Design and Making Process

The water bottle rocket design consists of low cost and recycled materials to ensure a cheap and environmentally safe build. For the top of the rocket, on the 500ml bottle, a piece of card was used to create a cone shape. This acted as the nose cone and made the rocket more aerodynamic. The nose cone was then covered in a thick layer of water proof tape to add strength and to minimise rocket damage upon impact. This also creates more weight at the top of the rocket and gave it a higher centre of mass. This allowed for the rocket to have more stability during flight.

The larger 2L rockets uses a second bottle cut in half, as well as a larger shaped card cone covered in tape for the nose cone. This allows for a stronger and also heavier top of the rocket. The 2L rockets also have a lot more tape wrapped around the nose cone to give more weight at the top, and therefore a higher centre of mass.

The fins are made from cardboard cut out into 4 identical triangle shapes, and are attached to the main body of the water bottle originally only using hot glue. After some initial testing, the fins of the rockets fell off after impact and so were reattached using hot glue and coated with extra strong water proof tape. The fins were attached at the bottom of the rocket to create a lower centre of pressure thereby creating an increase in the rocket’s stability. The rocket fins were chosen to be made out of cardboard as it is a lightweight material so they don’t lower the centre of mass of the rocket and decrease its stability. They were also made to be relatively small so the rocket experiences less drag during flight, therefore allowing it to reach higher speeds and heights as there is less force acting against thrust.

The nozzle is made using a needle valve and recycled cork and is attached to the base of the launching system. The cork needed to be cut so that the needle valve can pass completely through it. The valve easily presses through the cork and hot glue was used to seal it in place and ensure that no air or water can escape the bottle once the cork was in the bottle. This nozzle allows air to be pumped into the rocket until there is enough pressure acting down on the water that the cork is pushed out of the bottle and the water is released at a high velocity creating thrust for the rocket.

The launching system is made out of PVC pipe pieced together using hot glue and extra strong duct tape. The main body is made out of pipe with a diameter of 21.5mm to fit perfectly inside the bottle, although there is a slightly wider piece attached to stop the rocket from sliding down the pipe. To stop the rocket from shooting up before enough pressure is built there are two zip ties, one on the bottle and one on the launcher, bound together with a piece of string to create a quick release mechanism allowing the user to launch whenever they want.

How the launching system works:

As shown from the diagram above, the rocket and launcher both have zip ties attached. These zip ties are connected together with string to stop the rocket from being released. When the inside of the rocket has reached the desired pressure, the string is released and the rocket will launch upwards.

This is the final design of the rocket and launching system:

[2][3][4]