Control of Space Debris Using an Elastic Tether and Wave-Based Control

One proposed solution to the space debris problem involves sending an active spacecraft (or “chaser”) to rendezvous with the target debris and to make a physical connection with it by means of a net or harpoon at the end of an elastic tether. The chaser then needs to control the debris motion via the elastic tether, for example, to achieve a controlled deorbit. Compared with robotic capture, the use of an elastic tether reduces the need for precise chaser–target coordination during capture, reduces the danger of collisions, and limits subsequent jerk with its potentially damaging consequences. However, target motion control via an elastic tether presents control challenges, for example, due to the radically different system dynamics, depending on whether the tether is taut or slack. Tether entanglement is also a danger, especially if the debris is tumbling. This research focuses on using wave-based control to have the chaser give the target an arbitrary change in the magnitude and direction of its velocity, while maintaining tether and debris control. It then considers a complete, controlled deorbit maneuver. To test the technique, ESA’s Envisat is used as a representative debris satellite.