Numerical Analysis of Static and Dynamic Performances of Grid Fin Controlled Missiles

Abstract

Grid fins provide good maneuverability to missiles in supersonic flow because they can maintain lift at a higher angle of attack. Although static aerodynamic data exist, very little quantitative dynamic performance information is available for grid fin controlled missiles. The high drag associated with grid fins is also a concern. Dynamic simulations are carried out using computational fluid dynamics to investigate the dynamic stability of a generic missile, controlled by grid fins or planar fins, in supersonic and transonic regimes at angles of attack up to 30 deg. In supersonic flow, the pitch-damping derivative is found to be insensitive to the control fin type; however, in transonic flow, grid fins provide a lower damping in pitch than planar fins due to the blockage effect induced by its choked cells. The reduction of the high drag associated with grid fins is also investigated by comparing the performances of two isolated grid fin geometries with and without the use of a Busemann biplane configuration. The application of this concept to grid fins reduces its drag in the supersonic regime while maintaining its beneficial lift characteristics. Furthermore, the drag of grid fins in transonic flow can be reduced by using an optimized profile with a higher inlet-to-throat area ratio.