Removing Orbital Debris with Less Risk

Deorbit concepts have been proposed for dealing with the growing problems posed by orbital debris. Most devices use large structures that interact with the atmosphere, magnetic field, or solar environment to deorbit large objects more rapidly than natural decay. Some devices may be better than others relative to the likelihood of collisions during their use. Current guidelines attempt to address this risk by applying the metric of area-time product to compare the probability of a large object experiencing a debris-generating impact. However, this approach is valid only for collisions with very small debris objects. The peak in the distribution of the area of orbital debris occurs for objects with a characteristic size close to 2 m. For collisions with such objects, some of which are operating satellites, it is important to incorporate the augmented collision cross-sectional area, which takes into account the size of both colliding objects when computing the area-time product. This new approach leads to a more valid comparison among alternative deorbit approaches, which now indicates that inflatable drag enhancement devices result in the least risk. Finally, one deorbit device, an electromagnetic tether, is shown to have a very large collision cross section for disabling operating satellites.