A group of students wanted to learn more about rocket engines so they decided to build their own, using parts purchased at a local hardware store. Video demonstration after the jump.
The camera did not capture them, but we could clearly see shock diamonds (indicating a supersonic exhaust velocity) running the entire length of the plume. We would have begun working on getting run times longer and perfecting nozzle geometry, but parents made us stop the experiments completely after our first test
[via HackedGadgets]