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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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Transfer of water through nonwettable vinyl fluoride membranes has two unique features - /1/ very low water transfer rates can be held constant by holding temperature and solute concentrations constant, /2/ the pressure gradient against which water is transported is limited only by solution breakthrough or membrane strength.
Recent studies of the space power system (SPS) are integrated into a total social cost framework developed for terrestrial central electric power systems. Total social costs include the projection of commercial economics to the time frame of interest as well as the federal research, development and demonstration (RD&D) costs, the health impacts, the resources required, the environmental impacts and other social costs. The SPS system is limited to transporting all materials from the earth's surface to geosynchronous orbit. Only silicon photovoltaic is considered as the SPS energy conversion technique. Costs and impacts of the LWR are considered as a reference for nuclear systems, and the low BTU coal gasification with combined cycle gas and steam turbines is considered as a reference for a fossil central electric plant. The ground solar systems considered are solar thermal using the central receiver approach with thermal storage, and solar photovoltaic using the silicon cell with battery storage.
In space, limits on transportation effectiveness are set by requirements for reaction mass, since reaction mass must be carried on board and often comprises the majority of the launch mass of a space system. Thus, applications where a tether can be used for propulsion with no requirement of reaction mass are extremely attractive for space development. It is a remarkable fact that tethers can be used to increase orbital energy with no requirement for reaction mass.
The sodium-sulfur battery is emerging as a prime high-temperature energy storage technology for space flight applications. A Na-S cell demonstration is planned for a 1995-96 NASA Space Shuttle flight which focuses on the microgravity effects on individual cells. The experiment is not optimized for battery performance as such. Rather, it maximizes the variety of operating conditions which the Na-S cell is capable of in a relatively short 5-day flight. The demonstration is designed to reveal the effects of microgravity by comparison with ground test control cells experiencing identical test conditions but with gravity. Specifically, limitations of transport dynamics and associated cell performance characteristics should be revealed. The Na-S Cell Technology Flight Experiment consists of three separate experiments designed to determine cell operating characteristics, detailed electrode kinetics and reactant distributions.
The development of an algorithm for the solution of the compressible Euler equations at high Mach numbers on unstructured tetrahedral meshes is described. The basic algorithm is constructed in the form of a central difference scheme plus an explicit added artificial viscosity based upon fourth order differences of the solution. The stability of the solution in the vicinity of strong gradients is preserved by the incorporation of an additional artificial viscosity based upon a second order difference. Higher order accuracy is regained by using the ideas of flux corrected transport to limit the amount of added viscosity. The solution is advanced to steady state by means of an explicit multi-stage time-stepping method. The computational efficiency of the complete process is improved by incorporating an unstructured multigrid acceleration procedure. A number of flows of practical interest are analyzed to demonstrate the numerical performance of the proposed approach.
Two classes of material processing scenarios will feature prominently in future interplanetary exploration: in situ production using locally available materials in lunar or planetary landings and high performance structural materials which carve out a set of properties for uniquely hostile space environments. To be competitive, high performance materials must typically offer orders of magnitude improvements in thermal conductivity or insulation, deliver high strength-to-weight ratios, or provide superior durability (low corrosion and/or ablative character, e.g., in heat shields). The space-related environmental parameters of high radiation flux, low weight, and superior reliability limits many typical aerospace materials to a short list comprising high performance alloys, nanocomposites and thin-layer metal laminates (Al-Cu, Al-Ag) with typical dimensions less than the Frank-Reed-type dislocation source. Extremely light weight carbon-carbon composites and carbon aerogels will be presented as novel examples which define broadened material parameters, particularly owing to their extreme thermal insulation (R-32-64) and low densities (<0.01 g/cu cm) approaching that of air itself. Even with these low-weight payload additions, rocket thrust limits and transport costs will always place a premium on assembling as much structural and life support resources upon interplanetary, lunar, or asteroid arrival. As an example, for in situ lunar glass manufacture, solar furnaces reaching 1700 C for pure silica glass manufacture in situ are compared with sol-gel technology and acid-leached ultrapure (<0.1% FeO) silica aerogel precursors.
Two classes of material processing scenarios will feature prominently in future interplanetary exploration- in situ production using locally available materials in lunar or planetary landings and high performance structural materials which carve out a set of properties for uniquely hostile space environments. To be competitive, high performance materials must typically offer orders of magnitude improvements in thermal conductivity or insulation, deliver high strength-to-weight ratios, or provide superior durability (low corrosion and/or ablative character, e.g. in heat shields). The space-related environmental parameters of high radiation flux, low weight and superior reliability limits many typical aerospace materials to a short list comprising high performance alloys, nanocomposites and thin-layer metal laminates (Al-Cu, Al-Ag) with typical dimensions less than the Frank-Reed-type dislocation source. Extremely light weight carbon-carbon composites and car on aerogels will be presented as novel examples which define broadened material parameters, particularly owing to their extreme thermal insulation (R-32-64) and low densities (less than 0.01 g/cc) approaching that of air itself. Even with these low weight payload additions, rocket thrust limits and transport costs will always place a premium on assembling as much structural and life support resources upon interplanetary, lunar or asteroid arrival. As an example for in situ lunar glass manufacture, solar furnaces reaching 1700 C for pure silica glass manufacture in situ are compared with sol-gel technology and acid-leached ultrapure (less than 0.1% FeO) silica aerogel precursors.
CVD SiC and sintered alpha-SiC samples were exposed at 1316 C in a high pressure burner rig at total pressures of 5.7, 15, and 25 atm for times up to 100h. Variations in sample emittance for the first nine hours of exposure were used to determine the thickness of the silica scale as a function of time. After accounting for volatility of silica in water vapor, the parabolic rate constants for Sic in water vapor pressures of 0.7, 1.8 and 3.1 atm were determined. The dependence of the parabolic rate constant on the water vapor pressure yielded a power law exponent of one. Silica growth on Sic is therefore limited by transport of molecular water vapor through the silica scale.
Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weight, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L.) Heynh. (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2.5, 5.1, 10.1, 16.2, and 21.3 kPa O2, 0.035 kPa CO2 and the balance nitrogen under continuous light. Fully expanded leaves were harvested and processed for light and transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been described for plants grown under carbon dioxide enrichment. However, at the lowest oxygen treatment (2.5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespiration, resulting in very thick leaves and a dwarf morphology. This study establishes the leaf parameters that change during growth under low O2, and identifies the lower concentration at which O2 limitation on transport and biosynthetic pathways detrimentally affects leaf development. Grant numbers: NAG5-3756, NAG2-1020, NAG2-1375.
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Agricultural intensification in South Asia has resulted in the expansion and intensification of surface irrigation over the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrasts between the South Asian land surface and the equatorial Indian Ocean, potentially altering the South Asian Summer Monsoon (SASM) circulation. Prior studies have noted apparent declines in the monsoon intensity over the twentieth century and have focused on how altered surface energy balances impact the SASM rainfall distribution. Here, we use the coupled Goddard Institute for Space Studies ModelE-R general circulation model to investigate the impact of intensifying irrigation on the large-scale SASM circulation over the twentieth century, including how the effect of irrigation compares to the impact of increasing greenhouse gas (GHG) forcing. We force our simulations with time-varying, historical estimates of irrigation, both alone and with twentieth century GHGs and other forcings. In the irrigation only experiment, irrigation rates correlate strongly with lower and upper level temperature contrasts between the Indian sub-continent and the Indian Ocean (Pearson's r = -0.66 and r = -0.46, respectively), important quantities that control the strength of the SASM circulation. When GHG forcing is included, these correlations strengthen: r = -0.72 and r = -0.47 for lower and upper level temperature contrasts, respectively. Under irrigated conditions, the mean SASM intensity in the model decreases only slightly and insignificantly. However, in the simulation with irrigation and GHG forcing, inter-annual variability of the SASM circulation decreases by *40 %, consistent with trends in the reanalysis products. This suggests that the inclusion of irrigation may be necessary to accurately simulate the historical trends and variability of the SASM system over the last 50 years. These findings suggest that intensifying irrigation, in concert with increased GHG forcing, is capable of reducing the variability of the simulated SASM circulation and altering the regional moisture transport by limiting the surface warming and reducing land-sea temperature gradients.
Long-duration, deep-space exploration and habitation missions demand robust and reliable technologies to ensure crew health, safety, and mission success. Local food production will be essential for crew nutrition and morale. However, at $10,000/lb, the payload costs and mass/volume limitations to transport and provide the necessary resources, including fertilizer, for an anticipated 30-month mission become challenging over time. For mission success and sustainability, the Environmental Control and Life Support System (ECLSS) of the near future will need to recover resources from all “waste” sources and be near-closed loop. Organic wastes (e.g., fecal and food) offer a renewable source of C, N, P, water and other trace elements necessary to sustain crop production. However, these high solidwastes are often difficult to treatdue to factors includingheterogeneity, complexity, high organic strength, and the presence of pathogens. To date, there is no flight-ready technology capable of treating mixed organic wastes, creating a technology gap for future space missions. To address this need, a prototype Organic Processor Assembly (OPA) was developed through collaboration between the University of South Florida (USF) and NASA’s Kennedy Space Center (KSC). The OPA is based on the anaerobic membrane bioreactor (AnMBR), a hybrid technology coupling high-rate anaerobic digestion with membrane filtration. The system is designed for an early planetary base (EPB) scenario to aid in closing the resource recovery loop and decreaseresupply dependence. This presentation discusses initial research pertaining to: 1) design challenges in maximizing hydraulic/organic throughputandReliability, Availability, Maintainability, and Safety(RAMS)while minimizingmass and volume; 2) create capabilities for treating simulated high solids waste under steady and non-steady state conditions; and 3) measuresolids performance parameter(s). Future research and development pertaining to further optimization on system operation, performance, and expanded treatment capabilities arepresented.
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In secondary active transporters, a relatively limited set of protein folds have evolved diverse solute transport functions. Because of the conformational changes inherent to transport, altering substrate specificity typically involves remodeling the entire structural landscape, limiting our understanding of how novel substrate specificities evolve. In the current work, we examine a structurally minimalist family of model transport proteins, the small multidrug resistance (SMR) transporters, to understand the molecular basis for the emergence of a novel substrate specificity. We engineer a selective SMR protein to promiscuously export quaternary ammonium antiseptics, similar to the activity of a clade of multidrug exporters in this family. Using combinatorial mutagenesis and deep sequencing, we identify the necessary and sufficient molecular determinants of this engineered activity. Using X-ray crystallography, solid-supported membrane electrophysiology, binding assays, and a proteoliposome-based quaternary ammonium antiseptic transport assay that we developed, we dissect the mechanistic contributions of these residues to substrate polyspecificity. We find that substrate preference changes not through modification of the residues that directly interact with the substrate but through mutations peripheral to the binding pocket. Our work provides molecular insight into substrate promiscuity among the SMRs and can be applied to understand multidrug export and the evolution of novel transport functions more generally.
An initial assessment of a proposed High-Speed Civil Transport (HSCT) was conducted in the fall of 1995 at the NASA Langley Research Center. This configuration, known as the Industry Reference-H (Ref.-H), was designed by the Boeing Aircraft Company as part of their work in the High Speed Research program. It included a conventional tail, a cranked-arrow wing, four mixed-flow turbofan engines, and capacity for transporting approximately 300 passengers. The purpose of this assessment was to evaluate and quantify operational aspects of the Reference-H configuration from a pilot's perspective with the additional goal of identifying design strengths as well as any potential configuration deficiencies. This study was aimed at evaluating the Ref.-H configuration at many points of the aircraft's envelope to determine the suitability of the vehicle to accomplish typical mission profiles as well as emergency or envelope-limit conditions. Pilot-provided Cooper-Harper ratings and comments constituted the primary vehicle evaluation metric. The analysis included simulated real-time piloted evaluations, performed in a 6 degree of freedom motion base NASA Langley Visual-Motion Simulator, combined with extensive bath analysis. The assessment was performed using the third major release of the simulation data base (known as Ref.-H cycle 2B).
Based on the observed density of impact craters on the Venus surface obtained from Venera 15-16 radar images, a formalism to estimate the upper bounds on the contributions made to lithospheric heat transport by volcanism and lithospheric recycling is presented. The Venera 15-16 data, if representative of the entire planet, limit the average rate of volcanic resurfacing on Venus to less than 2 cu km/yr (corresponding to less than 1 percent of the global heat loss), and limit the rate of lithospheric recycling to less than 1.5 sq km/yr (and probably to less than 0.5 sq km/yr), corresponding to 25 percent (and to 9 percent) of the global heat loss. The present results indicate that heat loss at lithospheric levels in Venus is dominated by conduction.
The distance a solid biomass feedstock could be used to transport the feedstock when used as biobased fuel is critical information for transportation analysis. However, this information is not available. The break-even transportation distance (BTD) of various fuels from biomass feedstocks and fossil sources was analyzed for truck, rail, and ship transport modes based on bulk density, moisture content, and specific energy. Fourteen different biomass feedstocks, such as crop residues (e.g., corn stover), woody biomass (e.g., wood chips), including thermally pretreated (torrefied) and densified forms (pellets), cattle feedlot compost, and three standard fossil fuels, namely, coal, lignite, and diesel, were considered for BTD analysis and comparison. The BTD values were derived by comparing the energy content of biomass feedstocks with the energy expended in transporting the fuels through selected transportation modes. For ready reference, an alternative derivation of BTD equations and example calculations were also presented. Among the biomass feedstocks, torrefied pellets had the highest BTD (4.16 × 10 4 , 12.47 × 10 4 , and 54.14 × 10 4 km), and cattle feedlot compost had the lowest BTD (1.29 × 10 4 , 3.88 × 10 4 , and 9.23 × 10 4 km), respectively, for truck, rail, and ship. Higher bulk density and higher specific energy of the biomass feedstocks increased the BTD for all modes of transport. Transport is most efficient when mass-limited. Biomass feedstock bulk densities where transportation becomes mass-limited are 223, 1,480, and 656 kg/m 3 for truck, rail, and ship, respectively. Truck transport is typically mass-limited (payload limit restriction; increased BTD), whereas rail transport is entirely volume-limited (cargo space restriction; decreased BTD), and ship transport is mostly volume-limited for biomass feedstocks and mass-limited for densified biomass feedstocks. Ship transport is the most efficient, followed by rail and truck; on average for the materials (17) studied, rail is 3.1 times and ship is 9.2 times the truck's BTD. Based on the bulk density and higher specific energy of the biomass feedstocks, regardless of the refinery location, interstate truck transport of these feedstocks is not a limiting factor in the bio-refining process., with the studied biomass feedstock BTD per truckload representing between 0.89 and 2.88 times the US perimeter.
Several issues have arisen from experimental observations and/or theoretical postulation related to the behavior of helium in uranium hexafluoride (UF 6 ) matrices and how it may impact the ability to use this noble gas to quantify the fill date of the cylinder. A series of experiments was conducted to address several such issues, and the results and implications are reported here. Two issues relate to bias in the helium measurement due to ambient air from extraneous sources such as atmospheric air or from potential holdup in a large, activated alumina chemical trap. These issues are really a question of differential retention of helium versus three other inert gas isotopes (representative of other noble gases found in air) used as a calibration for air in leakage. Discernable bias was not detected in either case. Another issue had to do with helium potentially brought into the cylinder by a liquid UF 6 fill and subsequently released as the material solidifies and/or during storage. The solubility of helium in liquid UF 6 was measured to investigate this theory. The experiment quantified the potential magnitude of the initial helium contribution if present. The final issue was that of retention of helium in solid UF 6 . Investigation of this theory necessitated quantifying both the solubility and the diffusivity of helium in UF 6 . In one experiment, the solubility was measured at cryogenic temperature, allowing quantification of helium in solid UF 6 such as would be found in a cold trap. In a second experiment, transport of helium into and through a macroscopic plug of solid UF 6 was examined. The transport was very slight although apparently detectible. Effectively, only an upper limit to the transport could be determined, but that limit implied that helium holdup in solid UF 6 is a real possibility.