First time we tried them. We watched the RSC video on how to make them. In the vid the rocket went off with a 'Futtt' sound. So we made one and bfore school started set it up horizontally in a corridor. We lit it and BANG! staff came running from all parts of the school to find two science teachers rolling on the floor in fits of laughter witha small plastic bottle rolling around at the other end of the corridor. That was the moment we realised that it would have to happen outside. On the day we launched about 10 of these things one after the other. It sounded like Beiruit on a busy day.