The Perfect DIY Craft to Teach Your Little One About Trajectory

Now that summer is coming to an end, it’s time for the kids to put their thinking caps back on. And what better way to kick off the back-to-school season than by making a science craft? Get down to learning business by making this bottle rocket from Emma Vanstone’s This is Rocket Science to learn about trajectory!

Squeezy Bottle Rocket

Trajectory is the path an object follows as it flies through the air. Imagine the path a ball takes when you throw it. If you throw the ball straight upward, its trajectory is different than if you throw it forward toward someone else.

Rockets initially fly vertically upward through the lower, denser parts of the atmosphere but then turn so they are on the correct path to enter orbit around the Earth.

This means their overall trajectory is a curved path, rather than the vertical path you might expect.

This easy-to-construct rocket is great for investigating how the angle a rocket is launched from affects its flight. The rockets work because as you squeeze the bottle, air is forced out of the straw in the bottle and pushes against the rocket straw. This force causes the rocket straw to fly through the air.


  • Empty water bottles with a sports cap
  • Scissors
  • 2 straws, 1 wide enough fit over the other
  • Modeling clay
  • Cardstock or paper
  • Felt tip pens
  • Tape


To make the bottle part of the rocket, it’s really important to make sure the sports cap is completely airtight. If air can escape, your rocket won’t fly very far.

  1. Cut the thinner straw into quarters and put one segment into the center of the sports cap. Seal the straw around the cap using modeling clay. You can check if the seal is complete by squeezing the bottle: If the seal is secure, all of the air from the bottle should come out of the straw, not the bottle neck. This is your rocket launcher!
  2. To make the rocket part, first cut the wider straw into quarters and seal one end with tape; this is to stop air from escaping. Draw a rocket shape with felt tip pens on the cardstock or paper. Remember, the lighter the rocket, the farther it will fly.
  3. Attach the paper rocket onto one side of the rocket straw using tape and place it onto the straw in the rocket launcher. 

  4. Squeeze the rocket launcher hard, and you should find that the rocket shoots up into the air. Try launching at different angles to see how you can make the rocket fly farther.


Reprinted from This is Rocket Science by Emma Vanstone with permission from Page Street Publishing Co. Photography by Charlotte Dart.