Numerical Investigation of Stage Separation Control of Tandem Hypersonic Vehicles Based on Lateral Jet

The stage separation of hypersonic vehicles is critically challenged by severe aerodynamic interference, which induces significant attitude deviations and jeopardizes subsequent flight missions. This study investigates open-loop and closed-loop attitude control methods utilizing lateral jets to stabilize the forebody during separation. Dynamic CFD-based numerical simulations were conducted for a tandem hypersonic vehicle, analyzing trajectories and aerodynamic characteristics under free separation, open-loop, and closed-loop control. Results show that open-loop control achieves a maximum forebody pitch angle of only 0.27° at $\alpha =0°$, but performance degrades drastically to 24.88° at $\alpha =2.5°$, highlighting its sensitivity to freestream variations. In contrast, a cascade PID-based closed-loop control system dynamically adjusts lateral jet total pressure, reducing the maximum pitch angle to 0.006° at $\alpha =0°$ and maintaining it below 0.2° even at $\alpha =5.0°$. The closed-loop system exhibits periodic fluctuations in jet pressure, with amplitude increasing alongside angle of attack, yet demonstrates superior robustness against aerodynamic disturbances. Flow field analysis reveals enhanced shockwave interactions and vortex dynamics under closed-loop control, effectively mitigating pitch instability. While open-loop methods are constrained to specific conditions, closed-loop control significantly broadens applicability across variable flight environments.