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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

LANDSAT imagery of the Central Andes

The central Andes of South America extend from approximately 14 deg. S to 28 deg. S as an unbroken chain of mountains and volcanoes over 2000 km long. It is here that the Nazca plate dives under the South American plate at angles varying from 10 deg to 30 deg. Very little is known about the volcanoes comprising this classic, subduction-type plate margin. A catalogue of the volcanoes in the central Andes is being prepared by Dr. P.W. Francis and Dr. C.A. Wood at the NASA Lunar and Planetary Institute. At present, more than 800 volcanoes of Cenozoic age have been recognized in the chain, with an estimated 75-80 major, active Quarternary volcanoes. Approximately one hundred 1536 x 1536 pixel color composite Optronics positives were produced from six full LANDSAT Thermatic Mapper scenes and three partial TM scenes. These positives cover a large portion of the central Andes. The positives were produced from LANDSAT data using the VAX imaging package, LIPS. The scenes were first transferred from magnetic tape to disk. The LIPS package was then used to select volcanically interesting areas which were then electronically enhanced. Finally, the selected areas were transferred back to tape and printed on the Optronics equipment. The pictures are color composites using LANDSAT TM bands 7,4, and 2 in the red, green, and blue filters, respectively.

Komer, C. A.↗
NASA NTRS2004

The Influence of Tungsten on the Chemical Composition of a Temporally Evolving Nanostructure of a Model Ni-Al-Cr Superalloy

The influence of W on the temporal evolution of gamma' precipitation toward equilibrium in a model Ni-Al-Cr alloy is investigated by three-dimensional atom-probe (3DAP) microscopy and transmission electron microscopy (TEM). We report on the alloys Ni-10 Al-8.5 Cr (at.%) and Ni-10 Al-8.5 Cr-2 W (at.%), which were aged isothermally in the gamma + gamma' two-phase field at 1073 K, for times ranging from 0.25 to 264 h. Spheroidal-shaped gamma' precipitates, 5-15 nm diameter, form during quenching from above the solvus temperature in both alloys at a high number density (approx. 10(exp 23/cu m). As gamma' precipitates grow with aging at 1073 K, a transition from spheriodal- to cuboidal-shaped precipitates is observed in both alloys. The elemental partitioning and spatially resolved concentration profiles across the gamma' precipitates are obtained as a function of aging time from three-dimensional atom-by-atom reconstructions. Proximity histogram concentration profiles of the quaternary alloy demonstrate that W concentration gradients exist in gamma' precipitates in the as-quenched and 0.25-h aging states, which disappear after 1 h of aging. The diffusion coefficient of W in gamma' is estimated to be 6.2 x 10(exp -20) sq m/s at 1073 K. The W addition decreases the coarsening rate constant, and leads to stronger partitioning of Al to gamma' and Cr to gamma.

Sudbrack, Chantal K.↗
NASA NTRS2010

MAPIR: An Airborne Polarmetric Imaging Radiometer in Support of Hydrologic Satellite Observations

In this age of dwindling water resources and increasing demands, accurate estimation of water balance components at every scale is more critical to end users than ever before. Several near-term Earth science satellite missions are aimed at global hydrologic observations. The Marshall Airborne Polarimetric Imaging Radiometer (MAPIR) is a dual beam, dual angle polarimetric, scanning L band passive microwave radiometer system developed by the Observing Microwave Emissions for Geophysical Applications (OMEGA) team at MSFC to support algorithm development and validation efforts in support of these missions. MAPIR observes naturally-emitted radiation from the ground primarily for remote sensing of land surface brightness temperature from which we can retrieve soil moisture and possibly surface or water temperature and ocean salinity. MAPIR has achieved Technical Readiness Level 6 with flight heritage on two very different aircraft, the NASA P-3B, and a Piper Navajo.

Laymon, C.↗
NASA NTRS2011

What the UV SED Tells us About Stellar Populations and Galaxies

The UV SED parameter b as in f(sub 1) ~ 1(sup b), is commonly used to estimate fundamental properties of high-redshift galaxies including age and metallicity. However, sources and processes other than age and metallicity can influence the value of b. We use the local starforming dwarf galaxy, I Zw 18, in a case study to investigate uncertainties in age and metallicity inferred from b due errors or uncertainties in: mode of star formation (instantaneous starburst vs. continuous SF), dust extinction, nebular continuous emission (2-photon emission, Balmer continuum flux), and presence of older stars.

Heap, Sara R.↗
NASA NTRS2015

Are the Clast Lithologies Contained in Lunar Breccia 64435 Mixtures of Anorthositic Magmas

The anorthositic crust of the Moon is often used as the archtypical example of a primary planetary crust. The abundance and purity of anorthosite in the Apollo sample collection and remote sensing data are generally attributed to an early global magma ocean which produced widespread floating plagioclase cumulates (the ferroan anorthosites; FANs. Recent geochronology studies report evidence of young (less than 4.4 Ga) FAN ages, which suggest that either some may not be directly produced from the magma ocean or that the final solidification age of the magma ocean was younger than previous estimates. A greater diversity of anorthositic rocks have been identified among lunar meteorites as compared to returned lunar samples. Granted that these lithologies are often based on small clasts in lunar breccias and therefore may not represent their actual whole rock composition. Nevertheless, as suggested by the abundance of anorthositic clasts with Mg# [Mg/(Mg+Fe)] less than 0.80 and the difficulty of producing the extremely high plagioclase contents observed in Apollo samples and the remote sensing data, modification of the standard Lunar Magma Ocean (LMO) model may be in order. To ground truth mission science and to further test the LMO and other hypotheses for the formation of the lunar crust, additional coordinated petrology and geochronology studies of lunar anorthosites would be informative. Here we report new mineral chemistry and trace element geochemistry studies of thick sections of a composite of FAN-suite igneous clasts contained in the lunar breccia 64435 in order to assess the significance of this type of sample for petrogenetic studies of the Moon. This work follows recent isotopic studies of the lithologies in 64435 focusing on the same sample materials and expands on previous petrology studies who identified three lithologies in this sample and worked on thin sections.

Simon, J. I.↗
NASA NTRS2016

Analysis of One-Way Laser Ranging Data to LRO, Time Transfer and Clock Characterization

We processed and analyzed one-way laser ranging data from International Laser Ranging Service ground stations to NASA's Lunar Reconnaissance Orbiter (LRO), obtained from June 13, 2009 until September 30, 2014. We pair and analyze the one-way range observables from station laser fire and spacecraft laser arrival times by using nominal LRO orbit models based on the GRAIL gravity field. We apply corrections for instrument range walk, as well as for atmospheric and relativistic effects. In total we derived a tracking data volume of approximately 3000 hours featuring 64 million Full Rate and 1.5 million Normal Point observations. From a statistical analysis of the dataset we evaluate the experiment and the ground station performance. We observe a laser ranging measurement precision of 12.3 centimeters in case of the Full Rate data which surpasses the LOLA (Lunar Orbiting Laser Altimeter) timestamp precision of 15 centimeters. The averaging to Normal Point data further reduces the measurement precision to 5.6 centimeters. We characterized the LRO clock with fits throughout the mission time and estimated the rate to 6.9 times10 (sup -8), the aging to 1.6 times 10 (sup -12) per day and the change of aging to 2.3 times 10 (sup -14) per day squared over all mission phases. The fits also provide referencing of onboard time to the TDB (Barycentric Dynamical Time) time scale at a precision of 166 nanoseconds over two and 256 nanoseconds over all mission phases, representing ground to space time transfer. Furthermore we measure ground station clock differences from the fits as well as from simultaneous passes which we use for ground to ground time transfer from common view observations. We observed relative offsets ranging from 33 to 560 nanoseconds and relative rates ranging from 2 times 10 (sup -13) to 6 times 10 (sup -12) between the ground station clocks during selected mission phases. We study the results from the different methods and discuss their applicability for time transfer.

Bauer, S.↗
DOE OSTI2020

Verification of Reactor Activation Modelling with Physical Characterization Data and the Impact on Long Term Assessments - 20303

Whiteshell Laboratories, located in Manitoba, Canada, provided research facilities for the Canadian nuclear industry since the early 1960's. The facility was centered on Whiteshell Reactor 1 (WR-1), an organically cooled, heavy water moderated nuclear reactor. WR-1 was safely shut down in 1985, defueled and drained, and has been in a safe Storage with Surveillance (Deferred Decommissioning) state until present day. In support of an Environmental Assessment for proposed in-situ disposal of WR-1, detailed characterization information regarding the reactor core components (calandria, calandria tubes, and pressure tubes) was necessary to provide confidence that the long-term impacts of the facility can be assessed adequately. A simplified estimate of the total activation of core components was completed in 1992 using conservative assumptions, expected reactor configuration and computer models built with WIMS-CRNL, ONEDANT and ORIGEN-S. Due to the simplification, and age of the work, there was considerable doubt that the modelled inventory estimate of the core components was sufficient to support long-term performance modeling of the planned in-situ decommissioning. Additional data would be required to provide this confidence. Several options were considered for characterizing the WR-1 core components, but it was decided to collect only a limited number of samples in an effort to validate the 1992 simplified estimate as bounding. The limited number of samples reduced risks to workers, both radiological and non-radiological, and significantly reduced the costs required to confidently define and bound the radiological inventory of activation products in the core. The results of the sampling were compared to the simplified activation estimation. There was good agreement between the modelled and sampled results, with all major contributors to total activity showing similar relative quantities. The samples were generally lower than predicted by the models, with few exceptions. Notable exceptions included Nb-94, which were higher in the sample results than the model. This was determined to be caused by the use of Niobium containing steel alloys in the stainless steel pressure tube that were not accounted for in the models. The comparison of results provided confidence that the original inventory estimates produced through the simplified model are conservative and bounding, and therefore suitable for use in the long-term assessment of in situ disposal of the WR-1 reactor. This paper provides details of the simplified computer model results, their comparison to results of the sampling, and the changes adopted in the assessment of the in-situ decommissioning of WR-1 as a result. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Utilizing Environmental Tracers to Reduce Groundwater Flow and Transport Model Parameter Uncertainties

Abstract Non‐uniqueness in groundwater model calibration is a primary source of uncertainty in groundwater flow and transport predictions. In this study, we investigate the ability of environmental tracer information to constrain groundwater model parameters. We utilize a pilot point calibration procedure conditioned to subsets of observed data including: liquid pressures, tritium ( 3 H), chlorofluorocarbon‐12 (CFC‐12), and sulfur hexafluoride (SF 6 ) concentrations; and groundwater apparent ages inferred from these environmental tracers, to quantify uncertainties in the heterogeneous permeability fields and infiltration rates of a steady‐state 2‐D synthetic aquifer and a transient 3‐D model of a field site located near Riverton, Wyoming (USA). To identify the relative data worth of each observation data type, the post‐calibration uncertainties of the optimal parameters for a given observation subset are compared to that from the full observation data set. Our results suggest that the calibration‐constrained permeability field uncertainties are largest when liquid pressures are used as the sole calibration data set. We find significant reduction in permeability uncertainty and increased predictive accuracy when the environmental tracer concentrations, rather than apparent groundwater ages, are used as calibration targets in the synthetic model. Calibration of the Riverton field site model using environmental tracer concentrations directly produces infiltration rate estimates with the lowest uncertainties, however; permeability field uncertainties remain similar between the environmental tracer concentration and apparent groundwater age calibration scenarios. This work provides insight on the data worth of environmental tracer information to calibrate groundwater models and highlights potential benefits of directly assimilating environmental tracer concentrations into model parameter estimation procedures.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Molecular dynamics discovery of an extraordinary ionic migration mechanism in dislocation-containing TlBr crystals

TlBr can surpass CZT as the leading semiconductor for γ- and X-radiation detection. Unfortunately, the optimum properties of TlBr quickly decay when an operating electrical field is applied. Quantum mechanical studies indicated that if this property degradation comes from the conventional mechanism of ionic migration of vacancies, then an unrealistically high vacancy concentration is required to account for the rapid aging of TlBr seen in experiments. Here, we have applied large scale molecular dynamics simulations to study the effects of dislocations on ionic migration of TlBr crystals under electrical fields. We found that electrical fields can drive the motion of edge dislocations in both slip and climb directions. These combined motions eject enormous vacancies in the dislocation trail. Both dislocation motion and a high vacancy concentration can account for the rapid aging of the TlBr detectors. These findings suggest that strengthening methods to pin dislocations should be explored to increase the lifetimes of TlBr crystals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Lifetime risk of suicide among survivors of the atomic bombings of Japan

Abstract Aims The long-term physical health effects of the atomic bombings of Hiroshima and Nagasaki are well characterised, but the psychological effects remain unclear. Therefore, we sought to determine whether measures of exposure severity, as indirect measures of psychological trauma arising from exposure to the atomic bombings, are associated with suicide mortality among atomic bomb survivors. Methods The Life Span Study is a prospective cohort study of 93 741 Japanese atomic bomb survivors who were located within 10 km of the hypocentre in Hiroshima or Nagasaki at the time of the bombings in 1945, and 26 579 residents of Hiroshima and Nagasaki who were not in either city at the time of the bombings, matched to survivors on city, sex and age. Measures of exposure severity included: proximity to the hypocentre, type of shielding between the survivor and the blast and self-reported occurrence of acute radiation and thermal injuries. Date of death was obtained from the Japanese National Family Registry system. Cause of death was obtained from death certificates. Adjusted hazard ratios (HRs) were estimated from Cox regression models overall and stratified by sex and age. Results During the 60-year follow-up period (1950–2009), 1150 suicide deaths were recorded among 120 231 participants (23.6 per 100 000 person-years): 510 among 70 092 women (17.2 per 100 000 person-years) and 640 among 50 139 men (33.6 per 100 000 person-years). Overall, there was no association of proximity, type of shielding or the occurrence of acute injuries with suicide mortality. Among those <25 years of age at the time of the bombings, increased suicide risk was observed for survivors outside v . shielded inside any structure (HR: 1.24; 95% confidence interval (CI): 1.03, 1.48; interaction p = 0.054) and for those who reported flash burns (HR: 1.32; 95% CI: 1.00, 1.73; interaction p = 0.025). Sex-stratified analyses indicated that these associations were limited to men. Among women, closer proximity to the hypocentre was associated with a non-significant increase in suicide risk, with a positive association between proximity and suicide risk observed among women <15 years of age (HR: 1.09 per km; 95% CI: 1.00, 1.18; interaction p = 0.067). Conclusions Proximity to the hypocentre, shielding and acute injury presence do not generally appear to influence suicide mortality among atomic bomb survivors. However, heterogeneity may exist by age and sex, with younger survivors potentially more sensitive to psychological trauma. Coupled with other studies, our results suggest the importance of long-term monitoring of mental health among young populations exposed to catastrophic events or mass trauma.

Psychiatry↗
DOE OSTI2026

Battery Life Prediction Using Reduced-Order Physics Models and Machine Learning (CRADA Final Report)

Phase 1 (Original CRADA, plus no-cost extension modifications #1-3, 6/1/2017 to 3/13/2021): The Australian Department of Defence (AUDoD) is performing accelerated aging tests of Li-ion batteries to benchmark their reliability and degradation characteristics. Using its previously developed battery lifetime predictive model framework, the National Laboratory of the Rockies (NLR) will develop analytical models based the AUDoD data to predict lifetime of the multiple Li-ion battery chemistries under real-world use scenarios of interest to AUDoD. The NLR model is based on physical degradation mechanisms encountered by Li-ion batteries and has been previously validated. Phase 2 (CRADA modification #4, plus no-cost extension modification #5, 2/22/2021 to 3/30/2025): Train and support Australian Department of Defence personnel to use NLR software for model-based estimation of Li-ion battery lifetime using accelerated battery aging data collected by the Australian Department of Defence. Under separate DOE funding from 2019 to 2021, NLR enhanced its battery life-prediction software using machine learning algorithms to automate portions of the model-fitting process, requiring significantly less labor and expert judgment and also adding uncertainty quantification, increasing statistical rigor. Under Phase 2, NLR will customize NLR Software and provide it to AuDoD. NLR will enhance its NLR Model to capture aging modes of AuDoD's multi-cell modules, including cell-balancing effects. NLR will develop example single-cell and multi-cell models based on one AuDoD battery aging dataset. NLR will train AuDoD personnel on NLR Software. By the conclusion of the project, NLR will have provided AuDoD the training materials, a user manual and software needed to perform their own analysis of additional and/or future battery aging datasets.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

On the Impact of Income, Age, and Travel Distance on the Value of Time

The value of time (VOT) is a fundamental component used in transportation modeling, policy analysis, and economic appraisal. Decades of research and practice have empirically estimated the VOT across many factors (e.g., mode, purpose, time, comfort, etc.), yet little is known about its underlying form. Although it is well established that VOT can vary, it is still unclear whether patterns exist in this variation. The objective of this paper is not to merely estimate the VOT, but to model the VOT across multiple continuous and interacting variables. The purpose is to reveal its functional form with respect to mode, age, gender, purpose, income, and time of day to provide a generalizable understanding for future research and practice. Such an understanding can help develop simpler models and reduce the need for bespoke estimations for every conceivable variable perturbation. This research utilized a household travel survey containing 14,159 reported trips with imputed travel time and costs for the alternative mode choices. The average overall estimated VOT is 40.32 $/h, with results showing VOT varying log-linearly with income and trip distance, but following a Gaussian function (normal curve) with age. Overall, the results show that travel distance dominates VOT variation, which increases exponentially at a rate that is 3.61 times higher per mile of distance than per $10,000 of income, and that VOT by age peaks at age 54. This basic understanding of how the VOT varies sets the foundation for answering the subsequent question for why it might vary.

Engineering↗
DOE OSTI2015

Groundwater age, brine migration, and large‐scale solute transport in the A lberta B asin, C anada

Abstract There is a great contrast in geochemical and hydrogeologic estimates of the residence times of pore fluids in sedimentary basins. This contrast is particularly evident in the Alberta Basin, Canada, which has served as the study area for important studies of long‐term fluid flow and transport. To address these differences, we developed two‐dimensional simulations of groundwater age, constrained by both hydrogeologic and geochemical observations, to estimate the residence time of fluids and the amount and timing of flushing by meteoric waters in the Alberta Basin. Results suggest that old, residual brines have been retained in the deepest parts of the basin since their formation ca. 400 Ma, but significant dilution by younger waters has reduced the age of these pore waters to no more than approximately 200 My. Shallower formations have been flushed extensively by fresh, young waters. Loss of brines and dilution of older pore waters occurred primarily after the uplift of the Rockies with the introduction of the gravity‐driven flow regime. Despite these large changes in flow regime, solute exchange between deep saline aquifers and the overlying vigorous freshwater flow system was found to be consistent with long‐term dispersive mixing across subhorizontal concentration gradients rather than by direct flushing. Sensitivity studies using an analytic solution supported the use of 100 m for transverse dispersivity in large‐scale numerical models. These simulations confirm that the age and origin of brines are in many cases poor indicators of long‐term solute transport rates in sedimentary basins, but the geochemical indicators that are used to determine the origin of brines can provide useful constraints for calculating groundwater age and are far more commonly available than isotopic groundwater age tracers.

Gupta, I.↗
DOE OSTI2016

A new approach to cosmogenic corrections in 40 Ar/ 39 Ar chronometry: Implications for the ages of Martian meteorites

Anomalously old 40 Ar/ 39 Ar ages are commonly obtained from Shergottites and are generally attributed to uncertainties regarding the isotopic composition of the trapped component and/or the presence of excess 40 Ar. Old ages can also be obtained if inaccurate corrections for cosmogenic 36 Ar are applied. Current methods for making the cosmogenic correction require simplifying assumptions regarding the spatial homogeneity of target elements for cosmogenic production and the distribution of cosmogenic nuclides relative to trapped and reactor-derived Ar isotopes. To mitigate uncertainties arising from these assumptions, a new cosmogenic correction approach utilizing the exposure age determined on an un-irradiated aliquot and step-wise production rate estimates that account for spatial variations in Ca and K is described. Data obtained from NWA 4468 and an unofficial pairing of NWA 2975, which yield anomalously old ages when corrected for cosmogenic 36 Ar using conventional techniques, are used to illustrate the efficacy of this new approach. For these samples, anomalous age determinations are rectified solely by the improved cosmogenic correction technique described herein. Ages of 188 ± 17 and 184 ± 17 Ma are obtained for NWA 4468 and NWA 2975, respectively, both of which are indistinguishable from ages obtained by other radioisotopic systems. For other Shergottites that have multiple trapped components, have experienced diffusive loss of Ar, or contain excess Ar, more accurate cosmogenic corrections may aid in the interpretation of anomalous ages. In conclusion, the trapped 40 Ar/ 36 Ar ratios inferred from inverse isochron diagrams obtained from NWA 4468 and NWA 2975 are significantly lower than the Martian atmospheric value, and may represent upper mantle or crustal components.

40Ar/39Ar↗
NASA NTRS1988

Loss of radiogenic argon from shocked granitic clasts in suevite deposits from the Ries Crater

Five granite clasts from the Otting and Aumuehle quarries in the suevite ejecta deposits from the Ries Crater, Germany, were characterized with respect to modal composition, the degree of shock, and the loss of radiogenic Ar. The results were used to estimate the relative fractions of total crater volume, which were characterized by undisturbed K-Ar ages, partly reset ages, and essentially complete gas loss. The results suggest that the loss of Ar form the Ries suevite samples occurred in a 'hot' post-impact ejecta layer. It was estimated that less than 50 percent of the material composing the hot Ries ejecta should show at least partially reset K-Ar ages; such materials compose no more than 5 percent of the total displaced crater volume.

Bogard, Donald↗
NASA NTRS1993

Nd-142/Nd-144 in bulk planetary reservoirs, the problem of incomplete mixing of interstellar components and significance of very high precision Nd-145/Nd-144 measurements

Apart from the challenge of very high precision Nd-142/Nd-144 ratio measurement, accurate applications of the coupled Sm-(146,147)-Nd-(142,143) systematics in planetary differentiation studies require very precise knowledge of the present-day (post-Sm-146 decay) Nd-142/Nd-144 ratios of bulk planetary objects (BP). The coupled systematics yield model ages for the time of formation of Sm/Nd-fractionated reservoirs by differentiation of Sm/Nd-unfractionated bulk planetary reservoirs. Estimates of (Nd-142/Nd-144)(sub BP) and (Nd-143/Nd-144)(sub BP) therefore provide the critical baseline relative to which these model ages are referenced. In the Sm-147-Nd-143 systematics, Nd-143/Nd-144 variations are mostly large; therefore, small variations in initial Nd-143/Nd-144 ratios generally can be ignored. However, in the case of Sm-146-Nd-142, the range of Nd-142/Nd-144 divergence for differentiated planetary reservoirs is much smaller. Consequently Sm-(146,147)-Nd-(142,143) model ages are sensitive to small variations in bulk planetary Nd-142/Nd-144 (both present-day and initial). One major unanswered question is whether or not Nd shelf standards (CIT Nd beta/Ames metal, La Jolla, NASA-JSC/Ames metal) have Nd-142/Nd-144 identical to the bulk Earth or otherwise might record some degree of radiogenic evolution in an early-fractionated reservoir. Our discussions of earth Earth differentiation based on Nd-142/Nd-144 in Isua and Acasta samples have employed a working assumption: (Nd-142/Nd-144)(sub Nd beta) = (Nd-142/Nd-144)(sub Bulk Earth). This requires experimental justification and is apparently contradicted by chondrite Nd-142/Nd-144 measurements, which have been interpreted to indicate: (Nd-142/Nd-144)(sub JSC/Ames metal) = ((Nd-142/Nd-144)(sub CHUR) = 35 plus or minus 8 ppm). At present, interpretations of the early Earth and Moon hinge largely on this issue. Because Ba in bulk chondrite samples exhibit similar magnitude nuclear anomalies, attributable to incomplete mixing of interstellar components, a critical question is whether or not nuclear effects are also present in Nd-142/Nd-144, both in bulk chondrites and between planetary objects.

Harper, C. L., Jr.↗
DOE OSTI2018

SAVY-4000 O-Ring and Filter Lifetime Extension Report

The 3-year accelerated aging study of the SAVY-4000 O-ring detailed in our previous Lifetime Extension Report showed very little evidence of significant degradation to samples subjected to aggressive elevated temperature and radiation conditions. Whole container thermal aging studies followed by helium leakage testing and compression set measurements were used to establish a failure criterion estimate for O-ring compression set of ≥ 65 %, which led to an O-ring lifetime estimate of greater than 65 years at 80°C. Herein, we describe a statistical model of the 3-year accelerated aging study and present additional results gathered in FY17 that further support the lifetime extension of the O-ring to 40 years at 80°C. Because we are choosing an extremely conservative lifetime value (40 years) compared to the aging study results (>65 years), the O-ring lifetime could be extended further, especially if supported by surveillance results collected over the years to come.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Recent Elysium volcanism: Effects on the Martian atmosphere

A vast area of smooth plains in southeastern Elysium near 5 deg N, 195 deg was identified as young volcanic plains. These plains represent flood eruptions of very low viscosity lavas at a point in time much later than the volcanism that produced the major volcanoes of Elysium. Since volcanism is a principal mechanism by which gases are supplied to the atmosphere, and since these gases can have important climatic effects, it is important to consider the amount of H2O, CO2, and other gases that were possibly released. We present estimates of input and release rates from this volcanic episode. The age is defined by the density of superposed craters; there are 89 +/- 15 craters greater than or equal to 1 km per 10(exp 6) sq km corresponding to the Upper Amazonian making this the youngest major volcanic episode. Lavas, covering 1.5 x 10(exp 6) sq km and presumably erupted through fissures, filled a topographic low and then flowed through knobby terrain into westernmost Amazonis. The western plains are characterized by scattered low shields having radial lava flows. Unit thickness is uncertain, individual flows are about 10 m thick; the entire deposit buries older knobby terrain having local relief of 200-400 m (estimated by Earth-based radar data); hence the volcanics must be thick enough to bury that relief. On the basis of unit morphology, length of flows, and the extent of the deposit, it can be inferred that the lava was of low viscosity and mafic to ultramafic composition. The age and petrology of the shergottites suggest they may have come from this unit.

Plescia, J. B.↗