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Alternatives to the ISS Plasma Contacting UnitsA spacecraft in a high-density equatorial LEO plasma will float negative relative to the ambient plasma. Because of the electron collection of exposed conductors on its solar arrays, it may float negative by up to its array voltage. The floating potential depends on the relative areas of electron and ion collection of the spacecraft. Early estimates of the International Space Station (ISS) potential were about -140 V relative to the surrounding plasma, because of its 160 V solar array string voltage. Because of the possibility of arcing of ISS structures and astronaut EMUs (spacesuits) into the space plasma, Plasma Contacting Units (PCUs) were added to the ISS design, to reduce the highly negative floating potentials by emitting electrons (effectively increasing the ion collecting area). In addition to the now-operating ISS PCUs, safety rules require another independent arc-hazard control method. In this paper, I discuss alternatives to the ISS PCUs for keeping the ISS floating potential at values below the arc-thresholds of ISS and EMU surface materials. Advantages and disadvantages of all of the recline loss will be presented.
Document ID
Document Type
Technical Memorandum (TM)
Ferguson, Dale C. (NASA Glenn Research Center Cleveland, OH United States)
Date Acquired
September 7, 2013
Publication Date
May 1, 2002
Subject Category
Spacecraft Design, Testing and Performance
Report/Patent Number
NAS 1.15:211488
AIAA Paper 2002-0934
Meeting Information
40th Aerospace Sciences Meeting and Exhibit(Reno, NV)
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.

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