<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>wnkrshm</author><text>Since atmopsheric transmission windows dictate which kind of wavelengths you&amp;#x27;d use for a laser weapon and which kinds of wavelengths can efficiently be created, multilayer coatings could conceivably reflect a lot of incoming power. In the 90s, the US DoD asked for &amp;#x27;laser armor&amp;#x27; and got photonic crystal structures (1-d multilayer) that omnidirectionally reflect  [1]. Further details about this are also available in the book &amp;quot;Photonic Crystals&amp;quot; (preprint for free here [2]).&lt;p&gt;What is probably way easier though (and actually survives launch and particles hitting it and is already proven in practice) is to use ablative heat shields on missiles. The materials available are already optimized for mass vs. effectiveness due to the engineering constraints in space flight. Missile optics would probably need to be coated though or distributed.&lt;p&gt;[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.osapublishing.org&amp;#x2F;ol&amp;#x2F;abstract.cfm?uri=ol-23-20-1573&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.osapublishing.org&amp;#x2F;ol&amp;#x2F;abstract.cfm?uri=ol-23-20-1...&lt;/a&gt;
[2] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;ab-initio.mit.edu&amp;#x2F;book&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;ab-initio.mit.edu&amp;#x2F;book&amp;#x2F;&lt;/a&gt;</text><parent_chain><item><author>thaumaturgy</author><text>No, it doesn&amp;#x27;t work like that. The military is of course tight-lipped about exactly how powerful SHiELD is, but at least one site claims that the goal is 50kw [1]. That&amp;#x27;s a lot of power. A few years ago, a 30kw laser test made the rounds in news outlets for destroying a few targets during testing. [2]&lt;p&gt;Mirrors don&amp;#x27;t perfectly reflect light in all frequencies. Mirrors are designed to reflect mostly visible light, lasers at this power level are infrared. Any imperfections in the reflective surface would immediately heat up, damaging the reflective surface, which would then heat up even more. And even if it were perfect, and were designed to reflect whatever frequency of radiation the laser&amp;#x27;s putting out, it&amp;#x27;s still not going to reflect 100% of the laser&amp;#x27;s output, and you&amp;#x27;ve probably got yourself a material that&amp;#x27;s pretty impractical for a rocket.&lt;p&gt;[1]: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2018-03-air-fighter-mounted-laser-summer.html&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2018-03-air-fighter-mounted-laser-summ...&lt;/a&gt;&lt;p&gt;[2]: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;newatlas.com&amp;#x2F;lockheed-martin-laser-truck&amp;#x2F;36377&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;newatlas.com&amp;#x2F;lockheed-martin-laser-truck&amp;#x2F;36377&amp;#x2F;&lt;/a&gt;</text></item><item><author>gingabriska</author><text>Don&amp;#x27;t we simply need a missile covered with mirrors to defy these lasers?&lt;p&gt;It&amp;#x27;s just a light bean albeit concentrated one, how hard can it be to deflect it?&lt;p&gt;Edit: don&amp;#x27;t understand the downvoting, please enlighten. Your wisdom is not obvious to me. Thanks</text></item></parent_chain></comment><story><title>U.S. Air Force has shot down multiple air-launched missiles in a test</title><url>https://www.thedrive.com/the-war-zone/27795/the-air-force-just-shot-down-multiple-missiles-with-a-laser-destined-for-fighter-aircraft</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>Retric</author><text>50kw is actually not that powerful in terms of lasers.  Petawatt systems are being built.  The real question is how how much power you can deliver to a target.&lt;p&gt;In that context rotating reflective missiles make this much harder as does slightly thicker casings.  Anything you deploy optimized for today’s missiles is easy to design around, so you need to design for countermeasures.</text><parent_chain><item><author>thaumaturgy</author><text>No, it doesn&amp;#x27;t work like that. The military is of course tight-lipped about exactly how powerful SHiELD is, but at least one site claims that the goal is 50kw [1]. That&amp;#x27;s a lot of power. A few years ago, a 30kw laser test made the rounds in news outlets for destroying a few targets during testing. [2]&lt;p&gt;Mirrors don&amp;#x27;t perfectly reflect light in all frequencies. Mirrors are designed to reflect mostly visible light, lasers at this power level are infrared. Any imperfections in the reflective surface would immediately heat up, damaging the reflective surface, which would then heat up even more. And even if it were perfect, and were designed to reflect whatever frequency of radiation the laser&amp;#x27;s putting out, it&amp;#x27;s still not going to reflect 100% of the laser&amp;#x27;s output, and you&amp;#x27;ve probably got yourself a material that&amp;#x27;s pretty impractical for a rocket.&lt;p&gt;[1]: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2018-03-air-fighter-mounted-laser-summer.html&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;phys.org&amp;#x2F;news&amp;#x2F;2018-03-air-fighter-mounted-laser-summ...&lt;/a&gt;&lt;p&gt;[2]: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;newatlas.com&amp;#x2F;lockheed-martin-laser-truck&amp;#x2F;36377&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;newatlas.com&amp;#x2F;lockheed-martin-laser-truck&amp;#x2F;36377&amp;#x2F;&lt;/a&gt;</text></item><item><author>gingabriska</author><text>Don&amp;#x27;t we simply need a missile covered with mirrors to defy these lasers?&lt;p&gt;It&amp;#x27;s just a light bean albeit concentrated one, how hard can it be to deflect it?&lt;p&gt;Edit: don&amp;#x27;t understand the downvoting, please enlighten. Your wisdom is not obvious to me. Thanks</text></item></parent_chain></comment><story><title>U.S. Air Force has shot down multiple air-launched missiles in a test</title><url>https://www.thedrive.com/the-war-zone/27795/the-air-force-just-shot-down-multiple-missiles-with-a-laser-destined-for-fighter-aircraft</url></story>