From Republic's press release: "Commando Cody's rocketship is taken to Mercury by the Ruler. There the Ruler hopes to destroy Cody's dispeller ray, but is in for a surprise."
Earth is menaced by an evil alien "Ruler" who desires to add the Earth to his list of conquests. The Ruler uses a number of diabolical devices to carry out a series of attacks against the Earth. These devices generate floods and typhoons, spread germ warfare, block out the sun, generate additional… More suns, and pull the Earth and the moon out of their orbits. Scientist Commando Cody develops a "Cosmic Dust Blanket" to protect the Earth. However, the Ruler uses guided missiles to penetrate the shield. Cody, assisted by Joan Gilbert and Ted Richards, constructs an atomic-powered rocketship to travel into space and combat the Ruler and his evil henchmen and robots.
When did you first see this series? Was it when it first appeared in 1955 or later when it was rerun on sydication?