The age of electric flight is finally upon us • Hacker News Board

Re: The age of electric flight is finally upon us

#21

Post by mannykannot » Fri, Jun 21, 2019, 2:34 PM UTC

A battery fire is a scary prospect unless the fire can be effectively contained and the hot gases vented (I don't suppose extinguishing one is likely to be an option.) There has been at least one crash involving fire, though I have not been able to find out if it was a propulsion battery fire. [1]

In Eviation's Alice, the failure or shutdown of one of the wingtip's motors would require the shutdown of the other, on account of asymmetric thrust. It can be flown on the rear motor alone, but I do not know how well it would climb in the case of a motor failure on takeoff. Maybe an EE can step in and say whether electric motors can be over-powered for relatively short durations (in this case, a few minutes to return to the airfield) without much increase in the risk of it failing?

BTW, I see that this prototype is a tail-dragger, though rendered images show a tricycle gear.

[1] https://electrek.co/2018/06/04/siemens-electric-plane-protot...

Re: The age of electric flight is finally upon us

#22

Post by taf2 » Fri, Jun 21, 2019, 2:37 PM UTC

I wonder if with electric we can fly higher like much higher maybe 80k to 90k since we don’t have to worry about the engine stalling. Could this also make the flight times comparable or faster? For sure less turbulence. As someone who lives on a flight path I’m eager for the change in noise pollution too- though I’m worried the transition will take decades...

Re: The age of electric flight is finally upon us

#23

Post by falcolas » Fri, Jun 21, 2019, 2:38 PM UTC

iambateman wrote: post #10

From the article: conventional fuel for a 100 mile flight costs $400, while electric energy would cost $12. This seems like such a tremendous difference that the market would be in an arms race to make it a reality. Especially considering electric motors have fewer moving parts and so require less maintenance. Oh and it would be so quiet.

Um, that’s comparing a jet engine to an electric prop. Apples and walnuts - the two propulsion methods couldn’t be much more dissimilar. A more equivalent prop plane (with similar capacity) would be well under $100 for fuel costs, potentially even under the $50 range.

Re: The age of electric flight is finally upon us

#24

Post by j9461701 » Fri, Jun 21, 2019, 2:40 PM UTC

SeanBoocock wrote: post #16

iambateman wrote: post #10

From the article: conventional fuel for a 100 mile flight costs $400, while electric energy would cost $12. This seems like such a tremendous difference that the market would be in an arms race to make it a reality. Especially considering electric motors have fewer moving parts and so require less maintenance. Oh and it would be so quiet.

From the article: > Even assuming huge advances in battery technology, with batteries that are 30 times more efficient and "energy-dense" than they are today, it would only be possible to fly an A320 airliner for a fifth of its range with just half of its payload, says Airbus's chief technology officer Grazia Vittadini. > "Unless there is some radical, yet-to-be invented paradigm shift in energy storage, we are going…

This is why I'm so excited for lithium-air batteries. Theoretically they'd carry ~40.1 MJ/kg, which is very competitive with gasoline's ~46.8 MJ/kg. Factoring in the higher efficiency of electric drives (95% vs. 35% for say a regular ICE car), you'd be getting effectively over double the energy per pound in terms of moving you around.

Re: The age of electric flight is finally upon us

#25

Post by CraftThatBlock » Fri, Jun 21, 2019, 2:40 PM UTC

taf2 wrote: post #22

I wonder if with electric we can fly higher like much higher maybe 80k to 90k since we don’t have to worry about the engine stalling. Could this also make the flight times comparable or faster? For sure less turbulence. As someone who lives on a flight path I’m eager for the change in noise pollution too- though I’m worried the transition will take decades...

Higher means lower air density, meaning less lift, meaning higher power usage, which is even more critical with electric

Re: The age of electric flight is finally upon us

#26

Post by falcolas » Fri, Jun 21, 2019, 2:40 PM UTC

This plane wouldn’t even be capable of getting me to the closest aircraft hub at its maximum range, let alone with a safety margin (I live an hour and a half, by jet, from Denver). Not to mention it will be slow and badly impacted by storms (since it has an operating ceiling of 10,000 ft).

Re: The age of electric flight is finally upon us

#27

Post by rootusrootus » Fri, Jun 21, 2019, 2:41 PM UTC

taf2 wrote: post #22

I wonder if with electric we can fly higher like much higher maybe 80k to 90k since we don’t have to worry about the engine stalling. Could this also make the flight times comparable or faster? For sure less turbulence. As someone who lives on a flight path I’m eager for the change in noise pollution too- though I’m worried the transition will take decades...

I imagine planes could fly a bit higher, but aeroydynamics are still going to be a big factor. See also coffin corner.

Re: The age of electric flight is finally upon us

#28

Post by dewey » Fri, Jun 21, 2019, 2:47 PM UTC

falcolas wrote: post #26

This plane wouldn’t even be capable of getting me to the closest aircraft hub at its maximum range, let alone with a safety margin (I live an hour and a half, by jet, from Denver). Not to mention it will be slow and badly impacted by storms (since it has an operating ceiling of 10,000 ft).

It's a prototype.

Re: The age of electric flight is finally upon us

#29

Post by Tade0 » Fri, Jun 21, 2019, 2:49 PM UTC

mannykannot wrote: post #21

A battery fire is a scary prospect unless the fire can be effectively contained and the hot gases vented (I don't suppose extinguishing one is likely to be an option.) There has been at least one crash involving fire, though I have not been able to find out if it was a propulsion battery fire. [1] In Eviation's Alice, the failure or shutdown of one of the wingtip's motors would require the shutdown of the other, on a…

Electric motors in their specs usually have an entry specifying a 30s or one minute window during which the motor can operate at around twice the power without damage.

In this state the motor cannot maintain temperature, so going beyond that time window will shorten its lifespan or cause damage if continued.

Hobbyst EVs often take advantage of this by having a small motor and overloading it when accelerating.

Re: The age of electric flight is finally upon us

#30

Post by rootusrootus » Fri, Jun 21, 2019, 2:50 PM UTC

NickM wrote: post #17

ginko wrote: post #2

I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene. The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.

Yeah I have wondered about this option as well. Hydrogen fuel cell cars make very little practical sense for a lot of reasons, but most of those reasons don't seem to apply so much when you're dealing with air travel: - It'll be a long time before fuel cells are cost competitive with gas or electric cars, but for planes the cost of fuel and operation is much more significant than with a car, so the upfront cost for b…

> if a plane crashes there's a good chance everyone dies anyway

That's actually not the case. Overall your odds of surviving an accident in a plane are something like 95%. Still above 50% for "serious" incidents. Sure, if the plane drills the ground everyone is going to die, but planes crash somewhat regularly with most/all surviving.