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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

A Statistical Treatment of the Regional Slope Characteristics of Venus and Earth

Regional slope is a scale dependent parameter that describes the planar gradient over some (relative broad) area of topography. As such, it has a fundamental relevance to the geological evolution of a planetary surface. It is controlled by the interaction of those processes which tend to increase or reduce surface relief (e.g., tectonism, volcanism, impact cratering, weathering, viscous relaxation) and in turn, exerts control on the erosion, transportation and deposition of surface materials. The regional slope values, measured over 3 by 3 regions for Venus and Earth are calculated. The regional slope frequency distribution information was analyzed for Venus and Earth. The effects on terrestrial regional slope resulting from the removal of the ocean load from sea floor topography were examined.

Shapiro, V. I.↗
NASA NTRS1990

MBE growth technology for high quality strained III-V layers

The III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group III and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation of low temperature, and to permit the film to relax to equilibrium. The method of the invention: (1) minimizes starting step density on sample surface; (2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 monolayers at a time); (3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and (4) uses time-resolved RHEED to achieve aspects (1) through (3).

Grunthaner, Frank J.↗
DOE OSTI2023

FY23 Update: Surface Sampling Activities for the Canister Deposition Field Demonstration

This report describes the results of a field demonstration of the proposed surface sampling techniques and plan for the multi-year Canister Deposition Field Demonstration (CDFD). The CDFD will evaluate salt deposition rates on three commercial 32PTH2 NUHOMS welded stainless steel storage canisters in Advanced Horizontal Storage Modules. Exposure testing is planned for up to 10 years and will incorporate periodic surface sampling campaigns. The goal of the planned dust sampling and analysis is to determine important environmental parameters that impact the potential occurrence of stress corrosion cracking on spent nuclear fuel (SNF) dry storage canisters. Specifically, measured dust deposition rates and deposited particle sizes will improve parameterization of dust deposition models employed to predict the potential occurrence and timing of stress corrosion cracks on the stainless steel SNF canisters. Previously, a preliminary sampling plan was developed, identifying possible sampling locations on the canister surfaces and sampling intervals; possible sampling methods were also described. Building from previous work, this report documents hand sampling from a spent nuclear fuel canister on a transfer skid mockup designed by Sandia National Laboratories. The sampling took place from a boom lift and salts were collected from mounted sample plates. The results of these efforts are presented in this report and compared to previous laboratory-controlled tests. The information obtained from the CDFD will be critical for ongoing efforts to develop a detailed understanding of the potential for stress corrosion cracking of SNF dry storage canisters.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1993

An overview of the on-orbit contamination of the Long Duration Exposure Facility (LDEF)

Contamination that leads to degradation of critical surfaces becomes a vital design issue for many spacecraft programs. One of the processes that must be considered is the on-orbit accumulation of contaminants. The Long Duration Exposure Facility (LDEF) has presented an opportunity to examine the deposits on surfaces returned from orbit in order to help in understanding the deposition processes and the current models used to predict spacecraft contamination levels. The results from various investigators on the contamination of LDEF have implications for material selection, contamination models, and contamination control plans for the design of future spacecraft.

Stuckey, W. K.↗
DOE OSTI2021

Evaluation of Tritium Behavior in Forest Vegetation for the Purpose of Determining Appropriate Non-Zero Deposition Velocities for Tritium Oxide

Modeling and field measurements have been conducted between 2019 and 2021 to assess the practicality of using a non-zero deposition velocity for safety basis estimates of tritium oxide fate and transport modeling. A model was developed which used a complex deposition algorithm designed to assess how tritium oxide would mix based on the turbulent motions and wind speed effects that the forest canopy has on the atmosphere. The model was driven based on measurements of wind and turbulence taken from the Aiken AmeriFlux Tower which measures these properties at five levels located within and just above the forest. The model was then validated against a series of field experiments which were designed to test the model predictions and estimate the deposition velocity occurring over the forest environment at the Savannah River Site. The field releases used deuterium oxide as a surrogate for tritium oxide and was released as a fine mist which rapidly evaporated, creating a gaseous tracer in the atmosphere. Using air samplers, the elevations in deuterium concentration in the air relative to background measurements was assessed and then modeled. Generally, the numerical model tended to underpredict the amount of deuterium being mixed from above the canopy to the forest floor, indicating that the predictions it provides are still conservative relative to what was measured during the field experiments. Across a suite of modeling runs, the 95 th and 99 th percentile deposition velocities were estimated to be 1.2 and 0.7 cm s -1 , respectively. Estimated deposition velocities in the 2021 field experiments, which specifically assessed a release above the forest canopy and its mixing to the surface, predicted deposition velocities ranging from 1.75 to 6.61 cm s -1 . While these field releases do not cover all possible meteorological conditions, it seems appropriate to use a non-zero deposition velocity when performing safety-basis modeling of tritium oxide. The recommendation presented in this report is to use 1.0 cm s -1 . This is between the 95 th and 99 th percentile value estimated from the modeling study, suggesting it should be appropriate for the majority of release scenarios given the model’s apparent conservatism relative to field measurements.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1978

Self-alining valve poppet and seat

Poppet-and-seat combination is useful in fluid-control system that has to operate at high temperatures with low leak rates. Contaminants in flow stream are removed before they reach sealing surfaces by altering direction of flow several times before it enters poppet-and-seat flow passage. Particles are separated and deposited on surfaces not affecting sealing performance.

Olivas, U. P.↗
NASA NTRS1992

Vapor Deposition Of Metal From Gas/Tungsten Arc

Vacuum gas/tungsten-arc vapor-deposition process yields highly reflective, smooth films reproducing contours of surfaces on which deposited. Rate of deposition controlled precisely, and surface texture varied. Capable of deposition at rates double those of standard sputtering. Useful in making thin metallic coats to serve as electrical conductors, radio reflectors or antenna elements, or optical mirrors of partial or ultrahigh reflectivity, and in making semiconductor devices.

Weeks, Jack L.↗
DOE OSTI2022

Scale-Up and Modeling Efforts Using an Omniphobic Surface Treatment for Mitigating Solids Deposition

Abstract Gas hydrates, waxes and asphaltenes represent some of the most significant flow assurance challenges, especially in subsea lines, where treatment options can be limited. Currently, complete avoidance is the primary strategy for hydrate management, while chemical or mechanical flushing/pigging may be utilized for other solids. Each system must also be treated with individualized solutions, as there have been no proved one-size-fits-all technologies demonstrated to date. As an alternative to constant chemical injection or thermodynamic controls such as insulation or heating, a robust omniphobic surface treatment material has been developed which has been shown in previous studies to significantly reduce the adhesion of flow assurance solids, resulting in lower risk for deposition and plugging of gas hydrates, waxes, and asphaltenes. As part of a Department of Energy study, laboratory scale tests were performed on a variety of apparatuses ranging from micromechanical force (micron scale) to laboratory flow loop testing (meter scale). While the results from these tests have been promising, there can be some disconnects between lab-scale observations and field-scale testing. Several factors can result in discrepancies between small-scale bench-top studies and deployment-scale efforts. These include flow conditions (Reynolds number, flow regime), chemistry (synthetic vs. crude oils, gas composition, and additives), physical differences (pipeline material, size, and geometry), etc. This work will describe the actions taken to better understand the deployment and performance of a material such as this omniphobic surface treatment in field scenarios, and to build confidence for deployment in a production scenario. These efforts include modeling field production scenarios using models developed from lab observations, application of the material to field-scale equipment to better understand application challenges, and expanded survivability and longevity testing. Understanding the bridge between laboratory testing and full-scale deployment allows for better technique and risk mitigation for field scale testing.

03 NATURAL GAS↗
NASA NTRS1972

The Alhazen to Abul Wafa swirl belt: An extensive field of light colored, sinuous markings, part T

Problematic causes and characteristics of light colored sinuous markings on the lunar surface are explored. Two processes, exogenetic and endogenetic, are examined in detailed. During the endogenetic process it is suggested that impact ejecta deposition and surface disturbances cause the markings. During the endogenetic process, it is suggested that extrusive volcanism and sublimation and/or alteration cause the markings.

El-Baz, F.↗
NASA NTRS1992

MBE growth technology for high quality strained III-V layers

III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group II and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation to low temperature, and to permit the film to relax to equilibrium. The method of the invention 1) minimizes starting step density on sample surface; 2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 mono-layers at a time); 3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and 4) uses time-resolved RHEED to achieve aspects (1)-14 (3).

Grunthaner, Frank J.↗
DOE OSTI2021

Translating nanoparticle dosimetry from conventional in vitro systems to occupational inhalation exposures

As encouraged by Toxicity Testing in the 21st Century, researchers increasingly apply high-throughput in vitro approaches to identify and characterize nanoparticle hazards, including conventional aqueous cell culture systems to assess respiratory hazards. Translating nanoparticle dose from conventional toxicity testing systems to relevant human exposures remains a major challenge for assessing occupational risk of nanoparticle exposures. Here, we explored existing computational tools and data available to translate nanoparticle dose metrics from cellular test systems to inhalation exposures of silver nanoparticles in humans. We used the Multiple-Path Particle Dosimetry (MPPD) Model to predict deposition of humans exposed to 20 and 110 nm silver nanoparticles at 0.9 µg/m3 over an 8 hr period, the proposed a National Institute of Occupational Safety and Health (NIOSH) recommended exposure limit (REL). MPPD predicts 1.88 and 0.98 µg of silver deposited in an 8 hr period for 20 and 110 nm nanoparticles, respectively, with 20 nm particles displaying nearly 11-fold higher total surface area deposited. Peak nanoparticle concentrations occurred more proximal in the pulmonary tract compared to mass deposition patterns (generation 5 vs. generations 20-21, respectively) due to regional differences in lung lining fluid volumes. Assuming 0.4% nanoparticle dissolution by mass as previously measured, we predict peak concentrations of silver ions in cells of 0.24 and 0.17 µg/mL for 20 and 110 nm particles, respectively. Both predicted concentrations are below the measured toxic threshold of 1.7 µg/mL of silver ions in cells from in vitro assessments. Assuming 4% dissolution by mass, we predict 10-fold higher silver concentrations in tissues, peaking at 2.4 and 1.7 µg/mL, for 20 and 110 nm nanoparticles respectively, exceeding the observed in vitro toxic threshold and highlighting the importance and sensitivity of dissolution rates. Overall, this approach offers a framework for extrapolating nanotoxicity results from in vitro cell culture systems to human exposures. Aligning appropriate dose metrics from in vitro and in vivo hazard characterizations and human pulmonary doses from occupational exposures are critical components for successful nanoparticle risk assessment and worker protection and provide guidance for designing future in vitro studies aimed at relevant human exposures.

Smith, Jordan N.↗
NASA NTRS1988

The effect of phosphorus and sulfur treatment on the surface properties of InP

Experimental results are presented for InP surfaces treated by using red phosphorus as a source to create an excess overpressure of phosphorus during annealing and prior to silicon dioxide deposition. The surface has been probed by in situ photoluminescence, noncontacting remote gate C-V, and conventional high-frequency and quasi-static C-V methods. A study has also been made of the surface of sulfurized InP following heating in aqueous (NH4)2S(x). MISFETs fabricated using the benefits of these surface treatments show high transconductances and stabilities approaching those of thermal SiO2/Si with less than 5-percent variation in drain current over a 12-hr period.

Iyer, R.↗
NASA NTRS1978

Synchronized flash photolysis and pulse deposition in matrix isolation experiments

An apparatus is described which permits flash photolysis of a pulse-deposited gas mixture in a matrix isolation experiment. This technique obviates the limitations of in situ photolysis imposed by the cage effect and by secondary photolysis. The matrix is deposited in pulses at 30-s intervals and photolyzed sequentially by four synchronized flashlamps approximately 1 ms before the pulse strikes the cold surface. Pulsed deposition maintains adequate isolation and causes line narrowing, which enhances spectral sensitivity. The efficacy of flash photolysis combined with pulsed deposition for producing and trapping transient species was demonstrated by infrated detection of CF3 (from photolysis of CF3I/Ar mixtures) and of ClCO (from photolysis of Cl2/CO/Ar mixtures). The apparatus was used to study the photolytic decomposition of gaseous tricarbonylironcyclobutadiene, C4H4Fe(CO)3. The results indicate that the primary photolytic step is not elimination of C4H4, as suggested earlier, but rather of CO.

Allamandola, Louis J.↗
NASA NTRS2008

Onboard Detection of Active Canadian Sulfur Springs: A Europa Analogue

We discuss a current, ongoing demonstration of insitu onboard detection in which the Earth Observing-1 spacecraft detects surface sulfur deposits that originate from underlying springs by distinguishing the sulfur from the ice-rich glacial background, a good analogue for the Europan surface. In this paper, we describe the process of developing the onboard classifier for detecting the presence of sulfur in a hyperspectral scene, including the use of a training/testing set that is not exhaustively labeled, i.e.not all true positives are marked, and the selection of 12, out of 242, Hyperion instrument wavelength bands to use in the onboard detector. This study aims to demonstrate the potential for future missions to capture short-lived science events, make decisions onboard, identify high priority data for downlink and perform onboard change detection. In the future, such capability could help maximize the science return of downlink bandwidth-limited missions, addressing a significant constraint in all deep-space missions.

autonomy↗
NASA NTRS1987

Oxygen-Barrier Coating for Titanium

Oxygen-barrier coating for titanium developed to provide effective and low-cost means for protecting titanium alloys from oxygen in environment when alloys used in high-temperature mechanical or structural applications. Provides protective surface layer, which reduces extent of surface oxidation of alloy and forms barrier to diffusion of oxygen, limiting contamination of substrate alloy by oxygen. Consists of submicron layer of aluminum deposited on surface of titanium by electron-beam evaporation, with submicron layer of dioxide sputtered onto aluminum to form coat.

Clark, Ronald K.↗
NASA NTRS2004

Vapor Deposition and Solar Wind Implantation on Lunar Soil-Grain Surfaces as Comparable Processes

Vapor deposited patinas (VDP) on lunar soil grains consist of a thin (less than 1 micron) layer of amorphous silicate (glass) embedded with nanoscale Fe(sup 0) globules as seen in many TEM images. VDPs are also present on larger space-weathered lunar rocks; these larger samples will not be discussed here although the process of vapor deposition is common to exposed grains of all sizes. Whether or not the majority of the Fe(sup 0) globules present in lunar soils reside in vapor deposited patina is a matter of some concern. Some Fe(sup 0) globules are clearly seen to reside within the glass of agglutinates and might represent remobilized Fe(sup 0) in agglutinitic melts. remobilized Fe(sup 0) in agglutinitic melts. We argue that because VDP coatings are present only on the surfaces of lunar soil grains, their distribution as a surface correlated component (SCC) of lunar soils should parallel those of Solar Wind Elements (SWE) implanted in the outermost rinds of lunar soil grains. SWE residing in the interior of soils grains make up the volume correlated component (VCC). Relative to Fe(sup 0) in VDP, the distribution of various SWE have been studied well. The reason is understandable because instrumentation for nanoscale imaging is not ubiquitous. In this study we use the distribution of SWE in lunar soils as a guide to understanding the fate of Fe(sup 0) in VDP.

Basu, A.↗
NASA NTRS2007

Considerations on Terrestrial Iron Depositing Analogs to Earliest Mars

Iron oxide and hydroxide minerals, including hematite, can mineralize and preservemicrofossils and physical biomarkers (Allen at al., 2004). Preserved remnants of phototrophic microorganisms are recognized as biosignatures of past life on Earth (Schopf, 2006). To date, two types of surface iron depositing environments have been studied as analogs to possible habitable environments on earliest Mars: the highly acidified Rio Tinto River (Iberian Belt, Spain) [Gomez Ortis et al., 2007], and the nearneutral iron depositing Chocolate Pots Hot Spring (Yellowstone National Park, US) [Parenteau at al., 2005]. While phototrophs in the Rio Tinto are only represented by eukaryotic algae (Amaral Zettler et all., 2002), Chocolate Pots is mainly populated with cyanobacteria (Pierson et all., 2000; Brown et all., 2007). Which of these environments is the closer analog to a potentially habitable early Mars? Paleobiological data, combined with recent "tree of life" interpretations, suggest that phototrophic eukaryotes evolved not earlier than 2.5 - 2.8 b.y. after Earth s accretion (4.6 b.y.), while cyanobacteria and /or their iron-tolerant predecessors evolved between 1 - 1.5 b.y. after accretion (Brown et al., 2007). Lindsay and Brasier (2002) postulated that microbial life on Mars surface could have lasted no more than 1-1.5 b.y. after Mars accretion (also 4.6 b.y.). Recent multispectral mapping of Mars suggests that near-neutral wet environments prevailed at approximately this time (Bibring, et al., 2006). Thus, near-neutral iron depositing hot springs such as Chocolate Pots Hot Spring seem to be the more likely habitable analogs for earliest Mars.

Brown, Igor I.↗
NASA NTRS2005

Albedo of the South Pole on Mars Determined by Topographic Forcing of Atmosphere Dynamics

The nature of the martian south polar cap has remained enigmatic since the first spacecraft observations. In particular, the presence of a perennial carbon dioxide ice cap, the formation of a vast area of black slab ice known as the Cryptic region and the asymmetric springtime retreat of the cap have eluded explanation. Here we present observations and climate modelling that indicate the south pole of Mars is characterized by two distinct regional climates that are the result of dynamical forcing by the largest southern impact basins, Argyre and Hellas. The style of surface frost deposition is controlled by these regional climates. In the cold and stormy conditions that exist poleward of 60 degrees S and extend 180 degrees in longitude west from the Mountains of Mitchel (about 30 degrees W), surface frost accumulation is dominated by precipitation. In the opposite hemisphere, the polar atmosphere is relatively warm and clear and frost accumulation is dominated by direct vapour deposition. It is the differences in these deposition styles that determine the cap albedo.

Colaprete, Anthony↗