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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The conversion of lignocellulosics to fermentable sugars - A survey of current research and applications to CELSS

This report provides an overview options for converting lignocellulosics into fermentable sugars in CELSS. A requirement for pretreatment is shown. Physical-chemical and enzymatic hydrolysis processes for producing fermentable sugars are discussed. At present physical-chemical methods are the simplest and best characterized options, but enzymatic processes will be the likely method of choice in the future. The use of pentose sugars by microorganisms to produce edibles is possible. The use of mycelial food production on pretreated but not hydrolyzed lignocellulosics is also possible. Simple trade-off analyses to regenerate waste lignocellulosics for two pathways are made, one of which is compared to complete oxidation.

Petersen, Gene R.↗
NASA NTRS1994

Reaction and Protection of Electrical Wire Insulators in Atomic-oxygen Environments

Atomic-oxygen erosion on spacecraft in low Earth orbit is an issue which is becoming increasingly important because of the growing number of spacecraft that will fly in the orbits which have high concentrations of atomic oxygen. In this investigation, the atomic-oxygen durability of three types of electrical wire insulation (carbon-based, fluoropolymer, and polysiloxane elastomer) were evaluated. These insulation materials were exposed to thermal-energy atomic oxygen, which was obtained by RF excitation of air at a pressure of 11-20 Pa. The effects of atomic-oxygen exposure on insulation materials indicate that all carbon-based materials erode at about the same rate as polyamide Kapton and, therefore, are not atomic-oxygen durable. However, the durability of fluoropolymers needs to be evaluated on a case by case basis because the erosion rates of fluoropolymers vary widely. For example, experimental data suggest the formation of atomic fluorine during atomic-oxygen amorphous-fluorocarbon reactions. Dimethyl polysiloxanes (silicone) do not lose mass during atomic-oxygen exposure, but develop silica surfaces which are under tension and frequently crack as a result of loss of methyl groups. However, if the silicone sample surfaces were properly pretreated to provide a certain roughness, atomic oxygen exposure resulted in a sturdy, non-cracked atomic-oxygen durable SiO2 layer. Since the surface does not crack during such silicone-atomic oxygen reaction, the crack-induced contamination by silicone can be reduced or completely stopped. Therefore, with proper pretreatment, silicone can be either a wire insulation material or a coating on wire insulation materials to provide atomic-oxygen durability.

Hung, Ching-Cheh↗
NASA NTRS1995

Enhancement of perfluoropolyether boundary lubrication performance: I. Preliminary results

A ball bearing simulator operating under starved conditions was used to evaluate the boundary lubrication performance of a perfluoropolyether (PFPE) Krytox 143 AB. Several approaches to enhance boundary lubrication were studied. These included: (1) soluble boundary additives, (2) bearing surface modifications, (3) 'run-in' surface films, and (4) ceramic bearing components. In addition, results were compared with two non-perfluorinated liquid lubricant formulations. Based on these preliminary tests, the following tentative conclusions can be made: (1) substantial improvements in boundary lubrication performance were observed with a beta-diketone boundary additive and a tricresyl phosphate (TCP) liquid surface pretreatment; (2) the use of rough Si3N4 balls (Ra = 40 micro-in) also provided substantial improvement but with concomitant abrasive wear; (3) marginal improvements were seen with two boundary additives (a phosphine and a phosphatriazine) and a neat (100%) fluid (a carboxylic acid terminated PFPE); and surface pretreatments with a synthetic hydrocarbon, a PTFE coating, and TiC coated 440C and smooth Si3N4 balls (R(sub a) less than 1 micro-in); and (4) two non-PFPE lubricant formulations (a PAO and a synthetic hydrocarbon) yielded substantial improvements.

Jones, W. R., Jr.↗
NASA NTRS1996

Enhancement of Perfluoropolyether Boundary Lubrication Performance

A ball bearing simulator operating under starved conditions was used to perform screening tests to evaluate the boundary lubrication performance of a branched perfluoropolyether (PFPE), K-143 AB. Several approaches to enhance boundary lubrication were studied. These included: (1) soluble boundary additives, (2) bearing surface modifications, (3) 'run-in' surface films, and (4) ceramic bearing components. In addition, results were compared with two non-perfluorinated liquid lubricant formulations. Based on these tests, the following tentative conclusions can be made: (1) Substantial improvements in boundary lubrication performance were observed with a beta-diketone boundary additive and a tricresyl phosphate (TCP) liquid surface pretreatment, (2) the use of rough Si3N4 balls (R(sub a) = 40 micro-inch) also provided increases in test duration, but with concomitant abrasive wear, (3) moderate improvements were seen with two boundary additives (a phosphine and a phosphatriazine) and a neat (100%) fluid (a carboxylic acid terminated PFPE); and small improvements with surface pretreatments with synthetic hydrocarbons, a polytetrafluoroethylene (PTFE) coating, and TiC coated 440 C and smooth Si3N4 balls (R(sub a) = 1 micro-inch), and (4) two non-PFPE lubricant formulations (a polyalphaolefin (PAO) and synthetic hydrocarbon) yielded substantial improvements.

Jones, W. R., Jr.↗
NASA NTRS1998

Central Renin Injections: Effects on Drinking and Expression of Immediate Early Genes

This study investigated the drinking response and the expression of Fos- and Egr-1-immunoreactivity (Fos-ir, Egr-1-ir) in the brain induced by endogenous angiotensin generated by intracerebroventricular (i.c.v.) injection of renin. Renin induced Fos-ir in the subformical organ (SFO), median preoptic (MnPO), supraoptic and paraventricular nuclei (SON and PVN), area postrema (AP), nuclei of the solitary tract (NTS) and lateral parabrachial nuclei (LPBN). Renin-induced Egr-1-ir exhibited a similar pattern of distribution as that observed for Fos-ir. The dose of i.c.v. renin that induced expression of immediate early gene (IEG) product immunoreactivity also produced vigorous drinking. When renin-injected rats were pretreated with captopril, an angiotensin converting enzyme inhibitor, drinking was blocked. With the same captopril pretreatment, both Fos- and Egr-1-ir in the SFO, MnPO, SON, PVN, AP and LPBN were also significantly reduced.

Xu, Zhice↗
NASA NTRS1999

Thermomechanical Characterization of SiC Fiber Tows and Implications for CMC

In order to better understand SiC fiber behavior within CMC microstructures, mechanical tests were performed on multifilament tows consisting of different types of as produced and pretreated fibers. Tensile strengths of tows and single fibers were measured at room temperature for nonstoichiometric Hi-Nicalon and ZMI fibers and for stoichiometric Hi-Nicalon-S, Tyranno SA. and Sylramic fibers. Based on simple bundle theory, measured strengths for as-produced and sized tows were in general agreement with the single fiber results. However, after sizing removal under inert conditions, tow strengths for the coarser grained stoichiometric fibers were typically lower than those predicted from individual fiber data. This effect is attributed to enhanced fiber-fiber mechanical interaction caused by sizing removal from the rough surfaces of these fibers. In support of this, tow strengths remained high for those fiber types with fine grains or excess surface carbon; and, when re-coated with a BN interphase coating, tow strengths for the coarser grained fibers returned to their as-produced values. When the tows were pretreated in air at intermediate temperatures, tow strengths decreased in a manner that could be correlated with the oxidation characteristics of each fiber type as measured by thermogravimetric analysis. The creep and rupture properties of Hi-Nicalon and Sylramic tows were also measured in air and argon from 1200 to 1400 C. Although displaying transient and environmental effects similar to single fibers, the tows crept faster at short times and slower at long times. This resulted in the tow rupture strengths at long time being much greater than the rupture strengths of single fibers. The CMC implications of the tow results are discussed, as well as the benefits and limitations of tow testing.

Yun, H. M.↗
NASA NTRS1988

Effect of salicylhydroxamic acid on endosperm strength and embryo growth of Lactuca sativa L. cv Waldmann's Green seeds

Salicylhydroxamic acid (SHAM) stimulated germination of photosensitive lettuce (Lactuca sativa L. cv Waldmann's Green) seeds in darkness. To determine whether SHAM acts on the embryo or the endosperm, we investigated separately effects of SHAM on growth potential of isolated embryos as well as on endosperm strength. Embryo growth potential was quantified by incubating decoated embryos in various concentrations of osmoticum and measuring subsequent radicle elongation. Growth potential of embryos isolated from seeds pretreated with 4 millimolar SHAM was equal to that of untreated controls. Rupture strength of endosperm tissue excised from seeds pretreated with SHAM was 33% less than that of controls in the micropylar region. To determine if the embryo must be in contact with the endosperm of SHAM to weaken the endosperm, some endosperms were incubated with SHAM only after dissection from seeds. Rupture strength of SHAM-treated, isolated endosperms in the micropylar region was 25% less than that of untreated controls. There was no difference in rupture strength in the cotyledonary region of endosperm isolated from seeds treated with SHAM in buffer or buffer alone. SHAM therefore stimulates germination not by enhancing embryo growth potential, but by weakening the micropylar region of the endosperm enclosing the embryo.

NASA Discipline Plant Biology↗
NASA NTRS1996

Complete disintegration of the microtubular cytoskeleton precedes its auxin-mediated reconstruction in postmitotic maize root cells

The inhibitory action of 0.1 microM auxin (IAA) on maize root growth was closely associated with a rapid and complete disintegration of the microtubular (MT) cytoskeleton, as visualized by indirect immunofluorescence of tubulin, throughout the growth region. After 30 min of this treatment, only fluorescent spots were present in root cells, accumulating either around nuclei or along cell walls. Six h later, in addition to some background fluorescence, dense but partially oriented oblique or longitudinal arrays of cortical MTs (CMTs) were found in most growing cells of the root apex. After 24 h of treatment, maize roots had adapted to the auxin, as inferred from the slowly recovering elongation rate and from the reassembly of a dense and well-ordered MT cytoskeleton which showed only slight deviations from that of the control root cells. Taxol pretreatment (100 microM, 24 h) prevented not only the rapid auxin-mediated disintegration of the MT cytoskeleton but also a reorientation of the CMT arrays, from transversal to longitudinal. The only tissue to show MTs in their cells throughout the auxin treatment was the epidermis. Significant resistance of transverse CMT arrays in these cells towards auxin was confirmed using a higher auxin concentration (100 microM, 24 h). The latter auxin dose also revealed inter-tissue-specific responses to auxin: outer cortical cell files reoriented their CMTs from the transversal to longitudinal orientation, whereas inner cortical cell files lost their MTs. This high auxin-mediated response, associated with the swelling of root apices, was abolished with the pretreatment of maize root with taxol.

Zea mays/cytology/drug effects/growth & developmen↗
NASA NTRS2000

Induction of a bystander mutagenic effect of alpha particles in mammalian cells

Ever since the discovery of X-rays was made by Rontgen more than a hundred years ago, it has always been accepted that the deleterious effects of ionizing radiation such as mutation and carcinogenesis are attributable mainly to direct damage to DNA. Although evidence based on microdosimetric estimation in support of a bystander effect appears to be consistent, direct proof of such extranuclear/extracellular effects are limited. Using a precision charged particle microbeam, we show here that irradiation of 20% of randomly selected A(L) cells with 20 alpha particles each results in a mutant fraction that is 3-fold higher than expected, assuming no bystander modulation effect. Furthermore, analysis by multiplex PCR shows that the types of mutants induced are significantly different from those of spontaneous origin. Pretreatment of cells with the radical scavenger DMSO had no effect on the mutagenic incidence. In contrast, cells pretreated with a 40 microM dose of lindane, which inhibits cell-cell communication, significantly decreased the mutant yield. The doses of DMSO and lindane used in these experiments are nontoxic and nonmutagenic. We further examined the mutagenic yield when 5-10% of randomly selected cells were irradiated with 20 alpha particles each. Results showed, likewise, a higher mutant yield than expected assuming no bystander effects. Our studies provide clear evidence that irradiated cells can induce a bystander mutagenic response in neighboring cells not directly traversed by alpha particles and that cell-cell communication process play a critical role in mediating the bystander phenomenon.

Non-NASA Center↗
NASA NTRS1981

Naloxone inhibits and morphine potentiates the adrenal steroidogenic response to ACTH

The administration of morphine to hypophysectomized rats potentiated the steroidogenic response of the adrenal cortex to exogenous adrenocorticotrophic hormone (ACTH) in a dose-dependent fashion. Conversely, the opiate antagonist naloxone inhibited the adrenal response to ACTH. Naloxone pretreatment also antagonized the potentiating effect of morphine on ACTH-induced steroidogenesis in a dose-dependent manner. Neither morphine nor naloxone, administered to hypophysectomized rats, had any direct effect on adrenal steroidogenesis. These adrenal actions were stereospecific since neither the (+)-stereoisomer of morphine, nor that or naloxone, had any effect on the adrenal response to ACTH. The administration of human beta-endorphin to hypophysectomized rats had no effect on the adrenal corticosterone concentration nor did it alter the response of the adrenal gland to ACTH. These results indicate that morphine can potentiate the action of ACTH on the adrenal by a direct, stereospecific, dose-dependent mechanism that is prevented by naloxone pretreatment and which may involve competition for ACTH receptors on the corticosterone-secreting cells of the adrenal cortex.

NASA Program Biomedical Research↗
NASA NTRS1994

Method of decontaminating a contaminated fluid by using photocatalytic particles

A system for decontaminating the contaminated fluid by using photocatalytic particles. The system includes a reactor tank for holding the contaminated fluid and the photocatalytic particles suspended in the contaminated fluid to form a slurry. Light irradiates the surface of the slurry, thereby activating the photocatalytic properties of the particles. The system also includes stirring blades for continuously agitating the irradiated fluid surface and for maintaining the particles in a suspended state within the fluid. The system also includes a cross flow filter for segregating the fluid (after decomposition) from the semiconductor powder. The cross flow filter is occasionally back flushed to remove any semiconductor powder that might have caked on the filter. The semiconductor powder may be recirculated back to the tank for reuse, or may be stored for future use. A series of such systems may be used to gradually decompose a chemical in the fluid. Preferably, the fluid is pretreated to remove certain metal ions which interfere with the photocatalytic process. Such pretreatment may be accomplished by dispersing semiconductor particles within the fluid, which adsorb ions or photodeposit the metal as the free metal or its insoluble oxide or hydroxide, and then removing the semiconductor particles together with the adsorbed metal ions/oxides/hydroxide/free metal from the fluid. A method of decontaminating a contaminated fluid is also disclosed.

Cooper, Gerald↗
NASA NTRS1992

Apparatus for photocatalytic treatment of liquids

Apparatus for decontaminating a contaminated fluid by using photocatalytic particles. The apparatus includes a reactor tank for holding a slurry of the contaminated fluid and the photocatalytic particles ultraviolet light irradiates the surface of the slurry, thereby activating the photocatalytic properties of the particles. Stirring blades for continuously agitate the irradiated fluid surface maintaining the particles in a suspended state within the fluid. A cross flow filter is used for separating the fluid from the semiconductor powder after the decomposition reaction is ended. The cross flow filter is occasionally back flushed to remove any caked semiconductor powder. The semiconductor powder may be recirculated back to the tank for reuse, or may be stored for future use. A series of reactor tanks may be used to gradually decompose a chemical in the fluid. The fluid may be pretreated to remove certain metal ions which interfere with the photocatalytic process. Such pretreatment may be accomplished by dispersing semiconductor particles within the fluid, which particles adsorb ions or photodeposit the metal as the free metal or its insoluble oxide or hydroxide, and then removing the semiconductor particles together with the adsorbed metal ions/oxides/hydroxide/free metal from the fluid.

Cooper, Gerald↗
NASA NTRS1998

Processes for treating cellulosic material

Disclosed are processes for pretreating cellulosic materials in liquid water by heating the materials in liquid water at a temperature at or above their glass transition temperature but not substantially exceeding 220.degree. C., while maintaining the pH of the reaction medium in a range that avoids substantial autohydrolysis of the cellulosic materials. Such pretreatments minimize chemical changes to the cellulose while leading to physical changes which substantially increase susceptibility to hydrolysis in the presence of cellulase.

Ladisch, Michael R.↗
NASA NTRS2010

Results and Interpretation of the WFRD ELS Distillation Down-Select Test Data

Testing of the Wiped-film Rotating-disk (WFRD) evaporator was conducted in support of the Exploration Life Support Distillation Down-Select Test. The WFRD was constructed at NASA Ames Research Center (ARC) and tested at NASA Marshall Space Flight Center (MSFC). The WFRD was delivered to MSFC in September 2009, and testing of solution #1 and solution #2 immediately following. Solution #1 was composed of humidity condensate and urine, including flush water and pretreatment chemicals. Solution #2 was composed of hygiene water, humidity condensate, and urine, including flush water and pretreatment chemicals. During the testing, the operational parameters of the WFRD were recorded and samples of the feed, brine, and product were collected and analyzed. The steady-state results of processing 414L of feed solution #1 and 1283L of feed solution #2 demonstrated that running the WFRD at a brine temperature of 50 C gave an average production rate of 16.7 L/hr. The specific energy consumption was 80.5W-hr/L. Data Analysis shows that the water recovery rates were 94% and 91%, respectively. The total mass of the WFRD as delivered to MSFC was 300 Kg. The volume of the tests stand rack was 1m width x 0.7m depth x 1.9m height or 1.5 cu m of which about half of the total volume is occupied by equipment. Chemical analysis of the distillate showed an average TOC of 20ppm, a pH of 3.5, and a conductivity of 98 mho/cm. The conductivity of the distillate, compared to the feed, decreased by 98.9%., the total ion concentration decreased by 99.6%, the total organics decreased 98.6%, and the metals were at or below detection limits

Delzeit, Lance Dean↗
NASA NTRS2012

Strategies for Stabilizing Nitrogenous Compounds in ECLSS Wastewater: Top-Down System Design and Unit Operation Selection with Focus on Bio-Regenerative Processes for Short and Long Term Scenarios

Water recycling and eventual nutrient recovery is crucial for surviving in or past low earth orbit. New approaches and syste.m architecture considerations need to be addressed to meet current and future system requirements. This paper proposes a flexible system architecture that breaks down pretreatment , steps into discrete areas where multiple unit operations can be considered. An overview focusing on the urea and ammonia conversion steps allows an analysis on each process's strengths and weaknesses and synergy with upstream and downstream processing. Process technologies to be covered include chemical pretreatment, biological urea hydrolysis, chemical urea hydrolysis, combined nitrification-denitrification, nitrate nitrification, anammox denitrification, and regenerative ammonia absorption through struvite formation. Biological processes are considered mainly for their ability to both maximize water recovery and to produce nutrients for future plant systems. Unit operations can be considered for traditional equivalent system mass requirements in the near term or what they can provide downstream in the form of usable chemicals or nutrients for the long term closed-loop ecological control and life support system. Optimally this would allow a system to meet the former but to support the latter without major modification.

Lunn, Griffin M.↗
NASA NTRS2005

Capture of Hydrogen Using ZrNi

Water, as ice, is thought to reside in craters at the lunar poles along with CH4 and H2 . A proposed robotic mission for 2012 will utilize metal/metal hydrides for H2 recovery. Specifications are 99% capture of H2 initially at 5 bar and 100C (or greater), and degassing completely at 300C. Of 47-systems examined using the van't Hoff equation, 4 systems, Mg/MgH2, Mg2Ni/Mg2NiH4, ZrNi/ZrNiH2.8, and Pd/PdH0.77, were considered likely candidates for further examination. It is essential, when selecting a system, to also examine questions regarding activation, kinetics, cyclic stability, and gas impurity effects. After considering those issues, ZrN1 was selected as the most promising candidate, as it is easily activated and rapidly forms ZrNiH 2.8 . In addition, it resists oxide poisoning by CO2, and H2O, while some oxidation by O2 is recommended for improved activation . The presence of hydrogen in the as received Zr-Ni alloy from Alfa Aesar posed additional technical problems. X-ray diffraction of the Zr-Ni powder (-325 mesh), with a Zr:Ni wt% ratio of 70:30, was found to consist of ZrH2, ZrNiH2.8, and ZrNi. ZrH2 in the alloy presented the risk that after degassing that both Zr and ZrNi would be present, and thus lead to erroneous results regarding the reactivity of ZrNi with H2 . Fortunately, ZrH2 is a highly stable hydride that does not degas H2 to any significant extent at temperatures below 300C. Based on equilibrium calculations for the decomposition of ZrH2, only 1 millionth of the hydride decomposed at 300C under a N2 atmosphere flowing at 25 ccm for 64 hours, the longest time for pretreatment employed in the investigation. It was possible, from the X-ray results and knowledge of the Zr:Ni ratio, to compute the composition of a pretreated specimen as being 76 wt% ZrNi and the balance ZrH2.

Patton, Lisa↗
NASA NTRS2015

Coiled Brine Recovery Assembly (CoBRA): A New Approach to Recovering Water from Wastewater Brines

Brine water recovery represents a current technology gap in water recycling for human spaceflight. The role of a brine processor is to take the concentrated discharge from a primary wastewater processor, called brine, and recover most of the remaining water from it. The current state‐of‐the‐art primary processor is the ISS Urine Processor Assembly (UPA) that currently achieves 70% water recovery. Recent advancements in chemical pretreatments are expected to increase this to 85% in the near future. This is a welcome improvement, yet is still not high enough for deep space transit. Mission architecture studies indicate that at least 95% is necessary for a Mars mission, as an example. Brine water recovery is the technology that bridges the gap between 85% and 95%, and moves life support systems one step closer to full closure of the water loop. Several brine water recovery systems have been proposed for human spaceflight, most of them focused on solving two major problems: operation in a weightless environment, and management and containment of brine residual. Brine residual is the leftover byproduct of the brine recovery process, and is often a viscous, sticky paste, laden with crystallized solid particles. Due to the chemical pretreatments added to wastewater prior to distillation in a primary processor, these residuals are typically toxic, which further complicates matters. Isolation of crewmembers from these hazardous materials is paramount. The Coiled Brine Recovery Assembly (CoBRA) is a recently developed concept from the Johnson Space Center that offers solutions to these challenges. CoBRA is centered on a softgoods evaporator that enables a passive fill with brine, and regeneration by discharging liquid brine residual to a collection bag. This evaporator is meant to be lightweight, which allows it to be discarded along with the accumulated brine solids contained within it. This paper discusses design and development of a first CoBRA prototype, and reports initial test results.

Pensinger, Stuart J.↗
NASA NTRS2013

Bulk Cutting of Carbon Nanotubes Using Electron Beam Irradiation

According to some embodiments, the present invention provides a method for attaining short carbon nanotubes utilizing electron beam irradiation, for example, of a carbon nanotube sample. The sample may be pretreated, for example by oxonation. The pretreatment may introduce defects to the sidewalls of the nanotubes. The method is shown to produces nanotubes with a distribution of lengths, with the majority of lengths shorter than 100 tun. Further, the median length of the nanotubes is between about 20 nm and about 100 nm.

Ziegler, Kirk J.↗