Comparative study of power control methods for a space nuclear electric propulsion system with a compact gas-cooled reactor Brayton cycle

As deep space exploration missions increase in scope and duration, conventional solar and chemical propulsion systems struggle to meet the demands for high specific impulse and long operational life. The space nuclear electric propulsion system (SNEPS) based on a compact gas-cooled reactor Brayton cycle offers a promising alternative. Understanding its power control behavior is essential for safe and efficient operation. In this paper, a dynamic model of the SNEPS is developed by integrating the nuclear thermal module and the electrical module. Using this model, the power control characteristics of three feasible methods—control drums, bypass valves, and parasitic loads—are investigated under representative step-change transients. The results show that all three methods can effectively regulate system power. Control drums adjust reactor reactivity and turbine inlet temperature, achieving full-range power control (0–100%) with the highest energy utilization efficiency, but with a slow response (minutes) due to thermal inertia. Bypass valves modify local flow distribution, enabling full-range regulation with a faster response (seconds) at the cost of lower efficiency. Parasitic loads redistribute electrical power, providing the fastest (instantaneous) response but with the lowest efficiency and a limited range (0–40%). A comparative analysis further identifies optimal application scenarios: control drums are suitable for missions requiring large power swings and tolerating slower response, whereas bypass valves and parasitic loads are preferred for fast-response requirements. This study provides a reference for selecting and implementing power control strategies in space nuclear electric propulsion systems.