A jet backpack worn by an astronaut in order to be able to move accurately through space during an extravehicular activity. The MMU, which connects to the primary life-support system (PLSS), provides propulsion by means of nitrogen jets. The 24 thrusters are operated by hand controls on the end of arm rests, and the jets allow an astronaut to move forwards, backwards, sideways, up, and down. The device weighs about 139.5 kg on Earth. Astronauts retrieve and service nearby satellite payloads by using the MMU.
Subjects: Astronomy and Astrophysics.