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At least 1,225 records · Page 68

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NASA NTRS1991

Further identification and treatment modalities in telephone mediated lightning strike

The results are presented of a prospective survey of people injured by lightning impulses transmitted by the public telephone system. The results are compared with those of a previous retrospective survey. Various deficiencies in the methodology of the latter survey are addressed. A division into a population with severe injury and a population with mild injury is made based on medical history and examination taken immediately after a strike. The best predictors of severe injury were found to be the presence of symptoms beyond one week after the strike, and also the initial presence of musculoskeletal injuries. Psychological upset is also seen to be a significant factor in severe injury. The only physical parameter of strike which could be used as a predictor of severe injury was the presence of concomitant power system damage. The importance of earth bonding between power and telephone system is thus supported in a protection strategy. One author draws on experience in treating patients with these injuries to propose a treatment regimen for those with ongoing symptoms. The importance of evaluating and treating psychological and physical aspects is stressed.

Andrews, Christopher J.↗

NASA NTRS1991

Interferometry

The following recommended programs are reviewed: (1) infrared and optical interferometry (a ground-based and space programs); (2) compensation for the atmosphere with adaptive optics (a program for development and implementation of adaptive optics); and (3) gravitational waves (high frequency gravitational wave sources (LIGO), low frequency gravitational wave sources (LAGOS), a gravitational wave observatory program, laser gravitational wave observatory in space, and technology development during the 1990's). Prospects for international collaboration and related issues are also discussed.

Ridgway, Stephen↗

NASA NTRS1990

Doppler lidar atmospheric wind sensor - Reevaluation of a 355-nm incoherent Doppler lidar

Reliable Nd:YAG laser technology and currently available optical sensors are presently used to reevaluate the performance of an incoherent Doppler lidar system operating at 354.7 nm. This system makes a more efficient use of output laser power than heretofore possible through a matching of the usable and detectable field of view of the Fabry-Perot interferometer receiver with that of the transmitter. Major advantages accrue to this system from the lower output power requirement, which is a primary cost driver for the prospective Spaceborne Doppler Wind Lidar.

Rees, David↗

NASA NTRS1990

Active optical sensor technology

An account is given of the development status, performance capabilities, and prospective applications of lidar systems in earth remote sensing, as envisioned by researchers at NASA-Marshall, NASA-Goddard, NASA-Langley, and NASA-Wallops Island. Lidar systems can conduct measurements in research efforts concerned with wind fields, altimetry, ozone depletion, water vapor mixing ratios, temperature and pressure, phytoplankton chlorophyll fluorescence, forest folliage, and ice sheets. It is in all cases that lidar lasers be lightweight, compact, and efficient; most lasers need to be tunable. Detectors used range from photomultipliers to photodiodes.

Melfi, Harvey↗

NASA NTRS1990

Viscous drag reduction via surface mass injection

Slot injection systems on the surfaces of aerodynamic bodies have been noted to consistently furnish substantial local skin friction reductions which are predictable on the basis of current numerical methods. Only crude systems studies, however, have been thus far completed. The most common configuration for slot ingestion in the literature involves tangential injection of air along a two-dimensional surface on which air constitutes the mainstream flow; attention is presently given to slot injection in low-speed and high-speed flows, as well as a discussion of aircraft applications and an evaluation of prospective possibilities for practical drag-reduction systems.

Hefner, Jerry N.↗

NASA NTRS1990

Lunar rover developments at JPL

Results of previous JPL developments are summarized and the current work related to lunar roving missions is discussed. Objectives of a long lunar transverse are reviewed and include lunar resource prospecting and base site surveys. Rover design criteria are presented, noting that payload instrumentation would include both television cameras for driving and cameras producing panoramic facsimile for high-fidelity scientific imaging and landmark navigation, as well as a multipurpose imaging system with multispectral, close-up, and microscopic capabilities. Instrumentation providing for chemical and mineral analysis, a gravimeter, and a magnetometer are also important. Rover performance requirements include a capability to support a 50 kg payload mass with a rover mass of 500 to 600 kg, powering and supporting the payload, managing the on-board resources available to each instrument, and handling all of the mission data. Desert tests of lunar roving navigation and field geology are discussed.

Burke, James D.↗

NASA NTRS1990

Dispersal of gases generated near a lunar outpost

The dispersal of gases evolved by prospective lunar base operations is presently modeled analytically using continuous (mining and habitat-venting) and impulsive (primarily rocket exhaust) injections of gases. In the case of impulsive injection, the neutral atmosphere and associated ionosphere both decay on time-scales of about 20 min; in that of continuous injection, the atmosphere near the base grows and achieves a steady state after about 20 min. Both direct and diffusive transport mechanisms are considered, and it is concluded that for the injection rates and assumptions presently employed the artificial lunar atmospheres produced are not significantly detrimental to astronomical observations and high-vacuum materials processing operations.

Burns, Jack O.↗

NASA NTRS1990

X-ray study of superclusters

The Batuski-Burns list of candidate superclusters was searched for X-ray emission in the HEAO 1 A-2 data base. No significant flux in excess of integrated member cluster emission was detected in directions associated with estimated supercluster centroids; a 3 sigma upper limit to the mean individual excess flux is 5 x 10 to the -12th ergs/sq cm/s. Implications of this bound are discussed in terms of fainter member clusters, hot diffuse gas, and active and normal galaxies. Prospects of supercluster observations related to future X-ray missions are also outlined.

Persic, M.↗

NASA NTRS1990

U.S.-Japan Workshop on Smart/Intelligent Materials and Systems, Honolulu, HI, Mar. 19-23, 1990, Proceedings

Topics presented include the concept of intelligent materials, the molecular engineering of channel proteins, the prospects, limitations, and requirements of intelligent micro motion systems, the modeling of a shape memory integrated actuator for vibration control of large space structures, and intelligent materials for future electronics. Also presented are the slewing of an active structure, the health monitoring of control system components, the numerical modeling of the microstructure of crystals with symmetry-related variants, and the intelligent material system concept.

Ahmad, Iqbal↗

NASA NTRS1990

Supersonic laminar flow control on commercial transports

This paper provides an overview of the status of supersonic laminar flow control. Existing research into the aerodynamic problems of subsonic and supersonic laminar flow control is first reviewed to provide a prospective for subsequent discussions of recent studies to evaluate the potential performance benefits of the application of laminar flow control to supersonic transports. A flight research program to provide a realistic assessment of the technical feasibility is then described.

Wagner, R. D.↗

NASA NTRS1991

Mining the air - Resources of other worlds may reduce mission costs

It is proposed that the mining of resources on another planet to support operations there and also to provide a means for the return trip to earth provides a less expensive way to send humans beyond low earth orbit to live on the moon and to explore Mars. Since a large fraction of any chemical propellant combination is the oxidizer that burns with the fuel to generate the rocket jet, and for life support, the generation of oxygen from any of its atmospheric or mineral compounds is a valuable capability. Such materials include the lunar minerals ilmenite and anorthite, Martian permafrost, water ice at the Martian poles, and atmospheric carbon dioxide on Mars. The possibilities of developing such technologies are discussed and the prospects of developing building materials for such facilities from local resources are considered. The role of the Space Engineering Research Center at the University of Arizona in exploring the use of local planetary resources is noted.

Ramohalli, Kumar↗

NASA NTRS1991

Stellar photometry with the Hubble Space Telescope Wide-field/Planetary camera - A progress report

The prospects for the use of the Wide-Field/Planetary Camera (WFPC) for stellar photometry are described. The large halos of the point-spread function (PSF) resulting from spherical aberration and from spatial, temporal, and color variations of the PSF are the main limitations to accurate photometry. Degradations caused by crowding are exacerbated by the halos of the PSF. An attempt is made to quantify these effects and determine the current accuracy of stellar photometry with the WFPC. In realistic cases, the brighter stars in crowded fields have 0.09 mag errors; fainter stars have larger errors depending on the degree of crowding. It is shown that measuring Cepheids in Virgo Cluster galaxies is not currently possible without inordinate increases in exposure times.

Holtzman, Jon A.↗

NASA NTRS1991

Ceramic thermal barrier coatings for commercial gas turbine engines

The paper provides an overview of the short history, current status, and future prospects of ceramic thermal barrier coatings for gas turbine engines. Particular attention is given to plasma-sprayed and electron beam-physical vapor deposited yttria-stabilized (7 wt pct Y2O3) zirconia systems. Recent advances include improvements in the spallation life of thermal barrier coatings, improved bond coat composition and spraying techniques, and improved component design. The discussion also covers field experience, life prediction modeling, and future directions in ceramic coatings in relation to gas turbine engine design.

Meier, Susan Manning↗

NASA NTRS1991

The binary Feige 24 - The mass, radius, and gravitational redshift of the DA white dwarf

Observations are reported which refine the binary ephemeris of the Feige 24 system, which contains a peculiar hot DA white dwarf and an M dwarf with an atmosphere illuminated by extreme ultraviolet radiation from the white dwarf. With the new ephemeris and a set of IUE high-dispersion spectra, showing phase-dependent redshifted C IV, N V, and Si IV resonance lines, the orbital velocity, and hence the mass (0.54 + or - 0.20 solar masses), and the gravitational redshift of the white dwarf (14.1 + or - 5.2 km/s) are determined independently. It is shown that the measured Einstein redshift is consistent with an estimated radius for the white dwarf obtained from a model atmosphere solid angle and a parallax measurement. This radius is twice the Hamada-Salpeter radius for the given mass and offers a prospect to investigate the presence of a massive hydrogen envelope in that white dwarf star.

Vennes, Stephane↗

NASA NTRS1990

Human exploration - Moon/Mars mission

The Space Eploration Initiative launched by the Bush Administration in May, 1990, will intensively explore alternative mission architectures involving the use of the moon as a staging post for manned exploration of Mars. The advanced technologies to be analyzed by the 'Pathfinder' program for prospective use in the alternative missions thus far defined encompass aerobraking, space-based chemical engines, cryogenic fluid systems, space nuclear power, nuclear-thermal and nuclear-electric propulsion, high-rate communications, and planetary photonics. Extensive use of robotics is anticipated in both the lunar and Martian components of the missions being studied.

O'Handley, Douglas A.↗

NASA NTRS1990

The cosmic microwave background - A probe of particle physics

The current status of spectral distortions and angular anisotropies in the cosmic microwave background is reviewed, with emphasis on the role played by weakly interacting particle dark matter. Theoretical predictions and recent observational results are described, and prospects for future progress are summarized.

Silk, Joseph↗

NASA NTRS1991

Electrically conducting polymers for aerospace applications

Current research on electrically conducting polymers from 1974 to the present is reviewed focusing on the development of materials for aeronautic and space applications. Problems discussed include extended pi-systems, pyrolytic polymers, charge-transfer systems, conductive matrix resins for composite materials, and prospects for the use of conducting polymers in space photovoltaics.

Meador, Mary Ann B.↗

NASA NTRS1991

High temperature superconductor analog electronics for millimeter-wavelength communications

The performance of high temperature superconductor (HTS) passive microwave circuits up to X-band was encouraging when compared to their metallic counterparts. The extremely low surface resistance of HTS films up to about 10 GHz enables a reduction in loss by as much as 100 times compared to copper when both materials are kept at about 77 K. However, a superconductor's surface resistance varies in proportion to the frequency squared. Consequently, the potential benefit of HTS materials to millimeter-wave communications requires careful analysis. A simple ring resonator was used to evaluate microstrip losses at Ka-band. Additional promising components were investigated such as antennas and phase shifters. Prospects for HTS to favorable impact millimeter-wave communications systems are discussed.

Romanofsky, R. R.↗