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To have a fire you need three things: oxygen, heat and flammable material, therefore the cold vacuum of space is the last place you would expect something to burn. I was, however, wondering if a very large damaged spaceship would change this.

Suppose for instance that an explosion has happened aboard a spaceship, which not only has damaged a fuel pipe inside the spaceship, such that anything close to the explosion has been soaked in flammable liquids and has caught fire, but which also has made a significant hole in the exterior hull of the ship.
If the hole is big enough, and if the ship has so much air that it will not be emptied too quickly, I assume that the pressure of the air inside the ship would be enough to blow several of the fuel-soaked and burning things near the hole out into space.
As these burning pieces of debris leave the damaged spaceship, I was, however, wondering if they would keep burning for a short period of time, or if the fire would die out as soon as they left the spaceship.

My first hypothesis was that the burning debris could keep burning, at least the first few seconds after leaving the spaceship, since oxygen needed for the burning debris to keep burning would be provided by the air flowing out of the spaceship, the temperature by the combined heat of the burning debris and the air – which would have been heated up by the fire inside the spaceship – (also keep in mind that since there are no matter in space, the only way for the air and debris to lose thermal energy is through radiation, which is not very efficient) and the flammable material by the leaked fuel in which the burning debris is assumed to be soaked.

My second hypothesis was however that the burning debris would stop burning the very second it flew through the hole in the spaceship – perhaps even before that because the expansion of the air leaving the ship would cause it to cool down very rapidly, such that the air surrounding the burning debris very quickly would absorb almost all the thermal energy of the debris, thus making the fire die out.

My question is, therefore, taking all this into account (and perhaps more factors that I have completely missed) is it likely that burning debris in the given situation, could keep burning for more than a few seconds in space -- at least long enough to justify using burning debris as a visual effect in games or animations -- or is burning debris in space simply unthinkable.

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    $\begingroup$ My guess is the oxygen would spread way to fast in space to hold up a flammable "atmosphere" around the fire. Stuff would glow hot a long time though, since there's no heat dissipation over convection in space ;) $\endgroup$ – Fl.pf. Jun 8 '17 at 9:49
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    $\begingroup$ Note the fire incedent abord Mir. Read up on that for not only the possibility but real details of how fire behaves in microgravity. $\endgroup$ – JDługosz Jun 8 '17 at 10:03
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    $\begingroup$ A fire inside a spaceship/station is completely different $\endgroup$ – Fl.pf. Jun 8 '17 at 10:10
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    $\begingroup$ @SZCZERZOKŁY It is not a given that using nuclear power gets rid of reaction mass to blast out of drives. You're assuming that the power plant is also the propulsion, which isn't necessarily the case. Also, Oxygen is an oxidizer, but not every oxidizer is oxygen $\endgroup$ – Doomed Mind Jun 8 '17 at 11:07
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    $\begingroup$ The vacuum of space is not cold. Temperature is a property of matter, and where there's no matter there's no temperature. $\endgroup$ – Mike Scott Jun 8 '17 at 16:32
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First off, something that might seem like an inconsequential detail or perhaps even nitpicking, but really isn't in this case: You don't need oxygen for something to burn. What you need is an oxidizer, of which on Earth oxygen happens to be one of the most readily available. Thus the typical fire triangle says oxygen, but that is really a simplification.


The Fire triangle created by Gustavb. Self-published work by Gustavb, used under CC-BY-SA-3.0.

Fuel plus oxidizer plus heat equals (typically exothermic) chemical reaction A.K.A. fire.

There are quite a few materials that do not require an external source of oxidizer to burn. For example, lithium-based battery chemistries typically contain their own oxidizer, and as such can create very difficult-to-put-out fires. Compare for example Why is there so much fear surrounding LiPo batteries? on Electrical Engineering, perhaps particularly metacollin's answer which discusses this directly.

What's more, spacecraft typically contain lots of such compounds. Quite a few rocket fuels are hypergolic, which means that two components will spontaneously combust upon contact. This is used for a variety of reasons, not the least of which is the relative simplicity (hypergolics are nasty, but they are a known nasty; in return, you don't need to worry about e.g. ignition). Even those that aren't hypergolic are typically highly energetic, and of course being designed to operate in a vacuum, a rocket will be bringing its own oxidizer along with the fuel. One of the workhorses of rocket propellants is cryogenic liquid hydrogen as fuel and liquid oxygen as oxidizer, which combine in the well-known chemical reaction to form dihydrogen monoxide -- also known as water, typically in the form of water vapor due to the high temperatures involved.

If a fuel pipe has been ruptured aboard a spacecraft, there is a very good chance that a nearby oxidizer pipe has also been damaged. (Typical spacecraft use bipropellants, but monopropellants are also a thing.) Depending on the exact conditions and the specific propellant combination in use, the two may combust spontaneously (hypergolics) or not (non-hypergolics), but there's a good chance that whatever damaged the spacecraft might have caused a spark, providing a source of ignition. As long as the fuel and oxidizer flow is maintained, then, they will continue to react with each other.

Once a sufficiently hot fire comes into contact with flammable materials, those materials will also start to burn, but only so long as there is a suitable oxidizer present.

Also keep in mind that the ability of a material to burn is typically a function of the amount of oxidizer present. Apollo 1 illustrated this quite well, and one quote sticks in my mind from a Nova documentary on the US moon program: At 15 pounds per square inch of oxygen, aluminum burns. We don't typically think of metals as flammable, but they are. Even iron is flammable in the presence of typical amounts of oxygen, although at a very slow rate: we refer to it as rusting, but just like hydrogen and oxygen forms dihydrogen monoxide, iron and oxygen forms ferrite oxide.

All this to say that yes, depending on specific conditions, having things burning in outer space is absolutely possible. All you need is a suitable local concentration of both fuel and oxidizer, as well as something to get the chemical reaction started. Localized spacecraft damage can easily provide all three.

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    $\begingroup$ Aluminum burns quite nicely in standard atmosphere, as long as you get the geometry right. I've seen helicopters reduced to a pile of ash, leaving a helicopter-shaped burn area. $\endgroup$ – WhatRoughBeast Jun 8 '17 at 14:28
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    $\begingroup$ This seems like an excellent opportunity to reference Derek Lowe’s reporting of some lovely chemicals that are better oxidizers than oxygen, like chlorine triflouride or dioxygen difluoride. The former appears in Ignition!, which notes that it is “hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water—with which it reacts explosively.” $\endgroup$ – KRyan Jun 8 '17 at 14:34
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    $\begingroup$ @KRyan "Now it is clear that anyone working with rocket fuels is outstandingly mad. I don’t mean garden-variety crazy or a merely raving lunatic. I mean a record-shattering exponent of far-out insanity. There are, after all, some chemicals that explode shatteringly, some that flame ravenously, some that corrode hellishly, some that poison sneakily, and some that stink stenchily. As far as I know, though, only liquid rocket fuels have all these delightful properties combined into one delectable whole." Ignition!, quote borrowed from space.stackexchange.com/q/3805/415. $\endgroup$ – a CVn Jun 8 '17 at 14:38
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    $\begingroup$ @Rekesoft The OP specified "damaged" fuel plumbing. That could mean virtually everything from a small hole, to completely broken-off pipes with pumps still running at full whallop. My answer tries to give some background to back up the main statement near the end, which itself is qualified with the depending on specific conditions. Obviously if the tankage is wide open that won't last long, but for the duration, it stands to reason that an exothermic chemical reaction could be sustained. If you feel you can provide an even better answer, then by all means please do! $\endgroup$ – a CVn Jun 8 '17 at 14:50
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    $\begingroup$ @Rekesoft Take something like the explosion aboard Apollo 13, which completely destroyed one oxygen tank and damaged the other one sufficiently for its contents to leak out over a time period of minutes. It's not too hard to imagine a similar scenario but damage also to a fuel tank. If they happen to be positioned in just the right (wrong) way, and especially if their contents were hypergolic with respect to each other, well; you've got an even bigger problem than an initial main B bus undervolt condition... $\endgroup$ – a CVn Jun 8 '17 at 15:00
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To have fire you need an oxydant, energy and an oxydable material. Oxygen is a common oxydant, but not the only.

Keep in mind that in microgravity combustion can be less efficient, as convective motion does not happen and gaseous oxydant must rely only on diffusion to reach the reaction site (look at footages of a candle lit in microgravity). This said, as long as there is contact/mixing between the oxydant and the oxydable material, there can be combustion.

Since liquid and gas would hardly last in space vacuum, the only possible long lasting fire is given by solid state materials reacting (i.e. thermite would keep burning even in vacuum, it doesn't need gaseous oxygen).

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  • $\begingroup$ To follow up on what you wrote: Cody's Lab has shown on YouTube that a pile of gunpowder in a vacuum won't ignite, even though it has it's own oxidizer. $\endgroup$ – RonJohn Aug 21 '17 at 20:57
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Have you ever heard about Chlorine trifluoride? This hellboy is very strong oxydizer and will put on fire almost everything even without oxygen and ignition (water, glass, metals and humans included).

Here is quote from Wiki:

ClF3 is a very strong oxidizing and fluorinating agent. It is extremely reactive with most inorganic and organic materials, including glass and Teflon, and will initiate the combustion of many otherwise non-flammable materials without any ignition source. These reactions are often violent, and in some cases explosive. Vessels made from steel, copper, or nickel resist the attack of the material due to formation of a thin layer of insoluble metal fluoride, but molybdenum, tungsten, and titanium form volatile fluorides and are consequently unsuitable. Any equipment that comes into contact with chlorine trifluoride must be scrupulously cleaned and then passivated, because any contamination left may burn through the passivation layer faster than it can re-form. Chlorine trifluoride has also been known to corrode otherwise known non-corrodible materials such as iridium.

The power to surpass the oxidizing ability of oxygen leads to extreme corrosivity against oxide-containing materials often thought as incombustible. Chlorine trifluoride and gases like it have been reported to ignite sand, asbestos, and other highly fire-retardant materials. It will also ignite the ashes of materials that have already been burned in oxygen. In an industrial accident, a spill of 900 kg of chlorine trifluoride burned through 30 cm of concrete and 90 cm of gravel beneath. Fire control/suppression is incapable of suppressing this oxidation, so the surrounding area must simply be kept cool until the reaction ceases. The compound reacts violently with water-based suppressors, and oxidizes in the absence of atmospheric oxygen, rendering atmosphere-displacement suppressors such as CO2 and halon completely ineffective. It ignites glass on contact.

You can't put out fire from Chlorine trifluoride with vacuum, you can't put out fire from Chlorine trifluoride with sand, you can't put out fire from Chlorine trifluoride with water.

It will burn in space. And it is used as component in rocket fuels so it's perfectly normal to find this chemical on a spaceship.

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    $\begingroup$ For an even better write-up for ClF3, see Sand won't save you this time $\endgroup$ – Martin Bonner supports Monica Jun 8 '17 at 14:27
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    $\begingroup$ What do you mean, "used as a component in rocket fuels"? All that I've heard indicates that it was abandoned for that purpose after initial testing, due to not being controllable enough for rocketry (though if I'm wrong, I'd love to hear about it - things that ignite sand are fascinating). $\endgroup$ – Ethan Kaminski Jun 8 '17 at 16:10
  • $\begingroup$ @EthanKaminski we speak about fictional world. Author can make technologies in the future advanced enough to control such a thing and use it to ignite fuel effictively. $\endgroup$ – Exerion Jun 8 '17 at 17:05
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    $\begingroup$ @Exerion your answer specifically states "And it is used as component in rocket fuels", not "it's a reasonable idea for a story". $\endgroup$ – RonJohn Aug 21 '17 at 21:05
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I like both of these answers, but I would also like to point out that when a space craft is ruptured the oxygen doesn't just flow out quickly, it is called "explosive evacuation." When the hole happens in the ship all of the air that can leave, does leave nearly instantaneously. It's not like on the movie Aliens where people can struggle against the flow until they can get the door closed. So I wouldn't use air from inside the ship to keep your fires burning.

As an example, the crew of the Mir space station struggled like Ripley in Aliens against a stream of atmosphere leaving the station, but the holes the air was leaving through were so small, they never found them to patch them and that module was never used again.

Hope this helps.

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  • $\begingroup$ I don't think this is true. For example, people don't even get sucked out of modest sized holes in airplanes. You need something big, like the Aloha Airlines Flight 243, where the front third of the top of the plane ripped off. Even then, the plane landed successfully, and only one person died. $\endgroup$ – RonJohn Aug 21 '17 at 21:02
  • $\begingroup$ I'm sorry, but I'm pretty sure you are wrong. On the MIR space station two astronauts had to close a door against a stream of air so powerful they said it was like closing the door in the middle of stream of flowing water and that was from a hole so small they never found it. And recently a woman was sucked out of a window on a Southwest airplane. If she didn't have her seat belt on, I'm pretty sure she would have been pulled all of the way out since her entire upper torso was out and it took more than one person to pull what was left back into the aircraft. $\endgroup$ – ozone Jan 31 at 14:21
  • $\begingroup$ Just saw I already had that in my response. But let's do a rudimentary calc here. Surface area of a normal sized man ~3000 in^2. He's only pushed from behind so cut it in half ~1500 in^2. Let's say the sides don't count and make it an even 1000 in^2. Let's say 90% of the air flows around him and doesn't even push him. At 1 atm that still leaves a force of 1,470 lbs. $\endgroup$ – ozone Jan 31 at 14:44
  • $\begingroup$ If there's a hole with an area of 1 square inch, if the vessel is pressurized to 1 ATM, then the force at the hole is only going to be 14.7 lb. $\endgroup$ – RonJohn Feb 1 at 16:24
  • $\begingroup$ Certainly not ANY hole will cause this. I don't think we are talking about a tiny hole. $\endgroup$ – ozone Feb 2 at 18:29
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No. The Cody's Lab video Is Fire Possible in a Vacuum? demonstrates the necessity of a fire quadrangle: fuel, oxidizer, heat and pressure to keep the fuel and oxidizer near to each other. Otherwise, the energy of ignition blows the heat away and you get a little puff of smoke instead of combustion.

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As pointed out out before combustion is entirely possible in vacuum, proof given by all rocket engines; in particular solid rocket fuel will happily burn in space even in absence of the "engine" itself.

OTOH "normal" fire as developed inside your spaceship (relying on atmospheric oxygen as oxidant) would die rather quickly once outside the containment due to two factors:

  1. drop in oxidant pressure, which means less oxidant molecules will strike the burnable material.
  2. drop in temperature. Expanding gas will become cold very fast, without the need to radiate its heat (contrary to what You state). Opening a bottle of highly compressed gas results in frost around the exhaust in matter of seconds.

So, depending on the specifics of the burning materials, they can continue burning (unlikely, things exhibiting such behavior simply aren't laying around unprotected) or stop burning almost instantly once pressure around them drops.

As seen from outside, if the amount of non-gaseous burning material is high, you could see a long flame erupting from the spaceship, mostly due to hot materials still radiating (even if not actively burning anymore).

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