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13 hours ago, kerbiloid said:

Should the visible center of the hot gas cloud match the visible projection of the center of the explosion process?
We can see where the gas cloud breaks out through the weakest place of the hull, but not where the explosive has exploded.

There's definately failure modes that could go both ways, either exploding out from where the root cause was or bursting out from where the pressure system was the weakest.

Especially for systems of enclosed pressurized liquids (low compressibility), the overpresurization can travel very quickly within the inside of the pressure system (2km/s), so the whole inside of the system is subject to the high pressure almost instantaneously relative to normal reaction rates. Most systems I've worked with or troubleshot that have burst (hydraulics, pressure vessels, chemical equipment, etc.) wound up bursting from where the system was weakest and not from the source of the root cause. To be fair, I've thankfully managed to avoid working with systems of enclosed monopropellants, so take it with a grain of salt! The normal operational pressure of dragon's propellant systems are ~7MPa (1kpsi) which is backed up by the Helium tank, so any weak point that goes pop will cause quite the sudden resulting kaboom.

On the other hand, several of the possible root causes would explode right from the source. An example could be creating a hot spot which would both start the reaction and weaken the metals to allow the system to burst. Or something that causes a shock of pressure very suddenly on the microseconds timescales, would just explode right then and there.

So, could be either!

 

I wanted to mention because I didn't yesterday, I honestly look at the explosion as a good thing! Troubleshooting is part of the process of making something new, such as for a new computer program in beta the mantra is "There will be bugs." Teasing critical problems out of a system during testing can be difficult, so it's actually very fortunate it showed up now and didn't try to hide itself until later. They specifically run these tests to find failures before they happen for realsies, so getting it to explode in a safe and controlled condition like they did was one of the two success conditions. The true measure of success isn't whether or not they face problems (which they will), but how quickly completely and cheaply they can find the root cause and fix the problems moving forward. The alternative to discovering the occasional explosion in testing is to overengineer the system like crazy during the design phase (like STS / SLS) and this has its own issues. So for me, it's less "Oh no, there was a problem" and more "Oh good, they found something to fix." Of course I'm not the one who has to pay for all the overtime of the engineers :D

 

Edited by Cunjo Carl
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I don't tend to think of manned space capsules as something that are likely to explode violently. Sure, you expect rockets to explode... but I can't think of any examples of previous manned spacecraft (including unmanned tests and ground tests) where the capsule blew up. Even on Apollo 13 where the oxygen tank blew out the side of the service module, the capsule itself remained fine. So it's unsettling to think of sitting in a Dragon capsule that could suddenly blow up.

But I guess that's what you get when you incorporate powerful rocket engines into the manned capsule itself. 

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25 minutes ago, Brotoro said:

So it's unsettling to think of sitting in a Dragon capsule that could suddenly blow up. 

Leave alone the dragon riders...

Imagine this kaboom next to ISS.

Spoiler

Almaz kinda says "Keep ur dragons away from me".
landscape-1447437433-zak-1.jpg?resize=48

 

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36 minutes ago, sh1pman said:

Does Crew Dragon capsule have COPVs inside it? In hypergolic fuel tanks maybe?

Not inside the tanks, but the Super Dracos are pressure fed.

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7 hours ago, Brotoro said:

I don't tend to think of manned space capsules as something that are likely to explode violently. Sure, you expect rockets to explode... but I can't think of any examples of previous manned spacecraft (including unmanned tests and ground tests) where the capsule blew up. Even on Apollo 13 where the oxygen tank blew out the side of the service module, the capsule itself remained fine. So it's unsettling to think of sitting in a Dragon capsule that could suddenly blow up.

But I guess that's what you get when you incorporate powerful rocket engines into the manned capsule itself. 

Come to mention it, it's a bit surprising that there haven't been any explosions with MMH/N2O4 attitude control thrusters that I've heard of either. They've been in use since Gemini after all! I guess they have had some rather serious problems, but no explosions per say. Examples of failures include Gemini 8, Soyuz TM17 and maybe the STS-9 fire if you want to count the Hydrazine auxiliary power units. Similar problems in ground tests, I doubt we'd ever have heard of. And though I avoid talking about actual accidents, involving cabins becoming suddenly bad places...

Spoiler

 

would be the Apollo fire, the Apollo-Soyuz mishap, and Soyuz 11 .

 

I both agree with you completely, and am also coming at it from the opposite direction. I'm surprised there haven't been problems with hypergolic attitude control thrusters even more often! Go rocket scientists.

The major differences here are the higher pressure required for the LES engine as you mentioned (Dragon 2 is ~10x higher pressure than say shuttle / Soyuz) and the re-use after splashing in the ocean. I wonder if these had anything to do with it or not? In any case, sudden explosion is definitely an unsettling thought. Let's see what they do to fix it.

Something's telling me they're trying not to say anything until they know exactly what went wrong and what they're going to do about it.

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8 hours ago, tater said:

Not inside the tanks, but the Super Dracos are pressure fed.

So there are some kind of pressure vessels. One of them could explode. If the leaked video is legit, then the explosion was relatively minor, compared to the energy stored in ~1t of hypergolic fuel.

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Spoiler
1 hour ago, magnemoe said:

how to make an locomotive into an tentacle monster. 
is it more information about that event? 

Googled for pictures "boiler explosion locomotive", there are several such pictures with links.

 

Edited by kerbiloid
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I wonder if steam locomotives were intentionally designed so that the front plate was the weakest point in the pressure vessel? I mean, you don't want them to explode, but if they do explode, then that's probably the safest way for them to explode.

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