This weekend Seth and I built a soda bottle water rocket.

We used a 2 liter soda bottle Just fill it about 30% with water then pump it full of air and watch it blast off.

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The launcher design I used is pretty simple to make. I took a 10" long piece of black pipe, that was 1/2" in diameter. That just about matched the inside diameter of a 2 liter bottle opening. The I found a PVC elbow joint to screw it into. I got a pvc plug for the elbow joint. Drilled a hole in the pvc plug then put a car tire valve stem in the hole. I used one of the chrome valve stems because they are metal and use a nut to hold them in place. Then I put the plug into the elbow and glued it together.

Around the base of the black pipe I wrapped a few rounds of electrical tape. Just enough to make the bottle have tight fit. Then fill the bottle up about 1/3 with water and put the bottle over the black pipe. Then pump it up until the bottle blasts off. Other designs have snap ring that holds the bottle in place. I stuck with the KISS (keep it simple stupid) principle. The bottle just shoots off whenever the pressure builds up enough. You don't have as much control, but it is much easier to make.

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The bottle would shoot pretty high. Well over the power lines and trees. After a while we quit using water and would just pump up the bottle with air. It wouldn't fly as high, but was eaiser to work with on a very cold winter day.

If you build one of these please keep safety in mind. These bottles shoot off surprisingly fast. The first time I pumped it up, it shot right passed my face. I made sure to move the pump farther away from the launcher after that.