S80-36889 (24 July 1980) --- Astronaut Bruce McCandless II uses a simulator at Martin Marietta?s space center near Denver to develop flight techniques for a backpack propulsion unit that will be used on Space Shuttle flights. The manned maneuvering unit (MMU) training simulator allows astronauts to "fly missions" against a full scale mockup of a portion of the orbiter vehicle. Controls of the simulator are like those of the actual MMU. Manipulating them allows the astronaut to move in three straight-line directions and in pitch, yaw and roll. One possible application of the MMU is for an extravehicular activity chore to repair damaged tiles on the vehicle. McCandless is wearing an extravehicular mobility unit (EMU).