it's very easy to make and with luck you can launch it about 200 feet.
all you need is a plastic 16 oz. bottle with a cheap lid. (crystal geyser works great)
and baking soda and vinegar.
this is my first instructable so don't judge it too hard
Step 1: Mix!!
put in baking soda and vinegar, about 2 tablespoons of each, and shake until the bottle is good and hard.
you can experiment and put different amounts of the stuff but make sure it doesn't blow up!
i'm not liable for anything bad that happens during your experimenting, broken windows, broken bones, loss of limbs, ect.
Step 2: Now Comes the Fun Part
when the bottle is on the verge of exploding, throw it on the ground about 6 feet in front of you and with luck the lid will hit the ground and the bottle will take off in the direction you threw it in.
do not be an idiot and aim it at someone. i have broken my friends nose with one of these.
they sure are fun though.
try not to reuse the bottles because they tend to explode more easily. and they hurt pretty bad.