Controlled re-entry Apollo Command Module Simulator Task assignments in actual space flight were concocted on Earth in dynamic simulators. The Apollo flights required the addition of more complicated duties because of the nature of the missions. The Apollo manned spacecraft was going further than any craft had gone before. It was going to the moon. Crews must be fully prepared for all contingencies before embarking on each flight.
Simulators provide as close an approximation of space flight as was possible on Earth.