Flyable folding fin

Abstract

A method and apparatus for flying a folding fin from a stored folded position on a flight vehicle housing to a deployed erect position, using available aerodynamic or fluid forces to control the fin deployment. The fin is erected in several stages. First, a hinge spring bias or lifting wedge means, or combination of fin and body shape, raises the fin surface sufficiently to engage the high-speed fluid flow over the vehicle housing. Next, a motion sensor measures the fin erection angle. Finally, a feedback control system adjusts the fin control angle to increase or reduce the time rate of change of fin erection angle, as necessary. In this manner, the fin can be 'flown' into its deployed position in a smooth and controlled manner whereupon it is locked into the deployed erect position on the vehicle housing. A flyable folding fin apparatus having a fixed hinge line has the additional advantage of providing vehicle stabilization immediately following launch because an independently controlled movable surface in the foldable fin assembly can be deflected without aerodynamic assistance to provide a stable aerodynamic shape immediately. Once the flight vehicle is in stable flight, this fixed hinge line fin assembly can then be erected similarly to the movable hinge line fin embodiment.