Madmole, that leads my curiosity to the next question: ؟There is different tiers of the rocket launcher?
Maybe something like:
Tier 1: Very primitive, A big pipe (Like a hand-cannon, with a very low reloading time, shoots home made cannonballs with gunpowder inside.
Another idea for Tier 1: A 3 pipe contraption, that shoots 3 mini-cannonballs, also low reloading time. Ammo = 5 rocks + 3 gunpowder per cannonball (easy to craft early game).
Tier 2: Maybe the grenade launcher, from II World War era.
TIer 3: Good old rocket launcher.