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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Aerosol nucleation in the winter Arctic and Antarctic stratospheres

The formation rate of sulfuric-acid-water aerosol particles is calculated as a function of altitude for the conditions of the winter Arctic and Antarctic stratospheres. The theoretical results indicate that sulfate particle formation can occur in the polar winter stratosphere. Conditions for new particle formation are increasingly favorable as the altitude increases between 20 and 30 km because of the decrease in surface area of preexisting particles and increasing sulfuric-acid vapor supply. The theoretical predictions are consistent with observations of a high-altitude CN layer over Antarctica in the spring. Available vapor-pressure data indicate that ternary particles composed of sulfuric acid, nitric acid, and water are not thermodynamically stable under winter stratospheric conditions.

Hamill, Patrick↗
NASA NTRS2001

Auburn Micrometeoroid Impact Test Data Analysis

This presentation provides an overview and summary of micrometeoroid impact testing performed by Auburn University and an analysis of the test results. The testing at Auburn utilized existing facilities at Auburn to generate hypervelocity impacts into multiple layers of thin Kapton films representative of the NASA concept for the NGST sunshield. The test data consists of impactor particle mass and velocity, and for each film layer, the number and size of holes generated by the initial impact and resulting impact debris. The analysis consists of combining the test data with existing impact effects models and the micrometeoroid environment at the L2 operating location of NGST to predict sunshield degradation.

Perrygo, Charles↗
NASA NTRS1973

Evidence for confinement of low-energy cosmic rays ahead of interplanetary shock waves.

Short-lived (about 15 min), low-energy proton increases associated with the passage of interplanetary shock waves have been previously reported. In the present paper, we have examined in a fine time scale (about 1 min) the concurrent particle and magnetic field data, taken by detectors on Explorer 34, for four of these events. Our results further support the view that these impulsive events are due to confinement of the solar cosmic-ray particles in the region just ahead (about 1,000,000 km) of the advancing shock front.

Palmeira, R. A. R.↗
NASA NTRS1999

Predicting Slag Generation in Sub-Scale Test Motors Using a Neural Network

Generation of slag (aluminum oxide) is an important issue for the Reusable Solid Rocket Motor (RSRM). Thiokol performed testing to quantify the relationship between raw material variations and slag generation in solid propellants by testing sub-scale motors cast with propellant containing various combinations of aluminum fuel and ammonium perchlorate (AP) oxidizer particle sizes. The test data were analyzed using statistical methods and an artificial neural network. This paper primarily addresses the neural network results with some comparisons to the statistical results. The neural network showed that the particle sizes of both the aluminum and unground AP have a measurable effect on slag generation. The neural network analysis showed that aluminum particle size is the dominant driver in slag generation, about 40% more influential than AP. The network predictions of the amount of slag produced during firing of sub-scale motors were 16% better than the predictions of a statistically derived empirical equation. Another neural network successfully characterized the slag generated during full-scale motor tests. The success is attributable to the ability of neural networks to characterize multiple complex factors including interactions that affect slag generation.

Wiesenberg, Brent↗
NASA NTRS2003

A new dynamical atmospheric ionizing radiation (AIR) model for epidemiological studies

A new Atmospheric Ionizing Radiation (AIR) model is currently being developed for use in radiation dose evaluation in epidemiological studies targeted to atmospheric flight personnel such as civilian airlines crewmembers. The model will allow computing values for biologically relevant parameters, e.g. dose equivalent and effective dose, for individual flights from 1945. Each flight is described by its actual three dimensional flight profile, i.e. geographic coordinates and altitudes varying with time. Solar modulated primary particles are filtered with a new analytical fully angular dependent geomagnetic cut off rigidity model, as a function of latitude, longitude, arrival direction, altitude and time. The particle transport results have been obtained with a technique based on the three-dimensional Monte Carlo transport code FLUKA, with a special procedure to deal with HZE particles. Particle fluxes are transformed into dose-related quantities and then integrated all along the flight path to obtain the overall flight dose. Preliminary validations of the particle transport technique using data from the AIR Project ER-2 flight campaign of measurements are encouraging. Future efforts will deal with modeling of the effects of the aircraft structure as well as inclusion of solar particle events. Published by Elsevier Ltd on behalf of COSPAR.

Aviation↗
NASA NTRS1973

Energetic particle flux experiment (IMP F and G)

The data reduction procedures and programs for analysis of the IMP F and G energetic particle flux experiments are summarized. The IMP-F experiment contained two thin-window Geiger-Mueller detectors and an ionization chamber. There were two IMP-G experiments: one with six Geiger-Mueller detectors and an ionization chamber, and the other with two funnel mouthed channeltrons in a parallel plate electrostatic analyzer. These experiments measured particles in the energy range above 20 keV (IMP-F) and above approximately 5 keV (IMP-G). A bibliography is presented of papers containing the scientific results. These data were predominantly used for the study of low energy solar particles from flares.

Anderson, K. A.↗
NASA NTRS2019

Analysis of the Global Microwave Polarization Data of Clouds

Information about the characteristics of ice particles in clouds is necessary for improving our understanding of the states, processes, and subsequent modeling of clouds and precipitation for numerical weather prediction and climate analysis. Two NASA passive microwave radiometers, the satellite-borne Global Precipitation Measurement (GPM) Microwave Imager (GMI) and the aircraft-borne Conical Scanning Millimeter-Wave Imaging Radiometer (CoSMIR), measure vertically and horizontally polarized microwaves emitted by clouds (including precipitating particles) and Earth’s surface below. In this paper, GMI (or CoSMIR) data are analyzed with CloudSat (or aircraft-borne radar) data to find polarized difference (PD) signals not affected by the surface, thereby obtaining the information on ice particles. Statistical analysis of 4 years of GMI and CloudSat data, for the first time, reveals that optically thick clouds contribute positively to GMI PD at 166GHz over all the latitudes and their positive magnitude of 166-GHz GMI PD varies little with latitude. This result suggests that horizontally oriented ice crystals in thick clouds are common from the tropics to high latitudes, which contrasts the result of Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) that horizontally oriented ice crystals are rare in optically thin ice clouds.

Xiping Zeng↗
NASA NTRS1988

Observations of the plasma environment during an active ionospheric ion beam

This paper presents detailed data on positive ion flux observations acquired during an active rocket-borne ion beam injection experiment, using the hemispheric electrostatic energy and pitch angle spectrometer (HEEPS) which was separated from the beam-emitting payload by distances along and across geomagnetic field lines which varied systematically during the experiment. The data obtained by the HEEPS illustrate a number of outstanding features of the ion flux environment near the HEEPS instrument during beam operations, some of which are not understood. It is shown that particle, field, and photometric data support a picture of particularly intense beam-plasma interactions in the immediate vicinity of the beam-emitting payload.

Pollock, C. J.↗
NASA NTRS1974

Auroral displays near the 'foot' of the field line of the ATS-5 satellite

Summary of an extensive correlative study of ATS-5 particle and magnetic field data with all-sky photographs from Great Whale River which is near the 'foot' of the field lines passing through the ATS-5 satellite. In particular, an effort is made to identify specific particle features with specific auroral displays during substorms, such as a westward traveling surge, poleward expansive motion, and drifting patches. It is found that, in early evening hours, the first encounter of ATS-5 with hot plasma is associated with the equatorward shift of the diffuse aurora, but not necessarily with westward traveling surges (even when the satellite is embedded in the plasma sheet). In the midnight sector, an injection corresponds very well to the initial brightening of an auroral arc. Specific features of morning sector auroras are difficult to correlate with specific particle features.

Akasofu, S.-I.↗
NASA NTRS1972

Composition of the Venus cloud tops in light of recent spectroscopic data.

The observed chemical composition of the atmosphere near the Venus cloud tops, the refractive index of cloud particles as deduced from polarization data, and the 3-4-micron reflectivity of the clouds are discussed. The data are shown to be consistent with and to strongly support the possibility that the topmost clouds of Venus are composed of concentrated aqueous HCl solutions.

Lewis, J. S.↗
NASA NTRS1974

Further characteristics of the evening energetic electron decreases during substorms

Evaluation of the results of studying the evening energetic electron decreases observed at synchronous altitudes with the use of high-resolution data (25.6-sec averages). The high-resolution data show that the evening particle events sometimes undergo rapid time variations, faster than the 6-min time-averaged data previously used by Lezniak and Winckler (1970). Periodic structures of 2- to 12-min period often accompany the evening particle decreases. Interpretation of these observations in terms of enhanced plasma energy density at synchronous altitudes during substorms, as evidenced by DeForest and McIlwain (1971) and Sharp and Johnson (1972), suggests that such plasma regions are highly nonuniform and turbulent.

Lin, C. S.↗
NASA NTRS1999

Localized Ionospheric Particle Acceleration and Wave Acceleration of Auroral Ions: Amicist Data Set

Research supported by this grant covered two main topics: auroral ion acceleration from ELF-band wave activity, and from VLF-spikelet (lower hybrid solitary structure) wave activity. Recent auroral sounding rocket data illustrate the relative significance of various mechanisms for initiating auroral ion outflow. Two nightside mechanisms are shown in detail. The first mechanism is ion acceleration within lower hybrid solitary wave events. The new data from this two payload mission show clearly that: (1) these individual events are spatially localized to scales approximately 100 m wide perpendicular to B, in agreement with previous investigations of these structures, and (2) that the probability of occurrence of the events is greatest at times of maximum VLF wave intensity. The second mechanism is ion acceleration by broadband, low frequency electrostatic waves, observed in a 30 km wide region at the poleward edge of the arc. The ion fluxes from the two mechanisms are compared and it is shown that while lower hybrid solitary structures do indeed accelerate ions in regions of intense VLF waves, the outflow from the electrostatic ion wave acceleration region is dominant for the aurora investigated by this sounding rocket, AMICIST. The fluxes are shown to be consistent with DE-1 and Freja outflow measurements, indicating that the AMICIST observations show the low altitude, microphysical signatures of nightside auroral outflow. In this paper, we present a review of sounding rocket observations of the ion acceleration seen nightside auroral zone lower hybrid solitary structures. Observations from Topaz3, Amicist, and Phaze2 are presented on various spatial scales, including the two-point measurements of the Amicist mission. From this collection of observations, we will demonstrate the following characteristics of transverse ion acceleration (TAI) in LHSS. The ion acceleration process is narrowly confined to 90 degrees pitch angle, in spatially confined regions of up to a few hundred meters across B. The acceleration process does not affect the thermal core of the ambient distribution, and does not directly create a measurable effect on the ambient ion population outside the LHSS themselves. Within the LHSS region, it creates a high energy tail beginning at a few times the thermal ion speed. The ion acceleration events are closely associated with localized wave events. Accelerated ions bursts are also seen without a concurrent observation of a localized wave event, for two possible reasons. In some cases, the pitch angles of the accelerated tail ions are elevated above perpendicular; that is to say, the acceleration occurred below the observer and the mirror force has begun to act upon the distribution, moving it upward from the source. In other cases, the accelerated ion structure is spatially larger than the wave event structure, and the observation catches only the ion event. The occurrence rate of these ion acceleration events is related to the ambient environment in two ways: (1) its altitude dependence can be modelled with the parameter B(exp2)/n(sub e), (2) and it is highest in regions of intense VLF activity. The end result of this study of auroral ion acceleration processes is a manuscript entitled "Auroral Ion Acceleration from Lower Hybrid Solitary Structures: A Summary of Sounding Rocket Observations", by Lynch, Arnoldy, Kintner, Schuck, Bonnell, and Coffey. This manuscript has been submitted for publication to the Journal of Geophysical Research.

Lynch, Kristina A.↗
NASA NTRS2010

Composition Changes After the "Halloween" Solar Proton Event: The High-Energy Particle Precipitation in the Atmosphere (HEPPA) Model Versus MIPAS Data Intercomparison Study

We have compared composition changes of NO, NO2, H2O2,O3, N2O, HNO3 , N2O5, HNO4, ClO, HOCl, and ClONO2 as observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat in the aftermath of the "Halloween" solar proton event (SPE) in October/November 2003 at 25-0.01 hPa in the Northern hemisphere (40-90 N) and simulations performed by the following atmospheric models: the Bremen 2D model (B2dM) and Bremen 3D Chemical Transport Model (B3dCTM), the Central Aerological Observatory (CAO) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the ECHAM5/MESSY Atmospheric Chemistry (EMAC) model, the modeling tool for SO1ar Climate Ozone Links studies (SOCOL and SOCOLi), and the Whole Atmosphere Community Climate Model (WACCM4). The large number of participating models allowed for an evaluation of the overall ability of atmospheric models to reproduce observed atmospheric perturbations generated by SPEs, particularly with respect to NOS, and ozone changes. We have further assessed the meteorological conditions and their implications on the chemical response to the SPE in both the models and observations by comparing temperature and tracer (CH4 and CO) fields. Simulated SPE-induced ozone losses agree on average within 5% with the observations. Simulated NO(y) enhancements around 1 hPa, however, are typically 30% higher than indicated by the observations which can be partly attributed to an overestimation of simulated electron-induced ionization. The analysis of the observed and modeled NO(y) partitioning in the aftermath of the SPE has demonstrated the need to implement additional ion chemistry (HNO3 formation via ion-ion recombination and water cluster ions) into the chemical schemes. An overestimation of observed H2O2 enhancements by all models hints at an underestimation of the OH/HO2 ratio in the upper polar stratosphere during the SPE. The analysis of chlorine species perturbations has shown that the encountered differences between models and observations, particularly the underestimation of observed ClONO2 enhancements, are related to a smaller availability of ClO in the polar night region already before the SPE. In general, the intercomparison has demonstrated that differences in the meteorology and/or initial state of the atmosphere in the simulations causes a relevant variability of the model results, even on a short timescale of only a few days.

Funke, B.↗
NASA NTRS2012

Aerosol Remote Sensing from Space - Where We Stand, Where We're Heading

The MISR and MODIS instruments aboard the NASA Earth Observing System's Terra Satellite have been collecting data containing information about the state of Earth's atmosphere and surface for over twelve years. Among the retrieved quantities are the amount and type of wildfire smoke, desert dust, volcanic effluent, urban and industrial pollution particles, and other aerosols. Data from these instruments have been used to develop a global, monthly climatology of aerosol amount that is widely used as a constraint on climate models, including those used for the 2007 IPCC assessment report. However, the broad scientific challenges of understanding aerosol impacts on climate and health place different, and very exacting demands on our measurement capabilities. And these data sets, though much more advanced in many respects than previous aerosol data records, are imperfect. The next frontier in assessing aerosol radiative forcing of climate is aerosol type, and in particular, the absorption properties of major aerosol air masses. In this presentation, I will summarize current understanding of MISR and MODIS aerosol product strengths and limitations, discuss how they relate to the bigger aerosol science questions we must address, and give my view of the way forward.

Kahn, Ralph↗
NASA NTRS1999

Mars 2001 Mission: Addressing Scientific Questions Regarding the Characteristics and Origin of Local Bedrock and Soil

The Mars Surveyor Program 2001 Mission will carry instruments on the orbiter, lander and rover that will support synergistic observations and experiments to address important scientific questions regarding the local bedrock and soils. The martian surface is covered in varying degrees by fine materials less than a few mms in size. Viking and Pathfinder images of the surface indicate that soils at those sites are composed of fine particles. Wheel tracks from the Sojourner rover suggest that soil deposits are composed of particles <40 mm. Viking images show that dunes are common in many areas on Mars and new MOC images indicate that dunes occur nearly everywhere. Dunes on Mars are thought to be composed of 250-500 microns particles based upon Viking IRTM data and Mars wind tunnel experiments. If martian dunes are composed of sand particles > 100 microns and soils are dominated by <10 micron particles, then where are the intermediate grain sizes? Have they been wom away through prolonged transport over the eons? Were they never generated to begin with? Or are they simply less easy to identify because do they not form distinctive geomorphic features such as dunes or uniform mantles that tend to assume superposition in the soil structure?

Saunders, R. S.↗
NASA NTRS1995

Determining orbital particle parameters of impacts into germanium using morphology analysis and calibration data from hypervelocity impact experiments in the laboratory

This paper describes the work that is done at the Lehrstuhl fur Raumfahrttechnik (lrt) at the Technische Universitat Munchen to examine particle impacts into germanium surfaces which were flown on board the LDEF satellite. Besides the description of the processing of the samples, a brief overview of the particle launchers at our institute is given together with descriptions of impact morphology of high- and hypervelocity particles into germanium. Since germanium is a brittle, almost glass-like material, the impact morphology may also be interesting for anyone dealing with materials such as optics and solar cells. The main focus of our investigations is to learn about the impacting particle's properties, for example mass, velocity and direction. This is done by examining the morphology, various geometry parameters, crater obliqueness and crater volume.

Paul, Klaus G.↗
NASA NTRS2017

Conjunction Assessment Techniques and Operational Results from the Magnetospheric Multiscale Mission

This paper will describe the results that have been obtained to date during the MMS mission concerning conjunction assessment. MMS navigation makes use of a weak-signal GPS-based system: this allows signals to be received even when MMS is flying above the GPS orbits, producing a highly accurate determination of the four MMS orbits. This data is downlinked to the MMS Mission Operations Center (MOC) and used by the Flight Dynamics Operations Area (FDOA) for both maneuver design and conjunction assessment. The MMS fly in tetrahedron formations around apogee, in order to collect simultaneous particles and fields science data. The original plan was to fly tetrahedra between 10 and 160 km in size; however, after Phase 1a of the mission, the science team requested that smaller sizes be flown if feasible. After analysis (to be detailed in a companion paper), a new minimum size of 7 km was decided upon. Flying at this reduced scale size makes conjunction assessment between the MMS spacecraft even more important: the methods that are used by the MMS FDOA to address this problem will be described in the paper, and a summary given of the previous analyses that went into the development of these techniques. Details will also be given of operational experiences to date. Finally, two CA mitigation maneuver types that have been designed (but never yet required to actually be performed) will also be outlined.

conjunction Assessment↗