Author Topic: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD (1)  (Read 1541204 times)

Offline Jet Black

From the TEL and with such cold temps I wonder if a LOX ball valve fractured with enough force in the flow to break through just outside the vehicle? If there was a filter it could go through it as well...

Pressure propagation down a pipe? Ever done the thing where you whack the top of a part full beer bottle and then laugh at the holder as it erupts into foam?
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline Jim

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2021 on: 09/09/2016 04:04 pm »

During development the launch vehicle has many strain gauges mounted, but what about the ground equipment?

No need for it in the ground equipment.

Offline Rocket Science

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2022 on: 09/09/2016 04:04 pm »
From the TEL and with such cold temps I wonder if a LOX ball valve fractured with enough force in the flow to break through just outside the vehicle? If there was a filter it could go through it as well...

Pressure propagation down a pipe? Ever done the thing where you whack the top of a part full beer bottle and then laugh at the holder as it erupts into foam?
No, I live a boring life... My point is that the piece break though near the LOX tank connection and deflects into the RP-1 tank section close by. Materials are very brittle at the temps SpaceX are working with and any material/manufaturing flaw could reveal itself in a spectacular fashion...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline glennfish

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2023 on: 09/09/2016 04:09 pm »
Another imaging tidbit derived from something called Lucky Imaging.  No I didn't make up the term:

https://en.wikipedia.org/wiki/Lucky_imaging

The first frame is about 20 seconds prior to frame1

The second frame is about 1 second prior to frame1

The third frame is frame 0

At this scale, my observation could be:
1.  Thermals between the camera and the F9
2.  MPEG artifacts

OR it may be downward motion of the white blob pointed to by the red lines.

It only moves down 1-2 pixels, if it's moving at all.

Someone with a more recent version of photoshop than what I have could do a much better job following this guide.

http://petapixel.com/2015/02/21/a-practical-guide-to-creating-superresolution-photos-with-photoshop/

I used some astrophotography processing software that has to run under XP emulation.

« Last Edit: 09/09/2016 04:12 pm by glennfish »

Online matthewkantar

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2024 on: 09/09/2016 04:18 pm »
I looked carefully top to bottom at the "uber resolution" picture of the TEL. There was was rust, overspray, tape, bondo-looking stuff, zip ties, etc. The TEL spends lots of time in the damp salt air of the Florida coast. I could easily be convinced that some component of this shop worn assembly let loose, but in a thirtieth of a second with no visible evidence?

Matthew

Offline Multivac

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2025 on: 09/09/2016 04:29 pm »
Since Elon's tweet re the sound:
"Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else."

I went back and did a much more detailed listen (and look using spectrogram) to the sound track of the video.

From the 60fps video I was able to determine a 12.14 sec sound travel time in air using the first visible sign of explosion (whatever the correct term is). I used this offset to time correct the spectrogram (attached) so that it is synchronised with the video.

Just out of interest I also tried a 4 sec time offset to see of any sounds match up with the video. IMHO they do, but nothing of great interest other then it appears the explosion would have been heard via the ground before hearing via the air.

Using some high and low pass filtering I was able to clearly hear many birds and to my surprise many frogs reasonably clearly from the video sound track.

IMO there are only two sounds that cannot identified. They occur 1 second apart.
I'm guessing these are the sounds Elon is referring to in his tweet?

They occur at 1:06.5 and 1:07.5 in the below time offset spectrogram.
Or at 1:18.64 and 1:19.64 in the original video.

Understanding the source of these sounds may help provide answers as the first sounds occurs 5.2 secs before the explosion.

Edit: Spelling, more image annotations.
« Last Edit: 09/09/2016 04:45 pm by Multivac »

Offline Pete

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2026 on: 09/09/2016 04:51 pm »
Just how big is that initial explosion?

The initial bang seems to be some form of fuel-air(oxygen) explosion. Has anyone given a reasonable estimate of just HOW MUCH fuel would be needed to form a bang of that size?
A few grams? A few kilograms? Hundreds?

Assuming the initial explosion is from somehow-vented/sprayed/aerosolysed RP1, we could go a long way to eliminating likely causes if we have a better idea of the actual volume of fuel needed to create that explosion.

I've tried to find info on this earlier in the thread, but my search-fu failed me.

Thanx,
Pete.

Offline tdenk

About this "sound through ground" discussion,
sorry guys, but why should be audible only the initial bang,
and not all the cacophony of the subsequent explosions?

Doesn't convince at all...

Thorsten

Offline SWGlassPit

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2028 on: 09/09/2016 05:03 pm »
A further thought: the "pre-thunk" takes place about three seconds after the big boom (which did produce a shock wave in the air), which would give a wave propagation speed of about 1300 m/s, making it a much more likely candidate than the initial stage two boom.

Offline Spacedog49

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2029 on: 09/09/2016 05:05 pm »
I'm not attempting to start a conspiracy theory, but has USLaunchReport published a video with more than 22 seconds before the anomaly? As a retired engineer, now video producer, I would like to review the video prior to any propellant loading onto the vehicle. I know that it will be very boring, but 22 seconds prior is not sufficient for analysis.           

Offline glennfish

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2030 on: 09/09/2016 05:18 pm »
Just how big is that initial explosion?

The initial bang seems to be some form of fuel-air(oxygen) explosion. Has anyone given a reasonable estimate of just HOW MUCH fuel would be needed to form a bang of that size?
A few grams? A few kilograms? Hundreds?

Assuming the initial explosion is from somehow-vented/sprayed/aerosolysed RP1, we could go a long way to eliminating likely causes if we have a better idea of the actual volume of fuel needed to create that explosion.

I've tried to find info on this earlier in the thread, but my search-fu failed me.

Thanx,
Pete.

Page 84, reply 1677

Offline Fan Boi

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2031 on: 09/09/2016 05:24 pm »
I think that sound before the explosion is a steel strut failing. Listen closely to the sounds in the video below and then listen again to the AMOS video (with headphones if possible). Both have that same distinctive ringing sound.


Offline SWGlassPit

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2032 on: 09/09/2016 05:44 pm »
I think that sound before the explosion is a steel strut failing. Listen closely to the sounds in the video below and then listen again to the AMOS video (with headphones if possible). Both have that same distinctive ringing sound.


Compare how close those guys were standing vs how close the recording was taken from.  Atmospheric attenuation hits high frequencies much harder than low frequencies.  The spectrograph posted earlier shows that "pre-thunk" has pretty substantial energy up through the 4kHz band (btw, would it be possible for someone to get a snapshot spectrograph in dB/Hz for that brief sound?).

A frequency-based attenuation table is available here.

If that sound had the vehicle as a direct source, you would see a much stronger bias to the low frequencies than you do over that kind of distance.  In particular, a 4 km distance would result in an attenuation of around 100 dB in the 4 kHz band, which would basically render that effectively inaudible.  There's simply no way that sound doesn't have a source much closer to the camera than the rocket.

Online meekGee

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2033 on: 09/09/2016 05:47 pm »
About this "sound through ground" discussion,
sorry guys, but why should be audible only the initial bang,
and not all the cacophony of the subsequent explosions?

Doesn't convince at all...

Thorsten

The initial event was very sharp.  Supersonic or almost so.

The following collapse and fire would be less likely to generate a sharp shock that propagates as described.
ABCD - Always Be Counting Down

Offline rakaydos

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2034 on: 09/09/2016 05:53 pm »
Anyone think that, if a root cause does not present itself, SpaceX will take another page out of the Silicon Valley playbook?

"Attempt to replicate the bug?"

Offline ellindsey

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2035 on: 09/09/2016 05:56 pm »
Anyone think that, if a root cause does not present itself, SpaceX will take another page out of the Silicon Valley playbook?

"Attempt to replicate the bug?"

The problem is that there are a nearly infinite number of ways to make a rocket explode, and much of the hardware was completely destroyed.  The T/E and much of the GSE will have to be rebuilt from scratch, and once you've done that if you fail to replicate the explosion, how do you know if the flaw was some hidden defect or failure in the now-destroyed GSE or some rare fault caused by a still-present design flaw?

Offline rakaydos

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2036 on: 09/09/2016 06:02 pm »
Anyone think that, if a root cause does not present itself, SpaceX will take another page out of the Silicon Valley playbook?

"Attempt to replicate the bug?"

The problem is that there are a nearly infinite number of ways to make a rocket explode, and much of the hardware was completely destroyed.  The T/E and much of the GSE will have to be rebuilt from scratch, and once you've done that if you fail to replicate the explosion, how do you know if the flaw was some hidden defect or failure in the now-destroyed GSE or some rare fault caused by a still-present design flaw?
A problem I'm told many programmers are famiiar with.

Offline Jim

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2037 on: 09/09/2016 06:33 pm »
Anyone think that, if a root cause does not present itself, SpaceX will take another page out of the Silicon Valley playbook?

"Attempt to replicate the bug?"

The problem is that there are a nearly infinite number of ways to make a rocket explode, and much of the hardware was completely destroyed.  The T/E and much of the GSE will have to be rebuilt from scratch, and once you've done that if you fail to replicate the explosion, how do you know if the flaw was some hidden defect or failure in the now-destroyed GSE or some rare fault caused by a still-present design flaw?
A problem I'm told many programmers are famiiar with.

No, there is no parallelism.   The programmers still have intact computers, keyboards and monitors.  Also their code also remains intact.

Offline MP99

Hydrazine is not feasible.  It would have gone off in the fairing

Nice to see your personal and professional experience jibes with my engineering intuition.

So assuming an external fuel/air explosive event, any ideas how enough fuel could or would rise the 10' or so from the the apparently-unpressurized RP1 umbilicals? If RP1 loading was complete but the tank not yet at flight pressure, how does that happen? Could a check valve in the RP1 QD have failed, combined with a hole in the umbilical causing a vertical spray or mist up in the clouds of venting O2 gas?

I just don't get the mechanism yet.

The RP1 is loaded cooled.

If there is (made up number) 3% of ullage, and the RP1 warms enough to expand 4%, then all ullage gas would be expelled and then liquid RP1 would follow (at high pressure, I think?)

But, it doesn't seem possible for this to happen without SpaceX realising long before the situation became critical.

Cheers, Martin

Offline dorkmo

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Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #2039 on: 09/09/2016 06:37 pm »
just to touch on copv's one more time...

what state would the copv's be in now? would they have survived intact?

it would be nice to see pictures of them. just to put my mind at ease.

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