Why battery-powered aircraft will never have significant range

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Island_flyer

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Nice content of the Martine Rothblatt flight, though it's interesting that they carefully avoided including any video of the takeoff or landing. Obviously it's capable of CTOL in addition to VTOL, which is a good thing.
 

blane.c

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Hydrogen backed by the government.

 

tspear

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Nice content of the Martine Rothblatt flight, though it's interesting that they carefully avoided including any video of the takeoff or landing. Obviously it's capable of CTOL in addition to VTOL, which is a good thing.
Last I checked Beta is doing flight tests with the VTOL engines and props folded. They are working on fixed wing aspects first. From what i have read previously, some (or one) of the engineers at Beta felt the fixed wing portion of flight is harder to get correct and requires more testing, and the FAA has the same position. The VTOL portion is more a matter of brute force and failure modes, so it will be done after what they believe will be a confirming prototype for the fixed wing design.


Tim
 

Saville

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Wrong.It is counterintuitive.The "cost" is more than paid back in reduced resistance and therefor heat,which is proof of increased overall efficiency.
Pick up your game.
2nd law of Thermodynamics says otherwise. You can't "pay back" the costs, let alone more than pay back the costs. Otherwise you have a perpetual motion machine.

And there's no need to get snarky
 
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dog

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2nd law of Thermodynamics says otherwise. You can't "pay back" the costs, let along more than pay back the costs. Otherwise you have a perpetual motion machine.

And there's no need to get snarky
Strike two.
Its not a heat engine.
Its a non linear chemical reaction that is
counter-intuitive in that there is specific temp
(higher than ambiant),where resistence is lower,current is lower,therfore total heat generated in the charge and discharge cycles
is lower.
Back to school baby.
Your lucky to get snarky,some of the best here
will manage to assign remedial reading without
ever quite acknowleging your existance.
 

Saville

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Strike two.
Its not a heat engine.
Its a non linear chemical reaction that is
counter-intuitive in that there is specific temp
(higher than ambiant),where resistence is lower,current is lower,therfore total heat generated in the charge and discharge cycles
is lower.
Back to school baby.
Your lucky to get snarky,some of the best here
will manage to assign remedial reading without
ever quite acknowleging your existance.
ok so you choose to retain the snark. Noted. You might not like what that brings.

Just because you are talking about an electric motor doesn't relieve you of the 2nd law, (ie.e Entropy) because YOU wrote [emphasis mine - and I retained your typos] :

"One counterintuitive aproach to battery temp management is to HEAT the battery....reduced the resistance,therefore current, and therefor heat."

YOU
are talking about heat. Therefore whatever that addition of heat does to battery efficiency cannot do it with 100% efficiency. Neither can you generate and transmit the heat with 100% efficiency.

Can you? No you can't.

Why?

2nd law. Entropy.

Losses. And then whatever efficiency gain you get from heating a battery cannot give you MORE than what you expended to get it: Entropy.

The thing is you have to treat all of it as one system - you cannot just look at an efficiency increase in one aspect and ignore the losses you incurred to get that.

And I'm skeptical about that - usually resistance goes down when you chill something, not heat something - but I don't know about your 'application". And since you mention that you are "going from memory here"

...and didn't provide a reference to the paper but said only " ,but recent work published this year."......

I can't really speak to it. But I'm skeptical about that.

So go ahead with your snark. But this comment of yours:

Its not a heat engine.

...tells me that you might not understand basic physics.
 
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Sockmonkey

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It sounds like "heat the battery a little to lower the current it puts out, which heats the wiring and motor less." It's not breaking rules.
 

dog

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ok so you choose to retain the snark. Noted. You might not like what that brings.

Just because you are talking about an electric motor doesn't relieve you of the 2nd law, (ie.e Entropy) because YOU wrote [emphasis mine - and I retained your typos] :

"One counterintuitive aproach to battery temp management is to HEAT the battery....reduced the resistance,therefore current, and therefor heat."

YOU
are talking about heat. Therefore whatever that addition of heat does to battery efficiency cannot do it with 100% efficiency. Neither can you generate and transmit the heat with 100% efficiency.

Can you? No you can't.

Why?

2nd law. Entropy.

Losses. And then whatever efficiency gain you get from heating a battery cannot give you MORE than what you expended to get it: Entropy.

The thing is you have to treat all of it as one system - you cannot just look at an efficiency increase in one aspect and ignore the losses you incurred to get that.

And I'm skeptical about that - usually resistance goes down when you chill something, not heat something - but I don't know about your 'application". And since you mention that you are "going from memory here"

...and didn't provide a reference to the paper but said only " ,but recent work published this year."......

I can't really speak to it. But I'm skeptical about that.

So go ahead with your snark. But this comment of yours:

Its not a heat engine.

...tells me that you might not understand basic physics.
Wow.
A battery is not nor was it ever a heat engine.
And your atempt to somehow hijack the point
and blather on about the second law is disingenious or a go to knee jerk reaction to
a PERCIEVED voilation of the first principal,
that energy can not be created or destroyed.
Snark off,pedant on.
In the case bieng comented on,the anode is
partialy composed of a semiconductor,that is
reacting chemicaly with in this case lithium,
that reaction takes place at a rate partialy goverend by temperature as temp changes internal resistence,but in no way is used to
power the reaction itself.Hence nonlinear and
coumterintuitive.Below a certain temp resistance rises as the physical structure of the
material in the anode and cathode contract and
they can not accept and donate electrons at a high rate.The porrige is to cold.
Above a certain temp those came materials start to swell,physicaly compromising the structure,AND as the electrolight is a liquid hydrocarbon there is an absolute limit to how much heat it will take till we enter the relm that you think ,wrongly,that we are discussing.
The porrige is too hot.
So the idea is to raise the temp of the battery to the sweet spot and hold it there,allowing for
a faster and deeper charge and discharge cycle.The porrige is just right.
Ok I lied ,snark is stuck on.
Further all developed batteries have the nessesary heating and cooling equipment installed and this is just a further refinement of
systems that are in the early adopter stage.
And the strategic use of partial out of context quotes is bad mannered and gets you snark.
 

Saville

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In the meantime - YOU said "heat up
Wow.
A battery is not nor was it ever a heat engine.

Irrelevant. As has been explained.

And your atempt to somehow hijack the point

Too bad you think that pointing out a problem with your "view" is a hijack.
That's the sort of response I expect from a teenager.


"....and blather on about the second law is disingenious or a go to knee jerk reaction to
a PERCIEVED voilation of the first principal,
that energy can not be created or destroyed."

My point has nothing to do with energy being created nor destroyed. That's the First Law of Thermo. My point has to do with the second. So this snarky attempt to say something relevant fails.

Also, Entropy has a say in realms outside of Thermodynamics as well. That's why I introduced the term.

You clearly do not, can not, or refuse to, think about this.


......
So the idea is to raise the temp of the battery to the sweet spot and hold it there,allowing for
a faster and deeper charge and discharge cycle.

You can repeat this all you want but it doesn't address my point.

As I wrote I cannot comment on whether or not heating a battery helps it's efficiency in some regime. You didn't supply a reference to the paper you claim this all came from. It sounds odd to me but as I said until I read something authoritative I won't claim that the counterintuitive notion of heating an electrical system makes it more efficient is wrong.

But of course that has nothing to do with my point either.


..........
And the strategic use of partial out of context quotes is bad mannered and gets you snark.

Nope. You are snarky because you think it makes you cool or you think it lends weight to what you say, or something. Whatever the reason it's childish.

Especially since what tripped your hysterical reaction was this one sentence:


"Which [i.e. your heating up the battery] takes energy and therefore must be added to the "cost"/energy utilization etc."

Which is pretty innocuous and merely states that you cannot ignore the cost of generating the heat to heat the battery.

Picking and choosing quotes is done to focus you on the part of your comments that are faulty. All the rest of the garbage you write is still there in your post and not hidden. Long posts get to the TLDR stage quickly so selecting the pertinent phrases or sections is done for efficiency.

You should know that when I reply to a post my reply is aimed at everyone - not just the person I'm replying to. So TLDR matters there too.

You are now trying to attack my method of reply and NOT what I'm saying. That plus you keep repeating that heating the battery speeds up recharge are the clearest indicators you don't know what my point is and/or understand it. It makes me think you are more evangelical than engineer.
When you argued with the sentence, which was my first comment:

"Which [i.e. your heating up the battery] takes energy and therefore must be added to the "cost"/energy utilization etc."

...and with snark, it was clear you aren't thinking but emoting.

When you wrote that a battery is not a heat engine and therefore my comments are wrong you made it abundantly clear to me that you do not know what I'm saying, and that your grasp of physics could be seriously wanting. Entropy has a say in realms outside of Thermodynamics as well. That's why I introduced the term.

And when I said, at the start, this one sentence:

"Which [i.e. your heating up the battery] takes energy and therefore must be added to the "cost"/energy utilization etc."

And your reply was:

"The "cost" is more than paid back in reduced resistance and therefor heat,which is proof of increased overall efficiency."

That "more than paid back" shows how much you do not know.

And I don't have the time to educate you and I don't think you want to learn anything anyways.

You are attacking my method of reply and not addressing what I'm saying.

You are repeating, over and over, how heating the battery makes recharging more efficient and ignoring the larger picture, and not addressing the issue.

So this is my last reply to your junky posts on this particular facet of electrical airplanes.

You have to treat the system as whole. You cannot just look at an improvement in one part and ignore losses in the procedure you used to get that efficiency increase.

No system that we can make is perfect and there are always losses. You are using heat to affect the battery and the moment you do that you incur thermodynamic losses. There are other kinds too - like resistance in a wire. So no matter how much you want to blather on that a battery is not a heat engine - even though it generates heat as part of its operation, it's irrelevant to my point and it doesn't change the fact that you are ignoring part of the total system.

So I put you down as yet another one of the long line of evangelists more mouth than brain.

You earned it.
 
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EzyBuildWing

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Archer eVTOL has 200 orders from United...... sounds promising for "Archer Promotions",.....
but in the comments section: "Archer stocks hasn't been great, the entire stock market is **** at the moment.. ".........!

 

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Those interested in experimenting with hydrogen fuel based here is 161hp for less than $20k.

2019 Hyundai NEXO Blue KM8J74A6XKU001139 | KARPLUS WAREHOUSE INC. Pacoima, CA (888karplus.com)
That dealership is just across the street from my home airport. Anyone who wants to come look at the hydrogen car mentioned above, you can fly in to KWHP and I'll cheerfully drive you across the street to see the car. There's even a pretty good Mexican restaurant that just opened catty-corner across the street the other way... if you like good Ceviche !
 

Dan Thomas

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This, boys and girls, is from 1967. And it's just one silly little example of why we old guys are so skeptical of the current marketing hype around electric airplanes or VTOLs or hydrogen fuel cells or almost anything else these days.

1624930555107.png

It was posted over on Pilots of America. Some interesting comments about stuff like this. Hindsight is a wonderful thing, since it makes your baloney detector much more sensitive. Young people don't have hindsight yet. They have to be repeatedly fooled by stuff like this before it develops. Or they need a good degree in physics; that alone will smarten them up.

"A Sucker Is Born Every Minute" Dept.
 

Rhino

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Hydrogen backed by the government.

Backed by the government. Why does that inspire absolutely no confidence in me whatsoever? Oh, that's right. I worked for the government, or government contractors, for about 30 years, and worked with a lobbying group for a while. I've come to the firm conclusion the only thing government does well is break things and kill people, and sometimes they also screw that up, usually due to some political crap.
 

Dusan

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This, boys and girls, is from 1967. And it's just one silly little example of why we old guys are so skeptical of the current marketing hype around electric airplanes or VTOLs or hydrogen fuel cells or almost anything else these days.

View attachment 112486

It was posted over on Pilots of America. Some interesting comments about stuff like this. Hindsight is a wonderful thing, since it makes your baloney detector much more sensitive. Young people don't have hindsight yet. They have to be repeatedly fooled by stuff like this before it develops. Or they need a good degree in physics; that alone will smarten them up.

"A Sucker Is Born Every Minute" Dept.
Myself being an 'old guy' having enough experience and a masters degree in engineering, I agree with a lot that was said, but I think that electric propulsion makes a small VTOL aircraft viable for the following reasons:
- it has high efficiency regardless of power setting - it has 90%+ efficiency when providing happily for a short time 150% of rated power for hovering, or cruising at 30% 'throttle' setting for effective cruise
- simpler design for distributed propulsion
- electric motors have high specific power

For these reasons I believe a personal VTOL aircraft can be built successfully today, and if sized for short flight - e.g. for under 30 minutes, fun flying or commuting - the propulsion system could be even lighter than equivalent piston ICE, even using the low specific energy batteries we have right now.

That being said, I don't agree with current VTOL configurations. Designing an effective VTOL is hard, the aerodynamics is a compromise, the rotors are too small for effective hover, but too large to provide efficiently high speed cruise thrust, or if stopped - are a source of extra drag, compromising the cruise performance. There is no configuration yet to ensure both hover and cruise performance. A multi-rotor cannot compete in hovering performance with the classic single rotor helicopter due to disk loading and reduced Reynolds number flow of smaller rotors. A cruise wing-borne VTOL aircraft has too many sources of drag to compete even to a very poor performing fixed wing. I think a good VTOL configuration is yet to be developed, and that is the job of aerodynamicists and not software designers or electrical engineers.

The vertiport hubs proposed today by so many interested parties is supposed to reduce travel time, but best time travel reduction is only realised by point to point direct flight, especially for short flights. Short duration flights increases the proportion of hover flight segment and since the hover performance is driven by disk loading that is linearly dependent on weight, it makes more sense to develop small personal VTOL aircraft, maybe for 1-2 peoples, but able to take off and land anywhere, from small verti-pads easily installed in personal driveways, backyards and local grocery stores. Sure, a lot of things need to change before that, from public acceptance, safety, personal weather awareness, to regulation point of view, and I guess large vertiport hubs are a step toward that.
 
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dog

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Myself being an 'old guy' having enough experience and a masters degree in engineering, I agree with a lot that was said, but I think that electric propulsion makes a small VTOL aircraft viable for the following reasons:
- it has high efficiency regardless of power setting - it has 90%+ efficiency when providing happily for a short time 150% of rated power for hovering, or cruising at 30% 'throttle' setting for effective cruise
- simpler design for distributed propulsion
- electric motors have high specific power

For these reasons I believe a personal VTOL aircraft can be built successfully today, and if sized for short flight - e.g. for under 30 minutes, fun flying or commuting - the propulsion system could be even lighter than equivalent piston ICE, even using the low specific energy batteries we have right now.

That being said, I don't agree with current VTOL configurations. Designing an effective VTOL is hard, the aerodynamics is a compromise, the rotors are too small for effective hover, but too large to provide efficiently high speed cruise thrust, or if stopped - are a source of extra drag, compromising the cruise performance. There is no configuration yet to ensure both hover and cruise performance. A multi-rotor cannot compete in hovering performance with the classic single rotor helicopter due to disk loading and reduced Reynolds number flow of smaller rotors. A cruise wing-borne VTOL aircraft has too many sources of drag to compete even to a very poor performing fixed wing. I think a good VTOL configuration is yet to be developed, and that is the job of aerodynamicists and not software designers or electrical engineers.

The vertiport hubs proposed today by so many interested parties is supposed to reduce travel time, but best time travel reduction is only realised by point to point direct flight, especially for short flights. Short duration flights increases the proportion of hover flight segment and since the hover performance is driven by disk loading that is linearly dependent on weight, it makes more sense to develop small personal VTOL aircraft, maybe for 1-2 peoples, but able to take off and land anywhere, from small verti-pads easily installed in personal driveways, backyards and local grocery stores. Sure, a lot of things need to change before that, from public acceptance, safety, personal weather awareness, to regulation point of view, and I guess large vertiport hubs are a step toward that.
Your take is an interesting departure from any I have heard so far.
The market is desperate to be seen bieng seen ingressing sleek E taxis that wisk them from exclusive residential locations to bleak ultra modern buisiness districts and thence to explore retail and entertainment oportunities.
And one thing that is an absolute nessesity for all that is very quiet opperation.
Another part that has already being monetised and planned around is that a consortium allready owns many thousands of parking garages in major city centers worldwide,all with flat roofs.
So you are 100% right on all of the efficiency side,but a highly loaded disk is going to be too loud.The one good description of a evtol with many small tilting ducted fans ,pointed out that while the energy use in take off, hover ,and landing was huge,it is also 5% of flight time.
The other advantage of ducted fans is saftey,which will also have an impact on how much set back is required in landing pads ,leaving room for waiting and exit areas,which will have an impact on turn around times.
Your idea of small 1or 2 person evtols just might fit the requirements imposed by the proposed landing pad/parking garages even with open rotors.
Then off course there is this.

 
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