The inception of snapover on solar arrays - A visualization technique

Ferguson, Dale C.; Hillard, G. B.; Snyder, David B.; Grier, N. T.

doi:10.2514/6.1998-1045

Cited by 13 publications

(9 citation statements)

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“…Since these glows are produced only by high energy electrons (> 120 eV, Ferguson et al 19 ) it is unclear whether their measurement records true plasma front propagation speeds, or only the propagation speed of the high energy electron tail in the plasma cloud (which produces little discharge current). That is, these measurements may be irrelevant to the speed of the important discharging electrons in the plasma cloud.…”

Section: Round Robin Testsmentioning

confidence: 98%

“…Given the wide variation in results reported for the flashover current rate [7][8][9][10][11][12][13][14][15][16][17][18][19][20] , and the first results specifically call out the Langmuir probe data as unreliable 21 , it is imperative to improve on the measurements. One technique that may produce results is to utilize the instantaneous measurement capabilities of the Triple Langmuir Probe (TLP) 22 .…”

Section: Triple-langmuir Probesmentioning

confidence: 99%

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Spacecraft Solar Array Charging Research in the Spacecraft and Instrument Calibration Laboratory

Wheelock

Ferguson

Hoffmann

2012

4th AIAA Atmospheric and Space Environments Conference

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The Spacecraft Charging and Instrument Calibration Laboratory (SCICL) is now operational at Kirtland AFB, Albuquerque, NM. SCICL is a comprehensive one-stop shop for testing R&D spacecraft solar array coupons, novel materials, dielectric charging, and modeling of spacecraft effects from relevant materials. Electron guns of up to 100keV or LEO plasma sources reproduce the charging environment. Characterization of sample charging and the chamber environment is done through TREK probes and plasma probes mounted on an up-to four axes of motion system.In addition to the ISO-11221 testing, a round-robin test has begun with SCICL and other US charging laboratories to characterize the rate of spacecraft discharging through the socalled "flashover" current. The rate of discharge through the flashover determines the ESD current waveform. If the expanding plasma completely discharges all dielectrics, all of the spacecraft surface capacitances will add to the total discharge current and energy. If the expanding plasma discharges surfaces only slowly and incompletely, the currents will be less and the total energy released will be less. Finally, if the ESD arc-current stops before all the surfaces are discharged, the total discharge energy will be severely curtailed. Thus, the expansion rate of the flashover plasma and the degree to which it discharges surfaces can mean the difference between a rapid, high current event, which may lead to power system disruptions, damaged solar cells, or even a sustained discharge on solar array surfaces or a slow, low current event, which leads to no disruptions or damage. During the flashover ESD, the plasma environment is expected to change in density by several orders of magnitude in a span of microseconds. In order to characterize this highly dynamic plasma environment, a series of triple-Langmuir probes are proposed. Design and implementation of the tripleLangmuir probes are considered, including the possibility of log-response probes. NomenclatureA p = Area of probe e, q = fundamental charge I p = total current to probe I s = reverse bias saturation current J e0 ,J i0 = thermal electron, ion currents k = Boltzmann's constant n = ideality factor, typically 1 T e ,T i = electron, ion temperature V D = diode voltage  = coefficients for fitting probe data  p , s = probe potential, space (plasma) potential 1 Electronics Engineer, Senior Member AIAA.

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Section: Round Robin Testsmentioning

confidence: 98%

Section: Triple-langmuir Probesmentioning

confidence: 99%

Spacecraft Solar Array Charging Research in the Spacecraft and Instrument Calibration Laboratory

Wheelock

Ferguson

Hoffmann

2012

4th AIAA Atmospheric and Space Environments Conference

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“…As a general rule of thumb, the neutral pressure in a plasma test should be kept lower than about 10 −4 torr if possible, or electron ionization of the neutral gas (Paschen discharge) may be a factor. When the neutral pressure is too high, and Paschen discharge occurs, it will be visible as a glow that extends for many centimeters through the vacuum chamber (see [2]). If it is not possible to run at neutral pressures below about 10 −4 torr, one should be on the lookout for the Paschen glow.…”

Section: Vacuum Chambers Plasmas and Neutral Gases-the Importanmentioning

confidence: 98%

NASA GRC and MSFC Space Plasma Arc Testing Procedures

Ferguson

Vayner

Galofaro

et al. 2006

IEEE Trans. Plasma Sci.

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“…For the particular case under investigation, this threshold is as low as 50 V, although snapover threshold is believed to be above 120 V for solar arrays. 32 Current-voltage characteristic curves are shown in Fig. 12 for the virgin plate and the plate having undergone 600 arcs.…”

Section: Plasma Contamination and Surface Degradationmentioning

confidence: 99%

Arcing on Aluminum Anodized Plates Immersed in Low-Density Plasmas

Vayner

Doreswamy

Ferguson

et al. 1998

Journal of Spacecraft and Rockets

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A number of experiments have been done to study characteristics of the plasma contamination and electromagnetic radiation generated by arcing on anodized aluminum plates immersed in low-density plasma. The low-Earthorbit plasma environment was simulated in a plasma vacuum chamber, where the parameters could be controlled precisely. Diagnostic equipment included two antennas, a mass spectrometer, a spherical langmuir probe, a wire probe, and a very sensitive current probe to measure arc current. All data except for mass spectrometry were obtained in digitalform with a samplinginterval of 2.5 ns that allowed us to study the radiationspectrum at frequencies up to 200 MHz. We found that the level of interference considerably exceeds the limitations on the level of electromagnetic noise set by technical requirements on Space Shuttle operation. Experiments with two independently biased plates have shown that the arcing onset on one plate generates a pulse of current on the second plate and that the secondary current pulse has a signi cant amplitude. The sampling interval for mass spectrometry was 250 ms. This allowed us to obtain the rate of plasma contamination due to arcing. A signi cant degradation of the coating layer was determined by measurement of the resistance of the plate, which had experienced a few hundred arcs. NomenclatureA = atomic number a = diameter of hole in the shield, m C = capacitance, F D = langmuir probe diameter, m D h = diameter of damaged area, m d = thickness of coating layer, m E = electrical eld strength, V/m e = electron charge, C F = ux of atoms, atoms/m 2 s f = frequency, Hz f e = plasma frequency, Hz I m = amplitude of discharge current, A L = distance between plates, m l = antenna length, m M = atomic mass, kg N e = number of electrons N i = number of ions n e = electron number density, m ¡3 p = neutral gas pressure, torr Q = electrical charge, C R = resistance, Ä T e = electron temperature, eV t = time, s t d = time delay, s U = bias voltage, V U a = amplitude of antenna voltage, V V p = plasma expansion speed, m/s ± = skin depth, m ½ = coating material density, kg/m 3 ¿ = pulse duration, s

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The inception of snapover on solar arrays - A visualization technique

Cited by 13 publications

References 1 publication

Spacecraft Solar Array Charging Research in the Spacecraft and Instrument Calibration Laboratory

Spacecraft Solar Array Charging Research in the Spacecraft and Instrument Calibration Laboratory

NASA GRC and MSFC Space Plasma Arc Testing Procedures

Arcing on Aluminum Anodized Plates Immersed in Low-Density Plasmas

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