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Flight stability of a dual-spin projectile with canards

The concept of roll-decoupled course correction fuze with canards can provide a cost-effective solution to improve the delivery accuracy for conventional unguided ammunitions. Due to the dual-spin configuration and canards for such a projectile, the basic projectile stability theory should be extended to well perceive its behavior of motion. The seven degree-of-freedom dynamic equations of motion for the dual-spin projectile are established in the fixed-plane frame and the differential equation for the complex angle of attack is derived by the use of the projectile linear theory without the assumption of a flat trajectory. A revised stability criterion is established according to the Hurwitz stability criterion and analytic solutions of the stability boundaries for trim angles are developed. The new stability criterion can account for the possible flight instability of projectiles subjected to side forces applied at the nose, and can be reduced to the same form as the conventional spin-stabilized projectile case. Moreover, detailed trajectory simulations of two sample projectiles indicate that the new stability criterion gives satisfactory agreement with numerical results.