Nuclear Thermal Propulsion Exploration Upper Stage: Enabling Efficient Transfers to Distant Destinations

Nuclear Thermal Propulsion (NTP) is not a new concept and has been studied for decades. It was tested in the 1960s during the NERVA program, proving the technology. NTP has long been studied for human Mars exploration missions. In the concept presented here, the NTP stage would be evolved from the Space Launch System (SLS) Exploration Upper Stage (EUS) which was designed for deep space operations. The NTP EUS would leverage systems, structures, and the Hydrogen tank, from the current SLS/EUS, but would replace conventional LOX/H2 RL10 engines with an NTP engine. A departure point launch configuration for this paper includes an NTP stage which would be launched atop the SLS/EUS Block II configuration, operating as a third stage, and once reaching a nuclear safe orbit (NSO), the nuclear engine would be safely activated. The combination of SLS/EUS with an EUS derivative NTP stage provides the advanced capabilities needed for efficient transportation to undertake deep space human and robotic missions. NTP Specific impulse performance is nearly double that of the most chemically energetic combination of Liquid Oxygen (LO2) and Liquid Hydrogen (LH2), significantly improving efficiency for in-space propulsion. This technology could drastically reduce mission mass and transit time, two major challenges for all deep space exploration. This paper presents examples of robotic mission examples to highlight the value of including NTP in future deep space launch vehicle architectures. While this paper focuses on the important metric of mass delivered to various destinations, there are also trades between mass delivered and transit times which will be explored in subsequent studies.