This curious drone concept uses space-only technology

While the majority of the industry is interested in electric or hydrogen engines, a Florida startup wants to make its funny fly thanks to ionic propulsion.

Undefined Technologies, a Florida startup, has just unveiled the Silent Ventus, a one-of-a-kind drone concept. On the menu: low noise and zero greenhouse gas 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 bet on an extremely surprising technology for a machine of this type: ion propulsion. Technically, it is an electric mode of propulsion; but here, it is not a question of turning a rotor, as opposed to strictly electric motors. Here, the current is used to accelerate ions (an atom or molecule that carries an electrical charge) at very high speed to generate thrust.

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

Motors of this type usually produce a very low thrust. On the other hand, they show an exceptional performance. Features that allow ion-powered vehicles to cover immense distances in the vacuum of space, where there is almost no force likely to oppose the advance of the vehicle.

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

However, this is 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 thrust into the atmosphere“, says 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 indeed able to stay at altitude using its ion thrusters alone for 2.5 minutes. A small feat that the firm’s engineers achieved in less than a year of work on this technology !

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

A more reasonable path than electric motorization?

Indeed, 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 embarking batteries by definition very heavy; a paradox that does not mix well with the traditional constraints of aeronautics, and which has significant consequences on the energy efficiency of these machines.

All-electric VTOLs like the one from Joby Aviation are marvels of engineering, but that doesn’t stop many observers from having doubts about the concept’s relevance. © Joby Aviation

However, a device based on ionic propulsion would be better able to circumvent almost entirely these potentially prohibitive pitfalls; since ionic propulsion displays a much higher efficiency, this would considerably reduce the size of the batteries.

Traditional eVTOLs also tend to be very loud, 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. For comparison, eVTOLs like Joby’s regularly emit more than 90 dB, a noise comparable to that of a lawn mower.

So will we soon see other projects based on ionic propulsion flourish? He is still too early to tell, especially since the startup has not even proposed a more successful prototype than its initial 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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