Experimental study of Stagnation Pressure Reaction Control for mid-calibre non-spinning projectiles

Increased precision of gun-launched ammunition can reduce collateral damage and increase stand-off distance. It can maximize the tactical advantage of each shot and reduce the number of rounds needed to achieve mission success. Worldwide, technology for controlled smart munitions is being researched and demonstrated in various implementations. Although the use of aerodynamic control fins is an effective control means, such fins are complex to integrate with the projectile, they increase radar reflectivity (with associated risk of counter battery fire) and will reduce payload. The Netherlands Organisation for Applied Scientific Research has been developing a Stagnation Pressure Reaction Control technology without aerodynamic fins, for aerodynamically unstable projectiles. The on-off character of this control technology requires a tuned control algorithm in order to achieve stable and controllable projectile behaviour. This article discusses simulated projectile behaviour under different control algorithms and presents achieved test object performance in a supersonic wind tunnel experiment performed in 2018. The experiment demonstrated feasibility of the combination of the Stagnation Pressure Reaction Control Technology and the tuned control algorithm for a non-spinning, aerodynamically unstable test object, hinged through its centre of mass. In a Mach 2 wind tunnel flow, this test object was stabilized and put under a controlled angle of incidence up to 1.5 degrees with angular error bandwidths up to 0.3 degrees, requiring and realising actuator response times on the order of 2 ms. For higher stable angles of incidence, required for correcting disturbances such as wind gusts, the SPRC technology could be integrated into projectiles with a reduced margin of instability. The short response time would provide such a projectile with a high level of (end game) manoeuvrability, for instance against moving targets