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titleEffects of cryogenic temperatures on spacecraft internal dielectric discharges
Author(eng)Ferguson, Dale C.; Schneider, Todd A.; Jason, A.
Author Affiliation(eng)Marshall Space Flight Center, National Aeronautics and Space Administration (NASA/MSFC); Marshall Space Flight Center, National Aeronautics and Space Administration (NASA/MSFC); Marshall Space Flight Center, National Aeronautics and Space Administration (NASA/MSFC)
Issue Date2010-02-26
Japan Aerospace Exploration Agency (JAXA)
Publication title宇宙航空研究開発機構特別資料: 第6回「宇宙環境シンポジウム」講演論文集
JAXA special publication: Proceedings of the 6th Spacecraft Enivironment Symposium
Start page85
End page94
Publication date2010-02-26
AbstractMost calculations of internal dielectric charging on spacecraft use tabulated values of material surface and bulk conductivities, dielectric constants, and dielectric breakdown strengths. Many of these properties are functions of temperature, and the temperature dependences are not well known. At cryogenic temperatures, where it is well known that material conductivities decrease dramatically, it is an open question as to the timescales over which buried charge will dissipate and prevent the eventual potentially disastrous discharges of dielectrics. In this paper, measurements of dielectric charging and discharging for cable insulation materials at cryogenic temperatures (ca. 90 K) are presented using a broad spectrum electron source at the NASA Marshall Space Flight Center. The measurements were performed for the James Webb Space Telescope (JWST), which will orbit at the Earth-Sun L2 point, and parts of which will be perennially at temperatures as low as 40 K. Results of these measurements seem to show that Radiation Induced Conductivity (RIC) under cryogenic conditions at L2 will not be sufficient to allow charges to bleed off of some typical cable insulation materials even over the projected JWST lifetime of a dozen years or more. After the charging and discharging measurements are presented, comparisons are made between the material conductivities that can be inferred from the measured discharges and conductivities calculated from widely used formulae. Furthermore, the measurement-inferred conductivities are compared with extrapolations of recent measurements of materials RIC and dark conductivities performed with the charge-storage method at Utah State University. Implications of the present measurements are also given for other spacecraft that may operate at cryogenic temperatures, such as probes of the outer planets or the permanently dark cratered areas on the moon. The present results will also be of interest to those who must design or operate spacecraft in more moderate cold conditions. Finally, techniques involving shielding and/or selective use of somewhat conductive insulators are presented to prevent arc-inducing charge buildup even under cryogenic conditions.
DescriptionOriginal contains color illustrations
Meeting Information: 6th Spacecraft Enivironment Symposium (February 29-30, 2009. Kitakyushu International Conference Center)
形態: カラー図版あり
会議情報: 第6回宇宙環境シンポジウム (2009年2月29日-30日. 北九州国際会議場)
Document TypeConference Paper
JAXA Category特別資料
Report NoJAXA-SP-09-006

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