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

[edkyle99]

IMO the only part of the high pressure helium system that has the energetic potential to pop the upper stage in less than 1/10th of a second is a pressurized COPV letting go.

The strut incident destroyed the second stage in flight. If we believe the strut was at fault, a COPV failure was not needed to breech the the second stage.

Matthew

The difference was that the CRS-7 stage didn't disintegrate suddenly, as did this one.

 - Ed Kyle

[A12]

They still want to fly again in November which sounds optimistic.

Yeah. I would estimate 6 to 9 months if it's a quality control issue, 9 to 12 month if they have to redesign something or fabricate a long lead item.

I would say November ... 2017.

[Wolfram66]

People keep saying COPV.  The SpaceX statement doesn't say "COPV".  It says "cryogenic Helium system".  There is way more to this system than just the tanks (and the struts that support them.)  There is lots of piping, valves, regulators, and a supply system from the TEL.

Edit: correct quote from SpaceX

  http://www.spacex.com/news/2016/09/01/anomaly-updates
it actually says "large breach in the cryogenic helium system of the second stage liquid oxygen tank took place" IDK if this includes or excludes GSE or TEL malfunctions. It does say "of the..." not "in the..." so the focus could be ambiguous

[Dudely]

IMO the only part of the high pressure helium system that has the energetic potential to pop the upper stage in less than 1/10th of a second is a pressurized COPV letting go.

The strut incident destroyed the second stage in flight. If we believe the strut was at fault, a COPV failure was not needed to breech the the second stage.

Matthew

The difference was the the CRS-7 stage didn't disintegrate suddenly, as did this one.

 - Ed Kyle

In CRS-7 the COPV came loose. This means it ripped off the piping connecting it to the system and started to quickly leak into the tank.

AMOS-6 was different. If a COPV is breached then it would release all of its helium at once and the tank would fail very catastrophically, very quickly.

[ccicchitelli]

I'm not sure.  Couldn't a burst in the high pressure plumbing responsible for charging up those COPVs result in a breach in the common bulkhead of sufficient energy to allow enough mixing between LOX and RP-1 and make a nice boom?

This has been a hunch of mine from the get go, especially since the tanks in theory weren't completely filled yet.

[Jim]

.
The flash was chunks of the fitting going thru the side of the tank and the AL/LOX flash fire that resulted...

It was a RP-1/LOX fire, not AL

Call it RP-1/LOX/AL fire then... my opinion... 

Not Data supports that claim

[wannamoonbase]

I'm not sure.  Couldn't a burst in the high pressure plumbing responsible for charging up those COPVs result in a breach in the common bulkhead of sufficient energy to allow enough mixing between LOX and RP-1 and make a nice boom?

This has been a hunch of mine from the get go, especially since the tanks in theory weren't completely filled yet.

If there was a break in the plumbing of the He system, that was immersed in the subcooled LOx and the gaseous He was at a temperature that would help flash the subcooled LOx to a gas to a vapor it would have a multiplier affect on over pressuring the tank.

There are enough brains on the investigation that they could crunch through the numbers on the level of LOx, initial tank pressure, burst pressure and how much much of a flow rate of He would have been needed to burst in the less than 93 milliseconds.

The COPVs maybe fine, it wasn't the COPV that failed on CRS-7, it was the strut and in this case it may not be the bottle either.  Immersing a system into a subcooled cryogenic system may need to be revisited however. 

[wtrix]

.
The flash was chunks of the fitting going thru the side of the tank and the AL/LOX flash fire that resulted...

It was a RP-1/LOX fire, not AL

Call it RP-1/LOX/AL fire then... my opinion... 

Not Data supports that claim

I support that statement. LOX & Al fire is bright white due to extreme temperature. Also a lot of white smoke gets produced. This is completely unlike the relatively low temperature combustion that we saw.

[ElGuapoGuano1]

When I first read that update on Twitter, my initial thought was damn it, Jim was right. But just from re-reading the wording, I'm not convinced the COPV did pop, perhaps like was written above it was a fitting or some other piece of the plumbing. IF it really was the COPV failing, it's hard for me to believe that the November time frame would even be discussed.

[Oersted]

Anyone of those changes is IMO going to eat into F9's performance.

F9 performance has been significantly improved over the various iterations of the rocket. A complete redesign of the helium pressurization system will perhaps eat into it, but the performance may well remain within the original F9 specs.

[glennfish]

I'm not sure.  Couldn't a burst in the high pressure plumbing responsible for charging up those COPVs result in a breach in the common bulkhead of sufficient energy to allow enough mixing between LOX and RP-1 and make a nice boom?

This has been a hunch of mine from the get go, especially since the tanks in theory weren't completely filled yet.

If there was a break in the plumbing of the He system, that was immersed in the subcooled LOx and the gaseous He was at a temperature that would help flash the subcooled LOx to a gas to a vapor it would have a multiplier affect on over pressuring the tank.

There are enough brains on the investigation that they could crunch through the numbers on the level of LOx, initial tank pressure, burst pressure and how much much of a flow rate of He would have been needed to burst in the less than 93 milliseconds.

The COPVs maybe fine, it wasn't the COPV that failed on CRS-7, it was the strut and in this case it may not be the bottle either.  Immersing a system into a subcooled cryogenic system may need to be revisited however.

If any part of the helium system failed under pressure, see this comment about how fast loose or fragmenting things would try to move  (ignore the FAE commentary.  Not needed):
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583947#msg1583947

Remember your kinetic energy formula to find the energy for anything that's moving as a result of the failure to get up to ignition temperature:  KE = 1/2 (M * (V * V)) 

in one video frame time you can easily get 15 feet of object motion for bashing, mixing and booming.  You don't need a lot of mixed RP1 & LOX to get that boom started as seen in frame 1.

IMHO whatever happened after the "system failed under pressure" was really really fast.

The claim that they have 90 ms of data prior to loss of data would suggest to me that they would have 75 or more ms of data of whatever lead up to the event, assuming the data loss occurred within 16 ms of the breach.

What is intriguing to me is 90 ms is a long time, the last 5 frames in the USLR video don't show anything unusual, but could be covering the time line from onset to failure.

[rsdavis9]

I dont believe a complete redesign will be necessary.
Look at the record.
Yes they have had problems with the design.
Tanks are repeatedly pressurized with no long term failures.
S1 has had a lot of flight experience. Repeated use with no signs of wear.

They probably has some flaw which is escaping detection in testing. They will fix and continue to fly with this design which has a long(for them) flight history.

Looking forward(or backwards) they will probably never go with a helium pressurization system if they can avoid it.  Fix what you have and fly what you have.

[Space Ghost 1962]

What is supported is a rapid combustion event. By the time it is visible, it's clearly RP1/LOX.

There are two suggestions to support rapid combustion
 1. COPV failure (delamination? fitting tearout?) that allowed a high volume, high pressure event that caused loss of integrity (seams? common bulkhead) of the LOX tank
 2. Al/Ox fire consuming Al

In both cases presumption of ignition event, and we don't have an obvious Al/Ox fire to see.

We can't tell the early stages of the fire which might have all consumed its trigger.

Readout of pressurization system might tell use the ramp rate of its components, pressure of the LOX/RP1 tanks would give us spiking/shearing impulse, so we'd know the scale of the event.

1) has fewer things to go all at once thus more likely (but still don't have ignition source cause)
2) has more dependencies (again ignition, ramp, total consumption of Al before breach).

As to fix/consequences, nobody knows nothing, so irrelevant at this point.

Thank you SX for at least limiting it down to the pressurization system.

[Jim]

I support that statement. LOX & Al fire is bright white due to extreme temperature. Also a lot of white smoke gets produced. This is completely unlike the relatively low temperature combustion that we saw.

Still unsupported.  And you are just basing it from one camera view.  The camera just was over saturated and no smoke but white vapors.

[Jim]

When I first read that update on Twitter, my initial thought was damn it, Jim was right. But just from re-reading the wording, I'm not convinced the COPV did pop, perhaps like was written above it was a fitting or some other piece of the plumbing. IF it really was the COPV failing, it's hard for me to believe that the November time frame would even be discussed.

I said over-pressurization event.  I didn't limit myself to COPV

[Jim]

IDK if this includes or excludes GSE or TEL malfunctions. It does say "of the..." not "in the..." so the focus could be ambiguous

It does exclude.  GSE or TEL is not part of it, it is part of the GSE

[SWGlassPit]

I'm not sure.  Couldn't a burst in the high pressure plumbing responsible for charging up those COPVs result in a breach in the common bulkhead of sufficient energy to allow enough mixing between LOX and RP-1 and make a nice boom?

This has been a hunch of mine from the get go, especially since the tanks in theory weren't completely filled yet.

If there was a break in the plumbing of the He system, that was immersed in the subcooled LOx and the gaseous He was at a temperature that would help flash the subcooled LOx to a gas to a vapor it would have a multiplier affect on over pressuring the tank.

There are enough brains on the investigation that they could crunch through the numbers on the level of LOx, initial tank pressure, burst pressure and how much much of a flow rate of He would have been needed to burst in the less than 93 milliseconds.

The COPVs maybe fine, it wasn't the COPV that failed on CRS-7, it was the strut and in this case it may not be the bottle either.  Immersing a system into a subcooled cryogenic system may need to be revisited however.

If any part of the helium system failed under pressure, see this comment about how fast loose or fragmenting things would try to move  (ignore the FAE commentary.  Not needed):
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583947#msg1583947

Remember your kinetic energy formula to find the energy for anything that's moving as a result of the failure to get up to ignition temperature:  KE = 1/2 (M * (V * V)) 

in one video frame time you can easily get 15 feet of object motion for bashing, mixing and booming.  You don't need a lot of mixed RP1 & LOX to get that boom started as seen in frame 1.

IMHO whatever happened after the "system failed under pressure" was really really fast.

The claim that they have 90 ms of data prior to loss of data would suggest to me that they would have 75 or more ms of data of whatever lead up to the event, assuming the data loss occurred within 16 ms of the breach.

What is intriguing to me is 90 ms is a long time, the last 5 frames in the USLR video don't show anything unusual, but could be covering the time line from onset to failure.

Is the assumption valid that the cessation of data coincided with the emergence of the fireball?  Why couldn't the data cease, say, 30-40 ms after the fireball appears?  Or even longer?  The data doesn't stop just because the tank gets a big hole in it -- either the avionics equipment sending the telemetry or the transmission path has to fail.  There's no reason to assume that happened simultaneously with the tank breach.

[wtrix]

I support that statement. LOX & Al fire is bright white due to extreme temperature. Also a lot of white smoke gets produced. This is completely unlike the relatively low temperature combustion that we saw.

Still unsupported.  And you are just basing it from one camera view.  The camera just was over saturated and no smoke but white vapors.

I supported your position Jim, not the position, that there was a LOX/Al fire :-)

[Jim]

  There's no reason to assume that happened simultaneously with the tank breach.

Yes it does, because the avionics sits on top of the tanks and all data and power harnesses run along side of it.

[feynmanrules]

I agree- the timing of this update most likely isn't that they just discovered/confirmed this info and are racing to make sure everybody is informed on friday night.   They've probably known most if not all of this before today.   I'd imagine that even if they did have strong indication of what process failed to allow this event, that they wouldn't announce it w/out buy in from major customers like spacecom, ses, iridium, nasa, etc.     all takes time.   that they're reiterating nov is interesting in this context.

On the other, I think that if they had any level of confidence that a specific failure was the root cause they would have mentioned that in their update.

That isn't the way PR works. You say just enough to update folks, but not get ahead of the investigation team. There is a reason Elon isn't out their tweeting updates to the same extent like the last time (CRS-7). He is learning to let his communication team take the lead.

They will finalize the results when the official report comes out. From the sound of it, that could be in the next couple months. If RTF November/December is really in the cards.