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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 487 records · Page 27
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NASA NTRS2008

Simulating Sources of Superstorm Plasmas

We evaluated the contributions to magnetospheric pressure (ring current) of the solar wind, polar wind, auroral wind, and plasmaspheric wind, with the surprising result that the main phase pressure is dominated by plasmaspheric protons. We used global simulation fields from the LFM single fluid ideal MHD model. We embedded the Comprehensive Ring Current Model within it, driven by the LFM transpolar potential, and supplied with plasmas at its boundary including solar wind protons, polar wind protons, auroral wind O+, and plasmaspheric protons. We included auroral outflows and acceleration driven by the LFM ionospheric boundary condition, including parallel ion acceleration driven by upward currents. Our plasmasphere model runs within the CRCM and is driven by it. Ionospheric sources were treated using our Global Ion Kinetics code based on full equations of motion. This treatment neglects inertial loading and pressure exerted by the ionospheric plasmas, and will be superceded by multifluid simulations that include those effects. However, these simulations provide new insights into the respective role of ionospheric sources in storm-time magnetospheric dynamics.

Fok, Mei-Ching↗
NASA NTRS1988

The seasonal cycle of energetics from the GLAS/UMD climate GCM

The annual cycle of atmospheric energetics from a 2-year integration of the GLAS/UMD Climate GCM is computed and compared to results from the European Centre analyses of the GWE year, and to previously published results on a global basis. All calculations are done in the mixed space-time domain. The main conclusions are: (1) the seasonal cycle of today's eddy kinetic energy (in both hemispheres), and of the transient eddy available potential energy and the potential-to-kinetic energy conversions (mean and eddy) in the Northern Hemisphere are well simulated by the GCM; (2) the GCM's tendency to have anomalously large mean u-winds at upper levels in high latitudes leads to excessive wintertime values of mean kinetic and available potential energies, and causes distortions in the GCM latitude-height distribution of kinetic energy and of many of the conversions; (3) the eddy conversion of available potential-to-kinetic energy obtained from the ageostrophic wind in these analyses; and (4) the conversions in the Southern Hemisphere are not well simulated by the GCM, although the observations are somewhat questionable.

Straus, David M.↗
NASA NTRS1995

Investigation of water droplet trajectories within the NASA icing research tunnel

Water droplet trajectories within the NASA Lewis Research Center's Icing Research Tunnel (IRT) were studied through computer analysis. Of interest was the influence of the wind tunnel contraction and wind tunnel model blockage on the water droplet trajectories. The computer analysis was carried out with a program package consisting of a three-dimensional potential panel code and a three-dimensional droplet trajectory code. The wind tunnel contraction was found to influence the droplet size distribution and liquid water content distribution across the test section from that at the inlet. The wind tunnel walls were found to have negligible influence upon the impingement of water droplets upon a wing model.

Reehorst, Andrew↗
NASA NTRS1990

A model of stratospheric chemistry and transport on an isentropic surface

This paper presents a new photochemical transport model designed to simulate the behavior of stratospheric trace species in the middle stratosphere. The model has an Eulerian grid with the latitude and longitude coordinates on a single isentropic surface (hemispheric or global), in which both the dynamical and the photochemical processes can be accurately represented. The model is intgegrated for 12 days with winds and temperatures supplied by three-dimensional integration of an idealized wavenumber-one disturbance. The results for the long-lived tracers such as N2O showed excellent correlation with the potential vorticity distribution, validating the transport scheme. Calculations with zonally averaged wind and temperature fields showed that discrepancies in the calculation of the zonal mean were less than 10 percent for O3 and HNO3, compared with the zonal mean of the previous results.

Austin, John↗
NASA NTRS1996

Pioneer Venus Data Analysis

Analysis and interpretation of data from the Orbiter Retarding Potential Analyzer (ORPA) onboard the Pioneer Venus Orbiter is reported. By comparing ORPA data to proton data from the Orbiter Plasma Analyzer (OPA), it was found that the ORPA suprathermal electron densities taken outside the Venusian ionopause represent solar wind electron densities, thus allowing the high resolution study of Venus bow shocks using both magnetic field and solar wind electron data. A preliminary analysis of 366 bow shock penetrations was completed using the solar wind electron data as determined from ORPA suprathermal electron densities and temperatures, resulting in an estimate of the extent to which mass loading pickup of O+ (UV ionized O atoms flowing out of the Venus atmosphere) upstream of the Venus obstacle occurred. The pickup of O+ averaged 9.95%, ranging from 0.78% to 23.63%. Detailed results are reported in two attached theses: (1) Comparison of ORPA Suprathermal Electron and OPA Solar Wind Proton Data from the Pioneer Venus Orbiter and (2) Pioneer Venus Orbiter Retarding Potential Analyzer Observations of the Electron Component of the Solar Wind, and of the Venus Bow Shock and Magnetosheath.

Jones, Douglas E.↗
NASA NTRS2002

Mapping the Potential for Eolian Surface Activity in Grasslands of the High Plains using Landsat Images

There are over 100,000 square kilometers of eolian sand dunes and sand sheets in the High Plains of the central United States. These land-forms may be unstable and may reactivate again as a result of land-use, climate change, or natural climatic variability. The main goal of this thesis was to develop a model that could be used to map an estimate of future dune activity. Multi-temporal calibrated Landsats 5 Thematic Mapper (TM) and 7 Enhanced Thematic Map per Plus (ETM+) NDVI imagery were used in conjunction with the CENTURY vegetation model to correlate vegetation cover to climatic variability. This allows the creation of a predicted vegetation map which, combined with current wind and soil data, was used to create a potential sand transport map for range land in the High Plains under drought conditions.

Gutmann, Ethan Dain↗
NASA NTRSDate not supplied

Lunar Gateway Charging and Effects on Low-Energy Electron Measurements

The Electron Electrostatic Analyzer (EEA) is part of the HERMES instrument suite on Lunar Gateway and is designed to measure electrons in the energy range from 1 eV to 18 keV. Electrons in this range can be deflected or blocked from entering a detector by electric fields from a charged spacecraft platform, so many heliophysics missions (MMS, Cluster, etc.) use active potential control to minimize stray electric fields which would corrupt low-energy plasma measurements. Gateway, however, does not have such capabilities so the surface charging effects will influence the electron data. Further, some elements of Gateway partially block the instrument’s field of view to space. The effects of the Gateway platform on the low-energy electron population must be understood to maximize the accuracy of the EEA data. To investigate the electrostatic environment near Gateway and its effects on the EEA measurements, we use Nascap-2K to model the expected charging of Gateway under representative solar wind, magnetosheathic, and magnetospheric conditions. Next, we use the potential and electric field outputs from Nascap-2K along with in-house particle tracing codes to investigate how low-energy electrons are perturbed, blocked, or deflected by the spacecraft. We discuss how these perturbations impact the plasma moments computed from the EEA data and possible approaches for correcting the charging effects including application of advanced methods such as neural networks. In addition to electrons from the space environment being influenced by the electrostatic environment around Gateway, photoelectrons generated on Gateway surfaces will also be measured by EEA. We are investigating how knowledge of the potentials of various Gateway surfaces can be extracted from these measured photoelectrons using advanced numerical modeling and analysis. Such information would be valuable for validating charging models and planning mission operations around the platform. Finally, we discuss how the specific workflow developed for Gateway can be extended to a generalized process that is applicable to other future missions. As the space industry prepares for human exploration beyond low-Earth orbit, the need to obtain accurate space weather data from rideshare science payloads is critical. Our process for removing platform effects from the science data serves as a pathfinder for leveraging advanced simulations to maximize science returns and ensure the safety and success of future crewed missions.

Miles Bengtson↗
NASA NTRS1991

Development of a quiet supersonic wind tunnel with a cryogenic adaptive nozzle

The main objectives of this work is to demonstrate the potential of a cryogenic adaptive nozzle to generate quiet (low disturbance) supersonic flow. A drive system was researched for the Fluid Mechanics Laboratory (FML) Laminar Flow Supersonic Wind Tunnel (LFSWT) using a pilot tunnel. A supportive effort for ongoing Proof of Concept (PoC) research leading to the design of critical components of the LFSWT was maintained. The state-of-the-art in quiet supersonic wind tunnel design was investigated. A supersonic research capability was developed within the FML.

Wolf, Stephen D.↗
NASA NTRS1988

Contraction design for small low-speed wind tunnels

An iterative design procedure was developed for 2- or 3-dimensional contractions installed on small, low speed wind tunnels. The procedure consists of first computing the potential flow field and hence the pressure distributions along the walls of a contraction of given size and shape using a 3-dimensional numerical panel method. The pressure or velocity distributions are then fed into 2-dimensional boundary layer codes to predict the behavior of the boundary layers along the walls. For small, low speed contractions, it is shown that the assumption of a laminar boundary layer originating from stagnation conditions at the contraction entry and remaining laminar throughout passage through the successful designs is justified. This hypothesis was confirmed by comparing the predicted boundary layer data at the contraction exit with measured data in existing wind tunnels. The measured boundary layer momentum thicknesses at the exit of four existing contractions, two of which were 3-D, were found to lie within 10 percent of the predicted values, with the predicted values generally lower. From the contraction wall shapes investigated, the one based on a 5th order polynomial was selected for newly designed mixing wind tunnel installation.

Bell, James H.↗
NASA NTRS1995

Solar wind theory and modelling

The outflow of coronal plasma into interplanetary space is a consequence of the coronal heating process. Therefore the formation of the corona and the acceleration of the solar wind should be treated as a single problem. Traditionally the mass or particle flux emanating from the extended corona has been thought of as being determined by the coronal temperature or scale height and the coronal (base) density. This argument follows from considerations of the momentum balance of the corona-wind system from which one obtains models of a close to hydrostatic corona out to the critical point where the flow becomes supersonic. With this approach to the acceleration of the wind is has been difficult to reconcile the relatively small variation observed in the proton flux at 1 AU with the predicted exponential dependence of the proton flux on the coronal temperature. In this talk we would like to emphasize another approach in which coronal energetics play the primary role. The deposition of energy into the corona through some 'mechanical' energy flux is balanced by the various energy sinks available to the corona and the sum of these processes determine the coronal structure, i.e. its temperature and density. The corona loses energy through heat conduction into the transition region, through radiative losses, and through the gravitational potential energy and kinetic energy put into the solar wind itself. We will show from a series of models of the chromosphere transition region-corona-solar wind system that most of the energy deposited in a magnetically open region will go into the solar wind, with roughly half going into kinetic energy and half into lifting the plasma out of the solar gravity field. The coronal base density will adjust itself in such a way that the heat conductive flux flowing into the transition region is radiated away in the upper chromosphere. The coronal temperature is set by the requirements that most of the deposited energy goes into accelerating the solar wind; the coronal scale height will adjust itself so that the solar wind energy losses conform to the amplitude of the input energy. These processes are modified by the 'mode' of energy deposition, and we will show the effects on coronal structure of changing the parameters describing coronal heating as well as the effects of including a helium fluid in the models. However, the location, scale height and/or form of the energy deposition (i.e. heating or direct acceleration) are not too important for the solar wind, the coronal density and temperature structure will vary with the 'mode' of energy deposition, but the solar wind mass flux depends mainly on the amplitude of the energy flux.

Hansteen, Viggo H.↗
NASA NTRS2012

Experimental Validation of a Forward Looking Interferometer for Detection of Clear Air Turbulence due to Mountain Waves

The Forward-Looking Interferometer (FLI) is an airborne sensor concept for detection and estimation of potential atmospheric hazards to aircraft. The FLI concept is based on high-resolution Infrared Fourier Transform Spectrometry technologies that have been developed for satellite remote sensing. The FLI is being evaluated for its potential to address multiple hazards, during all phases of flight, including clear air turbulence, volcanic ash, wake vortices, low slant range visibility, dry wind shear, and icing. In addition, the FLI is being evaluated for its potential to detect hazardous runway conditions during landing, such as wet or icy asphalt or concrete. The validation of model-based instrument and hazard simulation results is accomplished by comparing predicted performance against empirical data. In the mountain lee wave data collected in the previous FLI project, the data showed a damped, periodic mountain wave structure. The wave data itself will be of use in forecast and nowcast turbulence products such as the Graphical Turbulence Guidance and Graphical Turbulence Guidance Nowcast products. Determining how turbulence hazard estimates can be derived from FLI measurements will require further investigation.

Schaffner, Philip R.↗
NASA NTRS2008

Estimates of Sputter Yields of Solar-Wind Heavy Ions of Lunar Regolith Materials

At energies of approximately 1 keV/amu, solar-wind protons and heavy ions interact with the lunar surface materials via a number of microscopic interactions that include sputtering. Solar-wind induced sputtering is a main mechanism by which the composition of the topmost layers of the lunar surface can change, dynamically and preferentially. This work concentrates on sputtering induced by solar-wind heavy ions. Sputtering associated with slow (speeds the electrons speed in its first Bohr orbit) and highly charged ions are known to include both kinetic and potential sputtering. Potential sputtering enjoys some unique characteristics that makes it of special interest to lunar science and exploration. Unlike the yield from kinetic sputtering where simulation and approximation schemes exist, the yield from potential sputtering is not as easy to estimate. This work will present a preliminary numerical scheme designed to estimate potential sputtering yields from reactions relevant to this aspect of solar-wind lunar-surface coupling.

Barghouty, Abdulmasser F.↗
NASA NTRS2009

Lunar Surface Potential Increases during Terrestrial Bow Shock Traversals

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. We present an analysis of Apollo 14 SIDE "resonance" events that indicate the lunar surface potential increases when the Moon traverses the dawn bow shock. By analyzing Wind spacecraft crossings of the terrestrial bow shock at approximately this location and employing current balancing models of the lunar surface, we suggest causes for the increasing potential. Determining the origin of this phenomenon will improve our ability to predict the lunar surface potential in support of human exploration as well as provide models for the behavior of other airless bodies when they traverse similar features such as interplanetary shocks, both of which are goals of the NASA Lunar Science Institute's Dynamic Response of the Environment At the Moon (DREAM) team.

Collier, Michael R.↗
NASA NTRS1988

Contraction design for small low-speed wind tunnels

An iterative design procedure was developed for two- or three-dimensional contractions installed on small, low-speed wind tunnels. The procedure consists of first computing the potential flow field and hence the pressure distributions along the walls of a contraction of given size and shape using a three-dimensional numerical panel method. The pressure or velocity distributions are then fed into two-dimensional boundary layer codes to predict the behavior of the boundary layers along the walls. For small, low-speed contractions it is shown that the assumption of a laminar boundary layer originating from stagnation conditions at the contraction entry and remaining laminar throughout passage through the successful designs if justified. This hypothesis was confirmed by comparing the predicted boundary layer data at the contraction exit with measured data in existing wind tunnels. The measured boundary layer momentum thicknesses at the exit of four existing contractions, two of which were 3-D, were found to lie within 10 percent of the predicted values, with the predicted values generally lower. From the contraction wall shapes investigated, the one based on a fifth-order polynomial was selected for installation on a newly designed mixing layer wind tunnel.

Bell, James H.↗
NASA NTRS2008

Highly Structured Wind in Vela X-1

We present an in-depth analysis of the spectral and temporal behavior of a long almost uninterrupted INTEGRAL observation of Vela X-1 in Nov/Dec 2003. In addition to an already high activity level, Vela X-1 exhibited several very intense flares with a maximum intensity of more than 5 Crab in the 20 40 keV band. Furthermore Vela X-1 exhibited several off states where the source became undetectable with ISGRI. We interpret flares and off states as being due to the strongly structured wind of the optical companion: when Vela X-1 encounters a cavity in the wind with strongly reduced density, the flux will drop, thus potentially triggering the onset of the propeller effect which inhibits further accretion, thus giving rise to the off states. The required drop in density to trigger the propeller effect in Vela X-1 is of the same order as predicted by theoretical papers for the densities in the OB star winds. The same structured wind can give rise to the giant flares when Vela X-1 encounters a dense blob in the wind. Further temporal analysis revealed that a short lived QPO with a period of 6800 sec is present. The part of the light curve during which the QPO is present is very close to the off states and just following a high intensity state, thus showing that all these phenomena are related.

Kreykenbohm, Ingo↗
NASA NTRS2004

Decision Support Tool Evaluation Report for General NOAA Oil Modeling Environment(GNOME) Version 2.0

NASA's Earth Science Applications Directorate evaluated the potential of NASA remote sensing data and modeling products to enhance the General NOAA Oil Modeling Environment (GNOME) decision support tool. NOAA's Office of Response and Restoration (OR&R) Hazardous Materials (HAZMAT) Response Division is interested in enhancing GNOME with near-realtime (NRT) NASA remote sensing products on oceanic winds and ocean circulation. The NASA SeaWinds sea surface wind and Jason-1 sea surface height NRT products have potential, as do sea surface temperature and reflectance products from the Moderate Resolution Imaging Spectroradiometer and sea surface reflectance products from Landsat and the Advanced Spaceborne Thermal Emission and Reflectance Radiometer. HAZMAT is also interested in the Advanced Circulation model and the Ocean General Circulation Model. Certain issues must be considered, including lack of data continuity, marginal data redundancy, and data formatting problems. Spatial resolution is an issue for near-shore GNOME applications. Additional work will be needed to incorporate NASA inputs into GNOME, including verification and validation of data products, algorithms, models, and NRT data.

Spruce, Joseph P.↗
NASA NTRS2020

Evaluation of Computational Fluid Dynamics for Testing at High Supersonic Speeds

Video is an overview of the AETC Capability Challenge: Evaluation of Computational Fluid Dynamics (CFD) for Testing at High Supersonic Speeds. Featuring assessments of a series of wind tunnel tests and CFD analysis conducted with a focus on air flow and the potential of optimizing future testing. This video is beneficial for sharing with other organizations that operate or test in wind tunnels.

CFD Studies↗
NASA NTRS1986

Potential influences of heavy rain on general aviation airplane performance

Recent NASA wind tunnel tests of airfoils in a simulated rain environment under extremely heavy rain conditions have shown reductions in maximum lift and increases in drag. Conventional airfoils were tested with and without high lift devices and tests of laminar-flow airfoils without high-lift devices were conducted. Both types of airfoils indicated performance decrements when exposed to a simulated heavy rain environment. For the laminar flow airfoil, the rain influence was observed to occur throughout the angle of attack range, whereas for the conventional airfoil in a high lift configuration, the rain influence occurred mostly at the higher angles of attack. The performance decrement for the laminar-flow airfoil appeared to be a result of laminar-to-turbulent boundary-layer transition whereas the performance penalty for the conventional airfoil appeared to be the result of premature separation. The results of these tests are presented and the implication of the results to general aviation airplanes are discussed.

Dunham, R. E., Jr.↗