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> Hydrogen's energy-density makes it by far the best possible fuel for aviation. gasoline: 45.8 MJ/kg hydrogen: 120 MJ/kg What about safety? I visited the Zep

> Hydrogen's energy-density makes it by far the best possible fuel for aviation. gasoline: 45.8 MJ/kg hydrogen: 120 MJ/kg What about safety? I visited the Zeppelin museum in Friedrichshafen last week... Wouldn't it be nice if turning CO2 into gasoline would enable us to re-use tall the existing infrastructure?

pfortuny 6y ago
Zeppelins were essentially giant gaseous hydrogen balloons. That is directly flammable. AFAIK liquid hydrogen tanks are orders of magnitude safer (as in “a totally different problem”).
- exged 6y ago
  Liquid hydrogen tanks are definitely a different problem, but I don't know if "orders of magnitude safer" is necessarily true. Many spacecraft have run into problems involving liquid hydrogen storage for a variety of reasons: - Liquid hydrogen is so cold that many metals weaken - Exposure to hydrogen itself weakens many metals (hydrogen embrittlement) - Liquid hydrogen expands rapidly if exposed to heat, so venting is needed - Hydrogen leaks through the smallest of seams Now imagine trying to build a tank that prevents all that from happening, and it has to be lightweight for usage on spacecraft / aircraft.
  - Kuinox 6y ago
    I know nothing about it, but what about hydrogen cells ? It doesn't solve this issue ?
    - ProZsolt 6y ago
      Hydrogen cells nothing to do with storage, it's for converting hydrogen to electricity
      - Kuinox 6y ago
        Oh, to me the name in french implied it stored energy. We say "Pile a Hydrogen". In french we differenciate "batterie" and "pile", "pile" are one use, but I thought due to the name that the hydrogen cell would store energy.
ncmncm 6y ago
The Hindenberg blew up because there was a bomb on board. No aircraft design is noted for resistance to onboard explosives. Furthermore, the flames seen in the film were from kerosine fuel. All the hydrogen released went up, up, up. It is quite difficult to ignite hydrogen at atmospheric pressure; it requires oxygen mixed in a narrow range of partial pressures. So, no, safety of H2 fuel is not a problem.

pfortuny 6y ago

Zeppelins were essentially giant gaseous hydrogen balloons. That is directly flammable. AFAIK liquid hydrogen tanks are orders of magnitude safer (as in “a totally different problem”).

exged 6y ago
Liquid hydrogen tanks are definitely a different problem, but I don't know if "orders of magnitude safer" is necessarily true. Many spacecraft have run into problems involving liquid hydrogen storage for a variety of reasons: - Liquid hydrogen is so cold that many metals weaken - Exposure to hydrogen itself weakens many metals (hydrogen embrittlement) - Liquid hydrogen expands rapidly if exposed to heat, so venting is needed - Hydrogen leaks through the smallest of seams Now imagine trying to build a tank that prevents all that from happening, and it has to be lightweight for usage on spacecraft / aircraft.
- Kuinox 6y ago
  I know nothing about it, but what about hydrogen cells ? It doesn't solve this issue ?
  - ProZsolt 6y ago
    Hydrogen cells nothing to do with storage, it's for converting hydrogen to electricity
    - Kuinox 6y ago
      Oh, to me the name in french implied it stored energy. We say "Pile a Hydrogen". In french we differenciate "batterie" and "pile", "pile" are one use, but I thought due to the name that the hydrogen cell would store energy.

ncmncm 6y ago

The Hindenberg blew up because there was a bomb on board. No aircraft design is noted for resistance to onboard explosives. Furthermore, the flames seen in the film were from kerosine fuel. All the hydrogen released went up, up, up. It is quite difficult to ignite hydrogen at atmospheric pressure; it requires oxygen mixed in a narrow range of partial pressures. So, no, safety of H2 fuel is not a problem.