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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

A penny shaped crack in a filament-reinforced matrix. 2: The crack problem

The elastostatic interaction problem between a penny-shaped crack and a slender inclusion or filament in an elastic matrix was formulated. For a single filament as well as multiple identical filaments located symmetrically around the crack the problem is shown to reduce to a singular integral equation. The solution of the problem is obtained for various geometries and filament-to-matrix stiffness ratios, and the results relating to the angular variation of the stress intensity factor and the maximum filament stress are presented.

Pacella, A. H.↗
NASA NTRS1977

ERDA's central receiver solar thermal power system studies

The utilization of solar energy for electrical power production was studied. Efforts underway on the central receiver solar thermal power system are presented. Preliminary designs are included of pilot plant utilizing large numbers of heliostats in a collector field. Safety hazards are also discussed, as well as the most beneficial location of such a plant within the United States.

Lippy, L. J.↗
NASA NTRS1976

Soft X-ray morphology of the Virgo, Coma, and Perseus clusters of galaxies

Soft X-ray emission profiles of the Virgo, Coma, and Perseus clusters of galaxies with 9.2-arcmin resolution are presented for the energy band from 0.5 to 3 keV. For Virgo, a profile is also given for the band from 0.1 to 0.28 keV. The profiles are compared with various models including extended and point sources, particularly a model with an extended source involving thermal bremsstrahlung from a hot gas located in the gravitational potential well of the cluster. It is found that the soft X-ray emission from Virgo is extended, symmetric, and centered on M87; that the emission from Coma is not dominated by any single galaxy; and that the emission from Perseus is centered within 3 arcmin of NGC 1275 and is narrower along a north-south axis than along the east-west axis containing the line of bright galaxies. Limits are set on the strength of possible point sources.

Malina, R.↗
NASA NTRS1978

The dynamics and control of large flexible space structures. Part A: Discrete model and modal control

Attitude control techniques for the pointing and stabilization of very large, inherently flexible spacecraft systems were investigated. The attitude dynamics and control of a long, homogeneous flexible beam whose center of mass is assumed to follow a circular orbit was analyzed. First order effects of gravity gradient were included. A mathematical model which describes the system rotations and deflections within the orbital plane was developed by treating the beam as a number of discretized mass particles connected by massless, elastic structural elements. The uncontrolled dynamics of the system are simulated and, in addition, the effects of the control devices were considered. The concept of distributed modal control, which provides a means for controlling a system mode independently of all other modes, was examined. The effect of varying the number of modes in the model as well as the number and location of the control devices were also considered.

Bainum, P. M.↗
NASA NTRS1978

Thermal integration of Spacelab experiments

The method of thermally integrating the experiments for Spacelab is discussed. The scientific payload consists of a combination of European and United States sponsored experiments located in the module as well as on a single Spacelab pallet. The thermal integration must result in accomodating the individual experiment requirements as well as ensuring that the total payload is within the Spacelab Environmental Control System (ECS) resource capability. An integrated thermal/ECS analysis of the module and pallet is performed in concert with the mission timeline to ensure that the agreed upon experiment requirements are accommodated and to ensure the total payload is within the Spacelab ECS resources.

Patterson, W. C.↗
NASA NTRS1978

Modal control of the planar motion of a long flexible beam in orbit

Attitude control techniques for the pointing and stabilization of very large, inherently flexible spacecraft systems are investigated. The attitude dynamics and control of a long, homogeneous flexible beam whose center of mass is assumed to follow a circular orbit is analyzed. In this study, first order effects of gravity-gradient are included, whereas external perturbations and related orbital station keeping maneuvers are neglected. A mathematical model which describes the system deflections within the orbital plane has been developed by treating the beam as having a maximum of three discretized mass particles connected by massless, elastic structural elements. The uncontrolled dynamics of this system are simulated and, in addition, the effects of the control devices are considered. The concept of distributed modal control, which provides a means for controlling a system mode independently of all other modes, is examined. The effect of varying the number of modes in the model as well as the number and location of the control devices are also considered.

Sellappan, R.↗
NASA NTRS1978

An analysis of the first two years of GASP data

Distributions of mean ozone levels from the first two years of data from the NASA Global Atmospheric Sampling Program (GASP) show spatial and temporal variations in agreement with previous measurements. The standard deviations of these distributions reflect the large natural variability of ozone levels in the altitude range of the GASP measurements. Monthly mean levels of ozone below the tropopause show an annual cycle with a spring maximum which is believed to result from transport from the stratosphere. Correlations of ozone with independent meteorological parameters, and meteorological parameters obtained by the GASP systems show that this transport occurs primarily through cyclogenesis at mid-latitudes. The GASP water vapor data, analyzed with respect to the location of the tropopause, correlates well with the simultaneously obtained ozone and cloud data.

Holdeman, J. D.↗
NASA NTRS1981

Natural Laminar Flow Flight Experiment

A supercritical airfoil section was designed with favorable pressure gradients on both the upper and lower surfaces. Wind tunnel tests were conducted in the Langley 8 Foot Transonic Pressure Tunnel. The outer wing panels of the F-111 TACT airplane were modified to incorporate partial span test gloves having the natural laminar, flow profile. Instrumentation was installed to provide surface pressure data as well as to determine transition location and boundary layer characteristics. The flight experiment encompassed 19 flights conducted with and without transition fixed at several locations for wing leading edge sweep angles which varied from 10 to 26 at Mach numbers from 0.80 to 0.85 and altitudes of 7620 meters and 9144 meters. Preliminary results indicate that a large portion of the test chord experienced laminar flow.

Steers, L. L.↗
NASA NTRS1984

Electron precipitation zones around major ground-based VLF signal sources

The spatial distribution of electron precipitation induced by VLF signals from ground-based transmitters is determined by using a test particle computer model of the gyroresonant wave-particle interaction (Inan et al., 1982). The results are presented as contours of energy flux on a map of the region around each transmitter. It is shown that the size of the precipitation zones is a strong function of the geographic location of the transmitter, as well as its radiated power and operating frequency. In general, the precipitation zones are much wider in longitude than in latitude and are oriented along lines of constant geomagnetic latitude. Assuming backscatter and/or wave echoing, precipitation zones around the points that are magnetically conjugate to the sources are also estimated. The results presented can be used to interpret satellite- or ground-based measurements of the precipitation induced by ground-based VLF transmitters.

Inan, U. S.↗
NASA NTRS1985

Reversal ion source - A new source of negative ion beams

A new type of ion source utilizing beams of electrons and target molecules, rather than a diffuse, volume plasma, is described. The source utilizes an electrostatic electron 'mirror' which reverses trajectories in an electron beam, producing electrons at their turning point having a distribution of velocities centered at zero velocity. A gas which attaches zero-velocity electrons is introduced at this turning point. Negative ions are produced by an attachment or dissociative attachment process. For many of the thermal electron-attaching molecules the cross sections can be quite large, varying as the inverse square root of the electron energy or just the s-wave threshold law. The efficiency and current density of the ion source for production of Cl(-) through the large, thermal energy attachment process is estimated. It is argued that the source can be used for the production of negative ions through attachment resonances located at higher energies as well.

Orient, O. J.↗
NASA NTRS1986

Development of a ROT22 - DATAMAP interface

This report (Contract NAS2-10331- Mod 10), outlines the development and validation of an interface between the three-dimensional transonic analysis program ROT22 and the Data from Aeromechanics Test and Analytics-Management and Analysis Package (DATAMAP). After development of the interface, the validation is carried out as follows. First, the DATAMAP program is used to analyze a portion of the Tip Aerodynamics and Acoustics Test (TAAT) data. Specifically, records 2872 and 2873 are analyzed at an azimuth of 90 deg, and record 2806 is analyzed at 60 deg. Trim conditions for these flight conditions are then calculated using the Bell performance prediction program ARAM45. Equivalent shaft, pitch, and twist angles are calculated from ARAM45 results and used as input to the ROT22 program. The interface uses the ROT22 results and creates DATAMAP information files from which the surface pressure contours and sectional pressure coefficients are plotted. Twist angles input to ROT22 program are then iteratively modified in the tip region until the computed pressure coefficients closely match the measurements. In all cases studied, the location of the shock is well predicted. However, the negative pressure coefficients were underpredicted. This could be accounted for by blade vortex interaction effects.

Shenoy, K. R.↗
NASA NTRS1987

Mass transport by Aeolian saltation on Earth, Mars and Venus: The effects of full saltation cloud development and choking

Wind tunnel tests were conducted to study the characteristics of particle motion and the quantity transported by wind under a variety of planetary environmental conditions. Analysis of the results indicates that, on Earth, saltation fully develops at near-threshold wind speeds and rarely chokes (retarding of saltation due to high particle concentration and subsequent increase of mid-air collisions). On Mars, saltation becomes fully developed only at favorable locations and at wind speeds well above threshold. The Martian saltation cloud has an insufficient particle concentration to cause choking, particularly over a partially rocky surface. On Venus, full saltation occurs at wind speeds very near threshold, but saltation flux increases less rapidly than expected at relatively modest wind speeds due to choking.

Williams, S. H.↗
NASA NTRS1987

Heat generation in Aircraft tires under yawed rolling conditions

An analytical model was developed for approximating the internal temperature distribution in an aircraft tire operating under conditions of yawed rolling. The model employs an assembly of elements to represent the tire cross section and treats the heat generated within the tire as a function of the change in strain energy associated with predicted tire flexure. Special contact scrubbing terms are superimposed on the symmetrical free rolling model to account for the slip during yawed rolling. An extensive experimental program was conducted to verify temperatures predicted from the analytical model. Data from this program were compared with calculation over a range of operating conditions, namely, vertical deflection, inflation pressure, yaw angle, and direction of yaw. Generally the analytical model predicted overall trends well and correlated reasonably well with individual measurements at locations throughout the cross section.

Dodge, Richard N.↗
NASA NTRS1988

Slender wing theory including regions of embedded total pressure loss

An aerodynamic theory of the flow about slender delta wings is described. The theory includes a treatment of the self-consistent development of the vortex wake patterns above the wing necessary to maintain smooth flow at the wing edges. The paper focuses especially on the formation within the wake of vortex 'cores' as embedded regions of total pressure loss, fed and maintained by umbilical vortex sheets emanating from the wing edges. Criteria are developed for determining the growing size and location of these cores, as well as the distribution and strength of the vorticity within them. In this paper, however, the possibility of vortex breakup is omitted. The aerodynamic consequences of the presence and evolution of the cores and the associated wake structure are illustrated and discussed. It is noted that wake history effects can have substantial influence on the distribution of normal force on the wing as well as on its magnitude.

Mccune, James E.↗
NASA NTRS1989

Remote sensing information sciences research group: Browse in the EOS era

The problem of science data browse was examined. Given the tremendous data volumes that are planned for future space missions, particularly the Earth Observing System in the late 1990's, the need for access to large spatial databases must be understood. Work was continued to refine the concept of data browse. Further, software was developed to provide a testbed of the concepts, both to locate possibly interesting data, as well as view a small portion of the data. Build II was placed on a minicomputer and a PC in the laboratory, and provided accounts for use in the testbed. Consideration of the testbed software as an element of in-house data management plans was begun.

Estes, John E.↗
NASA NTRS1989

Locating damaged members in a truss structure using modal test data - A demonstration experiment

An experiment is designed to demonstrate and verify the performance of the on-orbit assessment approach for large flexible space truss structures. The on-orbit assessment approach can be accomplished, in principle, with dynamic response information, structural identification methods, and model correlation techniques which produce an adjusted mathematical model. An optimal update of the structure model is formed using the response data, then examined to locate damaged members. The experiment uses a laboratory scale model truss structure which exhibits characteristics expected for large space truss structures. Vibration experiments are performed to generate response data for the damaged truss. The damage location approach is described, as well as analytical work performed in support of the vibration tests, the measured response of the test article, and some preliminary results.

Smith, Suzanne Weaver↗
NASA NTRS1989

Toward a CFD nose-to-tail capability - Hypersonic unsteady Navier-Stokes code validation

Computational fluid dynamics (CFD) research for hypersonic flows presents new problems in code validation because of the added complexity of the physical models. This paper surveys code validation procedures applicable to hypersonic flow models that include real gas effects. The current status of hypersonic CFD flow analysis is assessed with the Compressible Navier-Stokes (CNS) code as a case study. The methods of code validation discussed to beyond comparison with experimental data to include comparisons with other codes and formulations, component analyses, and estimation of numerical errors. Current results indicate that predicting hypersonic flows of perfect gases and equilibrium air are well in hand. Pressure, shock location, and integrated quantities are relatively easy to predict accurately, while surface quantities such as heat transfer are more sensitive to the solution procedure. Modeling transition to turbulence needs refinement, though preliminary results are promising.

Edwards, Thomas A.↗