I have a creature that was bio-engineered by an extremely capable society, and I need it to "produce" an explosive* fuel that is contained within the outer layer of flesh/fur. This fuel needs to be a solid bound to the flesh itself, or a very viscous oil. The fuel needs to act as a propellant, and does not need external oxygen (oxygen is stored alongside). The fuel needs to be producible within the creature itself. (70-90lb, 4ft, bipedal)
I am having trouble finding a suitable chemical/compound. Originally I had the fuel put down as just generic hydrocarbons but hydrocarbons are extremely complicated and while possible, would be very difficult to organically synthesize. The materials and chemicals needed to produce the fuel are a non-issue, as long as they can be found in decent quantity in and on the crust of a planet. (heavy terraforming targets, so .5 to 1.5g, goldilocks zone.)

To summarize, I need a chemical that is highly flammable, not a gas, that is somewhat easy to produce biologically.

  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Jul 10, 2023 at 5:58
  • $\begingroup$ Do I understand correctly that you want a solid or oily substance, produced naturally by the creature, that can be used as a propellant, and doesn't need an external supply of oxygen? As in, if this creature were ever struck by lightning or caught in a burning forest it would explode violently? Even if needing an external supply of oxygen, this creature would explode due to a good sunburn and would be very dangerous to be near. Rauchen verboten! Also, how does what you want compare to Sperm Oil? $\endgroup$
    – JBH
    Jul 10, 2023 at 6:18
  • $\begingroup$ @JBH yes, if the creature was ignited it would immediately explode. Sperm oil seems pretty close, but it doesn't look like it can be used as a propellant, which is the primary purpose of the substance. $\endgroup$ Jul 10, 2023 at 6:27
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    $\begingroup$ Why doesn't sugar work? That's what amateur rocket enthusiasts use for fuel. en.wikipedia.org/wiki/Rocket_candy . Oxidizers are everywhere in nature, like hydrogen peroxide or potassium nitrate. You could even make it edible. $\endgroup$ Jul 10, 2023 at 15:59
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    $\begingroup$ "hydrocarbons are extremely complicated and while possible, would be very difficult to organically synthesize": this isn't even remotely true. The simplest organic substances are hydrocarbons, and living things have no issue dealing with them. The lipids that every animal cell forms its membrane from are hydrocarbon chains attached to various hydrophilic "head" structures. It's the oxidizer that would be difficult to produce and handle, as it would want to react with everything around it, but some naturally evolved organisms can secrete such substances (the bombardier beetle, for example). $\endgroup$ Jul 10, 2023 at 17:36

3 Answers 3


Black powder

Black powder is one of the oldest explosives in existence and also works great for propulsion (fireworks). It consists of charcoal, sulfur and potassium nitrate. If you want to have oxygen stored somehow (I doubt this works, oxygen is hard to store if you want it in a state than can be used it as an oxidizing agent) you can skip the potassium nitrate and only use charcoal and sulfur.

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    $\begingroup$ Blackpowder contains its own oxidizer in the form of saltpeter or potassium nitrate (KNO3) $\endgroup$
    – James Cook
    Jul 10, 2023 at 17:14
  • $\begingroup$ I had forgotten how simple black powder is! It is a bit on the low end when it comes to energy density, but that's not a huge issue. $\endgroup$ Jul 10, 2023 at 20:51
  • $\begingroup$ Biology has no problem building complex molecules, but it's not great at acquiring certain elements in bulk to work with. Sulfur is only used as a micro nutrient in living things. A chemical made from only the 4 organic elements (hydrogen, carbon, oxygen and nitrogen) is much easier for an organism to produce in significant quantities. $\endgroup$
    – Nosajimiki
    Jul 11, 2023 at 14:04
  • $\begingroup$ Sulfur's technically a micronutrient for humans, but it's the 8th most abundant element in the human body and is a component of cysteine and methionine and thus many proteins, and there's bacteria that use sulfur compounds as an energy source, some of which produce deposits of native sulfur. $\endgroup$ Jul 11, 2023 at 18:03

In Larry Niven's Known Space series the ancient Slavers had biologically grown multi stage rockets used to launch spaceships. Stage trees.



So the idea of a biological organism designed to produce solid rocket fuel is already part of a famous science fiction series.

A mobile animal instead of a sessile plant might have ways to use up some of the fuel it produces. Thus it might not accumulate a large amount of fuel. If it was designed to produced a lot of fuel and not use it, it would be using a lot of food and energy to produce something which would be no apparent use to it, and so it would not be a very successful organism. Maybe the organism uses the fuel for insulation like some animals use fat and so benefits from it.

Salmon undergo changes as they return upstream to spawn where they were born. They die after spawning. Perhaps your creatures die by converting much of their flesh into fuel in the last stage of their lives, until they can no longer survive. So at a certain season of the year fuel could be harvested from the dead creatures of that species.

Niven's stage trees grown into a form which can have a spacecraft attached to it and be pretty much ready to launch. As relatively small animals, your fuel producers are not in the shape of booster rockets or any other vehicle which I can imagine. Thus the fuel would have to be harvested from them and assembled into a rocket or other vehicle.

There are many types of solid rocket fuels. And even solid rockets used in Earth's atmosphere do not seem to have any way to push oxygen inside rapidly, nor does their performance seem to change much as they climb to altitudes with much thinner air.

So I guess that most solid rocket fuels contain both fuel and oxidizer. So you need to study every known sold rocket fuel and oxidizer, to find one which a living creature could produce in their body. And possibly you will need different species or different genders of a species to produce the fuel and the oxidizer separately.

  • $\begingroup$ STAGE TREES is all I could think as was reading the question. +1 $\endgroup$
    – Qami
    Jul 10, 2023 at 16:01
  • $\begingroup$ Yes stage trees are more efficient, but animals collect energy much more quickly than plants. So, a stage tree might take centuries to grow, but an animal can in just a few years move around eating hundreds of plants over a very large area giving you a more on-demand (if not technically more efficient) fuel source. $\endgroup$
    – Nosajimiki
    Jul 11, 2023 at 15:01


There are many self oxidizing solid fuels out there, but most of them contain elements that are very rare in organisms. Your four organic elements are hydrogen, carbon, oxygen and nitrogen. These elements are found abundantly in every organism. Any solid fuel made from just these 4 elements will be something your organism will have no problem producing enmasse. Beyond this, you have Calcium and Phosphorous which are the most dominant minerals in biology, but both are <1% of total biomass make them only usable if they are lesser ingredients to the explosive's compound. All other elements occur at rates of <0.1% of biomass making them very limiting if you want an organic explosive.

RDX is the active ingredient in C4 and many other military grade explosives and propellants. It is a self oxidizing compound made purely of biological elements with a chemical formula of C3H6N6O6. While there are not Earth based organisms that naturally produce RDX, its chemical formula would be something perfectly plausible for an organism to be able to synthesize a lot of because of the elements that are used.

As a solid crystal or large grain powder RDX explodes very violently; however, by griding it down into finer particles, you can slow its chain reaction making it a suitable rocket fuel or propellant.

Designing an Organism around RDX

The biggest advantage from a biology standpoint about RDX is that is is actually a very stable explosive. You can drop it, shake its, leave it outside on a hot day, etc. and it will not explode. This is very important if you are planning any sort of animal since blowing up when you trip will cause the explosiveness gene to very rapidly be selected against. Because RDX generally takes some kind of high temperature spark, or other explosive to trigger it, your animals could evolve to only explode at moments when exploding offers an evolutionary advantage like when a predator has you in its jaws. This way, explosiveness can be selected for the same way that suicide stingers were selected for in bees. One dies, and but saves the colony, ensuring the continuance of its genetic line. The shock resistance of RDX also means it will typically not chain react from one critter to another when your organism blows up which would otherwise risk wiping out your entire colony.

If you want your critters to be able spontaneously combust, you need to give them a detonation organ. This could be something like a small pair of bladders containing a 2 part room-temperature explosive that could be mixed when needed. Or your critter could have a bioelectric organ that could set the explosive off.

  • $\begingroup$ Didn't know rdx was so simple chemically, thank you. Unfortunately the stability is more of a curse than a boon, as the system these creatures are a part of has no way of igniting it. The creatures do not live too long anyway, so a few here and there getting flash fried is not a big deal. $\endgroup$ Jul 10, 2023 at 20:47
  • $\begingroup$ @LornestFluke If you want them to blow up on command, just make it a bioelectric organism. While impact and heat won't blow them up very easily, electricity will. So something like an electric eel's shocking ability could trigger it to explode. $\endgroup$
    – Nosajimiki
    Jul 11, 2023 at 5:59

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