Science Experiments

Water Rockets

Sun, 10th Aug 2008

Part of the show The Final Frontier

What you Need

A pump

A bicycle or foot pump with a long tube on it

A bung

A bung you can attach to your pump (see below)

A launcher

A launcher of some kind to stabilise the rocket

A Lemonade Bottle

A lemonade bottle

What to do

The first thing you need for the rocket is some form of bung in the bottom of the bottle through which you can pump some air.  There are various ways of doing this, one of the best is to use a rubber bung or cork, similar to those which are used in science lessons and wine making.  You will need one that will jam into the neck of the bottle well.

If you can't get a rubber bung you can make one out of a wine bottle cork, ideally one that tapers so it is wider at one end than the other.  However, wine bottle corks are often too small, and for an ideal bottle rocket you will need something with more grip.  A good way to get this grip is to cover the cork with a couple of fingers cut from an old rubber glove - turn these inside out so that they make a good seal on the inside of the bottle.  Glue it all together to seal the gaps.

Rubber Bung with a football inflater

Rubber Bung with a bike valve

Cork with a football inflater

Cork with a valve

A rubber bung with a ball inflater

A rubber bung with a bike valve

A cork covered in rubber glove fingers with a ball inflater

A cork with a bike valve through the middle.

You then need to be able to connect the bung to the pump.  If you have a football inflating adapter you can push it into the bung, but you may have to drill from the other side to make a hole for it to meet.   You can also use a bike tyre valve to make a more robust version.

Keep safe - get an adult to do the drilling and if you are the adult be very careful drilling rubber - it is not predictable, and will catch in unexpected ways.   You could try holding the cork in the top of a bottle.

Once you have made your bung, you then need a launcher.  This can be as simple a 4 or 5 pieces of wood or dowel knocked into the ground around the rocket to hold it stable while it launches.

Put some (or no) water in your bottle, jam the cork in and pump it up!

Be careful not to stand over the rocket as it is a rocket, so is about to fly upwards very quickly!!

Try using different amounts of water to see how that affects the flight.

You could try adding fins to make it fly straighter.

What may happen

You should find that the bung is pushed out and then the rocket flies up into the air in a very satisfying way.

We tried launching a (very cheap) digital camera with ours and the results are below:

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