SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD (2)

[Jim]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

[The man in the can]

1st photo, an example of a "uniform" explosion, equal in all directions around the rocket.

No Roy, It wasn't an explosion on your 1st photo. It was a launch escape system activation.

[CameronD]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

[Jim]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

COPV's is not going to implode. 

[Roy_H]

The spectra was discussed at length Roy in thread 1. I'll let those posters comment on it, or you can use the search function if you are interested...

Thanks, a search for spectra, color, or explosion failed to turn up anything. The search function does allow limiting the search to SpaceX General, but not to a single thread. If someone could point me to the appropriate area I would appreciate it. Was there a consensus or conclusion? Is it confirmed to be RP1/Ox?

[Roy_H]

1st photo, an example of a "uniform" explosion, equal in all directions around the rocket.

No Roy, It wasn't an explosion on your 1st photo. It was a launch escape system activation.

Thanks, I just pulled the photo out of a search for rocket explosions.

[CameronD]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

COPV's is not going to implode.

Under any conditions?  Faulty weld + brittle fracture? High/sudden pressure differential/pressure shock??

Okay... if Jim says so it must be true.   

[Rocket Science]

The spectra was discussed at length Roy in thread 1. I'll let those posters comment on it, or you can use the search function if you are interested...

Thanks, a search for spectra, color, or explosion failed to turn up anything. The search function does allow limiting the search to SpaceX General, but not to a single thread. If someone could point me to the appropriate area I would appreciate it. Was there a consensus or conclusion? Is it confirmed to be RP1/Ox?

I use google to search NSF sometimes as its less sensitive of a search. Here is my post but others wrote a bit more but no general consensus IIRC...
post#1880
https://forum.nasaspaceflight.com/index.php?topic=30981.1880

[Targeteer]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

COPV's is not going to implode. 

With all the discussion about whether COPVs are to blame, an interesting note that they are tough enough to survive re-entry--largely intact.

http://www.satobs.org/seesat/Sep-2016/0203.html

https://ekliptika.wordpress.com/2016/09/26/roket-falcon-9-full-thrust-penerbangan-28-jatuh-di-pulau-madura/

[Jim]

Under any conditions?  Faulty weld + brittle fracture? High/sudden pressure differential/pressure shock??

Okay... if Jim says so it must be true.   

They are at higher pressure.

[mn]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

Actually I would not expect them to, at least not until they are ready to say WHY (assuming it did. I'm not saying it did, just questioning the assumption that they would have said that)

And while we are at it. Their repeated mentions of November suggests to me that they have a strong suspect root cause (with an easy fix) and think/hope maybe they can prove it in a relatively short time. (and not that I think this will happen just trying to make sense of what they are saying)

[CameronD]

Under any conditions?  Faulty weld + brittle fracture? High/sudden pressure differential/pressure shock??

Okay... if Jim says so it must be true.   

They are at higher pressure.

Unless, due to a shut valve or similar blockage of some sort in the He system, for some reason one wasn't.. but I finally found the timelime and, yes, it does seem Helium is loaded prior to LOX filling.  So I do accept and thank you for your answer, Jim.


Timeline:  If it helps others, here's a link to the timeline immersed in the previous thread.  For reference, it was reported this event happened around the T-0:08:00 mark:

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1576309#msg1576309

Now that we're onto two/three discussion threads already and with no end in sight, perhaps factual information like this could be placed somewhere the rest of us can easily find it??

[kevin-rf]

I keep seeing everyone talking about fragments going through the common bulkhead, seems to me due to the speed of sound in liquids a large pressure increase can compromise the bulkhead before any shrapnel reaches it. Remember the rupture most likely happened in a fluid, the liquid would impede and slow down the shrapnel.

[virnin]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

I readily admit I have done zero research into failure modes of aluminium lined COPVs but the LOX tank was being vented so ambient pressure couldn't have been much above 1 bar.  To implode, one would think the pressure inside the "stuck shut valve" COPV would have to be quite low, perhaps a few millibars.  The only way I see that happening is if the pre-fill, 1 bar pressure, He condensed, which it certainly isn't going to do at LOX temperatures, sub-cooled or otherwise.

[Rocket Science]

I keep seeing everyone talking about fragments going through the common bulkhead, seems to me due to the speed of sound in liquids a large pressure increase can compromise the bulkhead before any shrapnel reaches it. Remember the rupture most likely happened in a fluid, the liquid would impede and slow down the shrapnel.

True, but what was the proximity of the failure point to the common bulkhead?

[Jim]

Just a note.  In typical pressurant systems, all the tanks are ganged together.  There isn't valves on each tank. 

[kevin-rf]

Just a note.  In typical pressurant systems, all the tanks are ganged together.  There isn't valves on each tank. 

So if it is inside the LOX tank it's a pipe, flange, fitting, COPV, or interface between one or more failing suddenly?

[Johnnyhinbos]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

COPV's is not going to implode.

Under any conditions?  Faulty weld + brittle fracture? High/sudden pressure differential/pressure shock??

Okay... if Jim says so it must be true.   

Implode - pressure differential 1 bar max; explode - pressure differential 300 bar. Potential energy difference not even comparable.

[alang]

I would just like to make a point about various opinions about SpaceX's approach to it's LVs. IIRC they stated that Falcon was designed from the onset to be a "human rated" vehicle, thus from my perspective one should hold their feet to the fire to the standards they set for themselves... 2017 is not that far away for there to be "unknown, unknowns" for a vehicle to begin tests with crew aboard IMHO... Years back I stated that "I would strap my back onto an Atlas V today" given the chance to fly. Nothing has changed my opinion so far...

If only a launch vehicle was all that was needed.

[CameronD]

If it was a COPV, don't you think Spacex would have come forward with that vs just He system?

They might like to know a bit more about the event first.  eg. If it was a COPV, did it explode or implode?  There's a big difference in root cause but a similar outcome.

I readily admit I have done zero research into failure modes of aluminium lined COPVs but the LOX tank was being vented so ambient pressure couldn't have been much above 1 bar.
..............

That's not necessarily true.  To maintain the LOX as a liquid, what we are referring to as the "LOX vent" may actually be a pressure relief vent set a lot higher than 1 bar.

EDIT:  http://www.ehs.ufl.edu/programs/lab/cryogens/oxygen/