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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Region one Birkeland currents connecting to sunward convecting flux tubes

On the basis of Birkeland current observations, analytic stability arguments demonstrate that there may be a sector within the plasma sheet in the night side magnetosphere where plasma pressures are reduced relative to the surrounding regions. Physical arguments, in addition to this analysis, imply that a depleted region near the center of the magnetotail would be stable against the interchange instability, thereby generating currents of the same sense as the region-1 currents. The depleted region is presently simulated by means of computer experiments based on the Rice Convection Model. Results indicate that flux tube content gradients across the tailward boundary can cause region-1 currents to flow along sunward-convecting flux tubes, in general agreement with satellite data.

Karty, J. L.↗
NASA NTRS1984

Space station - The world connection

NASA has expressed an interest in acquiring foreign partners for its upcoming permanent, manned space station program who will participate as builders, operators and users, and will invest a significant portion of the financial and developmental research resources entailed by this ambitious undertaking. Cooperation, then, will not come to an end upon delivery of the hardware developed by a foreign partner, but will continue on the basis of ownership of the hardware and responsibility for its engineering and operational management. Attention is presently given to the prospective contributions of Canada, the European Space Agency, and Japan.

Freitag, R. F.↗
NASA NTRS1985

Series Connection of Solar Cells

Roll soldering from continuous string of cells. Automatic, continuous process attaches interconnecting strips to series string of silicon solar cells. Manufacturing process attaches each conductor from positive side of one cell to negative side of next. For reliability, 22 contacts are soldered on each side of each cell.

Keenan, R.↗
NASA NTRS1985

Electrically Connecting to Pressure Vessels

Resilient conductive disk eliminates need for holes in vessel walls. Grounding disk made from wire and solder and sandwiched between electrical-component support and pressure-vessel wall. Emplaced in component support, disk squeezed to 66 percent of its thickness. Disk conforms to surfaces of support and vessel wall when support attached to wall with adhesive. Disk thus forms reliable electrical contact from support (and its electrical component) to wall.

Rossi, P. J.↗
NASA NTRS1984

Asteroid-meteorite connection: Regolith effects implied by lunar reflectance spectra

The effect of soil formation on the spectral characteristics of asteroids were estimated in situ properties of materials affected by the space environment other than those associated with agglutinates. In his initial survey of the reflectance properties of lunar samples, J.B. Adams measured a few chips from the exterior and interior of Apollo rocks. For Apollo 12 basalts 12053-12063 , the exterior and interior spectra exhibited strong absorption bands which were very similar in nature; the exterior fragment was a bit brighter, which was attributed to microbrecciation. Mature lunar soils measured undisturbed surface areas at the landing sites. It was hypothesized that freshly exposed material at fresh impact craters should be comparable to powdered rock samples in the laboratory. This expected trend seemed to be true with the early reflectance data, but as the more complete near-infrared data has become available it is clear that there is no simple correspondence of rock type (laboratory powder or chip measurement) to freshly exposed surface material (telescopic measurements of fresh crater classes).

Pieters, C. M.↗
NASA NTRS1985

Stellar Winda: Observational Evidence for a Hot-cool Star Connection

Stellar wind data was collected for a total of 272 stars representing all spectral types including Wolf-Rayet stars. Two significant correlations are found relating the wind luminosity (L sub w = 1/2 MV sub infinity squared) to the bolometric luminosity and the terminal velocity of the stellar wind to the stellar effective temperature. Least-squared fits to the data suggest that the wind luminosity is approximately the bolometric luminosity squared and the terminal velocity is approximately the effective temperature to the 1.8 power. The surprising result is that all spectral types throughout the HR diagram are represented in these correlations.

Waldron, W. L.↗
NASA NTRS1984

On the connection between multigrid and cyclic reduction

A technique is shown whereby it is possible to relate a particular multigrid process to cyclic reduction using purely mathematical arguments. This technique suggest methods for solving Poisson's equation in 1-, 2-, or 3-dimensions with Dirichlet or Neumann boundary conditions. In one dimension the method is exact and, in fact, reduces to cyclic reduction. This provides a valuable reference point for understanding multigrid techniques. The particular multigrid process analyzed is referred to here as Approximate Cyclic Reduction (ACR) and is one of a class known as Multigrid Reduction methods in the literature. It involves one approximation with a known error term. It is possible to relate the error term in this approximation with certain eigenvector components of the error. These are sharply reduced in amplitude by classical relaxation techniques. The approximation can thus be made a very good one.

Merriam, M. L.↗
NASA NTRS1985

Attitude Control Tradeoff Study Between the Use of a Flexible Beam and a Tether Configuration for the Connection of Two Bodies in Orbit

Sometimes it is necessary to mount a payload remotely from the main body of a spacecraft or space station. The reasons for this vary from vibration isolation to avoidance of measurement contamination. For example the SP-100 project, which grew out of the increased interest in nuclear power in space for space stations and for deep space explorations, requires separation of the nuclear reactor from the user because of vibration, heat and radiation. The different attitude control problems for beam and tether configurations are discussed. The beam configuration uses a conservative design approach. The vibration, beam flexibility and deployment concerns are analyzed. The tether configuration offers some very attractive design features, but not without several thorny problems. These problems are analyzed. One configuration will be recommended for the main thrust of the SP-100 design effort based on attitude control considerations.

Graff, S. H.↗
NASA NTRS1985

On the connection between the 3HE-enrichment and spectral index of solar energetic particles

A model is presented which explains the observed tendency of events with large 3He/4He ratios to have steeper spectra. In this model preferential injection of 3He, acceleration by Alfven waves and Coulomb deceleration of ions are considered simultaneously. The observed tendency may be obtained as a result of competition between injection and acceleration processes.

Kocharov, L. G.↗
NASA NTRS1985

The modulation features of the long-period cosmic ray variations in connection with the sign change of the general magnetic field of the Sun

On the basis of the model and experimental investigations, the spatial distribution of cosmic ray anisotropy for the different epochs of solar activity is studied. A solution is offered to the anisotropic diffusion equation with regard to the electromagnetic conditions for the periods of minimum and maximum solar activity and cosmic ray particle drift in a regular interplanetary magnetic field. It is shown that the long period changes amplitude and phase of the diurnal variations of cosmic rays is limited not only by convection and diffusion of particles but also by the drift effect before and after the sing change of the general magnetic field of the Sun. The calculated model is compared with the results obtained on the basis of an analysis of the experimental data from the neutron super monitor station, and it is shown that for the periods when the lines of magnetic force of the Sun come from the Northern Hemisphere the phase of the first harmonic diurnal variation is shifted forwards to an earlier time.

Iskra, K.↗
NASA NTRS1984

The flight planning - flight management connection

Airborne flight management systems are currently being implemented to minimize direct operating costs when flying over a fixed route between a given city pair. Inherent in the design of these systems is that the horizontal flight path and wind and temperature models be defined and input into the airborne computer before flight. The wind/temperature model and horizontal path are products of the flight planning process. Flight planning consists of generating 3-D reference trajectories through a forecast wind field subject to certain ATC and transport operator constraints. The interrelationships between flight management and flight planning are reviewed, and the steps taken during the flight planning process are summarized.

Sorensen, J. A.↗
NASA NTRS1984

The cognitive connection: Software maintenance and documentation

With the goal of trying to understand what software maintainers do, talking aloud, video taped protocols with four expert maintainers were conducted as they were actively engaged in the process of enhancing a relatively small, interactive database program. The subjects exhibited a number of different types of information gathering strategies. Underlying these patterns of behavior, however, was the use of expectations about what should be seen in the program under examination. These expectations were generated on the basis of knowledge previously acquired as to the goals and programming plans that are typically employed in realizing interactive database programs. Thus, while the experts seemed to posses adequate programming knowledge, their actual code patches violated a basic principle of program structure. This failure by the programmers was attributed to ineffective program documentation. Suggestions for changes in the content of program documentation that should better facilitate software maintenance are presented.

Soloway, E.↗
NASA NTRS1985

The X-ray spectra and the rotation-activity connection of RS CVN binaries

Results from a survey of RS CVn binaries which were observed with the Imaging Proportional Counter (IPC) on board the Einstein Observatory are presented. Spectral analyses of the IPC pulse height spectra show that the coronae of RS CVn binaries always contain hot gas with temperatures 10 million K, similar to active late-type main sequence stars, and that at least 2 temperature components are necessary to account for the higher quality IPC spectra (when absorption is unimportant). It is argued that these bimodal temperature distributions indicate true distributions of emission measure vs temperature that are continuous (just as is the case for magnetically-confined coronal plasma loops observed on the Sun). It is shown that none of the derivable X-ray characteristics of RS CVn binaries depend on rotation period, implying that claims of period-activity relationships in RS CVn binaries are unfounded.

Majer, P.↗
NASA NTRS1986

Interplanetary dust: The interstellar connection

Although not proven, there is the widespread belief that comets consist, at least in part, of interstellar material that was originally present in the solar nebula. Furthermore, there are strong arguments in favor of the view that much of the interplanetary dust complex is derived from comets. The main arguments supporting this view are based on mass balance, analysis of the orbital parameters of meteors, and the long known association between meteor showers and specific comets. Laboratory measurements on interplanetary dust particles (IDPs) collected in the stratosphere have confirmed the view that many of the dust particles are primitive in the sense that they show striking enrichments of D/H relative to average solar system materials. It has also been demonstrated that the mid-infrared absorption spectra of one infrared red class of particles show strong similarities to IR sources such as the protostar W-33A. However, the laboratory studies of IDPs have shown that they represent a diverse set of objects and the measurement of the orbital parameters of specific dust particles is essential to answering the question of sources. The observation of the IRAS dust bands reopens the question of the role of asteroids in supplying a significant fraction of the dust and part of the diversity observed may be due to the fact that some of the dust is asteroidal and some cometary. In addition, some fraction of interplanetary dust must consist of an interstellar component intercepted by the solar system in its motion through the local interstellar medium. It has been shown that dust derived from nearby stars will have 75% of their orbits with eccentricities or equal to 1.1 and might be difficult to distinguish from interplanetary dust based on orbital measurements alone.

Carey, W. C.↗
NASA NTRS1986

X-ray spectra and the rotation-activity connection of RS Canum Venaticorum binaries

Results are presented from a survey of RS CVn binaries which were observed with the imaging proportional counter (IPC) on board the Einstein Observatory. Spectral analyses of the IPC pulse height spectra show that the coronae of RS CVn binaries always contain hot gas with temperatures in excess of 10 to the 7th K, similar to active late-type main-sequence stars, and that at least two temperature components are necessary to account for the higher quality IPC spectra (when absorption is unimportant). It is argued that these bimodal temperature distributions found by the IPC are indicative of true distributions of emission measure versus temperature that are continuous (just as is the case of magnetically confined coronal plasma loops observed on the sun). It is further shown that none of the derivable X-ray characteristics of RS CVn binaries depend on rotation period, implying that previous claims of period-activity relationships in RS CVn binaries were unfounded.

Majer, P.↗