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Latest candidate for SpaceX pad explosion
While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in the composite overwrapped pressure vessel that helium is stored in. This is how it would work. For this flight SpaceX was apparently trying to increase the degree of super-cryo chilling on the liquid oxygen, so they were pumping it even colder than normal (close to freezing point). Some of the super-chilled LOX could have gotten into the COPV and then frozen. As tank pressure went up, the solid oxygen could not be squeezed back out of the overwrap and detonated with the carbon composite wrapping. This breeched the helium pressurization tank, overpressuring the LOX tank and things go up from there. SpaceX has not confirmed that this is their leading theory (or even a theory). It is being reported as something that came out of a private conversation with Musk and SpaceX says they have a policy of not commenting on private conversations by Musk. If that's really the problem, it makes a return to flight easier. Just revert to the 'normal' amount of chilling that they used on previous flights. -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Dryden |
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Latest candidate for SpaceX pad explosion
On 18/10/2016 3:23 PM, Fred J. McCall wrote:
While they haven't confirmed it as the cause yet, the current leading candidate for the cause of the explosion is SOLID oxygen forming in the composite overwrapped pressure vessel that helium is stored in. This is how it would work. For this flight SpaceX was apparently trying to increase the degree of super-cryo chilling on the liquid oxygen, so they were pumping it even colder than normal (close to freezing point). Some of the super-chilled LOX could have gotten into the COPV and then frozen. As tank pressure went up, the solid oxygen could not be squeezed back out of the overwrap and detonated with the carbon composite wrapping. This breeched the helium pressurization tank, overpressuring the LOX tank and things go up from there. SpaceX has not confirmed that this is their leading theory (or even a theory). It is being reported as something that came out of a private conversation with Musk and SpaceX says they have a policy of not commenting on private conversations by Musk. If that's really the problem, it makes a return to flight easier. Just revert to the 'normal' amount of chilling that they used on previous flights. Customers might be less than happy with the idea that their production launch vehicle is being experimented on, though the contract may allow for that. Sylvia. |
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Latest candidate for SpaceX pad explosion
JF Mezei wrote:
On 2016-10-18 00:23, Fred J. McCall wrote: freezing point). Some of the super-chilled LOX could have gotten into the COPV and then frozen. As tank pressure went up, the solid oxygen could not be squeezed back out of the overwrap and detonated with the carbon composite wrapping. This breeched the helium pressurization tank, overpressuring the LOX tank and things go up from there. Is there a diagram somewhere ? Do you really need one? The helium pressurization tanks, wrapped in carbon composite, are inside the LOX tanks. What is "COPV" ? I said it in the original article and you cut it out. Composite Overwrapped Pressure Vessel. It's the helium tanks, but the fact that there is composite overwrapping is important. If something is solid, does it care that pressure around it is increasing? And while I am at it, are any liquids compressible ? TNT is a solid. Does it care about pressure? Yeah, press it and it makes a really big bang. H2O is at its densest at 4°C. So when its temprarture drops further it expands. Does LOX behave the same near its freezing temperature ? No. Most substances are denser in their solid phases than their liquid phases. Water, rubber, and a few other things are exceptions to this rule. It's a good thing water is. If, when solidifying, LOX expands, I could see this causing structural strain that could lead to a tank rupturing if it can't take the load. Oxygen under pressure as a solid being crushed by carbon leads to a fire. A very fast fire. One might even almost call it an explosion. What if Helium ruptured, and evaporating helium cooled the LOX into solid and then the solid expands, breaks the tank ? Once the helium tank ruptures you don't need any other explanation, since you just massively overpressured the LOX tank which blows things up. The question is why did the helium tank rupture? -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
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Latest candidate for SpaceX pad explosion
Fred J. McCall wrote:
While they haven't confirmed it as the cause yet, the current leading candidate for the cause of the explosion is SOLID oxygen forming in the composite overwrapped pressure vessel that helium is stored in. This is how it would work. For this flight SpaceX was apparently trying to increase the degree of super-cryo chilling on the liquid oxygen, so they were pumping it even colder than normal (close to freezing point). Some of the super-chilled LOX could have gotten into the COPV and then frozen. As tank pressure went up, the solid oxygen could not be squeezed back out of the overwrap and detonated with the carbon composite wrapping. This breeched the helium pressurization tank, overpressuring the LOX tank and things go up from there. SpaceX has not confirmed that this is their leading theory (or even a theory). It is being reported as something that came out of a private conversation with Musk and SpaceX says they have a policy of not commenting on private conversations by Musk. If that's really the problem, it makes a return to flight easier. Just revert to the 'normal' amount of chilling that they used on previous flights. They didn't pressurize helium tanks before loading LOX? -- Mvh./Regards, Niels Jørgen Kruse, Vanløse, Denmark |
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Latest candidate for SpaceX pad explosion
On 18/10/2016 11:31 PM, Jeff Findley wrote:
In article , ess says... On 18/10/2016 3:23 PM, Fred J. McCall wrote: While they haven't confirmed it as the cause yet, the current leading candidate for the cause of the explosion is SOLID oxygen forming in the composite overwrapped pressure vessel that helium is stored in. This is how it would work. For this flight SpaceX was apparently trying to increase the degree of super-cryo chilling on the liquid oxygen, so they were pumping it even colder than normal (close to freezing point). Some of the super-chilled LOX could have gotten into the COPV and then frozen. As tank pressure went up, the solid oxygen could not be squeezed back out of the overwrap and detonated with the carbon composite wrapping. This breeched the helium pressurization tank, overpressuring the LOX tank and things go up from there. SpaceX has not confirmed that this is their leading theory (or even a theory). It is being reported as something that came out of a private conversation with Musk and SpaceX says they have a policy of not commenting on private conversations by Musk. If that's really the problem, it makes a return to flight easier. Just revert to the 'normal' amount of chilling that they used on previous flights. Customers might be less than happy with the idea that their production launch vehicle is being experimented on, though the contract may allow for that. Sylvia, this quite often the case with SpaceX. It's still a young company and is still optimizing Falcon 9. Unfortunately, when you push the envelope like this, sometimes an "unknown unknown" bites you in the ass. Still, its customers might reasonably expect their satellites to be launched on proven hardware, operated in the proven way, with experiments involved with innovation done on hardware that isn't launching an expensive satellite. But we don't know what the contract says. Sylvia. |
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Latest candidate for SpaceX pad explosion
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