The image of space-suited astronaut Bruce McCandless flying free high above Earth is one of the most famous in spaceflight history, yet the device that made it possible, the manned maneuvering unit (MMU), had a surprisingly short career. The MMU flew for only ten hours, twenty-two minutes during three space shuttle flights in 1984.

The MMU measured 1.25 meters (49 inches) tall, 0.83 meters (33 inches) wide, and 1.2 meters (47 inches) from front to back with hand controller arms fully extended. Without nitrogen propellant, it weighed 142 kilograms (312 pounds). The MMU attached to the shuttle space suit's backpack by two spring-equipped latches.

The MMU was a product of maneuvering device development spanning nearly thirty years, and it became a stepping-stone to the Simplified Aid For EVA Rescue (SAFER) unit carried today during International Space Station (ISS) space walks. The first U.S. astronaut maneuvering aid was the Hand-Held Maneuvering Unit carried...