To make a gas giant flammable

Question

(Warning: do not try this at home-system)

Preamble

Hello humans, we need advice.

Let's say we have just successfully defeated and killed a Horror From Beyond Reason who happened to be multiple times the size of your planet (what's it called now? Earth?), and wanted to barbecue it (no, we don't want to eat it, why would you ask?! We just... want to make sure that it doesn't come back as a Zombie Horror From Beyond Reason. That sounds unpleasant.)

The first idea that comes to mind is to throw it in our star, but we would rather keep it as a trophy to warn potential enemy civilization not to intergalactically f*ck with us, so the star is a no-go (it would liquefy it! Plus, we don't really know what would happen and don't want to risk losing our lovely star to an Eldritch Explosion.)

Here comes the question:

How could we make a gas giant (suppose it's like your... Jupiter, is it?) flammable?

There are lots of elements in there (mainly helium, argon, carbon, nitrogen and, most importantly, oxygen, though not in its elemental form).

What can we do/change (using the fewest resources and energy possible) to be able to ignite a planetary-scale fire on Jupit- I mean, the planet we have that resembles your Jupiter?

Some chemical basics first : https://en.m.wikipedia.org/wiki/Oxyhydrogen?wprov=sfla1 read it . How long should the fire burn? — Raditz_35, Jan 23 '18 at 17:13
Jupiter's atmosphere does not contain oxygen. You cannot have at the same time hydrogen or methane and oxygen, because they would have combined a very long time ago. Similarly, you cannot have fluorine and almost anything else. In general, a gas mixture containing a gas which can burn and a gas which can maintain combustion is not stable. — AlexP, Jan 23 '18 at 17:13
Chemical energy of burning isn't going to do much to a planet sized creature even if you have a gas giant size ball of combustible gasses. — A. C. A. C., Jan 23 '18 at 17:50
No need to burn it. Chop it into pieces and let gravity take over. Inevitable reference to XKCD: https://what-if.xkcd.com/4/ — CaM, Jan 23 '18 at 19:46
@AlexP The Jupiter's atmospheric elemental abundances table on wikipedia says there is some oxygen... am I reading it wrong? — Hankrecords, Jan 23 '18 at 20:17
There are much easier ways to get where you are going without most likely ruining all life on your planet — Andrey, Jan 23 '18 at 20:22
If it is a gas giant it might not need much to ignite fusion at its core. Of course, A.C.Clarke already did that to Jupiter/Lucifer. But, what a wonderful trophy that was! Something visible a long way out! — Jyrki Lahtonen, Jan 23 '18 at 20:49
@Hankrecords The oxygen doesn't exist as pure oxygen and exist mostly as water. There might be traces of elemental oxygen but most of it would be converted to water or some other chemical. — A. C. A. C., Jan 23 '18 at 20:50
@JyrkiLahtonen - that was my first thought - fission enough helium into hydrogen, apply a little squeeze, and boom - All These World Belong To You, Except Europa. — Chris B. Behrens, Jan 24 '18 at 19:10
Related: How can I destroy a gas giant planet? (Full disclosure: My own question.) — user, Jan 24 '18 at 22:25

kingledion · Accepted Answer · 2018-01-24T23:00:47.257

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Cook the planet with the Sabatier reaction

The Sabatier process produces methane and water from carbon dioxide and hydrogen.

CO$_2$ + 4H$_2$ $\rightarrow$ CH$_4$ + 2H$_2$O ($\Delta H$ = -165 kK/mol)

The reaction is exothermic, but you need around 300-400 C temperatures to start it. The reaction is catalyzed by nickel.

Fortunately, the hydrogen and temperature are available deep within Jupiter. All we have to do is add Carbon Dioxide and nickel. For the nickel, find a nickel heavy asteroid and work it into low density zeolite pellets. Then find all the Carbon Dioxide you can. Obviously, you won't find as much carbon dioxide as there is hydrogen in Jupiter, but out beyond Saturn, carbon dioxide becomes more common. You can probably melt the crust of some of Uranus or Neptune's moons, or maybe some Kuiper belt objects and extract the carbon dioxide. You can definitely get some from comets.

Then toss all the ingredients into Jupiter and watch it burn!

Note

There aren't a lot of exothermic reactions with hydrogen (the main constituent of Jupiter) that don't involve pure oxygen, which is hard to make. Carbon dioxide is relatively common, so a hydrogen plus carbon dioxide reaction makes sense. Water is even more common than carbon dioxide, but I couldn't find another common ingredient to make an exothermic reaction with. Helium, of course, won't react with anything. So I think Sabatier is your best bet.

edited Jan 24 '18 at 23:00

answered Jan 23 '18 at 18:18

kingledion

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Thank you, kind human, this seems like the most efficient approach! (as a sign of gratitude, we are sending an escape shuttle your way... don't tell the others) – Hankrecords Jan 24 '18 at 08:05
@Ferrybig Look at the reaction equation. You don't need oxygen for this reaction to take place. That is the whole point; you don't have any oxygen so you must react something else. – kingledion Jan 24 '18 at 13:55
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"Alot" is not a word. ("Allot" is a word, but it doesn't mean "a lot", which is what I assume people mean when they type "alot". I'm not sure how that even got in the answer; this comment box won't even let me type "alot" without inserting the space for me.) Please fix that (if you can figure out how to make the system let you add one space and not make any other edits). – Monty Harder Jan 24 '18 at 16:19
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For Grah'xy'blarg's sake, it's just a space, isn't it? Sometimes we feel like humans get agitated for the tiniest things! – Hankrecords Jan 24 '18 at 16:46
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( @MontyHarder There's usually no auto-correction on PC, so this kind of typo is really common if you're not on mobile :) and I wouldn't really make a full edit just to insert a space... I don't think there's a way to "trick" the system) – Hankrecords Jan 24 '18 at 16:48
This solution, though technically not wrong, is very silly. As is any solution that involves chemical reactions. Dropping 1 mole of CO2 into the atmosphere of Jupiter produces 79.75 MJ from gravitational potential energy, while reacting that CO2 in the Sabatier process produces only 0.165 MJ from chemical potential energy. – Lex Jan 24 '18 at 22:39
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@MontyHarder Harsh dude, but as Hankrecords says I wouldn't demean myself to use a mobile device to answer questions. Hank deserves better than that :) – kingledion Jan 24 '18 at 23:02
@Lex I don't understand what you mean. Could you explain it like you're talking to a 9th grader? ('cause that's pretty much how far my knowledge of chemistry goes) How can a single mole of CO2 release the energy equivalent of 20kg of TNT? – Hankrecords Jan 25 '18 at 08:08
@Lex Well, the question asks about 'flammable' not 'generating energy.' So I was just trying to provide the most reasonable way to make Jupiter undergo some massive chemical reaction, as silly as it may be. – kingledion Jan 25 '18 at 13:37
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@Hankrecords The energy differential from deep space to Jupiter's surface is equivalent to the kinetic of Jupiter's escape velocity, which is equal to the potential energy and object falling to Jupiter would gain. Since you need to be going 59,500 m/s to escape Jupiter, that is 1.8 GJ/kg; or, an object falling from deep space will gain 1.8 GJ/kg of kinetic energy. Since a mole of CO$_2$ is 0.044 kg, then it will gain 40 MJ by falling to the surface of Jupiter. It will gain more if it falls to the core. I got slightly different numbers than Lex, but the principle is the same. – kingledion Jan 25 '18 at 13:42
@kingledion check you math, 1.8 GJ/kg*0.044 kg=79MJ. I think you divided by two for some reason. – Lex Jan 25 '18 at 19:08
@Lex Yep, 1.8 / 0.044 = 40; I divided and the answer must have looked close enough :). In any case, thats where the energy came from. – kingledion Jan 25 '18 at 19:31
@Hankrecords "Just a space"? Tell the guy whose business cards now call him "the rapist" that he can't really complain to the print shop about that little mistake. Either we care about getting things right or we don't. I do.
And I'm on a PC, not a mobile device.
– Monty Harder Jan 31 '18 at 21:18
@MontyHarder Good thing king's answer didn't make me a rapist. And you said this comment box won't even let me type "alot" without inserting the space for me. and automatic correction is not the norm on PC browsers (without add-ons), that's why I mentioned the mobile version. Plus, you generally pay for a print shop's work, so they'd better write that down damn perfectly. On the other hand, king's answer comes exclusively from his good will and helpfulness, so we're really comparing apples and oranges. Comments are not the place for this kind of discussion, anyway, we should probably stop – Hankrecords Feb 01 '18 at 00:02

Thucydides · Answer 2 · 2018-01-24T21:45:35.157

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To make a chemical fire out of a gas giant, you would need to supply an oxidizer in an amount similar to the amount of hydrogen in the gas giant itself. We would be talking about a "gas giant" sized planet made of oxygen colliding with the gas giant in question.

There is also the issue that most of the "fuel" for a chemical fire is not going to be accessible anyway, since it is in the form of liquid or metallic hydrogen compressed near the core:

Planetary cross section

Adding sufficient oxygen might not create a "fire" at all, but rather an even denser, more monstrous core of highly compressed metallic "ice". This diagram shows the phase diagram of various forms of ice, at the pressures and temperatures that make hydrogen a metal, you would probably have forms of ice ranging from ice VII on up:

Phase diagram of ice

Now most people understand that a barbecue is an exothermic, energetic event. While creating ice with oxygen and metallic hydrogen might possibly be exothermic (no one has done the experiment, and certainly no one has done anything on that scale), to be really sure, you should turn to nuclear reactions.

For a planet with a metallic hydrogen core, we can induce nuclear fusion though means of muon catalytic fusion. Since we need a lot of muons to displace the electrons in the degenerate metallic hydrogen, a massive muon generator shining a high intensity beam of muons to blanket the core will be needed in orbit. The displacement of electrons draws the hydrogen nuclei close enough together to overcome the coulomb barrier and induce fusion. The energetic fusion reactions will release more than enough energy (in the form of high energy radiation) to barbecue any conceivable being or device, particularly since the amount of fusion fuel will be massive and the reaction could continue for millennia.

Muon catalytic fusion

Instead of barbecue, you will have created an artificial star.

edited Jan 24 '18 at 21:45

answered Jan 23 '18 at 17:53

Thucydides

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I think you may have gotten "endothermic" and "exothermic" backwards. The verbage you wrote makes more sense if we swap those words. – Cort Ammon Jan 23 '18 at 18:47
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Why the 'Phase diagram of water' rather than the 'Phase diagram of hydrogen'? – Dan D. Jan 23 '18 at 19:56
Cort Ammon, thanks, changed it. Dan D, if you are adding Oxygen to hydrogen, you will get water, hence ice – Thucydides Jan 23 '18 at 20:38
The question says that they don't want to use a star. – Nat Jan 23 '18 at 21:59
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The argument about ice is kinda confusing. This answer seems to claim that oxygen+hydrogen would become water, which'd then become ice. The thing's that the process of oxygen and hydrogen becoming water is "fire", which seems to be exactly what they're after; so, is that really a problem? – Nat Jan 23 '18 at 22:06
If you add a jupiter sized oxygen gas giant to jupiter then also throw in a planet-sized monster, the chemical reactions will be more than exothermic enough for our purposes... but that's enough mass you'll probably be igniting a second star anyway – Nathan Smith Jan 23 '18 at 22:09
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@NathanSmith You need about 13 Jupiters for fusion, so adding a second Jupiter is no problem. – kingledion Jan 24 '18 at 01:21
@kingledion You need 13 jupiters for gravity induced fusion. This creates enough gravity to overcome the coloumb barrier and initiate the process of star creation naturally. Much like firing radiation into nuclear fuel to ignite it, you can start the process artificially without said gravity.
Gravity becomes the secondary factor in the question of how you keep the fusion reaction going, because the core of Jupiter is going to be subject to intense pressure and the densely packed atoms will be more than happy to trap the core for a few decades at least. Jupiter is BIG.
– user1901982 Jan 24 '18 at 17:10
@kingledion I didn't realize it would take 13; I'd assumed 3 or 4 would be enough. Still, you're going to get some pockets of fusion at the very least if you throw a giant planet of oxygen against a giant planet of hydrogen. (just letting metallic hydrogen turn into diatomic hydrogen releases huge amounts of energy, & it's going to want to do that as it combines with oxygen) – Nathan Smith Jan 24 '18 at 21:55

score 8 · Answer 3 · answered Jan 23 '18 at 17:39

I am a little worried you want to blow up a gas giant for some other reason. But considering monster corpse disposal: an explosion risks throwing the incompletely burned corpse some distance, and immersion in flame or sunstuff risks incomplete burning. Either way you lose track of the corpse.

Steady heating of the corpse, however, offers the prospect of energetic rearrangement of component elements and volitalization of others all in glorious plain sight. One could obtain said steady heating by putting the corpse in a toasty warm Mercury-like orbit near your sun. Best - you can keep an eye on the corpse to make sure it does not get up to any new shenanigans and make sure it is not spirited off by its compatriots. The corpse, merrily steaming and bubbling, will also serve your intended warning purpose as a head on a stake.

But the question: how to make something burn which is not burning. The answer: add something else which will burn in combination. Your gas giant contains oxygen (?!) and so I presume all else in such an atmosphere will be terminally oxidized. If you add a quantity of material which is not terminally oxidized it will terminally oxidize. Hydrogen, methane and ammonia are all readily oxidizable and handy in large amounts in the solar system. Your gas giant seems to have an unusual compostion, but planets like Neptune have lots of flammable hydrogen. Titan is handy with lakes of ethane and methane.

What are insinuating?! Of course we don't have another reason for igniting Jupi- *our* gas giant! We just need to cook the... Eldritch thing, yeah. Thank you for your insight anyway, human, especially the first part because that's absolutely the more important to us. — Hankrecords, Jan 24 '18 at 07:51
Your gas giant contains oxygen (?!) our mistake. Our gas giant is exactly the same as your Jupiter and, as other gentle humans have pointed out, Jupiter does not contain any elemental oxygen, so our giant (let's call it definitely-not-Jupiter) does not either. — Hankrecords, Jan 24 '18 at 07:54

score 3 · Answer 4 · answered Jan 23 '18 at 17:34

Well, if you want to lit a barbecue, you need to gather combustible and comburent.

Your combustible is this gas giant, and as you already noticed you need to add oxygen or fluorine or whatever oxidizing gas you need.

Scout the space searching for planets with atmosphere rich in such elements. As a bonus for us helping with this task, please spare Earth. Incidentally, you need to find planets like Earth, where living organisms keep a decent amount of oxygen in the atmosphere.

Once you have gathered a good bunch of these planets, throw them into the gas giant, and enjoy the view.

Do not worry, humans, we would never do such a thing to Earth. We are igniting our own gas giant (totally not Jupiter and thousands of light years away), and we have a long list of planets on which we have found life. Earth is absolutely not the first one ever after centuries of search. Thank you for your insight. — Hankrecords, Jan 24 '18 at 07:57

score 0 · Answer 5 · edited Jan 24 '18 at 16:23

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Fusion reaction

People are talking here about chemical reactions, as far as I see. What about atomic reactions? Ignite a fusion reaction on this almost-star.

Jupiter is too small to start a fusion reaction on its own. But we might help, with a coupe of Tsar-bombs, for example. A review of this from modern physics perspective is pending.

I also need to caution you that this plot idea is very old, Sir Arthur Clarke used it somewhere. I guess it was 2010: Odyssey Two, but unsure.

edited Jan 24 '18 at 16:23

gingerbreadboy

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answered Jan 23 '18 at 20:56

Oleg Lobachev

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As far as initiating fusion on Jupiter goes, it doesn't matter whether we add "Tsar-bombs" or party poppers.
if we captured a white dwarf from interstellar space, that could maybe do it though
– Nathan Smith Jan 23 '18 at 21:43
So you mean, there is no way to ignite all that hydrogen on Jup other that throwing another star on it? – Oleg Lobachev Jan 24 '18 at 09:05
Never mind, here is a more detailed answer: https://worldbuilding.stackexchange.com/a/102990/42059 – Oleg Lobachev Jan 24 '18 at 11:31
I think you are underestimating how huge Jupiter actually is. "a coupel of Tsar-bombs" would do nothing. Also, if you want Jupiter to undergo fusion, you don't just need to ignite it, you have to sustain it. Stars sustain fusion because their gravity is large enough to generate enough pressure to keep the fusion reaction going for billions of years. Gas giants don't have enough gravity, so you would have to constantly create pressure from the outside in order to keep the fusion reaction going. – Philipp Jan 24 '18 at 14:13
Oh, I see. My thought was about provoking uncontrolled fusion reaction with hydrogen, the kind that was feared in the early nuclear days with ocean water. But your comment makes perfectly sense, given that Jupiter is too small to be a star. – Oleg Lobachev Jan 24 '18 at 14:19
The actual Tsar bomb had a yield of 50 megatonnes of TNT. The theoretical yield was 100MT with an additional U238 tamper. Fragment G of comet Schumacher Levy 9 hit Jupiter with the equivalent of 6,000,000MT. So "a couple of Tsar bombs" is out by 4½ orders of magnitude from something that had only a transient effect on Jupiter. – Martin Bonner supports Monica Jan 25 '18 at 08:00