Do rockets have the most fire?
February 1, 2019 3:21 PM   Subscribe

My 3-year-old asked me this question and I didn't have a good answer for her. Do rockets create more fire than anything else, and if not what is capable of creating more? I figured the sun isn't exactly fire and I hoped the answer wasn't a nuclear bomb, as I'd rather not introduce her to the idea of warfare quite yet.
posted by thetruthisjustalie to Science & Nature (21 answers total) 9 users marked this as a favorite
Forest fires have a lot of fire.

Volcanoes also have a lot of fire, we're going to need a better method of quantifying fire before we can say whether rockets or volcanoes have more fire.
posted by GuyZero at 3:31 PM on February 1 [11 favorites]

Seems like a forest fire makes more fire than a rocket, in the sense that the fire coming out of a rocket is just in one place and a forest fire can make fire across a whole state. (On preview, I’ll buy you a Coke Zero, GuyZero)

If you’re not looking for strictly factual answers you could say a dragon makes more fire, since rockets run out of fuel but dragons never do.
posted by ejs at 3:32 PM on February 1 [6 favorites]

Depends what you mean by 'most'. A rocket engine is pretty much a machine for combustion, which generates thrust, so the fire is intentionally very concentrated. A forest fire involves 'more' fire, but that fire is much less concentrated. The sun doesn't work by combustion, so you're safe in assuming that it's not really fire. A volcano spews hot rock, but unless that rock causes something else to ignite, it's not fire as such.
posted by pipeski at 3:34 PM on February 1

There is a lot of fire inside a power station, but not as much as the biggest rocket.

The largest rocket ever, the Saturn V that took men to the moon had a peak power output of 160,000,000 horsepower, or 119 GW.

The largest fire driven power station in the world is the Tuoketuo coal power station in China, which has a rated output of 6.7 GW. With a typical efficiency of 40%, it might use 16 GW of fire at its peak.
posted by richb at 3:57 PM on February 1 [5 favorites]

If the sun isn't fire, a nuclear bomb probably isn't either, so you're safe there.

I would probably liberally define fire as 'what a particular kind of stuff does when you make it very hot', and write an exemption for volcanoes to be fire. Because lava can look like fire. And volcanoes are nifty.
posted by Sing Or Swim at 3:59 PM on February 1

Wait, how is the sun not fire? Isn't that all the sun is ... a giant ball of gas-fire?
posted by mccxxiii at 4:05 PM on February 1

To the best of my (extremely limited) understanding, fire is a chemical reaction, whereas fusion-like-in-the-sun is a nuclear reaction. "Nuclear reactions involve a change in an atom's nucleus, usually producing a different element. Chemical reactions, on the other hand, involve only a rearrangement of electrons and do not involve changes in the nuclei," says somebody who paid attention in school and knows more about it than me.
posted by Sing Or Swim at 4:29 PM on February 1 [4 favorites]

This whole thing kinda hinges on your definition of fire. Fire is what you get when you have rapid exothermic oxidation in an atmosphere. Rockets make fire. Forest fires make fire. The sun undergoes fusion. Volcanos are merely very hot rock. A three-year-old may not understand the difference though.

It's probably forest fires, to be honest. Having a hard time thinking what else it would be.
posted by Anticipation Of A New Lover's Arrival, The at 4:47 PM on February 1 [1 favorite]

Fire is what you get when you have rapid exothermic oxidation in an atmosphere. Rockets make fire

Rockets' fire still happens when they're outside the atmosphere.
posted by aubilenon at 4:58 PM on February 1 [1 favorite]

If the thought process is “A rocket is something that lots of fire comes out of. Is there something bigger than that that MORE fire comes out of that I should be prepared for?” I’d say the answer was no.
posted by bleep at 5:05 PM on February 1

Well, life has been described as “slow fire,” so it might be that the totality of all organisms has “the most fire,” but spread very evenly across the surface of the globe. This might be a good place to talk about the citric acid cycle and electron transport and ATP if I actually understood them. Since I don’t, I’ll just stop here...
posted by Gilgamesh's Chauffeur at 5:23 PM on February 1

It's definitely not less scary than other answers, but I found the Wikipedia page on the largest artificial non-nuclear explosions to be grim but compelling reading. One plausible answer there might be the T.A. Gillespie Company Shell Loading Plant explosion, which had an estimated yield equivalent to 6.0 kt of TNT. That's more than three times what Elon Musk said the Falcon Heavy would supposedly yield, so I'd speculate the plant explosion had 'more fire' than most rockets (note: I'm just googling--not any kind of expert--but I spent like two hours reading that Wikipedia list and related links a few months ago, because wow).
posted by Wobbuffet at 5:39 PM on February 1

Fire is what you get when you have rapid exothermic oxidation in an atmosphere.

Rockets' fire still happens when they're outside the atmosphere.

I think a better definition might just be "Fire is what you get when you have rapid exothermic oxidation". Rockets work in space because they provide the oxygen as well as the fuel. Like an oxy-acetylene torch (which is also definitely fire), rockets aren't reliant on the atmosphere to provide the oxygen because they require WAY more oxygen than our atmosphere is able to easily provide.
posted by autocol at 6:26 PM on February 1

Firestorms have the most fire, they form out of large and severe wildfires, and serve to make them more intense. In Australian eucalypt fires, entire flaming trunks can be launched dozens of meters, wispy flaming bark flies everywhere, and the air itself can flash ablaze due to aerosolized volatile oils. Many eucalypt species have basically evolved to make devastating fire and they are rather good at it, having had millions of years of practice.
posted by SaltySalticid at 6:39 PM on February 1 [1 favorite]

Incidentally, this source [PDF] gives an estimate for wildfires that might be compared with rockets, etc.: the Canberra bushfires of 2003 "released the energy equivalent of about 350 kilotons of TNT in the afternoon of 18th January." That's ~175 Saturn V rockets or ~58 Gillespie Co. explosions. Another footnote to the thread: SaltySalticid's link points out that the bombing of Hiroshima set off a firestorm as an aftereffect of the nuclear explosion, so it's a possible answer here too, even if nuclear reactions are excluded.
posted by Wobbuffet at 6:41 PM on February 1 [4 favorites]

Here's a nice video clip of clear air catching fire above a wildfire, I bet she'd like that, pretty awesome power of nature.
posted by SaltySalticid at 6:48 PM on February 1 [1 favorite]

Incoming meteor strike would pack a lot of fire: Chicxulub
posted by effluvia at 7:42 PM on February 1

A ship explosion in 1947 was horribly huge and the meteor impact in Siberia that knocked over trees for hundreds of miles would have been very hot due to compression so the trees were probably burnt to a crisp.
posted by sammyo at 8:08 PM on February 1

All of these answers come from adults. But the original question comes from a 3-year-old - who most emphatically does not need any information about nuclear bombs.

A rocket is probably the best answer when it comes to things made by people.

I like the reference to volcanoes WRT things that come from nature. That satisfies the child's interest in big booming things and gives the adult the chance to tell him a little bit about the earth he lives on.

But, please, just a little now. Leave some for later.
posted by yclipse at 8:16 PM on February 1 [1 favorite]

One way to compare fires would be by the amount of energy released. What follows are very back-of-the-envelope calculations with wide variances, but should be good enough for order-of-magnitude calculations.

The most powerful rocket ever made is the Saturn V. As fuel, it used ~770000 liters of kerosene in its first stage, and a combined ~1230000 liters of liquid hydrogen in its second and third stages. Density of kerosene = ~0.8kg/L, density of liquid hydrogen = ~0.07kg/L, heat of combustion = ~46MJ/kg for kerosene and ~142MJ/kg for hydrogen, math math math, and you get about 4.1*1013 joules, or 41TJ released by a Saturn V, equivalent to just 10 kT of TNT.

The 1997 Indonesian forest fires [insert debate about whether it's fair to count this as a single fire] released between 0.81 and 2.57 GT CO2. (1GT = 1012 kg) Which is a wide range, but it's a starting point. For convenience, lets take 1GT, near the low end of that range. Burning wood (well, woodchip, but remember, back-of-the-envelope) releases ~1500kg CO2 per 1MWh = 3.6*109 J, which works out to ~2.4*1018J, or 2.4EJ - about 50,000 times that of the Saturn V, or ~570MT TNT. That's the low end, multiply by 2.5 for the high end. As others have said, a nuclear explosion is not a fire, but for comparison the largest man-made nuclear explosion was the Tsar Bomba with a yield of just 58.6MT.

Of course, you can argue whether energy comparison is a reasonable measure of "the most fire." Power (energy released over time) might be more reasonable. As I like to point out, a metabolizing a king-sized Snickers bar releases as much energy as a stick of dynamite, but over hours or days rather than in a fraction of a second. The Saturn V burns for about 12 minutes, while the Indonesian wildfires lasted many months. In terms of average power, that puts the two around the same order of magnitude. (The initial fission stage of a nuclear weapon happens in less than a microsecond; the two stages of thermonuclear weapons combined, about 20 microseconds.)
posted by DevilsAdvocate at 8:21 AM on February 2 [3 favorites]

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