Research and Development of Ground Simulation Methods for Spacecraft Environment, and Degradation Experiments of Spacecraft Materials

开发了一个地面设施，用于模拟材料与空间等离子体的相互作用，并研究航天器的充放电现象。等离子体模拟器由一个真空箱、两个涡轮分子泵和一个磁场扩展等离子体加速器的电子回旋共振等离子体源组成。测量了氧、氮和氩的等离子体性质。该模拟器被发现具有很高的地面测试潜力。利用该模拟器，研究了高电压太阳电池阵列周围形成的离子鞘结构以及高能离子轰击引起的阵列附近表面材料的退化。将负偏压平板暴露在氧气等离子体流中。结果表明，偏置电压和攻角对离子电流和等离子体电势分布有很大影响，特别是一维离子鞘理论中的标度参数。此外，为了考察离子轰击对航天器表面材料化学结构的影响，将位于偏置平板上的聚酰亚胺BPDA-PDA Kapton聚合物薄膜暴露在氧气等离子体流中。XPS分析表明，由于离子通量较小，尾流条件下氧原子或离子的加成反应与Ram条件下相比可以忽略不计。结果发现，离子轰击发生了加成反应和结构组分的脱附。预计它们会导致航天器热控性能的下降。此外，为了了解等离子体流对航天器充电的松弛，即等离子体接触器操作，将高能电子束和串联带负电的金属板暴露在Ar等离子体流中，对Kapton和Teflon FEP薄膜进行了负电处理。负电荷迅速松弛，攻角影响中和电流的时间变化。

A ground facility was developed for simulation of material and space plasma interaction and for study of spacecraft charging and discharge phenomena. The plasma simulator consisted of a vacuum tank, two turbo-molecular pumps and an electron cyclotron resonance plasma source of a magnetic-field-expansion plasma accelerator. Oxygen, nitrogen and argon plasma properties were measured. The simulator was found to have a high potential for ground tests. Using the simulator, the structure of an ion sheath created around a high voltage solar array and the degradation of surface materials near the array due to high energy ion bombardment were investigated. A negatively biased plate was exposed to oxygen plasma flow. The ion current and the plasma potential distribution were found to be intensively changed by the biased voltage and the attack angle, particularly a scaling parameter derived from the one-dimensional ion sheath theory. Furthermore, in order to examine the influences of ion bombardment on chemical structures of spacecraft surface materials, polymer films of polyimide BPDA-PDA Kapton, located on the biased plate, were exposed to oxygen plasma flow. The XPS analysis showed that an addition reaction of oxygen atoms or ions at wake condition was negligible compared with that at ram condition because of a smaller ion flux. Consequently, the addition reaction and a desorption of structural components were found to occur by ion bombardment. They are expected to cause the decrease in performance of spacecraft thermal control. Furthermore, in order to understand the relaxation of spacecraft charging by plasma flow, i.e., plasma contactor operation, Kapton and Teflon FEP films negatively charged by exposure to high energy electron beams and metal plates in series with negatively charged condensers were exposed to argon plasma flow. Negative charging was rapidly relaxed, and the attack angle influenced the time variation of the neutralization current.