IFMU,
It would seem at high speeds that generating lift is not the problem. There is the whole V^2 thing going on.
Good point, but ....
At high speeds the air velocity will be greater on the advancing blades, but it will be less on the retreating blades. It will also be reduced on all azimuths as the rotational speed of the rotors is slowed to assure that the advancing tips do not get too close to Mach1.
Perhaps the generated lift will be less at high speeds.
Also, would you really want small rotors? That might be good for high speed but bad for hover and autorotation.
The thinking (or hope) is that the diameter of the rotors can be reduced somewhat by having an airfoil that goes all the way to the root of the blades, plus having a larger solidity ratio due to a substantial taper.
For hover it might be possible to have very large active negative twist on the blades.
For cruise, at tip speed ratios in excess of 1 or 2, the very slow turning rotors may result in the blades acting as airplane wings
(wings similar to those on the F-104 ~ but a greater aspect ratio)
________________
Heli-Ice,
Wacky ~ Yes
Professor ~ No
Dave