Disclaimer: As an AIRBUS employee I hope my contribution will help to find the best for the challenge. It is very interesting to see all the contributions and how the different proposals are evolving.
The aim of this proposal is to provide a design to meet the requirement for Airbus Cargo Dron Challenge.
The design is simple but I believe that it works since it is as simple as effective.
The 72% of the battery energy is used during cruise. Therefore the optimization of the cruise condition is key. In order to optimize this cruise, a generous slender ratio, moderate wing loading and straight and tappered fixed wing is choosen. The ratio between tip chord and root chord is 0,3. No rounded wing (i.e. eliptical) has been choosen in order to not incease the manufacturing complexity of the wing.
Pay load CG will be placed at the same x position as the CG of the dron. Taking into account that this CG will be around the 25% of the a.m.c. the center of the wing rotors should be placed a little forward this position, and the lift needed at the tail rotors is marginal compared with the main rotors (only for stability and hover control).
During hover the rotors lift the drone, mainly the wing ones, and during cruise the propellers are electronically aligned with the x axis to hide them inside the wing and horizontal tail plane tip pods.
The wing tip pods not only hide the propelles to reduce the parasitic drag, but also will reduce the tip vortex of the wing and therefore the aerodynamic performance.
Finally the concept of the pay-load box will allow to change easily the loads (several pay-load box could act as cargo containers) but also the change of the dron mission is as simple as to change this box by other with sensors, cameras, etc.