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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 865 records · Page 48
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NASA NTRS1999

Microstructures in the Polar Solar Wind: Ulysses

We find that small (10-200 rP) magnetic decreases comprise a dominant part of the polar solar wind microstructure at Ulysses distances (2.2 AU). These magnetic field dips are almost always bounded by tangential discontinuities, a feature which is not well understood at this time. Hundreds of these events have been examined in detail and a variety of types have been found. These will be described. It is speculated that these structures have been generated by perpendicular heating of ions closer to the Sun and have then been convected to distances of Ulysses. Such structures may be very important for the rapid cross- field diffusion of ions in the polar regions of the heliosphere.

Tsuruyani, Bruce T.↗
NASA NTRS2001

X-Ray Spectral Study of a Newly Ginga-Detected DQ Her

The goal of this proposal was to observe with ASCA, YY Dra, a DQ Her objected identified using archival Ginga data, in order to complete a high quality ASCA study of Ginga-detected DQ Her stars. There are relatively few DQ Her objects characterized by X-ray pulsations at the white dwarf spin period and optical pulsations at the orbital period and extremely complex X-ray spectra. The ASCA study included seven DQ Her objects. ASCA is able to resolve separate components of the Fe K emission and to set constraints on temperatures in the accretion column, and the mass of the white dwarf. The 40ksec observation, corresponding to roughly three orbital cycles, allowed the study of continuum changes with spin and orbital phase. The ASCA spectrum can be modelled as a bremsstrahlung with evidence for cold, helium-like and hydrogen-like iron emission, and helium-like argon emission. The lines yield a plasma temperature that is compatible with that from the continuum modelling (10-20 keV). The X-ray light-curve clearly shows sinusoidal variation from the spin pulse and shallow absorption dips at the orbital cycle. The derived parameters match well with the -accretion curtain, model for intermediate polars. The results will be presented together with the seven other DQ Her type sources observed with ASCA.

Vrtilek, S.↗
NASA NTRS2001

The Optical Spectrum of the Geminga Pulsar

We obtained an optical spectrum of the isolated pulsar Geminga at the Keck Observatory. The optical object is at the limit of spectroscopic capability of any telescope, with a continuum flux that is approx. 0.5% of the dark sky on Mauna Kea. With particular attention paid to the dominant systematics of sky subtraction in our observing and analysis methods, we attained approx. 0.1% systematics in heavily binned spectra. The resulting spectrum spanning 3700 - 8000 A has a flat power-law shape f(sub nu) proportional to nu(exp -0.8) and a broad dip over 6300 - 6500 A. Thermal radiation cannot explain the optical spectrum of Geminga. The dominant component can be modeled as either electron synchrotron emission and ion (proton) cyclotron absorption, or ion cyclotron emission, the latter in a 10(exp 11) G magnetic field.

Martin, Christopher↗
NASA NTRS1997

Reflective Self-Metallizing Polyimide Films

A silver organic complex, such as silver acetate, is solubilized in a polyamic acid resin or soluble polyimide solution using a suitable solvent such as hexafluoroacetyl acetone. The mixture is stable and can be applied to both flat and contoured surfaces. Application can be performed by casting, dip-coating, spraying, or other suitable techniques. In addition, the mixture can be cast or extruded as a polyimide film which is not applied to an underlying substrate. Upon curing, a flexible silver coated polyimide film is produced.

Thompson, David W.↗
NASA NTRS2001

Establishing a Geologic Baseline Of Cape Canaveral's Natural Landscape: Black Point Drive

The goal of this project is to identify the process responsible for the formation of geomorphic features in the Black Point Drive area of Merritt Island National Wildlife Refuge/Kennedy Space Center (MINWR/KSC), northwest Cape Canaveral. This study confirms the principal landscape components (geomorphology) of Black Point Drive reflect interaction between surficial sediments deposited in association with late-Quaternary sea-level highstands and the chemical evolution of late-Cenozoic subsurface limestone formations. The Black Point Drive landscape consists of an undulatory mesic terrain which dips westward into myriad circular and channel-like depression marshes and lakes. This geomorphic gradient may reflect: (1) spatial distinctions in the elevation, character or age of buried (pre-Miocene) limestone formations, (2) dissolution history of late-Quaternary coquina and/or (3) thickness of unconsolidated surface sediment. More detailed evaluation of subsurface data will be necessary before this uncertainty can be resolved.

Parkinson, Randall W.↗
NASA NTRS2000

Nutritional Evaluation of NASA's Rodent Food Bar Diet

Tests are being conducted on NASA's rodent Food Bar in preparation for long-term use as the rat and mouse diet aboard the International Space Station. Nutritional analyses are performed after the bars are manufactured and then repeated periodically to determine nutritional stability. The primary factors analyzed are protein, ash, fat, fiber, moisture, amino acids, fatty acids, and minerals. Nutrient levels are compared to values published in the National Research Council's dietary requirements for rodents, and also to those contained in several commonly used commercial rodent lab diets. The Food Bar is manufactured from a powdered diet to which moisture is added as it is processed through an extruder. The bars are dipped into potassium sorbate, vacuum-sealed, and irradiated. In order to determine nutrient changes during extrusion and irradiation, the powdered diet, the non-irradiated bars, and the irradiated bars are all analyzed. We have observed lower values for some nutrients (iodine, vitamin K, and iron) in the Food Bars compared with NRC requirements. Many nutrients in the Food Bars are contained at a higher level than levels in the NRC requirements. An additional factor we are investigating is the 26% moisture level in the Food Bars, which drops to about 15% within a week, compared to a stable 10% moisture in many standard lab chow diets. In addition to the nutritional analyses, the food bar is being fed to several strains of rats and mice, and feeding study and necropsy results are being observed (Barrett et al, unpublished data). Information from the nutritional analyses and from the rodent studies will enable us to recommend the formulation that will most adequately meet the rodent Food Bar requirements for long-term use aboard the Space Station.

Barrett, Joyce E.↗
NASA NTRS1994

Progress in Computational Aeroelasticity Using High Fidelity Flow and Structural Equations on Parallel Computers

Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft such as High Speed Civil Transport (HSCT) and Advanced Subsonic Transport (AST) which can experience complex flow/structure interactions. HSCT can experience vortex induced aeroelastic oscillations whereas AST can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional supercomputers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overcome the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENASERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations.

Guruswamy, Guru P.↗
NASA NTRS1994

Fluid/Structure Interaction Studies of Aircraft Using High Fidelity Equations on Parallel Computers

Abstract Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft such as High Speed Civil Transport (HSCT) and Advanced Subsonic Transport (AST) which can experience complex flow/structure interactions. HSCT can experience vortex induced aeroelastic oscillations whereas AST can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional super computers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overcome the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENSAERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations.

Guruswamy, Guru↗
NASA NTRS1995

Progress in Integrated Fluid/Structure/Controls Computations Using High Fidelity Equations

Aeroelasticity that involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of aircraft which can experience complex flow/structure interactions. Supersonic transports can experience vortex induced aeroelastic oscillations whereas subsonic transports can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Using these high fidelity methods, design quantities such as structural stresses can be directly computed. Computations using these high fidelity equations require state-of-the-art large computational resources. This paper will describe the transition from potential equations to Euler/Navier-Stokes equations for fluids and from modal equations to finite element equations for structures. Complexities associated with grids for moving control surfaces will be discussed. All contents of the paper will be limited to those already presented at domestic conferences within U.S. such as those sponsored by AIAA. It will not include any materials related to HPCCP computational work.

Guruswamy, Guru P.↗
NASA NTRS2002

The Relationship Between X-Rays and Relativistic Jets

We present recent multiwaveband observations centered on X-ray monitoring of blazars and the radio galaxy 3C 120 with the RXTE satellite, In 3C 120, we observed four X-ray dips, each followed by ejections of superluminal radio knots down the jet. This behavior, similar to that of the microquasar GRS 1915+105, is interpreted as infall of a piece of the inner accretion disk causing ejection of energy into the relativistic jet. The X-ray emission from the quasars PKS 1510-089, 3C 279, and 3C 273 is highly variable on timescales as short as approximately 1 day. Over 2 years, X-ray flares in PKS 1510-089 occurred about 2 weeks after radio outbursts, which can be explained by light-travel delays. In 3C 279 the X-ray and optical variations are usually well correlated, with very little, if any, time delay. We conclude that the X-ray and optical emission from blazars occurs near the radio core rather than close to the black hole.

Marscher, A. P.↗
NASA NTRS2001

Langmuir Probe Measurements of Inductively Coupled Plasmas in CF4/Ar/O2 Mixtures

Inductively coupled plasmas of CF4:Ar:O2, which have been of importance to material processing, were studied in the GEC cell at 80:10:10, 60:20:20, and 40:30:30 mixture ratios. Radial distributions of plasma potential (V(sub p)), electron and ion number densities (n(sub e) and n(sub i), electron temperature (T(sub e)), and electron energy distribution functions (EEDFs) were measured in the mid-plane of plasma across the electrodes in the pressure range of 10-50 mTorr, and RF (radio frequency) power of 200 and 300 W. V(sub p), n(sub e) and n(sub i), which peak in the center of the plasma, increase with decrease of pressure. T(sub e) also increases with pressure but peaks toward the electrode edge. Both V(sub p) and T(sub e) remain nearly independent of RF power, whereas n(sub e) and n(sub i) increase with power. In all conditions the EEDFs exhibit non-Maxwellian shape and are more like Druyvesteyn form at higher energies. They exhibit a broad dip in the energy range 0-10 eV suggesting an electron loss mechanism, which could be due to via resonance electron attachment processes producing negative ions in this rich electronegative gas mixture. This behavior is more prominent towards the electrode edge.

Rao, M. V. V. S.↗
NASA NTRS1997

MFLOP to GFLOP: The Impact on High Fidelity Based Computational Aeroelasticity

Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft which can experience complex flow/structure interactions. Even at moderate angles of attack supersonic aircraft can experience vortex induced aeroelastic oscillations. Near transonic speeds buffet associated structural oscillations are possible. Aircraft flying in transonic regime may experience a dip in the flutter speed. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional supercomputers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overco me the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENSAERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations. Modifications required in both fluids and structural solvers in order to run efficiently on parallel computers will be discussed. Implementation of moving grids and fluid/structural interface on parallel computers will be discussed.

Guruswamy, Guru P.↗
NASA NTRS2002

Establishing A Geologic Baseline of Cape Canaveral''s Natural Landscape: Black Point Drive

The goal of this project is to identify the process responsible for the formation of geomorphic features in the Black Point Drive area of Merritt Island National Wildlife Refuge/Kennedy Space Center (MINWR/KSC), northwest Cape Canaveral. This study confirms the principal landscape components (geomorphology) of Black Point Drive reflect interaction between surficial sediments deposited in association with late-Quaternary sea-level highstands and the chemical evolution of late-Cenozoic sub-surface limestone formations. The Black Point Drive landscape consists of an undulatory mesic terrain which dips westward into myriad circular and channel-like depression marshes and lakes. This geomorphic gradient may reflect: (1) spatial distinctions in the elevation, character or age of buried (pre-Miocene) limestone formations, (2) dissolution history of late-Quaternary coquina and/or (3) thickness of unconsolidated surface sediment. More detailed evaluation of subsurface data will be necessary before this uncertain0 can be resolved.

Parkinson, Randall W.↗
NASA NTRS2002

The Evolution of Disks and Winds in Dwarf Nova Outbursts - FUSE

This project was a project to study the FUV spectra of two proto-typical dwarf novae, U Gem and SS Cygni, through an outburst cycle. The luminosity of the boundary layer in the two systems, as evidenced by earlier EUVE observations, is different in the two systems. Our intensive study of the two systems was intended to (1) probe the ionization and kinematic structure of the wind as a function of system brightness, (2) isolate the contributions of the disk to the FUV spectra, and (3) examine physical conditions and abundances of material just being accreted onto the disk from the secondary. The U Gem and SS Cyg observations took place in March and October 2000, respectively. The data obtained with FUSE was of excellent quality. Analysis of the both observations is now essentially complete, although some modeling of the SS Cyg spectra is ongoing, as we complete an ApJ manuscript on this object. Our main results for U Gem are as follows: The plateau spectra have continuum shapes and fluxes that are approximated by steady state accretion disk model spectra with an accretion rate 7x10(exp 9) Msolar/yr. The spectra also show numerous absorption lines of H I, He II, and 2-5 times ionized transitions of C, N, O, P, S, and Si. There are no emission features in the spectra, with the possible exception of a weak feature on the red wing of the 0 VI doublet. The absorption lines are narrow (FWHM approx. 50 km/s), too narrow to arise from the disk photosphere, and at low velocities (less than or equal to 700 km/s). The S VI and O VI doublets are optically thick. The absorption lines in the plateau spectra show orbital variability: in spectra obtained at orbital phases between 0.53 and 0.79, low-ionization absorption lines appear and the central depths of the preexisting lines increase. The increase in line absorption occurs at the same orbital phases as previously observed EUV and X-ray light-curve dips. If the absorbing material is in (near-) Keplerian rotation around the disk, it must be located at large disk radii. The final observation occurred when U Gem was about 2 mag from optical quiescence. The spectra are dominated by emission from an approx. 43,000 K, metal-enriched white dwarf (WD). The inferred radius of the WD is 4.95x10(exp 8) cm, close to that observed in quiescence. Allowing for a hot heated region on the surface of the WD improves the fit to the spectrum at short (less than 960 A) wavelengths. Our main results for SS Cyg are as follows: The first two of four observations of SS Cyg show disk dominated spectra with accretion rates of order 10(exp -8) Msolar/yr. Except for narrow interstellar features (atomic and molecular H), the lines are all broad consistent with a disk or wind origin. The O VI line in the spectra is mostly of wind origin as detailed modeling with our Monte Carlo code (developed in part using funds from this project) show. The continua from spectra in observations 3 and 4, observed during the decline phase, are not well fit with steady-state disks, and show considerable resemblance to quiescent spectra obtained with HUT. The most probable interpretation for the emission features seen in the spectrum in the last two observations is that they arise from a photo-illuminated choronosphere above the disk, rather than a wind.

Long, Knox↗
NASA NTRS2002

Evaluation of Data Retention and Imprint Characteristics of FRAMs Under Environmental Stresses for NASA Applications

A major reliability issue for all advanced nonvolatile memory (NVM) technology devices including FRAMs is the data retention characteristics over extended period of time, under environmental stresses and exposure to total ionizing dose (TID) radiation effects. For this testing, 256 Kb FRAMs in 28-pin plastic DIPS, rated for industrial grade temperature range of -40 C to +85 C, were procured. These are two-transistor, two-capacitor (2T-2C) design FRAMs. In addition to data retention characteristics, the parts were also evaluated for imprint failures, which are defined as the failure of cells to change from a "preferred" state, where it has been for a significant period of time to an opposite state (e.g., from 1 to 0, or 0 to 1). These 256 K FRAMs were subjected to scanning acoustic microscopy (C-SAM); 1,000 temperature cycles from -65 C to +150 C; high temperature aging at 150 C, 175 C, and 200 C for 1,000 hours; highly accelerated stress test (HAST) for 500 hours; 1,000 hours of operational life test at 125 C; and total ionizing dose radiation testing. As a preconditioning, 10 K read/write cycles were performed on all devices. Interim electrical measurements were performed throughout this characterization, including special imprint testing and final electrical testing. Some failures were observed during high temperature aging test at 200 C, during HAST testing, and during 1,000 hours of operational life at 125 C. The parts passed 10 Krad exposure, but began showing power supply current increases during the dose increment from 10 Krad to 30 Krad, and at 40 Krad severe data retention and parametric failures were observed. Failures from various environmental group testing are currently being analyzed.

Sharma, Asbok K.↗
NASA NTRS2003

Visualization of Space-Time Ambiguities to be Explored by NASA GEC Mission with a Critique of Synthesized Measurements for Different GEC Mission Scenarios

The Grant supported research addressing the question of how the NASA Solar Terrestrial Probes (STP) Mission called Geospace electrodynamics Connections (GEC) will resolve space-time structures as well as collect sufficient information to solve the coupled thermosphere-ionosphere- magnetosphere dynamics and electrodynamics. The approach adopted was to develop a high resolution in both space and time model of the ionosphere-thermosphere (I-T) over altitudes relevant to GEC, especially the deep-dipping phase. This I-T model was driven by a high- resolution model of magnetospheric-ionospheric (M-I) coupling electrodynamics. Such a model contains all the key parameters to be measured by GEC instrumentation, which in turn are the required parameters to resolve present-day problems in describing the energy and momentum coupling between the ionosphere-magnetosphere and ionosphere-thermosphere. This model database has been successfully created for one geophysical condition; winter, solar maximum with disturbed geophysical conditions, specifically a substorm. Using this data set, visualizations (movies) were created to contrast dynamics of the different measurable parameters. Specifically, the rapidly varying magnetospheric E and auroral electron precipitation versus the slower varying ionospheric F-region electron density, but rapidly responding E-region density.

Sojka, Jan J.↗
NASA NTRS2003

Simultaneous Ocean Wave Measurements by the Jason and Topex Satellites, With Buoy and Model Comparisons

The verification phase of the Jason-1 satellite altimeter mission presents a unique opportunity for comparing near-simultaneous, independent satellite measurements. We here examine simultaneous significant wave height measurements by the Jason-1 and Topex/Poseidon altimeters. These data are also compared with in-situ measurements from deep-ocean buoys and with predicted wave heights from the Wave Watch 111 operational model. The rms difference between Jason and Topex wave heights is 21 cm, and this can be further lowered by application of median filters to reduce high-frequency noise. This noise is slightly larger in the Jason dataset, amounting to about 7 cm rms for frequencies above 0.05 Hz, which is the frequency at which the coherence between Topex and Jason measurements drops to zero. The probability density function for Jason shows a dearth of small waves relative to Topex. Buoy comparisons confirm that this problem lies with the Jason measurements. The buoy comparisons confirm previous reports that Topex wave heights are roughly 5% smaller than buoy measurements for waves between 2 and 5m; Jason heights in general are 2.7% smaller than Topex. Spurious dips in the Topex density function for 3- and 6-meter waves, a problem that has existed since the beginning of the mission, can be solved by waveform retracking..

Ray, Richard D.↗
NASA NTRS2003

Optical Reflectance and Fluorescence for Detecting Nitrogen Needs in Zea mays L.

Nitrogen (N) status in field grown corn (Zea mays L.) was assessed using spectral techniques. Passive reflectance remote sensing and, both passive and active fluorescence sensing methods were investigated. Reflectance and fluorescence methods are reported to detect changes in the primary plant pigments (chlorophylls a and b; carotenoids) in higher plant species. As a general rule, foliar chlorophyll a (Chl a) and chlorophyll b (Chl b) usually exist in approx.3:l ratio. In plants under stress, Chl b content is affected before Chl a reductions occur. For reflectance, a version of the chlorophyll absorption in reflectance index (CARI) method was tested with narrow bands from the Airborne Imaging Spectroradiometer for Applications (ASIA). CARI minimizes the effects of soil background on the signal from green canopies. A modified CARI (MCARI) was used to track total Chl a levels in the red dip of the spectrum from the corn canopy. A second MCARI was used to track the auxiliary plant pigments (Chl b and the carotenoids) in the yellow/orange/red edge part of the reflectance spectrum. The difference between these two MCARI indices detected variations in N levels across the field plot canopies using ASIA data. At the leaf level, ratios of fluorescence emissions in the blue, green, red and far-red wavelengths sensed responses that were associated with the plant pigments, and were indicative of energy transfer in the photosynthetic process. N stressed corn stands could be distinguish from those with optimally applied N with fluorescence emission spectra obtained from individual corn leaves. Both reflectance and fluorescence methods are sensitive in detecting corn N needs and may be especially powerful in monitoring crop conditions if both types of information can be combined.

McMurtrey, J. E.↗