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Results for “pulsed power”

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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Meteorological effects on laser propagation for power transmission

An examination of possible laser operating parameters for power transmission to earth from solar power satellites is presented, with particular attention paid to assuring optimal delivery at midlatitudes. The degradation of beam efficiency due to molecular scattering, molecular absorption, aerosol scattering, and aerosol absorption during beam propagation through the atmosphere can be alleviated by judicious choice of wavelength windows, elevating the receptor sites, using a vertical propagation path, or by hole boring, i.e., vaporizing the aerosol particles in the beam path. Analyses are given for the beam propagation through fog, haze, clouds, and snow using various transitions. Only weapons-quality lasers are seen as being capable of boring through clouds and aerosols, employing a CW beam with superimposed pulses at high power densities. It is concluded that further short wavelength transmission experiments be performed to demonstrate transmission feasibility with the CW/pulsed mode of beam propagation.

Beverly, R. E., III↗
NASA NTRS2003

Magnetic Flux Compression Experiments Using Plasma Armatures

Magnetic flux compression reaction chambers offer considerable promise for controlling the plasma flow associated with various micronuclear/chemical pulse propulsion and power schemes, primarily because they avoid thermalization with wall structures and permit multicycle operation modes. The major physical effects of concern are the diffusion of magnetic flux into the rapidly expanding plasma cloud and the development of Rayleigh-Taylor instabilities at the plasma surface, both of which can severely degrade reactor efficiency and lead to plasma-wall impact. A physical parameter of critical importance to these underlying magnetohydrodynamic (MHD) processes is the magnetic Reynolds number (R(sub m), the value of which depends upon the product of plasma electrical conductivity and velocity. Efficient flux compression requires R(sub m) less than 1, and a thorough understanding of MHD phenomena at high magnetic Reynolds numbers is essential to the reliable design and operation of practical reactors. As a means of improving this understanding, a simplified laboratory experiment has been constructed in which the plasma jet ejected from an ablative pulse plasma gun is used to investigate plasma armature interaction with magnetic fields. As a prelude to intensive study, exploratory experiments were carried out to quantify the magnetic Reynolds number characteristics of the plasma jet source. Jet velocity was deduced from time-of-flight measurements using optical probes, and electrical conductivity was measured using an inductive probing technique. Using air at 27-inHg vacuum, measured velocities approached 4.5 km/s and measured conductivities were in the range of 30 to 40 kS/m.

Turner, M. W.↗
NASA NTRS2004

Pulsed hall thruster system

A pulsed Hall thruster system includes a Hall thruster having an electron source, a magnetic circuit, and a discharge chamber; a power processing unit for firing the Hall thruster to generate a discharge; a propellant storage and delivery system for providing propellant to the discharge chamber and a control unit for defining a pulse duration .tau.<0.1d.sup.3.rho./m, where d is the characteristic size of the thruster, .rho. is the propellant density at standard conditions, and m is the propellant mass flow rate for operating either the power processing unit to provide to the Hall thruster a power pulse of a pre-selected duration, .tau., or operating the propellant storage and delivery system to provide a propellant flow pulse of duration, .tau., or providing both as pulses, synchronized to arrive coincidentally at the discharge chamber to enable the Hall thruster to produce a discreet output impulse.

Hruby, Vladimir J.↗
NASA NTRS1964

Portable PFM Simulator

Portable transistorized circuit pulse frequency modulation /PFM/ simulator with power supply regulator

TRANSISTOR CIRCUIT↗
NASA NTRS1972

Optimal Quasi-steady Plasma Thruster system characteristics.

The overall characteristics of a generalized Quasi-steady Plasma Thruster (QPT) system consisting of thruster head, power conditioning network, propellant supply subsystem are studied. Energy balance equations for the system are coupled with component mass relationships in order to determine overall system mass and performance. Power supply power levels varying from 100 to 10,000 watts with thruster power levels ranging from 300 kw to 30 Mw employing argon as the propellant are considered. The manner in which overall system mass, average thrust, and burn time vary as a function power supply power level, quasi-steady power level, and pulse time are studied. Results indicate the existence of optimum pulse times when system mass is employed as an optimization criterion.

Ludwig, D. E.↗
NASA NTRS1973

Exhaust pressure and density of various pulsed mpd-arc thruster systems

Exhaust flow in a new, 155 cm i.d., vacuum facility was compared with earlier measurements in a small (15.2 cm i.d.) duct. Reductions in post transient impact pressure were about 5:1 in the larger facility. Corresponding reduced electron number densities (approximately 2 x 10 to the 13th power/cucm) were noted. A new, 125 miscrosecond, pulse forming network power source produced no major differences in impact pressure compared to the crowbarred condenser bank used earlier. Comparing a puff gas feed of the arc chamber with a new 10 millisecond steady gas feed also showed no major difference in impact pressure for 125 miscrosecond powering.

Michels, C. J.↗
NASA NTRS1973

High-energy electron-beam deposition onto a hot graphite surface.

The momentum transfer and blow-off vapor yield resulting from the deposition of a pulsed high-power electron beam onto a plane graphite target with surface temperatures of 300 K and 5000 K are examined experimentally. The results show that with identical electron beams the momentum transfer and vapor yield are between two and three times larger when irradiating the 5000 K surface as compared with the 300 K surface.

Robin, J. E.↗
NASA NTRS1974

Research on fission fragment excitation of gases and nuclear pumping of lasers

Experimental investigations of fission fragment excited gases are reported along with a theoretical analysis of population inversions in fission fragment excited helium. Other studies reported include: nuclear augmentation of gas lasers, direct nuclear pumping of a helium-xenon laser, measurements of a repetitively pulsed high-power CO2 laser, thermodynamic properties of UF6 and UF6/He mixtures, and nuclear waste disposal utilizing a gaseous core reactor.

Schneider, R. T.↗
NASA NTRS1975

Increasing the isotropic properties of a discharge spark chamber with a large gap

The recording of particle tracks in the form of sparks or streamers running at different angles toward the electric field of the chamber was studied. The investigations were performed with two discharge spark chambers consisting of boxes filled with neon at 1 atm. The spark chambers were powered by a pulse with an amplitude of 300 kV applied from a pulse generator. The recording of particle tracks in the form of sparks took place at track angles smaller than 30 deg with respect to the electrical field. At angle larger than 40 deg the tracks are recorded in the form of streamers. Particle traces with respect to the angle are given.

Nurgozhin, N. N.↗
NASA NTRS1975

Underwater probing with laser radar

Recent advances in laser and electro optics technology have greatly enhanced the feasibility of active optical probing techniques aimed at the remote sensing of water parameters. This paper describes a LIDAR (laser radar) that has been designed and constructed for underwater probing. The influence of the optical properties of water on the general design parameters of a LIDAR system is considered. Discussion of the specific details in the choice of the constructed LIDAR is given. This system utilizes a cavity dumped argon ion laser transmitter capable of 50 watt peak powers, 10 nanosecond pulses and megahertz pulse repetition rates at 10 different wavelengths in the blue green region of the spectrum. The performance of the system, in proving various types of water, is demonstrated by summarizing the results of initial laboratory and field experiments.

Carswell, A. I.↗
NASA NTRS1976

Propellant side feed

New solid-propellant configurations increase thrust-to-power ratio of pulsed plasma microthruster and provide possibility of varying thrust. Techniques are adaptable to sputter coating of polymeric material or pulsed ablating light sources.

Guman, W. J.↗
NASA NTRS1976

Simplifier cut core inductor design

Advantages of specifying C cores and cut toroids fabricated from grain oriented silicon steels for use in high frequency power converters and pulse width modulated switching regulators are discussed. A method for rating cores assigns to each core a number which is the product of its window and core cross section area, called 'Area Product A sub p.' A correlation between the A sub p numbers and current density for a given temperature rise was developed. Also, straight line relationships were developed for A sub p and volume, A sub p and surface area, and A sub p and weight. These relationships can be used to simplify and standardize the process of inductor design. They also make it possible to design inductors of small bulk and volume or to optimize efficiency.

Mclyman, W. T.↗
NASA NTRS1980

Evaluation of pulsed RFI effects on digital satellite repeaters

This paper presents an analytical approach for assessing the effect of pulsed RFI on the error probability of a coherent phase-shift keyed signal through a nonlinear satellite repeater. The RFI is assumed to affect the uplink channel and to consist of CW pulses with random power levels and arriving randomly in time with a Poisson distribution. A model to approximate the effect of intermodulation products is introduced and the error probability conditioned on the output of the satellite repeater is computed. The classical moment technique is then used as an efficient method of averaging the conditional error probability over the numerous random parameters associated with the uplink signal.

Huang, T. C.↗
NASA NTRS1981

Lidar meteorology

Current and future lidar applications to meteorological studies are presented. In water vapor, temperature, and pressure measurement applications, differential absorption lidar (DIAL) techniques are used, employing a minimum of two wavelengths. The DIAL technique has proven particularly accurate in pressure measurements. For wind measurements, lidar investigations generally use the Doppler shifting of laser light backscattered from aerosols, and a pulsed low-power CO2 Doppler lidar is being developed for airborne platform applications. At visible to near-infrared wavelengths, spatial distribution of aerosol and clouds can be obtained from lidar, and this information can help determine such atmospheric parameters as mixed layer height and cloud height distributions. A Shuttle lidar facility, being developed for the end of the 1980's, will enable laser remote sensing techniques to be applied to studies of the lower atmosphere.

Browell, E. V.↗
NASA NTRS1982

Detection of trace quantities of dimethylacetamide during the curing process of a polyimide film

An experimental study of positive ion clustering of dimethylacetamide (DMAC) with water molecules using high pressure mass spectrometry techniques is reported. The possibilities of using these techniques to determine the concentration levels of DMAC evolved from a polyimide film during the curing process, are examined. The test sample of gas contained DMAC of the order of a few micrograms, water, nitrogen, oxygen, and other compounds that might evolve during the curing cycle of a polyimide film. It is found that PPM concentrations such as DMAC lost from polyimide during curing stages can be detected with this technique. Improvement of the detection of lower concentrations (50 picograms) can be made by using electron multipliers with a gain in the 10 to the 8th power range and pulse counting techniques.

Smith, A. C.↗