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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 361 records · Page 20
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NASA NTRS1983

Research on solar pumped liquid lasers

A solar pumped liquid laser that can be scaled up to high power (10Mw CW) for space applications was developed. Liquid lasers have the inherent advantage over gases in that they provide much higher lasant densities and thus high power densities. Liquids also have inherent advantages over solids in that they have much higher damage thresholds and are much cheaper to produce for large scale applications. Among the liquid laser media that are potential candidates for solar pumping, the POC13:Nd(3+):ZrC14 liquid was chosen for its high intrinsic efficiency as well as its relatively good stability against decomposition due to protic contamination. The development and testing of the laser liquid and the development of a large solar concentrator to pump the laser was emphasized. The procedure to manufacture the laser liquid must include diagnostic tests of the solvent purity (from protic contamination) at various stages in the production process.

Schneider, R. T.↗
NASA NTRS1982

Hydrology team

General problems faced by hydrologists when using historical records, real time data, statistical analysis, and system simulation in providing quantitative information on the temporal and spatial distribution of water are related to the limitations of these data. Major problem areas requiring multispectral imaging-based research to improve hydrology models involve: evapotranspiration rates and soil moisture dynamics for large areas; the three dimensional characteristics of bodies of water; flooding in wetlands; snow water equivalents; runoff and sediment yield from ungaged watersheds; storm rainfall; fluorescence and polarization of water and its contained substances; discriminating between sediment and chlorophyll in water; role of barrier island dynamics in coastal zone processes; the relationship between remotely measured surface roughness and hydraulic roughness of land surfaces and stream networks; and modeling the runoff process.

Ragan, R.↗
NASA NTRS1982

Observations of reverse polarity flux transfer events at the earth's dayside magnetopause

High resolution plasma and magnetic field measurements made by the ISEE 1 and 2 spacecraft have provided the first definitive observations of magnetic reconnection at the dayside boundary, occurring either as a large-scale, quasisteady process enduring on time scales of at least tens of minutes or as a transient process localized in both temporal and spatial extent. Observations of flux transfer events (FTEs) at the earth's dayside magnetopause are presented which have plasma and magnetic field signatures reversed in sign from those previously reported. These FTEs are interpreted in terms of localized and transitory reconnection with the spacecraft located south of the reconnection site. They are associated with a previously reported interval of quasisteady reconnection which is similarly located, indicating that a close physical connection exists between the two processes.

Rijnbeek, R. P.↗
NASA NTRS1983

Discovery of a nitrogen-rich UV-bright star in the globular cluster M5

Observations of a UV bright source in the globular cluster M5 using instrumentation on the Black Brant rocket are reported. Imagery was obtained by two cameras operating at 1540 A and 2360 A and bandpasses of 350 A and 880 A. The instruments are prototypes for cameras to be flown with the Spacelab. The UV-emitting object in the cluster was located off-center. Comparison of the data with data from the IUE for short-wavelength radiation indicated a temperature in the range 25,000-50,000 K, with a dereddened flux for the continuum near 1550 A of 4.2 x 10 to the -13th ergs/sq cm per sec per A. The object is concluded to be a post-AGB star with an envelope which has experienced CNO processing.

Bohlin, R. C.↗
NASA NTRS1983

The composition, propagation and acceleration of energetic solar particles - A review of United States research 1979-1982

The present review has the objective to cover major developments in American research related to solar energetic particles, both observational and theoretical, taking into account the period from late 1978 to late 1982. It is pointed out that particular progress has been made in the area of solar energetic particle composition with respect to elemental, isotopic, and the distribution of charge states. This progress is primarily the result of improved instrumentation available at a time of higher solar activity. An important aspect of solar particle studies is to understand the propagation of particles from the vicinity of the sun through interplanetary space to wherever the observing instruments are located. Almost all mathematical models for the transport of solar cosmic rays are derived in some sense from the same general Boltzmann or Vlasov equations. Attention is also given to advances related to an understanding of coronal propagation, and acceleration and injection processes.

Mcguire, R. E.↗
NASA NTRS1983

Comparative assessment of LANDSAT-4 MSS and TM data quality for mapping applications in the southeast

The initial objectives of analyses of the MSS data are two-fold: (1) to evaluate the geodetic accuracy of CCT-P data of the test sites; and (2) to improve the geodetic accuracy by additional processing if the original data either do not meet pre-launch specifications or mapping requirements. The location of 45 ground control points (GCP) digitized from 35 U.S. Geological Survey 1:24,000 scale quadrangles (UTM coordinates) were identified in terms of pixel and scan line values. These 46 points are used to establish UTM position error vector distributions in the scene. As an initial check on the geometric reliability of the MSS data, 28 well-distributed GCPs were input to a program which compares the scaled image distances between all possible point pairs with the corresponding map distances and computes the distance differences; that is, the relative positional errors. The relative errors obtained from initial computations averaged about +/- 200 m. These errors could result from a number of sources, including misidentification of GCP locations, UTM coordinate errors introduced by the map digitizing process or errors resulting from data acquisition and geometric processing.

Welch, R.↗
NASA NTRS1984

The STEP/STACBEAM experiment technology development for very large solar array deployers

The Stacking Triangular Articulated Compact Beam (STACBEAM) is discussed with reference to structural testing experiments afforded by ground simulation and the Space Technology Experiments Platform (STEP). The STACBEAM lends itself to a deployment technique which offers a radical improvement in flexible blanket solar array technology. A system for deployment and support of a solar array blanket is described which consists of the blanket, its containment structure, the support structure and its deployer, the blanket stiffening battens, and the deployable boom standoffs. In operation, the blanket is pulled out and supported by the STACBEAM which packages next to the folded blanket. Since the STACBEAM does not rotate during extension, complete control of the blanket is maintained during extension. Deployment of this system occurs one bay at a time in a sequential manner. The deployer provides sufficient rigidity so that beam stiffness is not degraded during the deployment process.

Samuels, R.↗
NASA NTRS1984

Radical and ion molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in RF plasmas at low pressures ( 1.0 torr)

The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes.

Avni, R.↗
NASA NTRS1984

An Easy-to-implement Coding Scheme for Multifrequency PPM

In implementing multifrequency PPM, a naturally arising question is: Let P be a fixed number; among all integer valued processes X1, X2, X3, with E ( X(n+1)-X(n) squared) less than or = P, which has the largest entropy? Earlier work by McEliece and Rodemich answered this question, but there is no obvious way to use this process to implement a code for multifrequency PPM. The present article describes an easy-to-implement process X1, X2, with E ( X(n+1)-X(n) squared) less than or = P, whose entropy is nearly as great as that of the McEliece-Rodemich process.

Mceliece, R. J.↗
NASA NTRS1984

Atomization of liquid sheets in high pressure airflow

An investigation of liquid sheet atomization is made with combustor simulated inlet air pressures varied from 0.10 to 2.1 MPa. Mean drop diameters are measured with an improved scanning radiometer and correlated with the liquid and air stream Reynolds numbers, RE(1) and RE(A) and the airstream pressure sensitive group GC(2). These data are used in the modeling of the combustion process.

Ingebo, R. D.↗
NASA NTRS1984

LANDSAT-4 Radiometric and Geometric Correction and Image Enhancement Results

Techniques were developed or improved to calibrate, enhance, and geometrically correct LANDSAT-4 satellite data. Statistical techniques to correct data radiometry were evaluated and were found to minimize striping and banding. Conventional techniques cause striping even with perfect calibration parameters. Intensity enhancement techniques were improved to display image data with large variation in intensity or brightness. Data were geometrically corrected to conform to a 1:100,000 map reference and image products produced with the map overlay. It is shown that these products can serve as accurate map products. A personal computer was experimentally used for digital image processing.

Bernstein, R.↗
NASA NTRS1984

Effects of shuttle bay environment on UV sensitive photographic film results of measurements aboard STS-7 and STS-8

Schumann emulsions, having low gelatin content and no protective gelatin overcoating, are extremely sensitive to environmental conditions and handling. Experiments using this emulsion are to be flown on the space shuttle within the cargo-bay. Because the environment of the cargo-bay is unknown, a Get-Away-Special payload was designed to expose Kodak-type SO 652 Schumann emulsion to the residual atmosphere of the cargo-bay. The experiment was programmed to make exposures for various time periods to determine the maximum length of time the film could be exposed in making a measurement and what precautions would be required to preserve the film during ascent into orbit and reentry. The results of the STS-7 and STS-8 flights indicated that long exposures in the shuttle bay do not produce high fog levels in orbit. Observations of severe bleaching of the latent image makes protection of the emulsion during reentry manditory and increase of fog levels with time set a limit of four weeks (preferably less than three) between installation and recovery of the emulsion for processing.

Kreplin, R. W.↗
NASA NTRS1983

A statistical study of interplanetary shock associated proton intensity increases

Large intensity increases of low-energy protons are frequently observed in connection with interplanetary forward shocks. Essentially two different particle acceleration mechanisms to explain these 'ESP events' are presently under discussion. To find out which is the dominant process for particle acceleration a large number of these events observed on ISEE-3 was analyzed. The events with the highest fluxes of 35-56 keV protons are associated with shocks which are quasi-parallel and originate close to the central meridian of the sun, and it is concluded that they are produced by a first order Fermi acceleration process.

Reinhard, R.↗
NASA NTRS1985

Signal Processor for Multirate PSK Signals

Any of six different data formats at any of five different data rates from phase-shift-key (PSK) modulated input signal extracted by digital radio receiver. Subcarrier Demodulator is Costas loop with hard limiter in inphase arm. There are six low-pass filters, each selectable for rate and format of data to be processed.

Helgesen, R. J.↗
NASA NTRS1985

High Lifetime Solar Cell Processing and Design

In order to maximize efficiency a solar cell must: (1) absorb as much light as possible in electron-hole production, (2) transport as large a fraction as possible of the electrons to the n-type terminal and holes to the p-type terminal without their first recombining, and (3) produce as high as possible terminal voltage. Step (1) is largely fixed by the spectrum of sunlight and the fundamental absorption characteristics of silicon, although some improvements are possible through texturizing induced light trapping and back surface reflectors. Steps (2) and (3) are, however, dependent on the recombination mechanisms of the cell. The recombination, on the contrary, is strongly influenced by cell processing and design. Some of the lessons during the development of point-contact-cell are discussed. Cell dependence on recombination, surface recombination, and contact recombination are discussed. Results show the overwhelming influence of contact recombination on the operation of the cell when the other sources of recombination are reduced by careful processing.

Swanson, R. M.↗
NASA NTRS1985

Quantitative analysis of geomorphic processes using satellite image data at different scales

When aerial and satellite photographs and images are used in the quantitative analysis of geomorphic processes, either through direct observation of active processes or by analysis of landforms resulting from inferred active or dormant processes, a number of limitations in the use of such data must be considered. Active geomorphic processes work at different scales and rates. Therefore, the capability of imaging an active or dormant process depends primarily on the scale of the process and the spatial-resolution characteristic of the imaging system. Scale is an important factor in recording continuous and discontinuous active geomorphic processes, because what is not recorded will not be considered or even suspected in the analysis of orbital images. If the geomorphic process of landform change caused by the process is less than 200 m in x to y dimension, then it will not be recorded. Although the scale factor is critical, in the recording of discontinuous active geomorphic processes, the repeat interval of orbital-image acquisition of a planetary surface also is a consideration in order to capture a recurring short-lived geomorphic process or to record changes caused by either a continuous or a discontinuous geomorphic process.

Williams, R. S., Jr.↗
NASA NTRS1984

Electromagnetic containerless undercooling facility and experiments for the Shuttle

An electromagnetic furnace is being prepared for flights aboard the Space Shuttle. This apparatus is capable of melting metals and alloys up to 1400 C melting point by induction heating with subsequent solidification of the freely levitated melt without contact with any container. The solidification can be carried out with greatly reduced fields resulting in minimal heating and stirring of the free melt. Sequential specimens can be processed during flight. Several experiments are planned for a series of flights, beginning in 1985 with an undercooling experiment of NiSn alloys. These will be interspersed with detailed studies of fluid flow caused by low and high field levels in order to quantify the corresponding effect upon the solidification process.

Frost, R. T.↗
NASA NTRS1985

Analysis of three-dimensional solidification interface shape

The determination of the shape of the solidification interface in a cooling melt by the thermal boundary conditions is investigated analytically, extending the analysis of Siegel (1982) and Siegel and Sosoka (1982) to the three-dimensional case. The solutions are generated by continuation into the solid region from conditions at the cooled wall, and some numerical results are presented in tables and graphs. These findings and the analytical approach employed are applicable to crystallization and metal-forming processes.

Siegel, R.↗