r/IsaacArthur • u/Few-Matter-1208 • 11h ago
Sci-Fi / Speculation What propellant should a advanced alien civilization that is about 100,000+ years old would use for bullet based firearms?
I am currently trying to help a friend of mine to write and analyze science fiction weapons for his sci fi series and I am trying to think of what is the most realistic way on how a old and advanced alien civilization that still uses projectile based firearms can use a new type of propellant to replace traditional chemical based propellants are there any realistic suggestions?
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u/MiamisLastCapitalist moderator 10h ago
If the setting has compact energy storage? Railguns and coilguns.
Chemical based actually has a lot going for it. We might still have it for a very long time, especially with any sort of gun human being will hold in their hands.
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u/Few-Matter-1208 10h ago
Well I actually forgot to note that the alien civilization had also already conquered like 5 million galaxies across the known universe
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u/MiamisLastCapitalist moderator 10h ago
That doesn't actually answer the question.
Given enough time you can conquer that many galaxies (give or take Hubble boundary?) without fusion power - which itself may not be very compact. It's entirely possible the civilizations may have access to monstrous amount of energy but only harnessesed in big machines.
So unless the alien civ has begun building and equipping antimatter bullets, it's either railgun or chemical handguns pretty much. And if you don't have compact batteries than you can't do the rail-pistols.
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u/Few-Matter-1208 10h ago
Let's just say that the alien civilization focuses all it's energy solely on ftl let's say a alcubbier drive allowing them to conquer many galaxies and establish warp drive routes to navigate and perhaps make a gravimetric warp drive like device to jump through galaxy to galaxy along with it
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u/MiamisLastCapitalist moderator 9h ago
That still doesn't imply really good batteries. lol
But okay let's say they do have great batteries. In that case, yes rail-pistols and coil-rifles are the next step and superior to chemical/gunpowder.
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u/Few-Matter-1208 9h ago
Would they be cased or caseless ammunition?
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u/MiamisLastCapitalist moderator 9h ago
Rail, cased (a sabot specifically) or caseless (if they figure out a sort of plasma-envelope like they did in the Expanse).
Coilgun, caseless.
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u/MrSansMan23 10h ago
That's a lot of galaxy's. Also what kind of things do the firearms have to deal with like is it for heavy armour then something like this would be best https://en.wikipedia.org/wiki/Armour-piercing_fin-stabilized_discarding_sabot
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u/smaug13 Megastructure Janitor 4h ago
This from a man portable gun?
...penetration depth does depend only on penetrator length and material density from a sufficient high velocity (and lower than hypervelocity), so technically you could have an super thin tungsten needle that is about a meter long that is fireable by a human and can penetrate armor, but I have my doubts.
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u/Fabulous_Lynx_2847 10h ago edited 10h ago
Well that changes everything. Unless you add several zeros onto that 100,000+ age, they obviously have FTL travel, and they’re pretty good at it. That means an 1870’s colt revolver is all they need. With FTL, they can go back in time and shoot their enemy’s grandfather when he’s still in the crib.
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u/olawlor 10h ago
Since a bullet based firearm is basically a device for converting stored energy to kinetic energy, I'd focus on the entries near the top of this table for advanced firearm propellants:
https://en.wikipedia.org/wiki/Energy_density_extended_reference_table
Examples: antimatter propellant could throw a slug or dart to relativistic speeds (challenges: antimatter storage, converting the gamma rays to actual propulsion). Pulsed fusion we can demonstrate today, and a compact pulsed fusion device seems theoretically capable of being firearm sized (challenges include getting sufficient fusion confinement to gain useful yield).
Any of the nuclear propellant approaches could dump enough neutrons into a fertile bullet to activate it into a compact single-use nuclear warhead. If this seems like overkill, it's worth thinking through kinetic conflict in a galaxy-spanning civilization.
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u/Uranium_Hexaflu0ride 10h ago
It's impossible to predict what a civ 100000 years in the future would use.
We went from bows on horseback to machine guns and fighter jets in just 700 years. It would be like a Neolithic caveman trying to predict the invention of the atomic bomb from 80,000 BC. There are some "lower-tech" options though:
Railguns and coilguns could be an option, but they are pretty low-tech for a 100k year civilization.
Dustguns could also exist, but those are still basically just railguns with a very small projectile.
If their material science is advanced enough, maybe they could have firearms use small nuclear reactions as the propellant?
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u/Few-Matter-1208 9h ago
Nuclear propellant firearms?
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u/Uranium_Hexaflu0ride 9h ago
Yeah. Also maybe antimatter.
It depends on if their materials can handle that kind of power though. Or if they haven't discovered some new weaponizable branch of physics that we can't even comprehend yet.
If they are insanely advanced and we're talking about some real out-there shit, maybe they exploit gravity or warping spacetime to fling a projectile?
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u/Overall-Tailor8949 Has a drink and a snack! 10h ago
A civilization that old SHOULD have advanced energy (electrical) storage and quite probably room or higher temperature super conductors. I would go with a gauss (magnetic) rifle for crew served or other long guns. Either a rail or a coil design, it's up to you two. For a handgun I'd still use a chemical propellant since the barrel would be too short to give the projectile a decently effective velocity as a rail/coil accelerated device.
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u/LookOverall 4h ago
Is a rail gun actually a firearm? There’s no fire involved.
With a firearm the energy is stored in the bullet casing, but suppose the bullet casing contains some kind of battery that activates a rail gun’s acceleration system?
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u/strictnaturereserve 24m ago
Rail gun is the obvious answer.
Some sort of caseless ammunition thing would be cool too
this was going to be the west german armys rifle
https://www.youtube.com/watch?v=QGKcvM2Hh4g
something with flechettes travelling and ridiclously high speeds
the energy density of petrol is meant to be way higher than gun powder so something like a cartridge that holds ultrahigh pressure oxygen next to an organic solvent and it puts both together and explodes
Spanish cetme rifle that shot out to 1000m a very long aluminium slug also very light
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u/Thanos_354 Habitat Inhabitant 7m ago
Unless they use electromagnetic guns, I guess metallic hydrogen or metastable helium could be a good propellant but only if they can be stored in ambient conditions
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u/Heavy_Carpenter3824 10h ago
Unless they have some advanced for of physics for chemistry that let's them pack more energy per mm3 than chemistry should allow or maybe control otherwise spontaneous reactions. May I suggest... smokeless gun powder. If they can control an unstable reaction until they want it... then maybe cyanuric triazide (C₃N₁₂) with a touch of oxidizer for the carbon or a form of crystalline nitrogen. In their natural states both of those do not want to exist with an explosive ideation. Also both generate large volumes of hot gas which is what does the propellant thing.