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What worries me about proposed H2-powered aircraft I see is that they always show H2 tanks mounted inboard. The fuel takes more room than would fit in the wings

What worries me about proposed H2-powered aircraft I see is that they always show H2 tanks mounted inboard. The fuel takes more room than would fit in the wings, but inboard tanks seem like a grave safety hazard. Nacelles slung under the wings should be safer: in a crash, the tanks would shear off and be left behind. The plumbing is entirely in the wing, eliminating possibility of leaked H2 building up in the cabin. Wherever LH2-fueled aircraft enter a market, petroleum-fueled craft will be immediately unable to compete. But building up on-site LH2 synthesis, storage, and delivery infrastructure at major airports will take a long time, and even longer at smaller ports. I don't know if the production process for aerogel is mature enough to use to insulate tankage and plumbing, but it seems an important prerequisite to mobile LH2.

alexfromapex 3y ago
Hydrogen fuel cells are a really dangerous method of storing energy. Hopefully a more inert way to store the hydrogen will be developed. Also the prospect of leaking cells poses a huge risk to climate change.
- angiosperm 3y ago
  A hydrogen fuel cell is a device to oxidize hydrogen to produce electrical power. Maybe you mean hydrogen pressure vessels? Well-ventilated low-pressure LH2 tanks are not especially dangerous. What would be dangerous is enclosing them in a poorly ventilated space, such as an aircraft cabin.
oceanplexian 3y ago
I’m going to guess it’s an engineering issue, almost certainly has to do with weight distribution. Fuel usually goes in the wings because that’s the center of gravity and as the fuel burns the CG doesn’t dramatically change. With hydrogen, I imagine the weight isn’t changing much, because all the weight is in the tanks. This means you can do weird stuff like put the tanks aft and counterbalance them in the front. Another thing I can think of is that cylindrical pressure vessels have inherent advantages. Wings don’t do cylindrical shapes well without wasting a bunch of space.
- angiosperm 3y ago
  Jet-A fuel usually goes in the wings also because it fits there, and the space (not usable for cargo) would otherwise be wasted. It would otherwise need to be in tanks between the wings, for the balance reason you note. H2 fuel would not fit in the wings, in any case. LH2 is lighter than Jet-A, but it does weigh, and so still affects balance. LH2 storage does not demand a pressure vessel, but does need insulation. You still want to minimize insulated surface area, so still favor a cylindrical container. So, nacelles slung under the wings seems like the best solution, provided their parasitic drag is not excessive.

alexfromapex 3y ago

Hydrogen fuel cells are a really dangerous method of storing energy. Hopefully a more inert way to store the hydrogen will be developed. Also the prospect of leaking cells poses a huge risk to climate change.

angiosperm 3y ago
A hydrogen fuel cell is a device to oxidize hydrogen to produce electrical power. Maybe you mean hydrogen pressure vessels? Well-ventilated low-pressure LH2 tanks are not especially dangerous. What would be dangerous is enclosing them in a poorly ventilated space, such as an aircraft cabin.

oceanplexian 3y ago

I’m going to guess it’s an engineering issue, almost certainly has to do with weight distribution. Fuel usually goes in the wings because that’s the center of gravity and as the fuel burns the CG doesn’t dramatically change. With hydrogen, I imagine the weight isn’t changing much, because all the weight is in the tanks. This means you can do weird stuff like put the tanks aft and counterbalance them in the front. Another thing I can think of is that cylindrical pressure vessels have inherent advantages. Wings don’t do cylindrical shapes well without wasting a bunch of space.

angiosperm 3y ago
Jet-A fuel usually goes in the wings also because it fits there, and the space (not usable for cargo) would otherwise be wasted. It would otherwise need to be in tanks between the wings, for the balance reason you note. H2 fuel would not fit in the wings, in any case. LH2 is lighter than Jet-A, but it does weigh, and so still affects balance. LH2 storage does not demand a pressure vessel, but does need insulation. You still want to minimize insulated surface area, so still favor a cylindrical container. So, nacelles slung under the wings seems like the best solution, provided their parasitic drag is not excessive.