Effect of Forebody Strakes on Missile Asymmetric Vortices

Abstract

Wind-tunnel tests were conducted on a l/7th-scale vertically launched surface-to-air missile model to investigate the effects of forebody strakes on the side forces and yawing moments induced by nose-generate d asymmetric vortices at high angles of attack. Test angles of attack ranged from 0 to 90 deg at a Reynolds number of 1.15 x 10 5, based on the model diameter, and at a Mach number of 0.11. The four-strake forebody demonstrated dramatic results in the elimination of yawing moments at high angles of attack. The eight-strake forebody showed mixed results, with three different responses over the angle-of-attack range from 45 to 75 deg. This configuration first caused a reduction in induced yawing moment, then a violent switching, and then at very high angles had no effect. Observations concerning the onset angles of forebody- and afterbody-generated asymmetric vortices indicate that an analysis of side forces alone is insufficient to consider possible control problems for a realistically configured missile.