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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 289 records · Page 16
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NASA NTRS2023

Distributions of Mesoscale Periodic Structures in the Elemental and Ionic Composition of the Solar Wind

Multiple statistical and event studies based on in situ observations have shown that the solar wind contains mesoscale (∼ 100 – 10,000 Mm) periodic structures in the proton number density. Remote observations of such structures and event studies of concurrent variations in composition have demonstrated that they can form in the solar atmosphere and be preserved while advecting outwards through the heliosphere. Viall, Kepko, and Spence (J. Geophys. Res. (Space Phys.) 113, A07101, 2008; J. Geophys. Res. (Space Phys.) 114, A01201, 2009) and Kepko, Viall, and Wolfinger (J. Geophys. Res. (Space Phys.) 125(8), e28037, 2020) have reported that periodic proton density structures preferentially occur at specific radial length scales and have published their distributions from Wind measurements near L1. Here, we conduct a statistical study of 14 years (1998 – 2011) of 12-minute composition data measured by the Solar Wind Ion Composition Spectrometer instrument aboard the Advanced Composition Explorer spacecraft. We found that the elemental and ionic composition also contain statistically significant mesoscale periodic structures and, for the first time, present occurrence distributions for elemental abundance ratios with low, intermediate, and high first ionization potentials as well as for key solar wind charge states. These distributions set important constraints on solar wind formation in general and the formation of periodic mesoscale solar wind structures specifically, as the elemental and ionic composition are known to be determined at the Sun and to not evolve during advection.

Solar wind↗
NASA NTRS1973

Ventifact evolution in Wright Valley, Antarctica.

Ventifacts occurring on extensive wind-deflated surfaces throughout the ice-free Wright Valley are the product of complex evolutionary processes. The wind produces a lag gravel which continues to evolve at a reduced rate as coarser granule and gravel fractions are removed. The morphology of ventifacts forming the lag gravels suggests that the distribution of wind-polished faces is determined largely by the shape of the original unpolished rock fragments. In the early stages ventifacts tend to be oriented either transverse or parallel to the wind direction. Salt weathering is also a major factor in determining the morphology of the Wright Valley ventifacts.

Lindsay, J. F.↗
NASA NTRS1987

Lumped-Parameter Representation of Wind Tunnel

Mathematical model of proposed wind-tunnel facility represents wind-tunnel circuit and associated equipment in terms of lumped-parameter components. Requires less computational effort and computing time than full three-dimensional aerodynamic computer analysis of system with many volume elements. Approximates distributed nature of wind tunnel well enough to simulate steady-state and transient behavior for analysis of proposed control subsystems and for training of operators. Lumped-parameter circuit model represents wind tunnel and associated equipment. Implemented on analog or digital computers to simulate wind-tunnel performance without risk to operators or equipment.

Krosel, Susan M.↗
NASA NTRS1995

Evolution of the solar wind acceleration region during 1990-1994

The single-station measurements of interplanetary scintillation (IPS) at 2 and 8 GHz have been made at the Kashima Space Research Center of the Communications Research Laboratory in the period from 1990 to 1994. These IPS data are used to study the radial distribution of solar wind velocity and density fluctuations near the sun (i.e. 10-70 Rs), and the long-term variation in these properties. The IPS co-spectrum technique is applied here to estimate the solar wind velocity. Derived velocities show that the solar wind gains a speed significantly in the radial range from 10 to 30 Rs (solar radii). which is much farther than the source surface of the thermally driven solar wind model. From the scintillation index analysis. it is found that the radial fall of density fluctuations is well described by the power-law function. A series of IPS observations reveals that a pronounced change in velocity and turbulence level for this radial range occurs at the polar region of the sun during 1990-1994. That is, the high speed wind and the reduced turbulence region develop there as the solar activity declines. On the other hand, little long-term variation is observed for the solar wind acceleration region at a low latitude. From the comparison with He 1O83 nm observations. it is demonstrated that the change of the solar wind structure is closely linked with the evolution of the coronal hole on the solar surface.

Tokumaru, M.↗
NASA NTRS1976

The internal plasma state of the high speed solar wind at 1 AU

The character of particle velocity distributions in the high speed solar wind is described. It is found that electron distribution shapes differ from simple bi-Maxwellians in that a hot strongly beamed high energy electron component is always present, and is observed to move relative to a distinct low energy electron component along the magnetic field direction away from the sun. The velocity difference between hot and cold electron components appears, at times, to be strongly correlated with the local Alfven speed. Proton velocity distributions are also best represented by two relatively convecting unresolved components. Evidence is presented which supports the idea that the two-component proton structure observed in high speed regions is intimately related to fine scale velocity variations at 1 AU, and probably to prominent spatial and/or temporal structures present throughout that part of the corona from which the solar wind evolves.

Feldman, W. C.↗
NASA NTRS1977

A distributed processing high data rate multiport wind-tunnel pressure measurement system

A multiport pressure measurement system has been developed for the high data rates and the in situ calibration of electronically scanned pressure (ESP) sensors. The system employs a stand-alone microcomputer, connected to a host computer, for data acquisition and preprocessing. The host computer provides several operational modes. Before each run the in situ calibration of each sensor is automatically performed. Using up to a maximum of 14 data acquisition and control units (DACU's), the system may be expanded from 16 to 10,752 pressure ports. Each DACU can make 20,000 measurements per second, average data, and perform statistical analyses before transferring data to the central unit. The system may be introduced into existing facilities and requires little user orientation.

Juanarena, D.↗
NASA NTRS1973

Wind-tunnel measurements of the chordwise pressure distribution and profile drag of a research airplane model incorporating a 17-percent-thick supercritical wing

The Langley 8-foot transonic pressure tunnel to determine the wing chordwise pressure distribution for a 0.09-scale model of a research airplane incorporating a 17-percent-thick supercritical wing. Airfoil profile drag was determined from wake pressure measurements at the 42-percent-semispan wing station. The investigation was conducted at Mach numbers from 0.30 to 0.80 over an angle-of-attack range sufficient to include buffet onset. The Reynolds number based on the mean geometric chord varied from 2 x 10 to the 6th power at Mach number 0.30 to 3.33 x 10 to the 6th power at Mach number 0.65 and was maintained at a constant value of 3.86 x 10 to the 6th power at Mach numbers from 0.70 to 0.80. Pressure coefficients for four wing semispan stations and wing-section normal-force and pitching-moment coefficients for two semispan stations are presented in tabular form over the Mach number range from 0.30 to 0.80. Plotted chordwise pressure distributions and wake profiles are given for a selected range of section normal-force coefficients over the same Mach number range.

Ferris, J. C.↗
NASA NTRS1995

The latitudinal distribution of magnetic holes in the solar wind

A large number of magnetic holes have been found in the Ulysses data during its cruise in the ecliptic. They are interpreted as convecting structures, probably caused by the mirror instability which exists in high beta plasmas with anisotropic temperatures. The characteristics of the holes reflect the solar wind condition of the region in which the holes are formed, and the point of observation may be far removed from where the instability occurs. A preliminary survey appears to indicate that the number of holes has no significant radial dependence. However, the number of holes does appear to increase with increasing heliographic latitude. Yet the large scale solar wind structures with their compression regions disappeared at approximately 57 deg south latitude. Thus any causal relationship between the holes and large scale solar wind structures is questionable. The temperature anisotropy and high beta required by the mirror instability must be generated by other mechanisms. In order to tie the magnetic holes and the mirror instability to their cause, the evolution of their characteristics with heliocentric distance and latitude needs to be investigated. With the progression of Ulysses around the sun a survey will be conducted to ascertain the characteristics of the magnetic holes as a function of heliographic latitude and heliocentric distance. A comparison of the results with the solar wind conditions may lead to the identification of the magnetic hole generating mechanism(s).

Winterhalter, D.↗
NASA NTRS1998

Wind-Tunnel Evaluation of the Effect of Blade Nonstructural Mass Distribution on Helicopter Fixed-System Loads

This report provides data obtained during a wind-tunnel test conducted to investigate parametrically the effect of blade nonstructural mass on helicopter fixed-system vibratory loads. The data were obtained with aeroelastically scaled model rotor blades that allowed for the addition of concentrated nonstructural masses at multiple locations along the blade radius. Testing was conducted for advance ratios ranging from 0.10 to 0.35 for 10 blade-mass configurations. Three thrust levels were obtained at representative full-scale shaft angles for each blade-mass configuration. This report provides the fixed-system forces and moments measured during testing. The comprehensive database obtained is well-suited for use in correlation and development of advanced rotorcraft analyses.

ARES-1(AEROELASTIC ROTOR EXPERIMENTAL SYSTEM 1)↗
NASA NTRS1980

Solar wind ions accelerated to 40 keV by shock wave disturbances

Observations in the solar wind with the LASL/MPI fast plasma experiment on ISEE 1 and 2 reveal the common presence of ions with energies extending from 100 eV up to at least 40 keV in a broad region, typically 10 million kilometers wide, following interplanetary shocks. Peak differential fluxes up to 5000/sq cm s sr keV at 28 keV are observed either at the shock or within the first 1.5 hours following shock passage. In the solar wind frame the distribution function of these ions is roughly isotropic, peaks near zero velocity, and above 5 keV can adequately be characterized as power law in energy with a spectral index of 2.7. The effective 'temperature' of these ions generally exceeds 100 million K. These suprathermal interplanetary ions are almost certainly solar wind ions which have been accelerated by some mechanism associated with the shock wave disturbance. Present evidence leads the authors to favor stochastic particle acceleration involving electrostatic and/or electromagnetic turbulence in the postshock flow.

Gosling, J. T.↗
NASA NTRS1987

Longitudinal peculiarities of meridional circulation in lower thermosphere and mesosphere

Average monthly longitudinal profiles of geostrophic wind in winter are presented. Positive values correspond to meridional movements from north to south. It is concluded that the normal longitudinal meridional circulation is characterized by the presence of sectors where meridional flows do not change their direction in the course of time comparable with synoptic periods. The longitudinal distribution of meridional wind in middle latitudes taken from the analysis results of radiometeor and ionospheric stations observational data obtained in 1976 to 1980 are presented. Meridional winds have a longitudinal variability that is equivalent to both the warm and cold half years.

Bekbasarov, R. B.↗
NASA NTRS1990

Heating of the polar wind due to ion beam instabilities

Recent DE 1 observations (Chen et al., 1990) in the polar cap region have detected upflowing field-aligned O(+) and H(+) beams of about 10 eV energy; it was suggested that these beams may interact with the polar wind and provide free energy to the polar wind which will alter its 'classical' description. This paper investigates both the linear and the nonlinear effects of upflowing O(+) and H(+) ion beams on an O(+) and H(+) polar wind by applying isotropic Maxwellian distributions for modeling the O(+) and H(+) polar-wind ions and using drifting Maxwellian distributions for the electrons, O(+), and H(+) beam ions. It is shown that, in the presence of O(+) and H(+) beams, the slow ion acoustic and slow ion cyclotron modes can couple to the normal modes of the plasma and be driven unstable. The O(+) ions are preferentially heated over the H(+) ions; this preferential heating couses enhanced outflow of O(+) ions along polar cap field lines by effectively increasing the O(+) scale height.

Chen, Margaret W.↗
NASA NTRS1994

Pressure distributions on a 0.02-scale Space Shuttle orbiter nose at Mach 21.5 in helium

Pressure distributions on a 0.02-scale model of the Space Shuttle orbiter forward fuselage were obtained in the 22-inch aerodynamic leg of the Langley Hypersonic Helium Tunnel Facility at a nominal free-stream Mach number of 21.5 and a ratio of specific heats of 1.67 for inclusion in the database of the Shuttle entry air data system (SEADS). The data were measured at model angles of attack of 0 deg to 50 deg in 5 deg increments for zero sideslip angle and at model sideslip angles of -5 deg to 5 deg for angles of attack equal to 5, 20, 35, and 40 deg. These data displayed trends similar to those observed in other wind tunnels at Mach 6 and 10 in air. Specifically noted is a shift in the location of the stagnation point at angles of attack above 15 deg; this effect did not, however, occur in flight. By comparison, the data obtained at Mach 6 in the Langley Hypersonic CF4 Tunnel, corresponding to a lower ratio of specific heats in the postshock region than those in helium and air, showed some reduction of the stagnation point shift at the higher angles of attack. The differences between flight and wind tunnel pressure distributions are believed due primarily to high-temperature gas chemistry effects in flight, which include lower effective specific heat ratios but which were not completely duplicated in the wind tunnels.

Ashby, George C., Jr.↗
NASA NTRS2001

Static and Wind Tunnel Aero-Performance Tests of NASA AST Separate Flow Nozzle Noise Reduction Configurations

This report presents the results of cold flow model tests to determine the static and wind tunnel performance of several NASA AST separate flow nozzle noise reduction configurations. The tests were conducted by Aero Systems Engineering, Inc., for NASA Glenn Research Center. The tests were performed in the Channels 14 and 6 static thrust stands and the Channel 10 transonic wind tunnel at the FluiDyne Aerodynamics Laboratory in Plymouth, Minnesota. Facility checkout tests were made using standard ASME long-radius metering nozzles. These tests demonstrated facility data accuracy at flow conditions similar to the model tests. Channel 14 static tests reported here consisted of 21 ASME nozzle facility checkout tests and 57 static model performance tests (including 22 at no charge). Fan nozzle pressure ratio varied from 1.4 to 2.0, and fan to core total pressure ratio varied from 1.0 to 1.19. Core to fan total temperature ratio was 1.0. Channel 10 wind tunnel tests consisted of 15 tests at Mach number 0.28 and 31 tests at Mach 0.8. The sting was checked out statically in Channel 6 before the wind tunnel tests. In the Channel 6 facility, 12 ASME nozzle data points were taken and 7 model data points were taken. In the wind tunnel, fan nozzle pressure ratio varied from 1.73 to 2.8, and fan to core total pressure ratio varied from 1.0 to 1.19. Core to fan total temperature ratio was 1.0. Test results include thrust coefficients, thrust vector angle, core and fan nozzle discharge coefficients, total pressure and temperature charging station profiles, and boat-tail static pressure distributions in the wind tunnel.

Mikkelsen, Kevin L.↗
NASA NTRSDate not supplied

Strategic Planning with Unscented Optimal Guidance for Urban Air Mobility

This study proposes a strategic trajectory planning framework to support development of Urban Air Mobility (UAM) traffic networks and optimization of UAM aircraft trajectories that are robust to uncertain wind fields. The development of UAM traffic networks considers static aviation constraints and dynamic weather constraints in urban airspace and the connections to ground transportation networks for preliminary selection of feasible time-optimal routes. The trajectory optimization of UAM aircraft utilizes an unscented optimal guidance approach to generate cost-optimal trajectories constrained on the selected sigma values of probability distribution of uncertain wind fields while ensuring that the end-point constraints are met for reducing wind-induced trajectory uncertainty. Unscented guidance commands are assessed based on trajectory perturbations at subsequent end-points in various wind fields by conducting Monte Carlo simulations.An example of wind-optimal UAM corridor and the associated trajectory-based operation volume is created utilizing the perturbations of the unscented trajectories for preliminary assessment of required aircraft separation minima without knowledge of aircraft navigation performance.

Strategic Planning↗
NASA NTRS2008

Variations of Strahl Properties with Fast and Slow Solar Wind

The interplanetary solar wind electron velocity distribution function generally shows three different populations. Two of the components, the core and halo, have been the most intensively analyzed and modeled populations using different theoretical models. The third component, the strahl, is usually seen at higher energies, is confined in pitch-angle, is highly field-aligned and skew. This population has been more difficult to identify and to model in the solar wind. In this work we make use of the high angular, energy and time resolution and three-dimensional data of the Cluster/PEACE electron spectrometer to identify and analyze this component in the ambient solar wind during high and slow speed solar wind. The moment density and fluid velocity have been computed by a semi-numerical integration method. The variations of solar wind density and drift velocity with the general build solar wind speed could provide some insight into the source, origin, and evolution of the strahl.

Figueroa-Vinas, Adolfo↗