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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Cosmic ray track production rates in lunar materials

A particularly favorable rock from the Apollo 16 mission (68815) has been used to derive an 'empirical track production energy spectrum' suitable for calculating track exposure ages from galactic cosmic rays in lunar materials. The spectrum is a long term average for the last 2m.y. and is independent of assumptions about the detailed nature of track registration in lunar minerals. The spectrum is close to that previously estimated from measurements of contemporary cosmic rays and does not support the recent suggestion that track exposure ages should be revised upwards.

Walker, R.↗
DOE OSTI2024

Parameterization of vacancy production rate in phase-field models of fission gas bubble evolution in nuclear fuel

Phase-field modeling has increasingly been used to study microstructural evolution in fission gas bubbles in nuclear fuel to improve understanding of fission gas release. To improve computational efficiency, often only vacancies and gas atoms are included as defect species. In this case, the net effects of vacancy and interstitial production, recombination, and biased sink absorption are included as a net vacancy source, or net vacancy source combined with an effective sink. However, there has been a lack of clarity on what parameter values should be used for these approaches to best match the more complete physical picture that includes interstitials and vacancies. Here, we compare a phase-field model of void growth to analytical models for the source-only and source plus sink approach to gain insight into how the phase-field models can be parameterized effectively. The source-only approach provides greater flexibility to match growth rates determined from the full vacancy-interstitial picture. A strategy was developed for determining the value of the net vacancy source term by comparing to an analytical model that includes vacancy and interstitial production, recombination, and biased sink absorption. Finally, this strategy can be used to parameterize phase-field models of fission gas bubble growth.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1987

An estimate of the NO(x) production rate in electrified clouds based on NO observations from the GTE/CITE 1 fall 1983 field operation

During the NASA GTE/CITE 1 fall 1983 airborne field operation the NASA Convair 990 penetrated the anvils of two active cumulonimbus clouds. While NO levels outside the anvils averaged about 20 parts per trillion per volume (pptv), the average NO inside the anvils was about 440 pptv. Extrapolation of this observation along with data on the amount of air typically advected out of cumulonimbus clouds and the total number of thunderclouds occurring over the globe at any moment, implies a rate of nitrogen fixation in electrified clouds of about 7 x 10 to the 6th trillion/yr. Although the data base used to make this estimate is quite limited, the approach differs from that used in previous studies of the global production of nitrogen oxides by lightning, and thus represents an independent assessment of the role of electrified clouds in the atmospheric nitrogen oxide budget.

Chameides, W. L.↗
NASA NTRS1991

Ca-41 in iron falls, Grant and Estherville - Production rates and related exposure age calculations

Results are presented of the first phase of a Ca-41 cosmogenic studies program aimed at establishing baseline concentrations and trends in selected meteorites and the use of Ca-41 in estimating exposure ages and preatmospheric meteorite radii. The average Ca-41 saturation activity recorded in four small iron falls is 24 +/-1 dpm/kg. This finding, together with measurements at the center and surface of the large iron Grant, indicates that production of Ca-41 from spallation on iron is weakly dependent on shielding to depths as large as 250 g/sq cm. The (K-41)-Ca-41 exposure age of Grant is estimated at 330 +/-50 My, and an upper limit to its terrestrial age of 43 +/-15 ky. A comparison of the Ca-41 contents of stony and metallic material separated from the mesosiderite Estherville identifies low-energy neutron capture on native Ca as a second important channel of production. It is found that the Ca-41 signal in the stone phase from three meteorites correlates with their size, and that the inferred low-energy neutron fluxes vary by a factor of at least 20.

Fink, D.↗
NASA NTRS1993

P/Halley - Effects of time-dependent production rates on spatial emission profiles

Spatial profiles of C2, CN, NH2, and O(D-1) in Comet P/Halley taken on 1986 March 1.54 and 2.55 and April 14.32 and 15.30 clearly show the effect of the 7 day periodic variation seen in photometric observations. With a time-dependent model based upon the light curve and employing standard scale lengths for each species reduced to the appropriate heliocentric distance, we are able to reproduce the highly variable profiles for all species. We computed the phase lag and amplitude correction between the actual gas production at the nucleus and the temporal/spatial filter imposed by the finite aperture photometry. For early March we find a phase lag and amplitude correction of 12 hr and -9 percent, respectively, whereas in mid-April the values are 6 hr and -27 percent. The same phase lag and amplitude correction work equally well for all four species despite their wide variation in photochemical lifetimes for production and decay. The same model integrated over circular apertures is able to reproduce the entire published March and April photometric light curves for C2. Our results require the use of the 7.60 day period for the March data as opposed to the 7.37 day period that is relevant for the April data, in agreement with the published analysis of the photometric data. Our results will help to reconcile the placement of active areas on the surface of Halley's comet with various remote observations and spacecraft images of the nucleus.

Combi, Michael R.↗
DOE OSTI2022

Analyzing Production Rate and Carbon Utilization Trade-offs in CO 2 RR Electrolyzers

Carbon utilization is a crucially important performance characteristic of CO 2 electrolyzers; however, applications of simple and accurate descriptive models to experimental data on this topic are currently lacking. Here, we apply a simple analytical reactor model to parameterize single-pass conversion as a function of feed-gas flow rate and show that it captures a wide body of experimental data in the literature exceptionally well. In doing so, we demonstrate that this simple conceptual approach can characterize progress and capture recent innovations in reactor design. To validate the extracted parameters, we employ a well-established comprehensive model to confirm that the results agree with physical expectations. Lastly, we explore the implications of the descriptive model by examining the inherent trade-off between single-pass conversion efficiency and reactor productivity. Understanding such trade-offs is crucially important for advancing this electrolyzer technology toward commercial applications.

36 MATERIALS SCIENCE↗
NASA NTRS2019

Quantifying the Evolution of Molecular Production Rates of Comet 21P/Giacobini–Zinner with iSHELL/NASA-IRTF

This paper presents results from our molecular characterization of comet 21P/Giacobini-Zinner during its 2018 apparition. We followed the comet during four observing runs, for a total of 8 nights. The high-resolution spectra of 21P were acquired using iSHELL - the near-IR high resolution immersion echelle spectrograph on NASA/IRTF (Mauna Kea, Hawaii). We detected many cometary emission lines across four customized iSHELL settings in the (2.9 – 5.2) μm range. CO abundances relative to water displayed a relatively constant behavior during the observing campaign, suggesting a possible correlation between the outgassing of water and CO. While CO mixing ratios in 21P are consistent with the reference median value for Jupiter Family comets (JFCs), ethane was depleted relative to the reference median value for JFCs, excepting one observing run (8th and 9th Aug) in which ethane appeared overabundant. We consider several possible causes: an ethane outburst, decreasing outgassing of water, or a seasonal effect owing to nucleus rotation. In the pre-perihelion runs, methanol was overabundant compared with the reference median value for JFCs, however it decreased steadily to a depleted value during 21P’s post-perihelion phase, suggesting a possible seasonal effect. We report 3-s upper limits for acetylene, formaldehyde, ammonia and methane. The ratios of our measured 3-s upper limits for acetylene and detections of hydrogen cyanide are consistent with the depletion of C2 relative to CN in 21P observed at optical wavelengths. This result confirms that 21P is depleted in the carbon chain primary volatile responsible for C2 production.

Faggi S.↗
DOE OSTI2024

Glass production rate in an electric melter: Melting rate correlation and primary foam stability

Waste loading and melting rate are major factors determining the lifecycle of nuclear waste disposal by vitrification in electric melters in which the heat to the cold cap is delivered from the melt pool. One of the crucial parameters that affect the rate of melting is the temperature at which the primary foam collapses at the cold cap bottom. Further, apart from the transient glass-forming melt viscosity, primary foam stability is affected by the shear stress imposed by the flow in the melt pool and the presence of residual solid particles.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Quantification of Methane Emissions from Marginal (Low Production Rate) Oil and Natural Gas Wells

The objective of this research was to measure methane emissions from marginal well sites at various basins across the United States. The goal was to collect and evaluate representative, defensible, and repeatable data and draw quantifiable conclusions on the extent of emissions from marginal wells across oil and gas producing regions of the U.S., and to compare these results to published data on the emissions from nonmarginal wells.

03 NATURAL GAS↗
NASA NTRS1974

Variability of the Al-26 production rate in ordinary chondrites

Fifteen ordinary chondrites for which unusually high spallogenic Ne-22/Ne-21 or He-3/Ne-21 ratios had been reported and one meteorite with marked shock characteristics were selected in order to investigate the relations between Ne-22/Ne-21 ratios, Al-26 contents and depth. We report Al-26 and K contents of 13 samples from 11 of these and noble gas contents of 30 samples from all of these stones.

Herzog, G. F.↗
NASA NTRS1979

Large impact basins on Mercury and relative crater production rates

Mariner 10 revealed evidence for 40 impact basins having diameters greater than or equal to 200 km on the portion of Mercury imaged at sufficient resolution. A log (cumulative number/unit area) vs. log (diameter) plot for the mercurian basins has a least squares slope of -2. Mercury has (in cumulative number/unit area) only 37 percent as many basins as does the Moon over the entire range of diameters greater than or equal to 300 km. If both the Moon and Mercury have had similar preservation times for craters and if common populations of impactors are involved, then Mars crossers may have been a dominant contribution to the basin forming objects.

Frey, H.↗
NASA NTRS1979

Large impact basins on Mercury and relative crater production rates

A search for impact basins on Mercury having diameters greater than 200 km revealed evidence for 40 such structures on the 47% of Mercury mapped at sufficient resolution by Mariner 10. This is similar to the number (35) found by Schaber et al. (1977), although there is disagreement in the details of both diameters (for basins observed by them and by the authors) and in the existence of individual basins. The differences are described in detail. A log (cumulative number/unit area)-log (diameter) plot for mercurian basins has a least squares slope of -2; basins show somewhat less scatter about this line than do the Schaber et al. basins. Mercury has (in cumulative number/unit area) only 37% as many basins as does the moon over the entire range of diameters greater than 300 km. If both the moon and Mercury have had similar preservation times for craters and if common populations of impactors are involved, then Mars-crossers may have been a dominant contribution to the basin-forming objects.

Frey, H.↗