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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

The effects of localized damping on structural response

The effect of localized structural damping on the excitability of higher order normal modes of the large space telescope was investigated. A preprocessor computer program was developed to incorporate Voigt structural joint damping models in a NASTRAN finite-element dynamic model. A postprocessor computer program was developed to select critical modes for low-frequency attitude control problems and for higher frequency fine-stabilization problems. The mode selection is accomplished by ranking the flexible modes based on coefficients for rate gyro, position gyro, and optical sensors, and on image-plane motions due to sinusoidal or random power spectral density force and torque inputs.

Merchant, D. H.↗
NASA NTRS1975

The use of local basis functions in unsteady aerodynamics

This paper reports a successful demonstration of using local basis functions to solve Kussner's integral equation for unsteady airloads. Pressure basis functions are defined over relatively small subsets of the aerodynamic surface and are zero elsewhere. This formulation combines the accuracy and smoothness of distribution methods with the simplicity and versatility of panel methods. Application is made to subsonic compressible flow about oscillating planar surfaces with controls. Numerical results are presented. Convergence with respect to panel size, extensions to more general classes of solutions, and areas needing additional investigation are discussed.

Fromme, J.↗
NASA NTRS1974

Determination of local values of gas and liquid mass flux in highly loaded two-phase flow

A measurement system using a deceleration probe was designed for determining the local values of gas and liquid mass flux in various gas/liquid droplet sprayfields. The system was used to characterize two-phase flowfields generated by gas/liquid rocket-motor injectors. Measurements were made at static pressures up to 500 psia and injected mass flow ratios up to 20. The measurement system can also be used at higher pressures and in gas/solid flowfields.

Burick, R. J.↗
NASA NTRS1975

Stability of localized plasma model in two and three dimensions

Stability against catastrophic radial collapse is demonstrated for initially well-behaved, localized solutions in a class of two- and three-dimensional wave equations characterized by saturating nonlinearities, which model various electrostatic and electromagnetic 'caviton' structures in an asymptotically uniform plasma. This result contrasts sharply with mathematical predictions of equations with low-order nonlinearities. Discrete classes of possible quasistationary modes exhibit features comparable to atomic wave functions and differ qualitatively from one-dimensional structures.

Wilcox, J. Z.↗
NASA NTRS1975

Heterodyne spectroscopy of astronomical and laboratory sources at 8.5 microns using diode laser local oscillators

The first 8.5 microns infrared heterodyne spectrometer has been constructed using tuneable semiconductor (PbSe) diode lasers and was used to measure absorption line profiles of N2O in the laboratory, as well as black-body emission from the moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz (6 millionths of a micron), and the minimum detectable (black-body) power was approximately 1 times 10 to the minus 16th power W for 8 min of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.

Mumma, M.↗
NASA NTRS1975

A tether tension control law for tethered subsatellites deployed along local vertical

A tethered subsatellite deployed along the local vertical is in stable equilibrium. This applies equally to subsatellites deployed in the direction towards the earth from the main spacecraft or away from the earth. Momentary perturbations from this stable equilibrium will result in a swinging motion, which decays very slowly if passive means are relied upon to provide damping. A control law is described which actively damps the swinging motion by employing a reel, or other mechanism, to apply appropriate tension as a function of tetherline length, rate of change of length, and desired length. The same control law is shown to be useful for deployment and retrieval of tethered subsatellites in addition to damping to steady state.

Rupp, C. C.↗
NASA NTRS1975

Ohio's statewide land use inventory: An operational approach for applying LANDSAT data to state, regional and local planning programs

The programmatic, technical, user application, and cost factors associated with the development of an operational, statewide land use inventory from LANDSAT data are described. The LANDSAT multispectral data are subjected to geometrical and categorical processing to produce map files for each of the 200 fifteen (15) minute quads covering Ohio. Computer compatible tapes are rescanned to produce inventory tapes which identify eight (8) Level I land use categories and a variety of Level II categories. The inventory tapes are processed through a series of ten (10) software programs developed by the State of Ohio. The net result is a computerized inventory which can be displayed in map or tabular form for various geographic units, at a variety of scales and for selected categories of usage. The computerized inventory data files are applied to technical programs developed by the various state agencies to be used in state, regional, and local planning programs.

Baldridge, P. E.↗
NASA NTRS1975

Land use, state and local users

The state and local and land use sessions involved a cross section of the expanding community of government managers who use remotely sensed information to make programmatic decisions. Problems that can be inferred from the presentations and resulting discussion are addressed. Recommendations are also given to facilitate utilization of remote sensing technology.

Parrish, C. M., III↗
NASA NTRS1975

Multidimensional stochastic approximation using locally contractive functions

A Robbins-Monro type multidimensional stochastic approximation algorithm which converges in mean square and with probability one to the fixed point of a locally contractive regression function is developed. The algorithm is applied to obtain maximum likelihood estimates of the parameters for a mixture of multivariate normal distributions.

Lawton, W. M.↗
NASA NTRS1975

Land use/state and local users, summary

Alternative approaches to remote sensing applications in state and local resource management problems are discussed. Examples of application of remotely sensed data are given. User requirements for future applications are emphasized.

Parrish, C. M., III↗
NASA NTRS1976

Study of short-haul aircraft operating economics. Phase 2: An analysis of the impact of jet modernization on local service airline operating costs

The objectives of this phase of the study were (1) to assess the 10 year operating cost trends of the local service airlines operating in the 1965 through 1974 period, (2) to glean from these trends the technological and operational parameters which were impacted most significantly by the transition to newer pure jet, short haul transports, and effected by changing fuel prices and cost of living indices, and (3) to develop, construct, and evaluate an operating cost forecasting model which would incorporate those factors which best predicted airline total operating cost behavior over that 10-year period.

Andrastek, D. A.↗
NASA NTRS1976

Results of an investigation to determine local flow characteristics at the air data probe locations using an 0.030-scale model (45-0) of the space shuttle vehicle orbiter configuration 140A/B (modified) in the NASA Ames Research Center unitary plan wind tunnel (OA161, A, B, C), volume 1

Results are presented of wind tunnel test 0A161 of a 0.030-scale model 45-0 of the configuration 140A/B (modified) space shuttle vehicle orbiter in the NASA Ames Research Center Unitary Plan Wind Tunnel facilities. The purpose of this test was to determine local total and static pressure environments for the air data probe locations and relative effectiveness of alternate flight-test probe configurations. Testing was done in the Mach number range from 0.30 to 3.5. Angle of attack was varied from -8 to 25 degrees while sideslip varied between -8 and 8 degrees.

Nichols, M. E.↗
NASA NTRS1976

Is the local supercluster a physical association

A quantitative measure of the degree of concentration of a sample of galaxies toward any great circle is described and applied to the Shapley-Ames and de Vaucouleurs catalogs of bright galaxies as well as to computer-simulated catalogs of galaxies. It is found that the observed distribution can be explained as the combined result of obscuration by our Galaxy, purely local clustering on angular scales of less than about 10 deg, and our proximity to a rather large and populous cluster, the Virgo cluster. In order for this interpretation to be correct, the Virgo cluster must have a mean angular radius of the order of or greater than 15 deg. This interpretation is supported by recent measurements which do not indicate any large inhomogeneities in the motions of nearby galaxy clusters and which show that the mean recessional velocity of the Virgo cluster is consistent with a uniform Hubble expansion. If the present interpretation is correct, it may be possible to determine the Hubble constant directly from measurements of individual distance indicators (such as H II regions and the brightest stars) with distance moduli less than about 32.

Bahcall, J. N.↗
NASA NTRS1976

A local diffusion process associated with the sweeping of energetic particles by Io

A local, turbulent diffusion process which may rapidly refill the partial cavity of energetic particles created by Io's passage through a flux tube is discussed. A model is developed of Io's sweeping action on energetic particles in which a wake is formed behind the flux tube threading Io. It is shown to be possible that this wake contains an excess of positive charge, thereby creating an electric field. The particle drift produced by this field, coupled with the density gradient of energetic protons, can generate an instability. It is this instability that is responsible for the turbulent diffusion process. The sweeping of energetic particles is also discussed in relation to particle energy and pitch angle distribution.

Huba, J. D.↗
NASA NTRS1976

Ultraviolet observations of cool stars. V - The local density of interstellar matter

A high-resolution Copernicus observation of the chromospheric Ly-alpha emission line of the nearby (3.3 pc) K dwarf epsilon Eri sets limits on the velocity, the velocity dispersion, and the density of atomic hydrogen in the local interstellar medium. Analysis shows that the interstellar Ly-alpha absorption is on the flat portion of the curve of growth. An upper limit of 0.12 per cu cm is derived for the atomic-hydrogen density. The value of this density is 0.08 (plus or minus 0.04 per cu cm if the velocity-dispersion parameter is 9 km/s, corresponding to a temperature of 5000 K. Also, the interstellar deuterium Ly-alpha line may be present in the spectrum.

Mcclintock, W.↗
NASA NTRS1976

Gas absorption cell photometer for rocket observations of local interstellar helium

A photometer sensitive in the 584-A line of He I, incorporating a helium-gas absorption cell, has been developed. The helium is confined at a pressure of 0.2 torr between thin-metal-foil broad-band ultraviolet filters. The cell contains sufficient helium to absorb 584-A radiation scattered from atmospheric helium. The ratio of fluxes seen with the cell full and empty provides a valuable datum for fitting models of the local interstellar medium, which is independent of solar 584-A flux, interstellar helium density, and photometer sensitivity.-

Freeman, J.↗
NASA NTRS1976

Local vertical motions and kinetic temperature from AE-C as evidence for aurora-induced gravity waves

In situ measurements of local vertical neutral particle motions have been made using the Neutral Atmosphere Temperature Instrument (NATE) on Atmosphere Explorer-C from observations of the direction of flow of neutral particles into the antechamber of the sensor (mass spectrometer). Values ranging from a few to more than 80 meters per second have been observed. The data show vertical motions greater than a few meters per second to be present most of the time, the magnitude being a function of many factors including magnetic activity, location, and magnetic storm history. In a specific case, it is concluded that the observed vertical motions and kinetic temperature are evidence of a travelling disturbance originating as a gravity wave in the auroral zone.

Spencer, N. W.↗