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6 Mission-critical info for UST professionals Platform one A team at the Massachusetts Institute of Technology has flown the first unmanned aircraft to use ionic propulsion rather than propellers or a jet engine (writes Nick Flaherty). Ionic propulsion, also called electro- aerodynamic thrust, uses a voltage of around 40 kV to generate ions from the air. The craft weighs 2.45 kg, has a wingspan of 5 m and travelled 60 m indoors on its first flight. “This is the first-ever sustained flight of a plane with no moving parts in the propulsion system,” said Steven Barrett, associate professor of aeronautics and astronautics at MIT. “It opens up possibilities for aircraft that are quieter, mechanically simpler and do not produce combustion emissions.” The idea of ionic propulsion has been around since the 1920s but has been limited by the power needed to generate the high voltage. Previously it has required a tether to a high- voltage supply. The latest high-voltage semiconductors and high energy density lithium-polymer batteries however have allowed untethered flight. The drive is formed from an array of thin wires that are strung along and beneath the front end of the wing. The wires act as positively charged electrodes, while similarly arranged thicker wires, running along the back end of the plane’s wing, serve as the negative electrodes. A custom, lightweight power supply developed by the Power Electronics Research Group in MIT’s Research Laboratory of Electronics produces the 40 kV voltage from a bank of lithium- polymer batteries in the fuselage. The front electrodes generate the ions, which then accelerate towards the rear wires, creating thrust to drive the aircraft forwards. “This was the simplest possible plane we could design that could prove the concept that an ion plane could fly,” said Prof Barrett. “It’s still some way away from an aircraft that could perform a useful mission though. It needs to be more efficient, fly for longer, and fly outside.” The team is working to reduce the voltage while producing more ionic wind, and to increase the thrust density. Its ultimate aim is to design an aircraft with no visible propulsion system, where the propulsion is part of the aircraft’s skin. Airborne vehicles Ionic power takes off December/January 2019 | Unmanned Systems Technology The craft’s propulsion comes from ions being accelerated by high voltage from the front end of the wing to the back