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In my story, people use handheld, high-power laser rifles, however, there was a problem with the weapon's concept:

Laser beams begin to cause plasma breakdown in the atmosphere at energy densities of around one megajoule per cubic centimetre. This effect, called "blooming," causes the laser to defocus and disperse energy into the surrounding air. Blooming can be more severe if there is fog, smoke, or dust in the air.

This both reduces the power and the efficiency of the weapon, and destroy its "invisibility".

The answer would be electrolasers, but what if the target is/is in a Faraday Cage?

I'm interested in whether is there a way to somehow, force the created plasma into the target without messing up the laser itself, thus cleaning the laser's path a bit, and dealing further damage to the target.

The method should work on 100 meters at least and should use as few materials as possible. (considering that the weapon's main advantage is its seemingly infinite magazine)

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  • $\begingroup$ Use an x-ray laser $\endgroup$
    – Fl.pf.
    Commented Jun 16, 2017 at 11:43
  • $\begingroup$ @Fl.pf. For what? $\endgroup$
    – user33944
    Commented Jun 16, 2017 at 11:44
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    $\begingroup$ Uh... if your target IS a Faraday cage, then just rip it apart with bullets, I suppose. Unless there's a reason ballistic ordinance no longer works, it's reasonable to assume there'd be scenarios where older weapons are still needed... $\endgroup$
    – Isaac Kotlicky
    Commented Jun 16, 2017 at 12:03
  • $\begingroup$ @IsaacKotlicky Yes, I can use this, but still, somehow forcing plasma into the target seems to have a potential, at least for me. $\endgroup$
    – user33944
    Commented Jun 16, 2017 at 12:26
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    $\begingroup$ Please try to understand the phenomenon first. The laser beam ionizes the air alongside the direction of propagation; basically it creates a "tube" of ionized air, which defocuses the beam. It does not magically drag the ionized air towards the target. $\endgroup$
    – AlexP
    Commented Jun 16, 2017 at 13:35

3 Answers 3

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Electrolasers + Faraday cages

A Faraday cage is to electromagnetic weapons what a bullet-proof vest is to ballistic weapons: you just need a bigger gun.

If your electrolaser has no trouble turning air into plasma at 100m away, it will have no problem with your average blocks-cell-signal Faraday cage, it will just melt away whatever part of the cage you're shooting at and hit the target instead. It'll take some more energy, that's all.

The advantage of pelting a Faraday cage both with plasma and electric currrent: metals become much less conductive when heated, which in turn causes heat to be generated more efficiently. So if your gun can sustain a strong beam long enough, you'll get through.

How to stop your electrolaser?

There are some ways to counteract this: building your cage out of a material that is a very good thermal and electrical conductor (like silver or copper) which is sufficiently bulky to dissipate the energy. It would be best if it's very reflective as well (this leaves silver). Effective but expensive.

Another way to beat this is with water, especially flowing water. Water is great at absorbing energy and conducting (away) electricity. Just make sure everything is grounded properly.
Added bonus: if you're shooting too much energy at it, it'll turn into fog (after evaporating against the slightly cooler nearby air) and dissipate your laser beam. Effective and cheap.

So, the easiest defense against your electrolasers might be one of these:

High tech electrolaser defense structure

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  • $\begingroup$ I get it, but what about the efficiency of the weapon? Also, this is all cool, but I'm interested in forcing the plasma into the target from a distance. $\endgroup$
    – user33944
    Commented Jun 16, 2017 at 13:17
  • $\begingroup$ The laser makes the plasma wherever it goes, the plasma itself doesn't really move. $\endgroup$
    – Swier
    Commented Jun 16, 2017 at 13:20
  • $\begingroup$ And this is my problem. $\endgroup$
    – user33944
    Commented Jun 16, 2017 at 13:35
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So you want the Plasma to move? Then use The Magic of Magnetism.

A lot of science is devoted to the containment of plasma using magnetic fields. Turn that on its head and use magnetism to push the plasma along.

Use your mega handwavium laser fire, as it passes through the atmosphere, clouds, smoke, people, and other stuff, to create plasma. That plasma will just kind of sit there. Follow each laser blast with a magnetic pulse from the same weapon. Laser-pulse, laser-pulse...

This may not be very accurate because I cannot think of a way to make what amounts to an electromagnetic pulse and make it directional. You are really just giving the plasma a rough shove away from you, but plasma flopping around all over the place can't be healthy for the enemy. Also, unsheilded electronics in the area are going to be toasted, adding to the general chaos. Don't forget You are also using the Mega Laser to cause a lot of damage as well.

I'm not really sure what kind of effective range you would get. Folks better versed in physics might be able to help you there.

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    $\begingroup$ Paul, see today’s xkcd! Might care to link “magic of magnetism” ☺ $\endgroup$
    – JDługosz
    Commented Jun 16, 2017 at 14:18
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    $\begingroup$ @JDługosz i.e: Charged particle flow dynamics? $\endgroup$
    – user33944
    Commented Jun 16, 2017 at 14:22
  • $\begingroup$ @JDługosz, Randall Munroe is my hero! Link added to answer :) $\endgroup$
    – Paul TIKI
    Commented Jun 16, 2017 at 14:56
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Plasma is an ionised gas, so is electrically charged. As such, it is affected by magnetic fields, following field lines, so you can channel it that way. As static (or slowly varying) magnetic fields will penetrate Faraday Cages, you just need to generate a suitable one (e.g. one with the field lines pointing towards the target, with a sufficiently large domain so that the field lines haven't spread out by the time it reaches the target).

Of course, you'll have other issues (e.g. what to do with the plasma that flows back around to the other end of your magnetic apparatus, but that might not be an issue if the plasma has lost its energy (or has dissipated) by the time it gets there.

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