Laser weapons create lots of heat. Particle weapons even more so.

What use would having a rotating triple barrel on the end of a large vehicle mounted laser/particle cannon be?

  • The goal is to let the barrel cool, yet keep firing
  • There is no problem with excess heat elsewhere
  • Such exposed barrels act as heat sinks
  • Letting them cycle allows for continued usage without risk of melting the weapon emitter

Could this work? I know that a rotating solid projectile weapon isn't the best option thanks to jams and other mechanical problems, but aside from the rotating barrel unit, an energy weapon doesn't have moving parts.

I'm aware that other methods for cooling the weapon can and would exist in this case, yet am exploring other solutions to the problem.

  • $\begingroup$ You mean the energy is lost as heat inside the barrel how inefficient, you shouldn't allow the beam to contact with the barrel at all times use magnetic field as guide. $\endgroup$
    – user6760
    Commented Oct 3, 2015 at 8:09
  • $\begingroup$ Lasers can't be deflected by magnets though, only particles with charge. $\endgroup$
    – Giacomo
    Commented Oct 5, 2016 at 11:13

2 Answers 2


Yes, there could be a feasible mechanism for this, although it isn't necessarily for heat dissipation for whole lasing units (which could just be static and fired in alternation), but based around some pseudo-science of how the imagined laser mechanism works.

Two important parts of a laser mechanism:

  • A primary source of incoherent energy (often light energy). For powerful military lasers, these sources can be unfamiliar such as a chemical laser - i.e. a laser that uses up a limited supply of ammunition. The primary sources can be high power, short-duration flashes resulting in pulse lasers - and this is a common restriction at higher power ratings.

  • A lasing cavity. A unit which absorbs the primary source and re-emits it coherently.

If you set up your imagined weapon with the following restrictions:

  1. The lasing cavity component is very expensive, maybe also heavy and/or bulky, but robust and can operate more or less continuously in theory, provided the energy keeps coming in.
  2. The primary energy source needs to go through a charge/release cycle, and charging takes significant time.
    • The primary energy source may also need to cool after discharging to keep the mechanism within operating temperature.
  3. The primary energy source needs to be closely coupled to the lasing cavity when firing.
  4. The primary energy source needs to be closely coupled to a charging system to charge.

None of the above are unrealistic from a scientific point-of-view. It depends on the power requirements of the weapon - which is likely to be high, therefore options become restrictive and if you go beyond known technology you can invent/decide which apply within a science fiction world.

If you apply the above design restrictions, it may be worth having a central cavity surrounded by multiple primary sources that are used in turn. That doesn't guarantee that it makes sense to also physically rotate them - for projectile weapons this arrangement is often so that projectiles can share a firing mechanism and/or barrel, which has several benefits (such as saving weight)

However, this could lead to some mechanics which physically move the primary energy sources and for example, vent heat/air around a central barrel in rotation to assist cooling whilst a source is being charged, then move it back into place to couple with the lasing cavity. The advantage of such a set up would be more rapid firing, at lower cost than replicating the whole laser mechanism. In terms of physical appearance and sci-fi cool factor, the effect could be much the same as a rotating unit.

You could place one further restriction that would make a rotating system more viable:

  • The nature of the lasing cavity means that only one coupling point is practical between the energy source and itself. That would mean if you want to increase rate of fire, you would need to have each energy source charged up then moved into position in turn. Variations of rotating sources, belt-feed or other mechanisms could then look good for getting charged energy sources available quickly.

It doesn't translate.

First, in guns you do have the barrel part separable from trigger mechanism. With lasers your gain medium is inside your "barrel". You don't achieve anything by rotating your block of lasers, you can just as well fire each one once in n seconds.

Second, it's highly unlikely your combat lasers will be ok with an air cooling (if there is air around, that is). They'll require at least water cooling (and look like Maxim machine gun), or, more probably, some scifi non-corrosive more effective coolant. Rotating your block of lasers will make even less sense if they are liquid-cooled.

If you want to show some cool and rugged machinery, make your lasers use something like Gast gun scheme: twin lasers, but instead of reloading each other they push (heat expansion) coolant for each other in a closed scheme through some futuristic radiator.

  • $\begingroup$ If we assume the barrels are basically giant heat sinks that can disperse to normal levels after several seconds, would a rotating barrel still not work? $\endgroup$
    – Nonafel
    Commented Oct 3, 2015 at 1:28
  • $\begingroup$ In guns the barrel is part of the "gain médium" too, keeping the gas produced by the charge compressed and pushing the bullet $\endgroup$
    – SJuan76
    Commented Oct 3, 2015 at 9:09
  • $\begingroup$ In a firearm, some of the heat energy is expelled with the gas, and some comes out with the casing as well, so the analogy is very poor for electrical lasers (like the current US Navy 100kW weapon). A chemical laser (like the ones popular in the 1980's) could dump the heat with the expended chemicals, but some chemical lasers used toxic brews which would be dangerous for the user to be near. A laser weapon would need a radiator or a heat sink to deal with the excess heat energy. $\endgroup$
    – Thucydides
    Commented Oct 4, 2015 at 5:37

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