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Electric Planes Usher in the Second Great Age of Aviation

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Re: Electric Planes Usher in the Second Great Age of Aviation

#31

Post by adventured »

masklinn wrote: post #16
simonsquiff wrote: post #14

Earlier quoted context omitted.

I'm not sure it's ignoring everything - as this article states, electric planes exist today, and are improving at a fast rate. Batteries are also improving (thanks to Musk and others), not that electric planes needs to be battery based - fuel cells could be the answer (though presumably these require oxygen so might have altitude issues). So whilst far away, it's an extrapolation from our current position. Nuclear pl…

> I'm not sure it's ignoring everything - as this article states, electric planes exist today Prop toys exist, not "future of aviation" anything. Props being an other issue, electric planes means no turbofans. > Batteries are also improving Batteries are not improving at a rate which would increase their specific energy by 2 orders of magnitude (the difference between the specific energy of the best batteries availab…

"That's a joke right? Tesla's battery innovations are related to manufacturing efficiency and structural sharing"

That's exactly what brings costs down: economies of scale via efficient mass production. Whether we're talking about dramatically boosting the electric car market, or the giga factory.

Dyson spheres? Now who's exaggerating. Electric airplanes already exist, and will continue to improve for decades to come. Dyson spheres do not exist, and are not on the horizon.

Re: Electric Planes Usher in the Second Great Age of Aviation

#32

Post by masklinn »

coryrc wrote: post #27
sokoloff wrote: post #24

Earlier quoted context omitted.

Electricity is not especially cheap compared to jet fuel. Jet Fuel has about 128kBTU/gal and is available around $2/gal, so 64kBTU/$. Electricity is about 3400BTU/kWhr and a kWhr is about $0.05, or about 68kBTU/$.

Except, electricity will be about 85-90% efficient and a turbofan is about 30% efficient [1], roughly tripling the cost advantage. Fuel costs are about 35%[1] of operating costs, so only a ~20% cost reduction is possible for fuel change, so your point is still mostly valid. [1] https://en.wikipedia.org/wiki/Jet_engine#Energy_efficiency [2] http://www.ajc.com/news/business/airlines-keep-adapting-to-h...

> Except, electricity will be about 85-90% efficient and a turbofan is about 30% efficient [1], roughly tripling the cost advantage.

But then batteries store 1% the energy per mass fuel does so even assuming triple the efficiency, the energy storage is 30 times easier (assuming everything else stays constant which it can't because now your craft is an order of magnitude heavier and your short-haul plane is as heavy as a 747)

Re: Electric Planes Usher in the Second Great Age of Aviation

#33

Post by csours »

coryrc wrote: post #27
sokoloff wrote: post #24

Earlier quoted context omitted.

Electricity is not especially cheap compared to jet fuel. Jet Fuel has about 128kBTU/gal and is available around $2/gal, so 64kBTU/$. Electricity is about 3400BTU/kWhr and a kWhr is about $0.05, or about 68kBTU/$.

Except, electricity will be about 85-90% efficient and a turbofan is about 30% efficient [1], roughly tripling the cost advantage. Fuel costs are about 35%[1] of operating costs, so only a ~20% cost reduction is possible for fuel change, so your point is still mostly valid. [1] https://en.wikipedia.org/wiki/Jet_engine#Energy_efficiency [2] http://www.ajc.com/news/business/airlines-keep-adapting-to-h...

Except, you will be carrying more weight, due to the weight of the battery.

Re: Electric Planes Usher in the Second Great Age of Aviation

#34

Post by gambiting »

"In a statement, Pipistrel said Siemens prohibited the use of its motor for a flight over water."

I am not sure how that could happen? Surely if they bought the engines they could have done whatever they wanted with them? Unless they were leased from Siemens or something.

Re: Electric Planes Usher in the Second Great Age of Aviation

#35

Post by masklinn »

adventured wrote: post #31
masklinn wrote: post #16

Earlier quoted context omitted.

> I'm not sure it's ignoring everything - as this article states, electric planes exist today Prop toys exist, not "future of aviation" anything. Props being an other issue, electric planes means no turbofans. > Batteries are also improving Batteries are not improving at a rate which would increase their specific energy by 2 orders of magnitude (the difference between the specific energy of the best batteries availab…

"That's a joke right? Tesla's battery innovations are related to manufacturing efficiency and structural sharing" That's exactly what brings costs down: economies of scale via efficient mass production. Whether we're talking about dramatically boosting the electric car market, or the giga factory. Dyson spheres? Now who's exaggerating. Electric airplanes already exist, and will continue to improve for decades to come…

> That's exactly what brings costs down

The problem of batteries on airliners is not cost, it's that they don't store enough energy per mass. Even if your batteries are free, when your plane can't take off because its mass has increased >10 fold there's very little point, you're left with an expensive bus too wide to take roads.

> Dyson spheres? Now who's exaggerating.

Same as before.

> Electric airplanes already exist, and will continue to improve for decades to come.

The original assertion is that they're the future of air travel, not the future of small-scale hobbyists.

> Dyson spheres do not exist, and are not on the horizon.

Both of which apply equally to electric airliners. Electric airliners require a literal technological revolution, so do dyson spheres.

Re: Electric Planes Usher in the Second Great Age of Aviation

#36

Post by termain »

6stringmerc wrote: post #29
termain wrote: post #26

Earlier quoted context omitted.

Exoskeleton? You mean monocoque construction (aka load bearing skin)?

No, I mean like the chassis components were on the outside of the car, like a bug. That was the crux of their entry, mollified by some talk of aerodynamic efficiency. From what I recall, the rendered images of their concept didn't even have a method of entry for the driver/passengers. No doors. It was...well, frustrating, as my tone probably conveyed. Re: Monocoque - my entry cited that format to give additional stre…

Ah, ok. I can definitely understand your frustration since exoskeleton and aerodynamic efficiency don't generally mix.

Re: Electric Planes Usher in the Second Great Age of Aviation

#37

Post by cmsmith »

simonsquiff wrote: post #5

I read a piece by Elon Musk, who was saying that electric planes - whilst very far away - are the future of air travel. Why? Because they will allow planes to fly higher - increasing efficiency and speed. Apparently the normal 30,000 feet cruising altitude is not higher because the reduced oxygen levels at higher altitudes impact the gasoline combustion too much. Even at 30,000 feet the air is thick as soup at cruisi…

>Apparently the normal 30,000 feet cruising altitude is not higher because the reduced oxygen levels at higher altitudes impact the gasoline combustion too much.

If this is true, wouldn't it make more sense to bring liquid oxygen up with you to burn with the fuel? That would only reduce your fuel energy density by a factor of 2 or 3, instead of the factor of 30-100 being claimed for batteries.

Of course that would not make sense, and rockets don't become the most efficient way to travel until you are a few times higher than 30,000 ft. But it's useful to put the idea of batteries in perspective.

Re: Electric Planes Usher in the Second Great Age of Aviation

#38

Post by [deleted] »

simonsquiff wrote: post #5

I read a piece by Elon Musk, who was saying that electric planes - whilst very far away - are the future of air travel. Why? Because they will allow planes to fly higher - increasing efficiency and speed. Apparently the normal 30,000 feet cruising altitude is not higher because the reduced oxygen levels at higher altitudes impact the gasoline combustion too much. Even at 30,000 feet the air is thick as soup at cruisi…

[deleted]

Re: Electric Planes Usher in the Second Great Age of Aviation

#39

Post by alexhawdon »

gambiting wrote: post #34

"In a statement, Pipistrel said Siemens prohibited the use of its motor for a flight over water." I am not sure how that could happen? Surely if they bought the engines they could have done whatever they wanted with them? Unless they were leased from Siemens or something.

Maybe to get permission for your flight plan when using an experimental vehicle you have to be able to show that the manufacturers of the major components have confidence it will be able to complete the proposed route safely?

Re: Electric Planes Usher in the Second Great Age of Aviation

#40

Post by pingec »

gambiting wrote: post #34

"In a statement, Pipistrel said Siemens prohibited the use of its motor for a flight over water." I am not sure how that could happen? Surely if they bought the engines they could have done whatever they wanted with them? Unless they were leased from Siemens or something.

Apparently Siemens loaned it to Pipistrel and suddenly wanted the motor back urgently.

Additional info this thread: https://news.ycombinator.com/item?id=9850330

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