Soda bottle rockets

Most people are familiar with model rockets, but here I have made a "rocket" out of an ordinary 2-liter soda bottle, and the "launch pad" is constructed out of PVC pipe. The "fuel" is air and water.

To make the launch pad, I used a 5' length of 1/2" PVC water pipe. I cut two 11" lengths which were glued into a slip/threaded T connector. One end was capped, while the other end was capped with a cap where a hole was drilled and a universal valve stem was inserted through the hole.

A threaded connector was screwed into the T connector, and I glued a 32" length of pipe into that. A 90 degree elbow connector was glued onto the open end, and the remaining 6" length of pipe was inserted into the elbow. At the end of the 6" piece, another male threaded connector was glued on, and the threads were wrapped a few times with electrical tape, just enough to make a tight seal when the 2-liter bottle is placed over the top. Test fit a soda bottle over the end to see if you have the right amount of tape.

To launch the rocket, a soda bottle is filled about 1/3 full of water. (Too much water will make the rocket too heavy to go high, while not enough water will prevent it from building up enough pressure.) Invert the bottle and quickly put it over the taped end, twisting it in the direction of the tape to ensure a good seal. (If you twist it the opposite way of the tape, you could cause the tape to loosen up and come off.) Use a bicycle pump attached to the valve to pump air into the system until enough pressure is built up and the rocket launches into the air. By using an automatic friction release, we won't end up putting so much air into the system that the bottle might explode before launch.

I spent about $3 at Lowe's on the PVC pipe and components, and an additional $3 at an auto parts store for a pair of valve stems. I had to purchase more PVC glue for about $4 because I had run out. (I still had a bottle of PVC cleaner.)

So, the total cost in materials was about $10. My kids spent the entire afternoon launching soda bottles into the air, so it was well worth it.