Fires on Ships - Your Opinion Needed!

[Alexb83]

As I said earlier, there are fires that supply their own oxygen (or other oxidising agents). Just because you flush out the oxygen or dose the fire in water, or whatever, some fires will keep on burning until they're exhausted. Thermite is a good example. Dousing thermite in water will actually make it burn more vigorously, or explode.

The thioformaldehyde example is also good, since it's a compound that's been detected in the interstellar medium.

 

[Alexb83]

on a ship the oxygen will all rush out very quick, leaving no oxygen left to burn as blast doors will close stopping the entire ships air supply form exiting. and what about those races that dont breath oxygen? have methane on board so a fire would be automatic death due to explosive gasses blowing the ship apart.

Methane will only burn in the presence of Oxygen Katadder, in fact high levelsof Methane in our atmosphere will not burn (about 15% or more, though dont quote me)

I wont quote you. Methane only makes up about 0.001745% of the atmosphere, by volume. Earth's atmosphere is about 80 percent N2, 20 percent 02, with the change, <1% as Argon and other traces (such as Methane, Krypton)

 

[katadder]

on a ship the oxygen will all rush out very quick, leaving no oxygen left to burn as blast doors will close stopping the entire ships air supply form exiting. and what about those races that dont breath oxygen? have methane on board so a fire would be automatic death due to explosive gasses blowing the ship apart.

Methane will only burn in the presence of Oxygen Katadder, in fact high levelsof Methane in our atmosphere will not burn (about 15% or more, though dont quote me)

so the races that breath methane are entirely safe from fires then think i will order a crapload of oxygen masks and fill my ships with methane

 

[Reaverman]

on a ship the oxygen will all rush out very quick, leaving no oxygen left to burn as blast doors will close stopping the entire ships air supply form exiting. and what about those races that dont breath oxygen? have methane on board so a fire would be automatic death due to explosive gasses blowing the ship apart.

Methane will only burn in the presence of Oxygen Katadder, in fact high levelsof Methane in our atmosphere will not burn (about 15% or more, though dont quote me)

I wont quote you. Methane only makes up about 0.001745% of the atmosphere, by volume. Earth's atmosphere is about 80 percent N2, 20 percent 02, with the change, <1% as Argon and other traces (such as Methane, Krypton)

Thats overall, I am talking about levels artificially released (say from a canister)

 

[Alexb83]

on a ship the oxygen will all rush out very quick, leaving no oxygen left to burn as blast doors will close stopping the entire ships air supply form exiting. and what about those races that dont breath oxygen? have methane on board so a fire would be automatic death due to explosive gasses blowing the ship apart.

Methane will only burn in the presence of Oxygen Katadder, in fact high levelsof Methane in our atmosphere will not burn (about 15% or more, though dont quote me)

so the races that breath methane are entirely safe from fires then think i will order a crapload of oxygen masks and fill my ships with methane

Actually, I imagine if you supply it with any other oxidising agent, and sufficient activation energy, it will burn in the presence of them as well. Combustion is just another chemical reaction (or sequence thereof). It's difficult to imagine the different chemicals which would be liberated and mixed (and burn) at ultra-high temperatures if your exotic hull was penetrated by superheated plasma, or a high energy laser or particle beam.

 

[katadder]

dont you remember your fire safety lessons as a kid tho, with that triangle. 3 things needed to start a fire and keep it burning. and if oxygen aint there you not gonna flame it.

 

[Alexb83]

Thats overall, I am talking about levels artifially released (say from a canister)

This is because combustion of methane is a several stage reaction. You need to pre-heat it sufficiently to make it burn on contact with a lit flame. If it's concentrated enough, the lit flame itself may be sufficient to start the reaction, but it you've just popped open a canister in a large room, it may not.

 

[Alexb83]

dont you remember your fire safety lessons as a kid tho, with that triangle. 3 things needed to start a fire and keep it burning. and if oxygen aint there you not gonna flame it.

As you point out, that's just for kids. Combustion simply needs a fuel, an oxidising agent (one that loses electrons in a chemical reaction) and activation energy. For most domestic fires, the oxidising agent is oxygen. But there are many other elements on the periodic table which will happily give up their electrons.
Also, there are many compounds which contain oxygen, or other oxidising agents, and will just as happily facilitate combustion.

Edit: actually, do oxidising agents reduce things, or oxidise them? I forget.
Oxidation is loss, Reaction is gain. So I guess they actually take electrons, rather than donate them.

 

[katadder]

thought for something to oxidise it had to have oxygen as part of its makeup?
well anyway if fires can still be started those who breath explosive atmospheres better get the fire out in a turn or 2 or the whole ship will exlpode

 

[Alexb83]

thought for something to oxidise it had to have oxygen as part of its makeup?
well anyway if fires can still be started those who breath explosive atmospheres better get the fire out in a turn or 2 or the whole ship will exlpode

Just because it has 'oxi' in it, doesn't mean it requires O2 It just requires an element which will readily remove electrons from other substances. Wikipedia has quite a good article on the subject (http://en.wikipedia.org/wiki/Oxidise)

 

[katadder]

still the explosive atmosphered ships are doomed then.

 

[Alexb83]

still the explosive atmosphered ships are doomed then.

I don't know what you mean by 'explosive atmosphere'. Methane is a combustible fuel, but for it to be an 'explosive environment' it would have to have an oxidising agent present in a sufficient quantity for it to combust on contact with a naked flame. I imagine the environment for methane breathers would represent our own - 20% or so methane, with 80% inert gases (like nitrogen or argon). So it's not explosive.

Remember, the hulls of these ships are metals for the most part. Metals do burn, and do so at very high temperatures. I seem to remember reading fluff somewhere that discussed how EA neutronium hulls actually enhanced the cutting efficiency of Minbari neutron cannons...

It's an SF universe, but in many ways it's based on real science (like the use of newtonian physics.) I guess the point is that fire /is/ possible surrounded by a vacuum, but also that it's not too difficult to expel fire from the ship, if you have sufficient damage control procedures.

The exceptions I guess would be fires deep within the ship caused by secondary explosions.

 

[Voronesh]

Well, sry bout the LOX part wulf. missed the L.....

But apparently LOX does explode.

And still, what tactical depth do we gain from fires? (realism and canonness doesnt count, cause with a priority lvl system it is impossible to get all ship right)

But there are many votes against it.

So yes you cant have a fire in vacuum, only one surrounded by vaccum.

 

[Nomad]

Fires burning in a vacuum? (Or setting fire to the atmosphere of Jupiter) Known Physics...just wrong.

There's nothing to stop fire burning in a vacuum, provided that fuel and oxygen are there with the ignition source. So, if you were in the atmosphere of Jupiter and found a gas cloud with a sufficient hydrogen/oxygen mix, you could ignite it, simple as. Also, you'd have a nice floating cloud of water vapour afterward.
If a missile hit your ship, the propellant (usually consisting of an oxidising agent as well as the fuel) would keep burning, even if it was sat in a compartment open to space, until such time as either the fuel or oxygen ran out.

As has already been pointed out, a vacuum that contains enough oxygen to sustain combustion is, by definition, a pretty lousy vacuum.

Clouds of oxygen on Jupiter are about as common as clouds made of argon are on Earth - it makes up a similar (vanishingly small) proportion of the jovian atmosphere.

Water on Jupiter? NASA expected to find a significant amount, in the event the Galilleo probe found virtually none. Go figure.

In any event, had there ever been enough of anything in the atmosphere of Jupiter to combust with all that hydrogen - somewhere between 75 and 90 %, depending on your source - it would have burned up long ago thanks to events like Schumaker-Levy 9.

Setting fire to the atmoshpere of Jupiter? Known planetary science - just wrong.

Liquid-fuelled rocket engines can sustain combustion in a chamber open to a vacuum - true. All it takes is a lot of very careful design and a set of high powered turbopumps ramming in oxidant and propellant at a rate of several tons per minute - substances often selected because they are hypergolic (ie they explode on contact). Same thing as a compartment initially at sea-level pressure explosively decompressing through battle damage? I don't think so.

If a missile hit your ship, the propellant (usually consisting of an oxidising agent as well as the fuel) would keep burning

Not if it's warhead has detonated it won't. Additionally, you're assuming a chemical rocket. Given that it needed 3000+ tons of chemically powered Saturn V to push the (tiny, compared to, say, a Hyperion) Apollo moonshots out of Earth orbit I find that assumption questionable.

 

[LaranosTZ]

We had this discussion on the SST forums as well. Just because something is explosively combustable on earth does not mean it reacts the same way in other environments.

For example, Methane in medium concentrations on earth can be very combustable. However in an environment where methane is the primary gas (ie, a methane planet) it is not any more explosively combustable then oxygen is in the atmosphere on earth.

Any kind of fire on a ship is extremely bad, but usually controllable, as long as you don't mind killing a few dozen people to deal with it immediately. As dramatic as the movies are, any reaosnably technological race would have fast automatic bulkheads would contain any signifigant blaze before it extended anywhere, and then without any additional fuel the fire would burn itself out very quickly. Admittedly, this would really be little consolation to the individuals left in the affected sector to burn, but I sincerely doubt you'd get the dramatic movie moment where you see bulkheads slowly sliding down while frantic crewmen run desperately through the closing gap. Hell, we have bulkheads and doors now that in an emergency can close in seconds.

I guess this is my roundabout way of saying that I don't think there needs to be a fire 'mechanic' in the rules. If you wish to make crew and fires more important, ramp up the fire chat, but I think the mechanic will over complicate things.

 

[Voronesh]

Yep. Thats what id like.

Simply up the numbers on the crew damage table, to represent fires being dealth with by clsoing bulkheads and venting areas of the ship.

One shot damage, no mehcanic needed. Since you roll a d6, maybe twice or thrice during the whole game on the crew damage table, that is as good as rolling a d6 multiple times to suppress a fire.

ACTA is an effects based system, often touted by play testers and heavily supported by the game system. Fighters shooting first without AF reactions, works great with few exceptions. Hull/Armor determines how often your hit, not speed or size of the ship. All a very good system, that is quick and fun to play. We dont need an extra mechanic to represent something that is barely supported in the show, and unsupported by physics. And does not add a great deal of tactics.

Let me present something else, an idea:
Some effect or special action, that lets ships, and/or especially fighters to target engines and provoke engine crits. Or simply allow for a negative modifier to go for more engine crits, thses not as extra crits, but a transfer of other crits into engine ones. And maybe gunnery ones. Damaging exposed turrets and the like.

 

[Alexb83]

Water on Jupiter? NASA expected to find a significant amount, in the event the Galilleo probe found virtually none. Go figure.

Hydrogen + Oxygen -combustion-> water, was all I was trying to point out.

'traces' of oxygen, water vapour etc. are all floating around in the jovian atmosphere. Whilst I'm sure clouds of argon here are rare, jupiter is that much larger, there'd be more clouds of oxygen, even if they were equally as rare :wink:

But really, this is science fiction - as I pointed out elsewhere, the activation energy provided from a high powered super-duper neutron cannon might well be sufficient to start all sorts of exotic reactions in the Jovian atmosphere, and no, they needn't necessarily be chain reactions, and would likely be highly localised (in the area around the laser beam, say).

As for chemical rockets in space... why not? Gravity is not an issue up there, it's only an issue when trying to get up there. Note, the issue of chemical propellants was for the missiles, not for the ships. And if a warhead did go bang, any unburned propellant would add to the explosion. If it did not, as with HMS sheffield, it would just sit inside the ship with its solid propellant merrily burning away, vacuum or no.
JMS never specified how EA ships were propelled, but it seemed to based on fusion reactors.

 

[katadder]

Let me present something else, an idea:
Some effect or special action, that lets ships, and/or especially fighters to target engines and provoke engine crits. Or simply allow for a negative modifier to go for more engine crits, thses not as extra crits, but a transfer of other crits into engine ones. And maybe gunnery ones. Damaging exposed turrets and the like.

i came up with something smiilar, make a fighters crit hit table

1-3:engines
4-5:weapons
6: crew

as these are the things generally outside a ship apart from crew but crew are just inside those hulls so its like the fighter attacks versus the deathstar, you see explosions taking down crew.
the reactor and most other vital systems are deep inside so fighter weapons usually wouldnt penetrate that deep. this would also lower fighters ability to comlpetely blow up a ship when firing 1st with a 6,6 crit.

 

[Voronesh]

Well i guess there are some kicks from having a 6.6 crit from a fighter. (someone left the missle bay a wee little bit unprotected didnt we, though normally youd need high grade torps and not some starndard Fury unipulse cannon for that effect...)

But yes something along those lines would be great.

And also it doesnt really make fighters weaker, but more predictable. Which is good. Send in the fighters, and get a slow enemy ship. Boarding parties get ready, and stuff like that.

 

[katadder]

well thats the idea with fighters, you send them out to nuetralise the enemys weapons and guns as they are generally better at that job than standard shooting.