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firefighting in space

fire suppression in spacecraft
 
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I was reading something the other night about the fire on Mir and thought of two fairly simple solutions in a similar situation... 1. Evacuate the module, seal it off, and purge all of the air ... but that seemed a little drastic, a waste of air, and it puts a lot of stress on the craft. So there obviosly had to be a better solution... 2. Evacuate the module, seal the hatch, fill the module with pure nitrogen(better than CO2 because it doesn't have to be filtered out). Shut off the power if there are any electrical shorts. After the fire burns itself out the air is filtered out and returned to the normal 25/75 oxy/nitrogen mix. (unfortunately, this probably would not have worked in Mir's situation because the fire came from a canister of lithium perchlorate which basically makes more oxygen as it burns)
tazmase2, Jul 19 2003

CO2 MSDS http://www.hoopersupply.com/msds/co2.htm
Typical and toxic concentrations listed here... [scad mientist, Oct 04 2004, last modified Oct 06 2004]

CO2 and hemoglobin http://www.everythi...de=carbon%20dioxide
Near the bottom of this page is an explanation of why CO2 is dangerous even if there is enough oxygen. [scad mientist]

Fires in spacecraft. http://www.me.berke...es/mcl_overview.pdf [scad mientist, Oct 04 2004, last modified Oct 06 2004]

Fires in spacecraft. http://www.me.berke...es/mcl_overview.pdf
[2 fries shy of a happy meal, Oct 04 2004]

Candle flames in microgravity http://microgravity...n/cfm/cfm_index.htm
[2 fries shy of a happy meal, Oct 04 2004, last modified Oct 06 2004]

[link]






       The problem with fire in space is not so much the fire itself (flames are spherical in space, and don't spread the way they do on the ground), but the smoke, and the fact that the space craft occupants can't simply evacuate and douse the fire from the outside. And why does carbon dioxide have to be filtered out? It's as harmless as nitrogen. You need to do some more reading.
DrCurry, Jul 19 2003
  

       1. flames in an oven used for experimental purposes are spherical.. but flames and hot blobs of metal from a closed container can be just as bad as a torch. 2. i did not mean evacuate the ship.. just close that section off from the rest of the ship. 3 co2 buildup can kill you quite quickly (watch apollo 13) and is usually filtered out, not saved 4 nitrogen is a non-flammable gas and also makes up %70-%75 of the air
tazmase2, Jul 19 2003
  

       The danger on Apollo 13 was not from the carbon dioxide itself, but that the oxygen was depleted. Replace it with nitrogen, and you'll suffocate just as quickly.
DrCurry, Jul 19 2003
  

       An atomosphere of 20% oxygen and 80% CO2 would be rapidly toxic. I don't remember at what levels CO2 becomes problematic, but there is a reason both spacecraft and submarines have scrubbers.   

       BTW, modern submarines generate and jettison considerable quantities of hydrogen.
supercat, Jul 19 2003
  

       // fire burns itself out //
Think a minute about what's burning. What gets taken into space? Not much, considering it's ten thousand bucks a pound to get it there. If it's not a critical need, it probably doesn't get taken into space in the first place. Second, since fire is such a serious matter aboard a spacecraft, flammable materials need an even higher level of justification before they'll make the cut. Therefore, the stuff that you are allowing to burn out is very probably stuff that is absolutely critical to your mission, or even your survival. You sure you want to keep the air in there? You won't be able to breath it anyway, 'cause of the smoke...
  

       When you say "fill the module with pure nitrogen", are you saying mix it with the existing atmosphere, or are you going to purge first? Just adding nitrogen does not decrease the oxygen content of the existing air. It does increase the pressure to something your craft wasn't designed for - vacuum outside and overpressure inside will be lots more stressful than vacuum inside & out.
lurch, Jul 19 2003
  

       drcurry: you do not breathe the pure nitrogen air.. yes it would suffocate you.   

       supercat: 80% nitrogen.. not co2.. also, the hydrogen can be used as fuel.   

       Lurch: good point, perhaps purge the air and replace it with nitrogen to keep the pressure from changing rapidly... in this case a simple facemask and oxygen tank could be worn while you fight the fire
tazmase2, Jul 19 2003
  

       tazmase2: My point was that CO2 is nowhere near as biologically inert as nitrogen; we can accept an 80% N2 concentration at 1ATM, but an 80% CO2 concentration would be rapidly toxic; actually, I think even 5% is very bad.<p>   

       BTW, one thing I was wondering... do spacescraft have non-space-suit breathers? It would seem that such a thing might be a useful compromise between a space-suit and a reliance upon life-support systems.
supercat, Jul 19 2003
  

       something similar to the little oxygen masks that drop down on a plane in a emergency?
tazmase2, Jul 19 2003
  

       co3 - carbon trioxide??? never heard of it
tazmase2, Jul 21 2003
  

       sorry.. forgot about carbonates. and yes, carbon dioxide is toxic
tazmase2, Jul 21 2003
  

       //flames are spherical in space//   

       That's something I *really* want to see!
snarfyguy, Jul 21 2003
  

       If you have a friend with an airplane you can see it today. Have the friend climb and push over for a zero g arc and then you can strike a match. The flame will be spherical and will grow rapidly until it goes out (lasts only a second or so before lack of convection kills it). I haven't witnessed this first hand but have been told about it many times. Most common (paraphrased) description: "Like a slow motion flash bulb."
bristolz, Jul 21 2003
  

       i was talking to a friend of mine on Sunday about this and he wanted to prove me wrong when i said flames are only spherical under certian conditions, aside from weightlessness .. so we went up and did a zero g flight and i lit a match and set it in (or above?) an ashtray.. the whole thing was burning (not very brightly though) in about a second and burned out after about 7 seconds.. and yes the flames were semi-spherical (should have taken a picture!!!)
tazmase2, Jul 21 2003
  

       [sealorator] - please don't put URLs in your annos. There is a space for them right under the idea text.   

       // being cooked alive because a single dust particle a millimeter in diameter hit something flammable at 53,000 km/s //
If you get hit by something millimeter scale going .17c, I really doubt flammability will be any issue at all.
  

       CO2... toxic... //we exhale the stuff//
And just imagine for a moment if you couldn't. Once the CO2 partial pressure in the atmosphere reaches that of your blood stream, gas exchange in the alveoli stops. It'll start up again once your blood CO2 gets high enough. As your blood gasses go wonky, you'll note a few things... a tendency to hyperventilate; nausea; vertigo; and severe headache. It's a problem for scuba divers.
lurch, Jul 21 2003
  

       Couple of microgravity fire sights, [links]. Pretty cool stuff.
I couldn't find a decent video though.
  

       Also, think how bad Coke burps burn when they go up your nose. That is pure CO2, baby. Forming carbonic acid when it hits the water in your delicate noseholes.
bungston, Jul 22 2003
  
      
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