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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 343 records · Page 19
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NASA NTRSDate not supplied

Active Swarm Resiliency in the HelioSwarm Mission

Designed to observe plasma turbulence dynamics in solar wind over a distributed volume of space, the HelioSwarm mission comprises a primary chief spacecraft and eight smaller deputy satellites in uniquely assigned “loops” of periodic relative motion in a P/2 lunar resonant orbit. If one or more deputies fail, this multi-satellite architecture facilitates resiliency for science goals through repositioning of satellites to contingency loops. This strategy of Active Swarm Resiliency mitigates risk by modeling quantitative results ahead of time for mission operators to make informed decisions. Responsive actions meet minimum science objectives based on past and predicted system performance, an approach with applications to future missions with similar architecture and requirements.

Fault Management↗
NASA NTRSDate not supplied

Active Swarm Resiliency in the HelioSwarm Mission

Designed to observe plasma turbulence dynamics in solar wind over a distributed volume of space, the HelioSwarm mission comprises a primary chief spacecraft and eight smaller deputy satellites in uniquely assigned “loops” of periodic relative motion in a P/2 lunar resonant orbit. If one or more deputies fail, this multi-satellite architecture facilitates resiliency for science goals through repositioning of satellites to contingency loops. This strategy of Active Swarm Resiliency mitigates risk by modeling quantitative results ahead of time for mission operators to make informed decisions. Responsive actions meet minimum science objectives based on past and predicted system performance, an approach with applications to future missions with similar architecture and requirements.

Fault Management↗
NASA NTRS1985

Gravity Waves

In recent years it has been widely recognized that vertically propagating gravity waves play an important role in the dynamics of the middle atmosphere in partly determining the large scale temperature and wind structure through their energy and momentum transport. In particular, the meridional temperature distribution and the mean wind profile in the upper mesosphere are considered to be largely affected by the turbulence diffusion and friction that gravity waves induce through their breaking. For an understanding of the middle atmosphere circulation, it is therefore very important to know the global distribution and temporal variation of gravity waves in a climatological sense. The results of the statistics for gravity wave activity in the stratosphere and mesosphere are presented as a function of latitude and month, with the aid of meteorological rocket network observations.

Hirota, I.↗
NASA NTRS1990

Pitch angle and velocity diffusions of newborn ions by turbulence in the solar wind

The temporal evolution of the distribution function of newborn ions under the influence of intrinsic low-frequency solar wind turbulences is studied. In particular, an initial ring-beam distribution of newborn ions under the influence of hydromagnetic waves is considered. A simplified treatment of the resonance broadening effect is given, and its role in the pickup process is discussed. Two different configurations of wave polarization amd direction of propagation are considered. The conditions that lead either to the formation of anisotropic shells as a long-duration transient state or to rapid isotropization of the ion pitch angle distribution are discussed, as are the conditions which lead to significant acceleration of the ions.

Ziebell, L. F.↗
NASA NTRS1979

IMF orientation, solar wind velocity, and Pc 3-4 signals - A joint distribution

Separate studies using the same micropulsation data base in the period range 10-150 s have shown earlier that signal levels recorded during September, October, and November 1969 at Calgary correlated positively with both solar-wind alignment of the IMF and solar-wind speed, but each correlation contained enough scatter to allow for the influence of the other factor. In this report, joint correlations of velocity and field direction with parameters representing hourly distributions rather than minima of IMF orientation angle display the relative effect of the two agents on magnetic pulsation signal levels. The joint correlations reduce the overall scatter and show that solar-wind speeds above 200-300 km/s and angles between the IMF and the sun-earth line of less than 50-60 deg are associated with enlarged magnetic pulsation amplitudes. These threshold effects tend to support both the bow-shock origin and the Kelvin-Helmholtz amplification of daytime signal transients in the Pc 3, 4 period ranges.

Greenstadt, E. W.↗
NASA NTRS1988

Winds aloft statistical analysis in support of day of launch Shuttle systems evaluation

In connection with the development of the Meteorological Interactive Data Display System (MIDDS) for utilization by the Launch Systems Evaluation Advisory Team (LSEAT), requirements have been established to expand the pre-launch analysis of winds aloft for the Space Shuttle. Statistical analyses developed for the system include: comparison of pre-launch wind component profiles to wind component extremes at each altitude calculated from launch site historical data; conditional probability ellipses for wind vectors at a future time given the wind vector at an initial time; comparison of observed extreme wind shear and associated wind speed with launch site historical data utilizing the bivariate extreme value (Gumbel) distribution; estimation of extremes of wind speed or wind shear at a future time given the extremes of either variable at an initial time, utilizing the conditional extreme value distribution; power spectrum analysis for tracking wind perturbation energy in sequential pre-launch Jimsphere wind profiles.

Adelfang, S. I.↗
NASA NTRS1974

Neutral and ion exosphere models for lunar hydrogen and helium

A general neutral exosphere model, which includes density and temperature variations at the exobase, is applied to the moon to obtain surface and radial density distributions for H, H2, and He. It is assumed that the source for these constituents derives from accretion of solar wind ions. The surface distributions are determined by requiring that the sum of the neutral and solar wind ion fluxes for a given constituent vanish at all points on the surface. On this basis, maximum dayside surface densities for H, H2, and He and maximum nightside surface densities for H, H2, and He are obtained that are consistent with either measured values or upper limits. In addition, model ion density distributions for H2(+) and He(+) are constructed. This ion exosphere is produced by ionization of the neutral exosphere in the solar wind, which efficiently sweeps the ions past or onto the lunar surface. Saturated H2(+) and He(+) densities ranging from about .001 to .015 per cu cm and .00003 to .0004 per cu cm over 1.5 to 3 selenocentric radii on the dayside, respectively.

Hartle, R. E.↗
NASA NTRS1985

Mean Winds of the Upper Middle Atmosphere (60-110 Km): a Global Distribution from Radar Systems (MF, Meteor, VHF)

During the last decade a large number of radars have been developed, which have produced substantial quantities of tidally corrected mean winds data in the upper middle atmosphere. The distribution of the radars is not global, but many areas are well covered. Zonal and meridional wind height-time cross sections from 60 to 80 km (MF/meteor radar) to approx. 110 km were preared for the last 5 to 6 years. They are compared with cross sections from CIRA 1972 for zonal winds, and GROVES (1969) for meridional winds. It is shown that while CIRA 1972 is still a useful model for many purposes, significant differences exist between it and the new radar data. The latter demonstrate important seasonal, latitudinal, longitudinal and hemispheric variations. The new meridional cross sections are of great value. The common features with GROVES (1969) are the equatorward cells in summer near 85 km; however, their strength (approx. 10 m/s) and size are less. Systematic and somewhat different variations emerge at (higher 52 N) and lower (35 to 44 deg) latitudes.

Manson, A. H.↗
NASA NTRS1978

A theory of local and global processes which affect solar wind electrons. 1: The origin of typical 1 AU velocity distribution functions: Steady state theory

A detailed first principle kinetic theory for electrons which is neither a classical fluid treatment nor an exospheric calculation is presented. This theory illustrates the global and local properties of the solar wind expansion that shape the observed features of the electron distribution function, such as its bifurcation, its skewness and the differential temperatures of the thermal and suprathermal subpopulations. Coulomb collisions are substantial mediators of the interplanetary electron velocity distribution function and they place a zone for a bifurcation of the electron distribution function deep in the corona. The local cause and effect precept which permeates the physics of denser media is modified for electrons in the solar wind. The local form of transport laws and equations of state which apply to collision dominated plasmas are replaced with global relations that explicitly depend on the relative position of the observer to the boundaries of the system.

Scudder, J. D.↗
NASA NTRS1995

Some remarks on waves in the solar wind

Waves are significant to the solar wind in two ways as modifiers of the particle distribution functions, and as diagnostics. In addition, the solar wind serves as an important laboratory for the study of plasma wave processes, as it is possible to make detailed measurements of phenomena which are too small to be easily measured by laboratory sized sensors. There are two areas where waves (we include discontinuities under this heading) must make important modifications of the distribution functions: in accelerating the alpha particles to higher speeds than the protons (Marsch et al.) and in accelerating the solar wind itself. A third area is possibly in maintaining the relative isotropy of the solar wind ion distribution in the solar wind rest frame. As the solar wind is nearly collisionless, the ions should conserve magnetic moment in rushing out from the sun, and therefore Tperp/B should be relatively constant, but it is obviously not. This has not received much attention. The waves, both electromagnetic and electrostatic, which are pan of the solar Type 111 burst phenomenon, have been extensively studied as examples of nonlinear plasma phenomena, and also used as remote sensors to trace the solar magnetic field. The observations made by Ulysses show that the field can be traced in this way out to perhaps a little more than an A.U., but then the electromagnetic pan of the type 111 burst fades out. Nevertheless, sometimes Langmuir waves appear at Ulysses at an appropriate extrapolated time. This seems to support the picture in which the electromagnetic waves at the fundamental plasma frequency are trapped in density fluctuations. Langmuir waves in the solar wind are usually in quasi-thermal equilibrium quasi because the solar wind itself is not isothermal. The Observatory of Paris group (Steinberg. Meyer-Vernet, Hoang) has exploited this with an experiment on WIND which is capable of providing density and temperature on a faster time scale than hitherto. Recently it has been found that Langmuir waves are associated with magnetic holes. This may help to elucidate the nature of magnetic holes. Nonlinear processes are important in the transformation of wave energy to panicle energy. Some recent examples from WIND data will be shown.

Kellogg, Paul J.↗
NASA NTRS1978

Analysis of vector wind change with respect to time for Cape Kennedy, Florida

Multivariate analysis was used to determine the joint distribution of the four variables represented by the components of the wind vector at an initial time and after a specified elapsed time is hypothesized to be quadravariate normal; the fourteen statistics of this distribution, calculated from 15 years of twice-daily rawinsonde data are presented by monthly reference periods for each month from 0 to 27 km. The hypotheses that the wind component changes with respect to time is univariate normal, that the joint distribution of wind component change with respect to time is univariate normal, that the joint distribution of wind component changes is bivariate normal, and that the modulus of vector wind change is Rayleigh are tested by comparison with observed distributions. Statistics of the conditional bivariate normal distributions of vector wind at a future time given the vector wind at an initial time are derived. Wind changes over time periods from 1 to 5 hours, calculated from Jimsphere data, are presented. Extension of the theoretical prediction (based on rawinsonde data) of wind component change standard deviation to time periods of 1 to 5 hours falls (with a few exceptions) within the 95 percentile confidence band of the population estimate obtained from the Jimsphere sample data. The joint distributions of wind change components, conditional wind components, and 1 km vector wind shear change components are illustrated by probability ellipses at the 95 percentile level.

Adelfang, S. I.↗
NASA NTRS1977

Load distribution on a closed-coupled wing canard at transonic speeds

A wind tunnel test where load distributions were obtained at transonic speeds on both the canard and wing surfaces of a closely coupled wing canard configuration is reported. Detailed component and configuration arrangement studies to provide insight into the various aerodynamic interference effects for the leading edge vortex flow conditions encountered are included. Data indicate that increasing the Mach number from 0.70 to 0.95 caused the wing leading edge vortex to burst over the wing when the wing was in the presence of the high canard.

Gloss, B. B.↗
NASA NTRS1995

Acceleration of solar wind ions by oblique interplanetary shocks

This paper compares observations of proton distributions made by the Solar Wind Ion Composition Spectrometer (SWICS) ion mass spectrometer on Ulysses at nearly interplanetary shocks with Monte Carlo simulations of particle acceleration at oblique collisionless shocks. The shock parameters are obtained from upstream measurements of the solar wind and magnetic field, and the input particles are drawn from convected Maxwellians, representing solar wind particles. Good agreement between downstream spectral measurements and the simulation predictions are obtained by allowing the parameter lambda/r(sub g), the ratio of the mean-free scattering length to the ionic gyroradius, to vary in an optimization of the fit to the data. Generally lambda/r(sub g) is found to be less than about 20, which corresponds to the case of strong scattering.

Baring, M. G.↗
NASA NTRS1994

Effects of spacecraft potential on three-dimensional electron measurements in the solar wind

Using the three-dimensional, low-energy electron spectrometer aboard the Ulysses spacecraft, we have measured the gyrotropicity of electron distributions in the solar wind. In order to make these observations, we have developed a new technique for correcting spacecraft charging effects in three-dimensional, low-energy particle measurements. Comparisons of ion and electron number and current densities, and the alignment of electron temperature anisotropies with the local magnetic field, are presented as evidence of the improvement in the accuracy of the electron moments resulting from the spacecraft charging corrections. The implications of our charging correction technique go beyond simple scalar corrections to the Ulysses measurements. We discuss the effects of our charging correction upon the measurements of temporal and radial gradients in a plasma environment and for two-dimensionally obtained low-energy particle data.

Scime, Earl E.↗
NASA NTRS1923

Point drag and total drag of navy struts no. 1 modified

This report deals with the results of tests on struts conducted at Washington Navy Yard. Two models of the modified Navy strut, no. 1, were tested in the 8 by 8 foot wind tunnel. The tests were made to determine the total resistance end effect and the pressure distribution at various wind-tunnel speeds with the length of the strut transverse to the current. Only the measurements made at zero pitch and yaw are given in this report.

Zahm, A F↗