A method of controlling floating potential for space station based on ion current magnification

摘要

The charging events of the International Space Station have been a focus of concern in recent years. Hollow cathode plasma contactors were applied to control the floating potential for their high emission currents of amps order. The in flight measurements showed that the floating potential was much smaller than predicted originally, and the actual emitted currents by the plasma contactors were well below amps level. In such case, a simpler method to control the floating potential may be applicable and suggested in the paper. By application of a metal sphere, which is biased at a high negative voltage relative to the structure and used as an ion current collector, the electron charging current of the structure can be effectively neutralized and the structure's floating potential can be controlled nearly to zero. The mechanism is introduced and the constraint condition for the system is investigated. Finally, a range of parameters for design are presented. Typically, for 100 V high voltage array, a sphere of r=0.3-0.7 m and biased at 500-200 V is enough. For its simplicity, the method has obvious advantages, such as no requirement of working gas, high reliability and long life, etc.