This guide is going to tell you how make a bottle rocket that will be filled with water and when pressurized with air cause the bottle go to rocket up in the air.

Materials

• 2 2L water bottles
• Duct tape
• Cardboard
• String
• 1 Pylon
• Water
• Garbage bag
• Hole puncher
• An air pump

Procedure

First, get 2 2L bottles and then cut the top and the bottom of the one bottle and attach it to the bottom of the normal bottle. Then cut out triangles from the cardboard after carefully measuring them, and using duct tape, stick them on the body. Using the same method, create holders for the pylon. Get a garbage bag and cut out a hexagon. This hexagon will be your canopy for the parachute. After that, put masking tape on the edges, and using a hole puncher, punch 6 holes on each side. Put the parachute inside the compartment in the 2nd 2L bottle. After that, cut the bottom of a pylon and put it on the top. Now your bottle rocket is complete and all that’s left is to pressurize it.

The Science

This rocket uses air pressure, diffusion, displacement, aerodynamics, and drag. We use the pump to cause air pressure in the bottle, then because of diffusion, the air particles inside will be really dense and will tend to go out of the container. when there is enough pressure the air particles will push the rocket up. This occurs because of displacement. When the air particles escape the container through the hole at the bottom, the rocket will be displaced. Since the hole is at the bottom the rocket will keep going up and up, to the opposite direction of where the pressurized air is released. When there is not enough pressure in the bottle it will be bound towards the ground by the force of gravity. This is when the air that is going up will push the pylon, and the eject the parachute. The air going up will be trapped underneath the parachute making the ride down a bit slower. 

here is an example of a soda bottle rocket in action