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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 NTRS1992

Soil nitrogen cycling and nitrous oxide flux in a Rocky Mountain Douglas-fir forest - Effects of fertilization, irrigation and carbon addition

Nitrous oxide fluxes and soil nitrogen transformations were measured in experimentally-treated high elevation Douglas-fir forests in northwestern New Mexico, USA. On an annual basis, forests that were fertilized with 200 kg N/ha emitted an average of 0.66 kg/ha of N2O-N, with highest fluxes occurring in July and August when soils were both warm and wet. Control, irrigated, and woodchip treated plots did not differ, and annual average fluxes ranged from 0.03 to 0.23 kg/ha. Annual net nitrogen mineralization and nitrate production were estimated in soil and forest floor using in situ incubations; fertilized soil mineralized 277 kg/ha/y in contrast to 18 kg/ha/y in control plots. Relative recovery of 15NH4-N applied to soil in laboratory incubations was principally in the form of NO3-N in the fertilized soils, while recovery was mostly in microbial biomass-N in the other treatments. Fertilization apparently added nitrogen that exceeded the heterotrophic microbial demand, resulting in higher rates of nitrate production and higher nitrous oxide fluxes. Despite the elevated nitrous oxide emission resulting from fertilization, we estimate that global inputs of nitrogen into forests are not currently contributing significantly to the increasing concentrations of nitrous oxide in the atmosphere.

Matson, Pamela A.↗
NASA NTRS1992

Catalytic methods using molecular oxygen for treatment of PMMS and ECLSS waste streams, volume 2

Catalytic oxidation has proven to be an effective addition to the baseline sorption, ion exchange water reclamation technology which will be used on Space Station Freedom (SSF). Low molecular weight, polar organics such as alcohols, aldehydes, ketones, amides, and thiocarbamides which are poorly removed by the baseline multifiltration (MF) technology can be oxidized to carbon dioxide at low temperature (121 C). The catalytic oxidation process by itself can reduce the Total Organic Carbon (TOC) to below 500 ppb for solutions designed to model these waste waters. Individual challenges by selected contaminants have shown only moderate selectivity towards particular organic species. The combined technology is applicable to the more complex waste water generated in the Process Materials Management System (PMMS) and Environmental Control and Life Support System (ECLSS) aboard SSF. During the phase 3 Core Module Integrated Facility (CMIF) water recovery tests at NASA MSFC, real hygiene waste water and humidity condensate were processed to meet potable specifications by the combined technology. A kinetic study of catalytic oxidation demonstrates that the Langmuir-Hinshelwood rate equation for heterogeneous catalysts accurately represent the kinetic behavior. From this relationship, activation energy and rate constants for acetone were determined.

Akse, James R.↗
NASA NTRSDate not supplied

Composition and Climate Impacts of Increasing Launches to Low Earth Orbit

We present simulations of an Earth system model in which launch vehicles inject gaseous and particulate combustion products into the stratosphere. We considered two plausible scenarios representative for the year 2050, one with 1000 launches per year and another with 10 times more, all of which assuming heavy lift (80 tons to low Earth orbit; LEO) launches using methane as a proxy for liquefied natural gas (LNG) fuel. An industry-standard plume flowfield model was used to predict emission of gaseous species including carbon monoxide, nitrogen oxides, and water vapor. Black carbon was introduced assuming vacuum emission equal 25% of equivalent kerosene engine. The gas emissions showed marginal or insignificant changes in atmospheric composition, while the black carbon emission was found to be the most influential component. Feedbacks involve tropopause and stratospheric warming, followed by a moistening of the stratosphere via tropospheric water vapor intrusions, together with a reduction in global albedo. The fact that LNG-fueled rockets could be a concern from aerosol emissions in our simulations, despite burning more efficiently than conventional fuels, underscores the need to better understand actual black carbon emissions from rocket engines in order to accurately predict the global impacts of launch vehicles on future climate.

Earth system model↗
NASA NTRS2008

Modeling of the Ablation of Fibrous Materials in the Knudsen Regime

During atmospheric entry of planetary probes, the thermal protection system (TPS) of the probe is exposed to high temperatures under low pressures. In these conditions, carbonous TPS materials undergo gasification in the Knudsen regime leading to mass loss and wall recession called ablation. This work aims to improve the understanding of materiaVenvironment interactions through a study of the coupling between carbon dioxide transport in the Knudsen regime, heterogeneous oxidation of carbon, and sutface recession. A 3D Monte-Carlo simulation tool is used for this study. The fibrous architecture of the materiils, consisting of high porosity random array of carbon fibers, is numerically reproduced on a 3D Cartesian grid. Mass transport in the Knudsen regime from the boundary layer to the surface, and inside this porous material is simulated by random walk. A reaction probability is used to simulate the heterogeneous oxidation reaction. The surface recession is followed by front tracking using a simplified marching cube approach. The output data of the simulations are ablation velocity and dynamic evolution of the material porosity. A parametric study is carried out to analyze the material behavior as a function of Knudsen number for the porous media (length of the mean free path compared to the mean pore diameter) and the intrinsic reactivity of the carbon fibers. The results enable extrapolation of laboratory experimental data to actual entry conditions.

Lachaud, J.↗
NASA NTRS1992

Purification system

A system for prolonging the life of a granulated activated charcoal (GAC) water treatment device is disclosed in which an ultraviolet light transparent material is used to constrain water to flow over carbon surfaces. It is configured to receive maximum flux from a UV radiation source for the purpose of preventing microbial proliferation on the carbon surfaces; oxidizing organic contaminants adsorbed from the water onto the carbon surfaces and from biodegradation of adsorbed microbial forms; disinfecting water; and oxidizing organic contaminants in the water.

Flanagan, David T.↗
NASA NTRS2022

Attribution of Stratospheric and Tropospheric Ozone Changes Between 1850 and 2014 in CMIP6 Models

We quantify the impacts of halogenated ozone-depleting substances (ODSs), greenhouse gases (GHGs), and short-lived ozone precursors on ozone changes between 1850 and 2014 using single-forcing perturbation simulations from several Earth system models with interactive chemistry participating in the Coupled Model Intercomparison Project Aerosol and Chemistry Model Intercomparison Project. We present the responses of ozone to individual forcings and an attribution of changes in ozone columns and vertically resolved stratospheric and tropospheric ozone to these forcings. We find that whilst substantial ODS-induced ozone loss dominates the stratospheric ozone changes since the 1970s, in agreement with previous studies, increases in tropospheric ozone due to increases in short-lived ozone precursors and methane since the 1950s make increasingly important contributions to total column ozone (TCO) changes. Increases in methane also lead to substantial extra-tropical stratospheric ozone increases. Impacts of nitrous oxide and carbon dioxide on stratospheric ozone are significant but their impacts on TCO are small overall due to several opposing factors and are also associated with large dynamical variability. The multi-model mean (MMM) results show a clear change in the stratospheric ozone trends after 2000 due to now declining ODSs, but the trends are generally not significantly positive, except in the extra-tropical upper stratosphere, due to relatively small changes in forcing over this period combined with large model uncertainty. Although the MMM ozone compares well with the observations, the inter-model differences are large primarily due to the large differences in the models' representation of ODS-induced ozone depletion.

Halogenated ozone-depleting substances↗
NASA NTRS1999

Continuous method of producing silicon carbide fibers

This invention pertains to a method for production of polycrystalline ceramic fibers from silicon oxycarbide (SiCO) ceramic fibers wherein the method comprises heating an amorphous ceramic fiber containing silicon and carbon in an inert environment comprising a boron oxide and carbon monoxide at a temperature sufficient to convert the amorphous ceramic fiber to a polycrystalline ceramic fiber. By having carbon monoxide present during the heating of the ceramic fiber, it is possible to achieve higher production rates on a continuous process.

Barnard, Thomas Duncan↗
NASA NTRS2015

Adsorption of Ammonia on Regenerable Carbon Sorbents

Results are presented on the development of reversible sorbents for the combined carbon dioxide, moisture, and trace-contaminant (TC) removal for use in Extravehicular Activities (EVAs), and more specifically in the Primary Life Support System (PLSS). The currently available life support systems use separate units for carbon dioxide, trace contaminants, and moisture control, and the long-term objective is to replace the above three modules with a single one. Data on sorption and desorption of ammonia, which is a major TC of concern, are presented in this paper. The current TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal, which is non-regenerable, and the carbon-based sorbent under development in this project can be regenerated by exposure to vacuum at room temperature. In this study, several carbon sorbents were fabricated and tested for ammonia sorption. Ammonia-sorption capacity was related to carbon pore structure characteristics, and the temperature of oxidative carbon-surface treatment was optimized for enhanced ammonia-sorption performance.

Wójtowicz, Marek A.↗
NASA NTRSDate not supplied

Degradation of Carbon Fiber Microstructures Due to Oxidative Etch Pitting

In order to understand the influence of etch pits on the material properties of carbon fiber microstructures, we use the Porous Microstructure Analysis (PuMA) software to create realistic pitted structures from virgin fiber structures and then analyze their degradation as the degree of pitting increases. For that purpose, we developed a pitting module within PuMA that creates pits with user-defined geometry (shape, size) and distribution (defect density) on the surface of arbitrary microstructures. In this work, we consider FiberForm microstructures, which are commonly used as the base material for ablative thermal protection systems (TPS). Using the new pitting module, we mimic the evolution of etch pits on FiberForm as it occurs from oxidation in ablative heating environments, by first importing the virgin FiberForm structure from a micrograph scan and then imposing different pitting conditions by varying pit radii and defect densities. We then leverage PuMA’s capabilities to calculate material properties for each structure. The results clearly show the degradation of thermal conductivity and structural integrity as etch pits grow, and furthermore highlight the complex evolution of the surface topology, which results in significant changes of the flowgeometry and chemical gas-surface interactions. Furthermore, a comparison of these changes with the case of shrinking fibers, which has heretofore been the standard for modelling ablation of carbon structures, yields significant differences. For example, we observe the formation of small chunks of fibers as pits grow in size, which could be released into the surrounding flow environment as spallation particles. This motivates us to continue our efforts of modelling pitting as an integral part of the structural degradation of carbon fiber structures in oxidation environments, which will ultimately improve our understanding of failure mechanisms in those materials.

PuMA↗
NASA NTRSDate not supplied

Degradation of Carbon Fiber Microstructures Due to Oxidative Etch Pitting

In order to understand the influence of etch pits on the material properties of carbon fiber microstructures, we use the Porous Microstructure Analysis (PuMA) software to create realistic pitted structures from virgin fiber structures and then analyze their degradation as the degree of pitting increases. For that purpose, we developed a pitting module within PuMA that creates pits with user-defined geometry (shape, size) and distribution (defect density) on the surface of arbitrary microstructures. In this work, we consider FiberForm microstructures, which are commonly used as the base material for ablative thermal protection systems (TPS). Using the new pitting module, we mimic the evolution of etch pits on FiberForm as it occurs from oxidation in ablative heating environments, by first importing the virgin FiberForm structure from a micrograph scan and then imposing different pitting conditions by varying pit radii and defect densities. We then leverage PuMA’s capabilities to calculate material properties for each structure. The results clearly show the degradation of thermal conductivity and structural integrity as etch pits grow, and furthermore highlight the complex evolution of the surface topology, which results in significant changes of the flowgeometry and chemical gas-surface interactions. Furthermore, a comparison of these changes with the case of shrinking fibers, which has heretofore been the standard for modelling ablation of carbon structures, yields significant differences. For example, we observe the formation of small chunks of fibers as pits grow in size, which could be released into the surrounding flow environment as spallation particles. This motivates us to continue our efforts of modelling pitting as an integral part of the structural degradation of carbon fiber structures in oxidation environments, which will ultimately improve our understanding of failure mechanisms in those materials.

PuMA↗
NASA NTRS1984

Carbon catalysis in the aqueous oxidation of SO2 by NO2 and air

Sulfur dioxide and an oxidant gas (air or NO2) were bubbled through aqueous suspensions of both washed and unwashed carbon black as well as through samples of wash water, which contained whatever soluble species were originally present on the carbon, and high-purity water. The sulfate yields obtained showed the washed and unwashed carbon to be equally catalytic for the oxidation of SO2 to sulfate by both oxidants, whereas little sulfate was generated in either the wash water or high-purity water in the absence of carbon. These results indicate that the sulfate yields produced in aqueous suspensions of the carbon studied are due to catalysis by the carbon particles rather than by soluble species dissolved from them.

Schryer, D. R.↗
NASA NTRS1996

Hydrothermal systems on Mars: an assessment of present evidence

Hydrothermal processes have been suggested to explain a number of observations for Mars, including D/H ratios of water extracted from Martian meteorites, as a means for removing CO2 from the Martian atmosphere and sequestering it in the crust as carbonates, and as a possible origin for iron oxide-rich spectral units on the floors of some rifted basins (chasmata). There are numerous examples of Martian channels formed by discharges of subsurface water near potential magmatic heat sources, and hydrothermal processes have also been proposed as a mechanism for aquifer recharge needed to sustain long term erosion of sapping channels. The following geological settings have been identified as targets for ancient hydrothermal systems on Mars: channels located along the margins of impact crater melt sheets and on the slopes of ancient volcanoes; chaotic and fretted terranes where shallow subsurface heat sources are thought to have interacted with ground ice; and the floors of calderas and rifted basins (e.g. chasmata). On Earth, such geological environments are often a locus for hydrothermal mineralization. But we presently lack the mineralogical information needed for a definitive evaluation of hypotheses. A preferred tool for identifying minerals by remote sensing methods on Earth is high spatial resolution, hyperspectral, near-infrared spectroscopy, a technique that has been extensively developed by mineral explorationists. Future efforts to explore Mars for ancient hydrothermal systems would benefit from the application of methods developed by the mining industry to look for similar deposits on Earth. But Earth-based exploration models must be adapted to account for the large differences in the climatic and geological history of Mars. For example, it is likely that the early surface environment of Mars was cool, perhaps consistently below freezing, with the shallow portions of hydrothermal systems being dominated by magma-cryosphere interactions. Given the smaller gravitational field, declining atmospheric pressure, and widespread, permeable megaregolith on Mars, volatile outgassing and magmatic cooling would have been more effective than on Earth. Thus, hydrothermal systems are likely to have had much lower average surface temperatures than comparable geological settings on Earth. The likely predominance of basaltic crust on Mars suggests that hydrothermal fluids and associated deposits should be enriched in Fe, Mg, Si and Ca, with surficial deposits being dominated by lower temperature, mixed iron oxide and carbonate mineralogies.

Review↗
NASA NTRS2009

Using Ozone To Clean and Passivate Oxygen-Handling Hardware

A proposed method of cleaning, passivating, and verifying the cleanliness of oxygen-handling hardware would extend the established art of cleaning by use of ozone. As used here, "cleaning" signifies ridding all exposed surfaces of combustible (in particular, carbon-based) contaminants. The method calls for exposing the surfaces of the hardware to ozone while monitoring the ozone effluent for carbon dioxide. The ozone would passivate the hardware while oxidizing carbon-based residues, converting the carbon in them to carbon dioxide. The exposure to ozone would be continued until no more carbon dioxide was detected, signifying that cleaning and passivation were complete.

Torrance, Paul↗
NASA NTRS2012

Searching for Bio-Precursors and Complex Organic Molecules in Space using the GBT

Using the latest microwave receiver technology, large organic molecules with abundances as low as approx. 10(exp -11) times that of molecular hydrogen are detectable in cold interstellar clouds via their rotational emission line spectra. We report new observations to search for complex molecules, including molecules of possible pre-biotic importance, using the newly-commissioned Kband focal plane array (KFPA) of the NRAO Robert C. Byrd Green Bank Telescope. Spectra are presented of the dense molecular cloud TMC-1, showing strict upper limits on the level of emission from nitrogen-bearing rings pyrimidine, quinoline and iso-quinoline, carbon-chain oxides C60, C70, HC60 and HC70, and the carbon-chain anion C4H-. The typical RMS brightness temperature noise levels we achieved are approx. 1 mK at around 20 GHz.

Cordiner, M.↗
NASA NTRS1988

Carbon dioxide electrolysis with solid oxide electrolyte cells for oxygen recovery in life support systems

The direct electrochemical reduction of carbon dioxide (CO2) is achieved without catalysts and at sufficiently high temperatures to avoid carbon formation. The tubular electrolysis cell consists of thin layers of anode, electrolyte, cathode and cell interconnection. The electrolyte is made from yttria-stabilized zirconia which is an oxygen ion conductor at elevated temperatures. Anode and cell interconnection materials are complex oxides and are electronic conductors. The cathode material is a composite metal-ceramic structure. Cell performance characteristics have been determined using varying feed gas compositions and degrees of electrochemical decomposition. Cell test data are used to project the performance of a three-person CO2-electrolysis breadboard system.

Isenberg, Arnold O.↗
NASA NTRS1990

New observations of interstellar organic molecules

Discussed here are new observations of 3-carbon-containing interstellar molecules which play an important role in the chemistry of dense molecular clouds: protonated carbon dioxide, formic acid, and propynal. In 1984 a new oxide of carbon, C3O, was discovered in the interstellar medium (Matthews et al. 1984; Brown et al. 1985). Theoretical models suggest that C3O is produced by dissociative electron recombination with the ion H3C3O+. Although no laboratory data for the branching ratios of such a recombination exist, it seemed to us likely that additional products would include H2C3O. This molecule has more than one isomeric form, but one stable species is propynal (HC2CHO), which had been suggested as a possible interstellar molecule by Winnewisser (1973). In observations at the National Radio Astronomy Observatory 43 m telescope in Green Bank earlier this year, researchers detected a line in the cold cloud TMC-1 which they assign to the 2(0,2)-1(0,1) transition of propynal. The observed line agrees with the laboratory frequency to well within the experimental uncertainty a few parts in 10 to the 7th power. Researchers sought and failed to detect the corresponding 2(1,1)-1(1,0) line, which is understandable given the presence of both a and b components of the electric dipole moment in propynal. The b type transitions will drain population from energy levels with K(sub p) does not equal 0 into the K(sub p) equal 0 stack. If the researchers' assignment is correct, this is the first interstellar detection of propynal. Assuming typical rotational temperatures for TMC-1 and that the line is optically thin, the column density determined is about 5 times 10 to the 12th power cm to the -2nd power, or about three times that for C3O. Formic acid (HCOOH) was the first organic acid to be observed in the interstellar medium, in the Galactic center source Sgr B2. The only other interstellar detection has been recently made in the giant molecular cloud in Orion. As part of the same project that led to the detection of propynal, researchers sought formic acid in the nearby, cold dark clouds TMC-1 and L134N. It is seen only in L134N. This difference between the two clouds appears to be consistent with a model in which the oxygen/carbon ratio is higher in L134N. This would be consistent with the higher abundances for SO and SO2, observed in that cloud, and the higher abundances of many carbon-rich species in TMC-1 (Irvine et al. 1985).

Irvine, W. M.↗
NASA NTRSDate not supplied

Tropospheric Ozone in the NASA GEOS Model: Effects of Satellite NO2 Data Assimilation and Improvements in Background NOx Chemistry

Tropospheric ozone is a major atmospheric oxidant, the primary source of the hydroxyl radical, and a greenhouse gas. In the troposphere, it is produced from the oxidation of carbon monoxide and volatile organic compounds in the presence of nitrogen oxides (NOx=NO+NO2) or has its origins in the stratosphere. The tropospheric ozone burdens in global atmospheric chemistry models disagree by a factor of 1.5, indicating an incomplete understanding of ozone sources and sinks. Here we examine the tropospheric ozone simulation in NASA Global Modeling and Assimilation Office’s (GMAO’s) GEOS model with the GEOS-Chem chemistry mechanism (version 14.2), using observations from satellites, aircraft, ozonesondes, and surface sites. This modeling framework is used to produce GMAO’s GEOS Composition Forecasts (GEOS-CF), and it has been updated extensively with new emission inventories, improved model physics, satellite data assimilation capability, and an up-to-date chemical mechanism that includes tropospheric halogen chemistry and NOx recycling from particulate nitrate. Earlier versions of the model using GEOS-Chem version 12.0 showed an underestimate in tropospheric ozone in the northern hemisphere. We evaluate the ozone simulation in the updated model, focusing on the effects of assimilating satellite NO2 data from the Ozone Monitoring Instrument (OMI), constraining stratospheric ozone to satellite data, and updates to the NOx chemistry. We will examine changes in the vertical profiles of tropospheric ozone over the US in support of the Tropospheric Emissions: Monitoring of Pollution (TEMPO), and discuss implications for the tropospheric ozone budget.

V. Shah↗