Manned Maneuvering Unit (MMU)
Commemorative Patch - 4" diameter

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The manned maneuvering unit (MMU) is a one-man, nitrogen-propelled backpack that latches to the astronaut's space suit. Using rotation and translation hand controllers, the crew member can fly with precision in or around the orbiter cargo bay or to nearby free-flying payloads or structures, and can reach many otherwise inaccessible areas outside the orbiter. Astronauts wearing MMU's have deployed, serviced, repaired, and retrieved satellite payloads.

The MMU propellant is gaseous nitrogen which is stored under high pressure and can be recharged from the orbiter. The unit has a dual parallel system rather than a backup redundant system. In the event of a failure in one parallel system, the remaining system can be used to return the MMU to the orbiter cargo bay. The MMU weighs 310 pounds and includes a 35-mm still photo camera that is operated by the astronaut while working in space.