Spacewalking Without a Rope

Manned Maneuvering Unit #3

Less than 20 years after Ed White became the first American to spacewalk (attached to a 26-foot tether while wielding an oxygen-jet gun), Bruce McCandless unveiled NASA’s new backpack propulsion device, the manned maneuvering unit (MMU). Without a tether, McCandless propelled himself some 300 feet from the space shuttle Challenger on February 7, 1984, creating one of the most iconic images in NASA’s history.

The manned maneuvering unit had been designed to give astronauts enhanced mobility for retrieving satellites. But the device was discontinued in November 1984 after only its third mission. A key reason for the retirement was that the space shuttle orbiter and its robotic arm could be piloted and maneuvered with such accuracy that satellite retrieval didn’t require an MMU. Another consideration was that safety measures implemented after the Challenger tragedy on January 28, 1986, would have required expensive changes to the manned maneuvering unit’s design. NASA transferred MMU #3—the one flown by McCandless and three other astronauts—to the National Air and Space Museum in 2001.

This article is from the Spring 2025 issue of Air & Space Quarterly, the National Air and Space Museum's signature magazine that explores topics in aviation and space, from the earliest moments of flight to today. Explore the full issue.

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