SUMMARY

Nuclear Thermal Propulsion (NTP) is an enabling technology for near-term cis-lunar operations and crewed missions to Mars. Developing a reactor design that can satisfy rocket engine performance requirements while maintaining adequate thermal and mechanical safety margins within the reactor during operation requires advanced modeling and simulation (M&S) tools. In this dissertation, a novel reduced-order thermal-hydraulic (T/H) and thermo-mechanics (T/M) code - ntpThermo is developed and verified against a series of benchmarks. Additionally, the Basilisk multiphysics framework was developed to couple ntpThermo with Serpent to perform full-core time-dependent Neutronic+T/H-T/M analysis. The results demonstrate that neglecting multiphysics feedback introduces significant errors into the spatial power distributions, which subsequently cause significant errors in the prediction of thermal and mechanical safety margins during engine operation.