Investigation of Grid Fin Aerodynamics

Grid fins are aerodynamic control surfaces commonly used on rockets and missiles for precise recovery due to their superior performance over traditional planar fins such as: enabling precise steering, vehicle stabilization, and reducing fuel consumption when landing, i.e., by guiding the booster and increasing drag. While they have been widely studied for supersonic and reentry applications, there is limited research on how geometric variations affect their aerodynamic performance in subsonic flight conditions. This study investigates how geometric parameters of grid fin designs—including open area percentage, number of junctions, and number of lifting members—influence the aerodynamic behavior and overall performance of the grid fin. Five distinct grid fin designs were chosen and fabricated, including a diagonal, diamond, hexagonal, honeycomb, and unihex design. The designs were tested in the San Diego State University Subsonic Wind Tunnel and subsequently compared through lift, drag, pitching moment, and aerodynamic efficiency to previous designs found in the literature. By maximizing the open area percentage of the geometry and reducing vertical members that induce drag, the Unihex Grid Fin outperformed other models by generating higher lift and lower drag values over the range of tested angles of attack, ultimately creating a more efficient design.