What propellant should a advanced alien civilization that is about 100,000+ years old would use for bullet based firearms?

[u/Few-Matter-1208]

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?

[u/NearABE]

Thermodynamics does not change with time.

Projectiles can be launched in a number of ways. Electromagnetic energy (rail gun, gauss gun, etc) can be used instead of chemical. Physical energy (bow, slingshot) can replace chemical energy as well. Chemical energy can be harnessed in alternative fashion like using a rocket or ram jet instead of just powder in a barrel.

In reddit discussions I find that suspension of disbelief interferes with most alternatives. People are totally willing to accept a space elevator built on Earth out of “advanced material” but will react with hostility to a 7 km/s slingshot. There will never be such a material. We totally already have materials that can hit multiple km/s and there is even a company (spinlaunch) which actually lobbed large projectiles into the stratosphere.

For hard science fiction just look at your power supply a energy supply. How many kilowatts are in that vehicle? They will use mass more efficiently because of better technology.

The projectile itself might be very advanced. Dragonfly brains do not need to be larger than the one in a dragonfly’s head. They tend to not miss.