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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Computer Code for Nanostructure Simulation

Due to their small size, nanostructures can have stress and thermal gradients that are larger than any macroscopic analogue. These gradients can lead to specific regions that are susceptible to failure via processes such as plastic deformation by dislocation emission, chemical debonding, and interfacial alloying. A program has been developed that rigorously simulates and predicts optoelectronic properties of nanostructures of virtually any geometrical complexity and material composition. It can be used in simulations of energy level structure, wave functions, density of states of spatially configured phonon-coupled electrons, excitons in quantum dots, quantum rings, quantum ring complexes, and more. The code can be used to calculate stress distributions and thermal transport properties for a variety of nanostructures and interfaces, transport and scattering at nanoscale interfaces and surfaces under various stress states, and alloy compositional gradients. The code allows users to perform modeling of charge transport processes through quantum-dot (QD) arrays as functions of inter-dot distance, array order versus disorder, QD orientation, shape, size, and chemical composition for applications in photovoltaics and physical properties of QD-based biochemical sensors. The code can be used to study the hot exciton formation/relation dynamics in arrays of QDs of different shapes and sizes at different temperatures. It also can be used to understand the relation among the deposition parameters and inherent stresses, strain deformation, heat flow, and failure of nanostructures.

Filikhin, Igor↗
NASA NTRS1986

Ion composition and dynamics at comet Halley

The Giotto space probe's ion mass spectrometer has obtained data on the composition and velocity distributions of cometary ions at distances of between 7.5 million and 1300 km from the comet Halley nucleus. Solar wind He(2+) was found throughout the coma, as close as 5000 km, with the He(+) produced by charge exchange being within about 200,000 km. A pile-up of heavy cometary ions was found at about 10,000 km from the nucleus. Inside the contact surface, which was found at about 4600 km, ion temperatures as low as about 340 K and outflow velocities of about 1 km/sec were found.

Balsiger, H.↗
NASA NTRS2006

New Software for Predicting Charging of Spacecraft

Charging System Analyzer Program (Nascap-2K) is a comprehensive update, revision, and extension of several NASA and Air Force codes for predicting electrical charging of spacecraft. Nascap-2K integrates the capabilities and models included in four independent programs: NASCAP/LEO for low-Earth orbits, NASCAP/GEO for geosynchronous orbits, POLAR for auroral charging in polar orbits, and DynaPAC (Dynamic Plasma Analysis Code) for time-dependent plasma interactions. While each of the earlier codes works well for the range of problems for which it was designed, by today s standards these codes are difficult to learn, cumbersome to use, and overly restrictive in their geometric modeling capabilities. Nascap-2K incorporates these models into a single software package that includes spacecraft surface modeling, spatial gridding, environmental specifications, calculating scripting, and post-processing analysis and visualization. The provided material properties database includes values from earlier programs as well as values from recent measurements. Development of Nascap-2K continues with future capabilities to include interactions with dense plasma such as those produced by electric propulsion.

Mandell, Myron↗
NASA NTRSDate not supplied

Electrostatic Regolith Interaction Experiment (ERIE) Electrometer Initial Flight Results

The Electrostatic Regolith Interaction Experiment (ERIE) is a suborbital flight payload studying electrostatically charged dust particle dynamics under microgravity, jointly developed by University of Central Florida (UCF) and NASA Kennedy Space Center (KSC). ERIE combines components from two systems, the COLLisions Into Dust Experiment (COLLIDE) from UCF and the Wheel Electrostatic Spectrometer (WES) from NASA KSC, to advance understanding of charged grain behavior on low gravity bodies such as the Moon and asteroids. ERIE slides a door containing an electrometer system monitoring various insulating disks across the surface of a regolith simulant bed. The experiment is activated when the payload enters the microgravity potion of the flight. The grains in the simulant bed tribocharge via agitation during launch as well as through frictional interactions with the door and its protruding insulators. As the retention door retracts, particles are allowed to loft into an open volume, achieving motion due to electrostatic repulsion. The electrometer system measures the charge transfer between the granular material and the insulators. As the charged grains exit the bed, they travel through an applied electric field and a camera observes the kinematics of the individual grains whose trajectories are determined by their net charges. The design of the ERIE electrometer instrument and initial results from the first flight was presented at the 2021 AGU Fall Meeting under P55E-2002. Shortly after microgravity was achieved and the retaining door began to open, the rate of charge acquisition measured by the electrometer increased, indicating the insulators were accumulating triboelectric charge. Charged grains were observed in the video data to traverse across the external electric field and become deflected from a linear path due to their charges. Pairs of grains were also observed to orbit one another as expected from two oppositely charged bodies in proximity to one another. Improvements to the design of the instrument and preliminary results obtained from the second flight scheduled for Q3 2022 will be presented at this meeting.

Electrostatics↗
NASA NTRSDate not supplied

Electrostatic Regolith Interaction Experiment (ERIE) Electrometer Initial Flight Results

The Electrostatic Regolith Interaction Experiment (ERIE) is a suborbital flight payload studying electrostatically charged dust particle dynamics under microgravity, jointly developed by University of Central Florida (UCF) and NASA Kennedy Space Center (KSC). ERIE combines components from two systems, the COLLisions Into Dust Experiment (COLLIDE) from UCF and the Wheel Electrostatic Spectrometer (WES) from NASA KSC, to advance understanding of charged grain behavior on low gravity bodies such as the Moon and asteroids. ERIE slides a door containing an electrometer system monitoring various insulating disks across the surface of a regolith simulant bed. The experiment is activated when the payload enters the microgravity potion of the flight. The grains in the simulant bed tribocharge via agitation during launch as well as through frictional interactions with the door and its protruding insulators. As the retention door retracts, particles are allowed to loft into an open volume, achieving motion due to electrostatic repulsion. The electrometer system measures the charge transfer between the granular material and the insulators. As the charged grains exit the bed, they travel through an applied electric field and a camera observes the kinematics of the individual grains whose trajectories are determined by their net charges. The design of the ERIE electrometer instrument and initial results from the first flight was presented at the 2021 AGU Fall Meeting under P55E-2002. Shortly after microgravity was achieved and the retaining door began to open, the rate of charge acquisition measured by the electrometer increased, indicating the insulators were accumulating triboelectric charge. Charged grains were observed in the video data to traverse across the external electric field and become deflected from a linear path due to their charges. Pairs of grains were also observed to orbit one another as expected from two oppositely charged bodies in proximity to one another. Improvements to the design of the instrument and preliminary results obtained from the second flight scheduled for Q3 2022 will be presented at this meeting.

Electrostatics↗
NASA NTRS1999

Integrated Dual Imaging Detector

A new type of image detector was designed to simultaneously analyze the polarization of light at all picture elements in a scene. The integrated Dual Imaging detector (IDID) consists of a lenslet array and a polarizing beamsplitter bonded to a commercial charge coupled device (CCD). The IDID simplifies the design and operation of solar vector magnetographs and the imaging polarimeters and spectroscopic imagers used, for example, in atmosphere and solar research. When used in a solar telescope, the vector magnetic fields on the solar surface. Other applications include environmental monitoring, robot vision, and medical diagnoses (through the eye). Innovations in the IDID include (1) two interleaved imaging arrays (one for each polarization plane); (2) large dynamic range (well depth of 10(exp 5) electrons per pixel); (3) simultaneous readout and display of both images; and (4) laptop computer signal processing to produce polarization maps in field situations.

Rust, David M.↗
NASA NTRS1995

Dynamic interactions between ionospheric plasma and spacecraft

Studies of the interactions between the Space Station Freedom and ionospheric plasma led to an improved understanding of the dynamics of these interactions. Some of the issues related to developing and sustaining arcs in ionospheric conditions are considered. A technique for the estimation of the amplitude and duration of arcs is presented. The technique uses the capacitance of the system to estimate the peak current and then uses the charge stored to estimate the arc duration. As new technologies are implemented on spacecraft, new environmental compatibility issues will arise. Some of the issues related to driving dielectric surfaces with alternating current voltages are considered. The steady state charging criteria is that over an oscillation, the ion charge collected is compensated for by the electron charge collected. This tends to drive the average potential negative so that the dielectric surface is positive for only a small portion of the cycle.

Snyder, David B.↗
NASA NTRS1994

Empirical models of the magnetospheric magnetic field

A general overview of magnetospheric modeling is given, along with a more detailed discussion of several empirical models which are widely used. These models are composed of representations of the Earth's main internal field (basically a bipolar field), plus external field contributions due to ring currents (carried by the particles in the Van Allen radiation belts), magnetopause currents (the boundary surface between the Earth's magnetic field and interplanetary magnetic field carried by the solar wind), and tail currents (carried by particles in the neutral sheet of the magnetotail). The empirical models presented here are the Mead-Fairfield, Olsen-Pfitzer tilt-dependent (1977), Tsyganenko-Usamo, Tsyganenko (1987), Olsen-Pfitzer dynamic (1988), Tsyganenko (1989), and Hilmer-Voight models. The derivations, agreement with quiet time and storm time data from the two satellite programs, Spacecraft Charging at High Altitudes (SCATHA) and Combined Release Radiation Effects Satellite (CRRES), and computational requirements of these models are compared.

Jordan, C. E.↗
NASA NTRS1994

Powder agglomeration in a microgravity environment

This is the final report for NASA Grant NAG3-755 entitled 'Powder Agglomeration in a Microgravity Environment.' The research program included both two types of numerical models and two types of experiments. The numerical modeling included the use of Monte Carlo type simulations of agglomerate growth including hydrodynamic screening and molecular dynamics type simulations of the rearrangement of particles within an agglomerate under a gravitational field. Experiments included direct observation of the agglomeration of submicron alumina and indirect observation, using small angle light scattering, of the agglomeration of colloidal silica and aluminum monohydroxide. In the former class of experiments, the powders were constrained to move on a two-dimensional surface oriented to minimize the effect of gravity. In the latter, some experiments involved mixture of suspensions containing particles of opposite charge which resulted in agglomeration on a very short time scale relative to settling under gravity.

Cawley, James D.↗
NASA NTRS1990

Modelling of piezoelectric actuator dynamics for active structural control

The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelectric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.

Hagood, Nesbitt W.↗
NASA NTRS1977

Time delay and integration array (TDI) using charge transfer device technology. Phase 2, volume 1: Technical

The 20x9 TDI array was developed to meet the LANDSAT Thematic Mapper Requirements. This array is based upon a self-aligned, transparent gate, buried channel process. The process features: (1) buried channel, four phase, overlapping gate CCD's for high transfer efficiency without fat zero; (2) self-aligned transistors to minimize clock feedthrough and parasitic capacitance; and (3) transparent tin oxide electrode for high quantum efficiency with front surface irradiation. The requirements placed on the array and the performance achieved are summarized. This data is the result of flat field measurements only, no imaging or dynamic target measurements were made during this program. Measurements were performed with two different test stands. The bench test equipment fabricated for this program operated at the 8 micro sec line time and employed simple sampling of the gated MOSFET output video signal. The second stand employed Correlated Doubled Sampling (CDS) and operated at 79.2 micro sec line time.

Source record↗
NASA NTRS1983

A dynamic model of thundercloud electric fields

A description is given of the first results obtained with a new type of dynamic electrical model of a thundercloud that allows the charge rearrangement produced in arc breakdown, as well as the conduction and displacement currents, to be calculated with realistic generator configurations. The model demonstrates the great complexity of behavior of thunderclouds owing to the interaction of the nonlinear breakdown mechanisms, the energy stored in the electric field, and a conductivity that varies with altitude. It is also seen that dynamic charge distributions and electric fields are quite different from static distributions. It is noted that these differences affect the initial conditions before and after lightning strokes. The conduction current density to the ionosphere is very much larger in the dynamic cases than in static simulations. Such basic properties of thunderclouds as the production of cloud-to-ground strokes are seen as compatible only with a very limited range of thundercloud models. Another finding is that coronal and convection currents cause the electric fields at the surface to be much smaller than they would be in their absence.

Nisbet, J. S.↗
NASA NTRS1997

Lunar and Planetary Science XXVIII

The present conference discusses such topics as density crossovers in lunar picrites, the geology of the Cassini impact basin, Mars, nanobacteria in carbonates, the properties of shocked aerogels, a chemical model of Comet Halley, lunar mascons, the impact evolution of icy regoliths, the geology of the Venera 8 landing site, the photogeologic mapping of northern Venus, HST observations of Mars, observational constraints on the rotational dynamics of Mars, and primordial magnetic field measurements from the moon. Also discussed are models of the S2 fluorescence spectra of comets, Martian crater ejecta, the heights of Venusian steep-sided domes, cloud-climate interactions on Venus, the Humorum basin geology from Clementine data, an early Amazonian lake in the Gale crater of Mars, nebular fractionations and Mn-Cr systematics, the Rock Chipper planetary surface sample collection, Mariner 10 stereo images of Mercury, remote and local stresses and Calderas on Mars, the electrostatic charging of saltating particles, SO2 detected on Callisto, the Mars Explorer Planetary Data System, an assessment of explosive venting on Europa, the sequential faulting history of the Mars Valles Marineris, a search for Martian sediments, the composition and internal structure of Europa, long-term and 'diurnal' tidal stresses on Europa, and episodic greenhouse climates on Mars.

Source record↗
NASA NTRS1985

Dynamics of the earth's ring current - Theory and observation

The development of currents within an arbitrary distribution of particles trapped in the geomagnetic field is described. These currents combine to form the earth's ring current and thus are responsible for the worldwide depressions of surface magnetic field strength during periods of magnetic activity known as magnetic storms. Following a brief review of trapped particle motion in magnetic fields, ring current development is described and presented in terms of basic field and particle distribution parameters. Experimental observations then are presented and discussed within the theoretical framework developed earlier. New results are presented which, in the area of composition and charge state observations, hold high promise in solving many long standing ring current problems. Finally, available experimental results will be used to assess the present understanding as to ring current sources, generation, and dissipation.

Williams, D. J.↗
NASA NTRS1996

The 29 July 1994 Merritt Island, Fl Microburst: A Case Study Intercomparing Kennedy Space Center Three-Dimensional Lightning Data (LDAR) and WSR-88D Radar Data

Many researchers have shown that the development and evolution of electrical discharges within convective clouds is fundamentally related to the growth and dynamics of precipitation particles aloft. In the presence of strong updrafts above the freezing level collisions among mixed-phase particles (i.e., hail. ice, supercooled water) promote the necessary charge separation needed to initiate intra-cloud lightning. A precipitation core that descends below the freezing level is often accompanied by a change in the electrical structure of the cloud. Consequently, more Cloud-to-Ground (CG) than Intra-Cloud (IC) lightning flashes appear. Descending precipitation cores can also play a significant role in the evolution of mesoscale features at the surface (e.g., microbursts, downbursts) because of latent heat and mass loading effects of water and ice. For this reason, some believe that lightning and microbursts are fundamentally linked by the presence of ice particles in thunderstorms. Several radar and lightning studies of microburst thunderstorms from COHMEX in 1986 showed that the peak IC lightning systematically occurred ten minutes before the onset of a microburst. In contrast, most CG lightning occurred at the time of the microburst. Many of the preceding studies have been done using high-resolution research radars and experimental lightning detection systems in focused field projects. In addition, these studies could only determine the vertical origin or occurrence of IC lightning, and not a true three-dimensional representation. Currently, the WSR-88D radar system and a real-time, state-of-the-art lightning system (LDAR) at the Kennedy Space Center (KSC) in Florida provide an opportunity to extend these kinds of studies in a more meaningful operational setting.

Hoffert, Steven G.↗
NASA NTRS2017

Revision of Paschen's Law Relating to the ESD of Aerospace Vehicle Surfaces

The purpose of this work is to develop a version of Paschens law that takes into account the flow of ambient gas past electrode surfaces. Paschens law does not consider the flow of gas past an aerospace vehicle whose surfaces may be triboelectrically charged by dust or ice crystal impingement while traversing the atmosphere. The basic hypothesis of this work is that the number of electron-ion pairs created per unit distance between electrode surfaces is mitigated by the electron-ion pairs removed per unit distance by the flow of gas. The revised theoretical model must be a function of the mean velocity vxm of the ambient gas and reduce to Paschens law when the mean velocity is zero. A new theoretical formulation of Paschens law, taking into account the Mach number and compressible dynamic pressure, derived by the authors, will be discussed. This equation has been evaluated by wind tunnel experimentation. Initial data of the baseline wind tunnel experiments show results consistent with the hypothesis. This work may enhance the safety of aerospace vehicles through a redefinition of electrostatic launch commit criteria. It is also possible for new products, such as antistatic coatings, to be formulated based on this data.

discharge↗
NASA NTRS2017

Revision of Paschen's Law Relating to the ESD of Aerospace Vehicle Surfaces

The purpose of this work is to develop a version of Paschen's law that takes into account the flow of ambient gas past electrode surfaces. Paschen's law does not consider the flow of gas past an aerospace vehicle whose surfaces may be triboelectrically charged by dust or ice crystal impingement while traversing the atmosphere. The basic hypothesis of this work is that the number of electron-ion pairs created per unit distance between electrode surfaces is mitigated by the electron-ion pairs removed per unit distance by the flow of gas. The revised theoretical model must be a function of the mean velocity vxm of the ambient gas and reduce to Paschen's law when the mean velocity is zero. A new theoretical formulation of Paschen's law, taking into account the Mach number and compressible dynamic pressure, derived by the authors, will be discussed. This equation has been evaluated by wind tunnel experimentation. Initial data of the baseline wind tunnel experiments show results consistent with the hypothesis. This work may enhance the safety of aerospace vehicles through a redefinition of electrostatic launch commit criteria. It is also possible for new products, such as antistatic coatings, to be formulated based on this data.

electrostatic↗
NASA NTRS1987

Charged drop dynamics experiment using an electrostatic-acoustic hybrid system

The design and the performance of an electrostatic-acoustic hybrid system and its application to a charge drop rotation experiment are presented. This system can levitate a charged drop electrostatically and induce drop rotation or oscillation by imposing an acoustic torque or an oscillating acoustic pressure. Using this system, the equilibrium shapes and stability of a rotating charged drop were experimentally investigated. A 3 mm size water drop was rotated as a rigid body and its gyrostatic equilibrium shapes were observed. Families of axisymmetric shapes, two-lobed shapes, and eventual fissioning have been observed. With the assumption of 'effective surface tension' in which the surface charge simply modified the surface tension of neutral liquid, the results agree exceptionally well with the Brown and Scriven's (1980) prediction for uncharged drops.

Rhim, W. K.↗