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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Detecting Uniform Areas for Vicarious Calibration using Landsat TM Imagery: A Study using the Arabian and Saharan Deserts

This paper discusses a method for detecting spatially uniform sites need for radiometric characterization of remote sensing satellites. Such information is critical for scientific research applications of imagery having moderate to high resolutions (<30-m ground sampling distance (GSD)). Previously published literature indicated that areas with the African Saharan and Arabian deserts contained extremely uniform sites with respect to spatial characteristics. We developed an algorithm for detecting site uniformity and applied it to orthorectified Landsat Thematic Mapper (TM) imagery over eight uniform regions of interest. The algorithm's results were assessed using both medium-resolution (30-m GSD) Landsat 7 ETM+ and fine-resolution (<5-m GSD) IKONOS multispectral data collected over sites in Libya and Mali. Fine-resolution imagery over a Libyan site exhibited less than 1 percent nonuniformity. The research shows that Landsat TM products appear highly useful for detecting potential calibration sites for system characterization. In particular, the approach detected spatially uniform regions that frequently occur at multiple scales of observation.

Hilbert, Kent↗
NASA NTRS2006

Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon(Registered Trademark) Insulation

A section of the retrieved Hubble Space Telescope (HST) solar array drive arm (SADA) multilayer insulation (MLI), which experienced 8.25 years of space exposure, was analyzed for environmental durability of the top layer of silver-Teflon (DuPont) fluorinated ethylene propylene (Ag-FEP). Because the SADA MLI had solar and anti-solar facing surfaces and was exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Ag-FEP, a commonly used spacecraft thermal control material. Data obtained included tensile properties, solar absorptance, surface morphology and chemistry. The solar facing surface was found to be extremely embrittled and contained numerous through-thickness cracks. Tensile testing indicated that the solar facing surface lost 60% of its mechanical strength and 90% of its elasticity while the anti-solar facing surface had ductility similar to pristine FEP. The solar absorptance of both the solar facing surface (0.155 plus or minus 0.032) and the anti-solar facing surface (0.208 plus or minus 0.012) were found to be greater than pristine Ag-FEP (0.074). Solar facing and anti-solar facing surfaces were microscopically textured, and locations of isolated contamination were present on the anti-solar surface resulting in increased localized texturing. Yet, the overall texture was significantly more pronounced on the solar facing surface indicating a synergistic effect of combined solar exposure and increased heating with atomic oxygen erosion. The results indicate a very strong dependence of degradation, particularly embrittlement, upon solar exposure with orbital thermal cycling having a significant effect.

deGroh, Kim, K.↗
NASA NTRSDate not supplied

Wide Bandgap Semiconductor Devices & Systems for Communications in Extreme Environment

The feasibility of Ka-band gallium nitride (GaN) based high power amplifier (HPA) for signal amplification in extreme planetary environment is investigated and its measured performance is presented. The data includes Pout, PAE, EVM for several waveforms and data rates, output spectrum, IMD, Noise Figure, and Gain. The data indicates excellent overall performance. Potential application of this HPA includes communication systems required to operate in the extreme hot environment of Mercury and Venus, extreme cold and high radiation environment of Jupiter’s icy moons, and Artemis missions that involve human/robotic exploration and long-term presence on the Moon.

Gallium Nitride↗
DOE OSTI2025

Quantifying the impacts of atmospheric rivers on the surface energy budget of the Arctic based on reanalysis

We present a comprehensive analysis of Arctic surface energy budget (SEB) components during atmospheric river (AR) events identified by integrated water vapor transport exceeding the monthly 85th-percentile climatological threshold in 3-hourly ERA5 reanalysis data from January 1980 to December 2019. Analysis of average anomalies in SEB components, net SEB, and the overall AR contribution to both the seasonal SEB components and net SEB climatology reveals clear seasonality and distinct land–sea–sea ice contrast patterns. Over the sea-ice-covered central Arctic Ocean, ARs significantly impact net SEB, inducing substantial surface warming in fall, winter, and spring. This warming is primarily driven by large anomalies in surface downward longwave radiation (LWD), which average 29–45 W m −2 during the cold seasons. In contrast, AR-related LWD anomalies are smaller in summer, averaging around 15 W m −2 , indicating a reduced impact during this season. Over sub-polar oceans, ARs have the most substantial positive impact on net SEB in cold seasons, mainly attributed to significant positive turbulent heat flux anomalies. AR-related turbulent heat anomalies reduce the upward turbulent flux, contributing up to −11 % relative to its seasonal climatology. In summer, ARs induce negative impacts on net SEB, primarily due to reduced shortwave radiation from increased cloud cover during AR events. Over continents, ARs generate smaller absolute impacts on net SEB because the large LWD anomalies are largely offset by corresponding increases in upward longwave radiation, particularly during cold seasons. Additionally, the seemingly large relative contributions of ARs to the net SEB over land primarily reflects the small magnitude of the climatological net SEB over continents. Greenland, especially western Greenland, exhibits significant downward longwave radiation anomalies associated with ARs, which drive large net SEB anomalies and contribute >54 % to mean SEB and induce amplified surface warming year-round. This holds significance for melt events, particularly during summer. Additionally, results of AR-related SEB impacts strongly depend on detection methods, as restrictive AR detection algorithms that emphasize extreme AR events, with large AR-related anomalies, do not necessarily indicate a large overall contribution to the SEB climatology due to the low occurrence frequency of these events. This study quantifies the role of ARs in the surface energy budget, contributing to our understanding of the Arctic warming and sea ice decline in ongoing Arctic amplification.

Arctic Sea ice change↗
NASA NTRSDate not supplied

Wide Bandgap Semiconductor Devices and Systems for Communications in Extreme Environment

The feasibility of gallium nitride based wide bandgap semiconductor devices for signal amplification in extreme planetary environment is investigated. The measured performance of these devices at S-band, X-band, and Ka-band are presented. The data indicates excellent performance at the above frequencies. Potential application of these devices includes communication systems required to operate in the extreme hot environment of Venus and in the extreme cold and high radiation environment of Jupiter’s icy moons.

Gallium Nitride↗
DOE OSTI2022

The Essential Role of Westerly Wind Bursts in ENSO Dynamics and Extreme Events Quantified in Model “Wind Stress Shaving” Experiments

Abstract Westerly wind bursts (WWBs)—brief but strong westerly wind anomalies in the equatorial Pacific—are believed to play an important role in El Niño–Southern Oscillation (ENSO) dynamics, but quantifying their effects is challenging. Here, we investigate the cumulative effects of WWBs on ENSO characteristics, including the occurrence of extreme El Niño events, via modified coupled model experiments within Community Earth System Model (CESM1) in which we progressively reduce the impacts of wind stress anomalies associated with model-generated WWBs. In these “wind stress shaving” experiments we limit momentum transfer from the atmosphere to the ocean above a preset threshold, thus “shaving off” wind bursts. To reduce the tropical Pacific mean state drift, both westerly and easterly wind bursts are removed, although the changes are dominated by WWB reduction. As we impose progressively stronger thresholds, both ENSO amplitude and the frequency of extreme El Niño decrease, and ENSO becomes less asymmetric. The warming center of El Niño shifts westward, indicating less frequent and weaker eastern Pacific (EP) El Niño events. Removing most wind burst–related wind stress anomalies reduces ENSO mean amplitude by 22%. The essential role of WWBs in the development of extreme El Niño events is highlighted by the suppressed eastward migration of the western Pacific warm pool and hence a weaker Bjerknes feedback under wind shaving. Overall, our results reaffirm the importance of WWBs in shaping the characteristics of ENSO and its extreme events and imply that WWB changes with global warming could influence future ENSO.

Meteorology & Atmospheric Sciences↗
DOE OSTI2022

Probing plasma physics with spectral index maps of accreting black holes on event horizon scales

The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of the supermassive black holes at the centre of our galaxy and at the centre of the elliptical galaxy M87. As both technology and analysis pipelines improve, it will soon become possible to produce spectral index maps of black hole accretion flows on event horizon scales. Here, in this work, we predict spectral index maps of both M87* and Sgr A* by applying the general relativistic radiative transfer (GRRT) code IPOLE to a suite of general relativistic magnetohydrodynamic (GRMHD) simulations. We analytically show that the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Consequently, spectral index maps grow more negative with increasing radius in almost all models, since all of these quantities tend to be maximized near the event horizon. Additionally, photon ring geodesics exhibit more positive spectral indices, since they sample the innermost regions of the accretion flow with the most extreme plasma conditions. Spectral index maps are sensitive to highly uncertain plasma heating prescriptions (the electron temperature and distribution function). However, if our understanding of these aspects of plasma physics can be tightened, even the spatially unresolved spectral index around 230 GHz can be used to discriminate between models. In particular, Standard and Normal Evolution (SANE) flows tend to exhibit more negative spectral indices than Magnetically Arrested Disc (MAD) flows due to differences in the characteristic magnetic field strength and temperature of emitting plasma.

(magnetohydrodynamics) MHD↗
DOE OSTI2025

Simulating Atmospheric Processes in Earth System Models and Quantifying Uncertainties With Deep Learning Multi‐Member and Stochastic Parameterizations

Abstract Deep learning is a powerful tool to represent subgrid processes in climate models, but many application cases have so far used idealized settings and deterministic approaches. Here, we develop stochastic parameterizations with calibrated uncertainty quantification to learn subgrid convective and turbulent processes and surface radiative fluxes of a superparameterization embedded in an Earth System Model (ESM). We explore three methods to construct stochastic parameterizations: (a) a single Deep Neural Network (DNN) with Monte Carlo Dropout; (b) a multi‐member parameterization; and (c) a Variational Encoder Decoder with latent space perturbation. We show that the multi‐member parameterization improves the representation of convective processes, especially in the planetary boundary layer, compared to individual DNNs. The respective uncertainty quantification illustrates that methods (b) and (c) are advantageous compared to a dropout‐based DNN parameterization regarding the spread of convective processes. Hybrid simulations with our best‐performing multi‐member parameterizations remained challenging and crash within the first days. Therefore, we develop a pragmatic partial coupling strategy relying on the superparameterization for condensate emulation. Partial coupling reduces the computational efficiency of hybrid Earth‐like simulations but enables model stability over 5 months with our multi‐member parameterizations. However, our hybrid simulations exhibit biases in thermodynamic fields and differences in precipitation patterns. Despite this, the multi‐member parameterizations enable improvements in reproducing tropical extreme precipitation compared to a traditional convection parameterization. Despite these challenges, our results indicate the potential of a new generation of multi‐member machine learning parameterizations leveraging uncertainty quantification to improve the representation of stochasticity of subgrid effects.

Behrens, Gunnar [Deutsches Zentrum für Luft‐ und R↗
NASA NTRS2015

Spatiotemporal Coherence of Mean and Extreme Aerosol Particle Events over Eastern North America as Observed from Satellite

Quantifying spatiotemporal scales of coherence and variability of aerosol particle properties provides (i) metrics for evaluating observational data sets and model simulations, (ii) inferences regarding dominant causes of variability, and (iii) information that is necessary to determine their climate forcing and air quality impacts. Accordingly, analyses of columnar aerosol optical depth (AOD) and Ångstrom exponent (AE) from the MODerate resolution Imaging Spectroradiometer (MODIS) on the Aqua and Terra satellites, and AErosol RObotic NETwork (AERONET) stations are used to evaluate the spatially averaged (Level-3) MODIS products, and to characterize the spatiotemporal scales of variability (and coherence) of aerosol particles over eastern North America (2000-2013). Results show a high degree of consistency in AOD retrievals from the different data sets but larger discrepancies in AE estimates, highest mean AOD and lowest day-to-day variability during the summer, and largest scales of spatial coherence in summer and fall. Consistent with the scales of spatial coherence from MODIS data, in both data sets power spectra indicate AOD variability is manifest primarily on synoptic and annual time scales. Conversely, AE variability in MODIS data is primarily focused on seasonal, semiannual, and annual time scales, and there is an additional mode of AE variability at approx. 30 days in the AERONET measurements. The frequency of cooccurrence of extreme AOD values (>local 90th percentile) decreases to below 50% at approx. 150 km from a central grid cell, but is above that expected by random chance over almost all of eastern North America, indicating supra-regional scale extreme events.

MODIS↗
DOE OSTI2022

Rapid Evaluation and Response to Impacts on Critical End-Use Loads Following Natural Hazard-Driven Power Outages: A Modular and Responsive Geospatial Technology

The disparate nature of data for electric power utilities complicates the emergency recovery and response process. The reduced efficiency of response to natural hazards and disasters can extend the time that electrical service is not available for critical end-use loads, and in extreme events, leave the public without power for extended periods. This article presents a methodology for the development of a semantic data model for power systems and the integration of electrical grid topology, population, and electric distribution line reliability indices into a unified, cloud-based, serverless framework that supports power system operations in response to extreme events. An iterative and pragmatic approach to working with large and disparate datasets of different formats and types resulted in improved application runtime and efficiency, which is important to consider in real time decision-making processes during hurricanes and similar catastrophic events. This technology was developed initially for Puerto Rico, following extreme hurricane and earthquake events in 2017 and 2020, but is applicable to utilities around the world. Given the highly abstract and modular design approach, this technology is equally applicable to any geographic region and similar natural hazard events. In addition to a review of the requirements, development, and deployment of this framework, technical aspects related to application performance and response time are highlighted.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS2024

Landslide Hazard is Projected to Increase Across High Mountain Asia

High Mountain Asia has long been known as a hotspot for landslide risk, and studies have suggested that landslide hazard is likely to increase in this region over the coming decades. Extreme precipitation may become more frequent, with a nonlinear response relative to increasing global temperatures. However, these changes are geographically varied. This article maps probable changes to landslide hazard, as shown by a landslide hazard indicator (LHI) derived from downscaled precipitation and temperature. In order to capture the nonlinear response of slopes to extreme precipitation, a simple machine-learning model was trained on a database of landslides across High Mountain Asia to develop a regional LHI. This model was applied to statistically downscaled data from the 30 members of the Seamless System for Prediction and Earth System Research large ensembles to produce a range of possible outcomes under the Shared Socioeconomic Pathways 2-4.5 and 5-8.5. The LHI reveals that landslide hazard will increase in most parts of High Mountain Asia. Absolute increases will be highest in already hazardous areas such as the Central Himalaya, but relative change is greatest on the Tibetan Plateau. Even in regions where landslide hazard declines by year 2100, it will increase prior to the mid-century mark. However, the seasonal cycle of landslide occurrence will not change greatly across High Mountain Asia. Although substantial uncertainty remains in these projections, the overall direction of change seems reliable. These findings highlight the importance of continued analysis to inform disaster risk reduction strategies for stakeholders across High Mountain Asia.

Thomas A Stanley↗
NASA NTRS2011

Psychophysiological Studies in Extreme Environments

This paper reviews the results from two studies that employed the methodology of multiple converging indicators (physiological measures, subjective self-reports and performance metrics) to examine individual differences in the ability of humans to adapt and function in high stress environments. The first study was a joint collaboration between researchers at the US Army Research Laboratory (ARL) and NASA Ames Research Center. Twenty-four men and women active duty soldiers volunteered as participants. Field tests were conducted in the Command and Control Vehicle (C2V), an enclosed armored vehicle, designed to support both stationary and on-the-move operations. This vehicle contains four computer workstations where crew members are expected to perform command decisions in the field under combat conditions. The study objectives were: 1) to determine the incidence of motion sickness in the C2V relative to interior seat orientation/position, and parked, moving and short-haul test conditions; and 2) to determine the impact of the above conditions on cognitive performance, mood, and physiology. Data collected during field tests included heart rate, respiration rate, skin temperature, and skin conductance, self-reports of mood and symptoms, and cognitive performance metrics that included seven subtests in the DELTA performance test battery. Results showed that during 4-hour operational tests over varied terrain motion sickness symptoms increased; performance degraded by at least 5 percent; and physiological response profiles of individuals were categorized based on good and poor cognitive performance. No differences were observed relative to seating orientation or position.

Toscano, William B.↗
NASA NTRS2011

Monitoring Delamination of Thermal Barrier Coatings During Interrupted High-Heat-Flux Laser Testing using Luminescence Imaging

This presentation showed progress made in extending luminescence-base delamination monitoring to TBCs exposed to high heat fluxes, which is an environment that much better simulates actual turbine engine conditions. This was done by performing upconversion luminescence imaging during interruptions in laser testing, where a high-power CO2 laser was employed to create the desired heat flux. Upconverison luminescence refers to luminescence where the emission is at a higher energy (shorter wavelength) than the excitation. Since there will be negligible background emission at higher energies than the excitation, this methods produces superb contrast. Delamination contrast is produced because both the excitation and emission wavelengths are reflected at delamination cracks so that substantially higher luminescence intensity is observed in regions containing delamination cracks. Erbium was selected as the dopant for luminescence specifically because it exhibits upconversion luminescence. The high power CO2 10.6 micron wavelength laser facility at NASA GRC was used to produce the heat flux in combination with forced air backside cooling. Testing was performed at a lower (95 W/sq cm) and higher (125 W/sq cm) heat flux as well as furnace cycling at 1163C for comparison. The lower heat flux showed the same general behavior as furnace cycling, a gradual, "spotty" increase in luminescence associated with debond progression; however, a significant difference was a pronounced incubation period followed by acceleration delamination progression. These results indicate that extrapolating behavior from furnace cycling measurements will grossly overestimate remaining life under high heat flux conditions. The higher heat flux results were not only accelerated, but much different in character. Extreme bond coat rumpling occurred, and delamination propagation extended over much larger areas before precipitating macroscopic TBC failure. This indicates that under the higher heat flux (and surface & interface temperatures), the TBC was more tolerant of damage. The main conclusions were that high heat flux conditions can not only accelerate TBC debond progression but can also grossly alter the pathway of delamination.

Eldridge, Jeffrey I.↗
NASA NTRS1985

MgS grain component in circumstellar shells

In this letter, far-infrared spectrophotometry (30-55 microns) and photometry (53-200 microns) are presented which define, for the first time, the long wavelength limit of the previously unidentified 30 micron emission feature found in certain extreme carbon star spectra. The spectral similarities are sufficiently similar to those of solid MgS that MgS is proposed to be the band carrier. This is interpreted as the first direct evidence that chemical surface reactions occur on dust grains in circumstellar environments. The presence of MgS indicates that either the oxygen abundance is relatively low and/or the sulfur abundance is high in extreme carbon stars.

Goebel, J. H.↗
DOE OSTI2021

Heterogeneous multiphase flow properties of volcanic rocks and implications for noble gas transport from underground nuclear explosions

Of interest to the Underground Nuclear Explosion Signatures Experiment are patterns and timing of explosion-generated noble gases that reach the land surface. The impact of potentially simultaneous flow of water and gas on noble gas transport in heterogeneous fractured rock is a current scientific knowledge gap. This article presents field and laboratory data to constrain and justify a triple continua conceptual model with multimodal multiphase fluid flow constitutive equations that represents host rock matrix, natural fractures, and induced fractures from past underground nuclear explosions (UNEs) at Aqueduct and Pahute Mesas, Nevada National Security Site, Nevada, USA. Capillary pressure from mercury intrusion and direct air–water measurements on volcanic tuff core samples exhibit extreme spatial heterogeneity (i.e., variation over multiple orders of magnitude). Petrographic observations indicate that heterogeneity derives from multimodal pore structures in ash-flow tuff components and post-depositional alteration processes. Comparisons of pre- and post-UNE samples reveal different pore size distributions that are due in part to microfractures. Capillary pressure relationships require a multimodal van Genuchten (VG) constitutive model to best fit the data. Relative permeability estimations based on unimodal VG fits to capillary pressure can be different from those based on bimodal VG fits, implying the choice of unimodal vs. bimodal fits may greatly affect flow and transport predictions of noble gas signatures. The range in measured capillary pressure and predicted relative permeability curves for a given lithology and between lithologies highlights the need for future modeling to consider spatially distributed properties.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2023

High Fluence Active Irradiation and Combined Effects Testing of Sapphire Optical Fiber Distributed Temperature Sensors [Slides]

All objectives have been completed. Heated irradiation indicates potential for sapphire fiber-based sensors to be used in extreme environments beyond silica fiber temperature limits. Sapphire optical fiber may not be appropriate for high fluence applications. Clad sapphire optical fibers have a temperature-dependent attenuation that has not been observed in unclad sapphire. With the appropriate pre-treatments and data post-processing, sapphire optical fiber has the potential to serve as a distributed sensor up to 1700ºC.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1972

Development and characterization of lubricants for use near nuclear reactors in space vehicles

The synthesis and evaluation program was conducted to develop wide-temperature range lubricants suitable for use in space vehicles particularly in the vicinity of nuclear reactors. Synthetic approaches resulted in nonpolymeric, large molecular weight materials, all based on some combination of siloxane and aromatic groups. Evaluation of these materials indicated that certain tetramethyl and hexamethyl disiloxanes containing phenyl thiophenyl substituents are extremely promising with respect to radiation stability, wide temperature range, good lubricity, oxidation resistance and additive acceptance. The synthesis of fluids is discussed, and the equipment and methods used in evaluation are described, some of which were designed to evaluate micro-quantities of the synthesized lubricants.

Robinson, G. L.↗
NASA NTRS1975

Net field-aligned currents observed by Triad

From the Triad magnetometer observation of a step-like level shift in the east-west component of the magnetic field at 800 km altitude, the existence of a net current flowing into or away from the ionosphere in a current layer was inferred. The current direction is toward the ionosphere on the morning side and away from it on the afternoon side. The field aligned currents observed by Triad are considered as being an important element in the electro-dynamical coupling between the distant magnetosphere and the ionosphere. The current density integrated over the thickness of the layer increases with increasing magnetic activity, but the relation between the current density and Kp in individual cases is not a simple linear relation. An extrapolation of the statistical relation to Kp = 0 indicates existence of a sheet current of order 0.1 amp/m even at extremely quiet times. During periods of higher magnetic activity an integrated current of approximately 1 amp/m and average current density of order 0.000001 amp/sq m are observed. The location and the latitudinal width of the field aligned current layer carrying the net current very roughly agree with those of the region of high electron intensities in the trapping boundary.

Sugiura, M.↗