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As a layman, I was shocked to learn that LASERs in real life are much more dangerous than Hollywood portrays. As I understand it, you can get permanent eye damage from a strong enough laser, even without looking directly into the beam's path.

Knowing this, as someone who likes to write Fiction, I find myself at a quandary. In order to have a laser weapon truly capable of slicing metal, for example, the wielder would need serious eye protection. Battles in space, with people shielded from exposure, might not be affected, but such constraints would seem to make ground combat with handheld devices very impractical.

Just about everyone likes how lasers look, myself included. But I also like to inject at least some realism into my work.

  • If I want to go down a more realistic path in weapons design, are there existing writing devices or explanations I can use to include high-powered lasers in atmospheric/ground combat situations that could pass for realism?

As I understand it, even the beam of a laser itself would be hard to see - if at all - in space, which was also quite disappointing to learn. It makes me wonder if such issue is the reason lasers are much less common than "Phasers" in Star Trek.

My instinct is to make up some fictional technology in arbitrary fashion, which is how I assume most Science Fiction explains this away, if the question is even posed. But I am a novice, and quite ignorant to the vastness of SciFi, so I would rather ask people who know a lot more about it. Thank you

Relevant video... "Laser Safety: Chapter 2 - Myths and Misconceptions of Lasers" https://www.youtube.com/watch?v=HvbXlx-WH9g

"Lasers in the Movies" http://laserstars.org/amateur/movies/myths.html

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    $\begingroup$ Most science fiction that I've read that tries to pass off high-power laser/maser weaponry in compact vehicles or devices typically use a high-energy-density power source. The power requirements to just melt (evaporate) through some metal are quite enormous. There's probably a good projectrho page for space-based laser combat. $\endgroup$
    – BMF
    Aug 14, 2020 at 23:22
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    $\begingroup$ Most science fiction that I've read doesn't bother to explain it at all. Handheld laser blasters are simply "futuristic guns"...flavor/scenery, with characteristics remarkably like current firearms. Since the gun isn't usually the center of the story, this is not surprising. Chekhov's Gun (no relation) dictates that if you make the reader learn all the new characteristics and power sources of the weapon, they must apply and benefit from that knowledge later in the story. Nobody wants to read a half-chapter of dead-end physics lecture, not even me. $\endgroup$
    – user535733
    Aug 14, 2020 at 23:49
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    $\begingroup$ "As I understand it, you can get permanent eye damage from a strong enough laser, even without looking directly into the beam's path." The explanation here seems to say the only danger to someone not in the direct path is from reflective surfaces that can bounce some of the beam back toward your eye. If you're shooting lasers in a place without much likelihood of it hitting a reflective surface, like a natural setting without water nearby, you might be safe from indirect dangers. $\endgroup$
    – Hypnosifl
    Aug 14, 2020 at 23:58
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    $\begingroup$ The nice thing about sci-fi tropes like lasers or plasma guns or orbital shuttles is that you don't have to explain them. Just say they exist and your audience - most of whom has a vague idea of these thing from other works - will fill in the blanks in their own time. As @user535733 says, stick to explaining what's unique and/or important to your world. $\endgroup$
    – Cadence
    Aug 15, 2020 at 0:26
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    $\begingroup$ To address your question, I'm sure there are many ways to explain and to make feasible high-power laser weaponry, but which of those explanations would best fit you? I can't quite figure out exactly what you're hunting for, other than a general info dump on prospective weapons-grade laser tech. $\endgroup$
    – BMF
    Aug 15, 2020 at 0:31

2 Answers 2

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The Good, the Bad, and the Ugly

Lasers are, indeed, uber cool. But it seems to me that people haven't used "lasers" (by specific name) in commercial fiction for a while. Am I wrong?

  • It's true that a low-power laser, one that won't even heat your fingertip, can blind you.

However... whether or not looking near the laser (some number of degrees off the axis of the beam) is damaging has more to do with the focusing optics and intent of the beam than it does the beam itself. A poorly focused beam spreads a lot of, shall we say, optical noise. A well-focused beam does not.

  • It's true that no laser of any wavelength is visible as a beam. If you think about it, no light at all is visible as a beam.

What you're actually seeing is reflections of that light off of dust, humidity, etc. (E.G., search lights.) The stronger the beam, the easier it is to see. In other words, you're seeing feral, uncontrolled photons that are no longer doing what they were expected to be doing — such as burning a hole in some deserving villain.

As the power level increases in an atmosphere what you could begin to see is plasma. That's hot, kinda burning gas. In a vacuum, you'd never see the beams. (Thanks for lying to us Hollywood!)

everyone likes how lasers look

What you mean by this is "everyone likes how Hollywood presents lasers." Hollywood doesn't reflect the truth of lasers at all. Hollywood (generally) presents a bright, easily seen, pulse. Nothing about that last sentence has anything to do with a laser — and that's the problem. If you want realism you're forced to walk away from what Hollywood's done to lasers completely.

And that's probably why I don't see a lot of scifi anymore that uses the word "laser" in the context of a weapon (or maybe I'm just not reading the right books). What I see more often is a cool Proper Noun (aka blaster, phaser, disruptor...) that means "energy weapon," and what "energy" that could be is left to the imagination of the reader/viewer. Personally, I like "death ray."

So, if you're trying to inject realism...

  • A laser "pulse" is complex. Think of it this way: you turn on the laser, count to ten, then turn it off. For there to be a "pulse" requires your enemy to be more than ten light-seconds away. That's more than 3,000,000 km distant. You can't see them. You can't detect them. But you shot at them. Yes, you could fire your laser for a micro-second (a 3 km pulse) or for a nano-second ( 3 meter pulse) or for a femto-second (3 mm pulse), but you also need to pack all the energy you need to damage your opponent into that smaller period. The math gets ugly. One watt = one joule per second. Let's say we want the Tsar Bomba in a femto-second laser. 240 peta-joules (240x1015) in a femto-second for a whalloping 240x10240 equivalent watts. (*cough*) Yup.

To be fair, I'm having fun overstating this. You're generating 240x1015 joules. Period. Tsar Bomba in a femtosecond. But it sounds fun the other way because it's a mega-Kardashev civilization type of thing. Sorry, I couldn't resist. But if you could turn that laser on for a full second... that's what you'd have... the luminosity of galaxies in a single one-second pulse.

  • A visibly traveling laser "pulse" is... well, it's laughable. Fun to watch! But laughable. Even if you fire your Tsar Bomba laser with a 3mm pulse, that pulse is traveling (in a vaccuum) the better part of 300,000 km/s. That means your target must be more than a light-second away to have any hope of actually seeing the pulse — which you couldn't anyway because you're in the vacuum of space (which isn't completely empty, but it mostly empty enough that I doubt you could see anything).

  • BTW, that second you're spending watching your pulse sail through the universe? Yup, your enemy is using that time to send something like 1015 pulses right back at you. While you were having fun watching a single pulse blow the nose of his ship off, he blew you up, vaporized your planet, and moved the timetable for your sun going supernova by a couple of eons.

I've always thought it was funny watching Han Solo slowly pulling the trigger and sending a couple of blasts at the approaching Storm Troopers. I mean, really! We've had Uzi technology for a while now! Just hold down the trigger, Han!

And just to make things interesting...

  • The battery/power-source needed to operate a death-level laser for any sensible period of ground combat time is, in this day and age, detrimental to the use of lasers in ground combat. However, if you use Clarkean magic to handwave the power source (see reasons to do this above), then you can use the same magic to handwave the optics, and the issue of blinding everyone within 10 meters of the target is a non-issue. Remember, feral photons are undesirable, they represent lower efficiency. Lower efficiency means you need a stronger power source to be sure a lethal dose of photonic wrath is dealt to your opponent.

  • And while we're on the subject of optics. The basic problem with photonic weapons is the need to focus. It's the difference between burning a hole clean through the villain and giving him (and everyone around him) a nice tan. All kinds of cool juju has been used to deal with the problem of having to focus the beam (my favorite is oil-lens optics, as if the laser wouldn't boil the oil...). If your laser carbine is focused to 250 meters, then the further away from 250 meters your opponent is (closer or more distant!) the more it's a nice tan and the less it is violent photonic death. Same problem with ships, just much, much worse.

  • Getting back to power generation, power generation on a ship is problematic, too. You must either have big mother-hubbard batteries that are breathtakingly dangerous to have around (what happens if their laser hits your battery before you can discharge your laser? Bad things...) or you need some form of magical power-on-demand, like chaining up a bunch of dynamos until you have peak power and then spinning them back down or some such. That could be cool, it means there's a measurable amount of time between shots (spinning up the chain). No more gatling lasers, but realism!

  • Lasers have two traditional nemeses — (1) ablative armor. Granted, ablative armor is kinda useless if your opponent can get a second shot off, but if it takes time to get to that second shot, then maybe the armor was worth it... and (2) people have suggested that mirrored armor could be good, too, but that depends on whether or not the mirroring material on the back of the proverbial glass can withstand the heat generated by photons that are not reflected. Theoretically, a perfect mirror (perfect mirroring and perfect glass) could reflect a laser of any power level. But, perfect's hard to achieve. My point is that it's not that hard to develop ways to avoid laser damage. I'm favoring squirting a million metric tons of sand between your ship and your opponent's. Your missiles will wreak havoc while your enemy is turning all that sand into glass. (Yeah, yeah, yeah... it's impractical to haul around millions of metric tons of sand. It's impractical to have all those batteries, too! Work with me, people!)

BTW, and not completely off the topic, the nature of lasing is that it can't really be done at radio wave frequencies — yet. I mean no one thought the inside of a light bulb could be frosted until Edison did it and no one thought a human could run a mile in less than four minutes until Sir Roger Bannister did it and the the mathematical band-aid known as "dark matter" is believed to be real by almost everyone under the age of 25 despite a total lack of non-mathematical evidence... My point is, I'm not a fan of "can't be done." Today's "can't be done" tends to become tomorrow's "eureka!" Therefore, I recommend you ignore reality and write a good story for which Hollywood would be willing to pay you beaucoup bucks. If the majority of book-buying people preferred reality, science fiction as a genre wouldn't exist. And in the end, you'll be laughing all the way to the bank while a handful of people still working 9-5 jobs grind their teeth and say, "lasers don't work that way!"

Edit: I wrote all that a long time ago, but I forgot to mention one important thing: someone's ability to see the laser in space is pretty darn impossible. It's not so bad when it's continuously on and in a medium (aka, filled with dust) that allows photons to become feral, but in the vacuum of space, it's a whole different matter. Light travels at, well, the speed of light! That means that the target would never see the beam. All they'd see is the result, hopefully a whole lot of burning metal. People on the death-sending ship (they that fired the laser) also wouldn't see anything unless a whole lot of feral photons were reflected backwards... in space.... People might see something (if there were enough dust to cause feral photons) as the beam passed — but it's just easier to understand that pretty much no one would see anything. Such is the nature of lasers.

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    $\begingroup$ Shields up, death rays to maximum! $\endgroup$
    – BMF
    Aug 15, 2020 at 10:48
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    $\begingroup$ Actually there are microwave frequency lasers (MASERS), and with a Free Electron Laser you can (within reason) adjust the output frequency to whatever you want. The big sticking points are the difficulties of focusing beams and aiming in these frequencies, and the very low conversion efficiencies to date - far more energy comes out as waste heat than "laser" energy. $\endgroup$
    – Thucydides
    Aug 15, 2020 at 20:15
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    $\begingroup$ FWIW, some settings actually have explanation for why 'lasers' look the way they do. Blasters in Star Wars are an example, they're actually plasma weapons per official lore (same for lightsabers, at least per the old 'legends' lore), and the color and light is the plasma fluorescing. $\endgroup$ Aug 16, 2020 at 0:26
  • $\begingroup$ YES DARK MATTER IS FAKE!!!!!!!!!! $\endgroup$
    – Rafael
    Oct 22, 2021 at 3:46
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You actually answered your own question:

My instinct is to make up some fictional technology in arbitrary fashion

Unless your story writing demands 100% rigid science compliance, you really don't need to justify laser weapons or even delve too deeply into how they work. If you write some kind of energy beam weapon fired from a gun-like device, your readers will simply assume that this is part of the technology of the fictional world they're delving into.

If your writing style would like to give a nod (and a wink) to realism, then you could very easily do this. You'd want to avoid the actual science (because we don't yet know how to pull off such a weapon), but you could address some of the issues that you bring up in your query.

For example: vision damage is a real thing with lasers. This is why serious laser users (medical field, science, and engineering) obtain the eye protection appropriate for the kind of laser they're using (one goggle does not defend against all lasers!). Some lasers are invisible; others produce extremely bright beams than can light up an entire room.

You could very easily provide your storm troopers with helmets that integrate a variety of eye shields. You could demonstrate your knowledge by integrating into the narrative some kind of error or malfunction -- maybe a new soldier taps the wrong button and brings down the wrong shield and is blinded. Maybe the commander orders his troops to bring down a certain shield, because the enemy are known to use weapons in that range, but surprise! The enemy has switched its own weapons' wavelength, now rendering our heroes vulnerable.

You could also develop weapons that, along with the destructive core beam, also emits a kind of shielding beam that eliminates the need for eye shielding. It might in some way cancel out or serve as a waveguide for the beam, at least close to. Anyone nearby can see the beam but be protected from vision damage. Farther away, the shielding might degrade, because, who cares whether your enemy's eyes are damaged or not!

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