Voting Result: 2.61961176135
Overview for Protean -- A versatile vertical take off cargo configuration
Protean is a versatile flying wing configuration that is able to take-off vertically, pitch down and fly horizontally. It consists of three sections that can be easily manufactured, assembled and inspected in case of failure.
A flying wing configuration was chosen for its simplicity and good L/D characteristics, enabling it to easily meet the mission range requirements for the different payload options. This shape, together with swept wings and reflexed camber profiles increase its stability and controllability. The span of the wing is 4.9 m.
The counter-rotating pairs of propellers at each side will give Protean the desirable redundancy, which will allow the configuration to fly and complete the mission after the failure of one of the propulsion systems. The initial thought was to place the propellers at the tips of the wing, but having placed them inboard made the design structurally stronger and more stable as the centre of gravity was moved further towards the leading edge.
In order to enhance the control power of the four frontal motors, their axis is rotated 10 degrees with respect to the horizontal plane. This will allow an even more agile vertical flight dynamics without noticeably sacrificing the horizontal flight efficiency. The low pitching moment of inertia of the configuration made it possible to complete a 90 degree turn in less than 6 seconds after reaching the required cruise altitude of 300ft. The vertical speed of the configuration at that point will be around 25 m/s, which is enough to safely complete the flight mode change.
The structural sizing was done using a load factor of approximately 5.6, as a gust of 10 m/s was considered. The safety factor was 1.5. The total mass of the configuration is estimated to be around 24 kg including the 5kg of payload.
The inboard wing consists of two spars in order to provide enough safety at the point where the propellers are mounted, as well as stability in torsion. The rest of the wing accommodates one spar. A less conservative design, regarding the flight envelope, would possibly lead to less power requirement and consequently to smaller batteries. This along with the decrease of structural mass would drop the final weight of the aircraft by 2-3 kg.
The payload will be easily slid out of its bay from the upper side of the wing. It will be located at approximately 1 m from the ground. All the electronics and other auxiliary devices can be accessed from another window, which is independent from the payload one. This guarantees the waterproofness and tamperproofness of delicate devices such as the inertial measurement system and the recovery system.