3 ms·

> Seems to me that everything is nonlinear in the domain of aircraft, particularly when concerned with "efficiency". The same physics applies to fast trains an

> Seems to me that everything is nonlinear in the domain of aircraft, particularly when concerned with "efficiency". The same physics applies to fast trains and other modes of transit. Fast electric trains have the advantage of not having to lug their fuel along with them at speed. > consider that energy is a function of both power and time applied; if you double the speed to fly from say London to NY, would you cut the time to fly to less than 1/8th what it would otherwise be? I think I understand what you’re trying to say, but note that by definition going twice as fast will get you there in half the time. Work and Energy are in alignment here because of the various efficiency losses you’re talking about. The Concorde did have some reprieve in that it flew 20k feet higher than the usual cruising altitude. https://aviation.stackexchange.com/questions/21881/at-what-altitude-did-concorde-go-supersonic https://aviation.stackexchange.com/questions/21881/at-what-a... Ultimately high speed transport is not about conservation of energy. It’s about conservation of human time. Weighing that against the environment and other factors are important but few people weigh their total use of energy in a given day.

ClumsyPilot 6y ago
Fast electric trains are also, well, electric already. Powering planes in a sustainable marrer is not a solved problem.
- Robotbeat 6y ago
  So I think that’s not really true. Even existing battery chemistry could do 1000km per stop (although it still needs certification for aircraft) and at comparable speed as HSR. That’s much longer than the California HSR project that was canceled, plus you just need a recharge (or swap) to continue on your way. With further efficiency improvements and battery chemistries in development right now like Li-S, we could potentially do 4000km flights (enough to reach Hawaii... and anywhere else using multiple hops, as Boom is planning). And shorter flights at higher than HSR speeds. HSR has its own unsolved problems. Like not being able to work over deep ocean... and insane infrastructure costs.
  - deleted 6y ago
    [deleted]
- Moto7451 6y ago
  Even if the train’s electric power comes from coal, not carrying fuel with you is a win from an efficiency standpoint. There are some military planes flying on biofuel, so ideally we’re not that far off. https://www.energy.gov/eere/bioenergy/aviation-fuels https://www.energy.gov/eere/bioenergy/aviation-fuels

ClumsyPilot 6y ago

Fast electric trains are also, well, electric already. Powering planes in a sustainable marrer is not a solved problem.

Robotbeat 6y ago
So I think that’s not really true. Even existing battery chemistry could do 1000km per stop (although it still needs certification for aircraft) and at comparable speed as HSR. That’s much longer than the California HSR project that was canceled, plus you just need a recharge (or swap) to continue on your way. With further efficiency improvements and battery chemistries in development right now like Li-S, we could potentially do 4000km flights (enough to reach Hawaii... and anywhere else using multiple hops, as Boom is planning). And shorter flights at higher than HSR speeds. HSR has its own unsolved problems. Like not being able to work over deep ocean... and insane infrastructure costs.
- deleted 6y ago
  [deleted]
Moto7451 6y ago
Even if the train’s electric power comes from coal, not carrying fuel with you is a win from an efficiency standpoint. There are some military planes flying on biofuel, so ideally we’re not that far off. https://www.energy.gov/eere/bioenergy/aviation-fuels https://www.energy.gov/eere/bioenergy/aviation-fuels