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The setting I'm trying to develop is a post-apocalyptic partial Dyson Swarm. The world has very advanced AI and one of those developed the system as a caretaker god inhabiting the star. It has gone eccentric however and civilization scrambles in the ruins. Some low level caretakers took measures to save the human population before they were purged.

The idea is that the natives got those seeds, feed the plants the proper chemical feedstocks and get fruits containing the processed chemicals. Is there a fundamental reason why I couldn't have an orchard growing high explosives? The natives were told how to take care of those plants.

What I'm looking for is a sanity check of the idea.

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    $\begingroup$ Remember as a worldbuilder you can have whatever you want in your world just by saying it exists. We don’t know the rules you’ve chosen to impose on your world. You may have something that makes it fundamentally impossible but you don’t give us the info to determine that. Why can’t you just allow explosive trees… $\endgroup$
    – sphennings
    Jan 19 at 11:44
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    $\begingroup$ @JBH Thanks for your help $\endgroup$
    – TheDyingOfLight
    Jan 19 at 11:50
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    $\begingroup$ Niven stage trees. larryniven.fandom.com/wiki/Stage_Tree $\endgroup$
    – Boba Fit
    Jan 19 at 14:36
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    $\begingroup$ When you say high explosive do you really mean a high explosive? High explosive means something very specific as opposed to low explosives. For example, dynamite is a high explosive but black powder is not. $\endgroup$
    – DKNguyen
    Jan 19 at 23:31
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    $\begingroup$ @DKNguyen I'm familiar with the difference. I need high explosives for the primary of the pure fusion bombs needed for Orion Drive spacecraft. $\endgroup$
    – TheDyingOfLight
    Jan 20 at 7:19

8 Answers 8

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You can grow high explosives on trees

Yet, in order for a stray bolt of lightning to not destroy the entire farm of your trees in a single fierce explosion, there needs to be a separate process that would "arm" those seeds by transforming whatever HE you've got inside into an explosive state. For example, you could just require your natives to dry the fruits in a place protected from direct sunlight, or immerse them in some liquid obtained elsewhere, or implement another process as simple as these, that takes time. And here you go, a grenade orchard. It's also possible that if that process is not performed within a certain time after collecting the fruit, the inside turns into something edible, or whatever, including sprouting. That would protect your natives from accidentally blowing themselves up on lost fruit.

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    $\begingroup$ Although good answer overall, I would like to point out that many HE require very specific ways to be detonated. TNT can be melted and cast without detonation. With the right explosives a lightning bolt might not be a problem. Even so a few well placed and connected lightning rids would suffice. I do wish to know if any real plant can harvest and process explosive substances without killing itself. There are examples of 'exploding' plants or animals, but as far as I know none use HE. $\endgroup$
    – Trioxidane
    Jan 19 at 16:41
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    $\begingroup$ @Matthias high explosives don't really need anything to oxidize at all... merely a compound that has a nice exothermic decomposition reaction which releases enough energy to trigger the decomposition of its neighboring molecules. You can make hydrazine go bang without the presence of any oxidizer, and hydrogen peroxide releases oxygen when it goes foom (though they're not really high explosive, but neither is mere fertilizer). $\endgroup$
    – Starfish Prime
    Jan 19 at 17:44
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    $\begingroup$ High explosives need a detonator to detonate them. The greater problem is that they are highly flammable substances, so such a tree would burn with far greater enthusuasm than an ordinary tree. But in a damp location, growing high explosive surrounded by a thick non-flammable skin ought to work. And separately, a tree that grows detonators (which are touchy but not large explosions). My sense of humour is exploring male and female trees of the same species .... $\endgroup$
    – nigel222
    Jan 20 at 10:16
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    $\begingroup$ Alternatively to the answer, the high explosive becomes unstable as the fruit ripens, while its seeds are embedded in its skin (think a big explosive strawberry). The eventual detonation scatters its seeds, just like a grenade scatters shrapnel. Here on Earth there are many seed pods which scatter seeds by a spring action rather than chemically. $\endgroup$
    – nigel222
    Jan 20 at 10:21
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    $\begingroup$ @Trioxidane, when I was a kid, a lightning bolt hit one of our corn fields. I can say that a lightning bolt doesn't need HE to explode crops. Where the lightning hit was a very obvious 10-20ft diameter where no organic matter remained and there was a small crater in the dirt. Around ground zero, plants were bent outwards, as if blown over. I think the point of lightning was that it would be an uncontrolled original source that would set off a chain reaction of explosions in other plants. $\endgroup$
    – computercarguy
    Jan 20 at 20:08
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I've only read the abstract, but Enzyme catalytic nitration of aromatic compounds is certainly tantalizing. Nitroaromatics are a broad class of chemicals, and include things you might have heard of such as trinitrophenol, also known as picric acid, trinitroresorcinol, also known as styphnic acid, and trinitrotolulene which I'm sure everyone has heard of. The latter is relatively stable, but the other two make for must less user-friendly compounds when dried out, and are good for detonators.

That means that there is already a nice biological chemical pathway towards getting the compounds you need. Obviously, its expression and use in your plants needs to be heavily modified in order to produce enough of the good stuff, and the fact that it can nitrate some aromatic compounds isn't the same as being able to make you TNT but it is very much a step in the right direction.

Starch and cellulose, common plant polysaccharides, can also be nitrated into nitrocellulose and nitrostarch. These are not high explosives, but do burn extremely vigorously when dried. If confined in a nice hard outer casing (like a coconut, perhaps) they could certainly make for a simple bomb if you drilled a hole and added a suitable fuse (or used plant-derived sensitive detonators, like the picric acid above). I couldn't find any information about natural biological pathways to form nitrated polysaccharides, but as enzymatic nitration is possible you don't have to wave your hands very hard.

Is there a fundamental reason why I couldn't have an orchard growing high-explosives?

You need a lot of bioavailable nitrates, and that's a kinda awkward thing to get. Ammonium nitrate fertilizer is a perfectly good chemical for making explosives with already (eg. ANFO) and you generally make it with nitric acid and if you have that then you can make nitrocellulose directly and avoid the weird plants altogether.

There's no obvious easy way to biologically synthesize nitrates from the air, so that's probably a bigger handwave. Volcanism and electrical storms help, if you can conjure up enough of those without toasting the people you're trying to give hazardous chemicals to. If there's a handy source of more biologically friendly nitrogen compounds, like ammonia, you can use the same trick that nitrifying bacteria to do oxidize it, but again... the ammonia has to come from somewhere. Handwaving all the way down.

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    $\begingroup$ there is a way to make nitrates from the air, it happens all the time, nitrogen fixing bacteria make ammonia from gaseous nitrogen, plants host the bacteria and turn the ammonia into nitrates or nitrides. $\endgroup$
    – John
    Jan 19 at 22:30
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    $\begingroup$ @John I was about to say the same. The trees are legumes but more so, or the nitrogen fixing biochemistry has been engineered into them so it has access to greater amounts fof nitrates through its leaves. $\endgroup$
    – nigel222
    Jan 20 at 10:24
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Eucalyptus trees naturally explode during forest fires.

The civilisation you describe is at an extremely high level of development, so yes, it's fair to say that they have amplified this natural effect to a higher yield.

I think anything that exists in nature passes a sanity check.

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    $\begingroup$ A eucalyptus trees exploding is not a result of a chemical explosion though, it’s a BLEVE (just like a boiler explosion) resulting from the very low boiling point of the eucalyptus sap combined with the fact that the tree forms an effective containment vessel. The resultant debris tends to catch fire almost instantly due to how flammable the vapor is, but there’s not anything involved that qualifies by most measures as a high explosive, so I’m not sure if this qualifies or not. $\endgroup$
    – Austin Hemmelgarn
    Jan 19 at 19:57
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    $\begingroup$ Technically, OP asked for high explosives. Whether or not OP realizes what their words actually mean is another matter. $\endgroup$
    – DKNguyen
    Jan 19 at 23:36
  • $\begingroup$ A superhuman AI that can build a Dyson sphere (however partial) can crank up the biochemistry to be more explosive. $\endgroup$
    – wokopa
    Jan 19 at 23:41
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Grease Fire

enter image description here

Picture from Epicurious dot com

Maybe you cannot grow explosive fruits. But you can certainly grow plants with highly flammable chemicals. Sunflower oil, rapeseed oil, canola oil, olive oil. These are all derived from plants. And they make big boom when prepared correctly.

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  • $\begingroup$ That seems like a good basis. Knowing plants can produce flammable substances, it at least seems plausible that they could be bio-engineered to produce more, and more highly concentrated versions. $\endgroup$
    – JamieB
    Jan 19 at 15:23
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    $\begingroup$ Technically, OP asked for high explosives. Whether or not OP realizes what their words actually mean is another matter. $\endgroup$
    – DKNguyen
    Jan 19 at 23:35
  • $\begingroup$ @DKNguyen I don't know what the heck a "high" explosive is so I have ignored it. $\endgroup$
    – Daron
    Jan 20 at 11:10
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    $\begingroup$ @Daron The difference between low and high explosives is the rate at which they burn. I believe that for the layman, the qualitative difference is that a high explosive needs no pressure vessel to actually explode. It burns fast enough that you don't need to contain the pressure to create an explosion. $\endgroup$
    – DKNguyen
    Jan 20 at 16:41
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    $\begingroup$ @DKNguyen, to your point, it's the velocity of the explosion that counts which leads to confined vs unconfined explosion. asteetrace.org/explosives $\endgroup$
    – computercarguy
    Jan 20 at 20:12
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Square-Cube Law here, directly from physicists heaven.

Think of popcorn. You heat a bag of it in a microwave, and you can hear the pops and see the bag shake as each popped kernel hits its walls from the inside.

Due to my sacred commandment, if you make a kernel with twice the regular diameter, it will have 4x the original surface area but will have 8x the original volume. This can go on and on, ever making for a much larger pop with each increment.

Now imagine a watermelon-sized corn kernel. Throwing it in a fire would be really educational, and a valid way of appeasing me.

But don't stop there. The largest plant harvests are those half-ton pumpkins people grow in Alaska.

Have your AI develop a 1,000 lbs corn kernel, cover it in animal grease and sacrifice it to me in a bonfire. Go on, it will be FUN! Just remember to keep a safe distance, unless you want a date with me really soon.

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    $\begingroup$ popcorn pops due to steam pressure not high explosives. $\endgroup$
    – John
    Jan 19 at 22:10
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    $\begingroup$ @John but primitive artillery barrels were made out of giant bamboo stalks. How about a genetically engineered seed/shell launcher? (Shading back to Niven's stage trees again). $\endgroup$
    – nigel222
    Jan 20 at 10:26
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You don’t need to feed the seeds chemicals. Meet the sandbox tree.

https://en.wikipedia.org/wiki/Hura_crepitans

Not only is this bad boy covered in spines, but it’s fruit explode when ripe at the slightest touch. This is a method for scattering seeds. And I do mean “explode.” Not fiery explosions, granted, but anyone within a yard of these little buggers should do well to duck and cover.

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Explosives require the mixture of a fuel and an oxidant. These can be in separate molecules, as in gunpowder (charcoal and sulphur fuel, potassium nitrate oxidizer) or in the same molecule, where molecules containing -OH groups (such as glycerine or cellulose) are nitrated to nitroglycerine and nitrocellulose. Toluene, a hydrocarbon, has a particular structure that allows it to be nitrated to TNT. Industrially, these reactions proceed using nitric acid and generate water as a byproduct. Sulphuric acid serves both as a catalyst and a water scavenger.

I'm not aware of any biological process mimicking this. The best natural sources of nitrate come from -NH2 containing waste such as bat droppings, which naturally convert to -NO3 in the presence of atmospheric oxygen over a relatively long timescale. The nitrogen rich waste is toxic, so the chances of an organism being able to hold concentrate it and hold onto it long enough to turn into nitrate (which can be even more toxic) are relatively low. Plants often struggle to find enough nitrogen. Animals lose the carbon they get from food through respiration, and have to excrete nitrogen in the form of waste.

There are, however, many biological systems that generate hydrogen peroxide. This is an intermediate step in respiration of atmospheric oxygen. The decomposition of hydrogen peroxide to water and oxygen 2 H2O2 --> 2 H2O + O2 is quite exothermic and can generate a pressure explosion. This reaction, accelerated by a catalyst (such as permanganate, blood, iodide, or yeast) is the basis of the "elephant's toothpaste" experiment of which numerous examples can be found on youtube. It has been used as a monopropellant in rockets and torpedoes, and premature decomposition of hydrogen peroxide in an enclosed space has caused accidental pressure explosions (incidentally, excessive pressure of carbon dioxide produced in alcohol fermentation has also caused pressure explosions.)

The power of hydrogen peroxide is much enhanced when it is used to oxidise a fuel source (and bipropellants consisting of hydrogen peroxide and a fuel source are excellent rocket fuel.) A fairly tranquil example of the use of hydrogen peroxide as a fuel source is in certain light-producing chemical reactions. It has been suggested that bioluminescence evolved from antioxidants which originally protected organisms from the toxic effects of hydrogen peroxide. https://en.wikipedia.org/wiki/Bioluminescence

A more dramatic use of hydrogen peroxide is in the bombardier beetle, which uses the oxidation of hydroquinones by hydrogen peroxide to attack predators. https://en.wikipedia.org/wiki/Bombardier_beetle

The oxidation of alcohols by air is a safety concern in laboratories, as it can lead to explosive organic peroxides. It's possible that a biological system could produce an organic peroxide which, after drying, could be quite a powerful explosive.

Acetone peroxide has been used as an improvised explosive in terrorist devices https://en.wikipedia.org/wiki/Acetone_peroxide as it is very easy to prepare from acetone and hydrogen peroxide. Acetone is produced in small quantities in biological systems. Compounds similar to acetone can also be made from degradation of alcohols, which are rather more common in biological systems (conveniently enough, degradation is by oxidation, which converts the C-OH group into a C=O group, known as a carbonyl, with the double bond then naturally reacting with substances such as other alcohols, carbonyls or hydrogen peroxide to form rings.)

TLDR: Peroxides, while less potent than nitrates, are more likely to arise naturally within an organism, already have several biological uses, and could produce a powerful explosive.

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Proteins

A major focus of genetic engineering fundamentally works by creating certain adjustments to the genetic code of an organism, such that the organism is able to produce certain proteins that it would not have otherwise been able to produce. Within the confines of currently known science, this means many forms of highly potent toxins can be readily produced by a variety of animals, plants, and fungi, as they have evolved to produce proteins that inhibit certain receptors or otherwise cause negative effects in the organisms that are likely to target them.

That said, exothermic reactions in organisms are typically what are known as catabolic reactions, which break molecules into smaller components, and thereby, through the breaking of bonds, enables the release of energy. This is very interesting for our purposes because releasing energy in high quantities is sufficient to adequately replicate a high explosive.

Enzymes, in turn, are proteins (catalysts) that speed up biochemical reactions, generally by minimizing the amount of energy necessary to initiate a reaction. What this means is that enzymes speed up reactions, allowing a greater net release of energy per unit time. By minimizing the amount of time that energy is released over, the same amount of energy that may have required several minutes, hours, or even decades to release can be done in a matter of seconds.

Now this is very interesting.

If the constraints of the question allows for the combination of, for example, the seeds of a plant with another substance, one could fairly easily imagine a situation where the plant can produce enzymes capable of rapidly breaking chemical bonds at such a speed where immense amounts of energy are released at one single amount of time. This would probably work best with an industrially-manufactured chemical counterpart, but could also technically work by breaking the bonds in the structure of the plant itself, basically self-destructing while releasing large amounts of energy.

That said, I am but an amateur biologist, so do take my commentary with a grain of salt. I recommend you do some more research on your own if you are interested in this direction.

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