You can build your own bottle rocket that uses air pressure to push water downward out of the rocket, which will propel the rocket upward for a big launch. YOU WILL NEED: 2-liter soda bottle, cardboard, duct tape, a bicycle pump with a pressure gauge, an inflation needle, a rubber stopper, and some stakes. Building Your Rocket 1. Make sure the rubber stopper can be inserted into the end of the soda bottle so it holds air inside. You can check for a seal by squeezing the bottle when the stopper is pushed in. 2. With the help of an adult, drill a small hole through the stopper so that when you push the inflation needle in, it fits tightly. Try starting with a smaller drill bit than you think you’ll need, and redrill the hole bigger later if you really need to. The goal is to have the rubber tight around the needle, making a good seal. 3. Push the inflation needle through the rubber stopper till the end pokes out a little bit. The end with the small hole should be poking out of the smaller tapered end of the stopper.
