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Kerosene burns, hydrogen explodes. And kerosene doesn't actively damage the tank it's stored in, like hydrogen does.[1] Also, while its energy density per kilog

Kerosene burns, hydrogen explodes. And kerosene doesn't actively damage the tank it's stored in, like hydrogen does.[1] Also, while its energy density per kilogram compares favourably to kerosene, its energy density per litre does not. Hydrogen is a great rocket fuel because its specific impulse is second to none, so why isn't it universally used? Because even by rocket fuel standards it's a bugger to work with. There are lots of things that react poorly to being set on fire. That doesn't make them all equally dangerous. [1] https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement

jeffreyrogers 6y ago
Hydrogen embrittlement depends on the type of tank. It does not occur with every material. Look, I'm not saying hydrogen is great and has no problems. I'm saying the problems are not in theory insurmountable. I have elsewhere made the same point as you with regards to mass vs volume. I'm aware of the drawbacks of hydrogen and am actually pessimistic on its use in aviation, but I think it is worth trying out.
- jacquesm 6y ago
  Hydrogen is not only in contact with the tank but with other materials en route to the fuel cell as well. And the problems don't need to be insurmountable in theory, they need to actually be solvable and that is a different thing entirely. I'm fine with people trying it out but I'm very skeptical about this ever making it to production. I think this is more of a PR piece than anything substantial.
  - masklinn 6y ago
    > Hydrogen is not only in contact with the tank but with other materials en route to the fuel cell as well. Isn't it also in contact with everything around the tank on account on there being basically nothing which is completely impermeable to hydrogen?
  - jeffreyrogers 6y ago
    I don't think hydrogen powered planes will substantially replace normal planes for reasons having to do partially with safety and partially with performance, but I think the engineering problems are surmountable. There are existing prototypes that have flown using hydrogen fuel cells, and the Tu-155 which ran on liquid hydrogen (used as fuel for its jet engines though, not to power fuel cells). So it's not like this stuff doesn't work. I think you are overestimating the difficulty of dealing with embrittlement. Many materials don't suffer from embrittlement at all, and others (like aluminum) only suffer at high temperatures. Edit: I also wanted to add to the person who made the claim "kerosene burns, hydrogen explodes" that kerosone can explode too, and it obviously is possible to handle hydrogen in a way that explosion is unlikely or it wouldn't be used as rocket fuel (where it is literally combusted with oxygen... combusted, not exploded). I agree that hydrogen is more dangerous than kerosene, but it's not like kerosene is that safe either and the question is whether you can create good enough processes around the storage and handling of hydrogen to offset the risk.

jeffreyrogers 6y ago

Hydrogen embrittlement depends on the type of tank. It does not occur with every material. Look, I'm not saying hydrogen is great and has no problems. I'm saying the problems are not in theory insurmountable. I have elsewhere made the same point as you with regards to mass vs volume. I'm aware of the drawbacks of hydrogen and am actually pessimistic on its use in aviation, but I think it is worth trying out.

jacquesm 6y ago
Hydrogen is not only in contact with the tank but with other materials en route to the fuel cell as well. And the problems don't need to be insurmountable in theory, they need to actually be solvable and that is a different thing entirely. I'm fine with people trying it out but I'm very skeptical about this ever making it to production. I think this is more of a PR piece than anything substantial.
- masklinn 6y ago
  > Hydrogen is not only in contact with the tank but with other materials en route to the fuel cell as well. Isn't it also in contact with everything around the tank on account on there being basically nothing which is completely impermeable to hydrogen?
- jeffreyrogers 6y ago
  I don't think hydrogen powered planes will substantially replace normal planes for reasons having to do partially with safety and partially with performance, but I think the engineering problems are surmountable. There are existing prototypes that have flown using hydrogen fuel cells, and the Tu-155 which ran on liquid hydrogen (used as fuel for its jet engines though, not to power fuel cells). So it's not like this stuff doesn't work. I think you are overestimating the difficulty of dealing with embrittlement. Many materials don't suffer from embrittlement at all, and others (like aluminum) only suffer at high temperatures. Edit: I also wanted to add to the person who made the claim "kerosene burns, hydrogen explodes" that kerosone can explode too, and it obviously is possible to handle hydrogen in a way that explosion is unlikely or it wouldn't be used as rocket fuel (where it is literally combusted with oxygen... combusted, not exploded). I agree that hydrogen is more dangerous than kerosene, but it's not like kerosene is that safe either and the question is whether you can create good enough processes around the storage and handling of hydrogen to offset the risk.