Water Rockets

Water rocket launch

Water rockets are another quality project to do with the kids outdoors.

Over the years We have improved our launch system, from the original being just a wine cork with a football inflation needle through the centre and rammed into an old lemonade bottle propped up with wood and buckets.

To our latest launch pad thats been 3D printed with a proper inflation nozzle, O ring seal and cord release mechanism.

The design pictured was published by Superbeasti on Thingiverse https://www.thingiverse.com/thing:3626084

I have since improved the release pin design as the original split a little too easily. In adapting the design I also made the pull cord attachment central so that the release of the rocket is more even.

The Setup

The rocket mount needs to be screwed down to a decent sized piece of wood to help support the rocket and be heavy enough not to move when the release cord is pulled.

The bottle adapter needs to be glued to an old lemonade bottle with epoxy, this ensures the screw thread is firmly sealed to the bottle. 3D printed threads tend to leak. You may want to print and glue a few together.

An O ring needs to be fitted to the inlet adapter and a pump or small compressor attached to the inlet fitting.

A pull cord of about 4 – 5 meters needs to be attached to the release pin.

Arming you rocket

Fill the lemonade bottle about to about 1/4 full with water.

Place the inlet adapter onto the bottle adapter and clamp them together with the release pin.

You now need to slightly pressurise the rocket before turning it over as this initial fill applies pressure to the O ring and seals the system together.

Once sealed the whole assembily can be slid into the launch base – this is a little tricky, just make sure you pin doesn’t come off.

You can now proceed to fully pressurise the rocket ready for launching. You can do this with a car tyre compressor or foot pump but we have a garage compressor with an extra long hose.


Hand the cord to the nearest child, perform your countdown and release the rocket with a tug of the cord.

Just make sure you are far enough away to not get soaked by the water ejected out of the rocket

Our rockets didn’t fire straight as they really needed fins adding to them for stability. However we still managed to get one on top of a neighbors house!

  • Water Rocket Launch sequence
  • Water Rocket Launch sequence
  • Water Rocket Launch sequence
  • Water Rocket Launch sequence
  • Water Rocket Launch sequence

Adding a few rough cardboard fins to the side of the rocket really did help but didn’t stay on for too long.

Water Rocket modifications

Our water rockets have just been bottles so far which don’t work too well. I’m now going to print fin adapters and nose cones allowing the children to customize them. Experiment with different options and see how well they work (or not).

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