Republic's inspiration for their Rocketman character probably originated from a comic book.  In 1940, artist Jon Small developed Bulletman, whose alter ego was Jim Barr, ballistics expert and vigilante cop.  Barr concocted a secret formula which gave him super strength and wore an open-face , bullet-shaped helmet which allowed him to fly.  Ably assisted by consummate hottie Bulletgirl and later Bulletboy, he dispatched all manor of crooks and evil doers.

Bulletman's exploits were originally featured in Fawcett's Nickel Comics beginning in May 1940.  A year later, he had his own title which ran from 1941-1946.