Relevance of an RF plasma source to satellite material testing in VLEO conditions

Satellites operating in Very Low Earth Orbit (VLEO) are exposed to a harsh environment composed of atomic oxygen and molecular nitrogen which can significantly degrade spacecraft materials. Novel atmosphere-breathing electric propulsion (ABEP) systems can introduce additional material erosion through the impingement of reactive atmospheric ions from the thruster plume backflow. This study presents ground-based experiments evaluating the erosion behavior of Kapton HN exposed to an oxygen-argon plasma beam with ion energies (~5 eV) representative of the VLEO environment. Experiments were conducted using the DRAG-ON facility equipped with an RF plasma source. Ion energy and flux were characterized with electrostatic probes, while erosion yields and the morphology of exposed samples were evaluated using stylus profilometry, confocal laser scanning microscopy and scanning electron microscopy. Our results reveal that Kapton HN erosion yields exposed to plasma are an order of magnitude higher than those reported for neutral atomic oxygen, with argon contributing minimally to surface degradation. Erosion exhibited a linear dependence on ion fluence and was strongly influenced by surface charging, as evidenced by non-uniform erosion patterns observed on Kapton and the uniform erosion observed on conductive graphite samples. These findings suggest that plasma-driven chemical reactions and charging effects significantly enhance material degradation, providing a conservative estimate of material aging compared to the one obtained in neutral conditions. Additionally, the results highlight the utility of this plasma source for reproducing plume contamination fluences in manageable test durations.