In two decades we have seen growth of manned spacecraft from a 3000-pound Mercury capsule to the highly complex 200,000-pound horizontal-landing Space Shuttle. The matrix of pilot control tasks and failure recovery modes increased proportionally. Actual inflight failures that required pilot intervention ranged from manual retrofire attitude control and entry control during the last Mercury flight to emergency EVA salvage of Skylab.
Unique Shuttle flying qualities and simulation requirements resulted from vehicle configuration constraints imposed by payload size, weight, and entry heating.
Our rapidly advancing digital technology poses a critical requirement for optimum design tradeoffs during integration of the flight crews' capabilities.