Potato cannons, not really rocket launchers.
Rocket implies it being a self propelling object, so more of a missile-launcher/cannon.
It may even be considered in closer relation to a mortar than rocket launcher.
Oh yes, you are absolutely right. I am not really into weaponry so I tend to bag rocket launchers, mortars, bazooka and the like together.
I’d never heard of that but we used to make something similar as kids with an aerosol can, a metal drain and whatever you want to fire, arrange upright like a mortar and with a small fire at the bottom.