Engineers at the Massachusetts Institute of Technology have successfully flown an airplane with no moving parts and no motor.
In an article in the journal Nature published on Nov. 21, the team described a plane powered by “ionic wind,” which produces no pollution.
“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, on MIT’s website.
“This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions,” Barrett continues.
The new plane, unlike every plane mass-produced since the Wright brothers’ first successful flight in 1903, does not use any sort of a fossil-fuel power—no piston engine, no jet engine.
Instead of a motor, the experimental plane generates ionic wind—a powerful flow of ions that propel the plane fast enough to take flight.
The concept is flightworthy on a small scale, but is a long way from replacing jet engines in commercial airliners. For now, MIT engineers are looking to build silent, ecologically friendly drones.
The next step, according to Barrett, might be hybrid systems, where ion-wind generators are paired with conventional motors to increase efficiency and limit pollution.
Inspired by ‘Star Trek’
Barrett said he would watch the science-fiction television series ‘Star Trek” as a child, where craft flew through the sky without moving parts and without exhaust trails.
“This made me think, in the long-term future, planes shouldn’t have propellers and turbines,” Barrett said. “They should be more like the shuttles in ‘Star Trek,’ that have just a blue glow and silently glide.”
Barrett started serious investigations of exhaust-free propulsion systems about nine years ago, according the MIT site.
He came across the idea of electro-aerodynamic thrust—“ionic wind”—which had first been proposed in the 1920s. Ionic wind is created when a current passes between a thin and a thick electrode—the current excites the air between to two electrodes enough to produce thrust.
Barrett made some assumptions, did some calculations, and determined that a powerful enough ion generator could actually push an airplane fast enough to generate lift with its wings.
“It was a sleepless night in a hotel when I was jet-lagged, and I was thinking about this and started searching for ways it could be done,” Barrett said.
“I did some back-of-the-envelope calculations and found that, yes, it might become a viable propulsion system,” he continued.
Calculating what was possible was a long way from producing a design that would actually work, Barrett said. “And it turned out it needed many years of work to get from that to a first test flight.”
Successful Small-Scale Test
Barrett’s ion plane team included members of professor David Perreault’s Power Electronics Research Group in the Research Laboratory of Electronics, and also Thomas Sebastian and Mark Woolston from Lincoln Laboratory.
The engineering team produced a glider-like craft with long, thin, wings. Wires are strung along the leading edge of the each 8-foot wing, while thicker wires run along the trailing edge.
Extremely high-voltage current—40,000 volts—is passed through the front set of wires to start the engine.
The current strips electrons off air molecules, which gives the air a positive charge. The air is then attracted to the thicker rear wires. As the air rushes from the front to the back, it creates a wind that is powerful enough to move the 5-pound plane.
“This was the simplest possible plane we could design that could prove the concept that an ion plane could fly,” Barrett said. “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.”
The team tested the plane inside the gymnasium at MIT’s duPont Athletic Center—the largest indoor space readily available. The team preformed 10 successful test flights of almost 200 feet each—the longest dimension of the gym.
As a point of comparison, the Wright brothers’ first flight was only 120 feet.
A Giant Step for Ion-Powered Flight
The engineering team is happy with what they have, but in no way satisfied. The concept has been proven but the scale is too small to be useful.
The next step will be to get more lift from less voltage.
Still, just getting a 5-pound model to stay airborne for a 200-foot flight represents a huge step forward in ionic wind technology.
Franck Plouraboue, senior researcher at the Institute of Fluid Mechanics in Toulouse, France, pointed out that prior ionic-wind experiments couldn’t lift more than a tenth of an ounce. Five pounds—80 ounces—is an 800-fold increase.
“The strength of the results are a direct proof that steady flight of a drone with ionic wind is sustainable,” Plouraboue said in the MIT article.
“[Outside of drone applications], it is difficult to infer how much it could influence aircraft propulsion in the future. Nevertheless, this is not really a weakness but rather an opening for future progress, in a field which is now going to burst.”
“It took a long time to get here,” Barrett stated.
“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,” he said.
