Exterior ballistics analysis for rocket propelled KE-penetrator - A conceptual simulation study within fluid mechanics and flight mechanics

Abstract: This study has investigated the conceptual feasibility of a rocket propelled kinetic energy penetrator (KEP), designed for the handheld recoilless rifle Carl-Gustaf® 84 mm calibre system, from an exterior ballistics perspective. The methodology is based upon evaluating the aerodynamic properties of different conceptual design proposals through CFD-simulations and then performing trajectory analysis to assess their exterior ballistic performance. In particular, the main focus has been to optimize the stability, velocity and spin rate of the KEP. The results of the study indicates that the final chosen KEP design retains, from an aerodynamic perspective, longitudinal stability for Mach numbers up to 4.5, regardless if the rocket motor is ignited or not. Furthermore, if using NK1384 propellant, the final chosen design in the study is, according to the calculations, able to achieve a maximum velocity of 0.7⋅v_ref and retain a minimum velocity of 0.628⋅v_ref in the horizontal range of [0.318⋅x_ref,0.648⋅x_ref] measured from the shooter. In addition, the angular spin velocity achieves a maximum value of 15.5 Hz, satisfying the performance limitation of the rocket motor which only functions properly for frequencies up to 30 Hz, while simultaneously providing a sufficiently considered spin rate in order to average possible thrust and mass deviations of the KEP. The results also show that if using ammonium dinitramide (ADN) propellant, the KEP is able to achieve a maximum velocity of 0.786⋅v_ref, retain a minimum velocity of 0.628⋅v_ref in the horizontal range of [0.28⋅x_ref,0.98⋅x_ref] and achieve a maximum spin rate of 17.5 Hz.