Plane without moving parts takes off | Science

When the Wright Flyer, the famous aircraft of Wilbur and Orville Wright, flew for the first time in 1903, he had to make a real racket, with his crude gasoline engine running on two propellers via transmission chains. Nearly 115 years later, another type of plane took flight, as silent as a ghost, with no moving parts. The new type of aircraft could usher in silent drones and perhaps much simpler planes, if researchers manage to overcome the daunting task of developing technology.

Instead of relying on a propeller or a jet engine, the plane, the size of a kayak for one person, propels itself through the air using electro -odynamics (EAD). This form of propulsion uses electrical effects to send air backward, giving the aircraft an equal push.

Aeronautical engineers have long thought that the aircraft could be powered by EAD, says Steven Barrett, aeronautical engineer at the Massachusetts Institute of Technology (MIT) in Cambridge. But no one had ever built an EAD plane that could lift its own weight. When Barrett and his colleagues finally succeeded, they shut up in silence, he said. "It took about 7 years of work just to take off."

In an EAD propulsion system, a powerful electric field generates a wind of fast – moving charged particles, called ions, that break into neutral air molecules and push them behind the plane, giving the plane a sense of urgency. a plane thrust. The technology – also known as ionic drive, ionic wind turbine or ionic propulsion – has already been developed by NASA for use in outer space and is now deployed on some satellites and spacecraft. Because space is a void, these systems lead to the inionization of a fluid, such as xenon, while the Barrett plane is designed to ionize nitrogen molecules in the ambient air.

However, it is much easier to deploy an ion reader in space than in the atmosphere. Gravity guides a satellite around the planet, with ion entrainment applying small course corrections. In contrast, an aircraft must produce enough thrust to maintain altitude and overcome the constant resistance of air resistance.

After conducting several computer simulations, the Barrett team opted for a plane with a wingspan of 5 meters and a mass of 2.45 kg, about the weight of a chicken. To generate the necessary electric field, sets of electrodes resembling venetian blinds pass under the wings of the aircraft, each consisting of a positively charged stainless steel wire, a few centimeters from the slice of heavily loaded foam negatively and covered with aluminum. The aircraft also features a custom battery stack and a converter to turn battery voltage from about 200 volts to 40 kilovolts. Although the highly charged electrodes are exposed on the frames of the aircraft, they can be activated and deactivated by remote control to avoid security risks.

The team tested the plane in an MIT gym at irregular hours to avoid colliding with sports teams. "There have been some pretty epic accidents," says Barrett. Finally, the team developed a sling-like device to help launch the aircraft. After hundreds of unsuccessful attempts, the aircraft was finally able to propel itself enough to remain suspended in the air. After more than 10 test flights, the aircraft flew up to 60 meters, a little further than the Wright brothers' first flight, in about 10 seconds, with an average height of half a meter, report the researchers this week at Nature.

"This is a great first step," says Daniel Drew, an electrical engineer at the University of California at Berkeley, who works on EAD microbots and did not participate in the study. However, he warned, "if they were trying to go much bigger with the size of the plane, they would have many problems." The fundamental problem is scaling down, says Drew. As the size of the aircraft increases, its weight will increase faster than the surface of its wings. So, to stay high, a bigger plane must produce a lot more thrust per unit of wing area, he says, which "would be extremely difficult to achieve from a physics point of view."

Barrett is not ready to exclude the possibility of a day of transporting human beings. "We are still far away and we need to improve a lot to get there," he says, "but I do not think anything can make this fundamentally impossible." The thrust could be improved by making the system Power converter and batteries more efficient, tests different creative strategies or integrates thrusters in the chassis of the aircraft to reduce drag, he says. Franck Plouraboué, a researcher in fluid mechanics at the CNRS and the University of Toulouse, says that one of the ways to propel EAD aircraft could be to use ultralight solar panels attached to the top of the plane.

Drew thinks we're more likely to see a swarm of smaller EAD devices someday. In this context, Barrett thinks that the main advantage of EAD aircraft will be the lack of noise. "If we want to use drones everywhere in our cities to haul things and monitor air quality, all those buzzing and noise could get pretty boring."