Fin-body interference for low aspect ratio missiles

Abstract

The supersonic missile interference factor, Kw (B), is the ratio of the force on the fin in the presence of the body to the force on the isolated fin. The importance of KW(*) is enhanced at low aspect ratios because the fin spans are smaller which leads to greater body influence on the fin lift. A finite volume Euler code is used to numerically generate the external flowfield for missiles with aspect ratios from 0.05 to 4.0. KW(B) data is presented for angles of attack from 0 to 20 deg and Mach numbers from 3 to 4, for fin span to body radius ratios from 1.3 to 2.0. KW(~) decreases as aspect ratio decreases and is less than 1.0 for a wide range of low aspect ratios (destructive interference). KW (B) is shown to be a strong and complicated function of angle of attack. When Mach number increases, KW(~) increases for all aspect ratios and angles of attack. Increasing the fin span to body radius ratio generally decreases KW(B) at low angles of attack and has a negligible effect on KW(B) at high angles of attack. The Euler results compare well with experimental data and extend the preliminary design data base for KW(B) to low aspect ratio fins.