On 7 February 1984, Bruce McCandless II released the last connection between himself and Space Shuttle Challenger and flew away. Strapped into the Manned Maneuvering Unit, a nitrogen-powered backpack, he became the first person to move freely through space with no tether to a spacecraft. The photograph of him alone against the black sky, with the Earth below, became one of the best-known images NASA has ever released.

From Fighter Pilot to Astronaut

McCandless graduated second in his class from the US Naval Academy in 1958 and became a naval aviator, flying the F4D Skyray and F-4B Phantom with VF-102 from the carriers Forrestal and Enterprise. Selected as a NASA astronaut in 1966, he served as a capsule communicator in Mission Control during Neil Armstrong and Buzz Aldrin’s moonwalk in July 1969.

320 Feet From Challenger

On the fifth day of STS-41-B, McCandless and Robert Stewart went out into the payload bay. McCandless backed into the MMU, which Martin Marietta had designed and built, and flew it out of the bay using hand controllers that fired its 24 small nitrogen thrusters. He moved out to about 320 feet from the orbiter and back. Both he and Stewart flight-tested the two MMUs on board over two days of spacewalks.

The famous photographs were taken from inside the cockpit by the crew, including pilot Robert “Hoot” Gibson, as McCandless floated in the distance with the Earth behind him.

A Short Career

The MMU flew on only three missions, all in 1984. On STS-41-C in April, George Nelson used it in an attempt to capture the Solar Maximum Mission satellite; the docking device failed to lock on and the satellite was eventually caught with the Shuttle’s robotic arm and repaired. In November, on STS-51-A, the MMU was used to recover two stranded communications satellites, Palapa B2 and Westar VI, which were brought home. After the Challenger disaster in 1986, the MMUs were not used again. MMU No. 3, the unit McCandless flew, is now displayed at the Smithsonian’s Steven F. Udvar-Hazy Center.

McCandless died on 21 December 2017 at the age of 80.

What the Popular Version Gets Right

The usual account is accurate: 7 February 1984, STS-41-B, the first untethered spacewalk, the nitrogen-powered MMU, about 320 feet from Challenger, and a speed of about 17,500 mph. One small correction: the Shuttle was about 170 miles above the Earth, not 180.

Sources: Adam Higginbotham, “The Inside Story of the First Untethered Spacewalk”, Smithsonian Magazine (2024); This Day in Aviation, Bruce McCandless II; Lockheed Martin, Manned Maneuvering Unit history; Smithsonian National Air and Space Museum, MMU No. 3 object record (A20010176000).