John Watts Young was an American astronaut, naval officer and aviator, test pilot, and aeronautical engineer. He 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 fly six space missions over the course of 42 years of active NASA service. He is the only person to have piloted and commanded four different classes of spacecraft: Gemini, the Apollo Command and Service Module, the Apollo Lunar Module, and the Space Shuttle. Before becoming an astronaut, Young received his Bachelor of Science degree with highest honors in Aeronautical Engineering from the Georgia Institute of Technology and joined the U.S. Navy. After serving at sea during the Korean War he became a naval aviator, and graduated from the U.S. Naval Test Pilot School, setting several world time-to-climb records as a test pilot. Young left the Navy in 1976 with the rank of captain.