Series House of the Dragon features fire-breathing dragons. Same thing in Game Of Thrones and in a number of works which mention these large winged reptiles. If they really existed, what would they do?
In the fantasy land of Westeros, imagined by George RR Martin and brought to the screen in Game Of Thrones And House of the Dragonthe spectacle of fire-breathing dragons captivates the audience with a clever mix of myth and fantasy. For me, at least, I also see it as a scientific curiosity.
Images of dragons unleashing torrents of flame in the new season of House of the Dragon got me thinking: if dragons existed, what biological mechanisms and chemical reactions might they use in the real world?
But first, a chemistry refresher. To ignite and maintain a flame, we need three components: a fuel, an oxidizing agent also known as an oxidant — generally oxygen in the air — and a heat source to initiate and maintain combustion.
Let’s start with the fuel. Methane could be a candidate. Animals produce it during digestion. Images from Westeros show that dragons happily eat sheep. However, our methane-powered dragons would have to have a diet and digestive system more like a cow’s to produce enough gas to burn down a city.
Storing sufficient quantities of methane is also a problem. A typical methane cylinder can be designed for a pressure of 150 atmospheres, while even an inflated intestine can tolerate only a little over one atmosphere. There is therefore no biological basis for land animals to store gases at high pressure.
A better solution would then be a liquid. Ethanol could be an option. Perhaps our dragons have a vat of fermenting yeast in their guts, or they could have a fish-like metabolic system Cyprinodon diaboliswhich lives in the hot springs of Nevada, USA. In low oxygen conditions, these fish adopt a form of respiration that produces ethanol.
However, storage is once again an issue. Ethanol rapidly crosses biological membranes, and keeping it at high concentrations and ready to be deployed at the signal of “dracarys” (which translates to “dragon fire” in the fictional High Valyrian language) would require otherworldly biology.
So if we stick to explanations that have at least one foot in real-world biology, my preferred option is something more oil-like. As anyone who has accidentally set fire to a frying pan knows, it can cause fearsome flames. There is a biological basis for this in fulmars.
These polar birds produce an energy-rich stomach oil that they regurgitate to feed their chicks. This oil also has a deterrent effect. When threatened, the fulmar vomits this sticky, foul-smelling oil onto its predators. Fortunately, these birds have not yet found a way to ignite their oil.
Fuel the fire
Now that we have a fuel source, let’s look at the oxidizer. As with most fires, it will likely be oxygen. However, it will take more than the oxygen in the surrounding air to generate a pressurized jet of flaming oil hot enough to melt an Iron Throne. The oxygen must be well mixed with the fuel. The more oxygen there is, the hotter the flame.
A dragon could take inspiration from the chemistry used by bombardier beetles. This insect has developed reservoirs suitable for storing hydrogen peroxide (the product used to bleach hair). When threatened, the beetle pushes the hydrogen peroxide into a vestibule containing enzymes that quickly break it down into water and oxygen.
This is an exothermic reaction, which transfers energy to the surroundings and, in this case, increases the temperature of the mixture to the boiling point. The reaction is so aggressive that it is sometimes used to power rockets. The increased pressure caused by rapid oxygen production and boiling water forces the harmful mixture out of a vent in the beetle’s abdomen and toward its prey or predator.
If used by a dragon, this reaction has some interesting characteristics. It would create the high pressure needed to power the fuel jet, the exothermic reaction would heat the oil, making it more suitable for combustion, and most importantly, it would generate oxygen which would fuel the combustion reaction.
All the dragon needs is some sort of biological equivalent to a gasoline engine carburetor to mix the oil with oxygen and create an explosive mixture. As a bonus, the erupting mixture would probably form a fine mist of oil droplets, like an aerosol, which would ignite all the more easily.
All it takes is a spark
Finally, we need a spark to ignite the mixture. For this, I would suggest that dragons evolved an electrical organ similar to that found in many fish, particularly electric eels.
These organs can generate brief pulses of up to 600 volts, which is enough to create a spark in the air. If these sparks form on the ducts at the back of a dragon’s mouth, they can ignite the high-pressure jet of oil and oxygen.
Although we’ll never see a dragon unleashing torrents of flame outside of the realm of fiction, it’s interesting to think about the science behind fantasy. So the next time you see a Targaryen commanding “dracarys”, think about the biology behind this magical inferno.
Mark Lorch, Professor of Science Communication and Chemistry, University of Hull
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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