The days of the highly toxic rocket fuel hydrazine are numbered – at least if Angelo Cervone and Barry Zandbergen from the space systems engineering research group (AE) have their way. They have developed an idea for a propulsion system that operates using ice. They have described their invention, which could be particularly interesting with regard to the mobility of nanosatellites, in a recent publication in Acta Astronautica. Once in space, ice sublimates. The water vapour molecules emerging from this process collide with a heated plate, thus being expelled at high speed from the nanosatellite and generating several milli-Newtons of propulsion. That is enough to steer nanosatellites once they are in orbit around the earth.