SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION

[QuantumG]

I don't care what you call it, but explaining what happened by saying "there was a sudden loss of pressure" is *not* explaining what caused that to happen. Root cause, any ideas? If not, keep looking.

[Jim]

The engine lost pressure by releasing gas, hence, there was an increase in pressure and it blew the panels off.  They were not "sucked"in. 

[meekGee]

The engine lost pressure by releasing gas, hence, there was an increase in pressure and it blew the panels off.  They were not "sucked"in. 

That's interesting, I was wondering what happened.  Do you have a source?

The formal line that I saw was that the fairing cannot sustain max-Q if there isn't a working engine under it, and so *it is inferred* that aerodynamic loads tore it apart after the engine broke.

I'd love to know if there's evidence that the engine blow out (hey - can we use "blow out"?  I like that term) knocked the fairing outwards against the flow.

But if there isn't any - why assume the opposite of what they said?

The reason I tend to believe their line is that a) why lie on such a detail, and b) if IIUC, the fuel under the fuel dome is still liquid.  Liquids don't store pressure energy very well.  (This is why you fill pressure vessels with water in burst tests)

[Jim]

The engine lost pressure by releasing gas, hence, there was an increase in pressure and it blew the panels off.  They were not "sucked"in. 

That's interesting, I was wondering what happened.  Do you have a source?

The formal line that I saw was that the fairing cannot sustain max-Q if there isn't a working engine under it, and so *it is inferred* that aerodynamic loads tore it apart after the engine broke.

I'd love to know if there's evidence that the engine blow out (hey - can we use "blow out"?  I like that term) knocked the fairing outwards against the flow.

There is nothing that says "pressure loss" in the aft compartment resulted in the loss of panels.  It is saying that pressure loss in the engine led to loss of panels.  The pressure loss in the engine is from a release of pressure and where does it go?

Read here:
http://www.nasaspaceflight.com/2012/10/dragon-iss-stay-minor-issues-falcon-9-investigation/

"The first stage issue related to Engine 1, one of nine Merlin 1Cs, after – it is understood – the fuel dome above the nozzle ruptured. The engine did not explode, but did cause the fairing that protects the engine from aerodynamic loads to rupture and fall away from the vehicle due to the engine pressure release."

Think people.  There isn't outside pressure on a surface parallel to the flow, in fact, it is the opposite, there is lower pressure.

[QuantumG]

"The first stage issue related to Engine 1, one of nine Merlin 1Cs, after – it is understood – the fuel dome above the nozzle ruptured.

Why did the fuel dome rupture?

I can play this game all day.

They haven't identified the root cause, which means it could happen again.

[dcporter]

Yay pointless semantics arguments. It exploded. It also held together to a large extent (telemetry) and disassembled itself in a planned way.

The engine lost pressure by releasing gas, hence, there was an increase in pressure and it blew the panels off.  They were not "sucked"in. 

True. But SpaceX doesn't get any extra credit since those panels were designed to blow off?

[meekGee]

"The first stage issue related to Engine 1, one of nine Merlin 1Cs, after – it is understood – the fuel dome above the nozzle ruptured.

I can play this game all day.

They haven't identified the root cause, which means it could happen again.

This is the most important question, there is no argument about that.
But while we're waiting for an answer, we're looking at what happened afterwards, just for kicks.

[meekGee]

The engine lost pressure by releasing gas, hence, there was an increase in pressure and it blew the panels off.  They were not "sucked"in. 

That's interesting, I was wondering what happened.  Do you have a source?

The formal line that I saw was that the fairing cannot sustain max-Q if there isn't a working engine under it, and so *it is inferred* that aerodynamic loads tore it apart after the engine broke.

I'd love to know if there's evidence that the engine blow out (hey - can we use "blow out"?  I like that term) knocked the fairing outwards against the flow.

There is nothing that says "pressure loss" in the aft compartment resulted in the loss of panels.  It is saying that pressure loss in the engine led to loss of panels.  The pressure loss in the engine is from a release of pressure and where does it go?

Read here:
http://www.nasaspaceflight.com/2012/10/dragon-iss-stay-minor-issues-falcon-9-investigation/

"The first stage issue related to Engine 1, one of nine Merlin 1Cs, after – it is understood – the fuel dome above the nozzle ruptured. The engine did not explode, but did cause the fairing that protects the engine from aerodynamic loads to rupture and fall away from the vehicle due to the engine pressure release."

Think people.  There isn't outside pressure on a surface parallel to the flow, in fact, it is the opposite, there is lower pressure.

I don't know what happened to the fairing, but it's definitely not a "think people" no-brainer.  I didn't invent the speculation that the fairing is supported from below by engine pressure, though I don't have a reference to the source of that.

The corner fairing sticks out of the main body cross-section quite a bit, and this was near max-Q, so I would actually expect an inwards/downwards force on it.

Anyway, it's really unimportant.  Liquid fuel came out of the dome, and either it knocked the fairing out, or the fairing collapsed.  Same difference.  Now that I realize the fuel was liquid, I don't even want to call it a blow-out, not to mention an explosion.  It is exactly what SpaceX said - loss in pressure.

(btw - a Merlin consumes ~80 lb of propellant per second, says the internet, out of which about 1/4 by mass is fuel?  If the shut-off happened within 0.1 seconds of the pressure drop-off (WAG), we're talking about 2 pounds of liquid still supplied at pressure.  And since there's no nozzle but rather a breaking wall, why would the speed of the fuel be much?)

Like I said before - unless you show a better source than SpaceX's statement, I'll continue to go by what they say, or as you call it, drinking the sweet red stuff.

And as QG keeps saying - what's really important is figuring out why the dome failed.

[Lars_J]

"The first stage issue related to Engine 1, one of nine Merlin 1Cs, after – it is understood – the fuel dome above the nozzle ruptured.

Why did the fuel dome rupture?

I can play this game all day.

They haven't identified the root cause, which means it could happen again.

Correction, they have not *announced* that they have found the root cause. There is significant difference. They do not need to release any more info to the public than they have to, and they certainly won't release more info then they have to if they feel that such information would be used against them - if that is the case. As long as NASA is happy, we'll just have to be happy with what we get.

[aero]

Well, this is a speculation thread so why don't we speculate about why the dome might have failed? The answer we have been given is somewhat circular, it is:

The operational lifetime of the dome due to testing and flight was exceeded by the time on the engine.

Or, the time on the engine, due to testing and flight, exceeded the operational lifetime of the dome.

Since no one flys an engine that has exceeded its design lifetime, the failure seems to have resulted from the difference between "operational" and "design" lifetimes.

[Jim]

Like I said before - unless you show a better source than SpaceX's statement, I'll continue to go by what they say, or as you call it, drinking the sweet red stuff.

They haven't said anything.  Also, no one has said only fuel was released.

This is why your posts have less credibility

[peter-b]

They haven't said anything.  Also, no one has said only fuel was released.

This is why your posts have less credibility

Just as much credibility as your claims that SpaceX are deliberately and purposefully lying in their press statements, Jim.

[go4mars]

Liquid fuel came out of the dome... Now that I realize the fuel was liquid... It is exactly what SpaceX said - loss in pressure.

It seems to me that a fluid was liberated from the higher pressure fuel dome to the relatively lower pressure area outside of the fuel dome (thus increasing the pressure of the area outside of the fuel dome).  This increase in pressure in the area outside of the fuel dome caused a fluid liberation event to the lower pressure area outside of the engine shroud. 

Just to be `that guy` because I feel the semantics are very unimportant here:  The best technical terms are `Rapid Unexpected Fluid Liberation Event (RUFLE)` or `Pressure Always from Higher to Lowest Through Ruptures`(PAHLTR). 

Anyway, it's really unimportant.

[Jim]

They haven't said anything.  Also, no one has said only fuel was released.

This is why your posts have less credibility

Just as much credibility as your claims that SpaceX are deliberately and purposefully lying in their press statements, Jim.

Please point out where I said they are lying. 

[JBF]

Everyone we've been through this whole conversation before, do we have to repeat it?

[kevin-rf]

Personally, I think Jim doing a wonderful job explaining what happened.

So if you have thrown your diner in a pressure cooker and the little pressure relief valve clogs, when the fuel dome, ...eeer lid fly's off coating your entire kitchen with diner, do you call it the lid flying off, or something else.

This is the same thing that is going here, the fuel dome did something similar (except you had torn metal), the word being used is failed, just like a pressure cooker lid flying off, the word failed under values how nasty this failure is. Very high pressure liquids (Kero and LOX) where released in large quantities inside the engine compartment. The loss of pressure was sensed and the turbo shut down, preventing an overspeed and an even worse RUD.

What has not been answered (and probably not possible without recovery, hence a lack of root cause) was what section of the fuel dome failed. Did the wall on it fail somewhere, did the weld between it and the combustion chamber fail dropping the whole combustion chamber in the ocean, ect? We do not know, SpaceX has said they have telemetry from after the event, does that mean all the sensors remained working, including pressure sensors on the combustion chamber, hence major parts did not fall off?

[kevin-rf]

btw. Jim, I like the balloon analogy.

[mlindner]

Personally, I think Jim doing a wonderful job explaining what happened.

So if you have thrown your diner in a pressure cooker and the little pressure relief valve clogs, when the fuel dome, ...eeer lid fly's off coating your entire kitchen with diner, do you call it the lid flying off, or something else.

This is the same thing that is going here, the fuel dome did something similar (except you had torn metal), the word being used is failed, just like a pressure cooker lid flying off, the word failed under values how nasty this failure is. Very high pressure liquids (Kero and LOX) where released in large quantities inside the engine compartment. The loss of pressure was sensed and the turbo shut down, preventing an overspeed and an even worse RUD.

What has not been answered (and probably not possible without recovery, hence a lack of root cause) was what section of the fuel dome failed. Did the wall on it fail somewhere, did the weld between it and the combustion chamber fail dropping the whole combustion chamber in the ocean, ect? We do not know, SpaceX has said they have telemetry from after the event, does that mean all the sensors remained working, including pressure sensors on the combustion chamber, hence major parts did not fall off?

I think we all mostly agree with this. You state you agree with Jim, but Jim keeps stating other more extreme things though.

[Jim]

but Jim keeps stating other more extreme things though.

What other more extreme things?

[meekGee]

Personally, I think Jim doing a wonderful job explaining what happened.

So if you have thrown your diner in a pressure cooker and the little pressure relief valve clogs, when the fuel dome, ...eeer lid fly's off coating your entire kitchen with diner, do you call it the lid flying off, or something else.

This is the same thing that is going here, the fuel dome did something similar (except you had torn metal), the word being used is failed, just like a pressure cooker lid flying off, the word failed under values how nasty this failure is. Very high pressure liquids (Kero and LOX) where released in large quantities inside the engine compartment. The loss of pressure was sensed and the turbo shut down, preventing an overspeed and an even worse RUD.

What has not been answered (and probably not possible without recovery, hence a lack of root cause) was what section of the fuel dome failed. Did the wall on it fail somewhere, did the weld between it and the combustion chamber fail dropping the whole combustion chamber in the ocean, ect? We do not know, SpaceX has said they have telemetry from after the event, does that mean all the sensors remained working, including pressure sensors on the combustion chamber, hence major parts did not fall off?

First, it matters a whole lot whether the cooker was 90% full of water or 10% full of water.

The pressure dome was 100% full of liquid propellant, which is the best case.

Second, when I was a kid, I was next to a pressure cooker doing exactly that. Let me tell you - it did not explode, not even close.  It made a hell of a mess on the hood, but did not even knock it away.