Dissipation of contrails with a powerful microwave beam aligned behind aircraft engines is being touted as a possible solution to help address air transport's effects on the climate. Speaking on 19 November at the Towards Sustainable Aviation Propulsion event organised by the Institution of Mechanical Engineers, Cranfield University's Frank Noppel described how his research led sponsor Rolls-Royce to file a patent on what he believes could be a cost-effective contrail avoidance technology. Noppel told delegates that ice particles could be prevented from forming, or be evaporated once formed, by remotely heating them, together with condensation nuclei such as soot in the exhaust plume. Contrails form as the engine exhaust mixes with ambient air, the temperature drops and humidity levels reach super-saturation, leading to the fo