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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

AC and DC Fault Management for Megawatt Electrified Aircraft Electrical Powertrains - Task 2: Power Quality Filtering Using Nanocrystalline Soft Magnetic Inductor

The NASA RTAPS program on AC and DC Fault Management for Megawatt Electrified Power Train is a multi-year joint project with Pratt & Whitney (P&W), Collins Aerospace (CA), and RTX Technology Research Center (RTRC). This research program focuses on the high-voltage distribution issues that present a significant technological obstacle in the adoption of Electrified Aviation Propulsion (EAP) systems. One challenge to the adoption of high-voltage distribution systems with power electronic converters is the need for filter elements to limit the generation and propagation of noise, protect the cable systems from premature aging and prevent against excessive heating within subcomponents due to high-frequency induced currents. While increased distribution voltages aide in reducing the cable mass for a fixed power system, the associated mass with the filtering elements for power electronic converter can grow with increasing distribution voltages – thereby mitigating any benefit associated with increasing the distribution system voltage. To enable high-voltage distribution systems with high system specific power densities, new magnetic materials must be developed. Therefore, the second task of the NASA RTAPS program is associated with the design and application of advanced soft magnetic components for Megawatt class electric propulsion systems, specifically the motor drive system. This report covers the collaborative work between NASA Glenn Research Center (GRC), RTRC, P&W and CA in the development of three types of magnetic components over the span of the three-year program. These critical magnetic components are the DC side EMI filter, which limits the propagation of harmful electromagnetic noise to the rise of the distribution system, and the AC side damping with the dv/dt filter, which limits the fast rise time of the power electronic converter output voltage to limit the degradation on the cable/motor insulation systems. Each of these components are investigated from component level design and are optimized at the system level with a combined modelling and testing effort. In the final experimental evaluation of the NASA developed soft magnetic material with a dv/dt filter, a commercial-off-the-shelf (COTS) magnetic core and the GRC magnetic core are optimized and loaded at 320Arms to evaluate their difference in performance. After a run time of 30 minutes in a MW-class motor driver at RTRC, the NASA GRC cores were found to not only offer a lower temperature rise of nearly 25°𝐶, but also a reduction in measured core loss of 25% (12.75W to 9.5W).

Elecrified Aircraft Propulsion↗
NASA NTRS2017

Fabrication of Lightweight Radiation Shielding Composite Materials by Field Assisted Sintering Technique (FAST)

Advances in radiation shielding technologies are needed to protect humans and electronic components from all threats of space radiation over long durations. In this paper, we report on the use of the innovative and novel fabrication technology known as Field Assisted Sintering Technology (FAST) to fabricate lightweight material with enhanced radiation shielding strength to safeguard humans and electronics suitable for next generation space exploration missions. The base materials we investigated were aluminum (Al), the current standard material for space hardware, and Ultra-High Molecular Weight Polyethylene (UHMWPE), which has high hydrogen content and resistance to nuclear reaction from neutrons, making it a good shielding material for both gamma radiation and particles. UHMWPE also has high resistance to corrosive chemicals, extremely low moisture sensitivity, very low coefficient of friction, and high resistance to abrasion. We reinforced the base materials by adding high density (ie, high atomic weight) metallic material into the composite. These filler materials included: boron carbide (B4C), tungsten (W), tungsten carbide (WC) and gadolinium (Gd).

Prasad, Narasimha↗
NASA NTRS1994

A Superconducting Hot Electron Bolometer Mixer for 530 GHz

This paper describes a superconducting hot electron bolometer mixer that uses diffusion rather than interactions with phonons as a cooling mechanism for the hot electrons. The bolometer is a 0.14 µm; wide niobium microbridge with a length less than 0.5 µm;. The submicron length ensures rapid diffusion of the hot electrons into contacting gold films. This mechanism is believed to be fast enough to allow mixer operation with intermediate frequencies of several GHz. An electron cooling time of 55 ps is inferred from DC resistance versus temperature measurements, indicating a roll-off frequency close to 3 GHz. Initial receiver measurements using a two-tuner waveguide mixer confirm heterodyne mixing at 532 GHz with an intermediate frequency of 1.4 GHz.

bolometer↗
NASA NTRS1972

An analysis of Pioneer 9 low-frequency wave observations near interplanetary discontinuities.

Observation of an unusually complex sector boundary on Feb. 2, 1969. Within a single seven-hour period the Pioneer 9 magnetometer and plasma probe detected a reverse shock, a slow shock, and a conventional fast shock. During this interval the electron gyrofrequency and the ion plasma frequency each varied by more than a factor of 10, and the low-frequency (broadband and 400-Hz) electric field wave levels were high and variable. It is shown that, near the discontinuities, enhanced 400-Hz wave levels were not generally associated with field gradients or current layers, but elevated 400-Hz wave levels were detected when the ion density fell within a fairly well-defined window. This suggests that modes related to ion sound waves were detected, and the observations are assessed in terms of various theories for interplanetary wave generation.

Scarf, F. L.↗
NASA NTRS1978

ISEE-C solar wind plasma experiment

Two 135 deg spherical section electrostatic analyzers furnish electron and ion measurements of the solar wind on ISEE-C. Each of these instruments utilizes a divided secondary emitter system to intercept the analyzed particles. Secondary electrons selected from all of the emitters simultaneously provide fast two-dimensional measurements of the particle fluxes integrated over polar angle; at a slower rate secondary electrons are successively selected from individual emitters to provide three-dimensional measurements. Speed of the ion measurements is increased by a factor of two by using an active proton peak tracking system to reduce the total range of energy per charge which has to be covered.

Bame, S. J.↗
NASA NTRS1985

Observational evidence for thermal wave fronts in solar flares

Images in 3.5-30 keV X-rays obtained during the first few minutes of seven solar flares show rapid motions. In each case X-ray emission first appeared at one end of a magnetic field structure, and then propagated along the field at a velocity between 800 and 1700 km/s. The observed X-ray structures were 45,000-230,000 km long. Simultaneous H-alpha images were available in three cases; they showed brightenings when the fast-moving fronts arrived at the chromosphere. The fast-moving fronts are interpreted as electron thermal conduction fronts since their velocities are consistent with conduction at the observed temperatures of 1-3 x 10 to the 7th K. The inferred conductive heat flux of up to 10-billion ergs/s sq cm accounts for most of the energy released in the flares, implying that the flares were primarily thermal phenomena.

Rust, D. M.↗
NASA NTRS1986

Accelerated plasma flows at the near-tail magnetopause

ISEE-1 and -2 fast plasma data of ion and electron distributions at 16 energies and 16 velocities are used to study accelerated particle flow events at the near-tail dusk magnetopause. The flows separated the plasma sheet from the magnetosheath, a situation which normally arises when the local magnetosheath and plasma sheet magnetic fields are close to being antiparallel. The flows were directed tailward at speeds up to twice those in the adjoining magnetosheath and had densities similar to those in the magnetosheath. The attendant ion and electron temperatures were between those in the magnetosheath and in the plasma sheet. The flow region closest to the magnetosheath had the highest velocity and the lowest density, and a lowered-density field line region appeared on the earthward side of the accelerated flow region. The flows had the velocity changes of a tangential stress balance and are taken as the location of field line merging near (and perhaps tailward) of the dawn-dusk terminator. Significantly fewer accelerated flows are seen in the dawn tail magnetopause, an asymmetry attributed to a seasonally dependent warping of the midtail neutral sheet or a superimposition of interplanetary magnetic field lines over the dusk magnetopause.

Gosling, J. T.↗
NASA NTRS1993

Thermal structure of ions and electrons in Saturn's inner magnetosphere

A theoretical model of thermal ion and electron temperatures in Saturn's inner magnetospheres is presented which is based on a fast model of radial diffusive plasma transport. It is shown that the ion and electron temperatures and the latitudinal behavior of temperatures are consistent with the fast diffusion hypothesis, assuming that O(+) is the dominant ion and that its source is the Dione-Tethys plasma torus. The present results reinforce the conclusions of Barbosa (1990).

Barbosa, D. D.↗
NASA NTRS1991

Particle displacement tracking applied to air flows

Electronic Particle Image Velocimeter (PIV) techniques offer many advantages over conventional photographic PIV methods such as fast turn around times and simplified data reduction. A new all electronic PIV technique was developed which can measure high speed gas velocities. The Particle Displacement Tracking (PDT) technique employs a single cw laser, small seed particles (1 micron), and a single intensified, gated CCD array frame camera to provide a simple and fast method of obtaining two-dimensional velocity vector maps with unambiguous direction determination. Use of a single CCD camera eliminates registration difficulties encountered when multiple cameras are used to obtain velocity magnitude and direction information. An 80386 PC equipped with a large memory buffer frame-grabber board provides all of the data acquisition and data reduction operations. No array processors of other numerical processing hardware are required. Full video resolution (640x480 pixel) is maintained in the acquired images, providing high resolution video frames of the recorded particle images. The time between data acquisition to display of the velocity vector map is less than 40 sec. The new electronic PDT technique is demonstrated on an air nozzle flow with velocities less than 150 m/s.

Wernet, Mark P.↗
NASA NTRS1991

Particle displacement tracking applied to air flows

Electronic Particle Image Velocimetric (PIV) techniques offer many advantages over conventional photographic PIV methods such as fast turn around times and simplified data reduction. A new all electronic PIV technique was developed which can measure high speed gas velocities. The Particle Displacement Tracking (PDT) technique employs a single CW laser, small seed particles (1 micron), and a single intensified, gated CCD array frame camera to provide a simple and fast method of obtaining two-dimensional velocity vector maps with unambiguous direction determination. Use of a single CCD camera eliminates registration difficulties encountered when multiple cameras are used to obtain velocity magnitude and direction information. An 80386 PC equipped with a large memory buffer frame-grabber board provides all of the data acquisition and data reduction operations. No array processors of other numerical processing hardware are required. Full video resolution (640 x 480 pixel) is maintained in the acquired images, providing high resolution video frames of the recorded particle images. The time between data acquisition to display of the velocity vector map is less than 40 sec. The new electronic PDT technique is demonstrated on an air nozzle flow with velocities less than 150 m/s.

Wernet, Mark P.↗
NASA NTRS1987

The eastward deflection of fast coronal mass ejecta in interplanetary space

Previous work has shown that a bidirectional solar wind electron heat flux is one of the more prominent signatures of a coronal mass ejection event in the solar wind at 1 AU. Using ISEE 3 solar wind electron measurements obtained during 1978 and 1979, this signature was used to identify the fast coronal mass ejecta driving 19 interplanetary shocks. In 17 of the 19 shock events an eastward deflection of the ejection plasma (apparent arrival from west of the sun) was observed. The average eastward deflection for all of the events was about 3 deg, corresponding to a typical transverse velocity of 25 km/s. Usually an oppositely directed (i.e., westward) flow deflection of comparable magnitude was observed within the compressed ambient plasma ahead of the ejecta. The sense of these deflections - first westward within the compressed ambient plasma and then eastward within the ejecta - is the same as is observed near the leading edges of quasi-stationary, corotating high speed streams.

Gosling, J. T.↗
NASA NTRS1992

Fast Vector-Quantizing Data Compressor

Proposed encoding digital electronic data-processing system compresses 7-Mb/s input stream of data into 1-Mb/s output stream. Intended to reduce flow of data from orbiting synthetic-aperture-radar (SAR) system to rate low enough for transmission to ground. Features include reliability, light weight, and low power. Proves advantageous in such terrestrial applications as compression of speech and of video signals.

Chang, Chi-Yung↗
NASA NTRS1996

Finest Filamentary Structures of the Corona in the Slow and Fast Solar Wind

Recent progress in our understanding of electron density fluctuations observed by radio occultation measurements has demonstrated that a break in the vicinity of 1 Hz in the temporal frequency spectrum of the density fluctuations provides a measure of the size of the finest filamentary structures in the solar corona.

interplanetary medium solar wind corona Sun occult↗
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↗
NASA NTRS1987

Iterative solution of the multistream electron transport equation. I - Comparison with laboratory beam injection experiments

The Neumann iteration method presently used for solving the electron transport equation in which energy, attitude, and pitch angle are independent variables is fast, and can compute numerical point-response-function solutions of the electron transport equation. Because both the inelastic cross sections and angular elastic cross sections of the model are empirically based, the solutions obtained represent a test of compatibility between various sets of cross sections and energy deposition measurements. The use of a numerical quadrature based on analytic phase function forms yields accurate phase function integrals at low computational cost.

Porter, H. S.↗
NASA NTRS2005

Cosmic Ray Energetics and Mass (CREAM)

The CREAM instrument was flown on a Long Duration Balloon in Antarctica in December 2004 and January 2005, achieving a flight duration record of nearly 42 days. It detected and recorded cosmic ray primary particles ranging in type from hydrogen to iron nuclei and in energy from 1 TeV to several hundred TeV. With the data collected we will have the world's best measurement of the energy spectra and mass composition of nuclei in the primary cosmic ray flux at these energies, close to the astrophysical knee . The instrument utilized a thin calorimeter, a transition radiation detector and a timing charge detector, which also provided time-of-flight information. The responsibilities of our group have been with the timing charge detector (TCD), and with the data acquisition electronics and ground station support equipment. The TCD utilized fast scintillators to measure the charge of the primary cosmic ray before any interactions could take place within the calorimeter. The data acquisition electronics handled the output of the various detectors, in a fashion fully integrated with the payload bus. A space-qualified flight computer controlled the acquisition, and was used for preliminary trigger information processing and decision making. Ground support equipment was used to monitor the health of the payload, acquire and archive the data transmitted to the ground, and to provide real-time control of the instrument in flight.

Coutu, Stephane↗
NASA NTRS2001

The Need for Optical Means as an Alternative for Electronic Computing

An increasing demand for faster computers is rapidly growing to encounter the fast growing rate of Internet, space communication, and robotic industry. Unfortunately, the Very Large Scale Integration technology is approaching its fundamental limits beyond which the device will be unreliable. Optical interconnections and optical integrated circuits are strongly believed to provide the way out of the extreme limitations imposed on the growth of speed and complexity of nowadays computations by conventional electronics. This paper demonstrates two ultra-fast, all-optical logic gates and a high-density storage medium, which are essential components in building the future optical computer.

Adbeldayem, Hossin↗