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

研制了用于模拟材料与空间等离子体相互作用和研究航天器充放电现象的地面设施。等离子体模拟器由一个真空罐、两个涡轮分子泵和一个磁场膨胀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、氩等离子体的性能。该模拟器被发现具有很高的地面测试潜力。利用该模拟器，研究了高压太阳能电池阵列周围离子鞘的结构以及高能离子轰击对阵列附近表面材料的降解。负偏板暴露于氧等离子体流。研究发现，偏置电压和攻角对离子电流和等离子体电位分布有强烈的影响，尤其是一维离子鞘层理论推导出的标度参数。此外，为了研究离子轰击对航天器表面材料化学结构的影响，将位于偏置板上的聚酰亚胺BPDA-PDA Kapton聚合物薄膜暴露于氧等离子体流中。XPS分析表明，尾流条件下氧原子或离子的加成反应与湍流条件下相比可以忽略不计，因为离子通量较小。因此，发现离子轰击发生了加成反应和结构组分的脱附。它们将导致航天器热控制性能的下降。此外，为了了解等离子体流（即等离子体接触器操作）对航天器充电的弛豫作用，在高能电子束下将带负电荷的Kapton和Teflon FEP薄膜以及带负电荷的电容器串联的金属板暴露在氩等离子体流下。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.