Project Mercury also excluded civilian NASA X-15 pilot Neil Armstrong, though he had been selected by the US Air Force in 1958 for its Man In Space Soonest program, which was replaced by Mercury. Although Armstrong had been a combat-experienced NAP during the Korean War, he left active duty in 1952. Armstrong became NASA's first civilian astronaut in 1962 when he was selected for NASA's second group, and became the first man on the Moon in 1969. It was further stipulated that candidates should be between 25 and 40 years old, no taller than , and hold a college degree in a
Neil Armstrong collective bargaining group, so he decided to teach half-time. According to Armstrong, he had the same amount of work but received half his salary. In 1979, less than 10% of his income came from his university salary. Employees at the university did not know why he left. In 1970, after an explosion aboard Apollo 13 aborted its lunar landing, Armstrong was part of Edgar Cortright's investigation of the mission. He produced a detailed chronology of the flight. He determined that a 28-volt thermostat switch in an oxygen tank, which was supposed to have been replaced with a 65-volt version, lead