Atomic Robo: The Knights of the Golden Circle #5
Baron Heinrich von Helsingard is poised to conquer the West with his invincible army of automatic soldiers and Basilisk war zeppelin. Atomic Robo, Doc Holliday, and U.S. Marshal Bass Reeves stole aboard, but they're outmanned and outgunned, with no plans and no way out alive. Oh, and Robo's nearly out of nuclear fuel.