Ever since man took to the air more than a century ago – thanks to the Wright Brothers – aircraft have flown using moving parts such as propellers and turbines, powered by burning environmentally unfriendly fossil fuel.
A team of engineers at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, seem hell-bent on revolutionizing all of that.
Led by Steven Barrett, the MIT team has developed and demoed a prototype aircraft that has no moving parts and flies almost noiselessly, propelled by thrust generated by ionic winds.
The so-called ionic-wind is produced using onboard high-voltage electrodes to ionize the atmosphere and then accelerating the ionized air to generate the thrust required to propel the aircraft.
This system of electroaerodynamic propulsion is not only free of combustion emissions but eliminates noise-pollution, too.
“This is the first-ever sustained flight of a plane with no moving parts in the propulsion system,” Barrett said in a statement.
“This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions,” he added.
Partly inspired by ‘Star Trek,’ Barrett envisions a future with planes without propellers and turbines – somewhat on the lines of the fictional shuttles in the popular TV series emitting a bluish glow as they glide silently through the air.
Barrett says he was thrilled when he got an appointment at the university, as it gave him the opportunity to explore the concept and soon he was “looking for physics” that would make it a reality.
However, the principle that Barrett’s plane is based on is not new and can be traced all the way back to the 1920s when the concept of electroaerodynamic propulsion was first floated.
Although the principle has had its applications in the past, they have been limited to hobby projects such as using large voltage supplies to generate just about enough wind to keep a small craft briefly airborne.
The authors of the research paper published in the journal Nature write that “no aeroplane with such a solid-state propulsion system has yet flown,” going on to state that the team has been able to “demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelled heavier-than-air aeroplane.”
The idea first germinated in Barrett’s mind nearly a decade ago when he started looking for ways to design a propulsion system that would generate enough thrust for sustained solid-state flight.
“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,” he reminisces.
After some “back-of-the-envelope calculations,” he came to the conclusion that creating such a propulsion system was feasible.
“And it turned out it needed many years of work to get from that to a first test flight,” he said.
The 5-pound prototype with a 5-meter wingspan doesn’t look much different from a regular lightweight glider.
However, instead of conventional engines under the wings, the aircraft is fitted with a series of electrodes consisting of an array of very thin wires at the front, positively charged with 20,000 volts.
There’s also an array of negatively charged aerofoils along the back end of the wings’ underside, also set at 20,000 volts.
To explain the concept simply, the positively charged electrodes ionize the atmosphere, stripping away negatively-charged electrons from the surrounding air molecules.
The positively charged ions left behind are attracted to the negatively charged aerofoils at the back, colliding all the way with neutral air molecules, thereby generating the thrust needed to propel the aircraft forward.
As the experimental flights were conducted inside MIT’s duPont Athletic Center, the team was limited to only 60 meters in which to fly the prototype.
However, they did succeed in generating the thrust to keep the craft airborne the entire distance, achieving the feat ten times with similar results.
Barret said it was the “simplest possible plane” the team could come up with to prove that ionic winds could fly planes.
“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.”
While electroaerodynamic propulsion may still be some way away from a practical application on aircraft, a near-term application on drones is definitely foreseeable.
What is also possible in the near term is combining ionic wind propulsion with conventional systems based on combustion engines to develop fuel-efficient hybrid passenger planes and other large aircraft.
Franck Plouraboue, from the Institute of Fluid Mechanics in Toulouse, France, who was not part of the study, called the MIT prototype a “big step” toward proving the viability of electroaerodynamic propulsion.
“The strength of the results are a direct proof that steady flight of a drone with ionic wind is sustainable,” he said.
Apart from that, Plouraboue says “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,” he added.
Having proved that electroaerodynamically propelled solid-state flight of a heavier than air vehicle is possible, Barrett and his team are now working on improving their design efficiency to generate more propulsion from less voltage.
“It took a long time to get here,” Barrett said and added that “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.”