The Mighty Lasgun

Loopy here to help suss out something that’s been a hot-button issue of late. I was wondering about the actual feasibility of 100 brave Guardsmen of the implacable Astra Militarum taking out a tank with their Lasguns. After a few short Google searches, I have learned that it’s a lot more believable than you’d think.

It turns out that lasers are actually quite awful at killing people. Because of the nature of our bodies being made of, primarily, water, it takes about 50,000 joules of energy to kill a person with a laser. Some sources say you could use a weapon with an output as weak as a Kilowatt, but you’d have to shoot them right in the eye. At any rate, this is WAY more energy than a bullet requires. Of course, the reality of energy storage in the far future may mean that you can actually store more laser shots in a clip than bullets. But who knows what the reasons for using lasers are instead of the cheap and reliable bullet?

Who, indeed! You know as well as I do that there are things other than people that need to be shot at in the 41st Millennium. Things which lasers might be much better at killing. Things like… tanks!

Let’s continue with my assumption that a standard Lasgun’s output is about 50,000 joules, again, because it has to be able to kill your average human. In the game of Warhammer 40,000, a unit of 100 guardsmen could, at the maximum effective range of their lasguns, pump out 5,000,000 joules of energy into a tank. Of course, you need to concentrate all of that lasgun fire into a single spot on the tank in order to be effective. Well, that’s probably why you still need to roll to-hit when shooting the tank. Sure, you’re probably not gonna miss completely (it’s a TANK after all), but if your lasgun doesn’t add to the destructive power of the other lasguns, you’ve effectively “missed” the target.

So, we must acquiesce and reduce our destructive power by half in order to represent the Guardsman’s 4+ to hit: 2,500,000 joules.

1 ton of TNT produces the destructive power of 4,000,000,000 joules. That’s a lot of TNT, but we can calculate the destructive force of our barrage as being equal to about 1.25 pounds of dynamite.

Now, imagine that barrage at a range of 12″. Our damage output effectively doubles to 2.5 pounds of dynamite.

Add in a First Rank, Fire! Second Rank, Fire! and your destructive output increases to 5 pounds of dynamite. This is 10,000,000 joules being pulsed at a tank (and pulsing a laser works much better than a constant beam for whatever reason) in a very directed fashion. It’s not like an explosion near the tank… it’s being focused.

Oddly enough, 10 megajoules is a common energy output for modern anti-tank missiles with shaped charges.

So, 100 guardsmen hitting 200 times at their best range and orders will wound 33 times. A vehicle with a 2+ save takes 5 or 6 wounds and a vehicle with a 3+ save takes 11 wounds.

I don’t think this is too outrageous when you do the armchair math. This is also considering the output of the laser is probably better than I am assuming. I know I’ve read accounts where a lasgun has vaporised chest cavities and melted heads. Having said that, it’s always good to be conservative when calculating the real-world effects of fantastic magic and technology.

If any REAL physicists want to chime in, I’d love to hear your opinion/math.

And remember, Frontline Gaming sells gaming products at a discount, every day in their webcart!

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About adam Fasoldt

Loopy (Adam) has only been playing 40k since 2010, but is an active member of the community. He is a host of the Masters of the Forge podcast and also a moderator of the Independent Characters forums. He also belongs to gaming clubs at Grimfoe Games in East Greenbush, NY and Dirty Goblin Games in Queensbury, NY.

8 Responses to “The Mighty Lasgun”

  1. Threllen May 15, 2017 2:18 pm
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    I’m imagining a hundred guardsmen standing in a semi-circle in front of a tank all aiming about a meter in front of it. When their lasers cross beams they form one super laser that blows a hole in the tank.

    That sounds like totally realistic physics.

    • Beau May 15, 2017 4:27 pm
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      DON’T CROSS THE STREAMS!

    • Loopy May 16, 2017 6:16 am
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      Well, actually that’s exactly what happens when you focus light. It is additive.

  2. Greggor Bloodsing May 15, 2017 5:03 pm
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    If I recall correctly, las guns super heat up the water molecules or other some such stuff on surface of the target in a hyper split second, resulting in a small explosion, its why they don’t just stay on, but blink. That kinda of variable excitability is party why it can blow up a head or just bounce of a tank. In real life, if you super heat water super quick, it releases hydrogen and oxygen, both super nasty. but a steel plate? not so much. that’s why las guns have their infamous AP-. any sort of armor is effective if it is hit at all, but they still are super great in the grim dark world of giant meaty monsters.

    Its also why Las cannons are different and so good at melting through stuff. the laser focuses on the target and builds up to a beam with out the explosion. In real life that interference is the main reason why laser weapons lose power over range, expecting water molecules in the air. its considered a huge setback. so las cannons presumably figured that out, and lasguns exploit it to a good degree with multi lasers being the maximum example.

    not sure how nova cannons work though, and I’m pretty sure half of the bane blade cannons are just names with no fluff.

  3. Greggor Bloodsing May 15, 2017 5:04 pm
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    If I recall correctly, las guns super heat up the water molecules or other some such stuff on surface of the target in a hyper split second, resulting in a small explosion, its why they don’t just stay on, but blink. That kinda of variable excitability is partly why it can blow up a head or just bounce of a tank. In real life, if you super heat water super quick, it releases hydrogen and oxygen, both super nasty. but a steel plate? not so much. that’s why las guns have their infamous AP-. any sort of armor is effective if it is hit at all, but they still are super great in the grim dark world of giant meaty monsters.

    Its also why Las cannons are different and so good at melting through stuff. the laser focuses on the target and builds up to a beam with out the explosion. In real life that interference is the main reason why laser weapons lose power over range, expecting water molecules in the air. its considered a huge setback. so las cannons presumably figured that out, and lasguns exploit it to a good degree with multi lasers being the maximum example.

    not sure how nova cannons work though, and I’m pretty sure half of the bane blade cannons are just names with no fluff.

  4. winterman May 15, 2017 5:21 pm
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    Watch the final battle of Guardians of the Galaxy v2…there’s a part in there where I actually thought — Huh I can now see how lasguns take down land raiders 🙂

  5. WestRider May 15, 2017 6:06 pm
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    Pulsing the lasers is important because when they hit, they vapourize bits of the surface. If you just use a continuous beam, pretty quickly you’re mostly getting your energy dissipated or scattered by that vapour, and it can’t clear out because the particles are small enough that they can be sort of pushed back in by the force of the laser. Pulsing the beam gives the fraction of a second needed for that vapour to clear out so the next pulse is hitting the actual surface again.

  6. WestRider May 17, 2017 9:20 am
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    This seems relevant here: https://regimental-standard.com/2017/05/17/bring-it-down/