Capture and control of unknown space objects with flexible multi-link manipulators

The NASA asteroid capture challenge has created great excitement and interest in the public as well as worldwide science and engineering communities. A recent Keck Institute study [1] has concluded that it is feasible to autonomously capture and return an entire ~7-m diameter, ~500,000-kg near-Earth asteroid to a high lunar orbit. Studies are underway at NASA and other organizations to conceive and develop different alternative capture mechanisms and transport methods. These methods would involve autonomous spacecraft having large solar arrays, multi-link manipulators, deployable bag, and/or other capture mechanisms. The main problem is that asteroids have irregular shapes and their mass-inertia properties, and state (especially, the angular velocity vector- spin, precession, nutation) are unknown. The capture spacecraft will likely have significant elastic mode dynamics with several lightly damped elastic modes having uncertain and varying modal parameters (frequencies and mode-shapes). Because of these problems, capture, stabilization, and post-capture control of an asteroid constitute a formidable technical challenge.