"ALL ABOARD!" A metallic voice rasped over the loud-speakers and echoed through the lofty marble and aluminum concourse of the New Chicago Monorail Terminal. "Atom City express on Track Seven! Space Academy first stop! Passengers for Space Academy will please take seats in the first six cars!" As the crowd of people waiting in the concourse surged through the gate leading to Track Seven, three boys in the royal-blue uniforms of the Space Cadet Corps slowly picked up their plastic space bags and joined the mass of travelers. Wearily, they drifted with the crowd and stepped on the slidestairs leading down to the monorail platform. In the lead, Tom Corbett, the command cadet of the unit, a tall, curly-haired boy of eighteen, slouched against the handrail and looked back at his two unit-mates, Roger Manning and Astro. Manning, a slender cadet, with close-cropped blond hair, was yawning and blinking his eyes sleepily, while Astro, the third member of the unit, a head taller than either of his unit-mates and fifty pounds heavier, stood flat-footed on the step, eyes closed, his giant bulk swaying slightly with the motion of the slidestairs...