3 ms·

A pretty large portion of aviation (over 50% of miles traveled) is short-haul, which actually is amenable to battery-electric decarbonization. And much of the r

A pretty large portion of aviation (over 50% of miles traveled) is short-haul, which actually is amenable to battery-electric decarbonization. And much of the rest could be converted to a few short haul hops which can be electrified. For aviation, a lot of it is just the inertia of the industry (which is a duopoly) and regulators and the decades it takes to get any new large passenger aircraft designed and approved, let alone one using a new kind of powertrain.

908B64B197 5y ago
> A pretty large portion of aviation (over 50% of miles traveled) is short-haul, which actually is amenable to battery-electric decarbonization. I'm shocked and happily surprised at the same time.
- Robotbeat 5y ago
  At 1000-1500km range for short haul, it’s not easy and can’t be done just by drop-in replacement with existing airframes, but with clean sheet designs, it is feasible. Especially as lithium metal electrode and lithium sulfur becomes available. In fact, it may be feasible to do up to 4000km range eventually (big challenge, but feasible given state of the art aerodynamics and improved structure and battery… and definitely possible with out of the box thinking, as a crewed solar-electric aircraft has demonstrated a flight of nearly 9000km, ie from Japan to Hawaii).
  - 908B64B197 5y ago
    > At 1000-1500km range for short haul, it’s not easy and can’t be done just by drop-in replacement with existing airframes, but with clean sheet designs, it is feasible. If it can be made cheaper than the California High Speed Rail, I've got a market for you right here...
    - Robotbeat 5y ago
      Indeed. The eFlyer 800 by Bye Aerospace, 925km range (at max payload) at over 320mph cruise, would be faster than the 200mph Cali HSR project that would’ve been at most 850km in phase 1 (and that would’ve been multiple hops most likely). https://byeaerospace.com/electric-airplane/ https://byeaerospace.com/electric-airplane/ (They hope to certify it by 2025, but it’s going to be a tough road to get there.)
      - thedrbrian 5y ago
        So you’re saying we replace 1 737 or A320 with 30 eflyer 800s?
        Robotbeat 5y ago
        Yes. The capital cost is only slightly higher for 30 eFlyer 800s vs 1 new 737, but the operating cost is much lower. eFlyers are more flexible as they can operate at small rural and suburban airports that wouldn't be economically viable with large aircraft, and this also enables much less time spent in airport terminals as smaller airports are MUCH faster to get through compared to large airports like LAX. We're talking like 15 minutes vs an hour.
missedthecue 5y ago
A boeing 737 carries ~190 people and luggage. I don't see how that's going to be electrified. And I'm not talking in the sense of "technology isn't there yet", but more like "the laws of physics wouldn't appreciate that". In my mind, the carbon neutra solution seems to lie in adopting renewable biofuels and engineering those jet engines to be ever more efficient, both of which seem attainable.
- Robotbeat 5y ago
  > I don't see how that's going to be electrified. And I'm not talking in the sense of "technology isn't there yet", but more like "the laws of physics wouldn't appreciate that". Well, good news! The laws of physics don't really care (at least not directly). See, scale occurs nowhere in the range equation: https://en.wikipedia.org/wiki/Range_(aeronautics)#Electric_aircraft https://en.wikipedia.org/wiki/Range_(aeronautics)#Electric_a... No matter how much it's repeated, scale still doesn't matter in terms of the physics of flight and electrification. I know people find it counter-intuitive, but it really ISN'T harder from a physics perspective to electrify a 737 (although you generally want a longer wingspan than airports like, so you may choose 777x-like extending wingtips). Pet peeve of mine that people think "oh, it's big so it's hard to electrify" (without actually doing any fundamental physics on the idea) when the largest machines are actually already electric (think bucketwheel excavators). In fact, in some ways, efficiency IMPROVES with scale, but it depends on a few factors (may need truss-braced wings at long enough wingspan, but that's doable). See how L/D improves with increasing Reynolds Number: https://www.researchgate.net/figure/Lift-to-drag-ratio-variation-with-Reynolds-number-reproduced-from-73_fig1_258378934 https://www.researchgate.net/figure/Lift-to-drag-ratio-varia... I mean ask yourself: is a business jet much more efficient than a 737? No? Well then why would it be harder to electrify a 737, from a physics perspective? In fact, a 737 is far more efficient than most much smaller aircraft using jet technology. And a Cessna is like half as efficient (or less) in terms of L/D in spite of being slower and much smaller.
  - missedthecue 5y ago
    Even with the highest theoretical possibilities, batteries cannot be as energy dense as kerosene. Kerosene has about about 12,000 Wh/kg, a cutting edge lithium battery has only 200. Scientists speculate that on paper, chemical batteries can theoretically get to about 1100 Wh/kg. A perfect world is still not even close to close to kerosene. Batteries do not get lighter as they discharge like a fuel tank does, meaning a huge efficiency loss. Finally it's simply not physically possible to recharge a large airliner size battery as fast as a fuel tank can be refilled, and on short haul flights, turnaround matters. Some airlines go from arrival to departure in 30 minutes. Modern airliners do up to 8 flights a day!

908B64B197 5y ago

> A pretty large portion of aviation (over 50% of miles traveled) is short-haul, which actually is amenable to battery-electric decarbonization. I'm shocked and happily surprised at the same time.

Robotbeat 5y ago
At 1000-1500km range for short haul, it’s not easy and can’t be done just by drop-in replacement with existing airframes, but with clean sheet designs, it is feasible. Especially as lithium metal electrode and lithium sulfur becomes available. In fact, it may be feasible to do up to 4000km range eventually (big challenge, but feasible given state of the art aerodynamics and improved structure and battery… and definitely possible with out of the box thinking, as a crewed solar-electric aircraft has demonstrated a flight of nearly 9000km, ie from Japan to Hawaii).
- 908B64B197 5y ago
  > At 1000-1500km range for short haul, it’s not easy and can’t be done just by drop-in replacement with existing airframes, but with clean sheet designs, it is feasible. If it can be made cheaper than the California High Speed Rail, I've got a market for you right here...
  - Robotbeat 5y ago
    Indeed. The eFlyer 800 by Bye Aerospace, 925km range (at max payload) at over 320mph cruise, would be faster than the 200mph Cali HSR project that would’ve been at most 850km in phase 1 (and that would’ve been multiple hops most likely). https://byeaerospace.com/electric-airplane/ https://byeaerospace.com/electric-airplane/ (They hope to certify it by 2025, but it’s going to be a tough road to get there.)
    - thedrbrian 5y ago
      So you’re saying we replace 1 737 or A320 with 30 eflyer 800s?
      - Robotbeat 5y ago
        Yes. The capital cost is only slightly higher for 30 eFlyer 800s vs 1 new 737, but the operating cost is much lower. eFlyers are more flexible as they can operate at small rural and suburban airports that wouldn't be economically viable with large aircraft, and this also enables much less time spent in airport terminals as smaller airports are MUCH faster to get through compared to large airports like LAX. We're talking like 15 minutes vs an hour.

missedthecue 5y ago

A boeing 737 carries ~190 people and luggage. I don't see how that's going to be electrified. And I'm not talking in the sense of "technology isn't there yet", but more like "the laws of physics wouldn't appreciate that". In my mind, the carbon neutra solution seems to lie in adopting renewable biofuels and engineering those jet engines to be ever more efficient, both of which seem attainable.

Robotbeat 5y ago
> I don't see how that's going to be electrified. And I'm not talking in the sense of "technology isn't there yet", but more like "the laws of physics wouldn't appreciate that". Well, good news! The laws of physics don't really care (at least not directly). See, scale occurs nowhere in the range equation: https://en.wikipedia.org/wiki/Range_(aeronautics)#Electric_aircraft https://en.wikipedia.org/wiki/Range_(aeronautics)#Electric_a... No matter how much it's repeated, scale still doesn't matter in terms of the physics of flight and electrification. I know people find it counter-intuitive, but it really ISN'T harder from a physics perspective to electrify a 737 (although you generally want a longer wingspan than airports like, so you may choose 777x-like extending wingtips). Pet peeve of mine that people think "oh, it's big so it's hard to electrify" (without actually doing any fundamental physics on the idea) when the largest machines are actually already electric (think bucketwheel excavators). In fact, in some ways, efficiency IMPROVES with scale, but it depends on a few factors (may need truss-braced wings at long enough wingspan, but that's doable). See how L/D improves with increasing Reynolds Number: https://www.researchgate.net/figure/Lift-to-drag-ratio-variation-with-Reynolds-number-reproduced-from-73_fig1_258378934 https://www.researchgate.net/figure/Lift-to-drag-ratio-varia... I mean ask yourself: is a business jet much more efficient than a 737? No? Well then why would it be harder to electrify a 737, from a physics perspective? In fact, a 737 is far more efficient than most much smaller aircraft using jet technology. And a Cessna is like half as efficient (or less) in terms of L/D in spite of being slower and much smaller.
- missedthecue 5y ago
  Even with the highest theoretical possibilities, batteries cannot be as energy dense as kerosene. Kerosene has about about 12,000 Wh/kg, a cutting edge lithium battery has only 200. Scientists speculate that on paper, chemical batteries can theoretically get to about 1100 Wh/kg. A perfect world is still not even close to close to kerosene. Batteries do not get lighter as they discharge like a fuel tank does, meaning a huge efficiency loss. Finally it's simply not physically possible to recharge a large airliner size battery as fast as a fuel tank can be refilled, and on short haul flights, turnaround matters. Some airlines go from arrival to departure in 30 minutes. Modern airliners do up to 8 flights a day!