The National Aeronautics and Space Administration (NASA) has accomplished a “return to extravehicular activity (EVA)” on the Space Transportation System 37 (STS-37) mission that flew in April 1991. This first U.S. EVA in almost 6 years included both an unscheduled EVA on mission day 3 and a scheduled EVA on mission day 4. The unscheduled EVA occurred when the high-gain antenna on the Compton Gamma Ray Observatory (GRO) would not deploy when commanded from the ground. Mission specialists Jerry Ross and Jay Apt quickly donned their space suits, went into the Shuttle cargo bay for EVA, and freed the jammed antenna, saving the $617 million scientific spacecraft. During the scheduled EVA, crewmembers Ross and Apt successfully completed the Space Station Freedom (SSF) EVA Development Flight Experiment (EDFE). EDFE evaluated three classes of equipment planned for SSF: Crew and Equipment Translation Aids (CETA), Crew Loads Instrumented Pallet (CLIP), and EVA Translation Evaluation (ETE). Tests of four kinds of crew translation devices in the zero-g environment revealed that a simple sled pulled along by hand was perfectly adequate for transporting crew and equipment along the SSF long truss structure. Measured crew forces and torques will provide realistic design parameters for loads that the EVA crew can apply, as well as loads that must be reacted by SSF structure. EVA crew translation on the Shuttle's remote manipulator arm proved to be very time consuming, and manual translation along a single rope strung between two points was easier than expected.
This paper summarizes the unscheduled EVA to free the GRO antenna and presents the EDFE objectives, equipment description, and flight test results.