<a href="https://www.youtube.com/watch?v=OI_HFnNTfyU" rel="nofollow">https://www.youtube.com/watch?v=OI_HFnNTfyU</a><p>They could do it with stationary electromagnets. :)
This works better linearly than as a rotary system. See Inductrack.[1]<p>[1] <a href="https://en.wikipedia.org/wiki/Inductrack" rel="nofollow">https://en.wikipedia.org/wiki/Inductrack</a>
I'm naively surprised at the amount of torque and power required to spin the magnet heads. Those are huge motors.<p>It would require some serious refinement to have benefits over air cushions, but I can certainly see a practical use for moving heavy loads slowly.
Where Halbach arrays would excel is in levitating fast moving vehicles. Such levitation is passively self regulating, and uses tracks which can be simply manufactured out of bulk materials. (Basically, make a track out of conductive aluminum loops in the cheapest way you can think of.) Contrast this with maglev technologies that require fast reacting active regulation and supercooled magnets.
I wonder why this hasn't been "invented" yet. Halbach arrays have been around for a long time. My best guess is that the control circuitry to make sure the rotors are spinning in "just the right amount" is not so simple.
Reminds me of the hendo Hoverboard startup, which from looking at some of their prototypes i think used the same principle: <a href="http://hendohover.com/" rel="nofollow">http://hendohover.com/</a>
This technology (Halbach Arrays) has also been used to create passive electromagnetic bearings (a couple of windings of wire sent any field imbalance to the opposite side of the array).