I knew some guys who took a hollow driveshaft from a truck and cut the end off, and the interior diameter was enough to accommodate a 12 oz plastic soda bottle.
They would act like a two man mortar team, one guy would put dry ice chips into the bottle, put in some water, screw the cap on, and toss it into the bore, and the other guy would put various items in on top of it from a tennis ball, or another bottle completely filled with water.
It would shoot the thing hundreds of yards!
One of my own favorites was to take three tennis ball cans, remove both ends, tape them together with duct tape, then make a small touch hole with an ice pick. You could squirt in a little Ronson lighter fluid (though not enough for your dad to miss when filling his Zippo!) toss in a tennis ball, then light the touch hole...:)
Dry ice is a hoot but it is C02 and we all know THAT is bad for the planet.
When I was a lad we used Calcium Carbide.
Dang old carbon again..
I got my thumb messed up lighting the tin can cannon, but that was because the guy overloaded the muzzle.
know one was killed, and we learned to drill.
We used white rain hair spray as a Propellant. Gasoline in a nose mister is the best but it has it’s obvious drawbacks.