Step 5: Launch Day!
Hook the pump to the tire valve. Fill your 20oz soda bottle 1/4 to 1/3 full of water. Carefully and quickly shove the soda bottle down on the launch pipe. Some bottles will fit on easily; some are going to be much tighter. Hold the soda bottle with your hands and have another person pump air into the launcher. When the air pressure is too great to hold, let go! KEEP YOUR FACE AWAY FROM THE PATH OF THE ROCKET! I told you that you would get wet.