Another image from my Christmas trip to the National Air and Space Museum's Udvar-Hazy Center, this is the Manned Maneuvering Unit (MMU). The MMU was a backpack-like device that allowed astronauts to move about in space untethered. The MMU had two adjustable arms with thruster controls; roll, pitch, and yaw were on the on the right and directional controls were on the left. Propulsion was provided by two tanks of gaseous nitrogen, which could produce a velocity of about 80 feet/second.
The MMU was used in 1984 to recover two communications satellites that did not make it to the proper orbit, and was retired later that year.