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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

High density Schottky barrier IRCCD sensors for SWIR applications at intermediate temperature

Monolithic 32 x 64 and 64 x 1:128 palladium silicide (Pd2Si) interline transfer infrared charge coupled devices (IRCCDs) sensitive in the 1 to 3.5 micron spectral band were developed. This silicon imager exhibits a low response nonuniformity of typically 0.2 to 1.6% rms, and was operated in the temperature range between 40 to 140 K. Spectral response measurements of test Pd2Si p-type Si devices yield quantum efficiencies of 7.9% at 1.25 microns, 5.6% at 1.65 microns 2.2% at 2.22 microns. Improvement in quantum efficiency is expected by optimizing the different structural parameters of the Pd2Si detectors. The spectral response of the Pd2Si detectors fit a modified Fowler emission model. The measured photo-electric barrier height for the Pd2Si detectors is 0.34 eV and the measured quantum efficiency coefficient, C1, is 19%/eV. The dark current level of Pd2Si Schottky barrier focal plane arrays (FPAs) is sufficiently low to enable operation at intermediate temperatures at TV frame rates. Typical dark current level measured at 120 K on the FPA is 2 nA/sq cm. The operating temperature of the Pd2Si FPA is compatible with passive cooler performance. In addition, high density Pd2Si Schottky barrier FPAs are manufactured with high yield and therefore represent an economical approach to short wavelength IR imaging. A Pd2Si Schottky barrier image sensor for push-broom multispectral imaging in the 1.25, 1.65, and 2.22 micron bands is being studied. The sensor will have two line arrays (dual band capability) of 512 detectors each, with 30 micron center-to-center detector spacing. The device will be suitable for chip-to-chip abutment, thus providing the capability to produce large, multiple chip focal planes with contiguous, in-line sensors.

Elabd, H.↗
NASA NTRS1984

Thermal-mechanical fatigue crack growth in Inconel X-750

Thermal-mechanical fatigue crack growth (TMFCG) was studied in a gamma-gamma' nickel base superalloy Inconel X-750 under controlled load amplitude in the temperature range from 300 to 650 C. In-phase (T sub max at sigma sub max), out-of-phase (T sub min at sigma sub max), and isothermal tests at 650 C were performed on single-edge notch bars under fully reversed cyclic conditions. A dc electrical potential method was used to measure crack length. The electrical potential response obtained for each cycle of a given wave form and R value yields information on crack closure and crack extension per cycle. The macroscopic crack growth rates are reported as a function of delta k and the relative magnitude of the TMFCG are discussed in the light of the potential drop information and of the fractographic observations.

Marchand, N.↗
NASA NTRS1985

Thermal-mechanical fatigue crack growth in Inconel X-750

Thermal-mechanical fatigue crack growth (TMFCG) was studied in a 'gamma-gamma' nickel base superalloy Inconel X-750 under controlled load amplitude in the temperature range from 300 to 650 C. In-phase (T sub max at sigma sub max), out-of-phase (T sub min at sigma sub max), and isothermal tests at 650 C were performed on single-edge notch bars under fully reversed cyclic conditions. A dc electrical potential method was used to measure crack length. The electrical potential response obtained for each cycle of a given wave form and R value yields information on crack closure and crack extension per cycle. The macroscopic crack growth rates are reported as a function of delta k and the relative magnitude of the TMFCG are discussed in the light of the potential drop information and of the fractographic observations.

Marchand, N.↗
NASA NTRS2016

Effect of Solar Array Plume Interactions on Hall Thruster Cathode Common Potentials

In typical implementations of spacecraft electric propulsion (EP) systems the electrical ground of the EP power processing units are resistively isolated from the main spacecraft electrical ground. Telemetry measuring the potential difference between EP power processing unit and the spacecraft electrical ground is usually referred to as the “cathode common” potential. In this paper we review flight and laboratory data on natural and EP generated plasma interactions with solar arrays, present the theory of spacecraft floating potentials, show how this theory is consistent with flight data, and extend this theory to spacecraft with high power Hall effect thrusters.

Katz, Ira↗
NASA NTRS2011

Auroral Current and Electrodynamics Structure Measured by Two SOunding Rockets in Flight Simultaneously

On January 29, 2009, two identically instrumented sounding rockets were launched into a sub-storm auroral arc from Poker Flat Alaska. Labeled the Auroral Currents and Electrodynamics Structure (ACES) mission, the payloads were launched to different apogees (approx.350km and approx.120km) and staggered in time so as to optimize their magnetic conjunctions. The different altitudes provided simultaneous in-situ measurements of magnetospheric input and output to the ionosphere and the ionospheric response in the lower F and E region. Measurements included 3-axis magnetic field, 2-axis electric field nominally perpendicular to the magnetic field, energetic particles, electron and ion, up to 15keV, cold plasma temperature and density. In addition, PFISR was also operating in a special designed mode to measure electric field and density profiles in the plane defined by the rocket trajectories and laterally to either side of the trajectories. Observation of the measured currents and electrodynamics structure of the auroral form encountered are presented in the context of standard auroral models and the temporal/spatial limitations of mission designs.

Bounds, Scott R.↗
NASA NTRS1981

Characteristics of 30-centimeter mercury ion thrusters

The technology development of the 30 centimeter J series mercury ion thruster for prime propulsion application in solar electric propulsion systems is described. Thruster design is reviewed. A standardized set of test and data recording procedures formulated to allow for the characterization of the J series thruster is described. Characteristics measured are the magnetic baffle characterization, the neutralizer characterization, perveance, the minimum eV/ion measurement, and the electrical and propellant utilization efficiency measurements. Test results are presented.

Maloy, J. E.↗
NASA NTRS1989

A new source of horizontal electric fields in the mid-latitude stratosphere

Superpressure balloon-borne instruments that measure the vector stratospheric electric field at latitudes near 45 + or - 10 deg S reveal several features in fair weather that cannot be attributed to ionospheric, thunderstorm, or other known sources. Over 180 days of electric field, conductivity, and current density data have been taken at the constant altitude of 26 km, using long-duration balloon flights in the Southern Hemisphere. Throughout these data the fair-weather horizontal electric field has a magnitude (10-50 mV/m) that cannot be due to mid-latitude ionospheric dynamo action. Furthermore, the fields are highly variable in amplitude, almost turbulent in appearance, while the vector direction steadily rotates in a counterclockwise manner. The period of this rotation is close to the quasi-inertial wave period for the latitude of the balloon. For these flights, the electric field rotation period varies between 14 and 21 hours. Some possible causes that might explain the electric field and current measurements reported herein are discussed.

Holzworth, R. H.↗
NASA NTRS1979

A quasi-static model of global atmospheric electricity. I - The lower atmosphere

A quasi-steady model of global lower atmospheric electricity is presented. The model considers thunderstorms as dipole electric generators that can be randomly distributed in various regions and that are the only source of atmospheric electricity and includes the effects of orography and electrical coupling along geomagnetic field lines in the ionosphere and magnetosphere. The model is used to calculate the global distribution of electric potential and current for model conductivities and assumed spatial distributions of thunderstorms. Results indicate that large positive electric potentials are generated over thunderstorms and penetrate to ionospheric heights and into the conjugate hemisphere along magnetic field lines. The perturbation of the calculated electric potential and current distributions during solar flares and subsequent Forbush decreases is discussed, and future measurements of atmospheric electrical parameters and modifications of the model which would improve the agreement between calculations and measurements are suggested.

Hays, P. B.↗
NASA NTRS1992

Measuring Effects Of Lightning On Power And Telephone Lines

Spherical antenna senses both horizontal and vertical fields simultaneously. Measures "fast" components of electric field used in conjunction with other equipment, including antenna measuring "slow" vertical component of electric field; microphone that senses thunder; cameras making visual records, which locate lightning; magnetic-field sensor; optical sensors; and instruments measuring speed and direction of wind.

Jafferis, William↗
NASA NTRS1983

Middle atmospheric electrodynamics

A review is presented of the advances made during the last few years with respect to the study of the electrodynamics in the earth's middle atmosphere. In a report of the experimental work conducted, attention is given to large middle atmospheric electric fields, the downward coupling of high altitude processes into the middle atmosphere, and upward coupling of tropospheric processes into the middle atmosphere. It is pointed out that new developments in tethered balloons and superpressure balloons should greatly increase the measurement duration of earth-ionospheric potential measurements and of stratospheric electric field measurements in the next few years. Theoretical work considered provides an excellent starting point for study of upward coupling of transient and dc electric fields. Hays and Roble (1979) were the first to construct a model which included orographic features as well as the classical thunderstorm generator.

Kelley, M. C.↗
NASA NTRS1975

Photoconductivity of high voltage space insulating materials: Measurements with metal electrodes

The electrical conductivities of high voltage insulating materials were measured in the dark and under various intensities of illumination. The materials investigated included FEP Teflon, Kapton-H, fused quartz, and parylene. Conductivities were determined as functions of temperature between 22 and 100 C and light intensity between 0 and 2.5 kW/m2. The thickness dependence of the conductivity was determined for Teflon and Kapton, and the influence of spectral wavelengths on the conductivity was determined in several cases. All measurements were made in a vacuum to simulate a space environment, and all samples had metallic electrodes. The conductivity of Kapton was permanently increased by exposure to light; changes as great as five orders of magnitude were observed after six hours of illumination.

Coffey, H. T.↗
NASA NTRS1995

Measuring Work Functions Of "Dirty" Surfaces With A Vibrating Capacitive Probe

Apparatus measures work function of possibly contaminated surface of specimen of metal or other electrically conductive material. Measures work function of specimen indirectly, by vibrating capacitive measurement of contact potential. Work function of specimen affected by microstructure and by contamination.

Yost, William T.↗
DOE OSTI2022

Electric field distribution in a non-self-sustained RF discharge with ionization generated by Ns discharge pulses

Abstract Electric field in a capacitively coupled, non-self-sustained RF discharge nitrogen plasma with external ionization generated by high-voltage ns pulses has been measured by ps Electric field induced second harmonic generation (EFISH). The measurements are made both in the bulk of the plasma and in the sheaths, using the absolute calibration by the Laplacian field between two plane electrodes. The results are compared with the kinetic modeling calculations. The RF electric field in the sheaths is significantly higher compared to that in the plasma, due to the displacement of the electrons by the drift oscillations and the resultant plasma self-shielding. However, the kinetic modeling predictions indicate that the electron impact ionization in the sheaths is largely ineffective, due to the low electron density. The reduction of the electric field in the plasma by the self-shielding in the sheaths is moderate, such that the energy is coupled to the plasma by the below-breakdown RF field. The peak RF field in the plasma is in the range of 15–25 Td, indicating the efficient vibrational excitation of N 2 by electron impact. The modeling predictions suggest that the targeted vibrational excitation of molecular species in a non-self-sustained RF discharge with external ionization is scalable to high pressures, electron densities, and discharge powers. The present approach can be extended to the vibrational excitation of other molecular species where the vibrational relaxation is relatively slow, such as CO, CO 2 , and H 2 .

Physics↗
DOE OSTI2021

Evaluation of the rheological and electrical percolation of high‐density polyethylene/carbon black composites using mathematical models

Abstract In this work, conductive polymer composites (CPCs) of bio‐based polyethylene (BioPe) containing different concentrations of carbon black (CB) were developed. By using oscillatory rheology analysis, a Newtonian plateau was observed in BioPe, and all BioPe/CB composites had a behavior of a pseudo‐solid and that composites with volume fractions ranging from 0.24 to 0.56 presented higher viscosity, storage, and loss modulus. This suggests the formation of a percolated network and by using the power‐law models, it was observed that the electrical percolation threshold was higher than the rheological percolation threshold. The electrical conductivity was measured using the four‐point probe method and a sigmoid model was used to predict the CPCs' electrical conductivity percolation threshold. The results indicated that the four‐point probe method presented satisfactory results according to the calculated standard deviations and voltage–current characteristics for each round of measurements considering the same ranging as used in rheology analysis. The analytical model used showed a coefficient of determination ( R 2 ) higher than 95%, allowing the prediction of the electrical conductivity of the CPC and the percolation threshold as a function of the volumetric fraction of the CB.

da SiIva, Moacy P.↗
DOE OSTI2020

Remotely powered line monitor

Improved devices, apparatuses, systems, and methods involving the use of field probes with voltage-controlled variable impedance elements and surface-launched acoustic wave devices, including surface acoustic wave (SAW) devices and SAW sensor-tag wireless interface devices to measure voltage and current in current carrying conductors (CCCs) via measurement of the electric fields and magnetic fields around said CCCs are disclosed. The devices, apparatuses, systems, and methods taught in the present invention include a remotely powered line-mounted measurement unit that requires no connection to electrical ground for operation, and that has no internal energy source, no energy harvesting or power conditioning circuitry, no discrete energy storage components, and no radio. The devices, apparatuses, systems, and methods taught in the present invention also provide for determining the phase (leading or lagging) of the current relative to the voltage in AC power systems, and also provide for measurement of temperature of the conductor.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS2014

Detailed Uncertainty Analysis of the ZEM-3 Measurement System

The measurement of Seebeck coefficient and electrical resistivity are critical to the investigation of all thermoelectric systems. Therefore, it stands that the measurement uncertainty must be well understood to report ZT values which are accurate and trustworthy. A detailed uncertainty analysis of the ZEM-3 measurement system has been performed. The uncertainty analysis calculates error in the electrical resistivity measurement as a result of sample geometry tolerance, probe geometry tolerance, statistical error, and multi-meter uncertainty. The uncertainty on Seebeck coefficient includes probe wire correction factors, statistical error, multi-meter uncertainty, and most importantly the cold-finger effect. The cold-finger effect plagues all potentiometric (four-probe) Seebeck measurement systems, as heat parasitically transfers through thermocouple probes. The effect leads to an asymmetric over-estimation of the Seebeck coefficient. A thermal finite element analysis allows for quantification of the phenomenon, and provides an estimate on the uncertainty of the Seebeck coefficient. The thermoelectric power factor has been found to have an uncertainty of +9-14 at high temperature and 9 near room temperature.

Seebeck effect↗