Linear Induction Coilgun with superconducting projectile

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Discussion Overview

The discussion revolves around the behavior of a linear induction coilgun that utilizes a superconducting projectile. Participants explore the thermal effects on the superconducting wire and other materials within the projectile when subjected to high-frequency AC currents and strong magnetic fields. The context includes theoretical considerations of superconductivity, eddy currents, and the Meissner effect.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the superconducting wire will not heat up due to the absence of resistance in a superconductor.
  • Others argue that if the superconductor is subjected to a strong magnetic field, it may quench, leading to rapid heating and potential hazards.
  • One participant notes the importance of the environment, questioning whether the coilgun operates in air or vacuum, which affects thermal insulation and heating.
  • A later reply clarifies that the scenario is in a vacuum, with a very short transit time for the projectile.
  • Some participants inquire about the possibility of inducing eddy currents in a superconductor and whether this would lead to heating.
  • Another participant explains that the Meissner effect prevents the induction of currents inside the superconductor, asserting that any induced current would only occur on the surface, thus not generating heat within the superconductor.
  • It is mentioned that if a superconductor were to heat up, it would lose its superconducting properties and behave as a resistor, altering the scenario significantly.

Areas of Agreement / Disagreement

Participants express differing views on whether eddy currents can be induced in a superconductor and the implications for heating. There is no consensus on the thermal behavior of the superconducting projectile under the described conditions.

Contextual Notes

The discussion includes assumptions about the ideal behavior of superconductors and the specific type of superconductor (Niobium-titanium, Type II). Limitations regarding the practical application of these ideas in real-world scenarios are acknowledged but not resolved.

Treva31
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If you have:
A Linear Induction Coilgun, basically like a series of Induction Furnaces, using copper coils with high AC current at a high frequency.
Where the projectile traveling inside those coils has a shorted superconducting coil around the outside of it, embedded in the ceramic projectile casing.

A) Will the projectiles superconducting wire get hot?
I would assume not since there is no resistance.
B) Will metallic components or distilled water inside the projectile (within the superconducting coil) get currents induced in them or get hot?
I would assume not since the superconducting coil is shielding them like a Faraday cage.

See attached image.
 

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Assuming this is a made up idealized problem and we're not trying to find new and wonderful ways of hurting each other, the super conductor should expel any applied field, no field no heat. If it is a real question then the superconductor would rapidly quench in the applied field. The resulting fireball would expand rapidly so be sure to duck.
 
The OP does not say if the gun is in air or in a vacuum. If air, the superconductor needs very good insulation to avoid warming by the friction heated air.
 
Sorry it is in a vacuum.
Pre-cooled and transit through the barrel is less than a second.
 
No answers?
Put more simply:

If you induce eddy currents in a superconductor using a strong magnetic field, does the superconductor heat up at all?
 
Last edited:
Or can you not really induce eddy currents due to the Meissner effect??

It would be a Niobium-titanium superconductor by the way, so that is Type II.
 
Last edited:
Treva31 said:
No answers?
Put more simply:

If you induce eddy currents in a superconductor using a strong magnetic field, does the superconductor heat up at all?
Sorry, I didn't realize this was a test. The reply I gave is still correct.
 
Treva31 said:
If you induce eddy currents in a superconductor using a strong magnetic field, does the superconductor heat up at all?
The surface of a superconductor is a perfect reflector of magnetic fields. A current will flow on the surface of the superconductor that generates the exactly equal and opposite magnetic field needed to cancel the incident field. So you cannot use a magnetic field to induce a current inside a superconductor, only a current on the surface.
There will be physical forces between the magnet conductor and superconductor resulting from the magnetic field. If movement occurs then electrical energy will be converted to kinetic or potential energy, but not to heat in the superconductor.
Since no energy enters the superconductor it will not be heated. If a superconductor was heated it would become a resistor and the scenario would change instantly.
 
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Got it, thanks guys.
 

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