The most popular image in space history in the United States is from the challenger (STS-41-B) mission launched from the Kennedy Space Center on February 3, 1984. Astronaut Bruce McCandless II is engaged in the first untethered spacewalk, very high above the Earth.
What frightens a man the most is the emptiness of space and the dangers of being stuck there. That is why whenever there is any work done, it is connected to itself anywhere.
So how did Bruce do this?
The answer is in the picture itself. The sheer size of Bruce’s backpack will make anyone think.
Yes, the Manned Maneuvering Unit (MMU) is a device of extraordinary size that has provided astronauts with the mobility to operate outside space shuttles. These made it possible for astronauts to move without being attached anywhere in the payload bay of the space shuttle or slightly away from the shuttle.
The MMU has 24 small thrusters running on gaseous nitrogen. There are two hand-operated controllers to control these. The right controller is used to enable rotational acceleration (roll, pitch & yaw) and the left controller is used to enable translational acceleration (forward-backward, up-down, left-right).
The backpack had two aluminum tanks containing 5.9 kg of nitrogen each, which could operate for up to six hours depending on the mode of movement.
They were used on three space shuttle missions in 1984. However, NASA and the US military ceased use of space shuttles on January 28, 1986, following the Challenger (STS-51-L) disaster.
The MMU # 2 and # 3 used in the STS-41-B were stored by NASA until 1998 in a clean room in Lockheed, Denver. It was later moved to the # 3 National Air and Space Museum. It is hung for display on the top of the Discovery Shuttle.
# 2 on display at the US Space and Rocket Center in Huntsville, Alabama.