Dragonfly Entry Vehicle Dynamic Stability During the Preparation for Powered Flight Phase

NASA’s Dragonfly mission will deliver a rotorcraft lander 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 ([Formula: see text]). This paper discusses the dynamic stability characterization of the entry vehicle during the final phase of EDL, called preparation for powered flight (PPF). This phase of flight, under the main parachute, is particularly challenging with its very low freestream velocities and multiple configuration changes simultaneously with 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 was developed for the MC simulation studies. The data for this aerodynamic model were obtained by conducting static and forced oscillation tests in the NASA LaRC 20FT Vertical Spin Tunnel on subscale models of various PPF configurations. The results showed that the reduced frequency was the most important parameter for accurately modeling vehicle oscillatory dynamics. The MC studies, using the dynamic aerodynamic model, showed that the vehicle remains dynamically stable throughout the PPF flight phase.