Experimental Investigation of Hypersonic Performance Inlet at Sub-Design Mach Number with Varying Angle of Attack

The response of an underspeed, stream-traced hypersonic performance inlet undergoing an angle-of-attack sweep from -7.93 to 8.6 degrees is investigated. Fast-response pressure-sensitive paint is used to obtain temporally resolved surface pressure fields and associated shock structures, complemented by high-speed schlieren imaging of the external flow features. As the angle of attack increases, the inlet transitions from a started to an unstarted operating mode at 7.4 degrees, and remains unstarted until alpha is reduced to 6.3 degrees, demonstrating clear hysteresis in the unstart/restart process. The combined measurements highlight the capability of surface pressure-field imaging to capture distinct shock motions and unstart signatures during off-design pitch maneuvers.