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At least 343 records · Page 19

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NASA NTRS1986

Earth observing system. Data and information system. Volume 2A: Report of the EOS Data Panel

The purpose of this report is to provide NASA with a rationale and recommendations for planning, implementing, and operating an Earth Observing System data and information system that can evolve to meet the Earth Observing System's needs in the 1990s. The Earth Observing System (Eos), defined by the Eos Science and Mission Requirements Working Group, consists of a suite of instruments in low Earth orbit acquiring measurements of the Earth's atmosphere, surface, and interior; an information system to support scientific research; and a vigorous program of scientific research, stressing study of global-scale processes that shape and influence the Earth as a system. The Eos data and information system is conceived as a complete research information system that would transcend the traditional mission data system, and include additional capabilties such as maintaining long-term, time-series data bases and providing access by Eos researchers to relevant non-Eos data. The Working Group recommends that the Eos data and information system be initiated now, with existing data, and that the system evolve into one that can meet the intensive research and data needs that will exist when Eos spacecraft are returning data in the 1990s.

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NASA NTRS1985

Particle behavior in the magnetosphere

The Rice Convection Model deals with large-scale processes in the earth's inner and middle magnetosphere, including coupling to the ionosphere. Starting from appropriate initial and boundary conditions, the model computes the following physical parameters: ionospheric electric fields and currents; magnetospheric particle distributions, electric fields, and electric currents; and magnetic-field-aligned (Birkeland) currents connecting the two regions. This paper evaluates work on the model, with emphasis on the assumptions made, the basic equations, and the numerical methods. The theoretical basis of the model is compared and contrasted with standard magnetohydrodynamics. The limitations imposed by the major assumptions are discussed. Model inputs and boundary conditions are listed, and the methods of specifying them discussed. Some physical conclusions and insights that have been gained from the model are listed and described very briefly. References are given to published discussions of the major points of physics.

Wolf, R. A.↗

NASA NTRS1987

HMMR (High-Resolution Multifrequency Microwave Radiometer) Earth observing system, volume 2e. Instrument panel report

Recommendations and background are provided for a passive microwave remote sensing system of the future designed to meet the observational needs of Earth scientist in the next decade. This system, called the High Resolution Multifrequency Microwave Radiometer (HMMR), is to be part of a complement of instruments in polar orbit. Working together, these instruments will form an Earth Observing System (EOS) to provide the information needed to better understand the fundamental, global scale processes which govern the Earth's environment. Measurements are identified in detail which passive observations in the microwave portion of the spectrum could contribute to an Earth Observing System in polar orbit. Requirements are established, e.g., spatial and temporal resolution, for these measurements so that, when combined with the other instruments in the Earth Observing System, they would yield a data set suitable for understanding the fundamental processes governing the Earth's environment. Existing and/or planned sensor systems are assessed in the light of these requirements, and additional sensor hardware needed to meet these observational requirements are defined.

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NASA NTRS1986

On the early thermal state of the moon

New theories for the formation of the moon from an accretion disk thrown into circumterrestrial orbit after the collision of a planet-sized object with the earth have led to a reexamination of the tectonic consequences of an initially molten moon. Even the smallest estimates of radial contraction that would accompany cooling of the moon from an initially molten state predict accumulated near-surface horizontal compressive stresses considerably in excess of the compressive strength of the upper lunar crust, estimated to be 0.5 to 1 kbar on the basis of topographic relief, the stress levels necessary to form mare ridges in mascon mare basins, and measurements of rock friction. Various mechanisms for relieving or modifying such large near-surface stresses are considered, including viscoelastic effects, widespread development of major fault systems, impact gardening, and opposing stresses arising from other global-scale processes. All of these mechanisms face substantial difficulties when tested against geological and mechanical information from the moon and other terrestrial planets. These considerations pose a serious problem for theories of lunar origin that call for an initially molten state.

Solomon, Sean C.↗

NASA NTRS1987

Uranium nitride fuel fabrication for SP-100 reactors

Fuel pins of uranium mononitride clad in Nb-1 percent Zr were fabricated for irradiation tests in EBR-II. Laboratory scale process parameters to synthesize UN powders and fabricate UN pellets were developed. Uranium mononitride was prepared by converting UO2 to UN. Fuel pellets were prepared by communition of UN briquettes, uniaxial pressing, and high temperature sintering. Techniques for machining, cleaning, and welding Nb-1 percent Zr cladding components were developed. End caps were electron beam welded to the tubing. Helium back-fill holes were sealed with a laser weld.

Mason, Richard E.↗

NASA NTRS1990

Atmospheric dynamics of the outer planets

Despite major differences in the solar and internal energy inputs, the atmospheres of the four Jovian planets all exhibit latitudinal banding and high-speed jet streams. Neptune and Saturn are the windiest planets, Jupiter is the most active, and Uranus is a tipped-over version of the others. Large oval storm systems exhibit complicated time-dependent behavior that can be simulated in numerical models and laboratory experiments. The largest storm system, the Great Red Spot of Jupiter, has survived for more than 300 years in a chaotic shear zone where smaller structures appear and dissipate every few days. Future space missions will add to the understanding of small-scale processes, chemical composition, and vertical structure. Theoretical hypotheses about the interiors provide input for fluid dynamical models that reproduce many observed features of the winds, temperatures, and cloud patterns. In one set of models the winds are confined to the thin layer where clouds form. In other models, the winds extend deep into the planetary fluid interiors. Hypotheses will be tested further as observations and theories become more exact and detailed comparisons are made.

Ingersoll, Andrew P.↗

NASA NTRS1991

Aft segment dome-to-stiffener factory joint insulation void elimination

Since the detection of voids in the internal insulation of the dome-to-stiffener factory joint of the 15B aft segment, all aft segment dome-to-stiffener factory joints were x-rated and all were found to contain voids. Using a full-scale process simulation article (PSA), the objective was to demonstrate that the proposed changes in the insulation layup and vacuum bagging processes will greatly reduce or eliminate voids without adversely affecting the configuration of performance of the insulation which serves as a primary seal over the factory joint. The PSA-8 aft segment was insulated and cured using standard production processes.

Jensen, S. K.↗

NASA NTRS1991

Climatological perspectives, oceanographic and meteorological, on variability in the subtropical convergence zone in the northwestern Atlantic

The large-scale climatological environment of the Frontal Air-Sea Interaction Experiment (FASINEX) is described, with emphasis on the largest scales. Both long-term and annual sea surface temperature (SST) variability is discussed; a climatology of the west-central North Atlantic, derived from various sets of data obtained during the intensive phases of January-March, is presented, and the meteorological and oceanographic context for FASINEX is thus established. Surface marine observations and SST variability are discussed, and the marine meteorology of the FASINEX area is examined in terms of the surface pressure and winds, the sea-air temperature difference, and the cloud cover. Near 28 deg N in February is found to be a favorable time and place to observe large mean temperature gradients and downward Ekman pumping. The large-scale processes that set up the favorable environment for frontal activity are not limited to the winter months.

Hanson, Howard P.↗

NASA NTRS1991

Mean and inter-year variation of growing-season normalized difference vegetation index for the Sahel 1981-1989

Images are presented that show the mean and coefficient of variation of nine years (1981-1989) of NOAA AVHRR normalized difference vegetation index (NDVI) data for the growing season (July-October) in Africa, north of the equator. The variation in the growing season NDVI is represented by the coefficient of variation image that shows the large variation in the Sahelian growing season between years. It is concluded that these images illustrate some aspects of the perspective being brought to regional and continental scale processes by coarse resolution satellite sensors and the potential of these sensors to provide consistent, long-term datasets.

Tucker, C. J.↗

NASA NTRS1992

Energy transformations associated with the synoptic and planetary scales during the evolution of a blocking anticyclone and an upstream explosively-developing cyclone

The eddy kinetic energy (KE), release of eddy potential energy, generation of eddy kinetic energy, and exchange between eddy and zonal kinetic energy are investigated for a blocking anticyclone over the North Atlantic Ocean and an extratropical cyclone that developed during January 17-21, 1979. The results indicate that KE was maintained by baroclinic conversion of potential to kinetic. As released potential energy was being used to generate KE, a portion of the KE was barotropically converted to zonal KE. These transformations were dominated by the synoptic-scale component. While changes in the mass field depended not only on the synoptic scale but also on the interactions between the synoptic and planetary scales, the corresponding changes in the eddy motion fields responded largely to synoptic-scale processes.

Smith, Phillip J.↗

NASA NTRS1992

Role of the ocean in climate changes

The present program aimed at the study of ocean climate change is prepared by a group of scientists from State Oceanographic Institute, Academy of Science of Russia, Academy of Science of Ukraine and Moscow State University. It appears to be a natural evolution of ideas and achievements that have been developed under national and international ocean research projects such as SECTIONS, WOCE, TOGA, JGOFS and others. The two primary goals are set in the program ROCC. (1) Quantitative description of the global interoceanic 'conveyor' and it's role in formation of the large scale anomalies in the North Atlantic. The objectives on the way to this goal are: to get the reliable estimates of year-to-year variations of heat and water exchange between the Atlantic Ocean and the atmosphere; to establish and understand the physics of long period variations in meridianal heat and fresh water transport (MHT and MFWT) in the Atlantic Ocean; to analyze the general mechanisms, that form the MHT and MFWT in low latitudes (Ekman flux), middle latitudes (western boundary currents) and high latitudes (deep convection) of the North Atlantic; to establish and to give quantitative description of the realization of global changes in SST, surface salinity, sea level and sea ice data. (2) Development of the observational system pointed at tracing the climate changes in the North Atlantic. This goal merges the following objectives: to find the proper sites that form the inter annual variations of MHT; to study the deep circulation in the 'key' points; to develop the circulation models reflecting the principle features of interoceanic circulation; and to define global and local response of the atmosphere circulation to large scale processes in the Atlantic Ocean.

Gulev, Sergey K.↗

NASA NTRS1993

Atmospheric numerical modeling resource enhancement and model convective parameterization/scale interaction studies

Research will be undertaken in this contract in the area of Modeling Resource and Facilities Enhancement to include computer, technical and educational support to NASA investigators to facilitate model implementation, execution and analysis of output; to provide facilities linking USRA and the NASA/EADS Computer System as well as resident work stations in ESAD; and to provide a centralized location for documentation, archival and dissemination of modeling information pertaining to NASA's program. Additional research will be undertaken in the area of Numerical Model Scale Interaction/Convective Parameterization Studies to include implementation of the comparison of cloud and rain systems and convective-scale processes between the model simulations and what was observed; and to incorporate the findings of these and related research findings in at least two refereed journal articles.

Cushman, Paula P.↗

NASA NTRS1994

Papers presented to the Conference on Chondrules and the Protoplanetary Disk

The following topics are covered in the presented papers: (1) producing chondrules; (2) carbons, CAI's, and chondrules; (3) large scale processes in the solar nebula; (4) chondrule-matrix relationships in chondritic meteorites; (5) overview of nebula models; (6) constraints placed on the nature of chondrule precursors; (7) turbulent diffusion and concentration of chondrules in the protoplanetary nebula; (8) heating and cooling in the solar nebula; (9) crystallization trends of precursor pyroxene in ordinary chondrites; (10) precipitation induced vertical lightning in the protoplanetary nebula; (11) the role of chondrules in nebular fractionations of volatiles and other elements; (12) astronomical observations of phenomena in disks; (13) experimental constraints on models for origins of chondrules, and various other topics.

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NASA NTRS1993

Advanced composite fuselage technology

Boeing's ATCAS program has completed its third year and continues to progress towards a goal to demonstrate composite fuselage technology with cost and weight advantages over aluminum. Work on this program is performed by an integrated team that includes several groups within The Boeing Company, industrial and university subcontractors, and technical support from NASA. During the course of the program, the ATCAS team has continued to perform a critical review of composite developments by recognizing advances in metal fuselage technology. Despite recent material, structural design, and manufacturing advancements for metals, polymeric matrix composite designs studied in ATCAS still project significant cost and weight advantages for future applications. A critical path to demonstrating technology readiness for composite transport fuselage structures was created to summarize ATCAS tasks for Phases A, B, and C. This includes a global schedule and list of technical issues which will be addressed throughout the course of studies. Work performed in ATCAS since the last ACT conference is also summarized. Most activities relate to crown quadrant manufacturing scaleup and performance verification. The former was highlighted by fabricating a curved, 7 ft. by 10 ft. panel, with cocured hat-stiffeners and cobonded J-frames. In building to this scale, process developments were achieved for tow-placed skins, drape formed stiffeners, braided/RTM frames, and panel cure tooling. Over 700 tests and supporting analyses have been performed for crown material and design evaluation, including structural tests that demonstrated limit load requirements for severed stiffener/skin failsafe damage conditions. Analysis of tests for tow-placed hybrid laminates with large damage indicates a tensile fracture toughness that is higher than that observed for advanced aluminum alloys. Additional recent ATCAS achievements include crown supporting technology, keel quadrant design evaluation, and sandwich process development.

Ilcewicz, Larry B.↗

NASA NTRS1995

Numerical simulation of filling a magnetic flux tube with a cold plasma: Anomalous plasma effects

Large-scale models of plasmaspheric refilling have revealed that during the early stage of the refilling counterstreaming ion beams are a common feature. However, the instability of such ion beams and its effect on refilling remain unexplored. In order to learn the basic effects of ion beam instabilities on refilling, we have performed numerical simulations of the refilling of an artificial magnetic flux tube. (The shape and size of the tube are assumed so that the essential features of the refilling problem are kept in the simulation and at the same time the small scale processes driven by the ion beams are sufficiently resolved.) We have also studied the effect of commonly found equatorially trapped warm and/or hot plasma on the filling of a flux tube with a cold plasma. Three types of simulation runs have been performed.

Singh, Nagendra↗

NASA NTRS1994

Simulating fluxes from heterogeneous land surfaces: Explicit subgrid method employing the biosphere-atmosphere transfer scheme (BATS)

A vectorized version of the biosphere-atmosphere transfer scheme (VBATS) is used to study moisture, energy, and momentum fluxes from heterogeneous land surfaces st the scale of an atmospheric model (AM) grid cells. To incorporate subgrid scale inhomogeneity, VBATS includes two important features: (1) characterization of the land surface (vegetation and soil parameters) at N subgrid points within an AM grid cell and (2) explicit distribution of climate forcing (precipitation, clouds, etc.) over the subgrid. In this study, VBATS is used in stand-alone mode to simulate a single AM grid cell and to evaluate the effects of subgrid scale vegetation and climate specification on the surface fluxes and hydrology. It is found that the partitioning of energy can be affected by up to 30%, runoff by 50%, and surface stress in excess of 60%. Distributing climate forcing over the AM grid cell increases the Bowen ratio, as a result of enhanced sensible heat flux and reduced latent heat flux. The combined effect of heterogeneous vegetation and distribution of climate is found to be dependent on the dominat vegetation class in the AM grid cell. Development of this method is part of a larger program to explore the importance of subgrid scale processes in regional and global climate simulations.

Seth, Anji↗

NASA NTRS1994

Ozone as a laundry agent on orbit and on the ground

Ozone (03), is the strongest commercial oxidizing agent for aqueous systems and may be ideal for space station laundering operations. It can be generated electronically from air in situ. It kills virtually all microorganisms, attacks many organics and inorganics, and breaks down stable ring structures of benzene and related oils when coupled with ultra violet radiation. It cleans and disinfects in cold water without the need for detergent. It leaves no residues. Ozone permits up to 90% wash water recycling and it eliminates wash time, water volume, and recycling problems of a detergent rinse. Ozone is self purging and converts spontaneously to oxygen. It can be rapidly purged by well established catalytic and thermal processes. Scaling of an ozone laundering system for space station may have commercial applications in a consumer model for home use.

Agosto, William N.↗

NASA NTRS1997

Radiation Effects on Current Field Programmable Technologies

Manufacturers of field programmable gate arrays (FPGAS) take different technological and architectural approaches that directly affect radiation performance. Similar y technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices total dose and single event susceptibilities, including performance degradation effects and temporary or permanent re-configuration faults. Test results will concentrate on recent technologies being used in space flight electronic systems and those being developed for use in the near term. This paper will provide the first extensive study of various configuration memories used in programmable devices. Radiation performance limits and their impacts will be discussed for each design. In addition, the interplay between device scaling, process, bias voltage, design, and architecture will be explored. Lastly, areas of ongoing research will be discussed.

Katz, R.↗