Grid fins are actually an array of short lifting surfaces arranged in a lattice. They appeared in engineering literature in the late eighties of the last century, but they have probably been used in Russian military since late seventies. Notable current applications of these fins are found with the Falcon 9 launch vehicle, Soyuz ground escape capsule, and gliding weapons. Notwithstanding their high drag, they represent a viable alternative to conventional fins because they fold easily, have small hinge moment (because of their short chord length), are easy to manufacture, and have high strength to weight ratio.
In this study we develop an analytical aerodynamic theory of grid fins in subsonic flow. The solution is based on a number of small parameters of the problem, the most conspicuous of which are the ratio of the fin chord to its span, and the reciprocal of the number of the fin’s lifting surfaces. It is shown that even in the leading order approximation, the theory fits well both numerical simulations based on the vortex lattice method and the available experimental data.