Random events, improbabilities, the domino effect, good luck, bad luck. It's no secret that these things conspire to engrave names on history. The space program of the 1960s was a great example.
Consider the path of Mike Collins, Apollo 11's command module pilot. He was originally assigned to fly on Apollo 8, the first mission to orbit the moon, but a bone spur in his spinal column required surgery in June 1968. Collins was replaced by Jim Lovell, and one can only assume Collins felt some pangs of envy in his role as the mission's capsule communicator, or capcom, listening to the excited commentary from the crew as they were flung from Earth so fast they could see the planet shrink.
Chief astronaut Deke Slayton dropped Collins back into the rotation, which, in the foggy calculus of crew assignments, popped him up on the prime crew of the third mission following Apollo 8: Apollo 11. But in June of '68, Apollo 11 was far from guaranteed a moon landing. It wouldn't be until January of 1969 that NASA revealed the 11 crew as the first to train for a serious attempt. Though Collins didn't walk on the moon, he's got more name recognition than most moonwalkers other than Armstrong and Aldrin.
Speaking of Aldrin, he applied for a spot in the second (1962) class of astronauts, to which Armstrong was accepted. NASA was only hiring test pilots, and Buzz, a rank-and-file fighter pilot with 66 combat missions in Korea and two MiG kills, knew it. But he wanted his name on the radar for the next round. When NASA put out the call for the third (1963) class, they had lifted the test pilot restriction. Still, due to a bout of infectious hepatitis Buzz and his wife contracted from some bad wine in southern Italy, NASA had concerns over his liver function. In the end, it wasn't a deal killer.
Buzz's social standing in the astronaut office almost was, however. As other members of the third class got Gemini assignments—Dave Scott, Mike Collins, Gene Cernan—Buzz grew impatient, and even confronted Slayton to insist that he was qualified for selection. Aldrin later wrote: "When I finished, there was a moment of awkward silence before Deke politely said he'd take the matter under consideration." The most Buzz got was backup to Cernan for Gemini 10, which meant he'd skip two missions and be prime crew for Gemini 13. Except that Gemini 12 turned out to be the last of the Gemini missions, something that left Aldrin crushed. Then Charlie Bassett and Elliot See, the prime crew of Gemini 9, flew their T-38 into the McDonnell Douglas hangar in St. Louis and were killed, Cernan and Tom Stafford moved down from 10 to 9 to replace them, and the two prime crews after them also shifted a mission downward. Which meant Aldrin was suddenly prime crew for Gemini 12, during which he performed flawlessly throughout five hours of spacewalks. His Gemini crewmate was Jim Lovell.
A word about Lovell's luck: As he sped toward the moon on Apollo 8 in December, 1968, Slayton pulled Armstrong, the backup commander for that mission, into a small room at mission control. Slayton informed Armstrong he would command Apollo 11, and that it might be a landing attempt. Because Lovell, who had been backup for Apollo 8 until Collins's surgery, was flying now, Collins would get 11. And Aldrin, who was backup as well for Apollo 8, would probably stay with Armstrong for 11. But that was not assured, said Slayton, who asked for Armstrong's opinion. In his Armstrong biography First Man, James Hansen relates: "Slayton gave Armstrong the option of replacing Aldrin with Lovell, a choice that Neil, after much thought, did not make.There is good reason to think that Slayton had originally teamed Aldrin with Armstrong on the backup crew for Apollo 9—which became Apollo 8—because he felt that the other commanders would not work as well with Buzz as Neil would. Deke recognized that Aldrin's personality grated on several of the other astronauts."
Armstrong's rationale was that Lovell was a highly accomplished astronaut who deserved his own command, and he would get it when Slayton assigned him to Apollo 14, while Alan Shepard would command 13. But when NASA determined that Shepard, who hadn't flown in about a decade, needed more time to get up to speed, the crews of 14 and 13 switched missions. Instead of walking on the moon with Armstrong on 11, Lovell would become the only person to visit the moon twice without stepping onto it, and endure some of the worst nail-biting moments in the history of the space program during the ill-fated Apollo 13. His luck rubbed off on crewmate Jack Swigert, who had replaced Ken Mattingly only eight days before launch when NASA realized Mattingly had been exposed to measles; Swigert ended up getting the scare of a lifetime on Apollo 13 while Mattingly dodged a bullet and orbited the moon two years later on Apollo 16.
Finally, there's Armstrong's curious path to astronauthood. Undoubtedly qualified, he simply appeared to enjoy his job flying the X-15 at Edwards Air Force Base in the early 1960s. He had the least amount of time, 900 hours, in jets compared to everyone in the second class of astronauts. Frank Borman had the most with 3,600. But Armstrong was the only one of the nine who had flown a rocketplane, and he had far more experience in simulators than the others, a critical part of his appeal. Simulators were all NASA would have to prepare for flying a lunar lander above the moon.
On April 8, 1962, when NASA announced that it was accepting applications for the second class of astronauts, they made it clear that the deadline was June 1. Armstrong dragged his feet. Hansen writes: "Only one person besides Armstrong ever knew that Neil's application to Houston arrived late. This was Dick Day, the flight simulation expert with whom Armstrong worked closely ever since Neil joined the High-Speed Flight Station. In February, 1962, Day transferred from Edwards to Houston to become assistant director of the Flight Crew Operations Division at the Manned Spacecraft Center. In this capacity, Day oversaw all astronaut training programs and equipment. Two months after arriving in Houston, Day also found himself...not just a member of the selection panel for the second group of astronauts, but the panel's ad hoc secretary. According to Day, Armstrong's application for astronaut selection missed the June 1 deadline. Day explained how and why Neil's application was processed anyway: 'There were several people from Edwards who had gone on to Houston. Walt Williams, for one. Walt had gone on to be the operations director in Houston for the Space Task Group. He wanted Neil to apply, and I wanted Neil to apply. I really don't know why Neil delayed his application, but he did, and all the applications came to me, since I was the head of flight crew training. Neil's application came in late, definitely, by about a week. But he had done so many things so well at Edwards. He was so far and away the best qualified, more than any other, certainly as compared to the first group of astronauts. We wanted him in.' Technically, since Armstrong's application missed the deadline, NASA should not have accepted it...When it came in, Day slipped it into the pile with all the other applications prior to the selection panel's first meeting....Armstrong does not remember sending his application in late. Yet he does credit Day, who died in 2004, for his powers of persuasion: 'You were responsible for getting me to transfer over to Houston,' Neil wrote Day in a 1997 e-mail."