"Any power source added to an airframe must at least generate more power than it costs to hold the extra weight in the air to make sense. I do no have any data of this particular configuration to do the basic math but some estimates can be made.…"

"I have been looking at the ETH video too when it was announced. However I fail to see how this could be special. What I see is a quad that is converted to a rotor disk (or better cone) than is controlled by precession forces. Just like a helicopter…"