source: www.youthwork-practice.com | 2000 Games, Devotions, Themes, Ideas and more for Youth Work
only for private using

Air-water Rocket

This air-ground-water rocket can fly up to 15 metres high. Even with a small range we are still happy with it. However, saying this it is advisable to use this rocket outdoors on a field; as who wants to scrap the sitting-room lamp or make a hole in the ceiling?

Place a cork onto a 1.5L plastic bottle. This cork is prepared beforehand. Drill/make a hole in the cork in which you place a bicycle valve with a nut. Shorten the cork to the length of the valve.

Cut three wings out of thicker cardboard and stick onto the bottle (see picture) using sticky-tape or something similar. Try and secure these wings as much as possible so that the rocket is stable thus reducing the chance that it overturns and flies in the wrong direction.

The bottle is partially filled with water. The amount of water determines the flight height. Try various amounts starting with 1/3 water.

Attach the bicycle pump to the vent and pump forcefully; taking care not to bend over the bottle.

What is the principle?

The rocket motor is based on the conservation of momentum. As the air is compressible, it is energised during pumping. When there is enough pressure in the bottle, the vent is blown off, and the mix of air and water is expelled at high speed. As water has a much greater density than air, it is guaranteed that enough mass is ejected. Due to the water flowing out, the rocket becomes lighter and acceleration increases during flight.