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At least 253 records · Page 14

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NASA NTRS1976

Interstellar molecules

Progress in the discovery and study of interstellar molecules is summarized. The 36 molecular species thus far identified in interstellar space are listed in several groups which include simple hydrides, oxides, and sulfides, various derivatives of ammonia, molecules involving linear carbon chains, cyanides, and molecules related in structure to formaldehyde, alcohols, or ethers. Several free radicals are described, the discovery of molecules in external galaxies is discussed, and possible mechanisms for molecular formation are noted. Methods for examining relative isotopic abundances by measuring molecules in interstellar clouds are outlined, mechanisms for the excitation of interstellar molecules are reviewed, and values are presented for the C-12/C-13 abundance ratio in a number of interstellar clouds. The detection of interstellar masers is discussed along with pumping mechanisms and masing transitions in H2CO, CH, OH, and SiO. The nature of dense interstellar clouds is examined in terms of several simple and complex cloud models, with emphasis on multiple condensation models.

Townes, C. H.↗

NASA NTRS1976

New metal atom laser transitions in As, Bi, Ga, Ge, Hg, In, Pb, Sb, and Tl

A double discharge technique was used in the investigation. An initial discharge established between parallel arrays of tungsten pin electrodes was followed, after a variable time delay, by a high voltage (180 kV), short duration (50 nsec) secondary discharge between two aluminum main electrodes. Metal compounds, including metal alkyls, hydrides, and halides, were used to obtain the required metal atom concentrations. Twenty-four new laser transitions involving 9 different metal atoms were observed. The observed relations are shown in a number of partial energy-level diagrams.

Chou, M. S.↗

NASA NTRS1977

Inverse isotope effect and the x dependence of the superconducting transition temperature in PdHx and PdDx

First-principles electron-band-structure calculations and measured phonon properties are employed in a calculation of the concentration dependence of the superconducting transition temperatures for PdHx and PdDx, including the inverse isotope effect. Excellent agreement with the experimental results is obtained. Our model also gives a qualitative understanding of the enhanced transition temperatures in the palladium-noble-metal hydrides.

Klein, B. M.↗

NASA NTRS1977

ERDA's Chemical Energy Storage Program

The Chemical Energy Storage Program is described with emphasis on hydrogen storage. Storage techniques considered include pressurized hydrogen gas storage, cryogenic liquid hydrogen storage, storage in hydride compounds, and aromatic-alicyclic hydrogen storage. Some uses of energy storage are suggested. Information on hydrogen production and hydrogen use is also presented. Applications of hydrogen energy systems include storage of hydrogen for utilities load leveling, industrial marketing of hydrogen both as a chemical and as a fuel, natural gas supplementation, vehicular applications, and direct substitution for natural gas.

Swisher, J. H.↗

NASA NTRS1977

Infrared laboratory studies of synthetic planetary atmospheres

Topics covered include: the broadening of individual lines in the CO fundamental by various gases; total band absorptance as a function of absorber thickness and total effect pressure at various temperatures for bands of CO and N2O; nitric acid vapor content in the region of the ozone layer; optical properties of solid NH3; HSO4 concentration in Venus clouds; Burch's law of multiplicative transmittance for mixing absorbing gases when their lines are broadened by helium and hydrogen; ling strength and self-broadening parameters in the v3 fundamental of CO2 and N2O; optical constants of liquid ammonia, liquid methane, saturated hydrocarbons, ammonium hydride and ammonium salts.

Williams, D.↗

NASA NTRS1977

Lamination residual strains and stresses in hybrid laminates

An investigation is conducted of the effects of hybridization on the magnitude of lamination residual stresses. Eight-ply graphite/Kevlar 49/epoxy and graphite/S-glass/epoxy laminates were studied. The same matrix resin was selected for all basic materials to ensure compatibility and uniform curing of the various plies. The specimens, with inserted strain gages and thermocouples, were subjected to curing and postcuring cycles in an autoclave. Subsequently, the specimens were subjected to a thermal cycle from room temperature to 444 K and down to room temperature. It was found that hydridizing reduces apparently residual strains and stresses in the graphite plies. However, these strains were not affected much by the type and degree of hybridization.

Daniel, I. M.↗

NASA NTRS1977

Radiation protection design considerations for man in geosynchronous orbits

A description is presented of preliminary studies which have been carried out to identify design requirements and mission constraints imposed by the geosynchronous radiation environment. The radiation species of dominant impact are the trapped electrons and solar flare particles. The criterion used in the conducted shielding design analysis has been to limit the skin dose to 100 rems for 3 months. The analysis included the optimization of an electron/bremsstrahlung shield for residence within the vehicle, the minimization of the dose received in extravehicular activity, and the calculation of special shield requirements for solar flares. An investigation was conducted of the potential benefits accruing from a three-layered composite shield with part of the aluminum layer replaced with a lower atomic number material. The materials considered were polyethylene, carbon, beryllium, and lithium hydride.

Rossi, M. L.↗

NASA NTRS1978

Upper limits to trace constituents in Jupiter's atmosphere from an analysis of its 5 micrometer spectrum

A high-resolution spectrum of Jupiter at 5 micrometers recorded at the Kuiper Airborne Observatory is used to determine upper limits to the column density of 19 molecules. The upper limits to the mixing ratios of SiH4, H2S, HCN, and simple hydrocarbons are discussed with respect to current models of Jupiter's atmosphere. These upper limits are compared to expectations based upon the solar abundance of the elements. This analysis permits upper limit measurements (SiH4), or actual detections (GeH4) of molecules with mixing ratios with hydrogen as low as 10 to the minus 9th power. In future observations at 5 micrometers the sensitivity of remote spectroscopic analyses should permit the study of constituents with mixing ratios as low as 10 to the minus 10th power, which would include the hydrides of such elements as Sn and As as well as numerous organic molecules.

Treffers, R. R.↗

NASA NTRS1979

Hydrogen-fueled postal vehicle performance evaluation

Fuel consumption, range, and emissions data were obtained while operating a hydrogen-fueled postal delivery vehicle over a defined Postal Service Driving Cycle and the 1975 Urban Driving Cycle. The vehicle's fuel consumption was 0.366 pounds of hydrogen per mile over the postal driving cycle and 0.22 pounds of hydrogen per mile over the urban driving cycle. These data correspond to 6.2 and 10.6 mpg equivalent gasoline mileage for the two driving cycles, respectively. The vehicle's range was 24.2 miles while being operated on the postal driving cycle. Vehicle emissions were measured over the urban driving cycle. HC and CO emissions were quite low, as would be expected. The oxides of nitrogen were found to be 4.86 gm/mi, a value which is well above the current Federal and California standards. Vehicle limitations discussed include excessive engine flashbacks, inadequate acceleration capability the engine air/fuel ratio, the water injection systems, and the cab temperature. Other concerns are safety considerations, iron-titanium hydride observed in the fuel system, evidence of water in the engine rocker cover, and the vehicle maintenance required during the evaluation.

Hall, R. A.↗

NASA NTRS1978

Computational test of the infinite order sudden approximation for excitation of linear rigid rotors by collisions with atoms

The infinite order sudden approximation for excitation of linear rigid rotors by collisions with atom is tested by comparing integral state-to-state cross sections with accurate close coupling and coupled states results. The systems studied are HCl-Ar, HCl-He, CO-He, HCN-He, CS-H2 and OCS-H2. With the exception of diatomic hydrides (e.g., HCl) which have atypically large rotational constants the method is found to be very accurate to remarkably low collision energies. This approximation should generally be extremely useful for thermal energy collisions.

Green, S.↗

NASA NTRS1981

Gas absorption/desorption temperature-differential engine

Continuously operating compressor system converts 90 percent of gas-turbine plant energy to electricity. Conventional plants work in batch mode, operating at 40 percent efficiency. Compressor uses metal hydride matrix on outside of rotating drum to generate working gas, hydrogen. Rolling valve seals allow continuous work. During operation, gas is absorbed, releasing heat, and desorbed with heat gain. System conserves nuclear and fossil fuels, reducing powerplant capital and operating costs.

Miller, C. G.↗

NASA NTRS1978

Curable liquid hydrocarbon prepolymers containing hydroxyl groups and process for producing same

Production of hydroxyl containing curable liquid hydrocarbon prepolymers by ozonizing a high molecular weight saturated hydrocarbon polymer such as polyisobutylene or ethylene propylene rubber is discussed. The ozonized material is reduced using reducing agents, preferably diisobutyl aluminum hydride, to form the hydroxyl containing liquid prepolymers having a substantially lower molecular weight than the parent polymer. The resulting curable liquid hydroxyl containing prepolymers can be poured into a mold and readily cured, with reactants such as toluene diisocyanate, to produce highly stable elastomers having a variety of uses such as binders for solid propellants.

Rhein, R. A.↗

NASA NTRS1980

Prepolymer dianhydrides

A process for preparing dianhydrides that are miscible with hydroxyl prepolymers at moderate temperatures and can cure hydroxyl prepolymers to elastomers at moderate temperatures is disclosed. The dianhydrides are prepared by solution reaction of a prepolymer diol with excess hydride followed by removal of unreacted dianhydride. The prepolymer dianhydrides are miscible with hydroxyl substituted hydrocarbon prepolymers and cure the prepolymers to polyester-linked elastomers.

Rhein, R. A.↗

NASA NTRS1982

Infrared absorption of sulfur bearing compounds

The sulfur bearing molecules of most interest in studies of planetary atmospheres are the simple, stable hydrides and oxides, H2S, H2SO4, SO2, and SO3, and the carbon containing species OCS and CO2. For interpreting spectroscopic observations, the properties that must be known are: transition frequencies, transition intensities, transition assignments in terms of quantum number assignments and lower state energy levels, and pressure broadening constants (including their temperature dependence).

Maki, A.↗

NASA NTRS1981

Assessment of alternative power sources for mobile mining machinery

Alternative mobile power sources for mining applications were assessed. A wide variety of heat engines and energy systems was examined as potential alternatives to presently used power systems. The present mobile power systems are electrical trailing cable, electrical battery, and diesel - with diesel being largely limited in the United States to noncoal mines. Each candidate power source was evaluated for the following requirements: (1) ability to achieve the duty cycle; (2) ability to meet Government regulations; (3) availability (production readiness); (4) market availability; and (5) packaging capability. Screening reduced the list of candidates to the following power sources: diesel, stirling, gas turbine, rankine (steam), advanced electric (batteries), mechanical energy storage (flywheel), and use of hydrogen evolved from metal hydrides. This list of candidates is divided into two classes of alternative power sources for mining applications, heat engines and energy storage systems.

Cairelli, J. E.↗

NASA NTRS1982

Hydrogen diffusion and electronic structure in crystalline and amorphous Ti/sub y/CuH/sub x/

Hydrogen diffusion behavior and electronic properties of crystalline TiCuHo94, Ti2CuH1.90, and Ti2CuH2.63 and amorphous a-TiCuH1.4 were studied using proton relaxation times, proton Knight shifts, and magnetic susceptibilities. Crystal structure and hydrogen site occupancy have major roles in hydrogen mobility. The density of electron states at E sub F is reduced in amorphous a-TiCuH1.4 compared to the crystalline hydrides.

Bowman, R. C., Jr.↗

NASA NTRS1983

Cooling by conversion of para to ortho-hydrogen

The cooling capacity of a solid hydrogen cooling system is significantly increased by exposing vapor created during evaporation of a solid hydrogen mass to a catalyst and thereby accelerating the endothermic para-to-ortho transition of the vapor to equilibrium hydrogen. Catalyst such as nickel, copper, iron or metal hydride gels of films in a low pressure drop catalytic reactor are suitable for accelerating the endothermic para-to-ortho conversion.

Sherman, A.↗

NASA NTRS1983

Non-noble metal based metallization systems

The results of efforts to produce a nonsilver metallization system for silicon photovoltaic cells are given. The system uses a metallization system based on molybdenum, tin, and titanium hydride. The initial work in this system was done using the MIDFILM process. The MIDFILM process attains a line resolution comparable to photoresist methods with a process related to screen printing. The surface to be processed is first coated with a thin layer of photopolymer material. Upon exposure to ultraviolet light through a suitable mask, the polymer in the non-pattern area crosslinks and becomes hard. The unexposed pattern areas remain tacky. The conductor material is then applied in the form of a dry mixture of metal which adheres to the tacky pattern area. The assemblage is then fired to ash the photopolymer and sinter the conductor powder.

Garcia, A., III↗