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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Comparison of road load simulator test results with track tests on electric vehicle propulsion system

A special-purpose dynamometer, the road load simulator (RLS), is being used at NASA's Lewis Research Center to test and evaluate electric vehicle propulsion systems developed under DOE's Electric and Hybrid Vehicle Program. To improve correlation between system tests on the RLS and track tests, similar tests were conducted on the same propulsion system on the RLS and on a test track. These tests are compared in this report. Battery current to maintain a constant vehicle speed with a fixed throttle was used for the comparison. Scatter in the data was greater in the track test results. This is attributable to variations in tire rolling resistance and wind effects in the track data. It also appeared that the RLS road load, determined by coastdown tests on the track, was lower than that of the vehicle on the track. These differences may be due to differences in tire temperature.

Dustin, M. O.↗
NASA NTRS1984

Wind loading on solar concentrators: Some general considerations

A survey was completed to examine the problems and complications arising from wind loading on solar concentrators. Wind loading is site specific and has an important bearing on the design, cost, performance, operation and maintenance, safety, survival, and replacement of solar collecting systems. Emphasis herein is on paraboloidal, two-axis tracking systems. Thermal receiver problems also are discussed. Wind characteristics are discussed from a general point of view. Current methods for determining design wind speed are reviewed. Aerodynamic coefficients are defined and illustrative examples are presented. Wind tunnel testing is discussed, and environmental wind tunnels are reviewed. Recent results on heliostat arrays are reviewed as well. Aeroelasticity in relation to structural design is discussed briefly.

Roschke, E. J.↗
NASA NTRS1985

A preliminary investigation of the dynamic force-calibration of a magnetic suspension and balance system

The aerodynamic forces and moments acting upon a magnetically suspended wind tunnel model are derived from calibrations of suspension electro magnet currents against known forces. As an alternative to the conventional calibration method of applying steady forces to the model, early experiences with dynamic calibration are outlined, that is a calibration obtained by oscillating a model in suspension and deriving a force/current relationship from its inertia force and the unsteady components of currents. Advantages of dynamic calibration are speed and simplicity. The two methods of calibration applied to one force component show good agreement.

Goodyer, M. J.↗
NASA NTRS1985

Electrostatic instabilities in plasmas with two electron components

This paper considers the linear theory of electrostatic Vlasov instabilities driven by the relative drift between two Maxwellian electron components in an unmagnetized, homogeneous plasma bearing zero current. The dispersion properties, threshold drift speeds and growth rates of the electron beam instability, the conventional ion acoustic instability, and the ion acoustic beam instability are compared in detailed parametric studies. A new way of illustrating the parameter regimes in whih each of these three instabilities has the lowest threshold drift speed is demonstrated. This leads to clearly illustrated criteria for determining when enhanced electrostatic fluctuations between the ion and the electron plasma frequencies may be observed in plasmas with two electron components. In the case of a hot beam this criterion is a beam density n(b) which satisfies n(b)/n(e) is between 0.05 and 0.30 where n(e) is the total electron density.

Gary, S. P.↗
NASA NTRS1986

Synopsis of Magnetohydrodynamic Power Generation

Concise summary of magnetohydrodynamic (MHD) theory, history, and future trends presented in report. Worldwide research on MHD covered, and selected data from key research projects included. Magnetohydrodynamic generator produces electric current by passing fluid at high speed through strong magnetic field. Fluid ionized gas, plasma, or liquid metal. Magnetohydrodynamic generators offer potential for high efficiency, low power cost, and cleaner emissions.

Smith, J. L.↗
NASA NTRS1986

Origins of the solar wind in the corona

The coronal origins of the solar wind are considered. Potential sources of low-speed wind which are consistent with current data, including streamers and the interfaces between them and other coronal regions, await mass flow measurements for confirmation. A Doppler-dimming technique utilizing a white-light coronagraph and UV coronal spectrometer is to be employed aboard the Space Shuttle SPARTAN program, and its usage on Ulysses may provide information on mass flows in streamers and their surroundings.

Withbroe, G. L.↗
NASA NTRS1986

The Navier-Stokes computer

The Navier-Stokes computer (NSC) has been developed for solving problems in fluid mechanics involving complex flow simulations that require more speed and capacity than provided by current and proposed Class VI supercomputers. The machine is a parallel processing supercomputer with several new architectural elements which can be programmed to address a wide range of problems meeting the following criteria: (1) the problem is numerically intensive, and (2) the code makes use of long vectors. A simulation of two-dimensional nonsteady viscous flows is presented to illustrate the architecture, programming, and some of the capabilities of the NSC.

Nosenchuck, D. M.↗
NASA NTRS1987

Jet stream velocity errors in general circulation models

The longitude and time dependence of excessive wind speed errors above subtropical jets in current GCM forecasts is studied for 14 five-day winter forecasts using the NASA Goddard Laboratory for Atmospheres fourth-order GCM. Several distinct phenomena, which may be divided into four categories, are found to contribute to the excess winds. These categories are: (1) error growth above the jet near the Himalayas; (2) error growth above the jet initiated elsewhere followed by advection; (3) tropical moisture bursts appearing in equatorial regions and migrating northeastward to merge with and distort the jet; and (4) undulatory growth of waves in the meridional component of the jet stream velocity. The results of additional sensitivity studies of the Himalayan region error are also reported.

Tenenbaum, J.↗
NASA NTRS1988

An experimental test of the 'transmission-line model' of electromagnetic radiation from triggered lightning return strokes

Peak currents, two-dimensional average propagation speeds, and electric field waveforms for a number of subsequent return strikes in rocket-triggered lightning flashes were measured in order to test the 'transmission-line model' of return-stroke radiation of Uman and McLain (1970). Reasonable agreement is found between the propagation speeds measured with the streak camera and those deduced from the transmission-line model. A modification of the model is proposed in which two wave fronts travel upward and downward away from a junction point a short distance above the ground.

Willett, J. C.↗
NASA NTRS1988

On the surface magnetic fields of rapidly rotating stars with winds

The consistency of estimates of angular velocities and magnetic field strength obtained from magnetic rotator models is examined. Upper and lower bounds for the surface magnetic field are derived with constraints of interior theory using magnetohydrodynamic considerations. The formulas for the bounds are applied to rapidly rotating Be stars and Wolf-Rayet type stars using Eddington-Vogt speed relevant for the radiative diffusion zone. It is suggested that stars which have equatorially enhanced winds driven by magnetic rotator effects must have fields such that the Aflven speed is close to the speed of the Eddington-Vogt currents at the base of the stellar atmosphere.

Maheswaran, Murugesapillai↗
NASA NTRS1989

Traveling-wave induction launchers

An analysis of traveling-wave induction launchers shows that induction is a feasible method of producing armature current and that efficient accelerators can be built without sliding contacts or arcs. In a traveling-wave induction launcher the armature current is induced by a slip speed between the armature and a traveling magnetic field. At 9 m/s slip speed a 9 kg projectile with an aluminum armature weighing 25 percent of the total mass can be accelerated to 3000 m/s in a 5 m-long barrel with a total ohmic loss in the barrel coils and armature of 4 percent of the launch kinetic energy and with an average armature temperature rise of 220 deg C, but a peak excitation frequency of 8600 Hz is required. With a 2 kg launch mass the ohmic loss is 7 percent. A launcher system optimized for rotating generators would have a peak frequency of 4850 Hz; with an aluminum armature weighing 33 percent of the launch mass and a slip speed of 30 m/s the total ohmic loss in the generators, cables, and accelerator would be 43 percent of the launch kinetic energy, and the average armature temperature rise would be 510 deg C.

Elliott, David G.↗
NASA NTRS1990

Data compression applied to HHVT

A task order was written by the High Resolution, High Frame Rate Video Technology (HHVT) project engineers to study data compression techniques that could be applied to the HHVT system. Specifically, the goals of the HHVT data compression study are to accomplish the following: (1) Determine the downlink capabilities of the Space Shuttle and Space Station Freedom to support HHVT data (i.e., determine the maximum data rates and link availability); (2) Determine current and projected capabilities of high speed storage media to support HHVT data by determining their maximum data acquisition/transmission rates and volumes; (3) Identify which experiment in the HHVT Users' Requirement data base need data compression, based on the experiments' imaging requirements; (4) Select the best data compression technique for each of these users by identifying a technique that provides compression but minimizes distortion; and (5) Investigate state-of-the-art technologies for possible implementation of selected data compression techniques. Data compression will be needed because of the high data rates and larger volumes of data that will result from the use of digitized video onboard the Space Shuttle and Space Station Freedom.

Thompson, William K.↗
NASA NTRS1990

Equilibrium structure of the plasma sheet boundary layer-lobe interface

Observations are presented which show that plasma parameters vary on a scale length smaller than the ion gyroradius at the interface between the plasma sheet boundary layer and the lobe. The Vlasov equation is used to investigate the properties of such a boundary layer. The existence, at the interface, of a density gradient whose scale length is smaller than the ion gyroradius implies that an electrostatic potential is established in order to maintain quasi-neutrality. Strongly sheared (scale lengths smaller than the ion gyroradius) perpendicular and parallel (to the ambient magnetic field) electron flows develop whose peak velocities are on the order of the electron thermal speed and which carry a net current. The free energy of the sheared flows can give rise to a broadband spectrum of electrostatic instabilities starting near the electron plasma frequency and extending below the lower hybrid frequency.

Romero, H.↗
NASA NTRS1992

STARBASE: Database software for the automated plate scanner

The Automated Plate Scanner (APS) of the University of Minnesota, a unique high speed 'flying spot' laser scanner, is currently being used to scan and digitize the 936 O and E plate pairs of the first epoch Palomar Sky Survey. The resultant database will be used to produce a catalog of approximately a billion stars and several million galaxies. The authors describe the ongoing development of a dedicated APS database management system which will be made available to the astronomical community via INTERNET. A specialized DBMS called STARBASE has been written to provide fast access to the hundreds of millions of images collected by the APS. This system provides an initial reduction mode for parameterizing APS images and classifying image types using a novel set of neural network image classifiers. A second analysis mode, which will be that commonly used by the general user, provides for searches of the database which may be constrained by any combination of physical and positional parameters. Through the use of pointer hash trees, the system has been optimized for extremely fast positional searches using either right ascension and declination on the sky or linear X and Y positions on the POSS field. In addition to fast data retrieval, the system provides a graphical interface for displaying scatter plots or histograms of the collected data. In addition, a specialized image display system is being developed to allow the user to view densitometric data for all objects classified as extended by the neural network system. Finally, STARBASE has a flexible programmable interface which allows other programs to access information in the database. This allows users to write applications suited to their particular needs to process APS data.

Odewahn, S. C.↗
NASA NTRS1994

An acoustic charge transport imager for high definition television applications

The primary goal of this research is to develop a solid-state television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels/frame. This imager will offer an order of magnitude improvements in speed over CCD designs and will allow for monolithic imagers operating from the IR to UV. The technical approach of the project focuses on the development of the three basic components of the imager and their subsequent integration. The camera chip can be divided into three distinct functions: (1) image capture via an array of avalanche photodiodes (APD's); (2) charge collection, storage, and overflow control via a charge transfer transistor device (CTD); and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the optimization of each of these component devices. In addition to the development of each of the three distinct components, work towards their integration and manufacturability is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail.

Hunt, W. D.↗
NASA NTRS1994

An acoustic charge transport imager for high definition television applications

The primary goal of this research is to develop a solid-state high definition television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels per frame. This imager offers an order of magnitude improvement in speed over CCD designs and will allow for monolithic imagers operating from the IR to the UV. The technical approach of the project focuses on the development of the three basic components of the imager and their integration. The imager chip can be divided into three distinct components: (1) image capture via an array of avalanche photodiodes (APD's), (2) charge collection, storage and overflow control via a charge transfer transistor device (CTD), and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the development of manufacturable designs for each of these component devices. In addition to the development of each of the three distinct components, work towards their integration is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail in Sections 2-4.

Hunt, W. D.↗
NASA NTRS1994

Latitudinal variation of speed and mass flux in the acceleration region of the solar wind inferred from spectral broadening measurements

Spectral broadening measurements conducted at S-band (13-cm wavelength) during solar minimum conditions in the heliocentric distance range of 3-8 R(sub O) by Mariner 4, Pioneer 10, Mariner 10, Helios 1, Helios 2, and Viking have been combined to reveal a factor of 2.6 reduction in bandwidth from equator to pole. Since spectral broadening bandwidth depends on electron density fluctuation and solar wind speed, and latitudinal variation of the former is available from coherence bandwidth measurements, the remote sensing spectral broadening measurements provide the first determination of the latitudinal variation of solar wind speed in the acceleration region. When combined with electron density measurements deduced from white-light coronagraphs, this result also leads to the first determination of the latitudinal variation of mass flux in the acceleration region. From equator to pole, solar wind speed increases by a factor of 2.2, while mass flux decreases by a factor of 2.3. These results are consistent with measurements of solar wind speed by multi-station intensity scintillation measurements, as well as measurements of mass flux inferred from Lyman alpha observations, both of which pertain to the solar wind beyond 0.5 AU. The spectral broadening observations, therefore, strengthen earlier conclusions about the latitudinal variation of solar wind speed and mass flux, and reinforce current solar coronal models and their implications for solar wind acceleration and solar wind modeling.

Woo, Richard↗
NASA NTRS1995

Development of multiobjective optimization techniques for sonic boom minimization

An optimization procedure is developed for the simultaneous improvement of the aerodynamic and sonic boom characteristics of high speed aircraft. From a sonic boom perspective, it is desirable to minimize the first peak in the overpressure signal at a specified distance away from the aircraft. From aerodynamic point of view, the aerodynamic drag coefficient ratio must be minimized while maintaining the lift coefficient at desired level. The optimization procedure is applied to wing-body configurations related to high speed aircraft. The objectives of this current research are: (1) development of a multiobjective optimization procedure for aerospace vehicles with the integration of sonic boom and aerodynamic performance criteria; and (2) development of semi-analytical approach for calculating sonic boom design sensitivities.

Chattopadhyay, Aditi↗