Before manned space flights began, officials pondered what background they should seek in the crew for this bizarre new venture: Danger lover? Bullfighter? Mountain climber? Should they search for people who were self-aware and calm in extreme conditions? A deep-sea diver, perhaps? Finally, they settled on — and President Dwight Eisenhower supported — experimental test pilots, people who had already guided complex new flying machines. Thus the original seven astronauts were selected in 1959.

In 1962 I was a budding test pilot at Edwards Air Force Base in California — our Mecca — and much interested in joining NASA’s second crew selection. Pondering the competition, I wrote to my father on April 19 that “Neil Armstrong will be on the list . . . because he has by far the best background.” Neil, a former Navy fighter pilot, was a combat veteran employed by NASA at Edwards. He was testing new Air Force and Navy aircraft, as well as rocket ships. His flights in the rocket-powered X-15 alone put him a stratosphere above the rest of us.

It was no surprise that Neil advanced to make the first docking in space, as commander of Gemini 8, and then moved to Apollo, where Buzz Aldrin and I joined his crew. By then he had proven his technical competence many times over, but I didn’t really know the man behind the reputation....