Dual Centrifugal Blower Drone

The public knows about drones, they're wrong in most cases. What they're usually referring to is piloted hobby grade through to semi-professional aircraft most often used as camera platforms. The most common design for these is the quadcopter, 4 brushless DC motors spinning propellers at the ends of a rough X-shape with the batteries, controllers, and radio gear in the middle. The position of the propellers at the periphery makes them vulnerable to damage whenever the quadcopter hits anything, which is often.

To solve this, we can do a quick re-design. The main body in the center of the craft now contains a centrifugal blower spinning about a vertical axis. The air intake is at the top of the craft, air is compressed by the blower and exhausted through 4 tubes in the familiar X-shape. At the ends of the tubes, rotating nozzles direct the exhaust, mainly they will be directing it downward for lift. Small sliding valves can control air distribution to each of the 4 tubes and the rotating nozzles add additional control finesse.

The central blower, when accelerated/decelerated will impart torque on the whole aircraft. This could be countered by angling the nozzles at the end of the tubes. The smarter way would be to have 2 motors driving two concentric counter-rotating centrifugal blowers. By controlling the two, changes in thrust can be made with no net torque. Better yet, rotation of the craft can be achieved by speeding up one blower and slowing the other to cause torque with the same net thrust.

Because most of the force generated goes to opposing the aircraft weight, there's no actual need to have it generated at the ends of the X-shape, instead, a central exhaust constituting 50-90% of the thrust would be more efficient, and could perhaps be varied depending on the maneuverability requirements.

The tube-nozzle design will have some pumping losses associated but these can be offset. Larger motors are often more efficient than multiple small motors per unit of output. The tube nozzle system is used to good effect in quieter helicopter tail rotors <link>. The advantages should include lower noise, increased robustness and overall more flying saucer-like aesthetic, combined with spooky apparently reactionless rotation ability. The centrifugal blower with axial input will essentially operate like one of those fancy turbocharger compressors, all the work has already been done there.