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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Candidate sites for lunar observatories, with a recommended example - The NE Orientale Basin

This paper discusses site selection criteria for a moon-based observatory, using an area on the NE flank of the Orientale Basin at 80 deg W on the lunar equator as a recommended example. Such a site would provide the following advantages: visibility of essentially the entire celestial sphere, continual line of sight to earth, dynamic accessibility for minimum energy landings and takeoffs, closeness to the far-side for installation of instruments requiring a radio silent environment, trafficable and workable terrain, closeness to geologically important features, and closeness to volcanic features with potential resources. Polar and far-side sites have advantages as well, and no one site can meet all requirements. It is suggested that other candidate sites be evaluated by the criteria used for the Orientale Basin.

Lowman, Paul D., Jr.↗
NASA NTRS1992

Atomic oxygen undercutting of LDEF aluminized-Kapton multilayer insulation

Atomic oxygen undercutting is a potential threat to vulnerable spacecraft materials which have atomic oxygen protective coatings. Such undercutting is due to atomic oxygen attack of oxidizable materials at microscopic defects in the protective coatings. These defects occur during fabrication and handling, or from micrometeoroid and debris bombardment in space. An aluminized-polyimide Kapton multilayer insulation sample that was located on the leading edge of the Long Duration Exposure Facility (LDEF) was used to study low Earth orbit directed ram atomic oxygen undercutting. Cracks in the aluminized coatings located around vent holes provided excellent defect sites for evaluation of atomic oxygen undercutting. The experimentally observed undercutting profiles were compared to predictions from Monte Carlo models for normal incident ram atomic oxygen attack. The shape of the undercut profile was found to vary with crack width, which is proportional to the number of oxygen atoms entering the crack. The resulting profiles of atomic oxygen which occurred on LDEF indicated wide undercut cavities in spite of the fixed ram orientation. Potential causes of the observed undercutting are presented. Implications of the undercutting profiles relevant to the Space Station Freedom are also discussed.

Degroh, Kim K.↗
NASA NTRS2008

Rapid Ice Mass Loss: Does It Have an Influence on Earthquake Occurrence in Southern Alaska?

The glaciers of southern Alaska are extensive, and many of them have undergone gigatons of ice wastage on time scales on the order of the seismic cycle. Since the ice loss occurs directly above a shallow main thrust zone associated with subduction of the Pacific-Yakutat plate beneath continental Alaska, the region between the Malaspina and Bering Glaciers is an excellent test site for evaluating the importance of recent ice wastage on earthquake faulting potential. We demonstrate the influence of cumulative glacial mass loss following the 1899 Yakataga earthquake (M=8.1) by using a two dimensional finite element model with a simple representation of ice fluctuations to calculate the incremental stresses and change in the fault stability margin (FSM) along the main thrust zone (MTZ) and on the surface. Along the MTZ, our results indicate a decrease in FSM between 1899 and the 1979 St. Elias earthquake (M=7.4) of 0.2 - 1.2 MPa over an 80 km region between the coast and the 1979 aftershock zone; at the surface, the estimated FSM was larger but more localized to the lower reaches of glacial ablation zones. The ice-induced stresses were large enough, in theory, to promote the occurrence of shallow thrust earthquakes. To empirically test the influence of short-term ice fluctuations on fault stability, we compared the seismic rate from a reference background time period (1988-1992) against other time periods (1993-2006) with variable ice or tectonic change characteristics. We found that the frequency of small tectonic events in the Icy Bay region increased in 2002-2006 relative to the background seismic rate. We hypothesize that this was due to a significant increase in the rate of ice wastage in 2002-2006 instead of the M=7.9, 2002 Denali earthquake, located more than 100km away.

Sauber, Jeanne M.↗
NASA NTRS2008

Evaluating Mars Science Laboratory Landing Sites with the Mars Global Reference Atmospheric Model (Mars-GRAM 2005)

The Mars Global Reference Atmospheric Model (Mars-GRAM) is an engineering-level atmospheric model widely used for diverse mission applications. Mars-GRAM s perturbation modeling capability is commonly used, in a Monte-Carlo mode, to perform high fidelity engineering end-to-end simulations for entry, descent, and landing (EDL) [1]. From the surface to 80 km altitude, Mars-GRAM is based on the NASA Ames Mars General Circulation Model (MGCM). Mars-GRAM and MGCM use surface topography from Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA), with altitudes referenced to the MOLA areoid, or constant potential surface. Traditional Mars-GRAM options for representing the mean atmosphere along entry corridors include: (1) Thermal Emission Spectrometer (TES) mapping years 1 and 2, with Mars-GRAM data coming from NASA Ames Mars General Circulation Model (MGCM) results driven by observed TES dust optical depth or (2) TES mapping year 0, with user-controlled dust optical depth and Mars-GRAM data interpolated from MGCM model results driven by selected values of globally-uniform dust optical depth. Mars-GRAM 2005 has been validated [2] against Radio Science data, and both nadir and limb data from TES [3]. There are several new features included in Mars-GRAM 2005. The first is the option to use input data sets from MGCM model runs that were designed to closely simulate conditions observed during the first two years of TES observations at Mars. The TES Year 1 option includes values from April 1999 through January 2001. The TES Year 2 option includes values from February 2001 through December 2002. The second new feature is the option to read and use any auxiliary profile of temperature and density versus altitude. In exercising the auxiliary profile Mars-GRAM option, values from the auxiliary profile replace data from the original MGCM databases. Some examples of auxiliary profiles include data from TES nadir or limb observations and Mars mesoscale model output at a particular location and time. The final new feature is the addition of two Mars-GRAM parameters that allow standard deviations of Mars-GRAM perturbations to be adjusted. The parameter rpscale can be used to scale density perturbations up or down while rwscale can be used to scale wind perturbations.

Justh, H. L.↗
NASA NTRS2017

New Data-Driven Estimation of Terrestrial CO2 Fluxes in Asia Using a Standardized Database of Eddy Covariance Measurements, Remote Sensing Data, and Support Vector Regression

The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial carbon dioxide fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem carbon dioxide exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated carbon dioxide fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8 days are reproduced (e.g., r (exp 2) =0.73 and 0.42 for 8 day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r (exp 2)=1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land carbon dioxide fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land carbon dioxide fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land carbon dioxide fluxes. These data-driven estimates can provide a new opportunity to assess carbon dioxide fluxes in Asia and evaluate and constrain terrestrial ecosystem models.

chlorophyll fluorescence↗
NASA NTRSDate not supplied

Estimating Tropical Cyclone Threats to Floating Rigs in the Gulf of Mexico

Offshore drilling operations in the Gulf of Mexico are particularly vulnerable during hurricane season. When a weather threat arises, a decision to evacuate the rig and/or move to a safe location may need to be made. Depending on the activities in progress at the time of the threat, securing the well, evacuating, and/or moving to a safe location can take a considerable amount of time. This transition time is called T-time. T-time is not only rig dependent, but also depends on the activity being performed at the time of the threat. For these reasons it is important to assess tropical cyclone threats and the time it takes for them to reach the rig location. The objective of this study is to use the available 50 years of past cyclone history to estimate cyclone threats at any location in the Gulf of Mexico. The cyclone threat is estimated based on the rig location as well as the start date and duration of the offshore activity. By threat, it is meant the likelihood that a specific location with an associated offshore activity would be exposed to an upcoming cyclone whose forecasted track cone and storm size lies within that location. Three representative rig locations in the Gulf of Mexico were selected as assessment sites to evaluate the threat of incoming cyclones for different T-times. To conduct this tropical cyclone study, an Excel spreadsheet tool was developed to automate the analysis of the tropical cyclone data from the Best Track Archive for Climate Stewardship (IBTrACS) Version 4. The spreadsheet tool allows the user to input any location (i.e., longitude and latitude) in the Gulf of Mexico and displays a list of historical cyclones that have passed within 150 nautical miles of that location during the activity period selected by the user. Also, the tool allows the user to input a T-time to assess the threat of cyclones that would not provide adequate time to secure the well, evacuate, and/or move to a safe location.

Risk↗
NASA NTRS2022

Estimating Tropical Cyclone Threats to Floating Rigs in the Gulf of Mexico

Offshore drilling operations in the Gulf of Mexico are particularly vulnerable during hurricane season. When a weather threat arises, a decision to evacuate the rig and/or move to a safe location may need to be made. Securing the well, evacuating, and/or moving to a safe location can take a considerable amount of time. This transition time is called T-time. T-time is not only rig dependent, but also depends on the activity being performed at the time of the threat. For these reasons, it is important to assess tropical cyclone threats and the estimated time it will take the storm to reach the rig location from the time it is first detected. The objective of this study is to use 50 years of cyclone history from a National Oceanic and Atmospheric Administration’s (NOAA) database, the International Best Track Archive for Climate Stewardship (IBTrACS) to estimate cyclone threats at any location in the Gulf of Mexico. The cyclone threat is estimated based on the rig location as well as the start date and duration of the offshore activity. By threat, it is meant the likelihood that a specific location with an associated offshore activity lies within the forecasted track cone and storm size of the upcoming cyclone. Three representative rig locations in the Gulf of Mexico were selected as assessment sites to evaluate the threat of incoming cyclones for different T-times. To conduct this tropical cyclone study, an Excel spreadsheet tool was developed to automate the analysis of the tropical cyclone data. The spreadsheet tool allows the user to input any location (i.e., longitude and latitude) in the Gulf of Mexico and displays a list of historical cyclones that have passed within 150 nautical miles of that location during the activity period selected by the user. In addition, the tool allows the user to input any T-time to assess the threat of cyclones that would not provide adequate time to secure the well, evacuate, and/or move to a safe location.

Offshore Oil Drilling↗
NASA NTRSDate not supplied

UAS Traffic Management Beyond Visual Line of Sight (UTM BVLOS)

NASA is working with Industry and FAA to enable beyond visual line of sight (BVLOS) unmanned aerial systems (UAS) operations wherever it is needed. Prior to NASA involvement, the UAS Traffic Management (UTM) concept and architecture did not exist. Then, a system architecture to support UTM in the nation's airspace was pioneered by NASA and adopted externally. Now, NASA will be a dedicated partner with the ongoing Key Site Operational Evaluation in Texas. NASA is needed to help define how services can be approved and applied to enable BVLOS operations in the nation's airspace.

UTM↗
NASA NTRS1975

CARETS: A prototype regional environmental information system. Volume 12: User evaluation of experimental land use maps and related products from the central Atlantic test site

The user interaction and evaluation phase of the USGS/NASA Central Atlantic Regional Ecological Test Site was designed to obtain the input of local, regional, State, and Federal agency users of land-resource information into the development, of a regional information system; to provide users with assistance and data resulting from CARETS research; and to have user. organizations evaluate to what extent the CARETS products meet their needs. The evaluation of CARETS land use and related products revealed that most user agencies interviewed, at all governmental levels, require more detailed data than that provided by the CARETS project. Few agencies found utility in the generalized ERTS Level I land--use maps. Level II data, though reported valuable by several users, was generally considered of secondary utility by most users. The products considered most useful by users at all levels were the high--altitude color-infrared photographs and the USGS orthophotoquads. Recommendations resulting from the evaluation reflect the need to establish a flexible and reliable system for providing more detailed raw and processed land-resource information as well as the need to improve the methods of making information available to users.

Land-use planning↗
NASA NTRS2019

New Approach for Temporal Stability Evaluation of Pseudo-Invariant Calibration Sites (PICS)

Pseudo-Invariant Calibration Sites (PICS) are one of the most popular methods for in-flight vicarious radiometric calibration of Earth remote sensing satellites. The fundamental question of PICS temporal stability has not been adequately addressed. However, the main purpose of this work is to evaluate the temporal stability of a few PICS using a new approach. The analysis was performed over six PICS (Libya 1, Libya 4, Niger 1, Niger 2, Egypt 1 and Sudan 1). The concept of a “Virtual Constellation” was developed to provide greater temporal coverage and also to overcome the dependence limitation of any specific characteristic derived from one particular sensor. TOA reflectance data from four sensors consistently demonstrating “stable” calibration to within 5%—the Landsat 7 ETM+ (Enhanced Thematic Mapper Plus), Landsat 8 OLI (Operational Land Imager), Terra MODIS (Moderate Resolution Imaging Spectroradiometer) and Sentinel-2A MSI (Multispectral Instrument)–were merged into a seamless dataset. Instead of using the traditional method of trend analysis (Student’s T test), a nonparametric Seasonal Mann-Kendall test was used for determining the PICS stability. The analysis results indicate that Libya 4 and Egypt 1 do not exhibit any monotonic trend in six reflective solar bands common to all of the studied sensors, indicating temporal stability. A decreasing monotonic trend was statistically detected in all bands, except SWIR 2, for Sudan 1 and the Green and Red bands for Niger 1. An increasing trend was detected in the Blue band for Niger 2 and the NIR band for Libya 1. These results do not suggest abandoning PICS as a viable calibration source. Rather, they indicate that PICS temporal stability cannot be assumed and should be regularly monitored as part of the sensor calibration process.

Tuli, Fatima Tuz Zafrin↗
NASA NTRS2016

Performance Evaluation of Speech Recognition Systems as a Next-Generation Pilot-Vehicle Interface Technology

During the flight trials known as Gulfstream-V Synthetic Vision Systems Integrated Technology Evaluation (GV-SITE), a Speech Recognition System (SRS) was used by the evaluation pilots. The SRS system was intended to be an intuitive interface for display control (rather than knobs, buttons, etc.). This paper describes the performance of the current "state of the art" Speech Recognition System (SRS). The commercially available technology was evaluated as an application for possible inclusion in commercial aircraft flight decks as a crew-to-vehicle interface. Specifically, the technology is to be used as an interface from aircrew to the onboard displays, controls, and flight management tasks. A flight test of a SRS as well as a laboratory test was conducted.

Arthur, Jarvis J., III↗
NASA NTRS1974

Dynamic conversion of solar generated heat to electricity

The effort undertaken during this program led to the selection of the water-superheated steam (850 psig/900 F) crescent central receiver as the preferred concept from among 11 candidate systems across the technological spectrum of the dynamic conversion of solar generated heat to electricity. The solar power plant designs were investigated in the range of plant capacities from 100 to 1000 Mw(e). The investigations considered the impacts of plant size, collector design, feed-water temperature ratio, heat rejection equipment, ground cover, and location on solar power technical and economic feasibility. For the distributed receiver systems, the optimization studies showed that plant capacities less than 100 Mw(e) may be best. Although the size of central receiver concepts was not parametrically investigated, all indications are that the optimal plant capacity for central receiver systems will be in the range from 50 to 200 Mw(e). Solar thermal power plant site selection criteria and methodology were also established and used to evaluate potentially suitable sites. The result of this effort was to identify a site south of Inyokern, California, as typically suitable for a solar thermal power plant. The criteria used in the selection process included insolation and climatological characteristics, topography, and seismic history as well as water availability.

Powell, J. C.↗
NASA NTRS1980

A study of the comparative performance of six lightning warning systems

An analysis of mining explosive accident reports indicates a need for clear and ample warning of approaching electrical storms to reduce injuries/fatalities due to lightning induced premature detonation. Six lightning warning devices were comparatively evaluated at three test sites. The devices tested were: (1) flash counter, (2) corona point, (3) radioactive probe, (4) field mill, (5) azimuth/range locator, and (6) triangulation locator. The test sites were chosen to provide system evaluation under varied thunderstorm conditions. The devices were tested at San Antonio, Texas, Kennedy Space Center, Florida and Langmuir Laboratory, New Mexico. Comparative performance is reviewed in terms of alarm reliability, false alarm, and failure to alarm probabilities. Lightning warning system requirements and methods of relating warning criteria to explosive hazard are discussed.

Johnson, R. L.↗