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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 1,495 records · Page 83

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NASA NTRS1987

Radial force balance within Jupiter's dayside magnetosphere

A local field stress technique, developed previously in a study of the Saturnian magnetosphere, is introduced to the problem of determining the radial force balance characteristics of Jupiter's magnetosphere. The near-equatorial, radial magnetic force densities are estimated using the data obtained by Voyager 1 principally on the dayside (inbound) portion of its trajectory. Using the low-energy charged particle data (greater than about 30 keV) and other published data, ways in which the field forces might be balanced are explored. Inside 22 Jupiter radii, the magnetic radial forces match, in both magnitude and radial variation, the hot particle pressure gradient forces, assuming a mix of H(+) and O(n+) ions. Outside 22 Jupiter radii, a previously reported force balance problem is confirmed qualitatively, and two possible solutions are suggested.

Mauk, B. H.↗

NASA NTRS1988

Calculating Atmospheric Effects In Satellite Imagery: Part 2

Practical computational techniques developed. Report discusses practical considerations of calculation of three-dimensional radiative transfer. Extension of earlier theoretical developments described in "Calculating Atmospheric Effects in Satellite Imagery" NPO-16373.

Diner, David J.↗

NASA NTRS1988

Electrochemical Growth Of Crystals In Gels

Nucleation and growth rates readily controlled. Technique developed to grow crystals by controlling rate of transfer of one component into crystallization volume. Method involves electrochemically controlled generation of one of precipitation species, coupled with diffusion barrier. New procedure, developed in connection with formation of lead tin telluride by reaction in gels of metal ions with telluride ions.

Barber, Patrick G.↗

NASA NTRS1988

Microstructure Of MnBi/Bi Eutectic Alloy

Collection of three reports describes studies of directional solidification of MnBi/Bi eutectic alloy. Two of the reports, "Influence of Convection on Lamellar Spacing of Eutectics" and "Influence of Convection on Eutectic Microstructure," establish theoretical foundation for remaining document. Reports seek to quantify effect of convection on concentration field of growing lamellar eutectic. Remaining report, "Study of Eutectic Formation," begins by continuing theoretical developments. New technique under development by one of the authors helps to reveal three-dimensional microstructures of alloys.

Wilcox, William R.↗

NASA NTRS1988

Preventing Arc Welding From Damaging Electronics

Shielding technique developed to protect sensitive electronic equipment from damage due to electromagnetic disturbances produced by arc welding. Established acceptable alternative in instances in which electronic equipment cannot be removed prior to arc welding. Guidelines established for open, unshielded welds. Procedure applicable to robotics or computer-aided manufacturing.

Sargent, Noel↗

NASA NTRS1988

Powder-Metallurgy Process And Product

Rapid-solidification processing yields alloys with improved properties. Study undertaken to extend favorable property combinations of I/M 2XXX alloys through recently developed technique of rapid-solidification processing using powder metallurgy(P/M). Rapid-solidification processing involves impingement of molten metal stream onto rapidly-spinning chill block or through gas medium using gas atomization technique.

Paris, Henry G.↗

NASA NTRS1987

Institute for Computational Mechanics in Propulsion (ICOMP) first year summary

The Institute for Computational Mechanics in Propulsion (ICOMP) in Cleveland, Ohio, is operated jointly by Case Western Reserve University and the NASA Lewis Research Center. The purpose of ICOMP is to develop techniques to improve problem-solving capabilities in all aspects of computational mechanics related to propulsion. The Institute began operation in 1985. Described are the events leading to its formation, its organization and method of operation, and the technical activities of the first year.

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NASA NTRS1988

Advanced simulation and analysis of a geopotential research mission

Computer simulations have been performed for an orbital gradiometer mission to assist in the study of high degree and order gravity field recovery. The simulations were conducted for a satellite in near-circular, frozen orbit at a 160-km altitude using a gravitational field complete to degree and order 360. The mission duration is taken to be 32 days. The simulation provides a set of measurements to assist in the evaluation of techniques developed for the determination of the gravity field. Also, the simulation provides an ephemeris to study available tracking systems to satisfy the orbit determination requirements of the mission.

Schutz, B. E.↗

NASA NTRS1986

Low-disturbance wind tunnels

During the past years, there was an extensive program under way at the Langley Research Center to upgrade the flow quality in several of the large wind tunnels. This effort has resulted in significant improvements in flow quality in these tunnels and has also increased the understanding of how and where changes in existing and new wind tunnels are most likely to yield the desired improvements. As part of this ongoing program, flow disturbance levels and spectra were measured in several Langley tunnels before and after modifications were made to reduce acoustic and vorticity fluctuations. A brief description of these disturbance control features is given for the Low-Turbulence Pressure Tunnel, the 4 x 7 Meter Tunnel, and the 8 Foot Transonic Pressure Tunnel. To illustrate typical reductions in disturbance levels obtained in these tunnels, data from hot-wire or acoustic sensors are presented. A concept for a subsonic quiet tunnel designed to study boundary layer stability and transition is also presented. Techniques developed at Langley in recent years to eliminate the high intensity and high-frequency acoustic disturbances present in all previous supersonic wind tunnels are described. In conclusion, the low-disturbance levels present in atmospheric flight can now be simulated in wind tunnels over the speed range from low subsonic through high supersonic.

Beckwith, I. E.↗

NASA NTRS1988

Thematic mapper study of Alaskan ophiolites

The two principle objectives of the project Thematic Mapper Study of Alaskan Ophiolites were to further develop techniques for producing geologic maps, and to study the tectonics of the ophiolite terrains of the Brooks Range and Ruby Geanticline of northern Alaska. Ophiolites, sections of oceanic lithosphere emplaced along island arcs and continental margins, are important to the understanding of mountain belt evolution. Ophiolites also provide an opportunity to study the structural, lithologic, and geochemical characteristics of ocean lithosphere, yielding a better understanding of the processes forming lithosphere. The first part of the report is a description of the methods and results of the TM mapping and gravity modeling. The second part includes papers being prepared for publication. These papers are the following: (1) an analysis of basalt spectral variations; (2) a study of basalt geochemical variations; (3) an examination of the cooling history of the ophiolites using radiometric data; (4) an analysis of shortening produced by thrusting during the Brooks Range orogeny; and (5) a study of an ophiolite using digital aeromagnetic and topographic data. Additional papers are in preparation.

Bird, John M.↗

NASA NTRS1988

Institute for Computational Mechanics in Propulsion (ICOMP)

The Institute for Computational Mechanics in Propulsion (ICOMP) is operated jointly by Case Western Reserve University and the NASA Lewis Research Center in Cleveland, Ohio. The purpose of ICOMP is to develop techniques to improve problem-solving capabilities in all aspects of computational mechanics related to propulsion. Described are the activities of ICOMP during 1987.

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NASA NTRS1987

Structure of unsteady flows at leading- and trailing-edges: Flow visualization and its interpretation

Unsteady two- and three-dimensional flow structure at leading and trailing edges of bodies can be characterized effectively using recently developed techniques for acquisition and interpretation of flow visualization. The techniques addressed here include: flow image/surface pressure correlations; 3-D reconstruction of flow structure from flow images; and interactive interpretation of flow images with theoretical simulations. These techniques can be employed in conjunction with: visual correlation and ensemble-averaging, both within a given image and between images; recognition of patterns from images; and estimates of velocity eigenfunctions from images.

Rockwell, D.↗

NASA NTRS1988

The Shuttle Imaging Radar B (SIR-B) experiment report

The primary objective of the SIR-B experiment was to acquire multiple-incidence-angle radar imagery of a variety of Earth's surfaces to better understand the effects of imaging geometry on radar backscatter. A complementary objective was to map extensive regions of particular interest. Under these broad objectives, many specific scientific experiments were defined by the 43 SIR-B Science Team members, including studies in the area of geology, vegetation, radar penetration, oceanography, image analysis, and calibration technique development. Approximately 20 percent of the planned digital data were collected, meeting 40 percent of the scientific objectives. This report is an overview of the SIR-B experiment and includes the science investigations, hardware design, mission scenario, mission operations, events of the actual missions, astronaut participation, data products (including auxiliary data), calibrations, and a summary of the actual coverage. Also included are several image samples.

Cimino, Jo Bea↗

NASA NTRS1988

Thrust chamber thermal barrier coating techniques

Methods for applying thermal barrier coatings to the hot-gas side wall of rocket thrust chambers in order to significantly reduce the heat transfer in high heat flux regions was the focus of technology efforts for many years. This paper describes a successful technique developed by the Lewis Research Center that starts with the coating of a mandrel and then builds the thrust chamber around it by electroforming appropriate materials. This results in a smooth coating with exceptional adherence, demonstrated in hot fire rig tests. The low cycle fatigue life of chambers with coatings applied in this manner was increased dramatically compared to uncoated chambers.

Quentmeyer, Richard J.↗

NASA NTRS1988

The SAMEX Vector Magnetograph: A Design Study for a Space-Based Solar Vector Magnetograph

This report presents the results of a pre-phase A study performed by the Marshall Space Flight Center (MSFC) for the Air Force Geophysics Laboratory (AFGL) to develop a design concept for a space-based solar vector magnetograph and hydrogen-alpha telescope. These are two of the core instruments for a proposed Air Force mission, the Solar Activities Measurement Experiments (SAMEX). This mission is designed to study the processes which give rise to activity in the solar atmosphere and to develop techniques for predicting solar activity and its effects on the terrestrial environment.

Hagyard, M. J.↗

NASA NTRS1987

A solar chromosphere and spicule model based on far-infrared limb observations

Techniques developed for LTE radiative transfer problems in a rough atmosphere were used to compute a model chromosphere containing spicules consistent with high-resolution solar limb observations from 100 microns to 2.6 mm. The model consists of a smooth, plane-parallel temperature minimum region extending from the photosphere to a height of 1000 km and randomly distributed cylindrical spicules above this height. It is found that the observed limb brightness profiles are well fitted by spicules with electron temperatures on the order of 7000 K.

Braun, D.↗

NASA NTRS1988

The use of a helicopter mounted ranging scatterometer for estimation of extinction and scattering properties of forest canopies-II: Experimental results for high-density aspen

An analytic expression is derived that describes the backscatter power from a semi-infinite plane parallel homogeneous canopy as a function of distance from an airborne radar. This model is fitted to observed data for a high-density aspen canopy by a modification of a technique developed by Tyapkin (1960). This inversion of the model provides unbiased estimates of the canopy extinction and backscattering parameters. An active radar calibrator located underneath the canopy provides an independent method of determining the volume extinction coefficient. The results reported indicate that the coefficients change throughout the year. A comparison of these coefficients with Eom and Funk's (1984) disk model, using measured canopy properties, shows that at C-band frequency, only a part of the scattering and absorption can be attributed to the canopy leaves.

Pitts, David E.↗

NASA NTRS1988

Quasi-steady flight to quasi-steady flight transition for abort landing in a windshear - Trajectory optimization and guidance

Trajectory optimization and trajectory-guidance problems for abort-landing maneuvers in the presence of low-altitude wind shear are investigated by means of numerical simulations, with a focus on methods designed to achieve quasi-steady flight recovery (final values of the relative velocity, path inclination, and angle of attack equal to those for quasi-steady steepest climb). The derivation of the governing equations is outlined; the modeling techniques are explained; and results for a B-727 transport aircraft approaching a sea-level airfield at temperature 100 F are presented in extensive tables and graphs and characterized in detail. The techniques developed are shown to be effective in restoring the aircraft to stable quasi-steady flight.

Miele, A.↗