Afterwards he served in the US Navy , retiring at the rank of captain in 1973 .
He was the first astronaut to travel in space four times and is one of only 24 men to Orbit the moon .
Afterwards astronaut served in the US Navy , retiring at the rank of captain in 1973 .
He was the first astronaut to travel in space four times and is one of only 24 men to Orbit the moon .