Subsonic and Transonic Aerodynamic Stability Characterization of the Dragonfly Aeroshell

NASA’s Dragonfly mission, led by the Johns Hopkins University Applied Physics
Laboratory, will deliver a relocatable lander to explore prebiotic chemistry and habitability
of Saturn’s moon, Titan. The Entry, Descent, and Landing (EDL) phase of the mission will
have an Entry Vehicle (EV) system that will deliver a rotorcraft lander to an above surface
release altitude. The EV system uses a supersonically deployed drogue parachute to decelerate
and dynamically stabilize the aeroshell. A high-fidelity characterization of the dynamic
stability of the aeroshell is needed to assure the EV system successfully completes the nearly
2-hour descent before releasing its heatshield. A 12.4%-scaled model of the aeroshell was
tested in the NASA Langley Transonic Dynamics Tunnel, in air and R134a test mediums,
using captive static and forced oscillation test techniques. It will be shown how the drogue
design impacts test planning and execution. The objective of the test was to acquire the static
and dynamic aerodynamic coefficients, at Titan flight similitude, that can be used in the
Dragonfly 6-DOF Monte Carlo (MC) simulation studies. Metrics from the MC simulation
studies are used to determine if the entry performance requirements are satisfied. The results
show that the dynamic stability derivatives have large unstable values with nonlinear
sensitivities to Mach, total angle of attack, and reduced frequency. In general, the data show
that increasing the reduced frequency results in less unstable values of the dynamic stability
derivatives which is beneficial to overall system performance.