With this solid, durable metal launcher equipped with a simple triggering mechanism, and using an ordinary bicycle pump, you can turn almost any plastic soda bottle into a rocket with water as the propellant. 

Students can vary the fin size and placement, vary the water level and air pressure, measure rocket altitude with the included paper astrolabe, and even loft a full-size soccer ball with this investigation of the conservation of action and reaction momenta. 

The launcher stakes must be pushed into the ground or supported by the Bottle Rocket Launch Pad.