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Comment by ExcelSaga | Hacker News Reader

Fiber lasers are part of the solution, but blooming in air, and from target ablation is still a problem. What we really need for “ray guns” are phased array lasers and/or FEL’s. Just pumping more energy through conventional optics will make the problems I mentioned worse, not better.

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ISTM "target ablation" might be the purpose of a ray gun? It sounds painful, anyway.

I’m having a hard time imagining what this kind of damage would be like. What would happen for instance if it were fired at a person’s head?

Blindness, 2nd and then 3rd degree burns. Think of it more like a heat ray, and you get the idea. Human heads don’t have the option of countermeasures though, such as ablative costing which dramatically increase blooming, while insulating the target. You need more than 100kw to either punch through that, or take advantage of non-linear effects.

At these energies it’s less about ablation and more about thermal effects on propellant and warhead assemblies. The problem is that coating a missile in a thin layer of something designed to ablate is a lot cheaper than building a laser to overcome those countermeasures.

Yes but all you need to do to the missile is perturb its flight or damage its steering fins causing it to miss - you don't need to blow it up.

Ballistic missiles often don't have steering fins, and are guided using thrust vectoring. Also, missile defence often has to take place in the terminal stage of flight (e.g. THAAD), where the missile is carried to its target by its momentum, as you can't station your defence system in your enemy's territory.

I was talking about PD (point defence) on the battle field where your not targeting ICBM's but RPG's, MANPADS and CPR rounds mortar's especially

Yes, to me these problem with laser weapons seem fundamental.

The thing which makes light interesting and useful is that it interacts so strongly with matter. So strongly in fact that they can be hugely affected by such things are air-density variations, fine particles in the air etc. So it seems the makers of anti-laser defences will always have options.

Bullets and bombs on the other hand have the "nice" property that they interact strongly with solid matter but fairly weakly with gasses. (Yes, it's more complicated than that).

Blooming could be partially compensated by using probing lasers and adaptive focusing optics such as in big astro telescopes.

Basically one uses a standard laser to determine air interference and then use rams to reform a semi-flexible mirror to compensate.

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