I spent the summer of '00 working for Professor Chris Edwards in the Stanford Mechanical Engineering department, designing a hybrid rocket to allow students to explore complex, highly-turbulent multi-phase flows (with paraffin fuel we had solid, liquid, and gas flowing simultaneously). The idea was to create a hands-on environment where they would model the flows and reactions using MATLAB code, hypothesize improvements in thrust or specific impulse, and eventually test with their own improved fuel grains and nozzles. During a run in the spring, an agressively-ported fuel grain with a small nozzle overpressurized the case. The graphite nozzle sheared from its mount and was sent out the exhaust stack, which it was designed to do if the pressure got too high, but it sounded like a bomb had gone off. The rocket is still running in the new lab building at Stanford.