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ISS NASA Space Science

Fire Burns Differently In Space 146

Posted by timothy
from the half-as-long-twice-as-bright dept.
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 show me altoids (1183399) on Thursday December 01, 2011 @11:08AM (#38225998)
    Yeah, but with no convection to carry away the combustion byproducts and bring in more oxygen, it is much more difficult.
  • by Dan East (318230) on Thursday December 01, 2011 @11:24AM (#38226194) Homepage 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.

  • 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 Anonymous Coward on Thursday December 01, 2011 @12:08PM (#38226706)
    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 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 The_Crisis (2221344) on Thursday December 01, 2011 @01:00PM (#38227342)

    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 increase the pressure and cause airflow away from the center of the combustion source which would prevent much if any O2-rich air from circulating, in effect choking itself out.

  • by Anonymous Coward on Thursday December 01, 2011 @01:44PM (#38228154)

    If I remember right: ISS, MIR... are/were very noisy because everything electronic has to be cooled by forced convection (fans). Without natural convection even a low powered circuit board that would easily dissipate the heat on Earth could eventually overheat in zero G as the heated air just sits there next to the components.

  • 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.

  • by mcgrew (92797) * on Thursday December 01, 2011 @04:26PM (#38230856) Homepage Journal

    You do know that we went from the founding of this country to 1913 without an income tax, right?

    There was no income tax, but there was taxation. My grandfather was 17 years old in 1913. Few know (as far as I can tell) that when the federal income tax was enacted, only the rich were taxed.

    The tax was to pay for a war, which is pretty much where most of your federal income taxes go anyway.

    Without income taxes you would not have the interstate highway system (which, incidentally, was built by a Republican administration). I was a little kid when they started building it, and I remember that getting from St Louis to Springfield was a three or four hour drive, vs the hour and a half (or less) on the interstate.

    Without federal income taxes you would not have the hoover dam. Americans would not have landed on the moon. America wouldn't have been able to reap the financial winfall of rebuilding Europe after WWII.

    The only downside to taxes is that you're a greedy selfish money grubber. Since you seem to be a tea party type, you probably consider yourself to be a Christian (hint: there are no Christians in the Tea Party, it is definitely against everything Jesus taught), you might want to open that bible you like to thump and read Matthew 22:21.

"Marriage is like a cage; one sees the birds outside desperate to get in, and those inside desperate to get out." -- Montaigne

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