As part of an envisioned autonomous swarm exploration mission in Valles Marineris on Mars a design investigation of a high-range scout UAV is performed in this work. Two VTOL configurations, a coaxial helicopter and a transition tailsitter, are examined to assess their suitability. A preliminary design framework using Python and the optimization framework OpenMDAO is created using the preliminary design software NDARC. To model the rotor performance, comprehensive analysis simulations are executed using CAMRAD II. Structural 2D-FEM beam models are created for the rotor blades and the wing for weight modeling. Design sizings are executed for operation in the extremely thin atmosphere and the mission performance for a scouting mission as part of the robotic Valles Marineris Explorer (VaMEx) swarm is examined. A behavioral model is created to evaluate the controllability of the configurations. The results for a mission with a cruise flight of 30 km and 1.4 kg of payload show that for such a mission the transition configuration does not offer advantages over a more conventional coaxial helicopter design. To understand design sensitivities and to evaluate the respective effects on vehicle performance parameter sweeps are conducted.

T-tail configurations are a promising approach to increase vertical tail efficiency, reduce fuselage download and hub load cycle amplitudes in low speed transition. However, the horizontal tail can be subject to rotor wake impingement in cruise flight which might lead to high dynamic loads and structural fatigue. The involved aerodynamics are in addition highly complex and hence difficult to be predicted by simulation. In this work a simulation approach for empennage structural loads and vibration prediction is established based on free-wake analysis and modal fuselage approximation, focusing on the expectedly most dominant aerodynamic interaction effects at the T-tail. The results are compared to flight test data to evaluate the approach, and sensitivities of the framework are assessed. The results indicate that the motion of the horizontal tail is characterized only by a few modeshapes, predominantly driven by rotor wake influence, rather than rotor loads via the structural load path. At the same time, high sensitivities are associated with these particular modes and are evaluated in this work to identify the driving mechanisms of T-tail vibrations of the investigated configuration. Discrepancies in the structural model are identified against bang test data. Taking these discrepancies into account, the simulation approach yields reasonable results for T-tail vibrations and loads in comparison to flight test data. In the front part of the fuselage, flight test data is significantly underpredicted as expected and attributed to the employed simplifications in the main rotor blade model.

Aerodynamic interactions between the rotor and the empennage can have a significant impact on steady and unsteady loads and often result in challenges in a rotorcraft design phase. In the present work, numerical analysis of rotor-empennage aerodynamic interactions were compared to full-scale flight test data with respect to steady and unsteady interactional aerodynamic effects. The flight tests provided loads for a low-empennage and a T-Tail configuration for various forward flight velocities. For the T-Tail configuration, additional pressure sensors provided validation data for steady and unsteady interaction effects. The numerical analysis was focused on an unsteady panel method, complemented by high-fidelity CFD/CSM-coupling results for a level flight state. Furthermore, a supplemental validation of the unsteady panel method was performed against an isolated wing-vortex interaction experiment. The flight test data revealed a strong asymmetry in mean empennage loads, which increases with forward flight velocity. The numerical analysis showed coherent results with a slight over-prediction in high-speed. The T-Tail configuration is furthermore subject to 3D effects between the vertical- and horizontal tail. These effects influence pressure and load-distributions on the T-Tail, which was captured by both numerical methods. The general characteristics of the unsteady pressure signatures were captured by both methods. The panel method showed slightly better representation of amplitude.