To facilitate the development of a space nuclear propulsion module for manned flights to Mars, requirements must be established early in the technology development cycle. The long lead times for the acquisition of the engine system and nuclear test facilities demands that the engine system, size, performance, safety goals and condition monitoring philosophy be defined at the earliest possible time. These systems are highly complex and require a large multi-disciplinary systems engineering team to develop and track the requirements and to ensure that the as-built system reflects the intent of the mission. An effective methodology has been devised coupled with sophisticated computer tools to effectively develop and interpret the functional requirements. These requirements then can be decomposed down to the specification level for implementation. This paper discusses the application of the methodology and the analyses to develop condition monitoring requirements under a contract with the National Aeronautics and Space Administration (NASA) Lewis Research Center (LeRC) Nuclear Propulsion Office (NPO).