George Mueller was instrumental in restructuring NASA during the early 1960s, and was heavily involved with the Apollo program at the beginning. While working with the Office of Manned Space Flight, Mueller proposed ways to put the Apollo missions back on schedule and budget. Part of this involved changing the testing of the Saturn rockets, switching it to all-up testing. It was a risky venture that proved successful. Mueller also played a key part in the design of Skylab and championed the space shuttle's development, earning him the title “Father of the Space Shuttle.”
He resigned from NASA in 1969 and was awarded three NASA distinguished service medals as well as the Smithsonian’s Lifetime Achievement trophy from the National Air and Space Museum.