Modeling and analysis of heat rejection subsystems for space power systems: steady-state and transient thermal management

High-power space nuclear power systems are the development direction for future deep space exploration, aiming to provide stable and reliable power to loads in environments lacking solar energy and in complex conditions. However, only a small portion of the heat generated by space nuclear power systems is converted into electric energy through the power conversion system, while most of the heat must be effectively dissipated into outer space to ensure the Heat Rejection Subsystem (HRS) operates within its normal temperature range. Therefore, space power systems require a reliable heat rejection subsystem to dissipate excess heat via radiation. This study develops a detailed mathematical-physical model for the heat rejection subsystem of space power systems, and constructs a transient analysis model based on a heat pipe-fin unit consisting of a single titanium-water heat pipe and radiation fins. Considering the operational characteristics of the space environment, the study designs different steady-state and transient conditions for the space heat rejection subsystem and conducts an analysis of the operational characteristics, providing recommendations for the design of the space nuclear power system's heat rejection subsystem and factors to consider during transient operation.