🚀 go-pugleaf

J. Baez's posting of a plausible antigravity device inspires
me to describe one of my own.

Imagine a spinning superconducting rotor of suitably clever
configuration.  I think of something like one of those toy flying
devices with a hub, several radially disposed airfoils with
non-zero angle of attack, and an outer ring surrounding all the 
airfoils:
          _________
         /___    __\
	//   |  |  \\
       //    |  |   \\
      //     |  |    \\
     ||_____/    \____||   / \
     | _____      ____ |    |
     ||     \    /    ||    |
      \\     |  |    //     |
        \\   |  |   //
         \\__|  |__//
          \________/ 

Now the magnetic field equations have the same form as the
hydrodynamic equations and since the devide is superconducting
these will be the Euler equations.  Thus in the earth's magnetic
field the rotor will act like the toy and produce lift.  Since
the conduction is perfect, the lift will be without drag (Euler
equation paradox).  The spinning rotor will thus produce a constant
force against the earth mediated by the magnetic field.  

If the force vector is oriented vertically and the rotor is large
enough and spins fast enough it should levitate.  Note that nothing
is violated.  As the rotor rises, it will loose mechanical energy of
rotation and slow down until its weight balances the magnetic lift.
Conversely if it falls, gravitational potential energy increases the 
speed increasing the mangetic lift.  Thus the rotor should leviatate
stably at a fixed height.  To raise it spin the rotor faster, to
lower it decrease the spin rate.  [This reminds me not only on
Dick Tracy's space coupe, but of the levitation devices described by
Heinlein in _Door into Summer_ Don't worry how they work, just
absorb the engineering properties and use them.]

Lots of problems of engineering problems of course, probably need
counterotating pairs to counter torque reactions. There would be
difficulties in handling the varying direction of the geomagnetic
field.  How do you start the rotor: rotate then cool or cool then
rotate? etc. etc.

More seriously, could it work?  Is there a clever superconducting rotor 
design that losslessly converts angular rotation into magnetic lift?
Given the in-principle possiblity of such a rotor, could one built
out of realistic materials be rotated fast enough to generate useful lift
in the earth's magnetic field?  If these devices were practicle and
came into general use, would they cause some environemntal catastrophe
like reversing the earth's magnetic field :-)?
 
I'm not sure about how to answer these questions.  Given indefinitely
large currents in the rotor, the answer would seem to be yes.  But
maybe I'm missing something. 
--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
(407)658-5030, FAX: (407)658-5059, clarke@acme.ucf.edu