Manned maneuvring unit space walk, 1984. Astronaut Robert L. Stewart floats free above the Earth in his manned manoeuvring unit (MMU) on 7th February 1984, during the 10th space shuttle flight (mission 41B). Stewart was the second astronaut to float freely from the Space Shuttle using the MMU. The first was Bruce Mccandless earlier on the same day. The MMU is propelled by small nitrogen thrusters which are controlled by the astronaut's hands. Because no tether attaches the astronaut to the spacecraft, it gives much greater mobility than was available to earlier spacewalkers. Mission 41B was launched from the Kennedy Space Center (KSC) on 3rd February 1984, and landed back at KSC on 12th February.