Pilot Pirx's Inquest.

Pirx, an experienced pilot, is hired to go on a top-secret mission to evaluate some 'nonlinears' (an experimental model of android) for use as crewmembers on future space flights. Pirx and this intriguing crew are sent out to launch two satellites into the rings of Saturn, but he is determined to find out and identify a hostile unhuman coworker among them.