In 1984, Bruce McCandless hovered 320 ft away, untethered from the Challenger and made it back safely using a nitrogen jetpack called Manned Maneuver Unit
Testing the MMU for the first time in space required a lot of focus and bravery, but McCandless and Stewart had faith in the hardware. Weighing 300 lbs. /136 kg, the MMU was powered by 24 small compressed nitrogen thrusters with two motion-controlled handles on either armrest for simple maneuvering. It was developed by engineer Charles Whitsett, and McCandless tested the MMU underwater and inside the Skylab space station prior to his famous spacewalk.
