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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Comprehensive Assessment of Models and Events Using Library Tools (CAMEL) Framework: Time Series Comparisons

The Comprehensive Assessment of Models and Events using Library Tools (CAMEL) framework leverages existing Community Coordinated Modeling Center services: Run on Request post processing tools that generate model time series outputs and the new Community Coordinated Modeling Center Metadata Registry that describes simulation runs using Space Physics Archive Search and Extract metadata. The new CAMEL visualization tool compares the modeled time series with observational data and computes a suite of skill scores such as Prediction Efficiency, Root Mean Square Error, and Symmetric Signed Percentage Bias. Model data pairs used for skill calculations are obtained considering a user selected maximum difference between the time of observation and the nearest model output. The system renders available data for all locations and time periods selected using interactive visualizations that allow the user to zoom, pan, and pick data values along traces. Skill scores are reported for each selected event or aggregated over all events for all participating model runs. Separately, scores are reported for all locations (satellites or stations) and for each location individually. We are building on past experiences with model data comparisons of magnetosphere and ionosphere model outputs from GEM2008, GEMCEDAR Electrodynamics Thermosphere Ionosphere, and the SWPC Operational Space Weather Model challenges. The CAMEL visualization tool is demonstrated using three validation studies: (a) Wang Sheeley Arge heliosphere simulations compared against OMNI solar wind data, (b) ground magnetic perturbations from several magnetosphere and ionosphere electrodynamics models as observed by magnetometers, and (c) electron fluxes from several ring current simulations compared to Radiation Belt Storm Probes Helium Oxygen Proton Electron instrument measurements, integrated over different energy ranges.

Rastätter, Lutz↗
NASA NTRS2017

Long-Lived In-Situ Solar System Explorer (LLISSE)

Venus, while having similar size, mass, and location in the solar system to Earth, varies from Earth in many ways. The differences include its climate, atmosphere, and surface conditions. Surface conditions present formidable engineering challenges due to the high temperature and pressure. To date, landed missions have not been able to last more than about 2 hours on the surface [1]. This has resulted in significant knowledge gaps about the surface conditions of this important body in the solar system. The science community has effectively no in-situ temporal data on Venus surface conditions (temperature, pressure, winds and chemistry). These data are critical for the development of a thorough understanding of Venus' weather and the processes by which chemical species interact with each other, and are transported throughout the atmospheric column. This will help understand aspects of the atmosphere/planet interactions such as momentum exchange. To date, no capability has been available to enable a long lived surface probe to make these kinds of measurements. However, recently developed Silicon Carbide based electronics, sensors, and other technologies have matured to a state where a simple, but powerful long-life scientific probe would be feasible for Venus. It is now possible to directly qualify the durability and functionality of these components in a simulated Venus surface environment and demonstrate the ability to return valuable scientific data.

Probe↗
NASA NTRS1975

An analysis of communications blackout for Pioneer Venus entry probes

Estimates of the maximum duration of communications blackout are presented for a proposed Pioneer Venus mission involving a multiprobe entry targeted to individual impact sites. Calculations of the inviscid flow about the probes have been made using both finite-rate chemistry and equilibrium chemistry computer codes. Equilibrium boundary-layer calculations including ablation are also presented both with and without the presence of alkali metal contaminants from the heat shield. Methods are described for estimating maximum electron density in the inviscid wake and the recirculation region at the base of the probes. The results presented provide a conservative basis for planning for storage and subsequent telemetry of data during the entry phase of the mission.

Grose, W. L.↗
NASA NTRS2014

The Comprehensive Inner Magnetosphere-Ionosphere Model

Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5-9 April 2010 and then compared our results with data from the Two Wide-angle Imaging Neutral-atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self-consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.

Inner Magnetosphere↗
NASA NTRS1976

The chemistry of some individual lunar soil agglutinates

The inquiry is centered on the composition of agglutinate glasses examined via microprobe techniques. The glass chemistry of the agglutinates is brought into relation with compositions of constituent detritus and bulk compositions of the parent soils, with recent reported results taken into cognizance. Electron microprobe analysis data were examined for possible chemical fractionation resulting from meteoritic impacts and formation of agglutinates in the lunar regolith; individual agglutinates from lunar soils 78222, 71061, and 60009 were probed. Differences between impact glasses and corresponding bulk soils were scrutinized. Agglutinate glass analyses tend to cluster near the bulk soil compositions. A slight enrichment in mafic elements in grand averages of the agglutinate clusters relative to the bulk soils was found. Evidence of total impact melts and minor partial shock melts is examined.

Gibbons, R. V.↗
NASA NTRS1998

Langmuir Probe Measurements in an Inductively Coupled GEC Reference Cell Plasma

Measurements of electron number density, electron temperature, and electron energy distribution function (EEDF) using a compensated Langmuir probe have been performed on an inductively (transformer ) coupled Gaseous Electronics Conference (GEC) reference cell plasma. The plasma source is operated with CH4, CF4, or their mixtures with argon. The effect of independently driving the electrode supporting the wafer on the probe data is studied. In particular, we find that the plasma structure depends on the phase in addition to the magnitude of the power coupled to the electrode relative to that of the transformer coil. The Langmuir probe is translated in a plane parallel to the electrode to investigate the spatial structure of the plasma. The probe data is also compared with fluid model predictions.

Ji, J. S.↗
NASA NTRS2012

Measurements and IRI Model Predictions During the Recent Solar Minimum

Cycle 23 was exceptional in that it lasted almost two years longer than its predecessors and in that it ended in an extended minimum period that proved all predictions wrong. Comparisons of the International Reference Ionosphere (IRI) with CHAMP and GRACE in-situ measurements of electron density during the minimum have revealed significant discrepancies at 400-500 km altitude. Our study investigates the causes for these discrepancies with the help of ionosonde and Planar Langmuir Probe (PLP) data from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. Our C/NOFS comparisons confirm the earlier CHAMP and GRACE results. But the ionosonde measurements of the F-peak plasma frequency (foF2) show generally good agreement throughout the whole solar cycle. At mid-latitude stations yearly averages of the data-model difference are within 10% and at low latitudes stations within 20%. The 60-70% differences found at 400-500 km altitude are not seen at the F peak. We will discuss how these seemingly contradicting results from the ionosonde and in situ data-model comparisons can be explained and which parameters need to be corrected in the IRI model.

Bilitza, Dieter↗
NASA NTRS1982

A determination of the current density in electron beams

Current gathering rotating probe techniques were used to examine the envelope shape and power density profile of electron beams used in electron beam welding devices. The electron power density contours which determine the shape of the weld vapor cavity, penetration, and local heat distribution were considered. A mathematical analysis consistent with a rotating probe technique necessary to determine the current density distribution (assumed symmetrically radial) in a cross-section of the beam is provided. An explanation of the experimental technique for obtaining data, a BASIC language computer program to determine the current density from the data, and a study indicating the level of confidence to be associated with results obtained are also provided. An example of the application of the analysis to some experimental electron beam data is included.

Beil, R. J.↗
NASA NTRS1978

Photon-scattering cross sections of H2 and He measured with synchrotron radiation

Total (elastic + inelastic) differential photon-scattering cross sections have been measured for H2 gas and for He, using an X-ray beam. Absolute measured cross sections agree with theory within the probable errors. Relative cross sections (normalized to theory at large S) agree to better than 1% with theoretical values calculated from wave functions that include the effect of electron-electron Coulomb correlation, but the data deviate significantly from theoretical independent-particle (e.g., Hartree-Fock) results. The ratios of measured absolute He cross sections to those of H2, at any given S, also agree to better than 1% with theoretical He-to-H2 cross-section ratios computed from correlated wave functions. It appears that photon scattering constitutes a very promising tool for probing electron correlation in light atoms and molecules. The degree of polarization of the synchrotron radiation beam has been measured by rotating the scattering plane about the beam axis; results are compared with theory.

Ice, G. E.↗
NASA NTRS1977

Photon scattering cross sections of H2 and He measured with synchrotron radiation

Total (elastic + inelastic) differential photon scattering cross sections have been measured for H2 gas and He, using an X-ray beam. Absolute measured cross sections agree with theory within the probable errors. Relative cross sections (normalized to theory at large S) agree to better than one percent with theoretical values calculated from wave functions that include the effect of electron-electron Coulomb correlation, but the data deviate significantly from theoretical independent-particle (e.g., Hartree-Fock) results. The ratios of measured absolute He cross sections to those of H2, at any given S, also agree to better than one percent with theoretical He-to-H2 cross-section ratios computed from correlated wave functions. It appears that photon scattering constitutes a very promising tool for probing electron correlation in light atoms and molecules.

Ice, G. E.↗
NASA NTRS2001

Plasma Reactor Modeling and Validation Experiments

Plasma processing is a key processing stop in integrated circuit manufacturing. Low pressure, high density plum reactors are widely used for etching and deposition. Inductively coupled plasma (ICP) source has become popular recently in many processing applications. In order to accelerate equipment and process design, an understanding of the physics and chemistry, particularly, plasma power coupling, plasma and processing uniformity and mechanism is important. This understanding is facilitated by comprehensive modeling and simulation as well as plasma diagnostics to provide the necessary data for model validation which are addressed in this presentation. We have developed a complete code for simulating an ICP reactor and the model consists of transport of electrons, ions, and neutrals, Poisson's equation, and Maxwell's equation along with gas flow and energy equations. Results will be presented for chlorine and fluorocarbon plasmas and compared with data from Langmuir probe, mass spectrometry and FTIR.

Meyyappan, M.↗
NASA NTRS2003

On the Utilization of In-flight Radiation-induced Performance Data and Anomaly Resolution of Commercial Off the Shelf (COTS) Electronics

This viewgraph presentation presents an overview of the use of in-flight science data to review the radiation effects on commercial off the shelf (COTS) electronics used in recent spacecraft missions. The authors review the hazards that the space radiation environment pose for spacecraft electronics. They specifically discuss long term effects such as total ionizing dose (TID) and short term effects like single particle events (SEE). The advantages of using COTS electronics despite not being radiation hardened are mentioned. The reasons cite for tracking in-flight performance of COTS electronics include: anomaly resolution, validate ground tests and environmental predictions and provide lessons for future designers. Sample radiation impacts of science data from the following missions are analyzed: SOHO/LASCO 3 Coronograph, Microwave Anisotrophy Probe, Hubble Space Telescope and Chandra X-Ray Observatory.

Kenneth A. LeBel↗
NASA NTRS1979

The near-wake structure of the Atmosphere Explorer C /AE-C/ satellite - A parametric investigation

Measurements of ion current, electron temperature, and values of space potential obtained from the cylindrical electrostatic probe on board the Atmosphere Explorer C (AE-C) satellite were used to examine, in a parametric manner, the angular distribution of charge around the satellite. Interest is focused on nighttime equatorial data in the altitude range 275-620 km, which yields a wide range for the parameter R sub D (the radius of the satellite divided by the ambient value of the Debye lengths), including R sub D greater than 100, which is of practical significance to large space platforms. The variations of normalized ion current in the wake zone of the AE-C satellite appear to display an exponential dependence on R sub D for 'constant' values of other relevant parameters. The angular variations of electron temperature and space potential in the close vicinity of the satellite's surface were examined and compared with results from the Explorer 31 satellite. The variation of the ratio of measured to computed space potential with electron temperature was examined using data from both the AE-C and Explorer 31 satellites. It was found that the ratio is greater than unity. Possible causes for the above inequality are discussed.

Samir, U.↗
NASA NTRS1992

Observations of the structure and vertical transport of the polar upper ionosphere with the EISCAT VHF radar. II - First investigations of the topside O(+) and H(+) vertical ion flows

EISCAT VHF radar was used to investigate the vertical flows of H(+) and O(+) ions in the topside high-latitude ionosphere. The radar transmitted a single long pulse to probe the ionosphere from 300 to 1200 km altitude. A calculation scheme is developed to deduce the H(+) drift velocity from the coupled momentum equations of H(+), O(+), and the electrons, using the radar data and a neutral atmosphere model. The H(+) vertical drift velocity was expressed as a linear combination of the different forces acting on the plasma. Two nights, one very quiet, one with moderate magnetic activity, were used to test the technique and to provide a first study of the morphology and orders of magnitudes of ion outflow fluxes over Tromso. O(+) vertical flows were found to be downward or close to zero most of the time in the topside ionosphere; they appeared to be strongly correlated with magnetic activity during the disturbed night. H(+) topside ion fluxes were always directed upward, with velocity reaching 500-1000 m/s. A permanent outflow of H(+) ions is inferred.

Wu, Jian↗
NASA NTRS1985

Absolute electron density measurements in the equatorial ionosphere

Accurate measurement of the electron density profile and its variations is crucial to further progress in understanding the physics of the disturbed equatorial ionosphere. To accomplish this, a plasma frequency probe was included in the payload complement of two rockets flown during the Condor rocket campaign conducted from Peru in March 1983. This paper presents density profiles of the disturbed equatorial ionosphere from a night-time flight in which spread-F conditions were present and from a day-time flight during strong electrojet conditions. Results from both flights are in excellent agreement with simultaneous radar data in that the regions of highly disturbed plasma coincide with the radar signatures. The spread-F rocket penetrated a topside depletion during both the upleg and downleg. The electrojet measurements showed a profile peaking at 1.3 x 10 to the 5th per cu cm at 106 km, with large scale fluctuations having amplitudes of roughly 10 percent seen only in the upward gradient in electron density. This is in agreement with plasma instability theory. It is further shown that simultaneous measurements by fixed-bias Langmuir probes, when normalized at a single point to the altitude profile of electron density, are inadequate to correctly parameterize the observed enhancements and depletions.

Baker, K. D.↗
NASA NTRSDate not supplied

Additional Trials & Tribulations in Synthesizing a Sulfide Standard

Well-characterized sulfide reference materials that can serve as matrix-matched calibrants for in-situ trace element analyses via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remain elusive. Here, we describe the creation an in-house sulfide standard at NASA JSC that will be used to measure siderophile and chalcophile trace elements in low pressure experimental products, specifically pentlandite ([FeNi]9S8) and pyrrhotite ([FeNi]1-xS), as well as natural sulfides in terrestrial and meteoritic mineral assemblages. Recent methods in creating a homogenous sulfide standard include pressed pellets, synthesized chips, or fused glass [e.g. 1-3]. Other studies, however, have had success in forming homogenous FeS standards via synthesization methods [e.g. 4-6]. We present a variation of the method described in [4], in which we create a pyrrhotite standard doped with a variety of trace elements (Zn, As, Se, Mo, Ru, Rh, Pd, Sn, Sb, Te, W, Os, Ir, Pt, Au) at ~10-40 ppm and Cu at ~200 ppm. Sulfide compositions were constructed using Fe and Ni metal and elemental sulfur powders. Trace elements were added to elemental sulfur from Atomic Absorption Spectroscopy (AAS) elemental standards as either nitrate or chloride solutions to prevent oxidation of the metal powders. The dried sulfur mixture was mixed with Fe and Ni powders and mechanically mixed before two aliquots were placed in separate SiO2 tubes. Each tube was held under vacuum for ~30 minutes, sealed under vacuum, and then heated at 800C for 48 hours. Like [4], the synthesis products were composed of pourous sulfide crystals. Major element analyses of both experimental aliquots, collected using an Electron Probe Microanalyser (EPMA), yield indistinguishable major element compositions (uncertainties in 2SE & 2RSE[%]), with an average of 57.90  0.09 (0.16 %), 4.95  0.03 (0.55 %), and 39.70  0.14 (0.34 %), for Fe, Ni, and S, respectively. Trace element data were measured using a Photon Machines 193nm laser ablation system coupled to a Thermo-Scientific Element-XR ICP-MS. Spot sizes were limited to 50 μm due to the porous nature of the sulfide target material. Trace element abundances, normalized to Fe as an internal standard, were also found to be homogenous between the two aliquots, with weighted mean 2RSE (%) values of <3.0 for all trace elements. Synthesized products were re-powdered and absolute concentrations measured via solution ICP-MS. Although the sulfide appears to be homogenous, sintering experiments will be performed to more closely match the standard density to natural sulfides and minimize differences in ablation behavior. Improved density also allows for higher sensitivity (i.e. more compact target material) and larger spot sizes or traverses, as void space is eliminated. Additional major and trace element analyses on the products of the sintering experiments will be undertaken.

Jacob B Setera↗
NASA NTRS2019

Behavior of Triple Langmuir Probes in Non-Equilibrium Plasmas

A model of current collection in Langmuir probes is used to investigate the effect representative non- equilibrium plasmas under various conditions have on the electron temperature and number density that would be calculated through analysis of the probe collection characteristics. The model uses the distribution function to calculate the charged particle flux to a probe and then, for fixed applied voltages, the current values that satisfy continuity in the probes are determined. The triple probe is not scanned in voltage, so there is no practical way using experimental triple probe data to determine if the plasma is in equilibrium. As a consequence, a triple probe analysis typically relies on the assumption that the plasma is in equilibrium. Proceeding from this point, the numerically-generated non-equilibrium triple probe data are analyzed assuming that the plasma is in equilibrium, with the data compared to the initial distribution function inputs of plasma temperature and number density to determine the effect the non-equilibrium distribution has on plasma measurements. The temperature and number density are both significantly affected when a fraction of the particles in the distribution are shifted from the equilibrium configuration into the non-equilibrium part of the distribution function. For all instances studied, the computed electron temperature and number density are extremely sensitive to small deviations from equilibrium ( ≤ 5% of the plasma shifted into the non-equilibrium function). Shifting more of the plasma into the non-equilibrium distribution beyond this initial level does not produce a significant additional shift in the computed plasma properties.

Polzin, Kurt A.↗
NASA NTRS1995

Probing the Solar Corona with Radio Ranging Measurements

An asymmetry in the radial variation of electron density above the east and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. These older data are compared with white- light coronagraph measurements of the underlying corona collected by the Mark III K-coronameter at the Mauna Loa Solar Observatory.

solar corona Voyager coronameter coronagraph radio↗