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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 451 records · Page 25

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NASA NTRS1986

A three-dimensional MHD simulation of the interaction of the solar wind with the earth's magnetosphere - The generation of field-aligned currents

The time-dependent interaction of the solar wind with the earth's magnetosphere is simulated using a three-dimensional MHD model. The bow shock, magnetopause, magnetotail, and plasma sheet of the magnetosphere and Birkeland field-aligned currents that are dependent on the polarity of the z component of the IMF are produced. Twin convection cells and a dawn to dusk electric potential of 30-100 kV are detected at the equator in the magnetosphere. Four types of field-aligned currents are observed: region 1, region 2, dayside magnetopause currents in the dayside cusp region, and the dayside cusp currents for southward IMF. Region 1 and 2 field-aligned currents generated for all IMF conditions are 0.6-1.0 x 10 to the 6th A and 0.15-0.61 x 10 to the 6th A, respectively. The relationship between region 1 currents and field-aligned vorticity, and region 2 currents and pressure gradients are studied. The simulated data are compared with a theoretical analysis of the field-aligned currents and good correlation is observed.

Ogino, T.↗

NASA NTRS1975

Wind energy utilization: A bibliography with abstracts - Cumulative volume 1944/1974

Bibliography, up to 1974 inclusive, of articles and books on utilization of wind power in energy generation. Worldwide literature is surveyed, and short abstracts are provided in many cases. The citations are grouped by subject: (1) general; (2) utilization; (3) wind power plants; (4) wind power generators (rural, synchronous, remote station); (5) wind machines (motors, pumps, turbines, windmills, home-built); (6) wind data and properties; (7) energy storage; and (8) related topics (control and regulation devices, wind measuring devices, blade design and rotors, wind tunnel simulation, aerodynamics). Gross-referencing is aided by indexes of authors, corporate sources, titles, and keywords.

Source record↗

NASA NTRS1986

Aspects of the determination of winds by means of scatterometry and of the utilization of vector wind data for meteorological forecasts

The present paper provides a description of four aspects of scatterometer winds and their uses. The theory of wave generation by the wind is considered along with an analysis of the properties of superobservations, and studies of intermittent versus continuous data assimilation methods for numerical weather predictions which use remotely sensed data. A comparison of the sum of squares versus the maximum likelihood method for recovering the vector winds is also conducted. Questions regarding wind speed, friction velocity, or normal stress are discussed and synoptic scale fields from Seasat-SASS data are examined.

Pierson, W. J., Jr.↗

NASA NTRS2000

Enhancement of Directional Ambiguity Removal Skill in Scatterometer Data Processing Using Planetary Boundary Layer Models

Planetary boundary layer (PBL) models are utilized to enhance directional ambiguity removal skill in scatterometer data processing. The ambiguity in wind direction retrieved from scatterometer measurements is removed with the aid of physical directional information obtained from PBL models. This technique is based on the observation that sea level pressure is scalar and its field is more coherent than the corresponding wind. An initial wind field obtained from the scatterometer measurements is used to derive a pressure field with a PBL model. After filtering small-scale noise in the derived pressure field, a wind field is generated with an inverted PBL model. This derived wind information is then used to remove wind vector ambiguities in the scatterometer data. It is found that the ambiguity removal skill can be improved when the new technique is used properly in conjunction with the median filter being used for scatterometer wind dealiasing at JPL. The new technique is applied to regions of cyclone systems which are important for accurate weather prediction but where the errors of ambiguity removal are often large.

Kim, Young-Joon↗

NASA NTRS2007

Turbulent Aeroheating Testing of Mars Science Laboratory Entry Vehicle in Perfect-Gas Nitrogen

An experimental investigation of turbulent aeroheating on the Mars Science Laboratory entry vehicle heat shield has been conducted in the Arnold Engineering Development Center Hypervelocity Wind Tunnel No. 9. Testing was performed on a 6-in. (0.1524 m) diameter MSL model in pure N2 gas in the tunnel s Mach 8 and Mach 10 nozzles at free stream Reynolds numbers of 4.1x10(exp 6)/ft to 49x10(exp 6)/ft (1.3x10(exp 7)/m to 16x10(exp 7)/m) and 1.2x10(exp 6)/ft to 19x10(exp 6)/ft (0.39x10(exp 7)/m to 62x10(exp 7)/m), respectively. These conditions were sufficient to span the regime of boundary-layer flow from completely laminar to fully-developed turbulent flow over the entire forebody. A supporting aeroheating test was also conducted in the Langley Research Center 20-Inch Mach 6 Air Tunnel at free stream Reynolds number of 1x10(exp 6)/ft to 7x10(exp 6)/ft (0.36x10(exp 7)/m to 2.2x10(exp 7)/m) in order to help corroborate the Tunnel 9 results. A complementary computational fluid dynamics study was conducted in parallel to the wind tunnel testing. Laminar and turbulent predictions were generated for all wind tunnel test conditions and comparisons were performed with the data for the purpose of helping to define uncertainty margins on predictions for aeroheating environments during entry into the Martian atmosphere. Data from both wind tunnel tests and comparisons with the predictions are presented herein. It was concluded from these comparisons that for perfect-gas conditions, the computational tools could predict fully-laminar or fully-turbulent heating conditions to within 10% of the experimental data

Hollis, Brian R.↗

NASA NTRS2008

Turbulent Aeroheating Testing of Mars Science Laboratory Entry Vehicle

An experimental investigation of turbulent aeroheating on the Mars Science Laboratory entry vehicle heat shield has been conducted in the Arnold Engineering Development Center Hypervelocity Wind Tunnel No. 9. Testing was performed on a 6-in. (0.1524 m) diameter MSL model in pure N2 gas in the tunnel's Mach 8 and Mach 10 nozzles at free stream Reynolds numbers of 4.1 x 10(exp 6)/ft to 49 x 10(exp 6)/ft (1.3 x 10(exp 7)/m to 19 x 10(exp 6/ft) and 1.2 x 10(exp 6)/ft to 19 x 10(exp 6)/ft (0.39 x 10(exp 7)/m to 62 x 10(exp 7)/m), respectively. These conditions were sufficient to span the regime of boundary-layer flow from completely laminar to fully-developed turbulent flow over the entire forebody. A supporting aeroheating test was also conducted in the Langley Research Center 20-Inch Mach 6 Air Tunnel at free stream Reynolds number of 1 x 10(exp 6)/ft to 7 x 10(exp 6)/ft (0.36 x 10(exp 7)/m to 2.2 x 10(exp 7)/m) in order to help corroborate the Tunnel 9 results. A complementary computational fluid dynamics study was conducted in parallel to the wind tunnel testing. Laminar and turbulent predictions were generated for the wind tunnel test conditions and comparisons were performed with the data for the purpose of helping to define uncertainty margins on predictions for aeroheating environments during entry into the Martian atmosphere. Data from both wind tunnel tests and comparisons with the predictions are presented herein. It was concluded from these comparisons that for perfect-gas conditions, the computational tools could predict fully-laminar or fully-turbulent heating conditions to within 12% or better of the experimental data.

Hollis, Brian R.↗

NASA NTRS2017

Experimental Investigation of Mars Science Laboratory Entry Vehicle Aeroheating in AEDC Hypervelocity Tunnel 9

An experimental investigation of the aeroheating environment of the Mars Science Laboratory entry vehicle was conducted in the Arnold Engineering Development Complex Hypervelocity Wind Tunnel 9. Testing was performed on a 6-in. (0.1524 m) diameter model in the tunnel's Mach 8 and Mach 10 nozzles at free stream Reynolds numbers from 4.1×10*exp 6)/ft to 49×10(exp 6)/ft and from 1.2×10(exp 6)/ft to 19×10(exp 6)/ft, respectively, using pure nitrogen test gas. These conditions spanned the boundary layer flow regimes from completely laminar to fully turbulent flow over the entire forebody. A computational fluid dynamics study was conducted in support of the wind tunnel testing. Laminar and turbulent solutions were generated for all wind tunnel test conditions and comparisons of predicted heating distributions were performed with the data. These comparisons showed agreement for most cases to within the estimated +/-12% experimental uncertainty margin for fully-laminar or fully-turbulent conditions, while transitional heating data were bounded by laminar and turbulent predictions. These results helped to define uncertainty margins on the use of computational tools for vehicle design.

Hollis, Brian R.↗

NASA NTRS2008

Control System for Bearingless Motor-generator

A control system for an electromagnetic rotary drive for bearingless motor-generators comprises a winding configuration comprising a plurality of individual pole pairs through which phase current flows, each phase current producing both a lateral force and a torque. A motor-generator comprises a stator, a rotor supported for movement relative to the stator, and a control system. The motor-generator comprises a winding configuration supported by the stator. The winding configuration comprises at least three pole pairs through which phase current flows resulting in three three-phase systems. Each phase system has a first rotor reference frame axis current that produces a levitating force with no average torque and a second rotor reference frame axis current that produces torque.

Kascak, Peter E.↗

NASA NTRS2010

Control system for bearingless motor-generator

Kascak, Peter E.↗

NASA NTRS1983

Minor constituents in the solar wind originating from plasma-dust interactions

Atoms, molecules, and atomic and molecular ions generated by solar wind interactions with dust grains of the zodiacal cloud are discussed. The main processes leading to the generation of these particles are described and relevant methods of observation are examined.

Ripken, H. W.↗

NASA NTRS1999

Wind Forcing of the Pacific Ocean Using Scatterometer Wind Data

The long-term objective of this research was an understanding of the wind-forced ocean circulation, particularly for the Pacific Ocean. To determine the ocean's response to the winds, we first needed to generate accurate maps of wind stress. For the ocean's response to wind stress we examined the sea surface height (SSH) both from altimeters and from numerical models for the Pacific Ocean.

Kelly, Kathryn A.↗

NASA NTRSDate not supplied

Wind Tunnel Testing of Next-Generation High-Speed Engines

This talk will introduce students to supersonic and hypersonic flows as well as cover why these high-speed flow regimes are important to us today. The main focus is on the different propulsion systems used in Mach 3+ flight and how they are tested in wind tunnel facilities. Different wind tunnels at NASA Langley will used to demonstrate how ground tests facilitate the development of new engines from a proof-of-concept to a mature flight qualified design. There are many opportunities in field of high-speed aeronautics. I'll discuss my path to NASA Langley then give advice for internship and job opportunities at NASA.

Robin Hunt↗

NASA NTRS2016

Pre-Test Assessment of the Use Envelope of the Normal Force of a Wind Tunnel Strain-Gage Balance

The relationship between the aerodynamic lift force generated by a wind tunnel model, the model weight, and the measured normal force of a strain-gage balance is investigated to better understand the expected use envelope of the normal force during a wind tunnel test. First, the fundamental relationship between normal force, model weight, lift curve slope, model reference area, dynamic pressure, and angle of attack is derived. Then, based on this fundamental relationship, the use envelope of a balance is examined for four typical wind tunnel test cases. The first case looks at the use envelope of the normal force during the test of a light wind tunnel model at high subsonic Mach numbers. The second case examines the use envelope of the normal force during the test of a heavy wind tunnel model in an atmospheric low-speed facility. The third case reviews the use envelope of the normal force during the test of a floor-mounted semi-span model. The fourth case discusses the normal force characteristics during the test of a rotated full-span model. The wind tunnel model's lift-to-weight ratio is introduced as a new parameter that may be used for a quick pre-test assessment of the use envelope of the normal force of a balance. The parameter is derived as a function of the lift coefficient, the dimensionless dynamic pressure, and the dimensionless model weight. Lower and upper bounds of the use envelope of a balance are defined using the model's lift-to-weight ratio. Finally, data from a pressurized wind tunnel is used to illustrate both application and interpretation of the model's lift-to-weight ratio.

strain-gage balance↗

NASA NTRS1994

Optically broadcasting wind direction indicator

An optically broadcasting wind direction indicator generates flashes of light which are separated by a time interval that is directly proportional to the angle of the wind direction relative to a fixed direction, such as north. An angle/voltage transducer generates a voltage that is proportional to the wind direction relative to the fixed direction, and this voltage is employed by timing circuitry or a microprocessor that generates pulses for actuating a light source trigger circuit first at the start of the time interval, and then at the end of the time interval. To aid an observer in distinguishing between the beginning and end of the interval, two stop flashes can be provided in quick succession. The time scale is preferably chosen so that each second of the time interval corresponds to 30 deg of direction relative to north. In this manner, an observer can easily correlate the measured time interval to the wind direction by visualizing the numbers on a conventional clock face, each of which correspond to one second of time and 30 deg of angle.

Zysko, Jan A.↗

NASA NTRS2004

Tropospheric Wind Monitoring During Day-of-Launch Operations for National Aeronautics and Space Administration's Space Shuttle Program

The Environments Group at the National Aeronautics and Space Administration's Marshall Space Flight Center (NASA/MSFC) monitors the winds aloft at Kennedy Space Center (KSC) during the countdown for all Space Shuttle launches. Assessment of tropospheric winds is used to support the ascent phase of launch. Three systems at KSC are used to generate independent tropospheric wind profiles prior to launch; 1) high resolution Jimsphere balloon system, 2) 50-MHz Doppler Radar Wind Profiler (DRWP) and 3) low resolution radiosonde system. Data generated by the systems are used to assess spatial and temporal wind variability during launch countdown to ensure wind change observed does not violate wind change criteria constraints.

Decker, Ryan K.↗

NASA NTRS1979

Large horizontal axis wind turbine development

An overview of the NASA activities concerning ongoing wind systems oriented toward utility application is presented. First-generation-technology large wind turbines were designed and are in operation at selected utility sites. In order to make a significant energy impact, costs of 2 to 3 cents per kilowatt hour must be achieved. The federal program continues to fund the development by industry of wind turbines which can meet the cost goals of 2 to 3 cents per kilowatt hour. Lower costs are achieved through the incorporation of new technology and innovative system design to reduce weight and increase energy capture.

Robbins, W. H.↗

NASA NTRS1986

Observations of vertical winds and the origin of thermospheric gravity waves launched by auroral substorms and westward travelling surges

Several sequences of observations of strong vertical winds in the upper thermosphere are discussed, in conjunction with models of the generation of such winds. In the auroral oval, the strongest upward winds are observed in or close to regions of intense auroral precipitation and strong ionospheric currents. The strongest winds, of the order of 100 to 200 m/sec are usually upward, and are both localized and of relatively short duration (10 to 20 min). In regions adjacent to those displaying strong upward winds, and following periods of upward winds, downward winds of rather lower magnitude (40 to about 80 m/sec) may be observed. Strong and rapid changes of horizontal winds are correlated with these rapid vertical wind variations. Considered from a large scale viewpoint, this class of strongly time dependent winds propagate globally, and may be considered to be gravity waves launched from an auroral source. During periods of very disturbed geomagnetic activity, there may be regions within and close to the auroral oval where systematic vertical winds of the order of 50 m/sec will occur for periods of several hours. Such persistent winds are part of a very strong large scale horizontal wind circulation set up in the polar regions during a major geomagnetic disturbance. This second class of strong horizontal and vertical winds corresponds more to a standing wave than to a gravity wave, and it is not as effective as the first class in generating large scale propagating gravity waves and correlated horizontal and vertical oscillations. A third class of significant (10 to 30 m/sec) vertical winds can be associated with systematic features of the average geomagnetic energy and momentum input to the polar thermosphere, and appear in statistical studies of the average vertical wind as a function of Universal Time at a given location.

Rees, D.↗

NASA NTRS2013

Solar Wind Strahl Broadening by Self-Generated Plasma Waves

This Letter reports on the results of numerical simulations which may provide a possible explanation for the strahl broadening during quiet solar conditions. The relevant processes involved in the broadening are due to kinetic quasi-linear wave-particle interaction. Making use of static analytical electron distribution in an inhomogeneous field, it is found that self-generated electrostatic waves at the plasma frequency, i.e., Langmuir waves, are capable of scattering the strahl component, resulting in energy and pitch-angle diffusion that broadens its velocity distribution significantly. The present theoretical results provide an alternative or complementary explanation to the usual whistler diffusion scenario, suggesting that self-induced electrostatic waves at the plasma frequency might play a key role in broadening the solar wind strahl during quiet solar conditions.

strahl↗