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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Estimate of conjugate gamma and gamma prime compositions in Ni-base superalloys

Approaches for estimating the composition of the matrix phase of alloys from the melt composition are reviewed. The first method is based on assigning essentially fixed stoichiometry to precipitating phases and is typified by PHACOMP. The second method uses analytical geometry to interpret phase diagrams and is applicable to a two-phase region of a six-component Ni-base system. The geometric method is also applicable to commercial Ni-base superalloys.

Dreshfield, R. L.↗
NASA NTRS1977

Carburization and heat treatment to cause carbide precipitation in gamma/gamma prime-delta eutectic alloys

In an attempt to improve their longitudinal shear strength, several directionally solidified eutectic alloy compositions with minor element modifications were pact, carburized, and heat treated to provide selective carbide precipitation at the cell and grain boundaries. The directionally solidified Ni-17.8 Nb-6Cr-2.5Al-3Ta (weight percent) alloy was selected for the shear strength evaluation because it showed the shallowest delta-denuded zone at the carburized surface. The carburization-carbide precipitation treatment, however, did not appear to improve the longitudinal shear strength of the alloy.

Tewari, S. N.↗
NASA NTRS1977

Estimation of conjugate gamma and gamma-prime compositions in Ni-base superalloys

To control the formation of unwanted phases, superalloy metallurgists have developed methods of estimating the composition of the matrix phase of alloys. That composition is then used to estimate the alloy's propensity toward sigma and other unwanted phase formations upon prolonged exposure to elevated temperatures in service. This paper reviews two approaches for estimating phase composition from the melt composition. One method is based on assigning essentially fixed stoichiometry to precipitating phases and is typified by 'PHACOMP'. The second method uses analytical geometry to interpret phase diagrams and is shown to be applicable to a two-phase region of a six-component Ni-base system. The geometric method is also shown to be applicable to commercial Ni-base superalloys.

Dreshfield, R. L.↗
NASA NTRS1979

A study of the excitation and radiative decay of the 3s-prime 3D-0 and 3d 3D-0 levels of atomic oxygen

The absolute cross-sections for the excitation of the 989 A, 1027 A, 7990 A, 8446 A, 1.1287 micron and 1.3164 micron multiplets of atomic oxygen by electron impact dissociation of O2 are reported. The radiative branching ratios for these transitions are calculated from these results and compared with the NBS compilation of Wiese et al. (1966) and the recent theoretical calculations of Pradhan and Saraph (1977). The cascade models of O(+) radiative recombination and of electron-impact excitation of the O I(3S) state in the terrestrial airglow are discussed in the light of the laboratory measurements, and the effects of the resonant absorption of components of the lambda 989 A and lambda 1027 A multiplets by the Birge-Hopfield band system of N2 are investigated. This process is shown to depend sensitively on the N2 vibrational temperature and to cause characteristic changes in the OI EUV emission spectrum in auroras and in the sunlit F-region at high exospheric temperatures.

Zipf, E. C.↗
NASA NTRS1981

Observations of the gas stream in the mass transfer binary HR 2142 prime 1

The mass transfer binary system HR 2142 was observed at selected phases with the high resolution spectrograph on IUE. The observations were scheduled throughout the interval 0.91 phi 0.00 in order to allow viewing of the light of the primary star through the gas stream as it presents different orientations to the line of sight. Numerous UV lines formed in the gas stream were identified. The strengths and velocity variations displayed by these lines are compared with those observed in the ground based spectral region. As part of a preliminary analysis of the IUE data, column densities and velocities from Si III (4), Si IV (1), and Ti III (1) are used to deduce electron densities in the gas stream as well as its thickness. Possible evidence for stratification in the gas stream is presented.

Peters, G. J.↗
NASA NTRS1980

Measurements of temperature and pressure fluctuations in the T prime 2 cryogenic wind tunnel

Cold wire measurement of temperature fluctuations were made in a DERAT T'2 induction powered cryogenic wind tunnel for 2 types of liquid nitrogen injectors. Thermal turbulence measured in the tranquilization chamber depends to a great extent on the injector used; for fine spray of nitrogen drops, this level of turbulence seemed completely acceptable. Fluctuations in static pressure taken from the walls of the vein by Kulite sensors showed that there was no increase in aerodynamic noise during cryogenic gusts.

Blanchard, A.↗
NASA NTRS1981

Optimal orbital transfers and prime rib curves for mission design

Battin's work on optimal one impulse transfers from circular orbits is extended. Optimal one impulse trajectories from orbits of arbitrary eccentricity through a specified point are determined. This work is then further extended to optimal two impulse transfers between massive planets. Curves derived using this technique are presented showing flyby and rendezvous Delta V requirements for all combinations of launch and arrival true anomalies. Similar curves for times of flight corresponding to the trajectories with minimum total Delta V are derived using Lambert's methods. Possible further extension of these techniques are outlined. The use of these curves for mission design is presented in a companion paper by Hulkower and Ross (1971).

Ross, D. J.↗
NASA NTRS1981

Prime agricultural land monitoring and assessment component of the California Integrated Remote Sensing System

The use of digital LANDSAT techniques for monitoring agricultural land use conversions was studied. Two study areas were investigated: one in Ventura County and the other in Fresno County (California). Ventura test site investigations included the use of three dates of LANDSAT data to improve classification performance beyond that previously obtained using single data techniques. The 9% improvement is considered highly significant. Also developed and demonstrated using Ventura County data is an automated cluster labeling procedure, considered a useful example of vertical data integration. Fresno County results for a single data LANDSAT classification paralleled those found in Ventura, demonstrating that the urban/rural fringe zone of most interest is a difficult environment to classify using LANDSAT data. A general raster to vector conversion program was developed to allow LANDSAT classification products to be transferred to an operational county level geographic information system in Fresno.

Estes, J. E.↗
NASA NTRS1983

Fluorescence branching ratios from the A2Sigma + (v-prime = 0) state of NO

The emission spectrum of NO from several rotational levels in the first excited state has been recorded. Branching ratios have been measured and Franck-Condon Factors calculated from the experimental data. Lifetimes of the lines used have been measured and Einstein A-values calculated.

Mcgee, T. J.↗
NASA NTRS1987

Design, development and test of shuttle/Centaur G-prime cryogenic tankage thermal protection systems

The thermal protection systems for the shuttle/Centaur would have had to provide fail-safe thermal protection during prelaunch, launch ascent, and on-orbit operations as well as during potential abort. The thermal protection systems selected used a helium-purged polyimide foam beneath three rediation shields for the liquid-hydrogen tank and radiation shields only for the liquid-oxygen tank (three shields on the tank sidewall and four on the aft bulkhead). A double-walled vacuum bulkhead separated the two tanks. The liquid-hydrogen tank had one 0.75-in-thick layer of foam on the forward bulkhead and two layers on the larger area sidewall. Full scale tests of the flight vehicle in a simulated shuttle cargo bay that was purged with gaseous nitrogen gave total prelaunch heating rates of 88,500 Btu/hr and 44,000 Btu/hr for the liquid-hydrogen and -oxygen tanks, respectively. Calorimeter tests on a representative sample of the liquid-hydrogen tank sidewall thermal protection system indicated that the measured unit heating rate would rapidly decrease from the prelaunch rate of approx 100 Btu/hr/sq ft to a desired rate of less than 1.3 Btu/hr/sq ft once on orbit.

Knoll, Richard H.↗
NASA NTRS1987

Shuttle/Centaur G-prime composite adapters damage tolerance/repair test program

The Space Shuttle/Centaur Composite Adapters Damage Tolerance/Repair Test program had as its goals the determination of probable and potentially critical defects or damages on the adapters' strength and stability, as well as the adequacy of repairs on significantly damaged areas and the generation of NDT data for the upgrading of acceptance criteria. Such rational accept/reject criteria and repair methods reduce both engineering liason costs and any unnecessary parts-scrapping. Successful 'damage tolerant' design ensures that degradations of strength and stability due to undetected defects or damage will not be catastrophic.

Sollars, Teresa A.↗