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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Short term magnetospheric particle variations (1 minute T 1 day), appendix 1

A schematic representation of the generation and propagation processes for energetic particles of concern in solar terrestrial predictions is given. Particle precipitation at low, mid, and high altitudes is discussed with emphasis on prediction techniques. Methods given for testing of such techniques include traditional collaborations, enhanced collaborations, simulated prediction schemes, and field tests.

Higbie, P. R.↗
NASA NTRS1987

Thermo-oxidatively stable condensation polyimides containing 1,1,1-triaryl-2,2,2-trifluoroethane dianhydride and diamine monomers

Nine new condensation polyimides containing the trifluorophenylethylidene linkage were synthesized by the amic-acid route. Several other polyimides, including some with the hexafluoroisopropylidene linkage, were also prepared as controls. Amic-acid solutions were characterized by determining their inherent viscosities prior to thermal conversion into polyimide films. Glass transition temperatures (T sug g), thermogravimetric analysis (TGA), and isothermal weight loss data were obtained for the films. The films were pulverized into molding powders which, in turn, were thermally processed under pressure into neat resin discs. The discs were also characterized by T sub gs and 316 C and 371 C isothermal weight losses. The film study identified two new polyimides with T sub gs greater that 371 C and two new polyimides with low rates of weight loss. The resin discs exhibited the same overall trends in T sub g and weight loss as the respective films, however the weight loss per unit surface area was always greater, presumably due to voids or to mechanical degradation induced during preparation of the molding powders.

Alston, William B.↗
NASA NTRS1993

High frequency performance of Si(1-x)Ge(x)/Si(1-y)Ge(y)/Si(1-x)Ge(x) HBTs

The results of a theoretical study of the performance of high speed SiGe HBTs is presented. The study includes a group of SiGe HBTs in which the Ge concentration in the base is 20 percent higher than that in the emitter and collector (i.e., y = x + 0.2). It is shown that the composition dependences of f(T) and the f(max) are nonmonotonic. As the Ge composition in the emitter and collector layers is increased, f(T) and f(max) first decrease, then remain constant and finally increase to attain their highest values.

Rosenfeld, D.↗
NASA NTRS1995

Prepsolv (TM): The optimum alternative to 1,1,1-trichloroethane and methyl ethyl ketone for hand-wipe cleaning of aerospace materials

Engineers at Hercules Aerospace, a rocket motor manufacturer in Utah, have worked closely with chemists at Glidco Organics to study the feasibility of using terpenes for zero-residue wipe cleaning. The result of this work is a technological breakthrough, in which the barrier to ultra-low non-volatile residue formation has been broken. After 2 years of development and testing, SCM Glidco Organics has announced the availability of Glidsafe(registered trademark) Prepsolv(TM): a state-of-the-art ultra-low residue terpene wipe cleaning agent that does not require rinsing. Prepsolv(TM) can successfully be used in simple hand-wipe cleaning processes without fear of leaving surface residues. Industry testing has confirmed that Prepsolv(TM) is not only highly effective, but can even be less expensive to use than traditional cleaning solvents like methyl chloroform. This paper addresses the features and benefits of Prepsolv(TM), and presents performance and material compatibility data that characterizes this unique cleaning agent. Since its commercialization, Hercules Aerospace has chosen Prepsolv(TM) as the optimum cleaning agent to replace ozone-depleting solvents in their weapons factory in Magna, UT. Likewise, Boeing has approved Prepsolv(TM) for cleaning components in the manufacture of commercial aircraft at their facilities in Seattle, WA and Wichita, KS. Additional approvals are forthcoming for this uniquely safe and effective solvent.

Gallagher, R. Scott↗
NASA NTRS1994

Experiment K-7-21: Effect of Microgravity on 1: Metabolic Enzymes of Type 1 and Type 2 Muscle Fibers, and on 2: Metabolic Enzymes, Neurotransmitter Amino Acids, and Neurotransmitter Associated Enzymes in Selected Regions of the Central Nervous System: Metabolic Enzymes of Individual Muscle Fibers - Part 1

Individual fibers of any given muscle vary widely in enzyme composition, a fact obscured when enzyme levels of whole muscle are measured. Therefore, the purpose of this part of the study was to assess the effects of microgravity and hind limb suspension on the enzyme patterns within a slow twitch muscle (soleus) and a fast twitch muscle (tibialis anterior).

Lowry, O. H.↗
NASA NTRS2018

Femtosecond Laser Tagging in 1,1,1,2-Tetrauoroethane with Trace Quantities of Air

Femtosecond laser tagging is demonstrated for the first time in R134a gas, and in mixtures of R134a with small quantities of air. A systematic study of this tagging method is explored through the adjustment of gas pressure, mixture ratio and laser properties. It is found that the signal strength and lifetime are greatest at low pressures for excitation at both the 400 nm and 800 nm laser wavelengths. The relative intensities of two spectral peaks in the near-UV emission change as a function of gas pressure and can potentially be used for local pressure measurements. Single shot precision in pure R134a and R134a with 5% air is demonstrated at the exit of a subsonic pipe flow. The parameter space of these results are chosen to mimic conditions used in the NASA Langley Research Center's Transonic Dynamics Tunnel. The precision and signal lifetime demonstrate the feasibility of using this technique for measuring flowfields that induce airfoil utter.

Zhang, Yibin↗
NASA NTRS1978

Detailed 1 x 1 deg gravimetric Indian Ocean geoid and comparison with GEOS-3 radar altimeter geoid profiles

A new set of 1 x 1 deg mean free-air anomalies in the Indian Ocean is determined on the basis of previously published free-air anomaly maps (Talwani and Kahle, 1975) and the most recent Lamont surface ship gravity measurements. The data are then used to compute a (total) 1 x 1 deg gravimetric Indian Ocean geoid. The computation is carried out by combining the Goddard Space Flight Center (GSFC) GEM-6 geoid and a difference geoid that corresponds to the differences between the set of 1 x 1 deg surface gravity values and the GEM-6 gravity anomalies. The difference geoid is highest over the Madagascar Ridge (+20 m) and lowest over the Timor Trough (-30 m). The total geoid is compared with GEOS-3 radar altimeter-derived geoid profiles, and geophysical implications are discussed.

Kahle, H.-G.↗
NASA NTRS1980

Seyfert Type 1 galaxies observed with the HEAO 1 scanning modulation collimator

The paper deals with the detection of 16 X-ray sources (1.5 to 13.5 keV) during pointed observations with the HEAO 1 satellite of 19 Seyfert Type 1 (Sy 1) galaxies. For 15 sources, the Sy 1 galaxy nucleus, previously proposed as the X-ray source counterpart, lies within one of the 1 to 5 square arcmin uncertainty regions determined with the HEAO 1 modulation collimator experiment.

Dower, R. G.↗
NASA NTRS1980

Electron-impact excitation of the singlet states of N2. I - The Birge-Hopfield system /b 1 pi u - X 1 Sigma g +/

Results of a study of the electron-impact excitation of the b 1 pi u state of N2, one of the singlet states thought to be excited by precipitating electrons in the auroral zones, and of its predissociation and radiative relaxation through the emission of the Birge-Hopfield band system (b 1 pi u - X 1 Sigma g +) are presented. A collimated electron beam was passed through N2 gas producing a variety of atomic states through dissociative excitation, and the radiation resulting from relaxation of these states was observed by VUV and visible-IR monochromators. Absolute emission cross sections for 11 Birge-Hopfield bands are obtained for energies from threshold to 500 eV, and used to calculate the absolute transition probabilities for BH(1, v-prime) bands and the variation of the electric dipole moment with internuclear distance. With the exception of the v-prime equals 1, 5 and 6 vibrational levels, all b 1 pi u levels are found to predissociate with a specific predissociation branching ratio greater than 0.99, representing a major source of nitrogen atoms.

Zipf, E. C.↗
NASA NTRS1995

Thermospheric nitric oxide from the ATLAS 1 and Spacelab 1 missions

Spectral and spatial images obtained with the Imaging Spectrometric Observatory on the ATLAS 1 and Spacelab 1 missions are used to study the ultraviolet emissions of nitric oxide in the thermosphere. By synthetically fitting the measured NO gamma bands, intensities are derived as a function of altitude and latitude. We find that the NO concentrations inferred from the ATLAS 1 measurements are higher than predicted by our thermospheric airglow model and tend to lie to the high side of a number of earlier measurements. By comparison with synthetic spectral fits, the shape of the NO gamma bands is used to derive temperature as a function of altitude. Using the simultaneous spectral and spatial imaging capability of the instrument, we present the first simultaneously acquired altitude images of NO gamma band temperature and intensity in the thermosphere. The lower thermospheric temperature images show structure as a function of altitude. The spatial imaging technique appears to be a viable means of obtaining temperatures in the middle and lower thermosphere, provided that good information is also obtained at the higher altitudes, as the contribution of the overlying, hotter NO is nonnegligible. By fitting both self-absorbed and nonabsorbed bands of the NO gamma system, we show that the self absorption effects are observable up to 200 km, although small above 150 km. The spectral resolution of the instrument (1.6 A) allows separation of the N(+)(S-5) doublet, and we show the contribution of this feature to the combination of the NO gamma (1, 0) band and the N(+)(S-5) doublet as a function of altitude (less than 10% below 200 km). Spectral images including the NO delta bands support previous findings that the fluorescence efficiency is much higher than that determined from laboratory measurements. The Spacelab 1 data indicate the presence of a significant population of hot NO in the vehicle environment of that early shuttle mission.

Torr, Marsha R.↗
NASA NTRS2022

Isotropization and Evolution of Energy-Containing Eddies in Solar Wind Turbulence: Parker Solar Probe, Helios 1, ACE, WIND, and Voyager 1

We examine the radial evolution of correlation lengths perpendicular (l^ C) and parallel (  lC) to the magnetic-field direction, computed from solar wind magnetic-field data measured by Parker Solar Probe (PSP) during its first eight orbits, Helios 1, Advanced Composition Explorer (ACE), WIND, and Voyager 1 spacecraft. Correlation lengths are grouped by an interval’s alignment angle; the angle between the magnetic-field and solar wind velocity vectors (ΘBV). Parallel and perpendicular angular channels correspond to angles 0° < ΘBV < 40° and 50° < ΘBV < 90°, respectively. We observe an anisotropy in the inner heliosphere within 0.40 au, with  l l »^ 0.75 C C at 0.10 au. This anisotropy reduces with increasing heliocentric distance and the correlation lengths roughly isotropize within 1 au. Results from ACE and WIND support a reversal of the anisotropy, such that  l l »^ 1.29 C C at 1 au. The ratio does not appear to change significantly beyond 1 au, although the small number of parallel intervals in the Voyager data set precludes unambiguous conclusions from being drawn. This study provides insights regarding the radial evolution of the large, most energetic interacting turbulent fluctuations in the heliosphere. We also emphasize the importance of tracking the changes in sampling direction in PSP measurements as the spacecraft approaches the Sun, when using these data to study the radial evolution of turbulence. This can prove to be vital in understanding the more complex dynamics of the solar wind in the inner heliosphere and can assist in improving related simulations.

Manuel Enrique Cuesta↗
NASA NTRS1974

Quinoxaline polymers and copolymers derived from 1, 4-BIS(1'-napthalenyloxayl) benzene

A route for the synthesis of a new monomer, 1,4-bis(1'-naphthalenyl)-oxayl benzene, was devised, and six polymers and copolymers were prepared from this monomer, 1,4-bis(phenyloaxaly)benzene, 3,3'-diaminobenzidine and 3,3',4,4'-tetraaminobenzophenone. Thermogravimetric analysis showed that decomposition of these quinoxaline polymers and copolymers sets in at about 500 C but does not become significant in an inert atmosphere below 600 C. Oxidation becomes significant at about 550 C and the phenylquinoxaline homopolymer is somewhat more oxidation resistant than is the 1-naphthalenylquinoxaline homopolymer. Stress-relaxation measurements showed that, with two exceptions, the homopolymers and copolymers exhibited two second-order transition temperatures, one at about 204.4 C (400 F) and the other at about 315.6 C (600 F). No gross differences in the high temperature plasticity was observed between the naphthalenyl- and the phenyl-quinoaxaline homopolymers. Work was begun on a method for cross-linking polyquinoxalines. A new monomer, p-(methyloxaly)benzil, was synthesized, and model reaction studies showed that cross-linking of 2-methylquinoxaline polymers by a Michael condensation with dimaleimides will probably occur.

Port, W. S.↗
NASA NTRS1976

Quinoxaline polymers and copolymers derived from 1,4-bis(1'-naphthalenyloxalyl)benzene and their graphite composites

Experimental studies were performed with new polyquinoxalines and their graphite composites. Four polymers were synthesized, and then were characterized with respect to their inherent viscosity, elemental chemical analysis, mechanical, and thermodynamic properties. Structural formulas of the polymers and their precursors are given; methods of synthesis are described; and specifically examined was the preparation of polymers from 3,3' diamino-benzidine from 1,4- and 1,3- bis ((1'-napthalenyl) oxalyl) benzene respectively. Also considered was the preparation of polyquinoxalines from poly (p-benzil), and 1,2- aryldiamines.

Port, W. S.↗
NASA NTRS1982

The /A 1 Sigma +/ - /X 1 Sigma +/ system of the isotopic lithium hydrides - The molecular constants, potential energy curves, and their adiabatic corrections

The molecular constants and their adiabatic corrections have been determined for the (A 1 Sigma +) - (X 1 Sigma +) system of the isotopic lithium hydrides: (Li-6)H, (Li-7)H, (Li-6)D, and (Li-7)D. Using a fully quantum mechanical variational method, the potential energy curves (IPA potentials) are determined. Extending the variational method, we have obtained for the first time adiabatic corrections of potential energy curves from isotopic spectroscopic data. A significant difference between the potential energy curves of the lithium hydrides and the lithium deuterides has been observed. When Li-6 was replaced by Li-7, a significant difference was only observed for the (A 1 Sigma +) state, but not for the (X 1 Sigma +) state.

Vidal, C. R.↗
NASA NTRS1984

A second harmonic geomagnetic field line resonance at the inner edge of the plasma sheet - GEOS 1, ISEE 1, and ISEE 2 observations

A description is provided of observations made by GEOS 1, ISEE 1, and ISEE 2 of a hydromagnetic wave with a period approximately 90 s observed near 0200 LT between L = 9 and L = 6, close to the measured inner boundary of the plasma sheet. The wave magnetic oscillations perpendicular to and along the ambient field had similar amplitudes. Using primarily the transverse magnetic components, it is shown that the wave is a second harmonic resonance of the local geomagnetic field lines. ISEE 1 and 2 observed the opposite sense of polarization for about 30 min, although the spacecraft were separated by only 9 min in their orbit; this remarkable feature cannot be explained by either a stationary spatial boundary or a simple temporal boundary but could result from a rapid movement of the resonant region. It is argued that the most likely energy source is bounce resonance with medium energy (approximately 5 keV) ions. Calculations of the wave Poynting vector at ISEE 1 support this conclusion.

Hughes, W. J.↗