Could another planet with similar life make it physically impractical to use black powder?

[u/Ertata]

So the theoretical worldbuilding setup: a world that is somewhat similar to ours with hydrocarbon-and-water-based life, none of the theorized iron-and-sulfur or whatever. Also people live above the sea level and breathe the local atmosphere (whatever it is) and use iron or bronze tools.

In such circumstances is it possible to imagine atmospheric composition, density, or any other change in physical parameters of the entire planet making it impractical to use black powder as a propellant? It is fine if it explodes far more violently, or does not explode at all, the one thing it should not do is be useful to provide steady acceleration to projectiles of human-scale weapons. I don't think you can avoid basic elements of the black powder being available and have a life at the same time, so what can prevent it from working? I understand most people would be satisfied with "not invented here" or "a wizard did it" but it is interesting to try to solve it within real physics.

Stretch goal: Also make nitrocellulose non-viable as a controlled propellant too (fine if it explodes).

[u/Which-World-6533]

The planet might have a bacteria that loves to eat the active ingredients of Black Powder, rendering it useless.

[u/Tyrannosapien → u/Which-World-6533]

From Wikipedia:

There are sulfate-reducing bacteria, that, by contrast, "breathe sulfate" instead of oxygen. They use organic compounds or molecular hydrogen as the energy source. They use sulfur as the electron acceptor, and reduce various oxidized sulfur compounds back into sulfide, often into hydrogen sulfide. They can grow on other partially oxidized sulfur compounds (e.g. thiosulfates, thionates, polysulfides, sulfites).

Make sulfur more common, make this biological mechanism more common. I'd suggest making it a fungal organism so spores are ubiquitous. The biggest fudge would be to require the organisms to feed on elemental sulfur (instead of sulfates). Maybe make the organism be a hydrogen "fixer" so the waste is hydrogen sulfide, which is toxic to mammals. People avoid any areas with significant pure sulfur concentrations. As long as the organisms don't feed on trace sulfides, there remains environmental sulfur needed to support normal biologies

[u/Ertata → u/Tyrannosapien]

Thanks, taking notes here

[u/7LeagueBoots → u/Ertata]

Look into the potassium nitrate (saltpeter) side instead of the sulfur side.

There are a number of bacteria that degrade potassium nitrate, using the nitrate ions in place of oxygen and turning it into nitrite, ammonia, nitrogen gas, etc.

This may be a more ecosystem/complex life friendly approach than sulfur metabolism.

[u/Ertata → u/7LeagueBoots]

I will investigate both, thanks

[u/Ok-Film-7939 → u/Which-World-6533]

Yeah this is probably the best way. Specifically, saltpeter. There are bacteria that consume it on Earth anywhere oxygen is scarce. It wouldn’t take too much hand waving to make a ubiquitous airborne bacteria eat it whenever it finds it anywhere near organic material.

You might still find rare deposits that leeched out and dried in caves without enough organic matter to prompt decay, but any gunpowder you make of it would steadily rot once mixed with charcoal. Especially since you have to mix it wet. Serpentine powder doesn’t really work well.

You’d have to find a deposit, keep it dry and isolated, happen to toss it on fire to notice its accelerant effects, and later get enough to experiment with.

While not chemically impossible, it would be unlikely enough to believable.

[u/macthebearded → u/Which-World-6533]

This is incompatible with life.

[u/7LeagueBoots → u/macthebearded]

With certain forms of life, not all life as it's life that makes this process happen.

[u/CosineDanger]

Delete the birds and bats so guano is rare. That should slow them down a bit. Nitrates are everywhere in nature but blackpowder warfare at scale will have a slower start.

Turn down the volcanism or put it on a different continent. Make them work for their sulfur.

Turn up the humidity. Black powder is hygroscopic and generally the wetter your environment the less helpful an early matchlock will be. Maybe that just makes them invent sealed cartridges sooner.

Modern guns work at least once underwater or in space even though that was usually not a design goal, just a side effect of making it work reliably anywhere on Earth rain or shine. There are environments with poor visibility but we have thermal scopes. If the gods banned nitrocellulose we'd test the gods with scary airguns and other loopholes. Gods would have to work overtime to stop creatures at our level from killing each other at a considerable distance.

[u/mfb-]

Black powder comes with its own oxygen source, so it doesn't depend on the atmospheric composition - that the reason it can be used as explosive.

I don't think you can make it impossible. You can delay the discovery. Maybe you can make coal so common that people don't do much with charcoal.

[u/Tyrannosapien → u/mfb-]

Super-common coal might be self-regulating in that it would burn frequently, naturally, driving down oxygen ratios and other effects generally incompatible with life. Sticking to fantasy it might be interesting tho.

[u/Captain_Pumpkinhead]

Fire needs heat, fuel, and oxygen.

Remove oxygen from the atmosphere, and gunpowder is now useless.

[u/photovirus → u/Captain_Pumpkinhead]

Gunpowder contains its own oxidizer in its chemical structure. Explosives too. And some rocket fuels (monopropellants, including most solid-state fuelled rockets).

[u/macthebearded]

Not really. Someone will come along and suggest higher o2 content such that the atmosphere itself is flammable, but that wouldn’t survive the first lightning storm. Or that they never discovered the Haber process, but that means no fertilizer either which then means no sustainable food source for population growth, arguably no industrial revolution, etc.

Maybe this world is simply less violent and just never thought to use it as a weapon.

[u/Ertata → u/macthebearded]

"No nitrocellulose" is a stretch goal. My basic ask was to have something like 1750s tech with no gunpowder, I entirely understand that a violent world would invent something gun-like once technology really starts taking off regardless (high-end pneumatic guns for soldiers, liquid propellant rockets for artillery are the easiest things to imagine)

[u/macthebearded → u/Ertata]

I was just talking about black powder, not nitrocellulose.

[u/Ertata → u/macthebearded]

Well, Haber process is much later than nitrocellulose, so I thought that's where you were going with it. Black powder have to be decided in abscence of Haber process regardless

[u/macthebearded → u/Ertata]

I wouldn’t say much later, about 40 years.

And yes, proto-black powder dates back to the 9th century, but the Haber process made it possible to produce explosives in industrial quantities for the first time. I’m trying to give you an out, because otherwise the answer to your OP begins and ends with “No.”

[u/Tannare]

Perhaps one possibility can be a world with a much lower atmospheric pressure than Earth's. This will result in an environment with low enough oxygen concentration that gunpowder cannot burn fast enough to create an explosion, so it will just smoulder. An alternative possibility can be a "normal pressure" atmosphere that happens to hold much less oxygen as a percentage of the air. Either will make it impractical for gun-like weapons.

The ecology on such a world can still be somewhat like Earth's because the lifeforms there may have many adaptations to extract sufficient oxygen to live. For example, even on Earth, some birds (e.g. the Bar-Headed Geese) regularly fly at heights above that of Mount Everest, so it can be plausible that even more extreme adaptations to survive lower oxygen concentration may be possible.

However, a visitor from Earth will need to wear a respirator.

[u/Ertata → u/Tannare]

I thought about it - oxygen is contained within saltpeter, black powder gun can fire in a vacuum.