Captain John Watts Young (born September 24, 1930) is a retired American astronaut, naval officer and aviator, test pilot, and aeronautical engineer, who became the ninth person to walk on the Moon as Commander of the Apollo 16 mission in 1972. Young enjoyed the longest career of any astronaut, becoming the first person to make six space flights over the course of 42 years of active NASA service, and is the only person to have piloted, and been commander of, four different classes of spacecraft: Gemini, the Apollo Command/Service Module, the Apollo Lunar Module, and the Space Shuttle.