Active Store Trajectory Control in Supersonic Cavities Using Microjets and Low-Order Modeling

Abstract

Recently, there has been a concerted effort in controlling the trajectory of a store departing from a cavity in a supersonic flow so as to ensure safe separation. The candidate actuator that has achieved a safe departure in model-scale wind tunnel tests using minimum flow rate is a tandem array of microjets placed in the spanwise direction near the leading edge of the cavity. In this paper, a low-order model is derived that captures the dominant mechanisms that govern the store trajectory with and without microjets and conditions under which unsafe and safe departures occur are predicted. This model includes separate components to predict the pitch and plunge motion of the store when it is is inside the cavity, when it is passing through the shear layer at the mouth of the cavity and when it is completely outside the cavity. The model derivations are based on the assumptions of store ejection from the cavity middle, slender axisymmetric body aerodynamics, thin shear layer at the cavity mouth, high Reynolds number external crossflow, plane shock waves associated with the microjet actuators, and quiescent cavity. The model predictions are compared to the results of store drop experiments performed under the HIFEX Program at Mach 2.0 and 2.46 using a generic subscale weapons bay for different control inputs