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London-Paris electric flight 'in decade'

bbc.co.uk

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Re: London-Paris electric flight 'in decade'

#21

Post by notahacker »

It's good to see YCombinator funding some ambitious and really hard projects, but I'll believe the "in a decade" when I see it. Even if a decade's worth of battery technology improvements allows it to get off the ground, there's still a lot of painful certification processes to work through (and certification authorities likely to be less-receptive than average due to it being a new entity and having less commonality with previous generation aircraft)

A little surprised they seem to be going after the ultracompetitive A320/737 market rather than the shorter-haul, lower-speed, turboprop market as well (closer to their starting point, less competition, even more fuel price-sensitive, airline customers less conservative etc.)

Re: London-Paris electric flight 'in decade'

#23

Post by dredmorbius »

tankenmate wrote: post #8
koolba wrote: post #2

I'm not at the forefront of this field so maybe I missed some great advances in battery technology or airplane efficiency, but how could this possible work when the energy density of a battery (.3-.9 MJ/kg) is 50x less than that of jet fuel (46 MJ/kg)[1]? Or is that simply enough for (very) short haul flights? [1]: https://en.wikipedia.org/wiki/Energy_density

The equation isn't just energy density; it's also the efficiency of harnessing that energy. Good electric motors are way more efficient than a turbofan.

That buys you roughly a factor of three.

Subtract again for the fact that you're not shedding half your takeoff weight in fuel over the course of a flight. You land with as much battery as you started with.

More if you're using metal-air batteries.

Re: London-Paris electric flight 'in decade'

#24

Post by notahacker »

throwaway2048 wrote: post #6
macspoofing wrote: post #4

>A new start-up says that it intends to offer an electric-powered commercial flight from London to Paris in 10 years. There is no way a startup without any experience in aviation will design, build, certify and sell a commercial 150-seat airplane in 10 years. Not even mention the immense R&D groundwork required to even prove the concept of using batteries to power short haul flights. Why do they put out bullshit like…

Magical thinking is a very effective VC cash magnet, especially when you have entered the "fear of missing out" stage. Uber is a company that has a 60 Billion dollar valuation contingent on the idea that it will somehow both develop driverless cars, and maintain a monopoly on them (dispite having zero expertise in this area whatsoever, and competing against entire industries that do) before they run out of money losi…

I guess the more realistic exit strategy in the next ten years (strategic acquisition by Airbus or Boeing to work on their own projects with much longer time horizons) is less attractive for PR purposes...

Re: London-Paris electric flight 'in decade'

#25

Post by blutack »

tankenmate wrote: post #8
koolba wrote: post #2

I'm not at the forefront of this field so maybe I missed some great advances in battery technology or airplane efficiency, but how could this possible work when the energy density of a battery (.3-.9 MJ/kg) is 50x less than that of jet fuel (46 MJ/kg)[1]? Or is that simply enough for (very) short haul flights? [1]: https://en.wikipedia.org/wiki/Energy_density

The equation isn't just energy density; it's also the efficiency of harnessing that energy. Good electric motors are way more efficient than a turbofan.

Electric motors would need to be orders of magnitude more efficient than turbofans (which they aren't). You also need to compare the overall efficiency developed as thrust, not just thermal efficiency.

There's also the issue of the mass of batteries not going away during the flight, unlike fuel, which will require maximum landing weight to equal maximum takeoff weight - this will impose a structural penalty versus IC aircraft.

Re: London-Paris electric flight 'in decade'

#26

Post by fdej »

koolba wrote: post #2

I'm not at the forefront of this field so maybe I missed some great advances in battery technology or airplane efficiency, but how could this possible work when the energy density of a battery (.3-.9 MJ/kg) is 50x less than that of jet fuel (46 MJ/kg)[1]? Or is that simply enough for (very) short haul flights? [1]: https://en.wikipedia.org/wiki/Energy_density

That's correct, but note that an electric motor is about twice as efficient as a combustion engine, reducing the factor to about 25x (at least ideally). Typical medium range aircraft burn about 3 kg fuel per km [1], so to fly 1000 km you would need about 3 * 25 * 1000 kg = 75 tonnes of batteries. This should be in the ballpark of what we can pack into an aircraft already, but I guess at least another 2x improvement is needed to make it economical (we want to haul some useful payload, not just the batteries).

[1] https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft

Re: London-Paris electric flight 'in decade'

#27

Post by koolba »

dredmorbius wrote: post #23
tankenmate wrote: post #8

Earlier quoted context omitted.

The equation isn't just energy density; it's also the efficiency of harnessing that energy. Good electric motors are way more efficient than a turbofan.

That buys you roughly a factor of three. Subtract again for the fact that you're not shedding half your takeoff weight in fuel over the course of a flight. You land with as much battery as you started with. More if you're using metal-air batteries.

Not necessarily!

Imagine a system where the plan actually jettisons the spent batteries along the way. They could glide/parachute down to a collection depot to be recharged and sent back to the airport for installation.

Re: London-Paris electric flight 'in decade'

#28

Post by alex_duf »

ptaipale wrote: post #11

TL;DR: If I read things right, the BBC article is highly misleading and the plane still uses jet fuel. Longer version: The article mentions "removing the need for jet fuel" but does not explain how the engines of this "electric" plane work. Propellers run by electric motors, or what? No. Wright Electric's own site is scant on technical details and concentrates on praising the great team in its blog. From browsing oth…

I think the image you can see on the electrek article is from this blog post: https://weflywright.com/2017/02/12/wright-weekly-weport-feb-...

The legend for that image is:

>This image shows the potential subsystems that could be powered electrically. (Note: an fuel plane can also install electric subsystems – for example the 787 is making headway in this direction – but the subsystems in an electric plane will be all electric!)

From what I read from the blog, it looks like they are going all electric. So I'm not sure what magic they intend to use in order to propel the plane, but I'll assume propellers until proven wrong.

Re: London-Paris electric flight 'in decade'

#29

Post by notahacker »

thriftwy wrote: post #10

What's the point if you can just take an electric train? Isn't it basically 'a flight' on rails? They should have chosen a better city pair.

Tell that to the double-digit number of airlines already flying between London and Paris...

It's a [hypothetical] aircraft, not a hyperloop. It can fly other routes.

Re: London-Paris electric flight 'in decade'

#30

Post by jakozaur »

I appreciate Y Combinator at grabbing ppl attention. We need to do more of this ambitious projects.

However, I'm rather disappointed lack of even fundamental technical vision. I get that if you shoot to fly in a decade you can optimistically base your model on other technical advances (e.g. better batteries), but too much short-term hype can be deceiving.

It will take many years to get there and probably it would be easier to create first small turboprope electric plane. Something like: https://en.wikipedia.org/wiki/Bombardier_Dash_8

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