Abstract: Deep space exploration missions such as planetary soft landing and sample return impose strict requirements on the deep throttling capability of propulsion systems. Electric pump-fed rocket engines have attracted significant attention due to their advantages including simple structures and decoupled control. Addressing the thrust regulation problem of electric pump-fed engines, this paper proposes an optimal torque regulation scheme based on the vector control of permanent magnet synchronous motors. This scheme achieves rapid responses during thrust reduction and increase processes through the feedforward intervention of braking and accelerating torques. A system dynamics model for the electric pump-fed rocket engine is established, and combined with multi-condition simulations, the impact of different motor torque schemes on thrust regulation time is analyzed. Results show that optimal torque regulation reduces the thrust reduction time by 74% to 86% and the thrust increase time by 45% to 75%. Furthermore, the fuel motor plays a dominant role in thrust regulation, whereas the liquid oxygen motor regulates faster, resulting in limited intervention effects. Operating condition sensitivity analysis demonstrates that lower engine thrust levels, greater thrust regulation depths, or shorter set intervention times impose heavier torque burdens on the motor. Considering the physical limits of the inherent torque range of the motor, the optimal torque regulation scheme proposed in this study is more suitable for multi-stage deep throttling tasks in rocket engines.

Key words: Electric pump-fed engine, Liquid oxygen-methane engine, Deep throttling, Torque control, Control strategy