In view of criticality of objective diagnostics of mental performance and thereupon prediction of operational efficiency of crew members for safety and success of space mission, Institute for Biomedical Problems undertook a series of investigations towards the development of a system-psychological concept as a basis for practical diagnostics of mental performance of crew on a mission. The investigations made it possible to foresee the work style and probability of successful fulfillment of manual vehidce control using the knowledge of the types of mental performance.