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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
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Comparison of V-4 and V-5 Exercise/Oxygen Prebreathe Protocols to Support Extravehicular Activity in Microgravity

The Prebreathe Reduction Program (PRP) used exercise during oxygen prebreathe to reduce necessary prebreathe time prior to depressurizing to work in a 4.3 psi suit during extravehicular activity (EVA). Initial testing produced a two-hour protocol incorporating ergometry exercise and a 30 min cycle of depress/repress to 10.2 psi where subjects breathed 26.5% oxygen/balance nitrogen (Phase II - 10 min at 75% peak oxygen consumption [VO2 peak] followed by 40 min intermittent light exercise [ILE] [approx. 5.8 mL-per kilogram- per minute], then 50 min of rest). The Phase II protocol (0/45 DCS) was approved for operations and has been used on 40 EVAs, providing significant time savings compared to the standard 4 h resting oxygen prebreathe. The Phase V effort focused on performing all light in-suit exercise. Two oxygen prebreathe protocols were tested sequentially: V-4) 160 min prebreathe with 150 min of continuous ILE. The entire protocol was completed at 14.7 psi. All exercise involved upper body effort. Exercise continued until decompression. V-5) 160 min prebreathe with 140 min of ILE - first 40 min at 14.7 psi, then 30 min at 10.2 psi (breathing 26.5% oxygen) after a 20 min depress, simulating a suit donning period. Subjects were then repressed to 14.7 psi and performed another 50 min of lower body ILE, followed by 50 min rest before decompression. The V-4 protocol was rejected with 3 DCS/6 person-exposures. Initial V-5 testing has produced 0 DCS/11 person-exposures (ongoing trials). The difference in DCS rate was significant (Fisher Exact p=0.029). The observations of DCS were significantly lower in early V-5 trials than in V-4 trials. Additional studies are required to evaluate the relative contribution of the variables in exercise distribution, the 10.2 psi depress/repress component, pre-decompression rest, or possible variation in total oxygen consumption.

Pollock, N. W.↗
NASA NTRS1980

Effect of hyperbaric oxygenation on carbohydrate metabolism protein synthesis in the myocardium during sustained hypodynamia

Glycolysis and the intensity of protein synthesis were studied in 140 white male rats in subcellular fractions of the myocardium during 45 day hypodynamia and hyperbaric oxygenation. Hypodynamia increased: (1) the amount of lactic acids; (2) the amount of pyruvic acid; (3) the lactate/pyruvate coefficient; and (4) the activities of aldolase and lactate dehydrogenase. Hyperbaric oxygenation was found to have a favorable metabolic effect on the animals with hypodynamia.

Makarov, G. A.↗
NASA NTRS1975

Anomalous composition and energy spectra of cosmic rays below 20 MeV/nucleon

The relative abundances and energy spectra of C, N, O, Ne, and Fe are investigated as a function of the interplanetary low energy proton intensity using observations obtained over a 17-month period by IMP-8. The oxygen intensity was enhanced when proton activity was at its lowest level, while all other heavy elements almost disappeared. Nuclei of less than 3 MeV/nucleon showed a strong intensity fluctuation strongly correlated with the interplanetary proton flux and displayed a velocity anisotropy along the garden-hose angle, indicating that they are of solar origin. The anomalous oxygen hump between 3 and 20 MeV is apparently not of solar origin. The observations are compatible with the model proposed by Fisk et al. (1974), in which these oxygen nuclei are considered to be interstellar neutral oxygen atoms which are ionized and accelerated to the observed energies by magnetic field irregularities in the outer solar system.

Klecker, B.↗
NASA NTRS2003

Component Activity Measurements in the Ti-Al-O System by Knudsen Cell Mass Spectrometry

Titanium-aluminides (containing (alpha)2-Ti3Al and gamma-TiAl intermetallic phases) have received continued research focus due to their potential as low-density materials for structural applications at intermediate temperatures. However their application above about 850C is hindered by poor oxidation resistance, characterized by the formation of a non-protective TiO2+Al2O3 scale and an oxygen-enriched subsurface zone. Consistent with this are measured titanium and aluminum activities in "oxygen-free" titanium-aluminides, which indicate Al2O3 is only stable for aluminum concentrations greater then 54 atom percent at 1373 K. However, the inability to form a protective Al2O3 scale is in apparent conflict with phase diagram studies, as experimental isothermal sections of the Ti-Al-O system show gamma-TiAl + alpha2-Ti3Al structures are in equilibrium only with Al2O3. The apparent resolution to this conflict lies in the inclusion of oxygen effects in the thermodynamic measurements

Copland, Evan↗
NASA NTRS1992

Influence of exercise training on the oxidative capacity of rat abdominal muscles

Our purpose was to determine if endurance exercise training would increase the oxidative capacity of the abdominal expiratory muscles of the rat. Accordingly, 9 male rats were subjected to an endurance training protocol (1 h/day, 6 days/week, 9 weeks) and 9 litter-mates served as controls. Citrate synthase (CS) activity was used as an index of oxidative capacity, and was determined in the following muscles: soleus, plantaris, costal diaphragm, crural diaphragm, and in all four abdominal muscles: rectus abdominis, transversus abdominis, external oblique, and internal oblique. Compared to their non-trained litter-mates, the trained rats had higher peak whole body oxygen consumption rates (+ 16%) and CS activities in plantaris (+34%) and soleus (+36%) muscles. Thus, the training program caused substantial systemic and locomotor muscle adaptations. The CS activity of costal diaphragm was 20% greater in the trained animals, but no difference was observed in crural diaphragm. The CS activity in the abdominal muscles was less than one-half of that in locomotor and diaphragm muscles, and there were no significant changes with training except in the rectus abdominis where a 26% increase was observed. The increase in rectus abdominis CS activity may reflect its role in postural support and/or locomotion, as none of the primary expiratory pumping muscles adapted to the training protocol. The relatively low levels of CS activity in the abdominal muscles suggests that they are not recruited frequently at rest, and the lack of an increase with training indicates that these muscles do not contribute significantly to the increased ventilatory activity accompanying exercise in the rat.

Non-NASA Center↗
NASA NTRS1986

Effects of the low Earth orbital environment on spacecraft materials

It is evident from space flights during the last three years that the low Earth orbital (LEO) environment interacts with spacecraft surfaces in significant ways. One manifestation of these interactions is recession of, in particular, organic-polymer-based surfaces presumably due to oxidation by atomic oxygen, the major component of the LEO environment. Three experiments have been conducted on Space Shuttle flights 5, 8 and 41-G to measure reaction rates and the effects of various parameters on reaction rates. Surface recession on these flights indicates reaction efficiencies approximately 3 x 10(-24) cu cm/atoms for unfilled organic polymers. Of the metals, silver and osmium are very reactive. Effects on spacecraft or experiment surfaces can be evaluated using the derived reaction efficiencies and a definition of the total exposure to atomic oxygen. This exposure is obtained using an ambient density model, solar activity data and spacecraft parameters of altitude, attitude and operational date. Oxygen flux on a given surface is obtained from the ambient density and spacecraft velocity and can then be integrated to provide the total exposure or fluence. Such information can be generated using simple computational programs and can be converted to various formats. Overall, the extent of damage is strongly dependent on the type of surface and total exposure time.

Leger, L. J.↗
NASA NTRS2014

Determining the Source of Water Vapor in a Cerium Oxide Electrochemical Oxygen Separator to Achieve Aviator Grade Oxygen

More than a metric ton of water is transported to the International Space Station (ISS) each year to provide breathing oxygen for the astronauts. Water is a safe and compact form of stored oxygen. The water is electrolyzed on ISS and ambient pressure oxygen is delivered to the cabin. A much smaller amount of oxygen is used each year in spacesuits to conduct Extra Vehicular Activities (EVAs). Space suits need high pressure (>1000 psia) high purity oxygen (must meet Aviator Breathing Oxygen "ABO" specifications, >99.5% O2). The water / water electrolysis system cannot directly provide high pressure, high purity oxygen, so oxygen for EVAs is transported to ISS in high pressure gas tanks. The tanks are relatively large and heavy, and the majority of the system launch weight is for the tanks and not the oxygen. Extracting high purity oxygen from cabin air and mechanically compressing the oxygen might enable on-board production of EVA grade oxygen using the existing water / water electrolysis system. This capability might also benefit human spaceflight missions, where oxygen for EVAs could be stored in the form of water, and converted into high pressure oxygen on-demand. Cerium oxide solid electrolyte-based ion transport membranes have been shown to separate oxygen from air, and a supported monolithic wafer form of the CeO2 electrolyte membrane has been shown to deliver oxygen at pressures greater than 300 psia. These supported monolithic wafers can withstand high pressure differentials even though the membrane is very thin, because the ion transport membrane is supported on both sides (Fig 1). The monolithic supported wafers have six distinct layers, each with matched coefficients of thermal expansion. The wafers are assembled into a cell stack which allows easy air flow across the wafers, uniform current distribution, and uniform current density (Fig 2). The oxygen separation is reported to be "infinitely selective" to oxygen [1] with reported purity of 99.99% [2]. Combined with a mechanical compressor, a Solid Electrolyte Oxygen Separator (SEOS) should be capable of producing ABO grade oxygen at pressures >2400 psia, on the space station. Feasibility tests using a SEOS integrated with a mechanical compressor identified an unexpected contaminant in the oxygen: water vapour was found in the oxygen product, sometimes at concentrations higher than 40 ppm (the ABO limit for water vapour is 7 ppm). If solid electrolyte membranes are really "infinitely selective" to oxygen as they are reported to be, where did the water come from? If water is getting into the oxygen, what other contaminants might get into the oxygen? Microscopic analyses of wafers, welds, and oxygen delivery tubes were performed in an attempt to find the source of the water vapour contamination. Hot and cold pressure decay tests were performed. Measurements of water vapour as a function of O2 delivery rate, O2 delivery pressure, and process air humidity levels were the most instructive in finding the source of water contamination (Fig 3). Water contamination was directly affected by oxygen delivery rate (doubling the oxygen production rate cut the water level in half). Water was affected by process air humidity levels and delivery pressure in a way that indicates the water was diffusing into the oxygen delivery system.

Graf, John↗
NASA NTRS1978

A Microwave Pressure Sounder

An instrument to measure atmospheric pressure at the earth's surface from an orbiting satellite would be a valuable addition to the expanding inventory of remote sensors. The subject of this report is such an instrument - the Microwave Pressure Sounder (MPS). It is shown that global-ocean coverage is attainable with sufficient accuracy, resolution and observational frequency for meteorological, oceanographic and climate research applications. Surface pressure can be deduced from a measurement of the absorption by an atmospheric column at a frequency in the wing of the oxygen band centered on 60 GHz. An active multifrequency instrument is needed to make this measurement with sufficient accuracy. The selection of optimum operating frequencies is based upon accepted models of surface reflection, oxygen, water vapor and cloud absorption. Numerical simulation using a range of real atmospheres defined by radiosonde observations were used to validate the frequency selection procedure. Analyses are presented of alternative system configurations that define the balance between accuracy and achievable resolution.

Flower, D. A.↗
NASA NTRS1990

Blood biochemical and cellular changes during decompression and simulated extravehicular activity

Blood biochemical and cellular parameters were measured in human subjects before and after exposure to a decompression schedule involving 6 h of oxygen prebreathing. The exposure was designed to simulate extravehicular activity for 6 h (subjects performed exercise while exposed to 29.6 kPa). There were no significant differences between blood samples from subjects who were susceptible (n = 11) versus those who were resistant (n = 27) to formation of venous gas emboli. Although several statistically significant (P less than 0.05) changes in blood parameters were observed following the exposure (increases in white blood cell count, prothrombin time, and total bilirubin, and decreases in triglycerides, very-low-density lipoprotein cholesterol, and blood urea nitrogen), the changes were small in magnitude and blood factor levels remained within normal clinical ranges. Thus, the decompression schedule used in this study is not likely to result in blood changes that would pose a threat to astronauts during extravehicular activity.

Decompression Sickness/blood/etiology/prevention &↗
NASA NTRS2009

The Active Oxidation of Silicon Carbide

The high temperature oxidation of silicon carbide occurs in two very different modes. Passive oxidation forms a protective oxide film which limits further attack of the SiC: SiC(s) + 3/2 O2(g) = SiO2(s) + CO(g) Active oxidation forms a volatile oxide and may lead to extensive attack of the SiC: SiC(s) + O2(g) = SiO(g) + CO(g) Generally passive oxidation occurs at higher oxidant pressures and active oxidation occurs at lower oxidant pressures and elevated temperatures. Active oxidation is a concern for reentry, where the flight trajectory involves the latter conditions. Thus the transition points and rates of active oxidation are a major concern. Passive/active transitions have been studied by a number of investigators. An examination of the literature indicates many questions remain regarding the effect of impurity, the hysteresis of the transition (i.e. the difference between active-to-passive and passive-toactive), and the effect of total pressure. In this study we systematically investigate each of these effects. Experiments were done in both an alumina furnace tube and a quartz furnace tube. It is known that alumina tubes release impurities such as sodium and increase the kinetics in the passive region [1]. We have observed that the active-to-passive transition occurs at a lower oxygen pressure when the experiment is conducted in alumina tubes and the resultant passive silica scale contains sodium. Thus the tests in this study are conducted in quartz tubes. The hysteresis of the transition has been discussed in the detail in the original theoretical treatise of this problem for pure silicon by Wagner [2], yet there is little mention of it in subsequent literature. Essentially Wagner points out that the active-to-passive transition is governed by the criterion for a stable Si/SiO2 equilibria and the passive-to-active transition is governed by the decomposition of the SiO2 film. A series of experiments were conducted for active-to-passive and passive-to-active transitions by increasing and decreasing oxygen pressure, respectively. For pure silicon a dramatic difference was found; whereas for SiC the difference was not as great. This may be due to the oxidation of the carbon in SiC which may break down the scale [3]. The third area is the effect of total pressure. In the literature, low oxygen potentials are achieved via either low total pressure or low oxygen pressure in an O2/Ar mixture. Both types of experiments are done in this study and the differences are discussed with regard to the presence or absence of a boundary layer.

Jacobson, Nathan S.↗
NASA NTRS2009

Metabolic Cost of Experimental Exercises

Although the type and duration of activity during decompression was well documented, the metabolic cost of 1665 subject-exposures with 8 activity profiles from 17 altitude decompression sickness (DCS) protocols at Brooks City-Base, TX from 1983-2005 was not determined. Female and male human volunteers (30 planned, 4 completed) performed activity profiles matching those 8 activity profiles at ground level with continuous monitoring of metabolic cost. A Cosmed K4b2 Cardio Pulmonary Exercise Testing device was used to measure oxygen uptake (VO2) during the profiles. The results show levels of metabolic cost to the females for the profiles tested varied from 4.3 to 25.5 ml/kg/min and from 3.0 to 12.0 ml/kg/min to the males. The increase in VO2 from seated rest to the most strenuous of the 8 activity profiles was 3.6-fold for the females and 2.8-fold for the males. These preliminary data on 4 subjects indicate close agreement of oxygen uptake for activity performed during many subject-exposures as published earlier. The relatively low average oxygen uptake required to perform the most strenuous activity may imply the need for adjustment of modeling efforts using metabolic cost as a risk factor. Better definition of metabolic cost during exposure to altitude, a critical factor in DCS risk, may allow refinement of DCS prediction models.

Webb, James T.↗
NASA NTRS1992

Atomic oxygen exposure of LDEF experiment trays

Atomic oxygen exposures were determined analytically for rows, longerons, and end bays of the Long Duration Exposure Facility (LDEF). The calculations are based on an analytical model that accounts for the effects of thermal molecular velocity, atmospheric temperature, number density, spacecraft velocity, incidence angle, and atmospheric rotation on atomic oxygen flux. Results incorporate variations in solar activity, geomagnetic index, and orbital parameters occurring over the 6-year flight of the spacecraft. To facilitate use of the data, both detailed tabulations and summary charts for atomic oxygen fluences are presented.

Bourassa, R. J.↗
NASA NTRS1985

Sulfur transformations at the hydrogen sulfide/oxygen interface in stratified waters and in cyanobacterial mats

Stratified water bodies allow the development of several microbial plates along the water column. The microbial plates develop in relation to nutrient availability, light penetration, and the distribution of oxygen and sulfide. Sulfide is initially produced in the sediment by sulfate-reducing bacteria. It diffuses along the water column creating a zone of hydrogen sulfide/oxygen interface. In the chemocline of Solar Lake oxygen and sulfide coexist in a 0 to 10 cm layer that moves up and down during a diurnal cycle. The microbial plate at the chemocline is exposed to oxygen and hydrogen sulfide, alternating on a diurnal basis. The cyanobacteria occupying the interface switch from anoxygenic photosynthesis in the morning to oxygenic photosynthesis during the rest of the day which results in a temporal build up of elemental sulfur during the day and disappears at night due to both oxidation to thiosulfate and sulfate by thiobacilli, and reduction to hydrogen sulfide by Desulfuromonas sp. and anaerobically respiring cyanobacteria. Sulfate reduction was enhanced in the light at the surface of the cyanobacterial mats. Microsulfate reduction measurements showed enhanced activity of sulfate reduction even under high oxygen concentrations of 300 to 800 micrometer. Apparent aerobic SO sub 4 reduction activity is explained by the co-occurrence of H sub 2. The physiology of this apparent sulfate reduction activity is studied.

Cohen, Y.↗
NASA NTRS1987

Model ozone photochemistry on the basis of Solar Mesosphere Explorer mesospheric observations

Morning and afternoon mesospheric ozone profiles (50-90 km) measured by the Solar Mesosphere Explorer (SME) satellite are analyzed with one-dimensional photochemical models. The observed ozone abundances are 40 percent and 100 percent greater than the model ozone abundances at 50 and 80 km, respectively. Diurnal model calculations are compared with SME observations of ozone profiles at about 0400 and 1400 LT for high northern summer latitudes. Analysis of the ratios of these early morning and midafternoon ozone profiles provides the additional constraint that larger odd-oxygen production rates are required if lower odd-hydrogen activity is invoked to increase model O3 abundances. The increase in odd-oxygen production must be solar zenith angle independent in the mesosphere, ruling out significant changes in the Schumann-Runge band O2 opacities from Allen and Frederrick (1982).

Clancy, R. T.↗
NASA NTRS2007

Electrochemically Controlled Reconstitution of Immobilized Ferritins for Bioelectronic Applications

Site-specific reconstituted nanoparticles were fabricated via electrochemically-controlled biomineralization through the immobilization of biomolecules. The work reported herein includes the immobilization of ferritin with various surface modifications, the electrochemical biomineralization of ferritins with different inorganic cores, and the electrocatalytic reduction of oxygen on the reconstituted Pt-cored ferritins. Protein immobilization on the substrate is achieved by anchoring ferritins with dithiobis-N-succinimidyl propionate (DTSP). A reconstitution process of site-specific electrochemical biomineralization with a protein cage loads ferritins with different core materials. The ferritin acts as a nano-scale template, a biocompatible cage, and a separator between the nanoparticles. This first demonstration of electrochemically controlled site-specific reconstitution of biomolecules provides a new tool for biomineralization and opens the way to produce the bio-templated nanoparticles by electrochemical control. The nanosized platinum-cored ferritins on gold displayed good catalytic activity for the electrochemical reduction of oxygen, which is applicable to biofuel cell applications. This results in a smaller catalyst loading on the electrodes for fuel cells or other bioelectronic devices.

Kim, Jae-Woo↗
NASA NTRS1990

High-resolution X-ray spectroscopy of four active galaxies - Probing the intercloud medium

The focal plane crystal spectrometer (FPCS) on the Einstein Observatory has been used to perform a high-resolution spectroscopic search for oxygen X-ray line emission from four active galaxies: Fairall 9, Mrk 421, Mrk 501, and PKS 0548 - 322. Specifically, O VIII Ly-alpha and Ly-beta, whose unredshifted energies are 653 and 775 eV, respectively, were sought. No narrow-line emission was detected within the energy bands searched. Upper limits are calculated on the line flux from these sources of 30 eV equivalent width and use a photoionization model to place corresponding upper limits on the densities of diffuse gas surrounding the active nuclei. The upper limits on gas density range from about 0.02-50/cu cm and probe various radial distances from the central source. This is the first time high-resolution X-ray spectroscopy has been used to place constraints on the intercloud medium in active galaxies.

Lum, Kenneth S. K.↗
NASA NTRS1991

Mechanisms of ilmenite reduction and their impact on the design of effective reactor systems

One of the first activities at a lunar base could be oxygen recovery from ilmenite (FeTiO3). Oxygen produced from lunar soils could be used to fuel transportation vehicles operating in near-earth space. The first step in developing a suitable reactor system for lunar operation is to determine the mechanisms and rates of oxygen removal from ilmenite. In-situ gravimetric measurements and microscopic examinations were used to determine the hydrogen reduction mechanisms of synthetic ilmenite discs between 823 to 1353 K. A shrinking core reaction model, modified to account for the growth of an iron film on the surface of discs, was capable of predicting experimentally observed conversion-time relationships. The observed reduction mechanism, kinetic rates, and associated activation energy established a base line from which comparisons could be made to improve oxygen yield and removal rates. One proposed technique to improve the rate and extent of oxygen removal was to preoxidize ilmenite. Preoxidation is commonly used during the reduction of ilmenite ores in the iron industry and has been employed for many years to lower operating temperatures and increase reduction rates. This technology could prove beneficial for oxygen production facilities on the Moon as less massive reactor vessels and/or less energy could be associated with a process including preoxidation. X ray diffraction and energy dispersive spectroscopy were utilized to follow the progression of ilmenite oxidation at 1123 and 1140 K and the reduction of pseudobrookite (Fe2TiO5) at 873 and 973 K. Structures formed during the progress of oxidation were related to the system's phase diagrams. Results indicated that after initially producing ilmenite-hematite solutions and rutile (TiO2), pseudobrookite was the end product of oxidation at all temperatures examined (1049 to 1273 K). Initial results from the reduction of pseudobrookite indicate a series of phases are produced including ferropseudobrookite (FeTi2O5), ulvospinel (Fe2TiO4), and ilmenite. Rates of pseudobrookite reduction were typically 50 to 200 times that of ilmenite.

Briggs, R. A.↗