How to Make a Rocket from a Plastic Bottle

Create an exciting water-powered rocket using a plastic bottle and simple materials for a fun family science experiment.

  1. What You'll Need. Gather these materials: one 2-liter plastic bottle (empty and clean), a cork that fits snugly in the bottle opening, a bike pump with a needle attachment (like for pumping basketballs), water, food coloring (optional), and safety glasses for everyone. You'll also want masking tape, cardboard for fins, scissors, and a large outdoor space like a park or big backyard.
  2. Prepare Your Rocket. Remove all labels from your plastic bottle and make sure it's completely clean and dry. Cut three triangular fins from cardboard, each about 4 inches tall. Tape these fins evenly around the bottom of the bottle using masking tape, making sure they're sturdy and straight. The fins help your rocket fly straight and look more authentic.
  3. Add Water and Pressure. Fill your bottle about one-third full with water. Add a few drops of food coloring if you want to see the water spray more clearly. Push the cork firmly into the bottle opening, making sure it's tight but not impossible to remove by hand. Insert the pump needle through the cork, pushing it all the way through so it reaches into the bottle.
  4. Launch Your Rocket. Take everything outside to your launch area. Have everyone put on safety glasses and stand well back from the rocket. Place the bottle upside down on the ground or hold it pointing away from people and buildings. Start pumping air into the bottle. As pressure builds, the cork will eventually pop out with great force, and water will spray out the bottom, propelling your rocket forward or upward. The rocket can travel 50 feet or more.
  5. Understanding the Science. Your bottle rocket demonstrates Newton's third law of motion: for every action, there's an equal and opposite reaction. When pressurized water shoots out the bottom of the bottle, it pushes the rocket in the opposite direction. The more pressure you build and the less water you use, the higher your rocket will fly. Too much water makes it heavy, while too little water doesn't provide enough mass for propulsion.