Implementation of a Comprehensive Reduced Order Methodology for Transient Analysis of Nuclear Thermal Propulsion Engines

Nuclear thermal propulsion offers high thrust and specific impulse engine capabilities for future manned missions to Mars and beyond. Legacy nuclear engine designs developed and experimented with highly enriched uranium engine systems. Currently, extensive research is performed to analyze the behavior of low enriched uranium reactors to meet the current regulation limits. Most of these analyses are focused on complicated multiphysics steady-state calculations to determine key engine performance parameters. Often time these computational frameworks decouple various engine components in the calculation phase, resulting in uncertainties of the engine's performance. The challenges and limiting factors associated with transient operations in low enriched uranium reactors, such as engine startups and shutdowns, must be well understood. The objective of this paper is to present a reduced-order computational transient framework that examines a systemwide low enriched uranium nuclear thermal engine. The framework includes a steady-state solver used to converge on pumping requirements and conserve enthalpy prior to the start of a transient. The novel approach here relies on the steady-state component within the framework to generate operational maps. The latter indicate the feasibility of control based on nozzle chamber conditions for a given engine design in lieu of publicly unavailable pump curves. The framework is applied to investigate uprate in power maneuvers in conjunction with sensitivity studies to show the feasibility of an engine startup.