lasers

Supergreen

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“Why will we use green lasers for starwisp and light sail propulsion?

“Because stars aren’t green. Can’t be green, in fact, because a black-body spectrum that peaks in the green is broad enough that there’s plenty of other-colored light to make it not sum to green. That makes green the least stealthy color in space.

“So when you’re going to be shining a few hundred terawatts into someone else’s star system, a monochromatic 530 nm green is as good as it gets in letting them know up front that you aren’t trying to sneak something in on them.”

– Argil Medanis-ith-Medanis, Laserider Network

On Lasers

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So, I gather more’n a few laser fans are coming to visit these days, so just to save time, here’s the canonical reason that lasers are the ‘verse’s secondary weapons system, not its primary one:

(It turns out that this is really a recapitulation of points raised in Non-Standard Starship Scuffles, so if you’re already nodding along to that, you can more or less skip the rest. I’ll just hit a few high points.)

Lasers, for the most part, are useful weapons systems under many circumstances. (Obviously they have to be, given their use as point-defense; if you couldn’t get effective results from lasing a k-rod, they wouldn’t be used.) As mentioned elsewhere, you can get an effective result out of a laser weapon, due to collimation, up to around a light-second, which is the entirety of the inner engagement envelope, and as such every military starship mounts a passel of phased-array plasma lasers for point-defense, and larger classes cram in some broadside offensive lasers too.

You can actually collimate reasonably effective beams at rather longer distances than that, as the existence of starwisp tenders demonstrates – although they themselves are of little use for military purposes despite the incidents mentioned in that article, seeing as they shift angular vector and alter their focus with all the grace and speed of apatosauruses mating. One would, however, make a dandy generator for a laser web.

(Yes, they exist in the ‘verse, and have done ever since the Admiralty paid the Spaceflight Initiative to launch Sky-Shield, the homeworld’s first orbital defense grid, back in the day. Orbital defense grids remain their main military use, along with civilian beamed power.)

It’s just that the IN sees no particular point in paying in either cashy money or mass/volume budget for collimation to make them effective beyond the inner engagement envelope, because you aren’t going to hit any actively evading targets at that range anyway, golden BBs and spies having gotten you a copy of their drunkwalk algorithms aside, and kinetics/AKVs work better for the geometry games played in the outer envelope.

Here, though, is the spoiler in the deck where military lasers are concerned:

Thermal Superconductors.

(The laws of physics do permit them, I am assured, and local materials science is more than up to producing them.)

In up-to-date designs, starship armor is woven through with a dense mesh of the stuff, with wicking into big heat-sink tanks of thermal goo. This causes something of a problem for weaponized lasers, because it makes it ridiculously hard to create a hot spot that’ll vaporize – instead, you just add heat to the whole starship. Which is not useless by any means, if you can manage lots of repeated hits or keep a beam on target, because if you can pump enough heat into a starship, either it, the crew, or both, will go into thermal shutdown; but this is what lasers are for in ‘verse starship combat. If you want to blast things apart, you go for kinetics, because you can’t tank (sic) big lumps of baryons.

Of course, this defense has its limitations: a laser grid at short range can hit its target with enough power to overcome the armor and, indeed, to chop its target neatly into a pile of small cubes. But that’s for definitions of short range meaning “inside knife-fight range”, and any Flight Commander who let the range close that much without having his entire propulsion bus shot off first would be summarily cashiered for incompetence.

And that’s why lasers aren’t the primary or only weapons system around these parts.

 

The Range of Range

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“You will hear it said that lasers have ‘a pathetically low range’ and are ‘suitable only for point defense and the inner engagement envelope’. To put this statement into its proper context, one must understand the proper scale of starship engagements; i.e., that the pathetically low range in question is approximately a light-second, or to put it another way, that the enemy vessel must close to within a distance roughly equal to twenty-five diameters of your home planet before you can engage them with this notoriously short-ranged weapon.”

– The Dirtsider’s Guide to Interplanetary Warfare

Not For Kitchen Use

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At its simplest, a point-defense laser grid is a system of hundreds of meshed, phased-array, variable-frequency, plasma laser elements (on its parent starship, these are the glossy black domes speckling the hull), capable of outputting an arbitrary number of variable-power beams, limited only by the capacity of the controlling computer, along an equally arbitrary number of bearings.

In its most benign civilian application, the laser grid protects the hull against incoming mass, by vaporizing small particles entirely, and by causing outgassing of the surface elements of larger ones in such a way as to produce thrust sufficient to redirect their course – acting, in effect, as a portable laser broom. A standard military laser grid fulfils this function on a larger scale, vaporizing and redirecting incoming kinetic slugs using the same essential principle, while penetrating and disabling AKVs. Such a grid is typically able, in full-autonomic mode, to keep the volume of space within a dodeciad miles of the parent starship clear of all material objects not explicitly tagged by IFF as friendly.

A military-grade grid, of course, has certain other applications. One, for example, is serving to propel various otherwise-unguided packages by use of the grid to heat inert ablative propellant attached to them, functioning as the power element of a laser thermal drive. Another, less advertised, is that of dealing with enemy starships that have been disabled, but which decline to surrender and which do not possess any unusual value to be recovered by an opposed boarding action: specifically, a disabled starship within effective range of a laser point-defense grid can be conveniently sliced and diced into effectively-inert fist-sized cubes.

 

Birthday Present

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Peréä System, far orbit, 4016

“Now?”

“Okay, go ahead and open your eyes.”

“You got me a giant laser! Wait, where did you get me a giant laser? … And, um, why did you get me a giant laser?”

“In order: yes, the Laserider Network’s fire sale, and –”

“Fire sale?”

“Yeah. It hasn’t hit the public ‘weave yet, but word from the Deep Space Relay is that someone back Home has cracked the fittling problem and they’re sending us the necessary, so the interstellar light-sail network concept is dead in space. Helén Inuriannon is taking the news about as well as possible for someone whose reason for being here just took a long walk out a short airlock, but they’re in full close-it-out, sell-it-off mode already. I picked the main laser array up for a short song and a handful of considerations.”

“We have FTL now –  no, never mind, in a minute. So why do we – I – whichever want a giant laser?”

“Think of it less as a laser and more the prospect of being independently wealthy.”

“Right now I’m thinking of it less as an explanation and more the prospect of being annoyingly smug.”

“If they have FTL, we’ll be getting more colonists, more quickly. That means the ecotects are going to be even hungrier for metal than they are now. And that laser…”

“…is going to be a thousand sideritic asteroids smelted down and put on the market first.”

“So, you like it?”

“Be as smug as you want today, love.”

Giving Flak Some Flak

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Don't do this. Don't ever do this.

Don’t do this. Don’t ever do this.

There is one other small point to make, it occurs to me, regarding lasers and appropriate uses of same.

One of which is that the Imperial Navy, by and large, uses carefully targeted laser weapons for short-range point defense, the intent being to vaporize small projectiles, blind sensors, overheat close-in AKVs and send ’em into thermal shutdown (being small, they have precious little heat-dumping capacity, relying instead on avoiding being hit), and convince missile warheads (for those people who feel the need to use missile warheads, kinetic energy being plenty of fun on its own) to explode before they actually get to their target starship.

Some folks (the screenshot on the right is from Battlestar Galactica) are of the opinion that an even better way to do this would be good old-fashioned flak. Mount point-defense turrets on your ship, and fill space around you with enough projectiles that anything incoming gets shredded by those before reaching you.

What those folks forget is that Sir Isaac Newton is the deadliest son-of-a-bitch in space!, ’cause all those projectiles – all those clouds of projectiles – will keep moving, with all their kinetic energy, until they hit something, and ruin its day. If you’re lucky, that will be whatever poor bastard is next to you in the same formation, weapons and small craft you’re trying to use, or your own ship on some future occasion, and you’ll only manage to hurt yourself. If you’re unlucky, they’ll just carry merrily on hitting things completely unrelated to the original target at random and providing people with casus belli, atrocity fodder, and other reasons to whup your ass for the next ten thousand years or more.

Cleaning up the debris after a space battle to ensure this sort of thing doesn’t happen is already a giant pain in the ass (the kind that there’s even a dedicated class of fluffship – crewing which is generally thought to be the worst job in the IN – to handle) when all you have to worry about is hulks, spallation debris, ricochets and accidental misses, and such-like, without deliberately making the problem a million times worse by filling the sky with high-KE flak. You don’t fire anything without a firing solution attached to it. Here endeth the lesson.

Or, as Mass Effect 2 put it in a somewhat more pithy manner:

Trope-a-Day: Frickin’ Laser Beams

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Frickin’ Laser Beams: Invisible.  Recoilless.  Travel at the speed of light.  In short, just like actual frickin’ laser beams.

(See Energy Weapons and Kinetic Weapons Are Just Better for where they are used, and why they’re not usually considered the primary weapon set in the Eldraeverse, which I didn’t particularly feel like repeating right here.)

As a side note of things mentioned elsewhere on the defensive side, the chief purpose of lasers as ship-to-ship weapons is for pumping heat into the enemy. The defense against this is twofold: one, thermal superconductor (or, previously to the invention of this particular piece of exotic material, mere thermal-very-good-conductor-convector-etc.) plating to avoid localized hot spots heating up and exploding, and lots of goo of very high thermal heat capacity to dump heat into and then pump overboard. This doesn’t stop you from eventually having to heave to, extend your radiators, and quit the fight, but it does slow down getting to that point rather a lot. Similar plating to the former used in personal armor makes personal laser-arms, while not unuseful on the battlefield, certainly not the most useful thing which you can carry.

tl;dr They have their place in combat, but they’re not magically supreme on the field, and indeed are unlikely to be your primary weapons.

Also, while it would certainly be technologically possible to attach them to cyborg sharks, so far as I know, it’s never actually been done.

 

Trope-a-Day: Energy Weapons

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Energy Weapons: Present, even if by and large Kinetic Weapons Are Just Better and therefore much more used.  Lasers and grasers exist, despite their limitations, primarily as heat-pumping weapons, knife-fight range point defense, and as blinding lasers, as do electrolaser stunners/anti-machine weapons, with all their limitations of atmospheric composition and humidity.  Plasma lances exist too, although they only work at point-blank range, even in space, due to dissipation.  (And regular flamethrowers, of course.)  There are microwave heaters and other kinds of algetics.  And there are limited-use, short-range, vector-control based gravitic weapons (based off the tractor-pressor principle, either to yank, slam, or vibrate).

But for all that existing, it’s still the slugthrowers that see the most use.

Trope-a-Day: Kinetic Weapons Are Just Better

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Kinetic Weapons Are Just Better: For most things, yes.  It’s not that they don’t have perfectly functional energy weapons, or power cells which can manage the job – if you can run a mass driver that can get a flechette or slug up to a respectable fraction of the speed of light, yep, you can power a laser with it too, just fine.  Nor do energy weapons lack their place – lasers are a damn fine way of pumping heat into things, which is very handy in starship combat, for example, and electrolasers (fire the laser to ionize a path through the air to your target, then dump a lot of voltage down it) make excellent stunners and anti-machine weapons, and EMP weapons are also handy for the latter, if really hard on the infrastructure.  Blinding lasers are effective on at least many species and relatively humane.

But in practice, it’s a lot easier to solve the problems of making really awesome kinetic weapons than of dealing with beam dispersion (while you can do some cool blasting-shit-apart – not slicing it up – with a big laser or graser, you would generally prefer not to have to let it get that close), atmospheric humidity (a big problem for electrolasers), and other such things, and in some cases vulnerability that varies sharply by the precise way the energy is delivered, and suchlike.  So while energy weapons of various types are part of the arsenal, in the special uses for which they excel, the jack-of-all-trades weapons still Throw Stuff At You Really Damn Fast.