Water bottle rocket is a simple device made using ordinary bottle in which the bottle is made to rise up in the air like a rocket under the influence of a water jet coming out of a nozzle fitted on the mouth of the bottle. The process of making and operating a water bottle rocket is very simple and safe. This procedure is described below.
- Take any old PET water bottle. Do not use glass bottle as it is heavier and poses risk of hurting people from glass pieces flying off from bottles broken accidentally.
- Fill the bottle partially with water - say about two third of the bottle.
- Fit a nozzle on the mouth of bottle and fill air under pressure in the bottle through the nozzle. A simple bicycle pump may be used for this.
- Keeping the mouth of the nozzle sealed, position the bottle so that its mouth with the nozzle is facing downwards. When this is done, the water collects below and the compressed air rises to the top.
- Remove the nozzle seal. With this the water is forced down the nozzle by the compressed air creating a water jet, this propels the bottle up like a rocket.
Various means can be adopted to modify the behavior of the water bottle rocket. For example salt can be added to water to increase the thrust. Soap added to water increases the duration of release of jet. Wings can be stuck outside the bottle to improve its balance and direction in its trajectory.