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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Can we understand the turbulent solar wind via turbulent simulations?

We attempt to assess the present understanding of the turbulent solar wind using numerical simulations. The solar wind may be considered as a kind of wind tunnel with peculiar properties: the tunnel is spherical; the source of the wind is rotating; and the medium is a plasma containing a large-scale magnetic field. These constraints lead to anisotropic dynamics of the fluctuations on the one hand, and to non-standard (turbulent?) transport properties of the global plasma on the other hand. How much of this rich physics can we approach today via numerical simulations?

Grappin, R.↗
NASA NTRS2003

Mercury Conditions for the MESSENGER Mission Simulated in High- Solar-Radiation Vacuum Tests

The MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) spacecraft, planned for launch in March 2004, will perform two flybys of Mercury before entering a year-long orbit of the planet in September 2009. The mission will provide opportunities for detailed characterization of the surface, interior, atmosphere, and magnetosphere of the closest planet to the Sun. The NASA Glenn Research Center and the MESSENGER spacecraft integrator, the Johns Hopkins University Applied Physics Laboratory, have partnered under a Space Act Agreement to characterize a variety of critical components and materials under simulated conditions expected near Mercury. Glenn's Vacuum Facility 6, which is equipped with a solar simulator, can simulate the vacuum and high solar radiation anticipated in Mercury orbit. The MESSENGER test hardware includes a variety of materials and components that are being characterized during the Tank 6 vacuum tests, where the hardware will be exposed to up to 11 suns insolation, simulating conditions expected in Mercury orbit. In 2002, ten solar vacuum tests were conducted, including beginning of life, end of life, backside exposure, and solar panel thermal shock cycling tests. Components tested include candidate solar array panels, sensors, thermal shielding materials, and communication devices. As an example, for the solar panel thermal shock cycling test, two candidate solar array panels were suspended on a lift mechanism that lowered the panels into a liquid-nitrogen-cooled box. After reaching -140 C, the panels were then lifted out of the box and exposed to the equivalent of 6 suns (8.1 kilowatts per square meters). After five cold soak/heating cycles were completed successfully, there was no apparent degradation in panel performance. An anticipated 100-hr thermal shield life test is planned for autumn, followed by solar panel flight qualification tests in winter. Glenn's ongoing support to the MESSENGER program has been instrumental in identifying design solutions and validating thermal performance models under a very aggressive development schedule. The test data have assisted Johns Hopkins engineers in selecting a flight solar array vendor and a thermal shield design. MESSENGER is one in a series of missions in NASA's Discovery Program. Infrared thermography provides data on the thermal gradients in the MESSENGER components during high solar insolation vacuum testing.

Wong, Wayne A.↗
NASA NTRS2017

Finding the Needles in the Haystacks: High-Fidelity Models of the Modern and Archean Solar System for Simulating Exoplanet Observations

We present two state-of-the-art models of the solar system, one corresponding to the present day and one to the Archean Eon 3.5 billion years ago. Each model contains spatial and spectral information for the star, the planets, and the interplanetary dust, extending to 50 au from the Sun and covering the wavelength range 0.3-2.5 micron. In addition, we created a spectral image cube representative of the astronomical backgrounds that will be seen behind deep observations of extrasolar planetary systems, including galaxies and Milky Way stars. These models are intended as inputs to high-fidelity simulations of direct observations of exoplanetary systems using telescopes equipped with high-contrast capability. They will help improve the realism of observation and instrument parameters that are required inputs to statistical observatory yield calculations, as well as guide development of post-processing algorithms for telescopes capable of directly imaging Earth-like planets.

extrasolar planetary systems↗
NASA NTRS1985

Estimating solar radiation for plant simulation models

Five algorithms producing daily solar radiation surrogates using daily temperatures and rainfall were evaluated using measured solar radiation data for seven U.S. locations. The algorithms were compared both in terms of accuracy of daily solar radiation estimates and terms of response when used in a plant growth simulation model (CERES-wheat). Requirements for accuracy of solar radiation for plant growth simulation models are discussed. One algorithm is recommended as being best suited for use in these models when neither measured nor satellite estimated solar radiation values are available.

Hodges, T.↗
NASA NTRS1992

Solar wind-magnetosphere interaction as simulated by a 3-D EM particle code

We present here our first results of simulating the solar wind-magnetosphere interaction with a new three-dimensional electromagnetic particle code. Hitherto such global simulations were done with MHD codes while lower-dimensional particle or hybrid codes served to account for microscopic processes and such transport parameters as have to be introduced ad hoc in MHD. Our kinetic model attempts to combine the macroscopic and microscopic tasks. It relies only on the Maxwell curl equation and the Lorentz equation for particles, which are ideally suited for computers. The preliminary results shown here are for an unmagnetized solar wind plasma streaming past a dipolar magnetic field. The results show the formation of a bow shock and a magnetotail, the penetration of energetic particles into cusp and radiation belt regions, and dawn-dusk asymmetries.

Buneman, Oscar↗
NASA NTRS1993

Solar wind-magnetosphere interaction as simulated by a 3D, EM particle code

The results of simulating the solar wind-magnetosphere interaction with a three dimensional, electromagnetic (EM) particle code are presented. Hitherto such global simulations were done with magnetohydrodynamic (MHD) codes while lower dimensional particle or hybrid codes served to account for microscopic processes and such transport parameters as have to be introduced ad hoc in MHD. The kinetic model combines macroscopic and microscopic tasks. It relies only on the Maxwell curl equations and the Lorentz equation for particles. The preliminary results are for an unmagnetized solar wind plasma streaming past a dipolar magnetic field. The results show the formation of a bow shock and a magnetotail, the penetration of energetic particles into cusp and radiation belt regions, and dawn to dusk asymmetries.

Buneman, O.↗
NASA NTRS1986

Simulation of the solar wind interaction with the outer regions of the coma

Interaction of the solar wind with newly born cometary ions, O(+), is studied through hybrid simulations (particle ions, fluid electrons). The results show that depending on the orientation of the interplanetary magnetic field (IMF) with respect to the solar wind velocity, two kinds of interaction are possible. When IMF is exactly or nearly parallel to the solar wind velocity, momentum transfer between the protons and the O(+) ions takes place solely through the excitation of large amplitude electromagnetic waves. On the other hand, as IMF becomes more oblique to the solar wind velocity, momentum transfer occurs on a faster time scale through the motional electric field in the solar wind. This more rapid deceleration can lead to the formation of a shock.

Omidi, N.↗
NASA NTRS1984

The role of the Shuttle Engineering Simulator in the Solar Max rescue mission

Background information concerning the makeup of the SES, the role it traditionally plays in support of the Shuttle Program, its capabilities and the specific work performed on the simulator during the sixteen months proceedings the Solar Max repair mission is presented. The SES plays a significant role in the preparations for the STS 41-C Solar Max repair mission and during the mission in the development of the plan and procedures to retrieve the satellite after the MMU docking attempts failed. The development of the on orbit simulation capabilities required to support this mission is to a very large extent simply an expansion of the capabilities designed into the SES to support previous engineering simulation requirements for the Space Shuttle program.

St.john, R. H.↗
NASA NTRS1974

Simulation of lunar carbon chemistry. I - Solar wind contribution

Simulation experiments were conducted to identify the role of solar and lunar winds in the evolution of lunar carbon chemistry. Major conclusions are that (1) implantation of solar wind C, D, and N ions in silicates synthesizes small molecules that can be released into vacuum either by ion sputtering or by heating; (2) this synthesis is highly specific when compared to other processes accounting for the formation of molecules in the solar nebula or in interstellar space; (3) the carbon injected by the solar wind in the crystalline component of mature soils should reach a saturation concentration of about 200 ppm; and (4) the carbon chemistry of the crystalline component of mature soils is dominated by solar wind implantation effects.

Bibring, J. P.↗
NASA NTRS2004

A solar sail integrated simulation toolkit

This paper describes an integrated set of high fidelity software tools that are being developed for the design of solar sail missions and analysis of the guidance, navigation and control (GNC) of these missions.

Lawrence, Dale↗
NASA NTRS2010

Attempts to Simulate Anisotropies of Solar Wind Fluctuations Using MHD with a Turning Magnetic Field

We examine a "two-component" model of the solar wind to see if any of the observed anisotropies of the fields can be explained in light of the need for various quantities, such as the magnetic minimum variance direction, to turn along with the Parker spiral. Previous results used a 3-D MHD spectral code to show that neither Q2D nor slab-wave components will turn their wave vectors in a turning Parker-like field, and that nonlinear interactions between the components are required to reproduce observations. In these new simulations we use higher resolution in both decaying and driven cases, and with and without a turning background field, to see what, if any, conditions lead to variance anisotropies similar to observations. We focus especially on the middle spectral range, and not the energy-containing scales, of the simulation for comparison with the solar wind. Preliminary results have shown that it is very difficult to produce the required variances with a turbulent cascade.

Ghosh, Sanjoy↗
NASA NTRS1982

The dynamics of the Venus ionosphere. I - A simulation of the solar wind compression of the upper dayside ionosphere

One of the most exciting discoveries by the Pioneer Venus mission is the extreme variability in the structure of the Venus atmosphere. The solar wind plays a major, although as yet not well-defined, role in the dynamics of the ionosphere. An investigation is being conducted regarding the response of the dayside Venus ionosphere to changing solar wind conditions, in particular to the varying solar wind dynamic pressure. In the present study the dynamics of the upper (h equal to or greater than 200 km) ionosphere are simulated numerically using a one-dimensional, spherically symmetric, Lagrangian hydrodynamic code developed by Stein and Schwartz (1972). The ionosphere is assumed to be unmagnetized and is represented with a two-fluid model. The initial ionosphere is chosen to be in pressure equilibrium with the solar wind at the ionopause. It is shown how some of the time-dependent features of the Venus ionosphere may be simulated with the considered model.

Wolff, R. S.↗
NASA NTRS1999

Performance Simulation of Autonomous Solar Navigation

The performance of a new type of autonomous solar navigation system is analyzed in this paper. Such efficient autonomous navigation systems will reduce operation costs and alleviate the Deep Space Network workload in future space missions. The method is demonstrated by applying it to the STEREO mission. Orbit determination is simulated through the use of the mission-defined trajectory profile and solar angular data acquired by the on-board science instruments currently being considered. The study shows that the orbit solution derived by this new type of solar navigation system can satisfy the mission's navigation requirements; the position uncertainties obtained in the simulations are well below the mission allowable values, and are comparable to the results obtained with the conventional Doppler tracking system in some cases.

Guo, Yanping↗
NASA NTRS1990

Global simulation of the solar wind-magnetosphere interaction - The importance of its numerical validity

This paper examines the global interaction of the solar wind with the geomagnetic field, using a newly developed three-dimensional high-precision MHD simulation code which employs the fourth-order Runge-Kutta-Gill scheme in time and the direct finite-difference method in space, and which allows much less numerical error than the conventional code. The simulation reveals in detail the formation processes of the magnetosphere and the bow shock, as well as the plasma sheet formation process. It is shown that, contrary to the conventional understanding, no Kelvin-Helmholtz instability occurs along the magnetopause in an ideal MHD.

Watanabe, K.↗
NASA NTRS1973

Low-thrust solar electric propulsion navigation simulation program

An interplanetary low-thrust, solar electric propulsion mission simulation program suitable for navigation studies is presented. The mathematical models for trajectory simulation, error compensation, and tracking motion are described. The languages, input-output procedures, and subroutines are included.

Hagar, H. J.↗