A team of MIT engineers has flown what was long thought impossible – a heavier than air craft that needs no moving parts for achieving powered lift. The 5-lb (2.3-kg) prototype with a 16-ft (5-m) wingspan doesn't use propellers, turbines, or fans, but instead relied on a silent stream of ionized air to maintain steady flight on an indoor course of over 197 ft (60 m) at MIT's duPont Athletic Center.
The principle behind the MIT team's 10 recent test flights is called "electroaerodynamics" and uses an ionic wind to create thrust. The idea isn't new. The effect was first observed in the 1920s, and thanks to the work of Major Alexander de Seversky and others, it has gained a niche following in aeronautical and hobbyist circles.
The basic idea is to build a grid consisting of a series of wires or lengths of foil, with one set acting as a positive electrode and the other as a negative electrode. When charged, the positive electrode strips the electrons away from surrounding air molecules, which are then attracted to the negative electrode, and as they rush along, they collide with neutral molecules and push them. This creates a tiny, but measurable thrust.
Until now, the problem has been that electroaerodynamics has been little more than a lab bench toy with its practical applications limited to things like electronic air purifiers. This is because the technology doesn't scale very well. The amount of thrust can be increased by making the craft bigger, but doubling the size only increases the grid's surface area by its square, while the craft's volume, and hence its weight, increases by its cube.
The result is the tiny flying machine quickly becomes too heavy to lift itself, which is why most such machines have been tiny gossamer things dependent on outside power tethers to barely hover – a far cry from de Seversky's dream of passenger-carrying ioncraft silently whisking commuters to and fro.
According to MIT, the breakthrough came as a result of Steven Barrett, associate professor of aeronautics and astronautics at MIT, being inspired by the silent fictional shuttlecraft of Star Trek. Taking this as his starting point, Barrett and his team worked for nine years on an ion propulsion system that needs no moving parts.
They managed this by making a glider-like drone with an airfoil made up of thin wires toward the leading edge and thicker wires aft, looking like a radio antenna from the early 20th century. These act as the electrodes to move the air molecules and provide forward thrust. Meanwhile, inside the fuselage is a bank of lithium-polymer batteries and an electrical system devised by Professor David Perreault's Power Electronics Research Group in the Research Laboratory of Electronics to supply 40,000 volts to the electrodes. It's bit primitive, but it does fly instead of merely hover or glide.
"This was the simplest possible plane we could design that could prove the concept that an ion plane could fly," Barrett says. "It's still some way away from an aircraft that could perform a useful mission. It needs to be more efficient, fly for longer, and fly outside."
According to Barrett, the new ion flyer has a lot of potential applications, from silent, non-polluting drones to supplemental propulsion for more conventional aircraft. To this end, the team is now working on improving the efficiency of the design, increasing the electrode array's surface without adding too much weight, and devising new flight control mechanisms.
"It took a long time to get here," says Barrett. "Going from the basic principle to something that actually flies was a long journey of characterizing the physics, then coming up with the design and making it work. Now the possibilities for this kind of propulsion system are viable."
The video below discusses the first ion wind flight, and the research was published in Nature.
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