The rotor is driven only by tip jets. Air from a gas turbine is piped to the rotor tips where it is burned with fuel. Much whizzing round, no torque reaction. Oh, and NO GEARBOX in the rotor system. It seems that there will be far fewer plumet-out-the-sky-right-now single points of failure when compared to a helicopter with mechanically driven rotors.
A commercial failure in the 1950's apparently due to very high noise levels from the tip-jets.
https://en.wikipedia.org/wiki/Tip_jet
The Rotodyne was "A helicopter at take-off and an autogyro during forward flight".
A singe rotor variant was developed first. The best known model confusingly had three rotors (as per this thread's terminology) however only one of them was used for vertical takeoff, hovering and landing, the two conventional propellers being just that and used for high speed forward flight only. True single rotor variants were built.
Single rotor variants
Fairey UL Helicopter
Hiller Hornet
Fairey Rotodyne
https://en.wikipedia.org/wiki/Fairey_Rotodyne
https://www.theengineer.co.uk/issues...e-of-aviation/
https://www.britishpathe.com/video/r...ry/US+AIRLINER
8mins, no sound
https://www.bbc.co.uk/news/magazine-35521040
Why did the half-plane, half-helicopter not work?