ᴜɴɪᴠᴇʀsɪᴀ on Instagram: "Forget science fiction – this was the real deal. Meet the Manned Maneuvering Unit (MMU), NASA's incredible backpack propulsion system that let astronauts fly completely untethered during spacewalks outside the Space Shuttle. Think of it as a personal spaceship. Using simple hand controllers, astronauts could fire small nitrogen gas thrusters to navigate freely in the vacuum of space, totally disconnected from the safety lines anchoring them to the shuttle. It was designe