The setting of Ace Astro's adventures is the twenty-first century where "the select Star Rovers, the strongest and bravest men in the U.S.A., patrol the universe in their interplanetary rockets, living in gigantic plastic bubble cities, keeping the world safe from deadly outer space attack." Note the presence of an animal in the above cover picture. It is a dog named Sirius. Like the two star rovers, Sirius must have a spacesuit to survive on the Moon, Of course, Sirius's barking cannot be heard except via radio transmission which the artist has attended to by including a radio transmitter and antenna on the dog's back.