Considerations for Nuclear Thermal Propulsion Reactor Technology Readiness Level Advancement

Nuclear thermal propulsion (NTP) is a candidate in-space propulsion technology for crewed missions to Mars. An NTP engine relies on the use of a reactor as a heat exchanger to directly heat a hydrogen propellant which is expanded through a nozzle for high specific impulse (>
850s), high thrust (>15 klbf) propulsion. NTP reactor and engine technologies are currently being developed to enable a future NTP engine prototype demonstration. Technology readiness level (TRL) definitions are a useful tool to plan necessary technology advancement tasks as they provide guidance on expected development activities and necessary level of fidelity of test article or testing conditions for demonstration tasks. However, technology readiness definitions for an NTP reactor and related demonstration tasks have not yet been defined. This paper
identifies relevant TRL definitions by the National Aeronautics and Space Administration (NASA) and Department of Energy (DOE). Based on these definitions, preliminary recommendations on testing conditions and important parameters to consider for NTP reactor technology development planning are provided for TRL 1 - 6. As a part of this effort, functional characteristics and important performance parameters for the reactor are identified, as well as a summary of relevant literature which was considered when assessing development tasks capable of meeting TRL definition criteria.