Human performance is the essential element of manned space flight. Manned space flight need not exist were robots or other devices sufficient to accomplish our specific goals in space. However, we know that humans are required for certain tasks, and we also know that the costs associated with humans in space are high. Therefore, anything which can be done to lower costs and improve human performance without jeopardizing safety are in the best interests of manned space flight. We advocate the use of simulations, not only to prepare and train for mission operations, but to analyze and improve the Human Factors aspect of space systems design. We herein describe the steps necessary to create these simulations and the anticipated benefits.