Explanation:
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 astronautRobert 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 in space.
The MMU was replaced with the
SAFER backpack propulsion unit.
