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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Reflectance and Mossbauer spectroscopy of ferrihydrite-montmorillonite assemblages as Mars soil analog materials

Spectroscopic analyses show that Fe(3+)-doped smectites prepared in the laboratory exhibit important similarities to the soils on Mars. Ferrihydrite has been identified as the interlayer ferric component in Fe(3+)-doped smectites by a low quadrupole splitting and magnetic field strength of approximately 48 tesla in Mossbauer spectra measured at 4.2 K, as well as a crystal field transition at 0.92 micrometer. Ferrihydrite in these smectites explains features in the visible-near infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. Clay silicates have met resistance in the past as Mars soil analogs because terrestrial clay silicates exhibit prominent hydrous spectral features at 1.4, 1.9, and 2.2 micrometers; and these are observed weakly, if at all, in reflectance spectra of Mars. However, several mechanisms can weaken or compress these features, including desiccation under low-humidity conditions. The hydration properties of the interlayer cations also effect band strengths, such that a ferrihydrite-bearing smectite in the Martian environment would exhibit a 1.9 micrometers H2O absorption that is even weaker than the 2.2 micrometers structural OH absorption. Mixing experiments demonstrate that infrared spectral features of clays can be significantly suppressed and that the reflectance can be significantly darkened by mixing with only a few percent of a strongly absorbing opaque material. Therefore, the absolute reflectance of a soil on Mars may be disproportionately sensitive to a minor component. For this reason, the shape and position of spectral features and the chemical composition of potential analogs are of utmost importance in assessing the composition of the soil on Mars. Given the remarkable similarity between visible-infrared reflectance spectra of soils in bright regions on Mars and Fe(3+)-doped montmorillonites, coupled with recent observations of smectites in SNC meteorites and a weak 2.2 micrometers absorption in some Mars soils, ferrihydrite-bearing smectites warrant serious consideration as a Mars soil analog.

NASA Discipline Exobiology↗
NASA NTRS2016

The Mapping X-Ray Fluorescence Spectrometer (MAPX)

MapX will provide elemental imaging at ≤100 micron spatial resolution over 2.5 X 2.5 centimeter areas, yielding elemental chemistry at or below the scale length where many relict physical, chemical, and biological features can be imaged and interpreted in ancient rocks. MapX is a full-frame spectroscopic imager positioned on soil or regolith with touch sensors. During an analysis, an X-ray source (tube or radioisotope) bombards the sample surface with X-rays or αlpha-particles / gamma rays, resulting in sample X-ray Fluorescence (XRF). Fluoresced X-rays pass through an X-ray lens (X-ray μ-Pore Optic, "MPO") that projects a spatially resolved image of the X-rays onto a CCD. The CCD is operated in single photon counting mode so that the positions and energies of individual photons are retained. In a single analysis, several thousand frames are stored and processed. A MapX experiment provides elemental maps having a spatial resolution of ≤100 micron and quantitative XRF spectra from Regions of Interest (ROI) 2 centimers ≤ x ≤ 100 micron. ROI are compared with known rock and mineral compositions to extrapolate the data to rock types and putative mineralogies. The MapX geometry is being refined with ray-tracing simulations and with synchrotron experiments at SLAC. Source requirements are being determined through Monte Carlo modeling and experiment using XMIMSIM [1], GEANT4 [2] and PyMca [3] and a dedicated XRF test fixture. A flow-down of requirements for both tube and radioisotope sources is being developed from these experiments. In addition to Mars lander and rover missions, MapX could be used for landed science on other airless bodies (Phobos/Deimos, Comet nucleus, asteroids, the Earth's moon, and the icy satellites of the outer planets, including Europa.

Blake, David↗
NASA NTRSDate not supplied

The Nature of Space Weathering in Samples From Asteroid (162173) Ryugu Revealed By Coordinated Analysis

Space weathering, driven primarily by micrometeorite bombardment and solar wind ion irradiation, alters the morphology, microstructure, and chemistry of the surface regolith on airless bodies. The accumulation of microstructural and chemical space weathering features, including melt deposits, amorphous rims, and nanophase iron-bearing particles (npFe), are associated with alterations of the spectral properties of the regolith. In particular, space weathering changes the spectral slope and reflectance of surface materials, and causes the attenuation of characteristic absorption bands in the visible to near-infrared wave-lengths, as well as a shift towards longer wavelengths of the Christiansen feature (CF)in thermal infrared spectra. Previous studies of space weathering characteristics have focused on siliceous bodies like the Moon and S-type asteroid Itokawa. However, observations of asteroid Ryugu by the JAXA Hayabusa2 spacecraft and subsequent analyses of returned samples revealed carbonaceous and hydrated materials. These samples provided our first opportunity to constrain the effects of space weathering processes on primitive, C-type asteroids. Analyses of returned samples to understand the space weathering of carbonaceous materials are important for accurately interpreting remote sensing observations of carbonaceous asteroids. In addition, the analysis of Hayabusa2 samples from Ryugu paved the way for the analysis of samples from the asteroid Bennu, re-turned by the NASA OSIRIS-REx mission. As space weathering impacts the microstructure, chemistry, and spectral characteristics of asteroidal surfaces, here we report the results of a coordinated analytical study of the micro-and nano-scale signatures of space weathering in samples returned from Ryugu.

L E Melendez↗
NASA NTRS1978

Precondensed matter - Key to the early solar system

Explicit astrophysical details are developed for the hypothesis that chemical and isotopic anomalies in primitive solar-system samples reflect routine initial chemical conditions within precondensed matter. The central feature of this theory concerns the chemical state of presolar dust, which is regarded as never having been vaporized in the region where the most chemically primitive samples (carbonaceous meteorites) accumulated. It is suggested that the initial chemical state of heavy atoms during meteorite and planetary accumulation was distributed between a refractory-mineral component from high-temperature condensation and a volatile component resulting from cold matter adhering to preexisting grains. Thermal conditions in the solar nebula are considered along with the existence of supernova condensates and other thermal condensates in the interstellar dust. Fractionation into volatile and refractory elements is idealized in terms of four distinct interstellar components, and the fractionated precondensed matter is described.

Clayton, D. D.↗
NASA NTRS1985

A survey of chemical information systems

A survey of the features, functions, and characteristics of a fairly wide variety of chemical information storage and retrieval systems currently in operation is given. The types of systems (together with an identification of the specific systems) addressed within this survey are as follows: patents and bibliographies (Derwent's Patent System; IFI Comprehensive Database; PULSAR); pharmacology and toxicology (Chemfile; PAGODE; CBF; HEEDA; NAPRALERT; MAACS); the chemical information system (CAS Chemical Registry System; SANSS; MSSS; CSEARCH; GINA; NMRLIT; CRYST; XTAL; PDSM; CAISF; RTECS Search System; AQUATOX; WDROP; OHMTADS; MLAB; Chemlab); spectra (OCETH; ASTM); crystals (CRYSRC); and physical properties (DETHERM). Summary characteristics and current trends in chemical information systems development are also examined.

Dominick, Wayne D.↗
NASA NTRS1985

Basalts of Mars: Constraints on Volatile Evolution

The mineralogy of relatively unweathered rocks on Mars place important constraints on models of planetary oxidation state, volcanism and associated outgassing, accretion and associated volatile inventory, and geochemical changes over time. Reflectance spectra (300 to 2500 nm) provide direct mineralogic information about the surface materials. Spectra measured using Earth-based telescopes were analyzed by a multiple high-order derivative spectroscopy technique. Nine areas, measured during the 1978 opposition, were analyzed by the technique. Each contained suites of well-defined absorption bands. These bands can be interpreted in terms of constituent mineralogy by the technique of Adams. Among the features extracted from the spectra were bands attributed to iron oxides. Other bands can be attributed to silicates within chemically unweathered rocks/fines. Absorption features suggest the presence of Mg-olivine and plagioclase feldspar.

Huguenin, R. L.↗
NASA NTRS1980

Application of a reversible chemical reaction system to solar thermal power plants

Three distributed dish solar thermal power systems using various applications of SO2/SO3 chemical energy storage and transport technology were comparatively assessed. Each system features various roles for the chemical system: (1) energy storage only, (2) energy transport, or (3) energy transport and storage. These three systems were also compared with the dish-Stirling, using electrical transport and battery storage, and the central receiver Rankine system, with thermal storage, to determine the relative merit of plants employing a thermochemical system. As an assessment criterion, the busbar energy costs were compared. Separate but comparable solar energy cost computer codes were used for distributed receiver and central receiver systems. Calculations were performed for capacity factors ranging from 0.4 to 0.8. The results indicate that SO2/SO3 technology has the potential to be more cost effective in transporting the collected energy than in storing the energy for the storage capacity range studied (2-15 hours)

Hanseth, E. J.↗
NASA NTRS1982

New oxidation features in NiCrAl-Zr revealed by an Auger microprobe

A NiCrAl-0.5 (wt %) Zr alloy, oxidized in air for 1 h at 1180 C was studied using a 30-nm resolution Auger microprobe. Depth analysis was achieved using crater edge profiling. This first application of AES to these alloys enabled several new observations of the chemical composition of microstructural features in the corrosion layer. The external oxide was rough, about 2-3 microns thick, and contained Ni, Cr, Al, and O. It was discovered that stoichiometric Al2O3 was restricted to a homogeneous layer about 300-nm thick between the oxide and the base metal. The metal immediately beneath this Al2O3 layer was found to be depleted in Al and roughly ten times richer in Zr than the bulk alloy. These observations are compared with the predictions of current models of the oxidation of MCrAl alloys.

Larson, L. A.↗
NASA NTRS1972

An ERTS multispectral scanner experiment for mapping iron compounds

There are no author-identified significant results in this report. An experimental plan for enhancing spectral features related to the chemical composition of geological targets in ERTS multispectral scanner data is described. The experiment is designed to produce visible-reflective infrared ratio images from ERTS-1 data. Iron compounds are promising remote sensing targets because they display prominent spectral features in the visible-reflective infrared wavelength region and are geologically significant. The region selected for this ERTS experiment is the southern end of the Wind River Range in Wyoming. If this method proves successful it should prove useful for regional geologic mapping, mineralogical exploration, and soil mapping. It may also be helpful to ERTS users in scientific disciplines other than geology, especially to those concerned with targets composed of mixtures of live vegetation and soil or rock.

Vincent, R. K.↗
NASA NTRS1993

Chemical fractionations in group IIIAB iron meteorites - Origin by dendritic crystallization of an asteroidal core

Results of an investigation of the crystallization history of the asteroidal core that produced nearly 200 iron meteorites of group IIIAB are presented. The accuracy of the published distribution of coefficients between solid and liquid metal for seven elements and their dependence on the concentrations of S and P are critically assessed to develop a nonideal fractional crystallization model that reproduces all of the major features of the overall chemical trends in group IIIAB. It is suggested that the apparent distribution coefficient of S was was much higher than its equilibrium value (not greater than 0.01) and that it increased during crystallization. In the present preferred model the apparent distribution coefficient for S increases from 0.6 to 0.8, while the S concentration of the liquid increases from 6 to 13 wt pct. It is inferred that light S-rich liquid accumulates preferentially at the top of the core and in structural traps formed by the advancing solid.

Haack, Henning↗
NASA NTRS2022

The hierarchical organization of autocatalytic reaction networks and its relevance to origin of life

Abiogenesis has long been suspected to require that chemical reaction networks contain multiple autocatalytic cores, but little is known about what features of these networks allow for the gradual accretion of complexity. To identify realistic scenarios for the emergence of life-like properties, we develop the concept of a seed-dependent autocatalytic system (SDAS), which is a subnetwork that can autocatalytically self-maintain given a flux of food, but cannot be initiated by food alone. Rather, initiation of SDASs requires the transient introduction of chemical “seeds”. We show that, depending on the topological relationship of SDASs in a chemical reaction network, a food-driven system can accrete complexity in a historically contingent manner, governed by rare seeding events. We develop new algorithms for detecting and analyzing SDASs in chemical reaction databases and describe parallels between multi-SDAS networks and biological ecosystems. Applying our algorithms to both an abiotic reaction network and a biochemical one, each driven by a set of simple food chemicals, we detect SDASs that are organized as trophic tiers, of which the higher tier can be seeded by relatively simple chemicals if the lower tier is already activated. This indicates that sequential activation of trophically organized SDASs by seed chemicals that are not much more complex than what already exist could be a mechanism of gradual complexification from relatively simple abiotic reactions to more complex life-like systems. Interestingly, in both reaction networks, higher-tier SDASs include chemicals that might alter emergent features of chemical systems and could serve as early targets of selection. Our analysis provides computational tools for analyzing very large chemical/biochemical reaction networks and suggests new approaches to studying abiogenesis in the lab.

Zhen Peng↗
NASA NTRS1995

Reflectance spectroscopy of ferric sulfate-bearing montmorillonites as Mars soil analog materials

Spectroscopic analyses have shown that smectites enhanced in the laboratory with additional ferric species exhibit important similarities to those of the soils on Mars. Ferrihydrite in these chemically treated smectites has features in the visible to near-infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. New samples have been prepared with sulfate as well, because S was found by Viking to be a major component in the surface material on Mars. A suite of ferrihydrite-bearing and ferric sulfate-bearing montmorillonites, prepared with variable Fe3+ and S concentrations and variable pH conditions, has been analyzed using reflectance spectroscopy in the visible and infrared regions, Mossbauer spectroscopy at room temperature and 4 K, differential thermal analysis, and X-ray diffraction. These analyses support the formation of ferrihydrite of variable crystallinity in the ferrihydrite-bearing montmorillonites and a combination of schwertmannite and ferrihydrite in the ferric sulfate-bearing montmorillonites. Small quantities of poorly crystalline or nanophase forms of other ferric materials may also be present in these samples. The chemical formation conditions of the ferrihydrite-bearing and ferric sulfate-bearing montmorillonites influence the character of the low temperature Mossbauer sextets and the visible reflectance spectra. An absorption minimum is observed at 0.88-0.89 micrometers in spectra of the ferric sulfate-bearing samples, and at 0.89-0.92 micrometers in spectra of the ferrihydrate-bearing montmorillonites. Mossbauer spectra of the ferric sulfate-bearing montmorillonites indicate variable concentrations of ferrihydrite and schwertmannite in the interlaminar spaces and along grain surfaces. Dehydration under reduced atmospheric pressure conditions induces a greater effect on the adsorbed and interlayer water in ferrihydrite-bearing montmorillonite than on the water in ferric sulfate-bearing montmorillonite. Reflectance spectra of ferric sulfate-bearing montmorillonite include a strong 3-micrometers band that is more resistant to dry atmospheric conditions than the 3-micrometers band in spectra of similarly prepared ferrihydrite-bearing montmorillonites.

NASA Discipline Exobiology↗
NASA NTRS1973

Competition between charge exchange and chemical reaction - The D2/+/ + H system

Study of the special features of molecular charge exchange and its competition with chemical reaction in the case of the D2(+) + H system. The trajectory surface hopping (TSH) model proposed by Tully and Preston (1971) is used to study this competition for a number of reactions involving the above system. The diatomics-in-molecules zero-overlap approximation is used to calculate the three adiabatic surfaces - one triplet and two singlet - which are needed to describe this system. One of the significant results of this study is that the chemical reaction and charge exchange are strongly coupled. It is also found that the number of trajectories passing into the chemical regions of the three surfaces depends very strongly on the surface crossings.-

Preston, R. K.↗
NASA NTRS1963

Introduction to Nuclear Propulsion: Lecture 15 - Nuclear Test Operations

The test operation of nuclear power plants, specifically nuclear rockets, bears some interesting similarities to the operation of chemical rocket tests as well as, of course, many differences. A significant feature common to both nuclear and chemical rocket tests is that all the fuel for the entire operation is loaded at the start of the test. As a direct consequence of this fact, the operation of nuclear power plants must be surrounded with adequate safety precautions, as is indeed the case in the operation of chemical rockets, A second direct consequence is that in both types of testing a very thorough and complete checkout is made before starting the test.

TEST METHOD↗
NASA NTRS1972

General chemical kinetics computer program for static and flow reactions, with application to combustion and shock-tube kinetics

A general chemical kinetics program is described for complex, homogeneous ideal-gas reactions in any chemical system. Its main features are flexibility and convenience in treating many different reaction conditions. The program solves numerically the differential equations describing complex reaction in either a static system or one-dimensional inviscid flow. Applications include ignition and combustion, shock wave reactions, and general reactions in a flowing or static system. An implicit numerical solution method is used which works efficiently for the extreme conditions of a very slow or a very fast reaction. The theory is described, and the computer program and users' manual are included.

Bittker, D. A.↗
NASA NTRS1984

GCKP84--General Chemical Kinetics Code for Gas-Phase Flow and Batch Processes Including Heat Transfer Effects

A general chemical kinetics code is described for complex, homogeneous ideal gas reactions in any chemical system. The main features of the GCKP84 code are flexibility, convenience, and speed of computation for many different reaction conditions. The code, which replaces the GCKP code published previously, solves numerically the differential equations for complex reaction in a batch system or one dimensional inviscid flow. It also solves numerically the nonlinear algebraic equations describing the well stirred reactor. A new state of the art numerical integration method is used for greatly increased speed in handling systems of stiff differential equations. The theory and the computer program, including details of input preparation and a guide to using the code are given.

David A Bittker↗
NASA NTRS1986

On the radiative balance of the stratosphere

The zonally averaged radiative balance of the stratosphere based on the measured temperature structure and gas concentrations available from the LIMS instrument is examined in detail. These data are extant for seven months (November 1978 to May 1979). The contribution to the net radiative balance due to the individual components of solar heating and longwave cooling is discussed. These components are further broken down by individual gas constituent to understand the role each gas plays in determining the total radiative heating/cooling. The deficiencies of employing a latitudinally and temporally independent Newtonian damping coefficient are also explored. In particular, the Newtonian damping time is shown to vary by a factor of two in both latitude and season. Net zonally averaged stratospheric radiative heating for the seven months of LIMS data are presented. These net heating rates are important in determining the role of advective transport of chemical constituents. An important feature that appears in the derived radiative heating is the existence of a region of net radiative cooling near the equatorial stratopause.

Kiehl, J. T.↗