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ISS NASA Space Science

Fire Burns Differently In Space 146

New submitter black6host writes with this interesting snippet from Space.com: "NASA is playing with fire on the International Space Station — literally. Since March 2009, the space agency's Flame Extinguishment Experiment, or FLEX, has conducted more than 200 tests to better understand how fire behaves in microgravity, which is still not well understood. The research could lead to improved fire suppression systems aboard future spaceships, and it could also have practical benefits here on Earth, scientists said."
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Fire Burns Differently In Space

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  • by Anonymous Coward on Thursday December 01, 2011 @10:57AM (#38225896)

    Oh my god what are you idiots d

    • by dubsnipe ( 1822200 ) on Thursday December 01, 2011 @10:59AM (#38225924)

      Well, as long as there is oxygen around, things should combust.

      • Re: (Score:3, Interesting)

        Yeah, but with no convection to carry away the combustion byproducts and bring in more oxygen, it is much more difficult.
        • Re: (Score:3, Interesting)

          by Anonymous Coward
          There's still convection (heat/mass transfer by movement of fluid). Air still moves. The heated gases will expand and flow away from the fire, probably in a not entirely uniform way. And I would imagine that airflow from other sources (ventilators, moving objects) also exists. You don't have the expected convection from hot gases rising, that's why they're looking into how fire works in microgravity, because it works differently.
        • by tmosley ( 996283 )
          I love it when people don't even accept the premise of the title of the summary, much less RTFA.
        • <quote>Yeah, but with no convection ... it is much more difficult.</quote>

          Or more easy,  excessive cooling by convection is one of the main problems to start a new fire. 
      • by syousef ( 465911 ) on Thursday December 01, 2011 @11:09AM (#38226010) Journal

        Well, as long as there is oxygen around, things should combust.

        Sure, in a crude way you're right and there are a lot of electricals and combustibles on spacecraft. But HOW does it burn when there is no UP? We're so use to hot air rising that our everyday ideas of how to deal with a fire, like get down low, will not work in space. These are ideas that save lives here but are of no use if a fire were to break out. We can only develop new ideas if we get some direct experimental experience. Also it may lead to an ability to harness the differences inherent in a zero g process for industrial/manufacturing processes (but I'm just speculating here). This is worthwhile basic science.

        • by Dan East ( 318230 ) on Thursday December 01, 2011 @11:24AM (#38226194) Journal

          I would think that the worst possible thing (or best possible thing, from Invader Zim's viewpoint) that could happen with a fire in zero G is air flow / turbulence. If there isn't any movement of air, then the oxygen surrounding the fire is consumed and the fire burns very slowly. Since convection currents are a product of gravity, they don't occur in zero G so no fresh O2 is sucked into the fire for combustion as it does here on earth. So I would think anywhere there is an air vent blowing air, or even people just moving around in the environment, you'd have blowtorch like fire forming where the air is disturbed. I bet you could literally see the turbulence in the air as wisps of flame. Kind of disturbing to think of.
          An example of this is in a swimming pool. Have you noticed that if you hold very still in motionless, cold water, that you will begin to feel warmer, but as soon as you move it feels cold again (and no, I'm not talking about heating the pool with your pee). That is because the molecules closest to your body heat up, and since they aren't flowing and being replaced by colder molecules, only conduction takes heat away. It's sort of the same principle with fire in zero-g, where the fuel has consumed the oxygen near it (and it is also surrounded by combustion byproducts as well), so as long as fresh air isn't wafted into it, combustion almost grinds to a halt.

          • But would the temperature difference in itself create some fluid movement ?

            • by Anonymous Coward

              Heat causes the air to expand, but it expands in all directions.
              So you get a bubble of low density CO2 around the fire, but not any movement, because there is no gravity to organize low density air above high density air.

              • by bberens ( 965711 ) on Thursday December 01, 2011 @12:10PM (#38226732)
                I would be quite shocked to find that there wasn't constant airflow in the space station. It's not going to be a wind tunnel in there but there's going to be constant circulation from temperature control systems, whatever they use to filter the excess CO2 out of the air, etc.
              • Re: (Score:3, Interesting)

                by The_Crisis ( 2221344 )

                So you get a bubble of low density CO2 around the fire, but not any movement

                That's correct, except for the parts where it's backwards and/or wrong. The heat given off as the product of combustion should increase the pressure of CO (and/or other products of combustion) (see: Charles' Law) which we are guessing would radiate away in all directions. That pressure increase should cause airflow from the area of higher pressure to the area of lower pressure (see: Wind). So (totally guessing/hypothesizing here) it seems to me that the heat generated as a result of combustion would increa

                • by a whoabot ( 706122 ) on Thursday December 01, 2011 @02:47PM (#38229370)

                  What you, grandparent, and great-grandparent have overlooked is just how inveterate motion is. Matter is always in motion above zero degrees Kelvin. The environment of the space station is going to be around room temperature, well above 0K, meaning lots of atomic motion. The molecules of this CO2 "bubble" will quickly disperse as they follow down their concentration gradient. Conversely, molecules of O2 will quickly reach the flame as they follow down their concentration gradient. The astronauts could stop oxygen from getting to the flame by sealing it, but not by staying very still.

              • by mikael ( 484 )

                Assuming you had a perfectly spherical object burning evenly. Some easy to consider examples down on Earth are the hazards of igniting powders like coal dust and flour, hazards in coal mines and traditional windmills. These would cause explosions simply because of the small particle size and rapid oxidisation. No need to consider gravity, as Brownian motion of air molecules compensate for the force of gravity.

                A large burning object like a candle or one of those jumbo matchsticks would probably spin around i

          • So from what you're leading to if you see a fire in microgravity and try to run away from it your motion would pull in oxygen and make the flames fly towards you!?

            The more you move the worse the fire gets as you create more convection. Yikes!
            There goes stop drop and roll, would be more like Stop and remain motionless.

          • Wouldn't the fire spread outward in all directions equally assuming no air movement? Since it would consume the oxygen next to the source (increasing the flame), which would then consume the oxygen next to it and so on? So maybe expanding out in a sphere, but only the outer edge is actually on fire?
            • by Anonymous Coward on Thursday December 01, 2011 @12:56PM (#38227276)

              You require 3 things to keep a conventional fire going. Heat, fuel, and oxygen. The fire would not spread outwards unless there was fuel to burn as well. The same was that a campfire doesn't just keep spreading outwards away from the fire pit, since all the wood (fuel) is in the pit. Now if you were to spill a container of oil or other combustible liquid inside the space station, and then set it on fire. Now the fire could theoretically spread outwards in all directions as the liquid also spread outwards.

              On Earth, most fire suppression systems work on removing the heat and to some extent oxygen from the fire triangle. We use compressed CO2, which cools the area as it expands while also displacing some of the oxygen. Or by dousing it with a lot of water, which again cools the surrounding area and displaces some of the oxygen with steam.

              In a space station, I think the easiest way to stop a fire would be to vent the atmosphere since removing the oxygen would kill the fire right away. Though the downside is that humans also require oxygen so it'd kill any crew members in that section as well (Assuming they weren't in protective suits).

            • by Anonymous Coward

              The reason a flame rises on Earth is because of the very slight pressure difference between the bottom of the flame and the top. There is negligible lateral pressure differences, so the flame is roughly cylindrically symmetric. As the OP says, this is indirectly due to gravitational acceleration (though the gravitational field is essentially the same in LEO).

              This is why you see an almost spherical flame in space. The pressure is approximately equal all around it and the flame expands outwards.

          • by izomiac ( 815208 )
            It seems like simple diffusion should provide enough oxygen to feed a fire. Oxygen should flow from an area of higher partial pressure to an area of lower, as should the CO2 flow away from the fire. The gases shouldn't be forming bubbles, that goes against entropy and would make it impossible for humans to breath (we're effectively slow burning fires ourselves). In a swimming pool, water will form a hydration shell and interact with our skin, so that's a bit different.
        • Reading the heading of the article, I'm surprised they only got around to it now, we use combustion quite a bit as humans and it would be quite useful in space, I also wonder how artificial gravity would affect it considering something like http://en.wikipedia.org/wiki/Nautilus-X [wikipedia.org] .

        • by gl4ss ( 559668 )

          I'm just going wtf is this news of 2011?
          http://en.wikipedia.org/wiki/Flame#Flames_in_microgravity [wikipedia.org]

          I'm pretty sure I saw a similar picture in some book, magazine or something before 2000 too though. it's such an obvious experiment...

        • by Dadoo ( 899435 )

          Slightly off topic, but I read a book, a long time ago, about a space station in low earth orbit. In the book, there were a few paragraphs that discussed what might happen to a fire in micro-gravity. When a teacher lit a match, it burned with a spherical flame, and put it self out quickly, because there was no place for the CO2 to go. If you wanted the match to continue burning, you had to keep it moving.

          The book was science fiction, but it would be interesting to find out if they were correct.

      • by necro81 ( 917438 ) on Thursday December 01, 2011 @11:10AM (#38226022) Journal
        Which indicates there is a simple and obvious solution for extinguishing a fire in a spacecraft: just vent it out to space. The astronauts can just hold their breath, right?
        • by Anonymous Coward on Thursday December 01, 2011 @11:29AM (#38226230)

          That's a nice notion. However, there's a wicked problem with the bends. People say "your blood will boil", but that's not actually what happens; the bubbles will be dissolved gasses coming out of solution. even if you go with a straight oxygen environment (which we learned was a "bad idea" in the Apollo program), the oxygen dissolved in the astronaut's blood will come out of solution. Unfortunately, it won't dissolve again very quickly, which will leave you with bubbles in bad places, like the brain and lungs.

          You're also making the assumption that you have enough stored gas (call it air) to repressurize the spacecraft. Even if you live through the depressurization and repressurization, you haven't addressed the source of the fire, which will likely re-ignite. As long as spacecraft are small, gold-plated things, designing to current fire specs is a given. However, as they evolve into large vehicles, designing fire-proofing into everythign will become less and less feasible. People will want to bring clothes and food and shit like that.

          The other major thing to be considered is that while droplets behave differently, we also haven't looked at explosive combustion. I suspect it will be very similar. However, we might find that it's very different. Right now we cover military pilots in polyaramids, and accept that paying passengers are probably going to die in a flash fire. The assumption behind the flight suit is that the pilot's on an O2 mask, and so the lungs will be protected. Flash fires might behave very differently, and fire is a complex, complex beast.

          I've lived through a fire in an airplane, and it's scarry as fuck. Fortuantely, the aerospace community is very aware of it and designs against it.

          • by necro81 ( 917438 )
            While I appreciate your thorough analysis of my proposed solution, please keep in mind: I was joking!
          • Re: (Score:2, Informative)

            by LanMan04 ( 790429 )

            People say "your blood will boil", but that's not actually what happens; the bubbles will be dissolved gasses coming out of solution.

            Um, that's the definition of boiling: Dissolved gasses coming out of solution. Can be induced by heating the fluid, lowering the atmospheric pressure, or both.

            • by tmosley ( 996283 ) on Thursday December 01, 2011 @12:38PM (#38227060)
              Pretty sure boiling means the phase transition between liquid and gas.
            • by Bob-taro ( 996889 ) on Thursday December 01, 2011 @12:46PM (#38227152)

              People say "your blood will boil", but that's not actually what happens; the bubbles will be dissolved gasses coming out of solution.

              Um, that's the definition of boiling: Dissolved gasses coming out of solution. Can be induced by heating the fluid, lowering the atmospheric pressure, or both.

              I'm not sure either of you are right. Boiling is when something changes state from liquid to gas. If you lower pressure enough, your blood (the water in it anyway) would literally boil at room temperature. However, decompression sickness - gases coming out of solution - is a different phenomenon that would probably happen first (at a higher pressure).

            • People say "your blood will boil", but that's not actually what happens; the bubbles will be dissolved gasses coming out of solution.

              Um, that's the definition of boiling: Dissolved gasses coming out of solution. Can be induced by heating the fluid, lowering the atmospheric pressure, or both.

              Boiling is actually the transition of the liquid into a gas, not gasses dissolved in the liquid coming out of solution. They look incredibly similar, but boiling can happen with a pure liquid, while dissolved gasses kind of by definition cannot come out of solution in a pure liquid. (Yes, the liquid turns to a gas and then kind of dissolves itself in the liquid, but it turns out that a gaseous form of a substance dissolved in the liquid form of that same substance is indistinguishable from the liquid itself

            • No, boiling is the substance itself becoming gaseous.

            • by AvitarX ( 172628 )

              I don't think that's true.

              I've always took boiling to mean the liquid itself was converting to gas, this can happen in low pressure at room temperature, but is not the cause of the bends from diving. A vented space-station could cause it I imagine, though perhaps the skin would keep blood pressure high enough to keep the boiling point of water above room temperature.

              I'd be worried about eyeballs falling out.

          • by AJH16 ( 940784 )

            Just out of curiosity, I wonder if a quick flush would in fact cause the bends if re-compression was prompt. People can operate at pretty low PSI (space suits are 4.3, atmospheric at sea level is 14.7). Would momentary decompression be a large risk if it was brief enough (my personal knowledge of DCS is only in regards to SCUBA which is obviously on the much higher pressure side of things). My understanding was that DCS normally takes a small period of time to develop that might give a window, though I w

            • Yea, I think donning a breathing apparatus and flushing the atmosphere with something inert would be better. It would also give you more of a chance of recovering what was still viable in that atmosphere.

              You'd have to make sure it was a closed breather though, else the exhaust would just serve to provide oxidizer.

              • by AJH16 ( 940784 )

                Actually, now that I think about it more, since there is no convection, you might be able to just use a halon extinguisher. Using a dense gas to push out the oxygen in the immediate area should be sufficient without requiring a full flush of the atmosphere. The clean up might be a little tricky after and breathing apparatus would still be a very good idea, but it could save energy which is at a premium in space.

                • The trick may be to spray with something not so inert as halon... say, nitrogen. You may end up with some nitrous oxide as a byproduct, but it should be something that can isolate the burn and be easily scrubbed/diluted into the atmosphere after the fact. Add a bit of vanilla to the gas as a warning that you're entering a nitrogen-high zone before the fans have mixed it back into the system.

          • "You're also making the assumption that you have enough stored gas (call it air) to repressurize the spacecraft." Since the pressure on a space station 1atm (according to wikipedia, at least), you could depressurize to 1/10th that, low enough to squelch combustion, by using a giant hefty bag out in space to hold it until the fire's out, then pump it back in. Ok, a giant heatproof hefty bag that can hold in 1/10th atm.
        • by MozeeToby ( 1163751 ) on Thursday December 01, 2011 @11:53AM (#38226518)

          It's not as totally and completely insane as it sounds. Generally, people will recover from exposure to vacuum on their own if the exposure is short (less than 30s) and with surprisingly minor injuries if exposure is less than 90s. And that's without training and a warning of what's going to happen, given proper planning and equipment I suspect you could push the survival rate to the high 90%s, maybe even to two 9's.

          Given the choice between burning to death in inescapable zero-g fire and an automated 15 second emergency purge, with a quick re-pressurization system, O2 masks for quicker recovery, and the ability to manage air pressure afterwards to treat the bends... personally, I'd give it a shot. The only real question mark is if the source of the fire has been taken care of. If it's an ongoing short you might find yourself in the same boat you started in, but even that could be addressed by re-pressurizing the spacecraft with nitrogen and relying on O2 masks for the crew until everything is straightened out.

        • by slim ( 1652 )

          Yeah, I know you were only being flippant, but...

          There's a reason scuba divers are told to *never* hold their breath. If you don't release pressure from your lungs as the ambient pressure decreases (when diving, by ascending), you'll do catastrophic damage to your lungs.

          • by Guppy ( 12314 ) on Thursday December 01, 2011 @02:30PM (#38229122)

            If you don't release pressure from your lungs as the ambient pressure decreases (when diving, by ascending), you'll do catastrophic damage to your lungs.

            Not holding your breath in a vacuum presents another problem though. Gas exchange in your lungs is a passive process, driven by concentration gradients. As the partial pressure of O2 in your alveoli drops to zero, the diffusion goes into reverse; blood passing through your lungs actually has its remaining oxygen content sucked out, causing you to black out almost instantly.

        • You were joking but got close. Put the people on canned air and reduce the partial pressure of O2 until the flame dies. You can reduce the partial pressure of O2 a number of ways; reducing the over all pressure (your suggestion but not so far as vacuum);substitution of O2 with a gas that not only reduces O2 but futzes with the fire chemical reaction; chemically absorb the O2.
        • by Anonymous Coward
    • Tell that to the sun
  • by Anonymous Coward

    DO open the window.

    • by ledow ( 319597 )

      Hold your breath first, though.

      Seriously, fire on board something like that would be about the scariest thing to deal with. With loss of air or something, you don't have time to panic but if the fires are burning at 100th their normal rate but are large enough to be pretty much unextinguishable, you've got a lot of fighting to do before you eventually end up burning.

      It'll get into every possible escape route and keep following you, it'll slowly suck up all fuel everywhere (can't just "move stuff away" if t

      • Re:In case of fire: (Score:5, Informative)

        by 2fuf ( 993808 ) on Thursday December 01, 2011 @11:29AM (#38226228)

        relevant: http://www.youtube.com/watch?v=iSqOqRACxUM [youtube.com] (fire at the MIR station)

        • ..also known as the Russians got there first... as with most things in space

          they have done a lot of research on space stations already, they did send up 7 of them, have one manned for 10 years ... and built quite a significant proportion of the ISS ...

          The rest of the world have so far built 2 space stations, one is the ISS, jointly with Russia ...

      • by EdZ ( 755139 )

        Hold your breath first, though.

        Do NOT hold your breath in the case of sudden decompression. Rapid decompression is entirely survivable if you're recompressed within a minute or two, but holding your breath results in some very nasty damage to your lungs (essentially, your alveoli burst) that would not otherwise occur if you exhaled.

  • "Have you ever seen fire in zero gravity? It's beautiful. It's like liquid it... slides all over everything. Comes up in waves." I know it's not the same thing, but it reminded me of that film that I haven't watched in a while...
    • I absolutely love that movie. Sam Neil is one creepy dude (also see: In the Mouth of Madness).

  • ``Fireproof'' I think it was, in his collection _Space Lash (formerly published as _Small Changes_)_.

    Looks like his theorization on the science was good (as it usually is).

    That book, and The Mad Scientists Club books made a huge impact in my childhood.

  • Why? (Score:2, Insightful)

    by Anonymous Coward

    Why does everything have to be some stupid ass acronym?

  • Obligatory (Score:5, Funny)

    by mattie_p ( 2512046 ) on Thursday December 01, 2011 @11:21AM (#38226154)
    Screaming is different, too, from what I've heard. Or did I?
  • There is an increased risk of singed cheek hair on the members of the 200 Mile High Blue Flamer's Club.

  • by smooth wombat ( 796938 ) on Thursday December 01, 2011 @11:25AM (#38226208) Journal

    We all know what to do if a fire breaks out in a spaceship or station. Didn't you people watch Red Planet?

    You grab your fire extinguisher, point it at the fire, release the locking pin, pull the handle and get propelled across the room due to no gravity holding you in place and the fire retardant being ejected from the nozzle

    Come on you geeks, get with the program!

  • by Anonymous Coward

    Because FLEE would have been too unfortunate for a Space Station.

  • by Rogerborg ( 306625 ) on Thursday December 01, 2011 @12:06PM (#38226680) Homepage
    If you're trapped in a free-falling elevator, whether it's on fire or not is probably the least (or briefest) of your worries.
  • If the DoD was involved they could just launch a decommissioned space shuttle and set it ablaze... Then when it falls back to earth market it as a chance to win a piece of the shuttle! Talk about a great PR move!
  • Our tax dollars hard at work, fostering galactic pyromaniacs. Where can I opt out my hard earned cash?
  • This kind of experimentation provides research to something relevant to all of us, namely the Sun. It's something that very few people put any intense thought into, but is very important to us. There's also quite a bit about it that is not understood and every little bit helps, due to our dependence on its existence and how various unusual and not-well-understood (or not understood at all) phenomena can affect us.

    Two quotes from the article stand out to me:


    "In space, molecular diffusion draws oxygen

    • When one considers that less than 2% of the Sun is something other than Hydrogen and Helium, and Oxygen being only another chunk of that 2% with other elements having their chunks of that respective small percentage, that quote gives us considerable insight into why the Sun and other stars burn for as long as we believe they do.

      Two problems with what you said. First, the sun has gravity. It has a lot of gravity, and so hot gases do rise due to convection, as they do on earth. That said, the sun doesn't burn. The heat is generated from nuclear fusion in its core, and that is the reason why stars last so long.

  • ...no one can hear you scream.

I've finally learned what "upward compatible" means. It means we get to keep all our old mistakes. -- Dennie van Tassel