Spacewalker

In 1984, astronaut Bruce McCandless II performed the first untethered spacewalk during STS-41-B using NASA’s Manned Maneuvering Unit (MMU), a nitrogen-gas propelled backpack that allowed complete free flight outside the shuttle.

The MMU used 24 small thrusters powered by pressurized nitrogen, controlled via hand controllers for six degrees of freedom, giving astronauts precise maneuverability without physical connection to the spacecraft.

McCandless traveled up to 320 feet (98 meters) away from Challenger, testing the system’s safety and reliability in open space.

While groundbreaking, the MMU was retired after only three missions due to concerns about astronaut vulnerability and has since been replaced with the smaller, emergency-use SAFER system, which is worn during spacewalks as a backup rather than for long-range exploration.