Rainy day science: Make your own balloon rockets

August 28, 2018

While the damp weather has been raining on our summer holiday parade for the last two weeks and reminding us that school is just around the corner, there’s plenty you can do to keep your little ones busy and away from the sofa.

Turn those frowns upside down and keep your mini scientists entertained by investigating the science behind rocketry with this simple balloon rocket experiment.

You won’t even need to pop to the shops, as you’ll probably find everything you need in your own kitchen. Grab the materials below and get ready for your rainy-day fun to take-off.

Balloon Rocket experiment

You will need:

  • 1 balloon
  • 1 straw
  • 10-foot piece of string
  • Tape
  • Scissors
  • Glue
  • Permanent marker
  • Cargo (bottle tops, sweets, paperclips etc)
  • Cereal boxes (for the cargo containers)

The experiment

  1. Tie one end of the string to a supporting object e.g. chair or door handle.
  2. Thread the other end of the string through the straw, pull the string tight and tie to another supporting object.
  3. Use the permanent market to mark both ends of the string to make a start and finish line.
  4. Blow up the balloon and pinch the end to keep it inflated.
  5. Tape the balloon to the straw ensuring the opening of the balloon is horizontal with the ground.
  6. Holding the balloon opening closed, pull the balloon all the way back to the start of string so that the balloon opening is against one support.
  7. Let go of the balloon and watch it move along the string.
  8. Try testing different balloon shapes and using different methods to transport cargo across the finish line. What do you notice?

The science explained behind the balloon rocket

Although rocketry technology has improved over the years, the simple science behind rockets has stayed the same.

Blowing up a balloon fills it with gas particles, and these particles can move freely within the balloon and can collide with each other. As this happens, the particles exert pressure on the inside of the balloon.

Eventually, the pressure inside the balloon becomes greater than the pressure outside of it.

This means that when the opening of the balloon is released, gas quickly escapes which equalises the air pressure inside and outside the balloon. This escaping air exerts a force on the balloon.

The opposing force, thrust, propels the rocket forward.

If you’re looking to get out of the house next time the Welsh weather gets in the way of your plans, take a look at what we have on.

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  •   What is Techniquest?

    Techniquest is an educational charity, with a science centre in Cardiff Bay. Our mission is to embed science in Welsh culture through interactive engagement. We provide a range of services to schools and teachers to complement formal education provision in Wales and work extensively with public audiences.

  •   Where can I park?

    We are pleased to be able to offer all of our visitors discounted parking with Q-Park, our preferred parking partner.

    The Q-Park operates the Cardiff Bay car park in Pierhead Street which is around 8 minutes walk from Techniquest.

    We have agreed a special discount rate for our customers of 15% off all pre-bookings.
    Pre-book and guarantee your space here using the code TECHNI15.

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    We regret that there is no parking on-site at Techniquest.

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