An Aeroplane that Contains No Moving Parts and Creates No Emissions has Been Successfully Constructed and Flown by Aeronautical Engineers

An aeroplane that contains no moving parts and creates no emissions has been successfully constructed and flown by aeronautical engineers. The new model is heavier than a regular air-powered model.

The new plane has a five-metre wingspan and uses a solid-state propulsion system where electrical forces accelerate ions in a fluid. It was designed by a team led by Haofeng Xu of the Massachusetts Institute of Technology (MIT) in the US and is outlined in a paper published in the journal Nature.

Until now, all aircraft require a mechanical propulsion system that uses moving parts like turbines or propellers. The only exception was an unpowered glider or the few very early pedal-powered designs.

The electro-aerodynamics that use the ion-based system which Xu and his colleagues employed, has long been seen as an alternative. However, the physics behind the concept proved to be incredibly complicated.

The main issue was that the thrust delivered by an electro-aerodynamical engine is strongly affected by speed, air density and, thus, altitude. In 2017, an analysis was published in the journal of the American Institute of Aeronautics and Astronautics, which discovered that the thrust-to-power ratio of an electro-aerodynamical aeroplane would be reduced by approximately 80% as the vehicle climbed from ground level to 25 kilometres up.

But, the study’s authors, Christopher Gilmore and Steven Barrett (who are also co-authors on Xu’s paper), discovered that some tweaks to its design could be used to reduce the drop-off. They proposed to increase the size of the thruster as a way to compensate for the altitude-based loss.

They also remarked that the thrust to power is also expected to decrease with increasing forward velocity of an electro-aerodynamically propelled aircraft as a result of an increase in the effective mobility of ions produced by the propulsion system.

What’s more, this would still boost overall efficiency as speed increased. In their final analysis, Gilmore and Barrett concluded that an electro-aerodynamical thruster could be made to deliver a thrust-to-power balance widely comparable to that accomplished by propeller-based and turbine-based aircraft engines.

However, like all work on ion-based aeroplane engines, their 2017 study was theoretical. Until now, no one had actually built a functioning vehicle.

And, one can argue that they still haven’t. The model built and flown by Xu and his team is large, but not big enough to carry a person. Also, the researchers performed their test flights in an enclosed building, which is, of course, free from energy-sapping cross- or head-winds. Plus, it flew no more than two metres off the ground.

Regardless, the researchers say, the results are essential. Holding a specially designed ultra-lightweight 40-kilovolt battery onboard, they were able to accomplish ten successful test flights in a row.

The authors of the experiment wrote that this demonstrates how conventionally accepted limitations in thrust-to-power ratio and thrust density, which had limited the feasibility of electro-aerodynamics as a method of aeroplane propulsion can be overcome.

The authors also wrote that they offer a proof of concept for electro-aerodynamic aeroplane propulsion, which opens doors for aircraft and aerodynamic devices that are less noisy, mechanically simpler, and do not give off any combustion emissions.

Franck Plouraboué from Toulouse University in France wrote an editorial associated with this work in the same journal. There he highlights that the theory behind electro-aerodynamics has been known for more than one hundred years.

Plouraboué explained that when charged molecules in the air are subjected to an electric field, they are accelerated, and when these charged molecules collide with neutral ones, they transfer part of their momentum, leading to air movement, which is called an ionic wind.

He outlines the work of Xu and his colleagues as a breakthrough and particularly highlights the design of fine wire which, when exposed to an electric field, is called an “emitter.”

Plouraboué also writes that the field is strong enough to cause a chain reaction: free electrons in the area collide heavily enough with air molecules to ionize them, generating more electrons, which then ionize more molecules.

He also added that the cascade of electrons gives rise to charged air molecules in the area of the emitter — what is known as a corona discharge. Lastly, the charged molecules drift away from the emitter and produce a propulsive ionic wind as the electric field accelerates them towards a device dubbed the collector.

Thus, they have laid the groundwork to begin refining and improving the design.


Image Credit: Gokhan KIRCA / Shutterstock


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