Falcon 9 / Dragon CRS-7 ISS Resupply (mission thread)


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Draggendrop

If the IDA is involved I doubt it was so straightforward. Perhaps it was a resonance -a sympathetic vibration - that couldn't be modeled or ground tested, that lead to a failure somewhere. I'm betting on a COPV or a line letting go. On the other hand theres enormous flight experience with helium and all manner of payloads.

The one thing that  "Analytical Fault Finding" relies on........what "changed" this time in your process.......1) difficulty mating sections and 2) IDA stowage.....

 

Was the difficulty mating sections due to IDA stress on structure while positioned horizontally for several days ( there was an additional 2 day delay)?.........

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malenfant

Well I'm looking foward to finding out. Payload integration for me comes a bit lower down the list. Seems that an attachment failure could be determined pretty quickly. And just to be clear I was postulating an IDA related resonance.

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DocM

It'll be interesting to see the SpaceX IDA for Dragon 2. It's said to be less expensive, much lighter, and rather than using servos it's largely mechanically latched. There was a pic showing a prototype in a blurred background, so you couldn't make out much.

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SALSN

It'll be interesting to see the SpaceX IDA for Dragon 2. It's said to be less expensive, much lighter, and rather than using servos it's largely mechanically latched. There was a pic showing a prototype in a blurred background, so you couldn't make out much.

So the two IDAs are not identical? But if a vehicle is able to dock with one IDA, it will be able to dock with all, right, otherwise what would be the point of this new standard?

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DocM

IDA is an open international standard which can be implemented different ways. How it latches is one of them. Mechanical latching, in principle, allows it to be used if automation power fails and you're controlling the thrusters manually. Relying entirely on sevomotors may not have that fallback, and an adapter would be much heavier if it included both.

The NASA version of IDA is the NASA Docking System. Boeing is the prime contractor, but the main structure is made by RSC Energia and other parts come from 25 US states.

SpaceX rolled their own, giving them control over both costs and supply if Energia (Russia) gets testier than they already are.

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Draggendrop

Well I'm looking foward to finding out. Payload integration for me comes a bit lower down the list. Seems that an attachment failure could be determined pretty quickly. And just to be clear I was postulating an IDA related resonance.

That is what we were talking about with the adapter....

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Draggendrop

So far we have not been privy to actual sensors in use, but since vibration/harmonic/stress sensor's are pretty much standard practice in other industries, this would be one venue that I am more than sure, use them.........more so after the analysis by Richard Feynman on NASA operations (Challenger, the first stage vibrations really bothered him, and rightly so). This is what leads me to think that the trunk area had little, if any, form of sensor ability.......it would have shown itself, if not, the rest of Falcon would have had something and was not mentioned...........just speculation............SpaceX has some of the brightest people around and I am sure they really thought out the sensor requirements for the launch vehicle....continual improvement program........Cheers  

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malenfant

Yes, an IDA caused resonance that didn't cause a failure in the IDA itself but one further downstream was what I was trying to get across. I missed it if it was mentiontioned.

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malenfant

Just thinking out loud here. The visual image I'm getting is kind of like a giant speaker. A large heavy torus mounted maybe not very rigidly over a tank dome. Again with the resonance maybe causing pressure waves in the tank causing a failure somewhere. Credible?

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SarK0Y

 

Oh man. I really want to see how IDA-1 was flight secured for the trip uphill now. I was looking at how it was secured for cross-country shipping and I was like "Oh HELL no, they didn't send it to space like THAT, did they?!".

 

A couple of "red flags" for me, looking at the mounting pipes on the side of IDA-1 -- three to be exact. There's no way I would have signed off on that piece of equipment being secured by those three alone, from an Engineering standpoint.

 

See those mounting pipes holding the IDA-1 onto it's shipping arms? The hollow ones? They look quite small and flimsy relative to the IDA-1, don't they? My guess is that those were meant to be used in flight to secure the IDA to the Dragon. Not SpaceX's design or origin, of course. This item weighs 500 kg - 1,100 lbs. Half a ton. At flight inertia it will consistently weigh 3-5 times that much, as far as mass, the rocket (and gravity) is concerned.

 

There's absolutely no way that those three mounting pipes alone could (or would) bear the entire 3,300-5,500 pound (counting inertial mass) load during launch. Dry weight, on the ground, sure. In flight, not for long -- as we saw. I suspect the designers of the IDA-1 forgot that fairly important piece of information when they designed this thing. It needed at least three more hardpoints to remain secure, and double the thickness of each of those pipes holding it in place to prevent (or at least minimize) stress warpage.

 

I suspect that these pipes warped under stress during launch due to additional inertial mass loads that they were not designed to withstand. Eventually one of them either snapped or warped beyond a certain threshold and the IDA simply slid off the other two (or its' hardpoints) that were still attached. The IDA then fell downward, punched through the Dragon's Trunk sideways, crashed through the Avionics/Telemetry Package of the Falcon's S2 (destroying it) and impacted the LOX tank, rupturing it.

 

That's what I think happened.

  take yield strength for steel & estimate what diameter of tie(s) is appropriate for.
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SarK0Y

i suspect there was thermal insulation ruptured on s2, thereby over-chilled lox tank got exposed to hot air. such scenario ain't seen(however, it depends on sensors, their number & how they're deployed/placed) straightly in telemetry.

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DocM

The only insulation on the LOX tank is an overwrap of bonded cork, and its loss wouldn't cause a flashover like was seen.

It's more likely that there was a helium system leak, a faulty LOX vent valve or a failed weld. An impact by the IDA docking adapter breaking free of Drago's Trunk is still possible.

The next F9 flight will be the last F9 v1.1 core, and the last use of this upper stage tankage. After that there will be 2 types of v1.2 cores

1) Falcon 9 and Falcon Heavy side booster core

2) Falcon Heavy center core

Both will use super-chilled props (using liquid nitrogen), have the uprated Merlin 1D engines and a new stretched upper stage. The Falcon Heavy core will also be beefed up to handle the higher structural loads.

All launch sites are getting upgraded launcher-erectors and liquid nitrogen super-chilling equipment.

Net effect: >30% higher performance

Other upgrades will come later.

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SarK0Y

 

The only insulation on the LOX tank is an overwrap of bonded cork, and its loss wouldn't cause a flashover like was seen.

so lox tank holds rising pressure only thanks to its strength???

 

An impact by the IDA docking adapter breaking free of Drago's Trunk is still possible.

3 points to attach failed simultaneously???

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FloatingFatMan

so lox tank holds rising pressure only thanks to its strength???

3 points to attach failed simultaneously???

 

He said possible, not probable.  It's pointless to conjecture without any inside information. Let's just wait and see.

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SarK0Y

He said possible, not probable.  It's pointless to conjecture without any inside information. Let's just wait and see.

conjecture makes possible to pinpoint problem + some cases cannot be seen in telemetry.

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DocM

so lox tank holds rising pressure only thanks to its strength???

Not all rockets have insulated tanks, especially if they're constantly topped off before launch. They also don't have to be thick skinned. Take a look at the Atlas used for Mercury launches; its "balloon tanks" were only .015" to .048" thick.

Falcon 9 is a semi-balloon tank launcher; thicker skinned with internal stringers, but still pressure stabilized even during transit.

3 points to attach failed simultaneously???

Only one has to fail for the others to become hinges, allowing the unsupported part to fall. Of course once its moving the other two could also fail.

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ks8877

Elon Musk Tweets on July 5:

Elon Musk ?@elonmusk

Expect to reach preliminary conclusions regarding last flight by end of week. Will brief key customers & FAA, then post on our website.

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SarK0Y

2 DocM

 

Take a look at the Atlas used for Mercury launches; its "balloon tanks" were only .015" to .048" thick.

actually, placement of elements itself can serve as good thermal insulation.

 

Only one has to fail for the others to become hinges, allowing the unsupported part to fall. Of course once its moving the other two could also fail.

why??? ties must have additional strength.

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Draggendrop

Elon Musk Tweets on July 5:

Elon Musk ?@elonmusk

Expect to reach preliminary conclusions regarding last flight by end of week. Will brief key customers & FAA, then post on our website.

Excellent...Thanks for posting the tweet.......soon we'll know..... :)

 

He's got a great pic there....sort of like...

post-546174-0-78280500-1436153207.jpg

 

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Draggendrop

2 DocM

actually, placement of elements itself can serve as good thermal insulation.

why??? ties must have additional strength.

Actually a 3 point mount is not stable when one fails....an example is a high horsepower engine assembly that looses a mount...not a pretty sight. Just my opinion, but I would have liked to see a more robust mounting system and a barricade assembly. An analogy is holding a balance beam...then move in 20% and see the differential....then add "g" force and "runaway" vibrational damage...Cheers....Good questions though SarKoy.......

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DocM

In a congressional ISS hearing

jeff_foust (Space News)

Gerst: SpaceX already doing some stress testing of components in the lab as a parallel activity to the investigation.

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Unobscured Vision

I bet they're checking the valves and weld seams on tanks. Looking more and more like a genuine failure than the IDA coming loose. :(

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Draggendrop

Myself....I am still a bit fixated with the "over pressure" (counter intuitive).....??expecting a decrease upon start of use......heat source by tank.....dented tank showing pressure increase....bad sensor....And then, SpaceX stress testing, seams...tank..no......support structures yes......Idle spec....yes...Hopefully some idea soon....Cheers... :)

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Unobscured Vision

And that's not to say I'm favoring one type of failure over another, because NO failure is cause for celebration. I prefer a clear-cut, direct cause rather than something that potentially could have been detected and prevented on the ground.

 

In retrospect, it's better to get something like this sorted out and dealt with now versus later, when they have a manned Dragon on top. Murphy's Law still applies, so let's get it out of the way.

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