Jet Interaction Effect on the Precision Guided Mortar Munition (pgmm)

The XM395 Precision Guided Mortar Munition (PGMM) is a fin-stabilized, laser-guided projectile (Fig. 1) that was being developed for the US Army’s 120mm Mortar System. The combination of its precision capability and high-explosive warhead made it very effective against its required target set, personnel protected by masonry walls, bunkers and lightly armored vehicles. During the PGMM development, numerous projectile firings were conducted. Many of these tests utilized the mid-body thruster mechanism to maneuver the projectile. During these firings a phenomena known as jet interaction (JI) was encountered when thrusters were fired. The JI caused unexpected angular rates to be imparted to the projectiles, resulting in angular motion which decreased the projectile’s effectiveness. This report describes the challenges of understanding, characterizing and counteracting the undesirable JI effects.