AN EVALUATION OF HOLLOW POINT OGIVES ON AEROSPIKE PROJECTILES

Abstract

An aerospike projectile base is an inverted rocket nozzle shape intended to reduce the base drag on a projectile by forcing isentropic flow over a portion of the projectile base and reducing the size of the base recirculation region. Initial studies on aerospike bases showed a significant reduction in overall drag compared to a control projectile shape with the same ogive shape. Both the aerospike and control projectile were fabricated as monolithic copper based upon the shape of a well-studied Sierra 168 grain Boat Tailed Hollow Point (BTHP) reference projectile. It was observed in testing that the overall aerodynamic drag of the monolithic control projectile was significantly higher than the published drag of the reference projectile despite being ballistically similar with the exception of the hollow ogive cavity (hollowpoint). The original aerospike study was recreated with the addition of drilled hollow points in the control and aerospike projectiles. A statistically significant reduction of approximately 4% in aerodynamic drag was measured in both the control and aerospike projectile at Mach numbers greater than 2 in testing. No reduction in drag was observed in Mach numbers below 2. The hollowpoint did stabilize the control projectile at low supersonic and transonic speed allowing a better comparison of the aerospike to the control projectile.