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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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Computer graphics of vibrational effects in ion molecule collisions including electron tunneling oscillations, nuclear capture, and molecular oscillations and relaxation
Vacuum UV monochromators calibration by molecular branching ratio technique based on electron transition probabilities
Carbon dioxide electron impact energy loss spectrum and molecular orbit calculations, discussing fourth positive bands production in Mars upper atmosphere UV dayglow
A durable antistatic coating is achieved on polymethylmethacrylate plastic without affecting its optical clarity by applying to the surface of the plastic a low molecular weight solvent having a high electron affinity and a high dipole moment, such as acentonitrile or nitromethane alone or in the presence of photopolymerizable monomer. The treated polymethylmethacrylate plastic dissipates most of the induced electrostatic charge and retains its optical clarity. The antistatic behavior persists after washing, rubbing and vacuum treatment.
The paper presents the multiconfiguration-self-consistent (MCSCF) and configuration state functions (CSF) for the low-lying electronic states of MgO. It was shown that simple description of these states was possible provided the 1 Sigma(+) states are individually optimized at the MCSCF level, noting that the 1(3 Sigma)(+) and 2(1 Sigma)(+) states which nominally result from the same electron occupation are separated energetically. The molecular orbitals obtained at this level of approximation should provide a useful starting point for extended configuration interaction calculations since they have been optimized for the particular states of interest.
The Voyager 2 UV spectrometer was used to scan the Uranus atmosphere at wavelengths from 500-1700 A with a field of view of 0.1 x 0.86 deg. The temperature and composition of the upper atmosphere were determined through occultations of light from gamma Pegasi, nu Geminorum and the sun. The data indicated a substantial gas density (100 million H atoms/cu cm) at about 28,000 km from the Uranus center, suggesting that gas drag plays a significant role in ring evolution. The distributions of CH4 and C2H2 in the lower atmosphere were also estimated. An electroglow emission was detected on the sunlit side, and attributed to emissions from atomic and molecular hydrogen excited by low energy electrons. An auroral glow was also observed, and exhibited evidence of an energy input equal to that of the electroglow. Finally, estimates of the C2H2 mixing ratio and the vertical column abundance of H2 are calculated.
Continued interest by the research community in thermally stable, tough, high temperature adhesives has resulted in the investigation by Langley Research Center of two linear aromatic polyamide-imide (PAI) homopolymers and two linear aromatic PAI copolymers. The homopolymers were made with either 3,3'=DABA or 4,4'-DABA and BTDA. The two polymers were prepared with a monomer ratio of 0.75 DABP:0.25 DABA:1.00 BTDA. These aromatic PAIs possess high thermal stability because of intermolecular hydrogen bonding and chain stiffness. Lap shear strength (LSS) was the main criteria used to evaluate the polymers as adhesives. LSS of bonded Ti-6Al-4V was determined at room temperature (RT), 177, 204 and 232 C. The glass transition temperature and the type of bond failure were also determined. The best LSS values of the four adhesive systems investigated were obtained with the PAI copolymer identified in the report as LARC-TPI (25 percent 3,3'-DABA); however, it did not produce LSSs nearly as high as LARC-TPI. The poor flow properties observed appear to be due to a combination of high molecular weight and the increased interchain electronic interactions associated with the amide group.
Results are reported in the form of reaction diagrams, graphs, and tables of research being conducted to synthesize and characterize linear aromatic polyimides which are soluble in common organic solvents and optically transparent in the 400-600 nm spectral range. These flexible and high-temperature polymeric films and coatings are needed for specific applications on space components such as antennas, solar cells, and thermal control coating systems. Several series of these polyimide films have been produced by making variations in the polymer molecular structure aimed at reducing the electronic interactions between the polymer chains.
Continued interest by the research community in thermally stable, tough, high temperature adhesives has resulted in the investigation by Langley Research Center of two linear aromatic polyamide-imide (PAI) homopolymers and two linear aromatic PAI copolymers. The homopolymers were made with either 3,3'=DABA or 4,4'-DABA and BTDA. The two polymers were prepared with a monomer ratio of 0.75 DABP:0.25 DABA:1.00 BTDA. These aromatic PAIs possess high thermal stability because of intermolecular hydrogen bonding and chain stiffness. Lap shear strength (LSS) was the main criteria used to evaluate the polymers as adhesives. LSS of bonded Ti-6Al-4V was determined at room temperature (RT), 177, 204 and 232 C. The glass transition temperature and the type of bond failure were also determined. The best LSS values of the four adhesive systems investigated were obtained with the PAI copolymer identified in the report as LARC-TPI (25 percent 3,3'-DABA); however, it did not produce LSSs nearly as high as LARC-TPI. The poor flow properties observed appear to be due to a combination of high molecular weight and the increased interchain electronic interactions associated with the amide group.
Early Earth microbial communities that centered around the anaerobic decomposition of organic molecular hydrogen as a carrier of electrons, regulator of energy metabolism, and facilitator of syntroph'c microbial interactions. The advent of oxygenic photosynthetic organisms added a highly dynamic and potentially dominant term to the hydrogen economy of these communities. We have examined the daily variations of hydrogen concentrations in cyanobacteria-dominated microbial mats from hypersaline ponds in Baja California Sur, Mexico. These mats bring together phototrophic and anaerobic bacteria (along with virtually all other trophic groups) in a spatially ordered and chemically dynamic matrix that provides a good analog for early Earth microbial ecosystems. Hydrogen concentrations in the photic zone of the mat can be three orders of magnitude or more higher than in the photic zone, which are, in turn, an order of magnitude higher than in the unconsolidated sediments underlying the mat community. Within the photic zone, hydrogen concentrations can fluctuate dramatically during the diel (24 hour day-night) cycle, ranging from less than 0.001% during the day to nearly 10% at night. The resultant nighttime flux of hydrogen from the mat to the environment was up to 17% of the daytime oxygen flux. The daily pattern observed is highly dependent on cyanobacterial species composition within the mat, with Lyngbya-dominated systems having a much greater dynamic range than those dominated by Microcoleus; this may relate largely to differing degrees of nitrogen-fixing and fermentative activity in the two mats. The greatest H2 concentrations and fluxes were observed in the absence of oxygen, suggesting an important potential feedback control in the context of the evolution of atmospheric composition. The impact of adding this highly dynamic photosynthetic term to the hydrogen economy of early microbial ecosystems must have been substantial. From an evolutionary standpoint, the H2 generated in mats could have represented a very important new source of electrons and energy - but one that could not be harnessed without substantial adaptation to the highly variable chemistry of the mat surface. In addition, the emergent chemistry of anaerobic communities is often highly dependent on ambient hydrogen concentrations, so that incorporation of these communities into photosynthetic mats could have significantly affected the composition and flux of reduced "biosignature' gases to the environment.
Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.
We present a survey of the distribution of 20 chemical and isotopic molecular species along the central ridge of the Orion molecular cloud from 6' north to 6' south of BN-KL observed with the QUARRY focal plane array on the FCRAO 14 m telescope, which provides an angular resolution of approximately 50" in the 3 mm wavelength region. We use standard tools of multivariate analysis for a systematic investigation of the similarities and differences among the maps of integrated intensities of the 32 lines observed. The maps fall in three broad classes: first, those strongly peaked toward BN-KL; second, those having rather flat distributions along the ridge; and third, those with a clear north-south gradient or contrast. We identify six positions or regions where we calculate relative abundances. Line velocities and line widths indicate that the optically thin lines generally trace the same volume of dense gas, except in the molecular bar, where C18O, C34S, H13CO+, CN, C2H, SO, and C3H2 have velocities characteristic of the bar itself, whereas the emission from other detected species is dominated by the background cloud. The strongest abundance variations in our data are the well-known enhancements seen in HCN, CH3OH, HC3N, and SO toward BN-KL and, less strongly, toward the Orion-South outflow 1'.3S. The principal result of this study is that along the extended quiescent ridge the chemical abundances, within factors of 3-4, exhibit an impressive degree of uniformity. The northern part of the ridge has a chemistry closest to that found in quiescent dense clouds. While temperature and density are similar around the northern radical-ion peak near 3'.5N and in the southern core near 4'.2S, some abundances, in particular, those of the ions HCO+ and N2H+, are significantly lower toward 4'.2S. The areas near 4.'2S and the molecular bar itself around (1'.7E, 2'.4S) stand out with peculiar and similar properties probably caused by stronger UV fields penetrating deeper into the clumpy molecular gas. This leads to higher electron abundances and thereby reduced abundances of the ions, as well as a lack of complex molecules.
As part of a study to identify potential targets of calcium action in plant cells, a 35-kDa, annexin-like protein was purified from pea (Pisum sativum L.) plumules by a method used to purify animal annexins. This protein, called p35, binds to a phosphatidylserine affinity column in a calcium-dependent manner and binds 45Ca2+ in a dot-blot assay. Preliminary sequence data confirm a relationship for p35 with the annexin family of proteins. Polyclonal antibodies have been raised which recognize p35 in Western and dot blots. Immunofluorescence and immunogold techniques were used to study the distribution and subcellular localization of p35 in pea plumules and roots. The highest levels of immunostain were found in young developing vascular cells producing wall thickenings and in peripheral root-cap cells releasing slime. This localization in cells which are actively involved in secretion is of interest because one function suggested for the animal annexins is involvement in the mediation of exocytosis.
As humanity gears up for its return to the moon after more than half a century, collaborative efforts between NASA, Artemis Accords Partners, and private industry are underway to establish the necessary infrastructure and technologies for lunar habitation and eventual Mars exploration. However, the traditional ISS resupply and waste management model is impractical and economically infeasible for prolonged missions to the Moon and Mars. Advanced chemical conversion technologies are needed to generate vital consumable products from local planetary resources (ISRU) and recycled gasses and waste within semi-closed loop life-support systems. Low-temperature plasma reactors are emerging power-to-gas technologies with the potential to facilitate various chemical synthesis processes with hardware commonality and redundancy. In plasma-based systems, electrical power is used to ionize a feedstock gas, creating a highly reactive environment that leverages electron excitation chemistry to break stable molecular bonds and form value added products. Unlike thermal chemical processes, plasma reactors operate at non-equilibrium conditions, allowing for lower-temperature operation and instantaneous start-up, making them adaptable to intermittent power availability. Moreover, their scalability permits deployment in both portable astronaut systems and large-scale industrial setups for colonies. One promising application of plasmas is for CO 2 conversion. Carbon dioxide comprises 96% of the Martian atmosphere and is a byproduct of human respiration, which typically must be scrubbed and vented from space habitats. A plasma source integrated with membrane separation technology could generate a stream of oxygen for life support and rocket propellant. CO 2 splitting may also be beneficial as a precursor to manufacture carbon-based products and fuels in situ, like methane, methanol, and polyethylene. Plasma-assisted CO 2 conversion is a simpler case to study without the concern of selectivity and is the first step toward complex chemical synthesis. This work presents preliminary experimental case study from a plasma reactor for CO 2 conversion and casts a vision for the potential of plasma technologies in a sub-architecture for resource production to enable the next generation of human spaceflight activities.
We characterized the dissociation fraction of a thermal dissociation atomic hydrogen source byinjecting the mixed atomic and molecular output of the source into an electron beam ion trapcontaining highly charged ions and recording the x-ray spectrum generated by charge exchangeusing a high-resolution x-ray calorimeter spectrometer. We exploit the fact that the charge exchangestate-selective capture cross sections are very different for atomic and molecular hydrogen incidenton the same ions, enabling a clear spectroscopic diagnostic of the neutral species.
The plasma convection models of Volland (1975) and Heelis (1982) are utilized to study the ionosphere. The parameters for the two models are evaluated. The two-cell convection models have similar total cross tail electric potential, diameter of the polar cap, and potential falloff rate outside the polar cap; however, they differ in maximum potential, and the electric field in the polar cap. The input parameters for the high-latitude ionospheric model are described. Two high-latitude ionospheric model runs were conducted and the data are compared in terms of electron density at and above the F 2 peak, attitude of the F 2 peak, ion temperature, and molecular-atomic ion transition height. The altitude dependence of electron density is analyzed using coherent scatter radar data. The data reveal differences between the two models in the height of the F 2 peak and in the ion temperature. The altitude values of the Heelis model are higher than the Volland model in the region where plasma is transported into the polar cap and lower in the region plasma is transported out of the polar cap; the Heelis model also produces an increase in ion temperature. It is noted that the ionosphere has a limited dependence upon the details of the convection models.
Two nonlinear triggered lightning models have been developed for use in finite difference calculations. Both are based on three species of air chemistry physics and couple nonlinearly calculated air conductivity to Maxwell's equations. The first model is suitable for use in three-dimensional modeling and has been applied to the analysis of triggered lightning on the NASA F106B Thunderstorm Research Aircraft. The model calculates number densities of positive ions, negative ions, and electrons as a function of time and space through continuity equations, including convective derivative terms. The set of equations is closed by using experimentally determined mobilities, and the mobilities are also used to determine the air conductivity. Results from the model's application to the F106B are shown. The second model is two-dimensional and incorporates an enhanced air chemistry formulation. Momentum conservation equations replace the mobility assumption of the first model. Energy conservation equations for neutrals, heavy ions, and electrons are also used. Energy transfer into molecular vibrational modes is accounted for. The purpose for the enhanced model is to include the effects of temperature into the air breakdown, a necessary step if the model is to simulate more than the very earliest stages of breakdown. Therefore, the model also incorporates a temperature-dependent electron avalanche rate. Results from the model's application to breakdown around a conducting ellipsoid placed in an electric field are shown.
Aerospace environment effects (high energy electrons, thermal cycling, atomic oxygen, and aircraft fluids) on polymeric and composite materials considered for structural use in spacecraft and advanced aircraft are examined. These materials include Mylar, Ultem, and Kapton. In addition to providing information on the behavior of the materials, attempts are made to relate the measurements to the molecular processes occurring in the material. A summary and overview of the technical aspects are given along with a list of the papers that resulted from the studies. The actual papers are included in the appendices and a glossary of technical terms and definitions is included in the front matter.