Laser Death-Ray Countermeasures

When I was a kid, years and years and years ago – we’re talking very early 1990s, here – I played a ‘Buck Rogers’ sci-fi computer RPG for DOS, probably “Countdown to Doomsday”.

One of the few things I still remember about the game was that it featured a huge variety of weapons which you could equip your characters with, including laser weapons, which were relatively effective… unless you were fighting robots or cyborgs or something like that, as they had polished, mirrored surfaces that would reflect your laser fire. (I don’t recall if it went back at you, or in a random direction, but it didn’t damage what you were shooting at, anyway.)

Despite being a sci-fi game, as far as I can tell, the science there seemed pretty good – laser weapon plus a (say) 98% reflectivity surface is probably going to be interesting. There will be substantial heating, but that’s better than being vaporized… and on a large vehicle, possibly much less of a problem.

The real-world applicability of this is probably somewhat lacking, however.

Don’t get me wrong, a heavy battle tank covered in mirrors would be pretty seriously badass – hello, Disco Ball of Death! – but the camouflage implications are probably a bit detrimental. (Probably not a good sign when, on a clear day, your vehicles can be seen from a hundred miles away.) That got me to wondering if there was, in fact, a way to effectively protect, you know, giant war machines from laser death rays.

After a fun hour or two of insomnia, I come up with an idea that seemed to not completely suck.

The first idea was to basically mirror the surface of whatever you’d like to protect, then… cover it with something that would provide camouflage properties while not doing particularly bad things when hit by a laser death ray. I had all kinds of improbable ideas, like camouflage paints that vaporize at low temperatures, so they’d burn off and immediately expose the mirror underneath, but that seemed silly, high-maintenance, and unlikely to actually work.

But then, I thought – suppose you had a Mirror Tank that didn’t have a perfectly flat planar contour, but that had little polished convex nubbins sticking out (concave surfaces on something designed to be hit by a Death Ray seem like a bad idea) – little domed bits, kind of like rivet heads – over the top of which were laid very thin (like, inner-tube thickness) sheets of self-extinguishing rubber? (Produced in your camouflage colour or pattern of choice, of course.) Death ray hits rubber, burns through it like a hot knife through butter, then hits the mirror a half-inch beyond, and reflects off, burning through the rubber again.

Heat? I didn’t really feel like doing the math, which I’m not very good at, but let’s suppose you have a 95% reflective surface that’s hit by a crazy powerful 10MW (!) laser-death-ray-of-the-future on a real-world battlefield – one where smoke and dust and atmospheric conditions cut it’s effective energy by 10% – with a five-second burst. Imparted energy to the target? 450 kilowatts. 450 kilowatts * 5 seconds = 2,250 kilowatt-seconds, or 2.25 mega-joules.

Rounding off, the turret of an Abrams tank weighs (well over) 20,000 kilograms, i.e. twenty-million grams. Let’s pretend for the sake of convenience that the turret of a Mirror Tank is the same weight, cast from an alloy whose heat capacity is 0.5 thingamajiggies per whatsit (I can’t be arsed to work out the HTML markup to do scientific notation, sorry) – between that of pure iron and pure aluminum. Assuming that the random calculator I found online is correct, the temperature of that turret, overall, is going to rise around 23 degrees C, which seems… not-insurmountable. Until they shoot you a second time…

So, okay, no Mirror Tanks anytime soon, then. Bummer. On the plus side, we may never see a mobile 10MW laser in our lifetimes, so the future of warfare is still probably anybody’s guess. 🙂

Published in: Geekiness, General | on February 10th, 2011| 2 Comments »

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  1. On 2/11/2011 at 2:25 pm Jfraser Said:

    If you look at some of the comments regarding the Boeing YAL-1, it seems that the military is not so concerned with mirrored surfaces on ICBMs. Imparting that amount of energy in such a short period of time is not likely to heat up the entire structure (due to heat transfer within the materials) as stated in the tank example, but rather to act more like a miniature explosion at the point of focus as the metal boils and begins to ablate.

    Then you run into tradeoffs of weight vs. thickness of reflective material (even the best reflective surfaces are ~97% reflective, and in a dusty environment such as the battlefield this will go down), and I’m sure that if all these tanks suddenly started trading armor plate thickness for reflective armor thickness we would go back to traditional rounds… In fact a small round to damage the reflective coating followed by a laser strike seems like the next step in the arms race brought on by this new armor system. I’m very skeptical that these laser systems can be brought down to a reasonable size for battlefield use in the next few decades, so testing may have to wait 🙂

  2. On 2/12/2011 at 8:44 pm Nemo Said:

    Yeah, everything I’ve seen to date has suggested that the military sees lasers as a sort of surgical strategic weapon, rather than tactical – melt a power transformer in an urban area, say, while minimizing collateral damage, rather than taking on armor on the battlefield, or whatever.

    As to traditional rounds, I wouldn’t be surprised if completely inert kinetic rounds became increasingly important. The USN is real hung-ho about their hypervelocity railgun, and I wouldn’t be real surprised if that basic idea became real widespread – instead of using fancy HEAPI rounds and so on, just pound targets with 10kg alloy rounds traveling at 2.5Km/sec. Doesn’t really matter if you punch through all that high-tech armor, if you squeeze bend one side of the target against the other… 🙂