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

[kevin-rf]

I thought it was a sudden pressure loss...

[JBF]

That last semi-official word was a sudden pressure loss in the engine which caused an automatic shutdown. With the engine venting into the engine compartment the overpressure panels blew. As this happened near max-q one of the fairings broke free.

[Jim]

Yep, the flavored drink mix consumption is in full till. 
I frequently used the term "sudden pressure loss" when describing a balloon that instantly no long holds air.

[mlindner]

Yep, the flavored drink mix consumption is in full till. 
I frequently used the term "sudden pressure loss" when describing a balloon that instantly no long holds air.

Take a look at the article Chris just posted. http://www.nasaspaceflight.com/2013/01/spacex-win-contract-ahead-crs-2-mission/

"The pressure loss resulted in the fairing that protects the engine from aerodynamic loads to rupture, giving the impression of an explosion. However, this was not the case and the remaining eight engines were unaffected by the event."

"Preliminary source information noted the failure appeared to be related to a fracturing of the Merlin 1C engine’s fuel dome, localized solely in that area on Engine 1, explaining why the engine continued to send data after the event."

You're claiming an explosion. Which goes against how everything else has been stated.

[Jim]

You're claiming an explosion. Which goes against how everything else has been stated.

Just that "sudden pressure loss" is a gross understatement. 
Just keeping drinking and ignore the man behind the curtain.

Also, how is it not an explosion? Or rupture?

And furthermore, still sending data has no bearing on the definition of the event.

[kevin-rf]

I frequently used the term "sudden pressure loss" when describing a balloon that instantly no long holds air.

From asprin and headache standpoint it's easier on NSF to use that term

[LouScheffer]

You're claiming an explosion. Which goes against how everything else has been stated.

Disputes over what to call this event seem rather silly and even childish.  From an engineering point of view, we need to know:
   (a) What went wrong;
   (b) What were the consequences, and what could have been the consequences in other situations;
   (c) What will be done to prevent this from happening, limit the consequences, or otherwise deal with this problem.

These activities are completely independent of whether we call the event an explosion, a pressure loss, a RUD, or a hula dance for that matter.  I'm  certain that the professionals at SpaceX, NASA, and customers will treat it the same way no matter what it is called.

This reminds me of when president Carter forbade the economist Alfred Kahn from using the words depression or recession. So he used the word "banana" instead, as in "We’re in danger of having the worst banana in 45 years."  Surely we can be as smart as the average listener to a speech on economics, and realize it matters not at all what you call it, but only what you do about it.

[meekGee]

You're claiming an explosion. Which goes against how everything else has been stated.

Just that "sudden pressure loss" is a gross understatement. 
Just keeping drinking and ignore the man behind the curtain.

Also, how is it not an explosion? Or rupture?

And furthermore, still sending data has no bearing on the definition of the event.

As we already found out, "explosion" is used by different people to denote different things.

It "exploded" in the same way that a compressed air tank can "explode" - it is only a significant event if the tank is large.  For something the size of the fuel chamber, meh.

From the way I read it, it didn't even directly blow out the fairing - it's the loss of pressure under the fairing that caused aerodynamic pressure to break it.

In the context of a rocket engine under power, I wouldn't use the word explosion unless we're talking about propellant igniting very rapidly and uncontrollably, creating a shock-wave.  And even then we can argue (and have!) whether a rapid fire is truly an explosion.   None of that happened here.

The dome failed, the engine shut down, the fairing failed under aero loads - unless SpaceX is lying, but there's no evidence that I've seen indicating that they are.  Do you know something that we don't?

[SF Doug]

Yep, the flavored drink mix consumption is in full till. 
I frequently used the term "sudden pressure loss" when describing a balloon that instantly no long holds air.

Take a look at the article Chris just posted. http://www.nasaspaceflight.com/2013/01/spacex-win-contract-ahead-crs-2-mission/

"The pressure loss resulted in the fairing that protects the engine from aerodynamic loads to rupture, giving the impression of an explosion. However, this was not the case and the remaining eight engines were unaffected by the event."

"Preliminary source information noted the failure appeared to be related to a fracturing of the Merlin 1C engine’s fuel dome, localized solely in that area on Engine 1, explaining why the engine continued to send data after the event."

You're claiming an explosion. Which goes against how everything else has been stated.

I am not an engineer.  I welcome corrections.

A classic "rocket engine explosion" is a rupture of the combustion chamber.  Big bang.  It can also be any failure resulting in massive external mixing of high-pressure fuel and oxidiser.  The Falcon 9 is designed to contain such explosions.

The fuel dome fractured and caused
  1)  a reduced flow of fuel  into the combustion chamber.  This gave the pressure loss in the combustion chamber that was detected and triggered closure of the main fuel and oxidiser valves, shutting down the engine.
  2)  for a short time, fuel escaped into the space around the engine.

  Could the escaping fuel have mixed with atmospheric oxygen, resulting in a small "explosion?"  Is this a possible alternate cause of the fairing failure?  I don't think so.

I do know about drinking the mix.  I once attempted to launch my Dodge Dart into the sun.

I found this diagram helpful.

From http://pinehead.tv/space/under-the-hood-with-the-spacex-merlin-engine/

[kevin-rf]

Can someone correct me, but isn't the fuel dome pressure the same as the combustion chamber since it really is the top of the combustion chamber.

[cordor]

By definition, rocket is controlled explosion. So whatsever mishap, you can call it "explosion gone wrong".

[Robotbeat]

Can someone correct me, but isn't the fuel dome pressure the same as the combustion chamber since it really is the top of the combustion chamber.

Fuel dome pressure is always higher since there is a significant pressure drop across the injector(s).

[rklaehn]

As we already found out, "explosion" is used by different people to denote different things.

I really don't get this. We all love spacex and wish them all the best. I would invest in them in a second if they were public.

But it is perfectly correct to call what happened an explosion. The definition of explosion on wikipedia is just a rapid increase in volume and release of energy in an extreme manner, which is exactly what happened. There is even a subsection on wikipedia for this particular kind of explosion: http://en.wikipedia.org/wiki/Explosion#Mechanical_and_vapor.

There was no detonation (supersonic shockwave), and the combustion chamber did not explode. But there was an explosion. Makes it even more impressive that the vehicle survived and continued on its way.


Nothing to worry about. Just a rapid pressure release.

[meekGee]

As we already found out, "explosion" is used by different people to denote different things.

I really don't get this. We all love spacex and wish them all the best. I would invest in them in a second if they were public.

But it is perfectly correct to call what happened an explosion. The definition of explosion on wikipedia is just a rapid increase in volume and release of energy in an extreme manner, which is exactly what happened. There is even a subsection on wikipedia for this particular kind of explosion: http://en.wikipedia.org/wiki/Explosion#Mechanical_and_vapor.

There was no detonation (supersonic shockwave), and the combustion chamber did not explode. But there was an explosion. Makes it even more impressive that the vehicle survived and continued on its way.


Nothing to worry about. Just a rapid pressure release.

This is semantics, but there was no increase in pressure. The pressure container failed, and the pressure was orders of magnitude lower than when a chemical reaction causes a sudden rise in pressure....  Outside the dome, the outflow of propellant was not even enough to break the fairing.

In other contexts, people will say that a compressed air cylinder "exploded", and I'd have no problem with this usage.

When talking about an engine under thrust, I'd personally reserve this word to the case where something caused the reaction to accelerate, and this self-amplified to a very fast event.  You know - an explosion!

[padrat]

Makes it even more impressive that the vehicle survived and continued on.

I'd say this is what really matters. Yes, try to figure out what happened so you can prevent it from happening in the future. But when it comes down to it, it still accomplished the mission, besides Orbcomm. Which I think we know wasnt their call either....

[notsorandom]

The engine did not explode and it did not implode. However something clearly traumatic happened. Perhaps the most appropriate term would be that the engine "ploded". Can we leave it there?

[Robotbeat]

Asploded. It asploded.

[llanitedave]

If anything, I would have called it an implosion.  The engine shutdown caused a sudden pressure drop at the base of the fairing and essentially sucked it into the low-pressure zone under the force of the slipstream above it.

Call me a "flavored drink consumer", but at least I'm not addicted to sour mash.  That stuff warps your mind just as bad, if not worse.

[Robotbeat]

Makes it even more impressive that the vehicle survived and continued on.

I'd say this is what really matters. Yes, try to figure out what happened so you can prevent it from happening in the future. But when it comes down to it, it still accomplished the mission, besides Orbcomm. Which I think we know wasnt their call either....

Indeed, and I think the transition of space launch away from "brittle" systems with no margin for error is a very good sign. It's got to be really frustrating to engineers at ULA, SpaceX and others that whenever something goes wrong (but the main mission is accomplished), some people are quick to jump on the "anything wrong is a full failure" bandwagon. It's just dumb to equate partial failure of secondary missions to full launch failure, and such an attitude will keep spaceflight expensive, risky, and rare.

[IRobot]

If anything, I would have called it an implosion.  The engine shutdown caused a sudden pressure drop at the base of the fairing and essentially sucked it into the low-pressure zone under the force of the slipstream above it.

That is exactly how I read it.