
March 22, 2005
To Fly Free in Space

March 22, 2005
To Fly Free in Space
A little universe, just for you
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APOD published March 22, 2005. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was further out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured above, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk" during Space Shuttle mission 41-B in 1984. The MMU works by shooting jets of nitrogen and has since been used to help deploy and retrieve satellites. With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was replaced with the SAFER backpack propulsion unit.