This strange concept of a silent drone flies thanks to ionic propulsion

While the majority of the industry is interested in electric motors or hydrogen motors, a startup in Florida wants to have its fun escape thanks to ionic propulsion.

Undefined Technologies, a startup in Florida, has just unveiled Silent Ventus, a unique drone concept. On the menu: low noise level and no CO2 emissions. “Silent Ventus is a telling example of our ambition to create a more sustainable, progressive and less noisy urban environment.”, Explains Tomas Pribanic, CEO of the company in a press release spotted by Interesting Engineering.

And to give itself the means to realize this ambition, Undefined Technologies has chosen to focus on an extremely surprising technology for a machine of this type: ion propulsion. Technically, it is an electric propulsion mode; but here it is not a matter of turning a rotor, unlike strictly electric motors. Here the current is used to accelerate ions (an atom or molecule that carries an electric charge) at very high speed to generate propulsion.

An ion thruster test performed by NASA. The blue halo corresponds to the ionized air, which becomes visible thanks to Cherenkov radiation. © NASA / JPL

Atmospheric ion propulsion, a major engineering challenge

Engines of this type usually produce one very low pressure. On the other hand, they show a unique performance. Features that allow ion-powered vehicles to travel enormous distances in the vacuum of space, where there is almost no force that is likely to resist the vehicle’s advancement.

On the other hand, on a planet like Earth, it suddenly becomes much more complicated to exploit. Due to the very low pressure provided by these ion thrusters, it is traditionally difficult to overcome air resistance and gravity which seeks to attach the machine to the ground; it is largely because of these forces that ion propulsion is not used on Earth.

However, that’s what Undefined Technologies claims with its drone. “Silent Ventus uses proprietary technology to take advantage of the ion cloud that surrounds the vehicle to generate significant thrusts into the atmosphere“, it is stated in the press release.

And it’s not just empty words. In December 2021, the startup unveiled a tech demo that served as a proof of concept; it showed that its first prototype was actually able to remain at altitude using its ion thrusters alone for 2.5 minutes. A small feat that the company’s engineers achieved in less than a year of working with this technology!

It will therefore be very interesting to follow the development of Silent Ventus closely, at a time when more and more players are starting to explore air mobility in an urban environment. In this industrial niche, Undefined Technologies is currently an uninvited guest; but the startup could well be a game-changer if successful.

A more sensible path than electric motorization?

In fact, this segment is currently dominated by concepts of devices equipped with electric motors traditional. However, many observers are very critical of the relevance of this approach. It involves embarkation batteries by definition very heavy; a paradox that does not mix well with the traditional limitations of aviation and that has significant implications for the energy efficiency of these machines.

All-electric VTOLs like the one from Joby Aviation are marvels in technology, but that does not stop many observers from doubting the relevance of the concept. © Joby Aviation

However, a device based on ion propulsion would be better able to bypass almost completely these potentially insurmountable pitfalls; since ionic propulsion shows a much higher efficiency, this would reduce the size of the batteries significantly.

Traditional eVTOLs also tend to be very high, which is anything but ideal in a dense urban environment. The ionic propulsion, it is more discreet with about 70 dB at full speed, or about the noise of a washing machine in operation. By comparison, eVTOLs like Joby’s regularly emit more than 90 dB, a noise comparable to a lawn mower.

So will we soon see other projects based on ionic propulsion flourish? He still is too early to say especially since the startup has not even proposed a more successful prototype than its first proof of concept. But if this technology actually ends up taking hold, Undefined Technologies is certainly one of the companies best positioned to establish itself in this very interesting segment.

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