Abstract:
This paper presents the design space exploration of a novel concept capable of lifting tethered payloads. The system uses unmanned electric tethered aircraft capable of vertical takeoff, which then transition to a circular flight to lift the payload, and even to a horizontal flight to travel at a greater speed. The system takes advantages of the tether to transfer power from the payload or the ground station to the aircraft, which allows the aircraft to be light and takeoff vertically. A thorough description of the concept and details on the operating phases are given. A physical breakdown of the system is performed and four physics-based models are constructed: propeller efficiency, wing aerodynamics, tether and electric power production unit. An optimizer is then used to maximize the payload for a given available power. It is shown that a 40 kW, two 8 m span aircraft system can lift a 770 kg payload, and that a 1,200 kW, two 28 m span aircraft system can lift a 18,700 kg payload. Finally, a sensitivity analysis showed that the assumptions involved in the modeling of the rotor and the tether drag have significant impact on the payload capability, while the vehicle mass does not.