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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 217 records · Page 12

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NASA NTRS1989

Thermal Brushes For Memory-Metal Actuators

Thermoelectric elements with wire-brush contacts remove heat from or add heat to memory-metal actuators and thereby enable them to respond faster than previously possible. Memory-metal actuator formed to shape while hot, then to another shape while cold. When cold actuator heated so temperature rises above critical point, snaps from cold shape to hot shape. Upon cooling, actuator returns to cold shape, ready for another cycle. Clearly, faster actuator is heated and cooled, the faster it operates.

Wood, Charles↗

NASA NTRS1988

Concepts for interrelating ultrasonic attenuation, microstructure, and fracture toughness in polycrystalline solids

Conceptual models are advanced for explaining and predicting empirical correlations found between ultrasonic measurements and fracture toughness of polycrystalline solids. The models lead to insights concerning microstructural factors governing fracture processes and associated stress wave interactions. Analysis of the empirical correlations suggested by the models indicate that, in addition to grain size and shape, grain boundary reflections, elastic anisotropy, and dislocation damping are factors that underlie both fracture toughness and ultrasonic attenuation. One outcome is that ultrasonic attenuation can predict the size of crack blunting or process zones that develop in the vicinity of active cracks in metals. This forms a basis for ultrasonic ranking according to variations in fracture toughness.

Vary, A.↗

NASA NTRS1992

Lunar oxygen - The reduction of glass by hydrogen

The direct reduction of volcanic glass by hydrogen has been proposed as a method of extracting oxygen from the lunar soil. Experiments using lunar simulant glasses reacted with flowing hydrogen gas have demonstrated reduction at temperatures from 1000 to 1200 C. For melted samples ferrous iron was reduced to the metal, which formed large crystals at the expense of the glass. Samples held below the melting point rapidly devitrified, and iron was formed from submicrometer crystals of ilmenite and pyroxene. Weight losses of 3.6 - 4.5 percent, depending on glass composition, were achieved in 3 hours at 1100 C. A lunar oxygen plant operating at this efficiency and utilizing Apollo 17 orange glass as a feedstock could produce 50 kg of oxygen per ton of soil. The processes of reduction and sintering of lunar soil are synergistic, and could be combined to produce both oxygen and construction material at a moon base.

Allen, Carlton C.↗

NASA NTRS1993

Investigation of low cost material processes for liquid rocket engines

The development of low cost material processes is essential to the achievement of economical liquid rocket propulsion systems in the next century. This paper will present the results of the evaluation of some promising material processes including powder metallurgy, vacuum plasma spray, metal spray forming, and bulge forming. The physical and mechanical test results from the samples and subscale hardware fabricated from high strength copper alloys and superalloys will be discussed.

Nguyentat, Thinh↗

NASA NTRS1931

Full-Scale Wind-Tunnel Tests on Several Metal Propellers Having Different Blade Forms

This report gives the full-scale aerodynamic characteristics of five different aluminum alloy propellers having four different blade forms. They were tested on an open cockpit fuselage with a radial air-cooled engine having conventional cowling. The results show that (1) the differences in propulsive efficiency due to the differences in blade form were small; (2) the form with the thinnest airfoil sections had the highest efficiency; (3) it is advantageous as regards propulsive efficiency for a propeller operating in front of a body, such as a radial engine, to have its pitch reduced toward the hub.

Weick, Fred E↗

NASA NTRS1994

IDGE: Isothermal Dendritic Growth Experiment

The Isothermal Dendritic Growth Experiment (IDGE) flew on STS-62 to study the microscopic, tree-like structures (dendrites) that form within metals as they solidify from molten materials. The size, shape, and orientation of these dendrites affect the strength and usefulness of metals. Data from this experiment will be used to test and improve the mathematical models that support the industrial production of metals.

Source record↗

NASA NTRS1994

Loss of solar He and Ne from IDPS in subducting sediment: Diffusion and the effect of phase changes

The results of the diffusion experiment for solar He and Ne in IDP's in a magnetic separate from Pacific Ocean sediment suggest that solar He and Ne would be easily released from IDP grains and hence lost from subducting slabs at shallow depths. However, since the diffusion experiments was conducted under high vacuum, there may be a possibility that magnetite grains, which are supposedly the main constituent of the magnetic fraction, might be partly reduced to form a metal phase due to low oxygen fugacity in the experimental condition. If this is the case, such a phase change might affect the gas release and hence the results of the diffusion coefficients. In order to examine whether or not such a phase change really occurred in the condition of the diffusion experiment, I conducted a heating experiment for a magnetic separate from Pacific Ocean sediment. In the same condition as in the diffusion experiment, and the run products were examined with an x ray diffraction method. Three samples were prepared: they were wrapped with platinum foil, put in a vacuum line, and heated in a molybdenum crucible for two hours at 500 C, 800 C,and 950 C, respectively. After cooling the furnace, the samples were taken out from the crucible and analyzed with an x ray diffraction method.

Hiyagon, H.↗

NASA NTRS1995

NE VIII lambda 774 and time variable associated absorption in the QSO UM 675

We discuss measurements of Ne VIII lambda 774 absorption and the time variability of other lines in the z(sub a) approximately equal z(sub e) absorption system of the z(sub e) = 2.15 QSO UM 675 (0150-203). The C IV lambda 1549 and N V 1240 doublets at z(sub a) = 2.1340 (shifted approximately 1500 km/s from z(sub e) strengthened by a factor of approximately 3 between observations by Sargent, Boksenberg and Steidel (1981 November) and our earliest measurements (1990 November and December). We have no information on changes in other z(sub a) approximately equal z(sub e) absorption lines. Continued monitoring since 1990 November shows no clear changes in any of the absorptions between approximately 1100 and 1640 A rest. The short timescale of the variability (less than or approximately equal to 2.9 yr rest) strongly suggests that the clouds are dense, compact, close to the QSO, and photoionized by the QSO continuum. If the line variability is caused by changes in the ionization, the timescale requires densities greater than approximately 4000/cu cm. Photoionization calculations place the absorbing clouds within approximately 200 pc of the continuum source. The full range of line ionizations (from Ne VIII lambda 774 to C III lambda 977) in optically thin gas (no Lyman limit) implies that the absorbing regions span a factor of more than approximately 10 in distance or approximately 100 in density. Across these regions, the total hydrogen (H I + H II) column ranges from a few times 10(exp 18)/sq cm in the low-ionization gas to approximately 10(exp 20)/sq cm where the Ne VIII doublet forms. The metallicity is roughly solar or higher, with nitrogen possibly more enhanced by factors of a few. The clouds might contribute significant line emission if they nearly envelop the QSO. The presence of highly ionized Ne VIII lambda 774 absorption near the QSO supports recent studies that link z(sub a) approximately equal to z(sub e) systems with X-ray 'wamr absorbers. We show that the Ne VIII absorbing gas would itself produce measurable warm absorption -- characterized by bound-free O VII or O VIII edegs near 0.8 keV -- if the column densities were N(sub H) greater than or approximately equal to 10(exp 21)/sq cm (for solar abundances).

Hamann, Fred↗

NASA NTRS1997

Issues concerning the Orion gamma ray line observations: Line splitting and LiBeB origin

The phenomenon of broad gamma ray line splitting is discussed, together with a scenario for the suppression of the blue wings of these broad lines due to the geometry of the accelerated particle interaction region. The broad and narrow gamma ray line emissions are compared taking into account the line splitting effect. It is concluded that the observed gamma ray lines from Orion are most likely broad, implying that the low energy cosmic rays which produce this line emission consist mostly of C and heavier ions. The suppression of the proton and alpha particle abundances requires acceleration conditions such as the acceleration of the ejecta of the supernovae before mixing with the interstellar medium. Similar conditions are implied by observations of the B and Be in low metallicity stars formed during the first Gyr of galactic evolution.

Ramaty, R.↗

NASA NTRS2001

Characterizing Nearby Stars: Age and Activity

The funds in this grant were used to support costs for observing and data analysis over the past two years. During this time I have been obtaining low-resolution (R-2,000) spectra for about 5,000 solar-type stars (late-F and G dwarfs) that are within 60 parsecs of the Sun. The sample was defined with results from the Hipparcos mission, and the spectra were obtained at Kitt Peak National Observatory, using the Coude Feed telescope, and at Cerro Tololo Interamerican Observatory, using their 1.5 m telescopes for stars below -40 declination. Nearly all the observed spectra have been reduced and analyzed. What is determined is R-prime, an index of the chromospheric emission in the cores of the Ca II H and K lines relative to the nearby continuum, and normalized for the color of the star. Chromospheric emission arises from magnetic activity on the star, and that is turn is driven by rotation. Solar-type stars spin down as they age, and so they get weaker in their chromospheric emission as well. Thus this R-prime index can be used to estimate the ages of stars. A few stars remain to be observed at Kitt Peak, and follow-up high-resolution spectra are being obtained of the most active stars seen, but the majority of the starting sample have been completed. The spectra obtained are also being analyzed to yield an index of overall metallicity for each star, and this will be used to study Galactic evolution questions. These metallicities will form the first large dataset of high and consistent quality. Initial results from this work have been used to define targets for a SIRTF Legacy program, for stars to study for planetary transits, and for SETI efforts. Because of the large number of stars involved, most of the data will be made available on the web, although some specific papers about the results are in preparation. The web database is being constructed.

Soderblom, David↗

NASA NTRS2001

Nonlinear Ultrasonic Characterization of Fatigue Microstructures

Dislocation dipole substructures formed during metal fatigue are shown to produce a substantial distortion of ultrasonic waves propagating through the fatigued material. A model of ultrasonic wave-dislocation dipole interactions is developed that quantifies the wave distortion by means of a material nonlinearity parameter (beta). Application of the model to AA2024-T4 predicts a value of p approximately 300% larger in material cyclically loaded for 100 kcycles in stress-control at 276 MPa and R=0 than that measured for virgin material. Experimental measurements show a monotonic increase in p as a function of the number of fatigue cycles that closely approaches the predicted increase. The experiments also suggest that the relevant dislocation substructures are localized in the material.

Cantrell, John H.↗

NASA NTRS1980

Protective Coatings

General Magnaplate Corporation's pharmaceutical machine is used in the industry for high speed pressing of pills and capsules. Machine is automatic system for molding glycerine suppositories. These machines are typical of many types of drug production and packaging equipment whose metal parts are treated with space spinoff coatings that promote general machine efficiency and contribute to compliance with stringent federal sanitation codes for pharmaceutical manufacture. Collectively known as "synergistic" coatings, these dry lubricants are bonded to a variety of metals to form an extremely hard slippery surface with long lasting self lubrication. The coatings offer multiple advantages; they cannot chip, peel or be rubbed off. They protect machine parts from corrosion and wear longer, lowering maintenance cost and reduce undesired heat caused by power-robbing friction.

Source record↗

NASA NTRS1996

The infrared spectrum of the Galactic center and the composition of interstellar dust

We have obtained 5-8 micrometers spectra of the Galactic center from the Kuiper Airborne Observatory at resolving powers of approximately 50, approximately 150, and approximately 300. These spectra show absorption features at 5.5, 5.8, 6.1, and 6.8 micrometers. Together with previously observed features in the 3 micrometers region, these features are compared with laboratory spectra of candidate materials. The 3.0 and 6.1 micrometers features are due to the OH stretching and bending variations of H2O and are well fitted by water of hydration in silicates (e.g., talc). The 3.0 micrometer band is equally well fitted by ice mixtures containing 30% H2O, but such mixtures do not provide a good fit to the observed 6.1 micrometer band. The 3.4 and 6.8 micrometers features are identified with the CH stretching and deformation modes in CH2 and CH3 groups in saturated aliphatic hydrocarbons. The 6.1 micrometer band shows a short wavelength shoulder centered on 5.8 micrometer, attributed to carbonyl (C double bond O) groups in this interstellar hydrocarbon dust component. Finally, the narrow 5.5 micrometer feature is also attributed to carbonyl groups, but in the form of metal carbonyls [e.g., Fe(CO)4]. We have derived column densities and abundances along the line of sight toward the Galactic center for the various identified dust components. This analysis shows that hydrocarbon grains contain only 0.08 of the elemental abundance of C and contribute only a relatively minor fraction (0.1) of the total dust volume. Most of the interstellar dust volume is made up of silicates (approximately 0.6). Small graphite grains, responsible for the 2200 angstroms bump, account for 0.07 of the total dust volume. The remaining one-quarter of the interstellar dust volume consists of a material(s) without strong IR absorption features. Likely candidates include large graphite grains, diamonds, or amorphous carbon grains, which all have weak or no IR active modes. Finally, various models for the origin of the hydrocarbon dust component of the interstellar dust are discussed. All of them face some problems in explaining the observations, in particular, the absence of the spectroscopic signature of hydrocrbon grains in sources associated with molecular clouds.

NASA Discipline Exobiology↗

NASA NTRS2004

Self Assembled Structures by Directional Solidification of Eutectics

Interest in ordered porous structures has grown because of there unique properties such as photonic bandgaps, high backing packing density and high surface to volume ratio. Inspired by nature, biometric strategies using self assembled organic molecules dominate the development of hierarchical inorganic structures. Directional solidification of eutectics (DSE) also exhibit self assembly characteristics to form hierarchical metallic and inorganic structures. Crystallization of diphasic materials by DSE can produce two dimensional ordered structures consisting of rods or lamella. By selective removal of phases, DSE is capable to fabricate ordered pore arrays or ordered pin arrays. Criteria and limitations to fabricate hierarchical structures will be presented. Porous structures in silicon base alloys and ceramic systems will be reported.

Dynys, Frederick W.↗

NASA NTRS1998

High temperature thrust chamber for spacecraft

A high temperature thrust chamber for spacecraft (20) is provided herein. The high temperature thrust chamber comprises a hollow body member (12) having an outer surface and an internal surface (16) defining the high temperature chamber (10). The body member (12) is made substantially of rhenium. An alloy (18) consisting of iridium and at least alloying metal selected of the group consisting of rhodium, platinum and palladium is deposited on at least a portion of the internal surface (16) of the body member (12). The iridium and the alloying metal are electrodeposited onto the body member (12). A HIP cycle is performed upon the body member (12) to cause the coating of iridium and the alloying metal to form the alloy (18) which protects the body member (12) from oxidation.

Chazen, Melvin L.↗

NASA NTRS2008

Partitioning of Phosphorus and Molybdenum between the Earth's Mantle and Core and the Conditions of Core Formation

There are several hypotheses on the specific processes that might have occurred during the formation of the Earth. One hypothesis that has been proposed is that early in the Earth's formation, there was a magma ocean present, and within this body, siderophile elements separated out of the silicate liquid to form the metal core. This study addresses this hypothesis. P and Mo are moderately siderophile elements that are present in both the mantle and the core. The concentrations of P and Mo in silicate vs. metal can be measured and in turn used to determine the temperatures, pressures, oxygen fugacity and melt composition required to achieve the same concentrations as observed in the mantle. The data here include eight experiments examining the partitioning of P and Mo between metallic liquid and silicate liquid. The purpose of the experiments has been to gain a greater understanding of core-mantle separation during the Earth formation process and examines temperature effect on P and Mo, which has not been systematically studied before.

Acuff, K. M.↗

NASA NTRS2009

Composite Bipolar Plate for Unitized Fuel Cell/Electrolyzer Systems

In a substantial improvement over present alkaline systems, an advanced hybrid bipolar plate for a unitized fuel cell/electrolyzer has been developed. This design, which operates on pure feed streams (H2/O2 and water, respectively) consists of a porous metallic foil filled with a polymer that has very high water transport properties. Combined with a second metallic plate, the pore-filled metallic plates form a bipolar plate with an empty cavity in the center.

Mittelsteadt, Cortney K.↗

NASA NTRS2008

Nanophase Nickel-Zirconium Alloys for Fuel Cells

Nanophase nickel-zirconium alloys have been investigated for use as electrically conductive coatings and catalyst supports in fuel cells. Heretofore, noble metals have been used because they resist corrosion in the harsh, acidic fuel cell interior environments. However, the high cost of noble metals has prompted a search for less-costly substitutes. Nickel-zirconium alloys belong to a class of base metal alloys formed from transition elements of widely different d-electron configurations. These alloys generally exhibit unique physical, chemical, and metallurgical properties that can include corrosion resistance. Inasmuch as corrosion is accelerated by free-energy differences between bulk material and grain boundaries, it was conjectured that amorphous (glassy) and nanophase forms of these alloys could offer the desired corrosion resistance. For experiments to test the conjecture, thin alloy films containing various proportions of nickel and zirconium were deposited by magnetron and radiofrequency co-sputtering of nickel and zirconium. The results of x-ray diffraction studies of the deposited films suggested that the films had a nanophase and nearly amorphous character.

Narayanan, Sekharipuram↗