A group of engineers at MIT have built the first-ever aeroplane capable of flying without any moving parts. The aircraft uses an ion drive that produces a flow of ions powerful enough to propel it forwards, in place of the more traditional propellers or turbine blades. This means it doesn’t depend on fossil fuels to fly and is completely silent. The inspiration for the design came from sci-fi TV shows.
“In the long-term future, planes shouldn’t have propellers and turbines. They should be more like the shuttles in Star Trek, that just have a blue glow and silently glide,” said Prof Steven Barrett, from MIT’s department of aeronautics and astronautics. “This is the first-ever sustained flight of a plane with no moving parts in the propulsion system. This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions.”
In the near term, ion propulsion systems could be used to fly drones, but in the long term they could be paired with more conventional combustion systems to create more fuel-efficient, hybrid passenger planes and other large aircraft, according to Barrett.
The ion drive is powered by lithium-polymer batteries and generates an ‘ionic wind’ – a stream of ions produced when a current is passed between a thick and thin electrode – which provides enough thrust to keep the craft airborne.
The craft has a wingspan of about five metres and weighs roughly three kilograms. It completed 10 flights of approximately 60 metres inside a gym at MIT’s duPont Athletic Center in Cambridge, Massachusetts. The members of the team are now working on increasing the efficiency of the drive.
“It took a long time to get here,” said Barrett. “Going from the basic principle to something that actually flies was a long journey of characterising the physics, then coming up with the design and making it work. Now the possibilities for this kind of propulsion system are viable.”
Expert comment
Prof Guy Gratton - Aerospace engineer, and visiting professor at Cranfield University
“This is very clever application of the principle of ion thrusters to an aircraft, using high voltages to ionise then accelerate the air at high speeds.So far they have only been used on spacecraft, usually to help a satellite stay in position in orbit.
“It’s clearly early days, but the team at MIT have done something we never previously knew was possible: using accelerated ionised gas to propel an aircraft. Aeronautical engineers around the world are already trying hard to find ways to use electric propulsion. This technology will offer something else that in the futuremayallow manned and unmanned aircraft to be more efficient and non-polluting. In particular, the fact that they have already got this out of the laboratory, and flown a battery driven model aircraft – albeit on a small and controlled scale – is exciting.
“Ion thrusters were first suggested by Star Trek in the 1960s, but developed for real by scientists and engineers in the US and at Britain’s Royal Aircraft Establishment at Farnborough. They are only able to produce very low amounts of thrust, but are extremely efficient because they accelerate particles to an extremely high speed using electricity, rather than having to burn any kind
of fuel.”
This is an extract from issue 330 of BBC Focus magazine.
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