To facilitate the development of the Space Reactor Power System (SRPS) controller, a rapid prototyping and multi-phased development methodology is being utilized. The rapid prototyping environment used in the development models both the controller and the system being controlled. Since the validation of the SRPS control strategies is a long lead activity to ensure the required safety and control features, the SRPS controller development is carried out in phases, starting with normal modes of operation and followed by transient and off-normal modes. In every phase, the rapid prototyping of the control strategies is used (1) to establish well-defined controller requirements, (2) to perform fast identification of changes and refinement of the strategies, and (3) to conduct in-phase correction and optimization of the strategy and component development. This approach allows the validation of the component controllers individually and evaluation of the effect of the component integration to identify functional and safety issues in a timely manner. This SRPS controller development paradigm can significantly reduce the development risks and lowers total cost by providing a solid foundation for requirements definition and a coordinated optimization of hardware and software.