superconductive lift

[kragon]

gotan idea for a rather useless propulsion system

from what ivesee a superconducting materiel can be 'locked' to a magnetic field bycooling it to very low temperatures where by it will resist beingpushed both towards and away from the magnetic source.

couldthis be used to provide fuel-less propulsion to an orbitingspacecraft by:

locking a super conductor to the earthsmagnetic field.

pushing the space craft up with a liner motor(assuming the magnet is locked vaguely in place) unlocking thesuperconductor.

then reversing the motor and pulling thesuperconductor up.

am I right in assuming that this wouldprovide a small force to a craft every time this is repeated?

anybody have any reasons as to why this is a stupid idea and i should stop daydreaming?

[Charzy]

When you unlock it it moves back down, which cancels out the moving up.

[sgt_flyer]

The earth magnetic field is not strong enough - and not uniform enough to have a serious effect on supraconductors

[Kermunist]

Your understanding of superconductors is close, but not quite right.

In some superconductors (called type II) magnetic flux can be locked in by cooling through the transition temperature. This doesn't mean however that they will stay the same distance from a magnetic source. It means that it will try to move (and rotate) towards a position where the magnetic field is the same as when it was cooled. When you cool it close to a magnet, or even better an array of magnets, the trapped flux has quite a complicated shape. So the superconductor will only really find a similar pattern in the same place as it was when it was cooled. The earth's magnetic field however is quite uniform, so there would be little or no force pushing it back to where it was cooled down. There would be a small force trying to rotate the superconductor to the same orientation though, so you could use it instead of reaction wheels. A big enough slab of superconductor would be rather heavy, so it's easier to use little electromagnets instead, these are known as magnetorquers.

There is a decent looking wikipedia article on magnetotorques, which might be interesting to you.

There is also a wikipedia article on flux pinning, but it is very wrong. So don't read it.

[K^2]

Kermunist gave a really good explanation. But what it honestly boils down to is that it'd be easier to just try and get "lift" out of Earth's magnetic field, and the field just isn't strong enough to support a structure capable of making use of it. It's like trying to build an airplane on the Moon - there is some ionized gas there to provide lift. Just nowhere near enough to lift anything heavy enough to have the sufficient wing area.

[Everten P.]

Dude, the geomagnetic field couldn't hold a superconductor alone; how could it lift a whole ship?

[kragon]

Thanks for the input guys ,got some good science and some amusing imagery from this

@ 440-Charzy

Pinning a superconductor in a strong enough magnetic field creates the equivalent of a physical link between the super conductor and the magnetic source, where force applied to the superconductor gets transferred to the magnet.

so if you ignore the superconductor the idea would just be a closed system flailing around in space.

however if the conditions of the magnetic field where correct such a device would still be flailing around however every time the superconductor is pinned and pushed towards the planet ,the planets magnetic field would push back providing an external force and give a small force away from the planet

@ 65491-Kermunist

Thanks for the explanation,i see now that a superconductor would have to move a very long distance from where it was pinned to create enough difference to provide any noticeable difference in field to create a force,which would be rather impractical to build into a spacecraft.would replicating the magnetic field arraignment of the earths magnetic field hundreds or thousands of kilometres higher with an electromagnet before pinning a superconductor work as a way of generating a sufficient difference to generate a force.

Thinking about this again the rate of change of the field is still the same regardless of where the superconductor was pinned so distance wouldn't be a factor in the force generated,just the amount of times such a system should need to be reset to provide a given force,if there where the ability for it to be given.

@ 59402-sgt_flyer

if the field is too uneven would it not be possible to pin a superconductor and use the rotation of the earth and in essence let the variations provide the difference to propel a craft. Although this whould only provide a acceleration if the craft was orbiting slower than the planet so I doubt the field would be of any real strength and variation at a distance where the orbit was still stable

@59422-K^2 105968-Everten P.

if your in a stable orbit well away from the upper reaches of the atmosphere,there really isn't too much to slow you down so it would only require very minor forces to accelerate a craft,I wasn't thinking of it as a (in atmosphere) flying pogo stick where it would have to overcome gravity although that would be more amusing

Edited July 25, 2014 by kragon

[Seret]

There is also a wikipedia article on flux pinning, but it is very wrong. So don't read it.

Get editing then! Sounds like it needs your help.