Modeling supersonic missile fin-body interference for preliminary design

Abstract

Aerodynamic interference between adjacent surfaces plays an important role in the performance of missiles. Fin-body interference factors are used in the Missile Datcom method to predict missile aerodynamic characteristics using the equivalent angle-of-attack method. This investigation presents a simple, accurate, and rapid method to determine fin-body interference factors for preliminary design. Linearized potential theory is used to evaluate the effect of body upwash on the local velocity along the fin leading edge as a function of fin span. A panel method is applied to determine the change in equivalent angle of attack due to body upwash. Planar fin configurations are considered with the fins located symmetrically on the missile body; however, the results also apply to cruciform configurations. The fin-body interference factors are presented as a function of Mach number and changes in missile geometry, such as fin leading and trailing edge sweep, fin vertical position on the fuselage, and fuselage cross-sectional shape. Circular and elliptic fuselage cross sections are considered. The method is shown to be quite accurate.