Manned Maneuvering Unit
The Manned Maneuvering Unit (MMU ) was a jet backpack, which developed in the 1970s and was used in only three space shuttle missions by astronauts during spacewalks ( EVAs ).
The MMU was not part of the standard equipment of the U.S. space shuttle, but was only carried when it required the mission. It was conceived by the company Martin Marietta in Colorado for EVAs without assurance by the robotic arm or a leash, the rescue of astronauts, or the capture of continuous floating pieces of equipment. She was in the cargo bay of the orbiter in the so-called Flight Support Station (FSS ) housed. The astronaut left the airlock, floated in the payload bay and stood in the FSS, which was equipped with footrests. Then, the MMU has been created by the knapsack on the back of the astronaut einrastete with two locks on the inner part of the MMU.
MMU had a height of 1.27 m and a width of 85 cm. It was equipped with two extendable arm rests, at the end of the lever was attached to the controller. With arms retracted, the unit was 69 cm deep and 1.22 m with extended arms. Maneuvering the MMU 24 had thrusters working with nitrogen gas. The total weight was 153.4 kg (including 10.6 kg of gas, two tanks, each 5.3 kg ). The delta v of the MMU was a maximum of 23.4 m / s
The MMU was only in three missions in 1984 for use. For the first time the system was used in the mission STS -41 -B in February by the astronauts Bruce McCandless and Bob Stewart. All tests were successful, with the two up to 98 meters from the shuttle away.
The second mission took place on STS -41 -C in April 1984. George Nelson flew in the eight months earlier satellites launched Solar Max with the MMU, but could not stabilize him. The gripper arm of the shuttle began the satellite finally a two days later. After Solar Max was again repaired and exposed, James van Hoften undertook a second MMU further testing.
During the STS -51 -A in November 1984, the MMU was used the last time. The exposed from the shuttle in February satellite Westar VI and Palapa -B2 were recaptured and returned to Earth. The first EVA Palapa Joe Allen flew to and brought him to the shuttle. The second exit Dale Gardner undertook with Westar the same maneuver.
In each of the three flights the same MMU units were always used (two per mission). After that, the MMU was never used again. The mission was NASA too risky and their control proved to be too inaccurate. When working on the International Space Station (ISS ) would be unsuitable because of their bulky proportions.
Successor of the MMU is that - much smaller and lighter - Simplified Aid for EVA Rescue ( SAFER ).