane at longitudes of approximately 255 to 328 deg and 99 to 168 deg, respectively. In the former interval a significant increase in counting rate was observed when the spectrometer viewed the galactic plane. Locally generated backgrounds were removed from the galactic-plane spectrum by subtracting, on a spin-for-spin basis, the contribution measured at a viewing direction with a comparable declination north of the celestial equator. The net spectra from the galactic plane have been examined for evidence of gamma-ray lines. The possible presence of lines near 1121 and 1369 keV emitted from the galactic plane over the galactic longitudinal interval approximately 255 deg to approximately 328 deg is suggested by the data, but better statistics are needed to establish their existence firmly. Comparisons are made with previously reported extraterrestrial lines with assumed normalizations made for the different viewing directions in the two experiments.

Imhof, W. L.↗
NASA NTRS1977

Apollo 14 coarse fines (4-10 mm) sample location and classification

The 4 to 10 mm sieve fraction from the soil samples collected during the Apollo 14 Mission was identified and described. Examination and description of the fines were carried out in nitrogen-filled, stainless steel cabinets during a general examination of the Apollo 14 sample collection. Each particle was held between forceps, dusted in a jet of N2, and placed on a teflon-covered stage. They were examined with a binocular microscope, separated by lithology, and the lithologic types described. Weights of individual particles in the fraction ranged from about 0.10 to 0.50 gm, large enough in size for studies of age, chemistry, and petrology to be accomplished.

Kramer, F. E.↗
NASA NTRS1977

Optimal fine pointing control of a large space telescope using an Annular Momentum Control Device

This paper discusses the application of an Annular Momentum Control Device (AMCD) to fine pointing control of a large space telescope (LST). The AMCD represents a new development in the field of momentum storage devices. A linearized mathematical model is developed for the AMCD/LST system, including the magnetic suspension actuators. Two approaches to control system design are considered. The first approach uses a stochastic linear-quadratic Gaussian controller which utilizes feedback of all states. The second approach considers a more practical control system design in which the axial and radial loops are designed independently.

Nadkarni, A. A.↗
NASA NTRS1978

Statistical models of summer rainshowers derived from fine-scale radar observations

A statistical modeling of rain cell characteristics is presented; the modeling is based on high-resolution radar measurements of the cell structure. The analysis of the fine-scale three-dimensional structure of summer rainshowers in the mid-Atlantic region leads to statistical descriptions of the rain cells in terms of a variety of physical cell parameters. Core reflectivity profiles, contour area, and altitude extent of the cells have been determined along with the frequency of occurrence for various storm classes and categories. The statistical descriptions of the rain cells for the mid-Atlantic region were compared to descriptions for other areas, and the similarities and differences are described. Simplified models of rain cells based on the statistical descriptions are developed for the different rain categories as a function of frequency of occurrence.

Konrad, T. G.↗
NASA NTRS1975

A geochemical and petrographic study of 1-2-mm fines from Apollo 17

Samples of fines less than 1-mm and 155 1-2 mm particles from several Apollo 17 sites were analyzed for Na, Sc, Cr, Mn, Fe, Co, Ni, Hf, Ta, Th, and REE. Products of comminution and construction are present in the 1-2 mm particles, and the compositions of the rock fragments clearly indicate the general chemical characteristics of their parent rock types. The likely sources of materials for the glassy particles are considered. Glasses are enriched over their parent soils in Fe, Sc, Mn, and Cr, and are relatively enriched in light REE, so that some chemical fractionation accompanies glass-forming processes. Elements were determined by instrumental neutron activation analysis.

Blanchard, D. P.↗
NASA NTRS1975

The fine-scale lunar magnetic field

Measurements conducted with the aid of the Apollo 15 subsatellite reported by Coleman et al. (1972) showed that the lunar field was detectable at an altitude of 100 km. Since that time there has been much activity in mapping the lunar magnetic field from orbit. A review is presented of the mapping procedure used in producing lunar field maps and an investigation is conducted of the altitude dependence of the lunar magnetic field which significantly affects these maps. Attention is also given to the history of lunar magnetic field maps, the fine-scale maps, low-altitude Apollo 16 maps, the altitude dependence, and the source of the magnetization of the lunar crust. It is found that the strong altitude dependence evident in the records is different for the three components.

Russell, C. T.↗
NASA NTRS1978

ISEE-C attitude determination using fine sun sensor data only

Techniques developed to determine the spin axis attitude using Fine Sun Sensor (FSS) data only are described. At any given time, the Sun angle specifies the orientation of the spin axis relative to the sunline. The instantaneous time rate of change of the sun angle is directly proportional to the orientation of the spin axis relative to a reference plane that is normal to the ecliptic. Thus, the spin axis attitude can be determined when sufficient data has been collected to accurately measure the rate of change of the sun angle. The uncertainties can be computed directly from the uncertainties in the coefficients of the smoothed sun angle curve. The FSS-only technique is unique in that ephemeris vectors are required only to transform the attitude results to more conventional coordinate frames. The combination of the mission geometry and the FSS accuracy make ISEE-C an ideal mission for applying this method. However, the technique can be used on other missions, such as spin stabilized geosynchronous missions.

Gunshol, L. P.↗
NASA NTRS1979

Fine particulate capture device

To capture fine particulate matter in a gas such as air, a dielectric fluid is directed to the center of whichever face of a rotating disc is exposed to the air flow. The disc is comprised of two or more segments which bear opposite electrostatic potentials. As the dielectric fluid is centrifuged towards the periphery of the rotating disc, the fluid becomes charged to the same potential as the segment over which it is passing. Particulate matter is attracted to the charged segment and is captured by the fluid. The fluid then carries the captured particulate matter to a collection device such as a toroidal container disposed around the periphery of the disc. A grounded electrically-conductive ring may be disposed at the outer periphery of the disc to neutralize the captured particles and the fluid before they enter the container.

Peterson, V. S.↗
NASA NTRS1979

Properties and performance of fine-filament bronze-process Nb3Sn conductors

Fine-filament bronze-process Nb3Sn superconductors were fabricated to fulfill stringent requirements on critical current under tension in a one-inch bend diameter, current density, stability, and conductor losses. A large fraction of niobium filaments was incorporated in a bronze matrix, and a cable containing 4453 2-micron diameter filaments in each of six strands provided a current density of 85,000 A/sq cm at 10 to the -11th ohm-cm, 10 T, and 4.2 K. The next step was to incorporate copper stabilizer in a conductor with 20,538 filaments. These conductors, fabricated so that bend strains of about 1% would be experienced by the filaments in the one-inch bend, stably carried currents in the 200-500 A range. A quench current of 540 A in a 5-cm bend corresponds to 158,000 A/sq cm in the bronze and filament area, believed to be the highest critical current density reported for multifilamentary Nb3Sn.

Walker, M. S.↗
NASA NTRS1979

Fine-structure lines and elemental abundances in the Orion Nebula

Infrared observations of the forbidden fine-structure lines of Ne II at 12.81 microns, S IV at 10.51 microns, and Ar III at 8.99 microns in the Orion Nebula are presented. These measurements are combined with optical observations of forbidden Ne III, S II, S III, O II, and O III to derive total elemental abundances of neon, sulfur, and oxygen, Ne/H = 7.91, S/H = 7.34, and O/H = 8.60, which are very similar to solar abundances. While the commonly employed ionization correction formula scheme is found to work satisfactorily for neon, the method overcompensates for the abundance of S(3+) and leads to a higher sulfur abundance than is actually present, though the net discrepancy in the elemental abundance of sulfur in Orion is small.

Lester, D. F.↗
NASA NTRS1980

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

Hot isostatically pressed powder metallurgy Astroloy was obtained which contained 1.4 percent fine porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores averaged about 2 micrometers diameter and 20 micrometers spacing. They did influence fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 micrometers pore in one specimen resulting from a hollow particle did not reduce life by 60 percent. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in sigma sub u/E for the porous material.

Miner, R. V., Jr.↗
NASA NTRS1979

Observations of far-infrared fine structure lines - Forbidden O III 88.35 microns and forbidden O I 63.2 microns

Results are presented for observations of the fine-structure lines of forbidden O III at 88.35 microns and forbidden O I at 63.2 microns in a number of sources by means of an airborne far-IR spectrometer. The sources M17, NGC 7538, and W51 are mapped in the forbidden O III line with a resolution of 1 arcmin, and the emission peak is found to coincide with the maximum radio continuum in all cases. The far-IR continuum is simultaneously mapped where possible; the continuum peak is shown to be distinct from the center of ionization in the same three sources. The forbidden O III line is also detected in W3, W49, and several positions in M42 (Orion). The forbidden O I line is detected in M17, in M42, and marginally in DR 21. An unsuccessful search for the J = 1-0 transition of HD at 112 microns in the direction of the Kleinmann-Low nebula is also reported.

Storey, J. W. V.↗
NASA NTRS1979

Space Telescope fine guidance - A design for manufacturability

The NASA Space Telescope (ST) is a 2.4-m aperture, f/24 Ritchey-Chretien telescope coupled to five on-board astronomical scientific packages. The very accurate line-of-sight stability required by ST during operating periods of up to 24 hours is maintained by the Pointing Control System whose optical system, the Fine Guidance Subsystem (FGS), is described. The Pointing Control System includes three identical FGSs, any two of which provide line-of-sight stabilization by tracking guide stars while the third performs astrometry. The optical system for the ST FGS performs the field aberration correction within the FGS near a pupil plane measuring only 52.7 mm. The design is simple and easily corrected, and offers substantial advantages over the traditional approach in terms of manufacturability.

Friedman, I.↗
NASA NTRS1980

Far infrared fine structure lines in the interstellar medium

Fine structure lines in the far infrared possess properties that make them useful tools for diagnosing astrophysical plasmas. The line ratios are sensitive and accurate probes of density, elemental abundances, and ionization structure. Studies of line shapes and Doppler shifts should prove valuable in studies of the gross dynamics of H II regions and galaxies. In the present paper, the theory involved in the interpretation of these lines is reviewed, and available observations are summarized.

Watson, D. M.↗