February 29, 2024

Photo: NASA

“It may have been one small step for Neil,” McCandless quipped in reference to Armstrong’s famous words, “but it’s a heck of a big leap for me.” As The New York Times reported at the time, “Free of any lifeline and propelled into the dark void by tiny jets, they became, in effect, the first human satellites.”

The MMUs were powered by two dozen gaseous nitrogen thrusters stored in tanks on the astronaut’s backpack, enabling free movement in space. Control was achieved through hand controllers, allowing spacewalkers to adjust thrust and direction for precise navigation during extravehicular activities. The technology demonstration worked, but “many in the agency were fearful about the use of a self-propelled and untethered backpack in space,” as NASA historian Jennifer Ross-Nazzal wrote in her retrospective.