High Power Water Rocket

A few shots of me and my water rocket before we left the UK and I had too much grey hair!  This particular version uses two 2-litre lemonade bottles linked by a short length of garden hose. This enables a full 2-litres of water and 2-litres of compressed air to expel it.

 

The launch mechanism is machined from brass bar and uses a cantilevered clamp system to hold the bottle down. A double O-Ring system ensures a good seal even at maximum pressure of around 8 bar, much above this and the pop-bottles fail catastrophically!  

 

The rocket separates at apogee  courtesy of a shape-memory-alloy actuator, activated by an electronic timer and NiCad pack. The timer is initiated by a reed switch, operated by a magnet on the launch pad. Using some very rough trigonometry in the field I reckon the max altitude is around 80m

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A slightly simpler version on the launch pad. Move the mouse over the image to see lift-off.

I’ll add some details of the launch mechanism when I’ve got a mo...

 

By using a digital camera in movie mode and long ruler it is possible to calculate the acceleration and maximum speed of the rocket. I’ve compiled all the images, overlays and calculations using MS PowerPoint into a .pdf file which can be downloaded here. (~2MB). Best viewed in single page mode.

 

It could make an interesting variation on the ticker-tape, trolley and ramp experiment I remember from my O-level physics lessons, oooh that was a long time ago now.