Low Earth Orbit Plasma Wake Shaping and Applications to On-Orbit Proximity Operations

Abstract

A parametric investigation of plasma wake geometry is conducted to determine the applicability of Coulomb actuation to resident space objects (RSOs) in low earth orbit (LEO). The use of Coulomb forces could provide a touchless means to achieve the relative position and attitude adjustments between close-proximity objects on orbit. Theoretical models developed for techniques in the geosynchronous earth orbit (GEO) regime indicate that Coulomb actuation could facilitate on-orbit proximity operations in a highly fuel- and power-efficient manner. In LEO, however, only the plasma parameters in the wakes behind orbiting objects are a promising region for Coulomb actuation applications. These physical phenomena investigated by the charging hazards and wake studies (CHAWS), space experiments with particle accelerators (SEPAC), and other on-orbit experiments exhibit substantially decreased plasma density relative to the surroundings. This investigation considers the wake which forms behind objects of various potentials and cross-sectional areas, particularly focusing on methods of enhancing the wake with negligible changes in the objects' area, and therefore their mass. Experimental results are presented and compared with previous theoretical, numerical, and experimental works. The size of a wake formed by an uncharged object is shown to depend on its cross-sectional area. However, the same object charged to a positive potential generates a substantially larger wake. Additional experimental results indicate that a positively charged, sparse structure with similar dimensions, but significantly less cross-sectional area forms a wake similar to the previous, solid object charged to the same level. This indicates that a large wake can be generated without significantly increasing the mass or area-dependent perturbations such as the drag and the solar radiation pressure. These results increase the applicability of Coulomb actuation in LEO by enhancing the region in which the technique is feasible.