Like Gene Roddenberry, Walter Matt Jefferies was in the Army Air Corps during World War II and flew as a co-pilot and engineer in B-17s. Also like Roddenberry, he was a legitimate war hero. He earned the Air Medal and the Bronze Star for his service.
In civilian life, he became an aviation illustrator. His role as an illustrator eventually lead him to Hollywood...and then to Star Trek.
Gene Roddenberry hired Jefferies to do one thing: design a space ship for his new show. He had very limited guidance from Gene: No flames, no fins and no rockets. With those restrictions in place, it was up to Matt to find the shape of this new ship called Enterprise.
His eventual design has become iconic and it has influenced every other starship design that followed in the franchise.