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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

User interface enhancement report

The existing user interfaces to TEMPUS, Plaid, and other systems in the OSDS are fundamentally based on only two modes of communication: alphanumeric commands or data input and grapical interaction. The latter are especially suited to the types of interaction necessary for creating workstation objects with BUILD and with performing body positioning in TEMPUS. Looking toward the future application of TEMPUS, however, the long-term goals of OSDS will include the analysis of extensive tasks in space involving one or more individuals working in concert over a period of time. In this context, the TEMPUS body positioning capability, though extremely useful in creating and validating a small number of particular body positions, will become somewhat tedious to use. The macro facility helps somewhat, since frequently used positions may be easily applied by executing a stored macro. The difference between body positioning and task execution, though subtle, is important. In the case of task execution, the important information at the user's level is what actions are to be performed rather than how the actions are performed. Viewed slightly differently, the what is constant over a set of individuals though the how may vary.

Badler, N. I.↗
NASA NTRS1987

Some advances in digital flow visualization

The ability to visualize complex objects, concepts, interactions, and phenomena, to 'SEE' them in the mind's eye, has always been a fundamental component of the engineering discipline. Today, driven by increasingly demanding design requirements and an avalanche of data from powerful new computers and sophisticated experimental devices, the need to visualize data effectively is more important than ever before. This pressing need has resulted in the rapid increase in the use of computer-generated graphics in engineering. This is particularly true in the field of fluid dynamics where the internal structure of flow, not just surface or geometric effects, must be interpreted and communicated. This paper reports on several recent developments in the application of digital computer-generated graphics to engineering requirements for visualization of flow.

Belie, R. G.↗
NASA NTRS1988

An application of MSC/NASTRAN in the interdisciplinary analysis of large space-based structures

The Integrated Multidisciplinary Analysis Tool (IMAT), a computer software system developed at NASA Langley to analyze and simulate the dynamics of space-structure/control-system interactions, is described, and its application to the MAST problem (a 60-m truss with fundamental frequency less than 200 mHz and equipped with linear proof-mass actuators, to be deployed from the Space Shuttle as part of COFS-I flight experiment) is demonstrated. Particular attention is given to the IMAT procedures which facilitate the use of the MCS/NASTRAN code to recover physical results from time-domain state-space solutions obtained with an FEM control-design code. Diagrams, drawings, and graphs are provided.

Stockwell, Alan E.↗
NASA NTRS1993

Comment on 'A note on the possible connection between the El Chichon eruption and ocean production in the northwest Arabian Sea during 1982' by A. E. Strong

Strong argues that the El Chichon aerosol cloud resulted in relaxed southwest monsoon circulation and the dramatically reduced seasonal phytoplankton bloom documented in the northwestern Arabian Sea during summer and fall of 1982. It is argued here that Strong's ideas suggest a clear demonstration of an atmosphere-ocean interaction with implications for the ocean's biological CO2 pump. Strong's paper highlights the fundamentally different effects of volcanic aerosols on satellite infrared and visible band observations of the ocean.

Brock, John C.↗
NASA NTRS1995

On the nature of Alfven inward modes in the solar wind

Within the past decade there has been a remarkable production of papers both theoretical and observational that have shed some light on the intriguing and unsolved problem of the Alfvenic MHD turbulence in the solar wind. Although the scientific community has agreed upon many points which are at the basis of the temporal and radial evolution of the turbulence like the solar origin of most of the outward Alfven modes or the importance of non-linear interactions between outward and inward modes. there are still many open issues which are of fundamental importance for a complete understanding of the phenomenon. One of these key-issues is about the real nature of these inward modes. are they real propagating Alfven waves or rather static structures convected by the wind or a mixture of both? The present analysis represents an effort towards a better understanding of the nature and the role of these modes.

Bruno, R.↗
NASA NTRS2008

Simplified Modeling of Oxidation of Hydrocarbons

A method of simplified computational modeling of oxidation of hydrocarbons is undergoing development. This is one of several developments needed to enable accurate computational simulation of turbulent, chemically reacting flows. At present, accurate computational simulation of such flows is difficult or impossible in most cases because (1) the numbers of grid points needed for adequate spatial resolution of turbulent flows in realistically complex geometries are beyond the capabilities of typical supercomputers now in use and (2) the combustion of typical hydrocarbons proceeds through decomposition into hundreds of molecular species interacting through thousands of reactions. Hence, the combination of detailed reaction- rate models with the fundamental flow equations yields flow models that are computationally prohibitive. Hence, further, a reduction of at least an order of magnitude in the dimension of reaction kinetics is one of the prerequisites for feasibility of computational simulation of turbulent, chemically reacting flows. In the present method of simplified modeling, all molecular species involved in the oxidation of hydrocarbons are classified as either light or heavy; heavy molecules are those having 3 or more carbon atoms. The light molecules are not subject to meaningful decomposition, and the heavy molecules are considered to decompose into only 13 specified constituent radicals, a few of which are listed in the table. One constructs a reduced-order model, suitable for use in estimating the release of heat and the evolution of temperature in combustion, from a base comprising the 13 constituent radicals plus a total of 26 other species that include the light molecules and related light free radicals. Then rather than following all possible species through their reaction coordinates, one follows only the reduced set of reaction coordinates of the base. The behavior of the base was examined in test computational simulations of the combustion of heptane in a stirred reactor at various initial pressures ranging from 0.1 to 6 MPa. Most of the simulations were performed for stoichiometric mixtures; some were performed for fuel/oxygen mole ratios of 1/2 and 2.

Bellan, Josette↗
NASA NTRS2008

Using Lunar Module Shadows To Scale the Effects of Rocket Exhaust Plumes

Excavating granular materials beneath a vertical jet of gas involves several physical mechanisms. These occur, for example, beneath the exhaust plume of a rocket landing on the soil of the Moon or Mars. We performed a series of experiments and simulations (Figure 1) to provide a detailed view of the complex gas-soil interactions. Measurements taken from the Apollo lunar landing videos (Figure 2) and from photographs of the resulting terrain helped demonstrate how the interactions extrapolate into the lunar environment. It is important to understand these processes at a fundamental level to support the ongoing design of higher fidelity numerical simulations and larger-scale experiments. These are needed to enable future lunar exploration wherein multiple hardware assets will be placed on the Moon within short distances of one another. The high-velocity spray of soil from the landing spacecraft must be accurately predicted and controlled or it could erode the surfaces of nearby hardware. This analysis indicated that the lunar dust is ejected at an angle of less than 3 degrees above the surface, the results of which can be mitigated by a modest berm of lunar soil. These results assume that future lunar landers will use a single engine. The analysis would need to be adjusted for a multiengine lander. Figure 3 is a detailed schematic of the Lunar Module camera calibration math model. In this chart, formulas relating the known quantities, such as sun angle and Lunar Module dimensions, to the unknown quantities are depicted. The camera angle PSI is determined by measurement of the imaged aspect ratio of a crater, where the crater is assumed to be circular. The final solution is the determination of the camera calibration factor, alpha. Figure 4 is a detailed schematic of the dust angle math model, which again relates known to unknown parameters. The known parameters now include the camera calibration factor and Lunar Module dimensions. The final computation is the ejected dust angle, as a function of Lunar Module altitude.

Source record↗
NASA NTRS2007

Cratering Soil by Impinging Jets of Gas, with Application to Landing Rockets on Planetary Surfaces

Several physical mechanisms are involved in excavating granular materials beneath a vertical jet of gas. These occur, for example, beneath the exhaust plume of a rocket landing on the soil of the Moon or Mars. A series of experiments and simulations have been performed to provide a detailed view of the complex gas/soil interactions. Measurements have also been taken from the Apollo lunar landing videos and from photographs of the resulting terrain, and these help to demonstrate how the interactions extrapolate into the lunar environment. It is important to understand these processes at a fundamental level to support the ongoing design of higher-fidelity numerical simulations and larger-scale experiments. These are needed to enable future lunar exploration wherein multiple hardware assets will be placed on the Moon within short distances of one another. The high-velocity spray of soil from landing spacecraft must be accurately predicted and controlled lest it erosively damage the surrounding hardware.

Metzger, Philip T.↗
NASA NTRS2012

The Near-Earth Plasma Environment

An overview of the plasma environment near the earth is provided. We describe how the near-earth plasma is formed, including photo-ionization from solar photons and impact ionization at high latitudes from energetic particles. We review the fundamental characteristics of the earth's plasma environment, with emphasis on the ionosphere and its interactions with the extended neutral atmosphere. Important processes that control ionospheric physics at low, middle, and high latitudes are discussed. The general dynamics and morphology of the ionized gas at mid- and low-latitudes are described including electrodynamic contributions from wind-driven dynamos, tides, and planetary-scale waves. The unique properties of the near-earth plasma and its associated currents at high latitudes are shown to depend on precipitating auroral charged particles and strong electric fields which map earthward from the magnetosphere. The upper atmosphere is shown to have profound effects on the transfer of energy and momentum between the high-latitude plasma and the neutral constituents. The article concludes with a discussion of how the near-earth plasma responds to magnetic storms associated with solar disturbances.

Pfaff, Robert F., Jr.↗
NASA NTRS2019

In Situ Observation of Growth Dynamics in DECLIC Directional Solidification Insert Onboard ISS: DSI-R Flight Campaign

The study of solidification microstructure formation is of utmost importance for materials design and processing, as solid-liquid interface patterns largely govern mechanical and physical properties. Pattern selection occurs under dynamic conditions of growth in which the initial morphological instability evolves nonlinearly and undergoes a reorganization process. The dynamic and nonlinear nature of this instability renders in situ observation of the interface an invaluable tool to gain knowledge on the time-evolution of the interface pattern. Transparent organic analogs, which solidify like metallic alloys, allow direct visualization of interface dynamics. Extensive ground-based studies of both metallic and organic bulk samples have established the presence of significant convection during solidification processes that alters the formation of interfacial microstructures. A reduced-gravity environment is therefore mandatory for fluid flow elimination in bulk samples. In the framework of the CNES project MISOL3D (MIcrostrutures de SOLidification 3D) and the NASA projects DSIP (Dynamical Selection of 3D Interface Patterns), SPADES (SPAtiotemporal Evolution of three-dimensional DEndritic array Structures) and CAMUS (ComputAtional Studies of MicrostrUcture Formation During Alloy Solidification in Microgravity), we participated in the development of the Directional Solidification Insert (DSI) of the DEvice for the study of Critical Liquids and Crystallization (DECLIC). The DECLIC-DSI is dedicated to in situ and real-time characterization of solid-liquid interface patterns during directional solidification of transparent alloys in diffusive transport regime. Between April 2010 and March 2011, the first ISS campaign (DSI) explored the entire range of microstructures resulting in unprecedented observations. A second campaign (DSI-R), performed between October 2017 and December 2018, in which the insert contained an alloy of higher solute concentration, allowed to complete the benchmark database. The increase of solute concentration resulted in well-developed dendritic patterns at lower velocities (lower interface curvature and larger tip radius). The microstructure resulting from dendritic growth is dominant in metallurgy so that it is fundamental to understand the mechanisms of its formation. The main aims of this experimental campaign are to understand: the mechanisms of the cell to dendrite transition, the fundamental mechanisms of sidebranching formation, the dependence of dendrite tip shapes on growth conditions, the interaction of primary array and secondary sidebranches, and the influence of subgrain boundaries on the spatiotemporal organization of the array structure. Preparation, analysis and interpretation of the experiments performed onboard ISS are considerably enhanced by experiments performed on ground using thin-samples (Pr. Trivedi’s group) and phase-field simulations of microstructure formation in a diffuse growth regime (Pr. Karma’s group). In this summary, we will present an initial assessment of the results obtained during the DSI-R campaign. Nomenclature Vp: pulling velocity G: thermal gradient L: solidified length rtip: tip curvature radius Acronyms/Abbreviations CADMOS: Centre d'Aide au Développement des activités en Micro-pesanteur et des Opérations Spatiales CNES: Centre National d’Études Spatiales DECLIC: Device for the study of Critical LIquids and Crystallization DSI: Directional Solidification Insert DSI-R: Directional Solidification Insert - Refurbish ISS: International Space Station NASA: National Aeronautics and Space Administration PF: phase-field SCN: Succinonitrile 3D: three-dimensional

Mota, F.L.↗
NASA NTRS2021

Skin Friction Extracted from Surface Pressure in Incident Shock-Wave/Boundary-Layer Interaction

High-resolution skin-friction fields are extracted from pressure-sensitive paint (PSP) data obtained in shock-wave/boundary-layer interaction (SWBLI). The method of extracting skin friction from surface pressure is described, including the fundamental relation between skin friction and surface pressure, the variational method, error analysis, and an approximate iterative method. The proposed method is based on a coupling relation between skin friction and surface pressure, where the boundary enstrophy flux is suitably modeled or approximated. This method is applied to unsteady PSP data obtained in incident SWBLIs at Mach 2.5 for different Reynolds numbers, revealing the skin-friction structures of the flows: particularly, the separation bubble induced by the incident shock wave. The extracted results are in good agreement with the data obtained by the surface-stress-sensitive film.

skin friction↗
DOE OSTI2017

Monitoring nanoparticle synthesis in a carbon arc discharge environment, in situ

This work presents experimental and theoretical studies of gas-phase synthesis of fullerenes and carbon nanoparticles in the presence of an atmospheric-pressure, arc discharge plasma. Carbon arc discharges have been used for synthesizing carbon nanotubes for over 25 years, and have the potential for economically synthesizing industrial-scale quantities of fullerenes. However, the efficiency and selectivity of fullerene synthesis with carbon arc discharges are quite low. Optimizing carbon arc discharges for fullerene synthesis requires a thorough understanding of the dynamics behind gas-phase nanoparticle synthesis in the presence of an arc discharge plasma. We built a carbon arc discharge setup to study nanoparticle and fullerene synthesis. The laser-induced incandescence (LII) diagnostic was applied for monitoring nanoparticle synthesis, in situ. The LII diagnostic had previously been applied as a combustion diagnostic for in situ measurements of concentrations and sizes of soot particles in flame environments. Prior to the present study, it had never been applied for studying fullerenes, nor had it been applied to study nanoparticles in the presence of an atmospheric-pressure plasma. Therefore, experiments were designed that allowed for the calibration of the LII diagnostic with research-grade, arc-synthesized soot particles and carbon nanotubes. Additionally, the theory and models underpinning the LII diagnostic were adapted to include the presence of an atmospheric-pressure, arc-discharge plasma. Results presented in this work confirm the ability of the LII diagnostic to measure sizes of arc-synthesized nanoparticles in situ, and show the spatial location of high densities of arc-synthesized nanoparticles with respect to the arc discharge plasma. Determining the spatial location of nanoparticle synthesis and growth is crucial for understanding the background conditions (e.g. background gas temperature, electron densities ...) in which nanoparticles nucleate and grow in the arc discharge environment. Future work would involve combining the LII diagnostic with other laser-based diagnostics (e.g. Rayleigh scattering, laser-induced fluorescence) for a more comprehensive study of gas-phase nanoparticle synthesis and investigating fundamental basic-science questions related to low temperature plasma physics, and laser-nanoparticle interactions.

Nanotechnology↗
DOE OSTI2022

Parametric studies of stream instability-induced higher harmonics in plasma ionization breakdown near an emissive dielectric surface

Here, in this work, we comprehensively investigate the generation of higher harmonic (HH) electric fields normal to the applied rf electric field in multipactor-coexisting plasma breakdown by fully kinetic particle-in-cell (PIC) simulations and a theoretical model. Firstly, a base case at driving frequency 1 GHz, transverse rf electric field amplitude 3 MV m –1 , and background gas pressure 0.2 Torr, is studied in detail. The enhanced harmonic frequency observed is around ten times the fundamental rf frequency, significantly lower than the Langmuir frequency. A theoretical model reveals that the fundamental mechanism of HHs generation is stream–plasma instability, which originates from stream-like secondary electron emission interacting with plasma. The resulting HH frequency and the growth rate of its oscillating amplitude from the theoretical model, agree well with the PIC simulations. With increasing pressure, the HH oscillations are found to be significantly reduced. This is because at higher pressure the gas ionization rate is higher, which causes a more rapidly increasing plasma density, leaving less time for the growth of instability. Furthermore, the parameter space in terms of background gas pressure and rf field amplitude within which the HHs appear is revealed. Finally, the effect of the driving rf frequency on HHs is also investigated, and it is found that the instability-induced oscillating HHs field remains when the driving frequency is increased to 2 GHz, however, it is highly reduced at higher driving frequency of 5 GHz, as oscillations at the fundamental frequency start playing a more important role.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2005

Overview of Aerosol Distribution

Our knowledge of atmospheric aerosols (smoke, pollution, dust or sea salt particles, small enough to be suspended in the air), their evolution, composition, variability in space and time and interaction with clouds and precipitation is still lacking despite decades of research. Understanding the global aerosol system is fundamental for progress in climate change and hydrological cycle research. While a single instrument was used to demonstrate 50 years ago that the global CO2 levels are rising, posing threat of global warming, we need an array of satellites and field measurements coupled with chemical transport models to understand the global aerosol system. This complexity of the aerosol problem results from their short lifetime (1 week) and variable chemical composition. A new generation of satellites provides exciting opportunities to measure the global distribution of aerosols, distinguishing natural from anthropogenic aerosol and measuring their interaction with clouds and climate. I shall discuss these topics and application of the data to air quality monitoring.

Kaufman, Yoram↗
DOE OSTI2022

Absorption and Transport Effects Induced in Plasmas by the Interaction of Electrons with Laser Speckles

Here, we show that the ponderomotive force associated with laser speckles can scatter electrons in a laser-produced plasma in a manner similar to Coulomb scattering. Analytic expressions for the effective collision rates are given. The electron-speckle collisions become important at high laser intensity or during filamentation, affecting both long- and short-pulse laser intensity regimes. As an example, we find that the effective collision rate in the laser-overlap region of hohlraums on the National Ignition Facility is expected to exceed the Coulomb collision rate by 1 order of magnitude, leading to a fundamental change to the electron transport properties. At the high intensities characteristic of short-pulse laser-plasma interactions (I ≳ 10 17 W cm –2 ), the scattering is strong enough to cause the direct absorption of laser energy, generating hot electrons with energy scaling as E ≈ 1.44 (I/10 18 W cm –2 ) 1/2 MeV , close to experimentally observed results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Deprotonated Water Dimers: The Building Blocks of Segmented Water Chains on Rutile RuO2(110)

Despite the importance of RuO2 in photocatalytic water splitting and catalysis in general, the interactions of water with even its most stable (110) surface are not well-understood. In this study we employ a combination of high-resolution scanning tunneling microscopy imaging with density functional theory based ab initio molecular dynamics, and we follow the formation and binding of linear water clusters on coordinatively unsaturated ruthenium rows. We find that clusters of all sizes (dimers, trimers, tetramers, extended chains) are stabilized by donating one proton per every two water molecules to the surface bridge bonded oxygen sites, in contrast with water monomers that do not show a significant propensity for dissociation. The clusters with odd number of water molecules are less stable than the clusters with even number, and are generally not observed under thermal equilibrium. For all clusters with even numbers, the dissociated dimers represent the fundamental building blocks with strong intra-dimer hydrogen bonds and only very weak inter-dimer interactions resulting in segmented water chains.

ab initio molecular dynamics↗
DOE OSTI2019

Interaction Dynamics Between Ferroelectric and Antiferroelectric Domains in a Pb Zr O 3 -Based Ceramic

The antiferroelectric-ferroelectric phase transition in PbZrO 3 -based oxides is of both fundamental and practical importance. In ceramics in which such a transition readily occurs, the antiferroelectric and the ferroelectric phases often coexist in individual grains with a coherent interphase interface. In this work, the electric biasing in situ transmission electron microscopy technique is employed to directly observe a unique microstructural dynamic when ferroelectric and antiferroelectric domains are driven by a moderate electric field to interact. It is found that, under monotonic loading, the ferroelectric domain grows until it is blocked by the ferroelectric-antiferroelectric interface. At the same time, a kink is formed on the interface at the contact point. Here, the interaction of the growing domain with the interface is interpreted in terms of depolarization field-assisted phase transition, which is supported by our phase-field simulation. Upon further bipolar cycling, the ferroelectric domain becomes less mobile and no longer reaches the ferroelectric-antiferroelectric interface, indicative of electric fatigue of the ferroelectric phase.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Propagation effects in highly ionised gas media

The problem of propagation of an ultraintense pulse in a gas medium is solved by using a 3D nonadiabatic model extended to the case of multiple ionisation of atoms in the interaction region. A complex space – time coupling of the pulse during its propagation and strong spatial and temporal changes in the field distribution are shown. (extreme laser radiation: physics and fundamental applications)

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗