AN EVALUATION OF LIMIT CYCLE MOTION AND ITS IMPACT ON AEROSPIKE PROJECTILES

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. The aerospike design assumes zero angle of attack and the initial studies were conducted on projectiles that closely matched that assumption in flight. Some projectiles such as the M107 155mm artillery projectile are known to have a limit cycle motion where the average angle of attack is significant. This study places aerospike bases of inlet Mach 1 and outlet Mach 1.2, 1.4, and 1.6 on a 1:1000 scale model of the M107 projectile. The impact of the limit cycle motion on aerospike performance is then studied through live fire experiments.