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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

An intracloud lightning parameterization scheme for a storm electrification model

The parameterization of an intracloud lightning discharge has been implemented in the present storm electrification model. The initiation, propagation direction, and termination of the discharge are computed using the magnitude and direction of the electric field vector as the determining criteria. The charge redistribution due to the lightning is approximated assuming the channel to be an isolated conductor with zero net charge over its entire length. Various simulations involving differing amounts of charge transferred and distribution of charges have been done. Values of charge transfer, dipole moment change, and electrical energy dissipation computed in the model are consistent with observations. The effects of the lightning-produced ions on the hydrometeor charges and electric field components depend strongly on the amount of charge transferred. A comparison between the measured electric field change of an actual intracloud flash and the field change due to the simulated discharge shows favorable agreement. Limitations of the parameterization scheme are discussed.

Helsdon, John H., Jr.↗
NASA NTRS1989

Characterizations of electrical properties of highT(sub c) superconducting materials

The automated data acquisition system developed in the Space Science Laboratory at Marshall Space Flight Center for measuring electrical properties of high temperature superconductors is described. The acquisition system, consisting of a computer and computer-controlled hardware, allows large numbers of voltage, current, temperature, and magnetic measurements to be performed on bulk and thin film samples. Typical results are shown characterizing transition temperature (T sub c), critical current density (J sub c), and magnetic properties of bulk high T(sub c) materials as a function of temperature.

Sisk, R. C.↗
NASA NTRS2015

Electric Field Generation in Martian Dust Devils

Terrestrial dust devils are known to generate electric fields from the vertical separation of charged dust particles. The particles present within the dust devils on Mars may also be subject to similar charging processes and so likely contribute to electric field generation there as well. However, to date, no Marsin situ instrumentation has been deployed to measure electric field strength. In order to explore the electric environment of dust devils on Mars, the triboelectric dust charging physics from the MacroscopicTriboelectric Simulation (MTS) code has been coupled to the Mars Regional Atmospheric ModelingSystem (MRAMS). Using this model, we examine how macroscopic electric fields are generated within martian dust disturbances and attempt to quantify the time evolution of the electrodynamical system.Electric fields peak for several minutes within the dust devil simulations. The magnitude of the electric field is a strong function of the size of the particles present, the average charge on the particles and the number of particles lifted. Varying these parameters results in peak electric fields between tens of millivolts per meter and tens of kilovolts per meter.

Aeolian processes↗
NASA NTRS1981

Chatanika radar measurements of the electrical properties of auroral arcs

Ionospheric parameters measured in the presence of auroral arcs by the incoherent scatter Chatanika radar are used to define properties of the arcs. The radar broadcasts at 3-5 MW with a range resolution of 4.5 km along the radar line-of-sight, and has yielded auroral measurements on the variation of electron density, Hall and Pederson conductivity, horizontal electric fields, electrojet currents, precipitating electron energy flux, and the Joule heating rate. Elevation-scan techniques have been utilized to study the latitude and altitude variation of the ionospheric plasma parameters, and fixed-position scans allow determination of ionization conditions, including the electric fields and the acceleration of precipitating auroral electrons. Arcs in the diffuse aurora have been found to be local conductivity enhancements, while discrete arcs correspond to the boundary plasma sheet and have an asymmetric electric field pattern reduced on the northward side.

Vondrak, R. R.↗
DOE OSTI2024

Coherent homodyne detection for amplified cross-beam electric-field induced second harmonic

The electric-field induced second harmonic (E-FISH) signal sensing is commonly used as a nonlinear optical technique to probe electric fields inside a plasma region. Cross-beam E-FISH is being investigated to improve spatial resolution by defining the interaction volume via a controlled geometry of two overlapping noncolinear optical beams. This drastic reduction in interaction length of the electric field and laser region results in a significant signal reduction. Here, to overcome this signal reduction, we introduce coherent amplification of the cross-beam E-FISH signal by mixing the low E-FISH signal with a phase-locked bright local oscillator. We demonstrate enhancement of the signal. By introducing a local oscillator we can now derive the polarity of the measured electric field through the phase of the homodyne signal. To illustrate the technique, we, for the first time, to the best of our knowledge, measure the magnitude and the direction of the electric field in a cold atmospheric pressure plasma jet, which dynamically follows the profile of the applied bias current.

42 ENGINEERING↗
NASA NTRS2009

Improved Instrument for Detecting Water and Ice in Soil

An instrument measures electrical properties of relatively dry soils to determine their liquid water and/or ice contents. Designed as a prototype of instruments for measuring the liquid-water and ice contents of lunar and planetary soils, the apparatus could also be utilized for similar purposes in research and agriculture involving terrestrial desert soils and sands, and perhaps for measuring ice buildup on aircraft surfaces. This instrument is an improved version of the apparatus described in Measuring Low Concentrations of Liquid Water and Ice in Soil (NPO-41822), NASA Tech Briefs, Vol. 33, No. 2 (February 2009), page 22. The designs of both versions are based on the fact that the electrical behavior of a typical soil sample is well approximated by a network of resistors and capacitors in which resistances decrease and capacitances increase (and the magnitude and phase angle of impedance changes accordingly) with increasing water content. The previous version included an impedance spectrometer and a jar into which a sample of soil was placed. Four stainless-steel screws at the bottom of the jar were used as electrodes of a fourpoint impedance probe connected to the spectrometer. The present instrument does not include a sample jar and can be operated without acquiring or handling samples. Its impedance probe consists of a compact assembly of electrodes housed near the tip of a cylinder. The electrodes protrude slightly from the cylinder (see Figure 1). In preparation for measurements, the cylinder is simply pushed into the ground to bring the soil into contact with the electrodes.

Buehler, Martin↗
NASA NTRS1996

Constant-Current Source For Measuring Low Resistances

Constant-current source constructed for measuring electrical resistances up to few ohms in power-supply equipment. By setting current at 1 A and measuring resulting voltage drop across item under test, one obtains voltage reading numerically equal to resistance in ohms.

Toomath, Robert L.↗
NASA NTRS1991

An electrograph for measurement of macroscopic electric fields in prominences and flares

An 'electrograph' instrument designed for measurement of macroscopic electric fields in solar plasmas is described, using the polarization dependence of line width in Stark-broadened hydrogen Paschen emission lines. Observations of quiescent prominences and limb chromosphere with the electrograph at the NSO/Sac Peak Evans Coronal Facility provide upper limits of 5-10 V/cm for transverse macroscopic electric fields in these structures, averaged over an area of about 5 x 7 arcsec. Random thermal motions of hydrogen ions across magnetic field lines generate a quasi-static electric field, which should be distinguishable from pressure broadening in the intensely magnetized chromosphere over a sunspot, given an electrograph sensitivity a factor 2-3 better than that achieved here. Future electrograph measurements of limb flares, post-flare loops, and eruptive prominences, even at 5-V/cm sensitivity, could provide a useful new test of reconnection and discharge effects in such dynamic structures.

Moran, T.↗
DOE OSTI2020

A Preorganized Electric Field Leads to Minimal Geometrical Reorientation in the Catalytic Reaction of Ketosteroid Isomerase

Electrostatic interactions play a pivotal role in enzymatic catalysis and are increasingly modeled explicitly in computational enzyme design; nevertheless, they are challenging to measure experimentally. Using vibrational Stark effect (VSE) spectroscopy, we have measured electric fields inside the active site of the enzyme ketosteroid isomerase (KSI). These studies have shown that these fields can be unusually large, but it has been unclear to what extent they specifically stabilize the transition state (TS) relative to a ground state (GS). In the following, we use crystallography and computational modeling to show that KSI’s intrinsic electric field is nearly perfectly oriented to stabilize the geometry of its reaction’s TS. Moreover, we find that this electric field adjusts the orientation of its substrate in the ground state so that the substrate needs to only undergo minimal structural changes upon activation to its TS. This work provides evidence that the active site electric field in KSI is preorganized to facilitate catalysis and provides a template for how electrostatic preorganization can be measured in enzymatic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Development and fabrication of an augmented power transistor

The development of device design and processing techniques for the fabrication of an augmented power transistor capable of fast switching and high voltage power conversion is discussed. The major device goals sustaining voltages in the range of 800 to 1000 V at 80 A and 50 A, respectively, at a gain of 14. The transistor switching rise and fall times were both to have been less than 0.5 microseconds. The development of a passivating glass technique to shield the device high voltage junction from moisture and ionic contaminants is discussed as well as the development of an isolated package that separates the thermal and electrical interfaces. A new method was found to alloy the transistors to the molybdenum disc at a relatively low temperature. The measured electrical performance compares well with the predicted optimum design specified in the original proposed design. A 40 mm diameter transistor was fabricated with seven times the emitter area of the earlier 23 mm diameter device.

Geisler, M. J.↗
NASA NTRS2005

Preliminary low temperature electron irradiation of triple junction solar cells

JPL has routinely performed radiation testing on commercial solar cells and has also performed LILT testing to characterize cell performance under far sun operating conditions. This research activity was intended to combine the features of both capabilities to investigate the possibility of any room temperature annealing that might influence the measured radiation damage. Although it was not possible to maintain the test cells at a constant low temperature between irradiation and electrical measurements, it was possible to obtain measurements with the cell temperature kept well below room temperature.

annealing↗
NASA NTRS2007

Preliminary Low Temperature Electron Irradiation of Triple Junction Solar Cells

For many years extending solar power missions far from the sun has been a challenge not only due to the rapid falloff in solar intensity (intensity varies as inverse square of solar distance) but also because some of the solar cells in an array may exhibit a LILT (low intensity low temperature) degradation that reduces array performance. Recent LILT tests performed on commercial triple junction solar cells have shown that high performance can be obtained at solar distances as great as approx. 5 AU1. As a result, their use for missions going far from the sun has become very attractive. One additional question that remains is whether the radiation damage experienced by solar cells under low temperature conditions will be more severe than when measured during room temperature radiation tests where thermal annealing may take place. This is especially pertinent to missions such as the New Frontiers mission Juno, which will experience cell irradiation from the trapped electron environment at Jupiter. Recent testing2 has shown that low temperature proton irradiation (10 MeV) produces cell degradation results similar to room temperature irradiations and that thermal annealing does not play a factor. Although it is suggestive to propose the same would be observed for low temperature electron irradiations, this has not been verified. JPL has routinely performed radiation testing on commercial solar cells and has also performed LILT testing to characterize cell performance under far sun operating conditions. This research activity was intended to combine the features of both capabilities to investigate the possibility of any room temperature annealing that might influence the measured radiation damage. Although it was not possible to maintain the test cells at a constant low temperature between irradiation and electrical measurements, it was possible to obtain measurements with the cell temperature kept well below room temperature. A fluence of 1E15 1MeV electrons was selected as representative of a moderately high dose that might be expected for a solar powered mission. Fluences much greater than this would require large increases in array area and mass, compromising the ability of PV to compete with non-solar alternatives.

Stella, Paul M.↗
NASA NTRS1984

Spatial electron density and electric field strength measurements in microwave cavity experiments

Measurements of electron density and electric field strength have been made in an argon plasma contained in a resonant microwave cavity at 2.45 GHz. Spatial measurements of electron density, n sub e, are correlated with fluorescence observations of the discharge. Measurements of n sub e were made with Stark broadening and compared with n sub 3 calculated from measured plasma conductivity. Additional measurements of n sub 3 as a function of pressure and in mixtures of argon and oxygen are presented for pressures from 10 Torr to 1 atm. Measurements in flowing gases and in static systems are presented. In addition, limitations of these measurements are identified.

Peters, M.↗
NASA NTRS1984

Spatial electron density and electric field strength measurements in microwave cavity experiments

Measurements of electron density and electric field strength have been made in an argon plasma contained in a resonant microwave cavity at 2.45 GHz. Spatial measurements of electron density, n sub e, are correlated with fluorescence observations of the discharge. Measurements of n sub e were made with Stark broadening and compared with n sub e calculated from measured plasma conductivity. Additional measurements of n sub e as a function of pressure and in mixtures of argon and oxygen are presented for pressures from 10 Torr to 1 atm. Measurements in flowing gases and in static systems are presented. In addition, limitations of these measurements are identified.

Peters, M.↗
NASA NTRS1975

Nondestructive measurement of capillary tube internal diameter

Technique provides nondestructive method of making quick, accurate determination by measuring electrical resistance of capillary tube when it is filled with electrolyte of known conductivity. Apparatus consists of conductivity cell and equipment for measuring resistance and for monitoring and controlling temperature.

Ho, W. W.↗
NASA NTRS1991

Calorimetric output power measurements on a CW 20 kW 7.16 GHz microwave transmitter

A calorimetric measurement technique developed for NASA's Deep Space Network (DSN) transmitters that does not require data on the coolant's thermal parameters is described. Calibration of the measurement system is achieved by measuring the DC input power to the klystron and relating coolant temperature increases to this known power dissipation. Agreement between calorimetric and electrical measurements of total system power was good, the difference being less than 2 percent. The operation of the system was not greatly affected by the composition of the coolant, which was varied from pure water to 40 percent ethylene glycol by mass. Good accuracy was also shown at output power levels, which varied over a 3.6:1 range.

Perez, Raul M.↗
DOE OSTI2021

World Record Demonstration of > 30% Thermophotovoltaic Conversion Efficiency

Thermophotovoltaic (TPV) devices are solid-state heat engines that convert thermal radiation into electricity using semiconductor diodes, and have applications in energy storage, primary power conversion, and waste heat recovery. Higher temperature emitters and wider band gap photovoltaics (PVs) generally afford higher TPV efficiencies. High temperature emitters are accessible in thermal energy storage applications. We have demonstrated a world record 31% +/- 2% TPV conversion efficiency with a 0.9 cm2 GaAs-based PV device under a 2430 °C thermal emitter, producing an electrical output power of 2.23 W. Critical to the result was the cell’s high reflectance of photon energies below the device band gap. Unlike solar PV, for which sub-band gap (SBG) light is lost, a TPV cell can reflect and recycle SBG light to the thermal emitter. The demonstration was made on a custom-built measurement platform in which a ~100 cm2 graphite thermal emitter was heated under vacuum up to 2430 °C. The TPV efficiency was evaluated by comparing the measured electrical output power of the TPV with the calorimetrically measured total net power incident on the cell. The measured TPV efficiency as a function of thermal emitter temperature was corroborated by our full system modeling predictions. As far as the authors are aware, this is the highest TPV conversion efficiency ever measured, and device improvements should yield > 40% efficiency in the near future.

27 ARPA - Advanced Research Projects Agency-Energy↗