Thermal-Fluid Modeling and Material Analysis for a Centrifugal Nuclear Thermal Rocket Engine

A Centrifugal Nuclear Thermal Rocket (CNTR) is a theoretical method of spacecraft propulsion designed to support missions to deep space. Similarly to traditional Nuclear Thermal Propulsion Engines (NTPs), CNTRs utilize the heat generated by nuclear fission within a reactor to heat a propellant. Unlike NTPs, which use a solid uranium core, CNTRs utilize liquid uranium rotating in an annular region of a Centrifugal Fuel Element (CFE). By spinning the CFEs, a centrifugal force is applied that allows the liquid uranium to be retained against a porous medium. This enables the propellant to be heated by the liquid uranium as it diffuses, or bubbles, through the fuel, substantially increasing heat transfer efficiency. The resulting maximum specific impulse (Isp) of a CNTR could reach upwards of 1800 seconds—double that of conventional NTP designs and quadruple that of a typical bipropellant chemical engine. The enhanced performance of CNTRs makes them well-suited for long-term missions, reducing transit times to destinations such as Mars and the moons of Jupiter. Though the mission architecture exists for their application, CNTRs pose significant engineering challenges, which have hindered the development of prototypes. This paper extends earlier work by modeling and analyzing the fluid flow and heat transfer processes within a CNTR during steady-state operation. Additionally, the boundary conditions interfacing with the uranium annulus are assessed for the material selection of the walls in a CFE.