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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 199 records · Page 11
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NASA NTRS1982

Time code dissemination experiment via the SIRIO-1 VHF transponder

An experiment to evaluate the possibility of disseminating a time code via the SIRIO-1 satellite, by using the onboard VHF repeater is described. The precision in the synchronization of remote clocks was expected to be of the order of 0.1 to 1 ms. The RF carrier was in the VHF band, so that low cost receivers could be used and then a broader class of users could be served. An already existing repeater, even if not designed specifically for communications could be utilized; the operation of this repeater was not intended to affect any other function of the spacecraft (both the SHF repeater and the VHF telemetry link were active during the time code dissemination via the VHF transponder).

Detoma, E.↗
NASA NTRS1981

Meteorological inputs to advanced simulators

Weather simulation as it is currently implemented and some suggestions and questions considered in future simulator developments are described. Flight simulators represent weather in a considerably broader sense and with an almost limitless capability for future expansion. Realistic weather is important in pilot training simulators. It offers promising opportunity to provide training because it permits an element of environmental control not available in the real world.

Handberg, G. O.↗
NASA NTRS1980

LANDSAT technology transfer to the private and public sectors through community colleges and other locally available institutions

Major first year accomplishments are summarized and plans are provided for the next 12-month period for a program established by NASA with the Environmental Research Institute of Michigan to investigate methods of making LANDSAT technology readily available to a broader set of private sector firms through local community colleges. The program applies a network where the major participants are NASA, university or research institutes, community colleges, and obtain hands-on training in LANDSAT data analysis techniques, using a desk-top, interactive remote analysis station which communicates with a central computing facility via telephone line, and provides for generation of land cover maps and data products via remote command.

Rogers, R. H.↗
NASA NTRS1981

Wind response characteristics of horizontal axis wind turbines

It was the objective of the work reported here, and in the companion paper 1 . A broader examination of wind turbine dynamic response to turbulence, and attempts to ascertain the features of turbulence that wind turbines are most sensitive to were made. A statistical description of the wind input including all three wind components and allowing linear wind gradients across the rotor disk, was used together with quasi-static aerodynamic theory and an elementary structural model involving only a few degrees of freedom. The idea was to keep the turbine model simple and show the benefits of this type of statistical wind representation before attempting to use a more complex turbine model. As far as possible, the analysis was kept in the simplest form, while still preserving key physical responses.

Thresher, R. W.↗
NASA NTRS1982

A computer simulation approach to measurement of human control strategy

Human control strategy is measured through use of a psychologically-based computer simulation which reflects a broader theory of control behavior. The simulation is called the human operator performance emulator, or HOPE. HOPE was designed to emulate control learning in a one-dimensional preview tracking task and to measure control strategy in that setting. When given a numerical representation of a track and information about current position in relation to that track, HOPE generates positions for a stick controlling the cursor to be moved along the track. In other words, HOPE generates control stick behavior corresponding to that which might be used by a person learning preview tracking.

Green, J.↗
NASA NTRS1980

Training state agency personnel in satellite remote sensing technology - Solutions to a special problem

To aid state/local agencies in starting effective programs to apply Landsat and other remote sensing data, NASA's Eastern Regional Remote Sensing Applications Center (ERRSAC) has developed a comprehensive training program as part of its technology transfer mission. Skills in data processing and interpretation are produced through 'hands-on' experience with computer techniques used to conduct practical applications involving state-oriented projects, conducted jointly by agencies and ERRSAC. In time, ERRSAC will shift much of these training activities to universities where future agency personnel can obtain a broader foundation in remote sensing.

Short, N. M.↗
NASA NTRS1981

Ultrashort pulse generation in semiconductor lasers

Techniques to generate picosecond optical pulses from semiconductor lasers are reviewed. Experimental methods and results of theoretical analysis of active modelocking are presented. It is shown that modelocking will achieve the shortest pulses; but the use of a cumbersome external cavity will probably limit its practical use. Short pulses produced by direct modulation such as gain switching are considerably broader than those obtained by passive modelocking. However, no external cavity is needed; and the simplicity of this method makes it important to be explored further. Recent experimental results are discussed where picosecond pulses from a buried heterostructure laser diode with ultrashort current pulses obtained from a comb generator are generated. Also, 28 ps pulses were obtained at 2.5 GHz repetition frequency, using the gain switching method. An analytical analysis based on the rate equations shows qualitative agreement with our experimental results.

Auyeung, J.↗
NASA NTRS1981

The Venus ionopause current sheet - Thickness length scale and controlling factors

Data from the fluxgate magnetometer, plasma wave experiment and Langmuir probe aboard Pioneer Venus are used to investigate the characteristic thickness length scale of the ionopause current sheet, as well as how this length scale is controlled. Thickness is found to be a bistatic quality, large scales being associated with high field strengths and current sheet altitudes below 300 km, while smaller scales are found with lower field strengths and ionopause altitudes above 300 km. Ion collisions and plasma wave activity contribute to the formation of the broader, low-altitude ionopause current sheets. Although evidence suggests that the wave activity influences the thin ionopause current sheets, a simple model points to the control of the thin ionopause current sheets by ionospheric ion and electron temperatures

Elphic, R. C.↗
NASA NTRS1981

Mechanisms for intense relativistic electron precipitation

An analysis of data gathered over a period of 14 months by the S3-3 satellite has revealed the detection of 313 relativistic electron precipitation events with isotropic flux over the upward-looking hemisphere, of which the majority occur at night in a narrow latitudinal zone which is embedded within a broader region of intense energetic ion precipitation. Three classes of precipitation are found to be associated with strong, diffusion resonant scattering due to known magnetospheric plasma waves. It is also found that intense electron energy deposition is a major source of middle-atmospheric, odd-hydrogen and odd-nitrogen molecules at sub-auroral latitudes, leading to an observable catalytic destruction of mesospheric ozone.

Thorne, R. M.↗
NASA NTRS1981

Einstein imaging observations of clusters of galaxies

X-ray observations suggest a broad division between clusters having a centrally-located, X-ray dominant galaxy characterized by a centrally-peaked X-ray emission, and clusters with a broader X-ray profile. Within these categories, such evolutionary indicators as X-ray temperature, vorticity dispersion, spiral fraction and central galaxy density may indicate the relative stages of evolution. X-ray imaging observations are presented for (1) the Virgo cluster, (2) other dynamically unevolved clusters, (3) double clusters which may be in an intermediate evolutionary stage, and (4) dynamically evolved clusters. The data are analyzed under the assumption of an isothermal X-ray gas which is gravitationally bound by galaxies and clusters.

Forman, W.↗
NASA NTRS1982

Space Telescope design status and operations

The Space Telescope design concept is described in the context of the basic mission objectives. The orbiting telescope is designed to have 10 times better resolution, to see 50 times fainter stars and to have a much broader spectral range than the best existing ground observatories. The project is on schedule for launch in early 1985. Hardware assembly and test has started on the optical system, and the primary and secondary mirrors have been polished and coated. The five scientific instruments are beginning hardware assembly. The last major design review for the spacecraft has been completed, and good progress has been accomplished with the implementation of the pointing control system. The mission operations ground system has been defined and is under development. Control center design is complete and the science institute is under construction. The Space Telescope is designed to be serviceable in orbit and will be capable of return to the ground for refurbishment.

Speer, F. A.↗
NASA NTRS1981

Texas Symposium on Relativistic Astrophysics, 10th, Baltimore, MD, December 15-19, 1980, Proceedings

The present conference on relativistic astrophysics begins with consideration of such topics in the cosmology of the early universe as the implications of the neutrino rest mass, relic neutrino clustering, and the possibility of a matter-antimatter domain structure in the universe, and proceeds to the broader cosmological questions of the distances of extragalactic objects, the mass of the universe, and the dynamics of superclusters. Also considered are the cosmic microwave background, relativistic jet production and propagation in active galaxies, gravitational lenses, positron annihilation radiation from the galactic center region, supernova models, and the acceleration of cosmic rays by shock waves. Summaries are presented in closing, on workshops concerning such topics as gravitational radiation detectors, the UV cosmic ray background, pulsars, supernovae, active galaxies, and quasars.

Ramaty, R.↗
NASA NTRS1982

Broad helium emission in the galactic center

An infrared (K band) spectrum taken with a 3.8 arcsec-diameter aperture centered on the galactic center source IRS 16 exhibits weak CO band absorption and emission by hydrogen Brackett-gamma (Br gamma) and a singlet helium line near 4857/cm. The helium emission profile is much broader (FWHM about 1500 + or - 300 km/sec) than any feature seen previously at the galactic center. The broadening is probably due to Doppler motion of gas either flowing through an ionizing layer or orbiting about a massive object. The absence of hydrogen Br gamma emission with a similar profile suggests the galactic center H/He abundance ratio is reduced by a factor greater than about 500 from normal cosmic values.

Hall, D. N. B.↗
NASA NTRS1982

Why a variable G

An attempt is made to put the possible time variability of G in a broader context. It is suggested that the variable G is a popular and incomplete representation of the problem of the validity of the strong equivalence principle (SEP). Particular reference is made to a reanalysis of Viking Mars data to study, in a model independent way, the influence of atomic clocks in recording purely gravitational phenomena. These data ought to provide the most reliable test of the variability of G and the validity of the SEP.

Canuto, V. M.↗
NASA NTRS1982

NASA Thesaurus. Volume 1: Hierarchical listing

There are 16,713 postable terms and 3,716 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary.

Source record↗
NASA NTRS1981

Technology and benefits of aircraft counter rotation propellers

Results are reported of a NASA sponsored analytical investigation into the merits of advanced counter rotation propellers for Mach 0.80 commercial transport application. Propeller and gearbox performance, acoustics, vibration characteristics, weight, cost and maintenance requirements for a variety of design parameters and special features were considered. Fuel savings in the neighborhood of 8 percent relative to single rotation configurations are feasible through swirl recovery and lighter gearboxes. This is the net gain which includes a 5 percent acoustic treatment weight penalty to offset the broader frequency spectrum noise produced by counter rotation blading.

Strack, W. C.↗
NASA NTRS1982

Development and evaluation of polyvinyl-alcohol blend polymer films as battery separators

Several dialdehydes and epoxies were evaluated for their suitability as cross-linkers. Optium concentrations of several cross-linking reagents were determined. A two-step method of cross-linking, which involves treatment of the film in an acid or acid periodate bath, was investigated and dropped in favor of a one-step method in which the acid catalyst, which initiates cross-linking, is added to the PVA - cross-linker solution before casting. The cross-linking was thus achieved during the drying step. This one-step method was much more adaptable to commercial processing. Cross-linked films were characterized as alkaline battery separators. Films were prepared in the lab and tested in cells in order to evaluate the effect of film composition and a number of processing parameters on cell performance. These tests were conducted in order to provide a broader data base from which to select optimum processing parameters. Results of the separator screening tests and the cell tests are discussed.

Manzo, M. A.↗
NASA NTRS1981

ERRSAC contributions to the search for Appalachian hydrocarbons

The utility of lineaments identified on LANDSAT imagery as an exploration tool in the search for hydrocarbons within three Appalachian test sites were assessed. The optimum LANDSAT imagery enhancement technique for displaying lineaments was identified. The LANDSAT lineament data were analyzed and results were correlated with oil and gas field information for each of three tests sites. Good correlations were found for several states. Successful techniques can be incorporated into a broader exploration model.

Blodget, H. W.↗