- First used on STS-2 (November 1981), the 50-foot-long, Canadian-built arm was designed to deploy and retrieve payloads weighing up to 65,000 pounds. Work on the ISS, begun in the mid- 1990s, raised the requirement to 586,000 pounds, so the “wrist” got greater torque, enabling it to assist, if needed, in docking the shuttle to the station. The arm, however, was never used for that purpose.
- In 2000, all joints were refurbished, gear boxes and motor modules replaced, and, for better stability in space, asbestos brakes were swapped out in favor of ceramic ones.
- Starting with return-to-flight mission STS-114 (July 2005), NASA added a 50-foot extension to allow the crew to examine the shuttle’s belly for signs of foam impact damage.
Michael Klesius is an Air & Space associate editor.