Is this laser cannon really that big?

jacobmuller · 09-01-2010, 05:08 PM

Am I reading this right?
A Spaceships SM+14 Major battery Pulse Laser, in character terms, would be 6dx250 Cr Exp.
So, anyone standing less than a mile away from the "impact" is gonna want protection?
Explosion injury = Damage/(3xrange); 1 mile = 1,760 yards; average damage would mean 1 point of Cr Exp damage at 1,750 yards...

cf Beam laser = no collateral damage.

BlackLiger · 09-01-2010, 05:23 PM

Given that a PULSE laser is a pulsed weapon, it could splash, I suppose. I don't know the physics well enough. Might be a mistake though. Someone who owns a copy of UT rather than continually loaning a friends, confirm his numbers?

Kromm · 09-01-2010, 05:23 PM

Probably. That's flash-vaporizing (reducing to -10×HP) about 100 tons of solid matter. There's no believable way to do that without creating 100 tons of superheated gas leaving the impact point as a hypersonic shockwave. Based on the estimated velocity of the gas and the surface area of a man standing a mile away, that's the equivalent of a typical .25 ACP bullet. In GURPS terms, such a round does 1d pi-, averaging 1.75 HP of injury, so I'd say 1 point is in the right ballpark.

jacobmuller · 09-02-2010, 09:59 AM

Awesome! TQ.
Cue Independence Day scenes:)

Kraydak · 09-02-2010, 10:19 AM

Quote:

Originally Posted by Kromm

Probably. That's flash-vaporizing (reducing to -10×HP) about 100 tons of solid matter. There's no believable way to do that without creating 100 tons of superheated gas leaving the impact point as a hypersonic shockwave. Based on the estimated velocity of the gas and the surface area of a man standing a mile away, that's the equivalent of a typical .25 ACP bullet. In GURPS terms, such a round does 1d pi-, averaging 1.75 HP of injury, so I'd say 1 point is in the right ballpark.

One of the examples of why hp=mass^(1/3) doesn't really work well, especially if damage is supposed to scale with energy linearly.

Ejidoth · 09-02-2010, 10:24 AM

Quote:

Originally Posted by Kraydak

One of the examples of why hp=mass^(1/3) doesn't really work well, especially if damage is supposed to scale with energy linearly.

What? I thought this was a good example of GURPS and reality agreeing with each other pretty well.

Tyneras · 09-02-2010, 10:45 AM

At really high levels of energy, everything explodes.

Someone once asked what a sci-fi space laser cannon would look like when fired from orbit at the ground. The answer was like "the fist of God", imagine a nuclear explosion, only the "stalk" of the mushroom cloud goes up until the atmosphere ends. It would be spectacular to watch, assuming you weren't the target.

Also, damage doesn't scale with energy linearly, as I understand it, it scales with the square root of energy. so 1 damage = X energy, 2 damage = 4X energy, 12 damage = 144X energy, and so on.

Kraydak · 09-02-2010, 11:18 AM

Quote:

Originally Posted by Tyneras

At really high levels of energy, everything explodes.

Someone once asked what a sci-fi space laser cannon would look like when fired from orbit at the ground. The answer was like "the fist of God", imagine a nuclear explosion, only the "stalk" of the mushroom cloud goes up until the atmosphere ends. It would be spectacular to watch, assuming you weren't the target.

Also, damage doesn't scale with energy linearly, as I understand it, it scales with the square root of energy. so 1 damage = X energy, 2 damage = 4X energy, 12 damage = 144X energy, and so on.

I couldn't actually remember if it was Damage=E or D=E^(1/2), but either way, it scales wrong. Vaporizing stuff takes E=mass (chemical binding energy) or for large enough objects, which is relevant for lasers of this scale in space, E=mass^(5/3), the gravitational binding energy. It really bugs me when people use the mass^(1/3) to estimate the hp of the Earth, a mountain range or a large asteroid, for example.

Kromm · 09-02-2010, 10:49 AM

I think it agrees just fine. I have no idea what the intended criticism was supposed to be . . .

Ejidoth · 09-02-2010, 11:18 AM

Damage scales with the square root of energy, which is a good measure of penetration. Hit points scale with the cube root of mass, which means, at least for point applications of damage against a target that's an ideal cube or sphere or something, they scale with how much of you there is to penetrate - that is, width in one dimension.

That's not perfect. But it's a pretty good method, and a whole lot more internally consistent than most games, which base HP on 'Uh, yeah, that feels right ish.'

09-01-2010, 05:08 PM	#1
jacobmuller Join Date: Feb 2006 Location: Not in your time zone:D	Is this laser cannon really that big? Am I reading this right? A Spaceships SM+14 Major battery Pulse Laser, in character terms, would be 6dx250 Cr Exp. So, anyone standing less than a mile away from the "impact" is gonna want protection? Explosion injury = Damage/(3xrange); 1 mile = 1,760 yards; average damage would mean 1 point of Cr Exp damage at 1,750 yards... cf Beam laser = no collateral damage. __________________ "Sanity is a bourgeois meme." Exegeek PS sorry I'm a Parthian shootist: shiftwork + out of country = not here when you are:/ It's all in the reflexes

09-01-2010, 05:23 PM	#2
BlackLiger Join Date: Jun 2010	Re: Is this laser cannon really that big? Given that a PULSE laser is a pulsed weapon, it could splash, I suppose. I don't know the physics well enough. Might be a mistake though. Someone who owns a copy of UT rather than continually loaning a friends, confirm his numbers? __________________ In the name of Kane #Gurps IRC channel, irc.sorcery.net #gurps

09-01-2010, 05:23 PM	#3
Kromm *GURPS* Line Editor Join Date: Jul 2004 Location: Montréal, Québec	Re: Is this laser cannon really that big? Probably. That's flash-vaporizing (reducing to -10×HP) about 100 tons of solid matter. There's no believable way to do that without creating 100 tons of superheated gas leaving the impact point as a hypersonic shockwave. Based on the estimated velocity of the gas and the surface area of a man standing a mile away, that's the equivalent of a typical .25 ACP bullet. In *GURPS* terms, such a round does 1d pi-, averaging 1.75 HP of injury, so I'd say 1 point is in the right ballpark. __________________ Sean "Dr. Kromm" Punch <kromm@sjgames.com> *GURPS* Line Editor, Steve Jackson Games My DreamWidth [Just *GURPS* News]

09-02-2010, 09:59 AM	#4
jacobmuller Join Date: Feb 2006 Location: Not in your time zone:D	Re: Is this laser cannon really that big? Awesome! TQ. Cue Independence Day scenes:) __________________ "Sanity is a bourgeois meme." Exegeek PS sorry I'm a Parthian shootist: shiftwork + out of country = not here when you are:/ It's all in the reflexes

09-02-2010, 10:45 AM	#7
Tyneras Join Date: Oct 2007 Location: Kentucky, USA	Re: Is this laser cannon really that big? At really high levels of energy, everything explodes. Someone once asked what a sci-fi space laser cannon would look like when fired from orbit at the ground. The answer was like "the fist of God", imagine a nuclear explosion, only the "stalk" of the mushroom cloud goes up until the atmosphere ends. It would be spectacular to watch, assuming you weren't the target. Also, damage doesn't scale with energy linearly, as I understand it, it scales with the square root of energy. so 1 damage = X energy, 2 damage = 4X energy, 12 damage = 144X energy, and so on. __________________ GURPS Fanzine The Path of Cunning is worth a read.

09-02-2010, 10:49 AM	#9
Kromm *GURPS* Line Editor Join Date: Jul 2004 Location: Montréal, Québec	Re: Is this laser cannon really that big? I think it agrees just fine. I have no idea what the intended criticism was supposed to be . . . __________________ Sean "Dr. Kromm" Punch <kromm@sjgames.com> *GURPS* Line Editor, Steve Jackson Games My DreamWidth [Just *GURPS* News]

09-02-2010, 11:18 AM	#10
Ejidoth Join Date: Jul 2009	Re: Is this laser cannon really that big? Damage scales with the square root of energy, which is a good measure of penetration. Hit points scale with the cube root of mass, which means, at least for point applications of damage against a target that's an ideal cube or sphere or something, they scale with how much of you there is to penetrate - that is, width in one dimension. That's not perfect. But it's a pretty good method, and a whole lot more internally consistent than most games, which base HP on 'Uh, yeah, that feels right ish.'