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

[JohnFornaro]

Among the COPV expert's statements in the SpaceNews article, he said, "The kerosene needs to be pulverized, such as in a spray, to ignite."

I thought that this particular "explanation" had no meaning, knowing about kerosene heaters and lanterns.  But then I saw Fred's comment:

When the helium pressure surged (hammered), the pinched-off pressurized liquid may have flash-boiled and increased the temperature within the channel to the ignition point (or the pressure within the channel to a bubble burst point), rupturing a bullet-sized hole in the bottle which rapidly unraveled and/or burned.

If the kero got frozen solid, then it would need to be "pulverized".  But how does the temperature rise from that of LOX to the flash point of kero?

"The flash point of kerosene is between 37 and 65 °C (100 and 150 °F), and its autoignition temperature is 220 °C (428 °F). The pour point of kerosene depends on grade, with commercial aviation fuel standardized at −47 °C (−53 °F)."

https://en.wikipedia.org/wiki/Kerosene

[garidan]

Among the COPV expert's statements in the SpaceNews article, he said, "The kerosene needs to be pulverized, such as in a spray, to ignite."

I thought that this particular "explanation" had no meaning, knowing about kerosene heaters and lanterns.  But then I saw Fred's comment:

When the helium pressure surged (hammered), the pinched-off pressurized liquid may have flash-boiled and increased the temperature within the channel to the ignition point (or the pressure within the channel to a bubble burst point), rupturing a bullet-sized hole in the bottle which rapidly unraveled and/or burned.

If the kero got frozen solid, then it would need to be "pulverized".  But how does the temperature rise from that of LOX to the flash point of kero?

"The flash point of kerosene is between 37 and 65 °C (100 and 150 °F), and its autoignition temperature is 220 °C (428 °F). The pour point of kerosene depends on grade, with commercial aviation fuel standardized at −47 °C (−53 °F)."

https://en.wikipedia.org/wiki/Kerosene

In this scenario you don't burn kero you burn carbonio fiber and lox. Anyway a copv making an hole in the lox/kero bulkhead is enough to start a burst

Inviato dal mio XT1032 utilizzando Tapatalk

[Paul_G]

If the kero got frozen solid, then it would need to be "pulverized".  But how does the temperature rise from that of LOX to the flash point of kero?

"The flash point of kerosene is between 37 and 65 °C (100 and 150 °F), and its autoignition temperature is 220 °C (428 °F). The pour point of kerosene depends on grade, with commercial aviation fuel standardized at −47 °C (−53 °F)."

https://en.wikipedia.org/wiki/Kerosene

As I understand it, its not the Kerosene that is freezing. The COPV is in the sub cooled oxygen. If I read the current thought process correctly, the sub cooled liquid oxygen seeped into the COPV structure, where the sudden change in temperatures brought about by the new loading procedure caused the oxygen to freeze, and then when the pressures on the COPV materials increased, the frozen oxygen broke the COPV fibres, causing the COPV to fail quite energetically.

My chemistry is not good enough to explain whether the COPV fibers actually ignited with this release of energy, or whether they just punched though the common bulkhead to the kerosene with enough energy to pulverize the kerosene so it in turn ignited.


Rgds

Paul

[edkyle99]

Today's story by Stephen Clark included the following.  I'm not sure I've seen this written down in a news report until now.

http://spaceflightnow.com/2016/10/31/spacex-hopes-procedure-fix-can-allow-falcon-9-launches-to-resume/
"A Falcon 9 launch failure in June 2015 was most likely caused when a strut holding one of the helium tanks broke off in flight, according to SpaceX. The company could not determine the strut issue was the definite cause of that failure, and sources said NASA’s independent review of the mishap — which was carrying NASA cargo to the space station — was also unable to definitively identify the problem that led to the Falcon 9’s disintegration in flight.

NASA’s inquiry of last year’s Falcon 9 failure still has not been released."

 - Ed Kyle

[woods170]

Today's story by Stephen Clark included the following.  I'm not sure I've seen this written down in a news report until now.

http://spaceflightnow.com/2016/10/31/spacex-hopes-procedure-fix-can-allow-falcon-9-launches-to-resume/
"A Falcon 9 launch failure in June 2015 was most likely caused when a strut holding one of the helium tanks broke off in flight, according to SpaceX. The company could not determine the strut issue was the definite cause of that failure, and sources said NASA’s independent review of the mishap — which was carrying NASA cargo to the space station — was also unable to definitively identify the problem that led to the Falcon 9’s disintegration in flight.

NASA’s inquiry of last year’s Falcon 9 failure still has not been released."

 - Ed Kyle

I wonder where that came from. Gwynne and Elon both specifically stated: "The strut broke". They didn't say: "We think the strut broke, but are not 100% sure".

[guckyfan]

Today's story by Stephen Clark included the following.  I'm not sure I've seen this written down in a news report until now.

http://spaceflightnow.com/2016/10/31/spacex-hopes-procedure-fix-can-allow-falcon-9-launches-to-resume/
"A Falcon 9 launch failure in June 2015 was most likely caused when a strut holding one of the helium tanks broke off in flight, according to SpaceX. The company could not determine the strut issue was the definite cause of that failure, and sources said NASA’s independent review of the mishap — which was carrying NASA cargo to the space station — was also unable to definitively identify the problem that led to the Falcon 9’s disintegration in flight.

NASA’s inquiry of last year’s Falcon 9 failure still has not been released."

 - Ed Kyle

I wonder where that came from. Gwynne and Elon both specifically stated: "The strut broke". They didn't say: "We think the strut broke, but are not 100% sure".

The strut broke. There is no doubt about it. Not with SpaceX, not with NASA. NASA just thinks the reason why the strut broke is not with absolute certainty a bad strut. The possibility that SpaceX made a mistake while installing it, cannot be ruled out.

[Fred Bonyea]

Especially if this was not operator error but a planned experiment.

Loading a flight vehicle with a payload on top is probably not the time they'd want to be experimenting.

An alternative possibility to "operator error" is that they had to red-line (ie make an on-the-spot change to) the loading procedure because of, say, a stuck valve or other GSE problem that they had to work around, possibly resulting in performing some steps of the procedure out of the normal sequence.

That's something that would require engineering approval, but the cognizant engineer may have decided the change in procedure was minor enough to sign off on. And then they found out the hard way that what they thought was an insignificant change in procedure affected the COPV/LOX interaction in an unexpected way.

This would be a 'best case' scenario for SpaceX, though not much so for whoever did the buy-off.

We will know more when they release the conditions under which they have been able to duplicate bottle failure in Texas. If it is only when temperatures on the bottle drop below the freezing point of LOX; they may be able to proceed with procedure changes only. If the bottles occasionally fail at higher temperatures when liquid sloshing and such are thermally straining the COPV, it is much more problematic.

COPVs can 'let go' and fail with an extremely rapid pressure release, but they can also fail ballistically. If a breach occurs near the polar boss, a nozzle effect can occur. A 'nozzle' breach on the forward end would propel the bottle downward, crushing weak support struts. In this scenario, we now have two failures with essentially the same root cause.

[Fred Bonyea]

Among the COPV expert's statements in the SpaceNews article, he said, "The kerosene needs to be pulverized, such as in a spray, to ignite."

I thought that this particular "explanation" had no meaning, knowing about kerosene heaters and lanterns.  But then I saw Fred's comment:

When the helium pressure surged (hammered), the pinched-off pressurized liquid may have flash-boiled and increased the temperature within the channel to the ignition point (or the pressure within the channel to a bubble burst point), rupturing a bullet-sized hole in the bottle which rapidly unraveled and/or burned.

If the kero got frozen solid, then it would need to be "pulverized".  But how does the temperature rise from that of LOX to the flash point of kero?

"The flash point of kerosene is between 37 and 65 °C (100 and 150 °F), and its autoignition temperature is 220 °C (428 °F). The pour point of kerosene depends on grade, with commercial aviation fuel standardized at −47 °C (−53 °F)."

https://en.wikipedia.org/wiki/Kerosene

As Garidan stated, the fuel source is the bottle itself. In high pressure oxygen-rich environments, a pinpoint of carbon fiber heated to the ignition point will propagate a flame front like cordite. The reason is that the combustion gas that would rapidly expand and draws of heat away at lower pressures is cloistered near the source, trapping much more thermal energy.

Elon has stated that they were puzzled because there was no apparent source of ignition. This implies that they may have evidence that the COPV ignited before it burst. Oxygen trapped in a composite channel that is subjected to a gas hammer will reach ignition temperatures if the compression ratio is greater than ~15:1, even when it is supercooled. (O2 @ 50deg K and 60 psi hammered to 2000 psi would heat to ~1500 k)

[joncz]

We will know more when they release the conditions under which they have been able to duplicate bottle failure in Texas. If it is only when temperatures on the bottle drop below the freezing point of LOX; they may be able to proceed with procedure changes only. If the bottles occasionally fail at higher temperatures when liquid sloshing and such are thermally straining the COPV, it is much more problematic.

COPVs can 'let go' and fail with an extremely rapid pressure release, but they can also fail ballistically. If a breach occurs near the polar boss, a nozzle effect can occur. A 'nozzle' breach on the forward end would propel the bottle downward, crushing weak support struts. In this scenario, we now have two failures with essentially the same root cause.

It seems to me that many people are reading into SpaceX's update.  Nowhere have they said they've reproduced the issue in-situ in a 2nd stage.  They've only said they've caused COPVs to fail.

[kevin-rf]

I wonder if the carbon fiber could be the ignition source.

When a nylon climbing rope fails under load it will also put out a few puffs of smoke at the failure point as the nylon fibers slide past each other. Trust me, it looks like smoke, smells like smoke, and the failed area will have melt damage. 

While carbon fiber is not the same as nylon fiber, I do wonder if there is enough friction between fibers that as the COPV failed and the fibers slide they will generate enough localized heating to ignite in a LOX rich environment.

While not a great videos, watch the eight on a bight at the top of the test rigs... You can see the smoke a fraction of a second before failure.

[baldusi]

Today's story by Stephen Clark included the following.  I'm not sure I've seen this written down in a news report until now.

http://spaceflightnow.com/2016/10/31/spacex-hopes-procedure-fix-can-allow-falcon-9-launches-to-resume/
"A Falcon 9 launch failure in June 2015 was most likely caused when a strut holding one of the helium tanks broke off in flight, according to SpaceX. The company could not determine the strut issue was the definite cause of that failure, and sources said NASA’s independent review of the mishap — which was carrying NASA cargo to the space station — was also unable to definitively identify the problem that led to the Falcon 9’s disintegration in flight.

NASA’s inquiry of last year’s Falcon 9 failure still has not been released."

 - Ed Kyle

I wonder where that came from. Gwynne and Elon both specifically stated: "The strut broke". They didn't say: "We think the strut broke, but are not 100% sure".

The strut broke. There is no doubt about it. Not with SpaceX, not with NASA. NASA just thinks the reason why the strut broke is not with absolute certainty a bad strut. The possibility that SpaceX made a mistake while installing it, cannot be ruled out.

Root cause for the CRS-7 failure was probably a process issue. It's quite probable that everybody agrees that the strut did, in fact, broke. They might even agree that it was quite probably a strut with inferior materials. What they might discuss is why such a strut was able to get there.
I wonder, but may be SpaceX thinks that the root cause was not having acceptance testing for individual parts, and once implemented the root cause is solved. And may be the NASA engineers think that the root cause was a pervasive attitude towards reducing costs without correctly addressing the risks. May be the issue lays there?

[woods170]

Today's story by Stephen Clark included the following.  I'm not sure I've seen this written down in a news report until now.

http://spaceflightnow.com/2016/10/31/spacex-hopes-procedure-fix-can-allow-falcon-9-launches-to-resume/
"A Falcon 9 launch failure in June 2015 was most likely caused when a strut holding one of the helium tanks broke off in flight, according to SpaceX. The company could not determine the strut issue was the definite cause of that failure, and sources said NASA’s independent review of the mishap — which was carrying NASA cargo to the space station — was also unable to definitively identify the problem that led to the Falcon 9’s disintegration in flight.

NASA’s inquiry of last year’s Falcon 9 failure still has not been released."

 - Ed Kyle

I wonder where that came from. Gwynne and Elon both specifically stated: "The strut broke". They didn't say: "We think the strut broke, but are not 100% sure".

The strut broke. There is no doubt about it. Not with SpaceX, not with NASA. NASA just thinks the reason why the strut broke is not with absolute certainty a bad strut. The possibility that SpaceX made a mistake while installing it, cannot be ruled out.

The point is that a journalist, Stephen Clark, goes about saying that SpaceX "could not determine the strut issue was the definite cause of that failure". That is directly contradicting statements from both Elon and Gwynne pointing to a broken strut as THE definite cause of the CRS-7 failure.
So, once again: I wonder where Stephen Clark got this from.

[Stephen GW]

Today's story by Stephen Clark included the following.  I'm not sure I've seen this written down in a news report until now.

http://spaceflightnow.com/2016/10/31/spacex-hopes-procedure-fix-can-allow-falcon-9-launches-to-resume/
"A Falcon 9 launch failure in June 2015 was most likely caused when a strut holding one of the helium tanks broke off in flight, according to SpaceX. The company could not determine the strut issue was the definite cause of that failure, and sources said NASA’s independent review of the mishap — which was carrying NASA cargo to the space station — was also unable to definitively identify the problem that led to the Falcon 9’s disintegration in flight.

NASA’s inquiry of last year’s Falcon 9 failure still has not been released."

 - Ed Kyle

I wonder where that came from. Gwynne and Elon both specifically stated: "The strut broke". They didn't say: "We think the strut broke, but are not 100% sure".

The strut broke. There is no doubt about it. Not with SpaceX, not with NASA. NASA just thinks the reason why the strut broke is not with absolute certainty a bad strut. The possibility that SpaceX made a mistake while installing it, cannot be ruled out.

The point is that a journalist, Stephen Clark, goes about saying that SpaceX "could not determine the strut issue was the definite cause of that failure". That is directly contradicting statements from both Elon and Gwynne pointing to a broken strut as THE definite cause of the CRS-7 failure.
So, once again: I wonder where Stephen Clark got this from.

Not quite true.

In a talk Gwynne gave at APSCC 2016 she said:

Based on accelerometer data we knew exactly where the failure occurred. And the only thing in that area was a strut and we also had some of these purchased components in inventory and they did not pass screening. So: Do you know 100 percent? No. Do you know 99.9 percent? Yes. I believe the Air Force and NASA agreed with us, I’m pretty sure.

http://spacenews.com/spacexs-shotwell-on-falcon-9-inquiry-discounts-for-reused-rockets-and-silicon-valleys-test-and-fail-ethos/

[ZachS09]

Because the possible cause of the explosion has to do with the helium loading process, do you think that the reason of this cause can be linked to human error? I think so, but this "human error" was most likely unintentional to cause an explosion.

[rsdavis9]

Because the possible cause of the explosion has to do with the helium loading process, do you think that the reason if this cause can be linked to human error? I think so, but this "human error" was most likely unintentional to cause an explosion.

Engineers didn't forsee a problem with sub cooled LOX and copv helium tanks.
Is that human error?
I think it is SOP for rockets.
Now does spacex always experiment? Yes.
Do they experiment too much?

I personally think this is the growing pains of a launch vehicle. The more they explore the limits the safer the vehicle will be in the long run.

Also all of this "exploration" helps significantly in the design of the next vehicle(ITS).

[Jim]

I personally think this is the growing pains of a launch vehicle. The more they explore the limits the safer the vehicle will be in the long run.

Not really, there are limits that don't need to be explored.

[mn]

I personally think this is the growing pains of a launch vehicle. The more they explore the limits the safer the vehicle will be in the long run.

Not really, there are limits that don't need to be explored.

I have a broken lamp at home, my little children were experimenting to see how far they can push it before it falls over 

[mn]

According to Peter B. de Selding's tweet to this article:

http://spacenews.com/inmarsat-juggling-two-launches-says-spacex-to-return-to-flight-in-december/

SpaceX has found the root cause and is returning to flight in December.

“SpaceX has obviously spent some time investigating the reasons behind their recent launch failure,” Inmarsat Chief Executive Rupert Pearce said in a conference call with investors. “We believe they now have found a root cause that is fixable quite easily and quite quickly. So they should be able to return to flight in December.”

He's quoting Rupert Pearce, so the question is: is this just a slightly more optimistic take on the latest spacex public statements? or does he have additional definitive info that is not public yet?

[woods170]

According to Peter B. de Selding's tweet to this article:

http://spacenews.com/inmarsat-juggling-two-launches-says-spacex-to-return-to-flight-in-december/

SpaceX has found the root cause and is returning to flight in December.

“SpaceX has obviously spent some time investigating the reasons behind their recent launch failure,” Inmarsat Chief Executive Rupert Pearce said in a conference call with investors. “We believe they now have found a root cause that is fixable quite easily and quite quickly. So they should be able to return to flight in December.”

He's quoting Rupert Pearce, so the question is: is this just a slightly more optimistic take on the latest spacex public statements? or does he have additional definitive info that is not public yet?

Wouldn't be the first time that the status of a SpaceX failure investigation went public via non-SpaceX channels. Something similar happened during the CRS-7 investigation. SpaceX keeps it's customers well informed but Elon has no direct control over what those customers let "fly" in public statements.

[Space Ghost 1962]

Keep in mind that there are reasons why sensible designers don't push LV design too far in certain directions. You tempt the unknown. Which often bites back.

You are supposed to be responsible for all of it holding together, not just "most of it".

To many SX is far too caviler in adding blind risk into routine operation. So they aren't enthusiastic about "agile development" because it seems like "irresponsible" at times.

Its true that SX is getting further/faster in novel LV/systems.

Also true that it hasn't helped them approach Atlas V reliability as a service provider.

Suggest that to do true agile development at first class provider levels takes skills that SX has yet to demonstrate.

Congrats to the SX LV, ops, and qualification teams for a magnificent job in working this issue so fast.

Also looking forward to seeing that the last of the helium pressurization system anomalies are truly and finally addressed with this root cause and remedy.