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Comment by monkmartinez | Hacker News Reader

This is cool... and let me say I am no aerospace engineer. I am a flight enthusiast... mostly R/C quadcopter and plane as real planes are $$$.

It looks like an extremely large ducted fan R/C plane with VTOL. Calling it a "jet" in the parlance of today seems like a stretch. Are ducted fans "jets"? I guess the argument could be made. I would think the people buying these would very well think of a jet as propulsion from combustion. Also, the FAA and turbine (jet) rating... I could go on...

The VTOL is awesome, and something I think we'll see more of as quadcopter technology scales to more robust .gov missions. The applications for this tech are limitless...

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You find somebody that calls by "jet" anything that does not have exposed propellers. They also probably only use the name on their marketing material. Nobody goes out of their way to have regulators classify their engines as "jets".

It's a "jet" in the sense that it doesn't have a visible propeller, which is really the only meaning that word has any more. Virtually all the thrust produced by aircraft that people call "jets" comes from shrouded fans of some sort.

"Jets" are called "jets" because they produce a jet of matter (water or air) behind them, causing motion via Newton's third law. If the illustrations on the technology page are accurate, this fits the bill fine.

What useful definition of jet am I missing (beyond the trivial "can't be electric") where this can't usefully be called a jet?

Well, the only definition that matters would be the regulating body with jurisdiction. In the case of the US, that would be the FAA. It is squarely an experimental plane.

That's mostly what I'm getting at. They're called "jets" because the first ones used a turbojet engine, whose exhaust jet provided the thrust. The term is a colloquial contraction of the engine name, not a formal description of its operation.

Designers (of subsonic devices) rapidly moved to a more efficient turbofan design where the exhaust provides very little thrust and the engine core is used as merely a torque engine to turn a rather larger shrouded fan which actually produces the thrust.

So... if you pull out the internal combustion engine and replace it in a straightforward way with an electric motor that drives the same shaft, are you really changing the nature of the device?

> So... if you pull out the internal combustion engine and replace it in a straightforward way with an electric motor that drives the same shaft, are you really changing the nature of the device?

Just like "turbojet" derives from it being a turbine-powered jet, I think the new electric version should be called a "magnejet". Or just "jet" for short.

Why spend the time pontificating, asking others for things that are clearly explained on the website, when you could answer these questions yourself?

https://lilium.com/technology/

I saw that and it is not a jet in today's parlance of what most pilots would call a "jet". Hell, it looks like there are 36 extremely large brushless outrunner motors.

In order to avoid a goalpost-moving exercise, what is concrete the working definition of jet you feel most pilots would agree with? Is the difference between that and this as trivial as "has an ICE"?

From an engineering perspective, if something produces thrust primarily by producing a jet of surrounding matter (water or air) and taking advantage of Newton's third law, I'm not sure I see the issue. There's no exposed airfoil, and it doesn't appear to care about Bernouilli's law (except for lift).

Thanks, I missed that (I have to say I never even bothered looking; I've seen this kind of website before). It's pretty sparse on information. I managed to find that:

- they use lithium ion batteries.

- they use LEAPTech style engine layout with multiple small engines (they don't name check it, I just recognise it from https://www.nasa.gov/content/experimental-wing-tests-electri...).

- there's a backup parachute.

- they don't mention autonomous flying, but you also don't have direct control of the vehicle --- a computer mediates.

- for some reason they insist on calling ducted fans 'electric jet engines'.

That's about it. Anything I missed?

This page is completely devoid of any actual information. It's a SquareSpace marketing site.

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