The Cyborg from Earth — Charles Sheffield

Heir to a powerful military dynasty, Jeff Kopal has never lived up to his family's expectations. When he blows his naval entrance exams, he assumes his future is over. But if he's such a screwup, why is he being sent by the navy into deep space to deal with rebellious cyborgs? Something isn't right, and Jeff must figure out the real reasons behind the mission--or risk becoming a pawn in someone else's deadly game.