Wow, that looked cool -- but it was electric ducted fan, right? What diameter are those fans?=expected/estimated Specific Thrust ? [kG/kW]
BTW= CR Fan (Stator less !)...
Review on ducted fans for compound rotorcraft - Volume 124 Issue 1277www.cambridge.org
Can counter-rotating ducted fan be done with mechanical transmission? Or will it be too heavy?