Science Experiment 3: Balloon Rocket

By AG Education | August 9, 2016

Have you ever wondered how they shoot a rocket all the way up into space?

National Science Week (Aug 13-21) is here again, and the team at Australian Geographic is really excited! We’ll be getting along to some of the events at the Australian Museum and Powerhouse, though there are events on all around the country.

To celebrate, we’re putting up a different science experiment every day! You can try these at school or at home, and they’ll help you learn more about space, volcanoes and heaps more. Have fun!

Balloon Rocket

Rockets blasting off from Earth are an amazing sight. They can weight hundreds of tonnes at liftoff, but the hot gases they push out at very high speeds have enough power to lift the rocket off the ground. Rockets normally burn a fuel made of liquid hydrogen and liquid oxygen. In this activity you can explore how a rocket works using air as the fuel!

Materials

  • About 5m of strong string
  • A few plastic straws (not the bendy sort)
  • Sticky tape
  • Some balloons with a mixture of long and rounded shapes

Steps

  1. Tie one end of the string to a heavy fixture in the room such as a chair or door.
  2. Thread the other end of the string through the straw and pull it tight. Tie the loose end to another fixed object, keeping it tight.
  3. Cut two pieces of sticky tape and then blow up the balloon, pinching the end so that the air doesn’t come out. Tape the balloon under the straw using the tape. You might need some help with the tape while you hold the balloon.
  4. You’re ready for launch! Let go of the balloon and watch it fly across the room.

Like all rockets, yours works because of thrust. That’s the force that moves the rocket. The air pushing out from the balloon gives thrust to move your rocket forward. Try to experiment with different shapes of balloon, filling the balloon with more or less air and changing the size of the straw. See how the speed and distance travelled changes – can you determine the fastest design?

More science experiments to try at home: