4 ms·

How many people would be ready to drive a hydrogen bomb?

by baybal2 5y ago

throwaway0a5e 5y ago
Do you ride on a CNG city bus?
- jacquesm 5y ago
  Much higher activation energy, not to be compared.
- hydrogtehd 5y ago
  There’s no comparison in the risk of methane vs. H2. The only thing H2 has going for it, safety wise, is that it disperses very quickly. Otherwise methane is insanely safe, safer in all regards except pressurization than gasoline.
goodpoint 5y ago
More than a gasoline bomb, hopefully. Gasoline is more dangerous.
- baybal2 5y ago
  Few kg of hydrogen are surely more dangerous than 50 kg of gasoline.
  - MayeulC 5y ago
    120 MJ/kg for H2 vs 46 MJ/kg for gasoline. Both are explosive, so I think (I'm no authority on this) we can compare those values directly, without taking into account the storage pressure. Source: https://hypertextbook.com/facts/2005/MichelleFung.shtml https://hypertextbook.com/facts/2005/MichelleFung.shtml https://hypertextbook.com/facts/2003/ArthurGolnik.shtml https://hypertextbook.com/facts/2003/ArthurGolnik.shtml
    - jandrese 5y ago
      Gasoline will not explode in normal conditions. Even in an accident it is pretty safe, although the risk of fire must always be considered. A 10k PSI H2 tank is a straight up bomb. A gasoline tank can start a nasty fire but nobody is going to be torn apart by shrapnel or killed by the overpressure wave in an accident. Gasoline cars don't explode like they do in the movies. It must also be noted that the large batteries in EVs are also a fire hazard and in some ways worse than gasoline. For gasoline to act like a bomb it has to be aerosolized first and then ignited. In an accident there's not much that could achieve that. With a high pressure H2 tank something that cracked it open and allowed all of the H2 to be released at once would instantly create the conditions for a massive explosion. All it would need is a single spark.
  - jacquesm 5y ago
    The total amount isn't as much a problem as is the activation energy. Hydrogen will explode when you look at it cross eyed. For gasoline you will have to do some work.
    - goodpoint 5y ago
      Hydrogen does not explode unless mixed with oxygen or other comburents.
      - jacquesm 5y ago
        Fortunately there isn't any free oxygen in the atmosphere. Oh, wait.
        goodpoint 5y ago
        Fortunately the atmosphere is not inside the hydrogen tank. That's why it can flame out when pierced but not explode.
- adrianN 5y ago
  I'm relatively sure that a tank of hydrogen at ridiculous pressure makes a nicer fireball than a tank of gas at no pressure.
  - goodpoint 5y ago
    No: it's a myth that a hydrogen tank simply explodes. It would need to be mixed with oxygen. Instead, liquid flammables can leak around and then ignite. https://www.computerworld.com/article/2852323/heres-why-hydrogen-fueled-cars-arent-little-hindenburgs.html https://www.computerworld.com/article/2852323/heres-why-hydr... https://hydrogen.wsu.edu/2017/03/17/so-just-how-dangerous-is-hydrogen-fuel/ https://hydrogen.wsu.edu/2017/03/17/so-just-how-dangerous-is...
- hydrogtehd 5y ago
  No, it isn’t. Gasoline is dangerous, but it’s a liquid. H2 is a gas, under extreme pressure, and with a very low spark energy. The spark (ignition) energy is very important safety wise. Nothing will light without an ignition source. In fact hydrogen is more dangerous wrt to gasoline than gasoline is wrt to flour (yes, flour can explode). That is: Flour:gasoline < gasoline:hydrogen Hydrogen is dangerous. And that’s fine. [1] http://www.explosionsolutions.co.uk/110411020.pdf http://www.explosionsolutions.co.uk/110411020.pdf
hydrogtehd 5y ago
“Hydrogen bomb” is a little exaggerated. But to your detractors: “More than a gasoline bomb, hopefully. Gasoline is more dangerous.” Citation needed. How is gasoline more dangerous? While gasoline is very dangerous, gasoline is a liquid and will not burn until vaporized; Gasoline is dangerous because it vaporizes quickly. H2 is already a gas and has a ridiculously low spark energy. Furthermore H2 is under pressure. Gas does have a lower auto-ignition T than H2, that’s no fun, but overall H2 scores worse than gasoline. “Do you ride on a CNG city bus?” CNG stands for Compressed Natural Gas; i.e. methane. Methane is a lot easier and safer to use than H2 because it: - Packs a lot more energy vs. P so the tanks don’t have to be as strong - Doesn’t embrittle the container - Much higher spark energy (in fact, CH4 is kinda hard to light) - Smaller flammability range (i.e. mixture with air that will ignite) - lower auto-ignition T [1] https://en.wikipedia.org/wiki/Flammability_limit https://en.wikipedia.org/wiki/Flammability_limit
- wglb 5y ago
  And you can't see a hydrogen flame.
- JimTheMan 5y ago
  I work with a guy who was involved in a near miss incident with these cannisters. They are not risk free, although you could argue that the accidents are rare and potentially worth the risk? https://www.busnews.com.au/industry-news/1201/gas-bus-explosion-under-investigation https://www.busnews.com.au/industry-news/1201/gas-bus-explos... https://www.ctif.org/news/cause-stockholm-cng-bus-explosion-has-now-been-determined https://www.ctif.org/news/cause-stockholm-cng-bus-explosion-... https://hal-ineris.archives-ouvertes.fr/ineris-00976180/document https://hal-ineris.archives-ouvertes.fr/ineris-00976180/docu...
  - hydrogtehd 5y ago
    “ although you could argue that the accidents are rare and potentially worth the risk?” I agree. I don’t know if they’re technologically feasible at the price point necessary to put them in a few billion cars. But this “safety” obsession has gotten old.

How many people would be ready to drive a hydrogen bomb?

throwaway0a5e 5y ago

Do you ride on a CNG city bus?

jacquesm 5y ago
Much higher activation energy, not to be compared.
hydrogtehd 5y ago
There’s no comparison in the risk of methane vs. H2. The only thing H2 has going for it, safety wise, is that it disperses very quickly. Otherwise methane is insanely safe, safer in all regards except pressurization than gasoline.

goodpoint 5y ago

More than a gasoline bomb, hopefully. Gasoline is more dangerous.

baybal2 5y ago
Few kg of hydrogen are surely more dangerous than 50 kg of gasoline.
- MayeulC 5y ago
  120 MJ/kg for H2 vs 46 MJ/kg for gasoline. Both are explosive, so I think (I'm no authority on this) we can compare those values directly, without taking into account the storage pressure. Source: https://hypertextbook.com/facts/2005/MichelleFung.shtml https://hypertextbook.com/facts/2005/MichelleFung.shtml https://hypertextbook.com/facts/2003/ArthurGolnik.shtml https://hypertextbook.com/facts/2003/ArthurGolnik.shtml
  - jandrese 5y ago
    Gasoline will not explode in normal conditions. Even in an accident it is pretty safe, although the risk of fire must always be considered. A 10k PSI H2 tank is a straight up bomb. A gasoline tank can start a nasty fire but nobody is going to be torn apart by shrapnel or killed by the overpressure wave in an accident. Gasoline cars don't explode like they do in the movies. It must also be noted that the large batteries in EVs are also a fire hazard and in some ways worse than gasoline. For gasoline to act like a bomb it has to be aerosolized first and then ignited. In an accident there's not much that could achieve that. With a high pressure H2 tank something that cracked it open and allowed all of the H2 to be released at once would instantly create the conditions for a massive explosion. All it would need is a single spark.
- jacquesm 5y ago
  The total amount isn't as much a problem as is the activation energy. Hydrogen will explode when you look at it cross eyed. For gasoline you will have to do some work.
  - goodpoint 5y ago
    Hydrogen does not explode unless mixed with oxygen or other comburents.
    - jacquesm 5y ago
      Fortunately there isn't any free oxygen in the atmosphere. Oh, wait.
      - goodpoint 5y ago
        Fortunately the atmosphere is not inside the hydrogen tank. That's why it can flame out when pierced but not explode.
adrianN 5y ago
I'm relatively sure that a tank of hydrogen at ridiculous pressure makes a nicer fireball than a tank of gas at no pressure.
- goodpoint 5y ago
  No: it's a myth that a hydrogen tank simply explodes. It would need to be mixed with oxygen. Instead, liquid flammables can leak around and then ignite. https://www.computerworld.com/article/2852323/heres-why-hydrogen-fueled-cars-arent-little-hindenburgs.html https://www.computerworld.com/article/2852323/heres-why-hydr... https://hydrogen.wsu.edu/2017/03/17/so-just-how-dangerous-is-hydrogen-fuel/ https://hydrogen.wsu.edu/2017/03/17/so-just-how-dangerous-is...
hydrogtehd 5y ago
No, it isn’t. Gasoline is dangerous, but it’s a liquid. H2 is a gas, under extreme pressure, and with a very low spark energy. The spark (ignition) energy is very important safety wise. Nothing will light without an ignition source. In fact hydrogen is more dangerous wrt to gasoline than gasoline is wrt to flour (yes, flour can explode). That is: Flour:gasoline < gasoline:hydrogen Hydrogen is dangerous. And that’s fine. [1] http://www.explosionsolutions.co.uk/110411020.pdf http://www.explosionsolutions.co.uk/110411020.pdf

hydrogtehd 5y ago

“Hydrogen bomb” is a little exaggerated. But to your detractors: “More than a gasoline bomb, hopefully. Gasoline is more dangerous.” Citation needed. How is gasoline more dangerous? While gasoline is very dangerous, gasoline is a liquid and will not burn until vaporized; Gasoline is dangerous because it vaporizes quickly. H2 is already a gas and has a ridiculously low spark energy. Furthermore H2 is under pressure. Gas does have a lower auto-ignition T than H2, that’s no fun, but overall H2 scores worse than gasoline. “Do you ride on a CNG city bus?” CNG stands for Compressed Natural Gas; i.e. methane. Methane is a lot easier and safer to use than H2 because it: - Packs a lot more energy vs. P so the tanks don’t have to be as strong - Doesn’t embrittle the container - Much higher spark energy (in fact, CH4 is kinda hard to light) - Smaller flammability range (i.e. mixture with air that will ignite) - lower auto-ignition T [1] https://en.wikipedia.org/wiki/Flammability_limit https://en.wikipedia.org/wiki/Flammability_limit

wglb 5y ago
And you can't see a hydrogen flame.
JimTheMan 5y ago
I work with a guy who was involved in a near miss incident with these cannisters. They are not risk free, although you could argue that the accidents are rare and potentially worth the risk? https://www.busnews.com.au/industry-news/1201/gas-bus-explosion-under-investigation https://www.busnews.com.au/industry-news/1201/gas-bus-explos... https://www.ctif.org/news/cause-stockholm-cng-bus-explosion-has-now-been-determined https://www.ctif.org/news/cause-stockholm-cng-bus-explosion-... https://hal-ineris.archives-ouvertes.fr/ineris-00976180/document https://hal-ineris.archives-ouvertes.fr/ineris-00976180/docu...
- hydrogtehd 5y ago
  “ although you could argue that the accidents are rare and potentially worth the risk?” I agree. I don’t know if they’re technologically feasible at the price point necessary to put them in a few billion cars. But this “safety” obsession has gotten old.