Dynamic Stability Characterization of the Dragonfly Entry Vehicle Configurations During the EDL Preparation-For-Powered Flight Phase

NASA’s Dragonfly mission will deliver a rotorcraft to Saturn’s largest moon, Titan, to enable exploration and search for building blocks of life. The Entry, Descent, and Landing (EDL) phase of the mission will use an aeroshell to deliver the rotorcraft Lander to an above surface release altitude. This paper discusses the dynamic stability characterization of the Entry Vehicle during the final phase of EDL called Preparation for Power Flight (PPF). This phase of flight under the main parachute is particularly challenging with its very low free-stream velocities and multiple configuration changes along with the rotors spooling up. The Dragonfly program uses statistical metrics computed from Monte Carlo (MC) simulation results to determine if flight performance requirements are satisfied. A comprehensive dynamic aerodynamic model suitable for direct use in these MC studies was developed and then integrated with the other vehicle systems in the simulation environment. The data for this aerodynamic model were obtained by conducting static and forced oscillation tests in the NASA LaRC 20FT Vertical Spin Tunnel on 7.78% and 15.56%-scale models of various PPF configurations. The tests showed that the reduced frequency was by far the most important parameter for accurately modeling oscillatory dynamics of the PPF configurations.