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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Microchannel spatial light modulator

The Microchannel Spatial Light Modulator (MSLM), a versatile, highly sensitive, and optically addressed device being developed for real time optical information processing is discussed. The MSLM operates by converting an input optical image into a charge distribution at the surface of an electro-optic crystal. The charge distribution generates an electric field which modulates the refractive index of the crystal and thereby the phase or intensity of an image readout beam. Prototype devices employing 250 micron thick crystals exhibited a spatial resolution of 5 cycles/mm at 50% contrast, an exposure sensitivity of 2.2 nJ/cu cm and framing rates of 40 Hz with full modulation depth. The image processing operations that have been achieved using the internal processing mode of the MSLM include contrast reversal, contrast enhancement, edge enhancement, image addition and subtraction, analog and digital intensity thresholding, and binary level logic operations such as AND, OR, EXCLUSIVE OR, and NOR.

Warde, C.↗
NASA NTRS1984

Unusual structures of high-latitude stratospheric electric fields

A possible explanation is given for three unusual stratospheric electric field structures reported by Madsen et al. (1983). It is suggested that stratospheric vertical electric-current structures may arise as extensions into the stratosphere of tropospheric currents generated by convective charge transport. A convective tropospheric current generator is presented which is capable of producing, at altitudes of about 30 km, the vertical electric field intensities of several volts per meter that are sometimes (although very rarely) observed by balloon-borne sensors (Madsen et al., 1983).

Dangelo, N.↗
NASA NTRS1987

Observation by Pioneer 7 of He(+) in the distant coma of Halley's comet

Plasma analyzer data obtained by Pioneer 7 during its approach to about 12.1 million km from the nucleus of Comet P/Halley are presently interpreted as He(+) generated by charge exchange of the solar wind He(2+) with neutral cometary material. The maximum He(+) flux was detected several hours after the closest March 20, 1986 approach of the spacecraft, and is noted to be not only larger than expected, but also to exhibit large, discontinuous flux changes.

Mihalov, J. D.↗
NASA NTRS1993

Critical review of electrical conductivity measurements and charge distribution analysis of magnesium oxide

The electrical conductivity sigma of MgO single crystals shows a sharp increase at 500-800 C, in particular of sigma surface, generally attributed to surface contamination. Charge Distribution Analysis (CDA), a new technique providing information on fundamental properties that was previously unavailable, allows for the determination of surface charges, their sign and associated internal electric field. Data on 99.99% purity, arc-fusion grown MgO crystals show that mobile charge carriers start to appear in the bulk of the MgO crystals between 200 and 400 C when sigma (measured by conventional techniques) is in t he 10(exp -14) to 10(exp -16) /omega/cm range. Above 500 C, as sigma increases to 10(exp -6) to 10(exp -7)/omega/cm, more charges appear giving rise to a strong positive surface charge supported by a strong internal field. This indicates that charges are generated in the bulk and diffuse to the surface by an internally controlled process. On the basis of their positive sign they are identified as holes (defect electrons). Because of the low cation content of these very pure MgO crystals, theses holes cannnot be associated with transition metal impurties. Instead, they are associated with the O(2-) sublattice, e.g. consist of O(-) states or positive holes. This conclusion is supported by magnetic susceptibility data showing the appearance of 1000 +/- 500 ppm paramagnetic species between 200-500 C. The magnetic data are consistent with strongly coupled, diamagnetic O(-) pairs below 200-500 C, chemically equivalent to peroxy anions, O2(2-), and probably associated with cation vacancies in the MgO matrix. The formation of O2(2-) in arc-fusion grown MgO crystals is very unexpected because of the highly reducing growth conditions. Their presence implies an internal redox reaction involving dissolved 'water' by which OH(-) pairs convert to O2(2-) plus H2 molecules. This redox conversion is supported by mass spectroscopic measurements of the H2 release from highly OH(-)-doped, finely divided MgO and by wet-chemical analysis of its oxidant concentration.

Freund, Friedemann↗
NASA NTRS1966

Storable Propellant Combustion Instability Program at Lewis Research Center

An experimental program at Lewis Research Center investigates acoustical-mode combustion instability in liquid propellant rockets. One phase of this program is concerned with nitrogen tetroxide and a 50-50 fuel blend of hydrazine-UDMH. Effects on combustor stability and performance by variations in injection velocities, impingement angle and distance, amd thrust per element of triplet injectors were studied in a 10.77-inch- diameter cylindrical combustor at chamber pressures of 100 and 300 psia. Nominal thrust levels were 6700 and 20 000 pounds. Stability rating was accomplished by the use of various size RDX explosive charges to generate tangential pressure disturbances. The injection velocity effect correlated by using a ratio V(sub o)/V(sub f). Stability correlation with V(sub o)/V(sub f) resulted in a sharply humped curve with maximum stability at a ratio of 1.2. Performance decreased with increase in V(sub o)/V(sub f) after a maximum at 0.7, which agreed fairly well with the "uniform mixture ratio distribution" criteria of the Jet Propulsion Laboratory. Variation of impingement angle from 38 deg to 120 deg indicated that performance correlated with the absolute velocity ratio V(sub o)/V(sub f), but stability correlation appeared to be best with a velocity ratio using the radial component of the fuel injection velocity V(sub o)/V(sub fr). Impingement distances from 0.5 to 1.0 inch appeared to have only slight effect on stability and performance. Investigation of injector thrust per element for V(sub o)/V(sub fr) ranging from 0.8 to 2.8 yielded convex maxima curves. Acoustic liners were also tested to improve a liner design computer program, to obtain design criteria, and to develop flight-type liners. A marginally stable and spontaneously unstable combustor were used to evaluate linear configurations. All liners were effective in the marginally stable configuration, and only liners with large theoretical absorptivity were successful in the spontaneously unstable combustor.

Tabata, William K.↗
NASA NTRS2007

Biomarker for Space Radiation Risk: Painting Analysis of Chromosome Aberrations Induced by Energetic Heavy Ions in Human Cells

Energetic heavy ions pose a great health risk to astronauts in extended ISS and future Lunar and Mars missions. High-LET heavy ions are particularly effective in causing various biological effects, including cell inactivation, genetic mutations, cataracts and cancer induction. Most of these biological endpoints are closely related to chromosomal damage, which can be utilized as a biomarker for radiation insults. Over the years, we have studied chromosomal damage in human fibroblast, epithelia and lymphocyte cells exposed in vitro to energetic charged particles generated at several accelerator facilities in the world. We have also studied chromosome aberrations in astronaut s peripheral blood lymphocytes before and after space flight. Various fluorescence in situ hybridization painting techniques have been used to identify from only the telomere region of the chromosome to every chromosome in a human cell. We will summarize the results of the investigations, and discuss the unique radiation signatures and biomarkers for space radiation exposure.

Hada, Megumi↗
NASA NTRS1985

Sealed bipolar multi-cell battery

A low maintenance battery comprises a sealed casing (102) having a cavity (204) receiving a stack (108) of monopolar and bipolar plates (110, 112) interspersed with mats (122) of fiberglass felt immobilizing electrolyte and forming a gas path for diffusion of oxygen to the negative electrode (112). The casing contains a single, resealable vent (202). During charging, oxygen generated at the positive plate (110) diffuses through the mat (122) and decomposes at the negative plate (112). The negative plate (112) has a larger capacity than the positive plate (110) to prevent evolution of hydrogen. Voltage potential is increased or decreased by placing one or more bipolar plates (120) in series relation between alternating positive and negative monopolar plates that are connected in parallel to respective positive and negative battery terminals (104, 106). The monoplates (110, 112) are connected in parallel to respective positive and negative battery terminals (104, 106) by way of bus plates (114, 116, 130, 132). The resealable vent permits operation by way of the oxygen cycle which prevents loss of electrolyte. The vent prevents invasion of oxygen from the ambient to discharge negative plates.

Rowlette, John J.↗
NASA NTRS1987

Edge passivated charge-coupled device image sensor

A charge-coupled device (CCD) image sensor includes in a substrate of single crystalline silicon of one conductivity type an array of a plurality of spaced, parallel channel regions of the opposite conductivity type extending along one major surface of the substrate. A plurality of parallel conductive gates are over the one major surface of the substrate and extend transversely across the channel regions. The outermost channel regions of the array are positioned adjacent edges of the substrate so that a plurality of the image sensors can be mounted in edge-to-edge relation with the channel regions of the various sensors being close together. The sensor includes passivating means between each outermost channel region and the adjacent edge to prevent charge carriers generated by the edge from being injected into the outermost channel region. The passivating means includes a highly conductive drain region of a conductivity type opposite to that of the substrate within the substrate and extending along the one major surface between the outermost channel region and the edge. Also, a highly conductive region of the same conductivity type as the substrate is on the substrate and extends along the one major surface directly at the edge.

Kosonocky, Walter F.↗
NASA NTRS2010

Improved OTEC System for a Submarine Robot

An ocean thermal energy conversion (OTEC), now undergoing development, is a less-massive, more-efficient means of exploiting the same basic principle as that of the proposed system described in "Alternative OTEC Scheme for a Submarine Robot" (NPO-43500), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 50. The proposed system as described previously would be based on the thawing-expansion/freezing-contraction behavior of a wax or perhaps another suitable phase-change material (PCM). The power generated by the system would be used to recharge the batteries in a battery- powered unmanned underwater vehicle [UUV (essentially, a small exploratory submarine robot)] of a type that has been deployed in large numbers in research pertaining to global warming. A UUV of this type travels between the ocean surface and depths, measuring temperature and salinity. At one phase of its operational cycle, the previously proposed system would utilize the surface ocean temperature (which lies between 15 and 30 C over most of the Earth) to melt a PCM that has a melting/freezing temperature of about 10 C. At the opposite phase of its operational cycle, the system would utilize the lower ocean temperature at depth (e.g., between 4 and 7 C at a depth of 300 m) to freeze the PCM. The melting or freezing would cause the PCM to expand or contract, respectively, by about 9 volume percent. The PCM would be contained in tubes that would be capable of expanding and contracting with the PCM. The PCM-containing tubes would be immersed in a hydraulic fluid. The expansion and contraction would drive a flow of the hydraulic fluid against a piston that, in turn, would push a rack-and-pinion gear system to spin a generator to charge a battery.

Chao, Yi↗
NASA NTRS2010

Investigation of the Internal Electric Field in Cadmium Zinc Telluride Detectors Using the Pockels Effect and the Analysis of Charge Transients

The Pockels electro-optic effect can be used to investigate the internal electric field in cadmium zinc telluride (CZT) single crystals that are used to fabricate room temperature x and gamma radiation detectors. An agreement is found between the electric field mapping obtained from Pockels effect images and the measurements of charge transients generated by alpha particles. The Pockels effect images of a CZT detector along two mutually perpendicular directions are used to optimize the detector response in a dual anode configuration, a device in which the symmetry of the internal electric field with respect to the anode strips is of critical importance. The Pockels effect is also used to map the electric field in a CZT detector with dual anodes and an attempt is made to find a correlation with the simulated electric potential in such detectors. Finally, the stress-induced birefringence effects seen in the Pockels images are presented and discussed.

Groza, Michael↗
NASA NTRS2014

Internal Charging

(1) High energy (>100keV) electrons penetrate spacecraft walls and accumulate in dielectrics or isolated conductors; (2) Threat environment is energetic electrons with sufficient flux to charge circuit boards, cable insulation, and ungrounded metal faster than charge can dissipate; (3) Accumulating charge density generates electric fields in excess of material breakdown strenght resulting in electrostatic discharge; and (4) System impact is material damage, discharge currents inside of spacecraft Faraday cage on or near critical circuitry, and RF noise.

Minow, Joseph I.↗
NASA NTRS2014

Improved Measurement of Ejection Velocities From Craters Formed in Sand

A typical impact crater is formed by two major processes: compression of the target (essentially equivalent to a footprint in soil) and ejection of material. The Ejection-Velocity Measurement System (EVMS) in the Experimental Impact Laboratory has been used to study ejection velocities from impact craters formed in sand since the late 1990s. The original system used an early-generation Charge-Coupled Device (CCD) camera; custom-written software; and a complex, multicomponent optical system to direct laser light for illumination. Unfortunately, the electronic equipment was overtaken by age, and the software became obsolete in light of improved computer hardware.

Cintala, Mark J.↗
NASA NTRS2018

Radiation Testing Electronics with Heavy Ions-The Best Way to Hit a Target Moving Ever Exponentially Faster

In 1972, when engineers at Hughes Aircraft Corporation discovered that errors in their satellite avionics were being caused by cosmic rays (so-called single-event effects, or SEE), Moore's Law was only 7 years old. Now, more than 45 years on, the scaling that drove Moore's Law for its first 35 years has reached its limits. However, electronics technology continues to evolve exponentially and SEE remain a formidable issue for use of electronics in space. SEE occur when a single ionizing particle passes through a sensitive volume in an active semiconductor device and generates sufficient charge to cause anomalous behavior or failure in the device. Because SEE can occur at any time during the mission, the emphasis of SEE risk management methodologies is ensuring that all SEE modes in a device under test are detected by the test. Because a particle's probability of causing an SEE generally increases as the particle becomes more ionizing, heavy-ion beams have been and remain the preferred tools for elucidating SEE vulnerabilities. In this talk we briefly discuss space radiation environments and SEE mechanisms, describe SEE test methodologies and discuss current and future challenges for use of heavy-ion beams for SEE testing in an era when the continued validity of Moore's law depends on innovation rather than CMOS scaling.

space radiation environments↗
NASA NTRS2021

Angle Dependence of Focused X-Ray-Induced Single Event Transients in an Epitaxial Silicon Diode

Focused X-Ray single event transient (SET) experiments are performed at small angles on an epitaxial silicon diode at two reverse bias conditions. For both biases, the collected charge and peak current results follow the cosine law, while the transient fall time remains independent of incident angle. This demonstrates that only the amount of charge being generated is affected by angle and not the fundamental device response.

Heavy ions↗
NASA NTRS2022

Angle Dependence of Focused X-Ray-Induced Single Event Transients in an Epitaxial Silicon Diode

Focused X-Ray single event transient (SET) experiments are performed at small angles on an epitaxial silicon diode at two reverse bias conditions. For both biases, the collected charge and peak current results follow the cosine law, while the transient fall time remains independent of incident angle. This demonstrates that only the amount of charge being generated is affected by angle and not the fundamental device response for these relatively large devices.

Focused X-ray↗
NASA NTRS1993

Electrostatically Enhanced Vortex Separator

Proposed device removes fine particles from high-pressure exhaust gas of chemical reactor. Negatively charged sectors on rotating disks in vortex generator attracts positively charged particles from main stream of exhaust gas. Electrostatic charge enhances particle-separating action of vortex. Gas without particles released to atmosphere.

Collins, Earl R.↗
NASA NTRS1987

Secondary electron generation, emission and transport: Effects on spacecraft charging and NASCAP models

Secondary electrons control a spacecraft's response to a plasma environment. To accurately simulate spacecraft charging, the NASA Charging Analyzer Program (NASCAP) has mathematical models of the generation, emission and transport of secondary electrons. The importance of each of the processes and the physical basis for each of the NASCAP models are discussed. Calculations are presented which show that the NASCAP formulations are in good agreement with both laboratory and space experiments.

Katz, Ira↗