Study on Mitigation of Charging and Discharge of Energy Apparatus in Space Environment

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 11450113
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 電力工学・電気機器工学
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: HIKITA Masayuki Kyushu Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (40156568)
• Co-Investigator(Kenkyū-buntansha): CHO Mengu Kyushu Institute of Technology, Faculty of Engineering, Associate Professor, 工学部, 助教授 (60243333) ; HAGINOMORI Eiichi Kyushu Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (20242290)
• Project Period (FY): 1999 – 2001
• Keywords: Space Environment / Solar Array / Arcing Suppression / Low Earth Orbit / Plasma Environment

Research Abstract

A large spacecraft which requires high power (>100kW), such as Solar Power Satellite (SPS) needs to be operated at a high voltage, typically higher than 100V. When a solar array has such a high voltage in Low Earth Orbit, however, most of the high voltage becomes negative, due to interaction with the space plasma. Therefore, ions from the surrounding ionospheric plasma are attracted to the surface of coverglass of the solar array. The insulator surface of coverglass is charged by the positive ions, and the electric field at the vicinty of the triple junction (the position where vacuum, interconnector and adhesive meet) is intensified and leads to arcing. When the arc occurs, it causes degradation of the surface, electromagnetic interference and other undesired side-effects.
In this paper, we report the results of experiments where we place solar arrays in the vacuum chamber which simulates the plasma conditions at Low Earth Orbit and test several mitigation techniques to suppress the ar cing. Because the charging of the coverglass by positive ions is the reason of arcing, we place PET film in front of the coverglass to physically prevent the charging by ions.
First, we place two solar arrays of conventional design inside the vacuum chamber. One array is covered by PET film with the separation distance of L. The other array is not modified at all. We apply a negative voltage to the two arrays, and detect arcs by monitoring the current to the array and also by video camera. The results shows that as the separation distance, L, is shortened to less than 5mm, the PET film acts to suppress both the arc rate and the scale of arc. But by placing PET film in front of the solar array, the degradation of efficiency is unavoidable.
In order to minimize the efficiency loss, we made holes of the PET film over the coverglass while keeping the film only over the interconnector, The results show that by covering the solar array only partially, the arcing rate is still suppressed but the scale of arc, (peak current and electrical charge) cannot be suppressed.