To ensure safety during extravehicular activity (EVA), crewmembers must use tethers that constrain them and their tools to the spacecraft. A prototype automated tether system has been designed to increase the efficiency of such tether use. The system consists of a remotely releasable robotic gripper that serves to anchor the system, and a retractor that contains and controls the length of the tether in the workspace. In this paper, dynamic simulations of the system are derived and analyzed to predict retraction behavior in an orbital environment. The system was also tested using air bearing facilities to simulate a microgravity environment. Functional tests of the system are also discussed in order to characterize and quantify its performance.

An automated tether system has been developed for the purpose of improving the efficiency of micro-gravity activities of fully suited astronauts. System features include gripping of multiple anchor types, remote release of the tether from an anchor, and controlled retraction of the tether. Two main mechanisms make up the system. First, a remotely releasable, self-locking robotic gripper with opposing jaws that grasps a variety of anchors such as handrails, tether loops, and guide wires. Second, an automated tether retractor that is capable of active or passive operation. Passive retractor operation saves power by emulating existing safety tether systems and active operation expedites tether retraction and allows towing.