Towards Design of a 3D Printable Prandtl Box-Wing Unmanned Aerial Vehicle

This paper explores the design of a 3D printable Prandtl Box-Wing UAV suitable for long-endurance solar powered flight. Long-endurance UAVs, enabling extended imaging campaigns and beyond-horizon communication in support of remote exploration, environmental assessment, disaster and post-disaster reconnaissance and assistance, hold great promise for data-driven decision making. Yet, they also create a range of unique challenges for the vehicle design, propulsion system and power source, navigation and guidance, and payload package. The presented UAV design is a joined box-wing monocoque, a biplane with oppositely swept wings, with wing tips interconnected by winglets, offering a range of structural and aerodynamic design optimization opportunities, aimed at providing a balance between, flight performance, efficiency, flutter resistance, and adequate surface area for solar power generation, with a wingspan allowing for easy field deployment. The wing and its payload oriented fuselage are the result of aerodynamic, topology, and structural optimization, focused on enhancing structural resilience and weight, hand-in-hand with efficiency and sustainability of the resulting airframe. The aerodynamics of the wing were analyzed using high fidelity Computer Fluid Dynamic (CFD) with the goal of optimizing the Lift/Drag ratio of the wing, winglet and fuselage. In addition we performed high fidelity Finite Element Method (FEM) analysis on spars, ribs, skins, the box wing and the assembly of all the structural components. This allowed us to optimize material allocation in order to reduce weight and maximize the flight time of the vehicle. Mechanical and electrical components were chosen to optimize vehicle autonomy and automatically placed by an optimization algorithm aimed at properly placing all components inside the fuselage envelope, while maintaining the center of gravity target where desired, allowing for tasks specific optimization functions for the overall system. Using a combination of additive and composite manufacturing, the UAV can be entirely built using thermoplastics and fiber reinforced polymer.