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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Response of lead-acid batteries to chopper-controlled discharge

The preliminary results of simulated electric vehicle, chopper, speed controller discharge of a battery show energy output losses at up to 25 percent compared to constant current discharges at the same average discharge current of 100 A. These energy losses are manifested as temperature rises during discharge, amounting to a two-fold increase for a 400-A pulse compared to the constant current case. Because of the potentially large energy inefficiency, the results suggest that electric vehicle battery/speed controller interaction must be carefully considered in vehicle design.

Cataldo, R. L.↗
NASA NTRS1976

Probe studies in a modified Penning discharge

The axial and radial floating potential distribution in a modified Penning discharge have been studied at different values of the background pressure, discharge voltage, and magnetic field. An array of small disc probes arranged radially with their planes perpendicular to the magnetic field and movable along the axial direction was inserted in the plasma through one open end of the magnetic mirror system. Results show that depending on the operating conditions, the discharge can undergo different mode transitions in which the plasma can sustain different floating potentials in the radial as well as in the axial directions. Preliminary results of measurement, using RF probes in the modified Penning discharge plasma are also discussed.

Sen, C.↗
NASA NTRS1978

Electron beam injection experiments - The beam-plasma discharge at low pressures and magnetic field strengths

The paper describes electron beam injection experiments which clarify observational results obtained in rocket flights. A column of enhanced density plasma, exceeding the density expected from ionization by primary beam electrons, was observed in a large vacuum system at low magnetic fields (1 to 1.5 G) and low ambient pressures (10 to the minus 6 to 10 to the minus 5 torr). The peak luminosity of the discharge was about 10 times that of the beam alone, and the radius increased by a factor of three. In the absence of the discharge, RF emission is observed at 1.1 to 1.2 times the cyclotron frequency, and a strong band of RF noise with upper frequency cutoff at about the cyclotron frequency is observed in the discharge mode, along with higher frequency noise at or near the plasma frequency. The onset of the plasma discharge is critically dependent on beam current. The described results agree with observations obtained at much higher densities and magnetic fields in fusion research studies.

Bernstein, W.↗
NASA NTRS1979

Model for breakdown process in dielectric discharges

A heuristic model to explain the blowoff of charge during an electron-induced dielectric discharge is presented. It is proposed that blowoff of charge is initiated by a punchthrough or a flashover. The discharge time is assumed to be governed by an LC time constant where L is the inductance of the electrons flowing in the branches of the Lichtenberg figures at an electron range below the irradiated surface and C is the capacitance between the trapped electrons and the substrate for the discharged area. Experiments to verify that blowoff is a consequence of punchthrough or flashover and to measure the punchthrough current and the variation of discharge time with the sample area and thickness were conducted.

Leadon, R.↗
NASA NTRS1979

NASCAP modelling of environmental-charging-induced discharges in satellites

The charging and discharging characteristics of a typical geosynchronous satellite experiencing time-varying geomagnetic substorms, in sunlight, were studied utilizing the NASA Charging Analyzer Program (NASCAP). An electric field criteria of 150,000 volts/cm to initiate discharges and transfer of 67 percent of the stored charge was used based on ground test results. The substorm characteristics were arbitrarily chosen to evaluate effects of electron temperature and particle density (which is equivalent to current density). It was found that while there is a minimum electron temperature for discharges to occur, the rate of discharges is dependent on particle density and duration times of the encounter. Hence, it is important to define the temporal variations in the substorm environments.

Stevens, N. J.↗
NASA NTRS1979

NASCAP modelling of environmental-charging-induced discharges in satellites

A study of the charging and discharging characteristics of a typical geosynchronous satellite experiencing time-varying geomagnetic substorms, in sunlight, is conducted. The NASA Charging Analyzer Program (NASCAP) is used. An electric field criteria of 1.5 x 10 to the 5th volts/cm to initiate discharges and transfer of 67% of the stored charge is used in this study, based on ground test results. The substorm characteristics are arbitrarily chosen to evaluate effects of electron temperature and particle density (which is equivalent to current density). It has been found that while there is a minimum electron temperature for discharges to occur, the rate of discharges is dependent on particle density and duration times of the encounter. Hence, it is important to define the temporal variations in the substorm environments.

Stevens, N. J.↗
NASA NTRS1980

Voyager spacecraft electrostatic discharge testing

The program of environmental testing undergone by the Voyager spacecraft in order to simulate the transient voltage effects of electrostatic discharges expected in the energetic plasma environment of Jupiter is reported. The testing consists of studies of the electrostatic discharge characteristics of spacecraft dielectrics in a vacuum-chamber-electron beam facility, brief piece part sensitivity tests on such items as a MOSFET multiplexer and the grounding of the thermal blanket, and assembly tests of the magnetometer boom and the science boom. In addition, testing of a complete spacecraft was performed using two arc sources to simulate long and short duration discharge sources for successive spacecraft shielding and grounding improvements. Due to the testing program, both Voyager 1 and Voyager 2 experienced tolerable electrostatic discharge-caused transient anomalies in science and engineering subsystems, however, a closer duplication of the spacecraft environment is necessary to predict and design actual spacecraft responses more accurately.

Whittlesey, A.↗
NASA NTRS1981

Brushfire arc discharge model

A one dimensional arc discharge model incorporating a brushfire-type propagation of a discharge wavefront was investigated. A set of equations, developed and their which include electrical, thermal and plasma parameters, were solutions shown to be consistent with a propagating brushfire wavefront. Voltage, current, plasma density, temperature, and resistivity profiles were obtained. Mechanical forces, magnetic and electrostatic were considered in evaluating the flashover to blowout current ratio, G', for arc discharges with the brushfire parameters developed in the model. This ratio is an important factor in determining the electromagnetic interference (EMI) impact of arc discharges on spacecraft electrical subsystems. The conclusion of the analysis is that electrostatic forces are much more important than magnetic forces. The magnitude of the G' factor obtained, 58.5 percent, is within the range of those obtained by experimental means. Improvements in the analytical model as well in the experimental approach are recommended.

Lnouye, G. T.↗
NASA NTRS1980

Aspect dependence and frequency spectrum of electrical discharges on the P78-2 (SCATHA) satellite

The satellite charging at high altitudes (SCATHA) P78-2 satellite payload includes a charging electrical effects analyzer (CEEA) which measures the characteristics of electrical discharges in both the frequency and time domain. Pulses are detected in response to commands during electron and ion beam operations and during natural discharge events. The pulse analyzer measures the shape of pulses on four sensors and is the primary CEEA diagnostic for the natural discharges. Only five discharges were found in the data at a time when the pulse analyzer was in mode with sufficient time resolution to resolve the frequency components in the waveform.

Koons, H. C.↗
NASA NTRS1982

Threshold criterion for a space simulation beam-plasma discharge

An experimental and theoretical study of the threshold characteristics of a space simulation beam-plasma discharge with emphasis on density profiles and a density-dependent ignition criterion. The study included various beam-plasma conditions covering beam currents from 8 to 85 mA, beam energies from 0.8 to 2.0 keV, and magnetic fields at 0.9 and 1.5 G. The study included experimental determinations of radial profiles of electron density for each of the selected conditions extending from a low-density, pre-beam-plasma discharge state to a strong beam-plasma discharge condition. The experimental results are shown to agree with detailed model calculations, which consider the beam-plasma discharge to be produced by large-amplitude electron plasma waves resulting from the beam-plasma interaction.

Szuszczewicz, E. P.↗
NASA NTRS1983

Expected cycle life vs. depth of discharge relationships of well-behaved single cells and cell strings

The present investigation is concerned with the factors which might influence the cycle life vs. depth of discharge relationship, taking into account the rate of loss of cell capacity, the amount of excess capacity built into the cells, and the penalty in capacity loss resulting from the use of deep depths of discharge. 'First principles' are used to develop a cell life model for somewhat arbitrary conditions. This model is then used to estimate the cycle life vs. depth of discharge relationships for 'well behaved' cells. The stochastic variations associated with groupings of single cells are then introduced to the battery pack cycle life model. The term 'well behaved' cell is used to describe a single cell which does not suffer any abrupt failure mode during the course of its operation. It gradually loses capacity for any number of the usual reasons at a rate which is the product of the fractional depth of discharge and a factor which is characteristic of the cell under consideration.

Thaller, L. H.↗
NASA NTRS1983

Low temperature operation of an S2 laser using radio frequency simmer discharges

Technological problems stemming from high temperature operation of the sulfur resonator have hindered its development as a tunable, efficient, discharge pumped laser. The use of RF simmer discharges is shown to reduce previous temperature constraints by dissociating polyatomic sulfur molecules into the dimer, such that lasing is achieved when pumped by an XeCl excimer laser. The peak power output of the S2 laser and the transmission spectra through sulfur discharges are used to infer the effectiveness of the discharge in dissociating the vapor.

Killeen, K. P.↗
NASA NTRS1985

Laboratory studies of spacecraft response to transient discharge pulses

The in-orbit measurement of spacecraft discharge properties was investigated. The experiments include design and fabrication of appropriate sensors and effects of spacecraft electromagnetic responses on the interpretation of the discharge data. Electric field sensors especially designed to response to high-speed transient signals were installed on a mock-up of a satellite. The simple mock-up was basically a sheet of aluminum rolled to form a cylinder. A movable spark-discharge noise source designed to be electromagnetically isolated from its power supply system was used to induce transient signals at various locations on the spacecraft's outer surface. The measurements and their implications are described. It is concluded that practical orbital measurements to define discharge noise source properties should be possible, and that simple mock-ups of the type described below are useful in sensor system design and data interpretation.

Nanevicz, J. E.↗
NASA NTRS1985

Characterization of EMI generated by the discharge of a VOLT solar array

The interaction of a high-voltage solar array with the space plasma environment is investigated in a laboratory simulation experiment. Discharges are observed to occur when the solar array is at a sufficiently high negative bias with respect to the plasma. The frequency of occurrence of discharge is found to depend critically on the plasma density and on the geometry of the array. The electromagnetic interference (EMI) associated with a discharge is also measured. The amplitude of EMI increases with the magnitude of the high voltage. Since the discharge-generated EMI is of significant amplitude, its effect on the performance of systems in space must be evaluated.

Leung, P.↗
NASA NTRS1986

Characteristics of electromagnetic interference generated by arc discharges

Electromagnetic interference (EMI) signatures resulting from arc discharges are characterized, and the effects of electrostatic discharges (ESDs) on the design of spacecraft systems are investigated. EMI characterization experiments were performed on Mylar, Teflon, Kapton, fused silica, and fiberglass in a vacuum chamber with acrylic walls; the experimental design and procedures are described. Discharge current pulses and RF spectra generated by the sample materials are examined. The relation between the magnitude of EMI generated during an ESD event and the material, environment, and geometry is studied. The solar-array/plasma interaction is analyzed; particular attention is given to the rate of discharge as a function of plasma density. The physical mechanisms of ESD-generated EMI are discussed. The data reveal that ESD parameters are dependent on the test environment.

Leung, Philip↗
NASA NTRS1988

Ring cusp/hollow cathode discharge chamber performance studies

An experimental study was performed to determine the effects of hollow cathode position, anode position, and ring cusp magnetic field configuration and strength on discharge chamber performance. The results are presented in terms of comparative plasma ion energy cost, extracted ion fraction, and beam profile data. Such comparisons are used to demonstrate whether changes in performance are caused by changes in the loss rate of primary electrons to the anode or the loss rate of ions to discharge chamber walls or cathode and anode surfaces. Results show: (1) the rate of primary electron loss to the anode decreases as the anode is moved downstream of the ring cusp toward the screen grid; (2) the loss rate of ions to hollow cathode surfaces are excessive if the cathode is located upstream of a point of peak magnetic flux density at the discharge chamber centerline; and (3) the fraction of the ions produced that are lost to discharge chamber walls and ring magnet surfaces is reduced by positioning of the magnet rings so the plasma density is uniform over the grid surface, and adjusting their strength to a level where it is sufficient to prevent excessive ion losses by Bohm diffusion.

Vaughn, J. A.↗
NASA NTRS1990

Electron-impact ionization and electron attachment cross sections of radicals important in transient gaseous discharges

Electron-impact ionization and electron attachment cross sections of radicals and excited molecules were measured using an apparatus that consists of an electron beam, a molecular beam and a laser beam. The information obtained is needed for the pulse power applications in the areas of high power gaseous discharge switches, high energy lasers, particle beam experiments, and electromagnetic pulse systems. The basic data needed for the development of optically-controlled discharge switches were also investigated. Transient current pulses induced by laser irradiation of discharge media were observed and applied for the study of electron-molecule reaction kinetics in gaseous discharges.

Lee, Long C.↗
NASA NTRS1990

Television image of a large upward electrical discharge above a thunderstorm system

A low light-level TV camera is used to obtain an unusual image of luminous electrical discharge over a thunderstorm 250 km from the observation site. The image is presented and the discharge in the image is described. It is suggested that the image is probably due to two localized electric charge concentrations at the cloud tops. The hazard of these discharges for aircraft and rocket launches is examined. Consideration is given to the possibility that these discharges may account for unexplained photometric observations of distant lightning events that show a low rise rate of the luminous pulse and no electromagnetic sferic pulse like that in cloud-to-earth lightning strokes. The photometric events of this type that occurred on September 22-23, 1989 during hurricane Hugo are noted.

Franz, R. C.↗