Orphans of the Sky by Robert A. Heinlein

He won science fiction's Hugo Award for Best Novel four times, and in addition, three of his novels were given Retrospective Hugos fifty years after publication. Heinlein (1907-1988) is widely acknowledged to be the most important and influential American science fiction author of the twentieth century. But could he make his people believe him before it was to late? Could he make them believe that he must be allowed to fly the ship? Read more And he learned the true nature of the Ship and its mission between the stars. Then Hugh was captured by the muties and met their leader (or leaders), Joe-Jim, with two heads on one body. Were they evil incarnate, or merely a divine check on the population, keeping humanity from expanding past the capacity of the Ship to support? Of course, there were the muties, grotesquely deformed parodies of humans, who lurked in the upper reaches of the Ship where gravity was weaker.

Indeed, how could the Ship move, since its miles and miles of metal corridors were all there was of creation? Science knew that the Ship was all the Universe, and as long as the sacred Convertor was fed, the lights would continue to glow and the air would flow, and the Creator's Plan would be fulfilled. But he also understood this was actually allegory for a voyage to spiritual perfection. Hugh had been taught that, according to the ancient sacred writings, the Ship was on a voyage to faraway Centaurus. A fix-up consisting of the novelette 'Universe' (1941) and the novella 'Common Sense' (1941).

Orphans of the Sky by Robert A. Heinlein