Aerodynamic Modeling for Thrust Vector Control Rocketry

Guidance, navigation, and control (GNC) systems are widely used in the aerospace industry for vehicle stabilization and control. In rockets, methods such as thrust vector control (TVC) allow for controlled maneuvers and active stabilization. However, rocket fins also passively stabilize the trajectory by inducing restoring moments in the roll, pitch, and yaw axes. These forces and moments can interfere with the GNC system. Both static and dynamic stability aspects must be considered by characterizing the vehicle's natural aerodynamic response to disturbances such as angle of attack (AOA) and rotation rates. The GNC team under the Georgia Institute of Technology Ramblin' Rocket Club (RRC) aims to implement a jet vane TVC system on a solid-propellant rocket. Computational fluid dynamics (CFD) methods were used to develop a nonlinear regression that predicts aerodynamic forces and moments associated with static stability. Unstructured mesh generation and simulations were performed using the commercial CFD software Ansys Fluent with a pressure-based solver and the k-ω SST turbulence model. The rocket was simulated under varying angles of attack from 0 to 5 degrees and Mach numbers from 0.1 to 0.7. To characterize dynamic stability responses to roll, pitch, and yaw rates, a combination of theoretical and empirical relations was used. The resulting combined aerodynamic model was used to model the rocket's trajectory and tune jet vane control parameters. The insights from this process provide a methodology for feasible, medium-fidelity analysis of the static and dynamic stability of rockets.