Modular Drone design - the idea was to make the drone that could be used for various purposes - civil, scientific or military. Based on the needs, drone parts get exchanged.
I had the idea where the drone has a special platform for landing (no landing gear on the drone) or storing (when not in use) and the same platform is used for quick modular parts change. I didn't make it though because i would up making the entire environment and to keep the quality and details consistent that would take a lot of time so i decided to move on to different things instead. :)
Main engines don't have blades (propellers) so the noise is reduced to minimum. They kind of a work like super advanced versions of those fancy "Dyson bladeless fans".
UPDATE > Added bunch of close up viewport screenshots of Modular Drone since a lot of details are not really quite visible on the final renders.