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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 703 records · Page 39

Simulating Sources of Superstorm Plasmas

We evaluated the contributions to magnetospheric pressure (ring current) of the solar wind, polar wind, auroral wind, and plasmaspheric wind, with the surprising result that the main phase pressure is dominated by plasmaspheric protons. We used global simulation fields from the LFM single fluid ideal MHD model. We embedded the Comprehensive Ring Current Model within it, driven by the LFM transpolar potential, and supplied with plasmas at its boundary including solar wind protons, polar wind protons, auroral wind O+, and plasmaspheric protons. We included auroral outflows and acceleration driven by the LFM ionospheric boundary condition, including parallel ion acceleration driven by upward currents. Our plasmasphere model runs within the CRCM and is driven by it. Ionospheric sources were treated using our Global Ion Kinetics code based on full equations of motion. This treatment neglects inertial loading and pressure exerted by the ionospheric plasmas, and will be superceded by multifluid simulations that include those effects. However, these simulations provide new insights into the respective role of ionospheric sources in storm-time magnetospheric dynamics.

Fok, Mei-Ching↗

Three dimensional ray tracing Jovian magnetosphere in the low frequency range

Ray tracing of the Jovian magnetosphere in the low frequency range (1+40 MHz) has resulted in a new understanding of the source mechanism for Io dependent decametric radiation (DAM). Our three dimensional ray tracing computer code has provided model DAM arcs at 10 deg. intervals of Io longitude source positions for the full 360 deg of Jovian system III longitude. In addition, particularly interesting arcs were singled out for detailed study and modelling. Dependent decametric radiation arcs are categorized according to curvature--the higher curvature arcs are apparently due to wave stimulation at a nonconstant wave normal angle, psi. The psi(f) relationship has a signature that is common to most of the higher curvature arcs. The low curvature arcs, on the other hand, are adequately modelled with a constant wave normal angle of close to 90 deg. These results imply that for higher curvature arcs observed for from Jupiter (to diminish spacecraft motion effects) the electrons providing the gyroemission are relativistically beamed.

Menietti, J. D.↗

Thermonuclear processes and accretion onto neutron star envelopes - X-ray burst and transient sources

A Lagrangian, fully implicit, one-dimensional hydrodynamic computer code is used to investigate the evolution of thermonuclear runaways in the thick accreted hydrogen-rich envelopes of 1.0-solar-mass neutron stars having radii of 10 km and 20 km. The simulations produce outbursts that range in time scale from about 2000 seconds to more than a day. For the 10-km study, the peak effective temperature is 3.3 x 10 to the 7th K, and the peak luminosity is 2 x 10 to the 5th solar luminosities. The 20-km neutron star produces a peak effective temperature and luminosity of 5.3 x 10 to the 6th K and 5.9 x 10 to the 2nd solar luminosities. Also investigated are the effects of changes in the rates of the O-14(alpha, proton) and O-15(alpha, gamma) reactions on the evolution. Hydrodynamic expansion on the 10-km neutron star produces a precursor lasting about 10 to the -6th sec. The evolution of a gas cloud impacting the surface of a 20-km, 1-solar-mass neutron star is studied in an attempt to simulate the magnetospheric gate model of the X-ray burst sources.

Starrfield, S.↗

Mercury-T: A New Code to Study Tidally Evolving Multi-Planet Systems. Applications to Kepler-62

A large proportion of observed planetary systems contain several planets in a compact orbital configuration, and often harbor at least one close-in object. These systems are then most likely tidally evolving. We investigate how the effects of planet-planet interactions influence the tidal evolution of planets. We introduce for that purpose a new open-source addition to the Mercury N-body code, Mercury-T, which takes into account tides, general relativity and the effect of rotation-induced flattening in order to simulate the dynamical and tidal evolution of multi-planet systems. It uses a standard equilibrium tidal model, the constant time lag model. Besides, the evolution of the radius of several host bodies has been implemented (brown dwarfs, M-dwarfs of mass 0:1 M(sub ⨀), Sun-like stars, Jupiter). We validate the new code by comparing its output for one-planet systems to the secular equations results. We find that this code does respect the conservation of total angular momentum. We applied this new tool to the planetary system Kepler-62. We find that tides influence the stability of the system in some cases. We also show that while the four inner planets of the systems are likely to have slow rotation rates and small obliquities, the fifth planet could have a fast rotation rate and a high obliquity. This means that the two habitable zone planets of this system, Kepler-62e ad f are likely to have very different climate features, and this of course would influence their potential at hosting surface liquid water..

Dynamical evolution and stability↗

A directional gamma-ray telescope using coded aperture techniques

A directional detector for gamma-ray astronomy has been developed to image sources in the energy range 0.1 to 5 MeV. An array of 35 gain stabilized bismuth germanate detectors, together with a coded aperture mask based on a uniformly redundant array allows imaging in 4 deg square sky bins over a 16 x 24 deg field-of-view. The position of a strong point source, such as the Crab Nebula, can be determined to within not more than about 1 deg. A complementary 'anti-mask' greatly reduces systematic effects arising from nonuniform background rates amongst the detectors. The telescope has an effective area of 190 sq cm and an energy resolution of 19.5 percent FWHM at 662 keV. Results of laboratory tests of the imaging system, including the ability to image multiple sources, uniformity of response over the field-of-view, and the effect of the 'anti-mask', are in good agreement with computer simulations. Features of the flight detector system are described and results of laboratory tests and computer simulations are reviewed. A balloon flight of the telescope is planned for the fall of 1982.

Mcconnell, M. L.↗

The Cumulus Ecosystem: Open Source and Beyond to Foster Collaboration

NASA’s Earth Observing System Data and Information System (EOSDIS) open source Cumulus software is designed as a common set of code and services that can be used to create a pipeline to deliver and manage earth science data in the cloud. Cumulus strives to create an ecosystem on the foundation of open source that unites those with shared problems and goals by encouraging users to contribute solutions back to the platform. Large parts of ingesting and managing data are common and much of what is created can be used by others. Our goal is to maximize collaboration and code reuse while allowing users to design a custom solution that meets their needs without having to take on extraneous functionality. In this talk we will describe how the Cumulus ecosystem works beyond just open source software. We will review the technology, the successes and challenges, and the evolution and future of Cumulus as an ecosystem.

Cumulus↗

PPUAS--photopeak unfolding and self-shielding program

Computer code was developed to determine radioactive emission rates of nuclear fuels. Code is basically written for two different source geometries; however, unfolding routine can be executed for other source geometries.

Taherzadeh, M.↗

Transport jet aircraft noise abatement in foreign countries: Growth, structure, impact. Volume 2: Pacific basin, August 1980

Noise control measures at the international airports of Hawaii, New Zealand, Australia, Hong Kong, Japan, and Singapore were studied. Factors in noise control, such as government structure are examined. The increasing power of environmental agencies vis-a-vis aviation departments is noted. The following methods of dealing with aircraft noise are examined by type of control: noise at the source control; noise emmission controls, zoning, building codes, subsidies for relocation, insulation, loss in property values, and for TV, radio and telephone interference; and noise-related landing charges.

Spencer, F. A.↗

The heating of the solar wind by the interstellar neutral gas

Solar wind heating by ionization and assimilation of the interstellar neutral wind is investigated using a numerical model of the interaction. The model is a time-dependent, one-dimensional, spherically symmetric, one-fluid code which includes mass, momentum, and energy sources due to the efficient incorporation of ionized interstellar hydrogen. Solar wind data at 1 AU from October 12, 1978 to February 25, 1980 were input to the inner boundary of the model and propagated out to 10 AU. Then, 52-day averages of proton temperature as functions of radius were produced for three values of the interstellar hydrogen density: 0.0, 0.03, and 0.1 per cu cm. It is concluded that, within the context of the model, the observations of solar wind proton temperatures at Voyager 1 and Pioneer 11 are consistent with heating of the solar wind by an interaction with inflowing interstellar neutral hydrogen. The density of this inflowing gas is near 0.03/cu cm.

Isenberg, P. A.↗

New coding advances for deep space communications

Advances made in error-correction coding for deep space communications are described. The code believed to be the best is a (15, 1/6) convolutional code, with maximum likelihood decoding; when it is concatenated with a 10-bit Reed-Solomon code, it achieves a bit error rate of 10 to the -6th, at a bit SNR of 0.42 dB. This code outperforms the Voyager code by 2.11 dB. The use of source statics in decoding convolutionally encoded Voyager images from the Uranus encounter is investigated, and it is found that a 2 dB decoding gain can be achieved.

Yuen, Joseph H.↗

Scoping Calculations of Power Sources for Nuclear Electric Propulsion

This technical memorandum describes models and calculational procedures to fully characterize the nuclear island of power sources for nuclear electric propulsion. Two computer codes were written: one for the gas-cooled NERVA derivative reactor and the other for liquid metal-cooled fuel pin reactors. These codes are going to be interfaced by NASA with the balance of plant in order to make scoping calculations for mission analysis.

Difilippo, F. C.↗

Exhausted Plume Flow Field Prediction Near the Afterbody of Hypersonic Flight Vehicles in High Altitudes

A two-dimensional computer code to solve the Burnett equations has been developed which computes the flow interaction between an exhausted plume and hypersonic external flow near the afterbody of a flight vehicle. This Burnett-2D code extends the capability of Navier-Stokes solver (RPLUS2D code) to include high-order Burnett source terms and slip-wall conditions for velocity and temperature. Higher-order Burnett viscous stress and heat flux terms are discretized using central-differencing and treated as source terms. Blocking logic is adopted in order to overcome the difficulty of grid generation. The computation of exhaust plume flow field is divided into two steps. In the first step, the thruster nozzle exit conditions are computed which generates inflow conditions in the base area near the afterbody. Results demonstrated that at high altitudes, the computations of nozzle exit conditions must include the effects of base flow since significant expansion exists in the base region. In the second step, Burnett equations were solved for exhaust plume flow field near the afterbody. The free stream conditions are set at an altitude equal to 80km and the Mach number is equal to 5.0. The preliminary results show that the plume expansion, as altitude increases, will eventually cause upstream flow separation.

Chou, Lynn Chen↗

Unexplained Discontinuity in the US Radiosonde Temperature Data: Stratosphere - Part 2

In part I of this paper, the United States (US) radiosonde temperature data are shown to have significant and unexplained inhomogeneities in the mid-troposphere. This part discusses the differences between observations taken at 0 and 12 UTC especially in the stratosphere by the Vaisala RS80 radiosondes that are integrated within the National Weather Service's (NWS) Micro-ART system. The results show that there is a large maxima in the horizontal distribution of the monthly means of the 0/12 UTC differences over the central US that is absent over Canada and this maxima is as large as 5 C at 10 hPa. The vertical profiles of the root-mean-square of the monthly means are much larger in the US than those else where. The data clearly shows that the 0/12 UTC differences are largely artificial especially over the central US and originate in the post processing software at observing stations, thus confirming the findings in part I. Special flight data from the NWS's test facility at Sterling, Va. have been obtained. This data can be used to deduce the bias correction applied by Vaisala's post processing system. By analyzing the correction data, it can be shown that the inconsistencies with non-US Vaisala RS80 data as well as most of the large 0/12 UTC differences over the US can be accounted for by multiplying the reported elapsed time (i.e. time since launch) by the factor which is incorrectly applied by the post processing software. After being presented with the findings in this paper, Vaisala further isolated the source of the inconsistencies to a software coding error in the radiation bias correction scheme. The error effects only the software installed at US stations.

Redder, Christopher R.↗

Improving Rotor-Stator Interaction Noise Code Through Analysis of Input Parameters

There are two major sources of aircraft noise. The first is from the airframe and the second is from the engines. The focus of the acoustics branch at NASA Glenn is on the engine noise sources. There are two major sources of engine noise; fan noise and jet noise. Fan noise, produced by rotating machinery of the engine, consists of both tonal noise, which occurs at discrete frequencies, and broadband noise, which occurs across a wide range of frequencies. The focus of my assignment is on the broadband noise generated by the interaction of fan flow turbulence and the stator blades. such as the sweep and stagger angles and blade count, as well as the flow parameters such as intensity of turbulence in the flow. The tool I employed in this work is a computer program that predicts broadband noise from fans. The program assumes that the complex shape of the curved blade can be represented as a single flat plate, allowing it to use fairly simple equations that can be solved in a reasonable amount of time. While the results from such representation provided reasonable estimates of the broadband noise levels, they did not usually represent the entire spectrum accurately. My investigation found that the discrepancy between data and theory can be improved if the leading edge and the trailing edge of the blade are treated separately. Using this approach, I reduced the maximum error in noise level from a high of 30% to less than 5% for the cases investigated. Detailed results of this investigation will be discussed at my presentation. The objective of this study is to investigate the influence of geometric parameters

Unton, Timothy J.↗

OBPR Product Lines, Human Research Initiative, and Physics Roadmap for Exploration

The pace of change has increased at NASA. OBPR s focus is now on the Human interface as it relates to the new Exploration vision. The fundamental physics community must demonstrate how we can contribute. Many opportunities exist for physicists to participate in addressing NASA's cross-disciplinary exploration challenges: a) Physicists can contribute to elucidating basic operating principles for complex biological systems; b) Physics technologies can contribute to developing miniature sensors and systems required for manned missions to Mars. NASA Codes other than OBPR may be viable sources of funding for physics research.

Israelsson, Ulf↗

JavaGenes Molecular Evolution

JavaGenes is a general-purpose, evolutionary software system written in Java. It implements several versions of a genetic algorithm, simulated annealing, stochastic hill climbing, and other search techniques. This software has been used to evolve molecules, atomic force field parameters, digital circuits, Earth Observing Satellite schedules, and antennas. This version differs from version 0.7.28 in that it includes the molecule evolution code and other improvements. Except for the antenna code, JaveGenes is available for NASA Open Source distribution.

Lohn, Jason↗

Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs: Detailed Photoionization Modeling of Fe K-Shell Absorption Lines - 2

X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \sim10,000km/s (\sim0.03c) up to \siml00,000kmis (\sim0.3c), with a peak and mean value of\sim42,000km/s (\sim0.14c). The ionization parameter is very high and in the range log\xi 3-6 erg s/cm, with a mean value of log\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

Tombesi, Francesco↗

Collaborating With Xarray to Enable Reading Hierarchical Data Files

NASA has a lot of expertise, but doesn’t need to write every single piece of code. Pangeo is a fantastic open-source community of tools for geoscience research. Xarray, a Python package, is a widely used part of this ecosystem for accessing and analyzing geoscience data.

Owen Littlejohns↗