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I think for electric planes hydrogen fuel cells may be a real option since liquid hydrogen is so much lighter than pretty much any fuel or battery out there. Th

by ginko 5y ago

I think for electric planes hydrogen fuel cells may be a real option since liquid hydrogen is so much lighter than pretty much any fuel or battery out there. The main problem is the density though.

jillesvangurp 5y ago
Liquid hydrogen or some other type of fuel cell is definitely a solution for flying big heavy jets. Another potential solution is simply burning the hydrogen in jet engines. Or methane. Both have been used as rocket fuel. Both could be sourced in a sustainable way. The technology to build jet engines that burn that type of fuel already exists. The reason that fuel cells are potentially interesting is getting better efficiencies in combination with light yet powerful electrical engines such as described in the article. The reason we still use kerosene is simply that the infrastructure to distribute that is there and it's a cheap fuel to create. Changing that industry is about ramping up the manufacturing and fuel infrastructure to the point where it is profitable. It's a very slow and expensive process. The right question to ask though is why big heavy jets are interesting to begin with. They are big, heavy, expensive, and complicated machines. Why do we go through the trouble of building those at a cost of around 100M per vehicle for a small one? This has to do with a lot of things but the two main ones that stand out are that fuel is expensive and pilots are expensive (and scarce). So the optimal conventional plane is one that moves around a lot of stuff with a minimum amount of fuel per kg of useful payload and the requisite two pilots. Hence the A380 briefly existed until it got to expensive to operate it. An autonomous small battery operated plane would fix both those pain points. Electricity is comparatively cheap and autonomous vehicles means no expensive pilots are needed anymore. People that are talking about making electrical airbuses or boeings are missing the point: these form factors become a lot less relevant when we can fly dozens/hundreds of autonomous vehicles for orders of magnitude less money. Mostly small planes are pretty cheap to manufacture. So, are electrical engines and batteries. And the electronics needed to run them. You could feasibly build hundreds of them for the price of a single A320. And they'd be comparatively dirt cheap to maintain and operate. And a lot more flexible in where they could go. You are not going to cross ocean in one any time soon. But short haul flight is a different matter. Neither of the best selling jets (737 & A320) is commonly used for intercontinental flights. They are used for short haul flights.
- xyzzyz 5y ago
  Liquid hydrogen sounds rather impractical, with its deep cryogenic requirements, compared to regular compressed hydrogen. Compressed hydrogen already has high energy density by volume to easily compete with hydrocarbon based fuels.
- GordonS 5y ago
  > these form factors become a lot less relevant when we can fly dozens/hundreds of autonomous vehicles for orders of magnitude less money A big and multi-faceted factor not considered here is airport capacity, in terms of terminal building footprint, aircraft ground handling, flight control and airspace. Many large airports are already at capacity, so it's difficult to see how higher numbers of aircraft could work.
  - fire 5y ago
    You make a good point; Now I'm curious how efficiently capacity is used with flight schedules exchanging large numbers of passengers with each flight, and whether smaller but more frequent flights would have any real impact on that equilibrium.
  - jillesvangurp 5y ago
    The counter point here is that small electrical and autonomous planes don't need large airports or long runways. They are very efficient in terms of space. All of the long suffering smaller airports that can't even handle jets would potentially be of use for this. And given the lower noise and pollution levels, building more airports would not be as controversial as building new airports for jets currently is. Possibly even within city limits. And that is of course before you consider VTOL.
  - pestatije 5y ago
    Trains solve all of those issues: short haul, high capacity, electric
    - GordonS 5y ago
      I certainly agree that many countries (US & UK included) should be investing much more in rail, but there is the pesky problem of rails and land to put them on - it's very expensive, and takes a lot of time.
deleted 5y ago
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by ginko 5y ago

I think for electric planes hydrogen fuel cells may be a real option since liquid hydrogen is so much lighter than pretty much any fuel or battery out there. The main problem is the density though.

jillesvangurp 5y ago

Liquid hydrogen or some other type of fuel cell is definitely a solution for flying big heavy jets. Another potential solution is simply burning the hydrogen in jet engines. Or methane. Both have been used as rocket fuel. Both could be sourced in a sustainable way. The technology to build jet engines that burn that type of fuel already exists. The reason that fuel cells are potentially interesting is getting better efficiencies in combination with light yet powerful electrical engines such as described in the article. The reason we still use kerosene is simply that the infrastructure to distribute that is there and it's a cheap fuel to create. Changing that industry is about ramping up the manufacturing and fuel infrastructure to the point where it is profitable. It's a very slow and expensive process. The right question to ask though is why big heavy jets are interesting to begin with. They are big, heavy, expensive, and complicated machines. Why do we go through the trouble of building those at a cost of around 100M per vehicle for a small one? This has to do with a lot of things but the two main ones that stand out are that fuel is expensive and pilots are expensive (and scarce). So the optimal conventional plane is one that moves around a lot of stuff with a minimum amount of fuel per kg of useful payload and the requisite two pilots. Hence the A380 briefly existed until it got to expensive to operate it. An autonomous small battery operated plane would fix both those pain points. Electricity is comparatively cheap and autonomous vehicles means no expensive pilots are needed anymore. People that are talking about making electrical airbuses or boeings are missing the point: these form factors become a lot less relevant when we can fly dozens/hundreds of autonomous vehicles for orders of magnitude less money. Mostly small planes are pretty cheap to manufacture. So, are electrical engines and batteries. And the electronics needed to run them. You could feasibly build hundreds of them for the price of a single A320. And they'd be comparatively dirt cheap to maintain and operate. And a lot more flexible in where they could go. You are not going to cross ocean in one any time soon. But short haul flight is a different matter. Neither of the best selling jets (737 & A320) is commonly used for intercontinental flights. They are used for short haul flights.

xyzzyz 5y ago
Liquid hydrogen sounds rather impractical, with its deep cryogenic requirements, compared to regular compressed hydrogen. Compressed hydrogen already has high energy density by volume to easily compete with hydrocarbon based fuels.
GordonS 5y ago
> these form factors become a lot less relevant when we can fly dozens/hundreds of autonomous vehicles for orders of magnitude less money A big and multi-faceted factor not considered here is airport capacity, in terms of terminal building footprint, aircraft ground handling, flight control and airspace. Many large airports are already at capacity, so it's difficult to see how higher numbers of aircraft could work.
- fire 5y ago
  You make a good point; Now I'm curious how efficiently capacity is used with flight schedules exchanging large numbers of passengers with each flight, and whether smaller but more frequent flights would have any real impact on that equilibrium.
- jillesvangurp 5y ago
  The counter point here is that small electrical and autonomous planes don't need large airports or long runways. They are very efficient in terms of space. All of the long suffering smaller airports that can't even handle jets would potentially be of use for this. And given the lower noise and pollution levels, building more airports would not be as controversial as building new airports for jets currently is. Possibly even within city limits. And that is of course before you consider VTOL.
- pestatije 5y ago
  Trains solve all of those issues: short haul, high capacity, electric
  - GordonS 5y ago
    I certainly agree that many countries (US & UK included) should be investing much more in rail, but there is the pesky problem of rails and land to put them on - it's very expensive, and takes a lot of time.

deleted 5y ago

[deleted]