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.