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Launch Pad Explosion during Static Test Fire - Sept 1 2016

Discussion in 'SpaceX' started by NigelM, Sep 1, 2016.

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  1. Cosmacelf

    Cosmacelf Well-Known Member

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    Here's the relevant exchange on reddit (turns out I still have the screen up on my browser, I guess I should screenshot the whole thing) about the sniper.

    upload_2016-10-14_8-19-10.png
     
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  2. Model 3

    Model 3 Active Member

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    So it was a mock-up second stage (not necessarily at 1:1 scale). Makes it a bit more believable.
     
  3. glhs272

    glhs272 Unnamed plug faced villian

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    That could also be interpreted as a non-flight article (i.e. without engines). Perhaps one of their structural test articles that were built for qualification testing (and no longer being used) were sacrificed for these tests.
     
  4. Model 3

    Model 3 Active Member

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    Your right, and that sounds even more likely to me.
     
  5. Grendal

    Grendal SpaceX Moderator

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    I have to say that Elon and SpaceX are awesome. They don't mess around and get right to heart of the problem. The company gets a vast amount of data from the explosion but it doesn't give any clear indication of the actual fault. There is an outside chance of sabotage and so the company hires a sharpshooter to fire a couple rounds at a mock up/test article stage to see what happens. Apparently SpaceX learned a lot from that test. Enough information to determine it is unlikely that was the cause which seems to have clarified what the real problem probably is. They also learned enough that there is a danger that needs to be addressed for future launches.

    Of course it could still be the bird-like drones controlled by aliens....

    Now we just have to patiently wait a couple months before we can see the next launch...
     
  6. ecarfan

    ecarfan Well-Known Member

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    Sorry, my error in typing "first stage". I meant second stage.

    @Cosmacelf, I wasn't accusing you of anything, I understood you were just passing on information.

    @glhs272 what "pictures of McGregor test site" are you referring to?
     
  7. ecarfan

    ecarfan Well-Known Member

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    Based on the reddit screen capture that @Cosmacelf posted upthread, I interpret that as saying that what SpaceX did with firing a bullet on a mockup 2nd stage demonstrated that they could replicate the explosion. I don't understand why you are saying that the test showed that scenario was "unlikely".
     
  8. Grendal

    Grendal SpaceX Moderator

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    Elon's quote from the NRO speech said "We don’t think that is likely this time around, but we are definitely going to have to take precautions against that in the future."

    So I'm just going by what Elon said.

    He also said "The other thing we discovered is that we can exactly replicate what happened on the launch pad if someone shoots the rocket."

    I think that means that you can blow up the rocket if you fire a bullet at it though. Which is why SpaceX will be more cautious about such a thing in the future.
     
  9. hockeythug

    hockeythug Active Member

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    He is talking about L2 content from NSF which is against the rules to be posted outside of L2.
     
  10. palmer_md

    palmer_md Member

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    People keep referencing the Reddit post where they quote Elon. Is there any confirmation that he actually said these things? The Reddit thread was pulled down. Was it pulled down because he didn't say it or was it pulled down because they didn't want that information getting out there.
     
  11. glhs272

    glhs272 Unnamed plug faced villian

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    The pictures themselves are L2 but the discussion of the stage mock-up has been going on the Amos-6 public thread, public info so I don't think I broke any rules...
     
  12. Cosmacelf

    Cosmacelf Well-Known Member

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    The comments were made at a classified briefing of some sort. No official record of it is likely to emerge. You either believe the veracity of the people who witnessed it or you don't. I'm not plugged in enough to the space crowd to vouch for anyone. You kinda have to follow a trust chain back to decide for yourself whether or not you believe it. For instance, there are a bunch of people on this forum that i would believe if they vouched for something, but that's based on my own interactions with them.
     
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  13. Cosmacelf

    Cosmacelf Well-Known Member

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    Is there a public link to that Thread?
     
  14. glhs272

    glhs272 Unnamed plug faced villian

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    #254 glhs272, Oct 14, 2016
    Last edited: Oct 14, 2016
    • Informative x 1
  15. palmer_md

    palmer_md Member

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    Thanks. As long as there are some people who believe the posters are reliable that is OK with me. I just thought I'd bring it up since it is odd that it got removed. It will be interesting to hear/read the official press release on the matter when they are done with the investigation.
     
  16. jkn

    jkn Member

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    SpaceX: Sept. 1 failure likely caused by breach in Falcon 9 second-stage helium tank - SpaceNews.com
    tells: "from first signs of an anomaly to loss of data is about 93 milliseconds"

    I'm sure they monitored He pressure, so it did not rise earlier than 93 ms before loss of data. I don't think Thermo-Acoustic Oscillations is that fast.

    O2 boils at -183 C and freezes at -218 C. That's not huge difference. Thin structures cool and contracts faster than thicker parts. If tank was too warm when filled, rapid cooling might have broken something. This caused a leak.

    My video editing program told that explosion video is 30 fps. Others claimed 60 fps. I figured out why: High resolution video is 60 fps. Higher resolution did not give me anything new. But extra frames did: Initial detonation was even faster. First frame with fire:
    fl1738.jpg
    Rocket is 41 pixels wide = 3.66 m. So one pixel is 0.0893 m

    Fireball is 96 pixels = 8.6 m wide and 170 high = 15.2 m
    All that in 1/60 s or less. At least 1.5 * speed of sound.

    Guessing volume of fireball in first frame: 9 * 9 * 15 = 1200 m^3. -> About 150 kg of explosive (RP-1 mixed with LOX) detonated.

    Smoke ring has radius about 30 pixels = 2.7 m. At least 1/2 speed of sound.

    Lens flare is visible in 6 frames, but not exactly in same position. So it does not give accurate point of ignition.

    I found:

    TechX

    Exploding vertical pipe would explain shape of initial fireball and initial high speed of it. I have nothing to add...
     
  17. HVM

    HVM Savolainen

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    If we trust reddit leak:

    “We are close to figuring it out. It might have been formation of solid oxygen in the carbon over-wrap of one of the bottles in the upper stage tanks. If it was liquid it would have been squeezed out but under pressure it could have ignited with the carbon. This is the leading theory right now, but it is subject to confirmation."

    Thermo-Acoustic Oscillations stuff, was because of another reddit rumor:

    "just had dinner with a credible source i trust that spacex is about 99% sure a COPV issue was the cause. 'explosion' originated in the LOX tank COPV container that had some weird harmonics while loading LOX.

    i dont have any more detailed info beyond that, just wanted to share.

    the good thing is, they know the cause, that means they can come up with a solution to fix it and hopefully get back to business soon!"
     
  18. ecarfan

    ecarfan Well-Known Member

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    Does that mean that solid/frozen O2 formed inside the the carbon over-wrap material? In other words, under pressure LOX was forced into the tank wall material where it then froze solid and in solid form is capable of spontaneously igniting the carbon material?

    If so, does that imply a defect in the COPV material or is it simply the nature of the material that makes such an event possible?

    Is the solution then to slightly reduce the LOX temperature, reduce the pressure, both, or construct the COPV tanks differently?
     
  19. scaesare

    scaesare Well-Known Member

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    The bullet test was using a mock-up of the stage as a target.
     
  20. HVM

    HVM Savolainen

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    #260 HVM, Oct 15, 2016
    Last edited: Oct 15, 2016
    No, not spontaneously. After 380 bar of He-pressure is applied to COPv.

    No defect, (probably...)

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