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Plasma Interaction with International Space Station High Voltage Solar ArraysThe International Space Station (ISS) is presently being assembled in low-earth orbit (LEO) operating high voltage solar arrays (-160 V max, -140 V typical with respect to the ambient atmosphere). At the station's present altitude, there exists substantial ambient plasma that can interact with the solar arrays. The biasing of an object to an electric potential immersed in plasma creates a plasma "sheath" or non-equilibrium plasma around the object to mask out the electric fields. A positively biased object can collect electrons from the plasma sheath and the sheath will draw a current from the surrounding plasma. This parasitic current can enter the solar cells and effectively "short out" the potential across the cells, reducing the power that can be generated by the panels.

Predictions of collected current based on previous high voltage experiments (SAMPIE (Solar Array Module Plasma Interactions Experiment), PASP+ (Photovoltaic Array Space Power) were on the order of amperes of current. However, present measurements of parasitic current are on the order of several milliamperes, and the current collection mainly occurs during an "eclipse exit" event, i.e., when the space station comes out of darkness. This collection also has a time scale, t approx. 1000 s, that is much slower than any known plasma interaction time scales. The reason for the discrepancy between predictions and present electron collection is not understood and is under investigation by the PCU (Plasma Contactor Unit) "Tiger" team. This paper will examine the potential structure within and around the solar arrays, and the possible causes and reasons for the electron collection of the array.
Document ID
20020068812
Acquisition Source
Marshall Space Flight Center
Document Type
Contribution to a larger work
Authors
John W. Heard
(University of Pennsylvania Philadelphia, Pennsylvania, United States)
Date Acquired
August 20, 2013
Publication Date
July 1, 2002
Publication Information
Publication: Research Reports-2001 NASA/ASEE Summer Faculty Fellowship Program
Publisher: Marshall Space Flight Center
Volume: NASA/CR-2002-211840
Issue Publication Date: July 1, 2002
Subject Category
Plasma Physics
Funding Number(s)
CONTRACT_GRANT: NAG8-1786
Distribution Limits
Public
Copyright
Public Use Permitted.
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