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How wrong is it to think of "carbon composite" as "charcoal"? Because with that conceptualization, it seems like an inherent risk to store liquid oxygen in a c

How wrong is it to think of "carbon composite" as "charcoal"? Because with that conceptualization, it seems like an inherent risk to store liquid oxygen in a charcoal container on a rocket ship.

hguant 10y ago
Very. This is the first thing that pops up when you google 'carbon composite': https://en.wikipedia.org/wiki/Carbon_fiber_reinforced_polymer https://en.wikipedia.org/wiki/Carbon_fiber_reinforced_polyme... I had a vision of a massive porous mass of carbon (a la water filters and the like) storing all that lox, but it seems not to be the case.
schiffern 10y ago
Charcoal has a surface area of a few acres per teaspoon (which makes sense when you look at a micrograph, since all the woody cell walls are preserved https://www.youtube.com/watch?v=kF10i39VQ4w https://www.youtube.com/watch?v=kF10i39VQ4w), whereas carbon fiber composites are impregnated with resin. Obviously all it takes is one oxygen/carbon interface to cause an explosion, as we saw. Similar to explosives, the more thoroughly mixed it is the more energetic the reaction. Pouring LOX over charcoal and soaking charcoal in LOX are very different (the first ignites vigorously, the latter explodes like a stick of dynamite). http://www.popsci.com/diy/article/2009-09/most-dangerous-way-light-grill http://www.popsci.com/diy/article/2009-09/most-dangerous-way...
- azernik 10y ago
  On a similar note, all kinds of materials that you wouldn't expect become very flammable with high surface area and/or pure oxygen environments. See e.g. the thermal lance, which is a very powerful cutting tool that works by running oxygen over iron (rust at high speed!). Or the very serious risk of explosions in flour mills due to high amounts of dust suspended in the air.
  - freehunter 10y ago
    Yup. Growing up on a farm, it wasn't uncommon to hear of explosions in grain silos from a spark in the dust or barn fires from undried hay bales. That's right, wet hay bales can and will spontaneously combust. It sounds counter-intuitive, but wet hay bales are more dangerous than dry hay bales, because hay actually heats up as it dries. As the hay gets hotter, it starts giving off flammable gas. The heat it is generating combined with the gas it is giving off means they could light on fire at any moment if they've been stored before fully drying. And where is hay commonly stored? In a barn, with an attached grain silo. And that grain silo is sometimes full of fine dust. Which, like flour, can easily explode at the smallest spark or flame.
    - slededit 10y ago
      The main ingredient is bacteria feeding on the hay, which causes an exothermic reaction. Above a certain temperature the thermophilic bacteria get happy and a runaway reaction occurs. These bacteria need moisture to survive.
      - schiffern 10y ago
        Essentially you're creating a compost pile unintentionally. This phenomenon is easy to exploit actually. Laying out "sheet mulch" with 9-12" of hay on top of an opaque layer (typically newspaper or cardboard) can greatly accelerate the production rate of soil and repair degraded soils. No tilling or digging required, the mulch retains water and cuts down evaporation, and weeds are smothered by the opaque layer. This yields high quality produce without fertilizer and with a minimum of labor. The late Bill Mollison of permaculture design describes it here (@21m): https://vimeo.com/142711756 https://vimeo.com/142711756
    - Florin_Andrei 10y ago
      Given the volumes involved, the deflagration must be monumental.
      - freehunter 10y ago
bluehawk 10y ago
About as wrong as thinking of it as being made of diamond.
- Elv13 10y ago
  Your comment is correct, but not the way you seem to think it is ;) https://www.youtube.com/watch?v=0tcP9SLKEG4 https://www.youtube.com/watch?v=0tcP9SLKEG4 Given the right conditions, carbon+oxygen is carbon+oxygen, usually resulting in a combustion.
toss1 10y ago
Not entirely wrong. As noted earlier by schiffern, charcoal has a huge surface area, and carbon fiber has a different structure with much less surface area. But, I'd still expect it to burn very nicely in the presence of concentrated oxygen. Carbon fiber, is solid fibers about 5-7 microns thick and of arbitrary length. The fiber is embedded in a matrix, typically of epoxy. A typical ratio for a high-performance part would be about 64% carbon fiber and 36% epoxy. If built properly, the epoxy or other matrix material will completely encapsulate the carbon, including a thin coating on the surfaces. That said, the first thing I'd want to do in the presence of 100% liquid oxygen is to coat the entire carbon composite to ensure that the composite and the oxygen stay apart. The epoxy itself is an organic compound, and the thickness of the coating is at most a few hundred microns (you have to be very careful sanding the surface to prep it for a more durable coating, or you'll get into the carbon). Source: I'm a carbon fiber designer and fabricator.

How wrong is it to think of "carbon composite" as "charcoal"? Because with that conceptualization, it seems like an inherent risk to store liquid oxygen in a charcoal container on a rocket ship.

hguant 10y ago

Very. This is the first thing that pops up when you google 'carbon composite': https://en.wikipedia.org/wiki/Carbon_fiber_reinforced_polymer https://en.wikipedia.org/wiki/Carbon_fiber_reinforced_polyme... I had a vision of a massive porous mass of carbon (a la water filters and the like) storing all that lox, but it seems not to be the case.

schiffern 10y ago

Charcoal has a surface area of a few acres per teaspoon (which makes sense when you look at a micrograph, since all the woody cell walls are preserved https://www.youtube.com/watch?v=kF10i39VQ4w https://www.youtube.com/watch?v=kF10i39VQ4w), whereas carbon fiber composites are impregnated with resin. Obviously all it takes is one oxygen/carbon interface to cause an explosion, as we saw. Similar to explosives, the more thoroughly mixed it is the more energetic the reaction. Pouring LOX over charcoal and soaking charcoal in LOX are very different (the first ignites vigorously, the latter explodes like a stick of dynamite). http://www.popsci.com/diy/article/2009-09/most-dangerous-way-light-grill http://www.popsci.com/diy/article/2009-09/most-dangerous-way...

azernik 10y ago
On a similar note, all kinds of materials that you wouldn't expect become very flammable with high surface area and/or pure oxygen environments. See e.g. the thermal lance, which is a very powerful cutting tool that works by running oxygen over iron (rust at high speed!). Or the very serious risk of explosions in flour mills due to high amounts of dust suspended in the air.
- freehunter 10y ago
  Yup. Growing up on a farm, it wasn't uncommon to hear of explosions in grain silos from a spark in the dust or barn fires from undried hay bales. That's right, wet hay bales can and will spontaneously combust. It sounds counter-intuitive, but wet hay bales are more dangerous than dry hay bales, because hay actually heats up as it dries. As the hay gets hotter, it starts giving off flammable gas. The heat it is generating combined with the gas it is giving off means they could light on fire at any moment if they've been stored before fully drying. And where is hay commonly stored? In a barn, with an attached grain silo. And that grain silo is sometimes full of fine dust. Which, like flour, can easily explode at the smallest spark or flame.
  - slededit 10y ago
    The main ingredient is bacteria feeding on the hay, which causes an exothermic reaction. Above a certain temperature the thermophilic bacteria get happy and a runaway reaction occurs. These bacteria need moisture to survive.
    - schiffern 10y ago
      Essentially you're creating a compost pile unintentionally. This phenomenon is easy to exploit actually. Laying out "sheet mulch" with 9-12" of hay on top of an opaque layer (typically newspaper or cardboard) can greatly accelerate the production rate of soil and repair degraded soils. No tilling or digging required, the mulch retains water and cuts down evaporation, and weeds are smothered by the opaque layer. This yields high quality produce without fertilizer and with a minimum of labor. The late Bill Mollison of permaculture design describes it here (@21m): https://vimeo.com/142711756 https://vimeo.com/142711756
  - Florin_Andrei 10y ago
    Given the volumes involved, the deflagration must be monumental.
    - freehunter 10y ago

bluehawk 10y ago

About as wrong as thinking of it as being made of diamond.

Elv13 10y ago
Your comment is correct, but not the way you seem to think it is ;) https://www.youtube.com/watch?v=0tcP9SLKEG4 https://www.youtube.com/watch?v=0tcP9SLKEG4 Given the right conditions, carbon+oxygen is carbon+oxygen, usually resulting in a combustion.

toss1 10y ago

Not entirely wrong. As noted earlier by schiffern, charcoal has a huge surface area, and carbon fiber has a different structure with much less surface area. But, I'd still expect it to burn very nicely in the presence of concentrated oxygen. Carbon fiber, is solid fibers about 5-7 microns thick and of arbitrary length. The fiber is embedded in a matrix, typically of epoxy. A typical ratio for a high-performance part would be about 64% carbon fiber and 36% epoxy. If built properly, the epoxy or other matrix material will completely encapsulate the carbon, including a thin coating on the surfaces. That said, the first thing I'd want to do in the presence of 100% liquid oxygen is to coat the entire carbon composite to ensure that the composite and the oxygen stay apart. The epoxy itself is an organic compound, and the thickness of the coating is at most a few hundred microns (you have to be very careful sanding the surface to prep it for a more durable coating, or you'll get into the carbon). Source: I'm a carbon fiber designer and fabricator.