Aerodynamic and Ballistic Analysis of a 155 mm Rocket-Assisted Projectile

<title>Abstract</title> <p>The interaction between the exhaust plume and the external supersonic flow in 155 mm Rocket-Assisted Projectiles (RAPs) generates complex aerodynamic phenomena that affect base pressure, wake structure, and drag, although experimental and numerical data on these effects remain limited. This work presents an integrated computational fluid dynamics (CFD) and ballistic investigation of a 155 mm RAP, focusing on propulsion-induced modifications to the base flow and their impact on projectile range. Reynolds-Averaged Navier-Stokes simulations were performed for propelled and non-propelled configurations over a Mach range from 0.7 to 2.5. Numerical uncertainties were quantified using the Grid Convergence Index methodology, and the results were validated against PRODAS data. The simulations show that the exhaust plume produces a more compact recirculation region and increases aerodynamic drag by approximately 70% to 90% relative to the non-propelled configuration, although this difference decreases at higher Mach numbers. The aerodynamic coefficients were incorporated into a ballistic solver simulating 3300 trajectories. Results indicate that plume effects can reduce maximum range by up to 720 m near optimal firing angles, with influence concentrated during the first 50 s of flight. The proposed framework supports ignition and grain optimization for performance enhancement in extended-range artillery systems.</p>