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Superconductors will be a revolutionary enabling technology for many aspects of space construction. One such use is a magnetic field to protect a craft from solar activity, in the same manner that Earth is protected.

But interstellar space is filled with hydrogen atoms and dust, which are not charged particles.

A light-weight spacecraft will want to avoid massive shielding, but at speeds >10% c, the interstellar medium becomes a big hazard.

How can electric/magnetic shields be used in combination with other techniques to provide safe passage at speed? The problem with simply using an ionization laser shining ahead is the huge amount of energy expended.

Being a solar sail, can the launch laser help?

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  • $\begingroup$ Related: Real deflector shield $\endgroup$
    – Frostfyre
    Aug 17 '16 at 0:34
  • $\begingroup$ The accepted answer of real deflector shield notes «What about the non-magnetic and non-charged items? A magnetic field will not protect anyone in that case. Fear any missile made of ceramic, or a weak magnetic field producer!» as is my case with interstellar gas and dust. $\endgroup$
    – JDługosz
    Aug 17 '16 at 1:58
  • $\begingroup$ I only said it was related, since they're both questions about magnetism-based shielding. $\endgroup$
    – Frostfyre
    Aug 17 '16 at 3:19
  • $\begingroup$ Interstellar dust is affected by magnetic fields at least in some manner. link It's not a translation of the grains but alignment of their angluar momentum with the magnetic field. $\endgroup$
    – Smartybartfast
    Aug 18 '16 at 12:03
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I'm no physicist, so I will offer this as a springboard (or dart board) for smarter minds than my own...

Instead of using the superconductor's magnetic field itself to deflect approaching hydrogen atoms and dust, why not use it to hurl a spray of magnetically responsive atoms out in front of the ship. Those atoms (or whatever ity-bitty particle is most appropriate for the purpose) would act as really small anti-missle missles, knocking the non-magnetic particles out of the ship's path.

Then as the ship enters the location where the collisions have just occurred, another magnetic field can collect the now spent magnetic particles, draw them out of the way of the ship and prepare them for reuse against locations even further out front.

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  • $\begingroup$ I think I’ve heard this called “fountain” style shielding. $\endgroup$
    – JDługosz
    Aug 17 '16 at 3:46
  • $\begingroup$ I see two problems with this approach, 1. Supply of shield particles, yes they're small but you're going to need a lot of them and 2. Momentum transfer. Essentially what you have is an ion thruster pushing against your direction of motion. You'll have to fire an equivalent engine at the other end of your ship constantly, or slowly grind to a halt. $\endgroup$
    – Joseph Rogers
    Aug 25 '16 at 10:02
  • $\begingroup$ @JosephRogers, you are correct on both points. To solve your first point, I included a particle recycling system in the last paragraph. There would be losses but hopefully those would be offset by magnetic particles encountered along the way. As for the second point, the vessel is a solar sail presumably being fed by a planet sourced laser, so they can offset for the reverse thrust by sending more power tot the sail. $\endgroup$
    – Henry Taylor
    Aug 25 '16 at 14:57
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The magnetic shield is only going to be one component of a protective system for an interstellar (or even interplanetary) ship.

As you note, the magnetic field will repel charged particles but uncharged particles will slip through the field. A magnetic field might be useful for protecting a ship against uncharged particles if it is being used to shape and hold a cloud of plasma around the ship. A plasma generator onboard can be used to "inflate" the magnetic field (making it larger and covering a greater area, while incoming particles will interact with the plasma. Since the plasma will be moving at high speed relative to the particles, very small particles like dust will most likely be vapourized, and the energy might be sufficient to ionize the particles and allow the magnetic field to displace them.

This is something like a Mini-Magnetospheric Plasma Propulsion (M2P2) system except that instead of allowing solar wind to push the plasma bubble, it is "anchored" to the moving ship and being used to push particles out of the way.

Of course this only works for very tiny particles. The ship should still have a wake shield to absorb the impact of larger particles that slip through the magnetic field and plasma. IF the ship is moving at relativistic velocities, the problem is even molecules of hydrogen will be impacting with massive amounts of energy. The wake shield may have to be a solid or laminated mass of ice several metres thick.

If the ship is powered by a light sail, then the laser itself can be used to carve a path head of the ship. The beam simply has to be fired along the path of the ship (this can be done during the testing phase) and the energy will have the potential to push a good fraction of the dust and gas out of the way, prior to the launching of the ship itself.

So you will have a multiple set of tools for your ships protection: shining the launch laser ahead of the launch to clear a path, using a powerful magnetic field to move charged particles out of the way and hold a plasma shield in place, and a solid ice wake shield to absorb the impact of anything which gets past.

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    $\begingroup$ Two concerns. The M2P2 system might act as a Bussard brake. The launch laser might push the ship to a terminal velocity & for deceleration the M2P2 does the braking. "The wake shield may have to be a solid or laminated mass of ice several metres thick." Light sail vessels need extraordinary low mass per unit area ratios. While the laminated ice wake shield is intended for relativistic velocities, no light sail craft will be able to make it due to the excessive mass loading. $\endgroup$
    – a4android
    Aug 17 '16 at 5:21
  • $\begingroup$ Robert L Forward's conception of laser launchers for starships beamed terawatts of energy at the sail, and had the sail hundreds of kilometres in diameter. If you scale things up enough, you can do almost anything. On a more practical level, the wake shield could simply be treated as a separate spacecraft and accelerated separately with its own sail. $\endgroup$
    – Thucydides
    Aug 17 '16 at 19:22
  • $\begingroup$ My first thought was travel at lower velocities. Interesting alternative for the wake shield, but I'm not certain about the configuration of launching two spacecraft relative to the beamed-power. With terawatts to burn, that makes for lots of possiblities. $\endgroup$
    – a4android
    Aug 18 '16 at 5:47

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