An orthodox, somewhat overextended expansion of a fair sf short story, ""Aztecs"" (Fireflood and Other Stories, 1979). To navigate in multi-dimensional hyperspace (""transit""), starship pilots must undergo a drastic operation in which their hearts are replaced by mechanical pumps under conscious control; subsequently they hold aloof from other crew members and ordinary mortals. Laenea, convalescing after her operation and engaged in a torrid affair with lowly crewman Radu, soon discovers why: her machine-driven metabolism and Radu's organic one are incompatible. Shocked and saddened, Radu flees on the first available ship, while Laenea departs on her first training mission. Only pilots can remain conscious and survive transit; everyone else sleeps. But, despite the drugs, Radu keeps waking up, forcing his pilot Vasili to drop into normal space. And somehow Radu endures transit, survives. . . and later uses his new-found faculties to guide a rescue ship through the unexplored seventh dimension to find the stranded Laenea. Bland, but smoothly told and occasionally absorbing--with the sturdy character conflicts snugly worked into the hyperspace-navigation backdrop.