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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Wide-angle flat field telescope

Described is an unobscured three mirror wide angle telescopic imaging system comprised of an input baffle which provides a 20 deg (Y axis) x 30 deg (X axis) field of view, a primary mirror having a convex spherical surface, a secondary mirror having a concave ellipsoidal reflecting surface, a tertiary mirror having a concave spherical reflecting surface. The mirrors comprise mirror elements which are offset segments of parent mirrors whose axes and vertices commonly lie on the system's optical axis. An iris diaphragm forming an aperture stop is located between the secondary and tertiary mirror with its center also being coincident with the optical axis and being further located at the beam waist of input light beams reflected from the primary and secondary mirror surfaces. At the system focus following the tertiary mirror is located a flat detector which may be, for example, a TV imaging tube or a photographic film. When desirable, a spectral transmission filter is placed in front of the detector in close proximity thereto.

Hallam, K. L.↗
NASA NTRS1985

Optimization of an interactive distributive computer network

The activities under a cooperative agreement for the development of a computer network are briefly summarized. Research activities covered are: computer operating systems optimization and integration; software development and implementation of the IRIS (Infrared Imaging of Shuttle) Experiment; and software design, development, and implementation of the APS (Aerosol Particle System) Experiment.

Frederick, V.↗
NASA NTRS1986

The use of tethered satellites for the collection of cosmic dust and the sampling of man made orbital debris far from the space station

The use of a tethered subsatellite employed downward into the earth's upper atmosphere to an altitude of about 110 km above the earth would eliminate the orbital contamination problem while at the same time affording a measure of atmospheric braking to reduce the velocities of many particles to where they may be captured intact or nearly so with properly designed collectors. The same technique could also be used to monitor the flux of all types of man-made orbital debris out to a distance of more than a hundred kilometers in any direction from the space station. In this way the build up of any debris belt orbiting earth could be determined. The actual collecting elements used for both purposes could be of several different materials and designs so as to optimize the collection of different types of particles with different densities. Stacks of foils, films, plastics, and foams, as well as simple capture cells would be mounted in clusters around the outside of a tethered satellite and protected by iris covers until the tethered had been fully deployed. If the orientation history of the satellite were known the direction of the incoming material could be infered. A chief advantage in deploying such tethered collectors from the Space Station instead of from the shuttle is the ability to maintain deployment of the tether for days instead of hours resulting in much greater yields of intact particles and impact debris.

Corso, G. J.↗
NASA NTRS1986

Titan's latitudinal temperature distribution and seasonal cycle

Voyager IRIS brightness temperature measurements of Titan at a wavelength of 530/cm are crudely indicative of ground or lower tropospheric temperatures and indicate 93 K for the equator and 91 K for both northern and southern high latitudes. The symmetry between north and south is unexpected for the time of Voyager encounter (Northern Titan spring). It is shown that this near-symmetry can arise naturally in a model where the poles are 'pinned' year-round at the dew point of CH4-N2 lakes or, more probably, a CH4-N2 rich surface layer on a deep ethane-rich ocean. For a polar temperature of 91 K, the model implies that the atmosphere contains somewhat less than 8 percent mole fraction of CH4.

Stevenson, D. J.↗
NASA NTRS1985

Physics and chemistry of sulfur lakes on Io

Based on data from Loki and other hot spot regions, a model for a convecting sulfur lake that is heated from below is constructed. Temperature profiles and fluxes in the silicate and sulfur regions are consistent with the observed Loki highest-temperature component and excess flux. Evaporatin of sulfur sets a strong upper limit on the lake surface temperature, and the intermediate temperature in the Loki region is identified with sulfur vapor condensing primarily along lake shores. Simple models of sulfur vapor transport can be used to match the Voyager IRIS data, assuming sulfur vapor condensed on the shore radiates like a blackbody. The 1 - 100 year lifetime of such a lake in steady state implies that long-term earth-based observations interpreted with this model could detect variations in the Loki thermal output. The sodium-sulfur phase diagram is also presented and used to show that evaporated lakes may leave behind sodium-rich residue which could supply the torus with sodium. Finally, uncertainties in the model are assessed, including the lack of sulfur emission features in the Loki spectrum.

Lunine, J. I.↗
NASA NTRS1986

Transformation of two and three-dimensional regions by elliptic systems

Efforts in transferring computational work from the LRC computer to the IRIS Graphics Workstation at MSU are reported and the computation of a conservative solution of a simple hyperbolic equation on an overlapping grid is discussed. Several conclusions concerning computations on overlapping grids are apparent. Problems only occur when there is a major difference in grid spacing on the individual component grids. In the case of hyperbolic equations, it is necessary that both interpolation and extrapolation be applied at the grid boundaries. When interpolated values are used at outflow boundary points, excessive oscillations in the numerical solution may be the result. The same conclusions would be valid for more complicated systems of hyperbolic equations such as the Euler equations for inviscid flow. Some of the solution values would be extrapolated at the overlap boundary, the exact number depending on the number of characteristics pointing out of the overlap region. It is also possible that similar boundary conditions may be needed for some parabolic equations such as high Reynolds number viscous flow equations. Efforts were also expended on the development of three-dimensional conservative interpolation procedures. Finally, the investigation of grid smoothing procedures were initiated during this reporting period. It was decided that the first grid smoothing algorithms will be based on the concepts of variational grid generation.

Mastin, C. W.↗
NASA NTRS1985

Space shuttle/mesoscale lightning experiment

A payload integration plan (PIP) is now being developed with Johnson Space Center integration personnel which covers management, structural thermal, electrical power/avionics, training, ground operations, safety requirements, etc., in support of this experiment. If a Shuttle flight can be identified, researchers hope to conduct the experiment in the late summer or fall of 1985. Some preliminary TV lightning data has been collected by Shuttle crews on 41D and 51D and researchers are doing an analysis of it. Additional flights will be conducted to obtain data on Mesoscale Lightning Observations. Researchers will continue to study how to improve the data collection using the onboard TV cameras. By more interaction with the crews who have used the TV camera to obtain TV of lightning, they are planning to optimize the crew time and have better TV camera operations management to produce more useful data. As the crews are better trained in the use of the gain control settings and/or camera iris operations, the quality of the TV data will be improved.

Vaughan, O. H., Jr.↗
NASA NTRS1986

Para hydrogen equilibration in the atmospheres of the outer planets

The thermodynamic behavior of the atmospheres of the Jovian planets is strongly dependent on the extent to which local thermal equilibration of the ortho and para states of molecular hydrogen is achieved. Voyager IRIS data from Jupiter imply substantial departures of the para hydrogen fraction from equilibrium in the upper troposphere at low latitudes, but with values approaching equilibrium at higher latitudes. Data from Saturn are less sensitive to the orth-para ratio, but suggest para hydrogen fractions near the equilibrium value. Above approximately the 200 K temperature level, para hydrogen conversion can enhance the efficiency of convection, resulting in a substantial increase in overturning times on all of the outer planets. Currently available data cannot definitively establish the ortho-para ratios in the atmospheres of Uranus and Neptune, but suggest values closer to local equilibrium than to the 3.1 normal ratio. Modeling of sub-millimeter wavelength measurements of these planets suggest thermal structures with frozen equilibrium lapse rates in their convective regions.

Conrath, Barney J.↗
NASA NTRS1986

Vertical cloud structure models for the NTRZ EQZ, SEB and STRZ of Jupiter

Latitude-dependent models of the vertically inhomogeneous Jovian cloud structure are presented. The models assume an atmospheric composition with (CH4)/(H2) = 2.0 x .003, (He)/(H2) = 0.11 and (NH3)/(H2) = 2.0 x .0004 consistent with the Voyager IRIS measurements and employ refractive indices appropriate for ammonia ice particles and a photochemical stratospheric aerosol layer. The free parameters of the models are determined by fitting the results of multiple, scratching calculations to the near-infrared center and limb spectra of Clark and McCord and the center-to-limb 6190, 6350, 7250, 7500, 8900 and 9500 A photometric measurements of West. The resulting synthetic center-to-limb profiles are in excellent agreement with the observations. Of the regions studied the tropical zones are the most similar, with the observed differences explained by variations in the vertical extent of the cloudy layers. The Equatorial Zone is a unique region with denser NH3 clouds than either of the tropical zones. At visible and near-infrared wavelengths the belt-zone contrasts can be explained by opacity differences. The optical depth of the stratospheric aerosol layer is larger in a belt, while the tropospheric clouds are deeper and thinner.

Carlson, B. E.↗
NASA NTRS1986

Study of the ammonia ice cloud layer in the north tropical zone of Jupiter from the infrared interferometric experiment on Voyager

An average of 51 Voyager 1 IRIS spectra of Jupiter's North Tropical Zone was analyzed to infer the abundance, vertical extent, and size distribution of the particles making up the ammonia cloud in this region. It is assumed that the cloud base coincides with the level at which 100% saturation of ammonia vapor occurs. The vertical distribution of particulates above this level is determined by assuming a constant total ammonia mixing ratio and adjusting the two phases so that the vapor is saturated throughout the cloud. A constant scaling factor then adjusts the base number density. A radiative transfer program is used that includes the effects of absorption and emission of all relevant gases as well as anisotropic scattering by cloud particles. Mie scattering from a gaussian particle size distribution is assumed. The vertical thermal structure is inferred from a temperature retrieval program that utilizes the collision induced S(0) and S(1) molecular hydrogen lines between 300 and 700.cm, and the 1304.cm methane band.

Shaffer, William A.↗
NASA NTRS1986

Eddy processes in the general circulation of the Jovian atmospheres

Two fundamentally different views of the general circulation of Jovian atmospheres have emerged. According to one view, the observed jet streams at the cloud tops are controlled by the vorticity transfers of small scale eddies generated by planetary wave instabilities within a shallow atmospheric layer. According to the alternate point of view, the zonal jets are surface manifestations of deep interior convection organized into cylindrical motion with axes parallel to the planetary rotation axis. Both approaches may be considered in the context of the very different roles assumed by the potential vorticity. A possible reconciliation of the two kinds of dynamical systems is considered in which the interior motion is overlaid with a statically stable cappling layer driven by turbulent energy injection from below. A simple model for the eddy driving of quasi-geostrophic dynamics in the capping layer is presented which is consistent with the tentative evidence for up-gradient momentum flux on Jupiter and IRIS observations of thermal contrast correlations with cyclonic and anticyclonic shear zones. Certain synoptic-scale cloud features in Jupiter's atmosphere are interpreted as breaking waves, which may also influence the lateral mixing of tracers such as the ortho-para hydrogen ratio.

Leovy, Conway↗
NASA NTRS1986

Transformation of two and three-dimensional regions by elliptic systems

Grid smoothing and orthogonalization procedures were developed and implemented in the construction of two and three dimensional grids. The procedures are based on the variational methods of grid generation. The two-dimensional examples were computed using the MSU IRIS Graphics Workstation. It was demonstrated that the elliptic grid generation equations, with arbitrary forcing functions, can be solved, in their variational formulation, using a gradient method. Since gradient methods have a global convergence property, the divergence problems often encountered when using SOR iterative methods can be avoided. It is not to be concluded, however, that SOR methods should be abandoned, since gradient methods tend to converge very slowly. In fact, slow convergence was the major problem encountered in the three-dimensional grids. Further progress was made on the continuing effort to develop conservative interpolation formulas for overlapping grids.

Mastin, C. Wayne↗
NASA NTRS1986

Possible detection of the earth's free-core nutation

The 5.5 years of VLBI observations primarily collected under project IRIS are used to search for evidence of the free-core nutation (FCN). The observations are consistent with an irregular excitation process, and a model which assumes a step excitation in the FCN amplitude to about 2.0 milliseconds of arc in late 1985 fits the data well. Theoretical analysis appears to rule out the strong Mexican earthquake of September 19, 1985, as a cause of the excitation.

Robertson, D. S.↗
NASA NTRS1986

Zonal mean properties of Jupiter's upper troposphere from Voyager infrared observations

Voyager IRIS spectra of Jupiter are used to derive zonal averages for 270- and 150-mb temperatures, as well as optical depths through the troposphere at two temperatures, ammonia concentrations near the 680-mb level, and the parahydrogen fraction near the 270-mb level. Simple modeling of an axisymmetric circulation incorporating the linear damping of perturbations from a uniform state for both winds and temperature yields results that are consistent with observed thermal wind shears and with the vertical motion field.

Gierasch, P. J.↗
NASA NTRS1986

Polar motion and length of day determination from satellite laser ranging

The kinematic and dynamic models used in obtaining the GSFC MERIT solution (using data from satellite laser ranging) for the x and y coordinates of the earth's rotation pole and the excess length-of-day (LOD) are discussed together with the analysis technique. Comparisons of the GSFC polar motion time series with the time series from the Bureau International de l'Heure shows small but consistent systematic differences (4.6 milliarcsec rms about a mean offset of 1 milliarcsec in the x component, and 2.9 milliarcsec rms about a 21 milliarcsec offset in the y component). A comparison with the data of the National Geodetic Survey's IRIS network shows departures of 2.5 milliarcsec rms about the mean for the x component and 2.0 milliarcsec rms for the y component. The precision of the GSFC earth orientation is estimated to be better than 1 milliarcsec for polar motion and 0.1 msec for excess LOD.

Smith, David E.↗
NASA NTRS1986

A GSFC alternative to the SLR MERIT constants

The use of the Lageos satellite to monitor the earth's orientation is examined. The derivations of long wavelength ocean tidal parameters, a geocentric gravitational constant of 398,600.436 cu km/ sq sec + or - 0.0001 cu km/sq sec, and Love numbers using Lageos laser ranging data are described. The uncertainties of the geopotential model, GEM-L2 of Lerch et al. (1982), are discussed. The calculation of polar motion using the Lageos constants is considered. The Lageos constants are tested by applying them to independent laser ranging data. It is determined that the new constants improve the rms of fit to independent Lageos data and improve the earth orientation parameters compared to VLBI data obtained during the IRIS project.

Christodoulidis, Demosthenes C.↗
NASA NTRS1988

Designing A Microwave Band-Stop Filter

Lumped-circuit design techniques applied to iris-coupled cavities. Waveguide/cavity filter imitates lumped series and parallel combinations of inductance and capacitance over narrow stopband centered at 7.190 GHz. Filter made of standard WR125 waveguide stock.

Manshadi, F.↗
NASA NTRS1988

Image Control In Automatic Welding Vision System

Orientation and brightness varied to suit welding conditions. Commands from vision-system computer drive servomotors on iris and Dove prism, providing proper light level and image orientation. Optical-fiber bundle carries view of weld area as viewed along axis of welding electrode. Image processing described in companion article, "Processing Welding Images for Robot Control" (MFS-26036).

Richardson, Richard W.↗