Thrusters Pairing Guidelines for TrajectoryCorrections of Projectiles

Abstract

Abstract : A novel method for correcting the trajectory of spin- and fin-stabilized projectiles using pairs of impulse thrusters located away from the center of mass is described in this paper. The impulses are generated from the detonation of a very small quantity of explosive. By locating the impulse thrusters away from the center of mass, it is possible to significantly increase the trajectory correction. This is explained by the fact that, in such a case, the deflection results from the aerodynamic jump due to the projectile oscillation in addition to that of the impulses. An optimal combination of thrusters can be achieved by considering pairs of impulses that have the double objective of maximizing the deflection and minimizing the drag due to the oscillations. In this paper, the linear theory of ballistics is used to develop an analytical model representing the motion of a projectile subjected to impulse thrusters. Using the linearized equations of angular motion and considering ideal cases, the optimization scheme for using double impulses is defined by a set of three rules. The latter are then assessed in the case of actual projectiles, using six-degree- of-freedom computations. The course correction process for a 30-mm fin-stabilized air-defense projectile and a standard 105-mm spin-stabilized artillery shell are presented.