Evaluation of Crew Capabilities to Handle and Stabilize Heavy Masses in Microgravity

Abstract

One of the purposes of NASA's Shuttle missions is to deploy and retrieve satellites. Some of these missions require extravehicular activities (EVAs). During EVAs, crew members wear pressurized suits for protection from hazardous conditions and use a Remote Manipulator System (RMS) to transfer heavy objects from one location to another. Prior to the Hubble Space Telescope repair mission (STS-61), concerns were raised whether crew members would be able to hold onto the modules if the RMS started or stopped unexpectedly. An experiment was conducted to measure the handle forces during such a scenario and to determine whether these forces and moments were well within the capabilities of the crew. Four subjects participated in the study. Mockups were built to represent the characteristics of the actual unit and tests were conducted at the Precision Air Bearing Facility (PABF) which simulates a nearly friction-free environment. Force plates were attached to the mockups to monitor forces and moments during the test. Controlled translation and rotation tasks were also conducted to compare the results with those of sudden RMS run start/stop tasks. The results from this study showed that the forces and moments exerted by subjects during sudden stopping and starting conditions were well within the capabilities of the crew members. This study thus provided quantitative data for NASA to be assured of a safe and successful mission.