Algodoo

A device made to produce thrust using airfriction. It wastes a lot of energy pushing sideways (just disable one side of the rotors to see), but whatever, it looks neat and it works well enough. The design's weight limit is 250Kg. If you up the RPM it becomes horribly unstable, and if you up the airfrictionmult on the rotors, it'll become unstable at a lower RPM.

2000 RPM is pretty much the speed limit. Any higher and it gets too unstable. Be sure not to turn the motor torque up too high either, since it needs to ease into the speed to some degree. It's fairly robust, but if you try to go 0-2000 in 0.01 seconds, you're gonna have a bad time.

Vertical velocity is limited to 27 m/s.

Enter/Return key to toggle power on/off.

Set to run at 960Hz. Any higher and it lags too much for my taste, and it gets weaker at lower Hz. It will run at 60Hz, but it's much less stable at higher RPM, and can't really lift anything.

I might try to go further with this sort of design, since I've always been fascinated by thrusters that utilize airfriction, but I feel like airfriction is just doomed to go slow forever. Maybe if I get tiny blades on the ends of huge rotors it could go faster...