An idealized approach to developing design criteria for a ground support system, assessing the system effectiveness, and improving system design is described.System design starts with mission objectives and performance requirements. As the flight system is designed the assembly, test, and checkout functions are identified. These generate requirements to be satisfied by the ground system. Requirements are allocated to the system elements as design criteria and provide the basis for ground system design and procurement. The system is designed and fabricated to these criteria.Since typical space programs include a very limited number of space vehicles of high cost and complexity, it is important to assess and ensure system performance before the hardware is operational. Computer simulation of system operation, including reliability and maintainability, provides a system effectiveness prediction and identifies soft spots so that early remedial action is possible.This approach to requirements and criteria has been applied in part on the Saturn V Program and a simulation of the entire Saturn V activities at the launch pad has been developed. The most significant results achieved to date will be discussed. This work is sponsored by NASA-MSFC, R-P&VE-VOR.