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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Electrostatic discharge test apparatus

Electrostatic discharge properties of materials are quantitatively measured and ranked. Samples are rotated on a turntable beneath selectable, co-available electrostatic chargers, one being a corona charging element and the other a sample-engaging triboelectric charging element. Samples then pass under a voltage meter to measure the amount of residual charge on the samples. After charging is discontinued, measurements are continued to record the charge decay history over time.

Smith, William Conrad↗
NASA NTRS1987

Charged drop dynamics experiment using an electrostatic-acoustic hybrid system

The design and the performance of an electrostatic-acoustic hybrid system and its application to a charge drop rotation experiment are presented. This system can levitate a charged drop electrostatically and induce drop rotation or oscillation by imposing an acoustic torque or an oscillating acoustic pressure. Using this system, the equilibrium shapes and stability of a rotating charged drop were experimentally investigated. A 3 mm size water drop was rotated as a rigid body and its gyrostatic equilibrium shapes were observed. Families of axisymmetric shapes, two-lobed shapes, and eventual fissioning have been observed. With the assumption of 'effective surface tension' in which the surface charge simply modified the surface tension of neutral liquid, the results agree exceptionally well with the Brown and Scriven's (1980) prediction for uncharged drops.

Rhim, W. K.↗
NASA NTRS1988

Electrostatic waves stimulated by coherent VLF signals propagating in and near the inner radiation belt

The excitation of electrostatic waves by whistler-mode VLF signals propagating along magnetic-field lines in and near the earth's inner radiation belt is examined on the basis of ISEE-1 observations obtained during July-December 1983. The data are presented in extensive graphs and characterized in detail. The effect is seen in about 60 percent of the ISEE-1 orbits penetrating the belt and for signals originating in both hemispheres, with an electrostatic-wave effective bandwidth roughly proportional to the local magnetic-field strength. These results are interpreted in terms of a theoretical model in which scattering of the VLF waves off magnetic-field-aligned plasma density irregularities is followed by particle pitch-angle scattering and precipitation in the radiation belt; the latter effect could then produce new irregularities via a feedback mechanism.

Bell, T. F.↗
NASA NTRS1988

Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

Nishikawa, K.-I.↗
NASA NTRS1988

Electrostatic ion-cyclotron waves in a two-ion component plasma

The excitation of electrostatic ion cyclotron (EIC) waves is studied in a single-ended Q machine in a two-ion component plasma (Ca+ and K+). Over a large range of relative concentrations of Cs+ and K+ ions, two modes are excited with frequencies greater than the respective cyclotron frequencies of the ions. The results are discussed in terms of a fluid theory of electrostatic ion cyclotron waves in a two-ion component plasma.

Suszcynsky, David M.↗
NASA NTRS1987

On the generation of broadband electrostatic noise

Linear theory analysis and particle simulation studies were carried out to understand the mechanisms generating broadband electrostatic noise (BEN) and the effects of BEN on particles as well as the nonlinear saturation level in the geomagnetic tail region. Streaming ion beams as well as warm ions and electrons are used to model the plasma-sheet particle population. When the beam ion temperature is comparable to the temperature of the warm plasma-sheet particles, electrostatic ion cyclotron instabilities become unstable, giving rise to low-frequency noise at omega less than about n(Omega i), where Omega i is the ion gyrofrequency.

Ashour-Abdalla, M.↗
NASA NTRS1988

Simulation and non-linear stage of the electrostatic waves observed during the AMPTE lithium release in the solar wind

During the AMPTE lithium releases in the solar wind intense electrostatic waves with frequencies between a few tens of Hz to several kHz were observed outside the diamagnetic cavity. The results of linear Vlasov theory have suggested that these waves may be generated through two types of instabilities. One is the ion-ion instability associated with the relative drift between the lithium ions and the solar wind protons, and the other is the ion-acoustic instability due to the relative drift between the electrons and the ions. In order to look at the non-linear behavior of the wave-particle interactions, and discern the effect of waves on the particles, full particle electrostatic simulations have been performed, and the results are presented here. It is shown that the ion-ion instability whose phase velocity is oblique to the solar wind velocity can cause considerable anisotropic 'heating' of both the lithium ions and the solar wind protons.

Omidi, N.↗
NASA NTRS1989

Electrostatic Spraying With Conductive Liquids

Thin, uniform polymer coatings applied in water base normally impossible to charge. Electrostatic sprayer modified so applies coatings suspended or dissolved in electrically conductive liquids. Nozzle and gun constructed of nonconductive molded plastic. Liquid passageway made long enough electrical leakage through it low. Coaxial hose for liquid built of polytetrafluoroethylene tube, insulating sleeve, and polyurethane jacket. Sprayer provided with insulated seal at gun-to-hose connection, nonconductive airhose, pressure tank electrically isolated from ground, and special nozzle electrode. Supply of atomizing air reduced so particle momentum controlled by electrostatic field more effectively. Developed to apply water-base polyurethane coating to woven, shaped polyester fabric. Coating provides pressure seal for fabric, which is part of spacesuit. Also useful for applying waterproof, decorative, or protective coatings to fabrics for use on Earth.

Kosmo, Joseph J.↗
NASA NTRS1988

Electrostatic testing of thin plastic materials

Ten thin plastic materials (Velostat, RCAS 1200, Llumalloy, Herculite 80, RCAS 2400, Wrightlon 7000, PVC, Aclar 22A, Mylar, and Polyethylene) were tested for electrostatic properties by four different devices: (1) The static decay meter, (2) the manual triboelectric testing device, (3) the robotic triboelectric testing device, and (4) the resistivity measurement adapter device. The static decay meter measured the electrostatic decay rates in accordance with the Federal Test Method Standard 101B, Method 4046. The manual and the robotic triboelectric devices measured the triboelectric generated peak voltages and the five-second decay voltages in accordance with the criteria for acceptance standards at Kennedy Space Center. The resistivity measurement adapter measured the surface resistivity of each material. An analysis was made to correlate the data among the four testing devices. For the material tested the pass/fail results were compared for the 4046 method and the triboelectric testing devices. For the limited number of materials tested, the relationship between decay rate and surface resistivity was investigated as well as the relationship between triboelectric peak voltage and surface resistivity.

Skinner, S. Ballou↗
NASA NTRS1989

Simulation of electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

A spatially two-dimensional electrostatic PIC simulation code was used to study the stability of a plasma equilibrium characterized by a localized transverse dc electric field and a field-aligned drift for L is much less than Lx, where Lx is the simulation length in the x direction and L is the scale length associated with the dc electric field. It is found that the dc electric field and the field-aligned current can together play a synergistic role to enable the excitation of electrostatic waves even when the threshold values of the field aligned drift and the E x B drift are individually subcritical. The simulation results show that the growing ion waves are associated with small vortices in the linear stage, which evolve to the nonlinear stage dominated by larger vortices with lower frequencies.

Nishikawa, K.-I.↗
NASA NTRS1988

A simulation study of broadband electrostatic noise in the presence of ionospheric electrons

Ion beams have been observed flowing along magnetic field lines in the earth's plasma sheet boundary layer and are believed to generate intense electrostatic wave activity known as broadband electrostatic noise. Cold electrons of ionospheric origin have also been observed in this same region and it has been shown that the addition of these cold electrons modifies substantially the plasma wave dispersion properties. With cold electrons present, four instabilities can be excited: (1) ion acoustic, (2) electron acoustic, (3) beam resonant, and (4) Buneman two stream. These instabilities can generate waves with large growth rates at frequencies consistent with broadband electro-static noise. Using computer simulations, consideration is given to the wave energy frequency spectra generated by these instabilities, as well as cold electron heating and nonlinear effects on the ion beam.

Schriver, D.↗
NASA NTRS1988

Experience, problems, and subtleties of electrostatic discharge at JPL

Approaches used to control electrostatic discharge (ESD) at the JPL are discussed. ESD control problems generally occur in the following: (1) wrist straps; (2) outer garments that preclude the generation of static charge; and (3) materials, items, techniques, or processes permitting the development of a static charge. Consideration is given to the cleaning of antistatic materials, outside contracts, vapor degreasing, and electrostatically charged electrical cables.

Woods, William R.↗
NASA NTRS1989

Local generation of electrostatic bursts at Comet Giacobini-Zinner - Modulation by steepened magnetosonic waves

The ICE spacecraft observed in the vicinity of Comet Giacobini-Zinner electrostatic noise with burstlike features seemingly modulated by the relative orientation of the interplanetary magnetic field and the solar wind velocity. The adequacy of ion acousticlike instabilities stimulated by photoelectron or newborn ion beams to the interpretation of the electrostatic bursts is discussed. It is concluded that the mode fed by the photoelectrons exhibits characteristics compatible with the observations.

Brinca, Armando L.↗
NASA NTRS1989

Electrostatic wave generation above and below the plasma frequency by electron beams

The unmagnetized electrostatic dispersion equation is solved numerically to study the growth of electrostatic waves near the plasma frequency resulting from a unstable electron beam. An attempt is made to find the dispersion relations, frequencies of maximum growth, and the resonant or nonresonant character of the waves for particular beam parameters. It is found that the unstable waves do not have the Langmuir dispersion relation except in the limit of a very dilute beam with growth on the connected mode of O'Neil and Malmberg. The properties of the unstable mode depend strongly on beam parameters such as beam density, speed, and temperature.

Cairns, Iver H.↗
NASA NTRS1989

Low-frequency electrostatic instabilities excited by injections of an electron beam in space

One-dimensional particle simulations have been carried out to study the low-frequency broadband electrostatic noise that propagates almost perpendicularly from the magnetic field line when a nonrelativistic electron beam is injected into space from a spacecraft. For T(e) = T(i) the electrostatic ion cyclotron waves appear as well as the waves near the lower hybrid frequency. When the magnetic field is reduced so that Omega(e) is much less than omega(pe) in a nonisothermal plasma, T(e) greater than T(i) oblique ion acoustic instabilities appear to propagate almost perpendicular to the magnetic field. In addition, a very low frequency mode at omega much less than Omega(i) is found to be generated by the electrons flowing into the conductor. Both the injected beam electrons as well as the ambient electrons flowing into the spacecraft are responsible for generating those instabilities, which accelerate ions perpendicular to the magnetic field.

Hwang, Y. S.↗
NASA NTRS1989

Electrostatic prepregging of thermoplastic matrices

Thermoplastic towpregs of PEEK/AS-4, PEEK/S-2 glass and LaRC-TPI/AS-4, produced by electrostatic deposition of charged and fluidized polymer powders on spread continuous fiber tows, are described. Processing parameters for combining PEEK 150 powder with unsized 3k AS-4 carbon fiber are presented. The experimental results for PEEK 150/AS-4 reveal that electrostatic fluidized bed coating may be an economically attractive process for producing towpreg.

Muzzy, John D.↗
NASA NTRS1990

Electrostatic Linear Actuator

Electrically charged helices attract or repel each other. Proposed electrostatic linear actuator made with intertwined dual helices, which holds charge-bearing surfaces. Dual-helix configuration provides relatively large unbroken facing charged surfaces (relatively large electrostatic force) within small volume. Inner helix slides axially in outer helix in response to voltages applied to conductors. Spiral form also makes components more rigid. Actuator conceived to have few moving parts and to be operable after long intervals of inactivity.

Collins, Earl R., Jr.↗
NASA NTRS1990

Electrostatic Dispersion Of Drops In Clusters

Electrical charging speeds evaporation. Report presents theoretical study of evaporation and dispersion of electrostatically charged clusters of drops in liquid fuel sprays. Represents extension of studies described in article, "More About Evaporation of Drops in Clusters" (NPO-17594). Undertaken in effort to learn how electrostatic atomization used to disperse fuel better in order to reduce formation of soot in diesel engines and other power and combustion systems.

Bellan, Josette↗