PROJECTILE FIN DAMAGE FROM PROPELLANT COMBUSTION

Thermal ablation of anodized (hard coated) aluminum fins on high-veloc ity, gun-launched kinetic energy penetrators is a serious problem at l ong ranges. It degrades flight performance by reducing stability and r oll. Additionally, uneven ablation creates aerodynamic asymmetries tha t further increase projectile dispersion. The problem is known to begi n in-bore. A fin-testing procedure is used to create in-here heating c onditions similar to those of a normal launch, without actually launch ing the fin. Postfired examination of the fins is then used to ascerta in the fin damage mechanism for the nonlaunched fins as well as to inf er the fin damage mechanism for normally launched fins. A two-phase fl ow interior ballistic code is also used to model the fin temperature p rofile for both the nonlaunch and the normal launch configuration. Qua litative comparison is made between the effects expected from modeling and those actually observed. Experimentally, the nonlaunched fins sus tained mostly leading-edge damage, entailing Loss of hard coat followe d by the uneven downstream ablation. Modeling appears to underpredict the observed effects, but this is thought to be a consequence of negle cting, a priori, the possibility of rapid fin surface oxidation (burni ng).