First aircraft with ion wind drive

Prototype flies with electric thrust - without propeller or turbine

The ion wind aircraft on maiden flight - it gets its thrust without propellers or nozzles. © Steven Barrett / Nature
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Historic maiden flight: For the first time, a plane with a propeller without propeller or nozzles flew - a world premiere. Because the unmanned ultralight vehicle is driven by the ion wind - an ionization of the air generated by electrodes. So far this drive technology has been considered too ineffective and weak, the maiden flight refutes this now. Although the prototype weighs only a few kilograms, but the successful test could now open ways to develop this technique.

With the first gliding flights of Otto Lilienthal more than 120 years ago, humans conquered the airspace for the first time. A little later, pioneers such as the Wright brothers and Gustav Weisskopf completed the first engine flights. Today, aviation has long been part of everyday life. But whether jet, electric aircraft or the solar-powered Solar Impulse 2: Allen has in common that they are driven by moving parts - propellers, rotors or turbines.

"Star Trek" provided the inspiration

But now, for the first time, an airplane has risen into the air, which has no moving components - and flies completely silent. During the maiden flight, the prototype with five meters wingspan and about 2.5 kilograms of weight easily covered 60 meters - more space was not in the terminal. "This is the very first powered flight of an aircraft with no moving parts in the propulsion system, " says Project Manager Steven Barrett of the Massachusetts Institute of Technology (MIT).

The inspiration for this unusual flying object gave the researchers the space ferries in the science fiction series "Star Trek". "I thought it would be possible to build aircraft that did not have propellers or turbines, " says Barrett. "Instead they should glide silently like these shuttles, powered by a bluish glow."

Tensioned wires serve the prototype as electrodes © Steven Barrett / Nature

Thrust by an ionized airflow

But how do you make science fiction a reality? This was made possible by a drive technology that was already conceived in the 1920s, the so-called electro-aerodynamic thrust or ion wind. In this case, the gas particles of the air are ionized by a positive electrode on the wing leading edge. In the prototype, it consists of several horizontal strained wires. display

These charged air particles are attracted to a negative electrode at the rear edge of the wing. Because the ions also collide with other air molecules on their way and pass on their energy, an air flow, the so-called ion wind, is created. "This ion wind generates a thrust that counteracts the direction of the ion flow, " explain the researchers.

Maiden flight successful

"Although there have been a number of proposals for electro-aerodynamic powered aircraft, none have ever flown, " say Barrett and his colleagues. One of the reasons: So far, the ion wind drive was far too ineffective to bring larger flying objects into the air. But the researchers did not settle for this and used a computer-aided optimization method to develop a flyable ion wind vehicle.

An aircraft with ion wind power - that's how it works Nature Video

With success: During the maiden flight in a large hall, her prototype flew about 60 meters in a height of around one and a half meters more space was not available in the sports hall. "Because of the limited space we had to use a bungee cord system to bring the plane within five feet to five meters per second, " the researchers report. But then the effect of the ion wind drive began, the prototype rose independently and continued to fly at just five meters per second.

Optimizations needed - and feasible

The ion-wind aircraft and its drive are still not very effective, as Barrett puts it. "First of all, we wanted to prove that an ion wind aircraft can fly at all, " says the researcher. Above all, the conversion of electrical energy into thrust must still be significantly optimized. So far, the prototype gets the necessary power from lithium batteries of 600 watts of power, which generate 40, 000 volts using a high-voltage converter.

However, only about 2.5 percent of this electrical energy has been converted into thrust. But that is also because the prototype does not yet have the optimum wingspan. "Airplanes with an efficiency of five percent are also easily feasible with the current technology, " said Barrett and his team. Their model calculations also suggest that the efficiency of such ion wind propulsion systems increases significantly with increasing speed: at an airspeed of 300 meters per second, it already lags at 50 percent.

Way to quieter and greener aircraft

"This technology opens up new and unexplored possibilities for aircraft, which are quieter and, thanks to the lack of moving parts, mechanically simpler, " says Barrett. "In addition, they do not emit any combustion emissions." In the near future, the researchers see first applications of the ion wind, especially in drones. Later, however, this drive could also be used on large passenger and cargo machines. Combined with conventional drives, the ion wind could then significantly reduce the fuel consumption of these aircraft.

"It's still a long way to go, " says Barrett. He and his team now want to increase the efficiency of their ion wind aircraft. In addition, they are working on designs where the electrodes are embedded in the wing - this is to improve safety and aerodynamics. "It is important that we now know that this type of drive is feasible, " says the researcher. (Nature, 21018; doi: 10.1038 / s41586-018-0707-9)

(Massachusetts Institute of Technology, Nov. 22, 2018 - NPO)