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?

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).

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.

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.

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...

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.

(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.)

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

Also ran into this which you might find interesting. Hehehe. Inflict dice pool penalties on the runners for being unaccustomed to the air mixture.

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.

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.

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.

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.

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!

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

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.

Because it has to be holywood interesting.

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.

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.

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).

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.

What? No Deep Star Six?

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?

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

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.

Ahh. Thanks. That was the only scene of the movie I saw and was for the most part confused.
And I'll have to go get The Sphere, I liked the book well enough (shame Hollywood ruined Timeline--that book was awesome and internally consistent, the movie? Pfft).

If you do watch the abyss make sure to get the directors cut which turns it into a 3 hour movie but ending is better in my opinion. It was one of the classics that I still enjoy watching that came out of the 80's

I figure it would work similarly to self-sealing bicycle tubes, a thin layer of sealant inside the wall, which bleeds out into a puncture and closes it.

I mean if you want to limit your players to "soft" ammo, no problem. But you don't have to do it.

Have an NPC tell them that they should and ask if anyone brings along normal or other ammo types anyway.

You know somebody will.

Then you can play off the result: everybody brings lethal ammo, then its not a big deal (habitat is more durable in this regard than was expected) or only one guy does, shoots out a window on accident, nearly gets everyone killed, then the rest of the players can slap him around a bit for being stupid.

Yeah even if the bullet doesn't actually damage the hull there is always ricochet. Being inside a sardine can firing rounds can't be healthy for you.

I think what I am going to do is limit Hull damage to if someone critical glitches and glitches may result in someone on the team resisting the round just fired from ricochet.

Plus you never know what kinds of ultra-light (aka ultra-thin) space-aged materials they are using to build underwater habitats in 2072. Could be they have great structural properties, but are easily punctured... maybe... in theory...

It's not liquid oxygen - which requires either temperatures or pressures that are completely lethal for any air-breather. It's a liquid wich can dissolve enough oxygen to the lungs - IRL animal experiments of the sort have been performed with adequate results.

the idea is that a non-compressible fluid makes it easier to balance the pressure inside the body and outside of it. It also prevents the absorption of gazes from the breathing mix into the blood (nitrogen narcosis, the bends, all those funny problems).

Note : if the atmosphere inside the station is kept at the same pressure as the water outside, you won't have the implosion/catastrophic failure issues that you would have with a lesser pressure. The submarine in Abyss imploded beause it was at station-depth pressure and went down way beyond that. Firing holes in the hull remains a bad idea, but it's not an instant disaster.

the thing I am trying to do is break them out of their typical element. I'm just wanting them to not be able to rely on their traditional shut em up and collect the loot style.

Hmmm, or maybe have the Johnson tell the players "no problem, the habitat is build to last and seal small cracks will even be healed automatically". After the first fight the players find out that the repair system is obviously offline and have to bring it back online, in a short time frame and with no good way to fight off [whatever is in there] until the system is restarted ²

At 500 meters a hole in the hull will be like a laser beam, particularly in anything at 1 atmosphere. The water will have enough pressure behind it to cut like a knife, even through things you wouldn't expect.

http://en.wikipedia.org/wiki/Water_jet_cutter


Oh, and high pressure air is very dense. It transmits shockwaves and sound better that 1 atmosphere air.

Is there a reason you want it to be a saturated diving environment? I don't know if its stated in canon, but I would assume that by 2070 any semi-permanent habitat would be pressure controlled inside, so its all kind of moot so long as A.) you don't make any holes (as kzt has pointed out) and B.) you don't intend to venture outside the habitat. Otherwise you can just assume the pressure inside the habitat is ~1 atm and discourage them from doing really dumb stuff (like tossing grenades around every corner or launching LAW rockets down hallways or whatever).

don't you know? Shadowrunners can't swim!!

This is the biggest reason to have the place suffer catastrophic failures from bullets (even if it isn't the kind that just kills people). If it was just as safe as firing a gun inside a building then...why did you go underwater?



And such a jet would easily tear itself a bigger hole, making for a flooding issue, rather than a laser beam of death. In either case, its near impossible to repair.

The reason you use a saturation environment is because the people inside need to be regularly (like every day) going out to work directly in the water. Given SR4 drones I don't see how a saturation environment could be a cost effective solution for anything other then possibly research. And a picture of an abandoned saturation habitat is what you see when you look up "insanely dangerous places to explore" in 2060. Without constant maintenance it's going to go to hell.

BTW, decompression from a saturation dive takes about an hour per meter, and descent is typically limited to 2.5 meters per minute. So it will take over 3 hours to get to the habitat and on the order of a month to leave if they are there long. Hope they are being paid by someone who doesn't decide to cut their cost be opening a valve on the deco chamber.

Saturation diving means the station would be at 50 atmospheres, no water cutter of doom

You know a really amusing scenario comes to mind. You've been worrying about the players behaving sensibly and not puncturing the hull. A fun little trick in these sorts of situations is to take them on at their own game by giving them enemies that are even less responsible than they are...


The enemy might be drones that aren't bothered by water, shedim that have nothing to lose or psychos that don't care or wont listen. The trick is to get in their first before the PCs raise the issue. Then they have to respond to your irresponsibility.

Also, you don't have to make the whole thing a straight choice between no harm or insta-death. With liberal use of sealable bulkheads throughout the station, they can accidentally block off useful routes, lines of retreat or - my favourite - "You fool! You've flooded the weapons storage! Now we can't get all the good stuff the GM put there for us."

Anyway, this sounds really good. Any chance of you posting back here with an account of how it went?

K.

I almost posted that scenario myself, but figured it was best left implied than stated.

You're like my mother.

The facility is a research facility testing background counts on dual natured critters. The facility is located on a strong Domain (+5) and has been sculpted in several areas. Recently EVO found some bacterial samples on mars and transferred them to the facility for genetic decoding. The Facility is owned by PensoDyne one of Evo's genetic research subsidiaries. PensoDyne lost contact with the facility 24 hours before the run starts. After 48 hours pensodyne assumes that the facility has become overrun by a infectious substance and detonates the facility to prevent any contaminant leak as well as cover up any information that may lead back to them. One of the researchers hires the runners to investigate and extract his wife (or her body).

From Johnsoning for Dummies, 2065 Edition: "Never hire runners to retrieve someone or their body. Dead bodies are easier to transport and so this is an incitement for the less moral shadowrunner to kill the intended rescuee. Note "less moral shadowrunner" is all of them."

Sounds like a good plot, btw.

At least one of us is.

Well technically she is aswell, so that's two of you.

I was just thinking how she plays Trivial Pursuit. Any time she doesn't get an answer, she waits for it to be read out and then says: "Oh, I was going to say that".

I was meaning "us" as in "you" and "I."



My mother was the only one in my family who could win that game.

Mostly owing to the fact that 90% (or more) of the questions related to events before I was born. So she might have had an unfair advantage.

Hmmm. I would be prepared to pay your runners a serious chunk of change. You're asking them to go into a highly isolated and inherently dangerous environment, which happens to be even more dangerous because of a pathobiological catastrophe with little intel as to what is actually going on...

Cha-ching!