Dynamics and Control of Shock Motion in a Near-Isentropic Inlet

Inlet pressure recovery of supersonic aircraft could be improved using a near-isentropic inlet with only a weak normal shock aft of the throat; however, such an inlet is highly susceptible to unstart. Small perturbations can move the shock ahead of the throat, where it is unstable. The dynamics of the inlet and shock are analyzed using a low-order model that captures both the nonlinear shock motion and inlet acoustic propagation. This model allows parametric exploration of both the potential and limitations of using control to stabilize actively the shock, including actuator authority as a function of location, actuator authority, and bandwidth requirements, and sensor requirements. A simple control law is shown to be sufficient to stabilize the shock motion.