Skyhooks

Skyhooks, also known as rotating orbital tethers, provide a method for transferring momentum between orbiting systems and payloads launched from a planetary surface. A skyhook can capture suborbital payloads and accelerate them to escape or orbital velocities using its rotational energy, thus sharply reducing the propulsion requirements for the initial launch. Current studies (e.g., Pearson et al., 2000; NASA Tether Fact Sheet, 2008) indicate that skyhooks composed of advanced polymers or carbon nanotube composites could be deployed on the Moon or Mars with present martian materials. On the Moon, where the gravitational and atmospheric constraints are minimal, a skyhook could reduce surface-to-orbit transportation costs by over 90%, with estimates approaching 96% reduction.

Early orbital tether experiments (e.g., YES2, NASA Small Satellite Tethers) have validated the fundamental principles and operational reliability of tethers at relevant scales. The next technical milestones are the long-term survivability of tethers in the space environment, rendezvous and payload capture systems, and autonomous maintenance protocols.