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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 1,243 records · Page 69
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Shock-tube measurements of carbon to oxygen atom ratios for incipient soot formation with C2H2, C2H4 and C2H6 fuels

The critical atomic carbon to oxygen ratios, Phi sub C, for incipient soot formation in shock heated acetylene, ethylene, ethane/oxygen/ argon mixtures was measured over the temperature range 2000 K to 2500 K for reactant partial pressures between 0.1 and 0.4 atoms. Absorption of light from a He-Ne laser at 6328A was was used to detect soot. It was observed that the values of Phi sub C for all three fuels increased uniformly with temperature such that at the highest temperatures Phi sub C was considerably greater than unity, i.e. greater than the value of about unity at which solid carbon should have been precipitated on a thermochemical equilibrium basis. Observations were made over periods extending up to about one millisecond, which was well in excess of the time required for the major heat release of the combustion reactions. The relevance of these experimental findings to the problem of soot formation in gas turbine combustion chambers is discussed.

Radcliffe, S. W.↗
NASA NTRS1971

Deformed Brueckner-Hartree-Fock calculation for light nuclei

For the first time the Brueckner-Hartree-Fock (BHF) method was applied to nuclei whose intrinsic structure is nonspherical. One aim was to investigate whether the energy dependent reaction matrix calculated from a realistic nucleon-nucleon interaction leads to deformations similar to, or different from, those obtained from energy independent interactions in Hartree-Fock (HF) calculations. Reaction matrix elements were calculated as a function of starting energy for the Hamada-Johnston interaction, using a Pauli operator appropriate to O-16 and a shifted oscillator spectrum for virtual excited states. Binding energies, single-particle energies, radii, and shape deformations of the intrinsic state in unrenormalized as well as renormalized BHF are discussed and compared with previous HF studies. Results are presented for C-12, O-16, and Ne-20.

Braley, R. C.↗
NASA NTRS1971

Theoretical studies of ionic and atomic impact phenomena

An absorbing sphere model based on the Landau-Zener method was developed for calculating the energy dependence of the total cross sections for the reaction A(+) + B(-) yields A star + B + Delta E, in which A or B may be atomic or molecular species. It was found that the cross sections were highly dependent on the electron detachment energy of B(-). The ionization total cross sections for Ne star (2p5 3s 3P) + Ar were calculated over a large energy range and compared with experiments.

Olson, R. E.↗
NASA NTRS1972

The design of a source to simulate the gamma-ray spectrum emitted by a radioisotope thermoelectric generator

A simulated source was designed to duplicate the gamma spectrum of a uniform cylindrical 2200-watt Pu02 radioisotope thermoelectric generator containing 81% Pu-238 and 1.2 ppm Pu-236. Gamma rays from the decay of Pu-238, Am-241, Pu-239, and the 0-18(alpha,n)Ne-21 reaction were catalogued in broad energy groups. Two 46- and one 22-mc Th-228 sources provided simulation at various times in the life of the fuel capsule up to 18 years, which covers the time span of an outer planet mission. Emission from Th-228 represents the overwhelming contribution of the gamma spectrum after the first few years. The sources, in the form of 13-inch rods, were placed in a concentric hole in a cylinder of depleted uranium, which provided shielding equivalent to the self-shielding of the fuel capsule. The thickness of the U-238 cylinder (0.55cm) was determined by Monte Carlo calculations to insure that the spectrum emerging from the simulated source matched that of the fuel capsule.

Reier, M.↗
NASA NTRS1972

Short-range correlations in carbon-12, oxygen-16, and neon-20: Intrinsic properties

The Brueckner-Hartree-Fock (BHF) method has been applied to nuclei whose intrinsic structure is nonspherical. Reaction matrix elements were calculated as functions of starting energy for the Hamada-Johnston interaction using the Pauli operator appropriate to O-16 and a shifted oscillator spectrum for virtual excited states. Binding energies, single particle energies, radii, and shape deformations of the intrinsic state, in ordinary as well as renormalized BHF, are discussed and compared with previous HF studies and with experiment when possible. Results are presented for C-12, 0-16 and Ne-20. It is found that the binding energies and radii are too small, but that separation energies are well reproduced when the renormalized theory is used.

Braley, R. C.↗
NASA NTRS1971

Amplitude and polarization asymmetries in a ring laser

Asymmetric amplitude effects between the oppositely directed traveling waves in a He-Ne ring laser are analyzed both theoretically and experimentally. These effects make it possible to detect angular orientations of an inner-cavity bar with respect to the plane of the ring cavity. The amplitude asymmetries occur when a birefringent bar is placed in the three-mirror ring cavity, and an axial magnetic field is applied to the active medium. A simplified theoretical analysis is performed by using a first order perturbation theory to derive an expression for the polarization of the active medium, and a set of self-consistent equations are derived to predict threshold conditions. Polarization asymmetries between the oppositely directed waves are also predicted. Amplitude asymmetries similar in nature to those predicted at threshold occur when the laser is operating in 12-15 free-running modes, and polarization asymmetry occurs simultaneously.

Campbell, L. L.↗
NASA NTRS1971

A case for catastrophic early degassing of the earth.

Evidence is given for the occurrence in early earth history of massive escape of volatiles from the interior of the earth to its surface, which must have had catastrophic proportions. The mechanism and time of this event are inferred from the abundances and distribution of volatiles in the atmosphere, hydrosphere and crust, and from meteorite studies, and geophysical and astronomical observations. This event is linked to the melting of the earth during accretion which resulted in the concentration of U, Th, K and Pb in the outermost portion of the earth and in virtually complete expulsion of nonradiogenic Ar, Ne and Kr from its interior.

Fanale, F. P.↗