Wikipedia:POTD column/January 29, 2006

A Manned Maneuvering Unit (MMU) is a jetpack (propulsion backpack that snaps onto the back of the spacesuit) which has been used on untethered spacewalks from NASA's Space Shuttle, allowing an astronaut to move independently from the shuttle. The MMU was used on three Shuttle missions in 1984. It was first tested on February 7 during mission STS-41-B by astronauts Bruce McCandless (seen here) and Robert L. Stewart.

Photo credit: NASA
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