Fin Design

The fin design for this year's rocket envisions a more elaborate configuration than in years past. The rocket will employ a variable drag control system to improve target apogee accuracy. An array of pins around the fin section will be extended out of the rocket body radially to a distance that will produce additional drag as determined by the flight computer. The extension distance will depended on expected apogee and velocity conditions after motor burnout. To reduce the computational load on the flight computer, a dictionary of pre-calculated scenarios will be loaded into an onboard memory bank to be accessed with velocity and altitude values. Aerodynamic responses to pin extension will be recorded and analyzed prior to launch. The wind tunnel data, combined with validated CFD results, will be used in building a guidance database and loaded onto memory accessible by the flight computer.

The pin hub, shown in purple, will control the pin extension when rotated. The drive shaft, shown in dark gray, transfers rotation from a stepper motor above the motor to the pin hub. The pins will be driven by a single stepper motor above the engine block to prevent any aerodynamic asymmetry resulting from the extended pins.