The Module Servicing Tool is a power wrench for use by a spacewalking astronaut. It was specifically designed to service the Multimission Modular Spacecraft, a basic satellite "bus" that could be modified for different purposes. Its first version, the Solar Maximum Mission, or Solar Max satellite, launched in 1980, and visited by a space shuttle mission crew in February 1984, after some of its components prematurely ceased to operate. The Solar Max repair mission crew used this battery-powered device, with its long drive shaft, to loosen and tighten recessed bolts, enabling replacement of the failed attitude control system module. Solar Max revived and operated until 1989. Although the satellite had not been designed for in-orbit servicing, this tool and related equipment and procedures demonstrated that orbital servicing of the planned Hubble Space Telescope was feasible and likely to succeed. NASA later developed several more compact power tools for such tasks. NASA released one of two flown Module Servicing Tools from storage and transferred it to the Museum in 2012.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.