[Ultra-Tech] [Spaceships] Building a cosmic-powered setting

[Michael Thayne]

Originally Posted by Fred Brackin

That series did have grav beamers that could vaporize human-sized bodies. They tended to be too large for normal humans to use as rifles but not for cyborg augments. Probably rather like the 70lb/Min ST 18 "semi-portable" class from UT. With much more damage than UT grav beamers too.

What kind of situations were the grav beamers used in? How much attention was paid to the issue of collateral damage? Because if you can vaporize a human body, a stray shot can probably collapse one of a building's supports.

[AlexanderHowl]

Vaporizing the average human body requires around 3 GJ of energy, which deals 3d×100 damage according the Spaceships. That is a respectable amount of damage, enough to threaten a c-level super, and is the equivalent of a SM+10 major battery. Since each hit would deal an average of 1050 points of damage, I am not even sure if a human would count as any form of cover.

[Fred Brackin]

Originally Posted by Michael Thayne

What kind of situations were the grav beamers used in?

Basically all situations. It was the dominant weapon of the setting's technology.

[Michael Thayne]

Originally Posted by AlexanderHowl

Vaporizing the average human body requires around 3 GJ of energy, which deals 3d×100 damage according the Spaceships. That is a respectable amount of damage, enough to threaten a c-level super, and is the equivalent of a SM+10 major battery. Since each hit would deal an average of 1050 points of damage, I am not even sure if a human would count as any form of cover.

Is the 3GJ figure based on doing physics math about literally boiling bodily fluids? Because I suspect people may use "disintegrate" loosely to include e.g. reducing the entire body to red mist, or charcoal. According to Ultra-Tech, to totally disintegrate someone with the disintegrators listed there, you only need to reduce the body to -10xHP. 6d6x6 damage will do that nicely.

[Rupert]

I get about 20MJ to turn the water in an average man into steam. That'd be about 6dx8 damage using Spaceships' scale, which looks about right.

Now turning someone into steam won't turn them into fire mist or dust, but if the energy is reasonably evenly applied they should blow up nicely.

[Jack Sawyer]

I suspect he's referencing one of the papers or similar sources that discuss such things:

https://journals.le.ac.uk/ojs1/index...ticle/view/705

https://blogs.scientificamerican.com...orize-a-human/

But there IS a semantic distinction here even if you allow for vaporizing. Human bodies are mostly water, and it only takes a few MJ/kg to vaporize bodies so you can vaporize with far less energy potentially (as a further note, several GJ is also the same magnitude of energy you need almost completely cremate a human body.. or at least the energy expended in modern crematoria.)

If you want to rely more on mechanical damage that yield can be even lower (a hand grenade/stick of Dynamite by Mythbusters was roughly enough to blow apart a human torso and 400 j per sq cm will ''flay flesh from bone' via steam explosion so single digit MJ can arguably 'vaporize' too.)

[Michael Thayne]

When we're talking about vaporizing a human body—what kind of collateral damage is that going to cause? Like if you fire a (non-explosive) tank cannon at a person, a second person standing to the side of the first a yard away might not be hurt? I think? (Standing behind the victim is obviously another matter.) But I think beam weapons might plausibly work differently, if the victim explodes, or the beam loses its coherence. Is that right?

[lwcamp]

Originally Posted by Michael Thayne

When we're talking about vaporizing a human body—what kind of collateral damage is that going to cause? Like if you fire a (non-explosive) tank cannon at a person, a second person standing to the side of the first a yard away might not be hurt? I think? (Standing behind the victim is obviously another matter.) But I think beam weapons might plausibly work differently, if the victim explodes, or the beam loses its coherence. Is that right?

It depends on how fast the person vaporizes. At the very least, the person will expand in volume something like 1000 times (the exact amount depends on how hot the final vapor cloud is). Assuming a 70 kg person, this gives something like a 4 to 5 meter diameter cloud. As steam, it will cause normal burning damage to those engulfed. If it is really hot, not only will the cloud be bigger, it might also act more like fire (as in, igniting things) than steam.

Faster energy deposit will cause an explosion. This could be at any level, say a follow-up 3d or 6d or 6dx5 cr ex attack.

Luke

[Michael Thayne]

Originally Posted by lwcamp

It depends on how fast the person vaporizes. At the very least, the person will expand in volume something like 1000 times (the exact amount depends on how hot the final vapor cloud is). Assuming a 70 kg person, this gives something like a 4 to 5 meter diameter cloud. As steam, it will cause normal burning damage to those engulfed. If it is really hot, not only will the cloud be bigger, it might also act more like fire (as in, igniting things) than steam.

Faster energy deposit will cause an explosion. This could be at any level, say a follow-up 3d or 6d or 6dx5 cr ex attack.

Luke

Would 1/3 of a second or less be fast enough to cause an explosion? 1/10th of a second?

[lwcamp]

Originally Posted by Michael Thayne

Would 1/3 of a second or less be fast enough to cause an explosion? 1/10th of a second?

As a rough scale, I'd say the energy should be deposited faster than sound can escape from the person. So, figuring 30 cm as a typical distance, and a speed of sound of 1500 m/s (although this is temperature dependent, and will change as the tissue evaporates and turns into a gas), the energy should be deposited in less than a millisecond. This will give a detonation, you could still get a gunpowder-like deflagration explosion with a longer energy deposition.

Luke