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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Creep-rupture behavior of candidate Stirling engine alloys after long-term aging at 760 deg C in low-pressure hydrogen

Nine candidate Stirling automotive engine alloys were aged at 760 C for 3500 hr in low pressure hydrogen or argon to determine the resulting effects on mechanical behavior. Candidate heater head tube alloys were CG-27, W545, 12RN72, INCONEL-718, and HS-188 while candidate cast cylinder-regenerator housing alloys were SA-F11, CRM-6D, XF-818, and HS-31. Aging per se is detrimental to the creep rupture and tensile strengths of the iron base alloys. The presence of hydrogen does not significantly contribute to strength degradation. Based percent highway driving cycle; CG-27 has adequate 3500 hr - 870 C creep rupture strength and SA-Fll, CRM-6D, and XF-818 have adequate 3500 hr - 775 C creep rupture strength.

Titran, R. H.↗
NASA NTRS1984

Splitting of C IV lines in a QSO absorption-line system

The C IV doublet in the z = 1.795 absorption-line system in the QSO B2 1225 + 317 has been observed with the Multiple Mirror Telescope echelle spectrograph at a resolution of 10 km/s. The profile of C IV, previously known to contain at least three velocity components, is shown to consist of at least eleven. Individual components have Doppler width upper limits of 6.4-13.2 km/s. These low upper limits, plus a study of published profile shapes for several other species, suggest that the observed gas is not in an equilibrium state of collisional ionization, and that electron temperatures are 35,000 K or lower. The width of the aggregate profile (approximately 500 km/s) is larger by a factor of 5 than any C IV or Si IV profile observed through the halo of the Galaxy, while individual components are narrower than those in the Galaxy. Thus, intervening galaxies with halos similar to that of the Galaxy, even if occurring in groups, may not explain this QSO absorption-line system.

York, D. G.↗
NASA NTRS1984

Dynamics of solar filaments. III - Analysis of steady flows in H-alpha and C IV lines

A statistical analysis of intensities and radial velocities of several solar plage filaments (i.e. prominences seen on the solar disk) observed at disk center is presented. Intensity and radial (= vertical) velocity maps were derived from simultaneous 2D measurements of the H-alpha chromospheric line with the Multichannel Subtractive Double Pass spectrograph operating on the Meudon solar tower, and also obtained from 2D recordings of the C IV transition-zone line (1548 A) with the UV Spectrometer and Polarimeter aboard the Solar Maximum Mission satellite. A good correlation (around 0.5) is found between intensities in both lines, as well as between velocities. Persistent upflows are measured in both lines at the filament location. The mean vertical velocities are respectively 0.5 km/s in H-alpha and 5.6 km/s in C IV. The analysis of mass fluxes suggests that C IV upflows occur in the transition region around prominences rather than below, in the chromosphere-corona transition zone.

Schmieder, B.↗
NASA NTRS1985

STPI/LARC: A 200 deg C polyimide adhesive

A copolyimide, STPI/LARC, was prepared from the reaction of 3,3'4'benzophenonetetracarboxylic dianhydride (BTDA), equimolar quantities of m-phenylenediamine and 4,4'-oxydianiline, and a small amount of phthalic anhydride to control the molecular weight. The processability and adhesive properties of STPI/LARC were compared to those of a commercially available form of LARC-TPI. LARC-TPI, a thermoplastic polyimide, from the reaction of BTDA and 3,3'-diaminobenzophenone, had previously shown promise as a high temperature structural adhesive. Lap shear specimens were fabricated using adhesive tape prepared from each of the two polymers. Lap shear tests were performed at room temperature, 177 C, and 204 C before and after exposure to a 72-hour water-boil and to aging at 204 C.

Progar, D. J.↗
NASA NTRS1985

On a possibility of inelasticity partial coefficient K sub gamma determination in pi C and pi Pb interactions at 10 to the 14th power eV (experiment PAMIR 1)

The investigation of hadron-nuclear interactions in Pamir experiment is carried out by means of X-ray emulsion chambers of two types: carbon (C) and lead (Pb). While comparing the results from the chambers of both types it was found a discrepancy in n sub h and E sub h(1)R values. The observed discrepancy in C and Pb chambers is connected with the difference in values of effective coefficients of energy transfer to the soft component K sub eff for C and Pb chambers.

Borisov, A. S.↗
NASA NTRS1985

Exotic interactions among C-jets and Pb-jets

The C-jets and Pb-jets were surveyed on the part of Chacaltaya emulsion chamber No.19 amounting to an exposure of 28.8 sq m yr. It is shown that the adopted events make up an unbiased sample of C-jets for sigma sub E gamma TeV. Mini-Centauro interaction gives the most natural explanation for the eight pinaught-less C-jets with three or more constituent shower core. Out of the eight double-cored pinaught-less events, three are found to have visible invariant masses 1.8 GeV/c. Three Pb-jets-lower are composed of double cores whose respective visible transverse momenta are greater than 0.5 GeV/c, suggesting that they are of Geminion origin or chiron origin. The energies of the parent particles are estimated to be 100 to 200 TeV for all three kinds of events. The implications of this energy estimate and the frequency of observed exotic events are discussed.

Source record↗
NASA NTRS1984

A study of fatigue damage mechanisms in Waspaloy from 25 to 800 C

The objective of the study was to examine the effect of various microstructures on the fatigue and damage accumulation behavior of Waspaloy, a nickel-base alloy commonly used in aircraft engines. Shearing was the dominant deformation mode in specimens with coarse grains and small (50-80 A) gamma prime particles, whereas Orowan looping was dominant in fine-grained specimens with large (about 900 A) gamma prime particles. At temperatures up to 500 C, cracks initiated transgranularly, while at 800 C the failure process was intergranular for both coarse-grained and fine-grained specimens. At temperatures above 500 C, a significant decrease in the fatigue life was observed for both coarse-grained and fine-grained material.

Lerch, B. A.↗
NASA NTRS1986

Auger electron spectroscopy, secondary ion mass spectroscopy and optical characterization of a-C-H and BN films

The amorphous dielectrics a-C:H and BN were deposited on III-V semiconductors. Optical band gaps as high as 3 eV were measured for a-C:H generated by C4H10 plasmas; a comparison was made with bad gaps obtained from films prepared by CH4 glow discharges. The ion beam deposited BN films exhibited amorphous behavior with band gaps on the order of 5 eV. Film compositions were studied by Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The optical properties were characterized by ellipsometry, UV/VIS absorption, and IR reflection and transmission. Etching rates of a-C:H subjected to O2 dicharges were determined.

Pouch, J. J.↗
NASA NTRS1986

RR Lyrae stars - A theoretical study of Bailey type c variables

New theoretical models of stars pulsating in the first overtone have been constructed to simulate RR Lyr variables of Bailey type c. Despite the use of different opacities, these new models agree very well with earlier models built by Christy and Stellingwerf. Quantitative comparisons using empirical light curves and velocity curves of metal-poor type c variables confirm the validity of the models. Masses of 0.55-0.65 solar mass and luminosities of 40-50 solar luminosities derived here for the type c variables, are consistent with previous results obtained for type ab variables. A Christy echo of the kind normally associated with fundamental-mode pulsators was detected in the interior velocity structure of one first-overtone model that happens to have a large velocity amplitude.

Hubickyj, Olenka↗
NASA NTRS1987

Hydrogenated amorphous carbon (a:C-H) in the planetary nebula NGC 7027

A spectroscopic identification of the infrared continuum radiation is proposed for the planetary nebula NGC 7027. Hydrogenated amorphous carbon (a:C-H) is shown to account for the undulating spectrum between 5 and 15 microns. The unidentified infrared emission bands lie at the peaks in the a:C-H spectrum, pointing to their association with a carbon polymorph, possibly a:C-H or polycyclic aromatic hydrocarbon molecules. Except for atomic emission lines, all the infrared emission from NGC 7027 comes from one or another polymorph of carbon.

Goebel, John H.↗
NASA NTRS1988

Tribological properties of alumina-boria-silicate fabric from 25 to 850 C

Demanding tribological properties are required of the materials used for the sliding seal between the sidewalls and the lower wall of the variable area hypersonic engine. Temperatures range from room temperature and below to operating temperatures of 1000 C in an environment of air, hydrogen, and water vapor. Candidate sealing materials for this application are an alumina-boria-silicate, ceramic, fabric rope sliding against the engine walls which may be made from copper- or nickel-based alloys. Using a pin-on-disk tribometer, the friction and wear properties of some of these potential materials and possible lubrication methods are evaluated. The ceramic fabric rope displayed unacceptably high friction coefficients (0.6 to 1.3) and, thus, requires lubrication. Sputtered thin films of gold, silver, and CaF2 reduced the friction by a factor of two. Sprayed coatings of boride nitride did not effectively lubricate the fabric. Static heat treatment tests at 950 C indicate that the fabric is chemically attacked by large quantities of silver, CaF2, and boron nitride. Sputtered films or powder impregnation of the fabric with gold may provide adequate lubrication up to 1000 C without showing any chemical attack.

Dellacorte, Christopher↗
NASA NTRS1988

A thermally modified polymer matrix composite material with structural integrity to 371 C

The potential for utilizing surface coatings to inhibit the thermal oxidation of polymer matrix composites was studied. Isothermal, inert gas exposures of graphite/PMR-15 composites indicated that after an initial loss of weight, no significant amounts of thermal degradation products are given off during high temperature exposures in the absence of oxygen. As long as a coating remains effective, the composite material should remain stable. It was also found that the glass transition temperature T sub g of the matrix resin could be increased to values in excess of 400 C. This resulted in measured short beam shear strengths of 75.9 MPa (11 Ksi), flexural strengths of 1172 MPa (170 Ksi) and flexural moduli of 141 GPa (20.5 Msi) for the material at a test temperature of 371 C. The treatment that was used caused a decrease in the PMR-15 resin density from 1.31 to 1.29 gm/cc. It was concluded that state-of-the-art composites, protected by oxygen-impervious coatings, can be used as materials of construction with structural integrity to at least 371 C and possibly above.

Bowles, Kenneth J.↗
NASA NTRS1987

Estimation of biophysical properties of forest canopies using C-band microwave data

A scatterometer ranging experiment is described in which C-band data and boresight photography were collected using a helicopter so as to provide a capability to study scattering processes in forest canopies in the Superior National Forest in Minnesota. An inversion scheme is used to determine C-band volume extinction and scattering coefficients for high density aspen sites. Analysis of data through the season indicates that VV, HH, and VH volume extinction coefficients change during the year and are presumably affected by the emergence and senescence of leaves. A linear relationship was observed between sigma(0) (VV) and leaf area index for low and medium density aspen sites, but a large decrease occurred in sigma(0) for both high density sites. Calculations using the Fung disk model, which accounts only for the leaves, shows an underestimate of sigma(0) by a factor of two or three indicating that scattering by branches and soil background may be important at C-band.

Pitts, David E.↗
NASA NTRS1988

The C IV doublet ratio intensity effect in symbiotic stars

High-resolution UV spectra in the 1200-2000 wavelength range of the symbiotic variable R Aqr and its nebular jet were obtained in July 1987 with the IUE. The line profile structure of the C IV 1548, 1550 doublet in the jet indicates multicomponent velocity structure from an optically thin emitting gas. The C IV doublet profiles in the compact H II region engulfing the Mira and hot companion binary also suggest multicomponent structure with radial velocities up to about -100 km/s. The value of the doublet intensity ratio in the R Aqr H II region has been observed in other similar symbiotic stars, such as RX Pup. It is suggested that the anomalous behavior of the C IV doublet intensities may be useful for studying the spatial structure and temporal nature of winds in symbiotic stars.

Michalitsianos, A. G.↗
NASA NTRS1988

The origin of type C inclusions from carbonaceous chondrites

The origin of type C inclusions found in carbonaceous chondrites and the relationship of the type C inclusions to other Ca- and Al-rich chondrules are discussed on the basis of major-element composition of these objects. The results on bulk composition analysis of primary phase assemblages in eight Allende-type inclusions and an Allende glass-spinel inclusion were found to be consistent with the following scenario: (1) the condensation of melilite + spinel + perovskite +/- hibonite +/- CaAl4O7; (2) the reaction of melilite + spinel with SiO2(g); (3) the removal of inclusions from further interaction with the reacting gas; (4) melting with little or no volatilization; (5) crystallization; (6) alteration; and (7) incorporation of inclusions into host meteorite. Type C inclusions are considered to be precursors to Al-rich chondrules in ordinary and enstatite chondrites, i.e., they are considered to be a spinel-rich class of type A that reacted with silica from a coexisting gas to produce anorthite plus diopside.

Beckett, John R.↗
NASA NTRS1988

Adhesion, friction, and wear of plasma-deposited thin silicon nitride films at temperatures to 700 C

The adhesion, friction, and wear behavior of silicon nitride films deposited by low- and high-frequency plasmas (30 kHz and 13.56 MHz) at various temperatures to 700 C in vacuum were examined. The results of the investigation indicated that the Si/N ratios were much greater for the films deposited at 13.56 MHz than for those deposited at 30 kHz. Amorphous silicon was present in both low- and high-frequency plasma-deposited silicon nitride films. However, more amorphous silicon occurred in the films deposited at 13.56 MHz than in those deposited at 30 kHz. Temperature significantly influenced adhesion, friction, and wear of the silicon nitride films. Wear occurred in the contact area at high temperature. The wear correlated with the increase in adhesion and friction for the low- and high-frequency plasma-deposited films above 600 and 500 C, respectively. The low- and high-frequency plasma-deposited thin silicon nitride films exhibited a capability for lubrication (low adhesion and friction) in vacuum at temperatures to 500 and 400 C, respectively.

Miyoshi, K.↗
NASA NTRS1989

Microwave time delays for the dual L-C-band feed system

A new dual-frequency feed system at Goldstone is designed to receive the Phobos spacecraft signal at L-band (1668 + or - 40 MHz) and transmit to the spacecraft at C-band (5008.75 + or - 5.00 MHz) simultaneously. Hence, calculations of the time delay from the C-band range calibration coupler to the phase center of the L-C dual feed and back to the L-band range calibration coupler are required to correct the range measurements. Time delays of the elements in the dual-frequency feed system are obtained mostly from computer calculations and partly from experimental measurements. The method used and results obtained are described.

Chen, J.↗
NASA NTRS1989

Predicted performance of InP solar cells in Cassegrainian and slats space concentrator arrays at 20 to 100 AM0, 80 to 100 C

Researchers have calculated the expected performance dependence of near-optimally designed shallow homojunction n+pp+InP solar cells on incident intensities up 200 AM0 and temperatures up to 100 C (373K). Both circular and rectangular cells have been considered, the former for use in a Cassegrainian concentrator array at 100 AM0, 80 to 100 C and the latter for use in a Slats type concentrator array at 20 AM0 80 to 100 C. Calculation of the temperature dependence of the performance parameters I sub sc, V sub oc, FF and eta was done by first verifying that the use of the measured temperature variation of I sub sc, of the best published value of the temperature dependence of the bandgap of InP, and of the temperature dependences of the lifetimes and mobilities of electrons and holes the same as in equivalently doped GaAs, gave calculated results that closely matched measured data on the temperature variation of I sub sc, V sub oc, and FF of four existing InP cells at 1 AM0. It was then assumed that the same temperature dependences of I sub sc, the bandgap and lifetimes and mobilities would hold in the near-optimally designed cells at the higher concentrations.

Goradia, Chandra↗