Saturation Diving Adventure, Underwater Fun Options

[Tsithlis]

So I'm working on an adventure that will take place in an underwater habitat and I was wondering if anyone has any information on whether or not a firearm will detonate the bullet under the saturation of Heliox or Triox? Heliox is a helium/oxygen mixture with the oxygen being considerably lower than at surface concentrations (I believe around 10% as opposed to 21%) and Triox is a Nitrogen/Helium/Oxygen mixture that is slightly better at preventing the hypothermia threat from Heliox but is more likely to cause nitrogen narcosis. Anyway I called around to some research facilities and most of them were very familiar with the problems that could be caused but none of them really had an idea if a firearm would work at such pressures. They also said that at those depths its entirely possible that the bullets themselves may fail completely before they were ever even fired. Anyone have any input on this?

[Draco18s]

If you can use a gas stove, then you can fire a gun.

I suspect there wouldn't be any real issue getting the firearm to ignite and produce a projectile at a high enough velocity to inflict wounds.

The reason for using Heliox or Trimix (aka Triox) is that the mixtures are of such a ratio to reduce medical complications due to the high pressure (the bends), by adding abnormally high concentrations of helium (an inert gas), but there is still sufficient concentrations of oxygen that divers don't suffer asphyxiation symptoms normally associated with a low oxygen environment (similar to what hikers experience in high altitudes).

I suspect that, if anything, the muzzle velocity would be lower, but not significantly. I'd knock 1 point off the base DV of all guns.

The real issue with firearms in this environment is missing. Due to the high pressures on the external walls of the facility I'd treat them as having only 1 to 5 points of structure, simulating the barrier already being near a catastrophic failure point. Single bullets in this environment would likely cause a complete structural collapse (think "every space sci-fi movie and TV show ever" where the glass cracks--underwater (high pressure) is even more dangerous than space (low pressure) because even a pin sized hole in 3" steel will let in enough water fast enough to cause the metal to collapse like a damn made out of sand, where as the same hole leaking air out into a void doesn't have enough force to make the hole larger).

[Dahrken]

The basic operation of the weapon will work, as the propellant in the cartridge does not rely on the ambiant oxygen for it's combustion.

[Tsithlis]

Thanks, I'll make sure to add some of this to the debugging sections for sure. To keep characters from outright killing themselves I'll have the johnson warn them about firearms and the hull. Do you know anything about the bullet situation? One of the guys I spoke to said he took a portable CD player down once and it imploded before he even got near the bottom because of the air pressure difference.

[Dahrken]

What depth do you plan your habitat to be ? If it's not several kilometers underwater it's unlikely firearms and cartridge will be adversely affected.

During it's operating cycle a firearm (and the bullet comming out) are exposed to internal pressures equivalent to 10 to 40 kilometer depth, and possibly more for very energic load in high-pressure calibers...

[Draco18s]

I don't know why the CD player would have imploded, there aren't any air tight components that I'm aware of. Bullets are likely small enough that they'd not suffer enough to matter. Its one of those "realism vs. fun" issues that comes up. It's hard to know what is real and finding out just gets in the way.

Canned drinks are probably no-go though. (IMG:style_emoticons/default/wink.gif)

(Also: on firearms and the hull. While the game doesn't make us track individual bullets, wide bursts tend to leave a lot of bullet holes in the walls, which is significant when the walls don't like getting shot.)

[Sengir]

One of the guys I spoke to said he took a portable CD player down once and it imploded before he even got near the bottom because of the air pressure difference.

That was my first thought as well, how do percussion caps react to high ambient pressure? And while SR assumes caseless rounds per default, some bullet types (APDS, flechette) might still have some sort of sealed container that could be deformed by air pressure.


@Draco: The point of saturation diving is that divers remain at the pressure of their working environment at all times (IMG:style_emoticons/default/wink.gif)

[Draco18s]

Also ran into this which you might find interesting. Hehehe. Inflict dice pool penalties on the runners for being unaccustomed to the air mixture. (IMG:style_emoticons/default/devil.gif)

[Tsithlis]

Saturation Diving is usually for depths of 600+ feet. I was thinking about an underwater research lab around 1000-1500 feet. 1000 feet is our (now day) limit but I was assuming slightly further for 2070.

[Neowulf]

Arsenal, pg 151- Extreme Environment Modification for weapons, the level 2 version allows a weapon to fire under water and in space, though at half range in air/water and requiring 500Y worth of servicing every 100 shots.

Arsenal, pg 34- Frangible Rounds, meant to for places where you need to minimize damage to equipment while still killin doodz. Resisted with double barrier rating and has a +2 AP mod.


Other ideas:
Gel rounds, walls don't get stunned.
Capsule rounds, walls don't care about poisons.
Pistol crossbow, small, doesn't care about the gaseous content of the local environment. 2P damage couldn't hurt even a thin wall, and injection bolts make up the damage difference against fleshies.

[kzt]

Caseless would be solid, I wouldn't expect anything until you reach thousands of PSI. Cased ammunition is not designed for overpressure, but you'd need a LOT to seriously deform it, but less than caseless.

And for really deep diving Hydrox is sometimes used. It's O2 and hydrogen. It's non-explosive/flamable due to the less than 3% O2 (due to partial pressure a little O2 goes a long way at depth) but the players might not know that. Hydreliox is also sometimes used, it's helium, O2 and hydrogen, also non-flamable.

Well, it's non-flamable at depth, it you breathed it at sea level you have to put enough oxygen in to the mix that it is extremely flammable.

[Dahrken]

500 meter depth ? This means about 50 bars pressure, the effect on the primer and weapon operation/damage will be negligible at the indoor ranges that can be expected.

Cased, sealed cartridges may experience some troubles, like the bullet moving backward but even that is not very likely, a cartridge is a relatively sturdy package.

[Tsithlis]

So basically they can shoot guns just be careful where your shooting them.

[Draco18s]

So basically they can shoot guns just be careful where your shooting them.

Pretty much. It might also be advantageous to not dodge shots as the bullet going wild might "just kill everybody" rather than "just give me a serious wound." The latter is treatable!

[Tsithlis]

what about stick n shocks, I am assuming since these don't pierce skin they also will not penetrate a hull?

[Sengir]

Why are you so worried about the hull? I figure that an underwater habitat would have a quite sturdy outer hull, plus saturation diving means you don't have to worry about pressure differences. And even if the hull gets punctured, Augmentation lists Sealant Nanites and says they are widely used in space and sea habitats so there should be some sort of automated repair system.

Something else I just though of, firing a non-silenced gun inside a tight steel tube should produce a deafening noise. Some kind of ear protection might be a good idea, not just for this specific run but for enclosed spaces in general.

[Draco18s]

Why are you so worried about the hull?

Because it has to be holywood interesting. (IMG:style_emoticons/default/spin.gif)

[Tsithlis]

That and the fact that there is no one there to repair the hull. The station is deserted and the runners are there to find out why (btw its not deserted and that's what all the gun questions are about). I am sure they would not likely know where the sealant nanites are or even how to use them if they found them.

[Draco18s]

I do suggest a quick read of The Sphere by Michael Crichton. There's a few sections about compromised sections of the habitat which might prove interesting.

[Method]

It really depends on if they will be using the firearms outside the habitat (in high-pressure environments) or inside (in relatively low-pressure environments). Outside you might have issues, but I don't think you have to worry about firearms not working in any sealed saturation environment that humans can live in (without a JIM-type suit).

And frangible rounds could be very deadly if you come up with a way to limit armor (for example: maybe bulky armor cannot be worn under the dive suits the team needs to access the facility, etc).

[Tsithlis]

Just finished watching, Abyss, The Sphere (Movie version of the book), Leviathan, and Deep Blue Sea this morning, I have a lot of useful descriptions of sounds, sights, (and smells as I imagine them). I do like to be thorough in my research before writing.

[Method]

What? No Deep Star Six? (IMG:style_emoticons/default/smile.gif)

[Draco18s]

The Sphere (Movie version of the book)

Any good?

Also: I've seen an ending segment of some movie where a guy had to put on a pressure suit filled with (essentially) liquid oxygen so he could dive down deeper and do something, but I never caught the title of the movie. Any idea what movie that was?

[Tsithlis]

hmm was unaware of that one... going to get it now

[Tsithlis]

Also: I've seen an ending segment of some movie where a guy had to put on a pressure suit filled with (essentially) liquid oxygen so he could dive down deeper and do something, but I never caught the title of the movie. Any idea what movie that was?

That was the Abyss. The movie version of the sphere apparently follows quite true to the book according to the wiki which only lists like 7-10 differences between the two and all of them seem to be minor.