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This question already has an answer here:

I'm designing a futuristic combat of a sort. Currently I've figured that soldiers would still be firing slugs from guns by reason of mirror beats laser if lasers are too common.

So the question is: Would there be any reason to not equip soldiers with mirror armor if lasers were the majority weapon by far? Or do I need to think of something else?

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marked as duplicate by Mołot, sphennings, Aify, Vylix, L.Dutch Nov 4 '17 at 3:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ Why would you use lasers if mirrors work. Your premise is self defeating. $\endgroup$ – A. C. A. C. Nov 3 '17 at 19:12
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    $\begingroup$ If you question is really why would slug throwers still be a weapon of choice if lasers are common? perhaps you want to ask that directly. I think there are a lot of reasons that answer could be "yes" $\endgroup$ – P Chapman Nov 3 '17 at 19:24
  • $\begingroup$ Is multi-frequency lasers a concept in this future (if it was the only weapon, I'd hope so)? $\endgroup$ – Twelfth Nov 3 '17 at 20:36
  • $\begingroup$ Mirrors can melt, too. $\endgroup$ – Nic Hartley Nov 3 '17 at 20:52
  • $\begingroup$ Because carrying large mirrors around can be heavy and if they break, it's 7 years of bad luck per mirror broken, $\endgroup$ – Vincent Nov 3 '17 at 21:37

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Mirrors do not reflect every wavelength on the electromagnetic spectrum. Mirrors are designed to reflect the visual spectrum (350nm to 700nm) but there are lasers in a huge variety of wavelengths. As long as the laser is powerful enough you can destroy most things in it's way.

The word laser started as an acronym for "light amplification by stimulated emission of radiation". In modern usage, the term "light" includes electromagnetic radiation of any frequency, not only visible light, hence the terms infrared laser, ultraviolet laser, X-ray laser, gamma-ray laser, and so on. - Wikipedia

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    $\begingroup$ Yeah in terms of future rock paper scissors, it's not mirrors that beat lasers - it's smoke. $\endgroup$ – Tacroy Nov 3 '17 at 22:03
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    $\begingroup$ Additionally, no mirror perfectly reflects light. You can see the point where a laser pointer hits the glass on a mirror. If it were weapons-grade, it would end up heating the glass/mirror, which would end up causing it to be less reflective and less effective, etc. The benefits of a mirror would be momentary at best even against "ideal" wavelengths. $\endgroup$ – Andon Nov 4 '17 at 2:39
  • $\begingroup$ @Tacroy How is smoke supposed to stop lasers? You can hide your soldiers positions, but a laser is not gonna be stopped by smoke any more than a bullet is. It's not a laser pointer, it's a high energy LASER burning through dense matter. Smoke won't help at all to stop it. $\endgroup$ – ArtificialSoul Nov 4 '17 at 10:41
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Why would you use mirrors when you could use retro-reflectors?

Bicycle retro-reflectors

Unlike mirrors, which bounce the laser in some arbitrary direction, retro-reflectors always reflect it right back to the source. Needless to say, use this a few times, and you would find laser weapons highly unpopular.

In practical combat, there are enough material properties reasons to make these less popular in terms of armor.... that and the lack of directed energy weapons to date.

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    $\begingroup$ retro-reflectors always reflect it right back to the source? How? $\endgroup$ – Rolazaro Azeveires Nov 3 '17 at 22:03
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    $\begingroup$ @Rolazaro very specific arrangements of lenses and/or mirrors. E.g. these cats eyes (a thing on UK roads not actual eyes of a cat); en.m.wikipedia.org/wiki/Cat%27s_eye_(road). Looking at Cort''s image I think this case uses the open box of mirrors approach though $\endgroup$ – Richard Tingle Nov 3 '17 at 22:26
  • $\begingroup$ @RichardTingle: Quite interesting! Thanks. $\endgroup$ – Rolazaro Azeveires Nov 3 '17 at 22:39
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    $\begingroup$ @RolazaroAzeveires They are very fascinating. Smarter Every Day has an episode where they describe them and how they work. $\endgroup$ – Cort Ammon Nov 3 '17 at 23:10
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    $\begingroup$ The best thing about retroreflectors is that, if they're high enough quality, they don't need to be rigid. Safety vests (en.wikipedia.org/wiki/High-visibility_clothing) often incorporate strips of retroreflective material, so it may not be too much of a stretch to make entire garments out of the stuff. $\endgroup$ – DqwertyC Nov 3 '17 at 23:39
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The advantage of laser weaponry is not that it totally replaces projectile weapons but that it significantly cuts down on the amount of projectile ammo which you need to carry. In most modern (22nd century) firearms, the laser projector is the upper barrel and is used for the initial target assault. During that shot, if the weapon's visual systems detect that the target possesses reflective defenses, a 22 caliber projectile is automatically fired from the lower barrel along a similar attack vector (adjusted by the weapon's computer to account for distance, projectile weight, wind and humidity).

The effect of the supplemental projectile attack is to shatter the target's reflective defense, allowing subsequent laser fire to penetrate and terminate. Since the presence of functional, clean and properly configured reflective defense is relatively low in any real world combat scenario, the laser equipped commando only needs to carry a magazine or two of projectile ammo to be prepared for a week long active combat assignment.

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    $\begingroup$ magazine != clip $\endgroup$ – Jordan.J.D Nov 3 '17 at 20:25
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    $\begingroup$ Aiming from usual rifle is very different from targeting from laser. You have to take into account projectile speed, distance, in some cases wind and even humidity. Commando develops the habbit to correct aiming for years. So it could be difficult to accurate aiming in those rare cases. $\endgroup$ – ADS Nov 3 '17 at 20:34
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    $\begingroup$ also, why do you think the mirror armorm would be rare case? It's a question: reason to (not) equip soldiers with mirror $\endgroup$ – ADS Nov 3 '17 at 20:40
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    $\begingroup$ @Jordan.J.D, thanks! I have fixed the problem. $\endgroup$ – Henry Taylor Nov 3 '17 at 20:43
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    $\begingroup$ @ADS, I will make the computer attached to the weapon's vision system adjust the lower barrel to account for distance and projectile weight. Wind speed and humidity information could theoretically come from some sort of military wireless network, as adding atmospheric instruments to the weapon would negate the weight savings. $\endgroup$ – Henry Taylor Nov 3 '17 at 20:46
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I'm going to answer this from my experience with laser cutters.

Mirrors are used in laser cutters to transmit the laser from the source to the cutting head, so it is possible to reflect lasers.

As @ArtificialSoul mentioned, mirrors don't work with every wavelength, so you change the laser wavelength (ie: change the source radiation) and the person behind it is toast. Go from a CO2 laser to a solid state laser and you change wavelengths.

Dirty mirrors don't really works. As @PChapman suggested, mud, dirt, dust, or anything that sticks to the mirror is going to burn, which damages the mirror, decreasing it's effectiveness, causing the mirror itself to heat and then break. When this happens in a laser cutter, you get time to replace the mirror, since it stops cutting as easily. Clean the mirror, and you're back in business.

A dirty mirror could be prevented in certain instances by using hydrophobic materials, though.

Scratches and pitting in the mirror are not as bad as dirt (in some ways), but it still reduces the effectiveness of the mirror, causing heat, and eventual destruction. It also has the added detriment of being permanent.

Something that would work, to a limited extent, as a defense against lasers is a filter. Most laser cutters have a view screen to see your material being cut. This is usually a piece of glass or plastic that is treated or naturally filters out/absorbs the specific wavelength of the laser. Most of these materials absorb a large variety of wavelengths while many allow visible light through.

Acrylic is used as a view screen fairly often, because it absorbs the laser wavelengths naturally. This is the same reason it cuts so well on a laser cutter. Acrylic plastic can come in clear, without reducing it's laser absorbing capability. So, you can have a shield of acrylic, but it'll eventually be cut through, depending on the strength of the laser pointed at it.

Your soldiers can have their eyes protected from some indirect laser light by using the same type of laser goggles that people currently wear to protect themselves while laser cutting. Some of these are made with acrylic.

BTW, here's a link where you can get information about laser wavelengths and what kind of protection you need against them. It includes all kind of safety goggles, windows, and other documentation.

http://www.lasersafetyindustries.com/Selecting_Laser_Safety_Glasses_Goggles_and_Protection_s/55.htm

As an added bonus for you, polycarbonate, which also absorbs laser light effectively, is a material used as "bullet proof glass". Polycarb generally isn't used as laser cutter material due to it burning rather than vaporizing. It also comes in clear. You might be able to layer acrylic and polycarb together to get some sort of extra-strength laser and bullet proof material for shields and tank view ports.

With polycarb, the laser reaction is very visible, so you could use this as a way to locate where the laser is coming from, as most lasers are invisible to the human eye. Also, any laser strong enough to burn something from a significant distance is strong enough to make a person blind instantly. Even if the eye is left intact, the optical nerve will be destroyed. Anyone who gets a laser weapon shot across the face is simply, instantly, blind. Period.

A surgeon would have to replace the optical nerve to have even a chance of sight again. I don't know of any electronic devices available today bypass the optical nerve to restore sight to people or not, so that might be more research for you to do.

EDIT: I did some testing with the laser cutter I use, and here's the video: https://youtu.be/WkOQffTjsC8 .

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  • $\begingroup$ I believe this to be the best answer. $\endgroup$ – JBH Nov 3 '17 at 21:38
  • $\begingroup$ Unless you dye it, polycarbonate is only going to absorb frequencies near UV. $\endgroup$ – fectin Nov 4 '17 at 2:03
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As others have pointed out, maintenance would be an issue. Getting the armor to work effectively would take a lot of fine-tuning. That said, for any laser frequency there's probably a material that would work as a good mirror, even if it doesn't work as a mirror for the visible spectrum.

The main issue I can think of would be ricochet/reflection of the blast. A slight change in the angle that the laser comes in could mean a large change in the angle the laser goes out, especially if the mirrored armor is curved. This means that, while mirrored armor may (potentially) protect you, there's a lot more stray shots moving about unpredictably. The damage to the environment, innocent bystanders, and even allies could be a lot larger, and probably would outweigh the benefits of mirrored armor.

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Camouflage and Cost

It's a short answer Even if we have mirror armour that works on lasers. It might be too cost to make or maintain (is a mirror suit going to work covered in mud) and might be hard to get to work with camouflage.

Some things might be mirror armoured while others are not.

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Mirror armor may protect you from laser, but not from everything else. It also decrease your mobility, because any mirror armor is rigid, including glass mirror and metal armor.

Well, even if you use other kind of reflective material, there's an issue with environmental condition that may render the reflectiveness of your armor useless. One of the thing come up in my mind is mud and any other kind of liquid stain. If laser hits a stained part of your armor, it won't be reflected, but absorbed as heat. If there's a lot muddy areas on your armor, you'll be well done in, maybe 5 minutes?

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If you look for alternatives of mirror, you could think about fog generating equip.

Fog consist of liquid droplets/ice crystals. They are

  • Reflecting lihgt between them, effectively dispersing beam.
  • Consume energy, throwing up heat to the air.

Some pro and contra:

  • Attacker have to dispel fog before dealing damage to target
  • Fog could be the outer layer of armor. Soldiers could wear mirror plates or something else.
  • It's easy to see fog. Although it's hard to say is it soldier or false target
  • Fog could hinder own aiming and enemy detecting
  • Fog could consist of different particles, effective for different wavelengh

One approach is to keep surface of armor wet. Thin layer of liquid will go to the fog upon heating, i.e. when laser touch the armor. This is personal defence, activating on demand and without de-camouflaging.

Another is to use smoke grenades to cover whole battlefield. Maybe it's possible to create a smoke which would be transparent for ally vision/fire.


Mirrors have some disadvantages

  • they are heating up. Just add power and boil up target
  • they are unmasking soldier
  • they could lose effectiveness too easy. Just imagine mirror after soldier crawl on its belly dozen of meters.
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People are coming up with some delightful answers, but please consider the following:

Why would you refuse to equip any soldier with armor against the prevalent weapon?

It isn't just lasers, though each kind of weapon/armor has their pros and cons, but why wouldn't you do it at all?

Answer: because armor, all kinds of armor, have severe limitations. The most common is mobility. As armor increases, mobility decreases. This is the reason, of course, why armies are not simply 100% tanks. Because, despite the armor, tanks have poor mobility, poor flexibility, poor camouflage, etc.

Next question:

Lasers are used on the battlefield today, why don't we use mirrors today?

Answer: no matter how you try to hide them, mirrors are glaring beacons that can be seen with just sunlight from miles away.

But, let's give you a list of why no one in their right mind would wear mirrors to protect themselves against lasers.

  • Bounce The last thing you want to do is bounce the laser someplace else, especially an uncontrolled someplace else. You could set fire to the flora (here I am!), you could hit the guy next to you, or your supplies, or anything. The fact is, it's out of control, and one of the most demanding aspects of modern armor is bringing the situation back into your control.

  • Efficiency While a highly polished, stationary mirror is a very efficient way to reflect a laser, Steve Martin's mirrored jacket in Leap of Faith (follow the link I gave you above) demonstrates the problem with mirroring a uniform. If you use efficient ridged reflectors, there is space between them that is, well, regrettable in its weakness. If you try to mirror the cloth directly, the efficiency drops. As efficiency drops, thermal absorption increases, and the whole point of a laser is to deliver a whomping heap of thermal energy.

  • Visibility I've already mentioned that mirrors make you visible from miles away the moment the sun comes up. Anything you do to correct this will decrease the mirror's efficiency, leading to fried chicken.

  • Fragility There is almost always something fragile about mirrors. Made from glass, they're easy to shatter. Made from metal, they're easy to rip off the uniform. If the fabric itself is reflective, then it can be torn, or covered with dirt. It's very simple to render a mirror useless.

What is the purpose of armor, anyway?

Finally, it's worth remembering that the purpose of modern armor is NOT to keep the soldier from being injured. It is to keep the soldier alive. The cost of fixing a soldier is much lower than the cost of replacing he or she, but the cost of stopping all wounds is much higher than simply keeping the soldier alive. The economics of warfare are ruthless.

This is all especially true when you consider that mobility stops more wounds than flak jackets. Do you remember the 1997 North Hollywood Shootout?, where two men robbed a bank dressed in head-to-toe body armor? Yup, that armor stopped all the bullets. It also slowed the assailants down and stopped their escape. They won the battle, but they lost the war.

Ultimately, the reason your soldiers won't be dressed in mirrors is that it's cheaper to hide them (camouflage & mobility) than to protect them. Plan on your soldiers wearing ablative armor as flak jackets to keep them alive. But that's about it.

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You wouldn't wear mirrors because it would be easier to just use a specific type of gas to scatter the wavelength of light your opponents are using to shoot at you with.

The biggest issue with mirrors is that they're still made out of materials and therefor have material limits. It doesn't really matter if you're wearing mirrors if your opponents decide to attack you with lasers that can melt the material that the mirrors are made out of. This sounds like a really stupid point, but it's worth remembering that offensive options usually outpace defensive options. Also, if you're wearing a suit of mirrors you're probably screwed the first time someone decides to bring a big kinetic weapon to a light fight. If you can make lasers work well enough to replace guns, then you should have solved most of the issues involved in making hand held rail guns - the scifi kind, not the luxury gun kind.

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A laser is just a specific kind of maser. Adjust the wavelength of the maser weapon, and it'll eventually cut through anything. You'd need a kind of reflective device that can shift for reflection across different wavelengths.

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A few points:

  • mirror effectiveness is wavelength dependent
  • for optical or close to optical wavelengths, it is not hard to create an effective mirror
  • mirrors are not perfect but can reflect the vast proportion of the energy
  • with retro reflectors, the reflection goes straight back to the shooter
  • mirrors do have the downside of being easy to spot
  • even without retro reflectors, scattered energy is dangerous to all, especially in a confined space. See Banks' Consider Phlebas with the lasers inside the mirrored temple.

In reality I think this means lasers will struggle to be more effective than slugs.

I think the only angle is wavelength. You need the laser to hit a range of wavelengths such that no mirror can cover them all. Mirrors then become a liability due to visibility.

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  • $\begingroup$ "You need the laser to hit a range of wavelengths such that no mirror can cover them all". It's not only option. You could also have 2-3 types of lasers with different wavelength (green, ultraviolet, red). $\endgroup$ – ADS Nov 3 '17 at 22:51

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