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That’s just wishful thinking. So far nothing shows that batteries would allow even most current “short” flights by airliners, only some trivial extremely short

That’s just wishful thinking. So far nothing shows that batteries would allow even most current “short” flights by airliners, only some trivial extremely short regional connection flights at most. That’s also why no major aviation company is going towards batteries for airliners. Also, burning H2 does generate heat and water emissions, but it’s not the case with fuel cells. Those can be literally 0-emissions.

Robotbeat 5y ago
Nope. It’s not wishful thinking, it’s my day job. It pops out of analysis of what aerodynamics advances are possible, eg work by Pfenninger and others which is decades old. It’s fascinating how some confuse their own lack of familiarity with the state of the art research on this with lack of any sound ability. Boeing and Airbus have both invested millions in startups that are working on battery electric aircraft. But beyond that, it wasn’t Toyota or VW that made the Model S and the Model 3. Why would we expect a massive, slow-moving behemoth to be at the forefront of electric flight if the massive, slow-moving behemoths of land transport weren’t at the forefront of practical long distance electric cars? Companies such as Eviation, MagniX, and Bye Aerospace have promising approaches for the roughly 1000km range, with more advanced approaches (longer wings, pressurized cabin enabling higher altitudes, better battery chemistries, etc) enabling all short haul flights. Long-haul is a much bigger challenge, but still possible. And dropping water from high altitude will still cause water emissions. You’d need operational complexity such as freezing the water into pellets, or dumping the water occasionally at low altitudes. And compressed hydrogen has terrible energy density so you’ll want liquid hydrogen, which is still the lowest density liquid known to humankind plus is also almost the deepest cryogenic liquid, with a bunch of energy required for liquefaction and some pretty annoying/dangerous handling issues during refueling. Sure, it could be done, but it’s going to be harder than people think and the poor round trip efficiency is going to limit the economic case for it versus battery-electric.
- FabHK 5y ago
  Correct me if I'm wrong, but ultimately the energy requirement for flight boils down to optimal lift-drag ratio, doesn't it? My impression was that we were in a pretty sweet spot there already, and can only expect marginal improvements (higher aspect ratio (which comes with its own challenges - from airport suitability to structural stability), less zero-lift drag by reducing wetted area). Even if we double L/D (which would be a substantial achievement, no?), battery-electric flight would only have endurance of about an hour with current tech, and then maybe 2 hours in two decades after specific energy has doubled again, just about giving us a bit more than 1000 km (after reserves etc.).
  - coderenegade 5y ago
    There's also no reason to expect that an L/D improvement applicable to battery electric aircraft wouldn't also directly benefit aircraft using fossil fuels or hydrogen / ammonia. Unless you have batteries with triple the energy density to current technologies, hydrogen is still going to go further and have a faster refuel time.
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Robotbeat 5y ago

Nope. It’s not wishful thinking, it’s my day job. It pops out of analysis of what aerodynamics advances are possible, eg work by Pfenninger and others which is decades old. It’s fascinating how some confuse their own lack of familiarity with the state of the art research on this with lack of any sound ability. Boeing and Airbus have both invested millions in startups that are working on battery electric aircraft. But beyond that, it wasn’t Toyota or VW that made the Model S and the Model 3. Why would we expect a massive, slow-moving behemoth to be at the forefront of electric flight if the massive, slow-moving behemoths of land transport weren’t at the forefront of practical long distance electric cars? Companies such as Eviation, MagniX, and Bye Aerospace have promising approaches for the roughly 1000km range, with more advanced approaches (longer wings, pressurized cabin enabling higher altitudes, better battery chemistries, etc) enabling all short haul flights. Long-haul is a much bigger challenge, but still possible. And dropping water from high altitude will still cause water emissions. You’d need operational complexity such as freezing the water into pellets, or dumping the water occasionally at low altitudes. And compressed hydrogen has terrible energy density so you’ll want liquid hydrogen, which is still the lowest density liquid known to humankind plus is also almost the deepest cryogenic liquid, with a bunch of energy required for liquefaction and some pretty annoying/dangerous handling issues during refueling. Sure, it could be done, but it’s going to be harder than people think and the poor round trip efficiency is going to limit the economic case for it versus battery-electric.

FabHK 5y ago
Correct me if I'm wrong, but ultimately the energy requirement for flight boils down to optimal lift-drag ratio, doesn't it? My impression was that we were in a pretty sweet spot there already, and can only expect marginal improvements (higher aspect ratio (which comes with its own challenges - from airport suitability to structural stability), less zero-lift drag by reducing wetted area). Even if we double L/D (which would be a substantial achievement, no?), battery-electric flight would only have endurance of about an hour with current tech, and then maybe 2 hours in two decades after specific energy has doubled again, just about giving us a bit more than 1000 km (after reserves etc.).
- coderenegade 5y ago
  There's also no reason to expect that an L/D improvement applicable to battery electric aircraft wouldn't also directly benefit aircraft using fossil fuels or hydrogen / ammonia. Unless you have batteries with triple the energy density to current technologies, hydrogen is still going to go further and have a faster refuel time.

deleted 5y ago

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