Guidance of Medium Caliber Projectiles by Using an Impulse Thruster Coupled with a Navigation Module Based on Magnetometers-in-Flight Demonstration

Abstract

The in-flight deflection of a 40-mm spin-stabilized projectile using a pyrotechnical thruster and a navigation module has been successfully demonstrated by the French- German Research Institute of Saint-Louis. Each of the technologies was previously validated separately by performing free-flight test campaigns at the ISL proving ground. In 2018, the two technologies were finally merged. Projectiles with an embedded thruster and a control electronics were fired at ISL at a Mach number of 2.2 over a distance of 230 meters. The very fast impulse is delivered by a reliable and robust pyrotechnic thruster containing only secondary explosive for higher safety and located at the projectile center of mass. The navigation electronics composed of magnetometers and a computing unit allows the real-time estimation of the roll angle, taking into account magnetic distortion effects. For the free-flight test campaign a total of 8 projectiles equipped with an impulse thruster have been manufactured, two inactive models (i.e. without pyrotechnical loading) to be used as references and six active models to test the reproducibility of the deflection direction and amplitude. It was demonstrated that these latter are deviated in the expected direction from their nominal flight path by 80 cm at a remaining distance of 150 meters from the final target. The expected deviation direction is obtained thanks to the perfect synchronization of the thruster having a jitter of only ±6 μs with the 670-Hz roll angle estimation. Successful results were confirmed by video recordings and impact points determination on the net target.