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The age of electric flight is finally upon us

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Re: The age of electric flight is finally upon us

#251

Post by godelski »

Robotbeat wrote: post #176
godelski wrote: post #173

Earlier quoted context omitted.

I haven't seen the 1.5MJ/kg batteries but that is still pretty far from 10MJ/kg. Your first paragraph seems pretty hostile considering this fact. Look, we all want electric aircraft. I can't wait for them. But to say that it doesn't require a major (honestly several major) breakthrough (s) is an extreme understatement and does not requisite the hostility you are giving.

The key thing often missed is that jet fuel is much better than it needs to be , particularly for domestic flights. Batteries don't need to equal jet fuel in order for electric air travel to be viable. We have airplanes capable of 15,000km trips. But we were making transatlantic flights back when our aircraft could only do about 2000km range reliably. Going from from Labrador, Canada to Greenland to Iceland to Englan…

Most of these discussions I see, at least on HN, seem to understand efficiency. Yeah, a lot of fuel goes into heat and not into power for the engine. People understand that. But another thing that many people don't, is that heating isn't wasted energy. It is reclaimed for heating the cabin and deicing. Which icing is a HUGE problem on aircraft. Heating is also fairly power intensive.

But still, until we get into that efficiency range of batteries vs direct power of jet fuel, it is far from solved. But like you mention with greenhouse gasses, it does have to be solved. I have yet to see anyone here that is doubtful that electric aircraft will exist. I just see people (at least on HN) that are either bearish or bullish. But don't be hostile to people that are being bearish. We need both camps.

Re: The age of electric flight is finally upon us

#252

Post by MayeulC »

adminu wrote: post #223
FabHK wrote: post #197

Earlier quoted context omitted.

> > improved modern materials means you can just have most of your take-off mass be battery, compensating for the poorer specific energy > Again, this can be done for any aircraft, not just the electric ones. Not only that: you burn the fuel, so for the second half of the flight you only need to carry half the fuel. But you have to carry the full battery mass (modulo E=mc^2) all the way.

Well, that’s in part a point for the batteries, though. You spend a lot of energy to lift all that fuel that you just blow out with all its potential energy up in the air, whilst the batteries provide you with that very potential energy on the way down as well. Glider planes quiet commonly are filled with water to make them heavier so they can make more use of the potential energy they gain from the externally powere…

Which brings me to the ask the following:

Would electric towplanes be doable for passenger aircraft? (Long or short haul, electric or otherwise).

If one of the downside of electric planes is the range, while fuel is cheap, making them cheaper to operate, and take-off uses a significant portion of the total energy, I could see very powerful electric towplanes as a way to reduce the amount of fuel needed for takeoff. This would:

* Allow to travel longer distances with the same amount of fuel (enabling electric airplanes to fly longer distances). Alternatively, allow planes to fill up with less fuel for the same distance.

* Improve fuel efficiency of big airliners, and their carbon footprint if you consider regular ones.

One last question: aircraft that fly shorter routes typically embark less fuel, but would that be doable with electric planes?

Re: The age of electric flight is finally upon us

#253

Post by anticensor »

username444 wrote: post #91
NeedMoreTea wrote: post #74

Earlier quoted context omitted.

Average human at rest puts out about 100w of heat. That's probably not enough to keep the cabin warm let alone power the aircraft. Burning human fat stores seems a mite dystopian. ;) Edit: Human at rest. I imagine Ryanair might be keen on pedals for everyone, but I can't see that being popular with the holidaymakers.

https://www.cascadebiketrainers.com/news/2015/09/01/calculat... Seems a trained person can do 150-250w

We can extract 400 watts if we also suck power from the brains.

Re: The age of electric flight is finally upon us

#254

Post by nightwing »

alex_young wrote: post #6
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.

The main source (95%) of hydrogen fuel in the US is a by-product of Natural Gas extraction ( https://www.energy.gov/eere/fuelcells/hydrogen-production-na... ). What problem are we solving by moving to hydrogen?

Trying to make simpler and cheaper planes, not everything has to be about CO2.

Re: The age of electric flight is finally upon us

#255

Post by JasonFruit »

namirez wrote: post #245
audunw wrote: post #206

Earlier quoted context omitted.

I think the biggest point that you and others that bring this up is missing, is not just how electric designs gives you higher efficiency and close the gap (as others have mentioned). The main thing you're missing is that modern jet planes have absolutely ridiculous range, and a huge number of flights use only a fraction of that range. Electric planes don't need to match modern jet planes to be viable. They just have…

> A related aspect is that electric planes are much more quiet. I'm not so sure! Have you ever heard the sound of twin-turbo regional airplanes in small airports? That sound is not from the turboprop engine, but from the propeller itself. Electric planes do have propellers and propellers are usually very loud. Actually much louder than turbofans! Making propellers quieter has been an active field of research in fluid…

Illustrative anecdote: when you hear a lightplane or ultralight with a high-rpm 2-stroke engine and a reduction drive turning a slower prop, up close you hear the high whine of the engine, but when it gets farther away you hear only the prop, a much lower sound. It's amazing how much of the sound is from the propeller.

Re: The age of electric flight is finally upon us

#256

Post by abeld »

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…

About the accident in Hungary: the police investigation has been apparently closed, and the cause was ruled to be pilot error (If I understand it correctly, they did a too severe turn too low). There was no sign of a fire before the crash, so even though the wreckage burned out, the crash was not due to electrical issues or fire. A hungarian news article: https://hvg.hu/itthon/20190401_magnus_aircraft_elektromos_ki... (Unfortunately I couldn't find an English article, and the accident investigation of the transportation safety organization might not be finished yet, since they only issued a preliminary report for now.)

Re: The age of electric flight is finally upon us

#257

Post by igor47 »

godelski wrote: post #251
Robotbeat wrote: post #176

Earlier quoted context omitted.

The key thing often missed is that jet fuel is much better than it needs to be , particularly for domestic flights. Batteries don't need to equal jet fuel in order for electric air travel to be viable. We have airplanes capable of 15,000km trips. But we were making transatlantic flights back when our aircraft could only do about 2000km range reliably. Going from from Labrador, Canada to Greenland to Iceland to Englan…

Most of these discussions I see, at least on HN, seem to understand efficiency. Yeah, a lot of fuel goes into heat and not into power for the engine. People understand that. But another thing that many people don't, is that heating isn't wasted energy. It is reclaimed for heating the cabin and deicing. Which icing is a HUGE problem on aircraft. Heating is also fairly power intensive. But still, until we get into that…

Batteries also produce heat.

Also -- it's pretty easy to be negative. "That's dumb, it's not going to work", etc... I really appreciate this poster remaining positive in the face of OVERWHELMING negative feedback on this thread.

Re: The age of electric flight is finally upon us

#258

Post by verelo »

sandworm101 wrote: post #227
verelo wrote: post #119

Earlier quoted context omitted.

"Q. How much damage will be done to my plane if I land it with a parachute? A. In all likelihood the aircraft will suffer some significant damage. The terrain where you land will affect this greatly. Though the extent of damage has varied from plane to plane, most GA aircraft that have come down under a BRS deployment have eventually (or will soon) fly again." Call me a skeptic until they provide hard numbers and det…

How many are written off is irrelevant. What matters is passenger lives. Success is measured in total number of not-dead people because of not crashing as violently.

Agreed.

Re: The age of electric flight is finally upon us

#259

Post by salawat »

newsoul2019 wrote: post #121
stcredzero wrote: post #109

Earlier quoted context omitted.

Electric motors can enable something which jet fuel and gasoline cannot: beamed power. There could be a new class of vehicles which only have a small onboard power store for emergency purposes. The weight savings would be about 20%.

That is a fascinating idea, a plane being "handed off" from one beaming tower to the next, like a cell phone

The ATC systems required would be prohibitive, rest in peace any birds that fly into\through the beam, maintenance of the towers, and emitter tracking would all be huge problems.

Also, where/how is all that electricity getting generated/transmitted to the emitter, and what complications does that introduce? What about environmental conditions? How does that effect the efficiency? Does a storm front blowing through suddenly make regular ICE planes a better idea again?

Oh, yeah, don't forget the security aspect. Those emitters are more than 'interesting' enough to be weaponized in the wrong hands.

I mean, beamed power sounds cool and all, but you actually have to take into account a heck of a lot of variables first.

Re: The age of electric flight is finally upon us

#260

Post by AkashSKY »

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