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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Anemometers for Mars

An investigation is conducted concerning the problems involved in the conduction of wind measurements on the planet Mars, taking into account the currently known characteristics of the Martian atmosphere. Problems introduced by the presence of the lander are examined. The suitability of several different types of anemometers for making the measurements is discussed, giving attention to rotating anemometers, sonic anemometers, ion tracers, drag force anemometers, pitot tubes, and thermal anemometers.

Henry, R. M.↗
NASA NTRS1974

Relation of solar wind fluctuations to differential flow between protons and alphas

An analysis is made of the difference between the alpha particle and proton flow velocities in the solar wind as observed by the OGO 5 satellite. The alpha and proton velocities from each of 962 spectral scans are compared with the variance of 32 solar wind flux measurements made during the scans. The average velocity difference is plotted for each of 10 logarithmic variance intervals and is seen to decrease and approach zero when the variance is high. It is shown that such an anticorrelation may be due to the fact the wave/particle interactions provide the drag force between two streams of different velocity in a collisionless plasma.

Neugebauer, M.↗
NASA NTRS1975

High-latitude ionospheric winds related to solar-interplanetary conditions

Treated jointly, two recent results imply that the distribution of winds in the polar ionosphere should change as a function of the direction of the interplanetary magnetic field. From the motions of chemically released ion and neutral clouds, it is apparent that neutral winds in the high-latitude ionosphere are driven principally by ion drag forces. OGO 6 electric field measurements demonstrate that there are definite relationships between the time/latitude distribution of ionospheric plasma convection and interplanetary magnetic field parameters, and also that the distribution is most sensitive to the azimuthal angle of the inter planetary field. Although direct neutral wind to interplanetary magnetic field comparisons are not available, logic clearly implies a close relationship. Observations of infrasonic waves following sudden ionization enhancements indicate the existence of momentum transfer.

Heppner, J. P.↗
NASA NTRS1976

Electrodynamics of long conducting tethers in the near-earth environment

An analytical approach was developed to evaluate the electrodynamic interactions affecting a thin, bare metallic wire moving in the ionosphere. The wire's diameter was smaller than the Debye length; therefore, the plasma sheath around the wire was taken into account in computing inducing drag force and torque. Computer programs were prepared for the numerical evaluation of mathematical functions that were required to compute the distribution of the potential along the wire and of the current in the wire. Numerical calculations based on this software are shown.

Dobrowolny, M.↗
NASA NTRS1976

Experimental studies on the aerodynamic performance and dynamic response of flow direction sensing vanes

Systematic investigations were performed on a variety of aerodynamic surfaces to obtain their potential for possible application to wind vanes. Among the surfaces tested were: (1) single vanes consisting of flat plates of various planforms having aspect ratios between 0.5 and 5; (2) bi-vanes with aspect ratio 2.5; (3) various cone and box vanes; and (4) various cruciform configurations. The models were subjected to windtunnel tests. In addition to lift and drag force measurements, damping and frequency test were performed under a variety of flow conditions.

Barna, P. S.↗
NASA NTRS1976

Time development of the flow about an impulsively started cylinder

A method is developed to determine the time-dependent flowfield about an impulsively started circular cylinder. An outer potential flow model is interfaced with an inner viscous flow region. The wake is described by a set of elementary point vortices. The position at which the point vortices are shed from the cylinder is obtained from a solution to the unsteady incompressible laminar boundary-layer equations. A rear shear-layer is postulated to account for backflow induced vorticity. Wake development is detailed from the initial formation of the two symmetric vortices to subsequent asymmetry and eventual alternate shedding. Unsteady pressure distributions, lift and drag forces, and Strouhal number are calculated and compared with experiment.

Deffenbaugh, F. D.↗
NASA NTRS1977

Orbital construction demonstration study. Volume 2: Technical

The following items are discussed in reference to OCDA requirements; (1) flight mechanics and control, (2) effects of sun angle, (3) disturbance torques, (4) control system requirements, (5) OCDA orbit decay profile, and (6) aerodynamic drag forces. Structural design requirements are also given as well as basic design definition.

Source record↗
NASA NTRS1977

Studies of friction and wear characteristics of various wires for wire-brush skids

The friction and wear characteristics of 22 types and sizes of wires for potential use in wire-brush skids were studied. These characteristics were determined by placing brushes made from candidate wires on a belt sander whose moving belt simulated landing roll-out distance. At the same time, the drag force and wear behavior were monitored. Data were obtained over distances up to 3048 m (10,000 ft) at preselected bearing pressures of 172 to 1034 kPa (25 to 150 psi). In general, the friction coefficient developed by the candidate wires was found to be independent of bearing pressure and ranged between 0.4 and 0.6 under the test conditions of this investigation. The friction coefficient was not degraded when the surface was wetted and appears to be independent of wire diameter except perhaps when wire size is relatively large compared with the surface asperities. Generally, the high friction demonstrated by the soft materials was accompanied by high wear rates; conversely, the hard materials provided greater wear resistance but offered lower friction. For all test wires, the wear was shown to increase with increasing bearing pressure, in general, for the same bearing pressure, wear increased with increasing wire diameter and decreased when the surface was wetted.

Dreher, R. C.↗
NASA NTRS1978

Flight tests of a radio-controlled airplane mode with a free-wing, free-canard configuration

Flight characteristics, controllability, and potential operating problems were investigated in a radio-controlled airplane model in which the wing is so attached to the fuselage that it is free to pivot about a spanwise axis forward of its aerodynamic center and is subject only to aerodynamic pitching moments imposed by lift and drag forces and a control surface. A simple technique of flying the test vehicle in formation with a pickup truck was used to obtain trim data. The test vehicle was flown through a series of maneuvers designed to permit evaluation of certain characteristics by observation. The free-wing free-canard concept was determined to be workable. Stall/spin characteristics were considered to be excellent, and no effect on longitudinal stability was observed when center of gravity changes were made. Several problems were encountered during the early stages of flight testing, such as aerodynamic lockup of the free canard and excessive control sensitivity. Lack of onboard instrumentation precluded any conclusions about gust alleviation or ride qualities.

Gee, S. W.↗
NASA NTRS1977

The origin of the grooves on Phobos

Various theories for the long, linear depressions on the surface of Phobos are reviewed. Imagery from Viking Orbiters is used to map the surface distribution of the grooves, study their morphology, and date them by means of the density of superimposed impact craters. Data is presented which tends to support the hypothesis that the deep-seated fracturing was caused by a large, nearly catastrophic cratering event. It is suggested that the grooves were produced during the creation of the Stickney crater, rather than as the result of tidal stresses induced by Mars or by drag forces during the hypothetical capture of the satellite by Mars.

Thomas, P. C.↗
NASA NTRS1979

Dispersion of sound in a combustion duct by fuel droplets and soot particles

Dispersion and attenuation of acoustic plane wave disturbances propagating in a ducted combustion system are studied. The dispersion and attenuation are caused by fuel droplet and soot emissions from a jet engine combustor. The attenuation and dispersion are due to heat transfer and mass transfer and viscous drag forces between the emissions and the ambient gas. Theoretical calculations show sound propagation at speeds below the isentropic speed of sound at low frequencies. Experimental results are in good agreement with the theory.

Miles, J. H.↗
NASA NTRS1979

System noise analysis of the dumbbell tethered satellite for gravity-gradient measurements

An analysis of the dumbbell gravity gradiometer concept for measuring short wavelength variations in the earth's gravity gradient is presented. Variations in the gradient are recorded by measuring tension variations in a vertically stabilized satellite consisting of heavy masses connected by a long wire or rod. Tension noise arises from the excitation of various mechanical oscillations of the system. The principal noise sources that were identified are fluctuations in atmospheric drag heating and drag force resulting from density variations and winds. Approximate analytical expressions are presented for the tension noise as a function of the system design parameters for various possible configurations. Computer simulations using numerical integration were performed to study the tension noise for several sample cases. Three designs consistent with Shuttle launch capabilities are discussed.

Colombo, G.↗
NASA NTRS1979

DUMAND Summer Workshop, University of California, La Jolla, Calif., July 24-September 2, 1978, Proceedings. Volume 3 - Oceanographic and ocean engineering studies

The DUMAND (Deep Underwater Muon and Neutrino Detector) array, a hexagon 800 m on a side, 673 m high, and consisting of 22,698 sensor modules, is designed to detect neutrinos in the TeV range, hadronic cascades, muons and Cerenkov radiation. Its engineering, signal processing, and logistic aspects are considered, as are its optical detection (photomultiplier tubes) system and electronics. Geological and bottom current surveys were made at two proposed sites for the array (the Maui and Keahole Point basins of Hawaii), and a study of the steady-state response of a sensor string to current drag forces is reported. Biological interference with the DUMAND array, including mechanical entanglement by large animals, bioluminescence, and especially biofouling are considered, as well as the deployment, implantment and maintenance of the array.

Wilkins, G.↗
NASA NTRS1979

Dispersion of sound in a combustion duct by fuel droplets and soot particles

Dispersion and attenuation of acoustic plane wave disturbances propagating in a ducted combustion system are studied. The dispersion and attenuation are caused by fuel droplet and soot emissions from a jet engine combustor. The attenuation and dispersion are due to heat transfer and mass transfer and viscous drag forces between the emissions and the ambient gas. Theoretical calculations show sound propagation at speeds below the isentropic speed of sound at low frequencies. Experimental results are in good agreement with the theory.

Miles, J. H.↗
NASA NTRS1980

Experimental studies of the laminar separation bubble on a two-dimensional airfoil at low Reynolds numbers

The laminar separation, transition and turbulent reattachment near the leading edge of a two-dimensional NACA 663-018 airfoil were investigated using a low speed, smoke visualization wind tunnel. Lift and drag force measurements were made using an external strain gauge balance for a chord Reynolds number range of 40,000 to 400,000. An extensive flow visualization study was performed and correlated with the force measurements. Experiments were also conducted with distributed surface roughness at the leading edge and external acoustic excitation to influence the development of the airfoil boundary layer. This study delineates the effects of angle of attack and chord Reynolds number on the separation bubble characteristics and airfoil performance

Mueller, T. J.↗
NASA NTRS1981

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces: Hydromechanically controlled system

The investigation utilized one main gear wheel, brake, and tire assembly of a McDonnell Douglas DC-9 series 10 airplane. The landing-gear strut was replaced by a dynamometer. During maximum braking, average braking behavior indexes based upon brake pressure, brake torque, and drag-force friction coefficient developed by the antiskid system were generally higher on dry surfaces than on wet surfaces. The three braking behavior indexes gave similar results but should not be used interchangeably as a measure of the braking of this antiskid sytem. During the transition from a dry to a flooded surface under heavy braking, the wheel entered into a deep skid but the antiskid system reacted quickly by reducing brake pressure and performed normally during the remainder of the run on the flooded surface. The brake-pressure recovery following transition from a flooded to a dry surface was shown to be a function of the antiskid modulating orifice.

Tanner, J. A.↗
NASA NTRS1981

Cornering characteristics of the nose-gear tire of the space shuttle orbiter

An experimental investigation was conducted to evaluate cornering characteristics of the 32 x 8.8 nose gear tire of the space shuttle orbiter. Data were obtained on a dry concrete runway at nominal ground speeds ranging from 50 to 100 knots and over a range of tire vertical loads and yaw angles which span the expected envelope of loads and yaw angles to be encountered during space shuttle landing operations. The cornering characteristics investigated included side and drag forces and friction coefficients, aligning and overturning torques, friction force moment arm, and the lateral center of pressure shift. Results of this investigation indicate that the cornering characteristics of the space shuttle nose gear tire are insensitive to variations in ground speed over the range tested. The effects on cornering characteristics of variations in the tire vertical load and yaw angle are as expected. Trends observed are consistent with trends observed during previous cornering tests involving other tire sizes.

Vogler, W. A.↗