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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Adsorption of Water on Simulated Moon Dust Samples

A lunar regolith simulant dust sample (JSC-1a) supported on a silica wafer (SiO2/Si(111)) has been characterized by scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and Auger electron spectroscopy (AES). The adsorption kinetics of water has been studied primarily by thermal desorption spectroscopy (TDS) and also by collecting isothermal adsorption transients. The support has been characterized by water TDS. JSC-1a consists mostly of aluminosilicate glass and other minerals containing Fe, Na, Ca, and Mg. The particle sizes span the range from a few microns up to 100 microns. At small exposures, H2O TDS is characterized by broad (100 to 450 K) structures; at large exposures distinct TDS peaks emerge that are assigned to amorphous solid water (145 K) and crystalline ice (165 K). Water dissociates on JSC-1a at small exposures but not on the bare silica support. It appears that rather porous condensed ice layers form at large exposures. At thermal impact energies, the initial adsorption probability amounts to 0.92+/-0.05.

Goering, John P.↗
NASA NTRS1990

Calorimetry, activity, and micro-FTIR analysis of CO chemisorption, titration, and oxidation on supported Pt

The value of in situ analysis on CO chemisorption, titration and oxidation over supported Pt catalysts using calorimetry, catalytic and micro-FTIR methods is illustrated using silica- and titania-supported samples. Isothermal CO-O and O2-CO titrations have not been widely used on metal surfaces and may be complicated if some oxide supports are reduced by CO titrant. However, they can illuminate the kinetics of CO oxidation on metal/oxide catalysts since during such titrations all O and CO coverages are scanned as a function of time. There are clear advantages in following the rates of the catalyzed CO oxidation via calorimetry and gc-ms simultaneously. At lower temperatures the evidence they provide is complementary. CO oxidation and its catalysis of CO oxidation have been extensively studied with hysteresis and oscillations apparent, and the present results suggest the benefits of a combined approach. Silica support porosity may be important in defining activity-temperature hysteresis. FTIR microspectroscopy reveals the chemical heterogeneity of the catalytic surfaces used; it is interesting that the evidence with regard to the dominant CO surface species and their reactivities with regard to surface oxygen for present oxide-supported Pt are different from those seen on graphite-supported Pt.

Sermon, Paul A.↗
NASA NTRS1982

Origin of SiC impurities in silicon crystals grown from the melt in vacuums

A main source of high carbon levels in silicon crystals grown from melt under reduced pressures and contained in silica crucibles supported by graphite retainer/susceptor was identified by thermodynamic analysis. The calculations were verified by experimental results and the carbon level is reduced by approximately 50% with the use of molybdenum retainers.

Schmid, F.↗
NASA NTRS2010

Process for Making a Noble Metal on Tin Oxide Catalyst

To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

Davis, Patricia↗
NASA NTRS2016

Phosphate Stability in Diagenetic Fluids Constrains the Acidic Alteration Model for Lower Mt. Sharp Sedimentary Rocks in Gale Crater, Mars

The Mars rover Curiosity has encountered silica-enriched bedrock (as strata and as veins and associated halos of alteration) in the largely basaltic Murray Fm. of Mt. Sharp in Gale Crater. Alpha Particle X-ray Spectrometer (APXS) investigations of the Murray Fm. revealed decreasing Mg, Ca, Mn, Fe, and Al, and higher S, as silica increased (Fig. 1). A positive correlation between SiO2 and TiO2 (up to 74.4 and 1.7 wt %, respectively) suggests that these two insoluble elements were retained while acidic fluids leached more soluble elements. Other evidence also supports a silica-retaining, acidic alteration model for the Murray Fm., including low trace element abundances consistent with leaching, and the presence of opaline silica and jarosite determined by CheMin. Phosphate stability is a key component of this model because PO4 3- is typically soluble in acidic water and is likely a mobile ion in diagenetic fluids (pH less than 5). However, the Murray rocks are not leached of P; they have variable P2O5 (Fig. 1) ranging from average Mars (0.9 wt%) up to the highest values in Gale Crater (2.5 wt%). Here we evaluate APXS measurements of Murray Fm. bedrock and veins with respect to phosphate stability in acidic fluids as a test of the acidic alteration model for the Lower Mt. Sharp rocks.

Berger, J. A.↗
NASA NTRS2011

Fischer-Tropsch Catalyst for Aviation Fuel Production

As the oil supply declines, there is a greater need for cleaner alternative fuels. There will undoubtedly be a shift from crude oil to non-petroleum sources as a feedstock for aviation (and other transportation) fuels. The Fischer-Tropsch process uses a gas mixture of carbon monoxide and hydrogen which is converted into various liquid hydrocarbons; this versatile gas-to-liquid technology produces a complex product stream of paraffins, olefins, and oxygenated compounds such as alcohols and aldehydes. The Fischer-Tropsch process can produce a cleaner diesel oil fraction with a high cetane number (typically above 70) without any sulfur and aromatic compounds. It is most commonly catalyzed by cobalt supported on alumina, silica, or titania or unsupported alloyed iron powders. Cobalt is typically used more often than iron, in that cobalt is a longer-active catalyst, has lower water-gas shift activity, and lower yield of modified products. Promoters are valuable in improving Fischer-Tropsch catalyst as they can increase cobalt oxide dispersion, enhance the reduction of cobalt oxide to the active metal phase, stabilize a high metal surface area, and improve mechanical properties. Our goal is to build up the specificity of the Fischer-Tropsch catalyst while adding less-costly transition metals as promoters; the more common promoters used in Fischer-Tropsch synthesis are rhenium, platinum, and ruthenium. In this report we will describe our preliminary efforts to design and produce catalyst materials to achieve our goal of preferentially producing C8 to C18 paraffin compounds in the NASA Glenn Research Center Gas-To-Liquid processing plant. Efforts at NASA Glenn Research Center for producing green fuels using non-petroleum feedstocks support both the Sub-sonic Fixed Wing program of Fundamental Aeronautics and the In Situ Resource Utilization program of the Exploration Technology Development and Demonstration program.

deLaRee, Ana B.↗
NASA NTRS2012

Fischer-Tropsch Catalyst for Aviation Fuel Production

As the oil supply declines, there is a greater need for cleaner alternative fuels. There will undoubtedly be a shift from crude oil to nonpetroleum sources as a feedstock for aviation (and other transportation) fuels. The Fischer-Tropsch process uses a gas mixture of carbon monoxide and hydrogen which is converted into various liquid hydrocarbons; this versatile gas-to-liquid technology produces a complex product stream of paraffins, olefins, and oxygenated compounds such as alcohols and aldehydes. The Fischer-Tropsch process can produce a cleaner diesel oil fraction with a high cetane number (typically above 70) without any sulfur and aromatic compounds. It is most commonly catalyzed by cobalt supported on alumina, silica, or titania or unsupported alloyed iron powders. Cobalt is typically used more often than iron, in that cobalt is a longer-active catalyst, has lower water-gas shift activity, and lower yield of modified products. Promoters are valuable in improving Fischer-Tropsch catalyst as they can increase cobalt oxide dispersion, enhance the reduction of cobalt oxide to the active metal phase, stabilize a high metal surface area, and improve mechanical properties. Our goal is to build up the specificity of the Fischer-Tropsch catalyst while adding less-costly transition metals as promoters; the more common promoters used in Fischer-Tropsch synthesis are rhenium, platinum, and ruthenium. In this report we will describe our preliminary efforts to design and produce catalyst materials to achieve our goal of preferentially producing C8 to C18 paraffin compounds in the NASA Glenn Research Center Gas-To-Liquid processing plant. Efforts at NASA Glenn Research Center for producing green fuels using non-petroleum feedstocks support both the Sub-sonic Fixed Wing program of Fundamental Aeronautics and the In Situ Resource Utilization program of the Exploration Technology Development and Demonstration program.

DeLaRee, Ana B.↗
NASA NTRS1971

Tracer sensitive tapes

A leak detection system has been developed, consisting of a tape that can be wrapped around possible leak sites on a system pressurized with air or gaseous nitrogen. Carbon monoxide, at a level of 100 to 1000 parts per million is used as a trace gas in the pressurized system. The sensitive element of the tape is palladium chloride supported on specially prepared silica gel and specially dried. At a CO level of 100 ppm and a leak rate of 10-20 ml/hr, discoloration of the sensitive element is observed in 1.5 to 3 min. The tape and trace gas are compatible with aerospace hardware, safe to handle, and economically reasonable to produce and handle.

Burrows, W. H.↗
NASA NTRS2014

Organics Exposure in Orbit (OREOcube): A Next-Generation Space Exposure Platform

The OREOcube (ORganics Exposure in Orbit cube) experiment on the International Space Station (ISS) will investigate the effects of solar and cosmic radiation on organic thin films supported on inorganic substrates. Probing the kinetics of structural changes and photomodulated organic− inorganic interactions with real-time in situ UV−visible spectroscopy, this experiment will investigate the role played by solid mineral surfaces in the (photo)chemical evolution, transport, and distribution of organics in our solar system and beyond. In preparation for the OREOcube ISS experiment, we report here laboratory measurements of the photostability of thin films of the 9,10-anthraquinone derivative anthrarufin (51 nm thick) layered upon ultrathin films of iron oxides magnetite and hematite (4 nm thick), as well as supported directly on fused silica. During irradiation with UV and visible light simulating the photon flux and spectral distribution on the surface of Mars, anthrarufin/iron oxide bilayer thin films were exposed to CO2 (800 Pa), the main constituent (and pressure) of the martian atmosphere. The time-dependent photodegradation of anthrarufin thin films revealed the inhibition of degradation by both types of underlying iron oxides relative to anthrarufin on bare fused silica. Interactions between the organic and inorganic thin films, apparent in spectral shifts of the anthrarufin bands, are consistent with presumed free-electron quenching of semiquinone anion radicals by the iron oxide layers, electively protecting the organic compound from photodegradation. Combining such in situ real-time kinetic measurements of thin films in future space exposure experiments on the ISS with postflight sample return and analysis will provide time-course studies complemented by in-depth chemical analysis. This will facilitate the characterization and modeling of the chemistry of organic species associated with mineral surfaces in astrobiological contexts.

Organics↗
NASA NTRS1989

The flexure assembly design for the SIRTF one-meter primary mirror

A titanium flexure assembly for the Space Infrared Telescope Facility (SIRTF) 1-m primary mirror has been designed to accommodate: (1) the cryogenic cool-down effect on the optical performance of the mirror, (2) the Shuttle launch-load environment, and (3) the support-baseplate manufacturing tolerances. Numerous iterations involving a multidimensional design space search led to an assembly design that provides the stiffness and strength in the vertical (optical axis) and tangential directions to accommodate launch loads, but is compliant radially to accommodate cryogenic cool down. A 'folded back' titanium flexure system was required because of the differential thermal contraction of the aluminum telescope baseplate support and the fused-silica mirror. This unique and innovative flexure assembly represents a totally passive mechanism for accommodating the design launch loads, cryogenic cool down, and out-of-plane baseplate effects.

Richard, R. M.↗
NASA NTRS1977

Development of a high temperature capacitive pressure transducer

High temperature pressure transducers capable of continuous operation while exposed to 650 C were developed and evaluated over a full-scale differential pressure range of + or - 69 kPa. The design of the pressure transducers was based on the use of a diaphragm to respond to pressure, variable capacitive elements arranged to operate as a differential capacitor to measure diaphragm response and on the use of fused silica for the diaphragm and its supporting assembly. The uncertainty associated with measuring + or - 69 kPa pressures between 20C and 650C was less than + or - 6%.

Egger, R. L.↗
NASA NTRS1982

Crystal nucleation in glass-forming alloy and pure metal melts under containerless and vibrationless conditions

The undercooling behavior of large spheroids of Pd40Ni40P40 was investigated. By surface etching, supporting the specimens on a fused silica substrate, and successive heating and cooling, crystallization can be eliminated, presumable due to the removal of surface heterogeneities. By this method samples up to 3.2g with a 0.53 mm minor diameter, were made entirely glassy, except for some superficial crystals comprising less than 0.5% of the volume. These experiments show that a cooling rate of approximately 1 K/sec is adequate to avoid copious homogeneous nucleation in the alloy, and that by eliminating or reducing the effectiveness of heterogeneous nucleation sites, it is possible to form bulk samples of this metallic glass with virtually unlimited dimensions.

Spaepen, F.↗
NASA NTRS2015

Temperature-Dependent Refractive Index Measurements of Caf2, Suprasil 3001, and S-FTM16 for the Euclid Near Infrared Spectrometer and Photometer

Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we measured absolute refractive indices at temperatures from 100 to 310 K at wavelengths from 0.42 to 3.6 microns for CaF2, Suprasil 3001 fused silica, and S-FTM16 glass in support of lens designs for the Near Infrared Spectrometer and Photometer (NISP) for ESA's Euclid dark energy mission. We report absolute refractive index, dispersion (dn/dλ), and thermo-optic coefficient (dn/dT) for these materials. In this study, materials from different melts were procured to understand index variability in each material. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. For calcium fluoride (CaF2) and S-FTM16, we compare our current measurements with CHARMS measurements of these materials made in the recent past for other programs. We also compare Suprasil 3001's indices to those of other forms of fused silica we have measured in CHARMS.

geometrical optics↗
NASA NTRS2006

Process for the preparation of metal-containing nanostructured films

Metal-containing nanostructured films are prepared by electrodepositing a metal-containing composition within the pores of a mesoporous silica template to form a metal-containing silica nanocomposite. The nanocomposite is annealed to strengthen the deposited metal-containing composition. The silica is then removed from the nanocomposite, e.g., by dissolving the silica in an etching solution to provide a self-supporting metal-containing nanostructured film. The nanostructured films have a nanowire or nanomesh architecture depending on the pore structure of the mesoporous silica template used to prepare the films.

Lu, Yunfeng↗
NASA NTRS1984

Environmental control/life support

It is pointed out that the life support systems technology used on projects Mercury, Gemini, Apollo, and Space Shuttle required an employment of expendables. Skylab was the only manned space project which made use of regenerable life support technology, taking into account the employment of a silica gel/molecular sieve for carbon dioxide removal. A number of investigations indicate that significant launch weight and volume as well as recurring cost savings can be realized by using regenerative life support processes for a Space Station. A number of developed regenerative processes are believed to be applicable to a Space Station. Aspects of air revitalization are discussed, taking into account carbon dioxide reduction, oxygen generation, trace contaminant control, temperature and humidity control, instrumentation, and nitrogen supply. Attention is also given to water reclamation, solid waste treatment, and future development and testing programs.

Quattrone, P. D.↗
NASA NTRS1984

Design and performance analysis of a conical-aerobrake, orbital-transfer vehicle concept

A Shuttle-compatible systems design based on the core concept of attachable modules for the major vehicle components is proposed. The principal features include a disposable cargo/extra-propellant tank module; a porous, radiative, backscattering drag-brake surface material of thin silica cloth; and a lightweight carbon-composite support structure. The mission payload capability for delivery, retrieval, and combined operations is determined for a broad range of missions including NASA/DOD requirements and extending through cis-lunar space. The effects of finite-rate surface catalysis, negative lift, and multiple atmospheric passes in reducing the aerothermal heating rates are also investigated. In addition, the structural and thermal-protection problems of the drag-brake support apparatus are analyzed and recommendations are proposed for future design refinements.

Menees, G. P.↗
NASA NTRS1985

Design and Performance Analysis of a Conical Aerobrake Orbital Transfer Vehicle Concept

A Shuttle-compatible systems design based on the core concept of attachable modules for the major vehicle components is proposed. The principal features include a disposable cargo/extra-propellant tank module; a porous, radiative, back-scattering drag-brake surface material of thin silica cloth; and a lightweight carbon-composite support structure. The mission payload capability for delivery, retrieval, and combined operations is determined for a broad range of missions including NASA/DOD requirements and extending through cislunar space. The effects of finite-rate surface catalysis, negative lift, and multiple atmospheric passes in reducing the aerothermodynamic heating rates are also investigated. In addition, the structural and thermal protection problems of the drag-brake support apparatus are analyzed, and recommendations are proposed for future design refinements.

Menees, Gene P.↗
NASA NTRS2012

Widespread Weathered Glass on the Surface of Mars

Low albedo sediments cover >10(exp 7) sq km in the northern lowlands of Mars, but the composition and origin of these widespread deposits have remained ambiguous despite many previous investigations. Here we use near-infrared spectra acquired by the Mars Express OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite') imaging spectrometer to show that these sediments exhibit spectral characteristics that are consistent with both high abundances of iron-bearing glass and silica-enriched leached rinds on glass. This interpretation is supported by observations of low-albedo soil grains with possible rinds at the Phoenix Mars Lander landing site in the northern lowlands. By comparison with the extensive glass-rich dune fields and sand sheets of Iceland, we propose an explosive volcanic origin for these glass-rich sediments. We also propose that the glassy remnant rinds on the sediments are the result of post-depositional alteration, as these rinds are commonly formed in arid terrestrial volcanic environments during water-limited, moderately acidic leaching. These weathered, glass-rich deposits in the northern lowlands are also colocated with the strongest concentrations of a major global compositional surface type previously identified in mid-infrared spectra, suggesting that they may be representative of global processes. Our results provide potential confirmation of models suggesting that explosive volcanism has been widespread on Mars, and also raise the possibilities that glass-rich volcaniclastics are a major source of eolian sand on Mars and that widespread surficial aqueous alteration has occurred under Amazonian climatic conditions.

Horgan, Briony↗