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by young_hopper 2037 days ago
I wonder how the efficacy of these laser-powered weapons systems is affected by how reflective the target is. It'd be a bummer if the military spent millions on this only to be foiled by a glossy paint finish.
6 comments

Reflectivity of the target doesn’t matter. The specified power levels are high enough by design that a reflective surface will instantly be converted into plasma.

Even if you covered the target in dielectric mirrors specifically engineered for the wavelength of the laser, assuming such a thing was even feasible on a cost, weight, and functional basis for the target, you would have to keep them spotlessly clean in an operational military environment for them to be effective — an impossible task.

Hence why the military doesn’t concern itself with shiny targets. At the power levels they target, nothing real can be sufficiently shiny as a matter of practical physics.

I’ve seen videos from guys building laser equipment and supposedly a powerful enough laser can punch through typical mirrors and specialized ones are required.
Reflectivity doesn't matter in practice. No finish is sufficiently reflective and so the first part of the laser pulse burns it off and then the rest of the pulse gets through.

An ablative heat shield can be more effective, although that adds weight and interferes with sensors. Spinning the target can also help a little by spreading the heat across a wider surface area.

What about shooting out a gas that’s dark in infrared between yourself and the laser?
Nope, same issue, it would absorb the energy and turn into a very low density plasma, blocking nothing. That is equivalent to very weak ablation shielding.

In fact, using a high-power laser to punch a hole in the atmosphere, essentially creating a functional vacuum by superheating the atmosphere in the beam path, is an old school engineering trick for exotic systems. Though in those cases, they tune the laser so that it gets absorbed by the atmosphere (similar to the gas you are suggesting). The use case is roughly analogous to employing supercavitation on torpedos.

Where can I read up more on such applications?
Here's a YouTube video of a 500W laser cutting mirrors without any difficulty: https://www.youtube.com/watch?v=p-VlVmBZGI4
I'm guessing the most effective anti-drone weapons are more akin to narrow beam EMP than thermal lasers.

Less because of any sort of reflective countermeasure and more because it takes way less power and precision to attack the delicate integrated electronics within a drone then it does it attack it's physical integrity.

if you're very reflective then the old technologies can do their thing. e.g. anything with a radar