I've been reading about the Meissner Effect produced by superconducting
materials. As I understand the phenomenom, a magnet will remain
suspended (levitated) over a disk of superconducting material due to
the generation of a "mirror image" of the magnet's magnetic field in
the superconductor and it will remain in place (it won't slide off to
one side or the other) due to "flux pinning" - something which I only
vaguely understand.

I'm wondering if the opposite effect also applies - that is, would a
superconductor remain suspended in a magnetic field? I'm sure you all
see where I'm going with this, and I'm sure I'm not the first to
speculate about the space launch possibilities this effect might
provide. I'm also sure there are very good reasons why this effect is
impractical or impossible to use for spacecraft levitation. If this
were not so someone would already be doing it.

So, at the risk of sounding really dumb, I'd like to invite anyone's
comments on the possibility that a spacecraft could be encased in a
film of supercooled superconducting material and "launched" at the
magnetic North pole somewhere in Canada. Would it just levitate itself
a few inches off the ground? Would anything happen at all?

Chris

On 6/9/07, Chris Smyth wrote:
(...)
> I'm wondering if the opposite effect also applies - that is, would a
> superconductor remain suspended in a magnetic field?

Generally, yes. More specifically, a superconductor will nullify an
incoming magnetic field by generating an opposite field. It is akin to
the levitation of a magnet over another, provided that the same poles
are kept facing each other...

Of course the repulsion may not be enough to provide levitation, if
the magnetic field is too weak or if the superconductor is attached to
a large weight.

(...)
> So, at the risk of sounding really dumb, I'd like to invite anyone's
> comments on the possibility that a spacecraft could be encased in a
> film of supercooled superconducting material and "launched" at the
> magnetic North pole somewhere in Canada. Would it just levitate itself
> a few inches off the ground? Would anything happen at all?
(...)

The magnetic field of Earth is too weak to provide levitation by a
"passive" means like superconductor repulsion, I think. However, one
can imagine a "magnetic ship" that would *actively* provide a absurdly
strong magnetic field that would interact with Earth's field and push
the ship upwards. However, I would think that making such a ship would
be daunting for our current tech, given energy requirements, problems
intrinsic to super-strong mag fields, and so on.