Elon Musk: "Rocket discussion at noon on Monday (July 20th, 2015)."

/r/SpaceX CRS-7 Failure Investigation Teleconference Thread : spacex

Failure cause

"Preliminary conclusion is that a COPV (helium container) strut in the CRS-7 second stage failed at 3.2Gs."

"Strut about 2 feet long, an inch at its thickest point. Strut failed at 1/5th rated force, no evidence of damage to it in close-out photos before launch. This strut was designed to handle 10,000 lbs of load, failed at 2,000 lbs."


"Strut issue is fairly straightforward, switching to something with higher level of performance. Part that failed was from a supplier, not made in house. did not name the supplier, was relying on certification from the supplier. Not going to move strut work in-house, but will move to a different design likely from a different supplier. There are 100s of suppliers of minor components for us. We can't make everything."

Damn. It wasn't even SpaceX fault. Some bloody supplier gave false tolerances or didn't test the tolerance properly. It's probably a part less than $1000 that took out a $60 million rocket!

This is why rocketry is so difficult. You are working at the cutting edge of tolerances. The failure did occur just after max-q and the second stage warm up.

Good luck, SpaceX.

Grendal said:

Damn. It wasn't even SpaceX fault. Some bloody supplier gave false tolerances or didn't test the tolerance properly. It's probably a part less than $1000 that took out a $60 million rocket!

This is why rocketry is so difficult. You are working at the cutting edge of tolerances. The failure did occur just after max-q and the second stage warm up.

Good luck, SpaceX.

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yep, really a pity, to say the least. SpaceX team will surely triple-check every single detail of the rocket (and fuel) in future missions. I mean, in such a multi billion dollar business, trust is good, control is better. On the other hand, you can't distrust everyone, can you?

Sounds like it could have just been a single bad bolt on the strut.

Elon sure does like Inconel. It pops up increasingly in the SpaceX spacecraft (today Elon said they'd be using it with regard to the fix for this strut and bolt), and now, in the Model S (at least the P90D) as well.

(I wonder if the company that makes Inconel is worth investing in: Precision Castparts Corporation; PCP is stock symbol.)

hockeythug said:

Sounds like it could have just been a single bad bolt on the strut.

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From a corroded nut (Falcon 1 failure) to a bad bolt (Falcon 9 failure). Fasteners can be tricky ;-)

hockeythug said:

Sounds like it could have just been a single bad bolt on the strut.

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While possible, Elon mentioned that they have tested some of the other struts they have and some of them failed tolerance tests.

Space is hard. At least SpaceX has some confidence that they have identified the reason for the second stage failure and the next mission can proceed.

They also lost an engine on an ISS supply mission due to bad metallurgy in the fuel dome, apparently another case of a supplier certifying quality that actually wasn't there on every part, just almost all. The flight did make it since the avionics recalculated and was able to complete the mission on just 8 engines, although the secondary payload was put into a fairly useless orbit.

tinm said:

Elon sure does like Inconel. It pops up increasingly in the SpaceX spacecraft (today Elon said they'd be using it with regard to the fix for this strut and bolt), and now, in the Model S (at least the P90D) as well.

(I wonder if the company that makes Inconel is worth investing in: Precision Castparts Corporation; PCP is stock symbol.)

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They have had a rapidly growing business with high temperature high corrosion risk environments. These days lots of automotive (turbochargers, anything else dealing with exhaust), parts for aerospace, nuclear plants, etc. I have not examined their financials but i did order them a couple of weeks ago.

ecarfan said:

Space is hard. At least SpaceX has some confidence that they have identified the reason for the second stage failure and the next mission can proceed.

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I haven't seen anything on the updated launch schedule, everything still states "TBD". I wonder if their will be another announcement regarding the new launch schedule?

In a way, I'm happy to hear it wasn't something fundamentally wrong with SpaceX's Design or Engineering. I have read some criticism to the effect of "it was only a matter of time" based on how hard Elon pushes people. It gives me some confidence that the program is actually working, and this was likely just a sub-standard part.

c041v said:

I have read some criticism to the effect of "it was only a matter of time" based on how hard Elon pushes people.

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It's always a matter of time. Failure rates are non zero. Mishaps will happen eventually.

And they had to arrive at that particular strut with 0.893 secs of relevant data. Then I guess they started failure testing samples. I wonder if the F-9 is more heavily instrumented than legacy rockets like the Atlas and Delta.

If there's a silver lining: "...In addition, the Dragon spacecraft not only survived the second stage event, but also continued to communicate until the vehicle dropped below the horizon and out of range."
That could be some very useful data for NASA.

Doug_G said:

Elon said that they used strain gauge sensors as little "microphones", and used the timing of the shock to triangulate the approximate location of the source. That led them to the support strut.

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In one of the articles I read yesterday it said the strut was designed for 10 G tolerance. The strut apparently failed at 3.1 G. Testing other struts showed failures below the 3.1 G tolerance. If the source is accurate then the tolerance is way off or possibly wildly inconsistent.


Let's hope they aren't using any of these struts in the Model S. The P90D Ludicrous is now pulling over a G. :wink:

The audio from the press conference is on YouTube:

Elon Musk reveals the cause of CRS-7 explosion (2015) AUDIO - YouTube

In listening, the dragon capsule survived and could have deployed parachutes and successfully landed except that there wasn't a software contingency for what happened. Damn. I would thought that would have already been there.

Falcon 9 LOX tank cam - YouTube

For those interested, here's an operational view inside the 2nd stage LOx tank. In the frame, you can see a few of the carbon fiber He tanks. Once the liquid level gets below the He tanks, it's pretty easy to see the support struts near the bottom of the frame.

Videos like this one @doug, reminds me of a presentation I attended by Allistair Croll about the Business Singularity. Slides can be seen here:
http://cdn.oreillystatic.com/en/ass...eans Cycle Time Trumps Scale Presentation.pdf

The ending idea is "cycle time beats scale", which brings me back to SpaceX (I could make the same point using Tesla and GM/BMW/fill-in-the-blank). SpaceX is small compared to its competitors (heh - when you're in competition with countries...). In this specific instance, can you imagine ULA posting a video from their LOX cam during a launch? I don't actually know one way or the other - are their rockets instrumented to that degree? I sort of assume that they are, because how would you know what's happening inside the tank without something like a video feed during the launch.

The point here is that this is so deeply built into SpaceX's dna, they can't think about their problems any other way. Croll would say that ULA is thinking/behaving like an organization, and SpaceX is behaving like an organism.


Another point from the presentation, if you're outside of the learning organization looking in at the organization, they will frequently seem opaque, agile, and mysterious (slide 27). What they heck are they doing? If you're IN the learning organization, looking out at your competition, they will look like ants (slide 28). I interpret his point as they'll be industrious, but unchanging. Doing the same thing over and over, but not evolving. Mindless even.


Good stuff!