First untethered spacewalk

On this day in 1984, US astronaut Bruce McCandless II (pictured) performed the first untethered spacewalk. Four days after the launch of the space shuttle Challenger, McCandless exited the shuttle strapped to NASA’s manned maneuvering unit (MMU), a backpack propulsion device powered by 24 small nitrogen thrusters. With the use of hand controllers at the ends of the unit’s two arms, McCandless was able to maneuver the craft and fly some 90 m from the shuttle. The MMU, which was designed to be used in the servicing and recovery of satellites, ended up being deployed just three times, all in 1984. It was flown a total of 6 hours and 29 minutes. The device was ultimately deemed too risky, particularly because most extravehicular activities could be performed with manipulator arms or by astronauts tethered to the spacecraft. After the Challenger disaster in 1986, the MMU was permanently retired. (Photo credit: NASA)

Date in History: 7 February 1984