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 inletto-throat area ratio.

Grid fins have found different applications over the last three decades, from control surfaces in missiles and projectiles to emergency brakes and stabilization devices in space vehicles. Particularly, lattice fins provide a higher maneuverability to agile high-speed missiles in supersonic flow due to their capacity to maintain lift at higher angles of attack, while improving yaw and roll stability. The aerodynamic data available for such configurations includes static aerodynamic coefficients and stability derivatives, but there is only scarce information concerning dynamic stability derivatives such as the pitch damping derivative. Dynamic simulations have been carried out using the Stanford University Unstructured (SU 2 ) CFD code to investigate dynamic stability and maneuverability properties of a grid fin tail controlled generic missile in supersonic (Ma = 2) and transonic regimes (Ma = 0.9) at angles of attack up to 30˚. The pitch damping derivative is shown to be independent from the type of fin in supersonic regime whereas grid fins provide a lower damping in pitch than planar fins in transonic regime. The high drag generated by grid fins is also investigated numerically in this work. The Busemann biplane concept is applied to lattice fins and is shown to reduce significantly their drag in supersonic regime while maintaining their lift characteristics. The high drag in transonic flow can be reduced by using an "optimized Busemann" profile having a higher inlet-to-throat area ratio.