A portrait of Neil Armstrong aboard the Lunar Module Eagle on the lunar surface just after the first moon walk.
NASA—Corbis via Getty Images
July 31, 2017 12:48 PM EDT

Live with history long enough and it starts to seem immutable. In 2019, a full 50 years will have elapsed since Neil Armstrong became the first man on the moon; the near-half-century that has gone by since that transformative July night in 1969 has made it nearly impossible to conceive of anyone else in Armstrong’s role. Imagining Pete Conrad or John Young as first men on the moon (instead of the third and ninth, respectively) seems as odd as imagining James Madison as the first President.

But the fact is, in the mid-1960s, when NASA was flying the two-man Gemini spacecraft that preceded the three-man Apollo, Conrad and Young and more than a dozen other men had just as good a chance as Armstrong of getting the prime seat on the prime mission. Armstrong even had a worse chance than the rest of them—or at least he did on March 16, 1965, when he and his co-pilot Dave Scott took off aboard Gemini 8, both men’s rookie ride into space.

Gemini 8 was supposed to be a three day mission that would include a rendezvous and docking with an unmanned spacecraft, and a pair of spacewalks by Scott. Instead it was all over in less than 11 hours, and the most memorable thing the two men accomplished was the simple business of staying alive.

That flight, only four years into America’s now-long history of flying human beings in space, was the the first time NASA came close—horribly close—to losing a crew during a mission. The near-miss was owed to a very simple mechanical breakdown that almost pushed both the Gemini spacecraft and the astronauts themselves beyond the point that either could survive.

The fact that they did survive was due to the quick thinking and nimble piloting of Armstrong and Scott, and to the men at the consoles in Mission Control, who knew enough to offer whatever guidance they could during the unfolding crisis and then stand back and let the pilots work. That was enough—enough so that four years later Armstrong would indeed walk on the moon and, two years after that, so would Scott.

Episode Two of the TIME podcast Countdown tells the story of Armstrong’s and Scott’s harrowing day, and of what it took for them to get out of it with their lives.

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Write to Jeffrey Kluger at jeffrey.kluger@time.com.

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