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Smells Great (mander.xyz)
submitted 11 months ago by to c/science_memes@mander.xyz
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[–] 19 points 11 months ago (10 children)

I think that wouldn't necessarily work once you get to the right wavelengths for it to start interacting with the organic bases of the paints. There's only so much you can do when someone shoots an infrared laser at the resonant frequency of a C=C double bond.

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  • [–] 7 points 11 months ago (4 children)

    Wasn't that 1500 whatever-the-unit-was? Below 1000 whatever-the-unit-was was the fingerprint bands, 3400ish whatever-the-unit-was was the O-H bonds, 3100ish whatever-the-unit-was was N-H bonds, 2900ish whatever-the-unit-was was the triple-to-C-H bonds, etc.

    Ugh. The lab portion for that was so tedious. We would have to sketch the expected resonance patterns by hand for a bunch of different molecules. I loved the simplicity of the hydrogen bond nuclear resonance imaging so much more.

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  • [–] 1 point 11 months ago (2 children)

    uh, frequency is Hz (hertz) unit to my memory. if that's what you're using

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  • [–] 4 points 11 months ago (2 children)

    chemist was my weak point at uni. and I'm too tired to look that up, what's the frequency. I want to check if there are materials that can reflect it.

    the coating doesn't have to be organic, a thin metallic coating might reflect the laser.

    I'm not giving an expert opinions. but I'm personally betting that any laser weapon will be useless within weeks or days.

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  • [–] 3 points 11 months ago* (last edited 11 months ago) (1 child)

    So, did a bit of research and, when you get to the scale of "a laser that can destroy objects", it turns out that the reflectance of natural materials is just utterly insufficient. Consider the following: suppose that a mirror finish reflects 90% of the light from a laser in the range you're looking at (a fair assumption, from what I've read). Now, let's do some basic back-of-the-napkin math: we'll use a 30 kW laser, which is apparently standard for current destructive laser weapons. Let's further assume that the laser light is spread over a surface area of 0.04 m^2 (because a spot 20 cm on a side seems to me a fairly high estimate for the spread on a precision laser, even on a moving target, if it's motion-tracked, I should think). Let us be generous and assume that this reflective paint coating is 0.5mm (0.0005m) thick. Given the paint's approximate specific heat of 2.302 J/gK (polyethylene) and density of 1400000 g/m^3 (PVC), and let's also assume the breakdown temp of the reflectance is near the boiling point of PVA (spray paint), which is 112C.

    So, the mass of paint absorbing the energy is 0.04*0.0005*1400000=28 g.

    To heat the entirety of these 28 g of this material by about 90C (from 22 to 112), completely destroying the protective layer, we would need 2.302*28*90 = 5801J

    Now we know that we have 30000*0.9= 3000J/s, so it would take about 2 seconds of lancing to completely destroy the protection. Given that it already takes 2-5 seconds to destroy things with the laser, and it doesn't actually have to destroy the entire area for the reflectance to deteriorate and let the laser through, this would only be adding another second of work. I think that, no matter what you do, the laser's gonna win.

    I can give sources for any of these estimates.

    You know the actual reason why these things aren't on every military vessel? The lasers stop working if there's fog, dust or rain

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  • [–] 1 point 11 months ago

    Thanks for the numbers. it seems that paint coat is a good shield but not perfect.

    I think monochromatic mirrors can reach 99.9% reflection.

    There will be a arms race between stronger lasers and thicker stronger laser protection.

    a silver coating on a water cool plate might be able to completely block a strong laser, but that might be too heavy for a drone.

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