Comprehensive low-order analyses of control strategies for autogenous pressurization in liquid rocket systems

This study presents a comprehensive low-order modeling analysis of three pressurant control strategies—Proportional-Integral (PI) control, bypass-type hysteresis control (BP), and triple-valve hysteresis control (TV)—for autogenous pressurization in a liquid oxygen/liquid methane (LO x /LCH 4 ) propulsion system. A one-dimensional numerical model, developed using the EcosimPro software and FluidaPro toolkit, captures the coupled thermofluid behavior of a representative 3-ton-class liquid rocket engine. The control strategies are evaluated based on pressure and temperature regulation, pressurant mass flow dynamics, and system complexity. Results show that both BP and TV models outperform the PI model in pressure stability, with the TV model achieving the most precise regulation due to its dual-stage valve logic. From a reliability standpoint, the BP model demonstrates superior durability with minimal valve actuation, while the TV model, despite its accuracy, exhibits frequent switching that may compromise component longevity. This numerical study concludes that the BP strategy offers the most balanced performance in terms of control effectiveness and structural simplicity, making it a practical solution for autogenous pressurization in small-scale liquid rocket systems. To the best of our knowledge, this is the first systematic comparison of pressurant control strategies for autogenous pressurization in liquid rocket engines, offering valuable insights for the development of future small-scale launch vehicle systems. • Developed a unified low-order model to compare PI, bypass, and triple-valve pressurant controls. • Hysteresis-based control improved pressure stability and thermal performance over PI control. • First systematic comparison of pressurization strategies for small-scale LO X /LCH 4 engines.