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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Multi-frame x-ray radiography and image tracking for quantification of expansion in laser-driven tin ejecta microjets

One regime of experimental particle-laden flow study involves ejecta microjets—often defined as a stream of micrometer-scale particles generated through shock interaction with a non-uniform surface and generally travel above 1 km/s. In order to capture the change in characteristics as a function of propagation time, we apply a multi-frame x-ray radiography platform to observe and track the jet transport dynamics. A synchrotron x-ray source allows us to perform quantitative analyses and comparisons between the eight images captured by the imaging system. Observation of a single jet through time allows the use of a cross correlation algorithm to independently track various regions within the jet and quantify the jet expansion over time using normalized area and normalized areal density values. Through a comparison with the calculated values of ballistic transport, these findings show less expansion than expected for ballistically transporting particles. In conclusion, this work combines multi-frame synchrotron radiography with image tracking to establish a foundation for future studies on jet transport and particle interaction dynamics.

Sun, Yuchen [Lawrence Livermore National Laborator↗
DOE OSTI2025

A review of low-rank methods for time-dependent kinetic simulations

Time-dependent kinetic models are ubiquitous in computational science and engineering. The underlying integro-differential equations in these models are high-dimensional, comprised of a six–dimensional phase space, making simulations of such phenomena extremely expensive. In this article we demonstrate that in many situations, the solution to kinetics problems lives on a low dimensional manifold that can be described by a low-rank matrix or tensor approximation. We then review the recent development of so-called low-rank methods that evolve the solution on this manifold. The two classes of methods we review are the dynamical low-rank (DLR) method, which derives differential equations for the low-rank factors, and a Step-and-Truncate (SAT) approach, which projects the solution onto the low-rank representation after each time step. Thorough discussions of time integrators, tensor decompositions, and method properties such as structure preservation and computational efficiency are included. We further show examples of low-rank methods as applied to particle transport and plasma dynamics.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1992

Correlation function ratios and the identification of space plasma instabilities

Wave-particle transport in a collisionless plasma is due to particle scattering by enhanced fluctuations associated with the growth of instabilities. In particular, relatively short wave-length kinetic instabilities are frequently invoked to explain many different types of plasma transport in space. Although there is an extensive theoretical and simulation literature describing the potential applications of many such instabilities, there are only a few cases of clear-cut identification of kinetic modes in space. The research described in this paper uses linear Vlasov dispersion theory to study correlation functions and dimensionless correlation function ratios for fluctuations or instabilities in three space plasma regimes. This research shows that both the compressibility and the parallel compressibility are likely to be useful in distinguishing modes in the magnetosheath as well as in the plasma sheet boundary layer and that helicity remains a useful identifier of electromagnetic ion/ion instabilities in the foreshock.

Gary, S. P.↗
NASA NTRS1977

VLF transmission induced slot electron precipitation

A study is made of electrons in the drift and bounce loss cones of the magnetospheric slot region. It is observed that discrete events account for the arrival of most electrons in the 100-400 keV range into the drift loss cone. Most such events originate from a high power level VLF transmitter. Calculations of the loss rate caused by the events indicate that the electron flux in the slot region may decrease by as much as 50% per day. It is likely that wave-particle interaction occurs low on the field line due to the particular particle energies and wave frequencies. In order to transport particles to the lower interaction region, additional near-equator scattering, via power-line harmonic emissions or ELF hiss, may be required.

Vampola, A. L.↗
NASA NTRS1999

Transport Through Higher Subbands of a Carbon Nanotube

The sub-band spacing can be comparable to the bias and kT in large diameter carbon nanotubes. As a result, the role of higher sub-bands cannot be neglected in transport. We discuss two interesting effects involving single particle transport such nanotubes: (i) The transmission probability of electrons at the crossing bands (around E=0) and higher sub-bands are quantitatively different. As a result, we show that the small bias resistance may be larger when the Fermi energy is away from the band center as opposed to being close to the band center. (ii) The primary contribution to current flowing in the presence of an applied bias is due to the crossing sub-bands. This is a result of the electron in the higher sub-bands undergoing Bragg reflection. As a consequence, in an idealized case where scattering is neglected, the differential conductance cannot be much larger than 4e(2)/h.

Anantram, M.P.↗
NASA NTRS2009

Algorithm for Computing Particle/Surface Interactions

An algorithm has been devised for predicting the behaviors of sparsely spatially distributed particles impinging on a solid surface in a rarefied atmosphere. Under the stated conditions, prior particle-transport models in which (1) dense distributions of particles are treated as continuum fluids; or (2) sparse distributions of particles are considered to be suspended in and to diffuse through fluid streams are not valid.

Hughes, David W.↗
NASA NTRS1990

Large-scale patterns of eolian sediment transport on Venus - Predictions for Magellan

The atmosphere of Venus is likely to exert a major influence on the surface. Arecibo and Venera 15/16 observations of the population of impact craters with bright halos give direct evidence of surface modification, on the scale of centimeters, to smooth the surface on time scales of 50 - 250 my. Both chemical and mechanical modifications probably occur. Diurnal winds in the planetary boundary layer can transport particles. Using boundary layer theory, including the effects of topography, surface stresses and resulting transport and deposition of sand-size particles are calculated. Regional slopes are sites of largest surface stresses. Sand will be generally transported downhill, although there is a preferential net transport from east to west, in the same direction as the atmospheric superrotation. It is predicted here that streaks may be seen in the Magellan radar images which will indicate directions of net eolian transport on the surface of Venus.

Saunders, R. S.↗
NASA NTRS1985

Numerical and analytic descriptions of cosmic-ray transport

It is not trivial to solve the equations that describe charged particle transport with the aid of computers, for instabilities, inaccuracies, and subtle artifacts are well known afflictions of numerical analysis. Two specific points are discussed. First to avoid inaccuracies, pitch angle scattering must be treated with great care. In particular, slightly inappropriate numerical formulations give rise to mean free paths that are in error by large factors. Secondly, A previously unrecognized artifact, numerical dispersion, is very similar to the physical phenomenon of dispersion. To avoid misinterpretations arising from this similarity, the spatial increment of the finite difference grid must be a small fraction of the mean free path. These points are illustrated by calculations based upon finite difference approximations to the transport equation.

Earl, J. A.↗
NASA NTRS1985

Plasma-gas interactions studies in a hybrid plume plasma rocket

Plasma-gas interaction was investigated and the basic mechanisms for energy and particle transport. The solution approach assumes cylindrical geometry and includes a multiplicity of atomic reactions, and the presence of a strong magnetic field is described. The principal reactions are electron and ion impact ionization, and charge exchange between hot ions and cold neutrals. Radial particle and energy transport is mainly by diffusion. A modified Bohm diffusion model for plasma in the core of the plume, and classical neutral particle diffusion in the cooler regions of the flow are presented. Neutrals are allowed to free stream in the low density regions, where the collision mean-free-path becomes comparable, or even larger than the characteristic dimensions of the system.

Chang, F. R.↗
NASA NTRS1985

Numerical modeling of the hybrid plume plasma rocket

This paper reports on ongoing research in the area of numerical simulations of hybrid plume dynamics, and describes the basic mechanisms for energy and particle transport. The solution approach assumes cylindrical geometry and includes a multiplicity of atomic reactions, as well as the presence of a strong magnetic field. The principal reactions are electron impact ionization, and resonant charge exchange between hot ions and cold neutrals. Radial particle and energy transport is mainly by diffusion. The present description includes a modified Bohm diffusion model for plasma in the core of the plume, and classical neutral particle diffusion in the cooler regions of the flow. Neutrals are allowed to 'free stream' in the low density regions, where the collision mean-free-path becomes comparable, or even larger than the characteristic dimensions of the system. A parameteric scan of the various regimes of interest has been completed and the most significant results are presented.

Chang, F. R.↗
NASA NTRS1994

A unifying comparison of nearly scatter free transport models

Gombosi et al. (1993) recently derived a modified telegrapher's equation for charged particle transport under the influence of isotropic scattering. This equation obeys causality and disallows upstream diffusion for particles with random velocities smaller than the bulk flow velocity. The acausal diffusion equation was obtained to lowest order in the expansion of smallness prameters. The paper by Gombosi et al. (1993) prompted responses from Pauls et al. (1993) and Earl (1993). This paper is written to explain the differences between the methods, assumptions, and results of Gombosi et al. (1993), Pauls et al. (1993), and Earl (1993) and presents a new method of obtaining approximate solutions. It is shown that the assumptions used by Gombosi et al. (1993) and Pauls et al. (1993) are physically equivalent. In our solution method, the solution of the modified telegrapher's equation is obtained as the casual limit of solutions accurate to second order in the smallness parameter expansion. In order to investigate the coherent velocity, we have also developed `wavenumber eigenfunctions' which account for all the pitch angle dependence in our Boltzmann equation. Using truncation, Earl (1993) obtains approximations for the wavenumber dependence of the lowest two frequency modes, which correspond to two of the wavenumber eigenmodes. We find that a consequence of including only two wavenumber eigenmodes is that one obtains solutions which disobey causality at sufficiently short times. Furthermore, the coherent velocity of the two eigenmodes is strongly dependent on wavenumber and approaches the particle velocity in the limit of large wavenumber for both isotropic and anisotropic scattering processes. We conclude that Earl's (1993) solutions and solutions obtained using the new solution method implicitly assume weak acausality and reasonable behavior in the temporal regime, t less than 4 tau. The solutions are not strictly consistent with the behavior of the lowest two frequency modes but have similar behavior in the regime of low wavenumber.

Schwadron, N. A.↗
NASA NTRS2011

A Deterministic Electron, Photon, Proton and Heavy Ion Radiation Transport Suite for the Study of the Jovian System

A deterministic suite of radiation transport codes, developed at NASA Langley Research Center (LaRC), which describe the transport of electrons, photons, protons, and heavy ions in condensed media is used to simulate exposures from spectral distributions typical of electrons, protons and carbon-oxygen-sulfur (C-O-S) trapped heavy ions in the Jovian radiation environment. The particle transport suite consists of a coupled electron and photon deterministic transport algorithm (CEPTRN) and a coupled light particle and heavy ion deterministic transport algorithm (HZETRN). The primary purpose for the development of the transport suite is to provide a means for the spacecraft design community to rapidly perform numerous repetitive calculations essential for electron, proton and heavy ion radiation exposure assessments in complex space structures. In this paper, the radiation environment of the Galilean satellite Europa is used as a representative boundary condition to show the capabilities of the transport suite. While the transport suite can directly access the output electron spectra of the Jovian environment as generated by the Jet Propulsion Laboratory (JPL) Galileo Interim Radiation Electron (GIRE) model of 2003; for the sake of relevance to the upcoming Europa Jupiter System Mission (EJSM), the 105 days at Europa mission fluence energy spectra provided by JPL is used to produce the corresponding dose-depth curve in silicon behind an aluminum shield of 100 mils ( 0.7 g/sq cm). The transport suite can also accept ray-traced thickness files from a computer-aided design (CAD) package and calculate the total ionizing dose (TID) at a specific target point. In that regard, using a low-fidelity CAD model of the Galileo probe, the transport suite was verified by comparing with Monte Carlo (MC) simulations for orbits JOI--J35 of the Galileo extended mission (1996-2001). For the upcoming EJSM mission with a potential launch date of 2020, the transport suite is used to compute the traditional aluminum-silicon dose-depth calculation as a standard shield-target combination output, as well as the shielding response of high charge (Z) shields such as tantalum (Ta). Finally, a shield optimization algorithm is used to guide the instrument designer with the choice of graded-Z shield analysis.

Norman, Ryan B.↗
DOE OSTI2026

Measurement report: Role of organic coating and chemical composition on ice nucleation potential of atmospheric particles in European Arctic

Understanding the ice nucleation (IN) potential of Arctic aerosols is critical for predicting their influence on cloud formation and water cycles in this vulnerable region. This study investigates the role of particle composition, organic coatings, and aerosol sources in modulating ice nucleating particle (INPs) abundance across five aerosol samples collected at the Gruvebadet Observatory Station in Ny-Ålesund, Svalbard. The IN potential of Arctic aerosol particles was studied by investigating chemical, morphological, and INP abundance measurements. Single-particle analyses revealed distinct differences in mixing state, organic volume fraction (OVF), and organic coating morphology across samples. OVF distributions were linked to particle origin, with marine-influenced Na-rich particles often exhibiting thin organic coatings, while long-range transported particles showed thicker organic coatings. Biogenic contributions, though variable, were linked to heat-sensitive INPs, suggesting a role for labile biological macromolecules under certain meteorological conditions. Spearman rank correlation analysis between particle composition and immersion-mode INP concentrations at two freezing temperatures indicated that organic-rich and Na-rich particles were positively associated with enhanced INP abundance. However, discrepancies in INP abundance were observed for particles with thicker organic coatings, where the morphological configuration of the organic material may play a role. The results highlight that Arctic INP variability is governed not only by chemical composition but also by the morphological configuration of organic material, which can either enhance or inhibit ice nucleation depending on its abundance, distribution, thickness, and mixing state. These findings underscore the combined influence of source regions, atmospheric processing, and organic–inorganic interactions in shaping Arctic aerosol freezing behavior.

Lata, Nurun Nahar [Pacific Northwest National Labo↗
NASA NTRS2006

Numerical and Analytical Model of an Electrodynamic Dust Shield for Solar Panels on Mars

Masuda and collaborators at the University of Tokyo developed a method to confine and transport particles called the electric curtain in which a series of parallel electrodes connected to an AC source generates a traveling wave that acts as a contactless conveyor. The curtain electrodes can be excited by a single-phase or a multi-phase AC voltage. A multi-phase curtain produces a non-uniform traveling wave that provides controlled transport of those particles [1-6]. Multi-phase electric curtains from two to six phases have been developed and studied by several research groups [7-9]. We have developed an Electrodynamic Dust Shield prototype using threephase AC voltage electrodes to remove dust from surfaces. The purpose of the modeling work presented here is to research and to better understand the physics governing the electrodynamic shield, as well as to advance and to support the experimental dust shield research.

Calle, C. I.↗
DOE OSTI2026

Final Technical Report for DoE award DE‐SC0023367 “Energetic Electron Transport in Magnetized Plasma with Magnetic Islands”

This project investigated how plasmas interact with energetic particles and solid materials under extreme conditions relevant to fusion energy, space plasmas, and planetary environments. Using experiments on the DIII-D National Fusion Facility, the research first examined how high-energy electrons move, become trapped, and are released in plasmas containing magnetic islands—structures commonly found in fusion reactors and Earth’s magnetosphere—providing new insight into particle transport and acceleration processes. The project also explored plasma-driven chemical reactions that can occur during meteoroid entry into planetary atmospheres, demonstrating that simple molecules such as ammonia can be produced and survive in high-temperature plasma conditions. Together, these results improve understanding of plasma behavior across laboratory, space, and planetary systems while informing fusion plasma control and plasma–material interaction studies. The project additionally contributed to workforce development by training graduate students, undergraduates, and early-career researchers and by disseminating results through peer-reviewed publications and international scientific conferences.

Orlov, Dmitri Mikhailovich [UC San Diego] (ORCID:0↗
NASA NTRS1994

Coherent pulses in the diffusive transport of charged particles`

We present exact solutions to the diffusive transport of charged particles following impulsive injection for a simple model of scattering. A modified, two-parameter relaxation-time model is considered that simulates the low rate of scattering through perpendicular pitch-angle. Scattering is taken to be isotropic within each of the foward- and backward-pointing hemispheres, respectively, but, at the same time, a reduced rate of sccattering is assumed from one hemisphere to the other one. By applying a technique of Fourier- and Laplace-transform, the inverse transformation can be performed and exact solutions can be reached. By contrast with the first, and so far only exact solutions of Federov and Shakov, this wider class of solutions gives rise to coherent pulses to appear. The present work addresses omnidirectional densities for isotropic injection from an instantaneous and localized source. The dispersion relations are briefly discussed. We find, for this particular model, two diffusive models to exist up to a certain limiting wavenumber. The corresponding eigenvalues are real at the lowest wavenumbers. Complex eigenvalues, which are responsible for coherent pulses, appear at higher wavenumbers.

Kota, J.↗
NASA NTRS2004

Radiation analysis for manned missions to the Jupiter system

An analysis for manned missions targeted to the Jovian system has been performed in the framework of the NASA RASC (Revolutionary Aerospace Systems Concepts) program on Human Exploration beyond Mars. The missions were targeted to the Jupiter satellite Callisto. The mission analysis has been divided into three main phases, namely the interplanetary cruise, the Jupiter orbital insertion, and the surface landing and exploration phases. The interplanetary phase is based on departure from the Earth-Moon L1 point. Interplanetary trajectories based on the use of different propulsion systems have been considered, with resulting overall cruise phase duration varying between two and five years. The Jupiter-approach and the orbital insertion trajectories are considered in detail, with the spacecraft crossing the Jupiter radiation belts and staying around the landing target. In the surface exploration phase the stay on the Callisto surface is considered. The satellite surface composition has been modeled based on the most recent results from the GALILEO spacecraft. In the transport computations the surface backscattering has been duly taken into account. Particle transport has been performed with the HZETRN heavy ion code for hadrons and with an in-house developed transport code for electrons and bremsstrahlung photons. The obtained doses have been compared to dose exposure limits. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

NASA Center LaRC↗