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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

A three dimensional dynamic study of electrostatic charging in materials

A description is given of the physical models employed in the NASCAP (NASA Charging Analyzer Program) code, and several test cases are presented. NASCAP dynamically simulates the charging of an object made of conducting segments which may be entirely or partially covered with thin dielectric films. The object may be subject to either ground test or space user-specified environments. The simulation alternately treats (1) the tendency of materials to accumulate and emit charge when subject to plasma environment, and (2) the consequent response of the charged particle environment to an object's electrostatic field. Parameterized formulations of the emission properties of materials subject to bombardment by electrons, protons, and sunlight are presented. Values of the parameters are suggested for clean aluminum, Al2O3, clean magnesium, MgO, SiO2 kapton, and teflon. A discussion of conductivity in thin dielectrics subject to radiation and high fields is given, together with a sample calculation.

Katz, I.↗
NASA NTRS1978

NASA charging analyzer program: A computer tool that can evaluate electrostatic contamination

A computer code, the NASA Charging Analyzer Program (NASCAP), was developed to study the surface charging of bodies subjected to geomagnetic substorm conditions. This program will treat the material properties of a surface in a self-consistent manner and calculate the electric fields in space due to the surface charge. Trajectories of charged particles in this electric field can be computed to determine if these particles enhance surface contamination. A preliminary model of the Spacecraft Charging At The High Altitudes (SCATHA) satellite was developed in the NASCAP code and subjected to a geomagnetic substorm environment to investigate the possibility of electrostatic contamination. The results indicate that differential voltages will exist between the spacecraft ground surfaces and the insulator surfaces. The electric fields from this differential charging can enhance the contamination of spacecraft surfaces.

Stevens, N. J.↗
NASA NTRS1978

Ion tracking in an electrostatic potential distribution

An ion tracking system utilizing a single detector was designed to resolve two dimensional potential distributions in a vacuum. The ion detector consisted of a continuous dynode electron multiplier tube mounted behind a series of aperture plates. The detector was located on a track below a wedge shaped structure used to produce the desired potential distribution. A 150 volt electron beam aimed at selected regions, ionized the residual gas in the chamber. The ions were ejected from their source points by electrostatic forces causing them to drift downward toward the detector. Measurements of particle energy, detector position, and entry angle of the incoming particle flux were used to initialize a computer trajectory-tracing program. The program assumes a known theoretically calculated potential distribution near the wedge for computation of particle trajectories, providing a basis for evaluating the data. Special attention was given to characterization of the ion detector.

Ross, D. P.↗
NASA NTRS1978

Calculation of electrostatic fields in periodic structures of complex shape

A universal algorithm is presented for calculating electrostatic fields in an infinite periodic structure consisting of electrodes of arbitrary shape which are located in mirror-symmetrical manner along the axis of electron-beam propagation. The method is based on the theory of R-functions, and the differential operators which are derived on the basis of the functions. Numerical results are presented and the accuracy of the results is examined.

Kravchenko, V. F.↗
NASA NTRS1977

An electrostatically driven surface for flexible wall drag reduction studies

This paper describes the theoretical analysis, experimental development and surface motion data from an electrostatically driven flexible wall capable of producing high frequency, large amplitude, short wavelength standing wave motions. The driven wall was developed for use in studying flexible wall-turbulent boundary layer interactions. The theoretical analysis considers the coupled electrochemical system using a continuum model. For the system under consideration the electrical field is uncoupled from the mechanical system leading to a simplified analysis. The structural problem is a non-linear (moderately) large amplitude problem and details of the analysis are presented. Surface motion measurements, made using a modified schlieren type optical system, are discussed and details of the surface motion under different excitations are presented. Fair agreement is obtained between experimental measurements and theoretical calculations.

Weinstein, L. M.↗
NASA NTRS1978

12-cm magneto-electrostatic containment argon/xenon ion source development

The original 12 cm hexagonal magneto-electrostatic containment (MESC) discharge chamber described by Moore in 1969 has been optimized for argon and xenon operation. Argon mass utilization efficiencies of 65 to 77 percent were achieved at keeper-plus-main discharge energy consumptions of 244 to 422 eV/ion respectively. Xenon performance of 85 to 96 percent mass utilization were realized at 203 to 350 eV/ion. The paper discusses the optimization process and test results.

Ramsey, W. D.↗
NASA NTRS1977

The production and treatment of gaseous pollutants in an electrostatic precipitator

The production of ozone and nitric oxides and the oxidation of two organic contaminants, methane and acetylene, were studied in the corona discharge of a model cylindrical electrostatic precipitator. Both air and oxygen streams were passed through the discharge while current, voltage, electrode/wall radius ratio, residence time and wall temperature were varied. Under all conditions using air, much more ozone was produced in the negative than in the positive corona, in agreement with qualitative data reported in the literature. However, using oxygen, as much as three to four times more ozone is produced by the positive corona. Over a wide range of conditions ozone production is proportional to current. Limited analyses of nitric oxides formation in air indicated that levels were higher in the negative than in the positive corona. In contrast to previous work using an RF discharge, methane contamination was not removed by the corona discharge. However, the oxidation of acetylene was affected by the discharge and could not be accounted for by homogeneous ozonation alone.

Flamm, D. L.↗
NASA NTRS1978

Magnetospheric electrostatic emissions and cold plasma densities

A synoptic study of electric wave, magnetometer, and plasma data from IMP-6 was carried out for times when banded electrostatic waves are observed between harmonics of the electron gyrofrequency in the earth's outer magnetosphere. Four separate classes of such waves were previously identified. The spatial and temporal occurrences of waves in each class are summarized here, as are correlations of occurrence with geomagnetic activity. Most importantly, associations between the observations of waves of different classes and the relative portions of cold and hot electrons present at the position of the spacecraft are established. Finally, evidence for the signature of the loss cone is sought in the plasma data.

Hubbard, R. F.↗
NASA NTRS1977

Airborne particle monitoring by electrostatic precipitation

For qualitative analysis of atmospheric particulates by microscopy, the sampling device should preserve the particles in the state existing at the moment of capture. A collector is described that uses electrostatic precipitation to capture and disperse specimens on various substrates for direct insertion into microscopes. Sampling runs in various atmospheres are described. Micrographs are presented to show particle morphology and distribution on the substrates. Chemical identification by X-ray energy probe and electron diffraction is illustrated.

Robinson, J. C.↗
NASA NTRS1979

Electrostatic discharge properties of selected Voyager spacecraft materials

Twelve material and component samples were exposed to an electron beam in order to measure the time history and amplitude of resultant electrostatic discharges. The typical experimental design was to mount the test article with its dielectric surface facing the beam and its conductive portion isolated from ground except by way of a shielded cable on which a discharged pulse could be observed. The behavior of the sample was then observed at bombarding energies from 20 to 100 keV in increasing 20 keV increments and then 90 to 30 keV in decreasing 20 keV increments. Observations were made at each energy for nominally two hours at an electron flux of 4 x 10 to the 9th power/sq cm/sec.

Barengoltz, J. B.↗
NASA NTRS1979

Investigation of electrostatic discharge phenomena on conductive and non-conductive solar reflectors

A sample composed of non conductive optical solar reflectors (OSR) was irradiated with low energy electrons at the DERTS facility to study the effects of charge build up on thermal control coating materials. The degration effects on this panel due to electrostatic discharges were investigated to find possible alternatives to limit the amount of damage. The following systems are evaluated: (1) non conductive OSR (non conductive adhesive) (2) non conductive OSR (conductive adhesive); and conductive OSR (conductive adhesive).

S J Bosma↗
NASA NTRS1978

Economic comparison of fabric filters and electrostatic precipitators for particulate control on coal-fired utility boilers

The uncertainties and associated costs involved in selecting and designing a particulate control device to meet California's air emission regulations are considered. The basic operating principles of electrostatic precipitators and fabric filters are discussed, and design parameters are identified. The size and resulting cost of the control device as a function of design parameters is illustrated by a case study for an 800 MW coal-fired fired utility boiler burning a typical southwestern subbituminous coal. The cost of selecting an undersized particulate control device is compared with the cost of selecting an oversized device.

Cukor, P. M.↗
NASA NTRS1978

Electrostatic emissions between electron gyroharmonics in the outer magnetosphere

Electrostatic emissions are often observed by spacecraft in the outer magnetosphere at frequencies between low electron gyroharmonics. The emissions include the well-known odd half-harmonic emissions as well as weaker emissions which occur near the electron plasma frequency. A scheme is constructed for classifying the emissions, and it is shown that a theoretical model which has been previously used to explain '3/2' emissions can be extended to the other classes of emissions. All of the emissions therefore appear to be generated by the same basic mechanism: an unstable electron plasma distribution consisting of cold electrons (below 100 eV) and hot loss cone electrons (about 1 keV). Each emission class is associated with a particular range of model parameters; the wide-band electric field data can thus be used to infer the density and temperature of the cold plasma component. The model predicts that gyroharmonic emissions near the plasma frequency require large cold plasma densities.

Hubbard, R. F.↗
NASA NTRS1979

Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids

A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 microns from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.

Cantrell, J. H., Jr.↗
NASA NTRS1978

Voyager electrostatic discharge protection program

Tests and analysis indicated the need to protect the Voyager spacecraft from electrostatic discharges in the Jupiter energetic charged particle environment. This paper describes the identified problem areas, the test and analysis methods and results, the resultant design changes, and the final assessment of the design changes and verification methods.

Whittlesey, A. C.↗
NASA NTRS1978

A review of electrostatic wave measurements on auroral magnetic field lines

The review emphasizes experimental evidence for electrostatic waves on auroral zone magnetic field lines. Data were obtained from radar, balloon, rocket, and satellite observations. The paper is organized around three topics: (1) the turbulent density and velocity fields of the magnetospheric flow, (2) instabilities associated with the convection electric field and its interactions with the neutral atmosphere, and (3) waves and discontinuities in the dynamic region at about one earth radius above the auroral zone. Measurements of both the electric field and density fluctuation component of such waves are included. Although this is not a theoretical study, an attempt is made to organize the measurements about the existing theoretical framework.

Kelley, M. C.↗
NASA NTRS1978

The decrease in effective photocurrents due to saddle points in electrostatic potentials near differentially charged spacecraft

The reported investigation had the objective to illustrate the presence of important multidimensional effects in spacecraft charging. Two-dimensional codes have been under development by Parker (1976). A description is presented of a calculation which was performed using the three-dimensional NASA Charging Analyzer Program (NASCAP). NASCAP was run to calculate the electrostatic potentials on the surface of, and in the space surrounding, a sunlit Teflon-coated sphere. Currents to the sunlit surfaces were determined on the basis of an approximate photosheath model for strong differential charging.

Mandell, M. J.↗