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Climate change and the need to end the use of fossil fuels may force the return of the airship. People are working on making electric airplanes feasible, but th

Climate change and the need to end the use of fossil fuels may force the return of the airship. People are working on making electric airplanes feasible, but the weight of batteries makes it a tough problem. Airships are much more doable, although for any kind of frequent route, ground/sea travel is probably better. Heavier than air flight would probably need to use fuels synthesized from waste biomass, and be relegated to high-priority use. I'd also love to see more long-distance shipping move to advanced clipper ships using modern materials, computer-controlled rigging, highly optimized sail and hull designs, etc.

sokoloff 5y ago
It seems far more likely that jet flights would migrate to a synthetic fuel, taking yesterday’s CO2, making jet fuel today, and emitting that CO2 back tomorrow. It’s technically feasible but economically infeasible right now, the headline below notwithstanding. https://www.greenbiz.com/article/sustainable-aviation-fuels-technically-possible-economically-viable https://www.greenbiz.com/article/sustainable-aviation-fuels-...
- ant6n 5y ago
  Absorbing co2 at ground level and emitting it high in the atmosphere is equivalent to emitting fossil co2 at ground level -- at higher altitudes the green house effect is stronger, see radiative Forcing. Also, the overall energy efficiency is very poor. A plant creating synthetic cerosene just opened in Germany, and the reporting said the electricity->h2->cerosene->aircraft movement efficiency is 10-15%. Ouch.
  - marcosdumay 5y ago
    > at higher altitudes the green house effect is stronger Good thing the CO2 doesn't stay there forever. > Also, the overall energy efficiency is very poor. And energy efficiency is a good proxy for economic viability when you are comparing similar things, but completely useless when you comparing it with something. Why does the 10% efficiency matters? (By the way, expect that to increase. It always does.)
    - ant6n 5y ago
      I double checked. The co2 effect seems to be around 1.3 compared to the effect on the ground, but there are other factors that increase the greenhouse effect beyond that. There seems to be a fair bit of uncertainty on the numbers: https://en.wikipedia.org/wiki/Environmental_effects_of_aviation#Factors https://en.wikipedia.org/wiki/Environmental_effects_of_aviat... The 10% combined efficiency of the three energy conversions matter because energy itself isn't 100% green. With the current energy mix, there are more emissions from synthetic fuels than fossil ones.
      - marcosdumay 5y ago
        Oh, nobody on that thread is talking about doing it today. No doubt, today it's much better to just use fossil kerosene on our airplanes than synthesize it.
  - LargoLasskhyfv 5y ago
    Why do that h2->kerosene at all? Why not using the compressed h2 or something like https://en.wikipedia.org/wiki/Slush_hydrogen https://en.wikipedia.org/wiki/Slush_hydrogen to drive a fuel cell(or an array of them) or a micro gas turbine, to power hyper efficient electromotors built with something like https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide superconductors in a holistic concept which is using the h2 to cool the superconductors? I think I've read something like that not too long ago, maybe even here on hn. edit: Ah yes, see https://www.airbus.com/newsroom/stories/ascend-cryogenics-superconductivity-for-aircraft-explained.html https://www.airbus.com/newsroom/stories/ascend-cryogenics-su... addedit: Or less ambitious https://www.ainonline.com/aviation-news/air-transport/2020-09-18/conversion-plan-set-promote-early-switch-hydrogen-fuel https://www.ainonline.com/aviation-news/air-transport/2020-0...
    - ant6n 5y ago
      The idea for synthetic fuels is that they can act as a drop-in replacement for fossil fules, so you don't have to adapt the vehicles. I wouldn´t call using H2 a synthetic fuel, because it would require a different aircraft design (its probably more reasonable appraoch overall, although access to truly carbon free h2 is limited right now).
- Gravityloss 5y ago
  There exist already very efficient turboprops like ATR, but they don't sell well in the US since fuel is cheap and a faster jet plane can make more trips per week. Even in cargo usage.

sokoloff 5y ago

It seems far more likely that jet flights would migrate to a synthetic fuel, taking yesterday’s CO2, making jet fuel today, and emitting that CO2 back tomorrow. It’s technically feasible but economically infeasible right now, the headline below notwithstanding. https://www.greenbiz.com/article/sustainable-aviation-fuels-technically-possible-economically-viable https://www.greenbiz.com/article/sustainable-aviation-fuels-...

ant6n 5y ago
Absorbing co2 at ground level and emitting it high in the atmosphere is equivalent to emitting fossil co2 at ground level -- at higher altitudes the green house effect is stronger, see radiative Forcing. Also, the overall energy efficiency is very poor. A plant creating synthetic cerosene just opened in Germany, and the reporting said the electricity->h2->cerosene->aircraft movement efficiency is 10-15%. Ouch.
- marcosdumay 5y ago
  > at higher altitudes the green house effect is stronger Good thing the CO2 doesn't stay there forever. > Also, the overall energy efficiency is very poor. And energy efficiency is a good proxy for economic viability when you are comparing similar things, but completely useless when you comparing it with something. Why does the 10% efficiency matters? (By the way, expect that to increase. It always does.)
  - ant6n 5y ago
    I double checked. The co2 effect seems to be around 1.3 compared to the effect on the ground, but there are other factors that increase the greenhouse effect beyond that. There seems to be a fair bit of uncertainty on the numbers: https://en.wikipedia.org/wiki/Environmental_effects_of_aviation#Factors https://en.wikipedia.org/wiki/Environmental_effects_of_aviat... The 10% combined efficiency of the three energy conversions matter because energy itself isn't 100% green. With the current energy mix, there are more emissions from synthetic fuels than fossil ones.
    - marcosdumay 5y ago
      Oh, nobody on that thread is talking about doing it today. No doubt, today it's much better to just use fossil kerosene on our airplanes than synthesize it.
- LargoLasskhyfv 5y ago
  Why do that h2->kerosene at all? Why not using the compressed h2 or something like https://en.wikipedia.org/wiki/Slush_hydrogen https://en.wikipedia.org/wiki/Slush_hydrogen to drive a fuel cell(or an array of them) or a micro gas turbine, to power hyper efficient electromotors built with something like https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide https://en.wikipedia.org/wiki/Rare-earth_barium_copper_oxide superconductors in a holistic concept which is using the h2 to cool the superconductors? I think I've read something like that not too long ago, maybe even here on hn. edit: Ah yes, see https://www.airbus.com/newsroom/stories/ascend-cryogenics-superconductivity-for-aircraft-explained.html https://www.airbus.com/newsroom/stories/ascend-cryogenics-su... addedit: Or less ambitious https://www.ainonline.com/aviation-news/air-transport/2020-09-18/conversion-plan-set-promote-early-switch-hydrogen-fuel https://www.ainonline.com/aviation-news/air-transport/2020-0...
  - ant6n 5y ago
    The idea for synthetic fuels is that they can act as a drop-in replacement for fossil fules, so you don't have to adapt the vehicles. I wouldn´t call using H2 a synthetic fuel, because it would require a different aircraft design (its probably more reasonable appraoch overall, although access to truly carbon free h2 is limited right now).
Gravityloss 5y ago
There exist already very efficient turboprops like ATR, but they don't sell well in the US since fuel is cheap and a faster jet plane can make more trips per week. Even in cargo usage.