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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Atmospheric H2O and the search for Martian brines

Abundant martian brines would have important implication for current theories of volatile migration on Mars, since, although the presence of metastable brines is quite plausible, any brine in the reasonably near-surface should be completely depleted on a timescale short in relation to the age of Mars. It is important to determine whether brines exist in the martian subsurface, for the current paradigm for understanding martian volatile regime requires substantial alteration if they are found to exist. It is determined, however, that the prospect for detection of a subsurface brine via atmospheric water vapor measurements is marginal. Four reasons are given for this conclusion.

Zent, Aaron P.↗
NASA NTRS1989

Design of an active helicopter control experiment at the Princeton Rotorcraft Dynamics Laboratory

In an effort to develop an active control technique for reducing helicopter vibrations stemming from the main rotor system, a helicopter model was designed and tested at the Princeton Rotorcraft Dynamics Laboratory (PRDL). A description of this facility, including its latest data acquisition upgrade, are given. The design procedures for the test model and its Froude scaled rotor system are also discussed. The approach for performing active control is based on the idea that rotor states can be identified by instrumenting the rotor blades. Using this knowledge, Individual Blade Control (IBC) or Higher Harmonic Control (HHC) pitch input commands may be used to impact on rotor dynamics in such a way as to reduce rotor vibrations. Discussed here is an instrumentation configuration utilizing miniature accelerometers to measure and estimate first and second out-of-plane bending mode positions and velocities. To verify this technique, the model was tested, and resulting data were used to estimate rotor states as well as flap and bending coefficients, procedures for which are discussed. Overall results show that a cost- and time-effective method for building a useful test model for future active control experiments was developed. With some fine-tuning or slight adjustments in sensor configuration, prospects for obtaining good state estimates look promising.

Marraffa, Andrew M.↗
NASA NTRS1989

Approaches toward a blue semiconductor laser

Possible approaches for obtaining semiconductor diode laser action in the blue region of the spectrum are surveyed. A discussion of diode lasers is included along with a review of the current status of visible emitters, presently limited to 670 nm. Methods are discussed for shifting laser emission toward shorter wavelengths, including the use of II-IV materials, the increase in the bandgap of III-V materials by addition of nitrogen, and changing the bandstructure from indirect to direct by incorporating interstitial atoms or by constructing superlattices. Non-pn-junction injection methods are surveyed, including avalanche breakdown, Langmuir-Blodgett diodes, heterostructures, carrier accumulation, and Berglund diodes. Prospects of inventing new multinary semiconducting materials are discussed, and a number of novel materials described in the literature are tabulated. New approaches available through the development of quantum wells and superlattices are described, including resonant tunneling and the synthesis of arbitrary bandgap materials through multiple quantum wells.

Ladany, I.↗
NASA NTRS1988

Coastal Zone Color Scanner

The Coastal Zone Color Scanner (CZCS) spacecraft ocean color instrument is capable of measuring and mapping global ocean surface chlorophyll concentration. It is a scanning radiometer with multiband capability. With new electronics and some mechanical, and optical re-work, it probably can be made flight worthy. Some additional components of a second flight model are also available. An engineering study and further tests are necessary to determine exactly what effort is required to properly prepare the instrument for spaceflight and the nature of interfaces to prospective spacecraft. The CZCS provides operational instrument capability for monitoring of ocean productivity and currents. It could be a simple, low cost alternative to developing new instruments for ocean color imaging. Researchers have determined that with global ocean color data they can: specify quantitatively the role of oceans in the global carbon cycle and other major biogeochemical cycles; determine the magnitude and variability of annual primary production by marine phytoplankton on a global scale; understand the fate of fluvial nutrients and their possible affect on carbon budgets; elucidate the coupling mechanism between upwelling and large scale patterns in ocean basins; answer questions concerning the large scale distribution and timing of spring blooms in the global ocean; acquire a better understanding of the processes associated with mixing along the edge of eddies, coastal currents, western boundary currents, etc., and acquire global data on marine optical properties.

Johnson, B.↗
NASA NTRS1988

Microwave radar oceanographic investigations

The Radar Ocean Wave Spectrometer (ROWS) technique was developed and demonstrated for measuring ocean wave directional spectra from air and space platforms. The measurement technique was well demonstrated with data collected in a number of flight experiments involving wave spectral comparisons with wave buoys and the Surface Contour Radar (SCR). Recent missions include the SIR-B underflight experiment (1984), FASINEX (1986), and LEWEX (1987). ROWS related activity is presently concentrating on using the aircraft instrument for wave-processes investigations and obtaining the necessary support (consensus) for a satellite instrument development program. Prospective platforms include EOS and the Canadian RADARSAT.

Jackson, F. C.↗
NASA NTRS1989

Discussion of the potential and limitations of direct and large-eddy simulations

The full text of the discussion paper presented at the Whither Turbulence Workshop on the potential and limitations of direct and large-eddy simulations is provided. Particular emphasis is placed on discussing the role of numerics and mathematical theory in direct simulations of both compressible and incompressible flows. A variety of unresolved issues with large-eddy simulations such as their implementation in high-order finite difference codes, problems with defiltering, and modifications to accommodate integrations to solid boundaries are elaborated on. These as well as other points are discussed in detail along with the authors' views concerning the prospects for future research.

Hussaini, M. Y.↗
NASA NTRS1988

Feasibility of an uncooled imaging spectrometer for the exploration of the solar system

A state-of-the-art imaging spectrometer concept is presented for visible-midwavelength IR spectral region studies of the solar system that obviates the until-now essential use of cryogenic cooling. This uncooled imaging spectrometer configuration is evaluated in view of the prospective environments of the instrument in various spacecraft orbits, as well as in light of various available photodetector materials and sensor focal plane array configurations.

Liaw, H. M.↗
NASA NTRS1988

Study of nonlinear optical sBs phenomena in mid IR fibers

This is the first reported attempt at investigation of the sBs phenomena in mid IR fibers using externally fed or laser self generated low frequency and microwave frequency phonon waves as diagnostic probes of such processes. The observation of laser excited phonon emissions in the mid IR fiber and direct modulation of CO2 laser pulse transmission by externally imposed low frequency radiation is the first indication of the predicted low sBs threshold in these fibers in the phonon rich mid IR spectral region. The prospect of wide applications of the sBs process in optical switching, phase conjugation and ultimately optical computing and possible deleterious effects in mid IR laser heterodyne spectroscopy, sideband modulation and transmitted power limitation is discussed.

Yu, Chung↗
NASA NTRS1988

The Earth Observing System

NASA's Earth Observing System (EOS) is a prospective program for earth observation from space using various unmanned, sun-synchronous polar orbit sensor platforms in conjunction with the Space Station to conduct measurements over a period of 15 years. The most important instruments will be the Moderate-Resolution Imaging Spectrometer, the High-Resolution Imaging Spectrometer, a large-area coverage SAR, the Laser Atmospheric Wind Sounder, the Atmospheric IR Sounder, and a Geodynamics and Laser-Ranging System.

Soffen, Gerald A.↗
NASA NTRS1988

NASA launch vehicles - The next twenty years

Future space activities call for robust, reliable, cost-effective access to space, together with greater launch capacity. Attention is presently given to prospective developments in the field of cargo launch vehicle design, whose near-term goal for NASA is the Shuttle-C Space Shuttle-development unmanned vehicle. In the longer term, the Advanced Launch System will be developed jointly by NASA and the DOD for LEO placement of payloads of as much as 200,000 lb. NASA is studying ways of developing the current manned Space Shuttle Orbiter through incorporation of emerging technologies; eventually, a 'Shuttle-II' vehicle will be developed.

Branscome, Darrell R.↗
NASA NTRS1988

Long-term follow up of astronaut health indices

Ground-based research and reevaluation of flight data is currently in progress in order to develop suitable and operationally acceptable medical standards for extended-duration manned space missions. The large amount of data obtained thus far constitutes a unique data base representative of the astronaut population. In this paper, preliminary 10-year findings of prospective studies established in 1977 are described, and results obtained from retrospective studies conducted on data accumulated prior to the 1977 establishment of medical selection standards are summarized.

Nicogossian, A. E.↗
NASA NTRS1988

Aircraft engines. III

Prospective powerplant configuration advancements for tilt-rotor subsonic flight, supersonic commercial flight, and hypersonic flight are speculated upon, with a view to possibilities for the exploitation of novel materials and of such advanced fuels as liquid methane and hydrogen. Attention is given to the foldable tilt-rotor concept, which employs a hydraulic torque converter to engage the fan stage of the high-bypass turbofan engine used in forward flight after the tilt-rotor blades have been stowed, and several advanced cycles and turbomechanical configurations for cruise in the high supersonic regime and beyond, through the hypersonic regime, and into orbital velocity.

Mikkelson, Daniel C.↗
NASA NTRS1989

Planetary mission departures from Space Station orbit

The concept of orbital assembly and launch of oversized planetary (or lunar) spacecraft from a Space Station is rapidly coming of age. This prospect raises a host of new problems demanding timely resolution. The one most serious issue involved in launch from a rapidly precessing Space Station orbit (about -7.2 deg/day) is the need to cope with the generally out-of-plane orientation of the V-infinity departure vector. Methods dealing with single or multiple injection maneuvers, deep space plane changes, nodal shift caused by reboost strategy modifications, and departure window duration analysis are discussed.

Sergeyevsky, Andrey B.↗
NASA NTRS1989

An infrared view of the universe

Results from IRAS and the technical details of the IRAS satellite are reviewed. The IRAS telescope operation is briefly described. The observation of the Vega phenomenon, or the orbiting clouds of dust which encircle main sequence stars, is discussed. Also, the discovery that a large number of solar-type stars have excess IR radiation due to orbiting shells or disks of solid material is examined. In addition, the prospects for future telescopes are considered.

Soifer, Baruch T.↗
NASA NTRS1988

Target acquisition and track in the laser docking sensor

A sensor designed to aid in the docking of spacecraft is under development for NASA. This sensor uses three lasers to track the prospective target and to determine the required parameters necessary to calculate the ideal approach maneuver. The system combines the inputs from several sensors, including polarization, continuous tone DME, and a CID to achieve the desired results.

Clowes, Ted J.↗
NASA NTRS1988

Astrophysics from large databases - The example of IUE

Ways to access the IUE data base and methods for processing and analyzing the IUE data are discussed. The characteristics of the data base are described and the types of objects observed by the IUE are listed. The methods for searching the IUE catalogs and conducting multicatalog searches are considered. In addition, trends in the application of astronomical data bases are examined, including the prospects for future software packages for data processing and analysis.

Heap, Sara R.↗
NASA NTRS1989

Tropospheric aerosol backscatter background mode at CO2 wavelengths

A comparison is made between three climatologies of backscatter measurements in the troposphere and lower stratosphere at CO2 wavelengths. These were obtained from several locations using ground-based and airborne lidar systems. All three measurement sets show similar features, specifically, a high frequency of occurrence of low backscatter over a limited range of values in the middle and upper atmosphere (the 'background mode'). This background mode is important for the design and performance simulation of the prospective satellite sensors that rely on atmospheric aerosols as scattering targets.

Rothermel, Jeffry↗
NASA NTRS1989

Prediction of full system helicopter noise for a MDHC 500E helicopter using the Rotonet program

The long-term goal of the NASA/U.S. helicopter industry program designated 'Rotonet' is the achievement of a helicopter noise signature-prediction capability on the basis of helicopter geometry and operating condition data. A prediction-validation data base is being compiled through flight testing of an MDHC 500E helicopter; the data base will encompass acoustic spectra, noise-level time histories, and effective perceived noise levels incorporating actual meteorological conditions and helicopter dynamics. An evaluation is made of the Rotonet system as currently defined, with a view to prospective developments.

Weir, D. S.↗