Reducing practice projectile range by thermally induced expansion - of hollow sheet metal fins

摘要

Relatively long and slender projectile (19) with guidance fins (20) at its near end, when used for practice has the normal range shortened by modification of the fins. The fins (32) may contain a filling (50) of polyurethane foam or other material which under the effect of heat, e.g. from atmos. friction or the combustion of an inner tracer charge (40) expands to push out the sheet metal fin walls. In a variation, the fins are at least partly of memory metal, which when heated suddenly recovers an initial form. USE - Projectile maintains normal trajectory, e.g. for 200mm and starts rapid fall towards ground due to increased air resistance.