The H0 was the first hybrid rocket engine to be built by Aspirespace. It was constructed in 1995 to demonstrate the principles of a hybrid rocket and made numerous appearances at conferences and lectures around the UK and on national television. It burnt Perspex fuel in gaseous oxygen at a low pressure, and generated only a very low thrust. While this made the H0 impractical for use in a rocket vehicle, it was sufficiently safe to operate indoors in a lecture theatre and, with its transparent combustion chamber, was an ideal technology demonstrator.
Though the H0 is no more, Kingston University students have now constructed a very similar demonstrator engine.