The computers had been programmed with the orbital equations that would control the trajectory of the capsule in Glenn’s Friendship 7 mission from liftoff to splashdown, but the astronauts were wary of putting their lives in the care of the electronic calculating machines, which were prone to hiccups and blackouts. As a part of the preflight checklist, Glenn asked engineers to “get the girl”—Johnson—to run the same numbers through the same equations that had been programmed into the computer, but by hand, on her desktop mechanical calculating machine. “If she says they’re good,’” Katherine Johnson remembers the astronaut saying, “then I’m ready to go.”

Katherine Johnson, a mathematician for NASA manned spaceflight programs, passed away today at the age of 101. Read her remarkable story here...