Enabling Large-body Active Debris Removal

Research suggests that: (1) orbital debris has reached an unstable point whereby, even with no future launches, the amount of debris will continue to grow through collisions among large-body debris, and (2) removing as few as five large objects each year can stabilize debris growth. For large-body active debris removal (ADR), active technologies are required to safely and efficiently stabilize and capture the target debris. The interactions of these complex electromechanical systems (eg. imaging systems, LIDAR, robotic arms and grippers, etc) and control algorithms pose challenges best addressed by hardware-in-the-loop testing. Given the risks inherent in non-cooperative spacecraft proximity operations, and the firm requirement that ADR missions do not themselves produce additional debris, realistic ground-based testing is required for risk reduction. Testing space operations in ground-based facilities is notoriously difficult and limited. Our proposed approach significantly increases the capability and fidelity of such testing operations and elevates the chance of a successful ADR mission. We propose a combination of robotic technologies to allow for a large range of relative motion simulation with accurate contact dynamics. First, the target debris object is suspended from a thin rod and spun up to a desired rotational speed. The suspension point is actively controlled to remove the periodic pendulum effect while still allowing free motion from contact, and a universal joint permits free rotational motion. Second, the chaser spacecraft is mounted atop HOMER, an omnidirectional robot capable of unlimited planar motion and limited-range out-of-plane motion. HOMER was designed and built by Texas A & M to emulate the 6-DOF relative-motion trajectories common in spacecraft proximity operations. Along with careful attention paid to the design of mock-targets, these two systems will allow for large-scale motion with accurate contact dynamics for high-fidelity ADR testing.