3 ms·

What are the tech specs of this thing? What altitude does it fly at? Does it use the ground effect for efficiency? If not, the claimed range seems a little too

What are the tech specs of this thing? What altitude does it fly at? Does it use the ground effect for efficiency? If not, the claimed range seems a little too futuristic with current battery technology. 150 KW for flight ("it will require less than ten per cent of its maximum 2000 horsepower during cruise flight") x 1 hour range = 150 KWh and that's going to weigh more than the maximum takeoff weight of 640 Kg according to https://en.wikipedia.org/wiki/Lilium_Jet https://en.wikipedia.org/wiki/Lilium_Jet ...

FrojoS 7y ago
The max takeoff weight you cite is for the 2 seater, not the new 5 seater.
- DuskStar 7y ago
  That makes a lot more sense - I was wondering how they were managing to fit 5 people (plus wings, motors, structure and batteries) into 640Kg.
donquichotte 7y ago
In my experience, specs are omitted in technical articles IFF somebody is trying to hide something. Like super short flight time. The MIT battery primer [1] states a specific energy of 150Wh/kg for Li-Ion cells. 150kWh would therefore weigh 1000kg. Even at double the specific energy, the battery would still weigh in at 500kg, almost 80% of the maximum takeoff weight. If there is a future for electric airplanes, it is going to be in fixed-wing applications. [1] http://web.mit.edu/2.009/www/resources/mediaAndArticles/batteriesPrimer.pdf http://web.mit.edu/2.009/www/resources/mediaAndArticles/batt...
- simonvc 7y ago
  Another project the "BYE" electric trainer is getting FAA certification right now, with 260Wh/kg Li-Ion
  - simonvc 7y ago
    https://www.byeaerospace.com/bye-aerospace-announces-first-flight-of-sun-flyer-2/ https://www.byeaerospace.com/bye-aerospace-announces-first-f...
    - beenBoutIT 7y ago
      Bell's Rocket Belt still looks impressive until somebody mentions the price and 30 second maximum flight time.
- FrojoS 7y ago
  But it is fixed wing! Anyway, thanks for looking into it and doing the math.
  - fock 7y ago
    which means it's a little less stupid than what airbus is doing...

FrojoS 7y ago

The max takeoff weight you cite is for the 2 seater, not the new 5 seater.

DuskStar 7y ago
That makes a lot more sense - I was wondering how they were managing to fit 5 people (plus wings, motors, structure and batteries) into 640Kg.

donquichotte 7y ago

In my experience, specs are omitted in technical articles IFF somebody is trying to hide something. Like super short flight time. The MIT battery primer [1] states a specific energy of 150Wh/kg for Li-Ion cells. 150kWh would therefore weigh 1000kg. Even at double the specific energy, the battery would still weigh in at 500kg, almost 80% of the maximum takeoff weight. If there is a future for electric airplanes, it is going to be in fixed-wing applications. [1] http://web.mit.edu/2.009/www/resources/mediaAndArticles/batteriesPrimer.pdf http://web.mit.edu/2.009/www/resources/mediaAndArticles/batt...

simonvc 7y ago
Another project the "BYE" electric trainer is getting FAA certification right now, with 260Wh/kg Li-Ion
- simonvc 7y ago
  https://www.byeaerospace.com/bye-aerospace-announces-first-flight-of-sun-flyer-2/ https://www.byeaerospace.com/bye-aerospace-announces-first-f...
  - beenBoutIT 7y ago
    Bell's Rocket Belt still looks impressive until somebody mentions the price and 30 second maximum flight time.
FrojoS 7y ago
But it is fixed wing! Anyway, thanks for looking into it and doing the math.
- fock 7y ago
  which means it's a little less stupid than what airbus is doing...