Step 1: Things You Will Need:
You will need 2 TNT, at least 20-30 wood blocks, a bucket of water, 1 wood half slab, and 4 glass blocks (not glass panes).
Step 7: How to Operate:
Once you have built the cannon and put the TNT in the right place, light the TNT in the water first, then light the second one on the slab. The fist one will explode, sending the second one flying in the air, which will explode during flight or once it hits the ground. Hope you enjoy!