DESIGNING THE ROLL CHARACTERISTICS & PITCH-ROLL LOCK-IN OF AN UNGUIDED ARTILLERY ROCKET BY TAILORING THE CHAMFER ON FINS

The effect of the fin leading edge and trailing edge chamfers on the roll characteristics of an artillery rocket is studied. Computational fluid dynamics (CFD) simulations suggested a very high dependency of the rolling moment in the subsonic and transonic regime on the trailing edge chamfer while the leading edge chamfer dictates the rolling moment in the supersonic regime. Six degree-of-freedom trajectory simulations were carried out to estimate the roll frequency in flight and the separation of it from the pitch/yaw frequency. It showed that in certain configurations pitch/yaw and roll lock-in took place which could have hampered the flight stability. This strong sensitivity of the rolling moment to the fin chamfer, even with the fin sizing and the cant angle kept constant, can make or break the flight stability of the rocket.