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SpaceX Vehicles and Missions => SpaceX Falcon Missions Section => Topic started by: Chris Bergin on 01/29/2013 08:18 pm

Title: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD (1)
Post by: Chris Bergin on 01/29/2013 08:18 pm
This begins as pre-launch discussion and moves into post-Static Fire failure discussion.

NSF Threads for AMOS-6 : Discussion (https://forum.nasaspaceflight.com/index.php?topic=30981.0) / Updates (https://forum.nasaspaceflight.com/index.php?topic=40868.0) / L2 Coverage (pre-failure) (https://forum.nasaspaceflight.com/index.php?topic=40768.0) / L2 Coverage (post-failure) (https://forum.nasaspaceflight.com/index.php?topic=41066.0) / ASDS (https://forum.nasaspaceflight.com/index.php?board=66.0) / Party (https://forum.nasaspaceflight.com/index.php?topic=40089.msg1520968#msg1520968)
NSF Articles for AMOS-6 : Booster prep (1) (https://www.nasaspaceflight.com/2016/08/spacex-falcon-9-preparation-jcsat-16-amos-6/) / Booster prep (2) (https://www.nasaspaceflight.com/2016/08/by-sea-land-space-spacex-hardware/) / Falcon 9 explodes during AMOS-6 static fire test (https://www.nasaspaceflight.com/2016/09/falcon-9-explodes-amos-6-static-fire/)

September 01 2016, 0907 Local (1307 UTC) : Launch vehicle (Falcon 9-29) and payload destroyed during testing at SLC-40


I'll write it up, although I did have five seconds of thinking "Bloody hell, I wish we made money like space.com" ;D

Article:
http://www.nasaspaceflight.com/2013/01/spacex-win-contract-ahead-crs-2-mission/

Presser:

SPACECOM AND SPACEX ANNOUNCE AGREEMENT FOR AMOS-6 SATELLITE LAUNCH

Hawthorne, CA / Ramat-Gan, Israel, January 29, 2013 – Today, Space Exploration Technologies (SpaceX) and Space Communication Ltd. (Spacecom) announced an agreement to launch Spacecom’s AMOS-6 satellite on SpaceX’s Falcon 9 launch vehicle. Falcon 9 will insert the communications satellite into a geosynchronous transfer orbit (GTO), further enhancing Spacecom’s existing satellite fleet.

The AMOS-6 agreement is the latest in a series of wins for SpaceX.  The company closed out 2012 having signed 14 launch contracts—maintaining the company’s position as the world’s fastest growing launch services provider. 

“This last year has been one of great success and tremendous growth,” said Gwynne Shotwell, President of SpaceX.   “Spacecom was one of our earliest supporters—SpaceX is proud to be their partner and we look forward to launching their AMOS-6 satellite.” 

The AMOS-6 satellite, to be built by Israel Aerospace Industries (IAI), will provide communication services including direct satellite home internet for Africa, the Middle East, and Europe. AMOS-6 will replace AMOS-2, which is expected to end its service in 2016.

"We are excited to partner with SpaceX and its tremendous team. AMOS-6 will be larger and stronger than AMOS-2 and AMOS-3 combined, and signals a new age for Spacecom," commented David Pollack, President and CEO of Spacecom. "As we establish our position as a global satellite operator providing more services and capacity, AMOS-6 will be a key element of our business strategy and future."

The AMOS-6 mission is targeting a 2015 launch from Cape Canaveral, FL.



Other SpaceX resources on NASASpaceflight:
   SpaceX News Articles (Recent) (http://www.nasaspaceflight.com/tag/spacex/)
   SpaceX News Articles from 2006 (Including numerous exclusive Elon interviews) (http://forum.nasaspaceflight.com/index.php?topic=21862.0)
   SpaceX Dragon Articles (http://www.nasaspaceflight.com/tag/dragon/)
   SpaceX Missions Section (with Launch Manifest and info on past and future missions) (https://forum.nasaspaceflight.com/index.php?board=55.0)

   L2 SpaceX Section (https://forum.nasaspaceflight.com/index.php?board=60.0)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 01/29/2013 08:24 pm
Good to see the Israelis willing to continue do business with SpaceX after all the delays with the F9 that made AMOS-4 jumping ship to the Land Launch Zenit.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 01/29/2013 08:51 pm
Good to see the Israelis willing to continue do business with SpaceX after all the delays with the F9 that made AMOS-4 jumping ship to the Land Launch Zenit.  :)

Now all SpaceX has to do is up the launch rate. A lot.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: oiorionsbelt on 01/30/2013 04:14 am
I'll write it up, although I did have five seconds of thinking "Bloody hell, I wish we made money like space.com" ;D
Not the same as making money, but I almost never go to Space.com since finding this site.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: llanitedave on 01/30/2013 04:19 am
Yeah, it's changed my surfing habits, too.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cmj9808 on 01/30/2013 04:36 am
What confuses me is that Amos-6 weighs 5.5ton/12,125lbs according to SFN report, far beyond Falcon 9 GTO capability(4.85 ton/10,682lbs as described by SpX's F9 page). Or did I miss something?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: QuantumG on 01/30/2013 04:42 am
No, I don't think you did miss anything, but SpaceX is in the process of updating their line (to v1.1) and, as far as I recall, stats have not been announced for it yet, and 2015 is another 2 years away to boot.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Comga on 01/30/2013 05:57 am
Good to see the Israelis willing to continue do business with SpaceX after all the delays with the F9 that made AMOS-4 jumping ship to the Land Launch Zenit.  :)

So the SpaceCom launch added to the SpaceX manifest in November of 2011 was AMOS-4 and this is AMOS-6? 
Did SpaceX ever remove the first on from their manifest?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: joek on 01/30/2013 05:58 am
What confuses me is that Amos-6 weighs 5.5ton/12,125lbs according to SFN report, far beyond Falcon 9 GTO capability(4.85 ton/10,682lbs as described by SpX's F9 page). Or did I miss something?
No, I don't think you did miss anything, but SpaceX is in the process of updating their line (to v1.1) and, as far as I recall, stats have not been announced for it yet, and 2015 is another 2 years away to boot.

The published NASA NLS F9 v1.1 performance data (http://elvperf.ksc.nasa.gov/elvMap/elvMap.ui.PerfGraph0?ReqType=Graph&OrbitType=C3&Contract=2&Vehicles=4) does suggest v1.1 is short of putting 5.5tons into GTO.  Maybe that's without a  "delta-v mission kit" (http://forum.nasaspaceflight.com/index.php?topic=15900.msg367231#msg367231) for which we haven't yet seen details for v1.1?


edit: Now back to KSLV-1 (looking good!).  Congrats all and thanks to the NSF crew for the coverage!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jason1701 on 01/30/2013 06:21 am
It's possible that the spacecraft will be providing some of the delta-v to get to GTO, in addition to circularizing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 01/30/2013 07:56 am
Now all SpaceX has to do is up the launch rate. A lot.
Definitely. Did they launch anything that was not ISS related in 2012?

Having a solid launch manifest is good (they've all presumably put down some cash already) but regular launches keep your launch crew sharp and once a year does not really do it.

One a month?

You have to ask what's been on the list since 2009/10. That should be about ready to go.


[edit] I see Spacex are now expecting to do 6 launches this year. This sounds like excellent news and a great chance to show they can handle both the government (NASA initially but they are looking at payloads from the DoD EELV programme as well) and the commercial sector. [edit]
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 01/30/2013 06:04 pm
I'll write it up, although I did have five seconds of thinking "Bloody hell, I wish we made money like space.com" ;D
Not the same as making money, but I almost never go to Space.com since finding this site.  :)
Yep, same here, although I do help Anatoly Zak with his site, but he is really low on funding now so he had to make only an articles abstract publicly available and one now has to pay for the full article. May involve everything if site funding continues to decline. Hard times lay ahead for his site.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: grythumn on 01/30/2013 08:10 pm
What confuses me is that Amos-6 weighs 5.5ton/12,125lbs according to SFN report, far beyond Falcon 9 GTO capability(4.85 ton/10,682lbs as described by SpX's F9 page). Or did I miss something?
No, I don't think you did miss anything, but SpaceX is in the process of updating their line (to v1.1) and, as far as I recall, stats have not been announced for it yet, and 2015 is another 2 years away to boot.

The published NASA NLS F9 v1.1 performance data (http://elvperf.ksc.nasa.gov/elvMap/elvMap.ui.PerfGraph0?ReqType=Graph&OrbitType=C3&Contract=2&Vehicles=4) does suggest v1.1 is short of putting 5.5tons into GTO.  Maybe that's without a  "delta-v mission kit" (http://forum.nasaspaceflight.com/index.php?topic=15900.msg367231#msg367231) for which we haven't yet seen details for v1.1?


edit: Now back to KSLV-1 (looking good!).  Congrats all and thanks to the NSF crew for the coverage!

That's the high-energy orbit graph, wouldn't the elliptical graph be more appropriate for GTO? Punching in an 36km x 27.0 degree elliptical (Not sure if that's standard for GTO, but closest I can find in a couple minutes of searching), the same tool gives a payload of 5715mt. Does that leave enough margin for a kick motor?

Link (http://elvperf.ksc.nasa.gov/elvMap/elvMap.ui.PerfGraph3?ReqType=Query&OrbitType=GTO&Incl=&Option=&Selection=&Contract=2&Drop1=Apogee&Drop2=Incl&Entry1=36000.0&Entry2=27.0&Plot=Ap_Mass&Vehicles=4&Cfgid1=99&Cfgid2=94&image_type=OUTPUT_JPEG&saveAsFile=false)

-R C
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: joek on 01/30/2013 09:54 pm
That's the high-energy orbit graph, wouldn't the elliptical graph be more appropriate for GTO? Punching in an 36km x 27.0 degree elliptical (Not sure if that's standard for GTO, but closest I can find in a couple minutes of searching), the same tool gives a payload of 5715mt. Does that leave enough margin for a kick motor?
Yes, you're right (doh!); elliptical with standard GTO appogee plot...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cmj9808 on 01/31/2013 06:41 am
That's the high-energy orbit graph, wouldn't the elliptical graph be more appropriate for GTO? Punching in an 36km x 27.0 degree elliptical (Not sure if that's standard for GTO, but closest I can find in a couple minutes of searching), the same tool gives a payload of 5715mt. Does that leave enough margin for a kick motor?
Yes, you're right (doh!); elliptical with standard GTO appogee plot...


Well, I think that makes a lot of sense, thanks guys.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 08/25/2013 09:32 pm
http://www.exim.gov/newsandevents/releases/2013/SpaceX-Launch.cfm

Quote
Ex-Im Bank Approves $105.4 Million Loan to Finance SpaceX Launch

Washington, D.C. – Continuing its support of the space industry in America, the Export-Import Bank of the United States (Ex-Im Bank) has authorized a $105.4 million loan to Space Communication Ltd. of Ramat Gan, Israel, to finance the Space Exploration Technologies (SpaceX) launch of the Amos-6 communications satellite, the purchase of American made-solar arrays, and insurance brokered by Marsh USA (Marsh)

The transaction is Ex-Im Bank’s third in support of a SpaceX launch, and it will support approximately 600 U.S. jobs in California and elsewhere, according to bank estimates derived from Departments of Commerce and Labor data and methodology. In June of 2013, Ex-Im Bank announced that it had approved financing for the launches of two satellites manufactured by Space Systems/Loral LLC, and in November of 2012 the Bank announced that it had approved financing for the launches of two Boeing-manufactured satellites.

“Ex-Im Bank is always ready to help the American space industry boost its international sales and export its products to important markets,” said Ex-Im Bank Chairman and President Fred P. Hochberg. “Our support of American launches and exports levels the playing field for U.S. companies and keeps highly-skilled, well-paying jobs on American soil.”

Satellite financing represents Ex-Im Bank’s most prominent stand-out sector in the Bank's newly transformed portfolio. Just three years ago, satellites accounted for only $50 million in authorizations per year. This year numbers as the third consecutive year in which Ex-Im Bank's satellite sector authorizations will have topped $1 billion.

Amos-6, a geosynchronous satellite, will replace Space Communication’s Amos-2 and cover markets in Central and Eastern Europe and the Middle East. The satellite will also provide pan-European coverage and broadband services in Europe and Africa.

The launch is scheduled for 2015.

Founded in 2002 and headquartered in Hawthorne, Calif., SpaceX designs, manufactures and launches rockets and spacecraft. It is the first private company to build, launch, and dock spacecraft at the International Space Station, a mission previously accomplished only by government space entities. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sublimemarsupial on 08/26/2013 04:47 pm
So does this article give us a good upper bound for the actual cost of a Falcon 9 launch? It states that the loan of $105 million is for the launch, insurance, and for "American made-solar arrays". Anyone have a good idea of the proportion of that amount that would go to the solar arrays?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IRobot on 08/26/2013 05:08 pm
Don't forget engineering services from SpaceX...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sublimemarsupial on 08/26/2013 06:58 pm
Don't forget engineering services from SpaceX...

Yeah, that was what I meant, in that this price give us an upper bound for the actual launch cost including all of the payload specific engineering and processing costs? Subtract off whatever the insurance and solar array costs are and whatever is left is the price spaceX is charging them for the LV hardware plus all the engineering for their payload.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dcporter on 08/27/2013 03:20 am
Don't forget engineering services from SpaceX...

Yeah, that was what I meant, in that this price give us an upper bound for the actual launch cost including all of the payload specific engineering and processing costs? Subtract off whatever the insurance and solar array costs are and whatever is left is the price spaceX is charging them for the LV hardware plus all the engineering for their payload.

That's assuming that this loan funds the entire process, which I'm not sure you can assume.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IRobot on 08/27/2013 08:15 am
Insurance is what? 5% of the total value? (satellite + launch?)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: joek on 08/27/2013 08:50 am
The figure typically mentioned is 15%, but that varies significantly based on the launch vehicle and satellite pedigree, the health of the insurance industry, and what specifically is being insured.  The "what" may include, e.g.: satellite ground handling damage; launch vehicle failure; satellite failure post-separation; satellite failure during first year of operation; ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 02/03/2015 09:38 am
I have found some photos of AMOS-6 under construction at Israel Aerospace Industries (https://www.facebook.com/media/set/?set=a.841105292606559.1073741829.227366043980490&type=3) - these were posted last December.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Setys on 04/25/2015 02:48 pm
Launch appears pushed back to February-March 2016

http://www.globes.co.il/en/article-spacecom-to-raise-50m-1001016293 (http://www.globes.co.il/en/article-spacecom-to-raise-50m-1001016293)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 04/26/2015 03:54 am
Launch appears pushed back to February-March 2016

http://www.globes.co.il/en/article-spacecom-to-raise-50m-1001016293 (http://www.globes.co.il/en/article-spacecom-to-raise-50m-1001016293)

That's weird.  I read the article, which says, "The Amos 6 satellite is meant to replace the Amos 2 satellite, due to go out of service in 2016. In late February, Spacecom announced that the launch window for Amos 6 had been deferred, and that it was expected to be in February-March 2016." 

But Spacecom's website for the AMOS-6 satellite still lists launch target as Q4/2015.  In their media/press releases page, there's no release that mentions a change (though, there isn't one that mentions the details in the Globes article either).  A google search doesn't bring up hits on any such announcement, etc.  I'm not sure where the author is getting this information.  Maybe it isn't public?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 04/26/2015 06:27 pm
Launch appears pushed back to February-March 2016

http://www.globes.co.il/en/article-spacecom-to-raise-50m-1001016293 (http://www.globes.co.il/en/article-spacecom-to-raise-50m-1001016293)

That's weird.  I read the article, which says, "The Amos 6 satellite is meant to replace the Amos 2 satellite, due to go out of service in 2016. In late February, Spacecom announced that the launch window for Amos 6 had been deferred, and that it was expected to be in February-March 2016." 

But Spacecom's website for the AMOS-6 satellite still lists launch target as Q4/2015.  In their media/press releases page, there's no release that mentions a change (though, there isn't one that mentions the details in the Globes article either).  A google search doesn't bring up hits on any such announcement, etc.  I'm not sure where the author is getting this information.  Maybe it isn't public?
give them some time. Once assembly of the SC is complete date will be much firmer.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 04/27/2015 07:46 pm
Depending on how you are naming your quarters, it is also possible that January/February 2016 is still "Q4 2015".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: xm11 on 01/24/2016 07:03 am
http://www.calcalist.co.il/markets/articles/0,7340,L-3679157,00.html

There Date: Amos 6 will be launched into space in May 2016

Space Communications announced today the launch date of the new satellite revised - out of the sky delayed by over a year. Amos 6 will replace the Amos 2 will provide, among other things broadband services in Africa, cooperation with Facebook
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 01/24/2016 05:28 pm
http://www.calcalist.co.il/markets/articles/0,7340,L-3679157,00.html

There Date: Amos 6 will be launched into space in May 2016

Space Communications announced today the launch date of the new satellite revised - out of the sky delayed by over a year. Amos 6 will replace the Amos 2 will provide, among other things broadband services in Africa, cooperation with Facebook

appears pressure is building on this launch (good find).

" Space announced in December that previous satellite in the series, Amos 5, is total loss - three weeks after contact with him was lost.

IAI has produced for the four satellites in space first in a series of Amos, Amos 5 satellite when (severed contact with him recently lost) produced "

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 01/24/2016 05:52 pm
http://www.calcalist.co.il/markets/articles/0,7340,L-3679157,00.html

There Date: Amos 6 will be launched into space in May 2016

Space Communications announced today the launch date of the new satellite revised - out of the sky delayed by over a year. Amos 6 will replace the Amos 2 will provide, among other things broadband services in Africa, cooperation with Facebook

Good find. Title updated to reflect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ElGuapoGuano1 on 01/24/2016 06:08 pm
Chris,  While editing the thread subject you might as well pull out the v1.1.  I'm sure this will fly on the Full Thrust variant. I believe I remember hearing the preferred nomenclature going forward is just Falcon 9 without any addendum.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: macpacheco on 01/24/2016 08:53 pm
wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Dante80 on 01/24/2016 09:14 pm
Amos-6 is about the same weight as SES-9. SES-9 is reported to have an ASDS landing, so it might be safe to assume that this one will have too.

Regarding the mission profile (sub-synchronous or GTO-1800), we will have to see what happens with SES-9 first.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 01/24/2016 11:58 pm
wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.
...possibly even RTLS. And this could be something that is being negotiated right now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sewebster on 01/25/2016 12:57 am
wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.

Is a low thrust engine actually more appropriate for a sub synchronous orbit than a higher thrust engine?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: macpacheco on 01/25/2016 01:17 am
wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.

Is a low thrust engine actually more appropriate for a sub synchronous orbit than a higher thrust engine?

It's not about thrust, but about ISP.
Chemical propulsion satellites (aka regular) use hydrazine which sucks at ISP. You just can't drop a regular GEO bird on LEO and hope it will raise itself to GEO. If it gets there, it will be very short of station keeping fuel.

An electric satellite uses ion thrusters, which have ISP much higher even than the best chemical propulsion solution, LH2/LOX.
The low thrust also means a long time until operating station is reached. For that reason you'd still want to launch an all electric satellite as close as possible to GEO as possible.

But this makes it possible to build a massive GEO all electric bird, say 10 tons, with far more useable mission capabilities, launch it to LEO, and do the whole LEO to GEO transition while using less propellant mass than a chemical satellite would from GTO-1500m/s to GEO (actually far less).

Does this make sense ? Not rocket scientist...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sewebster on 01/25/2016 02:12 am
Is a low thrust engine actually more appropriate for a sub synchronous orbit than a higher thrust engine?

It's not about thrust, but about ISP.
Chemical propulsion satellites (aka regular) use hydrazine which sucks at ISP. You just can't drop a regular GEO bird on LEO and hope it will raise itself to GEO. If it gets there, it will be very short of station keeping fuel.

An electric satellite uses ion thrusters, which have ISP much higher even than the best chemical propulsion solution, LH2/LOX.
The low thrust also means a long time until operating station is reached. For that reason you'd still want to launch an all electric satellite as close as possible to GEO as possible.

But this makes it possible to build a massive GEO all electric bird, say 10 tons, with far more useable mission capabilities, launch it to LEO, and do the whole LEO to GEO transition while using less propellant mass than a chemical satellite would from GTO-1500m/s to GEO (actually far less).

Does this make sense ? Not rocket scientist...

I see what you are saying, thanks, but I guess I would assume that a normal GTO would still also be an appropriate target for an electric propulsion satellite. "Normal" satellites still have a lot of work to do to transition from GTO to GEO, right? So natural to replace that with electric. Of course, you can take it further to sub synchronous or even LEO in the extreme in theory (as you point out).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 01/25/2016 06:50 am
wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.

Is a low thrust engine actually more appropriate for a sub synchronous orbit than a higher thrust engine?

It's not about thrust, but about ISP.
Chemical propulsion satellites (aka regular) use hydrazine which sucks at ISP. You just can't drop a regular GEO bird on LEO and hope it will raise itself to GEO. If it gets there, it will be very short of station keeping fuel.

An electric satellite uses ion thrusters, which have ISP much higher even than the best chemical propulsion solution, LH2/LOX.
The low thrust also means a long time until operating station is reached. For that reason you'd still want to launch an all electric satellite as close as possible to GEO as possible.

But this makes it possible to build a massive GEO all electric bird, say 10 tons, with far more useable mission capabilities, launch it to LEO, and do the whole LEO to GEO transition while using less propellant mass than a chemical satellite would from GTO-1500m/s to GEO (actually far less).

Does this make sense ? Not rocket scientist...

The big problem with this method is that it would take A Very Long TimeTM.  Sure, your all-electric bird has a great Isp.  But what its engines don't have is very much actual thrust, so it ends up taking "forever" to raise the orbit.  This is a potential problem for 2 reasons.  1. You've lost revenue generating time to orbit raising time.  Depending on a company's economic analysis, maybe this is okay.  It could theoretically be made up for by lengthening the satellite's lifetime on orbit.  2. It means that the satellite also ends up spending quite a long time getting through the Van Allen radiation belts, which is not good for the hardware on the satellite.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sewebster on 01/25/2016 07:10 am
The big problem with this method is that it would take A Very Long TimeTM.  Sure, your all-electric bird has a great Isp.  But what its engines don't have is very much actual thrust, so it ends up taking "forever" to raise the orbit.  This is a potential problem for 2 reasons.  1. You've lost revenue generating time to orbit raising time.  Depending on a company's economic analysis, maybe this is okay.  It could theoretically be made up for by lengthening the satellite's lifetime on orbit.  2. It means that the satellite also ends up spending quite a long time getting through the Van Allen radiation belts, which is not good for the hardware on the satellite.

I guess Eutelsat 115 West B already made the transfer using all electric propulsion and is now operational? Edit and ABS-3A?

Here's a paper with a bunch of plots of various tradeoffs for this strategy:
http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/2007index/IEPC-2007-287.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 01/25/2016 07:41 am
The big problem with this method is that it would take A Very Long TimeTM.  Sure, your all-electric bird has a great Isp.  But what its engines don't have is very much actual thrust, so it ends up taking "forever" to raise the orbit.  This is a potential problem for 2 reasons.  1. You've lost revenue generating time to orbit raising time.  Depending on a company's economic analysis, maybe this is okay.  It could theoretically be made up for by lengthening the satellite's lifetime on orbit.  2. It means that the satellite also ends up spending quite a long time getting through the Van Allen radiation belts, which is not good for the hardware on the satellite.

I guess Eutelsat 115 West B already made the transfer using all electric propulsion and is now operational? Edit and ABS-3A?

Here's a paper with a bunch of plots of various tradeoffs for this strategy:
http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/2007index/IEPC-2007-287.pdf

Great link, thanks!  Just as a note though, macpacheco was talking about going from LEO to GEO, not GTO to GEO.  Though, I should have made clear that he already mentioned my "problem #1" in his post.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dkovacic on 01/25/2016 10:11 am
The big problem with this method is that it would take A Very Long TimeTM.  Sure, your all-electric bird has a great Isp.  But what its engines don't have is very much actual thrust, so it ends up taking "forever" to raise the orbit.  This is a potential problem for 2 reasons.  1. You've lost revenue generating time to orbit raising time.  Depending on a company's economic analysis, maybe this is okay.  It could theoretically be made up for by lengthening the satellite's lifetime on orbit.  2. It means that the satellite also ends up spending quite a long time getting through the Van Allen radiation belts, which is not good for the hardware on the satellite.

I guess Eutelsat 115 West B already made the transfer using all electric propulsion and is now operational? Edit and ABS-3A?

Here's a paper with a bunch of plots of various tradeoffs for this strategy:
http://erps.spacegrant.org/uploads/images/images/iepc_articledownload_1988-2007/2007index/IEPC-2007-287.pdf

Great link, thanks!  Just as a note though, macpacheco was talking about going from LEO to GEO, not GTO to GEO.  Though, I should have made clear that he already mentioned my "problem #1" in his post.

This is a great link, it basically shows the tradeoffs and you can simply see that low apogee greatly enhances days spent in LEO and going through Van-Allen belts. A rough estimate would be that LEO-GEO would be at least two times longer than GTO-GEO.
There is a third reason to avoid LEO as starting point for orbit raising - occultation effect. In LEO, satellite spends almost 50% in the Earths shadow, lasting 45 minutes. This leads to frequent temperature cycles. GEO comsats do carry batteries to continue operating during occultation periods, but these are not needed frequently roughly 1h per day during 60 days per year, totaling around 900 charge-discharge cycles for the lifetime of the satellite. Compare it to 200-day orbit raising from LEO with 8 cycles per day leading to 1600 cycles.

So I think pure LEO-to-GEO using electric propulsion is not really viable right now, despite 3x lower launch cost per kg. Various trade offs could be made for all-electric satellites launched to elliptical orbits. For example, 200x5000km orbit requires roughly 1km/s dV from LEO, perigee could be raised above 1200km in less than 10 days, reducing collision hazards and avoiding or reducing propulsion through Earths shadow. Unfortunately, as Figure 2 in the quoted document shows, there is no trick to avoid excessive passing through inner Van-Allen radiation belt - cumulative time will be at least 10 times longer than for GTO starting point.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FutureSpaceTourist on 06/23/2016 10:02 am
Quote
Peter B. de Selding ‏@pbdes 6m6 minutes ago

Spacecom of Israel: We are planning for an Aug. 22 launch, on SpaceX Falcon 9, of our Amos-6 Ku-/Ka-band telecom sat for 4 deg W.

https://twitter.com/pbdes/status/745918143797862401 (https://twitter.com/pbdes/status/745918143797862401)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 06/23/2016 01:00 pm
Date updated in the thread title.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 06/23/2016 02:15 pm

FCC has posted the latest transmitter permit application here:

https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=current&application_seq=72213&RequestTimeout=1000

Drone ship coordinates are:

28 6 11 N
74 34 0 W

This is about 45 miles west of the JCSAT-14 coordinates, ie closer to the Cape. This is quite a change, since the SES-9, JCSAT-14, Thaicom-8, and Eutelsat/ABS ASDS positions were all within 11 miles or so of each other.

The AMOS-6 launch date has just been announced as August 22, so this permit may be for AMOS-6, which is listed as 5500 kg. That's 700 kg more than JCSAT-14, which could explain the big difference in ASDS positions.

Also, 5500 kg is probably the upper limit for stage 1 recovery on GTO missions. The SpaceX F9 "capabilities" web page gives an F9 price of $62M for payloads up to 5500 kg to GTO. And LouScheffer's calculations have deduced an upper limit in this ballpark as well.

So AMOS-6 may turn out to be another "limiting case" stage 1 recovery experiment for SpaceX.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 06/23/2016 02:38 pm

FCC has posted the latest transmitter permit application here:

https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=current&application_seq=72213&RequestTimeout=1000

Drone ship coordinates are:

28 6 11 N
74 34 0 W

This is about 45 miles west of the JCSAT-14 coordinates, ie closer to the Cape. This is quite a change, since the SES-9, JCSAT-14, Thaicom-8, and Eutelsat/ABS ASDS positions were all within 11 miles or so of each other.

The AMOS-6 launch date has just been announced as August 22, so this permit may be for AMOS-6, which is listed as 5500 kg. That's 700 kg more than JCSAT-14, which could explain the big difference in ASDS positions.

Also, 5500 kg is probably the upper limit for stage 1 recovery on GTO missions. The SpaceX F9 "capabilities" web page gives an F9 price of $62M for payloads up to 5500 kg to GTO. And LouScheffer's calculations have deduced an upper limit in this ballpark as well.

So AMOS-6 may turn out to be another "limiting case" stage 1 recovery experiment for SpaceX.

So we really don't have any idea yet which launch this is for?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 06/23/2016 02:54 pm
Quote
So we really don't have any idea yet which launch this is for?

The applications usually don't say which commercial customer the launch is for, so it's a bit of a guessing game. But based on the dates given in the permit, it's probably the next GTO launch, which is apparently either JCSAT-16 or AMOS-6, so we can narrow it down to those two possibilities.

Beyond that, roll your own dice. I'm guessing the 5500 kg AMOS-6 explains the significant difference in ASDS positions, but it's admittedly only a guess.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: zubenelgenubi on 07/18/2016 03:58 pm
BUMP: AMOS 6 payload and Falcon 9 hardware

I'm guessing that since no one has reported any deliveries to the Cape, none of the hardware has arrived yet?

Any news of cargo aircraft inbound from Israel landing at the Skid Strip or the SLF?

We're a few days over 1 month from the launch date.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FutureSpaceTourist on 07/27/2016 09:07 am
Quote
Peter B. de Selding ‏@pbdes 20m20 minutes ago

New target date for SpaceX launch of Spacecom's Amos-6 geo telecom satellite is 3-4 Sept (was 22 Aug.)

https://twitter.com/pbdes/status/758222044911771648 (https://twitter.com/pbdes/status/758222044911771648)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ilikeboosterrockets on 07/31/2016 11:50 pm
Stage 1 possibly spotted headed towards McGregor by reddit user groundedengineer.

https://www.reddit.com/r/spacex/comments/4vfesm/saw_what_looked_like_a_black_shrink_wrapped/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: The Roadie on 08/02/2016 06:13 pm
JCSAT 14 returned stage (fuselage 024) removed from McGregor test stand this morning after three full duration tests. Presumably to allow 029 to be erected for AMOS-6 testing.

Reported in the Facebook group by member Keith Wallace.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 08/05/2016 11:31 pm
Update thread now live:

https://forum.nasaspaceflight.com/index.php?topic=40868.0

--

As we have this news:
https://www.nasaspaceflight.com/2016/08/spacex-falcon-9-preparation-jcsat-16-amos-6/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Tuts36 on 08/16/2016 04:09 pm
Any word on where the first stage is at this time?  Could the ongoing flooding & highway closures in LA (including sections of I-10 & I-12) cause a significant delay?

EDIT: Ugh, sorry. Please move to discussion thread if needs be :/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 08/17/2016 08:46 am
According to Reddit (https://www.reddit.com/r/spacex/comments/4pv7jl/amos6_launch_campaign_thread/), the core is now en-route to SLC-40 after completing its full-duration test burn at McGreggor.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: linxiaoyi on 08/17/2016 09:34 am
According to Reddit (https://www.reddit.com/r/spacex/comments/4pv7jl/amos6_launch_campaign_thread/), the core is now en-route to SLC-40 after completing its full-duration test burn at McGreggor.

That's just a speculation
Quote
Hopefully the stage is on its way to the Cape after the (reported) successful full engine burn at McGregor. If the stage arrives this weekend that would be 3 weeks away from a Sept. 3/4 launch date. ~3 weeks is the recent cadence between stage arrival at the Cape and launch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cuddihy on 08/17/2016 10:11 am
Yes, doutbful at this moment (8/17) -- I-10 and I-12 are both still experiencing total closures east of Baton Rouge due to the historic flooding: http://m.roadnow.com/i10/traffic_state.php?i=4&from=f and there's a lot of road work in progress, who knows if there's any lane closures. I'd think SpaceX would wait a couple more days.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: joncz on 08/17/2016 01:16 pm
Hopefully then SpaceX will decide to reroute up to I-20 through Atlanta. :D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 08/17/2016 01:18 pm
According to Reddit (https://www.reddit.com/r/spacex/comments/4pv7jl/amos6_launch_campaign_thread/), the core is now en-route to SLC-40 after completing its full-duration test burn at McGreggor.

That's just a speculation

There's L2 information about this, by the way.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 08/17/2016 03:16 pm
Let me guess this: the MECO-1 time for this mission will be around 156 seconds after launch...

I'm just making an assumption, by the way.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 08/17/2016 04:50 pm
Drone Ship Coordinates:
North  28  8  52    West  73  49  48    Autonomous Drone Ship
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 08/17/2016 10:53 pm

FCC has posted the latest transmitter permit application here:

https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=current&application_seq=72213&RequestTimeout=1000

Drone ship coordinates are:

28 6 11 N
74 34 0 W

This is about 45 miles west of the JCSAT-14 coordinates, ie closer to the Cape. This is quite a change, since the SES-9, JCSAT-14, Thaicom-8, and Eutelsat/ABS ASDS positions were all within 11 miles or so of each other.

The AMOS-6 launch date has just been announced as August 22, so this permit may be for AMOS-6, which is listed as 5500 kg. That's 700 kg more than JCSAT-14, which could explain the big difference in ASDS positions.

Also, 5500 kg is probably the upper limit for stage 1 recovery on GTO missions. The SpaceX F9 "capabilities" web page gives an F9 price of $62M for payloads up to 5500 kg to GTO. And LouScheffer's calculations have deduced an upper limit in this ballpark as well.

So AMOS-6 may turn out to be another "limiting case" stage 1 recovery experiment for SpaceX.

So we really don't have any idea yet which launch this is for?

In hindsight, that must have been for JCSAT-16. That position being 45 miles west of the JCSAT-14 position might explain why JCSAT-16 came back in better condition and why they had enough propellant to do a single engine landing burn.

Now back to AMOS-6...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 08/17/2016 11:53 pm
In hindsight, that must have been for JCSAT-16. That position being 45 miles west of the JCSAT-14 position might explain why JCSAT-16 came back in better condition and why they had enough propellant to do a single engine landing burn.

Now back to AMOS-6...

The satellites for the next several GTO missions are all expected to be heavier (5300-5500kg) than the JCSAT missions.  It will be interesting to see how they do.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cuddihy on 08/18/2016 02:39 am
As of 2330 GMT, I-12 and I-10 are both open, btw. Amazing work by Louisiana department of transportation.

Stage route is clear.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toastmastern on 08/20/2016 10:44 pm
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 08/20/2016 11:40 pm
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern

Read back a coupe days.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1570077#msg1570077
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toastmastern on 08/21/2016 09:11 am
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern

Read back a coupe days.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1570077#msg1570077

Yea I know that but I want proof that the stage is on route
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SmallKing on 08/21/2016 09:22 am
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern

Read back a coupe days.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1570077#msg1570077

Yea I know that but I want proof that the stage is on route
Now, I'm pretty sure
via FB group
Quote
Jim West
My son took a video of a rocket leaving McGregor. He put on fb but I can't figure how to move it to this group.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 08/21/2016 12:59 pm
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern

Read back a coupe days.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1570077#msg1570077

Yea I know that but I want proof that the stage is on route


If you'd have read the L2 info, the proof doesn't get more solid than that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toastmastern on 08/21/2016 01:26 pm
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern

Read back a coupe days.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1570077#msg1570077

Yea I know that but I want proof that the stage is on route


If you'd have read the L2 info, the proof doesn't get more solid than that.

I didn't ser an image of the stage on route did you?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DatUser14 on 08/21/2016 01:44 pm
Video posted to the Facebook group showing a stage leaving macgregor yesterday. Probably 029.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 08/21/2016 02:01 pm
Is the stage still in Texas? I've yet to see any  one spotting the core on the road to Florida.

The latest launches have had the 1st stage at CC 11 days before launch and we are closing in on that date for AMOS-6 now.

Toastmastern

Read back a coupe days.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1570077#msg1570077

Yea I know that but I want proof that the stage is on route


If you'd have read the L2 info, the proof doesn't get more solid than that.

I didn't ser an image of the stage on route did you?

If you'd have read the L2 info AND SEEN WHO POSTED IT, you wouldn't need a photo.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 08/21/2016 03:31 pm
If you'd have read the L2 info AND SEEN WHO POSTED IT, you wouldn't need a photo.

This back and forth isn't much fun... Be excellent to each other... and also do your homework. And when you urge others to do homework, giving links is helpful. It's OK to link to L2 content from here. Those not in L2 just can't follow the link usefully.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 08/22/2016 06:48 am
Apparently Amos booster en route to cape.
https://www.facebook.com/jerry.m.west/videos/10208691238137123/ (https://www.facebook.com/jerry.m.west/videos/10208691238137123/)

The vehicle seemed to be a bit slow turning the corner. Maybe that's one reason SpaceX can't make the booster any longer!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: QuantumG on 08/23/2016 12:13 am
I'm really happy for you Falcon, and I'm gunna let you finish, but Endeavour had the best trip through LA.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NX-0 on 08/24/2016 02:07 pm
No pressure, but...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 08/25/2016 08:41 pm
...but if successful, maybe Spacecom's new Chinese owners would prefer a domestic launch vehicle?...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rpapo on 08/25/2016 09:40 pm
...but if successful, maybe Spacecom's new Chinese owners would prefer a domestic launch vehicle?...
But if the public statements of the Chinese are to be believed, SpaceX is cheaper than anything they have.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zed_Noir on 08/26/2016 12:20 am
...but if successful, maybe Spacecom's new Chinese owners would prefer a domestic launch vehicle?...
But if the public statements of the Chinese are to be believed, SpaceX is cheaper than anything they have.
Well there is also the ITAR issue with US or Euro manufactured Comsats being launch from China.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 08/26/2016 01:49 am
...but if successful, maybe Spacecom's new Chinese owners would prefer a domestic launch vehicle?...
But if the public statements of the Chinese are to be believed, SpaceX is cheaper than anything they have.
Well there is also the ITAR issue with US or Euro manufactured Comsats being launch from China.

If the Chinese own the factory, what technology will remain to protect?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IntoTheVoid on 08/26/2016 02:23 am
...but if successful, maybe Spacecom's new Chinese owners would prefer a domestic launch vehicle?...
But if the public statements of the Chinese are to be believed, SpaceX is cheaper than anything they have.
Well there is also the ITAR issue with US or Euro manufactured Comsats being launch from China.

If the Chinese own the factory, what technology will remain to protect?
From one of the articles above, it must remain Israeli run, regardless of ownership. That may be false cover, but it's something.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zed_Noir on 08/26/2016 03:04 am
...but if successful, maybe Spacecom's new Chinese owners would prefer a domestic launch vehicle?...
But if the public statements of the Chinese are to be believed, SpaceX is cheaper than anything they have.
Well there is also the ITAR issue with US or Euro manufactured Comsats being launch from China.

If the Chinese own the factory, what technology will remain to protect?

Doubtful that the Chinese will be allow to buy GEO comsat manufacturers like Airbus, Boeing, Lockheed-Martin, Orbital-ATK, SSL or Thales Alenia. The AMOS-6 transponders is from SSL IIRC.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Barmaglot on 08/26/2016 03:33 am
If the Chinese own the factory, what technology will remain to protect?

SpaceCom is not the factory, just the operator. Amos-6 is built in Israel Aircraft Industries, which, to the best of my knowledge, is not for sale.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 08/26/2016 05:00 am
I'm a little lost as to the meaning of this whole Chinese launcher conversation.  AMOS-6 is launching on SpaceX in a week, before the company that owns AMOS-6 is sold.  What payload are you talking about launching on a Chinese rocket?  If you know of one, feel free to start a mission thread for it in the appropriate section.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 08/26/2016 07:22 am
If the Chinese own the factory, what technology will remain to protect?

SpaceCom is not the factory, just the operator. Amos-6 is built in Israel Aircraft Industries, which, to the best of my knowledge, is not for sale.

IAI, the company that built Amos-6, is not for sale and is in fact a wholly government-owned (State of Israel) company. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 08/29/2016 01:43 pm
Looks like amos-6 is just missing td9. Td9 should be well out to sea of cape canaveral.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacenut on 08/29/2016 02:10 pm
There is a 60% chance of rain on Sept 1st.  Do you guys think there might be a delay in launch?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sevenperforce on 08/29/2016 04:04 pm
I thought the launch was planned for the 3rd.

Speaking of which, is rain actually a problem for launches? I thought the usual weather scrubs were for high-altitude wind. Is there any reason that rain would be a problem for a Falcon 9 FT?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Comga on 08/29/2016 04:04 pm
There is a 60% chance of rain on Sept 1st.  Do you guys think there might be a delay in launch?

Did you mean Sept 3, the NET launch date?
If it rains, there will be a delay.  Of course there "might be a delay".
Given that they don't load the rocket until T-35 minutes, it will be interesting to see how long they go before calling any delay.
The generic, online weather forecast is for a more pleasant night, with much lower probability of rain, on the 5th, but someone here will post the CCAFS weather forecast as the day gets closer.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: The_Ronin on 08/29/2016 06:22 pm
Forecasting FL weather this far in advance is akin to (and reliable as) reading tea leaves.  Wait until PAFB releases the 72 hour forecast.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 08/29/2016 08:25 pm
This is one of those days where I won't be able to stay up until T0 for the launch and landing.

Because I need my sleep. I'll have to find out what happened the next morning.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacenut on 08/29/2016 09:03 pm
I meant the 3rd.  Not the first.  I was looking a a calendar on the first when I typed it.  Yes, early in the morning like that is least likely for thunderstorms.  What about the landing zone where the ship will be? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 08/30/2016 01:24 am
I thought the launch was planned for the 3rd.

Speaking of which, is rain actually a problem for launches? I thought the usual weather scrubs were for high-altitude wind. Is there any reason that rain would be a problem for a Falcon 9 FT?
I've never seen rain itself listed in an LCC,  but LCC typically include a lot of things that come along with rain.  From Wikipedia (https://en.wikipedia.org/wiki/Launch_commit_criteria#Falcon_9):

Quote
NASA has identified the Falcon 9 vehicle can not be launched under the following conditions. Some can be overridden if additional requirements are met.

* sustained wind at the 162 feet (49 m) level of the launch pad in excess of 30 knots (56 km/h; 35 mph)
* upper-level conditions containing wind shear[quantify] that could lead to control problems for the launch vehicle.
* launch through a cloud layer greater than 4,500 feet (1,400 m) thick that extends into freezing temperatures
* launch within 19 kilometres (10 nmi) of cumulus clouds with tops that extend into freezing temperatures,
within 19 kilometres (10 nmi) of the edge of a thunderstorm that is producing lightning within 30 minutes after the last lightning is observed.
* within 19 kilometres (10 nmi) of an attached thunderstorm anvil cloud
* within 9.3 kilometres (5 nmi) of disturbed weather clouds that extend into freezing temperatures
* within 5.6 kilometres (3 nmi) of a thunderstorm debris cloud,
through cumulus clouds formed as the result of or directly attached to a smoke plume,

The following should delay launch:

* delay launch for 15 minutes if field mill instrument readings within 9.3 kilometres (5 nmi) of the launch pad exceed +/- 1,500 volts per meter, or +/- 1,000 volts per meter
* delay launch for 30 minutes after lightning is observed within 10 nautical miles (19 km; 12 mi) of the launch pad or the flight path

These are NASA criteria, but I don't SpaceX's commercial criteria are much different.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OnWithTheShow on 08/30/2016 02:34 pm
From the update thread:

Interesting that the Air Force still classifies F9 flights as "expendable".

Do we have an idea of static fire date?  Unless they get it in today I think they will have to delay due to weather.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 08/30/2016 02:46 pm
From the update thread:

Interesting that the Air Force still classifies F9 flights as "expendable".


When has one been reused?  And what happens with the second stage or fairing?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: abaddon on 08/30/2016 02:51 pm
When has one been reused?
That doesn't really matter, even if it gets reused even as a building ornament it can hardly be called "expendable".  Also seems a bit dated given SES-10 is confirmed as launching on one this year.
Quote
And what happens with the second stage or fairing?
Do they classify airplanes with a drop tank as "expendable"?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 08/30/2016 02:52 pm
From the update thread:

Interesting that the Air Force still classifies F9 flights as "expendable".


When has one been reused?  And what happens with the second stage or fairing?

Exactly.  At best, an F9 is semi-reusable, since, as you say, the US and fairing are used in a completely expendable mode as of now, and this will continue for the foreseeable future.

Still, the system does feature a design allowing re-usability of a major (and expensive!) piece of the booster.  Certainly, this is not proven yet, but ought to be proven (if it can be) before this year is out.

It will be good to get past the standard line (oft-times quoted by you, Jim) that it's not a re-usable system until it's re-used... :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 08/30/2016 02:54 pm
Do they classify airplanes with a drop tank as "expendable"?

Yeah -- under this approach at the nomenclature, the Shuttle was an expendable launch system.

I mean, what happened with the ET?  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: abaddon on 08/30/2016 02:55 pm
All that said, this is the AMOS thread, so apologies for my participation in the derailment, and let's get back on track :D.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 08/30/2016 04:19 pm
Anyone have a time that Elsbeth III left PC? MT.com already has her out of range of shore AIS.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: 411rocket on 08/30/2016 04:42 pm
Anyone have a time that Elsbeth III left PC? MT.com already has her out of range of shore AIS.

6:45 PM yesterday, as posted on Reddit.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 08/30/2016 05:56 pm
Do they classify airplanes with a drop tank as "expendable"?

Yeah -- under this approach at the nomenclature, the Shuttle was an expendable launch system.

I mean, what happened with the ET?  ;)
But NASA didn't classify Shuttle as an expendable launch vehicle.  If you go here:
https://elvperf.ksc.nasa.gov/

...you see elv launches. As opposed to Shuttle launches. When pages like that were set up, it was assumed everything OTHER THAN SHUTTLE was expendable.

Also, "reusable" means "able to be reused." Doesn't imply they've already been reused.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 08/30/2016 06:03 pm
That doesn't really matter, even if it gets reused even as a building ornament it can hardly be called "expendable".

No, it is still an expendable launch vehicle.  Retrieving parts for other uses doesn't change that
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: abaddon on 08/30/2016 06:08 pm
That doesn't really matter, even if it gets reused even as a building ornament it can hardly be called "expendable".

No, it is still an expendable launch vehicle.  Retrieving parts for other uses doesn't change that
I'm going to agree to disagree; I'd call it a "recoverable" launch vehicle if it is recovered but not intended for reflight as a more accurate designation than either "expendable" or "reusable".  That said, the point is really moot, as SES-10 shows.  And frankly, SpaceX clearly plans to recover and reuse AMOS-6's booster.  If they are unable to recover and reuse the booster that might make it "expended" but not "expendable", just like an airplane crashing doesn't suddenly make that kind of airplane expendable.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IntoTheVoid on 08/30/2016 06:19 pm
That doesn't really matter, even if it gets reused even as a building ornament it can hardly be called "expendable".

No, it is still an expendable launch vehicle.  Retrieving parts for other uses doesn't change that

It's not expendable unless SpaceX is willing to throw it away, and since they are clearly making an effort to recover the booster, it is not expendable, regardless of whether they are successful or not, and regardless of what they do with it afterward.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 08/30/2016 06:44 pm
Recovery without reuse means it is expended.  It just happens to fly a little more than others after staging.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 08/30/2016 06:44 pm
Let's focus this thread on the mission in question.................from this point onwards.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacenut on 08/30/2016 07:28 pm
I live about 150 miles from the Gulf coast.  I'm still wondering about this tropical storm in the southern Gulf now that is supposed to cross north Florida.  I wonder whether it will delay the Amos 6 launch date. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 08/30/2016 07:36 pm
http://www.nhc.noaa.gov/refresh/graphics_at4+shtml/152206.shtml?gm_track#contents

at 7am cdt 9/3 it is 100's of miles off cape hatteras.
at 7am cdt 9/1 it is 100 miles west of tampa.
Might interfere with the static test fire.
I think it is very fast moving so it will be bad (10 in rain, 50knot winds) but short.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 08/30/2016 07:38 pm
Of course that says nothing about how bad it will be for the barge. A one day delay should make a big difference in wave height.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Flying Beaver on 08/30/2016 07:49 pm
Waves predicted by Windyty for Saturday morning, 1.6M (5.2ft for you Americans and Brits ;)), and wind at 17 knots from 230.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: high road on 08/31/2016 12:41 pm
Did anyone notice that this launch will make the US tie with Russia in number of launches this year? And surpass them later this month with non-SpaceX launches? I have no idea if there was ever a time that Russia did not dwarf all other nations in number of launches, but it's at least a decade ago, and probably before the STS. Pretty historic eh?

Whether this is related more to the US' increasing number of launches (with SpaceX responsible for most of the increase) or Russia's continuing decline, is still debatable. Don't count your chickens before they hatch fly.

If everybody knows and this horse has been beaten to death already, please tell me where. Way too many threads on here to keep track.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bdub217 on 08/31/2016 02:06 pm
Please direct me elsewhere if this question has already been addressed.
What goes into a GTO launch window?  This launch is happening in the absolute dead of night.  For ISS rendezvous missions - I get that launch windows are completely dictated by the orbital period of the stations.  For GTO launches, what constrains the launch window?  If there are no orbital physics restraints, what else would push a launch to the earliest of the early morning hours?  Would there be a preference on not wanting to load superchilled liquids in the heat of a florida summer day?  Less likelihood of stray pleasureboats scrubbing a launch?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 08/31/2016 02:13 pm
You want the satellite to be in sunlight for as long as possible after it detaches from the booster and the solar arrays are deployed. This maximises the battery recharge time after launch. So, ideally, you want S/C separation to be around orbital dawn. You then just calculate backwards from there using launch vehicle performance data to set your launch window.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacenut on 08/31/2016 02:38 pm
The storm I was referring to is in the Gulf of Mexico and is supposed to go across North Florida this weekend, bringing lots of rain and thunderstorms.  It may be moving further north.  Not in the Atlantic.  It is supposed to cross Florida west to east. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 08/31/2016 02:43 pm
Please direct me elsewhere if this question has already been addressed.
What goes into a GTO launch window?  This launch is happening in the absolute dead of night.  For ISS rendezvous missions - I get that launch windows are completely dictated by the orbital period of the stations.  For GTO launches, what constrains the launch window?  If there are no orbital physics restraints, what else would push a launch to the earliest of the early morning hours?  Would there be a preference on not wanting to load superchilled liquids in the heat of a florida summer day?  Less likelihood of stray pleasureboats scrubbing a launch?

All the above plus what Ben said...
The best reason I can figure is weather... my opinion...  ;)
Florida is known for it's afternoon pop up thunderstorm action... which all dies down by the wee hours of the morning...
Statistically... they are launching at the best time of the day... to avoid a weather related hold or scrub... 
Bonus is the loading of super cold prop in the dark and the pleasure boat crowd sleeping off the evening beer stash...
Not to mention what Ben said... puts the payload in the bright sun just as it needs it to set up shop in orbit.
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 08/31/2016 05:14 pm
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.

Most satellites use a combination of propellant and solar to get to their final destinations. The wee hour for this one is because the satellite is all electric, which incidentally is the weaker form of propulsion.

I can't see that any space company would prefer launches in the middle of the night, regardless of the fringe benefits. It must be a logistical nightmare to make sure all your crew is rested up to perform at their best at 3AM. You'd have to put everyone on a jet lag schedule days in advance.

However, all electric satellites can be seen as preferable for their significantly lower mass absent the mass of propellant. A more comfortable goal would likely be how to get them charged on the ground, not how to get them launched at 3AM.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: baldusi on 08/31/2016 06:06 pm
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.

Most satellites use a combination of propellant and solar to get to their final destinations. The wee hour for this one is because the satellite is all electric, which incidentally is the weaker form of propulsion.

I can't see that any space company would prefer launches in the middle of the night, regardless of the fringe benefits. It must be a logistical nightmare to make sure all your crew is rested up to perform at their best at 3AM. You'd have to put everyone on a jet lag schedule days in advance.

However, all electric satellites can be seen as preferable for their significantly lower mass absent the mass of propellant. A more comfortable goal would likely be how to get them charged on the ground, not how to get them launched at 3AM.
AMOS-6 uses electric for station keeping only. GTO transfer will be chemical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 08/31/2016 06:40 pm
Ben is right and weather has nothing to do with it nor the other stuff.  The reason is for the spacecraft lighting.  They want the spacecraft to be in full light after separation and during the climb to apogee.  This will help ensure that the spacecraft will be power positive.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 08/31/2016 06:52 pm
Weather has nothing to do with it. The reason is for the spacecraft lighting.  They want the spacecraft to be in full light after separation and during the climb to apogee.  This will help ensure that the spacecraft will be power positive.

Doesn't it take weeks to get to apogee? So is it safe to assume it takes weeks to fully charge if needing electric only for stationkeeping, and that it manages to stay in the full light vector that it started in?

I said it was all electric based on the much earlier quote below, w/o having read the article myself:

wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Hankelow8 on 08/31/2016 06:53 pm
James Dean says only 40% go for launch at 3am on Saturday
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 08/31/2016 06:55 pm
Weather has nothing to do with it. The reason is for the spacecraft lighting.  They want the spacecraft to be in full light after separation and during the climb to apogee.  This will help ensure that the spacecraft will be power positive.

Doesn't it take weeks to get to apogee? So is it safe to assume it takes weeks to fully charge if needing electric only for stationkeeping, and that it manages to stay in the full light vector that it started in?

I said it was all electric based on the much earlier quote below, w/o having reading the article myself:

wikipedia says AMOS-6 is an electric propulsion satellite, so its very likely going into a sub sync orbit, and then undergo slow transition to its GEO slot.
This suggests this launch will still be able to do ASDS landing attempt.

No, it gets to apogee in a matter of hours. But it's in a highly elliptical orbit with a low perigee. The perigee raising is what takes days, or weeks/months, depending on whether they use biprop or electric to raise perigee.

baldusi says perigee raising will be biprop, so that can be done in a matter of days.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 08/31/2016 07:04 pm
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.


Spacex has no real say in it.  It is driven by spacecraft requirements.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 08/31/2016 07:09 pm
James Dean says only 40% go for launch at 3am on Saturday

Ouch!

      So when is the next launch opportunity?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 08/31/2016 07:17 pm
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.


Spacex has no real say in it.  It is driven by spacecraft requirements.

I still don't get why they don't just charge up on the ground, if the satellite can reach apogee & sunlight in a matter of hours.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 08/31/2016 07:21 pm
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.


Spacex has no real say in it.  It is driven by spacecraft requirements.

I still don't get why they don't just charge up on the ground, if the satellite can reach apogee & sunlight in a matter of hours.

The batteries are fully charged at launch.  Power positive means they are receiving more power from the solar arrays than they using.  Battery power is only for launch prior to separation and eclipses (which are no greater than 90 minutes) while on station.  Batteries use is avoided when possible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: virnin on 08/31/2016 07:25 pm
I would expect SpaceX to continue this 'wee hour of the morning' practice from here on out... if they can.


Spacex has no real say in it.  It is driven by spacecraft requirements.

I still don't get why they don't just charge up on the ground, if the satellite can reach apogee & sunlight in a matter of hours.

They DO charge on the ground but everything runs from the batteries from launch until solar arrays are deployed and in sunlight.  The idea is to minimize the time spent on battery power so they have maximum time to recover from some off-nominal situation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 08/31/2016 07:50 pm
Thank you for all the answers, which I hope benefitted more than just me since I probably went over my personal daily allotment for questions. I'm probably stressed over the launch time because I've lived all night shifts myself in the past, and haven't really been the same since, although in my case it was to deliver a morning newspaper for a solid year for the business experience, and later to respond to the all too typical middle of the night house & apartment fires as a Red Cross volunteer for 10 years. That's all not to mention should we stay up to watch this launch or not?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 08/31/2016 11:28 pm
Did anyone notice that this launch will make the US tie with Russia in number of launches this year? And surpass them later this month with non-SpaceX launches? I have no idea if there was ever a time that Russia did not dwarf all other nations in number of launches, but it's at least a decade ago, and probably before the STS. Pretty historic eh?
...
Historic indeed.  And quite sudden.  For every year of the last decade, Russian launches have roughly equalled US and Chinese added together.  Even as recently as 8th June this was still true; after the Proton launch that day the totals for this year were Russia 14, USA 8, China 6  (I'm getting my data from Anatoly Zak's website at
http://www.russianspaceweb.com/2016.html ).

But after AMOS-6 the totals will be 16, 16, 12 or 13 (depending on Gaofen-10); and Russia will never be ahead again, this year or any other.  Truly the end of an era.

(And apologies from me too if this has been done to death on some other thread I haven't seen ...)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 09/01/2016 02:06 am
James Dean says only 40% go for launch at 3am on Saturday

Ouch!

      So when is the next launch opportunity?

September 4 is the delay date. There's a 60% chance of weather permitting on that day.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 09/01/2016 02:53 am
James Dean says only 40% go for launch at 3am on Saturday

Ouch!

      So when is the next launch opportunity?

September 4 is the delay date. There's a 60% chance of weather permitting on that day.
I wish they gave these odds in conditional format, as in:
What are the odd of weather permitting on the 4th /provided/ that the launch is delayed due to weather on the 3rd?

(this value is NOT the same as 60% since the two days have weather that is correlated in some way)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gadgetmind on 09/01/2016 10:50 am
Do we have a guess as to how long the main engine burn will be?

JCSAT-16 cut off at 2:30, so 3s earlier that usual, which let it do a single engine landing. AMOS-6 is a heavy bird at 5.5 tonnes, so they won't be able to do that again. I guess this one is going to come in as hot as JCSAT-14 (4.7mt) or even SES-9 (5.27mt)?

Sounds like it's going to be a lively landing between lack of fuel, high velocity, wind speed and wave height!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 09/01/2016 12:59 pm
gadgetmind, it's most likely that AMOS 6's first stage's trajectory will be similar to SES-9 due to the payloads' somewhat equal mass.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 01:19 pm
It blew up on the pad during hot fire

Well, damn.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kdhilliard on 09/01/2016 01:22 pm
It blew up on the pad during hot fire

Do we know if the payload was mated?

~Kirk

Followup:  It was.  Per SpaceX statement (https://twitter.com/SpaceX/status/771357538738577408):
Quote
SpaceX can confirm that in preparation for today’s static fire, there was an anomaly on the pad resulting in the loss of the vehicle and its payload. Per standard procedure, the pad was clear and there were no injuries.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlow on 09/01/2016 01:22 pm
I hope no one is hurt. I hope the damage to gse isn't bad. I hope there is a clear and well understood reason for whatever happened. I hope the recovery is swift.

Man this sucks.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: southshore26 on 09/01/2016 01:24 pm
Was the payload already on the rocket or did they just lose the launch vehicle?

This sucks....  :-\
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bynaus on 09/01/2016 01:24 pm
I hope no one is hurt. I hope the damage to gse isn't bad. I hope there is a clear and well understood reason for whatever happened. I hope the recovery is swift.

Man this sucks.

Agree on all. Oh damn.

I don't want to be too negative, but that was probably it for SpaceX flights this year. I hope I am wrong.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: philw1776 on 09/01/2016 01:29 pm
Unless the root cause is quickly ascribed to a static fire pad test mistake and not the vehicle, that will be it for 2016 launches.
Won't be re-using that core.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DPX on 09/01/2016 01:29 pm
Better to happen during test on the pad than in flight with payload loss, but still very grim news indeed.

Edit: My wishful thinking re the payload  :-[ No silver lining to this one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: hans_ober on 09/01/2016 01:31 pm
Was the payload on top? There have been missions with the fairing & payload on top.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bynaus on 09/01/2016 01:31 pm
Video feed from launch pad here: http://science.ksc.nasa.gov/shuttle/countdown/video/

EDIT: Launch towers intact. Black smoke. Blackened TE in the centre?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wannamoonbase on 09/01/2016 01:31 pm
Better to happen during test on the pad than in flight with payload loss, but still very grim news indeed.

Do we know if the payload was attached?   48 hrs to launch isn't much time. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jcm on 09/01/2016 01:32 pm
Do we know for sure this was the planned static test? (i.e. we have info it was planned for this morning?)
Obviously seems likely but not automatically the case
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 01:35 pm
Unless the root cause is quickly ascribed to a static fire pad test mistake and not the vehicle, that will be it for 2016 launches.
Won't be re-using that core.

Won't be re-using that pad either for a while, I'd imagine.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: psloss on 09/01/2016 01:35 pm
I hope no one is hurt. I hope the damage to gse isn't bad. I hope there is a clear and well understood reason for whatever happened. I hope the recovery is swift.

Man this sucks.
Agreed, but first and foremost hope everyone is OK.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 01:37 pm
Well, I guess one bright spot is that we'll finally have an answer to all those folks who claimed that the HIF was too close to the pad?  Of course, we don't know what that answer is yet.

This sucks.  Space is hard.  Hope everyone's okay.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 01:39 pm
From a friend at KSC (so this is third-hand info), incident seemed to occur at about F minus-3 minutes, so after prop load while stage was pressurizing to flight level.

I saw a tweet that I can't track down anymore that said the lox tank blew up. Not sure how reliable but if true... again?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 01:39 pm
From a friend at KSC (so this is third-hand info), incident seemed to occur at about F minus-3 minutes, so after prop load while stage was pressurizing to flight level.

So a tank rupture, something like that?  Pre-ignition, though there is plenty of energy around if the tanks pop.

But possibly lots of low energy combustion and not detonation.  All the pieces will still be in the general area to be found and scrutinized.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 09/01/2016 01:41 pm
This is a really bad failure for the Commercial Crew side of things.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 01:42 pm
This is a really bad failure for the Commercial Crew side of things.
Wasn't it SpaceX's position that crew should board only *after* propellant load?  And this is why...

It will also give hard data on the effectiveness of slide wire systems and shelter and such, so probably a good thing for overall crew safety, in the long run.  But agreed it certainly looks bad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: southshore26 on 09/01/2016 01:45 pm
They're taking a firefighter out by air medivac per KSC emergency radio  :'(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JWag on 09/01/2016 01:45 pm
Would the second stage prop have been loaded?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 01:47 pm
This is a really bad failure for the Commercial Crew side of things.
Wasn't it SpaceX's position that crew should board only *after* propellant load?  And this is why...

It will also give hard data on the effectiveness of slide wire systems and shelter and such, so probably a good thing for overall crew safety, in the long run.  But agreed it certainly looks bad.

normally people go on after the prop. SpaceX want to put them on before, since they only have 20 minutes or so with the supercooled oxygen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 01:47 pm
Would the second stage prop have been loaded?

Yes, it would also be finishing up LOX load at that point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 09/01/2016 01:49 pm
This is a really bad failure for the Commercial Crew side of things.
Wasn't it SpaceX's position that crew should board only *after* propellant load?  And this is why...

It will also give hard data on the effectiveness of slide wire systems and shelter and such, so probably a good thing for overall crew safety, in the long run.  But agreed it certainly looks bad.

I'm pretty sure SpaceX wants to board the crew before propellant load.  And not sure how much the escape system would help in a situation like this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bubbinski on 09/01/2016 01:49 pm
Were the engines firing or was this explosion during fuel load? Also was the explosion on the rocket or with ground equipment?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 01:49 pm
A bad mess. The big worry now is the condition of SLC-40; fixing the pad would probably take longer than any failure investigation and mitigation. If this was a  tank rupture, then most of the force would have been initially lateral; the T/E may be DOA but the pad sockets for core prop loading/drain may be intact if a bit toasty.

Several possibilities occur to me but, for now, everything would be speculation and it would be pointless to raise them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 01:50 pm
They're taking a firefighter out by air medivac per KSC emergency radio  :'(

Sh*t  :(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 01:50 pm
Would the second stage prop have been loaded?

Yes, it would also be finishing up LOX load at that point.
Is it possible that it was a problem with the loading side of things rather than the rocket itself?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 01:52 pm
They're taking a firefighter out by air medivac per KSC emergency radio  :'(

Sh*t  :(

On the other hand:

William Harwood ‏@cbs_spacenews
F9/AMOS6: Channel 13 in Orlando quotes 45th Space Wing saying no injuries have been reported
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 01:53 pm
Also from Doug Ellison of UMSF fame, who was at the Cape today:

Doug Ellison
‏@doug_ellison
@NASASpaceflight I drove from CAFS to KSCVC at about 8am - looked like 1st stage only was erected.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: hans_ober on 09/01/2016 01:53 pm
Transporter Erector seems okay. Smoke billowing from the base of the pad. No rocket in sight.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 01:54 pm
Also from Doug Ellison of UMSF fame, who was at the Cape today:

Doug Ellison
‏@doug_ellison
@NASASpaceflight I drove from CAFS to KSCVC at about 8am - looked like 1st stage only was erected.

Interesting... Has there been any talk of any of the recovered cores having a test fire today?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gongora on 09/01/2016 01:56 pm
Also from Doug Ellison of UMSF fame, who was at the Cape today:

Doug Ellison
‏@doug_ellison
@NASASpaceflight I drove from CAFS to KSCVC at about 8am - looked like 1st stage only was erected.

Interesting... Has there been any talk of any of the recovered cores having a test fire today?

It would have been the first two stages, not just the first stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 01:57 pm
Transporter Erector seems okay. Smoke billowing from the base of the pad. No rocket in sight.

There would only be duralinium confetti left of most of the vehicle; the octoweb and core engines might still be intact and on the pad though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MrEarl on 09/01/2016 01:57 pm
WESH is reporting two explosions.  One 20 mins after the first.  Is that true?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/01/2016 01:58 pm
Also from Doug Ellison of UMSF fame, who was at the Cape today:

Doug Ellison
‏@doug_ellison
@NASASpaceflight I drove from CAFS to KSCVC at about 8am - looked like 1st stage only was erected.

Interesting... Has there been any talk of any of the recovered cores having a test fire today?

It would have been the first two stages, not just the first stage.

Yes. The TE can't erect a first stage on its own. That would indicate though that the payload wasn't attached which would be a very good thing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Blizzzard on 09/01/2016 02:00 pm
Perhaps a pointless thing to say at this time, and assuming the issue has come from the rocket itself - but had this been a flight-proven Falcon 9 - would this have happened?

Very slight silver lining - might actually add more weight to using recovered stages...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 02:02 pm
Perhaps a pointless thing to say at this time, and assuming the issue has come from the rocket itself - but had this been a flight-proven Falcon 9 - would this have happened?

That is strongly dependent on the root cause of the explosion. Any conclusions would be highly speculative at this point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:02 pm
Is it possible that it was a problem with the loading side of things rather than the rocket itself?

What difference does it make? It's an integrated system, one cannot function without the other. Having this failure be down to GSE doesn't make it any better.

On the flip side, this is certainly going to be an interesting data point for pad abort risk assessments, blast overpressures and the like...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 02:03 pm
Reports of multiple explosions might indicate that some of the pad tankage was compromised by the initial blast and let go.  Which wouldn't mean anything re the initial failure, but would additionally complicate the work of getting the pad back on line.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rdale on 09/01/2016 02:03 pm
They're taking a firefighter out by air medivac per KSC emergency radio  :'(

They asked the helicopter to land and pick one up so he could see the fire from above.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 02:04 pm
Latest photos show that the T/E strongback seems intact! This is bizarre; I'm thinking that it must have been a tank top cap failure that directed most of the explosive force vertically upwards to avoid any collateral damage in that way!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GalacticIntruder on 09/01/2016 02:04 pm
Perhaps a pointless thing to say at this time, and assuming the issue has come from the rocket itself - but had this been a flight-proven Falcon 9 - would this have happened?

Very slight silver lining - might actually add more weight to using recovered stages...

The only silver would be if there was no satellite on-board. Blowing up another rocket for another reason, is not good. No way they get to launch again until another drawn out investigation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 02:05 pm
Is it possible that it was a problem with the loading side of things rather than the rocket itself?

What difference does it make? It's an integrated system, one cannot function without the other. Having this failure be down to GSE doesn't make it any better.

On the flip side, this is certainly going to be an interesting data point for pad abort risk assessments, blast overpressures and the like...

The difference is that if it is GSE side, there would be fewer concerns relating to the rocket once it is fuelled and up in the air. Additionally I'd expect that GSE stuff can be modified (e.g. thicker tank walls) with fewer ramifications.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 02:06 pm
Not a NASA payload==>not a NASA investigation.  The SpaceX investigation need not be drawn out (unless it needs to be because the root cause is elusive).  As pointed out above, it's likely that the pad reconstruction is going to take longer than the investigation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 02:07 pm
Latest photos show that the T/E strongback seems intact! This is bizarre; I'm thinking that it must have been a tank top cap failure that directed most of the explosive force vertically upwards to avoid any collateral damage in that way!

upright isn't the same as intact though. It may not be usable any more.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elvis in Space on 09/01/2016 02:08 pm
Not a NASA payload==>not a NASA investigation.  The SpaceX investigation need not be drawn out (unless it needs to be because the root cause is elusive).  As pointed out above, it's likely that the pad reconstruction is going to take longer than the investigation.

So could they move to LC-39 until the mess is cleaned up?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:09 pm
The difference is that if it is GSE side, there would be fewer concerns relating to the rocket once it is fuelled and up in the air.

That's not much of a consolation if you consider that the payload is up in the air on the rocket about the same length of time (30 min) as it is on the pad actively being loaded with all kinds of fluids.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/01/2016 02:11 pm
Not a NASA payload==>not a NASA investigation.  The SpaceX investigation need not be drawn out (unless it needs to be because the root cause is elusive).  As pointed out above, it's likely that the pad reconstruction is going to take longer than the investigation.

So could they move to LC-39 until the mess is cleaned up?


Cleaning up the mess may be way faster than the necessary investigation and design changes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:11 pm
upright isn't the same as intact though. It may not be usable any more.

Agreed. The discussion about the T/E likely shouldn't be about how "intact" it is, but perhaps how "salvageable".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/01/2016 02:12 pm
For once I'm in the "there is no silver lining" camp. :(

Hopefully they learn something valuable, but LOV on the pad during a static fire?  Unbelievable.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ElGuapoGuano1 on 09/01/2016 02:12 pm
It's really hard to tell where the smoke it coming from at this point, could either be smoldering remains or some of the GSE still on fire. Just hope no one was seriously injured. Everything is speculation at this point, but it appears SLC-40 will be out of commission for a while. I really hate "bad days".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/01/2016 02:14 pm
Not a NASA payload==>not a NASA investigation.  The SpaceX investigation need not be drawn out (unless it needs to be because the root cause is elusive).  As pointed out above, it's likely that the pad reconstruction is going to take longer than the investigation.

So could they move to LC-39 until the mess is cleaned up?


Cleaning up the mess may be way faster than the necessary investigation and design changes.
Unless it was a very clear case of human error. There is no idiot proofing of rockets.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 02:14 pm
The difference is that if it is GSE side, there would be fewer concerns relating to the rocket once it is fuelled and up in the air.

That's not much of a consolation if you consider that the payload is up in the air on the rocket about the same length of time (30 min) as it is on the pad actively being loaded with all kinds of fluids.

It's not so much the risk of loss that I am referring to - lets say it is a problem with the lox tanks on the rocket and they need making thicker or the welding needs changing or the piping needs changing, that would have impacts on the performance of the rocket, their manufacturing process and so on. On the other hand, if it is GSE, then only that part needs replacing (say it is a single point fault) and there are no impacts on the rocket performance or manufacturing process.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 02:14 pm
upright isn't the same as intact though. It may not be usable any more.

Agreed. The discussion about the T/E likely shouldn't be about how "intact" it is, but perhaps how "salvageable".

Or "how easily removable".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/01/2016 02:16 pm
Not a NASA payload==>not a NASA investigation.  The SpaceX investigation need not be drawn out (unless it needs to be because the root cause is elusive).  As pointed out above, it's likely that the pad reconstruction is going to take longer than the investigation.

So could they move to LC-39 until the mess is cleaned up?


Cleaning up the mess may be way faster than the necessary investigation and design changes.
The investigation will have to point out if there is in fact a need to change the design. Right now the cause is (publically) unknown. The cause could be something as simple as FUD in the tanks or a production fault. Those generally don't require design changes but changes to procedures.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 02:19 pm
Not a NASA payload==>not a NASA investigation.  The SpaceX investigation need not be drawn out (unless it needs to be because the root cause is elusive).  As pointed out above, it's likely that the pad reconstruction is going to take longer than the investigation.
Baseless speculation.
Nobody knows what happened, yet, so there's no way to tell how long it's going to take.
Other customers than NASA are also not going to put their expensive payloads on the vehicle unless they know what happened and that it got fixed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/01/2016 02:19 pm
Prayers that nobody was hurt.  Relief it wasn't during flight, that the payload seems to have been spared.  The root cause will be identified and fixed, and Falcons will fly again.  Courage to SpaceX folks during this difficult time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rockets4life97 on 09/01/2016 02:21 pm
There is conflicting reports about the payload being on top or not. I think we'll have to wait for an official source from SpaceX or the Amos-6 owner (SpaceCom Israel I think).

Edit: Now official reports from SpaceX that Amos-6 was lost in the incident.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 02:21 pm
Aside from hardware loss and pad damage, there is loss of confidence and maybe insurance price increases.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 02:22 pm
I am hearing that the payload was on top
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:23 pm
I am hearing that the payload was on top

This close to launch, I would expect the same. Extra bummer.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Dante80 on 09/01/2016 02:24 pm
Hope everyone is alright. This is terrible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Giovanni DS on 09/01/2016 02:24 pm
How much the fairing could protect the payload? The missile looks still standing in that photo.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/01/2016 02:24 pm
Video of secondaries on Youtube
https://www.youtube.com/watch?v=Auv1K-ciEWg#action=share

here is a series of reports via http://www.foxnews.com/science/2016/09/01/explosion-rocks-spacex-launch-site-in-florida-during-test.html
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 02:25 pm
Payload was on top as confirmed by Spacex
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/01/2016 02:25 pm
I am hearing that the payload was on top
As bad as a launch failure then.  Worse than most launch failures even, since some pad repair will be needed.

The year of "no failures" comes abruptly to an end, with yesterday's apparent CZ-4C failure and now this.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rdale on 09/01/2016 02:26 pm
SpaceX confirms it was a pad issue that caused it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 02:26 pm
No pressure, but...
Sigh.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul_G on 09/01/2016 02:26 pm
Wasn't the takeover of the firm who would operate AMOS-6 contingent on the successful launch of the sattelite?

Paul
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NX-0 on 09/01/2016 02:27 pm
I guess that sale to the Chinese won't be happening anytime soon.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meithan on 09/01/2016 02:27 pm
@SpaceflightNow on Twitter (https://twitter.com/SpaceflightNow/status/771352977315684352):

Quote
"SpaceX has confirmed the loss of both the Falcon 9 rocket and its $200 million payload in today’s explosion at the launch pad."
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/01/2016 02:27 pm
I am hearing that the payload was on top

Do they usually do the Static fire with the payload attached? are there different procedures for static fire WRT Dragon, GTO or LEO launches pertaing to payload onboard?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ElGuapoGuano1 on 09/01/2016 02:27 pm
Thanx for the confirmation Jim, that is a shame. I'm guessing from here on out, the payload won't be on the pad for static fires.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jak Kennedy on 09/01/2016 02:28 pm
At least the headlines I have read all mention that it happened during a test. Although a test very close to flight! A small improvement though on previous poor reporting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:28 pm
SpaceX confirms it was a pad issue that caused it.

Where? They said "an anomaly on the pad". Of course it was on the pad. Doesn't make it a pad issue, though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ap12 on 09/01/2016 02:28 pm
KSC video feed shows live view of burning pad. http://kscwmserv1.ksc.nasa.gov/channel4
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MostlyHarmless on 09/01/2016 02:29 pm
If the mishap occurred at T - 3:00 as was reported earlier, that is around the time that the Flight Termination System is armed.  Probably an odd coincidence, but curious, none-the-less.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Dante80 on 09/01/2016 02:29 pm
This is a really bad failure for the Commercial Crew side of things.
Wasn't it SpaceX's position that crew should board only *after* propellant load?  And this is why...

It will also give hard data on the effectiveness of slide wire systems and shelter and such, so probably a good thing for overall crew safety, in the long run.  But agreed it certainly looks bad.

The idea here is to have the Astronauts seated and the area cleared before the prop load happens. That way you make sure that the pad is clear and that any mishap will be countered by the LAS (it is designed for this contingency, aka a 0-0 launch abort).

The opposite can potentially be more dangerous since the astronauts and the support team have to walk to a loaded and pressurized rocket.

In the end though, the discussion may be informed by the way and reason this mishap happened (during prop load? during pressurization? etc etc).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/01/2016 02:30 pm
I am hearing that the payload was on top

Do they usually do the Static fire with the payload attached? are there different procedures for static fire WRT Dragon, GTO or LEO launches pertaing to payload onboard?
One thing is almost a given now. SpaceX won't be performing static fires with the payload on top from this point forward in time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Borklund on 09/01/2016 02:30 pm
Not good.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 02:31 pm
Wasn't the takeover of the firm who would operate AMOS-6 contingent on the successful launch of the sattelite?

Paul

That's correct.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wxmeddler on 09/01/2016 02:31 pm
Live feed with some good close up views from the local TV station helicopter:
https://www.facebook.com/wftv/videos/vb.72447968144/10154195747018145/?type=3&theater (https://www.facebook.com/wftv/videos/vb.72447968144/10154195747018145/?type=3&theater)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kirghizstan on 09/01/2016 02:32 pm
So what is the contingency plan for SpaceX KSC operations?  How fast can they get 39 up and running for F9 if the damage at the pad will take a long time to fix?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/01/2016 02:34 pm
If the mishap occurred at T - 3:00 as was reported earlier, that is around the time that the Flight Termination System is armed.  Probably an odd coincidence, but curious, none-the-less.
Isn't that also around the time that the T/E is being retracted?

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Endeavour_01 on 09/01/2016 02:34 pm
Terrible thing to see.  :( Best wishes for SpaceX as they look towards solving the problem and returning to flight.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Unobscured Vision on 09/01/2016 02:35 pm
It would be fixed before 39 is ready.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kosmos2001 on 09/01/2016 02:35 pm
Which is the point of testing the rocket engines while the P/L is on board? If there is any incident, like today's, the P/L is going to be lost anyway.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Tonioroffo on 09/01/2016 02:38 pm
Which is the point of testing the rocket engines while the P/L is on board? If there is any incident, like today's, the P/L is going to be lost anyway.

Time gains, surely?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 02:38 pm
So the payload was lost as well?

Even if it wasn't destroyed outright, it would have suffered severe enough damage to be an insurance write-off; it would be cheaper to build a new satellite than try to fix AMOS-6.

Which is the point of testing the rocket engines while the P/L is on board? If there is any incident, like today's, the P/L is going to be lost anyway.

As I understand it, the engines are already flight condition verified after they are fired at McGreggor; it's more of a case to ensure all vehicle systems are ready for flight as an integrated unit (including IU control of all systems and software parameters correct). Any structural failure at CCAFS raises more questions about post-test analysis at McGreggor than anything else (IMO).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:40 pm
If the mishap occurred at T - 3:00 as was reported earlier, that is around the time that the Flight Termination System is armed.  Probably an odd coincidence, but curious, none-the-less.
Isn't that also around the time that the T/E is being retracted?

Yes. Although the remains of this T/E don't look particularly retracted to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 02:41 pm
Strongback retraction begins at T-5:30.

Not for the "Full Thrust" variant.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 02:41 pm
I am hearing that the payload was on top

Do they usually do the Static fire with the payload attached? are there different procedures for static fire WRT Dragon, GTO or LEO launches pertaing to payload onboard?
One thing is almost a given now. SpaceX won't be performing static fires with the payload on top from this point forward in time.
Hm, that could definitely slow down their launch ops
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wannamoonbase on 09/01/2016 02:41 pm
SpaceX confirms it was a pad issue that caused it.

Where? They said "an anomaly on the pad". Of course it was on the pad. Doesn't make it a pad issue, though.

Another learning opportunity and chance to improve.

It's very disappointing that there isn't enough fail safes in the GSE to avoid a loss of vehicle on the ground.  That should be the easiest part of this business.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/01/2016 02:42 pm
So the payload was lost as well?

Even if it wasn't destroyed outright, it would have suffered severe enough damage to be an insurance write-off; it would be cheaper to build a new satellite than try to fix AMOS-6.

Which is the point of testing the rocket engines while the P/L is on board? If there is any incident, like today's, the P/L is going to be lost anyway.

As I understand it, the engines are already flight condition verified after they are fired at McGreggor; it's more of a case to ensure all vehicle systems are ready for flight as an integrated unit (including IU control of all systems and software parameters correct). Any structural failure at CCAFS raises more questions about post-test analysis at McGreggor than anything else (IMO)

Emphasis mine.
Cause of this accident is unknown at this time. Let's dispense with the unneccesary speculation shall we? Thank you.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MostlyHarmless on 09/01/2016 02:42 pm
Granted, the timelines I found apply to a launch -- not sure what variations there might be for a hot-fire test.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RobW on 09/01/2016 02:42 pm
Is the flight termination system armed during static fires?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IanH84 on 09/01/2016 02:44 pm
Closeup of the pad from the WFTV stream
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elvis in Space on 09/01/2016 02:45 pm
SpaceX confirms it was a pad issue that caused it.

Where? They said "an anomaly on the pad". Of course it was on the pad. Doesn't make it a pad issue, though.

Another learning opportunity and chance to improve.

It's very disappointing that there isn't enough fail safes in the GSE to avoid a loss of vehicle on the ground.  That should be the easiest part of this business.

Yeah, well that's the problem isn't it? It's generally easy to prevent the things you know about in advance. It will be another big learning opportunity for Spacex.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jakusb on 09/01/2016 02:45 pm
Closeup of the pad from the WFTV stream
Does not seem retracted.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: WBY1984 on 09/01/2016 02:46 pm
Which is the point of testing the rocket engines while the P/L is on board? If there is any incident, like today's, the P/L is going to be lost anyway.
If the payload is integrated then they can launch sooner once a good static fire is confirmed. Unfortunately, you also run the risk of something like this happening. :(

There is going to be a cascade of consequences stemming from the events of today. Between this and the still-recent CRS-7 failure, it effectively junks an impression that SpaceX likes to put forward - that it has the expertise and reliability necessary to go to Mars. Right now it is unable to even clear its satellite backlog.

The company is still very young, and this demonstrated lack of reliability relative to other companies/organisations underscores how far it has to go before it fulfills its undoubted potential.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SweetWater on 09/01/2016 02:47 pm
It's a pity about the payload, vehicle, and pad. Glad to hear that, so far, no one seems to have been hurt.

A question for someone more knowledgeable about insuring satellites than me: Do policies for spacecraft typically cover loss or damage incurred on the ground (for example, during transport or prepping for flight), or only during the actual launch of the vehicle? I work in auto claims, and my experience there would lead me to expect most of the liability here to be on SpaceX's side, but I'd be interested in hearing from a knowledgeable source.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/01/2016 02:48 pm
Is the flight termination system armed during static fires?

Don't know, but logically - knowing, what's the point of flight termination system, I would be almost certain that it's armed in any test where there's even remote chance that rocket gets airborne.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IanH84 on 09/01/2016 02:51 pm
FTS is armed during the static fire at T-3:05, same as flight.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sghill on 09/01/2016 02:55 pm
If the mishap occurred at T - 3:00 as was reported earlier, that is around the time that the Flight Termination System is armed.  Probably an odd coincidence, but curious, none-the-less.
Isn't that also around the time that the T/E is being retracted?

 - Ed Kyle

...And LOX top off termination.  I can see an ice dam build up and resultant poor hose seal or valve sealed shut being a culprit with this one.  The air is positively pregnant with moisture here right now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/01/2016 02:56 pm
September 1st. Back to School.

My heart is with SpaceX Team.
Rockets blow up, but humans keep flying.

Per aspera ad astra!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: as58 on 09/01/2016 02:56 pm
Test fire failures leading to a loss of payload must be rare. Has something like this happened before?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Michael Baylor on 09/01/2016 02:57 pm
Ok, so I wake up this morning, go to check the news as usual, and well this was the last thing I expected to see as the headline story on CNN.

Really not good for SpaceX considering last year's incident as well. If I was a customer and saw SpaceX with two fails in about a year, and ULA with over 100 successful launches in a row... Well... Umm... Really feel sorry for SpaceX though. Launch pad is gone. Time to get Pad 39a ready ASAP I guess. Devastating.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/01/2016 03:02 pm
If I remember correctly I think with the orbcomm mission there was some type of 'almost' anomaly during launch prep or static fire, saw some vague mentions, but never any details (probably details in L2)

edit - add link
Found discussion here: http://forum.nasaspaceflight.com/index.php?topic=33089.360 (http://forum.nasaspaceflight.com/index.php?topic=33089.360), Was just discussion, no idea if anything was ever confirmed, (and there is mention of perhaps something similar during SES-8)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 09/01/2016 03:03 pm
When I first heard of this news, my heart just stopped for like a second or two. I am so sorry about what happened.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MattMason on 09/01/2016 03:03 pm
Which is the point of testing the rocket engines while the P/L is on board? If there is any incident, like today's, the P/L is going to be lost anyway.
If the payload is integrated then they can launch sooner once a good static fire is confirmed. Unfortunately, you also run the risk of something like this happening. :(

There is going to be a cascade of consequences stemming from the events of today. Between this and the still-recent CRS-7 failure, it effectively junks an impression that SpaceX likes to put forward - that it has the expertise and reliability necessary to go to Mars. Right now it is unable to even clear its satellite backlog.

The company is still very young, and this demonstrated lack of reliability relative to other companies/organisations underscores how far it has to go before it fulfills its undoubted potential.

While you note fact, perhaps you can use the Wayback Machine known as the NASA and Air Force archives to count how many rockets were lost over the history of NASA and Cape Canaveral.

And we can make counts of losses from the Russians, ESA and others, too.

Is the loss ratio higher than others? Maybe. But fear, uncertainty and doubt isn't what spaceflight is about, and you know that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elvis in Space on 09/01/2016 03:04 pm
Ok, so I wake up this morning, go to check the news as usual, and well this was the lasting thing I expected to see as the headline story on CNN.

Really not good for SpaceX considering last year's incident as well. If I was a customer and saw SpaceX with two fails in about a year, and ULA with over 100 successful launches in a row... Well... Umm... Really feel sorry for SpaceX though. Launch pad is gone. Time to get Pad 39a ready ASAP I guess. Devastating.

It didn't stop the Russian's Proton.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sivasu on 09/01/2016 03:05 pm
Terrible news.
At least it won't be counted as a launch failure. Or would it?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rockets4life97 on 09/01/2016 03:06 pm
Terrible news.
At least it won't be counted as a launch failure. Or would it?

Test failure? Not sure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GalacticIntruder on 09/01/2016 03:06 pm
This would have a made a great pad abort test with Dragon2. Now they might have to rethink and reprogram some things for even more corner cases.

Hundreds of millions, if not more, in both real losses and deferred revenues. Higher insurance, delays on top of delays, more paperwork, more checks adding more time and money, more projects pushed back. No FH, No MCT reveal. No record launch cadence.

NOT GOOD, anyway shape or form.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SpaceXSLS on 09/01/2016 03:08 pm
This is terrible news  :'(

Could this jeapordize the company itself? SpaceX might not have a backlog problem anymore  :(

I mean, forget Mars 2018 or the Falcon Heavy, I'd expect the FH by Winter of next year or the year after next if we are lucky, and Mars is still as distant a dream as ever... Am I being too pessimistic about this?

Absolutely terrible that this happened so close to Elon Musk's unveiling of his MCT and associated Mars infrastructure plans, it makes it look like a joke now :(

Yes, you are overreacting.  I am sure that Spacex will take a hit, but I cannot see the failure being a threat to the existence of company.  The cost advantage of Spacex is significant even with the current failure rate.

Good, I know very little about how safe SpaceX is, I'm glad to hear this won't jeapordize its existence at least.

SpaceX has imo captured the hearts and minds of a generation. It would be terrible to see them go into the night like this. :(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: abaddon on 09/01/2016 03:08 pm
Sad to hear about this.  Unless it can be proven to be the GSE at fault that's likely the last SpaceX launch for the year, and the pressure on their commercial backlog, CRS and CC, and FH development are going to be severe.  All that said I expect they will pick themselves back up off the ground and move forward.  I'm glad that as of now nobody appears to have been injured in the incident.

My condolences and best wishes for the SpaceX team.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: teetlebomb on 09/01/2016 03:10 pm
Any word on the condition of the Hangar?

Being that close to the explosion, I would suspect significant damage, at least to the siding of the building, if not the structure itself. And even if Amos-6 wasn't on the rocket at the time, significant damage could have happened to it while in the hangar waiting processing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 03:11 pm
Note that apparently China had a launch failure yesterday as well.
https://twitter.com/elakdawalla/status/771360284212465665?s=09

I hope the rule of threes isn't in effect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: padrat on 09/01/2016 03:12 pm
If the payload is not on the rocket for static fire it isn't anywhere near the pad. It's back at the processing building waiting for static fire to occur.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickl on 09/01/2016 03:12 pm
Depending on the extent of damage to the pad, could they use this as an opportunity to upgrade LC-40 for Falcon Heavy?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vandersons on 09/01/2016 03:13 pm
Absolutely gutted for everyone at SpaceX. And just as they were starting to ramp up the launch rate, anouncement of the first relaunch, the imminent release of the Mars plans. Hope they pick this one up swiftly and thoruoghly.
I guess space is still hard.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/01/2016 03:13 pm
This was always going to include dramatic posts, due to what's happened, but I would urge people to remember that thousands of people read your post.

I don't think you want to be know as "that guy" who posted:

"OMGZ. Rocket dead?" ;)

Let's make posts worth reading....like this one (oh!)

Mods will remove crap posts, so don't quote crap posts and respond with "crap post!". That gives the mods twice the workload.

Thanks for listening. Carry on....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/01/2016 03:13 pm

Arianespace had multiple failures with loss of payload yet still became the worlds leading commercial launch provider. Proton had multiple failures, with loss of payload, yet continues launching commercial and government payload. Older versions of Atlas, Delta had multiple failures with loss of payload yet continued to fly for nearly 4 decades. That goes for multiple versions of Titan as well. All of these vehicles were operated by commercial entities. None of them folded because of failures.

Customers generally understand that space is hard. IMO SpaceX will suffer from this event, but it certainly will not endanger the continued existence of SpaceX as a company.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SpaceXSLS on 09/01/2016 03:14 pm
If the payload is not on the rocket for static fire it isn't anywhere near the pad. It's back at the processing building waiting for static fire to occur.

Payload was on the pad https://twitter.com/SciGuySpace/status/771352111657385984
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: padrat on 09/01/2016 03:16 pm
If the payload is not on the rocket for static fire it isn't anywhere near the pad. It's back at the processing building waiting for static fire to occur.

Payload was on the pad https://twitter.com/SciGuySpace/status/771352111657385984

I said IF the payload wasn't on the rocket, obviously not the case here...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CessnaDriver on 09/01/2016 03:17 pm
Absolutely gutted for everyone at SpaceX. And just as they were starting to ramp up the launch rate, anouncement of the first relaunch, the imminent release of the Mars plans. Hope they pick this one up swiftly and thoruoghly.
I guess space is still hard.

It is. And frankly I expect failures like this and the real test is how well they recover from them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SpaceXSLS on 09/01/2016 03:17 pm
If the payload is not on the rocket for static fire it isn't anywhere near the pad. It's back at the processing building waiting for static fire to occur.

Payload was on the pad https://twitter.com/SciGuySpace/status/771352111657385984

I said IF the payload wasn't on the rocket, obviously not the case here...

ok sorry, I thought you hadn't heard it yet...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 03:17 pm
C'mon SpaceX amazing peoples. Don't go straight from overly enthusiastic to totally fatalistic.

These things happen in Spaceflight. It's this (and not because they are stupid, wasteful morons) why NASA and all the others who've been in the business for longer are careful and have their cautious procedures.

But it won't be the end for SpaceX. They will learn from it just like everybody else did, they have a well proven vehicle, their customers have seen that and they understand this business and they know SpaceX can fix this.

Does it mean SpaceX is going to land us all on Mars in 5 years? Probably not, but that was never going to happen.

They will fix this, learn from it, become more reliable and iterate. And yes, over the time they will become more like "OldSpace" and then probably someone else comes around with bold plans and aggressive statements and then it's time to remember that only paper rockets are without failure...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacetraveler on 09/01/2016 03:17 pm
This is terrible news  :'(

Could this jeapordize the company itself? SpaceX might not have a backlog problem anymore  :(

I mean, forget Mars 2018 or the Falcon Heavy, I'd expect the FH by Winter of next year or the year after next if we are lucky, and Mars is still as distant a dream as ever... Am I being too pessimistic about this?

Absolutely terrible that this happened so close to Elon Musk's unveiling of his MCT and associated Mars infrastructure plans, it makes it look like a joke now :(

No need to be overly dramatic. Certainly a major setback, but there is no indication SpaceX won't be able to recover.
Arianespace had multiple failures with loss of payload yet still became the worlds leading commercial launch provider. Proton had multiple failures, with loss of payload, yet continues launching commercial and government payload. Older versions of Atlas, Delta had multiple failures with loss of payload yet continued to fly for nearly 4 decades. That goes for multiple versions of Titan as well. All of these vehicles were operated by commercial entities. None of them folded because of failures.

Customers generally understand that space is hard. IMO SpaceX will suffer from this event, but it certainly will not endanger the continued existence of SpaceX as a company.

Very true, a lot the hype and perception of SpaceX is based on their better than average track record of success with a new launch system thus far. A couple additional failures would just put them more in line with historical averages.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Dante80 on 09/01/2016 03:18 pm
Terrible news.
At least it won't be counted as a launch failure. Or would it?

Of course it would, and should. With the payload gone, this is a total launch campaign failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacetraveler on 09/01/2016 03:19 pm
So what is the contingency plan for SpaceX KSC operations?  How fast can they get 39 up and running for F9 if the damage at the pad will take a long time to fix?

The first task is not to analyze the time needed to get 39 up and running. It will be to fully understand the failure here and develop whatever changes and procedure modifications are needed to prevent it from recurring, since those same procedure changes would also likely need to be implemented at other pads as well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 03:19 pm
Had this happened without the satellite on top, I would have said that SpaceX has dodged a bullet much like the Grasshopper 2 incident, but since it was on board, it raises the problem that they are very probably the first commercial LSP to write off someone's satellite on the ground (I don't know how the insurers would think about this, for one). Given the uneasiness in the market to adopt them, such problems might scare off some of the customers and others (including NASA for Commercial Crew) would have their uneasiness risen on the company procedures.

The pad doesn't look too battered (much less than the Antares pad, that's for sure; and they have a potential back-up pad well on the way) and investigation should be somewhat easier than in-flight accidents, but I don't know how much psychological impact this weird accident will have for potential clients - maybe even more than a problem in flight since this was supposed to be the "safe part" of the operations.  :-\
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CraigLieb on 09/01/2016 03:20 pm
Dear SpaceX folks:
You give us hope for a multi-planetary future. Keep on striving and don't lose heart.
Certainly, you will do the hard science to find the cause of this failure and make all the systems more robust.
We will keep the faith with you.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: incoming on 09/01/2016 03:20 pm
there was an earlier post of the countdown events going back to about T-5 min.  I was wondering if anyone has the events for the 5 minutes before that - so from T-10 or so on? Fine if its for launch countdown vs. static fire, it should be close enough.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 03:21 pm
Terrible news.
At least it won't be counted as a launch failure. Or would it?

Of course it would, and should. With the payload gone, this is a total launch campaign failure.

Of somewhat more import, it's the first failure of F9 FT, and the second LOV/LOM failure in approximately 14 months. Customer confidence will be shaken at least somewhat, especially given the damage to launch facilities.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: padrat on 09/01/2016 03:21 pm

ok sorry, I thought you hadn't heard it yet...

Oh trust me, I've heard.....

Hi, I'm Padrat, nice to meet you, lol    (inside joke for the space vets on here)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 03:22 pm
In at least one way, this is worse than a launch failure, since that type of failure may leave the pad intact.

I'm really sad about this.  I hope they don't lose too many backlogged customers during the recovery period.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/01/2016 03:23 pm

ok sorry, I thought you hadn't heard it yet...

Oh trust me, I've heard.....

Hi, I'm Padrat, nice to meet you, lol    (inside joke for the space vets on here)
Padrat, how are the SpaceX folk holding up?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PreferToLurk on 09/01/2016 03:23 pm


Strongback retraction begins at T-5:30.  Although I saw a CBS news tweet that said something about 5 minutes before ignition.

T-0:05:55   Pressurization for Strongback Retract
T-0:05:30   Strongback Cradles Opening
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:46   Stage 1 & Stage 2 Auto Sequence starts
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:25   Strongback Retraction
T-0:04:10   Vehicle Release Auto Sequence
T-0:03:45   Verify Good Mvac TVC
T-0:03:40   TEA-TEB Ignition System Activation
T-0:03:30   Strongback Retraction complete
T-0:03:25   Flight Termination System to Internal Power
T-0:03:05   Flight Termination System Armed
T-0:03:00   LOX Topping Termination
T-0:03:00   Strongback Securing complete
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   FTS Countdown Sequence
T-0:02:30   Launch Director: Go for Launch
T-0:02:20   Propellant Tank Pre-Press
T-0:02:00   Range Verification
T-0:02:00   Flight Control to Self Alignment
T-0:01:35   Helium Loading Termination
T-0:01:30   Final Engine Chilldown, Pre-Valves/Bleeders Open
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:01:00   Pad Deck Water Deluge System Activation
T-0:00:55   Second Stage to Flight Pressure
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:40   First Stage to Flight Pressure
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF

Source for this?  JCSAT-16 launch had strongback BEGAN retracting at T-03:30, not retraction complete.  Strongback Securing/lockdown was called out at T-02:10, with apparent motion ending around T-02:30.   

FTS times though still seem to line up.  It appears that they are pushing fuel load (and hence full pressurization, and hence strongback retract) back in the sequence as far as possible. 

**Warning** severely premature armchair analysis incoming **Warning**
One thing that might come of this incident is a close look at SpaceX's penchant for continuously shaving margins in order to increase performance.   I think the question might be asked: "would this have happened with the same launch countdown sequence used 2 launches ago?  what about 4 launches ago? are we iterating on our countdown sequence too often?"

Maybe the answer to those questions is simply "NO", but from an outsiders perspective those are important questions to consider. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: StarTracker on 09/01/2016 03:24 pm
there was an earlier post of the countdown events going back to about T-5 min.  I was wondering if anyone has the events for the 5 minutes before that - so from T-10 or so on? Fine if its for launch countdown vs. static fire, it should be close enough.

Per the JCSAT-16 timeline, at T-7 engine chill down should have started.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 03:24 pm
when they do a static fire do they fully fuel the rocket or is it mostly empty?

do we have an estimate of % full?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kosmos2001 on 09/01/2016 03:25 pm
This is terrible news  :'(

Could this jeapordize the company itself? SpaceX might not have a backlog problem anymore  :(

I mean, forget Mars 2018 or the Falcon Heavy, I'd expect the FH by Winter of next year or the year after next if we are lucky, and Mars is still as distant a dream as ever... Am I being too pessimistic about this?

Absolutely terrible that this happened so close to Elon Musk's unveiling of his MCT and associated Mars infrastructure plans, it makes it look like a joke now :(

No need to be overly dramatic. Certainly a major setback, but there is no indication SpaceX won't be able to recover.
Arianespace had multiple failures with loss of payload yet still became the worlds leading commercial launch provider. Proton had multiple failures, with loss of payload, yet continues launching commercial and government payload. Older versions of Atlas, Delta had multiple failures with loss of payload yet continued to fly for nearly 4 decades. That goes for multiple versions of Titan as well. All of these vehicles were operated by commercial entities. None of them folded because of failures.

Customers generally understand that space is hard. IMO SpaceX will suffer from this event, but it certainly will not endanger the continued existence of SpaceX as a company.

Yes but in this particular case, the loss of the P/L was more avoidable than in an actual flight, imo.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/01/2016 03:25 pm
In at least one way, this is worse than a launch failure, since that type of failure may leave the pad intact.

I'm really sad about this.  I hope they don't lose too many backlogged customers during the recovery period.

It's hard to say at this point but, in terms of pad damage, it doesn't look as bad as the Antares failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/01/2016 03:27 pm
when they do a static fire do they fully fuel the rocket or is it mostly empty?

do we have an estimate of % full?
Test as you fly. It was a full rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 03:28 pm
Depending on the extent of damage to the pad, could they use this as an opportunity to upgrade LC-40 for Falcon Heavy?

Not feasible
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 03:30 pm
In at least one way, this is worse than a launch failure, since that type of failure may leave the pad intact.

I'm really sad about this.  I hope they don't lose too many backlogged customers during the recovery period.

It's hard to say at this point but, in terms of pad damage, it doesn't look as bad as the Antares failure.

Agreed that we don't know yet, but with all that LOX around, it could be a really intense fire too.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/01/2016 03:32 pm

ok sorry, I thought you hadn't heard it yet...

Oh trust me, I've heard.....

Hi, I'm Padrat, nice to meet you, lol    (inside joke for the space vets on here)
It's a rough day for us mere "fans", I can't imagine what it's like for you folks.  Here's hoping for a quick fault determination, resolution and return to flight.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 03:33 pm
Has there even been an accidental FTS firing?  (Not saying that's what this was, just asking).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/01/2016 03:35 pm
At this stage we can at most bound the consequences.

Best case:  root cause is clear, it's in the ground support equipment, and the same flaw is ruled out at Vandenburg.   SpaceX could launch again in a month or two from Vandenburg, then from the Cape as soon as the pad is fixed or the new pad comes on-line.

Worst case:  root cause is hard to determine, causing a lengthy investigation.  Results reveal changes needed to some fundamental part of the rocket, including those already manufactured, followed by significant re-testing.  (As in the Space Shuttle disasters).  Could result in a 2 year delay..

Given this huge range of possible consequences, it's pretty pointless to speculate on the impact to SpaceX until more is known about the cause.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: padrat on 09/01/2016 03:36 pm
Padrat, how are the SpaceX folk holding up?

As best as can be expected I guess.

Obviously things like this really suck and it will take some time to investigate and figure out what happened. But we'll bounce back and hopefully gain a lot of knowledge from this. It'll slow things down, but I'm pretty confident we'll still get there. The important thing is that no one to my knowledge was killed or injured from this. A personal request though for everyone... Yes you are free to post what you want on here (within reason), but maybe ask yourself "is this really the appropriate time to start the SpaceX doom and gloom" Just a thought....

And a little disclaimer, I'm not SpaceX public affairs, so I'm not making any official statements for the company. And even if I did know anything I wouldn't be able to say it anyways, as I'm sure you all know.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/01/2016 03:36 pm
AIUI, this happened before ignition, so following assumes that.

So bearing in mind the engines were not running, what can cause an explosion? Presumably since the fire was almost about to go ahead, the rocket was fully loaded with propellant, loading complete. What was going on that could actually cause the issue?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Norm38 on 09/01/2016 03:37 pm
I just got out of a meeting, during which my boss looked at his phone and said "A SpaceX rocket just exploded" and I got a big lump in my throat.  My thoughts immediately went to the engines, that it had been an engine failure during the static fire itself.
So I'm actually heartened to hear the reports that the failure occurred before ignition and was (likely?) due to the pad hardware side.  That immediately takes out a lot of variables.  For the moment, it seems that the basic design of the F9 is still sound.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 03:40 pm
AIUI, this happened before ignition, so following assumes that.

So bearing in mind the engines were not running, what can cause an explosion? Presumably since the fire was almost about to go ahead, the rocket was fully loaded with propellant, loading complete. What was going on that could actually cause the issue?

Typical causes for similar incidents with other vehicles in the past have been leaks of all kinds causing a fire.
Structural failure of a tank could also cause a fire and explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevinof on 09/01/2016 03:40 pm
My first thought was ground support equipment. Fuel lines under pressure,  stray spark or some screwup and that's all it would take. 



AIUI, this happened before ignition, so following assumes that.

So bearing in mind the engines were not running, what can cause an explosion? Presumably since the fire was almost about to go ahead, the rocket was fully loaded with propellant, loading complete. What was going on that could actually cause the issue?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 03:42 pm
Has there even been an accidental FTS firing?  (Not saying that's what this was, just asking).

I'm not aware of any. Those systems are designed and tested to be practically impossible to initiate accidentally. I've worked with FTS on Pegasus and TOS, and in my judgment accidental FTS initiation would be one of the least likely scenarios.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 03:42 pm
another COPV?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 03:42 pm
What was going on that could actually cause the issue?

Overpressurization of some component would be my guess. I'm looking at you, LOX tanks...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 03:43 pm
another COPV?

That's what I'm thinking.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/01/2016 03:43 pm
So bearing in mind the engines were not running, what can cause an explosion?

Falcon itself contains a lot of LOX which can combust under the right conditions. Both falcon and GSE contain TEA/TEB which are hypergolic with LOX so a leak on either sides tanks could easily cause problems. Payload contained Hydrazine, also hypergolic, so if something started up there it could have lead to the rest of the vehicle going with it. Electrical failure on vehicle or ground side could have ignited something. The engines are the only place you want a fire, but certainly not the only place you can get one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rnagiuh on 09/01/2016 03:43 pm
It is noteworthy that the issue appears to have been with the pad and ground systems, considering the small statement given by SpaceX, and not the rocket. But it is highly unfortunate that the payload was lost as part of the test. Hopefully if the issue is the GSE thus recovery can be quicker and not cause too much of a delay to the cadence. Best wishes to SpaceX and those who work so hard to get us to Mars.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/01/2016 03:43 pm
Fueling and launching a rocket has always been a complex task. This is a prime example of why they will never casually hook up some prop lines on that barge, on-load some prop and fly the S1 back from the open sea. From a risk assessment POV, the whole idea is outlandish.

I have to wonder what this does to Musk's unveiling of MCT in Mexico later this month. It might be too close to this and give too much fodder to naysayers. He may well be debating whether to delay the reveal.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 03:44 pm
another COPV?

Hm, now _that_ would really hurt SpaceX' reputation...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 03:44 pm
It is noteworthy that the issue appears to have been with the pad and ground systems, considering the small statement given by SpaceX,

The Spacex statement says nothing of the sort.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/01/2016 03:45 pm
Depending on the extent of damage to the pad, could they use this as an opportunity to upgrade LC-40 for Falcon Heavy?
Not feasible
To add more words to Jim's answer. LC-40 as built for Titan had two holes for the Titan III SRM flame trench. The Titan core was airlit in flight and did not need or have a flame trench. The Falcon 9 only uses one of those holes.  To convert LC-40 for Falcon Heavy a large amount of concrete needs to be removed to add a flame trench for the center core.  So to quote Jim not feasible in a way that is cost effective.

Plus they are working on three heavy capable pads at varying degrees of completeness. 

This is really reminding me of Discover 0 accident. Heart goes out to the SpaceX on this loss.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 03:45 pm
It is noteworthy that the issue appears to have been with the pad and ground systems, considering the small statement given by SpaceX, and not the rocket.

That's not what they meant by "on the pad." The rocket was on the pad too, and the failure could have started with the rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 03:45 pm
Is this test done to the exact-same conditions as the test in Texas?

If so, it suggests that either they were 'fortunate' not to have this happen there; or that the fault lies with the pad equipment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 03:46 pm
based on what I've seen on all of the NSF public threads and elsewhere, LoV happened in this chunk of the static fire countdown (most notable events in bold):

Excerpt F9FT countdown
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch

T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 03:47 pm
another COPV?

That's what I'm thinking.

Caused by a GSE issue (i.e. over pressurization), or by a flaw in the vehicle systems (relief valve, strut, tank itself, etc.)?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 03:47 pm
It is noteworthy that the issue appears to have been with the pad and ground systems, considering the small statement given by SpaceX,

The Spacex statement says nothing of the sort.

Agreed. People are running with the reported statement of an "anomaly on the pad" to vindicate the F9 itself and point at the GSE. The reality is we have no idea what happened - only SpaceX has the first clues to root cause yet, and they obviously won't say much very soon, unless Elon gets bored this weekend on Twitter.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/01/2016 03:47 pm
I just got out of a meeting, during which my boss looked at his phone and said "A SpaceX rocket just exploded" and I got a big lump in my throat.  My thoughts immediately went to the engines, that it had been an engine failure during the static fire itself.
So I'm actually heartened to hear the reports that the failure occurred before ignition and was (likely?) due to the pad hardware side.  That immediately takes out a lot of variables.  For the moment, it seems that the basic design of the F9 is still sound.

Root cause hasn't been announced. "Anomaly on the pad" doesn't mean "pad anomaly".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PahTo on 09/01/2016 03:48 pm

Bummer--my thoughts with SpX and the spaceflight community.

Having said that, and in keeping with my career at a project manager, a couple thoughts:

Based on the MARS experience, it would appear SLC40 will be out of commission for quite some time (a year?).  This would indicate ramping up pad 39A completion to get back to launch capability asap.  However, as padrat and others would attest, the skills required to get a pad flight ready are somewhat specialized, so the conundrum:  get 39A ready at the expense of repairing SLC40?  If the team(s) is split, that slows down both efforts.  This is a tough one for sure!

Years ago a number of us questioned (expressed concern?) the proximity of the HIF to 39A.  Others dismissed such questions with variations of "Its a prefab bldg., no big deal".  In light of today's events, I wonder if folks are so cavalier, especially considering the implications of having three flight ready cores in the HIF during a FH test or launch...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DragonRider on 09/01/2016 03:49 pm
We don't know the cause but can have some hope that it wasn't F9 given the circumstances, but we'll have to wait and see.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 03:49 pm
It is noteworthy that the issue appears to have been with the pad and ground systems, considering the small statement given by SpaceX,

The Spacex statement says nothing of the sort.

Agreed. People are running with the reported statement of an "anomaly on the pad" to vindicate the F9 itself and point at the GSE. The reality is we have no idea what happened - only SpaceX has the first clues to root cause yet, and they obviously won't say much very soon, unless Elon gets bored this weekend on Twitter.

In all fairness, the first one to come up with that misinterpretation on this thread was Jim himself, IIRC :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 09/01/2016 03:49 pm
I actually can compare this test failure to the infamous Atlas-Able static fire failure more than 50 years ago.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 03:49 pm
Payload contained Hydrazine, also hypergolic, so if something started up there it could have lead to the rest of the vehicle going with it.

Least likely.   But the payload could be an ignition source if the vehicle collapsed for other reasons
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 03:49 pm
only SpaceX has the first clues to root cause yet, and they obviously won't say much very soon, unless Elon gets bored this weekend on Twitter.

Or other hints leak out like the sudden collapse in she share price of a company further up the supply chain (materials smelting and rolling, etc).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: incoming on 09/01/2016 03:50 pm
there was an earlier post of the countdown events going back to about T-5 min.  I was wondering if anyone has the events for the 5 minutes before that - so from T-10 or so on? Fine if its for launch countdown vs. static fire, it should be close enough.

Per the JCSAT-16 timeline, at T-7 engine chill down should have started.

Source for the timeline is:  http://spaceflight101.com/falcon-9-countdown-timeline/    I haven't been able to find other sources with this level of detail, but most of the major events seem to line up with this one. 

I did see that this timeline applies to Falcon 9 V1.0 (missed that, earlier), so I'm guessing some of the events will have been shifted to accommodate the different fueling requirements.  Does any one have a more current countdown timeline?

The entire timeline I found is:

Time   Event
L-10:00:00   Falcon 9 to Vertical
L-8:30:00   Countdown Initiation, Launch Vehicle Power-Up
L-6:00:00   First Weather Balloon Release
L-5:00:00   Launch Area Evacuation
L-4:45:00   Range Controllers on Station
L-4:35:00   Falcon 9 Attitude Control System N2 Loading
L-4:50:00   Falcon 9 Reconfiguration for Propellant Loading
L-4:37:00   GO for Propellant Loading
L-4:20:00   Rocket Propellant 1 Loading
L-4:00:00   Eastern Range Countdown Initiation
L-4:00:00   LOX Systems Setup & Chilldown Ops
L-3:45:00   LOX Loading
L-2:45:00   Falcon 9 RF & Telemetry Checks
L-2:30:00   Falcon 9 Launch Vehicle Release System Test
L-2:25:00   TEA-TEB Bleed In
L-2:00:00   RP-1 Tanking complete
L-1:45:00   Comm & FTS Checks
L-1:40:00   Data Flow Tests with Downrange Tracking Stations
L-1:30:00   LOX Replenish
L-1:00:00   Weather Briefing
L-0:50:00   RF Link Checks
L-0:45:00   Flight Control System Setup (Flight Software Loading)
L-0:30:00   Final LOX Topping
L-0:27:00   Spacecraft to Internal Power
L-0:13:00   COUNTDOWN HOLD POINT
L-0:13:00   Launch Director Poll
L-0:11:00   Terminal Count Briefing
T-0:10:00   Terminal Countdown
T-0:09:55   Verify that Terminal Countdown has started
T-0:09:50   Range Recorders Start
T-0:09:45   Launch Enable to Flight Mode
T-0:09:30   First Stage Merlin Engine Chilldown, Pre Valves to Open
T-0:09:20   Ground TEA-TEB Setup
T-0:09:17   Merlin 1D: Lox Bleeder Valves Open
T-0:08:15   Engine Trim Valve Cycling
T-0:07:30   Go/No Go for Launch
T-0:07:00   Spacecraft on Internal Power
T-0:07:00   First Stage Heater Shutdown
T-0:07:00   First Stage ACS Close-Out
T-0:06:35   Second Stage Heater Shutdown
T-0:06:25   Falcon 9 to Internal Power
T-0:06:00   Transfer to Internal complete
T-0:05:55   Pressurization for Strongback Retract
T-0:05:30   Strongback Cradles Opening
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:46   Stage 1 & Stage 2 Auto Sequence starts
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:25   Strongback Retraction
T-0:04:10   Vehicle Release Auto Sequence
T-0:03:45   Verify Good Mvac TVC
T-0:03:40   TEA-TEB Ignition System Activation
T-0:03:30   Strongback Retraction complete
T-0:03:25   Flight Termination System to Internal Power
T-0:03:05   Flight Termination System Armed
T-0:03:00   LOX Topping Termination
T-0:03:00   Strongback Securing complete
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   FTS Countdown Sequence
T-0:02:30   Launch Director: Go for Launch
T-0:02:20   Propellant Tank Pre-Press
T-0:02:00   Range Verification
T-0:02:00   Flight Control to Self Alignment
T-0:01:35   Helium Loading Termination
T-0:01:30   Final Engine Chilldown, Pre-Valves/Bleeders Open
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:01:00   Pad Deck Water Deluge System Activation
T-0:00:55   Second Stage to Flight Pressure
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:40   First Stage to Flight Pressure
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF

I think this is pretty outdated - looks like it's pre-densified propellants.  I believe they fuel the rocket much later in the count now. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 03:50 pm
Can we say with confidence that it wasn't an engine problem, since it hadn't started them yet?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 03:50 pm
Everyone posting v1.0 or v1.1-pre-FT timelines, please stop.  Consider removing your posts.  It's actively unhelpful.  Fuel loading procedures changed significantly for 1.1 FT with its supercooled propellants.

For that matter, we don't even know if the failure happened around T-5 or T-3 yet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/01/2016 03:51 pm
At this stage we can at most bound the consequences.
True.
Quote
Worst case:  root cause is hard to determine, causing a lengthy investigation.  Results reveal changes needed to some fundamental part of the rocket, including those already manufactured, followed by significant re-testing.  (As in the Space Shuttle disasters).  Could result in a 2 year delay..
I strongly doubt SX would cease launches for 2 years.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rnagiuh on 09/01/2016 03:52 pm
It is noteworthy that the issue appears to have been with the pad and ground systems, considering the small statement given by SpaceX,

The Spacex statement says nothing of the sort.

Agreed. People are running with the reported statement of an "anomaly on the pad" to vindicate the F9 itself and point at the GSE. The reality is we have no idea what happened - only SpaceX has the first clues to root cause yet, and they obviously won't say much very soon, unless Elon gets bored this weekend on Twitter.

In all fairness, the first one to come up with that misinterpretation on this thread was Jim himself, IIRC :)

Right, apologies I read too much into their statement; "SpaceX can confirm that in preparation for today's static fire, there was an anomaly on the pad resulting in the loss of the vehicle and its payload. Per standard procedure, the pad was clear and there were no injuries.". Glad that there was no injuries, and all we can do is to look forward to more official updates.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/01/2016 03:53 pm
Can we say with confidence that it wasn't an engine problem, since it hadn't started them yet?

No. It could be a leak in the TEB/TEA lines or tanks of the engines.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 03:54 pm

Bummer--my thoughts with SpX and the spaceflight community.

Having said that, and in keeping with my career at a project manager, a couple thoughts:

Based on the MARS experience, it would appear SLC40 will be out of commission for quite some time (a year?).  This would indicate ramping up pad 39A completion to get back to launch capability asap.  However, as padrat and others would attest, the skills required to get a pad flight ready are somewhat specialized, so the conundrum:  get 39A ready at the expense of repairing SLC40?  If the team(s) is split, that slows down both efforts.  This is a tough one for sure!

Years ago a number of us questioned (expressed concern?) the proximity of the HIF to 39A.  Others dismissed such questions with variations of "Its a prefab bldg., no big deal".  In light of today's events, I wonder if folks are so cavalier, especially considering the implications of having three flight ready cores in the HIF during a FH test or launch...
Pad is said to have survived well in terms of damage. Charring is heavy but but SLC-40 did not suffer like MARS SLC-0A as that was an above pad explosion. where as the SLC-40 explosion saw flames shooting out the flame trench as well as upwards. Antares explosion was downwards and falling debris.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John.bender on 09/01/2016 03:54 pm
Dumb question but what is COPV?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DavidH on 09/01/2016 03:54 pm
Payload contained Hydrazine, also hypergolic, so if something started up there it could have lead to the rest of the vehicle going with it.

Least likely.   But the payload could be an ignition source if the vehicle collapsed for other reasons

Reminds me of the Atlas collapse.
https://www.youtube.com/watch?v=FmrrcAVOV4s (https://www.youtube.com/watch?v=FmrrcAVOV4s)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 03:54 pm
another COPV?

That's what I'm thinking.

seems like these guys go right to the top of the suspect list every time.

if it was copv it seems like it will be rather straight forward to pinpoint in this scenario

time will tell eh. pads still smokin. :/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/01/2016 03:56 pm
Dumb question but what is COPV?

Composite Overwrapped Pressure Vessel
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: topsphere on 09/01/2016 03:56 pm
Dumb question but what is COPV?

http://bfy.tw/7Us0
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Norm38 on 09/01/2016 03:57 pm
another COPV?

During the investigation last year I recall talk of the buoyancy force on the COPV tanks being in addition to the g-forces during launch. That put additional stress on the tanks that could not be simulated during any ground testing.

For this failure no g-forces and struts were redesigned.  But a COPV tank itself could have ruptured I suppose.  Not the same failure mode though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/01/2016 03:58 pm
Has there even been an accidental FTS firing?  (Not saying that's what this was, just asking).
Yes.  Happened on one of the first Titan 1 R&D missiles.  There were others too, I believe, more related to incorrect tracking data that forced an RSO decision, but hasn't happened in many years since.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jimbowman on 09/01/2016 04:00 pm
Usually the folks at USLaunchReport have a camera(from a distance) on the static fires. Haven't posted anything yet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 04:00 pm
Has there even been an accidental FTS firing?  (Not saying that's what this was, just asking).
Yes.  Happened on one of the first Titan 1 R&D missiles.  There were others too, I believe, but hasn't happened in many years since.

 - Ed Kyle

And the designs and qual requirements have improved since then.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:01 pm
Only reason to consider the FTS at all is the transition to autonomous FTS.  New hardware => new opportunities for bugs.  But I don't know if this was an autonomous FTS demo mission or not.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 04:01 pm
Everyone posting v1.0 or v1.1-pre-FT timelines, please stop.  Consider removing your posts.  It's actively unhelpful.  Fuel loading procedures changed significantly for 1.1 FT with its supercooled propellants.

For that matter, we don't even know if the failure happened around T-5 or T-3 yet.

Correct timeline (http://spaceflight101.com/falcon-9-ft-countdown-timeline/):
Falcon 9 FT – Countdown Timeline
All Times Approximate.
Time   Event
L-15:00:00   Falcon 9 to Vertical
L-10:00:00   Countdown Initiation, Launch Vehicle Power-Up
L-6:00:00   First Weather Balloon Release
L-5:00:00   Launch Area Evacuation
L-4:45:00   Range Controllers on Station
L-4:35:00   Falcon 9 Attitude Control System N2 Loading
L-5:00:00   Launch Area Evacuation
L-2:45:00   Falcon 9 RF & Telemetry Checks
L-2:30:00   Falcon 9 Launch Vehicle Release System Test
L-2:25:00   TEA-TEB Bleed In
L-1:45:00   Comm & FTS Checks
L-1:40:00   Data Flow Tests with Downrange Tracking Stations
L-1:00:00   Weather Briefing
L-0:50:00   RF Link Checks
L-0:45:00   Pre-Load Hold Point, Propellant Polls
L-0:45:00   Blast Danger Area Clear, Roadblocks Established
L-0:45:00   Flight Control System Setup (Flight Software Loading)
L-0:45:00   Final Tank Chill-In
L-0:40:00   Ready for Prop Load
L-0:38:00   Launch Readiness Poll
L-0:36:00   Tanks vented for Prop Loading
T-0:35:00   Automated Countdown Sequence, Master Script Running
T-0:34:45   Launch Enable to Flight Mode
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
T-0:32:30   Confirm nominal Fuel Flow Rates
T-0:32:00   Latest Prop Flow Start
T-0:29:30   Stage 1 Helium Load
T-0:27:00   Spacecraft to Internal Power
T-0:25:30   Fuel Collector Pre-Valves Closed
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
T-0:13:00   Countdown Recycle Point
T-0:12:45   Merlin 1D & MVac BTV Activation
T-0:10:15   Grid Fin Pneumatics Secured
T-0:10:05   Boostback Hazards Disabled
T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
T-0:06:45   Stage 2 Helium Transition to Pipeline
T-0:06:35   MVac Hydraulics at Bleed Pressure
T-0:06:05   M1D Engines to TVC-Null Position
T-0:05:20   Flight Computers in Self-Alignment
T-0:05:20   Stage 1 Fuel Loading Complete
T-0:05:15   Launch Vehicle Heater Deactivation
T-0:05:00   Falcon 9 to Internal Power
T-0:05:00   Range Control Comm Check
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:50   Pressurization for Strongback Retract
T-0:04:40   Stage 2 TVC Bleed
T-0:04:30   Stage 2 RP-1 Bleed
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:20   Verify Good Self-Alignment
T-0:04:10   Strongback Cradles Opening
T-0:04:00   Vehicle Release Auto Sequence
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch
T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
T-0:02:35   Strongback Retraction Complete
T-0:02:05   Stage 2 LOX at Flight Level
T-0:02:00   Falcon 9 Transfer to Internal Power Complete
T-0:01:35   Flight Control to Self Alignment
T-0:01:30   Launch Director: Go for Launch
T-0:01:30   Final Engine Chilldown
T-0:01:25   Helium Loading Termination
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:30   HOLD Call for Abort
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:07   Pad Deck Water Deluge System Activation
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/01/2016 04:01 pm
another COPV?

Hm, now _that_ would really hurt SpaceX' reputation...
True. However SX have always been very good at learning from their past mistakes. AFAIK they never make the same mistake twice.

On that basis I'd put the COPV's quite far down the list.  Although range safety does quantify their potential in lbs of TNT equivalent.

A key starting question would be where did the explosion/fire start? I'm pretty sure SX have a bunch of CCTV on the pad. Pad? 1st stage? 2nd stage? Payload?

That alone should prune whole branches of the fault tree before they start chewing on the telemetry.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 04:03 pm
Dumb question but what is COPV?

Composite Overwrap Pressure Vessel - the internal tanks for helium and nitrogen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/01/2016 04:03 pm
If it was a falcon failure, and its not possible to determine the cause from telemetry, there might be a better chance they'll recover the failed component given the failure was on the ground.  (looking for a silver lining here.)

Is any better telemetry available from the falcon while its on the pad, as compared to once its in flight?   Or does the rocket use radio telemetry at that point in the static fire?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 04:04 pm
Dumb question but what is COPV?

Composite overwrapped pressure vessel, holds helium for tank pressurisation. Failure of a strut / struts holding a COPV caused the loss of of CRS-7 - it  broke free and ruptured the second stage LOX tank.

https://www.nasaspaceflight.com/2015/07/spacex-falcon-9-failure-investigation-focuses-update/

As noted above, this failure occurred under significant g-loadings - which would not have been a factor while the vehicle was at the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scylla on 09/01/2016 04:04 pm
A Spanish language news report with zoomed in video of pad. It's a bit blurry but I havn't seen close up views anywhere else yet.

http://youtu.be/fyGMHdsnm4E
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/01/2016 04:04 pm
If I'm not mistaken, this will have been the most powerful ground explosion ever at the Cape or KSC.  AC-5 was the previous "most powerful". 

Sobering to think what would result from a similar Falcon Heavy incident.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:05 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 04:06 pm
One more thing - since this apparently happened well before ignition, this means that similar risks do exist to any rocket doing a Wet Dress Rehersal (WDR), including these:

- Atlas V (selective Cape flights and all VAFB flights, like the one next door for OSIRIS-Rex)
- Delta IV (all flights)
- Soyuz (selective flights)
- Delta II (selective flights I think?)

Can't remember if Ariane 5 or Antares or others does that.

Yet no-one except SpaceX puts some of the payloads on top of that. Which goes back to my previous post.....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 04:07 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.
Well if this is anything to go by:
Excerpt from the current F9FT countdown timeline:
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch

T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/01/2016 04:08 pm
Caused by a GSE issue (i.e. over pressurization), or by a flaw in the vehicle systems (relief valve, strut, tank itself, etc.)?

If another strut went ... yikes.  :(
What systems exist to prevent over-pressurization?  What would have had to have gone wrong?  I'm assuming a fair amount of redundancy between the rocket and the pad equipment....

There's an obvious preference for this to be pad support than rocket for flight purposes (though it's not clear if that helps much, really).  Are we looking for the proverbial "aluminum nut" in a hose/valve/electric-line assembly that's been exposed to too much salty air?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 04:08 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.

The best distance views are hard to make out from the angle. It looks like they might be opened, but the entire top of the T/E structure is bent over, whether due to explosive shock, or the heat of the fire is unclear.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:08 pm
I'm saying it looks to have happened before T-3:30, given that the strong back is vertical.
If the cradle is open, then after T-4:10.

There's a TEA-TEB system event in that time frame... Which might mean the engines aren't entirely free from suspicion.

OTOH, if it was ignition system initiated, there should be a telltale green color to the first flame, which would be a smoking gun on pad video.

If the cradle is closed, then TEA-TEB are innocent, and we can keep thinking about pressurization, ice dams, and leaks.

In either case, FTS is armed after strong back retract, so we can stop thinking about that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 04:09 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.

i think its possible the arms we're closed bc it looks like they were bent/pulled downward. not a for sure thing though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kdhilliard on 09/01/2016 04:12 pm
Do we have a list somewhere showing which previous F9 static fires were done with the payload mounted?

~Kirk
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 04:13 pm
Reconstructing things like the TE and other pad systems has historically (in similar events) taken a number of months described by two digits, correct?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 04:15 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.

i think its possible the arms we're closed bc it looks like they were bent/pulled downward. not a for sure thing though.

or possibly the rods that connect the top section of the TEL to the rest of it deformed from the heat?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:15 pm
Reconstructing things like the TE and other pad systems has historically (in similar events) taken a number of months described by two digits, correct?
Hard to say, since the TE has been rebuilt three or so times at Vandenberg alone, then twice more I think at LC39A?  The pad systems have also been a research project, what with the supercooling apparatus.  The design keeps changing as the rocket evolves.  If you're rebuilding an existing proven design with no changes---who knows?  I don't think we have any evidence on "SpaceX time" for this task, although we have timelines from MARS etc... which is a simpler pad but perhaps more heavily damaged.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PahTo on 09/01/2016 04:17 pm
Reconstructing things like the TE and other pad systems has historically (in similar events) taken a number of months described by two digits, correct?

That's what I'm thinking/asking, though russianhalo117 reports there are indications the damage isn't as bad as that at MARS.  Let's hope so!  Still will cause some logistical issues, given they're trying to get 39A flight ready and the skill sets required aren't a-dime-a-dozen...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 04:17 pm
If it was a falcon failure, and its not possible to determine the cause from telemetry, there might be a better chance they'll recover the failed component given the failure was on the ground.  (looking for a silver lining here.)

Is any better telemetry available from the falcon while its on the pad, as compared to once its in flight?   Or does the rocket use radio telemetry at that point in the static fire?

Better on the pad.  It is hardlined and not subject to transmitter bandwidth.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 04:18 pm
Dumb question but what is COPV?

Composite overwrapped pressure vessel, holds helium for tank pressurisation. Failure of a strut / struts holding a COPV caused the loss of of CRS-7 - it  broke free and ruptured the second stage LOX tank.

https://www.nasaspaceflight.com/2015/07/spacex-falcon-9-failure-investigation-focuses-update/

As noted above, this failure occurred under significant g-loadings - which would not have been a factor while the vehicle was at the pad.

That was the 2nd incident.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 04:18 pm
I'm going to venture a guess that rebuilding the other infrastructure -- particularly plumbing and tankage -- is going to be a fair amount more work than the TE itself.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 04:20 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.

i think its possible the arms we're closed bc it looks like they were bent/pulled downward. not a for sure thing though.
the top third or fourth on the TEL has been bent towards where the rocket once stood. Its current position is not fully indicative of the the position of the TEL at the time of LoV.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:21 pm
That was the 2nd incident.

Elaborating for Jim: earlier on in spacex history there was another helium copv failure during static fire. (EDIT: ugordon says 1st orbcomm mission.)

Strictly speaking, that earlier problem was in fact a copv leak.  In CRS-7 the root cause was actually the strut; the COPV by all accounts never let go, the helium leak was from the tubing attached to the COPV.  The tubing eventually twisted itself shut and the helium pressure held steady---good COPV---although by that point it was too late for the LOX tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DragonRider on 09/01/2016 04:21 pm
So rumour is it was a pad issue, hmm.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/01/2016 04:22 pm
That was the 2nd incident.

What was the first COPV indecent? I seem to have forgotten.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/01/2016 04:22 pm
Dumb question but what is COPV?

Composite overwrapped pressure vessel, holds helium for tank pressurisation. Failure of a strut / struts holding a COPV caused the loss of of CRS-7 - it  broke free and ruptured the second stage LOX tank.

https://www.nasaspaceflight.com/2015/07/spacex-falcon-9-failure-investigation-focuses-update/

As noted above, this failure occurred under significant g-loadings - which would not have been a factor while the vehicle was at the pad.

That was the 2nd incident.

When was the first? I thought the only other Falcon 9 failure was the partial failure due to an engine out on the first stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 04:23 pm
So rumour is it was a pad issue, hmm.

No such rumor
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 04:23 pm
That was the 2nd incident.

What was the first COPV indecent? I seem to have forgotten.

Unless there was another anomaly we never publicly heard of, the original OG-1 static fire (2014?) suffered a copious He leak and subsequent LOX venting to the point of people speculating the tank ruptured.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DragonRider on 09/01/2016 04:24 pm
Ex-employee on reddit:

No this was an issue with the pad itself, not the rocket.

It's not an assumption. Let's just say I'm connected
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 04:24 pm
CRS-7 - IIRC, the COPV struts gave way causing the helium tanks to crash into the upper stage LOX tanks, causing its catastrophic sudden depressurisation and a massive structural failure/break-up just before MECO1.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/01/2016 04:25 pm
That was the 2nd incident.

What was the first COPV indecent? I seem to have forgotten.

Unless there was another anomaly we never publicly heard of, the original OG-1 static fire (2014?) suffered a copious He leak and subsequent LOX venting to the point of people speculating the tank ruptured.

I'll take the liberty of quoting myself further upthread.

If I remember correctly I think with the orbcomm mission there was some type of 'almost' anomaly during launch prep or static fire, saw some vague mentions, but never any details (probably details in L2)

edit - add link
Found discussion here: http://forum.nasaspaceflight.com/index.php?topic=33089.360 (http://forum.nasaspaceflight.com/index.php?topic=33089.360), Was just discussion, no idea if anything was ever confirmed, (and there is mention of perhaps something similar during SES-8)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DaveS on 09/01/2016 04:25 pm
So rumour is it was a pad issue, hmm.

No such rumor
Jim is entirely correct. The origin for this seems to have been Eric Berger's Twitter account where he read the official SpaceX statement wrong and tweeted that a pad anomaly had destroyed the F9 and the payload. The statement in fact had nothing of the sort, it was "an anomaly on the pad".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 04:26 pm
Ex-employee on reddit:

No this was an issue with the pad itself, not the rocket.

It's not an assumption. Let's just say I'm connected

Likely based on another false report that was spread earlier.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/01/2016 04:26 pm
Dumb question but what is COPV?

Composite overwrapped pressure vessel, holds helium for tank pressurisation. Failure of a strut / struts holding a COPV caused the loss of of CRS-7 - it  broke free and ruptured the second stage LOX tank.

https://www.nasaspaceflight.com/2015/07/spacex-falcon-9-failure-investigation-focuses-update/

As noted above, this failure occurred under significant g-loadings - which would not have been a factor while the vehicle was at the pad.

That was the 2nd incident.
But can the COPV really be blamed for the strut failure?  Or are you lumping in the design that includes placing the COPVs inside the propellent tank?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DragonRider on 09/01/2016 04:27 pm
No, this is not correct, the supposed ex-employee source on reddit denies that. They state:

I'm not exactly allowed to reveal sources. It'll still be months before things settle down, but it was definitely a pad issue.

Look it may be baloney, we can't say anything for sure, that's why it's a rumour.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wannamoonbase on 09/01/2016 04:28 pm
It won't take long to figure this out.  I bet we know the cause in less than a week.  Maybe 1-2 days.

Rockets are hard, lots of things can go wrong.  This is obviously an avoidable mistake and I doubt it will be a big problem to fix.  Which will make it even more embarrassing for SpaceX, but they'll recover.

If it is proven to not be a vehicle problem then production needs to go full speed ahead.  Fill the hangers and get ready for RTF.

For all we know at this time, this may not have much of an impact on the VAFB launches.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Star One on 09/01/2016 04:28 pm
Ex-employee on reddit:

No this was an issue with the pad itself, not the rocket.

It's not an assumption. Let's just say I'm connected

Likely based on another false report that was spread earlier.

After all how easy these days is it for the pad to cause the launcher's destruction.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Star One on 09/01/2016 04:29 pm
It won't take long to figure this out.  I bet we know the cause in less than a week.  Maybe 1-2 days.

Rockets are hard, lots of things can go wrong.  This is obviously an avoidable mistake and I doubt it will be a big problem to fix.  Which will make it even more embarrassing for SpaceX, but they'll recover.

If it is proven to not be a vehicle problem then production needs to go full speed ahead.  Fill the hangers and get ready for RTF.

For all we know at this time, this may not have much of an impact on the VAFB launches.

Completely unsupportable supposition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: philw1776 on 09/01/2016 04:29 pm
I give zero cred to a supposed ex-employee being so connected that he/she knows the cause before most likely anybody in SX does
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:29 pm
Well, if it's the pad's fault, the responsible piece of equipment has already been thoroughly punished and decommissioned.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: butters on 09/01/2016 04:30 pm
The previous on-pad COPV failure didn't produce nearly as catastrophic an outcome, and during the CRS-7 investigation it was noted that the vent valve is sized to handle a COPV depressurization. Perhaps the vent valve was locked for tank press at the time and its overpressure prevention logic was inhibited?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 04:31 pm
I give zero cred to a supposed ex-employee being so connected that he/she knows the cause before most likely anybody in SX does

On the other hand, just because SX people aren't speaking (smart move BTW), doesn't mean they don't have any hints by now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/01/2016 04:31 pm
I give zero cred to a supposed ex-employee being so connected that he/she knows the cause before most likely anybody in SX does

I don't know about the ex-employee but I think it is highly likely that SX has a very good idea of what went wrong. (maybe yes, maybe not, but certainly highly likely).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 04:32 pm
It won't take long to figure this out.  I bet we know the cause in less than a week.  Maybe 1-2 days.

That may be a bit too optimistic but I'm not expecting a huge mystery that stretches out for weeks either.

Why? I'd say most of the vehicle's remains will be found and, as the rocket was plugged into the ground data lines until destruction, there is no possibility of loss of telemetry until the actual physical destruction of the data lines or the IU instrumentation package, whichever came first, both of which would have been post-failure (if only by hundredths of seconds). So, SpaceX's engineers will already have quality-A data and that will only improve as more and more debris is brought in an analysed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/01/2016 04:32 pm
It won't take long to figure this out.  I bet we know the cause in less than a week.  Maybe 1-2 days.

Rockets are hard, lots of things can go wrong.  This is obviously an avoidable mistake and I doubt it will be a big problem to fix.  Which will make it even more embarrassing for SpaceX, but they'll recover.

If it is proven to not be a vehicle problem then production needs to go full speed ahead.  Fill the hangers and get ready for RTF.

For all we know at this time, this may not have much of an impact on the VAFB launches.

"If" it involves a COPV failure (not strut), it could very well require design work and not be a quick fix. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: leetdan on 09/01/2016 04:37 pm
Usually the folks at USLaunchReport have a camera(from a distance) on the static fires. Haven't posted anything yet.

This might be cynical of me, but I wonder if they're shopping the video around.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Star One on 09/01/2016 04:37 pm
Jeff Foust –  ‏@jeff_foust

Oof: Iridium, major SpaceX customer, falling sharply now after a brief rebound. Shares down >6% for the day so far.  http://bit.ly/2ctInIR

https://mobile.twitter.com/jeff_foust/status/771383776450584576
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 04:39 pm


Quote
Parabolicarc.com ‏@spacecom 12m12 minutes ago California, USA

Hearing from a source that whatever went wrong happened very quickly. Windows blown in at KSC before pad fire alarm sounded #SpaceX #Falcon9

https://twitter.com/spacecom/status/771381094092410881 (https://twitter.com/spacecom/status/771381094092410881)
Of course. This was a sudden explosion, not a pad fire. Fire alarms only look for fire not explosions.

They mean that it wasn't something like an anomalous rising pressure in a tank or rising temperature in a compartment or evidence of a small fire on video that would have given spacex time to manually trigger the fire alarm before the whole thing let go.

It's not a huge data point, but it is saying something.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RonM on 09/01/2016 04:39 pm
It won't take long to figure this out.  I bet we know the cause in less than a week.  Maybe 1-2 days.

That may be a bit too optimistic but I'm not expecting a huge mystery that stretches out for weeks either.

Why? I'd say most of the vehicle's remains will be found and, as the rocket was plugged into the ground data lines until destruction, there is no possibility of loss of telemetry until the actual physical destruction of the data lines or the IU instrumentation package, whichever came first, both of which would have been post-failure (if only by hundredths of seconds). So, SpaceX's engineers will already have quality-A data and that will only improve as more and more debris is brought in an analysed.

That and the pad video cameras. Even if they are only standard cameras that's 30 frames per second and with a good close up. Could easily have a higher frame rate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: orulz on 09/01/2016 04:42 pm
If this is a pad failure then procedures are a likely culprit. Inadequate inspections, checks, etc?

If the root cause is traced to a procedural issue, that would goes a long way toward showing why rapid launch cadence is difficult to achieve. So many things have to happen in such rapid succession and in exactly the right order and with exactly the right timing, or else *BOOM*. The answer for why ULA can't launch faster than they do is not just that "old aerospace" is inefficient.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RonM on 09/01/2016 04:43 pm
Usually the folks at USLaunchReport have a camera(from a distance) on the static fires. Haven't posted anything yet.

This might be cynical of me, but I wonder if they're shopping the video around.

They're running a business, right? If they have exclusive footage they should get paid for it. At least get the credit.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 04:44 pm
It won't take long to figure this out.  I bet we know the cause in less than a week.  Maybe 1-2 days.

That may be a bit too optimistic but I'm not expecting a huge mystery that stretches out for weeks either.

Why? I'd say most of the vehicle's remains will be found and, as the rocket was plugged into the ground data lines until destruction, there is no possibility of loss of telemetry until the actual physical destruction of the data lines or the IU instrumentation package, whichever came first, both of which would have been post-failure (if only by hundredths of seconds). So, SpaceX's engineers will already have quality-A data and that will only improve as more and more debris is brought in an analysed.

That and the pad video cameras. Even if they are only standard cameras that's 30 frames per second and with a good close up. Could easily have a higher frame rate.
highspeed cameras would have been activated around the start of the automated sequence.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 04:45 pm
Even in a "best case" scenario of the root cause being found quickly and pointing to the pad equipment, I don't see FAA signing off on the investigation that soon. I'd also guess that return to flight, at least for east coast launches will occur from LC-39A and FH will be further deprioritized up until the point LC-40 is repaired. They won't risk their only (near-)operational east coast pad for that until they have the two pads back in operation IMHO.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 04:45 pm
If this is a pad failure then procedures are a likely culprit. Inadequate inspections, checks, etc?

If the root cause is traced to a procedural issue, that would goes a long way toward showing why rapid launch cadence is difficult to achieve. So many things have to happen in such rapid succession and in exactly the right order and with exactly the right timing, or else *BOOM*. The answer for why ULA can't launch faster than they do is not just that "old aerospace" is inefficient.
your statements are not valid.
Jim take it away with the facts on this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/01/2016 04:46 pm
Usually the folks at USLaunchReport have a camera(from a distance) on the static fires. Haven't posted anything yet.

This might be cynical of me, but I wonder if they're shopping the video around.

I don't know from where they record, perhaps their camera is located in a secure area and they cannot retrieve it until security is cleared?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/01/2016 04:48 pm
Maybe it should be noted that unlike the general public which is relying on rumors and large distance post-event closeups of shaky video, ...

SpaceX will have high res video stream recordings of pad camera from multiple angles, likely including thermal infrared as well as optical - as well as high res telemetry data from both pad equipment and vehicle until the initial explosion and likely well past (usually it takes a few milliseconds, sometimes seconds from the original event till full scale disassembly that stops telemetry)

Considering pad systems like fire suppression obviously kept working they'd likely have had pad equipment data well afterwards too, maybe still do.

If the part at fault was an actuator like a valve, its even possible that the sensors on this very part indicated the malfunction to operators and board computers even before the actual RUD (but too late to do anything about it)

Based on that, I think a claim by somepone at SpaceX - direct or indirect - that pad equipment were at fault - even at such an early time - would be completely credible.

They would most likely be able to tell by now (with high likelyhood) which part caused the RUD and the event chain that lead from part failure to RUD (just like they were able to tell 2nd stage oxygen tank overpressure right after CRS-7)

Finding the root cause might take longer, for that they might have to find debris of said component - be it ground or vehicle side. it's likely to be among the most affected by the fire/explosion.

But I have no doubts they already know what to look for.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/01/2016 04:49 pm
Dumb question but what is COPV?

http://bfy.tw/7Us0

Whoa, that freaked me out! :)

COPVs were a fun subject during Shuttle:
https://www.nasaspaceflight.com/?s=COPV

---

Not that there is any information this was an issue today of course.

We're all waiting for Elon to say something, like he did after CRS-7. That will likely be the first official info we get to know.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/01/2016 04:51 pm
Photos of the pad seem to show the strong back not retracted.  Can anyone tell if it looks like the cradle arms were opened?  If so, that bounds the time of the incident pretty well.

i think its possible the arms we're closed bc it looks like they were bent/pulled downward. not a for sure thing though.

or possibly the rods that connect the top section of the TEL to the rest of it deformed from the heat?

It is very possible that the TEL was deformed by the heat of the fire. Having worked on offshore drilling rigs, i have seen the aftermath of blowouts and fires. The effects of fire on the 3/4 inch thick steel of the derrick is amazing. bent and twisted like taffy. :o :-\

http://www.houstonchronicle.com/business/energy/article/Flames-engulf-Mexico-oil-platform-in-Gulf-6173928.php
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 04:53 pm
including thermal infrared


Not used on RP-1 vehicles
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 04:56 pm
I'm stating outright that the root cause here is the ISS and Orbital.  It seems Murphy doesn't want all the cargo resuppliers operational at the same time.

That has to be it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 04:58 pm
..

SpaceX will have high res video stream recordings of pad camera from multiple angles,


Don't know that
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacenut on 09/01/2016 04:59 pm
Well, at least we know it wasn't the rocket engines.  This took place before firing.  I've heard there were multiple explosions? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/01/2016 05:02 pm
Well, at least we know it wasn't the rocket engines.  This took place before firing.  I've heard there were multiple explosions? 
One big explosion, followed by a big fire and a series of secondary explosions.  Typical of a fire where multiple pressure vessels are present.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/01/2016 05:03 pm
No, this is not correct, the supposed ex-employee source on reddit denies that. They state:

I'm not exactly allowed to reveal sources. It'll still be months before things settle down, but it was definitely a pad issue.

Look it may be baloney, we can't say anything for sure, that's why it's a rumour.

Part of me hopes that it's something that is easy to fix. But if it's easy to fix, people will ask "why wasn't it detected?". The COPV would be bad news as it could imply that SpaceX is unable to fix that issue.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/01/2016 05:04 pm
If this is a pad failure then procedures are a likely culprit. Inadequate inspections, checks, etc?

If the root cause is traced to a procedural issue, that would goes a long way toward showing why rapid launch cadence is difficult to achieve. So many things have to happen in such rapid succession and in exactly the right order and with exactly the right timing, or else *BOOM*. The answer for why ULA can't launch faster than they do is not just that "old aerospace" is inefficient.
I see you are new. Welcome to the site.

Keep in mind that "fast launch cadence" in rocket terms is nothing like the fast cadence of say an F1 pit crew, or an ER team with a patient. It's usually more a question of having something to launch, IE payloads in the pipeline on a regular basis.

It's a weak data point but the DC-X team were ready to re-launch 8 hrs after a previous launch. It was simply the range crew that wanted to go home that delayed it to the following day. While a smaller vehicle (and non orbital) it could be (and often is) argued that LH2 is a much less forgiving fuel to handle than RP1.

AFAIK the usual concern with ELV companies is slow cadence, like the time between launches of SLS for example, where there is a real risk several staff will die or retire between one launch and the next. Nothing keeps a team sharp than the chance to regularly practice their skills in a live environment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 09/01/2016 05:07 pm
Well, at least we know it wasn't the rocket engines.  This took place before firing.  I've heard there were multiple explosions? 
One big explosion, followed by a big fire and a series of secondary explosions.  Typical of a fire where multiple pressure vessels are present.

 - Ed Kyle


Yes, best pics I've just found so far...
http://www.wesh.com/news/explosion-reported-at-cape-canaveral/41467356
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/01/2016 05:08 pm
Given that booster passed in McGregor.
Then transported to ksc.
Nothing happened to booster during transit.
Then the gse is the only variable.

P.s. also 2nd stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OnWithTheShow on 09/01/2016 05:08 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kosmos2001 on 09/01/2016 05:09 pm
Originated around upper stage oxygen tank.

Hmm...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 05:10 pm
Given that booster passed in McGregor.
Then transported to ksc.
Nothing happened to booster during transit.
Then the gse is the only variable.

"Given that this lightbulb worked the last time I turned on the lights, it must work this time as well"

See the problem in that kind of reasoning?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Joaosg on 09/01/2016 05:11 pm
LV related cause :( This means all flights grounded and no immediate cause found. Was hopping for a pad fault that couldn't happen at Vanderberg.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yatpay on 09/01/2016 05:12 pm
LV related cause :( This means all flights grounded and no immediate cause found. Was hopping for a pad fault that couldn't happen at Vanderberg.

No one said it was LV related. Elon just said "around upper stage oxygen tank". Could still be GSE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/01/2016 05:12 pm
Part of me hopes that it's something that is easy to fix. But if it's easy to fix, people will ask "why wasn't it detected?".
True.
Quote
The COPV would be bad news as it could imply that SpaceX is unable to fix that issue.
Just to be clear IIRC it was not the COPV in the LOX tank but the struts holding them that failed and (eventually) caused the COPV's to fail.

Historically COPV's have been pretty reliable components. They have (relatively) generous safety margins for space structures. They should be minimized not because of the danger but the paperwork  they generate to show they've been tested and inspected. IIRC the ones on the SSME's last the life of each orbiter without replacement, roughly 30 flights each.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cebri on 09/01/2016 05:13 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.

Well if there is a problem with the rocket... 2 major failures in 14 months... is going to be grounded for a while.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JDTractorGuy on 09/01/2016 05:15 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.

Forgive me if this is a stupid question, but what could cause an explosion around that tank?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kirghizstan on 09/01/2016 05:15 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.

Well if there is a problem with the rocket... 2 major failures in 14 months... is going to be grounded for a while.


Why, yes that is a lot, but that in no means there needs to be a long downtime.  This could be a very simple fix that has complete before the pad is fully operational again
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/01/2016 05:15 pm
Has consideration ever been given to s2 static fire at McGregor?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Joaosg on 09/01/2016 05:16 pm
LV related cause :( This means all flights grounded and no immediate cause found. Was hopping for a pad fault that couldn't happen at Vanderberg.

No one said it was LV related. Elon just said "around upper stage oxygen tank". Could still be GSE.

You and Kablooma ar right. And the wording of the spacex statement on twitter is very interesting. They say the anomaly was on the Launch Complex, so this may be GSE related (stronback bouncing, bad connections, etc..)

(https://pbs.twimg.com/media/CrSLsLqUMAAyjPv.jpg:orig)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 05:16 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.

Forgive me if this is a stupid question, but what could cause an explosion around that tank?

still dont know if it was an explosion either, could have been a slow burn at first?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: miki on 09/01/2016 05:17 pm
VIDEO!:  https://www.youtube.com/watch?v=_BgJEXQkjNQ   :o
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tdperk on 09/01/2016 05:17 pm
Around the upper stage LOX tank sounds to me like an umbilical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/01/2016 05:17 pm
Part of me hopes that it's something that is easy to fix. But if it's easy to fix, people will ask "why wasn't it detected?".
True.
Quote
The COPV would be bad news as it could imply that SpaceX is unable to fix that issue.
Just to be clear IIRC it was not the COPV in the LOX tank but the struts holding them that failed and (eventually) caused the COPV's to fail.

Historically COPV's have been pretty reliable components. They have (relatively) generous safety margins for space structures. They should be minimized not because of the danger but the paperwork  they generate to show they've been tested and inspected. IIRC the ones on the SSME's last the life of each orbiter without replacement, roughly 30 flights each.

Yes, I know about the struts. But wasn't there a COPV problem prior to CRS-7?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: StuffOfInterest on 09/01/2016 05:18 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.

Forgive me if this is a stupid question, but what could cause an explosion around that tank?


Upper stage fill line blows out spraying LOX all over the side of the rocket?

I can see there being several things that could go wrong around the upper stage but not be part of the upper stage.  Still, this is a lot of word parsing and it could really be something inside of the upper stage as well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cebri on 09/01/2016 05:18 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.

Well if there is a problem with the rocket... 2 major failures in 14 months... is going to be grounded for a while.


Why, yes that is a lot, but that in no means there needs to be a long downtime.  This could be a very simple fix that has complete before the pad is fully operational again

Even if the fix easy, which is total speculation until we know the cause, if there is a problem with the rocket, SpaceX is going to need time to rebuild their confidence again.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/01/2016 05:19 pm
I give zero cred to a supposed ex-employee being so connected that he/she knows the cause before most likely anybody in SX does

I don't know about the ex-employee but I think it is highly likely that SX has a very good idea of what went wrong. (maybe yes, maybe not, but certainly highly likely).

Actually, in principle, it could very well be that they "saw it happening" and know exactly what happened.
In practice though, Elon's tweet is counter-indicative of that.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 05:19 pm
Part of me hopes that it's something that is easy to fix. But if it's easy to fix, people will ask "why wasn't it detected?".
True.
Quote
The COPV would be bad news as it could imply that SpaceX is unable to fix that issue.
Just to be clear IIRC it was not the COPV in the LOX tank but the struts holding them that failed and (eventually) caused the COPV's to fail.

Historically COPV's have been pretty reliable components. They have (relatively) generous safety margins for space structures. They should be minimized not because of the danger but the paperwork  they generate to show they've been tested and inspected. IIRC the ones on the SSME's last the life of each orbiter without replacement, roughly 30 flights each.

Yes, I know about the struts. But wasn't there a COPV problem prior to CRS-7?

Yes, there was a leak/overpressure event on the pad on an earlier mission.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Joaosg on 09/01/2016 05:20 pm
VIDEO!:  https://www.youtube.com/watch?v=_BgJEXQkjNQ   :o

WOW. We can see the payload fall seconds after the first explosion. Maybe a dragon could fly away in time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/01/2016 05:20 pm
"Originated around upper stage lox tank". around

Could have the strong back started to retract while the cradle arms were still around the vehicle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 05:21 pm
definitely an explosion
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 05:22 pm
VIDEO!:  https://www.youtube.com/watch?v=_BgJEXQkjNQ   :o
can wait for Matthew Travis's 4K videos. Not sure if his closeup cameras would have survivied.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/01/2016 05:22 pm
Well the logic actually worked in this case.
Also given that SpaceX engineers no what they are doing when they design the McGregor test. And the last failure was from something nearly impossible to simulate. G force!
Given that booster passed in McGregor.
Then transported to ksc.
Nothing happened to booster during transit.
Then the gse is the only variable.

"Given that this lightbulb worked the last time I turned on the lights, it must work this time as well"

See the problem in that kind of reasoning?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elmar Moelzer on 09/01/2016 05:22 pm
freak lightning strike of sorts?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lars-J on 09/01/2016 05:23 pm
VIDEO!:  https://www.youtube.com/watch?v=_BgJEXQkjNQ   :o

Yikes, certainly looks like a high pressure event in the upper stage LOX tank.  :o
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tdperk on 09/01/2016 05:23 pm
That was quick.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/01/2016 05:23 pm
Oh, wow - I'm looking just at the first instance of visible event - it's damn sudden and energetic.

Doesn't look like a fire to me, maybe an over-pressure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/01/2016 05:24 pm
WOW. We can see the payload fall seconds after the first explosion. Maybe a dragon could fly away in time.

Maybe the crew Dragon but not the cargo Dragon. The cargo Dragon can now survive a CRS-7 type accident by deploying its parachutes but that doesn't help if the accident is at the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 05:24 pm
To watch frame-by-frame on YouTube:

- pause video
- press . to advance
- press , to go back
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/01/2016 05:24 pm
Elon Musk ‏@elonmusk  29s30 seconds ago
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.
Note what this does not say.

It does not specify upper stage, it says around upper stage O2 tank area.

So could still be GSE in that area. I thought the tanks were filled by umbilicals near the ground feeding both 1st and 2nd stages?

Obviously this focuses the attention to a much smaller area, which should speed up resolving root cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 05:26 pm
can wait for Matthew Travis's 4K videos. Not sure if his closeup cameras would have survivied.

Those are only placed immediately before the launch?

This is as good as it's gonna get IMHO.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 05:27 pm
First frame of the explosion:

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OnWithTheShow on 09/01/2016 05:27 pm
Looks like the initial overpressure from the explosion either split a weld seam on the 1st stage or the FTS fired after the 2nd stand exploded. Looks like a vertical split all the way down the 1st stage on the left side.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 05:28 pm
i think this is one frame before that

*not an expert* but i looks like the side closest to the TEL was explosing first
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/01/2016 05:29 pm
Oh, wow - I'm looking just at the first instance of visible event - it's damn sudden and energetic.

Doesn't look like a fire to me, maybe an over-pressure.
Looks to me like Jim was right about this one. 

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 05:30 pm
Immediately before/immediately after event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Tonioroffo on 09/01/2016 05:31 pm
Oh boy, 2nd stage again.  Also looks to fast for hypothetical dragon 2 Escape.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NX-0 on 09/01/2016 05:31 pm
A couple of things I see (and I am not expert)
1. No retraction of the strongback.
2. Initial burst is white and clean, no black smoke - that's O2.
3. Total collapse of the stack extremely quickly.
4. Fairing hung onto the strongback for, what I consider to be, quite some time before tumbling down, nose first.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kosmos2001 on 09/01/2016 05:31 pm
At 3:42 there is another explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kansan52 on 09/01/2016 05:32 pm
Looks like the payload and fairing was intact, held by the TEL, and it's weight caused the damage to the upper part of the TEL. Because when it dropped, there was no sign of the Falcon.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 05:33 pm

1.  It's a weak data point but the DC-X team were ready to re-launch 8 hrs after a previous launch. It was simply the range crew that wanted to go home that delayed it to the following day. While a smaller vehicle (and non orbital) it could be (and often is) argued that LH2 is a much less forgiving fuel to handle than RP1.

2.  AFAIK the usual concern with ELV companies is slow cadence, like the time between launches of SLS for example, where there is a real risk several staff will die or retire between one launch and the next. Nothing keeps a team sharp than the chance to regularly practice their skills in a live environment.

1.  Not even relevant.  No upper stage or payload. 

2.  No, quick cadence or back to back launches has been just as much a concern.  See Delta II and Atlas II in the 90's
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 05:33 pm
At 3:42 there is another explosion.

That looks like RP-1, maybe from GSE that wasn't still drained back?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vt_hokie on 09/01/2016 05:33 pm
That was quick.

But possibly enough time for the launch escape system to save the crew, had this been a launch of Crew Dragon?  I know, we're a long way from that right now, sadly, given today's events.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Shanuson on 09/01/2016 05:34 pm
For me, jumping between before and after event, the center of the first explosion lies not at the 2nd stage but somewhere on the strongback close to the 2nd stage.

Also testfiring the 1st stage at McGregor does not help with 2nd stage problems.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 05:35 pm
Assuming that the x-shaped lens flare of the initial explosion is centred somewhere near the hottest point, that should theoretically be the point of failure. I've circled it on the frame immediately before the explosion.

(First explosion frame added for comparison)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bob Shaw on 09/01/2016 05:35 pm
No question about it being the second stage (or loading thereof). And, of course, that's the part which doesn't return to be torn down. When I went through the YouTube video frame-by frame there seemed to be a distinct horizontal component on both sides of the top of the stage - but that may be a perspective artefact.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: The_Ronin on 09/01/2016 05:36 pm
That looks electrical on the TE.  Umbilical connection shorted?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: M_Puckett on 09/01/2016 05:38 pm
Give me enough O2 and I can make a rock burn.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/01/2016 05:38 pm
That looks electrical on the TE.  Umbilical connection shorted?

Damaged grounding strap?  Could cause a build up of static electricity that discharged.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/01/2016 05:38 pm
i think this is one frame before that

*not an expert* but i looks like the side closest to the TEL was explosing first
Yep.   Definitely looks centered on the edge of the stage or just to the right.
I'm wondering if the dark patch on the left side of the fireball is the remnants of the umbilical at that level (roughly the right size for that?)

The shadows on the vapor clouds from the first stage in that frame is also consistent with the explosion starting on the side of the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 05:39 pm


You and Kablooma ar right. And the wording of the spacex statement on twitter is very interesting. They say the anomaly was on the Launch Complex, so this may be GSE related (stronback bouncing, bad connections, etc..)


No, again, wrong interpretation.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 05:39 pm
For future reference, some stills from the payload composite hanging on and falling on the pad. Is is really apparent how its weight deformed the top of the TE after the initial upwards draft from the explosion dissipated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 05:39 pm
Based on the flash location and the fact there was immediate ignition, the common bulkhead looks like a suspect to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Joaosg on 09/01/2016 05:39 pm
Gif of the explosion. Seems the umbilical, or any other connection.

Could an O2 rich environment + electricak sparks cause this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: M_Puckett on 09/01/2016 05:40 pm
2 Questions:

Assuming this was the support equipment and a cause can be quickly identified:

1) How long will it take to repair the pad at Complex 40

2) How close are we to 39a going operational?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/01/2016 05:40 pm
What would be the ignition source if it was just an overpressurization?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RonM on 09/01/2016 05:40 pm
Great footage provided by USLaunchReport.com. Keep up the good work.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/01/2016 05:41 pm
So that makes sense for full duration. Maybe 2sec and nozzle would survive. Thereby testing a whole bunch of stuff.
Has consideration ever been given to s2 static fire at McGregor?

Can't do it because it would destroy the Mvac nozzle to fire it at sea level.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sunbingfa on 09/01/2016 05:41 pm
Very strange for the explosion. There is no sign of eruption of anything before the explosion. Maybe a spark somewhere near upper stage oxygen tank?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/01/2016 05:42 pm
Gif of the explosion. Seems the umbilical, or any other connection.
there's another frame between the two you showed (look at the bird flying right to left around the lighting tower just to the right of the vehicle).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SupaNova on 09/01/2016 05:42 pm
Gif of the first few frames, origin seems to be somewhat towards the strongback.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ncb1397 on 09/01/2016 05:43 pm
2 Questions:

Assuming this was the support equipment and a cause can be quickly identified:

1) How long will it take to repair the pad at Complex 40

Antares pad repair took about 12 months. Of course, that included wrangling about who was going to pay for it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 05:43 pm
Based on the flash location and the fact there was immediate ignition, the common bulkhead looks like a suspect to me.

Well isn't the common bulkhead where the COPVs are on stage 2?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 05:44 pm
Notice also that the 1st stage LOX tank let go even before that flaming inferno hit the ground.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachF on 09/01/2016 05:44 pm
Doing some freeze-framing it looks like the explosion is centered around the umbilical connection.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mheney on 09/01/2016 05:44 pm
At 3:42 there is another explosion.

That looks like RP-1, maybe from GSE that wasn't still drained back?

If you  watch closely, at about 3:33, there's a fade/cut.  (watch the smoke at the bottom of the frame by the lightning tower.)  So the second explosion was not at 3:42 - there are reports that said the second explosion was some 20 minutes later.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 05:45 pm
Based on the flash location and the fact there was immediate ignition, the common bulkhead looks like a suspect to me.

Well isn't the common bulkhead where the COPVs are on stage 2?
they were at least when they last caused a launch failure. I don't what changed for the FT variant.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 05:45 pm
Based on the flash location and the fact there was immediate ignition, the common bulkhead looks like a suspect to me.

Well isn't the common bulkhead where the COPVs are on stage 2?

I think they might be located a bit higher than that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Billium on 09/01/2016 05:46 pm
i think this is one frame before that

*not an expert* but i looks like the side closest to the TEL was explosing first
Yep.   Definitely looks centered on the edge of the stage or just to the right.
I'm wondering if the dark patch on the left side of the fireball is the remnants of the umbilical at that level (roughly the right size for that?)

The shadows on the vapor clouds from the first stage in that frame is also consistent with the explosion starting on the side of the stage.

I'm no expert, but I agree it seems like an explosion on the right side of the rocket, or beside the rocket. I also noticed debris going exactly vertical on the right side immediately after the explosion, which implies to me that the point of explosion was just to the right of the rocket rather than the rocket itself.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/01/2016 05:46 pm
Very strange for the explosion. There is no sign of eruption of anything before the explosion. Maybe a spark somewhere near upper stage oxygen tank?

But oxygen doesn't "burn", it oxidizes something else. i'm guessing it would be insulation on the umbilical or somewhere else, or the fuel?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/01/2016 05:47 pm
Looks to me like Jim was right about this one. 

 - Ed Kyle

Unfortunately, that's what happens when you "probably" fix things. Heck, I'm guilty of it myself.

At least this happened on the ground, they'll find all the pieces and get to a real root cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 05:48 pm

1) How long will it take to repair the pad at Complex 40


Won't really have a good answer on this until the damage can be surveyed.  Livestream shows pad 40 still smoldering, so it will be a while before it's cool enough for people to go in and investigate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 05:48 pm
Based on the flash location and the fact there was immediate ignition, the common bulkhead looks like a suspect to me.

Well isn't the common bulkhead where the COPVs are on stage 2?

I think they might be located a bit higher than that.

If a COPV let go on the side near the T/E, that might be consistent with what we see on the video.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jacqmans on 09/01/2016 05:48 pm
Looks like the payload falls down intact and then explodes...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/01/2016 05:49 pm
Assuming that the x-shaped lens flare of the initial explosion is centred somewhere near the hottest point, that should theoretically be the point of failure. I've circled it on the frame immediately before the explosion.

(First explosion frame added for comparison)

Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/01/2016 05:51 pm

Antares pad repair took about 12 months. Of course, that included wrangling about who was going to pay for it.

There was also some serious environmental contamination from the Antares' solid second stage, which required cleanup. That isn't the case here. I'm not sure, though, about what the spacecraft's hypergols and the rocket's TEA/TEB mean as far as environmental impacts go.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 05:51 pm
Looks like the payload falls down intact and then explodes...

I'm surprised that it held on to the strongback for that long with everything under vaporized.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/01/2016 05:54 pm
I'm no expert, but I agree it seems like an explosion on the right side of the rocket, or beside the rocket. I also noticed debris going exactly vertical on the right side immediately after the explosion, which implies to me that the point of explosion was just to the right of the rocket rather than the rocket itself.

There is definitely a right-leaning start to the explosion.  That said, I would (completely naively) expect that if something caught fire *outside* first, that the second stage letting loose would be a second explosion, and I don't get that sense from the video.  It seems more likely that something went boom and escaped first along the pathway of least resistance -- out the feed-side.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 05:54 pm
Doing some freeze-framing it looks like the explosion is centered around the umbilical connection.

Doesn't look that way to me. The umbilicals are at the 2nd stage-interstage connection, the part the explosion seems to originate at is the structural support and presumably common bulkhead location, circled in red in this image.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 05:56 pm
Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?

Having gone back and forwards again in the video, it doesn't look like it.

There's another frame that I may have been skipping over, so for the sake of neatness, here are the three in sequence:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 05:56 pm
It does seem clear that strongback was vertical and cradles closed, which puts the event before T-4:10.  FTS was therefore not armed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IanH84 on 09/01/2016 05:58 pm
edit: looks like it didn't capture the full frame, I'll try again and fix it later
http://imgur.com/a/WXKge
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: leetdan on 09/01/2016 05:59 pm
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mikes on 09/01/2016 06:00 pm
If you download the video from YouTube, then use VLC to synch the sound to allow for the distance from the pad to the camera

 Tools > Track sync > Sync > Audio > -12 seconds

there is a quiet bang about 5 seconds before the first visible explosion.

(Edit: Jinx!)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zed_Noir on 09/01/2016 06:00 pm
Can the FTS be activated from the initial explosion? Causing the 1st stage to unzipped.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/01/2016 06:02 pm
It does seem clear that strongback was vertical and cradles closed, which puts the event before T-4:10.  FTS was therefore not armed.
actually with the current countdown timeline:
Correct timeline (http://spaceflight101.com/falcon-9-ft-countdown-timeline/):
Falcon 9 FT – Countdown Timeline
All Times Approximate.
Time   Event
L-15:00:00   Falcon 9 to Vertical
L-10:00:00   Countdown Initiation, Launch Vehicle Power-Up
L-6:00:00   First Weather Balloon Release
L-5:00:00   Launch Area Evacuation
L-4:45:00   Range Controllers on Station
L-4:35:00   Falcon 9 Attitude Control System N2 Loading
L-5:00:00   Launch Area Evacuation
L-2:45:00   Falcon 9 RF & Telemetry Checks
L-2:30:00   Falcon 9 Launch Vehicle Release System Test
L-2:25:00   TEA-TEB Bleed In
L-1:45:00   Comm & FTS Checks
L-1:40:00   Data Flow Tests with Downrange Tracking Stations
L-1:00:00   Weather Briefing
L-0:50:00   RF Link Checks
L-0:45:00   Pre-Load Hold Point, Propellant Polls
L-0:45:00   Blast Danger Area Clear, Roadblocks Established
L-0:45:00   Flight Control System Setup (Flight Software Loading)
L-0:45:00   Final Tank Chill-In
L-0:40:00   Ready for Prop Load
L-0:38:00   Launch Readiness Poll
L-0:36:00   Tanks vented for Prop Loading
T-0:35:00   Automated Countdown Sequence, Master Script Running
T-0:34:45   Launch Enable to Flight Mode
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
T-0:32:30   Confirm nominal Fuel Flow Rates
T-0:32:00   Latest Prop Flow Start
T-0:29:30   Stage 1 Helium Load
T-0:27:00   Spacecraft to Internal Power
T-0:25:30   Fuel Collector Pre-Valves Closed
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
T-0:13:00   Countdown Recycle Point
T-0:12:45   Merlin 1D & MVac BTV Activation
T-0:10:15   Grid Fin Pneumatics Secured
T-0:10:05   Boostback Hazards Disabled
T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
T-0:06:45   Stage 2 Helium Transition to Pipeline
T-0:06:35   MVac Hydraulics at Bleed Pressure
T-0:06:05   M1D Engines to TVC-Null Position
T-0:05:20   Flight Computers in Self-Alignment
T-0:05:20   Stage 1 Fuel Loading Complete
T-0:05:15   Launch Vehicle Heater Deactivation
T-0:05:00   Falcon 9 to Internal Power
T-0:05:00   Range Control Comm Check
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:50   Pressurization for Strongback Retract
T-0:04:40   Stage 2 TVC Bleed
T-0:04:30   Stage 2 RP-1 Bleed
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:20   Verify Good Self-Alignment
T-0:04:10   Strongback Cradles Opening

T-0:04:00   Vehicle Release Auto Sequence
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch
T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
T-0:02:35   Strongback Retraction Complete
T-0:02:05   Stage 2 LOX at Flight Level
T-0:02:00   Falcon 9 Transfer to Internal Power Complete
T-0:01:35   Flight Control to Self Alignment
T-0:01:30   Launch Director: Go for Launch
T-0:01:30   Final Engine Chilldown
T-0:01:25   Helium Loading Termination
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:30   HOLD Call for Abort
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:07   Pad Deck Water Deluge System Activation
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachF on 09/01/2016 06:03 pm
Doing some freeze-framing it looks like the explosion is centered around the umbilical connection.

Doesn't look that way to me. The umbilicals are at the 2nd stage-interstage connection, the part the explosion seems to originate at is the structural support and presumably common bulkhead location, circled in red in this image.

Yeah it's blurry, looks like somewhere in this vicinity:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mongo62 on 09/01/2016 06:03 pm
It certainly looks like the origin point of the visible explosion was outside the rocket itself. In the first few frames, most of the brightness appears to be reflections off the rocket and T/E, and off the surrounding condensation clouds. So the actual light source must have been intensely bright and probably very concentrated, like a very powerful arc of electricity.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 06:05 pm
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

about 1:19 eh?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 06:06 pm
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

I think that's just someone messing around a car or something near the camera.

Interestingly enough, the small first bang heard is the original S2 explosion. The big bang 3 seconds later is the fuel-air type explosion when that fireball hit the ground and mixed up the RP-1 and LOX. Check out that light pole above the number "2" bending by the generated shockwave. I wonder what the extent of damage to the hangar must be.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/01/2016 06:06 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 06:09 pm
Can the FTS be activated from the initial explosion? Causing the 1st stage to unzipped.

I know nothing about SpaceX's FTS design, but there exist certain conditions that could result in an uncommanded FTS charge initiation, even when safed.  It's somewhere between exceedingly unlikely and practically impossible on the ground, but it is something that is considered in other environments.  Whether a nearby deflagration or detonation could initiate a charge is going to depend on design details I don't know.  I would assume that protecting against that hazard would be part of the design requirements, but again, I don't have any insight into this hardware.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Aerospace Dilettante on 09/01/2016 06:09 pm
Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?

Having gone back and forwards again in the video, it doesn't look like it.

There's another frame that I may have been skipping over, so for the sake of neatness, here are the three in sequence:

Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.  It crosses the screen in 15 frames and is in between the the lightning tower and the rocket at detonation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 06:10 pm
Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?

Having gone back and forwards again in the video, it doesn't look like it.

There's another frame that I may have been skipping over, so for the sake of neatness, here are the three in sequence:

Across over the lines of glare should give the centre of the brightest part, even though the explosion itself saturated the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Silmfeanor on 09/01/2016 06:11 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 06:12 pm
Across over the lines of glare should give the centre of the brightest part, even though the explosion itself saturated the camera.

Using the lens flare as a crosshair, it's around the point I've circled in red on the first frame.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/01/2016 06:14 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

Umbilical could leak, resulting in an explosive mixture of fuel vapors and atmospheric and/or vented/leaked oxygen  later ignited by a spark. The explosion would be initially centered on the source of the spark, not the source of the leak.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 06:14 pm
Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?

Having gone back and forwards again in the video, it doesn't look like it.

There's another frame that I may have been skipping over, so for the sake of neatness, here are the three in sequence:

Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.

Almost undoubtedly a bird or a bug just crossing the field of view.  There are dozens of them throughout the video.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/01/2016 06:15 pm
Frame by frame animation...

Edit: Missing Frames added.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachF on 09/01/2016 06:15 pm
Across over the lines of glare should give the centre of the brightest part, even though the explosion itself saturated the camera.

Using the lens flare as a crosshair, it's around the point I've circled in red on the first frame.

Using the flare as a crosshair I get a point of origin just outside of the rocket, just above the strongback attachment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 06:15 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.

Not easy to tell how much energy there is nothing seems to shake.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JDTractorGuy on 09/01/2016 06:16 pm
Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?

Having gone back and forwards again in the video, it doesn't look like it.

There's another frame that I may have been skipping over, so for the sake of neatness, here are the three in sequence:

Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.  It crosses the screen in 15 frames and is in between the the lightning tower and the rocket at detonation.

Seems to be a bird or other animal.  It flies harmlessly over the rocket as it explodes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kosmos2001 on 09/01/2016 06:16 pm
Peter B. de Selding:
SpaceX explosion didn't involve intentional ignition - E Musk said occurred during 2d stage fueling - & isn't covered by launch insurance.

https://twitter.com/pbdes/status/771409425475174400
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Galactic Penguin SST on 09/01/2016 06:18 pm
In other news....

Peter B. de Selding‏ @pbdes
Spacecom insured Amos-6 for $285M in marine cargo market, not space insurance market. Launch +1 yr policy would kick in at rocket ignition.

Peter B. de Selding‏ @pbdes
@cbs_spacenews Sat was insured as marine cargo for pre-launch phase. Launch policy didn't kick in because no ignition-w/-intent-to-launch.

Does that mean that Spacecom won't get as much insurance payment as if this happened above ground?  :-X
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Aerospace Dilettante on 09/01/2016 06:18 pm

Could that be a jet of vapor, streaming from the upper stage to the right?  The light patch exactly at the point you've marked.  All the other vapor in the photo is drifting to the left.   Could that a leak just before the explosion?

Having gone back and forwards again in the video, it doesn't look like it.

There's another frame that I may have been skipping over, so for the sake of neatness, here are the three in sequence:

Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.  It crosses the screen in 15 frames and is in between the the lightning tower and the rocket at detonation.

And 12 frames after detonation another object enters the frame from the lower left and transits the fire ball at seemingly equal high velocity. 

I'm breaking out my trusty tinfoil chapeau.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mongo62 on 09/01/2016 06:18 pm
Peter B. de Selding:
SpaceX explosion didn't involve intentional ignition - E Musk said occurred during 2d stage fueling - & isn't covered by launch insurance.

https://twitter.com/pbdes/status/771409425475174400

Ouch. So Spacecom has to eat the cost?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 06:19 pm
Frame by frame animation...

There's a frame missing - the initial explosion doesn't have the lens flare / cross-hair. It seems to be luck with YouTube whether you pause and get one sequence or the other. (Took me about three times before I noticed it). This is first frame of the explosion:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zach Swena on 09/01/2016 06:20 pm
Anyone else hear the vent just prior to the explosion.  To me, the audio sounded like there was a vent event that gained pressure as time went on and ended in an explosion of the second stage originating from the area discussed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/01/2016 06:20 pm
We have a fair few people doing some good work slicing and dicing the video that USLaunchReport shared.

But I would like to point out this text, attached to the vid on YouTube.

"Ask for permission before using or cutting. Sharing in the original version is fine"

Please keep that in mind, analysis here is likely to be viewed and shared widely.  I'm not sure I see an easy answer. Metadiscussion of this note discouraged, I'm bucking this upstairs.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 06:20 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/01/2016 06:20 pm
Peter B. de Selding:
SpaceX explosion didn't involve intentional ignition - E Musk said occurred during 2d stage fueling - & isn't covered by launch insurance.

https://twitter.com/pbdes/status/771409425475174400
Not covered by launch insurance. Do separate transport/handling/integration/testing policies exist? I can't imagine a $200 million asset would be totally unprotected in phases other than launch itself...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 06:22 pm
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

I think that's just someone messing around a car or something near the camera.

Interestingly enough, the small first bang heard is the original S2 explosion. The big bang 3 seconds later is the fuel-air type explosion when that fireball hit the ground and mixed up the RP-1 and LOX.

I hear three distinct "initial" sounds:

1:16--a very faint "plonk" like someone hitting a PVC pipe with a hammer in the distance...COPV rupture?
1:18--a faint pop/bang... S2 tank rupture?
1:23--very loud boom...the LOX/RP-1 explosion?

That first sound at 1:16 is unusual and seems to me like it may be the initiating event. A COPV or high pressure line/fitting letting go followed by S2 tank rupture 1-2 seconds later seems consistent.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/01/2016 06:22 pm
Superficially, this looks awfully similar to CRS-7: Increased venting of S2 starting about 10s 20s prior to what sure looks to me like an overpressure event leading to a rupture near the top of S2.

First frame showing explosion attached, overprocessed to bring out detail in the fireball and help identify the origin point. My read of it is a tank rupture on the left side.

(And don't worry, this post will be my only attempt at video analysis this time.)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachF on 09/01/2016 06:25 pm
In other news....

Peter B. de Selding‏ @pbdes
Spacecom insured Amos-6 for $285M in marine cargo market, not space insurance market. Launch +1 yr policy would kick in at rocket ignition.

Peter B. de Selding‏ @pbdes
@cbs_spacenews Sat was insured as marine cargo for pre-launch phase. Launch policy didn't kick in because no ignition-w/-intent-to-launch.

Does that mean that Spacecom won't get as much insurance payment as if this happened above ground?  :-X

It probably means many lawyers are pressing their suits and preparing for battle...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: The_Ronin on 09/01/2016 06:26 pm
Can someone point out this increase venting on S2 before the event?  I keep watching it and I do not see what they are talking about.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 06:26 pm
In other news....

Peter B. de Selding‏ @pbdes
Spacecom insured Amos-6 for $285M in marine cargo market, not space insurance market. Launch +1 yr policy would kick in at rocket ignition.

Peter B. de Selding‏ @pbdes
@cbs_spacenews Sat was insured as marine cargo for pre-launch phase. Launch policy didn't kick in because no ignition-w/-intent-to-launch.

Does that mean that Spacecom won't get as much insurance payment as if this happened above ground?  :-X
I'm reading this as "Spacecom will get a $285M payout from their marine cargo insurance, not <whatever amount> from their space launch insurance, since the incident happened before launch."

They'd be foolish to leave their cargo uninsured for any period of time: the incoming tropical storm could have taken out the payload before launch in some freak accident, for instance.  So it's just a question of who has to pay.

I could be wrong, of course.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Aerospace Dilettante on 09/01/2016 06:27 pm


Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.  It crosses the screen in 15 frames and is in between the the lightning tower and the rocket at detonation.

Seems to be a bird or other animal.  It flies harmlessly over the rocket as it explodes.

I don't know man, watch it in real time, it moves so fast you can hardly see it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/01/2016 06:28 pm
In other news....

Peter B. de Selding‏ @pbdes
Spacecom insured Amos-6 for $285M in marine cargo market, not space insurance market. Launch +1 yr policy would kick in at rocket ignition.

Peter B. de Selding‏ @pbdes
@cbs_spacenews Sat was insured as marine cargo for pre-launch phase. Launch policy didn't kick in because no ignition-w/-intent-to-launch.

Does that mean that Spacecom won't get as much insurance payment as if this happened above ground?  :-X
I'm reading this as "Spacecom will get a $285M payout from their marine cargo insurance, not <whatever amount> from their space launch insurance, since the incident happened before launch."

I could be wrong, of course.

Correct

add:

It's considered "transport" until "launch ignition". The premiums for that kind of casualty are considerably less than that of what follows.

Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

I think that's just someone messing around a car or something near the camera.

Interestingly enough, the small first bang heard is the original S2 explosion. The big bang 3 seconds later is the fuel-air type explosion when that fireball hit the ground and mixed up the RP-1 and LOX.

I hear three distinct "initial" sounds:
Me too.

Quote
1:16--a very faint "plonk" like someone hitting a PVC pipe in the distance...COPV rupture?
1:18--a faint pop/bang... S2 tank rupture?
1:23--very loud boom...the LOX/RP-1 conflagration?
Or:
1:16-- line/fitting rupture
1:18-- detonation from line arc/ignition
1:23-- tank seam

The payload falling likely led to a hyper tank penetration with secondary ignition/partial detonation/deflagration.

Venting seemed excessive prior to ignition. Coupling failure or pressurization system?

We're all about to see how professional they are about a very difficult situation. One to watch closely.

All launches are hard and dangerous. Because they are launches. All crews face the same.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 06:28 pm
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

I think that's just someone messing around a car or something near the camera.

Interestingly enough, the small first bang heard is the original S2 explosion. The big bang 3 seconds later is the fuel-air type explosion when that fireball hit the ground and mixed up the RP-1 and LOX. Check out that light pole above the number "2" bending by the generated shockwave. I wonder what the extent of damage to the hangar must be.

*not an explosion expert*

i think there are a few smaller pops throughout the first few seconds of the "big" explosion. could these be copv's or could it just be plumbing, etc?

it looks like you can see each pop give a flash within the falling orange flames. it'd be cool if someone could adjust the sound delay to the visuals.

*perhaps* the first pop could be a single copv giving way and then others quickly go as choas ensues
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JDTractorGuy on 09/01/2016 06:29 pm


Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.  It crosses the screen in 15 frames and is in between the the lightning tower and the rocket at detonation.

Seems to be a bird or other animal.  It flies harmlessly over the rocket as it explodes.

I don't know man, watch it in real time, it moves so fast you can hardly see it.

If you pause the video and use , and . to go frame-by-frame, you can tell it's a bird, and that it flies over the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/01/2016 06:31 pm
Can someone point out this increase venting on S2 before the event?  I keep watching it and I do not see what they are talking about.

Sorry, I meant to say 20s prior, not 10s. Venting starts at about 0:50 in the video. It may not be atypical, but I pointed it out because CRS-7 showed increased venting from the S2 starting about 20s before the stage exploded.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 06:31 pm
Objects close to the camera can "appear" to move at incredibly high speeds if you assume they are far away.   There is an extreme telephoto lens in use here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: StarryKnight on 09/01/2016 06:31 pm


Anybody have any idea what that apparently rapidly moving object is?  It enters the field of view from the right immediately before the explosion.  It crosses the screen in 15 frames and is in between the the lightning tower and the rocket at detonation.

And 12 frames after detonation another object enters the frame from the lower left and transits the fire ball at seemingly equal high velocity. 

I'm breaking out my trusty tinfoil chapeau.

That's a bird flying much closer to the camera than the launch pad. That's why it crosses the camera field of view so quickly.  It only appears to be flying right above the rocket because with a 2D image like this, you're brain thinks everything is the same distance away.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mmeijeri on 09/01/2016 06:33 pm
I wonder what the extent of damage to the hangar must be.

Hmm, what about the recovered cores? Are they stored in that hangar or is there another one?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zach Swena on 09/01/2016 06:33 pm
Can someone point out this increase venting on S2 before the event?  I keep watching it and I do not see what they are talking about.

I heard some sort of vent in the audio more then seeing it in the video.  I retract my previous observation, as it seems they had a fade cut in there, and there is a difference in the background audio noise that I mistook for venting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/01/2016 06:34 pm
I wonder what the extent of damage to the hangar must be.

Hmm, what about the recovered cores? Are they stored in that hangar or is there another one?

They are stored in the LC-39A HIF, some 3 miles away from LC-40.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 06:36 pm
Can someone point out this increase venting on S2 before the event?  I keep watching it and I do not see what they are talking about.

Sorry, I meant to say 20s prior, not 10s. Venting starts at about 0:50 in the video. It may not be atypical, but I pointed it out because CRS-7 showed increased venting from the S2 starting about 20s before the stage exploded.

it looks like the video was cropped there. not sure why or how much.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/01/2016 06:36 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Not the brightness - the behavior of the hot gas.  Looks like there was stored energy.

Even if the source was internal (e.g. COPV) the center of the ignition may be just outside
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheMightyM on 09/01/2016 06:37 pm
More from Peter B. de Selding on Twitter:

Quote
SpaceX policy begun this yr of putting sats on rocket for static tests to trim a day frm launch campaign caused insurer upset, but not alot (sic).

I’ll go out on a limb and predict that we don’t see any more comm sats on rockets for static fire tests after this any time soon.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/01/2016 06:37 pm
It looks to me to be an U/S LOX tank rupture, possibly at the common bulkhead. That will at the very least mean a careful look at the design of said bulkhead and how it attaches to the two prop tanks and possibly a redesign.

The good news? As the fault appears to be in the upper stage, the recycled cores should still be clear for reuse.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/01/2016 06:39 pm
It looks to me to be an U/S LOX tank rupture, possibly at the common bulkhead. That will at the very least mean a careful look at the design of said bulkhead and how it attaches to the two prop tanks and possibly a redesign.

The good news? As the fault appears to be in the upper stage, the recycled cores should still be clear for reuse.

I thought the bulkhead, and furthermore, the tankage was of a common design. If we are looking at common bulkhead failure in the second stage, I would assume the first stage design also would need to be reviewed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 06:40 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Not the brightness - the behavior of the hot gas.  Looks like there was stored energy.

Even if the source was internal (e.g. COPV) the center of the ignition may be just outside

If th source had leaked for even a short time before ignition, the combustible material could spread quickly, particularly if boiling rapidly. When ignited the flames would spread very fast, even if there wasn't a massive amount of energy in the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/01/2016 06:42 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Not the brightness - the behavior of the hot gas.  Looks like there was stored energy.

Even if the source was internal (e.g. COPV) the center of the ignition may be just outside

Mixed fuel and oxygen stores a lot of chemical potential energy, which can be released in milliseconds with an ignition source.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/01/2016 06:42 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Not the brightness - the behavior of the hot gas.  Looks like there was stored energy.

Even if the source was internal (e.g. COPV) the center of the ignition may be just outside

If th source had leaked for even a short time before ignition, the combustible material could spread quickly, particularly if boiling rapidly. When ignited the flames would spread very fast, even if there wasn't a massive amount of energy in the explosion.
True.  Still seems a bit much, but definitely possible
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PahTo on 09/01/2016 06:43 pm
I wonder what the extent of damage to the hangar must be.

Hmm, what about the recovered cores? Are they stored in that hangar or is there another one?

They are stored in the LC-39A HIF, some 3 miles away from LC-40.

As I noted upthread (now waaay upthread), the LC39A HIF is rather close to pad 39A.  Imagine a similar scenario, but with a FH on (that) pad...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 06:46 pm
Peter B. de Selding:
SpaceX explosion didn't involve intentional ignition - E Musk said occurred during 2d stage fueling - & isn't covered by launch insurance.

https://twitter.com/pbdes/status/771409425475174400

Ouch. That will hurt
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/01/2016 06:46 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Not the brightness - the behavior of the hot gas.  Looks like there was stored energy.

Even if the source was internal (e.g. COPV) the center of the ignition may be just outside


The failure of the overwrap on a COPV releases a fair amount of stored energy that can provide an ignition source, and the fuel is immediately available (the carbon winding and the matrix material are fuel).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 06:47 pm
https://www.youtube.com/watch?v=ZX1vdPjCh3Q

not sure if they got permission from US Launch Report but here is a video with the audio synced
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MostlyHarmless on 09/01/2016 06:47 pm
Everyone posting v1.0 or v1.1-pre-FT timelines, please stop.  Consider removing your posts.  It's actively unhelpful.  Fuel loading procedures changed significantly for 1.1 FT with its supercooled propellants.

For that matter, we don't even know if the failure happened around T-5 or T-3 yet.

I apologize for posting unhelpful information.... the offending posts have been removed.  I shan't make this mistake again.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/01/2016 06:48 pm
I think there's too much energy in the initial explosion for it to be umbilicals.

I'd vote COPV, or COPV+bulkhead.
agreed. There is just not as much explosive energy in the umbilicals. If they would pop you'd get a flow or stream, which might damage later. Not this very sudden very energetic event.
pressure in the stage getting released - either through COPV/associated plumbing is, imho, at this point way more likely.

The brightness can just be burning. Don't mistake an oversaturated image for lots of energy.
Not the brightness - the behavior of the hot gas.  Looks like there was stored energy.

Even if the source was internal (e.g. COPV) the center of the ignition may be just outside

If th source had leaked for even a short time before ignition, the combustible material could spread quickly, particularly if boiling rapidly. When ignited the flames would spread very fast, even if there wasn't a massive amount of energy in the explosion.
True.  Still seems a bit much, but definitely possible

The other thing that occurs to me is that you need a fuel oxygen mix.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 06:49 pm
It probably means many lawyers are pressing their suits and preparing for battle...

Nothing for them to do.
This means SpaceX will have to foot most of the bill if they ever want to see another customer.

There's no way a shipping insurance will cover this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PhillyJimi on 09/01/2016 06:50 pm
I am kind of thinking that maybe they really didn't fix the problem that caused the CRS-7 failure.  My spidey senses are telling me this.  Watching the CRS-7 videos again its seems to be just too similar.  Especially considering the 2nd stage wasn't even firing when the explosion happened again.   

I know this is pure speculation at this point but what else are we do today. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Billium on 09/01/2016 06:52 pm
It probably means many lawyers are pressing their suits and preparing for battle...

Nothing for them to do.
This means SpaceX will have to foot most of the bill if they ever want to see another customer

Or maybe SpaceX has their own property/liability insurance which would cover this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 06:55 pm
Or maybe SpaceX has their own property/liability insurance which would cover this.

Yea, that will likely be the case to a certain degree, doubt they will have full coverage, probably some level of insurance making the losses somewhat bearable.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 06:55 pm
Peter B. de Selding:
SpaceX explosion didn't involve intentional ignition - E Musk said occurred during 2d stage fueling - & isn't covered by launch insurance.

https://twitter.com/pbdes/status/771409425475174400

Ouch. So Spacecom has to eat the cost?

Some background on what this might mean for Spacecom: http://spacewatchme.com/2016/08/israels-spacecom-sold-chinese-group-launch-amos-6/

Basically, Spacecom was in trouble, among other things, after the 2-year postponement of the AMOS-6 launch, and it got sold for $285 million (note AMOS-6 was $195 million), BUT this was contingent on the capability offered by the now-destroyed satellite.

On other news, SpaceFlight101 is reporting some debris arrived in the LC-39A area.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Machdiamond on 09/01/2016 06:56 pm
Kudos to USLaunchReport for being a very patient observer of SpaceX static tests and capturing historical footage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/01/2016 06:56 pm
I wonder what the extent of damage to the hangar must be.

Hmm, what about the recovered cores? Are they stored in that hangar or is there another one?

They are stored in the LC-39A HIF, some 3 miles away from LC-40.

As I noted upthread (now waaay upthread), the LC39A HIF is rather close to pad 39A.  Imagine a similar scenario, but with a FH on (that) pad...

FH is worst case equivalent to 196 tons of TNT. The HIF is 1900 feet from LC-39A, and at that range the only effect should be some broken windows, and possibly some falling flamey bits - but neither are likely to cause major damage to a steel building or anything reasonably sturdy inside it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 06:58 pm
It probably means many lawyers are pressing their suits and preparing for battle...

Nothing for them to do.
This means SpaceX will have to foot most of the bill if they ever want to see another customer.

There's no way a shipping insurance will cover this.

Are you sure? PBdSelding later tweeted that the pre-launch phase was insured as marine cargo. Pre-launch means up until ignition for the actual launch.

Quote
41m41 minutes ago
Peter B. de Selding ‏@pbdes
@cbs_spacenews Sat was insured as marine cargo for pre-launch phase. Launch policy didn't kick in because no ignition-w/-intent-to-launch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/01/2016 07:00 pm
More from Peter B. de Selding on Twitter:

Quote
SpaceX policy begun this yr of putting sats on rocket for static tests to trim a day frm launch campaign caused insurer upset, but not alot (sic).

I’ll go out on a limb and predict that we don’t see any more comm sats on rockets for static fire tests after this any time soon.

That means some insurance company was probably on the hook for this. No reason to get "upset" if you aren't liable.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: topsphere on 09/01/2016 07:01 pm
It probably means many lawyers are pressing their suits and preparing for battle...

Nothing for them to do.
This means SpaceX will have to foot most of the bill if they ever want to see another customer.

There's no way a shipping insurance will cover this.

Why? If the customer chose not to get full "space-industry" insurance then that is their prerogative, but they will bear the cost.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 07:02 pm
Are you sure? PBdSelding later tweeted that the pre-launch phase was insured as marine cargo for $285 mil.

Yes, but if that's the case... if I'm not totally mistaken that kind of insurance is for transportation and associated handling. Which is why the rate is lower, these are lower-risk events.

However, putting the payload on top of a fully fueled LV during a test firing is not a normal shipping procedure and would not be covered.

It's like with a rental car: even if you buy all the insurance, if you then go to a skid track and do some crash car racing with it, good luck claiming any damages...

Of course SpaceX is aware of all of this and will have an own scheme in place to at least limit their exposure for this type of testing. I'd hope...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cebri on 09/01/2016 07:05 pm
I am kind of thinking that maybe they really didn't fix the problem that caused the CRS-7 failure.  My spidey senses are telling me this.  Watching the CRS-7 videos again its seems to be just too similar.  Especially considering the 2nd stage wasn't even firing when the explosion happened again.   

I know this is pure speculation at this point but what else are we do today.

Isn't out there a report from NASA pretty much saying they were not to happy with SpaceX conclusions in relation to the CRS 7 failure, saying it was not really proven the struts were the ultimate cause of the failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 07:05 pm
Why? If the customer chose not to get full "space-industry" insurance then that is their prerogative, but they will bear the cost.

Well, it was SpaceX destroying the cargo.
Of course they might have a contract explicitly stating that if SpaceX does risky things with the cargo they won't be liable for it but I can't imagine any customer being so stupid to sign something like that.

No, this will be SpaceX's bill, but there's quite some chance they have own coverage for at least some of it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 07:05 pm
Are you sure? PBdSelding later tweeted that the pre-launch phase was insured as marine cargo for $285 mil.

Yes, but if that's the case... if I'm not totally mistaken that kind of insurance is for transportation and associated handling. Which is why the rate is lower, these are lower-risk events.

However, putting the payload on top of a fully fueled LV during a test firing is not a normal shipping procedure and would not be covered.

It's like with a rental car: even if you buy all the insurance, if you then go to a skid track and do some crash car racing with it, good luck claiming any damages...

Except this was standard procedure (static fire after integration) and I can't imagine them buying satellite insurance with a giant hole in it after shipment to the Cape. Plenty of bad things can happen during integration, satellite gets damaged by accident, a hurricane destroys the HIF, etc. All of those you buy insurance for.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wannamoonbase on 09/01/2016 07:07 pm
Perhaps this has been mentioned and exhausted somewhere in the many posts today, if it has I apologize.

The venting nearer the top of the TE stops a few seconds before the fireworks. 

1) Is it safe to assume that is second stage LOx?
2) Was that normal for that point in time?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 07:10 pm

Except this was standard procedure (static fire after integration)


Not for every Spacex launch and for none of the other ones.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/01/2016 07:12 pm
Perhaps this has been mentioned and exhausted somewhere in the many posts today, if it has I apologize.

The venting nearer the top of the TE stops a few seconds before the fireworks. 

1) Is it safe to assume that is second stage LOx?
2) Was that normal for that point in time?
LOX vent valve clogged/closed unexpectedly m
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 07:12 pm

Except this was standard procedure (static fire after integration)


Not for every Spacex launch and for none of the other ones.

Standard as in, the customer agreed to the procedure beforehand and presumably took reasonable precautions with insurance.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IanH84 on 09/01/2016 07:13 pm
https://www.youtube.com/watch?v=ZX1vdPjCh3Q

not sure if they got permission from US Launch Report but here is a video with the audio synced
I think Kabloona might be onto something.
I hear three distinct "initial" sounds:

1:16--a very faint "plonk" like someone hitting a PVC pipe with a hammer in the distance...COPV rupture?
1:18--a faint pop/bang... S2 tank rupture?
1:23--very loud boom...the LOX/RP-1 explosion?

That first sound at 1:16 is unusual and seems to me like it may be the initiating event. A COPV or high pressure line/fitting letting go followed by S2 tank rupture 1-2 seconds later seems consistent.
Crank up the volume, the first sound could be the creak of metal bending. If that's the case, we might be hearing a strut bend and break, a COPV rupturing or helium hose popping, and the loud boom is the visible explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: topsphere on 09/01/2016 07:13 pm
Why? If the customer chose not to get full "space-industry" insurance then that is their prerogative, but they will bear the cost.

Well, it was SpaceX destroying the cargo.
Of course they might have a contract explicitly stating that if SpaceX does risky things with the cargo they won't be liable for it but I can't imagine any customer being so stupid to sign something like that.

No, this will be SpaceX's bill, but there's quite some chance they have own coverage for at least some of it.

I'm sure this is in the contract and there's no way of us knowing yet - but choosing an insurance package with less cover (i.e. marine insurance pre-launch rather than "space" insurance pre-launch) doesn't pass the buck of responsibility, otherwise no-one would ever buy the highest cover insurance. Unless any negligence on SpaceX's part can be proven then I would be very, very surprised if they have to pay for the cost of the satellite.

Of course, there is the many tens of millions that SpaceX will have to pay in pad repair, inspection, foregone revenues etc. etc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 07:16 pm
Except this was standard procedure (static fire after integration)
That kind of thing is not a standard practice for marine cargo. Heck, it isn't even for SpaceX let alone other launch providers.
Quote
and I can't imagine them buying satellite insurance with a giant hole in it after shipment to the Cape.
Well, if SpaceX (+ whatever insurance they have) covers extraordinary events it in between, why not?
Quote
Plenty of bad things can happen during integration, satellite gets damaged by accident, a hurricane destroys the HIF, etc. All of those you buy insurance for.
Yes, and all these things _are_ standard risks for any kind of high-value target.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 07:19 pm
Except this was standard procedure (static fire after integration)
That kind of thing is not a standard practice for marine cargo. Heck, it isn't even for SpaceX let alone other launch providers.
Quote
and I can't imagine them buying satellite insurance with a giant hole in it after shipment to the Cape.
Well, if SpaceX (+ whatever insurance they have) covers extraordinary events it in between, why not?
Quote
Plenty of bad things can happen during integration, satellite gets damaged by accident, a hurricane destroys the HIF, etc. All of those you buy insurance for.
Yes, and all these things _are_ standard risks for any kind of high-value target.



I've spent a lot of professional time parsing insurance contracts. Unless you've seen the applicable policy and all the riders thereto, you have no way to be quite as authoritative about coverage issues IN THIS INSTANCE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/01/2016 07:20 pm
Watching this in slow motion, it appears that in the first frame with fire that there is a long downward finger of flame and smoke that dissipates as the fire ball erupts.  Is there an umbilical that could have come off and sprayed something downward?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 07:20 pm
Not for every Spacex launch and for none of the other ones.

Yep, and that's exactly the point why it isn't practical to have it in the payload insurance and I won't believe it was.
This is a high risk event of which you don't know in advance (when you negotiate the insurance) whether it's going to happen at all. No way you want to cover this.

It's easier for SpaceX to cover it because _they_ know that they will occasionally do a hot fire with payload and it's not just one so it's feasible for them to negotiate insurance or even to self-insure (read: factor it into the launch cost).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 07:21 pm

Crank up the volume, the first sound could be the creak of metal bending. If that's the case, we might be hearing a strut bend and break

That would not be heard from this distance
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mark McCombs on 09/01/2016 07:21 pm
You might think that a rupture disk or pressure relief valve/system would have actuated just prior to ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/01/2016 07:23 pm
I've spent a lot of professional time parsing insurance contracts. Unless you've seen the applicable policy and all the riders thereto, you have no way to be quite as authoritative about coverage issues IN THIS INSTANCE.

Me too and I've never seen one where individual high-risk activities were optionally included upfront. This doesn't make sense for the insurer or the customer and insurers are very good at passing that kind of stuff on to an entity that has control over it and can value the risk.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dglow on 09/01/2016 07:24 pm
I think Kabloona might be onto something.
I hear three distinct "initial" sounds:

1:16--a very faint "plonk" like someone hitting a PVC pipe with a hammer in the distance...COPV rupture?
1:18--a faint pop/bang... S2 tank rupture?
1:23--very loud boom...the LOX/RP-1 explosion?

That first sound at 1:16 is unusual and seems to me like it may be the initiating event. A COPV or high pressure line/fitting letting go followed by S2 tank rupture 1-2 seconds later seems consistent.
Crank up the volume, the first sound could be the creak of metal bending. If that's the case, we might be hearing a strut bend and break, a COPV rupturing or helium hose popping, and the loud boom is the visible explosion.

The camera and mic are over 2.5 miles from the pad. We don't know what kind of microphone was in use. Other than the explosion itself, we don't know where those other sounds originated from.

There's a voice that precedes the explosion by several seconds – where was that coming from? I hear what sounds like someone inhaling or gasping right at the point where they would have seen the explosion – but not heard it yet.

To my ears, the faint 'plonk' sounds decidedly sharper and nearer to the camera than the explosion which follows. Again, wild speculation: we don't know the limitations of this recording.

Still, many thanks to USLaunchReport for sharing this video.   :D

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Oersted on 09/01/2016 07:34 pm
Will this lead to new SpaceX procedures for quick 'n easy mating of the payload after static test firing? Should make for more aggressive, safety-enhancing testing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 07:38 pm
Will this lead to new SpaceX procedures for quick 'n easy mating of the payload after static test firing. Should make for more aggressive, safety-enhancing testing.

Not really.  Still constrained by what the payload needs to do after mate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/01/2016 07:45 pm
I'm going to speculate wildly here (Mod, please delete if inappropriate);

Point 1; The CRX7 failure occurred in the second stage.
Point 2; This explosion *appears* to have originated in the second stage.

Speculation: to my eyes, this event appears to have been highly energetic from the first moment it appears.

Further speculation; would a COPV failure (sudden release of He into the LOX) fit observations? In other words, one of the COPV He tanks ruptures, resulting in massive overpressure of the LOX, leading to massive and sudden structural failure thereof, and thus an explosion as the LOX mixed with RP1, with ignition sources provided by the structural failure/electrical umbilical?

If the above is true, is point 2 significant (perhaps a COPV, not a strut, caused CRX7?) Or could a strut failure have caused today's explosion? 

One possible silver lining here; the debris to investigate are in a small area on land, not scattered on vast stretches of seabed.

Edit to add; what about lightning? I think we'd have seen a lightning strike, would we would not have seen a step/leader, which is more than enough to fry a human, and thus plenty to cause sparking. Any idea what the electrical field strength was? (I'm probably flat out wrong here, because the scrub limits for a static fire are probably the same as for a launch when it comes to lightning.)

 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/01/2016 07:47 pm
Whatever the anomaly was that destroyed the launch vehicle, it was very energetic.  ???
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PahTo on 09/01/2016 07:51 pm

Thanks for posting the video.  Boy, watching the payload tumble to the ground/from the cradle after the fact sure adds insult to injury...
Again, my thoughts are with all involved.  Glad there weren't any injuries (any followup to reports that a firefighter was injured?)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 07:58 pm
The flame in the first frames looks more characteristic of detonation than conflagration to my amateur eyes; it's sharp and white all around.

That may just be sensor saturation. A better indicator of detonation is wave speed. If that had been a high order detonation, the stage would just disappear in one frame. The relatively slow development of the fireball is more characteristic of conflagration.

Edit: or per below post, the sharp white " flame" is just interpolation, not actual footage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/01/2016 07:58 pm
These screen shots were posted by @John_Gardi on Twitter.  Taken from this slow-mo video.

The Slo-mo frames are just interpolated from the existing frames, so it's impossible to conclude anything from them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/01/2016 08:00 pm
These screen shots were posted by @John_Gardi on Twitter.  Taken from this slow-mo video. ...
Seems to me that there is a bunch of software interpolation creating "detail" not in the source video.  In other words, I think it's inventing frames to smooth the transitions.

Edit:  Ninja's by RoboGoofers
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 08:00 pm

Thanks for posting the video.  Boy, watching the payload tumble to the ground/from the cradle after the fact sure adds insult to injury...
Again, my thoughts are with all involved.  Glad there weren't any injuries (any followup to reports that a firefighter was injured?)
We had a follow-up that it wasn't a medevac, the firefighter just wanted a lift to better observe the fire from above.

I certainly hope that's the case.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/01/2016 08:01 pm
Some notes:
1. There's no similarity to CRS-7 event. "Excessive venting" that some people claim here is probably mostly due to the fact that surrounding air was almost saturated with moisture. Pressure vessel overpressure rupture would have caused massive cloud initially, which then would have perhaps detonated. Not the other way around.
2. Fixing blast initiation point by analyzing video frames is not very productive as the surroundings are foggy and this fog reflects blast light towards camera making it bigger and moving the origination point towards the rocket body
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Dagger on 09/01/2016 08:06 pm
Made a little gif. Don't know how accurate it is:

(https://i.makeagif.com/media/9-01-2016/psm9zl.gif)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/01/2016 08:07 pm
Watching this in slow motion, it appears that in the first frame with fire that there is a long downward finger of flame and smoke that dissipates as the fire ball erupts.  Is there an umbilical that could have come off and sprayed something downward?
Some of that looks to me looks like it could be light from the initial fireball illuminating preexisting vapor clouds around the top of the first stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/01/2016 08:15 pm
My two cents. I might know the cause in my completely unfounded opinion. The main thing that I'm drawing my thoughts from are the intense localized flash of the explosion (as noticed by the flash star in the video film).

I believe this was a pre-detonation of the either a portion of, or completely of the upper stage FTS. There was an intense flash at a single small point. You don't get that level of intense flashes from an ignition. If this was a COPV explosion we should be seeing a spray of LOX or fuel before the explosion occurs.

I look forward to the date that rockets get their FTS removed. Having explosives on a vehicle has always seemed like a bad idea to me despite the good reasons for protection of the public they allow.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/01/2016 08:19 pm
Where are the FTS charges located on this vehicle?  Are they running up the side like on a solid or are they on the tank domes or something?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 08:20 pm
I believe this was a pre-detonation of the either a portion of, or completely of the upper stage FTS. There was an intense flash at a single small point. You don't get that level of intense flashes from an ignition. If this was a COPV explosion we should be seeing a spray of LOX or fuel before the explosion occurs.
FTS was safed at the time, as evidenced in the timeline by cradle closed and strongback vertical.

Still could be an anomalous FTS incident (static discharge?) but should be much much much less likely if FTS is safed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 08:21 pm
My two cents. I might know the cause in my completely unfounded opinion. The main thing that I'm drawing my thoughts from are the intense localized flash of the explosion (as noticed by the flash star in the video film).

I believe this was a pre-detonation of the either a portion of, or completely of the upper stage FTS. There was an intense flash at a single small point. You don't get that level of intense flashes from an ignition. If this was a COPV explosion we should be seeing a spray of LOX or fuel before the explosion occurs.

I look forward to the date that rockets get their FTS removed. Having explosives on a vehicle has always seemed like a bad idea to me despite the good reasons for protection of the public they allow.

Except the FTS is, in my experience, one of the most thoroughly designed, tested, and safe systems on the rocket, precisely because Range Safety folks are so concerned about the possibility of accidental initiation. Speaking as someone who has worked with FTS systems, it's practically impossible to initiate them by mistake. So I'd be highly surprised if FTS turns out to be the culprit.

I'd much rather be standing next to an FTS than a fully pressurized COPV, for example.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/01/2016 08:26 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/01/2016 08:29 pm
Made a little gif. Don't know how accurate it is:
(https://i.makeagif.com/media/9-01-2016/psm9zl.gif)

It's hard to draw much from attempting to find the 2D mid-point of an over-exposure.  That said, I find it interesting how the payload fairing was illuminated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: king1999 on 09/01/2016 08:31 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
That exactly looks like what happened. The whole stack just exploded really fast.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 08:32 pm
Wise words from Jeff Foust.

Quote
1h1 hour ago
Jeff Foust ‏@jeff_foust
You’ll see a lot of amateur speculation and analysis of today’s F9 explosion. Use with caution; almost all of it will turn out to be wrong.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/01/2016 08:32 pm
One more nail to the coffin of FTS theory. FTS consists of small linear charge designed to rupture the pressure vessel. It is not designed to explode into a giant fireball 30 feet across in a split second.

There's a remote possibility that FTS initiated on charge detonator level and this caused fuel-air explosion nearby in a very unlikely event. But in order this to happen very unlikely things have to happen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 08:32 pm
Made a little gif. Don't know how accurate it is:
(https://i.makeagif.com/media/9-01-2016/psm9zl.gif)

It's hard to draw much from attempting to find the 2D mid-point of an over-exposure.

That's why most people that attempt to locate it use the diffraction spikes instead (hence the X shape above). They are much more localized as they trace out the highest intensity light source at that instant. It's reasonable to assume that's where the event originated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/01/2016 08:35 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
That exactly looks like what happened. The whole stack just exploded really fast.
No, it doesn't.  There was a very bright and fast event on the second stage near the oxygen tank.  That opened the kerosene tank, and then the burning fuel and debris falling downward tore apart and ignited the first stage.  A FTS trigger would have been simultaneous on the first and second stages, not starting on the second stage and then proceeding downward like this was.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 08:36 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
That exactly looks like what happened. The whole stack just exploded really fast.

It really didn't.  There was a localized explosion in the second stage with a relatively slow progressive failure down the stack.  If it was FTS, the whole vehicle would have ceased to exist in the span of two or three frames.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/01/2016 08:36 pm
Made a little gif. Don't know how accurate it is:
(https://i.makeagif.com/media/9-01-2016/psm9zl.gif)

It's hard to draw much from attempting to find the 2D mid-point of an over-exposure.

That's why most people that attempt to locate it use the diffraction spikes instead (hence the X shape above). They are much more localized as they trace out the highest intensity light source at that instant. It's reasonable to assume that's where the event originated.

Sorry, but in this case, those spikes (actually in-lens reflections) show the average center of the oversaturated fireball. Nothing else.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/01/2016 08:37 pm
The biggest thing I don't understand is what is the ignition source? Even if the O2 tank had an overpressure, underpressure, or any other failure mode, why would the first thing we see be blinding fire? Some static or something would probably catch it eventually, but without the engines running you could mix O2 and RP-1 and it would still not self detonate.

Am I missing something? I realize my optimism toward SpaceX might make me favor the least damaging outcome, but I just don't see how anything other than an explosive charge could have detonated so quickly. TEA-TEB or hypergolics could easily cause a bad day, but they don't appear to have been involved unless they were being loaded into S2 by the umbilical at the time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/01/2016 08:39 pm
Wise words from Jeff Foust.

Quote
1h1 hour ago
Jeff Foust ‏@jeff_foust
You’ll see a lot of amateur speculation and analysis of today’s F9 explosion. Use with caution; almost all of it will turn out to be wrong.

Agreed, thus why I explicitly put a low emphasis in my post.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/01/2016 08:40 pm
Made a little gif. Don't know how accurate it is:
(https://i.makeagif.com/media/9-01-2016/psm9zl.gif)

It's hard to draw much from attempting to find the 2D mid-point of an over-exposure.

That's why most people that attempt to locate it use the diffraction spikes instead (hence the X shape above). They are much more localized as they trace out the highest intensity light source at that instant. It's reasonable to assume that's where the event originated.

Yes this was exactly what I was doing (I was still reading 20 pages back at the time and hadn't seen the gif yet).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/01/2016 08:40 pm

FH is worst case equivalent to 196 tons of TNT. The HIF is 1900 feet from LC-39A, and at that range the only effect should be some broken windows, and possibly some falling flamey bits - but neither are likely to cause major damage to a steel building or anything reasonably sturdy inside it.

There's not really a practical way to get a similar burn rate of separate fuel and oxidizers as you get for TNT. Most of that energy is, as can be seen, is consumed in deflagration, not detonation, so the worst case is not nearly as bad as the TNT equivalent.

That said, according to HYDEsim, 0.2 kT of TNT can damage buildings 1900 feet away, but in this case we're talking about LC-40. The hangar for LC-40 is much closer than that, isn't it?
http://meyerweb.com/eric/tools/gmap/hydesim.html?dll=28.56212,-80.57729&mll=28.56246,-80.57759&yd=0.2&zm=15&op=156

I'm going to speculate wildly here (Mod, please delete if inappropriate);

Point 1; The CRX7 failure occurred in the second stage.
Point 2; This explosion *appears* to have originated in the second stage.

Speculation: to my eyes, this event appears to have been highly energetic from the first moment it appears.

Further speculation; would a COPV failure (sudden release of He into the LOX) fit observations?

You are not the first person to suspect this. In my opinion, it appears consistent with overpressurization, but a problem with GSE  or the valve that handles boiloff might also result in overpressurization.

The CRS-7 failure is believed to have been due to buoyant forces under several G's of loading. The buoyant forces while on the pad are far lower. Even if it was a COPV failure, I would be surprised if it was due to tank buoyancy breaking a strut.

Regardless, don't get too attached to the theory. For almost every high-visibility aerospace accident like this, there's usually half a dozen reasonable-sounding theories proposed early on. Most (sometimes all) of them turn out to be wrong.

Some notes:
1. There's no similarity to CRS-7 event. "Excessive venting" that some people claim here is probably mostly due to the fact that surrounding air was almost saturated with moisture. Pressure vessel overpressure rupture would have caused massive cloud initially, which then would have perhaps detonated. Not the other way around.

A failure of the common bulkhead would have allowed ignition to begin inside the tank.

Watching this in slow motion, it appears that in the first frame with fire that there is a long downward finger of flame and smoke that dissipates as the fire ball erupts.  Is there an umbilical that could have come off and sprayed something downward?

I originally had a similar thought, but the speed of the explosion progression makes me think more likely its due to the tanks failing along a vertical seam (either initial, or after a bulkhead failure). That is why I've started leaning towards over-pressurization, although I'm pondering whether an accidental FTS activation would look the same. A partial vehicle FTS firing seems extremely unlikely, but not completely impossible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/01/2016 08:41 pm
Wise words from Jeff Foust.

Quote
1h1 hour ago
Jeff Foust ‏@jeff_foust
You’ll see a lot of amateur speculation and analysis of today’s F9 explosion. Use with caution; almost all of it will turn out to be wrong.

Agreed, thus why I explicitly put a low emphasis in my post.

BTW, this applies to all amateur accident investigations.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 08:41 pm
Wise words from Jeff Foust.

Quote
1h1 hour ago
Jeff Foust ‏@jeff_foust
You’ll see a lot of amateur speculation and analysis of today’s F9 explosion. Use with caution; almost all of it will turn out to be wrong.

Agreed, thus why I explicitly put a low emphasis in my post.

I wasn't singling you out; that was for all of us, me included. ;-)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/01/2016 08:42 pm
Made a little gif. Don't know how accurate it is:
(https://i.makeagif.com/media/9-01-2016/psm9zl.gif)

It's hard to draw much from attempting to find the 2D mid-point of an over-exposure.

That's why most people that attempt to locate it use the diffraction spikes instead (hence the X shape above). They are much more localized as they trace out the highest intensity light source at that instant. It's reasonable to assume that's where the event originated.

Sorry, but in this case, those spikes (actually in-lens reflections) show the average center of the oversaturated fireball. Nothing else.

Sorry, but there is oversaturation and then there is oversaturation. According to you, those spikes should simply be as wide as the whited-out region, which is clearly not the case. My point is that it takes even more light intensity to produce spiking than it takes to saturate the detector at a region and that it was reasonable to assume that the highest physical brightness point corresponds to the point of origin. The spikes convey additional useful information about the brightness profile above the whited-out region precisely because they are more tightly constrained.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 08:42 pm
The biggest thing I don't understand is what is the ignition source? Even if the O2 tank had an overpressure, underpressure, or any other failure mode, why would the first thing we see be blinding fire? Some static or something would probably catch it eventually, but without the engines running you could mix O2 and RP-1 and it would still not self detonate.

Am I missing something? I realize my optimism toward SpaceX might make me favor the least damaging outcome, but I just don't see how anything other than an explosive charge could have detonated so quickly. TEA-TEB or hypergolics could easily cause a bad day, but they don't appear to have been involved unless they were being loaded into S2 by the umbilical at the time.

If the fuel-oxygen mix is right, it only takes a tiny spark.  Electrostatic discharge, a momentary arc from a switch opening or closing, really anything.  If you read the history (don't have a link handy, but it's out there) of when they built LC-39A, they had a LOX leak at the pad one day and discovered it when people's cars started bursting into flame.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/01/2016 08:42 pm
Sorry, but in this case, those spikes (actually in-lens reflections) show the average center of the oversaturated fireball. Nothing else.

Albeit there's probably a correlation between the centre of the lens flare, the brightest point of the image - and by derivation the hottest point of the fireball, which - given there's about 1/30 of a second between the start of the event and the explosion / lens flare - has a very good chance of being the initial point at which the event occurred.

Occam's Razor; or "if it look like a duck and quacks like a duck, then it probably is a duck".

*Why* it's a duck is a bit more problematic. The video footage almost certainly gives us the location of the failure - but certainly not the cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/01/2016 08:43 pm
The vehicle is sitting in a cloud of concentrated, evaporating oxygen and is holding thousands of kilograms more on board. A small leak and a spark is all that is needed to cause an event big enough to rupture the tanks leading the chain reaction. Oxygen is abundant in this scenario - we don't need an explosive to turn the situation bad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/01/2016 08:44 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
That exactly looks like what happened. The whole stack just exploded really fast.

It really didn't.  There was a localized explosion in the second stage with a relatively slow progressive failure down the stack.  If it was FTS, the whole vehicle would have ceased to exist in the span of two or three frames.

FTS isn't designed to obliterate the vehicle as much as it is to release the fuel to get rid of its mass, momentum, and explosive potential. When we've seen FTS before it causes a slow conflagration fireball just like we see here after that initial pop at the top of S2. It looked very much like the fireball we saw on GH2, although with a much better vantage point to see details.

For those saying FTS wouldn't cause a fireball, well, what other ignition source was there? We didn't see a green flash.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 09/01/2016 08:45 pm
The biggest thing I don't understand is what is the ignition source? Even if the O2 tank had an overpressure, underpressure, or any other failure mode, why would the first thing we see be blinding fire? Some static or something would probably catch it eventually, but without the engines running you could mix O2 and RP-1 and it would still not self detonate.

Am I missing something? I realize my optimism toward SpaceX might make me favor the least damaging outcome, but I just don't see how anything other than an explosive charge could have detonated so quickly. TEA-TEB or hypergolics could easily cause a bad day, but they don't appear to have been involved unless they were being loaded into S2 by the umbilical at the time.

If the fuel-oxygen mix is right, it only takes a tiny spark.  Electrostatic discharge, a momentary arc from a switch opening or closing, really anything...
Indeed. You might call this a *static*fire*. Heh.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rcoppola on 09/01/2016 08:52 pm
Wonder how the Dragon2 Trunk/Capsule would have dealt with this 2nd Stage RUD in a Pad Abort scenario?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mulp on 09/01/2016 08:53 pm
Ok, the cost to SpaceX for the rocket is manufacturing cost plus the direct opportunity cost of the lost use of its pad and personnel, all readily quantifiable, plus the harder to measure opportunity cost of loss of sales, plus some liability to the customer.

We know SpaceX rocket costs and launch capacity are transitioning to "volume".

The customer cost is the satellite hardware plus opportunity cost of the delay.

How much of the satellite hardware is in "volume" production?

Are things like antennas 3d printed or laser Cut?

Creating the specs for AMOS-6 might take years, but making the parts and integrating them only months. Or the process might still be in the stage of sending out orders for each part to be made custom.

Any idea where the satellite production is for AMOS-6 and for the majority in general?

I'm thinking of PBS NBR special reports this week on the multiple satellite Silicon valley startups getting tens of billions of cash to build satellites in volume, plus all the launcher startups.

Is the destruction of this hardware a really huge cost, or just a lot of labor cost flushed, but easily replaced by everyone working a few more hours a week for awhile and using the overtime to buy new boats?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 08:57 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
That exactly looks like what happened. The whole stack just exploded really fast.

It really didn't.  There was a localized explosion in the second stage with a relatively slow progressive failure down the stack.  If it was FTS, the whole vehicle would have ceased to exist in the span of two or three frames.

FTS isn't designed to obliterate the vehicle as much as it is to release the fuel to get rid of its mass, momentum, and explosive potential. When we've seen FTS before it causes a slow conflagration fireball just like we see here after that initial pop at the top of S2. It looked very much like the fireball we saw on GH2, although with a much better vantage point to see details.

For those saying FTS wouldn't cause a fireball, well, what other ignition source was there? We didn't see a green flash.

FTS is designed to cease acceleration and disperse the propellants.  This is often accomplished by a linear shaped charge running the length of the vehicle.  I suspect the Falcon is the same way.  You might not see an immediate fireball, but you would see the whole vehicle unzip basically at once if it were FTS, not the several seconds it took to completely come apart.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DarkenedOne on 09/01/2016 08:59 pm
The vehicle is sitting in a cloud of concentrated, evaporating oxygen and is holding thousands of kilograms more on board. A small leak and a spark is all that is needed to cause an event big enough to rupture the tanks leading the chain reaction. Oxygen is abundant in this scenario - we don't need an explosive to turn the situation bad.

Oxygen alone will not cause an explosion.  It does not react with itself.  You need a fuel source. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/01/2016 09:00 pm
The vehicle is sitting in a cloud of concentrated, evaporating oxygen and is holding thousands of kilograms more on board. A small leak and a spark is all that is needed to cause an event big enough to rupture the tanks leading the chain reaction. Oxygen is abundant in this scenario - we don't need an explosive to turn the situation bad.

Oxygen alone will not cause an explosion.  It does not react with itself.  You need a fuel source. 
In a sufficiently high concentration of oxygen, many traditionally nonflammable things become quite flammable.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/01/2016 09:02 pm
I heard from one of the reddit that some believe a hydrazine leak from the satellite may of caused the initial explosion.  Given the location of the explosion being close the top of the oxygen tank, and the initial size explosion it seems like this is certainly possible.  I know from chemistry that hydrazine is particularly reactive, volatile, and very dangerous.  I am not an expert on launch systems and satellites, but what is the likelihood that this was the case.

Probably near zero. The payload was well above the plane where the first flash occurred, encapsulated in a fairing that remained intact long after the initial explosion. Also there's no way for hydrazine to get *into* the LOX tank, which appeared to rupture, suggesting the event may have started inside the LOX tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vandersons on 09/01/2016 09:04 pm
Have watched the explosion frame by frame now for at least a couple dozen times. The initial bright flash is very baffling. It comes from the area where the LOX appears to be venting so there is lots of O2 there but on the other hand there is also a lot of wind blowing the vapour away so not much could have been just sitting there waiting on a spark to ignite stuff.

With that in mind, what is in that area of the bright flash that could potentially be oxidised in such a flash? From reading up thread the RP1 and LOX filling lines are further down near the interstage, the flash occurred much higher up (that would exclude RP1 leaking). Are any of the fittings near the flash area in any way flammable enough to produce a flash like that given enough O2 was present?

Could a static spark be strong enough to make a hole in the LOX tank and igniting the cork and/or aluminium therefore producing the first bright flash that with additional LOX gushing out of the tank gets bigger very quickly until it ruptures both tanks on S2?

Surprisingly S1 holds out for quite a while. Only until after it has been completely engulfed by the falling flaming fuel and LOX mix it gives up an produces the second big explosion (the third being the payload hitting the ground and blowing its hypergolic's tanks).

The COPV idea kind of doesn't quite add up in my mind. If only the LOX tank would go pop from an overpressure event then the first thing we should be seeing in the sequence is a white cloudy mass of LOX blowing out in various directions but no flames until the cloud hits something combustible and hot enough to start the explosion. It should look similar to how the S2 deflagrated on CRS7 - first a puff of white cloud, then mixing with some RP1, then hitting the exhaust flames and going up in a big fireball. In this case the sequence is very different - very bright flash, fireball starts spreading, some white cloud starts appearing leading the fireball, fuel-air explosion happens that triggers the S1 to blow up as well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/01/2016 09:07 pm
The vehicle is sitting in a cloud of concentrated, evaporating oxygen and is holding thousands of kilograms more on board. A small leak and a spark is all that is needed to cause an event big enough to rupture the tanks leading the chain reaction. Oxygen is abundant in this scenario - we don't need an explosive to turn the situation bad.

someone posted this upthread, but lot of fuel and LOx mixing without an explosion: Atlas 190D

https://youtu.be/FmrrcAVOV4s (https://youtu.be/FmrrcAVOV4s)

Quote
13,000 gallons of liquid oxygen and a full load of fuel sloshed over the stand and the nearby terrain.

here's a reference:
https://books.google.com/books?id=OVNuxBlXFHYC&lpg=PA32&ots=RWbZyy0by-&dq=1963%2C%20Atlas%20190D&pg=PA32#v=onepage&q=1963,%20Atlas%20190D&f=false (https://books.google.com/books?id=OVNuxBlXFHYC&lpg=PA32&ots=RWbZyy0by-&dq=1963%2C%20Atlas%20190D&pg=PA32#v=onepage&q=1963,%20Atlas%20190D&f=false)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/01/2016 09:07 pm
Wonder how the Dragon2 Trunk/Capsule would have dealt with this 2nd Stage RUD in a Pad Abort scenario?

Assuming the problem was recognized as severe by the computer and the LAS activated almost instantly, a second later the capsule would be 50+ feet away, and by the next second, roughly 300 feet away, etc.

If you pay attention in the video, after the explosion starts and the main fireball erupts and fades away, the fairing, halves still latched together, is visible falling starting about 7 seconds after the start. Given the smaller cross section of the Dragon 2, it's heat shielding, and potentially also stronger overall construction of the capsule, I think the crew has good odds in this kind of scenario. This is, after all, one of the design scenarios for the LAS.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/01/2016 09:07 pm
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

I think that's just someone messing around a car or something near the camera.

Interestingly enough, the small first bang heard is the original S2 explosion. The big bang 3 seconds later is the fuel-air type explosion when that fireball hit the ground and mixed up the RP-1 and LOX.

I hear three distinct "initial" sounds:

1:16--a very faint "plonk" like someone hitting a PVC pipe with a hammer in the distance...COPV rupture?
1:18--a faint pop/bang... S2 tank rupture?
1:23--very loud boom...the LOX/RP-1 explosion?

That first sound at 1:16 is unusual and seems to me like it may be the initiating event. A COPV or high pressure line/fitting letting go followed by S2 tank rupture 1-2 seconds later seems consistent.

Overanalyzation of the events.

1:16--unrelated
1:18--unrelated
1:23--corresponding to visual event at 1:11, there's an approximately 12 second delay

Explosion event at 1:11.721, explosion shockwave arrives at 1:23.817. Total sound delay is 12.096 (with some fake precision).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/01/2016 09:08 pm
The biggest thing I don't understand is what is the ignition source? Even if the O2 tank had an overpressure, underpressure, or any other failure mode, why would the first thing we see be blinding fire? Some static or something would probably catch it eventually, but without the engines running you could mix O2 and RP-1 and it would still not self detonate.

Am I missing something? I realize my optimism toward SpaceX might make me favor the least damaging outcome, but I just don't see how anything other than an explosive charge could have detonated so quickly. TEA-TEB or hypergolics could easily cause a bad day, but they don't appear to have been involved unless they were being loaded into S2 by the umbilical at the time.

If the fuel-oxygen mix is right, it only takes a tiny spark.  Electrostatic discharge, a momentary arc from a switch opening or closing, really anything...
Indeed. You might call this a *static*fire*. Heh.

That is exactly my point though, the mixture isn't right. They are totally separate until something goes wrong. It seems a stretch to think the O2 tank popped, which popped the RP-1 tank, and static happened at the right time and place to cause a spark, all within a few milliseconds. We should have seen a tank pop before it all went up.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/01/2016 09:09 pm
Anybody familiar enough with S2 to know what's near the center of the "X"?  I believe ugordan was speculating on page 24 that the horizontal feature you can see extending to the left across S2 from the cradle was the clamp that holds S2, which is located near the common bulkhead for the LH2/LOX tanks.

I'm trying hard to remember that even the apparent location of the brightest part of the image (at the center of the X) is only a 2D projection of a 3D event.  The actual problem could have started on the unobserved side of the vehicle and what we're seeing is something propagating around to this side, or it could be a weak point where the event found a place to exit the vehicle, or it could be a secondary result of a primary failure that occurred far away.

So sorry for all those affected.  But I have faith in SpaceX; what they're trying to do is hard, and they only make it *look* easy.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 09:12 pm
I heard from one of the reddit that some believe a hydrazine leak from the satellite may of caused the initial explosion.  Given the location of the explosion being close the top of the oxygen tank, and the initial size explosion it seems like this is certainly possible.  I know from chemistry that hydrazine is particularly reactive, volatile, and very dangerous.  I am not an expert on launch systems and satellites, but what is the likelihood that this was the case.


The fairing would not have remained intact then
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DarkenedOne on 09/01/2016 09:13 pm
I heard from one of the reddit that some believe a hydrazine leak from the satellite may of caused the initial explosion.  Given the location of the explosion being close the top of the oxygen tank, and the initial size explosion it seems like this is certainly possible.  I know from chemistry that hydrazine is particularly reactive, volatile, and very dangerous.  I am not an expert on launch systems and satellites, but what is the likelihood that this was the case.

Probably near zero. The payload was well above the plane where the first flash occurred, encapsulated in a fairing that remained intact long after the initial explosion. Also there's no way for hydrazine to get *into* the LOX tank, which appeared to rupture, suggesting the event may have started inside the LOX tank.

The explosion appears close to the base of the payload and the top of the LOX tank.  There is just nothing inside the LOX tank that can cause an explosion as far as I can tell.  It has to be something that mixed with the oxygen outside of the tank.  I think they vent oxygen that boils off right there. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Norm38 on 09/01/2016 09:13 pm
Wonder how the Dragon2 Trunk/Capsule would have dealt with this 2nd Stage RUD in a Pad Abort scenario?

It'll depend on if the software is active during a static fire.  Kind of how the CRS-7 parachute deploy software wasn't running.  I hope after this they'll have the Dragon2 primed and ready to abort once the rocket is vertical and into propellant loading.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/01/2016 09:15 pm
Crank up the volume, the first sound could be the creak of metal bending. If that's the case, we might be hearing a strut bend and break, a COPV rupturing or helium hose popping, and the loud boom is the visible explosion.

Please... This is an incessant problem on the internet to attribute new failures to previous issues. In engineering its the exception rather than the rule that a new failure is the same failure as before. If something fails its almost certainly something else that failed unless your engineers have no clue what they're doing or root cause was not found. This failure is NOT going to be related to struts. Forget the struts exist. That's a solved problem. Different metal suppliers, different stronger design, additional struts, impossible to be the same problem.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/01/2016 09:18 pm
FTS is designed to cease acceleration and disperse the propellants.  This is often accomplished by a linear shaped charge running the length of the vehicle.  I suspect the Falcon is the same way.  You might not see an immediate fireball, but you would see the whole vehicle unzip basically at once if it were FTS, not the several seconds it took to completely come apart.

It would be several shaped charges, not one running the full length across both stages. The second stage disappears instantly. The rest of the rocket took a while. That said, the payload took several seconds to fall off, but cutting line through the length of the tank does not necessarily make the whole tank buckle instantly.

An FTS activation by the controller should have destroyed both stages at once, but it is not entirely out of the question that something else caused a single detonator to go off. Just extremely unlikely due to how carefully tested FTS hardware is.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Firehawk153 on 09/01/2016 09:19 pm
Crank up the volume, the first sound could be the creak of metal bending. If that's the case, we might be hearing a strut bend and break, a COPV rupturing or helium hose popping, and the loud boom is the visible explosion.

Please... This is an incessant problem on the internet to attribute new failures to previous issues. In engineering its the exception rather than the rule that a new failure is the same failure as before. If something fails its almost certainly something else that failed unless your engineers have no clue what they're doing or root cause was not found. This failure is NOT going to be related to struts. Forget the struts exist. That's a solved problem. Different metal suppliers, different stronger design, additional struts, impossible to be the same problem.

I dunno, ever heard of Taurus, OCO, and Glory? Just saying...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 09:19 pm

Sorry, but there is oversaturation and then there is oversaturation. According to you, those spikes should simply be as wide as the whited-out region, which is clearly not the case. My point is that it takes even more light intensity to produce spiking than it takes to saturate the detector at a region and that it was reasonable to assume that the highest physical brightness point corresponds to the point of origin. The spikes convey additional useful information about the brightness profile above the whited-out region precisely because they are more tightly constrained.


The reflection off the T/E structure is most certainly biasing any correlation between saturation and 2D projection of the explosion initiation point, I would think. The right third (roughly) of the oversaturated area should be weighted by a function of the T/E reflectivity. In essence, I would argue the true point lies a few pixels more to the left.


Further, look at the symmetry of the expanding LOX cloud a few frames later. The right side is a bit muffled because of the interference with the T/E, obviously, but the near perfect oval shape for most of its circumference suggests the failure point was mostly toward the camera, not facing directly at the erector.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: joncz on 09/01/2016 09:23 pm
I heard from one of the reddit that some believe a hydrazine leak from the satellite may of caused the initial explosion.  Given the location of the explosion being close the top of the oxygen tank, and the initial size explosion it seems like this is certainly possible.  I know from chemistry that hydrazine is particularly reactive, volatile, and very dangerous.  I am not an expert on launch systems and satellites, but what is the likelihood that this was the case.

Probably near zero. The payload was well above the plane where the first flash occurred, encapsulated in a fairing that remained intact long after the initial explosion. Also there's no way for hydrazine to get *into* the LOX tank, which appeared to rupture, suggesting the event may have started inside the LOX tank.

The fairing remained with the payload as they fell free of the strongback.  When the payload impacts the ground, you can see another "explosion," presumably of the satellite's hypergols.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/01/2016 09:23 pm
One thought re: speculation about a COPV failure. The COTS-7 failure wasn't thought to be a COPV letting go per se, but a massive helium leak that led to an overpressure. A COPV flat-out failing might happen faster, and could lead to a more energetic explosion. For instance, isn't that how the S-IVB 503 upper stage was lost during a ground test (in very similar circumstances--during fueling before a hot-fire test)?

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MattMason on 09/01/2016 09:27 pm
Wouldn't the color of the initial detonation (orange) suggest an RP-1 leak?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/01/2016 09:28 pm
That is exactly my point though, the mixture isn't right. They are totally separate until something goes wrong. It seems a stretch to think the O2 tank popped, which popped the RP-1 tank, and static happened at the right time and place to cause a spark, all within a few milliseconds. We should have seen a tank pop before it all went up.

That's what i believe too.

At least with a copv bursting, it would send shrapnel through the tank walls into the fuel tank causing mixing.  someone mentioned upthread that the bursting of a copv might have enough energy to start the chemical chain reaction (not the kind of "classical" ignition source you'd imagine like a flame or spark), and the copv carbon would be flammable in a high oxygen environment.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Carl G on 09/01/2016 09:29 pm
A reminder, stupid posts will be deleted. Rumors from other sites that are stupid will be deleted. Members insisting on posting such things will be banned. People complaining there's speculation on here will also have their posts removed before this is the discussion thread, not the update thread. The update thread is for the official info.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: clegg78 on 09/01/2016 09:29 pm
Wouldn't the color of the initial detonation (orange) suggest an RP-1 leak?

I was thinking the same,  Its not like there was a gush of white vapor (LOX) that lead to an ignition/detonation.   IT was clearly orange fire initially (although energetic and obviously merged with LOX for the big boom at the top).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/01/2016 09:30 pm

Please... This is an incessant problem on this forum to attribute new failures to previous issues. In engineering its the exception rather than the rule that a new failure is the same failure as before. If something fails its almost certainly something else that failed unless your engineers have no clue what they're doing or root cause was not found. This failure is NOT going to be related to struts. Forget the struts exist. That's a solved problem. Different metal suppliers, different stronger design, additional struts, impossible to be the same problem.

I dunno, ever heard of Taurus, OCO, and Glory? Just saying...

AC-70 and AC-71.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/01/2016 09:30 pm
Accidentally (or deliberately) activated FTS would have activated the FTS for the entire vehicle, not just the second stage.  This failure was too localized to be FTS.
That exactly looks like what happened. The whole stack just exploded really fast.

It really didn't.  There was a localized explosion in the second stage with a relatively slow progressive failure down the stack.  If it was FTS, the whole vehicle would have ceased to exist in the span of two or three frames.

FTS isn't designed to obliterate the vehicle as much as it is to release the fuel to get rid of its mass, momentum, and explosive potential. When we've seen FTS before it causes a slow conflagration fireball just like we see here after that initial pop at the top of S2. It looked very much like the fireball we saw on GH2, although with a much better vantage point to see details.

For those saying FTS wouldn't cause a fireball, well, what other ignition source was there? We didn't see a green flash.

FTS is designed to cease acceleration and disperse the propellants.  This is often accomplished by a linear shaped charge running the length of the vehicle.  I suspect the Falcon is the same way.  You might not see an immediate fireball, but you would see the whole vehicle unzip basically at once if it were FTS, not the several seconds it took to completely come apart.

I'm somewhat doubting this theory now personally, but the upper stage and bottom stage necessarily have to be on different FTS circuits. What we indeed see is a sudden destruction of the upper stage and the contained liquid fuel of the upper stage falling to the ground and then an explosion indicative of the rupture of the lower stage followed by the impact at the bottom causing complete rupture of the lower stage and subsequent explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: acsawdey on 09/01/2016 09:31 pm
The vehicle is sitting in a cloud of concentrated, evaporating oxygen and is holding thousands of kilograms more on board. A small leak and a spark is all that is needed to cause an event big enough to rupture the tanks leading the chain reaction. Oxygen is abundant in this scenario - we don't need an explosive to turn the situation bad.

someone posted this upthread, but lot of fuel and LOx mixing without an explosion: Atlas 190D

https://www.youtube.com/watch?v=FmrrcAVOV4s (https://www.youtube.com/watch?v=FmrrcAVOV4s)

Quote
13,000 gallons of liquid oxygen and a full load of fuel sloshed over the stand and the nearby terrain.

here's a reference:
https://books.google.com/books?id=OVNuxBlXFHYC&lpg=PA32&ots=RWbZyy0by-&dq=1963%2C%20Atlas%20190D&pg=PA32#v=onepage&q=1963,%20Atlas%20190D&f=false (https://books.google.com/books?id=OVNuxBlXFHYC&lpg=PA32&ots=RWbZyy0by-&dq=1963%2C%20Atlas%20190D&pg=PA32#v=onepage&q=1963,%20Atlas%20190D&f=false)

Atlas 190D had only fuel on board no LOX:

Quote
The launch crew managed to
drain the LOX tank but ended up depressurizing it in the process, and so
it collapsed, dropping the Agena.

http://www.spacebanter.com/showthread.php?t=51063 (http://www.spacebanter.com/showthread.php?t=51063)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 09:32 pm

That is exactly my point though, the mixture isn't right. They are totally separate until something goes wrong. It seems a stretch to think the O2 tank popped, which popped the RP-1 tank, and static happened at the right time and place to cause a spark, all within a few milliseconds. We should have seen a tank pop before it all went up.


The RP-1 tank is pressurized too. A sudden catastrophic loss of pressure from the top tank (coupled with the immediate boiling and aerosolization of the remaining LOX) would have caused a very traumatic upward force event for the common bulkhead to withstand, causing it to fail upward and providing a kerosene spray from below. This, provided the bulkhead hadn't failed beforehand, causing the visible wall rupture.


A burning RP-1 stream starts to appear in the image (see arrow) at frame 10 after the explosion already: around 160 ms after the explosion started.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MattMason on 09/01/2016 09:33 pm
That is exactly my point though, the mixture isn't right. They are totally separate until something goes wrong. It seems a stretch to think the O2 tank popped, which popped the RP-1 tank, and static happened at the right time and place to cause a spark, all within a few milliseconds. We should have seen a tank pop before it all went up.

That's what i believe too.

At least with a copv bursting, it would send shrapnel through the tank walls into the fuel tank causing mixing.  someone mentioned upthread that the bursting of a copv might have enough energy to start the chemical chain reaction (not the kind of "classical" ignition source you'd imagine like a flame or spark), and the copv carbon would be flammable in a high oxygen environment.

And if either tank burst, logic suggests the integrity of the second stage would've failed far more quickly and the payload fairing would've fallen or been pushed away much earlier.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/01/2016 09:33 pm
I think there's evidence that the explosion initiated to the side of the rocket, not on or in the rocket.  The USLaunchReport video as a reference.   There is a fragment that has a trajectory that traces back to the strongback, not the rocket.  Reference images attached
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/01/2016 09:38 pm
Deleted a couple of "what is this thing transversing the vid" ... it's a bird.

People, it's fun to speculate but please review the thread before you post, and think. At least a little.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/01/2016 09:38 pm
I think there's evidence that the explosion initiated to the side of the rocket, not on or in the rocket.  The USLaunchReport video as a reference.   There is a fragment that has a trajectory that traces back to the strongback, not the rocket.  Reference images attached

Interesting. Can be ballistically reconstructed. Anyone up for this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: atsf90east on 09/01/2016 09:38 pm
I noticed this too.  I'm not familiar with the LOX fill line interface with the vehicle, but if the explosion started inside the second stage, wouldn't this object be blown outward, and not upward?

I think there's evidence that the explosion initiated to the side of the rocket, not on or in the rocket.  The USLaunchReport video as a reference.   There is a fragment that has a trajectory that traces back to the strongback, not the rocket.  Reference images attached
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/01/2016 09:41 pm
So what is Object X?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MattMason on 09/01/2016 09:44 pm
I think there's evidence that the explosion initiated to the side of the rocket, not on or in the rocket.  The USLaunchReport video as a reference.   There is a fragment that has a trajectory that traces back to the strongback, not the rocket.  Reference images attached

Interesting. Can be ballistically reconstructed. Anyone up for this?

I'm sure you're asking the right people, if NSF's CRS-7 forum investigation and F9 water landing video reconstruction are any indications. :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 09:46 pm
So what is Object X?

i think what you circled on the left side is some liquid oxygen that is being pushed away

and what you circled on the right side is the claw that holds onto the stage that is part of the Erector
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/01/2016 09:47 pm
I think there's evidence that the explosion initiated to the side of the rocket, not on or in the rocket.  The USLaunchReport video as a reference.   There is a fragment that has a trajectory that traces back to the strongback, not the rocket.  Reference images attached

it could also coming toward the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/01/2016 09:48 pm
So what is Object X?

That's what I was calling evidence of the LOX tank rupturing at top left, near the vents.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/01/2016 09:49 pm
So what is Object X?

i think what you circled on the left side is some liquid oxygen that is being pushed away

and what you circled on the right side is the claw that holds onto the stage that is part of the Erector

Correct. That is simply a backlit O2 vapor cloud. move along...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 09:49 pm
I think there's evidence that the explosion initiated to the side of the rocket, not on or in the rocket.  The USLaunchReport video as a reference.   There is a fragment that has a trajectory that traces back to the strongback, not the rocket.  Reference images attached

it could also coming toward the camera.

also spinning as it is catching different light from the flame
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/01/2016 09:53 pm
WOW. We can see the payload fall seconds after the first explosion. Maybe a dragon could fly away in time.

Maybe the crew Dragon but not the cargo Dragon. The cargo Dragon can now survive a CRS-7 type accident by deploying its parachutes but that doesn't help if the accident is at the pad.

It's hard to know if people would have survived if they had been in a crew Dragon on this rocket.  If there was no warning, the Dragon would have been subjected to a significant overpressure before it could have taken off.  Maybe the Dragon could have protected crew members from such an overpressure, maybe not.

There's also the issue of whether the overpressure would have damaged the SuperDraco engines and/or their prop tanks and/or the abort control system.  If any of those things failed, the crew would have died.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mvpel on 09/01/2016 09:56 pm
I've attached the one close-up I had of of the apparently relevant area of the CRS-8 booster which I took back in April. I'm not sure if there's anything visible that might be useful, but worth a shot I guess.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/01/2016 09:57 pm
WOW. We can see the payload fall seconds after the first explosion. Maybe a dragon could fly away in time.

Maybe the crew Dragon but not the cargo Dragon. The cargo Dragon can now survive a CRS-7 type accident by deploying its parachutes but that doesn't help if the accident is at the pad.

It's hard to know if people would have survived if they had been in a crew Dragon on this rocket.  If there was no warning, the Dragon would have been subjected to a significant overpressure before it could have taken off.  Maybe the Dragon could have protected crew members from such an overpressure, maybe not.

There's also the issue of whether the overpressure would have damaged the SuperDraco engines and/or their prop tanks and/or the abort control system.  If any of those things failed, the crew would have died.

its hard to say for sure but the payload seemed to be alright till it hit the ground. the dragon in the previous second stage mishap also survived till it hit the sea.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rcoppola on 09/01/2016 10:00 pm
WOW. We can see the payload fall seconds after the first explosion. Maybe a dragon could fly away in time.

Maybe the crew Dragon but not the cargo Dragon. The cargo Dragon can now survive a CRS-7 type accident by deploying its parachutes but that doesn't help if the accident is at the pad.

It's hard to know if people would have survived if they had been in a crew Dragon on this rocket.  If there was no warning, the Dragon would have been subjected to a significant overpressure before it could have taken off.  Maybe the Dragon could have protected crew members from such an overpressure, maybe not.

There's also the issue of whether the overpressure would have damaged the SuperDraco engines and/or their prop tanks and/or the abort control system.  If any of those things failed, the crew would have died.
(In this scenario) It was the trunk I was most concerned with as a Crew Abort needs the trunk healthy and fully attached for proper abort profiles. (COG, etc)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TrueBlueWitt on 09/01/2016 10:00 pm
WOW. We can see the payload fall seconds after the first explosion. Maybe a dragon could fly away in time.

Maybe the crew Dragon but not the cargo Dragon. The cargo Dragon can now survive a CRS-7 type accident by deploying its parachutes but that doesn't help if the accident is at the pad.

It's hard to know if people would have survived if they had been in a crew Dragon on this rocket.  If there was no warning, the Dragon would have been subjected to a significant overpressure before it could have taken off.  Maybe the Dragon could have protected crew members from such an overpressure, maybe not.

There's also the issue of whether the overpressure would have damaged the SuperDraco engines and/or their prop tanks and/or the abort control system.  If any of those things failed, the crew would have died.


Edit:
Very high probability of survival..
Note that the Payload and Fairing fell into the conflagration intact, significantly after the initial explosion.
It appears the top of S2 and Payload was still held in place by the strongback, which ultimately was not strong enough to hold it up. This, however, would give it a lot more time than in a situation where the strongback is retracted.
[size=78%]Super Draco's reach full thrust in <100ms, which from the video looks like they would have pulled away. [/size]
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/01/2016 10:06 pm
Just seen the video. From the flash to bang time can anyone confirm the mike was about 2.55 miles (4000 m) from the rocket?

The updates section reports that debris "small enough to fit in a shoe box" were found in a parking lot 1.8miles from the pad.  I suspect given the completeness of the destruction that will not be the farthest that debris is found.

NASA did do studies to estimate the explosive power of LOX/RP1 explosions for Saturn 1 and V but I think they were looking at a rupture/ignition/fire where this looks like an explosion.

AFAIK NASA never actually went as far as loading up a full Saturn 1 and testing their model but this will give them a data point to compare with.  :(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/01/2016 10:06 pm
One thought re: speculation about a COPV failure. The COTS-7 failure wasn't thought to be a COPV letting go per se, but a massive helium leak that led to an overpressure. A COPV flat-out failing might happen faster, and could lead to a more energetic explosion. For instance, isn't that how the S-IVB 503 upper stage was lost during a ground test (in very similar circumstances--during fueling before a hot-fire test)?

~Jon

Good memory. I've been trying to recall on-pad explosions in general, and it sounds like this could have some similarities. It doesn't look like the accident report is on NTRS, but other documents there discuss it:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970009949.pdf

Quote
The group finally traced the source of the explosion to one of the eight ambient-temperature helium storage spheres located on the thrust structure of the J -2 engine. The exploding sphere ruptured the propellant fill lines, allowing liquid oxygen and liquid hydrogen to mix and ignite, setting off an explosion that wrecked the stage. Further analysis showed that the sphere had been welded with pure titanium weld material, rather than the alloy material specified.

So it doesn't sound like an over-pressurization of the propellant tanks, but an initial event external to the propellant tanks.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Damon Hill on 09/01/2016 10:08 pm
I'm impressed by the sheer energy of the initial explosion, which seems centered slightly <outside> the second stage; it propelled at least one largish piece of hardware seemingly upwards.  The deflagrations that followed seemed slower in comparison.

It will be interesting to see what telemetry says in the seconds leading up to the initial explosion.  If everything looks normal, then bang!, it may point to an external cause.

We'll just have to wait for the full analysis of all data.  That will determine return to flight, but I doubt it'll be before the end of fall, unless it's clearly not the rocket's fault.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/01/2016 10:12 pm
So what is Object X?

That's what I was calling evidence of the LOX tank rupturing at top left, near the vents.

Does look like a panel has opened as the black outlined object looks solid under enhancement and something is venting out to the left.

Is there maybe a bulge on the left side of the 2nd stage 18ms before the fireball?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Grendal on 09/01/2016 10:18 pm
Hopefully someone has a video of the event from a different angle.  It appears to me that the event happened just outside of the second stage.  The video we have makes the determination more difficult because of the angle.  Thanks to USLaunchreport for providing this video for all of us to speculate with.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/01/2016 10:19 pm
Does look like a panel has opened as the black outlined object looks solid under enhancement and something is venting out to the left.

You have to be careful in over-interpreting the dark "thing."  The flame is back-lighting an oxygen vapor cloud, and the camera's response and dynamic lighting conditions might be doing very weird things. Notice how the shroud looks black on the left-hand edge in your cropped center frame? It *could* be a piece of debris, or it could be a curl of vapor.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mleigh on 09/01/2016 10:21 pm
NASA Statement on SpaceX Incident
Press Release From: NASA HQ
Posted: Thursday, September 1, 2016

“We remain confident in our commercial partners and firmly stand behind the successful 21st century launch complex that NASA, other federal agencies, and U.S. commercial companies are building on Florida’s Space Coast. Today’s incident -- while it was not a NASA launch -- is a reminder that spaceflight is an incredible challenge, but our partners learn from each success and setback.

“The situation at the Cape is being evaluated, and it’s too early to know whether the incident will affect the schedule for upcoming NASA-related SpaceX launches to the International Space Station. If there are SpaceX mission delays, other cargo spacecraft will be able to meet the station’s cargo needs, and supplies and research investigations are at good levels.

“The launch for NASA’s OSIRIS-REx mission remains on track for Sept. 8. Initial assessments indicate the United Launch Alliance Atlas V rocket and OSIRIS-REx spacecraft are healthy and secure in the Vertical Integration Facility at Space Launch Complex-41, which is 1.1 miles from SpaceX’s launch pad where the incident occurred.”

// end //

From: http://spaceref.com/news/viewpr.html?pid=49385
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/01/2016 10:22 pm
Does look like a panel has opened as the black outlined object looks solid under enhancement and something is venting out to the left.

You have to be careful in over-interpreting the dark "thing."  The flame is back-lighting an oxygen vapor cloud, and the camera's response and dynamic lighting conditions might be doing very weird things. Notice how the shroud looks black on the left-hand edge in your cropped center frame? It *could* be a piece of debris, or it could be a curl of vapor.
It could also be a JPEG/MPEG compression artifact, which create hard edges where none actually exist.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robertross on 09/01/2016 10:29 pm
NASA Statement on SpaceX Incident
Press Release From: NASA HQ
Posted: Thursday, September 1, 2016

“We remain confident in our commercial partners and firmly stand behind the successful 21st century launch complex that NASA, other federal agencies, and U.S. commercial companies are building on Florida’s Space Coast. Today’s incident -- while it was not a NASA launch -- is a reminder that spaceflight is an incredible challenge, but our partners learn from each success and setback.

“The situation at the Cape is being evaluated, and it’s too early to know whether the incident will affect the schedule for upcoming NASA-related SpaceX launches to the International Space Station. If there are SpaceX mission delays, other cargo spacecraft will be able to meet the station’s cargo needs, and supplies and research investigations are at good levels.

“The launch for NASA’s OSIRIS-REx mission remains on track for Sept. 8. Initial assessments indicate the United Launch Alliance Atlas V rocket and OSIRIS-REx spacecraft are healthy and secure in the Vertical Integration Facility at Space Launch Complex-41, which is 1.1 miles from SpaceX’s launch pad where the incident occurred.”

// end //

From: http://spaceref.com/news/viewpr.html?pid=49385

Well I certainly have my doubts as to SpaceX being able to have the root cause & solution figured out in around 70+ days (thinking static fire), let alone having the pad reconfigured.

I'm sure the strongback is in serious condition (metal fatigue due to heat), including the hydraulic cylinders, and pad commodity lines. Maybe December...but that could be pushing it; I'd put my money on February.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/01/2016 10:36 pm
Further, look at the symmetry of the expanding LOX cloud a few frames later. The right side is a bit muffled because of the interference with the T/E, obviously, but the near perfect oval shape for most of its circumference suggests the failure point was mostly toward the camera, not facing directly at the erector.

The first 'fire' frame is clearly brighter than the one after it.  That first frame shows highlighting of the fairing and erector which, if they both are primary reflections, would indicate a light source away from the body of the rocket, as you suggest, otherwise the fairing wouldn't be lit/flaring.  The shape of that highlighting also seems to indicate a right (towards erector) bias, however.

The frames thereafter show a distinct red shift (from green) and the lighting beneath the blast zone indicate a somewhat more centered bright zone (a bit farther from the erector and directed more towards the camera).  That zone doesn't appear to change for several frames, even as the conflagration proceeds.

The diffraction X pattern, on the other hand, shifts from frame to frame until smoke obscures enough to remove it entirely, so while I'm sympathetic to the argument that it is likely useful, the frame-to-frame instability of it makes me concerned.

I fear that attempts to locate the failure by locating the source of the brightest point may not be wise.  Anything other than elevation is going to be hard to determine, and there's no guarantee that the source of initial ignition is a reasonable proxy for the failure point.  It still seems most likely to me that the failure happened inside the rocket, and what we see is aftermath.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/01/2016 10:36 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 10:38 pm
Quick&dirty attempt at recreating the trajectory of the fragment propelled upward -which, by the way, to me doesn't mean the explosion originated outside: it could well be a T/E panel or a torn piece of 2nd stage wall located over the failure point.


What is apparent from trying to follow it when it passes in front of the saturated fireball is that it's coming toward the camera, as it appears precisely where you would expect after it clears the brightest part of the cloud.


The last 2-3 crops show it being carried sideways to the left by the wind draft.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/01/2016 10:43 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Khadgars on 09/01/2016 10:49 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Agreed.  SpaceX will be able to recover from this.  I don't think however, that they will be able to survive another failure in the near to mid future.

I believe SpaceX should takes its time investigating this, and all of their procedures.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Khadgars on 09/01/2016 10:52 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scylla on 09/01/2016 10:52 pm
Eric Bowen ‏@scrappydog
@elonmusk Would the Dragon escape pod have survived this event?

Elon Musk
Elon Musk – Verified account ‏@elonmusk

@scrappydog yes. This seems instant from a human perspective, but it really a fast fire, not an explosion. Dragon would have been fine.
https://twitter.com/elonmusk/status/771479910778966016
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Nomadd on 09/01/2016 10:59 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
The fact that most LOVs are early in the program seems pretty obvious. The Shuttle was an exception.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: adriankemp on 09/01/2016 11:03 pm
There is a lot of talk about COPV which to me can't possibly be very high on the failure list -- my thinking follows, please set me straight on anything I'm missing:

1 - The tank was fairly full at this time, based on the extreme nature of the event and the timeline.

2 - The COPVs would be already charged, as they are not supercooled and are far harder to fill quickly

3 - The pressure differential inside and outside the COPVs was decreasing with every passing second (understanding that the differential was still extremely large)

So then, to me it seems utterly unlikely that a COPV let go while it's job was actually getting easier by the second.

Is there some counter intuitive effect with them that would make this likely or plausible?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisGebhardt on 09/01/2016 11:04 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
The fact that most LOVs are early in the program seems pretty obvious. The Shuttle was an exception.

And Proton... and Delta II... and Taurus XL... and Soyuz...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: A_M_Swallow on 09/01/2016 11:04 pm
Some questions to be answered when the investigation is complete and the behaviour of the crew capsule has been modelled in this situation.

1. Is there a high probability that the launch abort system would have flown the crew to safety including missing any debris if this particular explosion had happened on a manned vehicle?
2. Would the sensors in the Falcon 9 have both detected the problem and triggered the abort before the explosion hit the Dragon? Are more sensors needed?
3. Should the launch abort system be armed during hot fires? At what time in the count down? (Killing the ground crew should be avoided.)
4. Does the ground equipment, pipes and tanks need instrumentation that can trigger the abort system?
5. Can the abort control system handle the ground equipment signal arm being retracted without triggering a false alarm?
6. As an option can some payloads be saved using a similar launch abort system?
7. Does NASA need to check that Orion and the other CCDev vehicles can handle similar situations?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/01/2016 11:07 pm
Quick&dirty attempt at recreating the trajectory of the fragment propelled upward -which, by the way, to me doesn't mean the explosion originated outside: it could well be a T/E panel or a torn piece of 2nd stage wall located over the failure point.


What is apparent from trying to follow it when it passes in front of the saturated fireball is that it's coming toward the camera, as it appears precisely where you would expect after it clears the brightest part of the cloud.


The last 2-3 crops show it being carried sideways to the left by the wind draft.

You did a much better job than I could have done.   Now, as a trajectory model, please explain how a panel from the 2nd stage gets blown to the right, then produces an arc up and to the left.  :)

You clearly demonstrated the point I was trying to make, albeit, we disagree as to why.  Great work!!! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/01/2016 11:08 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
The fact that most LOVs are early in the program seems pretty obvious. The Shuttle was an exception.

The smaller the sample size the less you can estimate. Proof only exists in logic and mathematics.

Also, when software is involved, mean time between failure no longer works - I think that has been understood for decades.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 11:09 pm
There is a lot of talk about COPV which to me can't possibly be very high on the failure list -- my thinking follows, please set me straight on anything I'm missing:

1 - The tank was fairly full at this time, based on the extreme nature of the event and the timeline.

2 - The COPVs would be already charged, as they are not supercooled and are far harder to fill quickly

3 - The pressure differential inside and outside the COPVs was decreasing with every passing second (understanding that the differential was still extremely large)

So then, to me it seems utterly unlikely that a COPV let go while it's job was actually getting easier by the second.

Is there some counter intuitive effect with them that would make this likely or plausible?

As was discussed extensively following the CRS-7 failure, composites don't "like" repeated cryogenic soak cycles, and there was some concern - before fault was pinned on a strut failure rather than the COPV itself - that perhaps SpaceX's practice of repeated tanking and tests prior to flight could have contributed.

To that point, although Elon pointed blame squarely at the failed strut, a GAO report regarding of NASA's handling of the CRS-7 failure investigation pointed out that the root cause was not 100% certain, with several other possible causes (I don't have a link handy and can't recall what other possible causes were implicated).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sunbingfa on 09/01/2016 11:10 pm

@scrappydog yes. This seems instant from a human perspective, but it really a fast fire, not an explosion. Dragon would have been fine.
https://twitter.com/elonmusk/status/771479910778966016

Elon is say this starts as a fire not explosion, meaning starting from outside? (anything from the pressuring environment inside F9 will be an explosion)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Khadgars on 09/01/2016 11:16 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
The fact that most LOVs are early in the program seems pretty obvious. The Shuttle was an exception.

And Proton... and Delta II... and Taurus XL... and Soyuz...

You are acting like SLS won't have a test flight (2 actually).  By this logic, a vehicle gets safer the longer and more often you fly it.  Except, that is not always the case.

In my opinion, what you are seeing here is SpaceX doing too much, too quickly that has resulted in two failures in just over a year.  Completely unrelated to SLS, so please leave it out of the discussion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/01/2016 11:16 pm

@scrappydog yes. This seems instant from a human perspective, but it really a fast fire, not an explosion. Dragon would have been fine.
https://twitter.com/elonmusk/status/771479910778966016

Elon is say this starts as a fire not explosion, meaning starting from outside? (anything from the pressuring environment inside F9 will be an explosion)

He is absolutely NOT saying that. He's explaining the difference between a deflagration (very fast fire) versus explosion. This was the same discussion people had following the loss of Challenger (STS-51L). The famous "explosion" was not in fact an explosion, but a deflagration of the hypergolic propellants in the RCS and OMS pods following aerodynamic breakup of the stack.

Here, he's saying the vehicle didn't "explode," it burned very quickly ("deflagrated" is the engineering term) but he's NOT addressing the cause of the fire or the ignition point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mvpel on 09/01/2016 11:19 pm
Elon is say this starts as a fire not explosion, meaning starting from outside? (anything from the pressuring environment inside F9 will be an explosion)

I think he's talking about the difference between a detonation and a deflagration, a distinction which Destin explains in the first Smarter Every Day:

https://www.youtube.com/watch?v=4OvywNsWWd4

It would be interesting if one of the video mavens could estimate the Falcon 9's flame front speed given the frame rate and the estimated size of the first frame's fireball.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/01/2016 11:22 pm
If this does turn out to be the second stage again then I think that SpaceX has to ask some very difficult management questions.
I doubt that working on the  second stage is 'sexy'. The 'sexy' things to work on will be the reusable first stage, Falcon Heavy core, Raptor and BFS/BFR.
I hate to reason from analogy and I am sure that mechanical engineering isn't as flaky as software 'engineering' but my experience suggests that trouble shooting never gets rewarded, if you solve a problem then people assume you caused it in the first place and people on the upward career path avoid projects that are associated with failure or don't deliver anything new. Even in a support team one is only judged by a contribution to delivery project. I doubt that a company with a large staff turnover will nurture staff who do what is necessary in an undramatic way.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/01/2016 11:32 pm
If this does turn out to be the second stage again then I think that SpaceX has to ask some very difficult management questions.
I doubt that working on the  second stage is 'sexy'. The 'sexy' things to work on will be the reusable first stage, Falcon Heavy core, Raptor and BFS/BFR.
I hate to reason from analogy and I am sure that mechanical engineering isn't as flaky as software 'engineering' but my experience suggests that trouble shooting never gets rewarded, if you solve a problem then people assume you caused it in the first place and people on the upward career path avoid projects that are associated with failure or don't deliver anything new. Even in a support team one is only judged by a contribution to delivery project. I doubt that a company with a large staff turnover will nurture staff who do what is necessary in an undramatic way.
That is a lot of alluding.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/01/2016 11:33 pm
If this does turn out to be the second stage again then I think that SpaceX has to ask some very difficult management questions.
I doubt that working on the  second stage is 'sexy'. The 'sexy' things to work on will be the reusable first stage, Falcon Heavy core, Raptor and BFS/BFR.
I hate to reason from analogy and I am sure that mechanical engineering isn't as flaky as software 'engineering' but my experience suggests that trouble shooting never gets rewarded, if you solve a problem then people assume you caused it in the first place and people on the upward career path avoid projects that are associated with failure or don't deliver anything new. Even in a support team one is only judged by a contribution to delivery project. I doubt that a company with a large staff turnover will nurture staff who do what is necessary in an undramatic way.
That is a lot of alluding.
I like to think it is a lot of iffing than alluding.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/01/2016 11:34 pm

You did a much better job than I could have done.   Now, as a trajectory model, please explain how a panel from the 2nd stage gets blown to the right, then produces an arc up and to the left.  :)

You clearly demonstrated the point I was trying to make, albeit, we disagree as to why.  Great work!!! :)

Thanks, but I stand by my interpretation (and in fact I would like to know what your proposed mechanism for the trajectory is if the debris is blown from the T/E side)

The trajectory can easily be identified as coming from the rocket as follows:

If the failure point on S2 was ~45º to the right of the line joining the F9 and the camera, and we assume an upper part of the S2 LOX tank wall was blown outward from an interior event, to then hinge on its upper section for a few milliseconds, until being ripped off the structure by the expanding cloud of oxidizer, centrifugal forces would blow it upward (and it would rotate along the axis parallel to the "hinge"). Further, if the "hinge" was at an angle with respect to the ground, or if hinge failure/departure from the rest of the stage happened before it reached a 180º pivoting, some of the centrifugal force would be propelling it toward the camera. This, plus a bit of wind drag pushing the piece to the left (the "vertical" trip is about 3x faster than the time period around the upper section of the arc) could perfectly explain the trajectory we see.

Or, it could just be a piece from the T/E that was blown off from the overpressure.

Either way, my point was: it's not clear at all from the available footage whether the explosion originated in the vehicle or the umbilicals (and in fact, I personally lean for the former) but certainly the flying debris doesn't tell us much either way.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/01/2016 11:35 pm
CNN USA is going to report on the event during this half hour is anyone wants to DVR it...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Martin.cz on 09/01/2016 11:48 pm
Thinking about possible causes second stage FTS came to my mind but I guess that's nonsense. While from the video it kinda looked like some localized high energy event followed by a slower deflagration, I'm sure FTS activation would look a lot different, eq. unzipping the tanks, not a localized flashy "boom".

Also the initial localized high energy event (if there really was any) might really just be the stage 2 tank/s failing under pressure in a fiery manner, followed by a slower burning once the internal pressure equalized.

BTW, a few observations/questions about the USLaunchReport video:
-the fireball suddenly brightens about 3-4 seconds into the fire - could it be some of the stage 1 tanks still holding pressure until then and bursting or maybe pressure vessels going off ?
- if is unfortunately plainly visible how the poor satellite falls down & explodes into million pieces (internal pressure vessels & fuel I guess)...
- after a minute after the explosion where the ramp is still burning there are still intermittent audible bursts/explosions - any candidates for that ? COPVs going off, GSE pressure vessels bursting due to the heat or echo of the initial bursts ?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/01/2016 11:50 pm
Either way, my point was: it's not clear at all from the available footage whether the explosion originated in the vehicle or the umbilicals (and in fact, I personally lean for the former) but certainly the flying debris doesn't tell us much either way.

Even watching it on super-slow-mo is inconclusive. :(

To my eye it has all of the hall-marks of a static (electricity) ignition which could happen in either the umbilicals or the rocket if the fuel flow-rates were just a teeny bit too high and the conditions were just right (wrong).  Anyone know what the weather (wind speed, humidity) was like at the pad?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/01/2016 11:57 pm
I'm going to speculate wildly here (Mod, please delete if inappropriate);

Point 1; The CRX7 failure occurred in the second stage.
Point 2; This explosion *appears* to have originated in the second stage.

Speculation: to my eyes, this event appears to have been highly energetic from the first moment it appears.

Further speculation; would a COPV failure (sudden release of He into the LOX) fit observations?

You are not the first person to suspect this. In my opinion, it appears consistent with overpressurization, but a problem with GSE  or the valve that handles boiloff might also result in overpressurization.

The CRS-7 failure is believed to have been due to buoyant forces under several G's of loading. The buoyant forces while on the pad are far lower. Even if it was a COPV failure, I would be surprised if it was due to tank buoyancy breaking a strut.

Regardless, don't get too attached to the theory. For almost every high-visibility aerospace accident like this, there's usually half a dozen reasonable-sounding theories proposed early on. Most (sometimes all) of them turn out to be wrong.

One thing I won't do is get too attached to my theory; I'm well aware that I have a pretty consistent track record on theories: mostly wrong. :)

As for the COPV tanks, is this the first time the S2 was fueled? If so, and given the massive change in thermal environment (being suddenly bathed in subcooled LOX) it does make me wonder.

The GSE or press valve is of course another suspect. 

And... I know the FTS is being ruled out because it would have unzipped the whole vehicle, but... that's if it was a commanded FTS. What if it's a short to the wire to the detonator in the S2 FTS det cord? There's an easy way to rule out the FTS entirely though; where is it? If the FTS det cord on S2 isn't in the area of the umbilical connections (the event apparently became visible in that general area) then it can't be the FTS. If, however, it was just the S2 FTS for whatever reason, and it's in that general area, wouldn't the event look much like this? A high energy initial event (the unzipping) and then a growing deflagration emanating from the point where the LOX and RP1 come into contact with each other.


Until I can find some weather data for that time, I still have a lightning step/leader charge event on my suspect list, too.

Heck, at this juncture, about the only thing not on my suspect list is the ASDS.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/01/2016 11:57 pm
Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
The fact that most LOVs are early in the program seems pretty obvious. The Shuttle was an exception.

And Proton... and Delta II... and Taurus XL... and Soyuz...

When the number of failures is small (one would hope) compared to the number  of launches, of course statistics make it likely that for some launch vehicles the failures come after a number of successful flights.

The question to ask is this: wasn't Shuttle safer after Challenger than before?  And wasn't Shuttle safer after Columbia than before?

You could ask the same about Delta II and Taurus XL failures -- in each case, changes were made that should prevent similar failures in the future.  There's no doubt in my mind that if Delta II and Taurus XL continued to fly the flights after their failures would have a lower failure rate in the long term.

The Russian failures may be an exception -- there's been an apparent decline in quality, probably related to political and economic issues.  I don't see any reason to think the same would happen at ULA or SpaceX in the forseeable future.

You can ride SLS if you want.  There's no way I'd choose that over a commercial crew vehicle for myself, my friend, my family, or anyone else.  And I think the reasons for that are sound.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/02/2016 12:03 am
That sure looked like an explosion to me, rather than a fast fire.  Sounded like that too.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/02/2016 12:19 am
As discussed upthread, the epicentre of the fireball may or may not be the source of the explosion, but if it is, the pixel at the centre of the fireball appears to correspond exactly with the LOX umbilical attachment point.

Edit: or the common bulkhead?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/02/2016 12:27 am
OK, I should have my head examined, since I'm going out on a limb here, but...

...COPVs composite matrix cracks form due to normal pressure cycling from any pressurization event, like acceptance testing.  LOX infiltrates these micro cracks and thus LOX or cold GOX is now in contact with a fuel source (carbon fiber and epoxy).  Normally it is in equilibrium, not having an ignition source available, but something (static electricity from mechanical motion of tank wall due to filling?) provides a suitable ignition source.  (Of course, ignition source is always considered to be "free" in these cases.)

COPV fiber ignites and burns, taking a few seconds, and then tank bursts abruptly as hoop fibers burn away.  This overpressure event fails the common bulkhead and stage sidewall since the vent can't possibly keep up with the massive release of helium into a LOX tank with perhaps 1-3% of ullage.  Mixing of propellants occurs and we see first evidence of explosion.

Personally, I think this is what happened in the in-flight failure as well, but I lack the data to make the argument persuasive.  This time, SpaceX may be able to recover sufficient debris to make a determination.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space OurSoul on 09/02/2016 12:30 am
Apparently not having learned not to speculate, I submit that the following fits what we can observe: that the umbilical connection partially disconnected. This could possibly cause aerosolization of RP-1 (like a finger almost fully closing a garden hose), and such aerosolization seems a requirement to explain the initial flash. It's also consistent with the subsequent downward-pointing flame (some of the RP-1 being aerosolized, but lots of it just dripping). If the umbilical were to part from the vehicle slowly and progressively, it could also provide a spark as the electricals parted, and in fact you'd expect the electricals to part company after the fluids started leaking since the electrical connections can travel a short distance (the length of the "prongs" in the plugs) before losing contact, whereas fluids will find any gap however small.
This is also consistent with the debris that flies straight up, which is otherwise difficult to reconcile with a cause within the vehicle. Lastly, we observe a lessening of the (GOX?) venting just prior to the explosion, consistent with a loss of pressure elsewhere in the system, i.e. at the umbilical interface.
I'm sure I'm wrong for reasons I haven't thought of, or insufficient knowledge, so I welcome counter-arguments.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/02/2016 12:32 am
Either way, my point was: it's not clear at all from the available footage whether the explosion originated in the vehicle or the umbilicals (and in fact, I personally lean for the former) but certainly the flying debris doesn't tell us much either way.

Even watching it on super-slow-mo is inconclusive. :(

Agreed.  Having initially discounted external sources given the lack of a post-initial-conflagration stage 2 event, I have to say that there is enough there to my untrained eye to reconsider.  The first frame seems to show an unshadowed event -- the lens artifacts that disappear in a few frames, the light up the fairing that disappears in two frames, the light reflecting off the far right lightning suppression structure which dims markedly after a single frame -- had an explosive exit occurred, I would have expected debris to obscure above and/or below immediately.  This does happen a few frames later as smoke builds.  I could be convinced that stage 2 lets go after the initial spark (liquid oxy plus ... almost any metal?) as watching the event in slow motion does convey the feeling that the initial burst has mounting momentum until somewhat after the initial shiny.  At the same time it's just as likely that this is a result of the amount of time required to get optimal mixing conditions.

Frustrating -- it would be useful to have seen many such explosions, but I'm sort of glad I haven't.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/02/2016 12:39 am
As discussed upthread, the epicentre of the fireball may or may not be the source of the explosion, but if it is, the pixel at the centre of the fireball appears to correspond exactly with the LOX fuel line attachment point.
Nope, that's the structural support at the common bulkhead. The umbilical attachment is lower.  Look earlier in the thread for a good picture.

And for everyone basing opinions on "super slow mo"---you do know that all those extra frames are made up, right?  You're basing your opinion on details fabricated by an interpolation algorithm.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: c on 09/02/2016 12:40 am
Just seen the video. From the flash to bang time can anyone confirm the mike was about 2.55 miles (4000 m) from the rocket?

Sound to the camera from the first detonation is 12 seconds. Sound speed at sea level (well, those pads are about 30’ above but who’s counting) is 340 m/s * 12 seconds = a tad over 4 km.

USLaunchReport likes to record static fire tests from an old testing area just northwest of the KSC industrial area.  It's just over 4 km from pad 40.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elmar Moelzer on 09/02/2016 12:49 am
SpaceX - Static Fire Anomaly - AMOS-6 - 09-01-2016
USLaunchReport - slow down & close up at 1080P 60fps

https://www.youtube.com/watch?v=XF253Gbi2S4
Not really 60 FPS but the same video "slowed down" with repeating frames.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/02/2016 12:52 am
That sure looked like an explosion to me, rather than a fast fire.  Sounded like that too.

There's nuanced terminology in play here. An explosion is a rapid increase in volume and or pressure. A detonation is supersonic combustion - not necessary, but usually an explosion. A deflagration is subsonic combustion, most commonly not an explosion, but it can be. When a deflagration is an explosion, that rapid expansion means it is rapidly displacing air, so it creates a sound wave, and you will get a boom - sometimes even a very punctuated one.

A decent number of people are aware these distinctions exist, but mix up the details. I think Musk is doing the same in the process of trying to downplay the risk to a Dragon crew in these conditions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: c on 09/02/2016 12:52 am
Check the audio, there's a small pop about 5 seconds before the sound from the actual explosions arrive.

I think that's just someone messing around a car or something near the camera.

Interestingly enough, the small first bang heard is the original S2 explosion. The big bang 3 seconds later is the fuel-air type explosion when that fireball hit the ground and mixed up the RP-1 and LOX.

I hear three distinct "initial" sounds:

1:16--a very faint "plonk" like someone hitting a PVC pipe with a hammer in the distance...COPV rupture?
1:18--a faint pop/bang... S2 tank rupture?
1:23--very loud boom...the LOX/RP-1 explosion?

That first sound at 1:16 is unusual and seems to me like it may be the initiating event. A COPV or high pressure line/fitting letting go followed by S2 tank rupture 1-2 seconds later seems consistent.

FWIW, the area this video was filmed contains metal scrap, old vehicles, etc.

The "plonk" sounds like an empty 55-gallon drum ever so slightly expanding/contracting, there's a bit of reverb on the back-end of that sound. I'd guess it's local to the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/02/2016 12:54 am
Apologies if I missed this upthread, and I have to point out the scales aren't the same, but the comparison is interesting:

https://fat.gfycat.com/ConcernedGreedyIbisbill.webm
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 12:55 am
Quote
And... I know the FTS is being ruled out because it would have unzipped the whole vehicle, but... that's if it was a commanded FTS. What if it's a short to the wire to the detonator in the S2 FTS det cord?

Once again, not possible. The safe/arm device which contains the FTS detonator typically has both mechanical and electrical inhibits to accidental initiation in the "safe" position. FTS was safed at the time of the accident.

You could take a hammer and a 12 volt car battery to pretty much any aerospace qualified FTS safe/arm device, and as long as it's in the "safe" position, not be able to set off the detonator after an hour of beating/zapping it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 12:58 am
Quote
The "plonk" sounds like an empty 55-gallon drum ever so slightly expanding/contracting, there's a bit of reverb on the back-end of that sound. I'd guess it's local to the camera.

Or the reverb is from a high-pressure component letting go inside the S2, which is just like a very distant, oversized 55-gallon drum.  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 12:59 am
As discussed upthread, the epicentre of the fireball may or may not be the source of the explosion, but if it is, the pixel at the centre of the fireball appears to correspond exactly with the LOX umbilical attachment point.

Look at the debris trajectory debate I tried to start.  You're about 5 meters to the left of where things started me thinks.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 01:00 am
Frustrating -- it would be useful to have seen many such explosions, but I'm sort of glad I haven't.

I've seen a few explosions in my time.. they all look like this. :)

As discussed upthread, the epicentre of the fireball may or may not be the source of the explosion, but if it is, the pixel at the centre of the fireball appears to correspond exactly with the LOX fuel line attachment point.
Nope, that's the structural support at the common bulkhead. The umbilical attachment is lower.  Look earlier in the thread for a good picture.

RP-1 has similar properties to Jet-A1 and one of those is very low conductivity.  It's also well known in the aviation industry that static ignition can occur within fuel pipes, tanks and hoses if the flow rate is too high and the conditions are right.

If I'm seeing what I think I am (very slim chance of that, but still non-zero at this point!) the purported umbilical disconnection could be a result of it being blown off the coupling by an explosion inside the pipework itself?

And for everyone basing opinions on "super slow mo"---you do know that all those extra frames are made up, right?  You're basing your opinion on details fabricated by an interpolation algorithm.

Well.. one can still hope it might show something obscured ms later by by the cloud. :)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 01:04 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 01:07 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...

Horizontal rupture rather than a vertical 'tin can'??
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 01:09 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...

Horizontal rupture rather than a vertical 'tin can'??
Perhaps a tank dome...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/02/2016 01:11 am
As discussed upthread, the epicentre of the fireball may or may not be the source of the explosion, but if it is, the pixel at the centre of the fireball appears to correspond exactly with the LOX umbilical attachment point.

Look at the debris trajectory debate I tried to start.  You're about 5 meters to the left of where things started me thinks.

I'm not saying you're wrong, just that that the epicentre of the fireball is where I marked it on the second stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 01:17 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...

Horizontal rupture rather than a vertical 'tin can'??
Perhaps a tank dome...
RP-1 tank or LOX??
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: c on 09/02/2016 01:19 am
Quote
The "plonk" sounds like an empty 55-gallon drum ever so slightly expanding/contracting, there's a bit of reverb on the back-end of that sound. I'd guess it's local to the camera.

Or the reverb is from a high-pressure component letting go inside the S2, which is just like a very distant, oversized 55-gallon drum.  ;)

Y'all are way too damn smart here  :)  I guess the next step is to calculate the decibels of that sound at source using inverse square. At 4 km the "plonk" had to be fairly loud there at the pad. Or find another audio source and start triangulating. 

Hmmm... gonna be a long night. I need to go check the property as H. Hermine is trying desperately to come in thru the front door. Then I can start in on the fun stuff  ;)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/02/2016 01:20 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...

Horizontal rupture rather than a vertical 'tin can'??
Perhaps a tank dome...
RP-1 tank or LOX??


Common bulkhead between the two perhaps.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 01:23 am
FWIW, this "event" even made news over here.  I first heard about it on the car radio on the way to work this morning..

http://www.abc.net.au/news/2016-09-02/spacex-rocket-explodes-on-launch-site-at-cape-canaveral/7807196

http://www.news.com.au/technology/science/space/explosion-at-spacex-launch-pad/news-story/c5ee6e6c83e386cfc1a88e1500253216

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 01:29 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...

Horizontal rupture rather than a vertical 'tin can'??
Perhaps a tank dome...
RP-1 tank or LOX??


Common bulkhead between the two perhaps.
You beat me to it Herb! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/02/2016 01:42 am
Personally, I think this is what happened in the in-flight failure as well, but I lack the data to make the argument persuasive.  This time, SpaceX may be able to recover sufficient debris to make a determination.

Before SpaceX announced the results of their investigation, I was convinced the in-flight failure involved combustion inside the LOX tank (since I thought I saw combustion at the vent ports and the MVac chill-down exhaust plume in the videos), but I couldn't come up with a plausible fuel source. Your theory makes a lot of sense to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 01:43 am
I find the "shape" of the detonation interesting as it has more in the horizontal than the vertical component...

Horizontal rupture rather than a vertical 'tin can'??
Perhaps a tank dome...
RP-1 tank or LOX??


Common bulkhead between the two perhaps.

Watching the footage again (several times) it does seem as if the entire S2 RP-1 load gets dumped out on the ground, leaving only a few streaks dripping from the payload (upper) end of the stage as it falls.  By then the fire on the rocket is mostly out (there being no RP-1 left to burn)... so you might be onto something there. :)
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/02/2016 01:44 am
If NASA is not comfortable with the fueling of the Dragon with astronauts on-board after this accident.  Can SpaceX forgo super-chilling the propellants(accepting the performance lose) so the F9 can be fueled before the astronauts board? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ww2planes1 on 09/02/2016 01:52 am
Do we have any confirmation of when in the countdown the anomaly occurred? Is it possible that SpaceX had significant advance warning that something was off-nominal?

I ask this because it was posted way up in this thread (albeit by a third-party source, not from an official SpaceX source), that the failure occurred at about the T-3 minute mark to the hot fire.  The countdown for an F9 Full Thrust shows that by the three minute mark, we should have seen that the strongback cradles were open and possibly that the retraction had begun.
T-0:04:10   Strongback Cradles Opening
T-0:03:30   Strongback Retraction

Plainly, the cradles were still closed and the rocket was at least 4-5 minutes away from being ready for the static fire, which means one of three things:
1) SpaceX uses a modified timeline for their static fires which compresses the strongback events.  I think this is unlikely as it reduces the value of the static fire, since it is no longer a true simulation of the launch countdown.
2) The guy who said they were at about 3 minutes was wrong and they were earlier in the count (prior to T-4:10 when the strongback cradles open), or SpaceX was working to a fairly loose schedule and they were going to do the fire when they were ready for it. This is definitely the most probable reason, but not the only reasonable one.
3) SpaceX had noticed an issue during the count and was in a hold or abort case when the catastrophic anomaly occurred.  This would be interesting because it would mean that the SpaceX team may have a lot more to go on than if this were a sudden event in an otherwise nominal countdown. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/02/2016 01:55 am
The visual evidence is inconclusive, I think.  It's consistent with either an explosive (as in combustion happening) deflagration from within stage 2, or with an explosion in the TEL right at the upper stage 2 umbilical port.  The end result is the same either way.

It seems pretty obvious that the explosion began at the umbilicals.  Now, I've seen estimates of this occurring anywhere from T-4:20 to T-3:10.  At some point between those two times, the strongback was supposed to retract.

What happens to the stack if the strongback starts to retract but the clamps holding stage 2 right under the payload shroud fail to open?  Would this slightly deform the rocket, the TEL, or both?  I ask because it's very obvious that the clamps were still closed, else the payload and fairing would not have been held up for as long as they were.  Indeed, it looks as if the payload only fell because the TEL bent from the spot of the initial explosion and tipped the payload and shroud out of the clamps.

I'd have to think that the rocket would fail before the TEL, if it began to retract without opening the upper clamps.  But maybe this is a convoluted series of events that starts with a semi-failed strongback release and results in a deformed umbilical port slipping and sparking right where a little LOX and RP1 are starting to leak from fill ports due to bending motions.

I'd think that if stage 2 overpressurized we'd have heard something along those lines somewhere, that's the kind of reading SpaceX would definitely have quite shortly after the event.  I'm guessing it's a GSE/TEL issue, but one that may have several small and almost inconsequential events combining to cause the big LOV event.

Beyond that, even with the good video feed we do have, this just isn't something we can do a lot of useful speculation about until we get more information from the people running the investigation, i.e., SpaceX...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 02:06 am
If we have a "graphics wiz" that can superimpose a Falcon cutaway over a video still, that would be great! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 02:10 am
Quote
I'd think that if stage 2 overpressurized we'd have heard something along those lines somewhere, that's the kind of reading SpaceX would definitely have quite shortly after the event. 

There are indications SpaceX already has a pretty good idea what happened, but they are being cautious about making public pronouncements. Nothing to be gained by jumping the gun.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/02/2016 02:14 am
Quote
And... I know the FTS is being ruled out because it would have unzipped the whole vehicle, but... that's if it was a commanded FTS. What if it's a short to the wire to the detonator in the S2 FTS det cord?

Once again, not possible. The safe/arm device which contains the FTS detonator typically has both mechanical and electrical inhibits to accidental initiation in the "safe" position. FTS was safed at the time of the accident.

You could take a hammer and a 12 volt car battery to pretty much any aerospace qualified FTS safe/arm device, and as long as it's in the "safe" position, not be able to set off the detonator after an hour of beating/zapping it.

IMHO, we need to be clear here; there's a difference between the detonators and the explosive. The explosive itself is quite safe; you can toss a chunk into a fire with no ill effect (or whack it with a hammer, etc). That's why you safe explosive egress systems on military aircraft by taking out the detonators, not the explosives.  The explosive itself (with no detonator present) is pretty much inert, and about as dangerous as a similar sized chunk of wax (unless exposed to very high temperatures/pressures such as from a high-order explosion, usually provided by a detonator).

Detonators, on the other hand, are very twitchy beasts. Hitting one with a hammer is not a good idea.

What this means in practice is that if the detonators were installed, accidental initiation via static charge or electrical fault is possible. If they are physically not in the det cord, it's pretty much impossible. If the detonators are not installed for a static fire, what I postulated is impossible. If the mechanical safing you mention involves physically removing the detonators, and that was in effect, what I postulated is impossible. However, if the detonators were physically present in the det cord, then what I postulated is not impossible (though still very unlikely) no matter what safeguards there are. 

To be clear, I'm not taking about an accidentally commanded FTS initiation, but an electrostatic event caused by a ground leader event (also called a step leader, and more than enough to kill a human) triggering a single detonator (I know them monitor the field density as part of the launch criteria, but do those apply for a static fire?). I think this scenario very unlikely, but possible, if and only if the location of the det cord is in the area the explosion was first seen. (Caveat: this scenario is also impossible sans significant electrostatic buildup).

For those curious on what a step leader is, here's a link;
http://www.lightningsafety.noaa.gov/science/science_initiation_stepped_leader.htm


 
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/02/2016 02:16 am
It definitely starts with a bright flash, then decreases in brightness for a few frames, then increases again.

To see this, look at the  US Launch report video (https://www.youtube.com/watch?v=_BgJEXQkjNQ) and single-step it, looking not at the explosion but on the light cast on the rightmost lightning tower top.  This does not saturate or run into JPG artifacts.  Looking at the leftmost tower, the initial flash does not illuminate it, but once the fireball is bigger than the rocket it's illuminated as well.  So the initial flash is smaller than the rocket diameter and on the erector side.

To me, this seems like some initial fire/explosion that peaks fast (less than one frame) then decreases in brightness.  But it breaches the tank, and when the propellants rush out of the tank, they burn, and the brightness goes up again.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 02:19 am
Quote
And... I know the FTS is being ruled out because it would have unzipped the whole vehicle, but... that's if it was a commanded FTS. What if it's a short to the wire to the detonator in the S2 FTS det cord?

Once again, not possible. The safe/arm device which contains the FTS detonator typically has both mechanical and electrical inhibits to accidental initiation in the "safe" position. FTS was safed at the time of the accident.

You could take a hammer and a 12 volt car battery to pretty much any aerospace qualified FTS safe/arm device, and as long as it's in the "safe" position, not be able to set off the detonator after an hour of beating/zapping it.

IMHO, we need to be clear here; there's a difference between the detonators and the explosive. The explosive itself is quite safe; you can toss a chunk into a fire with no ill effect (or whack it with a hammer, etc). That's why you safe explosive egress systems on military aircraft by taking out the detonators, not the explosives.  The explosive itself (with no detonator present) is pretty much inert, and about as dangerous as a similar sized chunk of wax (unless exposed to very high temperatures/pressures such as from a high-order explosion, usually provided by a detonator).

Detonators, on the other hand, are very twitchy beasts. Hitting one with a hammer is not a good idea.

What this means in practice is that if the detonators were installed, accidental initiation via static charge or electrical fault is possible. If they are physically not in the det cord, it's pretty much impossible. If the detonators are not installed for a static fire, what I postulated is impossible. If the mechanical safing you mention involves physically removing the detonators, and that was in effect, what I postulated is impossible. However, if the detonators were physically present in the det cord, then what I postulated is not impossible (though still very unlikely) no matter what safeguards there are. 

To be clear, I'm not taking about an accidentally commanded FTS initiation, but an electrostatic event caused by a ground leader event (also called a step leader, and more than enough to kill a human) triggering a single detonator (I know them monitor the field density as part of the launch criteria, but do those apply for a static fire?). I think this scenario very unlikely, but possible, if and only if the location of the det cord is in the area the explosion was first seen. (Caveat: this scenario is also impossible sans significant electrostatic buildup).

For those curious on what a step leader is, here's a link;
http://www.lightningsafety.noaa.gov/science/science_initiation_stepped_leader.htm

Yes, and what I'm saying is that the detonator is typically *inside* the safe/arm device, which has both electrical and mechanical inhibits to accidental initiation. The safe/arm device is designed to be shock resistant, so you can beat on it with a hammer and zap it with current and still not be able to set off the detonator inside, when the device is "safed." And even if the detonator does go off in the "safe" position, the mechanical inhibit prevents the shock wave from reaching the FTS explosive and setting it off.

The safe/arm device I worked with had an electromechanical rotor inside which contained the detonator. In the "safe" position, the rotor moved the detonator out of the path of the main explosive train, so that in "safe" position, even if the detonator went off, the shock wave could not reach the explosive train to initiate it.

So to summarize, the safe/arm device is typically designed such that when in the "safe" condition, even accidental detonator initiation will not propagate to the main FTS charge.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/02/2016 02:19 am
here's a link to the last launch count down. gives a look at where the umbilicals and such are

https://youtu.be/OERDIFnFvHs?t=13m29s
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/02/2016 02:28 am
It definitely starts with a bright flash, then decreases in brightness for a few frames, then increases again.

Are you taking into account the effect of the camera's autoexposure adjustments over that time period? Watch the sky away from the rocket to get an idea of how the exposure is changing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/02/2016 02:32 am
Yes, and what I'm saying is that the detonator is typically *inside* the safe/arm device, which has both electrical and mechanical inhibits. The safe/arm device is designed to be shock resistant, so you can beat on it with a hammer and zap it with current and still not be able to set off the detonator inside, when the device is "safed."

If that device includes some way of 100% isolating the detonators from an electrical surge of a magnitude inherent in a step leader (on the order of tens of thousands of volts), then what I'm postulating is impossible.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 02:33 am
Just impressions from watching the video at regular speed. The piece of flying debris that's been talked about looks like it bounced off the tower rather than originating from it. And the tower was deformed by the weight of the payload and fairing sitting on the cradle arms, suddenly without the support of the rocket structure.

Guess I'm not adding much. What a crappy day. The repercussions (so to speak) are going to be huge. Sad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 02:35 am
Yes, and what I'm saying is that the detonator is typically *inside* the safe/arm device, which has both electrical and mechanical inhibits. The safe/arm device is designed to be shock resistant, so you can beat on it with a hammer and zap it with current and still not be able to set off the detonator inside, when the device is "safed."

If that device includes some way of 100% isolating the detonators from an electrical surge of a magnitude inherent in a step leader (on the order of tens of thousands of volts), then what I'm postulating is impossible.

Once again, it's not just a matter of electrical inhibits/isolation. Typically there is also a *mechanical barrier* between detonator and main charge that prevents shock wave transmission in the "safe" condition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/02/2016 02:47 am
Yes, and what I'm saying is that the detonator is typically *inside* the safe/arm device, which has both electrical and mechanical inhibits. The safe/arm device is designed to be shock resistant, so you can beat on it with a hammer and zap it with current and still not be able to set off the detonator inside, when the device is "safed."

If that device includes some way of 100% isolating the detonators from an electrical surge of a magnitude inherent in a step leader (on the order of tens of thousands of volts), then what I'm postulating is impossible.

Once again, it's not just a matter of electrical inhibits/isolation. Typically there is also a *mechanical barrier* between detonator and main charge that prevents shock wave transmission in the "safe" condition.

AH! My apologies, I misunderstood. I thought that was for safing the system manually, not remotely changeable on the pad. I stand corrected.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 02:56 am
Yes, and what I'm saying is that the detonator is typically *inside* the safe/arm device, which has both electrical and mechanical inhibits. The safe/arm device is designed to be shock resistant, so you can beat on it with a hammer and zap it with current and still not be able to set off the detonator inside, when the device is "safed."

If that device includes some way of 100% isolating the detonators from an electrical surge of a magnitude inherent in a step leader (on the order of tens of thousands of volts), then what I'm postulating is impossible.

Once again, it's not just a matter of electrical inhibits/isolation. Typically there is also a *mechanical barrier* between detonator and main charge that prevents shock wave transmission in the "safe" condition.

..and IIRC, the FTS charge runs vertically up the side of the tank.  The post-explosion tank rupture (that caused S2 to spill it's hydrocarbon guts all over the pad) definitely appears to be horizontal running the FTS system right out of the picture.

FWIW, I don't see any evidence of any kind of lightning event here and the towers are intended to protect the rocket from that.  Static-induced sparks during fuelling are well-documented, more common that you might think and a different beastie entirely.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 03:01 am
Yes, and what I'm saying is that the detonator is typically *inside* the safe/arm device, which has both electrical and mechanical inhibits. The safe/arm device is designed to be shock resistant, so you can beat on it with a hammer and zap it with current and still not be able to set off the detonator inside, when the device is "safed."

If that device includes some way of 100% isolating the detonators from an electrical surge of a magnitude inherent in a step leader (on the order of tens of thousands of volts), then what I'm postulating is impossible.

Once again, it's not just a matter of electrical inhibits/isolation. Typically there is also a *mechanical barrier* between detonator and main charge that prevents shock wave transmission in the "safe" condition.

AH! My apologies, I misunderstood. I thought that was for safing the system manually, not remotely changeable on the pad. I stand corrected.

Here's what a typical safe/arm device looks like. The silver flex line coming out of the top is the explosive train leading to the main FTS charge.

http://www.eba-d.com/products/electro-mechanical-safe-arm-sa-device/

One electrical connector receives commands to rotate the internal detonator(s) between the safe and armed positions. The other connector receives the "fire" command to set off the detonator.

Usually the safe/arm commands can be sent to it either through ground lines during static fire tests or actual launches, or via flight computer autonomously for in-flight arming/safing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/02/2016 03:03 am
here's a link to the last launch count down. gives a look at where the umbilicals and such are

https://www.youtube.com/watch?v=OERDIFnFvHs?t=13m29s

And while you were posting this I was grabbing a screen shot.

So here are the umbilicals. Not the best angle but quite clear that the connection is at the bottom of the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Flying Beaver on 09/02/2016 03:14 am
CRS-8 2nd Stage overlayed:

 https://www.youtube.com/watch?v=wdlaYaah6Qk&feature=youtu.be
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 03:15 am
Just impressions from watching the video at regular speed. The piece of flying debris that's been talked about looks like it bounced off the tower rather than originating from it. And the tower was deformed by the weight of the payload and fairing sitting on the cradle arms, suddenly without the support of the rocket structure.

Guess I'm not adding much. What a crappy day. The repercussions (so to speak) are going to be huge. Sad.

The trajectory has that part going a few hundred yards off the bounce point in your theory.  Other than super balls, most materials will crumple on impact rather than bounce.  I don't buy the bounce idea, but... maybe it is a superball.  If you look at the part as it tumbles, it seems to be a "cap" to something.  Are there "cap" structures on the strongback?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 03:18 am

You did a much better job than I could have done.   Now, as a trajectory model, please explain how a panel from the 2nd stage gets blown to the right, then produces an arc up and to the left.  :)

You clearly demonstrated the point I was trying to make, albeit, we disagree as to why.  Great work!!! :)

Thanks, but I stand by my interpretation (and in fact I would like to know what your proposed mechanism for the trajectory is if the debris is blown from the T/E side)

The trajectory can easily be identified as coming from the rocket as follows:

If the failure point on S2 was ~45º to the right of the line joining the F9 and the camera, and we assume an upper part of the S2 LOX tank wall was blown outward from an interior event, to then hinge on its upper section for a few milliseconds, until being ripped off the structure by the expanding cloud of oxidizer, centrifugal forces would blow it upward (and it would rotate along the axis parallel to the "hinge"). Further, if the "hinge" was at an angle with respect to the ground, or if hinge failure/departure from the rest of the stage happened before it reached a 180º pivoting, some of the centrifugal force would be propelling it toward the camera. This, plus a bit of wind drag pushing the piece to the left (the "vertical" trip is about 3x faster than the time period around the upper section of the arc) could perfectly explain the trajectory we see.

Or, it could just be a piece from the T/E that was blown off from the overpressure.

Either way, my point was: it's not clear at all from the available footage whether the explosion originated in the vehicle or the umbilicals (and in fact, I personally lean for the former) but certainly the flying debris doesn't tell us much either way.

My problem with your hinge idea is that it has to hinge somewhere on the cylinder of the rocket.  That's ok, but if you use your own trajectory plot, it has to hinge THROUGH the strongback at the beginning of the journey.  It's a nice concept, but the starting point of that fragment doesn't strike me as a hinge action from the skin of the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 03:20 am
Apparently not having learned not to speculate, I submit that the following fits what we can observe: that the umbilical connection partially disconnected. This could possibly cause aerosolization of RP-1 (like a finger almost fully closing a garden hose), and such aerosolization seems a requirement to explain the initial flash. It's also consistent with the subsequent downward-pointing flame (some of the RP-1 being aerosolized, but lots of it just dripping).


RP-1 was already loaded.  There would not be any pressure in that part of the umbilical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/02/2016 03:28 am


Here's what a typical safe/arm device looks like. The silver flex line coming out of the top is the explosive train leading to the main FTS charge.

http://www.eba-d.com/products/electro-mechanical-safe-arm-sa-device/

One electrical connector receives commands to rotate the internal detonator(s) between the safe and armed positions. The other connector receives the "fire" command to set off the detonator.

Usually the safe/arm commands can be sent to it either through ground lines during static fire tests or actual launches, or via flight computer autonomously for in-flight arming/safing.

Thanks for the link!

You're 100% right; it does indeed mechanically separate the detonators from the ordinance train by remote command. Thus, a detonator going off in that state (unarmed) wouldn't trigger the det cord, and we were before the point where they'd arm it.

No matter what the real cause is, I hope they determine it with absolute certainty. Any degree of uncertainty would make this even worse IMHO.





Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: russianhalo117 on 09/02/2016 03:29 am
Apparently not having learned not to speculate, I submit that the following fits what we can observe: that the umbilical connection partially disconnected. This could possibly cause aerosolization of RP-1 (like a finger almost fully closing a garden hose), and such aerosolization seems a requirement to explain the initial flash. It's also consistent with the subsequent downward-pointing flame (some of the RP-1 being aerosolized, but lots of it just dripping).


RP-1 was already loaded.  There would not be any pressure in that part of the umbilical.
correct as they were in the Stage 2 LOX loading steps of the static test countdown at the time of the event(s).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/02/2016 03:31 am
Here is a possible scenario that seems to fit the pieces we have. The fact that the explosion seems to be centered on the middle of the upper stage at a very narrow vertical position is part of what's been troubling me.

Failure of a valve or sensor causes the O2 tank to over pressure during loading. The first thing that goes is the common bulkhead, mixing RP-1 and O2 before there are any obvious visual cues. Once a catastrophic failure like this has happened inside the stage, static could come from fluid reversing direction down a loading pipe or the bulkhead sliding down the inside of the tank. The resulting explosion could arise anywhere in the tank and where it would be most powerful is right where the propellants are mixing and the tank wall is already compromised by the tearing away of the bulkhead. This would all happen very quickly, but it allows the first visual sign of it to be the fiery explosive rupture of the overall S2 tank right at the line of the bulkhead.

Of course, that doesn't actually tell us root cause or even whether the fault lies with GSE, the rocket or something else (like russian UFO birds). But that explanation of what we are seeing answers all of my questions and falls in line with what we have heard so far.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 03:34 am
Just impressions from watching the video at regular speed. The piece of flying debris that's been talked about looks like it bounced off the tower rather than originating from it. And the tower was deformed by the weight of the payload and fairing sitting on the cradle arms, suddenly without the support of the rocket structure.

Guess I'm not adding much. What a crappy day. The repercussions (so to speak) are going to be huge. Sad.

The trajectory has that part going a few hundred yards off the bounce point in your theory.  Other than super balls, most materials will crumple on impact rather than bounce.  I don't buy the bounce idea, but... maybe it is a superball.  If you look at the part as it tumbles, it seems to be a "cap" to something.  Are there "cap" structures on the strongback?

Not a theory, just an impression as I said. Caveat: the scotch kicked in a couple hours ago.

"A few hundred yards" seems just as speculative. But strong dense objects can do amazing things when propelled at high velocities in energetic events.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/02/2016 03:38 am
Is the decision to have the payload attached our not attached during a static fire at the discretion of the customer?

I was looking back at static fire video and JCSAT-14,16 no payload attached and the same with EUTELSAT-ABS.

However Thaicom-8 payload was attached.  Also for CRS-8, CRS-9 Dragon was attached.

SpaceX really dodged a bullet that this didn't happen on CRS-9. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 09/02/2016 03:40 am
time for a lessons learned?


https://youtu.be/OpH684lNUB8


Maybe dropping the trunk is a good idea now?



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 03:41 am
Just impressions from watching the video at regular speed. The piece of flying debris that's been talked about looks like it bounced off the tower rather than originating from it. And the tower was deformed by the weight of the payload and fairing sitting on the cradle arms, suddenly without the support of the rocket structure.

Guess I'm not adding much. What a crappy day. The repercussions (so to speak) are going to be huge. Sad.

The trajectory has that part going a few hundred yards off the bounce point in your theory.  Other than super balls, most materials will crumple on impact rather than bounce.  I don't buy the bounce idea, but... maybe it is a superball.  If you look at the part as it tumbles, it seems to be a "cap" to something.  Are there "cap" structures on the strongback?

Not a theory, just an impression as I said. Caveat: the scotch kicked in a couple hours ago.

"A few hundred yards" seems just as speculative. But strong dense objects can do amazing things when propelled at high velocities in energetic events.

I had the same first impression, that the object rebounded off the top of the T/E towards the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chalz on 09/02/2016 03:42 am
Slightly off topic question. A helicopter could be heard later in the video. Presumably this is from the airbase. Was it in the air at the time or did they scramble it after the explosion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/02/2016 03:43 am
The thing about all the LOX overpressure speculation is that we know what that looks like -- it starts to puff out in big streams from the lox vents.  That wasn't happening.  There was no apparent change in the LOX venting in the seconds prior to the explosion.

As for seeing LOX vent spikes, that's normal.  I've seen that in the launches many times, right before the strongback was retracted.  I think it has to do with blowing out the fill lines, or something.  But again, I didn't see any LOX vent spikes within, say, five to ten seconds prior to the blast.

Whatever happened, I don't think it was the LOX tank overpressurizing in stage 2...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/02/2016 03:46 am
Slightly off topic question. A helicopter could be heard later in the video. Presumably this is from the airbase. Was it in the air at the time or did they scramble it after the explosion?

someone said earlier there was a medvac helicopter that picked up someone with the fire department to scout out the fire. long distance video from the vab showed a heli pretty close to the pad. not sure if its the same as you are hearing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/02/2016 03:48 am
The thing about all the LOX overpressure speculation is that we know what that looks like -- it starts to puff out in big streams from the lox vents.  That wasn't happening.  There was no apparent change in the LOX venting in the seconds prior to the explosion.

As for seeing LOX vent spikes, that's normal.  I've seen that in the launches many times, right before the strongback was retracted.  I think it has to do with blowing out the fill lines, or something.  But again, I didn't see any LOX vent spikes within, say, five to ten seconds prior to the blast.

Whatever happened, I don't think it was the LOX tank overpressurizing in stage 2...

Perhaps I misunderstand, but if the problem revolved around the mechanism or control structure designed to vent the LOX, then wouldn't an overpressure event happen and have no obvious outward cause?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/02/2016 03:48 am
It definitely starts with a bright flash, then decreases in brightness for a few frames, then increases again.

Looking at the leftmost tower, the initial flash does not illuminate it, but once the fireball is bigger than the rocket it's illuminated as well.

We agree -- that's what I saw as well.  You can also see the center of the peak lighting change between the first and third frames of the explosion on the fairing (in your video -- in mine it's the first and second :shrug: ).  The lens artifact shifts left as well, and though it shifts again to the right a bit after that, I take that to mean that the bright bits are becoming obscured by whatever soot, smoke or debris may now exist between there and the camera.

Of course, that shift could be from any number of causes.  Maybe the feed got disconnected and liqO2 is being sprayed away from the erector, or maybe the stage is splitting from right to left.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 03:50 am
time for a lessons learned?

Maybe dropping the trunk is a good idea now?

What lesson? The trunk is required for passive aerodynamic stability after SD's stop firing, while the stack is coasting up to apogee. Without the trunk, the capsule will tumble immediately after SD's stop firing, with unpleasant consequences for passengers.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 03:51 am
Whatever happened, I don't think it was the LOX tank overpressurizing in stage 2...

Agreed ..but I figure there aren't that many things up there that can cause an explosion like this.

We can plainly see the RP-1 tank rupture, but if RP-1 loading is complete and the tank is full it isn't going to explode on it's own even with a decent-sized spark nearby.  Can't be very many scenarios to check off of the list..


EDIT:  How about thermal failure?.. maybe a valve chilling down too fast or something (like part of a tank shell) not properly insulated that freezes, cracks and sparks??  LOX can do nasty things to gear that's not ready for it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 03:57 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 04:01 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?

Don't know, but Helodriver got a closeup photo of the returned stage outside Hawthorne showing the pressure gauges for the tanks. IIRC, one was around 10 psi and the other was less than 5 psi, so the difference there was in the single digits.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 04:02 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?

That wouldn't cause a bang in and of itself - this stuff is well below ignition point.  There'd first be a spray of stuff outward like we saw with the S2 launch failure.  This time the 'bang' seems to happen first.

..and it must have been at or near the bottom of the RP-1 tank for it to lose it's contents downwards like that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 09/02/2016 04:04 am
time for a lessons learned?

Maybe dropping the trunk is a good idea now?

What lesson? The trunk is required for passive aerodynamic stability after SD's stop firing, while the stack is coasting up to apogee. Without the trunk, the capsule will tumble immediately after SD's stop firing, with unpleasant consequences for passengers.


know that, several fixes for that but you need to drop some weight in my view or?


btw: doesn't SpaceX use the helium for the release of Dragon from the Falcon 9?   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/02/2016 04:04 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?

That wouldn't cause a bang in and of itself - there'd first be a spray of stuff outward like we saw with the S2 launch failure.  This time the 'bang' seems to happen first.

In CRS-7 it appeared that the LOX tank ruptured at the top rather than at the common bulkhead. If the Common bulkhead ruptures we won't see it right away but allows the fuel to mix to setup a scenario for a kaboom. Then there just has to be an ignition source.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John-H on 09/02/2016 04:06 am
From the location of the umbilical, can I assume that the fuel goes directly to the tank, while the LOX pipe runs through  or around the fuel tank. If there is a leak in this pipe,  an explosive mixture could build up and then go off suddenly, causing a flash and then a tank breech.

John 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/02/2016 04:09 am
In some ways I hope for SpaceX's case that is was some sort of subtle vehicle failure--one they can catch and design-out, not a GSE failure. The reason I say this is that the last time a US rocket blew up on the pad without an engine failure of some sort was over half a century ago. There've been well over 1000, and possibly over 2000 liquid fueled rocket launches since then, without any of them blowing up on the pad due to GSE issues. So having a pad systems failure actually makes SpaceX look a lot less professional than if it was a subtle design flaw.

On the what actually happened, it still really looks like the failure started inside the stage, not an external explosion that happened to rupture the tanks. That's not objective fact, and I may be misreading it, but that's what it looked like from the video. I just don't see some sort of "both umbilicals leaked in just the right way to also catch a spark" sort of scenario as being realistic. It's wild speculation, but I still think something to do with the common bulkhead did it.

People keep pointing out that it didn't look like the CRS-7 overpressurization, but that was a much slower event caused by a tube breaking, which meant you would've had choked flow out of a small diameter line. If you had a more rapid overpressurization event, it might look totally differently. A COPV failing more dramatically for instance might happen much. much faster, especially if it ruptured the common bulkhead. If say a dome came off of a COPV, it would probably be going fast enough that the whole bulkhead would be ruptured in less than one frame of the video. And the energy from that sort of a failure would not only mix the propellants, but could also quite possibly ignite the mixed propellants.

My Rambling $.02

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 04:10 am
From the location of the umbilical, can I assume that the fuel goes directly to the tank, while the LOX pipe runs through  or around the fuel tank. If there is a leak in this pipe,  an explosive mixture could build up and then go off suddenly, causing a flash and then a tank breech.

No, the LOX is colder than the RP-1 and at a higher pressure.  If there's a leak in the pipe LOX might enter the RP-1 tank (which is already full) and get released from a vent someplace which might then go 'bang' somewhere else.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 04:14 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?

That wouldn't cause a bang in and of itself - there'd first be a spray of stuff outward like we saw with the S2 launch failure.  This time the 'bang' seems to happen first.

In CRS-7 it appeared that the LOX tank ruptured at the top rather than at the common bulkhead. If the Common bulkhead ruptures we won't see it right away but allows the fuel to mix to setup a scenario for a kaboom. Then there just has to be an ignition source.

Electric signal and power wires could be sheared by a bulkhead that fails catastrophically under pressure? The liquid forms a short across suddenly exposed lines of different potential.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/02/2016 04:16 am
If we have a "graphics wiz" that can superimpose a Falcon cutaway over a video still, that would be great! :)

I'm hardly a 'graphics wiz', but it looks like the epicentre is adjacent the common bulkhead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Craftyatom on 09/02/2016 04:20 am
Is the decision to have the payload attached our not attached during a static fire at the discretion of the customer?

I was looking back at static fire video and JCSAT-14,16 no payload attached and the same with EUTELSAT-ABS.

However Thaicom-8 payload was attached.  Also for CRS-8, CRS-9 Dragon was attached.

SpaceX really dodged a bullet that this didn't happen on CRS-9.

I believe earlier info says it's the customer's decision.  CRS flights are attached because it's SpaceX's ship, and they decide to do it that way, for both mating and testing reasons (helps build confidence in attachments, resonance modes, electrical systems, etc).

Customers are generally given the choice between having their payload on during the static fire, which speeds up the timeline a bit and gives better test data, or not having it attached, which means the payload won't be damaged in the event of an anomaly.

I personally hope SpaceX and its customers continue to mate prior to static firing.  The chance of the type of anomaly seen today occurring is low, even before taking into account the fact that SpaceX will be taking a long, hard look at every inch of these systems in the next 6 months.  Choosing to give up test data because of such a slim chance seems a waste to me, but then again, it depends on whether your "launch insurance" is also "integration and testing insurance".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/02/2016 04:22 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?

That wouldn't cause a bang in and of itself - there'd first be a spray of stuff outward like we saw with the S2 launch failure.  This time the 'bang' seems to happen first.

In CRS-7 it appeared that the LOX tank ruptured at the top rather than at the common bulkhead. If the Common bulkhead ruptures we won't see it right away but allows the fuel to mix to setup a scenario for a kaboom. Then there just has to be an ignition source.

Electric signal and power wires could be sheared by a bulkhead that fails catastrophically under pressure? The liquid forms a short across suddenly exposed lines of different potential.

There is very little wiring inside the tanks and nothing would run through the common bulkhead. But I agree that once you have a massive failure like that there are lots of moving parts (that shouldn't be) and the potential of something producing a spark is much greater.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 04:26 am
In some ways I hope for SpaceX's case that is was some sort of subtle vehicle failure--one they can catch and design-out, not a GSE failure. The reason I say this is that the last time a US rocket blew up on the pad without an engine failure of some sort was over half a century ago. There've been well over 1000, and possibly over 2000 liquid fueled rocket launches since then, without any of them blowing up on the pad due to GSE issues. So having a pad systems failure actually makes SpaceX look a lot less professional than if it was a subtle design flaw.

On the what actually happened, it still really looks like the failure started inside the stage, not an external explosion that happened to rupture the tanks. That's not objective fact, and I may be misreading it, but that's what it looked like from the video. I just don't see some sort of "both umbilicals leaked in just the right way to also catch a spark" sort of scenario as being realistic. It's wild speculation, but I still think something to do with the common bulkhead did it.

People keep pointing out that it didn't look like the CRS-7 overpressurization, but that was a much slower event caused by a tube breaking, which meant you would've had choked flow out of a small diameter line. If you had a more rapid overpressurization event, it might look totally differently. A COPV failing more dramatically for instance might happen much. much faster, especially if it ruptured the common bulkhead. If say a dome came off of a COPV, it would probably be going fast enough that the whole bulkhead would be ruptured in less than one frame of the video. And the energy from that sort of a failure would not only mix the propellants, but could also quite possibly ignite the mixed propellants.

My Rambling $.02

~Jon

All good thoughts. Only problem is, repercussions from a COPV failure (ie major redesign) are going to be a lot more painful for them than a simple GSE issue. So I'm going to take the other side and hope it was in fact a GSE issue.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 04:30 am
The event is so sudden, instantaneous really, that it makes me think the most likely cause is failure of the common bulkhead with instant mixing of the LOX and kero. What is the pressure differential between the tanks?

That wouldn't cause a bang in and of itself - there'd first be a spray of stuff outward like we saw with the S2 launch failure.  This time the 'bang' seems to happen first.

In CRS-7 it appeared that the LOX tank ruptured at the top rather than at the common bulkhead. If the Common bulkhead ruptures we won't see it right away but allows the fuel to mix to setup a scenario for a kaboom. Then there just has to be an ignition source.

Electric signal and power wires could be sheared by a bulkhead that fails catastrophically under pressure? The liquid forms a short across suddenly exposed lines of different potential.

There is very little wiring inside the tanks and nothing would run through the common bulkhead. But I agree that once you have a massive failure like that there are lots of moving parts (that shouldn't be) and the potential of something producing a spark is much greater.

Conduits outside the tanks and maybe electrical interfaces with the t/e. Conductive liquids, flying metal and sheared wires...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 04:51 am
Conduits outside the tanks and maybe electrical interfaces with the t/e. Conductive liquids, flying metal and sheared wires...

The liquids in this case are non-conductive and hundreds of degrees F below ignition point.  No, I'm sticking with Jon's idea that a COPV failure or some similar plumbing failure inside the stage itself triggered the bulge pointed out several pages upthread. :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/02/2016 04:58 am
Conduits outside the tanks and maybe electrical interfaces with the t/e. Conductive liquids, flying metal and sheared wires...

The liquids in this case are non-conductive and hundreds of degrees F below ignition point.  No, I'm sticking with Jon's idea that a COPV failure or some similar plumbing failure inside the stage itself triggered the bulge pointed out several pages upthread. :)

O2 overpressure alone doesn't make a kaboom, just a pop. There has to be a mixing of fuels an an ignition source in order to cause an explosive boom like we saw. That is what we are trying to explain. Elon already confirmed the problem was in the S2 O2 tank, that is not in question.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: nisse on 09/02/2016 04:58 am
Is it really a fireball we see at first? Could a stuck lox-venting-valve cause an overpressure explosion? I mean they are near oxygen freezing temperatures which could form solid oxygen that plugs some venting valve. Once you have a overpressure explosion the rest you see happens.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/02/2016 05:14 am
Elon already confirmed the problem was in the S2 O2 tank, that is not in question.

Elon confirmed that the problem "originated around (the) upper stage oxygen tank (https://twitter.com/elonmusk/status/771394161756942336)," not necessarily that the fault was in or of the O2 tank itself.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: northenarc on 09/02/2016 05:21 am
 My take is its failure of a COPV, or associated helium plumbing, and sudden pressure introduction blew off/out one of the umbilical lines or associated internal plumbing which started a rapid external fire that propagated back inwards and further over pressured the LOX tank until the 'horizontal failure' seen on the video.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: winkhomewinkhome on 09/02/2016 05:27 am
Is it possible that what occurred with S2 is analogous with what happened with Apollo One - and electrical short exposed to a pure or close to pure oxygen environment.

I believe early in this thread, Jim answered someone's question regarding batteries, onboard power, shore power charging the system until just prior to or at launch.

Perhaps not the O2 umbilical, but rather the power came loose, arced and sparked into the high levels of O2, and from there things went south...

Any idea on the voltages, amperage, etc of the shore power connection(s)?  As the Boss so poetically put it, you can't have a fire without a spark.

To those at SpaceX, Mr Musk, and this NSF community - keep the faith, and continue to fight the good fight.

Thank you!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/02/2016 05:36 am
All good thoughts. Only problem is, repercussions from a COPV failure (ie major redesign) are going to be a lot more painful for them than a simple GSE issue. So I'm going to take the other side and hope it was in fact a GSE issue.

My concern is that if it's just a "simple GSE issue", why didn't they catch it? It's not like this type of failure is very common. If it is an easy problem, it kind of makes you wonder if there are other easy problems they've been overlooking? I'm hoping it's something more subtle because even though it'll be more painful to fix, I think it bodes better for SpaceX if they didn't screw up something that nobody's screwed up since the 60s.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/02/2016 05:38 am
Conduits outside the tanks and maybe electrical interfaces with the t/e. Conductive liquids, flying metal and sheared wires...

The liquids in this case are non-conductive and hundreds of degrees F below ignition point.  No, I'm sticking with Jon's idea that a COPV failure or some similar plumbing failure inside the stage itself triggered the bulge pointed out several pages upthread. :)

O2 overpressure alone doesn't make a kaboom, just a pop. There has to be a mixing of fuels an an ignition source in order to cause an explosive boom like we saw. That is what we are trying to explain. Elon already confirmed the problem was in the S2 O2 tank, that is not in question.

That's the thing, rapidly shearing metal and exposing fresh, unoxidized aluminum or titanium (if they have any in the tanks) may be able to release enough energy to set off a LOX/Kero mix without a separate ignition source.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Michael Baylor on 09/02/2016 05:49 am
Some of the media stories about the incident are totally pathetic and inaccurate. Drives me crazy!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 05:53 am
Some of the media stories about the incident are totally pathetic and inaccurate. Drives me crazy!

Let's put it this way.. they know less they we do and aren't paid to get their facts right - just to get the story out there before the next guy.

I find them amusing. :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Michael Baylor on 09/02/2016 05:56 am
I have seen this discussed briefly, but any thoughts on it being the same issue as with the CRS-7 failure? A faulty steel strut, while certainly possible, just doesn't seem like the type of thing you could be 100% certain about. I am sure SpaceX ruled out all other possible alternatives that they could think of, but that doesn't mean that it is impossible for them to miss something. Maybe some kind of design flaw with the second stage that has been problematic on multiple occasions?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Michael Baylor on 09/02/2016 05:59 am
Some of the media stories about the incident are totally pathetic and inaccurate. Drives me crazy!

Let's put it this way.. they know less they we do and aren't paid to get their facts right - just to get the story out there before the next guy.

I find them amusing. :)
Totally true, they just take some random journalist and get them on the story, even if they have never heard of SpaceX before.

They also like to over dramatize things, so that they get keep their viewers entertained. CNN for example, called the failed landings setbacks, while failing to mention that they are experimental in an article today. They just wanted more exciting explosions to discuss.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/02/2016 06:08 am
Conduits outside the tanks and maybe electrical interfaces with the t/e. Conductive liquids, flying metal and sheared wires...

The liquids in this case are non-conductive and hundreds of degrees F below ignition point.  No, I'm sticking with Jon's idea that a COPV failure or some similar plumbing failure inside the stage itself triggered the bulge pointed out several pages upthread. :)

O2 overpressure alone doesn't make a kaboom, just a pop. There has to be a mixing of fuels an an ignition source in order to cause an explosive boom like we saw. That is what we are trying to explain. Elon already confirmed the problem was in the S2 O2 tank, that is not in question.

That's the thing, rapidly shearing metal and exposing fresh, unoxidized aluminum or titanium (if they have any in the tanks) may be able to release enough energy to set off a LOX/Kero mix without a separate ignition source.

You can actually see that's true in the video: following the initial bang, the entire stack unzips from top to bottom leaving the payload hanging by itself several stories up.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 06:29 am
If we have a "graphics wiz" that can superimpose a Falcon cutaway over a video still, that would be great! :)

I'm hardly a 'graphics wiz', but it looks like the epicentre is adjacent the common bulkhead.
Thank you, you're still a "wiz" in my books! :) It pretty much confirms my estimation of the location of common bulkhead that may have failed. The area would possibly lead to a "pseudo" horizontally shaped detonation cloud with more energy directed in this direction than vertically.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chalz on 09/02/2016 06:49 am
Slightly off topic question. A helicopter could be heard later in the video. Presumably this is from the airbase. Was it in the air at the time or did they scramble it after the explosion?

someone said earlier there was a medvac helicopter that picked up someone with the fire department to scout out the fire. long distance video from the vab showed a heli pretty close to the pad. not sure if its the same as you are hearing.
It seemed like a really quick response time but I just noticed an edit in the video around 3:32 so there could have been much more time between explosion and response. More likely medics than the air force then.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 09/02/2016 06:50 am
Having just read this thread, I haven't seen any discussion of some new alterations in SpaceX's countdown procedures to allow some window extension--first mentioned in relation to JCSAT-16's static fire (https://www.nasaspaceflight.com/2016/08/spacex-static-fire-test-jcsat-16s-falcon-9/).  Were the additional holds incorporated for all subsequent static fires/launches?  Could these changes have any bearing on this failure?

Quote from: Chris Bergin
An additional element was added for Wednesday’s test, per L2 info (https://forum.nasaspaceflight.com/index.php?topic=40768.msg1567989#msg1567989), with a couple of holds added ahead of the terminal count to demonstrate performance during simulated window extensions.

Due to Falcon 9 now using super cooled propellent [sic], holds after prop loading begins around T-30 minutes provide an additional challenge of keeping the prop cold enough in the run up to T-0.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HighEnergy on 09/02/2016 06:57 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TakeOff on 09/02/2016 06:58 am
Can one rule out that both failures of the upper stage have the same root cause? That the diagnose of the first failure's cause was mistaken? It was hard to investigate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/02/2016 07:06 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

For my eye, that's the most plausible scenario this far. Due to the initial size of the fireball it seemed as fuel-air mixture being initiated by any spark. How the fuel-air mixture was created in first place, is another question. My guesses:
1. This s-bend fracture
2. Filling valve blocked from full closure
3. Any other tube fracture near the rocket

One thing to be noted is that those images and this video is 2D. Rocket itself however, is a 3D object and the initiation of the blast could have been still outside the S2 even if from image it seems at the S2 body line.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/02/2016 07:29 am
(http://uploads.tapatalk-cdn.com/20160902/5bbb7557d872e53b5910bdcc824bf39d.jpg)

Over on the Facebook SpaceX group user Ross Sackett posted this photo with the following caption:

"I used a trick we sometimes use to fix the position of a star in an astrophoto.  While the fireball is burned into the image making it hard to locate the center, the lens flares (probably diffraction spikes) are centered on the brightest part.  Make of this what you will."

All credit for image and words to Facebook user Ross Sackett


Sent from my iPhone using Tapatalk Pro
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachF on 09/02/2016 07:39 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

That seems like a highly probably scenario... That is roughly the exact right area the explosion seems to have originated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ricmsmith on 09/02/2016 07:44 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

This seems like a probable scenario to me too.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/02/2016 08:03 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

It definitely looks like it's some sort of fuel line, but the part we see looks like a housing, rather than a naked pipe. There's cabling of some sort that is in nearly direct contact with the second stage at the approximate center of the diffraction lines as well. If leaking fuel lines were an issue, the pending inclement weather may have exacerbated some sort of ground fault.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Blizzzard on 09/02/2016 08:04 am
Twitter User TJ Lee did an interesting video edit here, superimposing the Dragon abort test over the video of today's accident:
https://twitter.com/StateMachines/status/771535425328459780
Dragon would have had plenty of time to escape.

This is very interesting (assuming frame rates are matched exactly)! I wonder what the lag would be though? Surely this is best case. What trigger would the F9 systems have to detect a problem and launch the Dragon V2 abort that quickly? (speculation) If the 'explosion' does happen to be something like a fast-fire external to the rocket, would the rocket even be able to tell something was wrong before the damaging explosions happen?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/02/2016 08:19 am
time for a lessons learned?

<snip>

Maybe dropping the trunk is a good idea now?




IMO no it isn't because D2 needs the trunk for aerodynamic stability during abort. If the trunk is not there the entire aerodynamic shape of D2 will have to be altered or some other means of stability will have to be added to the design. Given that the trunk is mostly an empty shell it should not be too hard to "harden" it against over-pressure events coming from below. Given that the trunk has been in the design particularly for pad abort, I thinks it is pretty safe to conclude that the D2 trunk design already is optimised for over-pressure events from below. We also know that the trunk-to-capsule interface is hardened with a wipple-shield. That serves dual purposes:
1. MMOD protection of the primary heatshield in orbit
2. Protection of the capsule against high-velocity debris from a launcher mishap.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Post-It on 09/02/2016 08:55 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

99.9% sure that is an A/C duct.  There aren't any propellant feed lines that far up the TEL.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/02/2016 09:06 am

If we assume the event originated in the second stage, as it appears to do, I find it interesting that both of SpaceX's LOV/LOM events originated in the second stage, and did so while that stage's engine was not running.

Could be just a coincidence - and I don't like coincidences.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Star One on 09/02/2016 09:07 am
Some of the media stories about the incident are totally pathetic and inaccurate. Drives me crazy!

Rather like much of the speculation on here. Neither serves any useful purpose towards getting to the root cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/02/2016 09:23 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.

I'd concur that the initial blast looks like the ignition of vapour outside the vehicle.

There's no sign of any deformation of the upper stage before the blast (and even if there's a video frame skipped, that's 1/30 of a second); and the shape of the fireball as it ignites is more vertical than horizontal, i.e. as if a cloud of vapour has built up outside the vehicle and then been ignited.

That doesn't preclude a leak from the vehicle being ignited, but I'd be surprised if it turned out to be a catastrophic failure of a COPV / LOX tank rupture.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/02/2016 09:32 am

If we assume the event originated in the second stage, as it appears to do, I find it interesting that both of SpaceX's LOV/LOM events originated in the second stage, and did so while that stage's engine was not running.

Could be just a coincidence - and I don't like coincidences.

There are two stages. Let's say chances of a problem in any particular are 50:50,  or 1/2. That means the chances of something happening twice in the same stage are 1/4. ie one in four. That a much higher chance of happening in the same stage than throwing 2 sixes in a row.

It's a coincidence until shown otherwise.

So much jumping to conclusions here, without really thinking about the issue.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vapour_nudge on 09/02/2016 09:37 am
JCM how do you classify this event?  A payload and rocket were lost at the launch pad but it wasn't a launch failure as it wasn't a launch attempt. Watching your website to see how you classify it as it is probably the launch log of choice on the web
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/02/2016 10:10 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

It definitely looks like it's some sort of fuel line, but the part we see looks like a housing, rather than a naked pipe. There's cabling of some sort that is in nearly direct contact with the second stage at the approximate center of the diffraction lines as well. If leaking fuel lines were an issue, the pending inclement weather may have exacerbated some sort of ground fault.

One thing worth noting, if the center of the diffraction lines are useful for determining the brightest part of the flame (I think they are) this may point to the center of ignition, but not the center of the source of the fuel for the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/02/2016 10:11 am
Twitter User TJ Lee did an interesting video edit here, superimposing the Dragon abort test over the video of today's accident:
https://twitter.com/StateMachines/status/771535425328459780
Dragon would have had plenty of time to escape.

This is very interesting (assuming frame rates are matched exactly)! I wonder what the lag would be though? Surely this is best case. What trigger would the F9 systems have to detect a problem and launch the Dragon V2 abort that quickly? (speculation) If the 'explosion' does happen to be something like a fast-fire external to the rocket, would the rocket even be able to tell something was wrong before the damaging explosions happen?

Probably something similar to the escape system on the Saturn series. I believe 3-4 continuous lines were strung along the outside of the rocket, with escape being triggered the moment that one of those wires were broken. Extraordinarily simple circuit that worked surprisingly well. I'm sure SpaceX's avionics have access to a vastly more granular and detailed array of data from which to decide, ranging from pressure sensors to stress, acoustic, tensile, and more. So similar concept but far less likely to experience false-positive or false-negative events.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/02/2016 10:25 am

Over on the Facebook SpaceX group user Ross Sackett posted this photo with the following caption:

"I used a trick we sometimes use to fix the position of a star in an astrophoto.  While the fireball is burned into the image making it hard to locate the center, the lens flares (probably diffraction spikes) are centered on the brightest part.  Make of this what you will."

All credit for image and words to Facebook user Ross Sackett


I suggested this pages ago, when the images of the explosions were first released.  :)

To explain to people who might not know, why this works;

Basically recording media (film/the detector in a camera) can only record brightness levels up to the point that they saturate, so in a film, that's when all of the chemicals are activated and in a CCD, when it is sending its maximum signal. Any light in addition to that is not recorded. Diffraction however occurs around the edges of objects, particularly sharp edges like the stops and the iris in cameras. Now the diffracted light is much lower intensity than the direct light and can still be recorded, but the most diffraction will come from the brightest point. and so that is where the majority of the diffraction should have originated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/02/2016 10:28 am
I don't have a video editor so these are just screen grabs. Is there any frames in between?
Note the bird passing the lightning tower, I used that to compare frames.

Can anybody assign time to this in terms of T-x minutes?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/02/2016 10:32 am
I don't have a video editor so these are just screen grabs. Is there any frames in between?
Note the bird passing the lightning tower, I used that to compare frames.

Can anybody assign time to this in terms of T-x minutes?

Not sure about the frame question, but I do believe F9 was at approximately T-3:00 to ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/02/2016 10:34 am
I don't have a video editor so these are just screen grabs. Is there any frames in between?
Note the bird passing the lightning tower, I used that to compare frames.

Can anybody assign time to this in terms of T-x minutes?

Not sure about the frame question, but I do believe F9 was at approximately T-3:00 to ignition.

earlier than that as the strongback wasn't retracted. There's a good bit of discussion about this earlier on.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 09/02/2016 10:36 am
I don't have a video editor so these are just screen grabs. Is there any frames in between?
Note the bird passing the lightning tower, I used that to compare frames.

Can anybody assign time to this in terms of T-x minutes?

Not sure about the frame question, but I do believe F9 was at approximately T-3:00 to ignition.

That was what someone mentioned they heard second hand (?) earlier in the thread.  However, the cradle arms were not open nor was the strongback retracted at the time of the failure.  Ergo, it must have been before that point in the countdown (~T-3:30). 

edit: ninja'd by Jet Black
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kojak on 09/02/2016 10:37 am

If we assume the event originated in the second stage, as it appears to do, I find it interesting that both of SpaceX's LOV/LOM events originated in the second stage, and did so while that stage's engine was not running.

Could be just a coincidence - and I don't like coincidences.

There are two stages. Let's say chances of a problem in any particular are 50:50,  or 1/2. That means the chances of something happening twice in the same stage are 1/4. ie one in four. That a much higher chance of happening in the same stage than throwing 2 sixes in a row.

It's a coincidence until shown otherwise.

So much jumping to conclusions here, without really thinking about the issue.

I'd say it's actually 1/2, for ANY stage (1/4 for FS + 1/4 for SS)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Archibald on 09/02/2016 11:21 am
Just caught the news (I first saw the thread "Rebuilding LC-40")

 Hmmm, what rebuilding ? didn't SpaceX already rebuild it from the days of the Titan IVs ? 

Checked the SpaceX section

...oh crap.

Wow...

... a big KABOOM like in the ole days.

Compared to Atlas AC-5 it lacks the hydrogen on top to boost the fire. In league with Proton (july 2013) and Antares (October 2014)

It was a quiet day at the Cape, when all of sudden - all hell broke loose -
 massive explosion in eerie silence ;
... and then, as Amos 6 and the fairing fall to their destruction into the inferno, BRAAAAAAOOOMMM the sound hit. With the unfortunate camera rocket by explosions, blam blam blam.

How long The Cape hasn't seen such a big explosion ? 1998 and Titan IV maybe ? or Delta in January 1997 ? (the one which turned the parking lot into a Moonscape)

Space is hard.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevinof on 09/02/2016 11:25 am


Space is hard.

Space is not just hard, it's very unforgiving.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: toruonu on 09/02/2016 11:30 am
The only silver lining I can think of is that it's good it didn't happen on the SES-10 booster as that would have immediately been labelled as reuse doesn't work and you cannot trust a flown booster. Right now it happened to a brand new booster and once we know the actual cause it'll get fixed etc, but it may be something that was immaterial to the rocket (i.e. GSE fault) or it would have been eliminated by a previous flight making the re-used booster inherently safer bet.

Anyway, good luck to SpaceXers to get back up and keep going.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: coal_burner on 09/02/2016 11:30 am
Wasn't spacex's original FTS plan to just open the vent valve on the rp-1 tank and allow the pressure in the lox tank to tear the common bulkhead free and simultaneously tear the outer shell?
I seem to remember their first flight being pushed back as they tried and failed to convince the appropriate governing body that ordnance wasn't needed for their FTS.

If their rp-1 vent valve opened yesterday, quickly dropping the tank pressure to atmospheric,  it would have shot out a bunch of cold and invisible helium gas. The first really visible thing would have been the escaping fuel/lox mixture as it was being ignited by sparks made by the bulkhead scraping down along the tank wall stiffeners.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vapour_nudge on 09/02/2016 11:32 am


Space is hard.

Space is not just hard, it's very unforgiving.

Well, space wasn't involved today. I'd say the ground is hard. Very sad to see this happen. Let's hope they can turn it around fast. Also, great that these things happen now so they can be ironed out before the first human space flight on the F9. I'm sad for the satellite owner too.  I'm eager to see what pad damage there is
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 11:35 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

I like that.  Here's some thoughts as to why you might be right.

A typical weaponized fuel-air mixture burns at between 4,200 and 5,400 feet per second.

The horizontal diameter of the first frame showing an explosion shows pixel saturation of about 35 feet across and 85 feet tall.

Assuming 60 fps, and the pixel integration begins at the instant of detonation, that implies a detonation velocity of between 2,000 and 5,000 feet per second.

I think air-burst is the right term.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 09/02/2016 11:44 am
Somewhere in the volumes of written word from the last 24 hours, there was the phrase from SpaceX, "Catastrophic abort."  This seems to indicate that something was seen before the dramatic failure we are focusing on, and an attempt to abort the static fire was initiated -- but too late.

Since they have been through this sequence 60 times or so (two per launch, the static fire and launch itself), it is unlikely a basic process/procedure flaw.  Equipment aging or fatigue failures, possibly leading to lox leak and explosive atmosphere on the upper TEL is a possibility.  (Obviously, lots of things are possibilities...)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/02/2016 11:44 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

Just playing devil's advocate here. I agree with the airburst, but how about a crack or a pinhole in the rocket itself as the source? Is there anything that would preclude that or make one more likely than the other? (I'm half wondering whether the supercooled oxygen might be causing more damage to the GSE side of things than people imagine - though I counter that with the necessity for fuel in the explosion)

as a slight, but related aside, what is the viscocity of the supercooled oxygen like compared to normal lox? If that sort of s curve exists within lox lines, I wonder if something might happen to the fluid dynamics of the system? (asking more because I am interested than speculating on whether it is related to the issue or not)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Hywel1995 on 09/02/2016 11:52 am
Weren't SpaceX holding the old NASA radars systems by LC-40 ready for Boca?

Any status on those?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/02/2016 11:57 am
Could T-3 mins indicate that there was an issue and that the string back was in the process of being re-secured to the vehicle?

The video has a cut right a dozen or so seconds before the explosion. Maybe something like the failure of the umbilical to spool out, causing the fill / drain lines to connections to become fouled?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/02/2016 12:00 pm
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

A non engineer like me would assume that the S is there to cope with thermal expansion/contraction in a long pipe. If that is so then to what extent should it be constrained and how without removing the benefit it is intended to supply?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/02/2016 12:04 pm
Just playing devil's advocate here. I agree with the airburst, but how about a crack or a pinhole in the rocket itself as the source? Is there anything that would preclude that or make one more likely than the other? (I'm half wondering whether the supercooled oxygen might be causing more damage to the GSE side of things than people imagine - though I counter that with the necessity for fuel in the explosion)

Are the second stages put through a tanking cycle at MacGregor?

I appreciate that the MVac can't be started, but if the upper stage have been though a cycle, that would presumably have shown up any such defects. (In any instance, I'd assume the S2 tanks would be pressure tested before leaving the factory.)

If the stage had been fully pressurised and tested, then it puts a bit more suspicion on the pad equipment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 12:04 pm
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

ANOTHER reason you might be right.  The detonation profile appears to be taller than wider.  If RP-1 was becoming an aerosol, being heavier than air, the aerosol would be sinking over time, which would make a detonation cross section that's taller than wider.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 12:17 pm
Just impressions from watching the video at regular speed. The piece of flying debris that's been talked about looks like it bounced off the tower rather than originating from it. And the tower was deformed by the weight of the payload and fairing sitting on the cradle arms, suddenly without the support of the rocket structure.

Guess I'm not adding much. What a crappy day. The repercussions (so to speak) are going to be huge. Sad.

The trajectory has that part going a few hundred yards off the bounce point in your theory.  Other than super balls, most materials will crumple on impact rather than bounce.  I don't buy the bounce idea, but... maybe it is a superball.  If you look at the part as it tumbles, it seems to be a "cap" to something.  Are there "cap" structures on the strongback?

Not a theory, just an impression as I said. Caveat: the scotch kicked in a couple hours ago.

"A few hundred yards" seems just as speculative. But strong dense objects can do amazing things when propelled at high velocities in energetic events.

Ya, you're right. There's only data for the horizontal travel distance, not the to camera distance.  When it crosses the tower, it's moved at least 50 yards from the explosion center.  How far towards the camera is speculative.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/02/2016 12:23 pm

Ya, you're right. There's only data for the horizontal travel distance, not the to camera distance.  When it crosses the tower, it's moved at least 50 yards from the explosion center.  How far towards the camera is speculative.

I don't have an easy way to d/l the video and no software to analyze it; but if the angular "diameter" of the part can be measured, the angular diameter is inversely proportional to the distance.  I.e., if it looks twice the size in the last frame as compared to the first frame, it's half as far away in the last frame as it was in the first frame.

It's tempting to want to do a kinematic analysis of the part's flight, but I'd not trust the timestamps on a downloaded file that had been compressed for Youtube any farther than I could kick the bits in the file.  You could get the initial vertical velocity and see if friction was important (which depends on the mass/area ratio) but not sure that would give any useful info.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/02/2016 12:34 pm

I believe earlier info says it's the customer's decision.  CRS flights are attached because it's SpaceX's ship, and they decide to do it that way, for both mating and testing reasons (helps build confidence in attachments, resonance modes, electrical systems, etc).

Customers are generally given the choice between having their payload on during the static fire, which speeds up the timeline a bit and gives better test data, or not having it attached, which means the payload won't be damaged in the event of an anomaly.

I personally hope SpaceX and its customers continue to mate prior to static firing.  The chance of the type of anomaly seen today occurring is low, even before taking into account the fact that SpaceX will be taking a long, hard look at every inch of these systems in the next 6 months.  Choosing to give up test data because of such a slim chance seems a waste to me, but then again, it depends on whether your "launch insurance" is also "integration and testing insurance".

Assuming after this that the insurers providing coverage for the pre-launch activities will sign off on the payload being mated during a static fire. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JebK on 09/02/2016 12:36 pm
Are there any other cases where there has been a complete loss of launch vehicle and payload days before T-0?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 12:41 pm

I believe earlier info says it's the customer's decision.  CRS flights are attached because it's SpaceX's ship, and they decide to do it that way, for both mating and testing reasons (helps build confidence in attachments, resonance modes, electrical systems, etc).

Customers are generally given the choice between having their payload on during the static fire, which speeds up the timeline a bit and gives better test data, or not having it attached, which means the payload won't be damaged in the event of an anomaly.

I personally hope SpaceX and its customers continue to mate prior to static firing.  The chance of the type of anomaly seen today occurring is low, even before taking into account the fact that SpaceX will be taking a long, hard look at every inch of these systems in the next 6 months.  Choosing to give up test data because of such a slim chance seems a waste to me, but then again, it depends on whether your "launch insurance" is also "integration and testing insurance".

There is no valid test data that can be gained by having the spacecraft on the vehicle during static fire.  It is only a time saving measure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ApolloStarbuck on 09/02/2016 12:43 pm
If we have a "graphics wiz" that can superimpose a Falcon cutaway over a video still, that would be great! :)

I'm hardly a 'graphics wiz', but it looks like the epicentre is adjacent the common bulkhead.


Also not a graphics wiz
 :)


photo edited for switched fuel and oxidizer notations.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yoram on 09/02/2016 12:44 pm
Yes it happened to the Russians several times. The most famous one is probably the "Nedelin disaster" with an early ICBM, which resulted in a high number of fatalities too.

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

There was also one interesting case where the recovery rocket saved the payload (including crew) from an explosion on the pad

https://en.wikipedia.org/wiki/Soyuz_7K-ST_No._16L

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 12:45 pm
1.  Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
2.  Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
   


1.  It is an air burst because of a rupture.  Rupture came first.

2. That would be an AC line.  The second stage umbilical is lower
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 12:48 pm
Also not a graphics wiz
 :)

You switched the fuel and LOX tank positions. The LOX tank is noticeably bigger so when in correct position, the bulkhead is roughly in the same place as the apparent blast origin.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 12:50 pm

Ya, you're right. There's only data for the horizontal travel distance, not the to camera distance.  When it crosses the tower, it's moved at least 50 yards from the explosion center.  How far towards the camera is speculative.

I don't have an easy way to d/l the video and no software to analyze it; but if the angular "diameter" of the part can be measured, the angular diameter is inversely proportional to the distance.  I.e., if it looks twice the size in the last frame as compared to the first frame, it's half as far away in the last frame as it was in the first frame.

It's tempting to want to do a kinematic analysis of the part's flight, but I'd not trust the timestamps on a downloaded file that had been compressed for Youtube any farther than I could kick the bits in the file.  You could get the initial vertical velocity and see if friction was important (which depends on the mass/area ratio) but not sure that would give any useful info.

That's a good idea, but the imaging doesn't support it.  The order is from 1:11 to 1:14 in the video.  The lighting levels and background levels are swinging wildly.  While the object is coming towards the camera, the illumination either obscures parts, the orientation of the object shifts to narrow end towards camera, or it breaks up while inside the fireball.

Image order  Left down, then right down.  I tried to enhance to bring out the edges, didn't always work.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 12:53 pm

Probably something similar to the escape system on the Saturn series. I believe 3-4 continuous lines were strung along the outside of the rocket, with escape being triggered the moment that one of those wires were broken. Extraordinarily simple circuit that worked surprisingly well. I'm sure SpaceX's avionics have access to a vastly more granular and detailed array of data from which to decide, ranging from pressure sensors to stress, acoustic, tensile, and more. So similar concept but far less likely to experience false-positive or false-negative events.

No, again, most data goes overboard as telemetry and vehicle avionics doesn't see it.  Abort systems pick a few critical parameters (like tank pressures, breakwires, engine temps, etc) and just monitor them.  "Stress, acoustic, tensile, and more" are foreign to launch vehicle control avionics.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ricmsmith on 09/02/2016 12:57 pm

I believe earlier info says it's the customer's decision.  CRS flights are attached because it's SpaceX's ship, and they decide to do it that way, for both mating and testing reasons (helps build confidence in attachments, resonance modes, electrical systems, etc).

Customers are generally given the choice between having their payload on during the static fire, which speeds up the timeline a bit and gives better test data, or not having it attached, which means the payload won't be damaged in the event of an anomaly.

I personally hope SpaceX and its customers continue to mate prior to static firing.  The chance of the type of anomaly seen today occurring is low, even before taking into account the fact that SpaceX will be taking a long, hard look at every inch of these systems in the next 6 months.  Choosing to give up test data because of such a slim chance seems a waste to me, but then again, it depends on whether your "launch insurance" is also "integration and testing insurance".

There is no valid test data that can be gained by having the spacecraft on the vehicle during static fire.  It is only a time saving measure.

Is there a cost saving as well, perhaps from not having to have payload service structure at the pad or roll back to the assembly building after the test for example?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TaurusLittrow on 09/02/2016 01:02 pm
Are there any reliable (if not official) reports on the condition of the pad and GSE? Not speculation based on videos. I can't imagine even extensive repairs would pose a time constraint on future launches given the comparatively "benign" fuel involved in the event (no toxic solid fuel residue). Still, it would be nice to know the extent of the repairs necessary.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/02/2016 01:07 pm

I don't have an easy way to d/l the video and no software to analyze it; but if the angular "diameter" of the part can be measured, the angular diameter is inversely proportional to the distance.  I.e., if it looks twice the size in the last frame as compared to the first frame, it's half as far away in the last frame as it was in the first frame.


That's a good idea, but the imaging doesn't support it.  The order is from 1:11 to 1:14 in the video.  The lighting levels and background levels are swinging wildly.  While the object is coming towards the camera, the illumination either obscures parts, the orientation of the object shifts to narrow end towards camera, or it breaks up while inside the fireball.

I figured it wouldn't work, that's why my post was loaded with weasel words; but thanks for trying!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 01:08 pm
...I can't imagine even extensive repairs would pose a time constraint on future launches given the comparatively "benign" fuel involved in the event (no toxic solid fuel residue). ...

You might want to read Wolfram66's post on the potential effects of petroluem fires on structural steel:

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576421#msg1576421

No one yet knows the extent of damage, but even "benign" fuel can do serious damage that could take a long time to repair.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/02/2016 01:09 pm
SpaceX decided to immerse their COPVs in their propellant.  Given that choice, why did they choose to immerse them in the LOX, which is nasty stuff both chemically and thermally, instead of in the comparatively benign RP1?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 01:10 pm
Much lower temperature -> lower pressure per kg of loaded He -> more helium per bottle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 01:20 pm
Are there any reliable (if not official) reports on the condition of the pad and GSE? Not speculation based on videos. I can't imagine even extensive repairs would pose a time constraint on future launches given the comparatively "benign" fuel involved in the event (no toxic solid fuel residue). Still, it would be nice to know the extent of the repairs necessary.
After they do a survey they will still have to take in the environmental impact for the clean up procedures and to contain any residue from the combustion products. The firefighters more than likely have placed booms and berms either yesterday or today.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/02/2016 01:20 pm


Somewhere in the volumes of written word from the last 24 hours, there was the phrase from SpaceX, "Catastrophic abort." 

Nope, this was never said by SpaceX.

Other persistent misunderstandings: there were early conflicting reports that the incident happened at T-3 and T-5.  Evidence from the timeline and strongback/cradle position indicates that it happened some time before T-4:10, which is when the cradle is opened.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/02/2016 01:28 pm

Probably something similar to the escape system on the Saturn series. I believe 3-4 continuous lines were strung along the outside of the rocket, with escape being triggered the moment that one of those wires were broken. Extraordinarily simple circuit that worked surprisingly well. I'm sure SpaceX's avionics have access to a vastly more granular and detailed array of data from which to decide, ranging from pressure sensors to stress, acoustic, tensile, and more. So similar concept but far less likely to experience false-positive or false-negative events.

No, again, most data goes overboard as telemetry and vehicle avionics doesn't see it.  Abort systems pick a few critical parameters (like tank pressures, breakwires, engine temps, etc) and just monitor them.  "Stress, acoustic, tensile, and more" are foreign to launch vehicle control avionics.

Are there likely to be breakwires and things on this system, given that they plan to use it with a system that has an LAS.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 01:33 pm
1.  Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
2.  Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
   


1.  It is an air burst because of a rupture.  Rupture came first.

2. That would be an AC line.  The second stage umbilical is lower

Just to debate the idea that the rupture came first.  Based on the detonation profile that implies a fuel-air explosion, the absence of any visible plume changes prior to the explosion 1st frame, an oxygen tank rupture would create a plume, and would not itself cause a detonation.  An RP-1 rupture might not show a plume but would provide the material needed for a fuel-air explosion.  If there were an RP-1 rupture, how would that occur?

We go from one frame where there is no indication of abnormal plumes to a frame where the detonation is about 35 X 85 feet across.  In 1/60th of a second you have to fill that volume with RP-1 aerosol (not liquid) and it has to explode during that same window.

Can you explain how a rupture does that please?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: baldusi on 09/02/2016 01:34 pm
SpaceX decided to immerse their COPVs in their propellant.  Given that choice, why did they choose to immerse them in the LOX, which is nasty stuff both chemically and thermally, instead of in the comparatively benign RP1?
It's colder, and He expansion per J/kg is the highest of any element, basically, they can increase density by 20x "for free".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/02/2016 01:41 pm
SpaceX decided to immerse their COPVs in their propellant.  Given that choice, why did they choose to immerse them in the LOX, which is nasty stuff both chemically and thermally, instead of in the comparatively benign RP1?
It's colder, and He expansion per J/kg is the highest of any element, basically, they can increase density by 20x "for free".
Also as a gas is compressed it get hot.  Depending on the fill rate you could end up creating bubbles of RP1  vapor or start to polymerize it into a tarry mix.In the LOX tank you make O2 bubbles which vent (usually) harmlessly and top up with more LOX.

This has been a standard trick to squeeze more performance out of a design since at least Saturn 1 and possibly before.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 01:45 pm
Can you explain how a rupture does that please?

That is the only way the propellants became available to burn
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jaufgang on 09/02/2016 01:50 pm
1.  Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
2.  Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
   


1.  It is an air burst because of a rupture.  Rupture came first.

2. That would be an AC line.  The second stage umbilical is lower

Just to debate the idea that the rupture came first.  Based on the detonation profile that implies a fuel-air explosion, the absence of any visible plume changes prior to the explosion 1st frame, an oxygen tank rupture would create a plume, and would not itself cause a detonation.  An RP-1 rupture might not show a plume but would provide the material needed for a fuel-air explosion.  If there were an RP-1 rupture, how would that occur?

We go from one frame where there is no indication of abnormal plumes to a frame where the detonation is about 35 X 85 feet across.  In 1/60th of a second you have to fill that volume with RP-1 aerosol (not liquid) and it has to explode during that same window.

Can you explain how a rupture does that please?
Keep in mind there is an entire half of the rocket that is not visible in this video. Who knows what was happening on the far side of the rocket moments before it detonated?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 01:50 pm
Ya, you're right. There's only data for the horizontal travel distance, not the to camera distance.  When it crosses the tower, it's moved at least 50 yards from the explosion center.  How far towards the camera is speculative.

Hoping against hope the problem started outside the vehicle... although that's not much consolation. But it just seems too rapid a burst not to have come from the tanks. But what do I know.

On the subject of the line with the S-curve, the line looks like sheet metal, not a heavy pipe you'd push dangerous pressurized fuel through. Jim must be right, as usual.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 01:57 pm
Can you explain how a rupture does that please?

That is the only way the propellants became available to burn

Do you know where the 2nd stage RP1 lines are on the strong back?  Knowing that could help localize whether the detonation is consistent with their position, or not.  i.e. a fuel line problem is another source. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 02:00 pm

Do you know where the 2nd stage RP1 lines are on the strong back?  Knowing that could help localize whether the detonation is consistent with their position, or not.  i.e. a fuel line problem is another source. 

There is no RP-1 flowing at that time.
RP-1 lines are at the bottom of the stage
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/02/2016 02:06 pm

Do you know where the 2nd stage RP1 lines are on the strong back?  Knowing that could help localize whether the detonation is consistent with their position, or not.  i.e. a fuel line problem is another source. 

There is no RP-1 flowing at that time.
RP-1 lines are at the bottom of the stage

Even if the fuel is not flowing, do they drain the fill line after S2 fuel is full?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/02/2016 02:08 pm

Do you know where the 2nd stage RP1 lines are on the strong back?  Knowing that could help localize whether the detonation is consistent with their position, or not.  i.e. a fuel line problem is another source. 

There is no RP-1 flowing at that time.
RP-1 lines are at the bottom of the stage

Well, what happens in the lines when propellants are not flowing? Are they still filled with propellants? Are they pressurized? Is there air in the fuel line?

Wups, Saab beat me to it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 02:11 pm

Do you know where the 2nd stage RP1 lines are on the strong back?  Knowing that could help localize whether the detonation is consistent with their position, or not.  i.e. a fuel line problem is another source. 

There is no RP-1 flowing at that time.
RP-1 lines are at the bottom of the stage

It wouldn't have to be flowing.  Only leaking during fueling.  That's why I'm wondering where the 2nd stage RP1 lines are.

reference:  http://www.sciencedirect.com/science/article/pii/S1877705814036583
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/02/2016 02:20 pm
lot of discussion about what is where on the tower in relation to the explosion. 

this wired article has a couple of closeups of the tower and stage in the area you guys are talking about.  Older Falcon variant i think, but i doubt the geometry has changed much

http://www.wired.com/2012/05/the-launch-pad-spacex-falcon-9-ready-for-liftoff/

also here's a hi res closeup i found linked off reddit of interstage area, a little lower down, good view of the service lines on the tower

http://i.imgur.com/7LL2HUp.jpg

bottom line - unless i'm looking at the images wrong, there isn't much beyond ECS (AC) and power running up past the lower part of the 2nd stage.

Here is an image of a more up to date iteration of the vehicle: https://c2.staticflickr.com/2/1671/26217360302_b66c3e384e_o.jpg

Edit: And the fairing version:
https://c2.staticflickr.com/6/5766/23526044959_5bfe74bc88_o.jpg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 02:25 pm
It wouldn't have to be flowing.  Only leaking during fueling. 


And that would be seen and they would not have completed the tanking
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 02:26 pm

Well, what happens in the lines when propellants are not flowing? Are they still filled with propellants? Are they pressurized? Is there air in the fuel line?

Wups, Saab beat me to it.

Standard practice would be to not to hold pressure after loading
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/02/2016 02:28 pm
Curious, anyone know what kind of refrigerant gets used for the fairing's AC? I know a lot of big commercial air chillers use ammonia, which if there is a leak in the system can make a pretty flammable concoction...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/02/2016 02:31 pm
I agree with the air-burst observation, but also finding it hard to come up with sources for such a nice fuel aerosol other than from the rocket.

It could still be something simple like a fill port, I'm really hoping it was not a tank structural thing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kryten on 09/02/2016 02:32 pm
Are there any other cases where there has been a complete loss of launch vehicle and payload days before T-0?
As well as the Russian incidents that have already been mentioned, there was a relatively recent fatal incident of this type in Brazil; https://en.wikipedia.org/wiki/VLS-1_V03
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 02:34 pm
It wouldn't have to be flowing.  Only leaking during fueling. 


And that would be seen and they would not have completed the tanking

Well, I guess you blew my hypothesis out of the water.   :)

I'm almost ready to embrace a conspiracy theory.   8)

Two things bother me greatly.

1.  The onset speed of the detonation.
2.  The trajectory of that "thingee" that flies over the plume apparently from the strongback.

I'm sure the answers will come forward...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/02/2016 02:39 pm
There have been lots of posts about the possibility of a leak outside the vehicle catching fire, (far to many to know which one to quote)

(Aside from the fact (as has been pointed out over and over again) that the fuel lines are at the bottom of the stage, not where the fire occurred.)

Question: if we assume for a moment that the vehicle is intact and the fuel is coming from a leak outside the vehicle: would a fuel air mixture burning in open air breach the oxygen tanks? We know it makes for a nice fireball but as explained earlier it is not a bomb just a fire (to use laymen's terms for detonation vs deflagration).

So would a burning fuel/air mixture outside the vehicle rupture the vehicle tanks from the outside? or just burn to depletion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DaveS on 09/02/2016 02:42 pm
Curious, anyone know what kind of refrigerant gets used for the fairing's AC? I know a lot of big commercial air chillers use ammonia, which if there is a leak in the system can make a pretty flammable concoction...
None, they use air to create a positive pressure inside the fairing. What you're thinking is cooling while the AC is used to maintain a clean environment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 02:44 pm
There have been lots of posts about the possibility of a leak outside the vehicle catching fire, (far to many to know which one to quote)

To me, they all look like wishful thinking, just like like IDA-1 destroying the LOX tank on CRS-7 theories were. Wishing for the "better" outcome scenario (pad fault vs. vehicle) and then looking for scenarios which might fit.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 02:49 pm
Curious, anyone know what kind of refrigerant gets used for the fairing's AC? I know a lot of big commercial air chillers use ammonia, which if there is a leak in the system can make a pretty flammable concoction...
None, they use air to create a positive pressure inside the fairing. What you're thinking is cooling while the AC is used to maintain a clean environment.

The air is also cooled along with being filtered. But at that point in the countdown, it should be GN2
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DaveS on 09/02/2016 02:50 pm
Curious, anyone know what kind of refrigerant gets used for the fairing's AC? I know a lot of big commercial air chillers use ammonia, which if there is a leak in the system can make a pretty flammable concoction...
None, they use air to create a positive pressure inside the fairing. What you're thinking is cooling while the AC is used to maintain a clean environment.

The air is also cooled along with being filtered. But at that point in the countdown, it should be GN2
Yes, passive air cooling and I was not 100% certain if they did a air/GN2 change-over for the PLF purge.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: WHAP on 09/02/2016 02:53 pm
JCM how do you classify this event?  A payload and rocket were lost at the launch pad but it wasn't a launch failure as it wasn't a launch attempt. Watching your website to see how you classify it as it is probably the launch log of choice on the web

I'm not JCM, but do my own tracking of launches.  Even though the payload was lost in a prelaunch exercise, it counts as a failure in my book.  You don't necessarily have to distinguish between a launch failure or a ground failure.  But it's a fact that the vehicle failed to get the payload to orbit.  It's not like the vehicle failed without the payload and you just get a new booster and have a successful mission a few months later.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: BrightLight on 09/02/2016 02:58 pm
I don't know if this was previously reported on this site or thread but:
"The satellite was backed by a policy worth almost $300 million, said the person, who requested anonymity because the person wasn’t authorized to speak publicly. SpaceX declined to comment."

http://www.bloomberg.com/news/articles/2016-09-02/when-a-commercial-rocket-blows-up-who-pays
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JWag on 09/02/2016 03:00 pm
The LOX dome in the common bulkhead impinges the RP-1 tank, is that correct?

Bolded red here (side view): < Payload ] ( LOX ) RP1) |< M-vac

So it would take an RP-1 overpressurization (or LOX depress) to invert the dome. Right?

My own pet theory is that an RP-1 overpress inverted the bulkhead, overpressing the LOX tank and splitting the two at the now-weakened bulkhead. Hot twisted bulkhead metal ignited the mixing propellants.

Still, given the energy, it's difficult to imagine how the payload wasn't propelled upwards with the pressure from the LOX if the tank split circumferentially. Sort of like how STS-51L's ET was propelled forward when the aft LH2 dome split off.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/02/2016 03:01 pm
JCM how do you classify this event?  A payload and rocket were lost at the launch pad but it wasn't a launch failure as it wasn't a launch attempt. Watching your website to see how you classify it as it is probably the launch log of choice on the web

I'm not JCM, but do my own tracking of launches.  Even though the payload was lost in a prelaunch exercise, it counts as a failure in my book.  You don't necessarily have to distinguish between a launch failure or a ground failure.  But it's a fact that the vehicle failed to get the payload to orbit.  It's not like the vehicle failed without the payload and you just get a new booster and have a successful mission a few months later.

I agree. When I actually get around to updating the launch reliability statistics I've posted around here, I will be tallying it as a failure as well, since the rocket (and perhaps more importantly) the payload were destroyed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: whitelancer64 on 09/02/2016 03:02 pm
JCM how do you classify this event?  A payload and rocket were lost at the launch pad but it wasn't a launch failure as it wasn't a launch attempt. Watching your website to see how you classify it as it is probably the launch log of choice on the web

I'm not JCM, but do my own tracking of launches.  Even though the payload was lost in a prelaunch exercise, it counts as a failure in my book.  You don't necessarily have to distinguish between a launch failure or a ground failure.  But it's a fact that the vehicle failed to get the payload to orbit.  It's not like the vehicle failed without the payload and you just get a new booster and have a successful mission a few months later.
Yeah, that's how I've got it in my SpaceX launches spreadsheet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/02/2016 03:05 pm
Here's a distillation of discussion.

Fuel loading....
*Ploink* LOX tank/line failure. possible weld brittle failure of LOX tank dome due to deep cryo-LOX
Rapid release of LOX slush
*crinkling noise* Expansion/deformation of outer skin of S2 due to growing overpressure
pressure and deformation find the weakest point... the umbilical
Power/data + Fueling(possible) Umbilical detach or fail and spark leading to Fuel-Air detonation at single point [as seen in video]
a Jet of LOX-RP1 escaping near the partially detached & still live Power/data port would be like a static spark while filling your gas tank or any non-positive pressurized oil rig electrical device during a Natural Gas "Kick"/Blowout, only 1000 time more energetic
 = RUD

that's my 1.5 Cents.
Please discuss among yourselves while i go back to work
Cheers  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jaufgang on 09/02/2016 03:05 pm
Two things bother me greatly.

1.  The onset speed of the detonation.
2.  The trajectory of that "thingee" that flies over the plume apparently from the strongback.


I've looked closely at that "thingee" flying straight up from the strongback, stepping forwards and backwards in the video fame by frame several times. One thing I noticed is that if you assume that it originated at an elevation at or above where the explosion seems to be centered, and if you try to visually extrapolate the reverse-trajectory while stepping the video backwards, it seems like that part must have been launched a few frames after the initial explosion began (i.e. running backwards it seems it would reach it's expected starting point before the shrinking fireball disappears).  That might indicate that it was launched from some part on the strongback due to pressure buildup from the original explosion coming from a point on the rocket to the left and possibly a bit below.

Of course my technique is very inaccurate and I could be wrong about the timing of the trajectory but that's what it looks like to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/02/2016 03:21 pm
SpaceX decided to immerse their COPVs in their propellant.  Given that choice, why did they choose to immerse them in the LOX, which is nasty stuff both chemically and thermally, instead of in the comparatively benign RP1?

Someone may have already answered this, but the main reason is dry mass savings. GHe at LOX temps (90K) is about ~3x denser than the same pressure of GHe at room temperature (300K), or chilled Kerosene temps. Because pressure tank mass scales linearly with Pressure x Volume, a higher GHe storage density means you reduce the mass and volume of helium for the stage dramatically, saving a lot of dry mass on the stage. I should note that the GHe is warmed by some sort of device (not positive how on F9 US) before being routed back to the tanks, to reduce its density before putting it into the tanks as pressurant. This fits in with SpaceX's push for bleeding edge performance on its engines and stages...

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 03:25 pm


Question: if we assume for a moment that the vehicle is intact and the fuel is coming from a leak outside the vehicle: would a fuel air mixture burning in open air breach the oxygen tanks? We know it makes for a nice fireball but as explained earlier it is not a bomb just a fire (to use laymen's terms for detonation vs deflagration).

So would a burning fuel/air mixture outside the vehicle rupture the vehicle tanks from the outside? or just burn to depletion?

If you can create either an RP1 or an ammonia aerosol, and then provide an ignition source, it will detonate.  The shock-wave would rupture the tanks.

If it's not an aerosol, it will burn.

In the available video, it looks like the detonation speed is between 2,000 and 5,000 feet per second.  That would create a major shock-wave.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/02/2016 03:28 pm

Well, what happens in the lines when propellants are not flowing? Are they still filled with propellants? Are they pressurized? Is there air in the fuel line?

Wups, Saab beat me to it.

Standard practice would be to not to hold pressure after loading

And without pressure in the RP-1 line, I don't see any way it could've created an aerosol for a fuel-air explosion.

Also, when they're doing LOX loading, is the RP-1 in the tanks pressurized? Because if there's no pressurized fuel source at this point in the prop loading process (in the tanks or the feedlines) that would make an external fuel/air explosion seem a lot less likely, wouldn't it?

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 03:30 pm
Two things bother me greatly.

1.  The onset speed of the detonation.
2.  The trajectory of that "thingee" that flies over the plume apparently from the strongback.


I've looked closely at that "thingee" flying straight up from the strongback, stepping forwards and backwards in the video fame by frame several times. One thing I noticed is that if you assume that it originated at an elevation at or above where the explosion seems to be centered, and if you try to visually extrapolate the reverse-trajectory while stepping the video backwards, it seems like that part must have been launched a few frames after the initial explosion began (i.e. running backwards it seems it would reach it's expected starting point before the shrinking fireball disappears).  That might indicate that it was launched from some part on the strongback due to pressure buildup from the original explosion coming from a point on the rocket to the left and possibly a bit below.

Of course my technique is very inaccurate and I could be wrong about the timing of the trajectory but that's what it looks like to me.

If you make the following assumption, do you come to the same conclusion?

1.  The vertical component is < 50% of the total velocity
2.  The horizontal component towards the camera and left is > 50% of the total velocity.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: M.E.T. on 09/02/2016 03:35 pm
Not sure where to ask this type of question, and I think it is obvious why one would ask it after such an event, but how tight is security in the launch industry? Meaning throughout the process, from origin of the rocket up to ignition?


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 09/02/2016 03:38 pm
The LOX dome in the common bulkhead impinges the RP-1 tank, is that correct?

Bolded red here (side view): < Payload ] ( LOX ) RP1) |< M-vac

So it would take an RP-1 overpressurization (or LOX depress) to invert the dome. Right?

My own pet theory is that an RP-1 overpress inverted the bulkhead, overpressing the LOX tank and splitting the two at the now-weakened bulkhead. Hot twisted bulkhead metal ignited the mixing propellants.

Still, given the energy, it's difficult to imagine how the payload wasn't propelled upwards with the pressure from the LOX if the tank split circumferentially. Sort of like how STS-51L's ET was propelled forward when the aft LH2 dome split off.

This is a key indication that the initial explosion was external to the tank.

A detonation inside the tank would be vastly more energetic than the pressure from a COPV failure -- which itself would have sufficient energy to launch the payload upwards.  It just sat there...

External explosion compromises the second stage tankage, fuel/lox waterfalls onto pad below, lower stage detonates, and finally, payload comes tumbling down.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: b ramsey on 09/02/2016 03:43 pm
Have there been any helicopter aerial views of the pad anywhere on the net post accident. I haven"t seen any yet.  Question is how long is the pad out of commission per how much damage is there.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 03:49 pm
Also, when they're doing LOX loading, is the RP-1 in the tanks pressurized? Because if there's no pressurized fuel source at this point in the prop loading process (in the tanks or the feedlines) that would make an external fuel/air explosion seem a lot less likely, wouldn't it?

On JCSat-16 webcast, at T-4m 50s there was a callout "stage 1, stage 2 pressing for strongback retract".

I believe that was a standard procedure for all F9s, perhaps not pressed all the way to flight level, but certainly under pressure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jaufgang on 09/02/2016 03:51 pm
Two things bother me greatly.

1.  The onset speed of the detonation.
2.  The trajectory of that "thingee" that flies over the plume apparently from the strongback.


I've looked closely at that "thingee" flying straight up from the strongback, stepping forwards and backwards in the video fame by frame several times. One thing I noticed is that if you assume that it originated at an elevation at or above where the explosion seems to be centered, and if you try to visually extrapolate the reverse-trajectory while stepping the video backwards, it seems like that part must have been launched a few frames after the initial explosion began (i.e. running backwards it seems it would reach it's expected starting point before the shrinking fireball disappears).  That might indicate that it was launched from some part on the strongback due to pressure buildup from the original explosion coming from a point on the rocket to the left and possibly a bit below.

Of course my technique is very inaccurate and I could be wrong about the timing of the trajectory but that's what it looks like to me.

If you make the following assumption, do you come to the same conclusion?

1.  The vertical component is < 50% of the total velocity
2.  The horizontal component towards the camera and left is > 50% of the total velocity.

Yes, whether or not I'm right or wrong, I don't see how the horizontal component matters at all.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/02/2016 04:00 pm
lot of discussion about what is where on the tower in relation to the explosion. 

this wired article has a couple of closeups of the tower and stage in the area you guys are talking about.  Older Falcon variant i think, but i doubt the geometry has changed much

http://www.wired.com/2012/05/the-launch-pad-spacex-falcon-9-ready-for-liftoff/

also here's a hi res closeup i found linked off reddit of interstage area, a little lower down, good view of the service lines on the tower

http://i.imgur.com/7LL2HUp.jpg

bottom line - unless i'm looking at the images wrong, there isn't much beyond ECS (AC) and power running up past the lower part of the 2nd stage.

Here is an image of a more up to date iteration of the vehicle: https://c2.staticflickr.com/2/1671/26217360302_b66c3e384e_o.jpg

Edit: And the fairing version:
https://c2.staticflickr.com/6/5766/23526044959_5bfe74bc88_o.jpg

Posting from my phone, so apologies for this not being the most readable.

That second pic there shows that there is a bit of a "cradle" on the strong back right about where the intertank is, if I'm looking at it right.  This perks my interest and goes along with something else I've been wondering.  Watching the video, my mind sees relative motion between the rocket and strong back (very small probably nothing).  I've been thinking this was a trick of how far away the camera is etc.  But what if it isn't?  What if there was some relative motion there?  Could this "cradle" have actually punctured the skin of the rocket?  Does anyone know the wind speeds, it looked like a relatively stiff breeze from looking at the vent gasses (not really a good judge of things).  I'm sure there are wind constraints even for a static test right?

I honestly think I'm crazy on this theory, but thought I'd throw it out to be debunked here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/02/2016 04:04 pm


Not sure where to ask this type of question, and I think it is obvious why one would ask it after such an event, but how tight is security in the launch industry? Meaning throughout the process, from origin of the rocket up to ignition?

It's an Air Force Base.  Security is very high.  See Jim's posts earlier in this thread for more details.
Have there been any helicopter aerial views of the pad anywhere on the net post accident. I haven"t seen any yet.  Question is how long is the pad out of commission per how much damage is there.
It's an Air Force Base.  I'm sure there are strict restrictions on photographers in civilian news copters.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 04:07 pm
Two things bother me greatly.

1.  The onset speed of the detonation.
2.  The trajectory of that "thingee" that flies over the plume apparently from the strongback.


I've looked closely at that "thingee" flying straight up from the strongback, stepping forwards and backwards in the video fame by frame several times. One thing I noticed is that if you assume that it originated at an elevation at or above where the explosion seems to be centered, and if you try to visually extrapolate the reverse-trajectory while stepping the video backwards, it seems like that part must have been launched a few frames after the initial explosion began (i.e. running backwards it seems it would reach it's expected starting point before the shrinking fireball disappears).  That might indicate that it was launched from some part on the strongback due to pressure buildup from the original explosion coming from a point on the rocket to the left and possibly a bit below.

Of course my technique is very inaccurate and I could be wrong about the timing of the trajectory but that's what it looks like to me.

If you make the following assumption, do you come to the same conclusion?

1.  The vertical component is < 50% of the total velocity
2.  The horizontal component towards the camera and left is > 50% of the total velocity.

Yes, whether or not I'm right or wrong, I don't see how the horizontal component matters at all.

It would rise more slowly which would give a perception of a later instantiation while the horizontal component wouldn't be as obvious.  Just an idea.  I'll have to duplicate what you did to have a real opinion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/02/2016 04:09 pm
I previously said the initial explosion was fast and energetic.

However it is not IMO energetic enough to fit a total bulkhead failure.

I think in that case you'd get violent mixing of LOX and RP1 in large quantities, and then when it ignites, you'd get one HELL of an explosion, one that wouldn't leave the fairing intact like that.

It was indeed fast, but it was also relatively small. Just enough to cause the rest of the rocket to fail slowly.

So still I think something failed in the rocket, caused a fuel air or fuel gox mix to form, and then something else (what?) Ignited it.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/02/2016 04:13 pm
The LOX dome in the common bulkhead impinges the RP-1 tank, is that correct?

Bolded red here (side view): < Payload ] ( LOX ) RP1) |< M-vac

So it would take an RP-1 overpressurization (or LOX depress) to invert the dome. Right?

My own pet theory is that an RP-1 overpress inverted the bulkhead, overpressing the LOX tank and splitting the two at the now-weakened bulkhead. Hot twisted bulkhead metal ignited the mixing propellants.

Still, given the energy, it's difficult to imagine how the payload wasn't propelled upwards with the pressure from the LOX if the tank split circumferentially. Sort of like how STS-51L's ET was propelled forward when the aft LH2 dome split off.

This is a key indication that the initial explosion was external to the tank.

A detonation inside the tank would be vastly more energetic than the pressure from a COPV failure -- which itself would have sufficient energy to launch the payload upwards.  It just sat there...

External explosion compromises the second stage tankage, fuel/lox waterfalls onto pad below, lower stage detonates, and finally, payload comes tumbling down.
Even if the explosion was ignited outside the rocket a failure of the rocket could still be the source of the oxygen/rp-1.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/02/2016 04:23 pm
Posting from my phone, so apologies for this not being the most readable.

That second pic there shows that there is a bit of a "cradle" on the strong back right about where the intertank is, if I'm looking at it right.  This perks my interest and goes along with something else I've been wondering.  Watching the video, my mind sees relative motion between the rocket and strong back (very small probably nothing).  I've been thinking this was a trick of how far away the camera is etc.  But what if it isn't?  What if there was some relative motion there?  Could this "cradle" have actually punctured the skin of the rocket?  Does anyone know the wind speeds, it looked like a relatively stiff breeze from looking at the vent gasses (not really a good judge of things).  I'm sure there are wind constraints even for a static test right?

I honestly think I'm crazy on this theory, but thought I'd throw it out to be debunked here.

The cradle is in pretty much the exact place the explosion started.

Probably correlation, not causation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/02/2016 04:24 pm
How about this.

Let's say there was a small, maybe pin-hole leak in the RP-1 fueling umbilical, and during fueling it sprayed the top of the strongback with RP1.  Kerosene evaporates slowly so it can hang around for a while.

It looks like there's a GOX stream near the strongback.  See the arrow below.  That spot seems to correspond to the initiation location as determined by the diffraction spikes.

What if that GOX stream and the hypothetical slowly-evaporating RP-1 from the hypothetical leak finally got to sufficient concentrations, just due to just the right (or wrong) wind conditions that it could ignite into a fuel-air explosion given an ignition source?  That small-ish explosion ruptures the tanks, and everything falls, burning on the way down.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/02/2016 04:38 pm
Posting from my phone, so apologies for this not being the most readable.

That second pic there shows that there is a bit of a "cradle" on the strong back right about where the intertank is, if I'm looking at it right.  This perks my interest and goes along with something else I've been wondering.  Watching the video, my mind sees relative motion between the rocket and strong back (very small probably nothing).  I've been thinking this was a trick of how far away the camera is etc.  But what if it isn't?  What if there was some relative motion there?  Could this "cradle" have actually punctured the skin of the rocket?  Does anyone know the wind speeds, it looked like a relatively stiff breeze from looking at the vent gasses (not really a good judge of things).  I'm sure there are wind constraints even for a static test right?

I honestly think I'm crazy on this theory, but thought I'd throw it out to be debunked here.

The cradle is in pretty much the exact place the explosion started.

Probably correlation, not causation.

Yes, that's where the explosion appears to start, thus my question.

Clearly correlation is not causation, but merely stating a trite old saying doesn't rule it out either. 

What are the wind constraints for a static fire?  Is there something that guaruntees there can be no relative motion between the rocket and strongback in that location?  The skin wouldn't even necessarily need to be punctured either, a big enough dent could cause the tanks to buckle under pressure too.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 04:44 pm
There are clamps that hold the vehicle near the fairing that prevents relative motion
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 04:49 pm
If the concentration and pressures are high enough of the RP-1/LOX you could have a spontaneous ignition...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Asmegin on 09/02/2016 04:50 pm
User Squeazle (https://www.reddit.com/user/Squeazle) on reddit, claiming to be with the CCAFS FD, posted a few things re: pad status. Goes without saying that his information cannot be confirmed, but his post history does seem to back up his position.

Quote
While I am not an official spokesperson for either Cape Canaveral Air Force Station Fire Department or Kennedy Space Center Fire Department, I am a member of CCAFS FD and was on scene at yesterday's anomaly and was involved with the eventual extinguishment of the remaining fires. I can confirm that NO personnel from either side were injured or airlifted from the scene. The Air Force's Explosive Ordinance Disposal team preceded closely in front of fire crews and did a superb job clearing a path for us to follow and approach the pad.

(On how bad the pad was damaged) Quite. Granted, I'm not in construction or an engineer but it seems like it will be months before the pad is usable. Dozens of pressurized vessels and tanks were destroyed including 5-6 pressurized rail cars. The gantry itself, while still standing appears to be a total loss, as may be a lightening arrest tower at the corner of the pad. Several buildings located on or near the pad are either destroyed or severely damaged. There's no power at the moment and I can tell you from first-hand experience that the water mains and hydrants are compromised. Debris made it as far as pad 39A, which is quite a distance. They'll be finding pieces of it in the surrounding woods and beach line for years, just as they've found pieces of 1997's Delta II mishap as recently as a year or two ago. I have loads of pictures and video, including the initial walk-down of the pad with Fire, EOD, SpaceX, and AF investigators, and know people who have posted them to social media but without SpaceX' and the Air Force's expressed permission, I'm wary of posting them.

I'm fairly certain I saw a rocket motor, or at least it's nozzle, directly under the gantry on top of the pad and a black composite tank that looked fairly intact off in the field, but that's about all that was recognizable.

The hangar actually doesn't appear damaged but I'm sitting on the opposite side of the pad right now and can't see it close up. As for concrete, I'm not sure yet but plumbing and piping leading into/out of the pad definitely is.

(on debris flying to 39A) It does seem unlikely that it would travel that distance but a contingent of EOD was dispatched to 39A for report of debris.
When I have a better handle on permissions, I'll post some. They're pretty interesting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gadgetmind on 09/02/2016 04:52 pm
When you're dealing with a high oxygen content you don't even need a spark. Scuba tanks need oxygen safe cleaning for even mild oxygen enrichment as oil/grease can combust spontaneously, as can other materials.

I'm certain these risks are fully understood by all concerned, and that all materials including seals and lubricants are oxygen safe, but this is a "don't trust anything" investigation, and an ignition source not being present doesn't rule anything out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cro-magnon gramps on 09/02/2016 04:53 pm
I did a cursory search back to page 12, and no one had posted this... off of twitter, picked it up yesterday. The creator put the fire ball and the Dragon Abort vid together and sort of proved that Dragon would escape with plenty of margin... I hedged my comment, because I know that there may be purists who will knock his effort...


https://twitter.com/StateMachines/status/771535425328459780
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Patchouli on 09/02/2016 04:53 pm

Yes, passive air cooling and I was not 100% certain if they did a air/GN2 change-over for the PLF purge.

Somewhat crazy theory but what if AMOS-6 itself had a propellant leak wouldn't that fill the fairing with flammable gas which could have leaked outside and found an ignition source or just reacted with O2 from the LOX tank venting?

I did a cursory search back to page 12, and no one had posted this... off of twitter, picked it up yesterday. The creator put the fire ball and the Dragon Abort vid together and sort of proved that Dragon would escape with plenty of margin... I hedged my comment, because I know that there may be purists who will knock his effort...


https://twitter.com/StateMachines/status/771535425328459780

At least we now know at least one crew vehicle's LAS should be up to the task of escaping a worst case failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 04:54 pm
User Squeazle (https://www.reddit.com/user/Squeazle) on reddit, claiming to be with the CCAFS FD, posted a few things re: pad status. Goes without saying that his information cannot be confirmed, but his post history does seem to back up his position.

Quote
While I am not an official spokesperson for either Cape Canaveral Air Force Station Fire Department or Kennedy Space Center Fire Department, I am a member of CCAFS FD and was on scene at yesterday's anomaly and was involved with the eventual extinguishment of the remaining fires. I can confirm that NO personnel from either side were injured or airlifted from the scene. The Air Force's Explosive Ordinance Disposal team preceded closely in front of fire crews and did a superb job clearing a path for us to follow and approach the pad.

(On how bad the pad was damaged) Quite. Granted, I'm not in construction or an engineer but it seems like it will be months before the pad is usable. Dozens of pressurized vessels and tanks were destroyed including 5-6 pressurized rail cars. The gantry itself, while still standing appears to be a total loss, as may be a lightening arrest tower at the corner of the pad. Several buildings located on or near the pad are either destroyed or severely damaged. There's no power at the moment and I can tell you from first-hand experience that the water mains and hydrants are compromised. Debris made it as far as pad 39A, which is quite a distance. They'll be finding pieces of it in the surrounding woods and beach line for years, just as they've found pieces of 1997's Delta II mishap as recently as a year or two ago. I have loads of pictures and video, including the initial walk-down of the pad with Fire, EOD, SpaceX, and AF investigators, and know people who have posted them to social media but without SpaceX' and the Air Force's expressed permission, I'm wary of posting them.

I'm fairly certain I saw a rocket motor, or at least it's nozzle, directly under the gantry on top of the pad and a black composite tank that looked fairly intact off in the field, but that's about all that was recognizable.

The hangar actually doesn't appear damaged but I'm sitting on the opposite side of the pad right now and can't see it close up. As for concrete, I'm not sure yet but plumbing and piping leading into/out of the pad definitely is.

(on debris flying to 39A) It does seem unlikely that it would travel that distance but a contingent of EOD was dispatched to 39A for report of debris.
When I have a better handle on permissions, I'll post some. They're pretty interesting.

I'm thinking history will show JCSAT-16 as the last rocket launched from SLC-40.... it's done...  :'(  :(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/02/2016 04:56 pm
How about this.

Let's say there was a small, maybe pin-hole leak in the RP-1 fueling umbilical, and during fueling it sprayed the top of the strongback with RP1.  Kerosene evaporates slowly so it can hang around for a while.

It looks like there's a GOX stream near the strongback.  See the arrow below.  That spot seems to correspond to the initiation location as determined by the diffraction spikes.

What if that GOX stream and the hypothetical slowly-evaporating RP-1 from the hypothetical leak finally got to sufficient concentrations, just due to just the right (or wrong) wind conditions that it could ignite into a fuel-air explosion given an ignition source?  That small-ish explosion ruptures the tanks, and everything falls, burning on the way down.

This would fit what we know so far, except that the RP-1 umbilical is about 4 meters directly below where your arrow is pointed. That seems like a long way for a stream of liquid fuel to go, and the wind would quickly dissapate vapors or small droplets.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/02/2016 04:57 pm
Yes, that's where the explosion appears to start, thus my question.

Clearly correlation is not causation, but merely stating a trite old saying doesn't rule it out either. 

What are the wind constraints for a static fire?  Is there something that guaruntees there can be no relative motion between the rocket and strongback in that location?  The skin wouldn't even necessarily need to be punctured either, a big enough dent could cause the tanks to buckle under pressure too.

I've overlaid an image from immediately before the explosion over one a couple of minutes after it.

It shows the strongback buckled at pretty much the point you're referring to, which could be interpreted as it being damaged by the initial explosion and subsequently failing there.

However, it looks like the buckling of the strongback was caused by it taking the weight of the payload and was twisted as it fell - but it still failed at the same point.

 I've marked that point on a clean image of the top of the vehicle (with a Dragon) and the construction of the strongback is different at that point.

It looks like it has what I would consider to be bottle screws, which would enable the height of the top of the strongback to be altered by extending the. (No doubt someone can cast some light on what they are?)

This is probably the weakest point in the top of the structure, so it's not surprising that it deformed there.

In short: although strongback seems to have part-failed at the point of the initial explosion, it's probably nothing more than correlation.




Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: northenarc on 09/02/2016 04:57 pm

The air is also cooled along with being filtered. But at that point in the countdown, it should be GN2
Yes, passive air cooling and I was not 100% certain if they did a air/GN2 change-over for the PLF purge.

Some what crazy theory but what if AMOS-6 itself had a propellant leak wouldn't that fill the fairing with flammable gas which could have leaked outside and found an ignition source or just reacted with O2 from the LOX tank venting?
[/quote]
  I would think there would have been some indication of reddish hydrazine clouds around were that the case, and a different sort of explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 04:58 pm
User Squeazle (https://www.reddit.com/user/Squeazle) on reddit, claiming to be with the CCAFS FD, posted a few things re: pad status. Goes without saying that his information cannot be confirmed, but his post history does seem to back up his position.

Quote
While I am not an official spokesperson for either Cape Canaveral Air Force Station Fire Department or Kennedy Space Center Fire Department, I am a member of CCAFS FD and was on scene at yesterday's anomaly and was involved with the eventual extinguishment of the remaining fires. I can confirm that NO personnel from either side were injured or airlifted from the scene. The Air Force's Explosive Ordinance Disposal team preceded closely in front of fire crews and did a superb job clearing a path for us to follow and approach the pad.

(On how bad the pad was damaged) Quite. Granted, I'm not in construction or an engineer but it seems like it will be months before the pad is usable. Dozens of pressurized vessels and tanks were destroyed including 5-6 pressurized rail cars. The gantry itself, while still standing appears to be a total loss, as may be a lightening arrest tower at the corner of the pad. Several buildings located on or near the pad are either destroyed or severely damaged. There's no power at the moment and I can tell you from first-hand experience that the water mains and hydrants are compromised. Debris made it as far as pad 39A, which is quite a distance. They'll be finding pieces of it in the surrounding woods and beach line for years, just as they've found pieces of 1997's Delta II mishap as recently as a year or two ago. I have loads of pictures and video, including the initial walk-down of the pad with Fire, EOD, SpaceX, and AF investigators, and know people who have posted them to social media but without SpaceX' and the Air Force's expressed permission, I'm wary of posting them.

I'm fairly certain I saw a rocket motor, or at least it's nozzle, directly under the gantry on top of the pad and a black composite tank that looked fairly intact off in the field, but that's about all that was recognizable.

The hangar actually doesn't appear damaged but I'm sitting on the opposite side of the pad right now and can't see it close up. As for concrete, I'm not sure yet but plumbing and piping leading into/out of the pad definitely is.

(on debris flying to 39A) It does seem unlikely that it would travel that distance but a contingent of EOD was dispatched to 39A for report of debris.
When I have a better handle on permissions, I'll post some. They're pretty interesting.

I'm thinking history will show JCSAT-16 as the last rocket launched from SLC-40.... it's done...  :'(  :(

It is not done.  Spacex needs it more than the other pads
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kansan52 on 09/02/2016 04:59 pm
This is a very small reference point but the oxygen show at the local science museum burns a cotton ball, uses a new one dipped in liquid oxygen and causes an explosion that rattles the ceiling tiles and you feel the concussion rattling you.

Point is, that much concentrated oxygen can support rapid burning (explosion) with many materials that we wouldn't think of as explosive.

Once that initial point started, it took everything else with it. A distinctive pattern of arcing on the remains of the TEL may tell much.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 05:00 pm
No more theories on spacecraft leaking propellants.  The fairing was still intact after the initial explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/02/2016 05:06 pm
This is a very small reference point but the oxygen show at the local science museum burns a cotton ball, uses a new one dipped in liquid oxygen and causes an explosion that rattles the ceiling tiles and you feel the concussion rattling you.

Point is, that much concentrated oxygen can support rapid burning (explosion) with many materials that we wouldn't think of as explosive.

Once that initial point started, it took everything else with it. A distinctive pattern of arcing on the remains of the TEL may tell much.

I just saw that demonstration, and have pictures of the cotton ball "burning very rapidly".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 05:07 pm
This is a very small reference point but the oxygen show at the local science museum burns a cotton ball, uses a new one dipped in liquid oxygen and causes an explosion that rattles the ceiling tiles and you feel the concussion rattling you.

Point is, that much concentrated oxygen can support rapid burning (explosion) with many materials that we wouldn't think of as explosive.

Once that initial point started, it took everything else with it. A distinctive pattern of arcing on the remains of the TEL may tell much.
Ask any good welder about precautions around oxygen gas and hydrocarbons...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: blah on 09/02/2016 05:09 pm


Somewhere in the volumes of written word from the last 24 hours, there was the phrase from SpaceX, "Catastrophic abort." 

Nope, this was never said by SpaceX.

Other persistent misunderstandings: there were early conflicting reports that the incident happened at T-3 and T-5.  Evidence from the timeline and strongback/cradle position indicates that it happened some time before T-4:10, which is when the cradle is opened.

Do we know that SpaceX wasn't deep into processing an abort at the time of explosion, and that the strongback hadn't been retracted at some point?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 05:11 pm
Nope
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/02/2016 05:12 pm
So still I think something failed in the rocket, caused a fuel air or fuel gox mix to form, and then something else (what?) Ignited it.

The ignition source appears to be in the vicinity of the cradle -- metal scraping during retraction ops?  With enough O2, it really doesn't take much, and there's plenty of gox venting.  I don't think the cause of the ignition is that interesting.  The fact that there was something to ignite is the troubling bit.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/02/2016 05:22 pm




Somewhere in the volumes of written word from the last 24 hours, there was the phrase from SpaceX, "Catastrophic abort." 

Nope, this was never said by SpaceX.

Other persistent misunderstandings: there were early conflicting reports that the incident happened at T-3 and T-5.  Evidence from the timeline and strongback/cradle position indicates that it happened some time before T-4:10, which is when the cradle is opened.

Do we know that SpaceX wasn't deep into processing an abort at the time of explosion, and that the strongback hadn't been retracted at some point?

Look at the video posted by us space report.  It includes quite some time before the incident.  The strongback was never retracted.

I don't know where this "abort" theory comes from, but it's not NSF or SpaceX.  I've read every word published by spacex and every word of the NSF threads and I didn't see anything similar until AncientU's post.  I suspect you guys are getting unsourced speculation from less-credible sites and then getting it mixed up in your minds as something real.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/02/2016 05:25 pm
So still I think something failed in the rocket, caused a fuel air or fuel gox mix to form, and then something else (what?) Ignited it.

The ignition source appears to be in the vicinity of the cradle -- metal scraping during retraction ops?  With enough O2, it really doesn't take much, and there's plenty of gox venting.  I don't think the cause of the ignition is that interesting.  The fact that there was something to ignite is the troubling bit.
If you have a sudden fracture of the RP-1 under pressure a jet of fuel vapour could shoot out into the gaseous Ox vapour cloud, could with the energy of molecule collisions, cause a spontaneous ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/02/2016 05:27 pm
Are the COPVs in the LOX tank something that is only done in the Falcon 9's second stage? Where is the GHe on the booster?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/02/2016 05:28 pm


Somewhere in the volumes of written word from the last 24 hours, there was the phrase from SpaceX, "Catastrophic abort." 

Nope, this was never said by SpaceX.

Other persistent misunderstandings: there were early conflicting reports that the incident happened at T-3 and T-5.  Evidence from the timeline and strongback/cradle position indicates that it happened some time before T-4:10, which is when the cradle is opened.

Do we know that SpaceX wasn't deep into processing an abort at the time of explosion, and that the strongback hadn't been retracted at some point?
Nope

We have footage of the strongback upright and closed on the vehicle continuously for more than a minute before the fireball.
We have the SpaceX statement that the anomaly occurred "during propellant loading of the vehicle"; if they were several minutes into an abort they would likely have been draining prop, not loading it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/02/2016 05:29 pm
Are the COPVs in the LOX tank something that is only done in the Falcon 9's second stage? Where is the GHe on the booster?
Same design for both stages.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: smfarmer11 on 09/02/2016 05:31 pm
Could lc-39a be used as a launch site if lc-40 is not yet ready for when the falcon 9 is ready for return to flight?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 05:36 pm
Could lc-39a be used as a launch site if lc-40 is not yet ready for when the falcon 9 is ready for return to flight?

Yes... LC39A can launch both Heavy and FT versions... SLC-40 could not do Falcon Heavy
Building is too narrow to assemble Heavy... T/E too narrow to carry it...
Also issues with the current pad structure (concrete) to be able to modified it for Heavy without drastic measures...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Greg906 on 09/02/2016 05:37 pm
First, let me say as a layperson how much I appreciate this forum for discussions like this...thank you! 
Great discussions!

My question - does anyone know if/when more video will be released?  Does anyone know if there were any other cameras nearby?

This is separate from asking when SpaceX will share any info or video...thanks!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/02/2016 05:37 pm

We have footage of the strongback upright and closed on the vehicle continuously for more than a minute before the fireball.
We have the SpaceX statement that the anomaly occurred "during propellant loading of the vehicle"; if they were several minutes into an abort they would likely have been draining prop, not loading it.

No, the video is cut at the 0:50 second mark. We have approximately 23 seconds of continuous video before the anomaly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Khadgars on 09/02/2016 05:40 pm
First, let me say as a layperson how much I appreciate this forum for discussions like this...thank you! 
Great discussions!

My question - does anyone know if/when more video will be released?  Does anyone know if there were any other cameras nearby?

This is separate from asking when SpaceX will share any info or video...thanks!

Just wanted to second this statement.  Very impressed and appreciative for the fantastic discussions going on during these tough times.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 05:41 pm


Somewhere in the volumes of written word from the last 24 hours, there was the phrase from SpaceX, "Catastrophic abort." 

Nope, this was never said by SpaceX.

Other persistent misunderstandings: there were early conflicting reports that the incident happened at T-3 and T-5.  Evidence from the timeline and strongback/cradle position indicates that it happened some time before T-4:10, which is when the cradle is opened.

Do we know that SpaceX wasn't deep into processing an abort at the time of explosion, and that the strongback hadn't been retracted at some point?
Nope

We have footage of the strongback upright and closed on the vehicle continuously for more than a minute before the fireball.
We have the SpaceX statement that the anomaly occurred "during propellant loading of the vehicle"; if they were several minutes into an abort they would likely have been draining prop, not loading it.

Abort has many connotations.  It can mean backing out of a operation.  We don't know if this incident happened without any immediate indications or something was going bad and Spacex was trying to rectify the situation (i.e. aborting out of propellant load).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/02/2016 05:42 pm
Yes, that's where the explosion appears to start, thus my question.

Clearly correlation is not causation, but merely stating a trite old saying doesn't rule it out either. 

What are the wind constraints for a static fire?  Is there something that guaruntees there can be no relative motion between the rocket and strongback in that location?  The skin wouldn't even necessarily need to be punctured either, a big enough dent could cause the tanks to buckle under pressure too.

I've overlaid an image from immediately before the explosion over one a couple of minutes after it.

It shows the strongback buckled at pretty much the point you're referring to, which could be interpreted as it being damaged by the initial explosion and subsequently failing there.

However, it looks like the buckling of the strongback was caused by it taking the weight of the payload and was twisted as it fell - but it still failed at the same point.

 I've marked that point on a clean image of the top of the vehicle (with a Dragon) and the construction of the strongback is different at that point.

It looks like it has what I would consider to be bottle screws, which would enable the height of the top of the strongback to be altered by extending the. (No doubt someone can cast some light on what they are?)

This is probably the weakest point in the top of the structure, so it's not surprising that it deformed there.

In short: although strongback seems to have part-failed at the point of the initial explosion, it's probably nothing more than correlation.

Yes that mass bending is from having the payload sitting on the clamps unsupported post anomaly.  My crazy idea involves no plastic deformation of the structure but a much more "gentle" elastic movement.  Again, I'm most likely wrong.  As Jim says there are clamps not too far from this point anyway.  Are those absolutely rigid?  I would think there must be some "play" to account for the thermal expansion/contraction the rocket sees as it is tanked/unranked.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/02/2016 05:45 pm
I don't know where this "abort" theory comes from, but it's not NSF or SpaceX.  I've read every word published by spacex and every word of the NSF threads and I didn't see anything similar until AncientU's post.  I suspect you guys are getting unsourced speculation from less-credible sites and then getting it mixed up in your minds as something real.

I think it comes from the Brevard County Emergency Operations Center. I didn't take it too literally, though it's possible that they detected something was going south a few seconds before the fireball and attempted to abort.

Quote
"There is NO threat to general public from catastrophic abort during static test fire at SpaceX launch pad at CCAFS this morning," the Brevard County Emergency Operations Center said.

source: http://www.upi.com/Top_News/US/2016/09/01/SpaceX-Falcon-9-explodes-in-catastrophic-abort-on-Florida-launch-pad/4371472736796/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/02/2016 05:50 pm
I don't know where this "abort" theory comes from, but it's not NSF or SpaceX.  I've read every word published by spacex and every word of the NSF threads and I didn't see anything similar until AncientU's post.  I suspect you guys are getting unsourced speculation from less-credible sites and then getting it mixed up in your minds as something real.

I think it comes from the Brevard County Emergency Operations Center. I didn't take it too literally, though it's possible that they detected something was going south a few seconds before the fireball and attempted to abort.

Quote
"There is NO threat to general public from catastrophic abort during static test fire at SpaceX launch pad at CCAFS this morning," the Brevard County Emergency Operations Center said.

source: http://www.upi.com/Top_News/US/2016/09/01/SpaceX-Falcon-9-explodes-in-catastrophic-abort-on-Florida-launch-pad/4371472736796/

'Catastrophic abort' is another way of saying 'rapid unscheduled disassembly': it's someone watching their words rather than saying 'it exploded.'.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/02/2016 05:57 pm
I don't know where this "abort" theory comes from, but it's not NSF or SpaceX.  I've read every word published by spacex and every word of the NSF threads and I didn't see anything similar until AncientU's post.  I suspect you guys are getting unsourced speculation from less-credible sites and then getting it mixed up in your minds as something real.

I think it comes from the Brevard County Emergency Operations Center. I didn't take it too literally, though it's possible that they detected something was going south a few seconds before the fireball and attempted to abort.

Quote
"There is NO threat to general public from catastrophic abort during static test fire at SpaceX launch pad at CCAFS this morning," the Brevard County Emergency Operations Center said.

source: http://www.upi.com/Top_News/US/2016/09/01/SpaceX-Falcon-9-explodes-in-catastrophic-abort-on-Florida-launch-pad/4371472736796/

I doubt Brevard County Emergency Operations has any information we don't have about details about what was going on just before the boom.  It's not relevant to them at all.  From their perspective, it's enough to know that a big boom happened during a static fire attempt.  They might have details about how much fuel and oxidizer were on board, because that's relevant.  Whether SpaceX was trying to fix some problem they detected?  Not relevant.  Not something to be shared with Brevard County.

Whoever is writing press releases for Brevard County likely just didn't think the exact phrasing mattered or had only a vague idea what actually happened.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MP99 on 09/02/2016 06:11 pm


Every time we have one on these events my thoughts are always the same. Better now than when we have a crew on board. Pick up the pieces, find the cause(s), fix them and get flying again. Best of luck to the teams at SpaceX.

Yes, and this is exactly why I think it's so much more dangerous to put a crew on SLS than a crew on either commercial crew vehicle.  Atlas V and Falcon 9 have lots of non-crew launches to find problems before crews are put on them.  SLS does not.

Complete nonsense.  Please show me where launching fewer times has resulted in greater chance of loss of vehicle?
The fact that most LOVs are early in the program seems pretty obvious. The Shuttle was an exception.

Wasn't first flight a fairly close shave due to underestimating the SRB overpressure?

Cheers, Martin
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/02/2016 06:19 pm
I see lots of mentions of "No pressure in the RP-1 umbilicals, RP-1 was already fully loaded". How do we know this is the case? SpaceX only said it was "during propellant loading", no mention of whether said "propellant" was the fuel or the oxidizer.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: hartspace on 09/02/2016 06:20 pm
Here is the best image I could find showing the 2nd stage umbilicals (circled), clamps, etc.  I hope this helps with the discussion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/02/2016 06:28 pm
I see lots of mentions of "No pressure in the RP-1 umbilicals, RP-1 was already fully loaded". How do we know this is the case? SpaceX only said it was "during propellant loading", no mention of whether said "propellant" was the fuel or the oxidizer.

Musk said "during propellant loading" and then the next sentence was "Originated around upper stage oxygen tank."  I think people have been putting those two together, along with the knowledge that RP-1 is loaded first and LOX loading only starts after RP-1 loading is finished, to draw the conclusion that it happened after RP-1 was fully loaded.

So, while no official source actually said it, it seems very likely that RP-1 was fully loaded at the time.

Even without any statement from SpaceX, it just doesn't make sense that you could get a big boom if there wasn't any LOX on the rocket, and we know RP-1 is finished loading before LOX loading starts, so it stands to reason that RP-1 loading was finished at the time of the boom.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MP99 on 09/02/2016 06:31 pm
If this does turn out to be the second stage again then I think that SpaceX has to ask some very difficult management questions.
I doubt that working on the  second stage is 'sexy'. The 'sexy' things to work on will be the reusable first stage, Falcon Heavy core, Raptor and BFS/BFR.

A small increase to the performance of the second stage, including a reduction of second stage dry mass, frees up a disproportionate amount of mass (EG for recovery) in the first stage.

So, some types of improvements to the second stage would be very welcome.

Cheers, Martin
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 06:31 pm
Reading thru this thread... there seems to be some agreement that the T/E has a cradle/bumper like part that lines up with the dividing bulkhead on the inside of the S2 tank...
That makes sense as a place to place a fixed load point...

Question...
Suppose there is an major electrical fault that results in an arc being struck at that point...
Why... is not the question... the question is the outcome...

Put another way...
What happens if you (in effect) TIG weld (w/no shielding gas) on the outside of a thin wall aluminum tank full of ice cold LOX under pressure...

My guess is the AL will burn thru in a flash and then it all goes south from there...

On edit... add pic with highlighted cradle part
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 06:32 pm
When you're dealing with a high oxygen content you don't even need a spark. Scuba tanks need oxygen safe cleaning for even mild oxygen enrichment as oil/grease can combust spontaneously, as can other materials.

I'm certain these risks are fully understood by all concerned, and that all materials including seals and lubricants are oxygen safe, but this is a "don't trust anything" investigation, and an ignition source not being present doesn't rule anything out.

      I was wondering if some grease or cleaning solvent residue on the umbilical connectors could have caused the explosion.  That was my first theory.  Could have also been a natural contaminant that was wind borne into the proximity of the venting O2?  Unlike pad 39 A, pad 40 is both closer to sea level and has more potential sources of natural contaminants in closer proximity.  With a pure O2 environment, many different substances can and will spontaneously combust.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/02/2016 06:35 pm
Can't RP1 dispersed in air explode like that, if in the form of a fine mist?

Also, do they finish loading RP-1 on both stages before putting LOX on either?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 06:38 pm
Can't RP1 dispersed in air explode like that, if in the form of a fine mist?

Also, do they finish loading RP-1 on both stages before putting LOX on either?

Flour or even saw dust can combust like that, given enough dispersal and oxygen.

It's what is called a Fuel / Air Explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 06:38 pm
This thread is long but not unreadable. I would ask posters to at least try to skim through most of it, since we're getting several repetitions of the same theories/images interleaved with actual new discussion or data, and people treating them as new, going over the same points over and over.

Having said that...

How about this.

Let's say there was a small, maybe pin-hole leak in the RP-1 fueling umbilical, and during fueling it sprayed the top of the strongback with RP1.  Kerosene evaporates slowly so it can hang around for a while.

It looks like there's a GOX stream near the strongback.  See the arrow below.  That spot seems to correspond to the initiation location as determined by the diffraction spikes.

What if that GOX stream and the hypothetical slowly-evaporating RP-1 from the hypothetical leak finally got to sufficient concentrations, just due to just the right (or wrong) wind conditions that it could ignite into a fuel-air explosion given an ignition source?  That small-ish explosion ruptures the tanks, and everything falls, burning on the way down.

How could that pinhole leak, even if all the RP1 froze on the rocket's skin (which would bring it's flash point down, but anyway), be able to blow a hole in the wall from spontaneous ignition in open-air conditions, in 30 ms?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 09/02/2016 06:41 pm
I don't know where this "abort" theory comes from, but it's not NSF or SpaceX.  I've read every word published by spacex and every word of the NSF threads and I didn't see anything similar until AncientU's post.  I suspect you guys are getting unsourced speculation from less-credible sites and then getting it mixed up in your minds as something real.

I think it comes from the Brevard County Emergency Operations Center. I didn't take it too literally, though it's possible that they detected something was going south a few seconds before the fireball and attempted to abort.

Quote
"There is NO threat to general public from catastrophic abort during static test fire at SpaceX launch pad at CCAFS this morning," the Brevard County Emergency Operations Center said.

source: http://www.upi.com/Top_News/US/2016/09/01/SpaceX-Falcon-9-explodes-in-catastrophic-abort-on-Florida-launch-pad/4371472736796/

Thanks.
Shouldn't have posted the words without finding and supplying the quote source.
Only knew that I'd read them... how does one make up such phrasing?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/02/2016 06:43 pm
What I mean is, can we be sure that there was already LOX on board, and therefore, no pressure in the RP-1 umbilical?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 06:43 pm
Reading thru this thread... there seems to be some agreement that the T/E has a cradle/bumper like part that lines up with the dividing bulkhead on the inside of the S2 tank...
That makes sense as a place to place a fixed load point...


There is rubber bumpers there and on the clamps.  No metal to metal contact
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 06:47 pm
What I mean is, can we be sure that there was already LOX on board, and therefore, no pressure in the RP-1 umbilical?

Yes, look at the video of the vehicle. There is vapor coming off the whole length of it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlmanes52 on 09/02/2016 06:48 pm
Looking hard at the pictures posted by hartspace and John Allen, it appears that the cradle just under the payload fairing is actuated by a hydralic cylinder with 2 black curved lines (hoses?) going back into the interior of the strongback.  The anomaly happened close to the time the cradle should have been retracted.  Is it possible that a ruptured hydralic line sent a mist of fluid into the oxygen rich environment below?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 06:48 pm
Reading thru this thread... there seems to be some agreement that the T/E has a cradle/bumper like part that lines up with the dividing bulkhead on the inside of the S2 tank...
That makes sense as a place to place a fixed load point...


There is rubber bumpers there and on the clamps.  No metal to metal contact

Yes... but what if they are aged and damp with dew from the rapidly chilling S2...
Along with a MAJOR electrical fault in the GSE/Rocket resulting in a voltage potential at that point of near contact....
Question...
Suppose there is an major electrical fault that results in an arc being struck at that point...
Why... is not the question... the question is the outcome...

Put another way...
What happens if you (in effect) TIG weld (w/no shielding gas) on the outside of a thin wall aluminum tank full of ice cold LOX under pressure...

My guess is the AL will burn thru in a flash and then it all goes south from there...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/02/2016 06:50 pm
Can't RP1 dispersed in air explode like that, if in the form of a fine mist?

Also, do they finish loading RP-1 on both stages before putting LOX on either?

Flour or even saw dust can combust like that, given enough dispersal and oxygen.

It's what is called a Fuel / Air Explosion.

That's true, I just can't see how you'd get a fuel/air explosion in this case.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 06:51 pm

Suppose there is an major electrical fault that results in an arc being struck at that point...
Why... is not the question... the question is the outcome...

There are not those types of voltages and amperages used on the vehicle.   Voltage is around 28
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/02/2016 06:52 pm
How about this.

Let's say there was a small, maybe pin-hole leak in the RP-1 fueling umbilical, and during fueling it sprayed the top of the strongback with RP1.  Kerosene evaporates slowly so it can hang around for a while.

It looks like there's a GOX stream near the strongback.  See the arrow below.  That spot seems to correspond to the initiation location as determined by the diffraction spikes.

What if that GOX stream and the hypothetical slowly-evaporating RP-1 from the hypothetical leak finally got to sufficient concentrations, just due to just the right (or wrong) wind conditions that it could ignite into a fuel-air explosion given an ignition source?  That small-ish explosion ruptures the tanks, and everything falls, burning on the way down.

How could that pinhole leak, even if all the RP1 froze on the rocket's skin (which would bring it's flash point down, but anyway), be able to blow a hole in the wall from spontaneous ignition in open-air conditions, in 30 ms?

The idea is that there's a cloud of kerosene vapor in the air outside the rocket body from evaporating RP1 on the strongback, that cloud gets ignited in the presence of extra gaseous oxygen, and the shock wave from that detonation ruptures the nearby tank.

From the video, it looks to me like the time between the flash and the time I see an enlarging fireball from the prop is about four frames, or 67ms.  Since such a shock wave can move at several times the speed of sound and the speed of sound would allow it to move 23 meters in that time, it seems like there is sufficient time for that shock wave to rupture the tank and disperse the prop inside.

Obviously, there is insufficient evidence to support this sequence of events, so it's just a conjecture.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 06:52 pm

Yes... but what if they are aged and damp with dew from the rapidly chilling S2...
Along with a MAJOR electrical fault in the GSE/Rocket resulting in a voltage potential at that point of near contact....

Aged from what?  They are fairly new.  And what voltage potential? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/02/2016 06:52 pm
This thread is long but not unreadable. I would ask posters to at least try to skim through most of it, since we're getting several repetitions of the same theories/images interleaved with actual new discussion or data, and people treating them as new, going over the same points over and over.

Your message was reply #920 in this thread.  Asking people to read, or even skim, 920 posts is asking a lot.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mmeijeri on 09/02/2016 06:53 pm
Is a COPV bursting and damaging the common bulkhead still a possible scenario?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/02/2016 06:54 pm
Reading thru this thread... there seems to be some agreement that the T/E has a cradle/bumper like part that lines up with the dividing bulkhead on the inside of the S2 tank...
That makes sense as a place to place a fixed load point...

Question...
Suppose there is an major electrical fault that results in an arc being struck at that point...
Why... is not the question... the question is the outcome...

Put another way...
What happens if you (in effect) TIG weld (w/no shielding gas) on the outside of a thin wall aluminum tank full of ice cold LOX under pressure...

My guess is the AL will burn thru in a flash and then it all goes south from there...

Everyone seems to be ignoring the Very audible  *Ploink* 3-4 sec prior to the detonation. This is the LOX tank failing, (mechanism irrelevant at this point), a large Qty of LOX will then be filling the stage and boiling off.

 2 sec prior to detonation crinkling noise is heard, this is the straining of the stage bulkhead to contain the rapidly expanding LOX now GOX.

deformation of the stage causes the Power/Data umbilical to fail/partially detach causing a super-concentrated LOX stream at the failure point and detached power cable arcs... game over!

The Power/Data umbilical is normally turned off and Falcon is on internal power when this detaches at launch. The umbilical was still live when the failed LOX dome ruptured.

This could have been the source of the report of an attempted abort. Spx personnel heard/saw indications of LOX tank failure and just did not have time to shut off the power.

My guess is that this WAS the actual cause of the CRS-7 failure... not the strut. CRS-7 sensors only detected and "acoustic signature" (no actual proof other than post fail analysis of struts). SPX telemetry sensors Triangulated source puts the acoustic signature "in the vicinity" of the COPV HPHe tanks.

The "Acoustic signature"  *Ploink* still could have been the failure of the FSW seam of the LOX tank dome and then the RUD in flight.

Need analysis of affects of Deep-CryoLOX on FSW Joints of S2. thermal Cycle them and Xray looking for micro-fractures.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 06:55 pm

Yes... but what if they are aged and damp with dew from the rapidly chilling S2...
Along with a MAJOR electrical fault in the GSE/Rocket resulting in a voltage potential at that point of near contact....

Aged from what?  They are fairly new.  And what voltage potential?

460 volt from faulty GSE on the ground somewhere...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 06:59 pm
Everyone seems to be ignoring the Very audible  *Ploink* 3-4 sec prior to the detonation. This is the LOX tank failing, (mechanism irrelevant at this point), a large Qty of LOX will then be filling the stage and boiling off.

Do you not realize the distance that camera was at the time? Are you seriously implying that a "straining" bulkhead could be heard from 4 kilometers away???
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: 39B on 09/02/2016 06:59 pm
When you're dealing with a high oxygen content you don't even need a spark. Scuba tanks need oxygen safe cleaning for even mild oxygen enrichment as oil/grease can combust spontaneously, as can other materials.

I'm certain these risks are fully understood by all concerned, and that all materials including seals and lubricants are oxygen safe, but this is a "don't trust anything" investigation, and an ignition source not being present doesn't rule anything out.

      I was wondering if some grease or cleaning solvent residue on the umbilical connectors could have caused the explosion.  That was my first theory.  Could have also been a natural contaminant that was wind borne into the proximity of the venting O2?  Unlike pad 39 A, pad 40 is both closer to sea level and has more potential sources of natural contaminants in closer proximity.  With a pure O2 environment, many different substances can and will spontaneously combust.



At this stage, there's not too much that can be said. Presuming LOX or GOX was where it did not belong, in the concentrations it belongs in, a bird will do just fine for "natural contaminant." But we don't even know that much, so we'll just sit tight and let the people who work on these things, work on these things. I'm sure we'll have our answer, and I'm also sure that most of us will be proven wrong in the end. And that's ok. That's as it should be.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 07:02 pm
Is a COPV bursting and damaging the common bulkhead still a possible scenario?

Don't really think so.

     Having seen a number of internal explosions from rockets and aircraft in videos, that looks more like an external explosion to start with.  Can't be certain until we see video from some other angles.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 07:05 pm
Everyone seems to be ignoring the Very audible  *Ploink* 3-4 sec prior to the detonation. This is the LOX tank failing, (mechanism irrelevant at this point), a large Qty of LOX will then be filling the stage and boiling off.

Do you not realize the distance that camera was at the time? Are you seriously implying that a "straining" bulkhead could be heard from 4 kilometers away???

Over both flat land and calm water, small noises can travel a VERY long distance and still be heard.  In fact, sometimes there acoustic mirages that have sound traveling for way farther than 4 kilometers.  And some of these are normal conversations.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 07:12 pm

The idea is that there's a cloud of kerosene vapor in the air outside the rocket body from evaporating RP1 on the strongback, that cloud gets ignited in the presence of extra gaseous oxygen, and the shock wave from that detonation ruptures the nearby tank.

From the video, it looks to me like the time between the flash and the time I see an enlarging fireball from the prop is about four frames, or 67ms.  Since such a shock wave can move at several times the speed of sound and the speed of sound would allow it to move 23 meters in that time, it seems like there is sufficient time for that shock wave to rupture the tank and disperse the prop inside.

Obviously, there is insufficient evidence to support this sequence of events, so it's just a conjecture.

The wind was blowing toward the offending side of the rocket through the T/E. Any "cloud" would either be dispersed or deposited on the skin. I think already in the first frame you can see the LOX cloud shooting out, but it's irrelevant if we consider the hypothetical leaked kerosene to be so close to the stage.

Now, I have no idea of the properties of a thin layer of aerosolized or frozen kerosene in a 100% oxygen environment, so I cannot authoritatively show it wouldn't have enough energy to breach the stage so fast - but RP1 is not antimatter ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/02/2016 07:14 pm
Occam's razor says that the noises are more likely to originate within the junkyard in which the videographer was located.  This was discussed upthread.

Please don't post your personal theories multiple times.  We saw them the first time.  If you didn't get a response it's because we didn't think it credible, or interesting, it sufficiently different from the last person who posted that theory.

One theory post per person, please.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 07:16 pm
Question; can anyone get any video of this explosion from some other angles?  It'd help a lot if so.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 07:17 pm
This thread is long but not unreadable. I would ask posters to at least try to skim through most of it, since we're getting several repetitions of the same theories/images interleaved with actual new discussion or data, and people treating them as new, going over the same points over and over.

Your message was reply #920 in this thread.  Asking people to read, or even skim, 920 posts is asking a lot.


Nit: accident discussion starts at #130... but 790 are still quite a lot, I agree :)

However, with just 100-200 you'd get a good idea of the main ideas that were discussed previously and thoroughly shown to be off-basis or taken to a more complex level. Not to mention those 790 posts would be less than half if people had done that retroactively.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/02/2016 07:18 pm
Occam's razor says that the noises are more likely to originate within the junkyard in which the videographer was located.  This was discussed upthread.

Please don't post your personal theories multiple times.  We've saw them the first time.  If you didn't get a response it's because we didn't think it credible.

One theory post per person, please.

Several different people have mentioned the possible "precursor" noises, including me. Wolfram66 may have missed those earlier posts. I think you're seeing multiple different people noticing those noises and commenting on them individually.

Evidently he didn't see mine and others' posts on the subject from yesterday. This is a long thread now and not everyone has read every post.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 07:18 pm
This thread is long but not unreadable. I would ask posters to at least try to skim through most of it, since we're getting several repetitions of the same theories/images interleaved with actual new discussion or data, and people treating them as new, going over the same points over and over.

Your message was reply #920 in this thread.  Asking people to read, or even skim, 920 posts is asking a lot.

So, they need to read it to catch up. 
It even adding more from us to put up with the repeated theories
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 07:20 pm

Yes... but what if they are aged and damp with dew from the rapidly chilling S2...
Along with a MAJOR electrical fault in the GSE/Rocket resulting in a voltage potential at that point of near contact....

Aged from what?  They are fairly new.  And what voltage potential?

460 volt from faulty GSE on the ground somewhere...

What GSE?. It wouldn't be on the erector
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 07:21 pm
Two things bother me greatly.

1.  The onset speed of the detonation.
2.  The trajectory of that "thingee" that flies over the plume apparently from the strongback.


I've looked closely at that "thingee" flying straight up from the strongback, stepping forwards and backwards in the video fame by frame several times. One thing I noticed is that if you assume that it originated at an elevation at or above where the explosion seems to be centered, and if you try to visually extrapolate the reverse-trajectory while stepping the video backwards, it seems like that part must have been launched a few frames after the initial explosion began (i.e. running backwards it seems it would reach it's expected starting point before the shrinking fireball disappears).  That might indicate that it was launched from some part on the strongback due to pressure buildup from the original explosion coming from a point on the rocket to the left and possibly a bit below.

Of course my technique is very inaccurate and I could be wrong about the timing of the trajectory but that's what it looks like to me.

If you make the following assumption, do you come to the same conclusion?

1.  The vertical component is < 50% of the total velocity
2.  The horizontal component towards the camera and left is > 50% of the total velocity.

Yes, whether or not I'm right or wrong, I don't see how the horizontal component matters at all.

OK, I've looked at the thingee the same way you did, frame by frame.

I formally disagree with you.  Forgive me?   :)

The thingee is visible in Frame 4, where Frame 1 is the 1st frame of the explosion.

It's exiting at a higher speed than the fireball which suggests it had a very energetic kick in the pants more so than the tank rupture explosion could provide.  The more conventional explosion doesn't catch up with it until 2 seconds after it started its journey.

To me this suggests there are two events.  The first occurs in frame 1 and is over by frame 3.  The 2nd begins not later than Frame 3 and looks to me like the tank rupture event as evidenced by obscuring uncombusted clouds, presumably of LOX and RP-1, clearly visible by frame 4 forward.

The thingee is well on it's way before the rupture event destroys everything else.

For reference I used Frame by Frame for YouTube for Chrome, which is a free addon if you have Chrome.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 07:25 pm

Yes... but what if they are aged and damp with dew from the rapidly chilling S2...
Along with a MAJOR electrical fault in the GSE/Rocket resulting in a voltage potential at that point of near contact....

Aged from what?  They are fairly new.  And what voltage potential?

460 volt from faulty GSE on the ground somewhere...

What GSE?. It wouldn't be on the erector
In the pump house (or whatever it's called)...
My guess is 3 phase 480v pumps with Freq drives used to pump RP-1/LOX from tanks to the pad...
If they use something besides explosion proof off the shelf stuff... then correctly me please...

My points was not to argue the source of the voltage issue causing the arc...
My point was... IF an arc struck at that point of near contact... what would happen...
Since unshielded (by gas) AL usually vaporizes and burns in such a situation...
Aided by the escaping LOX liguid... poof then unzip...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 07:25 pm

Everyone seems to be ignoring the Very audible  *Ploink* 3-4 sec prior to the detonation. This is the LOX tank failing, (mechanism irrelevant at this point), a large Qty of LOX will then be filling the stage and boiling off.


What everyone seems to be ignoring about the "plonk" is the fact it is preceded by a creaking metallic noise just before, to be followed by several thrashing noises afterwards, and even what sounds like somebody stepping in gravel. Additionally, all these sounds appear much sharper than the explosion noises.

Is it more likely some freak sound mirage is making us privy of the last few seconds of internal failures before the boom, to then vanish away precisely at the same moment the explosion sound hits the mic, to never come back... or that somebody is leaving what he's doing and moving toward the camera to check if it's working just after seeing the explosion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 07:26 pm

In the pump house (or whatever it's called)... 3 phase 480v pumps used to pump fluids from tanks to the pad...

That is not on the erector.  It would be isolated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 07:30 pm

It's exiting at a higher speed than the fireball which suggests it had a very energetic kick in the pants more so than the tank rupture explosion could provide.  The more conventional explosion doesn't catch up with it until 2 seconds after it started its journey.


You do realize an expanding cloud of gas has a much different drag coefficient than a twisted piece of metal?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zach Swena on 09/02/2016 07:33 pm
Looking hard at the pictures posted by hartspace and John Allen, it appears that the cradle just under the payload fairing is actuated by a hydralic cylinder with 2 black curved lines (hoses?) going back into the interior of the strongback.  The anomaly happened close to the time the cradle should have been retracted.  Is it possible that a ruptured hydralic line sent a mist of fluid into the oxygen rich environment below?

Has this been discussed yet?  I would assume they would use something other then the normal flammable hydraulic oil for something that close to oxygen venting.  Hydraulic leaks are an easy way to get atomized hydrocarbons distributed in an area.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 07:42 pm

In the pump house (or whatever it's called)... 3 phase 480v pumps used to pump fluids from tanks to the pad...

That is not on the erector.  It would be isolated.

It should be electrically isolated... yes... but what if there is a fault in the equipment Jim...
Reposting my later edit to above post...
In the pump house (or whatever it's called)...
My guess is 3 phase 480v pumps with Freq drives used to pump RP-1/LOX from tanks to the pad...
If they use something besides explosion proof off the shelf stuff... then correctly me please...

My points was not to argue the source of the voltage issue causing the arc...
My point was... IF an arc struck at that point of near contact... what would happen...
Since unshielded (by gas) AL usually vaporizes and burns in such a situation...
Aided by the escaping LOX liguid... poof then unzip...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 07:45 pm
and the rubber pads are worn too?
But anyways, there isn't going to be that kind of voltage on the erector.  The pumps are hundreds of feet away from the launch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/02/2016 07:50 pm

In the pump house (or whatever it's called)... 3 phase 480v pumps used to pump fluids from tanks to the pad...

That is not on the erector.  It would be isolated.

It should be electrically isolated... yes... but what if there is a fault in the equipment Jim...
Reposting my later edit to above post...
In the pump house (or whatever it's called)...
My guess is 3 phase 480v pumps with Freq drives used to pump RP-1/LOX from tanks to the pad...
If they use something besides explosion proof off the shelf stuff... then correctly me please...

My points was not to argue the source of the voltage issue causing the arc...
My point was... IF an arc struck at that point of near contact... what would happen...
Since unshielded (by gas) AL usually vaporizes and burns in such a situation...
Added by the escaping LOX liguid... poof then unzip...

and the rubber pads are worn?
In some way not able to withstand the electrical potential that exists (in error) across the joint... YES!!
But anyways, there isn't going to be that kind of voltage on the erector.  The pumps are hundreds of feet away from the launch.
But what if (for some reason) there was....  ;)

Lets agree it's far fetched and let it be... I just put out the idea... I'm done...  :P
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 07:50 pm

It's exiting at a higher speed than the fireball which suggests it had a very energetic kick in the pants more so than the tank rupture explosion could provide.  The more conventional explosion doesn't catch up with it until 2 seconds after it started its journey.


You do realize an expanding cloud of gas has a much different drag coefficient than a twisted piece of metal?

Yah, I took a physics class or two in my time.  I think what I'm trying to suggest is this.  If you mix the RP1 and LOX you obviously get a bang, but the mixing still takes a finite time.  The two tanks don't merge equally and then go boom, there has to be a burn front following the mixing front which to me is why it takes relatively long (seconds) for the 2nd stage to combust.  A perfect mix probably has a burn rate of 5,000 feet per second, more or less.  Frame 1 indicates a burn rate of between 2,000 and 5,000 feet per second, which is certainly enough to kick the thingee beyond the combustion front of the tank rupture.   Several points.

A well mixed cloud will burn at thousands of feet per second.

A poorly mixed cloud will meander as you suggest.

However, a tank rupture is too slow and in the wrong place to get the thingee moving.

To me, something other than tank rupture propels the thingee on its path and initiates the tank rupture.  The tank rupture event is too slow to propel the thingee.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 07:57 pm

In some way not able to withstand the electrical potential that exists (in error) across the joint... YES!!

Meh, no.  Too many failures required.  RP-1 availability, bad rubber, short
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: toddbronco2 on 09/02/2016 08:04 pm
The so-called "thingee" is probably one of the high pressure helium bottles liberated by the 2nd stage rupture.  There seem to be a bunch of "it bounced off of this thing" or "banked off of that thing" or "was a secondary explosion" type comments, but I think it's simpler than that; it's probably a high pressure helium tank that is still venting helium and therefore does NOT follow a parabolic trajectory.  I'm struck by the similarity between the the "thingee" flying clear of the fireball yesterday for this SpaceX failure and the helium tank skipping along the water immediately after the Sea Launch NSS8 Failure in 2007. 

I assume that there are multiple COPV helium bottles in the second stage, so that even if one failed, there would still be others left flying about.  But I don't know about the internals of the F9, so I defer to others.

For the Sea Launch failure, the high pressure helium bottle is barely visible in the youtube versions of the video, but shows up much better in some of the L2 content
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 08:07 pm

In some way not able to withstand the electrical potential that exists (in error) across the joint... YES!!

Meh, no.  Too many failures required.  RP-1 availability, bad rubber, short

Got a point Jim.

     Do you think that a metallic fracture of an umbilical connector could provide enough heat to cause a combustion event in the high O2 environment that would result?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 08:20 pm
The so-called "thingee" is probably one of the high pressure helium bottles liberated by the 2nd stage rupture.  There seem to be a bunch of "it bounced off of this thing" or "banked off of that thing" or "was a secondary explosion" type comments, but I think it's simpler than that; it's probably a high pressure helium tank that is still venting helium and therefore does NOT follow a parabolic trajectory.  I'm struck by the similarity between the the "thingee" flying clear of the fireball yesterday for this SpaceX failure and the helium tank skipping along the water immediately after the Sea Launch NSS8 Failure in 2007. 

I assume that there are multiple COPV helium bottles in the second stage, so that even if one failed, there would still be others left flying about.  But I don't know about the internals of the F9, so I defer to others.

For the Sea Launch failure, the high pressure helium bottle is barely visible in the youtube versions of the video, but shows up much better in some of the L2 content

I like the idea, but there are a few things that make me disagree.

1.  eeergo attempted to do a trajectory analysis, picture 1 below.  You can actually trace it back to frame 4 of the explosion.  It's not coming from the F9, and if it's a bounce obscured by the 1st three frames, it's an amazing bounce.

2.  It doesn't resemble a helium bottle, picture 2 below.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/02/2016 08:25 pm

In some way not able to withstand the electrical potential that exists (in error) across the joint... YES!!

Meh, no.  Too many failures required.  RP-1 availability, bad rubber, short

Got a point Jim.

     Do you think that a metallic fracture of an umbilical connector could provide enough heat to cause a combustion event in the high O2 environment that would result?

Wouldn't the rubber itself burn rather nicely, perhaps explosively, in a pure oxygen environment?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 08:27 pm

Yah, I took a physics class or two in my time.  I think what I'm trying to suggest is this.  If you mix the RP1 and LOX you obviously get a bang, but the mixing still takes a finite time.  The two tanks don't merge equally and then go boom, there has to be a burn front following the mixing front which to me is why it takes relatively long (seconds) for the 2nd stage to combust.  A perfect mix probably has a burn rate of 5,000 feet per second, more or less.  Frame 1 indicates a burn rate of between 2,000 and 5,000 feet per second, which is certainly enough to kick the thingee beyond the combustion front of the tank rupture.   Several points.

A well mixed cloud will burn at thousands of feet per second.

A poorly mixed cloud will meander as you suggest.

However, a tank rupture is too slow and in the wrong place to get the thingee moving.

To me, something other than tank rupture propels the thingee on its path and initiates the tank rupture.  The tank rupture event is too slow to propel the thingee.

What I mean is: suppose a tank breach released that piece, whatever it is, at the same initial velocity as the expanding gas front.

Until you get a good mixture of LOX+RP1 (note some areas of the initial deflagration never reach that condition), the unmixed propellant will be shot out with great momentum at t=0, but will rapidly be stopped by drag with air. Not so for the metal piece, whose drag coefficient will be much lower because of its much larger mass-to-area ratio.

Therefore, I see as perfectly reasonable both the expanding cloud and the metallic piece depart the failure point at the same time, with the same velocity, and after a few ms the latter overtakes the former.

Out of curiosity: what "primary event" are you suggesting imparted such a phenomenal force to the (large) piece, that you claim overshadows the powerful burst+explosion acceleration?


EDIT: Agreed about it being a largely non-propulsive (i.e. not a helium bottle) piece.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 08:28 pm
The so-called "thingee" is probably one of the high pressure helium bottles liberated by the 2nd stage rupture.  There seem to be a bunch of "it bounced off of this thing" or "banked off of that thing" or "was a secondary explosion" type comments, but I think it's simpler than that; it's probably a high pressure helium tank that is still venting helium and therefore does NOT follow a parabolic trajectory.  I'm struck by the similarity between the the "thingee" flying clear of the fireball yesterday for this SpaceX failure and the helium tank skipping along the water immediately after the Sea Launch NSS8 Failure in 2007. 

I assume that there are multiple COPV helium bottles in the second stage, so that even if one failed, there would still be others left flying about.  But I don't know about the internals of the F9, so I defer to others.

For the Sea Launch failure, the high pressure helium bottle is barely visible in the youtube versions of the video, but shows up much better in some of the L2 content

I like the idea, but there are a few things that make me disagree.

1.  eeergo attempted to do a trajectory analysis, picture 1 below.  You can actually trace it back to frame 4 of the explosion.  It's not coming from the F9, and if it's a bounce obscured by the 1st three frames, it's an amazing bounce.

2.  It doesn't resemble a helium bottle, picture 2 below.


This lines up with the idea that the explosion was more likely external.

     As the payload appears to have still been attached to the gantry for several seconds after the explosion, it seems that it was more likely that the tanks were ruptured by an external explosion, as an internal explosion would have lifted the payload off the gantry and further away from the launch vehicle.  An internal explosion would have acted as more like a cannon in this respect, than as a rupturing tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/02/2016 08:29 pm

In some way not able to withstand the electrical potential that exists (in error) across the joint... YES!!

Meh, no.  Too many failures required.  RP-1 availability, bad rubber, short

Got a point Jim.

     Do you think that a metallic fracture of an umbilical connector could provide enough heat to cause a combustion event in the high O2 environment that would result?

Wouldn't the rubber itself burn rather nicely, perhaps explosively, in a pure oxygen environment?

Unlikely, as they would have chosen a material that would be more fire resistant than standard rubber, to avoid this sort of accident.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/02/2016 08:30 pm
Occam's razor says that the noises are more likely to originate within the junkyard in which the videographer was located.  This was discussed upthread.

Please don't post your personal theories multiple times.  We saw them the first time.  If you didn't get a response it's because we didn't think it credible, or interesting, it sufficiently different from the last person who posted that theory.

One theory post per person, please.

ok, Mr Occam, there are NO extraneous noises from said junkyard the minute plus prior to the explosion other than birds and bugs.

was this camera manned at the time or remote operated? was said junkyard manned or occupied during this test? was the *Ploink* the camera operator standing up when he/she saw the flash?

Ask Mr Occam to discuss Correlation not being causation? It cuts both ways, just because there is a junkyard doesn't necessarily mean it is in use and occupied during a static test. unless JIM can verify it's occupancy.  some of us have jobs and can't be glued to NSF all day.  Thanks Kabloona!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 08:31 pm
My problem with your hinge idea is that it has to hinge somewhere on the cylinder of the rocket.  That's ok, but if you use your own trajectory plot, it has to hinge THROUGH the strongback at the beginning of the journey.  It's a nice concept, but the starting point of that fragment doesn't strike me as a hinge action from the skin of the stage.

Coming back to this, since you re-used the trajectory composite for the helium bottle comparison: I don't see why it'd hinge through the T/E? I actually favor the idea of piece coming from the S2 wall at ~45º from the line-of-sight from the camera to the stage - that, or being a T/E piece blown upward and toward the camera by the blast.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Exci on 09/02/2016 08:34 pm
It seems folks have been looking for a source of ignition.  If we're looking at a tank rupture, could the fresh aluminum along the failure (or small particles dislodged) heat up due to oxidation in a high pressure oxygen rich environment?  It doesn't have to heat up much to ignite the kerosene wafting by shortly thereafter.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sevenperforce on 09/02/2016 08:47 pm
The pad abort overlay video showing the pad abort test in comparison to the exploding Falcon was very good, I thought, and shows that Commercial Crew is as safe as it can be. I can see SpaceX reposting or recutting it to use as a demonstrator video.

Eventually they'll have exactly that, in the launch abort test, but until then it will help.

SpaceX has always been pretty good with PR. It will be helpful to them if they can quickly pinpoint the cause as originating outside the launch vehicle, even if it's a serious problem that they caused themselves. It also helps tremendously with manufacturing since there's no need for rebuilding current systems.

Several have pointed out that a common bulkhead failure and internal detonation would almost surely have sent the payload soaring. That's encouraging, though I'm not sure whether the attachments between the payload fairing to the T/E would have been weak enough to fail. The explosion certainly seems to have an external origin, and without ANY visual indication of a preignition tank rupture I can't imagine that would have happened. An external ignition of any sort of aerosolized fuel would certainly be enough to rupture the tanks from outside.

Would an internal rupture exposing unoxidized aluminum to liquid oxygen go hypergolic?

If the venting LOX was a major factor in this, what are the chances that they'll start adding negative-pressure vent hoses to collect LOX boiloff during propellant loading?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HighEnergy on 09/02/2016 08:49 pm
> AC
The line with the S curve is insulated for cryogenic supply, either LOX or chilled RP-1.  In other images, one of the large stage 1 umbilicals comes directly off of it.  Looks like it's part of the LOX supply, with the bigger diameter pipe to the left being for oxygen gas return.  The bigger pipe splits and also goes to a vent at the top of the strongback.

Large cryogenic supplies are typically a loop, because the pipe has to be chilled before liquid can flow through safely / reasonably.  Its chilled by first pumping cold gas, recirculating the gas through a return pipe to a refrigerator that drives the temperature lower over time.

There is pressurized fuel and oxidizer in the supply lines all the way through liftoff.

Goes without saying that we're all hoping for a safe return to flight as soon as possible.

I'll bet we see a big new claw at the top of the strongback.  Big enough to hold the payload. =/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/02/2016 08:51 pm
The so-called "thingee" is probably one of the high pressure helium bottles liberated by the 2nd stage rupture.  There seem to be a bunch of "it bounced off of this thing" or "banked off of that thing" or "was a secondary explosion" type comments, but I think it's simpler than that; it's probably a high pressure helium tank that is still venting helium and therefore does NOT follow a parabolic trajectory.  I'm struck by the similarity between the the "thingee" flying clear of the fireball yesterday for this SpaceX failure and the helium tank skipping along the water immediately after the Sea Launch NSS8 Failure in 2007. 

I assume that there are multiple COPV helium bottles in the second stage, so that even if one failed, there would still be others left flying about.  But I don't know about the internals of the F9, so I defer to others.

For the Sea Launch failure, the high pressure helium bottle is barely visible in the youtube versions of the video, but shows up much better in some of the L2 content

I like the idea, but there are a few things that make me disagree.

1.  eeergo attempted to do a trajectory analysis, picture 1 below.  You can actually trace it back to frame 4 of the explosion.  It's not coming from the F9, and if it's a bounce obscured by the 1st three frames, it's an amazing bounce.

2.  It doesn't resemble a helium bottle, picture 2 below.


This lines up with the idea that the explosion was more likely external.

     As the payload appears to have still been attached to the gantry for several seconds after the explosion, it seems that it was more likely that the tanks were ruptured by an external explosion, as an internal explosion would have lifted the payload off the gantry and further away from the launch vehicle.  An internal explosion would have acted as more like a cannon in this respect, than as a rupturing tank.

Elon described it as a fast fire, not an explosion (at least the initial bit)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/02/2016 08:51 pm
Blaming He bottle is so illogical that I do wonder, why people stick to that. If He botlle would have ruptured we would have seen:
1. Pressure vessel rupture with huge cloud of oxygen bursting out without any explosion
2. No detonation into a 30x80ft firebal in split second as oxygen does not combust in air
3. Later explosion may have happened bor different reasons, but not in such a way as in video

As of He bottle, considering the immense pressure it has in it (~3000psi), the rupture would have propelled the helium tank in front of any fire cloud. Instead, the object emerged from the firecloud.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/02/2016 08:55 pm

I'll bet we see a big new claw at the top of the strongback.  Big enough to hold the payload. =/

What good would that do?  If the rocket blows up underneath it, the resulting thermal and vibration environments would be so far out of spec that the payload couldn't be relied upon anyway.  Then you have to figure out how to get the stupid thing down anyway.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scylla on 09/02/2016 08:58 pm
For any interested, reddit has started an AMA with one of the firefighters that responded to SLC-40 yesterday.

https://www.reddit.com/r/spacex/comments/50v8ac/iama_firefighter_at_cape_canaveral_air_force/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/02/2016 08:59 pm
> AC
The line with the S curve is insulated for cryogenic supply, either LOX or chilled RP-1.  In other images, one of the large stage 1 umbilicals comes directly off of it.  Looks like it's part of the LOX supply, with the bigger diameter pipe to the left being for oxygen gas return.  The bigger pipe splits and also goes to a vent at the top of the strongback.

Large cryogenic supplies are typically a loop, because the pipe has to be chilled before liquid can flow through safely / reasonably.  Its chilled by first pumping cold gas, recirculating the gas through a return pipe to a refrigerator that drives the temperature lower over time.


*If* that is correct, it's potentially very significant. (There are comments upthread that the S-bend is part of an air-conditioning system).

The point on the strongback where the explosion started is within a section that can be extended if required to adapt the height of the strongback to suit F9 vehicles with different payloads (and therefore different heights).

If a LOX line runs through that area, it would also have to be adaptable to the different lengths, thus there will be either sliding joints or interchangeable sections - these would be potentially more at risk of leaks than a fixed section.

There was, I think, a suggestion somewhere that one of the refrigeration units for the LOX supply had partially failed during loading?

Putting two and two together and making seventeen, that could result in warming LOX within the system and higher pressures - which could cause all manner of problems, either inside the vehicle or by causing leaks within the strongback plumbing system.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/02/2016 09:05 pm
> AC
The line with the S curve is insulated for cryogenic supply, either LOX or chilled RP-1.  In other images, one of the large stage 1 umbilicals comes directly off of it.  Looks like it's part of the LOX supply, with the bigger diameter pipe to the left being for oxygen gas return.  The bigger pipe splits and also goes to a vent at the top of the strongback.

Large cryogenic supplies are typically a loop, because the pipe has to be chilled before liquid can flow through safely / reasonably.  Its chilled by first pumping cold gas, recirculating the gas through a return pipe to a refrigerator that drives the temperature lower over time.

There is pressurized fuel and oxidizer in the supply lines all the way through liftoff.

Goes without saying that we're all hoping for a safe return to flight as soon as possible.

I'll bet we see a big new claw at the top of the strongback.  Big enough to hold the payload. =/
I find this post from a new user (today, 2 posts) fairly interesting as it directly contradicts info from Jim and couple of others who claimed no pressure in fuel lines and AC for the piping.

HighEnergy, do you mind to share any credentials? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: manboy on 09/02/2016 09:08 pm
Late to the thread but this failure makes me wonder why not just test fire the rocket without the payload at an adjacent stand so that if it goes boom you don't lose the pad and payload? Also maybe pads should be made to survive better from pad explosions, i.e. place tanks behind concrete barriers.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/02/2016 09:11 pm
Late to the thread but this failure makes me wonder why not just test fire the rocket without the payload at an adjacent stand so that if it goes boom you don't lose the pad and payload?
Because static fire checks the pad as much as it checks the vehicle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 09:12 pm

Out of curiosity: what "primary event" are you suggesting imparted such a phenomenal force to the (large) piece, that you claim overshadows the powerful burst+explosion acceleration?


The primary event occurs during Frame 1 of the explosion video sequence.  From Frame 0 where everything is fine, Frame 1 shows a measurable pixel saturation region of roughly 35 feet horizontal and 85 feet vertical.  That's an explosion with a wave front between 2,000 and 5,000 feet per second, depending on when it started during the integration time of the CCD or whatever the camera used.  A fuel air explosive would go about 5,000 feet per second.  TNT would go about 19,000 feet per second.  That first frame shows an explosion propagating at 2 to 5 times the speed of sound.  That to me is the "primary" event.

After frame 1, the fireball growth is significantly slower, which by Frame 4 includes the tank rupture explosion, which piddles along at maybe 100-200 feet per second.  That's to me, the secondary event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: manboy on 09/02/2016 09:13 pm
Late to the thread but this failure makes me wonder why not just test fire the rocket without the payload at an adjacent stand so that if it goes boom you don't lose the pad and payload?
Because static fire checks the pad as much as it checks the vehicle?
Other rockets don't require them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Colodie on 09/02/2016 09:15 pm
Late to the thread but this failure makes me wonder why not just test fire the rocket without the payload at an adjacent stand so that if it goes boom you don't lose the pad and payload?

Sure, but counterargument would be that, while yes, spaceflight is hard, it's been about 57 years since a rocket was lost on the ground in the US.  Is it worth the time and money to change procedures to prevent something that is very very rarely a problem?

"Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics who keeps a respected catalog of space activities, said he believes the last time such a mishap occurred at Cape Canaveral on an orbital-class rocket before liftoff was in 1959, when an Atlas-Able booster exploded during a static fire test."

https://spaceflightnow.com/2016/09/01/spacex-rocket-and-israeli-satellite-destroyed-in-launch-pad-explosion/space
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 09:21 pm
My problem with your hinge idea is that it has to hinge somewhere on the cylinder of the rocket.  That's ok, but if you use your own trajectory plot, it has to hinge THROUGH the strongback at the beginning of the journey.  It's a nice concept, but the starting point of that fragment doesn't strike me as a hinge action from the skin of the stage.

Coming back to this, since you re-used the trajectory composite for the helium bottle comparison: I don't see why it'd hinge through the T/E? I actually favor the idea of piece coming from the S2 wall at ~45º from the line-of-sight from the camera to the stage - that, or being a T/E piece blown upward and toward the camera by the blast.

I think the only way to resolve our difference is via SKYPE or something.  :)  I see that piece going vertical in Frame 4.  For it to hinge, it has to shoot to the right at some grotesque speed and then hinge up and left at some lower speed.  Kinda like the Dallas magic bullet.  Possible, but hard to explain off hand.

If the explosion starts in the tower and it's a piece of the tower getting blow up and left, it doesn't require hinging.

Also, if you look at the geometry, it's non-symmetric, appears to have a hole or divot, and might be a closed cylinder.  So the magic bullet not only changes the trajectory it blasts it from an aluminum tank wall into a doughnut.

Please read this as an attempt at gallows humor.  I don't know what really happened, but much as you're skeptical of some of my ideas, I'm a bit skeptical of this one from you.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/02/2016 09:21 pm
Some thoughts:

- the initial event seems to have had the majority of the force acting along the horizontal plane. It seems to have effectively acted as a cleaver to the payload / fairing. This seems very inconsistent with an internal LOX/RP-1 failure.

- very doubtful event was caused by leaking spacecraft prop. If it had been then there should have been combustion within the fairing as well.

- I don't recall exact prop pressures at flight pressure, but I believe it's relatively low - in the realm of LP rather than HP. The He tanks are HP, but not the prop tanks

- You DO need a source of ignition. For those talking about scuba tanks with a high O2 concentration contacting a fuel source such as skin oil or grease, you still need an ignition source. Standard scuba tank valves, when opened quickly, can release gas fast enough to cause adiabatic heating - there's your ignition source (I am pretty well versed in this as Dive Safety Officer, mixed gas diver, and rebreather diver).

- based on previous statement, an O2 GSE valve could have malfunctioned and created the ignition. This may explain the apparent location of the initial event and possibly the horizontal energy release. However, not sure where the fuel source came from in this scenario.

- the timing of the countdown, in conjunction with the position of the strong back at time of event is curious. I think there's perhaps some merit to the abort theory - perhaps this happened during an abort safeing operation, which is something that happens less frequently during normal static fires / launches. I wonder if a less often used  O2 valve was used for abort ops. This is a path less tested / utilized and therefore more prone to unpredictable behavior.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 09:25 pm

Out of curiosity: what "primary event" are you suggesting imparted such a phenomenal force to the (large) piece, that you claim overshadows the powerful burst+explosion acceleration?


The primary event occurs during Frame 1 of the explosion video sequence.  From Frame 0 where everything is fine, Frame 1 shows a measurable pixel saturation region of roughly 35 feet horizontal and 85 feet vertical.  That's an explosion with a wave front between 2,000 and 5,000 feet per second, depending on when it started during the integration time of the CCD or whatever the camera used.  A fuel air explosive would go about 5,000 feet per second.  TNT would go about 19,000 feet per second.  That first frame shows an explosion propagating at 2 to 5 times the speed of sound.  That to me is the "primary" event.

After frame 1, the fireball growth is significantly slower, which by Frame 4 includes the tank rupture explosion, which piddles along at maybe 100-200 feet per second.  That's to me, the secondary event.

What would be the initial speed of a LOX front decompressing from structural failure at S2's pressures? Couldn't this front have started at 2000-5000 ft/s and slowed down to 1/10th of that, from the aforementioned air drag, until reaching the deflagration speed you point out? (Not rhetorical questions, I really couldn't say, but those would speak against an external powerful event)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 09:25 pm
> AC
1.  The line with the S curve is insulated for cryogenic supply, either LOX or chilled RP-1.  In other images, one of the large stage 1 umbilicals comes directly off of it.  Looks like it's part of the LOX supply, with the bigger diameter pipe to the left being for oxygen gas return.  The bigger pipe splits and also goes to a vent at the top of the strongback.

2.  Large cryogenic supplies are typically a loop, because the pipe has to be chilled before liquid can flow through safely / reasonably.  Its chilled by first pumping cold gas, recirculating the gas through a return pipe to a refrigerator that drives the temperature lower over time.

3.  There is pressurized fuel and oxidizer in the supply lines all the way through liftoff.


4. I'll bet we see a big new claw at the top of the strongback.  Big enough to hold the payload. =/


1 Wrong as explained before, it is insulated for cold air.  It is not for LOX or RP-1.  That is in the lower in the erector.

2.  No, they are a single pass.  The fluid (liquid and cold gas) are used to chill down the pipes and are vented through the vehicle.  There is no recirculation.

3.  no, the fluids are allowed to drain back.  They are not under pressure

4.  Why? there is no reason for that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: manboy on 09/02/2016 09:29 pm
Late to the thread but this failure makes me wonder why not just test fire the rocket without the payload at an adjacent stand so that if it goes boom you don't lose the pad and payload?

Sure, but counterargument would be that, while yes, spaceflight is hard, it's been about 57 years since a rocket was lost on the ground in the US.  Is it worth the time and money to change procedures to prevent something that is very very rarely a problem?

"Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics who keeps a respected catalog of space activities, said he believes the last time such a mishap occurred at Cape Canaveral on an orbital-class rocket before liftoff was in 1959, when an Atlas-Able booster exploded during a static fire test."

https://spaceflightnow.com/2016/09/01/spacex-rocket-and-israeli-satellite-destroyed-in-launch-pad-explosion/space
That's a good point. I know one of the Russian N1 rockets fell onto the pad but that was also a long time ago. And Antares failed shortly after take off.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/02/2016 09:29 pm
Chronology of the video:
Frame 1: fuel-air explosive type of energetic event
Frame 3: Cloud of unburned material becomes visible behind the initial fireball
Frame 10: Unknown object emerges from the top of the fireball (while being not the first debris flying around, this one is largest)
Frame 32-33: First stage RP-1 tank rupture.
Frame 118: Stage 1 LOX tank BLEVE?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 09:33 pm

I think the only way to resolve our difference is via SKYPE or something.  :)  I see that piece going vertical in Frame 4.  For it to hinge, it has to shoot to the right at some grotesque speed and then hinge up and left at some lower speed.  Kinda like the Dallas magic bullet.  Possible, but hard to explain off hand.

If the explosion starts in the tower and it's a piece of the tower getting blow up and left, it doesn't require hinging.

Also, if you look at the geometry, it's non-symmetric, appears to have a hole or divot, and might be a closed cylinder.  So the magic bullet not only changes the trajectory it blasts it from an aluminum tank wall into a doughnut.

Please read this as an attempt at gallows humor.  I don't know what really happened, but much as you're skeptical of some of my ideas, I'm a bit skeptical of this one from you.  :)

I agree this is getting too far from data and too much into imagining things, so I won't try to advance my theory anymore, since I know what really happened as much as you :)

In any case, it was a proposed release mechanism, but doesn't really shed more light into the actual cause of the explosion: at the time I posted it, I was just skeptical at the large amount of people convincing themselves the rocket design couldn't possibly be at fault, and engineering their failure analysis around that dogma, pointing instead toward "silly" and easily-solvable GSE problems -including assuring the explosion source HAD to come from outside.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Senex on 09/02/2016 09:34 pm
John,

With respect, unless I am very mistaken, the release of pressurized gas would result in adiabatic cooling, not heating.  Boyle's law, etc.  As the pressure of a mass of air is decreased, it cools.

Please let me know if I'm missing something.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/02/2016 09:36 pm
John,

With respect, unless I am very mistaken, the release of pressurized gas would result in adiabatic cooling, not heating.  Boyle's law, etc.  As the pressure of a mass of air is decreased, it cools.

Please let me know if I'm missing something.

Gas flows through plumbing.  As it is forced to change direction, pressure gradients are created.  While the bulk tank is cooling down, you will get hot spots in your plumbing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Llian Rhydderch on 09/02/2016 09:37 pm
Late to the thread but this failure makes me wonder why not just test fire the rocket without the payload at an adjacent stand so that if it goes boom you don't lose the pad and payload?
Because static fire checks the pad as much as it checks the vehicle?
Other rockets don't require them.

"Require" is sort of a un-useful statement.  Forget "require".  SpaceX doesn't do static fires because they are "required."

They do static fires because, considering the relevant tradeoffs, economic and technical, they believe it is better to do static fires at the launch site rather than not do them.

Life is the real world is always full of tradeoffs.  SpaceX makes those tradeoffs, and makes a choice.  They are  a private company afterall, one that does a few US government flights every year as well. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/02/2016 09:42 pm
Mod speaking: Theories are good, but let's do our best to do our homework before posting, 800 or so posts is a lot to skim but please do before you post your theory, thanks. And we really like people who link back instead of just saying "this was already debunked".. it's extra work to do but helps everyone else. Thanks!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 09:42 pm
Chronology of the video:
Frame 1: fuel-air explosive type of energetic event
Frame 3: Cloud of unburned material becomes visible behind the initial fireball
Frame 10: Unknown object emerges from the top of the fireball (while being not the first debris flying around, this one is largest)
Frame 32-33: First stage RP-1 tank rupture.
Frame 118: Stage 1 LOX tank BLEVE?

Minor correction, or perhaps major, a smaller object with a similar trajectory becomes visible in Frame 4, not Frame 10, and is obscured by Frame12.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/02/2016 09:46 pm
heres a close up from a picture posted previously. i highlighted the area above the umbilical.

looks like there is a line the runs up along the outside of the RP1 tank up to the base of the LOX tank.

there is some sort of enlargement of the encasement of this line as it reaches the LOX tank.
the line then continues up the side of the LOX tank. but cant really see much as it reaches the top of the second stage.

not exactly sure what is happening in this area but i think they could be suspect
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 09:47 pm

"Require" is sort of a un-useful statement.  Forget "require".  SpaceX doesn't do static fires because they are "required."

They do static fires because, considering the relevant tradeoffs, economic and technical, they believe it is better to do static fires at the launch site rather than not do them.

Life is the real world is always full of tradeoffs.  SpaceX makes those tradeoffs, and makes a choice.  They are  a private company afterall, one that does a few US government flights every year as well. 


First off, this has nothing to do with US government flights or that Spacex is private company.  There is no reason to wave that standard for this topic.

And the rest of the statement is wrong.  Spacex does static fires because they think they are "required" to provide added insurance.  They must think that their other processes  to ensure missions success are lacking.

But the debate is not whether or they should perform static fires.  The debate is whether the spacecraft should be mated during the test. And this event has shown that they chose the wrong tradeoff.  Risking a multi hundred million spacecraft to save a couple days is not smart.  There has been some hubris involved.  If they are using the static fire to make sure the vehicle is good, what do they do when they find something wrong?  Now they have to deal with the payload in addition to fixing the problem.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/02/2016 09:52 pm
John,

With respect, unless I am very mistaken, the release of pressurized gas would result in adiabatic cooling, not heating.  Boyle's law, etc.  As the pressure of a mass of air is decreased, it cools.

Please let me know if I'm missing something.
A picture (or video) is worth a thousand words, so I give you this...

https://m.youtube.com/watch?v=SaBghGKAOBo
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 09:54 pm
John,

With respect, unless I am very mistaken, the release of pressurized gas would result in adiabatic cooling, not heating.  Boyle's law, etc.  As the pressure of a mass of air is decreased, it cools.

Please let me know if I'm missing something.
A picture (or video) is worth a thousand words, so I give you this...


Does that happen at 30 psi or so?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/02/2016 09:57 pm
Static fires and WDR are for reducing schedule risk and are not for mission success.  Any problems found during them would be found during the tanking or engines start of any vehicle with holddown capability (all US liquid vehicles) during a regular countdown.  If there is a problem then time would be needed to fix the problem before trying to launch again.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 10:00 pm

What would be the initial speed of a LOX front decompressing from structural failure at S2's pressures? Couldn't this front have started at 2000-5000 ft/s and slowed down to 1/10th of that, from the aforementioned air drag, until reaching the deflagration speed you point out? (Not rhetorical questions, I really couldn't say, but those would speak against an external powerful event)

Oh great, an easy question.

No easy answers.

It has an expansion ratio of 1:861 (not densified) which means it wants to create lots of volume once it's boiled off, but how fast it goes from liquid to gas depends on a ton of other things.


I can picture developing a software simulation to give a range of answers your question inside of a week.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mtakala24 on 09/02/2016 10:10 pm
Has anyone estimated the diameter of the fireball? To put it in perspective.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/02/2016 10:17 pm
John,

With respect, unless I am very mistaken, the release of pressurized gas would result in adiabatic cooling, not heating.  Boyle's law, etc.  As the pressure of a mass of air is decreased, it cools.

Please let me know if I'm missing something.
A picture (or video) is worth a thousand words, so I give you this...


Does that happen at 30 psi or so?
No. Good point - and a probable answer to the flight pressurization level...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/02/2016 10:20 pm
There is an initial fiery explosion, we never see O2 or RP-1 that aren't already burning.
The origin point of the visible explosion is right in line with the common bulkhead.
Musk said that the problem "originated around the upper stage oxygen tank".
It happened late in the fuel loading process but before FTS was armed. Likely around the T-4:10 mark just before the strong arm would have started retracting. We know it was during fuel load because Musk said so. We know it was well into it because the stage had already iced up through the top off the O2 tanks.
There was nothing outside the rocket that was flammable enough to cause the concussive explosion we saw.
There was no Russian UFO bird.
The propellant loading lines were a couple meters from where the explosion appeared to originate.

To me, this all points to a pressure difference between the O2 tank and the RP-1 tank that caused a breach in the common bulkhead which lead to fuel mixing. The ignition source could be anything with that much movement going on. This all happened nearly instantaneously and the first evidence seen is the outer hull being breached horizontally at the line of the ruptured bulkhead.

If the O2 tank had an over pressure it seems likely it would have blown upward as well as outward, but we clearly saw outward first. Also, an overpressure in the O2 tank should have been relieved by venting which should have at least slowed it down and would probably have had other visual cues. That leads me to think it was an underpressure in the RP-1 tank. This could be caused by a single spurious valve opening. That could be GSE, but is likely the rocket.

I stated most of this a few hundred posts ago and very few faults were pointed out. What do you guys think after further analysis?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/02/2016 10:25 pm

What would be the initial speed of a LOX front decompressing from structural failure at S2's pressures? Couldn't this front have started at 2000-5000 ft/s and slowed down to 1/10th of that, from the aforementioned air drag, until reaching the deflagration speed you point out? (Not rhetorical questions, I really couldn't say, but those would speak against an external powerful event)

Oh great, an easy question.

No easy answers.

It has an expansion ratio of 1:861 (not densified) which means it wants to create lots of volume once it's boiled off, but how fast it goes from liquid to gas depends on a ton of other things.

I can picture developing a software simulation to give a range of answers your question inside of a week.

That would be a major piece of work, I can't envision me asking that from you :) but it would certainly provide closure to the question. However, a rushing liquid expanding to ~1000x its compressed volume (10x linear dimension, one of the largest expansion ratios for any substance) is clear to pack quite a punch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/02/2016 10:31 pm

What would be the initial speed of a LOX front decompressing from structural failure at S2's pressures? Couldn't this front have started at 2000-5000 ft/s and slowed down to 1/10th of that, from the aforementioned air drag, until reaching the deflagration speed you point out? (Not rhetorical questions, I really couldn't say, but those would speak against an external powerful event)

Oh great, an easy question.

No easy answers.

It has an expansion ratio of 1:861 (not densified) which means it wants to create lots of volume once it's boiled off, but how fast it goes from liquid to gas depends on a ton of other things.


I can picture developing a software simulation to give a range of answers your question inside of a week.

The LOX is only at ~30 psi and is about as dense as water. There is absolutely no way it's moving at 1,000's of feet per second as a liquid, or vaporizing in anywhere near 1 frame worth of time, under that little pressure. If the tank burst, it would look more like a water tower splitting in half, showering all over the place. Not exploding 50 feet in 30 milliseconds.

Edit: Just look look at the showering burning RP-1 as the booster tanks burst and fireball. We're talking about 10's of feet per second, not 1,000's.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 09/02/2016 10:54 pm

What would be the initial speed of a LOX front decompressing from structural failure at S2's pressures? Couldn't this front have started at 2000-5000 ft/s and slowed down to 1/10th of that, from the aforementioned air drag, until reaching the deflagration speed you point out? (Not rhetorical questions, I really couldn't say, but those would speak against an external powerful event)

Oh great, an easy question.

No easy answers.

It has an expansion ratio of 1:861 (not densified) which means it wants to create lots of volume once it's boiled off, but how fast it goes from liquid to gas depends on a ton of other things.


I can picture developing a software simulation to give a range of answers your question inside of a week.

Actually just one.  Assuming the Lox is sub-cooled (not boiling at one atmosphere of pressure), gas generation is a simple function of energy input.  213 kJ/kg.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: llanitedave on 09/02/2016 10:55 pm
Occam's razor says that the noises are more likely to originate within the junkyard in which the videographer was located.  This was discussed upthread.

Please don't post your personal theories multiple times.  We saw them the first time.  If you didn't get a response it's because we didn't think it credible, or interesting, it sufficiently different from the last person who posted that theory.

One theory post per person, please.

ok, Mr Occam, there are NO extraneous noises from said junkyard the minute plus prior to the explosion other than birds and bugs.

was this camera manned at the time or remote operated? was said junkyard manned or occupied during this test? was the *Ploink* the camera operator standing up when he/she saw the flash?

Ask Mr Occam to discuss Correlation not being causation? It cuts both ways, just because there is a junkyard doesn't necessarily mean it is in use and occupied during a static test. unless JIM can verify it's occupancy.  some of us have jobs and can't be glued to NSF all day.  Thanks Kabloona!

Empty junk yards when there's a breeze blowing can produce all kinds of weird noises.  Trust me.   I know this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/02/2016 11:03 pm
... an overpressure in the O2 tank should have been relieved by venting which should have at least slowed it down and would probably have had other visual cues. That leads me to think it was an underpressure in the RP-1 tank. This could be caused by a single spurious valve opening. That could be GSE, but is likely the rocket.

How is the pressure equalized in the RP-1 tank if it has to be emptied before pressing for flight? If they just drain it, the evacuated fuel would pull a vacuum. Is that space filled with GHe from the flight press system?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/02/2016 11:06 pm
From SpaceX's website (http://www.spacex.com/news/2016/09/01/anomaly-updates)
Quote
September 2, 6:45pm EDT

SpaceX has begun the careful and deliberate process of understanding the causes and fixes for yesterday's incident.  We will continue to provide regular updates on our progress and findings, to the fullest extent we can share publicly.

We deeply regret the loss of AMOS-6, and safely and reliably returning to flight to meet the demands of our customers is our chief priority.  SpaceX's business is robust, with approximately 70 missions on our manifest worth over $10 billion.  In the aftermath of yesterday's events, we are grateful for the continued support and unwavering confidence that our commercial customers as well as NASA and the United States Air Force have placed in us.

Overview of the incident:

- Yesterday, at SpaceX's Launch Complex 40 at Cape Canaveral Air Force Station, an anomaly took place about eight minutes in advance of a scheduled test firing of a Falcon 9 rocket.

- The anomaly on the pad resulted in the loss of the vehicle.

- This was part of a standard pre-launch static fire to demonstrate the health of the vehicle prior to an eventual launch.

- At the time of the loss, the launch vehicle was vertical and in the process of being fueled for the test.  At this time, the data indicates the anomaly originated around the upper stage liquid oxygen tank.  Per standard operating procedure, all personnel were clear of the pad.  There were no injuries.

To identify the root cause of the anomaly, SpaceX began its investigation immediately after the loss, consistent with accident investigation plans prepared for such a contingency.  These plans include the preservation of all possible evidence and the assembly of an Accident Investigation Team, with oversight by the Federal Aviation Administration and participation by NASA, the United States Air Force and other industry experts.  We are currently in the early process of reviewing approximately 3000 channels of telemetry and video data covering a time period of just 35-55 milliseconds.

As for the Launch Pad itself, our teams are now investigating the status of SLC-40.  The pad clearly incurred damage, but the scope has yet to be fully determined.  We will share more data as it becomes available.  SpaceX currently operates 3 launch pads – 2 in Florida and 1 in California at Vandenberg Air Force Base.  SpaceX's other launch sites were not affected by yesterday's events.  Space Launch Complex 4E at Vandenberg Air Force Base is in the final stages of an operational upgrade and Launch Complex 39A at Kennedy Space Center remains on schedule to be operational in November.  Both pads are capable of supporting Falcon 9 and Falcon Heavy launches.  We are confident the two launch pads can support our return to flight and fulfill our upcoming manifest needs.

Again, our number one priority is to safely and reliably return to flight for our customers, as well as to take all the necessary steps to ensure the highest possible levels of safety for future crewed missions with the Falcon 9. We will carefully and thoroughly investigate and address this issue.

"We are confident the two launch pads can support our return to flight and fulfill our upcoming manifest needs."

Seems fairly clear they are going to use LC39A more than recent plans suggest.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/02/2016 11:10 pm
Empty junk yards when there's a breeze blowing can produce all kinds of weird noises.  Trust me.   I know this.
Additionally, people near the camera who see a very large explosion that might be uncomfortably close may well bump into things while deciding what to do before the blast/noise/fragments arrive.

I'm a little surprised we didn't hear any swearing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: catdlr on 09/02/2016 11:13 pm
So according to the above notice, the event occurred around T minus 8 minutes.  These processes would be occurring around that time on the pre-launch check list:

T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/02/2016 11:22 pm
So according to the above notice, the event occurred around T minus 8 minutes.  These processes would be occurring around that time on the pre-launch check list:

T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power

This article  (http://spaceflight101.com/falcon-9-jcsat-16/falcon-9-completes-static-fire-ahead-of-next-commercial-spacex-launch/)on the previous static fire mentioned:
Quote
It is also understood that the Static Fire was used to evaluate new techniques for launch window management which had become a challenge when Falcon 9 FT was introduced, given the strong desire to avoid the sub-cooled Liquid Oxygen to warm up during holds in the count.

A brief window for holding exists in the final countdown minutes prior to engine chilldown, but SpaceX was aiming to expand this capability to take advantage of longer windows such as JCSat’s two-hour launch slot.
so I wouldn't be surprised if this wasn't the exact sequence/timing they followed during this static fire..
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ulm_atms on 09/02/2016 11:30 pm
Looking hard at the pictures posted by hartspace and John Allen, it appears that the cradle just under the payload fairing is actuated by a hydralic cylinder with 2 black curved lines (hoses?) going back into the interior of the strongback.  The anomaly happened close to the time the cradle should have been retracted.  Is it possible that a ruptured hydralic line sent a mist of fluid into the oxygen rich environment below?

I have seen no one reply to this but this seems just as possible.

We are all going TEA/B...Spacecraft BiProp...RP-1!! but there are other, known flammable materials up there and hydraulic fluid is quite flammable.  I have personally seen a pinhole in a hydraulic line when i was doing some major yard work with a excavator.  When the pump was running...it was a very, very fine mist because the pressures are quite high.  Add that mist to gas LOX floating around everywhere...it wouldn't take much to boom.

Since we know that the clamps were not retracted but the time of the boom (if it was after 4:10) was when we thought they should of been...what about this:

They went to open the clamps, the hydraulic pressure increased to open, the hose broke and and instead of the clamp moving, it didn't, but instead sprayed hydraulic fluid everywhere in a possible misting type way(cracked hose instead of a complete break).  Then a spark happened(doesn't take much with high enough O2 content...static is a pain!)...boom...and since it was right by the 2nd stage...breached the tanks...and well...the video shows the rest.

I'm not just trying to find a way for it NOT to be the rocket...but from the video:

1.  Quick boom which appears close to the side of the rocket
2.  A nice slow (yes slow...there was no shock wave on this part from the video) expanding fireball from the top (you can actually see RP-1 falling almost straight down and very very dark burning(not much O2)  If this was energetic (mixing due to catastrophic bulkhead failure)...There would of been much more energy and the payload and fairing would not be sitting there.  Should of been blown right off.
3.  The whole rocket get coated in fire from the S2
4.  The 1st stage blows (the second expansion/shock wave you see once the entire rocket is engulfed in flames)
5.  The end.

My point is, this fits well with what we have seen and why we saw nothing weird with the vents and whatnot before the first point of explosion.  I just don't see the energy (payload is a giveaway to me) of a tank mixing type failure. 

my $.02


EDIT: Spelling
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 11:44 pm
Around T-8 mins, huh.

That would imply quite an incomplete LOX load, 1/4 to 1/5 of the tank might still have been empty and the tanks probably (?) weren't pressurized.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 09/02/2016 11:48 pm
Around T-8 mins, huh.

That would imply quite an incomplete LOX load, 1/4 to 1/5 of the tank might still have been empty and the tanks probably (?) weren't pressurized.

If practicing the hold, possibly little to no Lox was loaded.  Don't the Lox fills run with tank vented to atmosphere?
If so, tanks were probably depressurized -- helping to explain why an external blast could rip the upper stage apart to deliver the kero cascade.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/02/2016 11:50 pm
Quick question: is there a hydraulic system on S2? I know S1 has one, and it's an open system that uses RP-1 as the working fluid and drains into the main RP-1 tank. If S2 also has a similar setup, the S2 hydraulic tanks, or the umbilicals for filling them, would be good candidates.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/02/2016 11:52 pm

What would be the initial speed of a LOX front decompressing from structural failure at S2's pressures? Couldn't this front have started at 2000-5000 ft/s and slowed down to 1/10th of that, from the aforementioned air drag, until reaching the deflagration speed you point out? (Not rhetorical questions, I really couldn't say, but those would speak against an external powerful event)

Oh great, an easy question.

No easy answers.

It has an expansion ratio of 1:861 (not densified) which means it wants to create lots of volume once it's boiled off, but how fast it goes from liquid to gas depends on a ton of other things.


I can picture developing a software simulation to give a range of answers your question inside of a week.

Actually just one.  Assuming the Lox is sub-cooled (not boiling at one atmosphere of pressure), gas generation is a simple function of energy input.  213 kJ/kg.

Actually just not.

if you picture a spherical volume at a LOX temperature embedded in an ambient atmosphere, the ambient provides the energy input, but the boil-off reduces the ambient at a calculable rate, which reduces the energy input to that which is still liquid.  Your ambient atmosphere cools at a calculable rate, depending upon the boil off, and the boil off changes based on its interaction with the ambient.

I can picture a graduate thesis on this based on free-fall assumptions, but the answer will not be absolutely be 213 kj/kg.

It ain't an easy calculation even if you have that perfect sphere in a perfect ambient atmosphere where both initial temperatures are known and everything is in free-fall.

Gently, no, you're wrong.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Melanchthon on 09/02/2016 11:53 pm
Quick question: is there a hydraulic system on S2? I know S1 has one, and it's an open system that uses RP-1 as the working fluid and drains into the main RP-1 tank. If S2 also has a similar setup, the S2 hydraulic tanks, or the umbilicals for filling them, would be good candidates.

No. It's baseless speculation turned rumor. And it doesn't make sense in light of hydraulic fuel depletion of CRS-5.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/02/2016 11:53 pm
Around T-8 mins, huh.

That would imply quite an incomplete LOX load, 1/4 to 1/5 of the tank might still have been empty and the tanks probably (?) weren't pressurized.

If they weren't as full, and had gas above the liquid line, an in-tank explosion might not have created as much upward force as people are assuming it would...

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/02/2016 11:58 pm
If practicing the hold, possibly little to no Lox was loaded. 

Then they wouldn't have been at T-8 in the countdown as loading it takes around 30 min.

Don't the Lox fills run with tank vented to atmosphere?

Yes, but LOX becomes useless to them before that point. Subcooled LOX first heats up and expands in volume, reducing storable propellant mass inside the tank and becoming a performance liability.

Technically, I suppose they could have had a problem with a prolonged hold with a fully tanked vehicle (i.e. if the T-8 was after a test hold point) by being unable to drain the warming and expanding LOX. That would probably also end badly... I don't think they'd need to scrutinize the last milliseconds of telemetry for that, though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: eeergo on 09/03/2016 12:25 am
Around T-8 mins, huh.

That would imply quite an incomplete LOX load, 1/4 to 1/5 of the tank might still have been empty and the tanks probably (?) weren't pressurized.


Does S2 get loaded at the same time and flow as S1? In other words, where is subcooled LOX more critical, in the first or the second stage (or both equally)?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 12:27 am
Crank up the volume, the first sound could be the creak of metal bending. If that's the case, we might be hearing a strut bend and break, a COPV rupturing or helium hose popping, and the loud boom is the visible explosion.

Please... This is an incessant problem on the internet to attribute new failures to previous issues. In engineering its the exception rather than the rule that a new failure is the same failure as before. If something fails its almost certainly something else that failed unless your engineers have no clue what they're doing or root cause was not found. This failure is NOT going to be related to struts. Forget the struts exist. That's a solved problem. Different metal suppliers, different stronger design, additional struts, impossible to be the same problem.

I dunno, ever heard of Taurus, OCO, and Glory? Just saying...

I'm a bit late, but notably for Taurus they never found root cause, thus what I said.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:27 am
Around T-8 mins, huh.

That would imply quite an incomplete LOX load, 1/4 to 1/5 of the tank might still have been empty and the tanks probably (?) weren't pressurized.


The first stage was shedding vapor for most of the upper length.


I'm a bit late, but notably for Taurus they never found root cause, thus what I said.

Yes, they did.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/03/2016 12:37 am

Suppose there is an major electrical fault that results in an arc being struck at that point...
Why... is not the question... the question is the outcome...

There are not those types of voltages and amperages used on the vehicle.   Voltage is around 28

What about spacecraft battery charging.  Don't those go over a hundred?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 09/03/2016 12:44 am
JCM how do you classify this event?  A payload and rocket were lost at the launch pad but it wasn't a launch failure as it wasn't a launch attempt. Watching your website to see how you classify it as it is probably the launch log of choice on the web

I'm not JCM, but do my own tracking of launches.  Even though the payload was lost in a prelaunch exercise, it counts as a failure in my book.  You don't necessarily have to distinguish between a launch failure or a ground failure.  But it's a fact that the vehicle failed to get the payload to orbit.  It's not like the vehicle failed without the payload and you just get a new booster and have a successful mission a few months later.
Yeah, that's how I've got it in my SpaceX launches spreadsheet.
I don't think that's appropriate. It's not a launch failure, so it's not a launch failure. It was a testing failure, which led to destruction of the vehicle and also the payload because SpaceX shortsightedly (I almost want to say "foolishly") put it way too close.

There were other testing failures of stages, and those don't get counted as launch failures, either.


Or... consider this as a compromise: If SpaceX continues to mount payloads on the vehicle during static fires or wet dress rehearsals, then it's a failure. If they stop the practice, then it's a testing failure (and simultaneously a payload handling failure, like dropping the payload from a crane or a truck).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/03/2016 12:45 am
35 to 55 milliseconds of telemetry?

Something went boom.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:57 am

Suppose there is an major electrical fault that results in an arc being struck at that point...
Why... is not the question... the question is the outcome...

There are not those types of voltages and amperages used on the vehicle.   Voltage is around 28

What about spacecraft battery charging.  Don't those go over a hundred?

32 volts or so.  But they would not be charging batteries for this test.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 09/03/2016 01:05 am
...

But the debate is not whether or they should perform static fires.  The debate is whether the spacecraft should be mated during the test. And this event has shown that they chose the wrong tradeoff.  Risking a multi hundred million spacecraft to save a couple days is not smart....
This is pretty obvious, now. I don't think anyone should disagree with this.

You can MAYBE argue about whether or not SpaceX was being reasonable (though wrong) before, but now that we know for a fact that static fires can most certainly lead to loss of payload, no one can say it's a reasonable trade. In fact, with the benefit of hindsight (20/20, of course), it seems absurd that they would keep the payload attached for a static fire test when they have the option of not doing that with only a bit more work. People like Jim who said they were wrong to keep the payload on are now 100%, completely vindicated.

In fact, keeping the payload on is a poor idea from an agility/"fail-fast" perspective as well: you want to preserve the ability to make mistakes such that a failure here and there doesn't derail the whole company.

Imagine if this failure had occurred without the payload present. SpaceX could say: "We knew the LOx flowrate was higher than is usually done, but we took a calculated risk because we needed the speed. This is why we have a bunch of extra rockets waiting in the wings. We'll refly next month."

It really hurt them to fail in this way. In a way such that the bad outcome (loss of payload) really should've been foreseeable and preventable.

Not as bad as CRS7, but still.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 01:53 am

There is a principle in manufacturing that basically goes, the first 40 systems you build are all prototypes.  You tend to declare that you know how to do manufacturing after 10 or so, but you're wrong.  Dead wrong.

Things break.  If you can to that 40 mark, you actually have manufacturing processes that show promise, but anything less, it's all custom.

Elon fell for complacency again.

Software engineering is not the same as hardware engineering.

It's not that space is hard, or rockets are hard, it's that going from concept to production is hard, and if you assume you know what you're doing before you hit the numbers that translate into production, you get screwed. 


Not true.  They are all prototypes.  Rockets are constantly evolving.  There are subtle improvements, part changes due to obsolesce, etc.

Falcon 9 has gone through 2 upgrades that drastically changed the vehicle.

It IS that space is hard and rockets are hard because the environment is unforgiving.

Aircraft do not constantly evolve nor are they all prototypes.

A current model Cessna is not a prototype.  If it were, the FAA would only let it fly with an experimental license.

Elon want's to become a transportation company with a reliable reusable launcher.  Such a device is not a prototype.  It's a production model built on the same assembly line as the next 300 - 3,000 models.

As long as the answer is that it's a prototype, it's an at risk device of unknown reliability.

I contend that a prototype is a risk until you cease doing "upgrades" and build the same thing at least 40 times.

Otherwise, you're just waiting for the next RUD excuse.  "Thank you for our forgiving customers, we'll get you back to flight in 4-6 months... until we have the next RUD."  That's how you kill a company.

Space is forgiving if you have it nailed, otherwise, it nails you.  Elon hasn't learned that lesson yet.
SpaceX hasn't launched 40 Falcon 9s. Heck, this would've been only the 9th full thrust. They're still tweaking for fast fill of deeply subcooled propellants, a fact that probably contributed to the failure.

SpaceX could've stopped with the Falcon 9 v1.0, but then they couldn't have launched this payload at all.

They also could've tried to make a go out of Falcon 1 instead of pushing for COTS (and thus Falcon 9 and Dragon). They could've avoided reuse.

But they haven't. SpaceX wouldn't be where they are today without these significant improvements. They wouldn't be groundbreaking with reuse, they wouldn't be planning a trip to Mars in a couple years, and they sure as heck wouldn't be laying the groundwork for a space transportation architecture with the potential for actually colonizing Mars. Yes, they could've chosen the clear, safe course that leads ever downward into stagnation.

And a thing about Elon: he knows this is a risky path to take. He's well aware that it's risky and that SpaceX could fail.

God bless his dreams.

Manufacturability isn't a dream, it's an engineering issue.

From my point of view, his risky path is ready to kill SPACEX which I would be mortified to see.

However,  knowing the risks, without knowing the probabilities associated with risks is a path to failure.

IMHO, this RUD was avoidable.  Totally.  Whatever the cause.

That's what irritates me most.  He doesn't have to stop his dream or his testing or striving for the new-age of humanity.  That's what makes him great.

He could, however, recognize the engineering challenges which would let him succeed.

ANY manufacturing engineer could have predicted a failure soon, this one, or another, except those manufacturing engineers are 40-60 years old, and won't move to L.A. at any price.  His brilliant kids don't have the experience to know to ask what could go wrong.  They haven't failed before.

Elon has a cult more than a team, and he needs a team.

After this issue is resolved, he resets to zero, and my 40 count restarts.  If we're all lucky, he'll get it.  If we're not, we'll go another 20 +- launches before the next surprise.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 02:02 am
Using the term "commercial" rocket means you don't understand the business.   How the rocket is funded has no bearing on its probability of success.

Manufacturability has a role in a rocket's cost but not in its success rate
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 02:06 am
I have seen this discussed briefly, but any thoughts on it being the same issue as with the CRS-7 failure? A faulty steel strut, while certainly possible, just doesn't seem like the type of thing you could be 100% certain about. I am sure SpaceX ruled out all other possible alternatives that they could think of, but that doesn't mean that it is impossible for them to miss something. Maybe some kind of design flaw with the second stage that has been problematic on multiple occasions?

No. Just no. That failed specifically because of the high launch stresses and the tank pulling most on the strut at max-g. It's not going to have the same failure again. That kind of thing doesn't happen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 02:08 am
We just have shown two examples that same failures have occurred again
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 02:18 am
Not COPV or FTS.  Explosion is an external air burst.  No debris until much later, other than the big cap-like thing  that's shot straight up and tumbles.
Maybe a crack in the unconstrained S curve of this line (see attached) especially if that's the RP-1 line.  High pressure though the crack or pinhole would make an aerosol.  A line in that acoustic environment shouldn't have an unconstrained S.
 

ANOTHER reason you might be right.  The detonation profile appears to be taller than wider.  If RP-1 was becoming an aerosol, being heavier than air, the aerosol would be sinking over time, which would make a detonation cross section that's taller than wider.

People are forgetting that those pipes are A/C air pipes. You don't pump liquid through such a thick pipe. Can we forget about that S curve already? It's not related.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 02:21 am

I'm a bit late, but notably for Taurus they never found root cause, thus what I said.

Yes, they did.

They didn't find the root cause of the fairing separation failure before Glory launched. They found that the fairing didn't separate, but that's not a root cause. This is well known. If I'm wrong please point out information counter to that.

http://www.nasa.gov/pdf/728836main_T9_MIB_Public_Release_Summary.pdf

Quote from: NASA
Using this data, the MIB was able to analyze and determine that the proximate cause of
the mishap was the failure of the payload fairing system to separate. Detailed analysis
determined one of the side rails of the payload fairing system failed to fully fracture near
the fairing’s nose cap. However, no root cause for the fairing’s failure to separate was
able to be determined.

Quote from: NASA
The OCO T8 mishap investigation could not identify a root cause but did identify four potential intermediate causes:
1. Failure of the base ring frangible joint to completely fracture.
2. Failure of the electrical subsystem preventing ordnance from firing.
3. Failure of the fairing’s hot gas generator pneumatic system to pressurize resulting in a failure to push the fairing halves and/or side rails apart.
4. Snagging of the flexible confined detonating cord (FCDC) on one of the payload fairing side rail’s nut plate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/03/2016 02:24 am

I'm a bit late, but notably for Taurus they never found root cause, thus what I said.

Yes, they did.

They didn't find the root cause of the fairing separation failure before Glory launched. They found that the fairing didn't separate, but that's not a root cause. This is well known. If I'm wrong please point out information counter to that.

IIRC, they did eventually find that the material heat treat (or some other metallurigcal condition) on the frangible joint hadn't been properly controlled. But that was only after two fairing sep failures, by which time it was too late.

http://aviationweek.com/blog/taurus-xl-mishap-inquiry-could-affect-antares
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 02:25 am

I'm a bit late, but notably for Taurus they never found root cause, thus what I said.

Yes, they did.

They didn't find the root cause of the fairing separation failure before Glory launched. They found that the fairing didn't separate, but that's not a root cause. This is well known. If I'm wrong please point out information counter to that.

IIRC, they did eventually find that the material heat treat (or some other metallurigcal condition) on the frangible joint hadn't been properly controlled. But that was only after two fairing sep failures, by which time it was too late.

I edited my post while you were writing yours. "Eventually" finding is not what I'm referring to. They found no root cause before Glory launch occurred.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/03/2016 02:27 am
I've run the numbers on the Falcon 9's reliability both with and without this failure included, the results look like this:

Without the AMOS-6 failure:
(http://imgur.com/a/MaUXz)

With the AMOS-6 failure:
(http://imgur.com/a/E0GwR)

As you can see, it pretty significantly impacts the credible range of expected reliability, but the credible range is still pretty wide since the launch vehicle has limited history. I'm sticking with including AMOS-6 as a failure though. I've tried to keep the criteria that I use as simple as possible: Successful delivery of the primary payload. This means that the loss of the secondary payload on CRS-1 is not included as a failure, but AMOS-6 is. The payload was lost, and lost after SpaceX had custody of the satellite and had integrated it with the rocket. Should SpaceX lose another Falcon 9 during static fire but without the payload integrated, I will not include it as a failure based on the same methodology. Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

EDIT: imgur seems to be a bit finnicky with working today, in case the images don't load I'm attaching them to the post as well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ulm_atms on 09/03/2016 02:38 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris-A on 09/03/2016 02:46 am
snip

I believe you've not included the CRS-7 failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/03/2016 02:49 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

For the customer, the end result is the same.   ???
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 02:50 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

Yes, the pad is part of the system
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 02:52 am

As you can see, it pretty significantly impacts the credible range of expected reliability, but the credible range is still pretty wide since the launch vehicle has limited history. I'm sticking with including AMOS-6 as a failure though.


IMHO reliability refers to the system, not the device.  The F9 is the device.  The device didn't fail.  The system, in this case, appears to have failed.  If a crane had dropped the payload during integration, I would count that as a system failure, and would argue that it impacts the system reliability.  If I'm an insurance company with the payload on the hook, it doesn't matter why it broke, if it broke.  My rates go up accordingly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/03/2016 02:52 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

It would depend on the nature of the the root cause, but I'm still leaning heavily towards including it, simply because the payload was lost. If SpaceX had not integrated the satellite, that's another story. One of the biggest problems I had when putting together the numbers on rocket reliability statistics was methodology: What constitutes a failure. What if a rocket delivers a payload, but to not to the target orbit, impacting the lifespan of the satellite? That's happened to multiple LVs. What if a rocket delivers the payload successfully, but the payload is DOA? Suddenly what seems black and white gets muddled. The criteria I use is primary payload successfully delivered to the correct orbit. Obviously, there's some edge cases where that criteria ignores some near failures or partial failures, and I accept that as the trade off for producing a result that is useful and easily readable. Adding multiple ranges addressing full/partial/near failures would make the graphs harder to interpret, and also may give a false sense of precision that I'm trying to avoid. Ultimately, I feel that changing the criteria I use to ignore this incident would be editorializing the reliability estimate. Unless the investigation turns up something truly extraordinary (like intentional sabotage), I'm going to stand by this measure (at least as far as my reliability estimates go).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Melanchthon on 09/03/2016 02:52 am
Guys, you are getting bogged down in word definitions. Forget 'launch failure'. The customer doesn't care when and how the payload got destroyed, it's still a failure to provide services contracted for. Could as well have been dropped into the ocean by accident, the end result is the same.

A launch failure is just the typical way of losing payloads, doesn't mean it has to be the only one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vapour_nudge on 09/03/2016 02:54 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

Yes, the pad is part of the system

I suspect the Israelis would agree with you Jim
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/03/2016 02:56 am
snip

I believe you've not included the CRS-7 failure.

CRS-7 is included, CRS-1 is not, for a total of 27/28 without AMOS-6, 27/29 with AMOS-6. The rationale for this is in one of my previous posts. For what it's worth, if you tally CRS-1 as a failure as well, the reliability estimate would look like this:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Colodie on 09/03/2016 02:59 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

On that note, is there precedence for a loss of a rocket which is completely the fault of GSE?  I looked at Jonathan McDowell's list of rocket losses pre-launch he posted on Twitter, and he lists Atlas Able 9C (1959), R-16 (1960), Vostok (1980), VLS-1 (2003), and VS40M (2015).  I also found a few others, such as Kosmos-3M (1973).

I couldn't always find a lot of details, but they all seemed to have various causes aside from 'ground equipment'. Granted, there's not much detail, but there always seems to be other causes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 02:59 am
It isn't 27/29.  F9FT is not the same as the V1.1 or V1.0
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 03:03 am
Ultimately, I think ignoring the AMOS-6 incident would be discarding valid data about the reliability of the rocket.

The only thing I would say about this would be to wait until the cause of the accident was found.  If it happened to be something on the TEL that caused damage to the rocket and the subsequent LOV, that wouldn't be the rockets fault and should have no impact on the calculated "reliability".

What would you guys consider this as if the event that cause LOV wasn't rocket related?

On that note, is there precedence for a loss of a rocket which is completely the fault of GSE?  I looked at Jonathan McDowell's list of rocket losses pre-launch he posted on Twitter, and he lists Atlas Able 9C (1959), R-16 (1960), Vostok (1980), VLS-1 (2003), and VS40M (2015).  I also found a few others, such as Kosmos-3M (1973).

I couldn't always find a lot of details, but they all seemed to have various causes aside from 'ground equipment'. Granted, there's not much detail, but there always seems to be other causes.

Delta II had a crane fall on a spacecraft but it got repaired.

You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/03/2016 03:10 am
It isn't 27/29.  F9FT is not the same as the V1.1 or V1.0

I've mentioned this in the dedicated post I created for my rocket reliability estimates elsewhere. I completely agree, the FT is not the same as V1.0 or V1.1. That said, I include them because their reliability is still highly correlated with the FT, even if they are not fully equal. I also combine all variants of other rockets for the same reason. It's really a trade off of accuracy for precision. Without including prior versions, the Falcon 9 FT's estimate would cover a significantly larger range of potential true values of reliability, but would be more likely to include the true value within that range. Otherwise the credible interval becomes so large (and the precision so low) that it is essentially useless, even if it is technically more accurate. I've attached the estimate for the Falcon 9 FT by itself so that you can see the impact it has on the estimate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/03/2016 03:29 am
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did

Let's say "usually don't" not "don't".
https://www.youtube.com/watch?v=AUHLdJsoUOE
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rayleighscatter on 09/03/2016 04:02 am
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did

Let's say "usually don't" not "don't".
https://www.youtube.com/watch?v=AUHLdJsoUOE

The payload (TDRS-C) was installed 2 weeks after the FRF.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/03/2016 04:03 am
But there's definitely a spacecraft on the pad there ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/03/2016 04:06 am
It isn't 27/29.  F9FT is not the same as the V1.1 or V1.0

I've mentioned this in the dedicated post I created for my rocket reliability estimates elsewhere. I completely agree, the FT is not the same as V1.0 or V1.1. That said, I include it because their reliability is still highly correlated with the FT, even if they are not fully equal. It's really a trade off of accuracy for precision. Without including prior versions, the Falcon 9 FT's estimate would cover a significantly larger range of potential true values of reliability, but would be more likely to include the true value within that range. I also combine all variants of other rockets for the same reason. Otherwise the credible interval becomes so large (and the precision so low) that it is essentially useless, even if it is technically more accurate. I've attached the estimate for the Falcon 9 FT by itself so that you can see the impact it has on the estimate.
Would you also include Atlas III along with the Atlas V?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/03/2016 04:13 am
I'm sticking with including AMOS-6 as a failure though.
It is clearly a "failure", though not a "launch failure".   It falls into the same category as Thor 103, Atlas 9C/Able, the 3/18/80 pad explosion of Vostok-2M at Plestesk, and even Soyuz-U/Soyuz T-10-1.  Not to mention the first Falcon 1 flight article, which was destroyed during on-pad testing accidents prior to the first launch.  If you count F9-29 in the overall performance scheme, you also have to count the first Falcon 1 that never flew.  There was also at least one prior damaged or destroyed Falcon 9 stage if I recall correctly.

I consider Falcon 9 v1.2 at eight flights with no launch failures, but with a ninth vehicle and its payload destroyed and launch pad heavily damaged in a ground test accident. 

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/03/2016 04:36 am
Would you also include Atlas III along with the Atlas V?

Yes, because they share a good deal of components, including the upper stage and engine, their reliability should be highly correlated and so I include them as one launch system. That said, the Atlas III has very few launches compared to the Atlas V, and the Atlas V has a very, very good track record, so the difference is minimal.
Attached are some images showing the difference if you include Atlas 3 or not. Again, it's an accuracy vs precision tradeoff, but in that case it's not a significant difference.

It is clearly a "failure", though not a "launch failure"
...
I consider Falcon 9 v1.2 at eight flights with no launch failures, but with a ninth vehicle and its payload destroyed and launch pad heavily damaged in a ground test accident

That's a fair way of assessing it, and your launch reliability database is far and away the most thorough and detailed source on reliability there is. Since yours were based on launch failures, I agree that this shouldn't be tallied as one. My initial criteria for reliability differed slightly, since it was payload-delivery based. I feel that changing that criteria simply because the rocket failed before it was intended to launch would amount to editorializing my estimate. Nothing wrong with having multiple methodologies out there for assessing reliability, but each methodology should be internally consistent.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NaN on 09/03/2016 04:37 am
It isn't 27/29.  F9FT is not the same as the V1.1 or V1.0

I've mentioned this in the dedicated post I created for my rocket reliability estimates elsewhere. I completely agree, the FT is not the same as V1.0 or V1.1. That said, I include it because their reliability is still highly correlated with the FT, even if they are not fully equal. It's really a trade off of accuracy for precision. Without including prior versions, the Falcon 9 FT's estimate would cover a significantly larger range of potential true values of reliability, but would be more likely to include the true value within that range. I also combine all variants of other rockets for the same reason. Otherwise the credible interval becomes so large (and the precision so low) that it is essentially useless, even if it is technically more accurate. I've attached the estimate for the Falcon 9 FT by itself so that you can see the impact it has on the estimate.
Would you also include Atlas III along with the Atlas V?

This is not an exact science - if for example you started a new series every time they made a change to the rocket or GSE, you would throw away most of your data which was scant to start with.
A more impartial adjustment would be to weigh older launches less than recent ones via an exponential decay. This would count more recent events as more important in the reliability assessment, and make it less sensitive to including older variants. That would let us move on to arguing about decay rates instead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Patchouli on 09/03/2016 04:46 am
I'm sticking with including AMOS-6 as a failure though.
It is clearly a "failure", though not a "launch failure".   It falls into the same category as Thor 103, Atlas 9C/Able, the 3/18/80 pad explosion of Vostok-2M at Plestesk, and even Soyuz-U/Soyuz T-10-1.  Not to mention the first Falcon 1 flight article, which was destroyed during on-pad testing accidents prior to the first launch.  If you count F9-29 in the overall performance scheme, you also have to count the first Falcon 1 that never flew.  There was also at least one prior damaged or destroyed Falcon 9 stage if I recall correctly.

I consider Falcon 9 v1.2 at eight flights with no launch failures, but with a ninth vehicle and its payload destroyed and launch pad heavily damaged in a ground test accident. 

 - Ed Kyle


The failure does appear to have originated from the TE/strongback vs the LV.
I wonder if it may have been damaged during the last flight.

F9 v1.2 has more thrust then v1.1 and was the pad hardware change to deal with this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/03/2016 04:47 am
A more impartial adjustment would be to weigh older launches less than recent ones via an exponential decay. This would count more recent events as more important in the reliability assessment, and make it less sensitive to including older variants. That would let us move on to arguing about decay rates instead.

Someday I swear I'll get around to implementing this, but every time I think I've got enough free time to dig into building a model for it the time just disappears...
That said, I do evaluate the reliability with a bayesian prior based on global rocket reliability for active LV's, which has a similar effect--it tends to estimate rockets will revert to that mean until they have a substantial launch history. There is a way the models would differ slightly in the case of the Falcon 9, though: My current model leans towards higher reliability for the Falcon 9, since (for example), the Ariane 5 and Atlas V had failures early in their history followed by an extremely long sequence of successes. That's a fairly typical progression for most rockets, so it tweaks the estimate slightly assuming the Falcon 9 will follow that progression too. In contrast, a model weighting failures based on how recent they are would lean towards lower reliability, since both of Falcon 9's primary payload failures have been relatively recent.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/03/2016 05:00 am
In viewing this thread, I've seen many claims of sounds "before" the explosion being significant, and counterclaims that "it's local to the junkyard."

Elsewhere, I found this video that lines up those sounds with the events of the explosion very nicely, without any "gravel" noises before the explosion. I feel it might help the discussion.

https://www.youtube.com/embed/oT46cX_UH4I
(I do not know how to embed video)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TakeOff on 09/03/2016 05:11 am
Why did they fuel the upper stage before they test fired the first stage? It doesn't seem necessary, the small upper stage could be fueled rather quickly after the first stage has been tested. Seems as if it would've avoided this accident.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: catdlr on 09/03/2016 05:25 am
SpaceX to shift Florida launches to new pad after explosion

https://www.yahoo.com/news/spacex-shift-florida-launches-pad-explosion-003208139--finance.html?ref=gs

Quote
With its launch pad likely facing major repairs, SpaceX said it would use a second Florida site, called 39A, which is located a few miles north at NASA’s Kennedy Space Center and was used for space shuttle missions.

The pad is on schedule to be operational in November, SpaceX said. The company had planned to use the pad for the first time later this year for a test flight of its new Falcon Heavy rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: llanitedave on 09/03/2016 05:35 am

There is a principle in manufacturing that basically goes, the first 40 systems you build are all prototypes.  You tend to declare that you know how to do manufacturing after 10 or so, but you're wrong.  Dead wrong.

Things break.  If you can to that 40 mark, you actually have manufacturing processes that show promise, but anything less, it's all custom.

Elon fell for complacency again.

Software engineering is not the same as hardware engineering.

It's not that space is hard, or rockets are hard, it's that going from concept to production is hard, and if you assume you know what you're doing before you hit the numbers that translate into production, you get screwed. 


Not true.  They are all prototypes.  Rockets are constantly evolving.  There are subtle improvements, part changes due to obsolesce, etc.

Falcon 9 has gone through 2 upgrades that drastically changed the vehicle.

It IS that space is hard and rockets are hard because the environment is unforgiving.

Aircraft do not constantly evolve nor are they all prototypes.

A current model Cessna is not a prototype.  If it were, the FAA would only let it fly with an experimental license.

Elon want's to become a transportation company with a reliable reusable launcher.  Such a device is not a prototype.  It's a production model built on the same assembly line as the next 300 - 3,000 models.

As long as the answer is that it's a prototype, it's an at risk device of unknown reliability.

I contend that a prototype is a risk until you cease doing "upgrades" and build the same thing at least 40 times.

Otherwise, you're just waiting for the next RUD excuse.  "Thank you for our forgiving customers, we'll get you back to flight in 4-6 months... until we have the next RUD."  That's how you kill a company.

Space is forgiving if you have it nailed, otherwise, it nails you.  Elon hasn't learned that lesson yet.
SpaceX hasn't launched 40 Falcon 9s. Heck, this would've been only the 9th full thrust. They're still tweaking for fast fill of deeply subcooled propellants, a fact that probably contributed to the failure.

SpaceX could've stopped with the Falcon 9 v1.0, but then they couldn't have launched this payload at all.

They also could've tried to make a go out of Falcon 1 instead of pushing for COTS (and thus Falcon 9 and Dragon). They could've avoided reuse.

But they haven't. SpaceX wouldn't be where they are today without these significant improvements. They wouldn't be groundbreaking with reuse, they wouldn't be planning a trip to Mars in a couple years, and they sure as heck wouldn't be laying the groundwork for a space transportation architecture with the potential for actually colonizing Mars. Yes, they could've chosen the clear, safe course that leads ever downward into stagnation.

And a thing about Elon: he knows this is a risky path to take. He's well aware that it's risky and that SpaceX could fail.

God bless his dreams.

Manufacturability isn't a dream, it's an engineering issue.

From my point of view, his risky path is ready to kill SPACEX which I would be mortified to see.

However,  knowing the risks, without knowing the probabilities associated with risks is a path to failure.

IMHO, this RUD was avoidable.  Totally.  Whatever the cause.

That's what irritates me most.  He doesn't have to stop his dream or his testing or striving for the new-age of humanity.  That's what makes him great.

He could, however, recognize the engineering challenges which would let him succeed.

ANY manufacturing engineer could have predicted a failure soon, this one, or another, except those manufacturing engineers are 40-60 years old, and won't move to L.A. at any price.  His brilliant kids don't have the experience to know to ask what could go wrong.  They haven't failed before.

Elon has a cult more than a team, and he needs a team.

After this issue is resolved, he resets to zero, and my 40 count restarts.  If we're all lucky, he'll get it.  If we're not, we'll go another 20 +- launches before the next surprise.

Launching 40 test rockets without payloads would have killed the company a lot quicker.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elmar Moelzer on 09/03/2016 05:36 am
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did
Does anybody else do a static fire (which greatly reduces the launch risk) like SpaceX does?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: catdlr on 09/03/2016 05:37 am
Why SpaceX can weather its latest disaster

http://theweek.com/articles/646378/why-spacex-weather-latest-disaster

Quote
Given the huge amounts of money at stake in any given launch in the commercial satellite industry, customers place a high premium on both reliability and cheap launches. For the moment, and in the historical context of spaceflight, Thursday's explosion probably won't tarnish SpaceX on the reliability front enough to overcome its advantages on the efficiency front.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/03/2016 05:38 am
Some video of COPV failures. Attached is a paper on COPV failures. A possible, but I think very unlikely cause of a COPV failure is procedural error. If the cryo Helium is loaded before significant LOX loading, the Helium might heat up and over pressurise the tank, causing an explosion. Another possible cause is a tank defect. I would think SpaceX would know about these possible causes and have taken preventative measures, for example interlocks to prevent early cryo Helium loading and testing of the tanks before use. It will be interesting to find out what really caused this failure.

https://www.youtube.com/watch?v=5UdVnO10J3U
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/03/2016 05:51 am
Why did they fuel the upper stage before they test fired the first stage? It doesn't seem necessary, the small upper stage could be fueled rather quickly after the first stage has been tested. Seems as if it would've avoided this accident.

Mostly, I think it was for mass and vibration attenuation.  The empty tanks of the second stage would flex far more than full tanks and likely would have buckled.  They would also not likely been able to properly support the payload during the test.  The mass issue gives the rocket as a whole, a more realistic profile as a whole for the test. 

Although, to be honest, I'm surprised that for the test, they didn't use a mass simulator in place of the actual payload.

For a full on dry test, I could understand it, but for a full on engine test, that seems a bit odd.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 05:55 am
Occam's razor says that the noises are more likely to originate within the junkyard in which the videographer was located.  This was discussed upthread.

Please don't post your personal theories multiple times.  We saw them the first time.  If you didn't get a response it's because we didn't think it credible, or interesting, it sufficiently different from the last person who posted that theory.

One theory post per person, please.

ok, Mr Occam, there are NO extraneous noises from said junkyard the minute plus prior to the explosion other than birds and bugs.

was this camera manned at the time or remote operated? was said junkyard manned or occupied during this test? was the *Ploink* the camera operator standing up when he/she saw the flash?

Ask Mr Occam to discuss Correlation not being causation? It cuts both ways, just because there is a junkyard doesn't necessarily mean it is in use and occupied during a static test. unless JIM can verify it's occupancy.  some of us have jobs and can't be glued to NSF all day.  Thanks Kabloona!

Because it's simply not. Do you hear how muffled the explosions are for the rest of the video? That tells you that the higher pitched noises you're referring to won't propagate that distance. Also you can hear the junkyard noises at 4:17 and 4:20 as well. Also note how you can't hear the tremendous fire that is burning away at that distance when it would otherwise be making tons of noise. Additionally the air that day was extremely wet with a very high humidity which will also strongly dampen any sound. You can additionally hear that the sound comes from a different direction as noted by the stereo microphones on the camera. There's just too many reasons here to put any validity in your theory.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 05:59 am
> AC
The line with the S curve is insulated for cryogenic supply, either LOX or chilled RP-1.  In other images, one of the large stage 1 umbilicals comes directly off of it.  Looks like it's part of the LOX supply, with the bigger diameter pipe to the left being for oxygen gas return.  The bigger pipe splits and also goes to a vent at the top of the strongback.

Large cryogenic supplies are typically a loop, because the pipe has to be chilled before liquid can flow through safely / reasonably.  Its chilled by first pumping cold gas, recirculating the gas through a return pipe to a refrigerator that drives the temperature lower over time.

There is pressurized fuel and oxidizer in the supply lines all the way through liftoff.

Goes without saying that we're all hoping for a safe return to flight as soon as possible.

I'll bet we see a big new claw at the top of the strongback.  Big enough to hold the payload. =/

Payloads need a large supply of air conditioned for putting into the fairing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rayleighscatter on 09/03/2016 06:06 am
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did
Does anybody else do a static fire (which greatly reduces the launch risk) like SpaceX does?
There's certainly no consensus that static fires reduce risk. Some, in fact, believe it can hasten a failure that otherwise wouldn't have occurred.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 06:08 am

Out of curiosity: what "primary event" are you suggesting imparted such a phenomenal force to the (large) piece, that you claim overshadows the powerful burst+explosion acceleration?


The primary event occurs during Frame 1 of the explosion video sequence.  From Frame 0 where everything is fine, Frame 1 shows a measurable pixel saturation region of roughly 35 feet horizontal and 85 feet vertical.  That's an explosion with a wave front between 2,000 and 5,000 feet per second, depending on when it started during the integration time of the CCD or whatever the camera used.  A fuel air explosive would go about 5,000 feet per second.  TNT would go about 19,000 feet per second.  That first frame shows an explosion propagating at 2 to 5 times the speed of sound.  That to me is the "primary" event.

After frame 1, the fireball growth is significantly slower, which by Frame 4 includes the tank rupture explosion, which piddles along at maybe 100-200 feet per second.  That's to me, the secondary event.

Most of the saturated area is reflected light. There was a tremendously bright small event that caused everything around it to reflect all that light. You can see the velocity of the expansion cloud is much slower than that. You can also see several projectiles (I count 4) that lead the expansion cloud that likely originate from the explosion site. (2 pieces shoot downward, one shoots left but only appears for two frames and one shoots right. The two that shoot down are most visible.)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TakeOff on 09/03/2016 06:37 am
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did
Does anybody else do a static fire (which greatly reduces the launch risk) like SpaceX does?

Why did they fuel the upper stage before they test fired the first stage? It doesn't seem necessary, the small upper stage could be fueled rather quickly after the first stage has been tested. Seems as if it would've avoided this accident.

Mostly, I think it was for mass and vibration attenuation.  The empty tanks of the second stage would flex far more than full tanks and likely would have buckled.  They would also not likely been able to properly support the payload during the test.  The mass issue gives the rocket as a whole, a more realistic profile as a whole for the test. 

Although, to be honest, I'm surprised that for the test, they didn't use a mass simulator in place of the actual payload.

For a full on dry test, I could understand it, but for a full on engine test, that seems a bit odd.
Indeed. Testing with the payload mounted actually doubles part of the risk of losing the payload. It's not really a test anymore.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/03/2016 07:33 am
Some video of COPV failures. Attached is a paper on COPV failures. A possible, but I think very unlikely cause of a COPV failure is procedural error. If the cryo Helium is loaded before significant LOX loading, the Helium might heat up and over pressurise the tank, causing an explosion. Another possible cause is a tank defect. I would think SpaceX would know about these possible causes and have taken preventative measures, for example interlocks to prevent early cryo Helium loading and testing of the tanks before use. It will be interesting to find out what really caused this failure.

https://www.youtube.com/watch?v=5UdVnO10J3U

I've not changed my opinion that the COPVs are at the root of this as well as the in-flight and and original wet dress failures (see: https://www.nasaspaceflight.com/2014/05/spacex-targets-june-11-falcon-9-orbcomm/), but now additionally believe the failures may all be related to the tank's original design, and are possibly a CTE-related issue.  (Yes, this means I don't necessarily buy the SpaceX conclusion that the strut was the proximate cause of the in-flight breakup; I agree with NASA that other failure modes may have been given less than full consideration. This failure is eerily similar to the in-flight failure, even to the discussion of studying less than 100 ms of telemetry data around the event.)

What got me thinking was this recent (July 14, 2016) article says that the liners are aluminum, not stainless: http://www.waaytv.com/space_alabama/cimarron-composites-huntsville-s-lightweight-fuel-tank-experts/article_2f123dba-49e5-11e6-809e-07d4e6cc03db.html

To my mind, that is very risky practice when cryo submerged.  See: http://www.spaceflightinsider.com/organizations/space-exploration-technologies/2014-incident-may-provide-clue-to-cause-of-spacex-falcon-9-failure/  Based on the more recent story above, it also looks like SpaceX hasn't moved all COPV production in house as stated in this article.

Aluminum's CTE is grossly mismatched to carbon fiber composite.  It's a bad choice as a liner material submerged in LOX since the liner will pull away from the stiffer overwrap.  I've had discussions with this same vendor about procuring his bottles for other projects, but we have always baselined stainless liners as the material of choice.  Weight considerations may have driven SpaceX to use aluminum, but the savings are small at these minimum gauges, and I'd recommend going to stainless. 

Anyway, only my opinion as usual. Comments expressed are only as good as the input data, which is thinner than we'd like.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/03/2016 08:09 am
The failure does appear to have originated from the TE/strongback vs the LV.
I wonder if it may have been damaged during the last flight.

F9 v1.2 has more thrust then v1.1 and was the pad hardware change to deal with this?

The Pad 39a erector is a different design to that used at LC40 - it appears to have more sheeting either side of the latticework that would in theory shield the pipework etc..

It may just be a change that's required for FH or it may build on experience elsewhere. I don't think much can be inferred from it.

What gets built at LC40 to replace (/rebuild) the damaged erector will be the proof.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Davidgojr on 09/03/2016 09:55 am
Does anyone else notice the sounds in the video https://www.youtube.com/watch?v=_BgJEXQkjNQ at 1:16 and 1:19.   At a little past 1:16 there is an odd high pitched noise followed by a lower pitched noise at 1:19 that is reminiscent of metal bending.   These could be just local noises around where the camera was or more interesting if they did come from the rocket.

Sound from the first conflagration reaches the camera at 1:23.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/03/2016 10:17 am
Does anyone else notice the sounds in the video...

Yes, take some time to read the last 30+ pages of this thread and you'll find a spirited discussion of their possibly/probably/definitely (take your pick) unrelated origins in the "junkyard" where the video was reportedly filmed.

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576598#msg1576598
https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576680#msg1576680
https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576792#msg1576792
https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576930#msg1576930
https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576934#msg1576934
https://forum.nasaspaceflight.com/index.php?topic=30981.msg1577616#msg1577616
https://forum.nasaspaceflight.com/index.php?topic=30981.msg1577434#msg1577434
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:13 pm
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did

Let's say "usually don't" not "don't".


The space shuttle orbiter is part of a launch vehicle.  It contains the main propulsion system
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:17 pm

Yes, because they share a good deal of components, including the upper stage and engine, their reliability should be highly correlated and so I include them as one launch system. That said, the Atlas III has very few launches compared to the Atlas V, and the Atlas V has a very, very good track record, so the difference is minimal.


That is completely wrong.  The whole first stage structure and avionics is different.  The pad launchers are different.
Atlas III and Atlas V are as different as Thor Agena and Atlas Agena are different.

Move reliability discussion to another thread
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:21 pm
Why did they fuel the upper stage before they test fired the first stage? It doesn't seem necessary, the small upper stage could be fueled rather quickly after the first stage has been tested. Seems as if it would've avoided this accident.

Part of the test is tanking both stages and going through the standard countdown.  The vehicle never flies with the upper stage empty so firing the booster with it empty is an unknown and unflight like condition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:22 pm
You won't find a failure due to GSE because nobody puts the spacecraft at risk like Spacex did
Does anybody else do a static fire (which greatly reduces the launch risk) like SpaceX does?

Again, static fire does not reduce launch risk, it reduces schedule risk. 

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577595#msg1577595
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 12:23 pm

Out of curiosity: what "primary event" are you suggesting imparted such a phenomenal force to the (large) piece, that you claim overshadows the powerful burst+explosion acceleration?


The primary event occurs during Frame 1 of the explosion video sequence.  From Frame 0 where everything is fine, Frame 1 shows a measurable pixel saturation region of roughly 35 feet horizontal and 85 feet vertical.  That's an explosion with a wave front between 2,000 and 5,000 feet per second, depending on when it started during the integration time of the CCD or whatever the camera used.  A fuel air explosive would go about 5,000 feet per second.  TNT would go about 19,000 feet per second.  That first frame shows an explosion propagating at 2 to 5 times the speed of sound.  That to me is the "primary" event.

After frame 1, the fireball growth is significantly slower, which by Frame 4 includes the tank rupture explosion, which piddles along at maybe 100-200 feet per second.  That's to me, the secondary event.

Most of the saturated area is reflected light. There was a tremendously bright small event that caused everything around it to reflect all that light. You can see the velocity of the expansion cloud is much slower than that. You can also see several projectiles (I count 4) that lead the expansion cloud that likely originate from the explosion site. (2 pieces shoot downward, one shoots left but only appears for two frames and one shoots right. The two that shoot down are most visible.)

Wow!  you make me feel blind.  Totally missed the other fragments.  :)

Below are Frame 1 and Frame2 composited with the first fragment superimposed.  It vanishes by Frame3.

Linear trajectory assumption.

The black lines indicate the horizontal distance traveled if equal to the prior frame.

However, since there is no explosion in Frame0, the actual origin is somewhere to the right.

Whatever it is is moving an average of 1,000 feet per second.

The question would be, what's along the indicated red line?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Eerie on 09/03/2016 12:31 pm
I'm sorry if it was discussed already, but does anyone has any hypothesis in regard to the second explosion, the one at 3:42 in the video?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 12:33 pm
Does anyone else notice the sounds in the video <snip> at 1:16 and 1:19.   At a little past 1:16 there is an odd high pitched noise followed by a lower pitched noise at 1:19 that is reminiscent of metal bending.   These could be just local noises around where the camera was or more interesting if they did come from the rocket.

Sound from the first conflagration reaches the camera at 1:23.

Yes many many times. It's been shown that the location the video was taken from contains a bunk of metal scrap and what you're hearing is things rattling in the wind. Later in the video a little before 4:20 there are additional sounds of the same time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 12:36 pm
Most of the saturated area is reflected light. There was a tremendously bright small event that caused everything around it to reflect all that light. You can see the velocity of the expansion cloud is much slower than that. You can also see several projectiles (I count 4) that lead the expansion cloud that likely originate from the explosion site. (2 pieces shoot downward, one shoots left but only appears for two frames and one shoots right. The two that shoot down are most visible.)

Wow!  you make me feel blind.  Totally missed the other fragments.  :)

Below are Frame 1 and Frame2 composited with the first fragment superimposed.  It vanishes by Frame3.

Linear trajectory assumption.

The black lines indicate the horizontal distance traveled if equal to the prior frame.

However, since there is no explosion in Frame0, the actual origin is somewhere to the right.

Whatever it is is moving an average of 1,000 feet per second.

The question would be, what's along the indicated red line?

I can't understand your explanation and diagram. If you consider frame1 to be the first frame the explosion is visible, the fragment on the right is visible in frames 1,3,4,9,10,11,13,21 and possible a few others further down.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickl on 09/03/2016 12:37 pm
Does anyone else notice the sounds in the video

I haven't seen anyone mention it, but I can hear an intake of breath at the first appearance of the fireball.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 12:42 pm


Your explanation and diagram don't make sense to me.

OK, you see something in two frames at different locations.  You assume they are moving from an origin.

You connect the two points with a red line.  If there are no other factors, that line describes a possible trajectory of where the object was, or will be, in time.

You measure the horizontal distance between the two known object locations (black line on the right).  You duplicate it and place it an equal distance to the left, along the possible trajectory red line.

That gives you a first approximation of where that object was an equal time prior, provided the speed and trajectory do not change.

Where the bottom black line intersects the red trajectory line is a 1st approximation of where that part came from.

That might indicate where the initiating event occurred.

Hence the question, what's at the intersection of the bottom black line and the red line?  Whatever is there becomes suspect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 12:49 pm

The question would be, what's along the indicated red line?

Nothing that caused the incident.

Post the two separate frames
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 01:22 pm


Post the two separate frames
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/03/2016 01:31 pm
That could be something blasted from the back of the erector by the shockwave of the initial explosion.

It's bright, but that's likely to be just reflection of the explosion.

Jim - out of interest, do you know what is the white bit of equipment in the image attached?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/03/2016 01:36 pm
I'm sorry if it was discussed already, but does anyone has any hypothesis in regard to the second explosion, the one at 3:42 in the video?
I don't have the video handy, but my recollection is that the explosions are as follows:

1) initiating event
2) second stage lets go
3) first stage lets go
4) payload falls and explodes
5) ground support tanks (including multiple tanker cars) compromised and explode at various times afterward

EDIT: 3:46 appears to be the start of #5, and there are multiple secondary explosions as different parts of the GSE are compromised.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 01:39 pm
That could be something blasted from the back of the erector by the shockwave of the initial explosion.


For reference, it might be in the next frame too.  Under enhancement there might be something in the 3rd frame.  If so, its on the same trajectory line, but moved only 1/4 of the previous distance, and is dim.  It could also be a jpeg/mpeg artifact.  I'll post if I get confident that it's real.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/03/2016 01:44 pm

For reference, it might be in the next frame too.  Under enhancement there might be something in the 3rd frame.  If so, its on the same trajectory line, but moved only 1/4 of the previous distance, and is dim.  It could also be a jpeg/mpeg artifact.  I'll post if I get confident that it's real.

Pretty sure it is real - there are several such objects ejected in the early stage of the explosion in various directions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/03/2016 01:51 pm
There are a few problems with identifying what these objects are, no least that the video gives no idea of what their motion is like in the plane aligned with the view from the camera - i.e. you can't easily tell how much of their motion is towards (or away from) the camera.

There seems to be a (slight!) consensus that the initial explosion occurred outside the vehicle (whether of not caused by gas leaking from within), in which case some of the early material ejected will have been parts of the erector and associated equipment - and that makes identifying the cause of the explosion essentially impossible with just this one long-distance camera viewpoint.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 02:04 pm


Your explanation and diagram don't make sense to me.

OK, you see something in two frames at different locations.  You assume they are moving from an origin.

You connect the two points with a red line.  If there are no other factors, that line describes a possible trajectory of where the object was, or will be, in time.

You measure the horizontal distance between the two known object locations (black line on the right).  You duplicate it and place it an equal distance to the left, along the possible trajectory red line.

That gives you a first approximation of where that object was an equal time prior, provided the speed and trajectory do not change.

Where the bottom black line intersects the red trajectory line is a 1st approximation of where that part came from.

That might indicate where the initiating event occurred.

Hence the question, what's at the intersection of the bottom black line and the red line?  Whatever is there becomes suspect.

Yes but the black lines aren't needed. Just draw a straight line between the two points (and the following points). I don't see why you'd draw horizontal lines there.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 02:13 pm
There are a few problems with identifying what these objects are, no least that the video gives no idea of what their motion is like in the plane aligned with the view from the camera - i.e. you can't easily tell how much of their motion is towards (or away from) the camera.

There seems to be a (slight!) consensus that the initial explosion occurred outside the vehicle (whether of not caused by gas leaking from within), in which case some of the early material ejected will have been parts of the erector and associated equipment - and that makes identifying the cause of the explosion essentially impossible with just this one long-distance camera viewpoint.

One thing I'd like to do with my copious free time, which I don't have today, is trace the trajectory on multiple fragments and see where they originate.  I looked at three and they didn't converge to a point, but rather a region, still within the tower, but from different origins.  The ones I looked at didn't emerge from a single point, which might be consistent with a fuel-air type detonation, which would also tend to eliminate conventional explosives, which would be good.

WRT to the exemplar object that you commented on, if it is in Frame3, then it's undergoing deceleration, which in principle could put its origin further left on the red line, rather than right if it were constant velocity.

You're right, we only have X-Y measurements, no Z, with the possible exception of the thingee.

However, tracing to the origin of the various fragments would constrain the X-Y origin.

Jim seems certain that the "cause" isn't along the line I drew.  Is there a difference between the "cause" of the event, and the first explosion's location?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 02:24 pm


Yes but the black lines aren't needed. Just draw a straight line between the two points (and the following points). I don't see why you'd draw horizontal lines there.

Assume constant velocity (which is probably wrong), then the horizontal distance traveled between any two frames will be the same.

The right black line indicates the horizontal distance traveled for the two frames showing the object.

The red line indicates the inferred trajectory forward and backward in time.

If you want to know where the object was in the previous frame, given the above assumptions, you copy the length of the right black line.

You align the right hand side of the copy with the frame 1 location which indicates the horizontal distance in may have traveled from the previous frame.

Slide the yard stick (left black line) down until the left edge intersects the trajectory line.

With these assumptions, that now indicates a unique point where the part may have previously been.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vandersons on 09/03/2016 02:25 pm
The initial thingy flying to the right in the video apears to be tumbling and changing brightness rapidly. Could be a piece of the A/C duct blown off by the initial blast. It's quite reflective and due to the shape it could be reflecting very different amounts of light towards the camera when tumbling explaining why it appears to be missing in certain frames.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/03/2016 02:29 pm
WRT to the exemplar object that you commented on, if it is in Frame3, then it's undergoing deceleration, which in principle could put its origin further left on the red line, rather than right if it were constant velocity.

You're right, we only have X-Y measurements, no Z, with the possible exception of the thingee.

However, tracing to the origin of the various fragments would constrain the X-Y origin.

Jim seems certain that the "cause" isn't along the line I drew.  Is there a difference between the "cause" of the event, and the first explosion's location?

The fragments appear to be of sufficiently irregular shapes that that they will 'disappear' from frame to frame as they present larger or smaller sides to the camera / reflect back different amounts of light towards the camera; and similarly that will mean they will decelerate due to drag.

As far as the difference between 'cause' and 'location', then they are different: it seems *likely* that the initial explosion visible was external to the vehicle, in which case the 'location' would be wherever the spark that initiated the explosion occurred.

The cause - presumably - would be the fault that initiated the chain of events which resulted in the combination of a flammable substance, an oxidiser and probably a spark to initiate the first explosion.

As a speculative aside, I think we're looking at a significant LOX discharge, either from a tank failure within the vehicle; a valve failure (e.g. a massive discharge from the vehicle tank); or something going awry on the TEL.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/03/2016 02:41 pm


Yes but the black lines aren't needed. Just draw a straight line between the two points (and the following points). I don't see why you'd draw horizontal lines there.

Assume constant velocity (which is probably wrong), then the horizontal distance traveled between any two frames will be the same.

The right black line indicates the horizontal distance traveled for the two frames showing the object.

The red line indicates the inferred trajectory forward and backward in time.

If you want to know where the object was in the previous frame, given the above assumptions, you copy the length of the right black line.

You align the right hand side of the copy with the frame 1 location which indicates the horizontal distance in may have traveled from the previous frame.

Slide the yard stick (left black line) down until the left edge intersects the trajectory line.

With these assumptions, that now indicates a unique point where the part may have previously been.

No point in getting so complicated here with just doing the horizontal velocity here. With the errors and timespans we're talking about here any trajectory will be linear, even one going upward into the air. Linear approximations always work if you're looking close enough.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 03:10 pm
That could be something blasted from the back of the erector by the shockwave of the initial explosion.

It's bright, but that's likely to be just reflection of the explosion.

Jim - out of interest, do you know what is the white bit of equipment in the image attached?

AC filter box
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/03/2016 04:14 pm


Part of the test is tanking both stages and going through the standard countdown.  The vehicle never flies with the upper stage empty so firing the booster with it empty is an unknown and unflight like condition.

Jim,
Is it likely/possible that there is more time for each procedure in the static fire countdown?
Or would they just allow holds and recycle to some higher T- time as any issue arises? Is T-8:00 the same as T-8:00 in the Actual launch countdown?


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/03/2016 04:25 pm
Anyone have any info of the temperature differential of the loaded RP-1 and LOX? My thinking is along the lines of a stress fracture at the interface at the common bulkhead that I mentioned originally a couple of days back. A material "snap" failure would provide the energy and the prop mixing rapidly. That could account for the initial detonation and ensuing deflagration.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheSwiss on 09/03/2016 04:32 pm
Anyone have any info of the temperature differential of the loaded RP-1 and LOX? My thinking is along the lines of a stress fracture at the interface at the common bulkhead that I mentioned originally a couple of days back. A material "snap" failure would provide the energy and the prop mixing rapidly. That could account for the initial detonation and ensuing deflagration.

LOX: –207°C
RP1: -7°C
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/03/2016 04:36 pm
So I've read every post since the incident.
How much does the Vehicle change size vertically and radially as it is fueled? If it shrinks vertically then the support fixture at the bulkhead and clamps at the top of S2 must move vertically or the vehicle tank wall slides a bit downwards. What if a small ice dam prevented a smooth slide? Would the instantaneous snap release of the fixture when the ice dam breaks be enough to cause a static discharge ?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/03/2016 04:44 pm
Then I note someone pointed out the unprotected hydraulic hoses that move the clamps. Are they double walled? Could they in fact crack and leak due to the varying temperatures they may encounter? Could we hope for a Feynman analog dipping the hose into a bucket of ice-water to demonstrate how stiff it might get?
Would the non-flammable fluid they use truly be non-flammable in an oxygen rich environment?

Yes - grasping; but the Jason-3 leg failure is the one small glimmer of hope -  the humidity can do strange things.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Long EZ on 09/03/2016 05:25 pm
Thoughts about super chilled LOX.
If you over pressurize it it will go solid. If you loose pressure it has no vapor pressure; that is essentially vacuum. So my suggestion is that for some reason the lox tank lost pressure. Maybe a freeze up in the feed line due to the lox being a little extra cold or a little higher pressure. To make sure the lox tank has pressure it should be fed with helium because ox vapor condenses into super chilled lox liquid very quickly so there is no vapor pressure to speak of. Also you do not want the lox tank to completely fill with liquid as you can then have "water hammer" problem. So during fill you need to maintain a Helium bubble at the top of the tank. So if the Helium pressure has a hick-up; either the Helium feed or the tank pressure relieve valve sticking open of a moment I propose that the pressure of the lox tank could quickly drop.
Of course if the pressure of the lox tank drops the common bulkhead could fail and perhaps a crack of the exterior tank wall. This would result in a spray of lox/fuel to the side of the tank at the common bulkhead position, and then an ignition source could be splitting AlLi.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/03/2016 05:45 pm
Also super chilled lox (66k) condenses nitrogen out of air. Not that that would affect the anomaly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/03/2016 06:09 pm
Also super chilled lox (66k) condenses nitrogen out of air. Not that that would affect the anomaly.

More importantly, it condenses oxygen out of air (unless insulated), which has been observed on walls of uninsulated liquid hydrogen tanks. So there might be liquid oxygen in places where it should not be, without any leaks. Although I trust SpaceX took care to insulate everything.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/03/2016 06:31 pm
Hmm hole in insulation, something flammable, spark could make a good bomb. Maybe the brightness of the initial event equates to aluminum with oxygen. Thermite is very bright with what fe203 and al. Now we just need a hot spark.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/03/2016 07:48 pm
Does anybody know if they purge the insulation with helium? Or what exactly the insulation. Is made of?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 07:50 pm
No, it is no needed.  They don't even do that for hydrogen
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/03/2016 07:58 pm
Also super chilled lox (66k) condenses nitrogen out of air. Not that that would affect the anomaly.

More importantly, it condenses oxygen out of air (unless insulated), which has been observed on walls of uninsulated liquid hydrogen tanks. So there might be liquid oxygen in places where it should not be, without any leaks. Although I trust SpaceX took care to insulate everything.

More interestingly, is all the erector plumbing, fittings, etc. also insulated??  Rightly or wrongly I see the erector offering a lot of opportunities for the required spark.  Also, lots of material to react with any condensed O2...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 08:12 pm
What says there is any condensed O2?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/03/2016 08:16 pm
What says there is any condensed O2?

he almost certainly refers to the supercooled higher density lox.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 08:18 pm
That doesn't translate to Liquid O2 condensing on hardware. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GerryParnham on 09/03/2016 08:20 pm
So after reading 1100 odd posts what is there left to say.

That I'm a bit sad to be doing this again so soon...

Note that just about the first thing that happened with crs7 was that the payload popped off the top of the stack. This did not happen here, suggesting that the initial bang was outside the booster. So we have an explosion near the second stage during refuelling.

An explosion would need:
   1 vapour phase oxygen
   2 vapour phase kerosine due to the colour (or other similar vapourised fuel)
   3 a tiny spark
   4 preferably a confined space to work well

The initial site of the explosion seems to be at the second stage horizontal support on the strongback. In the frame before the explosion vapour can be seen coming from this location while the O2 boil-off ports are much higher.  My estimate is here, see picture 01:

(http://gerryparnham.com/spacex/site_of_explosion_02.jpg)

Assuming an rp1 leak from somewhere there is breeze of about 2-3mph at the time, enough to spread an rp1/lox aerosol mixture without dispersing it.

After a few seconds a spark (from static or equipment) ignites the mixture causing the initial deflagration.

Falcon9 uses open hydraulics, another potential source of fuel in a high-O2 atmosphere. I note that SpaceX flushes the inside of Falcon9 with N2, but you can't do that outside. Many of these points have already been made but below is another frame grab taken from the COTS1 flight. Note deflagration on the retracted Strongarm in the same place as that supposed for this event.

(http://gerryparnham.com/spacex/SpaceX_COTS_Demo_Flight_1.jpg)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 08:25 pm
Let's just stop with the external explosion idea.   There is nothing that excludes internal explosion or rupture.

Anyways, anything on the outside is just going to flash and not going to be an explosion and not have any force to damage the vehicle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/03/2016 08:27 pm
Assuming an rp1 leak from somewhere there is breeze of about 2-3mph at the time, enough to spread an rp1/lox aerosol mixture without dispersing it.

As has been pointed out several times already, there is no RP-1 line running that high up. Only an AC line for the fairing. The 2nd stage umbilical port is at the S2-interstage interface.

Note deflagration on the retracted Strongarm in the same place as that supposed for this event.

It's not at the same place, that happened literally to the umbilical line which, again, is lower down on the T/E than the point of explosion here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/03/2016 08:29 pm
Let's just stop with the external explosion idea.   There is nothing that excludes internal explosion or rupture.

Wishful thinking excludes it.

Anyways, anything on the outside is just going to flash and not going to be an explosion and not have any force to damage the vehicle

Probably. That COTS-1 event produced an audible bang for the pad microphones and that's with a background of 9 M1Cs running.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: butters on 09/03/2016 08:41 pm
It's possible that the payload cradle arms being closed could be responsible for the lack of vertical displacement of the payload, as compared to CRS-7. The payload seemed to be held pretty snugly by the TEL and did not come loose until it began to melt.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/03/2016 08:43 pm
Note to newbies who joined NSF to discuss this event - and I say this with the kindest of intentions - please note the "Location" listed below Jim's username. It's not a euphemism or aspiration. Jim's one of the few here who have worked in rocketry and spaceflight for decades. It's always a good idea to read what he writes and think carefully before trying to "correct" him with with an assertion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/03/2016 08:47 pm
Another speculation.

There should be rubber bushes, rubber pads or other rubber items up there on the mast. When there's continous small supercooled O2 leak onto this rubber, the rubber becomes brittle, develops microcracks and gets saturated with oxygen. All one needs to set it off is a decent hit with the hammer.

As of people claiming that it cannot be FA explosion - quite contrary. Whatever aerosol explosion of this magnitude (fireball 35x80ft) should destroy the launch vehicle without hesitation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 08:51 pm
This is all you are going to get with a leak in the GSE
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/03/2016 08:53 pm
Unless anyone is operating off of additional information not shared with the rest of us, I think the evidence so far make an external detonation more likely, which is about as definite a statement as can be made from that evidence.  (meaning - not very definite...)

Most of that evidence is in the first 3 frames of video. Everything after that is cascading failure and highly speculative.

The source of the combustible material (and oxidizer) can be the rocket or the GSE, there hasn't been much evidence to support either case.



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/03/2016 08:54 pm
This is all you are going to get with a leak in the GSE

You get this assuming you have fire started in the immediate vincinity of any leak. However, if fire gets initiated later, you get this:
https://www.youtube.com/watch?v=j9xCgNdZPKk
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 08:59 pm
Unless anyone is operating off of additional information not shared with the rest of us, I think the evidence so far make an external detonation more likely, which is about as definite a statement as can be made from that evidence. 

Not at all.  There is no public evidence that supports an external over internal explosion.  And certainly, nothing from this thread or those first 3 frames.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/03/2016 09:01 pm
This is all you are going to get with a leak in the GSE

You get this assuming you have fire started in the immediate vincinity of any leak. However, if fire gets initiated later, you get this:


Assuming good mix well above the LEL for the fuel. That said, did you notice the flow of free O2 vapor flowing off the vehicle? That's gonna make it very hard to get a high concentration around an exposed vehicle and the truss work of the T/E. What kind of fuel leak rate makes that level of concentration possible without itself becoming visible?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/03/2016 09:11 pm
Well I'm shocked, shocked I tell you, that we've had speculation posts! ;)

Ok, only joking, of course there was always going to be speculation, but that's why we have this thread and keep the update thread on the pure info. The value with sites like this is the speculation tends to be at the very least educated and we have a ton of industry folk who can field such posts and provide context or correction. See, I told you the internet wasn't all bad!

However, what I would say is "NO, for the love of God, NO!" to posts that link tabloids (like the Daily Star) claiming the F9 was killed by UFO-deployed kamikaze birds, or whatever. Let's shun such nonsense.

Bottom line is something went wrong with the rocket's second stage and rocket went boom. We'll find out what in due course, but hopefully I'm not overstepping my mark by confirming it was not aliens.

Oh and be civil with each other. Arguments make moderator Carl cry (sorry Carl ;D).

As you were.... :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/03/2016 09:13 pm
Unless anyone is operating off of additional information not shared with the rest of us, I think the evidence so far make an external detonation more likely, which is about as definite a statement as can be made from that evidence. 

Not at all.  There is no public evidence that supports an external over internal explosion.  And certainly, nothing from this thread or those first 3 frames.
Nothing conclusive, but the detonation is bright and visible, seems to be located at or near the wall, and there's a very distinct lack of debris.

Unlike other events that were "fast fires", this looked to me like a good and proper detonation.

If indeed RP1 was no longer being pumped as was suggested upthread, it would make the rocket the suspected source, but I'd still put the odds on the first event being external.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/03/2016 09:30 pm
Also super chilled lox (66k) condenses nitrogen out of air. Not that that would affect the anomaly.

More importantly, it condenses oxygen out of air (unless insulated), which has been observed on walls of uninsulated liquid hydrogen tanks. So there might be liquid oxygen in places where it should not be, without any leaks. Although I trust SpaceX took care to insulate everything.
Actually at that temperature I'd expect it to condense both N2 and O2 out of the air.  :)

This topic came up in the problems of designing reusable stages and it was astonishing (to me) how much insulation can be provided by as little as (relatively) thin coat of paint on a LOX tank. You wouldn't want to touch it with your hand but it's still above the freezing point of water.

This changes if such a layer is disrupted but the odds on bet would be that the first thing to condense (or rather freeze) out would be water. Only when that got cold enough would you start to see air liquefy.

The question of course is why (or what) would the coating be disrupted by to begin with?

As a general point I expect by this time next week SX to have a pretty good idea of what happened and why. While from an operational PoV this is a very bad place to have a LoV/LoP incident it's an excellent place in terms of debris recovery, telemetry by hard wired link, close range video etc.

Wheather they will be down to the root cause by then I'm less sure.  How long did they take to investigate the CRS LoV?  If they do then it's a question of rebuilding the pad and implementing the necessary design changes in the pad (and probably a few improvements they've spotted along the way in the previous launches) and the vehicle.

On the positive side it seems the issues centre around the interstage / 2nd stage area. If so that means most of the 5 1st stages they've recovered remain viable potential candidates for reuse. Not absolutely certain and it could be a dark horse in this context but reasonably promising.

BTW.
Yes dust explosions can be very large and very nasty. Where's the dust coming from in this context?

FAE's can also be nasty, hence the media tag of the "Poor mans atomic bomb" but these require both careful mixing of fuel and air and controlled ignition delay. I think they also like fuels with high flame or explosion propagation speeds and I don't think RP1 is very good at this.

True the fuel at the bottom of the 2nd stage is under a significant column pressure above the ullage pressurization but it needs a fairly carefully timed set of events to create an FAE effect.

Occam's Razor says keep the explanation simple. The more things you need to happen and at what time the less likely something is.  The biggest source of fuel for a fire on the stage is the RP1 tank. Probably the easiest thing to burn on the stage is the contents of the RP1 tank.  What's the odds on bet?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/03/2016 09:41 pm
If an energetic material failure occurred at a common bulkhead weld peripherally against the outer skin it would provide the appearance of an external detonation looking straight on at it. We should be able to agree that perspective plays into what we are interpreting from limited video evidence thus far.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/03/2016 09:44 pm
What about the payload support claw on the TEL? It's hydraulic. It grasps the second stage. *If* it does not have a physical hard stop to prevent it applying too much pressure, could a hydraulic anomaly have caused it to tighten a bit too much and cause structural failure of the second stage, thus triggering the explosive event?

What got me thinking along these lines is the loss of at least two 737 airliners due to a combined PCU/actuator for the rudder occasionally going uncommanded hard over.  It was exceedingly rare and hard to diagnose, so much so that it took the NTSB over a decade (and at least three in-flight occurrences, two of them fatal) to figure it out. In the case of the 737 actuator, thermal shock seemed to play a causal role (though didn't cause it on most occasions, just occasionally).
https://en.wikipedia.org/wiki/Boeing_737_rudder_issues

So, does the claw have hydraulic servos of that general type (dual servo) AND are they located near a LOX line (or at least are their hydraulic lines located near a LOX line?) I know there aren't any LOX lines located near the claw itself, but the servos could be well away from the claw and its actuators. 



 

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/03/2016 09:45 pm
I might as well provide my speculation here too. I think there was a crack in the weld that allowed RP1 to spray out towards the TLE and something ignited the cloud. How much stress is placed on the outer casing joint at the LOX/RP1 bulkhead due to the temperature differences? Is it weakened by the low temperatures?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/03/2016 09:47 pm
During a launch, there is often (always?) a camera looking right at the umbilical connections.  I'd assume this camera is also activated for hot fires, and the recording from this camera seems like the first thing to check.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/03/2016 09:47 pm
Unless anyone is operating off of additional information not shared with the rest of us, I think the evidence so far make an external detonation more likely, which is about as definite a statement as can be made from that evidence.  (meaning - not very definite...)

Most of that evidence is in the first 3 frames of video. Everything after that is cascading failure and highly speculative.

The source of the combustible material (and oxidizer) can be the rocket or the GSE, there hasn't been much evidence to support either case.





I (and I am sure others here also) labor under the burden of having good sources in the business who can't be revealed, and having certain knowledge that can't be shared, so yes, some of us are operating off of additional information – which may be right or wrong.  Also, I don't share rumors to which I am privy, however well-sourced they may be.  But I have, to my mind, fairly expressed certain COPV concerns in part due to "information received" and agree with Jim that an external event is likely to be insufficiently energetic to cause any appreciable damage to the vehicle.

The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

Edit: punctuation
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 09:49 pm
During a launch, there is often (always?) a camera looking right at the umbilical connections.  I'd assume this camera is also activated for hot fires, and the recording from this camera seems like the first thing to check.

The fire part is for hydrogen powered vehicles
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/03/2016 09:51 pm
Unless anyone is operating off of additional information not shared with the rest of us, I think the evidence so far make an external detonation more likely, which is about as definite a statement as can be made from that evidence.  (meaning - not very definite...)

Most of that evidence is in the first 3 frames of video. Everything after that is cascading failure and highly speculative.

The source of the combustible material (and oxidizer) can be the rocket or the GSE, there hasn't been much evidence to support either case.





I (and I am sure others here also) labor under the burden of having good sources in the business who can't be revealed, and having certain knowledge that can't be shared, so yes, some of us are operating off of additional information – which may be right or wrong.  Also, I don't share rumors to which I am privy, however well-sourced they may be.  But I have, to my mind, fairly expressed certain COPV concerns in part due to "information received" and agree with Jim that an external event is likely to be insufficiently energetic to cause any appreciable damage to the vehicle.

The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?  But an equally valid question is, what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?
Can't address information I'm not privy to.

Let's define "external"..  to me, a tank failure resulting in a spray of RP1 would count as external.

I was saying the detonation appeared external, not the cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/03/2016 09:58 pm
Anyways, anything on the outside is just going to flash and not going to be an explosion and not have any force to damage the vehicle

I presume you're limiting that to anything you'd consider to be a plausible external cause?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/03/2016 09:59 pm
HMXHMX,

Perhaps there is something I am missing here, not being privy to the non-public details of the vehicle's internal design. I agree (not that my agreement matters), that COPV's are a great candidate for causing high energy events, like this anomaly. What makes me very curious, is what is so different about the design of the second stage that these vessels are an issue? We have seen these booster stages go through some pretty harsh treatment, and, at least from what we have seen publicly, no COPV failures have caused a LOV. So what's the difference? Tank wall thickness? Lighter, less rugged COPV's on the upper stage?

I know you might not be able to answer the question, but I thought it worth asking.

Edit: I am aware there have been anomalies in the first stage involving COPV's as well. I guess a follow-on question would be why did these not result in LOV? I am genuinely interested in learning about how these vehicles function.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 10:00 pm
Anything on the outside would show up before the vehicle exploded and there would be two distinct events
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/03/2016 10:03 pm
>
FAE's can also be nasty, hence the media tag of the "Poor mans atomic bomb" but these require both careful mixing of fuel and air and controlled ignition delay. I think they also like fuels with high flame or explosion propagation speeds and I don't think RP1 is very good at this.
>

Haven't spent much time around grain elevators or bins? No careful mixing there at all. Vapors will also blow without careful mixing, been there with poorly stored fuels.

Things you learn growing up on a farm.

An improvised explosive can be made using a tin of flour and a small dispersion charge. Old tech my uncle used as a vintage SO. The damnedest things can be bombs.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 10:05 pm


The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"



Granted your decades long history in this industry and your recent focus on COPV in this current thread.

Assuming a COPV failure, which would be in the LOX tank I presume, which would obviously rupture that tank, and possibly the RP1 tank at the same time, I'm confused as to how we'd end up with a detonation rather than a deflagration.

To me the debris tracks are indicative of detonation, while the rest of the event looks like deflagration.

Your thoughts please?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/03/2016 10:09 pm
If one went with the COPV failure theory as root cause for both failures, it would be interesting to work out what the chances would have been that both failures happened during launch campaigns and not in Texas.

If there is no external factor like shaking involved (shaky assumption, but appears to be supported by the Amos 6 case) so it could be considered a statistical probability, one could naively expect the events to have occured in Texas acceptance testings. They undoubtedly had tanked up vehicles in Texas for far longer durations and many more times than on the launch pad and in the air.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/03/2016 10:10 pm
Since we are getting down to semantics now from my perspective the external point source of the detonation was an "effect" and not the "cause"...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vandersons on 09/03/2016 10:14 pm

(snip)

The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

Edit: punctuation

If it indeed comes down to be a COPV blowing up then how come only the 2nd stage is FUBARed by this and not the 1st stage? From reading on this thread and others it's been made clear that the COPVs are the same on both stages. S1 would just need a lot more of them, actually, increasing the likelihood of a bad bad one getting in there. Is it the smaller volume of the S2 LOX tank that makes any COPV failure a LOV while a bottle popping inside the S1 tank has enough volume to spread out for safety valves to be able to cope with it or is the S1 just so much beefier due to reuse requirements that it can just handle the extra pressure from a COPV blowout? How would the Merlins behave if a He bottle went pop early in the launch phase, lets say 20-30sec into flight? I'm sure the He would get mixed a good bit with the LOX and get sucked into the engines and being not exactly a reactive element it should have some sort of an effect.

If that's indeed the case then the S2 COPVs need a design review. Smaller bottles in greater numbers to scale it to the same ratios as in the 1st stage as that has never gone boom due to this issue (think I read about a close call on this same thread for the first Orbcom mission).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickl on 09/03/2016 10:17 pm
The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

That's what I'm thinking.  My eyebrows are raised.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/03/2016 10:17 pm

I (and I am sure others here also) labor under the burden of having good sources in the business who can't be revealed, and having certain knowledge that can't be shared, so yes, some of us are operating off of additional information – which may be right or wrong.  Also, I don't share rumors to which I am privy, however well-sourced they may be.  But I have, to my mind, fairly expressed certain COPV concerns in part due to "information received" and agree with Jim that an external event is likely to be insufficiently energetic to cause any appreciable damage to the vehicle.

The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

Edit: punctuation

Given that SpaceX's statement last night is that the incident occurred approximately 8 minutes before the scheduled hotfire, and that seems to correlate with the approximate time that helium loading is going on, you might well be onto something.

EDIT: Or perhaps not; I was going off a memory of this timeline, but that refers to Stage 1 helium loading. Does anyone know when in the count Stage 2 helium loading occurs?

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577625#msg1577625
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/03/2016 10:20 pm
My take is an internal pressure related event (COPV is just one of possible causes) vs an event that is external to the vehicle.

And that is not based on any inside information.   I have as much data as any man on the street, right now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/03/2016 10:23 pm
HMXHMX,

Perhaps there is something I am missing here, not being privy to the non-public details of the vehicle's internal design. I agree (not that my agreement matters), that COPV's are a great candidate for causing high energy events, like this anomaly. What makes me very curious, is what is so different about the design of the second stage that these vessels are an issue? We have seen these booster stages go through some pretty harsh treatment, and, at least from what we have seen publicly, no COPV failures have caused a LOV. So what's the difference? Tank wall thickness? Lighter, less rugged COPV's on the upper stage?

I know you might not be able to answer the question, but I thought it worth asking.

Edit: I am aware there have been anomalies in the first stage involving COPV's as well. I guess a follow-on question would be why did these not result in LOV? I am genuinely interested in learning about how these vehicles function.

I've gone about as far as I can on the design issues, unfortunately for the discussion.  Until more information appears in the public record, at least.  But I will reiterate that –my opinion – suggests a design issue.

I'm surprised to hear that there have been first stage COPV issues...I'm unaware of any, but would very much like links to any reports.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/03/2016 10:28 pm
I'm surprised to hear that there have been first stage COPV issues...I'm unaware of any, but would very much like links to any reports.

I may be misinterpreting, but in the launch log there are mentions of issues on flights 9, and 10.

http://forum.nasaspaceflight.com/index.php?topic=40544.0
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gliderflyer on 09/03/2016 10:33 pm
I'm surprised to hear that there have been first stage COPV issues...I'm unaware of any, but would very much like links to any reports.

Chris posted about it in the L2 ORBCOMM thread back in 2014: http://forum.nasaspaceflight.com/index.php?topic=34575.msg1197358#msg1197358
I don't remember if there was any other information on it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/03/2016 10:37 pm


The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"



Granted your decades long history in this industry and your recent focus on COPV in this current thread.

Assuming a COPV failure, which would be in the LOX tank I presume, which would obviously rupture that tank, and possibly the RP1 tank at the same time, I'm confused as to how we'd end up with a detonation rather than a deflagration.

To me the debris tracks are indicative of detonation, while the rest of the event looks like deflagration.

Your thoughts please?

If one of the two S2 COPVs fails catastrophically, that means the second COPV is also going to vent at a lower rate through what is left of its line.  But about 90-100 kg of helium is going to be instantaneously released into the LOX tank from just the first failing bottle...that is pressurizing an ullage that is tiny (between 1-3% of tank volume is standard).  Instantly the LOX tank is going to be at several hundred psia, failing the common bulkhead as well as the side walls.  And the general shock wave from the failure is likely to be sufficient to cause some propellant mixing, though not much is required for the event to begin.  It is also possible that COPV debris punctured the common bulkhead first, too.

I suggested a mechanism that might lead to in-tank combustion in a much early post but as the saying goes, "ignition is free."  I don't have a specific source for ignition, just notions.  Maybe torn wires sparking when the tank lets go? 

I agree that this was a low-grade detonation, for all the word-smithing going on about deflagration.  Actually, there are elements of both processes in the whole event.  Separately, there are self-propelled objects like the COPV seen flying up and over the payload fairing.  You can watch it vent helium as it tumbles along.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/03/2016 10:38 pm
My take is an internal pressure related event (COPV is just one of possible causes) vs an event that is external to the vehicle.

And that is not based on any inside information.   I have as much data as any man on the street, right now.

If this is true, then why didn't the pressure vessel burst open as in CRS-7 accident, but there was some kind of explosion instead? IMHO, the plauseible expectation in case of any pressure vessel failure, is first to see large cloud of condensate and only then ignition. That was not the case.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/03/2016 10:40 pm

(snip)

The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

Edit: punctuation

If it indeed comes down to be a COPV blowing up then how come only the 2nd stage is FUBARed by this and not the 1st stage? From reading on this thread and others it's been made clear that the COPVs are the same on both stages. S1 would just need a lot more of them, actually, increasing the likelihood of a bad bad one getting in there. Is it the smaller volume of the S2 LOX tank that makes any COPV failure a LOV while a bottle popping inside the S1 tank has enough volume to spread out for safety valves to be able to cope with it or is the S1 just so much beefier due to reuse requirements that it can just handle the extra pressure from a COPV blowout? How would the Merlins behave if a He bottle went pop early in the launch phase, lets say 20-30sec into flight? I'm sure the He would get mixed a good bit with the LOX and get sucked into the engines and being not exactly a reactive element it should have some sort of an effect.

If that's indeed the case then the S2 COPVs need a design review. Smaller bottles in greater numbers to scale it to the same ratios as in the 1st stage as that has never gone boom due to this issue (think I read about a close call on this same thread for the first Orbcom mission).

Luck of the draw?  I don't know, but another poster made reference to S1 COPV issues, which are news to me, if true.

Could also be installation issues, mounting differences, all sorts of things to which we aren't privy.  NASA hinted at assembly issues.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/03/2016 10:43 pm
If this is true, then why didn't the pressure vessel burst open as in CRS-7 accident, but there was some kind of explosion instead? IMHO, the plauseible expectation in case of any pressure vessel failure, is first to see large cloud of condensate and only then ignition. That was not the case.

We cant externally see either of the domes which also comprise the pressure vessel. Maybe CRS-7 was what happens when the forward dome fails, and this is what happens when the aft dome fails.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/03/2016 10:51 pm
Anything on the outside would show up before the vehicle exploded and there would be two distinct events

There's a couple of different, temporally spaced groups of diffraction flares at the start of the anomaly, if that counts?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/03/2016 10:53 pm


The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"




Granted your decades long history in this industry and your recent focus on COPV in this current thread.

Assuming a COPV failure, which would be in the LOX tank I presume, which would obviously rupture that tank, and possibly the RP1 tank at the same time, I'm confused as to how we'd end up with a detonation rather than a deflagration.

To me the debris tracks are indicative of detonation, while the rest of the event looks like deflagration.

Your thoughts please?

If one of the two S2 COPVs fails catastrophically, that means the second COPV is also going to vent at a lower rate through what is left of its line.  But about 90-100 kg of helium is going to be instantaneously released into the LOX tank from just the first failing bottle...that is pressurizing an ullage that is tiny (between 1-3% of tank volume is standard).  Instantly the LOX tank is going to be at several hundred psia, failing the common bulkhead as well as the side walls.  And the general shock wave from the failure is likely to be sufficient to cause some propellant mixing, though not much is required for the event to begin.  It is also possible that COPV debris punctured the common bulkhead first, too.

I suggested a mechanism that might lead to in-tank combustion in a much early post but as the saying goes, "ignition is free."  I don't have a specific source for ignition, just notions.  Maybe torn wires sparking when the tank lets go? 

I agree that this was a low-grade detonation, for all the word-smithing going on about deflagration.  Actually, there are elements of both processes in the whole event.  Separately, there are self-propelled objects like the COPV seen flying up and over the payload fairing.  You can watch it vent helium as it tumbles along.


Please don't mind me challenging you. :)

If you check my history in this particular thread, I've been chasing visible debris and trying to model their origins and velocity.

I know the difference between deflagration and detonation.  I'm one of a few humans on the planet who saw an airburst from operation Dominick in 1962-3.  I came from a long line of folks who play with things that go bang.

IMHO the item flying over the fairing is not a COPV, which is a long separate discussion, briefly, it's on a parabolic trajectory which I'm currently tracking user Tracker-4.94 which does such things.   Drop that discussion for now.

The initial debris of concern is seen the the first and 2nd and possibly 3rd frame of the USLaunchReport video shooting to the right and up, and is decelerating but with an average velocity of about 1,000 feet per second.  To me, that part can't seem to be moving that fast because of a deflagration.  Earlier in the thread I provided images and interpretation of that debris.  I'll replicate the images to save you time if you wish.

If a COPV fails, is the mixing and resulting combustion rate sufficient to propel debris at 1,000 feet per second, and if so, how?  My hydrodynamics training suggests there is a mixing front that precedes a burning front and that relatively incompressible liquids will slow things down, not speed things up.

I am puzzled about how rupturing a LOX and RP1 tank results in an immediate ignition that propels some external object at 1,000 feet per second.

My question is, in your experience, is there a COPV failure scenario you are aware of that can result in a detonation that would propel an external object at that velocity?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kamilfredo on 09/03/2016 10:57 pm
I've read whole thread, but I don't remember if any used this method...

(http://www.imageworld.sk/images/eui2uujqulujalb1cuj.png)
(http://www.imageworld.sk/images/u07gogyztkf3rysl0wf.png)
(http://www.imageworld.sk/images/ip1skd0mioh4trt5xqq.png)
(http://www.imageworld.sk/images/fipin68n9efb7gzea81e.png)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/03/2016 11:06 pm
I've read whole thread, but I don't remember if any used this method...

Method was first shown here... and again in some much later postings...

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1576505#msg1576505 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1576505#msg1576505)

It's a good method, has me leaning toward external issue at or near the cradle located there in fact...  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/03/2016 11:08 pm


The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"




Granted your decades long history in this industry and your recent focus on COPV in this current thread.

Assuming a COPV failure, which would be in the LOX tank I presume, which would obviously rupture that tank, and possibly the RP1 tank at the same time, I'm confused as to how we'd end up with a detonation rather than a deflagration.

To me the debris tracks are indicative of detonation, while the rest of the event looks like deflagration.

Your thoughts please?

If one of the two S2 COPVs fails catastrophically, that means the second COPV is also going to vent at a lower rate through what is left of its line.  But about 90-100 kg of helium is going to be instantaneously released into the LOX tank from just the first failing bottle...that is pressurizing an ullage that is tiny (between 1-3% of tank volume is standard).  Instantly the LOX tank is going to be at several hundred psia, failing the common bulkhead as well as the side walls.  And the general shock wave from the failure is likely to be sufficient to cause some propellant mixing, though not much is required for the event to begin.  It is also possible that COPV debris punctured the common bulkhead first, too.

I suggested a mechanism that might lead to in-tank combustion in a much early post but as the saying goes, "ignition is free."  I don't have a specific source for ignition, just notions.  Maybe torn wires sparking when the tank lets go? 

I agree that this was a low-grade detonation, for all the word-smithing going on about deflagration.  Actually, there are elements of both processes in the whole event.  Separately, there are self-propelled objects like the COPV seen flying up and over the payload fairing.  You can watch it vent helium as it tumbles along.


Please don't mind me challenging you. :)

If you check my history in this particular thread, I've been chasing visible debris and trying to model their origins and velocity.

I know the difference between deflagration and detonation.  I'm one of a few humans on the planet who saw an airburst from operation Dominick in 1962-3.  I came from a long line of folks who play with things that go bang.

IMHO the item flying over the fairing is not a COPV, which is a long separate discussion, briefly, it's on a parabolic trajectory which I'm currently tracking user Tracker-4.94 which does such things.   Drop that discussion for now.

The initial debris of concern is seen the the first and 2nd and possibly 3rd frame of the USLaunchReport video shooting to the right and up, and is decelerating but with an average velocity of about 1,000 feet per second.  To me, that part can't seem to be moving that fast because of a deflagration.  Earlier in the thread I provided images and interpretation of that debris.  I'll replicate the images to save you time if you wish.

If a COPV fails, is the mixing and resulting combustion rate sufficient to propel debris at 1,000 feet per second, and if so, how?  My hydrodynamics training suggests there is a mixing front that precedes a burning front and that relatively incompressible liquids will slow things down, not speed things up.

I am puzzled about how rupturing a LOX and RP1 tank results in an immediate ignition that propels some external object at 1,000 feet per second.

My question is, in your experience, is there a COPV failure scenario you are aware of that can result in a detonation that would propel an external object at that velocity?


To add to this excellent post, would there not be more debris visible in the first two frames if it were a purely internal explosion - regardless of the cause?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kamilfredo on 09/03/2016 11:15 pm
I've read whole thread, but I don't remember if any used this method...

Method was first shown here... and again in some much later postings...

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1576505#msg1576505 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1576505#msg1576505)

Ok...for me was not clear, if it was used light rays on that picture...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: sfxtd on 09/03/2016 11:18 pm
My take is an internal pressure related event (COPV is just one of possible causes) vs an event that is external to the vehicle.

And that is not based on any inside information.   I have as much data as any man on the street, right now.

If this is true, then why didn't the pressure vessel burst open as in CRS-7 accident, but there was some kind of explosion instead? IMHO, the plauseible expectation in case of any pressure vessel failure, is first to see large cloud of condensate and only then ignition. That was not the case.

Concurring with Jim, to me the likely process is an internal pressure event ruptures the LOX tank, probably at or near the common bulkhead, perhaps causing an RP-1 leak and encountering or generating an ignition source.

CRS-7 was not a COPV failure (rupture) but diagnosed as a strut failure leading to helium venting through the broken tubing. The rate of helium release would be much lower resulting in a much different LOX tank rupture scenario.  Combine that with operating in an accelerating, high-altitude vs. 1G, sea-level, condition, connected to GSE and one could hardly expect a similar pattern.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/03/2016 11:20 pm
I still see the potential of a focused shock detonation as a potential mechanism...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/03/2016 11:24 pm
Anything on the outside would show up before the vehicle exploded and there would be two distinct events

There are two distinct event, or at least two visible phases of destruction...  A detonation (3 video frames or so) and then the collapse of the entire rocket.

There may have been a "stage zero" inside the rocket, but if there was, it didn't show as any "cold" event that preceded the detonation.

A cloud of fuel vapor or aerosol would not necessarily have been visible.  Depends on the weather.  Also, if it sprayed from inside the rocket, it could have been very brief.

We don't have a video frame showing a detectable deformation in the rocket, or at least not a certain one.

--

Don't add meaning to what I say in the sense that I am not implying it's GSE.  Very minimalistically, I'm saying it looks like the first visible detonation was external.

It does not look like the tank burst outwards and then exploded, for example.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/03/2016 11:33 pm


The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"




Granted your decades long history in this industry and your recent focus on COPV in this current thread.

Assuming a COPV failure, which would be in the LOX tank I presume, which would obviously rupture that tank, and possibly the RP1 tank at the same time, I'm confused as to how we'd end up with a detonation rather than a deflagration.

To me the debris tracks are indicative of detonation, while the rest of the event looks like deflagration.

Your thoughts please?

If one of the two S2 COPVs fails catastrophically, that means the second COPV is also going to vent at a lower rate through what is left of its line.  But about 90-100 kg of helium is going to be instantaneously released into the LOX tank from just the first failing bottle...that is pressurizing an ullage that is tiny (between 1-3% of tank volume is standard).  Instantly the LOX tank is going to be at several hundred psia, failing the common bulkhead as well as the side walls.  And the general shock wave from the failure is likely to be sufficient to cause some propellant mixing, though not much is required for the event to begin.  It is also possible that COPV debris punctured the common bulkhead first, too.

I suggested a mechanism that might lead to in-tank combustion in a much early post but as the saying goes, "ignition is free."  I don't have a specific source for ignition, just notions.  Maybe torn wires sparking when the tank lets go? 

I agree that this was a low-grade detonation, for all the word-smithing going on about deflagration.  Actually, there are elements of both processes in the whole event.  Separately, there are self-propelled objects like the COPV seen flying up and over the payload fairing.  You can watch it vent helium as it tumbles along.


Please don't mind me challenging you. :)

If you check my history in this particular thread, I've been chasing visible debris and trying to model their origins and velocity.

I know the difference between deflagration and detonation.  I'm one of a few humans on the planet who saw an airburst from operation Dominick in 1962-3.  I came from a long line of folks who play with things that go bang.

IMHO the item flying over the fairing is not a COPV, which is a long separate discussion, briefly, it's on a parabolic trajectory which I'm currently tracking user Tracker-4.94 which does such things.   Drop that discussion for now.

The initial debris of concern is seen the the first and 2nd and possibly 3rd frame of the USLaunchReport video shooting to the right and up, and is decelerating but with an average velocity of about 1,000 feet per second.  To me, that part can't seem to be moving that fast because of a deflagration.  Earlier in the thread I provided images and interpretation of that debris.  I'll replicate the images to save you time if you wish.

If a COPV fails, is the mixing and resulting combustion rate sufficient to propel debris at 1,000 feet per second, and if so, how?  My hydrodynamics training suggests there is a mixing front that precedes a burning front and that relatively incompressible liquids will slow things down, not speed things up.

I am puzzled about how rupturing a LOX and RP1 tank results in an immediate ignition that propels some external object at 1,000 feet per second.

My question is, in your experience, is there a COPV failure scenario you are aware of that can result in a detonation that would propel an external object at that velocity?


Don't give a second thought to challenging me; I certainly don't mind.  I'm usually wrong in these sort of speculative analyses since I don't have access to all relevant information and data.  :)

I did step thought the video frame by frame, and what I believe I saw was a object with the approximate geometry and known dimensions of the helium COPV, self-propelled by venting helium though a tube that is somewhere between 1 and 1.5 inch diameter (tube dimension from photos of the vessels available on line).  The object is being propelled by the venting gas, not the force of the detonation-deflagration.  You can see the object nearly disappear in one frame when the tumble orients it base on to the camera and the cloud of venting gas obscures its shape.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/03/2016 11:36 pm
Anything on the outside would show up before the vehicle exploded and there would be two distinct events

There are two distinct event, or at least two visible phases of destruction...  A detonation (3 video frames or so) and then the collapse of the entire rocket.

There may have been a "stage zero" inside the rocket, but if there was, it didn't show as any "cold" event that preceded the detonation.

A cloud of fuel vapor or aerosol would not necessarily have been visible.  Depends on the weather.  Also, if it sprayed from inside the rocket, it could have been very brief.

We don't have a video frame showing a detectable deformation in the rocket, or at least not a certain one.

--

Don't add meaning to what I say in the sense that I am not implying it's GSE.  Very materialistically, I'm saying it looks like the first visible detonation was external.

It does not look like the tank burst outwards and then exploded, for example.


Also, Jim raises the very good point that a small external explosion would "flash" and not necessarily harm the vehicle.  So whatever happened was very substantial, possibly augmented by O2 vapours either internally or externally. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/03/2016 11:36 pm
You know what, I installed the frame-by-frame add-on and looked again.

It's more than I said before.

The first detonation event goes through about 5 key frames, expanding on the first 3, and then contracting.

As it does so, you can still see the "far" side of the stage, and it is undisturbed.

As the detonation event recedes, the there appears a lot of black smoke / liquid RP1, and the secondary melt-down ensues.

---

That was a description of what I saw.  Interpretation?  Still could equally be an external or internal failure.

--------

I recommend for all to install and watch for yourself.  "[" and "]" for stepping through the frames.  Get the 1080 video link from update thread.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Melanchthon on 09/03/2016 11:53 pm
As was discussed extensively following the CRS-7 failure, composites don't "like" repeated cryogenic soak cycles, and there was some concern - before fault was pinned on a strut failure rather than the COPV itself - that perhaps SpaceX's practice of repeated tanking and tests prior to flight could have contributed.

To that point, although Elon pointed blame squarely at the failed strut, a GAO report regarding of NASA's handling of the CRS-7 failure investigation pointed out that the root cause was not 100% certain, with several other possible causes (I don't have a link handy and can't recall what other possible causes were implicated).

In light of recent COPV discussion, I was interested enough to track down the report and try to find the statements you mention. I believe you're talking about this:

Quote
NASA’s Launch Services Program (LSP) conducted a separate, independent review of the failure, briefing
its results to senior NASA leadership on December 18, 2015. [24] LSP did not identify a single probable
cause for the launch failure, instead listing several “credible causes.” In addition to the material defects
in the strut assembly SpaceX found during its testing, LSP pointed to manufacturing damage or improper
installation of the assembly into the rocket as possible initiators of the failure. LSP also highlighted
improper material selection and such practices as individuals standing on flight hardware during the
assembly process, as possible contributing factors. [25]

[24] - LSP purchases commercial launch services for NASA customers, including missions of the Agency’s Science Mission Directorate. LSP had a contract with SpaceX to use the Falcon 9 to deliver a science mission payload.

[25] - In February 2016, the NASA Administrator and the Associate Administrator for the Human Exploration and Operations Mission Directorate sent a letter to SpaceX expressing concerns about the company’s systems engineering and management practices, hardware installation and repair methods, and telemetry systems based on LSP’s review of the failure.

NASA’S RESPONSE TO SPACEX’S JUNE 2015 LAUNCH FAILURE: IMPACTS ON COMMERCIAL RESUPPLY OF THE INTERNATIONAL SPACE STATION

https://oig.nasa.gov/audits/reports/FY16/IG-16-025.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 12:09 am

I did step thought the video frame by frame, and what I believe I saw was a object with the approximate geometry and known dimensions of the helium COPV, self-propelled by venting helium though a tube that is somewhere between 1 and 1.5 inch diameter (tube dimension from photos of the vessels available on line).  The object is being propelled by the venting gas, not the force of the detonation-deflagration.  You can see the object nearly disappear in one frame when the tumble orients it base on to the camera and the cloud of venting gas obscures its shape.

LOL, thank you for not casting me into the pit of despair as others have done on this forum.  :)  For all who would love to down-vote me if this were Reddit, I have a 10 acre farm, 13 patents, and have a better solution in process for global internet services than Elon.  We'll see who gets there first.  :)

Below is the image reference that I'm trying to understand WRT to COPV failure.

There seems to be one object in this composite of two frames, the first & second frame of the USLaunchReport video.  There are multiple assumptions that it's 60 frames per second, but it looks like the youtube version is 30 frames per second.  Your milage may vary.... :)

The image depicts a hypothetical trajectory on a linear basis.  That's the red line.

The black lines show the horizontal distance travel  (X) but not Y or Z.  The Right black line is the measurable line.  The left line is the inferred line pointing to where that object may have originated.  Frame 3 shows it on the same trajectory but 1/4 of the distance between frame suggesting that it is decelerating.

Assuming 30 fps, between Frame 1 and Frame 2, its average velocity is about 1,000 feet per second.

Now my problem is this.  In Frame 0, there is no indication of any failure of any kind.

1/30th of a second later this object can be found, and 1/30th of a second later its X velocity implies it's moving at 1,000 feet per second, more or less.

When a COPV fails, in 1/30th of a second, it has to rupture the LOX and RP1 tanks, ignition has to occur, and the resulting detonation/deflagration has to propel this visible object to  1,000+ feet per second.

I'm really curious to know how a COPV failure can do that.

I can accept that a COPV failure can rupture tanks.

I have difficulty seeing how in 1/30th of a second, a COPV failure and ignition results in propelling even a ping pong ball.  Gaining that kind of velocity from the resulting detontation/deflagration gets up to 1,000 feet per second if my photo interpretation is accurate.

I'm not saying a COPV failure didn't happen, I just don't know how that failure followed by tank failure, followed by ignition, gets my ping pong ball moving that fast.

You're clearly a COPV failure proponent, so I'm wondering if you can reconcile what I think I'm seeing, which is speculative, with what you know and have seen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/04/2016 12:25 am
I was looking at the frame by frame 1080p from the update thread. There is one object that out accelerates everything at :23. It appears to track diagonally from the point source of the detonation with a flare (burn) to it's appearance...
https://www.youtube.com/watch?v=Yk4huQ3Iyhg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/04/2016 12:26 am
If one went with the COPV failure theory as root cause for both failures, it would be interesting to work out what the chances would have been that both failures happened during launch campaigns and not in Texas.

My guess (for what it's worth) - the LOX is doing something to the composite overwrap that depends on the number of fill/drain cycles. These bottles are bursting. S2's LOX tank is smaller and has less head space than S1, so it has ruptured two times now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/04/2016 12:37 am
There seems to be one object in this composite of two frames, the first & second frame of the USLaunchReport video.  There are multiple assumptions that it's 60 frames per second, but it looks like the youtube version is 30 frames per second.  Your milage may vary.... :)
Youtube has multiple versions at different resolutions available - see the "Quality" menu which becomes available when you click on the gear on the lower right of the controls. 

In Chrome on OSX I see:

  1080p60
  720p60
  480p
  360p
  240p
  144p

but the available resolutions may depend on what video codecs are available in your browser.

The 1080p60 and 720p60 resolutions are 60fps; the others are 30fps -- look at the positions of the bird flying right to left.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NaN on 09/04/2016 12:55 am
The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

This reply is a bit late, but I have a question specifically about your implication that the CRS-7 failure could have been caused by a failed COPV rather than a failed strut.
The COPV are under very high pressures to start with and if they fail, they will do so catastrophically (burst, unzip from the point of failure) and release the helium very rapidly. Is that a true statement?
The CRS-7 failure was very different from the AMOS-6 failure, because it occurred over a much longer period of time. The helium leak occurred over about 250ms, and the telemetry indicated partial loss and then recovery of pressure within the helium system. This flow rate exceeded the relief valve capacity, which is why the manhole cover blew off the top, which ultimately caused S2 collapse - but IMO a failed COPV would have actually ruptured S2 'instantly' from the pressure wave and looked very different.
So, I'd like clarification on how you think a failed COPV could have ended up causing CRS-7 failure given the long timelines involved.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/04/2016 01:04 am
Out of curiosity, I have a couple of questions about this method of Helium storage. I see that several Russian launch vehicles (Zenit, Angara, Soyuz) submerge at least some of their helium containers in the LOX tanks. Now, I have only seen references and drawings which indicate that these are metal spheres, and not necessarily COPV's. I also haven't been able to find any references to these vehicles having failures due to these.

I understand that SpaceX is not unique using COPV's for spaceflight, but are they unique in using them submerged in LOX? Again, I have only been searching for half a day, but have been unable to find any failures like this on vehicles with the same fuel combination.

Edit: I see that Zenit used titanium spheres.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: andy_l on 09/04/2016 01:37 am
Interesting article here http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080009730.pdf from the Constellation programme back in 2008 about designing and testing COPV for cryo load and immersion (albeit test conditions were LN2).

Also a useful general primer on COPV including failure modes here https://ston.jsc.nasa.gov/collections/trs/_techrep/SP-2011-573.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John-H on 09/04/2016 02:16 am
There must be a regulator to get from COPV pressure to tank pressure. If the regulator fails open the tank will blow. Has this ever happened?  Does SpaceX use industry standard regulators?

John
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/04/2016 02:16 am
The general similarity of this event to the in-flight failure should be causing eyebrows to be raised.  The obvious retort is "how could the strut have failed again if the vehicle wasn't under acceleration?"  But an equally valid question is, "what if the proximate cause of the in-flight failure wasn't the strut but the COPV itself failing?"

This reply is a bit late, but I have a question specifically about your implication that the CRS-7 failure could have been caused by a failed COPV rather than a failed strut.
The COPV are under very high pressures to start with and if they fail, they will do so catastrophically (burst, unzip from the point of failure) and release the helium very rapidly. Is that a true statement?
The CRS-7 failure was very different from the AMOS-6 failure, because it occurred over a much longer period of time. The helium leak occurred over about 250ms, and the telemetry indicated partial loss and then recovery of pressure within the helium system. This flow rate exceeded the relief valve capacity, which is why the manhole cover blew off the top, which ultimately caused S2 collapse - but IMO a failed COPV would have actually ruptured S2 'instantly' from the pressure wave and looked very different.
So, I'd like clarification on how you think a failed COPV could have ended up causing CRS-7 failure given the long timelines involved.


Quick reply: they can fail by a number of methods; others have also posted links to papers on the subject.  Threaded and other joints to the tank boss can fail in slow leak mode.  (The SpaceX looks to not have a threaded joint; they must transition to stainless tube at some point but we don't know how that is done.)  If the winding fails, a much more "instantaneous" leak can unfold, of course.

I'll point out that a tube or joint failure will vent the COPV fairly quickly while also generating on the order of 10G of bottle acceleration...it is basically a helium rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/04/2016 02:31 am

I did step thought the video frame by frame, and what I believe I saw was a object with the approximate geometry and known dimensions of the helium COPV, self-propelled by venting helium though a tube that is somewhere between 1 and 1.5 inch diameter (tube dimension from photos of the vessels available on line).  The object is being propelled by the venting gas, not the force of the detonation-deflagration.  You can see the object nearly disappear in one frame when the tumble orients it base on to the camera and the cloud of venting gas obscures its shape.

LOL, thank you for not casting me into the pit of despair as others have done on this forum.  :)  For all who would love to down-vote me if this were Reddit, I have a 10 acre farm, 13 patents, and have a better solution in process for global internet services than Elon.  We'll see who gets there first.  :)

Below is the image reference that I'm trying to understand WRT to COPV failure.

There seems to be one object in this composite of two frames, the first & second frame of the USLaunchReport video.  There are multiple assumptions that it's 60 frames per second, but it looks like the youtube version is 30 frames per second.  Your milage may vary.... :)

The image depicts a hypothetical trajectory on a linear basis.  That's the red line.

The black lines show the horizontal distance travel  (X) but not Y or Z.  The Right black line is the measurable line.  The left line is the inferred line pointing to where that object may have originated.  Frame 3 shows it on the same trajectory but 1/4 of the distance between frame suggesting that it is decelerating.

Assuming 30 fps, between Frame 1 and Frame 2, its average velocity is about 1,000 feet per second.

Now my problem is this.  In Frame 0, there is no indication of any failure of any kind.

1/30th of a second later this object can be found, and 1/30th of a second later its X velocity implies it's moving at 1,000 feet per second, more or less.

When a COPV fails, in 1/30th of a second, it has to rupture the LOX and RP1 tanks, ignition has to occur, and the resulting detonation/deflagration has to propel this visible object to  1,000+ feet per second.

I'm really curious to know how a COPV failure can do that.

I can accept that a COPV failure can rupture tanks.

I have difficulty seeing how in 1/30th of a second, a COPV failure and ignition results in propelling even a ping pong ball.  Gaining that kind of velocity from the resulting detontation/deflagration gets up to 1,000 feet per second if my photo interpretation is accurate.

I'm not saying a COPV failure didn't happen, I just don't know how that failure followed by tank failure, followed by ignition, gets my ping pong ball moving that fast.

You're clearly a COPV failure proponent, so I'm wondering if you can reconcile what I think I'm seeing, which is speculative, with what you know and have seen.

Apologies, since I don't think I'm answering your question directly, mainly since I don't have much time left this weekend for further "analysis," but I wanted to show what I interpret to be one of the COPVs (presumably the one that didn't start the event in my model).

Now back to my regularly scheduled workload... :)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/04/2016 02:37 am
During a launch, there is often (always?) a camera looking right at the umbilical connections.  I'd assume this camera is also activated for hot fires, and the recording from this camera seems like the first thing to check.

Lou,

Yeah, the last SpaceX press release on the investigation talked about reviewing video data along with 3000 channels of telemetry. It's probably a safe guess that they have more and better camera angles than the publicly available video we're all speculating off of. Here's to hoping they find the root cause quickly, conclusively, and convincingly.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/04/2016 02:44 am
If this is true, then why didn't the pressure vessel burst open as in CRS-7 accident, but there was some kind of explosion instead? IMHO, the plauseible expectation in case of any pressure vessel failure, is first to see large cloud of condensate and only then ignition. That was not the case.

We cant externally see either of the domes which also comprise the pressure vessel. Maybe CRS-7 was what happens when the forward dome fails, and this is what happens when the aft dome fails.

Also CRS-7 might have been what happens when you get a slow leak, but this when you get something more rapid, and/or have high velocity debris from a pressure system failure hitting the common bulkhead? Who knows.

I wonder if SpaceX has their upper stage LOX tank internal camera powered-on during ground tests like this?

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/04/2016 02:50 am
I find the interpretation of the object going over the fairing right to left as a COPV very interesting because I can't come up with an explanation of that trajectory (even taking into account that we're seeing a 2d image of a 3d trajectory) that doesn't imply an object with some ongoing thrust, and the only thing I can think of with that potential is a high pressure tank of some sort, and the only ones I know of in the general origination area are COPV helium. (I think HMXHMX has it right- thank you HMXHMX for all the info)

So, if that object is a COPV full of helium, I can see how it could end up on that trajectory from an internal explosion, but not an external one.

Therefor, if this object is under pressurized gas propulsion as implied from its trajectory, does that rule out the external explosion theories? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/04/2016 02:56 am
Just as a bit of logic -- a COPV or two could be expected to be seen flying out of an explosion of a stage 2.  The COPVs are some of the few things that are likely to survive such a violent explosion intact.

If the flying "thingie" is a COPV (which wouldn't surprise me), after having been ripped out of its plumbing by a forceful explosion that literally shredded almost all of the tankage and likely all of the metal plumbing, I would also expect to see it venting its helium through the now-disconnected plumbing attached to the COPV.  That doesn't in the slightest imply that this COPV caused the accident -- and it says nothing, for or against, as to whether a COPV was at fault.

Prefacing this by saying I know no one has insinuated this, but I want to cover it in this bit of barracks-analysis -- while the "thingie" may be a COPV, I can't imagine, if a COPV failure caused this accident by itself explosively failing, that this could be the COPV that caused the accident.  If a COPV came apart, shredded pieces of it will be found, no more, and nothing recognizable would likely have been ejected from the fireball.

And, on another topic -- guys?  If this was a fault in the second stage and y'all think that this will be a simpler investigation than CRS-7 because there is debris to analyze, I wouldn't hold your collective breaths.  It will be years before all the debris is found, and no way to tell how far away from the pad a crucial fragment might have been tossed.  As has been noted elsewhere, debris from other pad failures has been found decades after the parent anomalies...  :(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/04/2016 03:03 am
I downloaded "the file" in 1080p 60fps from YouTube and stepped thru it frame by frame on the big monitor I have access to this weekend...   8)

Put me in the "a COPV blew up in S2" camp... at this time...   :o  :P  :'(

Ref initial flash seen... as frame #1...
By frame #2 and #3... two small pieces can be seen flying very fast away from the stage...
I highlighted the two in frame#4 and posted a zoomed screencap below...
They are seen very clearly as two bright points in frame #5 and vanish by frame #6...
My take is... this is two chunks of the COPV moving very fast... holed the stage and disappeared in 1/10 second.

Rocket Science up above points out another object seen flying away very fast... I too saw that...
It appears just after the two seen above disappear...

The second screencap is what appears to be a partial COPV first visible at frame #20 and shown at frame #25..
This is the item many others have been discussing for days as it arcs up and toward the camera...
My take is yes... this is the rest of the blown COPV ripped free of the stage and going flying...

I did not change my mind... till I read thru today's postings...
...then set a while in front of this big screen monitor...hooked to a high end video processing PC...

This is my latest and likely final opinion on topic...  ;)

I hope like hell the 4 pieces mentioned are found and survived the aftermath...  :(

On edit...
I'll download the just released 2160p (4K) version and see if my opinion changes...
See follow up... next page...
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578175#msg1578175 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578175#msg1578175)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Orbiter on 09/04/2016 03:07 am
USLaunchReport just released a new video:

https://www.youtube.com/watch?v=9rRDpX9F5U8
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: A_M_Swallow on 09/04/2016 03:23 am
The YouTube frame rate can be calculated from the number of frames needed to show the payload's fall. It is accelerating under gravity at 9.81 m/s/s or 32 feet/s/s.

v = u + at
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/04/2016 04:17 am
The new USLaunchReport video is 4K - 2160p...  8)  at 30 fps...  :(
https://www.youtube.com/watch?v=9rRDpX9F5U8 (https://www.youtube.com/watch?v=9rRDpX9F5U8)
Not near as useful to step thru frame by frame as the 1080p 60fps is... looking for objects flying at high speed... :P

On edit...
Attached 3rd frame screen cap (1st is initial flash seen) of the new video...
You can see the two pieces highlighted again... they vanish by frame #4 at 30 fps...
My opinion... they are hauling azz and took down the rocket... just my opinion...   ;)

See prior posting last page for shots from 1080p 60fps source... plus other comments...
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578168#msg1578168 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578168#msg1578168)

I will say the other later object thought to be a flying COPV does show much more detail as it tumbles...

Later edit... attached screenshot with possible tumbling COPV...
Folks... that looks like a tumbling COPV cylinder on the big screen in 4K... it really does...  :o
If you have access to a 4K monitor/TV... I urge you to watch for yourself and decide...


Much later edit...
I was advised the 4K explosion footage was up-scaled and overprocessed...
On review... I agree... and withdrawal my claim as struck thru above... 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/04/2016 06:40 am
You know what, I installed the frame-by-frame add-on and looked again.

It's more than I said before.

The first detonation event goes through about 5 key frames, expanding on the first 3, and then contracting.

As it does so, you can still see the "far" side of the stage, and it is undisturbed.

As the detonation event recedes, the there appears a lot of black smoke / liquid RP1, and the secondary melt-down ensues.

---

That was a description of what I saw.  Interpretation?  Still could equally be an external or internal failure.

--------

I recommend for all to install and watch for yourself.  "[" and "]" for stepping through the frames.  Get the 1080 video link from update thread.

FYI, you don't need to install anything. The , and . keys on youtube allow framesteping forward and backward. This may not work however if you have a very outdated browser that forces Youtube to use its flash player as opposed to its HTML player.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/04/2016 07:23 am

I'll download the just released 2160p (4K) version and see if my opinion changes...

FYI, that 4K isn't 4K. It's USLaunchReport trying to milk some more views on his video. It's an upscale that is actually lower quality with a bunch of extra pixelation (for the part where the explosion occurs) than the original 1080p. You shouldn't use the 4K for any analysis. He added a couple seconds of film of the pad burning that is actually 4K footage, but the rest of the video is not.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/04/2016 07:39 am

I'll download the just released 2160p (4K) version and see if my opinion changes...

FYI, that 4K isn't 4K. It's USLaunchReport trying to milk some more views on his video. It's an upscale that is actually lower quality with a bunch of extra pixelation (for the part where the explosion occurs) than the original 1080p. You shouldn't use the 4K for any analysis. He added a couple seconds of film of the pad burning that is actually 4K footage, but the rest of the video is not.

I checked and agree... I made changes in my 2nd post up above based on your finding... Thanks...  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jdeshetler on 09/04/2016 07:45 am

I'll download the just released 2160p (4K) version and see if my opinion changes...

FYI, that 4K isn't 4K. It's USLaunchReport trying to milk some more views on his video. It's an upscale that is actually lower quality with a bunch of extra pixelation (for the part where the explosion occurs) than the original 1080p. You shouldn't use the 4K for any analysis. He added a couple seconds of film of the pad burning that is actually 4K footage, but the rest of the video is not.

I concurred.
 
It looks like that their unmanned camera was left running during the static firing which is why the camera never shifted the whole time.
The 1080/60p mode was selected over 4K so their SSD storage won't get full if the static fire was delay a bit. It's either 1080/60p OR 4K format, not both....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mlindner on 09/04/2016 07:47 am

I'll download the just released 2160p (4K) version and see if my opinion changes...

FYI, that 4K isn't 4K. It's USLaunchReport trying to milk some more views on his video. It's an upscale that is actually lower quality with a bunch of extra pixelation (for the part where the explosion occurs) than the original 1080p. You shouldn't use the 4K for any analysis. He added a couple seconds of film of the pad burning that is actually 4K footage, but the rest of the video is not.

I checked and agree... I made changes in my 2nd post up above based on your finding... Thanks...  :)

I would agree with your thoughts that it's a tumbling COPV though. I've thought that since I first watched the video. The vertical shooting spinning object is quite obviously (to me) a COPV.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Nibb31 on 09/04/2016 08:00 am
Hopefully this time they will be able to recover some debris, including the COPVs, and perform some forensics. They couldn't do this for CRS-7.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/04/2016 08:13 am
Hopefully this time they will be able to recover some debris, including the COPVs, and perform some forensics. They couldn't do this for CRS-7.
This is what I am hoping as well. Last time the debris went in the drink and smashed into a million pieces this time even with the fire there should be some left.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/04/2016 08:27 am
The YouTube frame rate can be calculated from the number of frames needed to show the payload's fall. It is accelerating under gravity at 9.81 m/s/s or 32 feet/s/s.

v = u + at


Ctrl-click over a YouTube video (you may have to be on YouTube) brings up a contextual menu > click 'Stats for nerds' and the frame rate is there after the @ sign after 'Resolution'

(Might be a right click on Windows, I'm using OSX)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/04/2016 09:51 am
Any other component gases or potentially a tank component for the first few nano seconds which would compromise the tank after which the rp 1 tank would probably be compromised leading to an abundance of fuel.

Having combustible gas component in the oxygen tank ullage would denote a colossal GSE flaw. Incomplete purging of atmosphere would not suffice here. Would have to contaminate the tank with some light alkane or hydrogen.

Some other contamination, a big blob of grease etc? Maybe, but again a colossal procedural flaw.

A tank component burning? One would think people have learned from Apollo 13 but the COPVs themselves might sustain a fire if ignited. Even Teflon burns in pure oxygen so I guess composite resins too. Exposed carbon fiber most certainly would. Dunno if the COPVs are protected with some passive layer.

Anyhow, on a general note I think the COPV is one way or the other the most probable culprit. There seems to be nothing out of the ordinary in one frame and bigbadaboom well on its way in the next frame. Hard to imagine anything other than COPV or FTS exploding doing that. Shape of the explosion and long proven track record all but rule out FTS.

The COPVs appear to be in the upper part of the LOX tank, adjacent to tank walls. If one goes pop it is more like to immediately burst through the minimum resistance path, tank wall, than have time to rupture common bulkhead, mix RP-1 and oxygen at correct ratio, and then either ignite it inside the tank or spray a cloud of explosive mixture outside the vehicle and ignite that.

Btw the one in the imagery supposedly flying out venting helium might not be the one which originally failed, but one next to it deciding to exit the scene.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: andy_l on 09/04/2016 10:00 am
Before I go any further, I currently hold no opinion on the LOV incident, other than it was energetic and extremely fast. 3 frames of video shot from 4km away does not provide enough data to draw a conclusion. Having said that, there seems to be a lot of discussion regarding COPV cyro compatibility being insurmountable - two pages ago I posted a link to a NASA article on COPV cyro testing which is worth a read:


Quote
"The test articles will consist of vessels lined with Inconel 718 and Al-2219. Inconel 718 has been selected since it is LO2 compatible and it provides excellent corrosion resistance and provides good material fracture toughness at cryogenic temperatures.2 Al-2219 has been selected since it is lighter in weight and it can be used if the risk of exposure to LOX is acceptable based on the propulsion system design ... The 31-43B resin has been selected based on previous research and development work performed by ARDE’, Inc. The Toray T-1000 carbon fiber by Torayca has been selected since NASA plans to use it for the fabrication of the flight vessels."
...
Following are the test procedures to be performed on the series of test articles.

Ambient
1. Perform 2 proof pressure tests hydrostatically to 1.25 X MOP = 5625 psig.
2. Perform 100 pressure cycles from 0 to 4,500 psig with water.
3. Perform hydrostatic burst pressure tests using Digital Imaging Correlation (DIC) equipment to measure the strain as the pressure is increased to the rupture event.

Cryogenic
1. Perform 2 proof pressure tests to 1.25 X MOP = 5625 psig at -320°F where LN2 is in the COPV and GN2 is the pressurant.
2. Perform thermal cycle testing 5 times where the COPV is filled with and submerged in LN2 with no applied pressure.
3. Perform 100 pressure cycles charging to 4,500 psig at -320°F using LN2 where GN2 is the pressurant while the COPV is submerged in LN2.
4. Perform burst pressure tests with LN2 at -320°F.

...
These results for the burst tests for both Inconel 718 and Al-2219 show that the minimum burst pressure was met where the smallest burst pressure is 2.36 X MOP or 10,620 psig for the cryogenic burst tests of Inconel 718. Comparisons of the Al-2219 versus the Inconel 718 show that the Al-2219 provided higher burst pressures at a lower vessel weight than the Inconel 718. The Al-2219 vessels have more overwrap due to the reduced tensile strength of Al-2219 but the results show that Al-2219 can provide the required burst pressures after proof tests, pressure cycles and thermal cycles.
...
The remaining risk for COPVs that needs to be tested regards stress rupture life at cryogenic conditions.


100 cycles whilst charged to 4500psi with (and immersed in) LN2 seems like a good data point to me regarding performance of tailored composites in cryogenic conditions. I would be more interested in the LOX compatibility of the Al liner material, which the article somewhat sidesteps.

Cheers,


Andy
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/04/2016 10:01 am
Any other component gases or potentially a tank component for the first few nano seconds which would compromise the tank after which the rp 1 tank would probably be compromised leading to an abundance of fuel.

Having combustible gas component in the oxygen tank ullage would denote a colossal GSE flaw. Incomplete purging of atmosphere would not suffice here. Would have to contaminate the tank with some light alkane or hydrogen.

Some other contamination, a big blob of grease etc? Maybe, but again a colossal procedural flaw.

A tank component burning? One would think people have learned from Apollo 13 but the COPVs themselves might sustain a fire if ignited. Even Teflon burns in pure oxygen so I guess composite resins too. Exposed carbon fiber most certainly would. Dunno if the COPVs are protected with some passive layer.

Anyhow, on a general note I think the COPV is one way or the other the most probable culprit. There seems to be nothing out of the ordinary in one frame and bigbadaboom well on its way in the next frame. Hard to imagine anything other than COPV or FTS exploding doing that. Shape of the explosion and long proven track record all but rule out FTS.

The COPVs appear to be in the upper part of the LOX tank, adjacent to tank walls. If one goes pop it is more like to immediately burst through the minimum resistance path, tank wall, than have time to rupture common bulkhead, mix RP-1 and oxygen at correct ratio, and then either ignite it inside the tank or spray a cloud of explosive mixture outside the vehicle and ignite that.

Btw the one in the imagery supposedly flying out venting helium might not be the one which originally failed, but one next to it deciding to exit the scene.
We are more or less in agreement but I don't think an internal ignition of some kind can yet be ruled out.

Also, yes I have doubts that the COPV seen venting after ejection was the failed tank the failed one probably would have totally outgassed already. Still quite ineteresting however.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/04/2016 10:04 am
Before I go any further, I currently hold no opinion on the LOV incident, other than it was energetic and extremely fast. 3 frames of video shot from 4km away does not provide enough data to draw a conclusion. Having said that, there seems to be a lot of discussion regarding COPV cyro compatibility being insurmountable - two pages ago I posted a link to a NASA article on COPV cyro testing which is worth a read:


Quote
"The test articles will consist of vessels lined with Inconel 718 and Al-2219. Inconel 718 has been selected since it is LO2 compatible and it provides excellent corrosion resistance and provides good material fracture toughness at cryogenic temperatures.2 Al-2219 has been selected since it is lighter in weight and it can be used if the risk of exposure to LOX is acceptable based on the propulsion system design ... The 31-43B resin has been selected based on previous research and development work performed by ARDE’, Inc. The Toray T-1000 carbon fiber by Torayca has been selected since NASA plans to use it for the fabrication of the flight vessels."
...
Following are the test procedures to be performed on the series of test articles.

Ambient
1. Perform 2 proof pressure tests hydrostatically to 1.25 X MOP = 5625 psig.
2. Perform 100 pressure cycles from 0 to 4,500 psig with water.
3. Perform hydrostatic burst pressure tests using Digital Imaging Correlation (DIC) equipment to measure the strain as the pressure is increased to the rupture event.

Cryogenic
1. Perform 2 proof pressure tests to 1.25 X MOP = 5625 psig at -320°F where LN2 is in the COPV and GN2 is the pressurant.
2. Perform thermal cycle testing 5 times where the COPV is filled with and submerged in LN2 with no applied pressure.
3. Perform 100 pressure cycles charging to 4,500 psig at -320°F using LN2 where GN2 is the pressurant while the COPV is submerged in LN2.
4. Perform burst pressure tests with LN2 at -320°F.

...
These results for the burst tests for both Inconel 718 and Al-2219 show that the minimum burst pressure was met where the smallest burst pressure is 2.36 X MOP or 10,620 psig for the cryogenic burst tests of Inconel 718. Comparisons of the Al-2219 versus the Inconel 718 show that the Al-2219 provided higher burst pressures at a lower vessel weight than the Inconel 718. The Al-2219 vessels have more overwrap due to the reduced tensile strength of Al-2219 but the results show that Al-2219 can provide the required burst pressures after proof tests, pressure cycles and thermal cycles.
...
The remaining risk for COPVs that needs to be tested regards stress rupture life at cryogenic conditions.


100 cycles whilst charged to 4500psi with (and immersed in) LN2 seems like a good data point to me regarding performance of tailored composites in cryogenic conditions. I would be more interested in the LOX compatibility of the Al liner material, which the article somewhat sidesteps.

Cheers,


Andy


Spyx helium system is known to run in excess of 6000 psi. Fyi
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: andy_l on 09/04/2016 10:15 am

Spyx helium system is known to run in excess of 6000 psi. Fyi


4500psi was the design MOP for the test articles - that in itself does not preclude designing tanks for a higher MOP. FYI.

Additionally, as previously quoted the lowest burst pressure was "2.36 X MOP or 10,620 psig".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vapour_nudge on 09/04/2016 11:32 am
Hmm. SpaceX rockets are definitely cheaper but I wonder if their insurance costs will be higher now and eat into the previous cost savings over more expensive yet more reliable alternatives?
I wonder too how the cost of the rebuilding of the launch pad will be recovered and if they'll need additional procedures now that will raise costs. I'm interested to see if they'll lift their prices.

Also, to save multiple posts, I'm still interested to see how JCM classifies this one in his log:
http://planet4589.org/space/jsr/latest.html
I notice Steven Pietrobon has logged it on his site:
http://www.sworld.com.au/steven/space/uscom-man.txt
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/04/2016 11:46 am
Happy Sunday, peeps!

So! I hear there was a bit of an overnight fire sale on silly posts. Thankfully they've mainly been purged via natural moderation (PS bad posts get removed, so don't respond to them because the chain is removed, otherwise the bad post remains via you quoting it....so don't quote bad posts).

Anyway, let's try a version of what I said about 12 hours ago.

1) Nooooooo stupid links. I specifically provided the Daily Star as an example of that, and of course someone posted a link to it as soon as I had gone to bed to get some beauty sleep (*crowd shouts* "you don't need it Chris" - aww thanks! ;)). Mods have dealt with it, but come on now, down with tabloid nonsense, even if you post "Look at this nonsense".

2) One (actually a good) member rushed in admitting they hadn't been online for a few days and assumed it was already a COPV failure....and proceeded to go nuts about a second COPV event. That's only mentioned in the speculation (ugg) as a potential. There is no root cause at this time. Point is, always read back before posting.

3) If you come on here and say "sorry, can't say who I am" <-- that's fine. But you're going to get taken to task if you then run off some "listen to me, because I know" comment. If you really want, you can PM me and then I can at least say "hey, it's cool, this guy's legit", or something - not least as the real industry guys here will highly likely catch you out. But the last thing we need is someone signing up with billy_the_gamer_FTW and posting "Hi, I can't say who I am, but in my day to day job of running NASA I think the failure was caused by..." See what I mean? ;)

Otherwise this is - as always - an interesting thread. Let's keep it that way.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/04/2016 12:25 pm
Does anyone know when in the count Stage 2 helium loading occurs?

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577625#msg1577625

Bad form to quote myself but I haven't been able to find this info and the question may have been lost in the crush yesterday by someone who does know.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 12:27 pm
COPV or not COPV, that is the question.

Let me pose some puzzlers for the folks that are now in the pro-COPV camp.

1.  Image 1 below, showing the object moving up to the right, compared to  Image 2 below, showing the trajectory path through the F9.  Is there a COPV on any part of that trajectory path?  If not, how did it get on the observed trajectory?  Keep in mind, most things moving at 1,000 feet per second don't bounce very well on impact.

2.  Original first frame of the event, Image 3 below under different leveling modes.  How does a COPV failure also create a detonation front that consumes 35 X 85 feet of burn front in one frame? That detonation front is clearly not mostly reflection and lens aberrations.

3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.  Image 5

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheSwiss on 09/04/2016 12:37 pm
Does anyone know when in the count Stage 2 helium loading occurs?

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577625#msg1577625

Bad form to quote myself but I haven't been able to find this info and the question may have been lost in the crush yesterday by someone who does know.

Spaceflight 101 has it at
T-0:13:15   Stage 2 Helium Loading
http://spaceflight101.com/falcon-9-ft-countdown-timeline/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/04/2016 12:49 pm


COPV or not COPV, that is the question.

Let me pose some puzzlers for the folks that are now in the pro-COPV camp.

1.  Image 1 below, showing the object moving up to the right, compared to  Image 2 below, showing the trajectory path through the F9.  Is there a COPV on any part of that trajectory path?  If not, how did it get on the observed trajectory?  Keep in mind, most things moving at 1,000 feet per second don't bounce very well on impact.

... unless they are a pressurised COPV. That would bounce very good.

Quote

2.  Original first frame of the event, Image 3 below under different leveling modes.  How does a COPV failure also create a detonation front that consumes 35 X 85 feet of burn front in one frame? That detonation front is clearly not mostly reflection and lens aberrations.

3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.  Image 5

There are at least 4 COPVs in S2, iirc. If one of them failed, mangled the inside of the S2 and caused the propellants to mix and ignite, the other three would be torn loose and propelled by the pressurised helium inside them to basically any trajectory.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/04/2016 12:54 pm
Does anyone know when in the count Stage 2 helium loading occurs?

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577625#msg1577625

Bad form to quote myself but I haven't been able to find this info and the question may have been lost in the crush yesterday by someone who does know.

Spaceflight 101 has it at
T-0:13:15   Stage 2 Helium Loading
http://spaceflight101.com/falcon-9-ft-countdown-timeline/

Ah, thank you. I note several other helium events relating to S2 in particular. At T-13:00 there is "Stage 2 LOX Flow Adjustment for Helium Cryo Load." At T-6:45 there is "Stage 2 Helium Transition to Pipeline." As late as T-1:25 there is "Helium Loading Termination."

Clearly, the countdown is a pretty dynamic process - something with "lots of moving parts," that almost certainly will vary from day to day based on environmental conditions, hysteresis ("lag") in instrumentation or process equipment, etc. People without process engineering and spaceflight experience might not realize that.

At any rate, I still have a strong feeling this event will be something more complex than simply "ZOMG!!! A COPV failed!!!" Bad or lagging sensor data; malfunctioning GSE; subtle flaw in the sequencing code that runs the countdown; something. Major catastrophic failures rarely if ever result from a single causative factor.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/04/2016 01:44 pm
Okay, and I hate myself for asking this, but as I've not seen direct mention of it in this giant thread, I'll ask (and mods, please feel free to remove this post if it's too over the top)

What is seen streaking past the stage right at time of the anomaly? It's not a bug close to the lens, as it appears to go behind a lightning tower. It is not a bird, as it's not flapping, I believe it's going far to fast, it looks metallic in the reflection of the blast, it's going in a very linear line, and it doesn't veer from its path as you would assume a bird would do if something blows up next to you...

Look at right side of frame at :29

https://m.youtube.com/watch?v=HXqG-R8O39g
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JWag on 09/04/2016 01:47 pm
If it was behind the towers, it would be in focus. Since it's blurry, it's closer to the camera, and the benign explanation that it's a bird or bug (whose apparent motion would be very fast, being close to the camera) makes the most sense.

It's also foolish to make very many inferences from Youtube-compressed video. It's not meant for forensic analysis.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/04/2016 01:50 pm
If RP1 and LOX got mixed inside and then ignited, A) I think the initial detonation would have been much larger, shredding both tank and payload, and B) would not have subsided before the main meltdown began.

I vote for a cold failure that caused a spray outside and maybe weakened the structure, ignition, shock wave, collapse.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/04/2016 01:55 pm
Has anybody tried liquid helium storage in dewar flask as a helium source? Eliminates the high pressure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 02:00 pm
Has anybody tried liquid helium storage in dewar flask as a helium source? Eliminates the high pressure.


The gas is need for its pressure.  Liquid does no good.  How much does a dewar flask cost and weigh?  And have any flown before?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacenut on 09/04/2016 02:05 pm
What is the difference in the helium design of the second stage vs the first stage?  They have never had a problem with the first stage.  If they use basically the same kerolox engines.  Only difference is the upper engine is designed for vacuum. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/04/2016 02:11 pm
What is the difference in the helium design of the second stage vs the first stage?  They have never had a problem with the first stage.  If they use basically the same kerolox engines.  Only difference is the upper engine is designed for vacuum.

There have been He bottle related S1 problems. (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578107#msg1578107)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 02:12 pm


COPV or not COPV, that is the question.

Let me pose some puzzlers for the folks that are now in the pro-COPV camp.

1.  Image 1 below, showing the object moving up to the right, compared to  Image 2 below, showing the trajectory path through the F9.  Is there a COPV on any part of that trajectory path?  If not, how did it get on the observed trajectory?  Keep in mind, most things moving at 1,000 feet per second don't bounce very well on impact.

... unless they are a pressurised COPV. That would bounce very good.

Quote

2.  Original first frame of the event, Image 3 below under different leveling modes.  How does a COPV failure also create a detonation front that consumes 35 X 85 feet of burn front in one frame? That detonation front is clearly not mostly reflection and lens aberrations.

3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.  Image 5

There are at least 4 COPVs in S2, iirc. If one of them failed, mangled the inside of the S2 and caused the propellants to mix and ignite, the other three would be torn loose and propelled by the pressurised helium inside them to basically any trajectory.

OK, let's see some COPV hand waving on this one.

The first image below is a fragment shooting up and to the left, visible in three frames, with a line through it's trajectory path.  This one obviously could not have bounced off the tower.  (720p version on YouTube).

On that trajectory, how does a COPV or any other fragment get on this trajectory?  Is this also a COPV moving  at 700+ feet per second?  If it's not a COPV, why is the other one a COPV but this one isn't.

And what's at the intersection of the two mapped trajectories?

Just a little physics.  Assume a COPV weighs a paltry 20 kg and is moving at 300 meters per second.  It's got 900,000 joules of kinetic energy when it impacts a steal beam and bounces.  Exactly how does that become an elastic collision instead of a shattering event?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/04/2016 02:17 pm


COPV or not COPV, that is the question.

Let me pose some puzzlers for the folks that are now in the pro-COPV camp.

1.  Image 1 below, showing the object moving up to the right, compared to  Image 2 below, showing the trajectory path through the F9.  Is there a COPV on any part of that trajectory path?  If not, how did it get on the observed trajectory?  Keep in mind, most things moving at 1,000 feet per second don't bounce very well on impact.

... unless they are a pressurised COPV. That would bounce very good.

Quote

2.  Original first frame of the event, Image 3 below under different leveling modes.  How does a COPV failure also create a detonation front that consumes 35 X 85 feet of burn front in one frame? That detonation front is clearly not mostly reflection and lens aberrations.

3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.  Image 5

There are at least 4 COPVs in S2, iirc. If one of them failed, mangled the inside of the S2 and caused the propellants to mix and ignite, the other three would be torn loose and propelled by the pressurised helium inside them to basically any trajectory.

OK, let's see some COPV hand waving on this one.

The first image below is a fragment shooting up and to the left, visible in three frames, with a line through it's trajectory path.  This one obviously could not have bounced off the tower.  (720p version on YouTube).

On that trajectory, how does a COPV or any other fragment get on this trajectory?  Is this also a COPV moving  at 700+ feet per second?  If it's not a COPV, why is the other one a COPV but this one isn't.

And what's at the intersection of the two mapped trajectories?

Just a little physics.  Assume a COPV weighs a paltry 20 kg and is moving at 300 meters per second.  It's got 900,000 joules of kinetic energy when it impacts a steal beam and bounces.  Exactly how does that become an elastic collision instead of a shattering event?

Are you an expert on COPV construction, fracture mechanics and collision physics? How exactly did a 2 pound piece of foam result in the destruction of a an entire shuttle orbiter and loss of 7 crew members?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 03:12 pm

Are you an expert on COPV construction, fracture mechanics and collision physics? How exactly did a 2 pound piece of foam result in the destruction of a an entire shuttle orbiter and loss of 7 crew members?

Nope, are you?  Most of the knowledge here on COPVs comes from technical articles, testing reports from NASA and ESA, and some studies of truck collisions in the EU.  If someone has ever worked on manufacturing or destructive testing of COPVs it would be wonderful if they'd chime in.

Another fragment trajectory shown below, followed by the paths' intersections.  Clearly not converging to a single point.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/04/2016 03:18 pm

Are you an expert on COPV construction, fracture mechanics and collision physics? How exactly did a 2 pound piece of foam result in the destruction of a an entire shuttle orbiter and loss of 7 crew members?

Nope ...

Then really, should you be tossing out the barrage of conclusory remarks about what a COPV will or won't do in a decidedly off-nominal event in close proximity to a low-order detonation/high-energy deflagration like this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/04/2016 03:21 pm

Are you an expert on COPV construction, fracture mechanics and collision physics? How exactly did a 2 pound piece of foam result in the destruction of a an entire shuttle orbiter and loss of 7 crew members?

Nope, are you?  Most of the knowledge here on COPVs comes from technical articles, testing reports from NASA and ESA, and some studies of truck collisions in the EU.  If someone has ever worked on manufacturing or destructive testing of COPVs it would be wonderful if they'd chime in.

Another fragment trajectory shown below, followed by the paths' intersections.  Clearly not converging to a single point.
Is that green line the object I mentioned two pages back post#1164?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 03:23 pm
Not going to be a single point, there are more 6 COPVs in and on the stage
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 03:23 pm

Are you an expert on COPV construction, fracture mechanics and collision physics? How exactly did a 2 pound piece of foam result in the destruction of a an entire shuttle orbiter and loss of 7 crew members?

Nope ...

Then really, should you be tossing out the barrage of conclusory remarks about what a COPV will or won't do in a decidedly off-nominal event in close proximity to a low-order detonation/high-energy deflagration like this?

With all due respect, I was responding to a posting that asserted the COPVs will bounce.  Much as you're questioning my expertise, I was questioning his/hers.

As to what I should be doing here, I'll check with my mother and get back to you.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 03:25 pm
Also some of the items are from the ECS filter boxes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Tonioroffo on 09/04/2016 03:25 pm
To me it seems impossible to try to map a 3D trajectory of a moving object on a 2D compressed, artifacted youtube rendering.  We have no idea about distance, angle, lens used, aperture, possible lens pincushion or barrel at these distances.

I want to know as much as anyone what happened to (or around) S2 but for my peace of mind I'll wait until SpaceX comes forward with more information.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 03:28 pm


Is that green line the object I mentioned two pages back post#1164?

Yes it is, find any others?  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/04/2016 03:28 pm
So this was asked upthread a ways.
What do other vehicles use for helium bottles?
I noticed the atlas V uses helium bottles but I can't seem to find any info on their construction. They appear to be not inside of the tanks. Spaceflight101 just lists helium bottles. This diagram just shows their location for the rd180 and the rl10. The rl10 definitely isn't inside of a tank. Not sure about the lox tank for the rd180. Looks to be at the bottom of the lox tank.
http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf

 

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: madmardy on 09/04/2016 03:31 pm
interesting that no one has taken perspective into account when doing debris trajectories. Because the camera shows something moving down and to the left they seem to assume it is infact moving down and to the left where infact it could be heading towards the camera, with only one angle trajectory plots are just wild guesses. Also lens flares/starbusts do not always point to the brightest area on a flat image as the convex lens will bend light . if you notice lens flares (and u can even try this with your own camera) will occur at an angle to the lens never head on. starbursts are more accurate but even they can be affected by the lens and pan and tilt angles
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/04/2016 03:32 pm
Here is a liquid helium pressurization tank.
http://www.airliquideadvancedtechnologies.com/en/our-offer/space/programs/supercritical-helium-pressurization-tank-for-ariane-5.html
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/04/2016 03:34 pm


COPV or not COPV, that is the question.

Let me pose some puzzlers for the folks that are now in the pro-COPV camp.

1.  Image 1 below, showing the object moving up to the right, compared to  Image 2 below, showing the trajectory path through the F9.  Is there a COPV on any part of that trajectory path?  If not, how did it get on the observed trajectory?  Keep in mind, most things moving at 1,000 feet per second don't bounce very well on impact.

... unless they are a pressurised COPV. That would bounce very good.

Quote

2.  Original first frame of the event, Image 3 below under different leveling modes.  How does a COPV failure also create a detonation front that consumes 35 X 85 feet of burn front in one frame? That detonation front is clearly not mostly reflection and lens aberrations.

3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.  Image 5

There are at least 4 COPVs in S2, iirc. If one of them failed, mangled the inside of the S2 and caused the propellants to mix and ignite, the other three would be torn loose and propelled by the pressurised helium inside them to basically any trajectory.

OK, let's see some COPV hand waving on this one.

The first image below is a fragment shooting up and to the left, visible in three frames, with a line through it's trajectory path.  This one obviously could not have bounced off the tower.  (720p version on YouTube).

On that trajectory, how does a COPV or any other fragment get on this trajectory?  Is this also a COPV moving  at 700+ feet per second?  If it's not a COPV, why is the other one a COPV but this one isn't.

And what's at the intersection of the two mapped trajectories?

Just a little physics.  Assume a COPV weighs a paltry 20 kg and is moving at 300 meters per second.  It's got 900,000 joules of kinetic energy when it impacts a steal beam and bounces.  Exactly how does that become an elastic collision instead of a shattering event?

On the two items seen in the first 5 frames... one going left... one going right...
And including the 3rd item that I and others noted in about frames 6 thru 10 or so...
You seem to be thinking in 2D... based on my interpretation of the talking points your making...
The LONG zoom lens on the camera is messing with us... that I am sure of...  ;)

My opinion... there is a lot of movement towards or away from the camera on all three flying small items...
And the only thing I'm kinda sure about... is the 3rd item is going away fast...  :-\
The left and right items... I am not sure how much Z speed they have... and in which direction.
In any case... the Z speed will drastically alter the intersection point... assuming these came from about the same place...

As to the likely COPV chunk seen long after the situation unfolds...
It's about as interesting as the COPV much later chucked from S1 and impacting the right lightning tower... to me...
It's interesting that it first appeared at about 1/3 second after it all started...
But at 1/3 of a second... there wasn't much left structurally of S2... in my opinion...

Edits - grammer and spelling
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/04/2016 03:35 pm


Is that green line the object I mentioned two pages back post#1164?

Yes it is, find any others?  :)
Thanks, not yet... I'm getting a bit "cross-eyed" looking for them with the bird distractions. ;D I'll get back to you all if I do. A suggestion would be to add some vector arrowheads to yours lines clarity... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 03:35 pm
Here is a liquid helium pressurization tank.
http://www.airliquideadvancedtechnologies.com/en/our-offer/space/programs/supercritical-helium-pressurization-tank-for-ariane-5.html

Super critical is not the same as liquid
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/04/2016 03:35 pm
So this was asked upthread a ways.
What do other vehicles use for helium bottles?
I noticed the atlas V uses helium bottles but I can't seem to find any info on their construction. They appear to be not inside of the tanks. Spaceflight101 just lists helium bottles. This diagram just shows their location for the rd180 and the rl10. The rl10 definitely isn't inside of a tank. Not sure about the lox tank for the rd180. Looks to be at the bottom of the lox tank.
http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf

After looking into the topic over the past day, the Zenit launch vehicle, which appears to be the closest analog to the Falcon, uses titanium spheres for helium storage, submerged in the LOX tanks. Whether there are other materials in addition to titanium, such as some sort of overwrap, I have been unable to determine this. The Angara uses the same system.

I can not find another explicitly stated example of a launch vehicle which submerges COPV's in cryogenic Oxygen, although that doesn't mean there aren't any. From what I have found, vehicles which use COPV's for helium storage do not submerge them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/04/2016 03:36 pm
interesting that no one has taken perspective into account when doing debris trajectories. Because the camera shows something moving down and to the left they seem to assume it is infact moving down and to the left where infact it could be heading towards the camera, with only one angle trajectory plots are just wild guesses. Also lens flares/starbusts do not always point to the brightest area on a flat image as the convex lens will bend light . if you notice lens flares (and u can even try this with your own camera) will occur at an angle to the lens never head on. starbursts are more accurate but even they can be affected by the lens and pan and tilt angles
I mentioned perspective several pages back...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/04/2016 03:40 pm
Here is a liquid helium pressurization tank.
http://www.airliquideadvancedtechnologies.com/en/our-offer/space/programs/supercritical-helium-pressurization-tank-for-ariane-5.html

Super critical is not the same as liquid

at 4 kelvin helium is liquid?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steve D on 09/04/2016 03:41 pm
Any reports on the condition of the launch pad?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/04/2016 03:41 pm
It isn't clear which system ariane V uses currently.
Here is a copv version.

http://www.sciencephoto.com/media/87925/view
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/04/2016 03:46 pm
Any reports on the condition of the launch pad?

I don't have links handy... but several posts elsewhere indicate it's in pretty bad shape...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Saabstory88 on 09/04/2016 03:52 pm
It isn't clear which system ariane V uses currently.
Here is a copv version.

http://www.sciencephoto.com/media/87925/view

Looks like external COPV's: http://www.zamandayolculuk.com/pu-3/roket_ar5_corestage.jpg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/04/2016 03:57 pm
3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.

The trajectory has been concerning me as far as labelling it a COPV is concerned.

Your composite image shows it originating from a point to the right of the vehicle - for it to have been part of the vehicle, it would have had to deflect off the erector to change the trajectory, otherwise it would have headed towards the right of the frame.

I'm with your later comment that it's highly unlikely to be a COPV deflecting off the erector. Regardless of the elasticity of various components, there are two problems with that being the COPV:

(1) The odds of it hitting a part of the erector that deflected it would be very slight - firstly, it would have had to hit an outer upright exactly evenly, otherwise it would have ended up embedded within the lattice of the structure. Secondly, had it not bounced off an upright and gone into the frame of the erector, it wouldn't come out.  Thirdly, it would have had to pass through the clamping structure that holds the top of the vehicle - and that remained intact enough to hold the payload fairing for several seconds after.

(2) If you count the frames from the initial explosion to the point the object becomes visible flying out of the fireball, it's 20 (+/-1). Count forwards 20 frame from there and take a fix on the position and it's a couple of metres above the top of the fairing. That gives you an approximate distance travelled in the 20 frames after it becomes visible, so assuming a relatively constant velocity, the same distance back from the frame it was first visible should give you the approximate start point. (See attached image).

On that basis, it's unlikely this is a COPV (or anything else that was part of the vehicle). My guess would be this is part of the erector, liberated by the shockwave of the blast. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/04/2016 04:02 pm
It isn't clear which system ariane V uses currently.
Here is a copv version.

http://www.sciencephoto.com/media/87925/view

Looks like external COPV's: http://www.zamandayolculuk.com/pu-3/roket_ar5_corestage.jpg

That diagram shows liquid helium as the label.
And I am pretty sure the vapor pressure of helium at 4 kelvin is 1 atm.

EDIT: didnt look closely looks like they use one liquid helium and 2 copv.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steve D on 09/04/2016 04:02 pm
Don,t forget the COPV is pressurized. Unless it was ripped in half to start with it could be flying around under thrust from the high pressure helium.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 04:07 pm


On the two items seen in first 5 frames... one going left... one going right...
And including the 3rd item that I and others noted in about frames 6 thru 10 or so...
You seem to be thinking in 2D... based on my interpretation of the talking points your making...
The LONG zoom lens on the camera is messing with us... that I am sure of...  ;)

My opinion... there is a lot of movement towards or away from the camera on all three flying small items...
And the only thing I'm kinda sure about... is the 3rd items is going away fast...  :-\
The left and right items... I am not sure how much Z speed they have... and in which direction.
In any case... the Z speed will drastically alter the intersection point... assuming these came from about the same place...

As to the likely COPV chunk seen long after the situation unfolds...
It's about as interesting as the COPV much later chucked from S1 and impacting the right lightning tower... to me...
It's interesting that it first appeared at about 1/3 second after it all started...
But at 1/3 of a second... there wasn't much left structurally of S2... in my opinion...

Regarding your comment and several prior comments about thinking in 3D or not. 

Absolutely this is a 3D problem.  HOWEVER, tracing a trajectory can be done in 2D, as the exemplars show.  The origin can reasonably be presumed to be on a plane that intersects the trajectory, at least in the three cases provided, assuming they didn't deviate from the path between onset and first visibility.

As to whether the origin is on the near side, far side, or in the middle, absolutely no data exists in this video to answer that question.  The trajectories provide a plane in 3D along which the object is moving. 

We can measure X-Y displacement, and from that determine a minimum X-Y velocity assuming the object motion has no Z component.  If we had a Z component we could measure an actual velocity.

To me, this may not point to a root cause, but for the initial event which seems to me to have been a detonation rather than a deflagration, tracing multiple objects helps constrain the physical volume of that event.  The counter argument seems to be that a bunch of COPVs lose their He and become little rockets that shoot out ahead of the deflagration which would make the tracing exercise meaningless.

For me, for now, I'm assuming an external detonation is the first energy release in the event, and the trajectory tracing helps constrain the scope of that event.  Others heartily disagree.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/04/2016 04:15 pm
To me, this may not point to a root cause, but for the initial event which seems to me to have been a detonation rather than a deflagration, tracing multiple objects helps constrain the physical volume of that event.  The counter argument seems to be that a bunch of COPVs lose their He and become little rockets that shoot out ahead of the deflagration which would make the tracing exercise meaningless.

For me, for now, I'm assuming an external detonation is the first energy release in the event, and the trajectory tracing helps constrain the scope of that event.  Others heartily disagree.

If the initial explosion was spread across several metres within a cloud of concentrated oxygen, then there would be several trajectories which did not originate from a single point - which I think is what we see.

There may also be objects liberated by the initial shockwave.

My humble opinion is that we're looking at an initial explosion outside the body of the vehicle (regardless of whether the oxygen and possibly fuel had come from within the vehicle), which was spread across a wide enough area for the initial debris not to point towards a single point.

That, incidentally, appears to correspond with the initial physical size of the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/04/2016 04:49 pm
Still, the appearance of the COPVs, if that's indeed what they are, is relatively early.in the sequence.

I cant find a way by which the COPVs managed to get out so quickly without there being more evidence of structural failure.

High speed video would help (not to mention telemtry data...)

In other words, heavy pieces should be last to exit, not first.  And self propelled COPV should be even slower.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/04/2016 04:56 pm
Wouldn't the complex structure of the t/e cause all sorts of shockwave reflections that could do crazy things both to objects already flying free and stuff still intact?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 04:57 pm
3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.

The trajectory has been concerning me as far as labelling it a COPV is concerned.

Your composite image shows it originating from a point to the right of the vehicle - for it to have been part of the vehicle, it would have had to deflect off the erector to change the trajectory, otherwise it would have headed towards the right of the frame.

I'm with your later comment that it's highly unlikely to be a COPV deflecting off the erector. Regardless of the elasticity of various components, there are two problems with that being the COPV:

(1) The odds of it hitting a part of the erector that deflected it would be very slight - firstly, it would have had to hit an outer upright exactly evenly, otherwise it would have ended up embedded within the lattice of the structure. Secondly, had it not bounced off an upright and gone into the frame of the erector, it wouldn't come out.  Thirdly, it would have had to pass through the clamping structure that holds the top of the vehicle - and that remained intact enough to hold the payload fairing for several seconds after.

(2) If you count the frames from the initial explosion to the point the object becomes visible flying out of the fireball, it's 20 (+/-1). Count forwards 20 frame from there and take a fix on the position and it's a couple of metres above the top of the fairing. That gives you an approximate distance travelled in the 20 frames after it becomes visible, so assuming a relatively constant velocity, the same distance back from the frame it was first visible should give you the approximate start point. (See attached image).

On that basis, it's unlikely this is a COPV (or anything else that was part of the vehicle). My guess would be this is part of the erector, liberated by the shockwave of the blast.

This image shows the emergence of the object frame by frame.  Also, using a 17' fairing size as reference, the object appears to have a longest dimension of about 5 feet.  If you look at the images to the left of where its appearance is obvious, it is obscuring parts of the tower several frames prior to your 20 frame point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/04/2016 05:22 pm
Please remember, everyone, be excellent to each other. If someone snipes at you about something, let it go, or report to mod. Don't snipe back. Thanks.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 05:27 pm
3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.

The trajectory has been concerning me as far as labelling it a COPV is concerned.

Your composite image shows it originating from a point to the right of the vehicle - for it to have been part of the vehicle, it would have had to deflect off the erector to change the trajectory, otherwise it would have headed towards the right of the frame.

I'm with your later comment that it's highly unlikely to be a COPV deflecting off the erector. Regardless of the elasticity of various components, there are two problems with that being the COPV:

(1) The odds of it hitting a part of the erector that deflected it would be very slight - firstly, it would have had to hit an outer upright exactly evenly, otherwise it would have ended up embedded within the lattice of the structure. Secondly, had it not bounced off an upright and gone into the frame of the erector, it wouldn't come out.  Thirdly, it would have had to pass through the clamping structure that holds the top of the vehicle - and that remained intact enough to hold the payload fairing for several seconds after.

(2) If you count the frames from the initial explosion to the point the object becomes visible flying out of the fireball, it's 20 (+/-1). Count forwards 20 frame from there and take a fix on the position and it's a couple of metres above the top of the fairing. That gives you an approximate distance travelled in the 20 frames after it becomes visible, so assuming a relatively constant velocity, the same distance back from the frame it was first visible should give you the approximate start point. (See attached image).

On that basis, it's unlikely this is a COPV (or anything else that was part of the vehicle). My guess would be this is part of the erector, liberated by the shockwave of the blast.

Merging your trajectory with the others is this image.

Your scaling and mine don't match so I had to do some manual corrections to make them almost line up.  Not as good as it should be, but it adds to whichever debate we're having.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/04/2016 05:40 pm
3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.

The trajectory has been concerning me as far as labelling it a COPV is concerned.

Your composite image shows it originating from a point to the right of the vehicle - for it to have been part of the vehicle, it would have had to deflect off the erector to change the trajectory, otherwise it would have headed towards the right of the frame.

I'm with your later comment that it's highly unlikely to be a COPV deflecting off the erector. Regardless of the elasticity of various components, there are two problems with that being the COPV:

(1) The odds of it hitting a part of the erector that deflected it would be very slight - firstly, it would have had to hit an outer upright exactly evenly, otherwise it would have ended up embedded within the lattice of the structure. Secondly, had it not bounced off an upright and gone into the frame of the erector, it wouldn't come out.  Thirdly, it would have had to pass through the clamping structure that holds the top of the vehicle - and that remained intact enough to hold the payload fairing for several seconds after.

(2) If you count the frames from the initial explosion to the point the object becomes visible flying out of the fireball, it's 20 (+/-1). Count forwards 20 frame from there and take a fix on the position and it's a couple of metres above the top of the fairing. That gives you an approximate distance travelled in the 20 frames after it becomes visible, so assuming a relatively constant velocity, the same distance back from the frame it was first visible should give you the approximate start point. (See attached image).

On that basis, it's unlikely this is a COPV (or anything else that was part of the vehicle). My guess would be this is part of the erector, liberated by the shockwave of the blast.

This image shows the emergence of the object frame by frame.  Also, using a 17' fairing size as reference, the object appears to have a longest dimension of about 5 feet.  If you look at the images to the left of where its appearance is obvious, it is obscuring parts of the tower several frames prior to your 20 frame point.

The COPV is about 22 inches in diameter and about 60 inches long.  Just for reference.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/04/2016 05:46 pm
Two questions:

1. What equipment is on the T/E near S2?  Obvious items include the cradle arms, the hydraulic pistons that open the cradle, the RP-1 and LOX umbilicals, and the payload umbilical. Is there any active equipment up there like a pump, heat exchanger, etc?

2. What's the combined thickness of the S2 outer skin + the wall of the LOX tank?

Just to clue you in on where I'm going with this, I'm pondering whether a piece of shrapnel from failing equipment on the T/E might have impacted the stage and/or the LOX umbilical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/04/2016 05:59 pm
Two questions:

1. What equipment is on the T/E near S2?  Obvious items include the cradle arms, the hydraulic pistons that open the cradle, the RP-1 and LOX umbilicals, and the payload umbilical. Is there any active equipment up there like a pump, heat exchanger, etc?

2. What's the combined thickness of the S2 outer skin + the wall of the LOX tank?

Just to clue you in on where I'm going with this, I'm pondering whether a piece of shrapnel from failing equipment on the T/E might have impacted the stage and/or the LOX umbilical.

As to your question #1...
I've been looking at this picture zoomed in close for 2 days now asking the same question...
Source...
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577399#msg1577399 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577399#msg1577399)

On edit...
It's from the other side... and from an earlier mission obviously...
But it still seems useful on close inspection... zoomed in...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/04/2016 06:06 pm

Spyx helium system is known to run in excess of 6000 psi. Fyi


4500psi was the design MOP for the test articles - that in itself does not preclude designing tanks for a higher MOP. FYI.

Additionally, as previously quoted the lowest burst pressure was "2.36 X MOP or 10,620 psig".

Interesting going to check into it more.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 06:09 pm

The COPV is about 22 inches in diameter and about 60 inches long.  Just for reference.

This is what it looks like at the top of it's arc, before it goes into the cloud.  Scaled X 3, no enhancments.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: WHAP on 09/04/2016 06:21 pm
So this was asked upthread a ways.
What do other vehicles use for helium bottles?
I noticed the atlas V uses helium bottles but I can't seem to find any info on their construction. They appear to be not inside of the tanks. Spaceflight101 just lists helium bottles. This diagram just shows their location for the rd180 and the rl10. The rl10 definitely isn't inside of a tank. Not sure about the lox tank for the rd180. Looks to be at the bottom of the lox tank.
http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf


Atlas and Centaur use COPV's at lower MEOP than what was stated for Falcon 9 earlier in this thread (can't vouch for the accuracy of the Falcon 9 numbers).  The bottles are not there for the engines, although they happen to be nearby.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/04/2016 06:23 pm
Not that there's any information to say it was a COPV...here some more COPV content as I started writing about those spherical troublemakers since Shuttle:

https://www.nasaspaceflight.com/?s=COPV

--

Again, easy for someone jumping in, reading the past three pages and thinking "Oh, so it was a COPV". We don't know that, we're just chatting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 06:23 pm
Two questions:

1. What equipment is on the T/E near S2?  Obvious items include the cradle arms, the hydraulic pistons that open the cradle, the RP-1 and LOX umbilicals, and the payload umbilical. Is there any active equipment up there like a pump, heat exchanger, etc?

2. What's the combined thickness of the S2 outer skin + the wall of the LOX tank?

Just to clue you in on where I'm going with this, I'm pondering whether a piece of shrapnel from failing equipment on the T/E might have impacted the stage and/or the LOX umbilical.

As to your question #1...
I've been looking at this picture zoomed in close for 2 days now asking the same question...
Source...
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577399#msg1577399 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1577399#msg1577399)

On edit...
It's from the other side... and from an earlier mission obviously...
But it still seems useful on close inspection... zoomed in...

The flash started higher up on the stage.  Near the middle of it
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/04/2016 06:51 pm
Question. Anybody have a diagram or related graphic that shows where all FTS related hardware is and if any is on stage two?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/04/2016 07:11 pm
Has anybody tried liquid helium storage in dewar flask as a helium source? Eliminates the high pressure.


The gas is need for its pressure.  Liquid does no good.  How much does a dewar flask cost and weigh?  And have any flown before?
Now that's a silly question Jim. You darn well know that Helium dewar flasks have flown on a number of launches, just not as part of the rocket ;-)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/04/2016 07:21 pm
The flash started higher up on the stage.  Near the middle of it

Pretty much at the intertank / the s-bend on the pipe running up the erector at the point where it appears to have been stretched to transition from F9 1.1 to FT.

Either of these could be part of the cause of the anomaly, or neither of them.

I'm tending towards the ignition location of the explosion not necessarily being the same as the root cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vandersons on 09/04/2016 07:24 pm
3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.

The trajectory has been concerning me as far as labelling it a COPV is concerned.

Your composite image shows it originating from a point to the right of the vehicle - for it to have been part of the vehicle, it would have had to deflect off the erector to change the trajectory, otherwise it would have headed towards the right of the frame.

I'm with your later comment that it's highly unlikely to be a COPV deflecting off the erector. Regardless of the elasticity of various components, there are two problems with that being the COPV:

(1) The odds of it hitting a part of the erector that deflected it would be very slight - firstly, it would have had to hit an outer upright exactly evenly, otherwise it would have ended up embedded within the lattice of the structure. Secondly, had it not bounced off an upright and gone into the frame of the erector, it wouldn't come out.  Thirdly, it would have had to pass through the clamping structure that holds the top of the vehicle - and that remained intact enough to hold the payload fairing for several seconds after.

(2) If you count the frames from the initial explosion to the point the object becomes visible flying out of the fireball, it's 20 (+/-1). Count forwards 20 frame from there and take a fix on the position and it's a couple of metres above the top of the fairing. That gives you an approximate distance travelled in the 20 frames after it becomes visible, so assuming a relatively constant velocity, the same distance back from the frame it was first visible should give you the approximate start point. (See attached image).

On that basis, it's unlikely this is a COPV (or anything else that was part of the vehicle). My guess would be this is part of the erector, liberated by the shockwave of the blast.

This image shows the emergence of the object frame by frame.  Also, using a 17' fairing size as reference, the object appears to have a longest dimension of about 5 feet.  If you look at the images to the left of where its appearance is obvious, it is obscuring parts of the tower several frames prior to your 20 frame point.

The COPV is about 22 inches in diameter and about 60 inches long.  Just for reference.

For us metric minded people that's around 55cm in diameter and about 1.5m in length.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/04/2016 07:50 pm
I wonder how many test cycles of helium pressurisation and depressurization these COPV's go through. Also would that be mostly done in a supercooled liquid oxygen environment or largely just in air?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/04/2016 07:57 pm
>
FAE's can also be nasty, hence the media tag of the "Poor mans atomic bomb" but these require both careful mixing of fuel and air and controlled ignition delay. I think they also like fuels with high flame or explosion propagation speeds and I don't think RP1 is very good at this.
>

Haven't spent much time around grain elevators or bins? No careful mixing there at all. Vapors will also blow without careful mixing, been there with poorly stored fuels.

Things you learn growing up on a farm.

An improvised explosive can be made using a tin of flour and a small dispersion charge. Old tech my uncle used as a vintage SO. The damnedest things can be bombs.
It seems unlikely to me that enough aerosol would collect upwind of the rocket, well above the umbilical cords, without some sort of obvious pressurized spray.  But I don't know how to estimate the size of the initial explosion nor how much RP-1/O2 aerosol it would take to generate it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/04/2016 08:14 pm
The flash started higher up on the stage.  Near the middle of it

Pretty much at the intertank / the s-bend on the pipe running up the erector at the point where it appears to have been stretched to transition from F9 1.1 to FT.

Either of these could be part of the cause of the anomaly, or neither of them.

I'm tending towards the ignition location of the explosion not necessarily being the same as the root cause.

I pulled the image from a post done originally by user hartspace, which already has the stage 2 RP1 and LOX umbilicals circled in dark blue.  I have taken the liberty of cropping it and circling various things in the TEL, and its interface with the rocket, for discussion and clarification purposes.

First, the area I have circled in red, I think we can all agree, contains the location where the initial flash was observed.  This is indeed very close to the common bulkhead between the RP1 tank on the bottom and the LOX tank on the top.  If you look closely at the skin of stage 2, you can see what appears to be a circumferential strengthening band or exterior weld line, barely visible; it almost looks like it's just a place where they laid a big strip of outer insulation horizontally instead of vertically, maybe two to six inches thick.  It appears to define (if anything on the exterior skin does) where the common bulkhead lies inside.

This is also the point where the TEL contacts the stage with a "soft cradle" -- Jim says it has rubber tips -- again, right at the level of the common bulkhead.  The best guesstimate I've seen (and that I have, from watching the video) is that the initial bright flash occurred almost exactly at the spot where the stage rests against this cradle while horizontal.  (I make no insinuation of causality, just pinning down the locations of things.)

Next, what on the TEL could have gone flying in the early stages of the explosion, especially at the extremely energetic beginning, which grew from non-existent to an extremely bright flash of expanding, combusting gas with extent ranging from 20 to 30 feet in less than a 30th of a second?  That was an extremely energetic first several milliseconds of activity, and could likely rip a lot of the stuff mounted in the TEL off and send it flying.

Jim says the area I've circled in green, and the S-curve pipe right across from the soft cradle, are parts of the payload shroud AC system.  I wonder a bit, though -- near the bottom of the area outlined in green, there are two conduits of roughly equal circumference that come up.  One of them goes into what appears, from what Jim says is present up there, the AC filtering system.  This is all within the green circle.

I don't, at least in what can be seen of the TEL even in the original image, see how the conduit that continues up, and does the S-curve near the soft cradle, connects to the filtering system.  The conduit that leads up to the payload area seems to pass along the top of the filtering system, but doesn't appear to connect to it.  Just a curiosity, certainly not saying Jim is wrong in his identification.

Next, there is another conduit that appears to run behind the AC conduit, because it becomes visible above the point of the latter's S-curve.  It's narrower than the AC conduit -- I'm sort of assuming it's a payload power/data conduit.  I circled a length of that in orange.

Finally, near the top, I've circled in purple the extensible umbilicals that run from the retracted strongback out to the payload until just before lift-off.  They hang down while the TEL is fully upright and the clamps still hold the payload adapter.

It seems to me that the payload umbilicals could easily have been blown off the payload and the TEL in the initial, energetic second of the explosion.  And the only things that would seem to have been relatively easily blown off, and located above the initial flash point, would be these umbilicals and the AC and power/data conduits.  Unless the positioning of the AC filtering system has changed since the Orbcomm launch config shown in the picture, pieces of the that whole filter pack installation outlined in green would, you would think, be subject to an outward and downward force, not a force that would have blow it up into the vector from which the initial combustion was spreading.

If anyone has any better identification of the things we see here, or any better idea of what might or might not be susceptible to being blown off the TEL in an explosion, I'd welcome your comments... :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 08:24 pm
There is no separate payload umbilical line.  It is part of the second stage lines.  The only thing going into the fairing is the AC duct.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/04/2016 08:29 pm
There is no separate payload umbilical line.  It is part of the second stage lines.  The only thing going into the fairing is the AC duct.

Okay, kewl.  Then perhaps the line I circled in orange is for operations of the TEL separate from the rocket -- controls and hydraulic fluid for the upper cradle arm open/close mechanism, perhaps.  It does tend to visually disappear into the girder structure below we get to that level of the TEL.

Thanks!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/04/2016 08:45 pm
I've read most of the comments in this thread.
Currently 2 plauseible scenarios stand out and both have their faults:

Scenario 1: COPV failure.
Goes like this:
1. COPV (carbon fiber on top of aluminium) fails for unknown reason (may be delamination, may be something else)
2. It is safe to say that when carbon fiber fails, it has tremendous energy stored in it (high tensile strength and stiffness combined). That makes us assume, that possibly helium COPV (at ~6000psi) fails like in https://www.youtube.com/watch?v=5UdVnO10J3U, and then carbon fiber and epoxy will be dispersed as a fine dust into LOX, thereby turning immediate vincinity of the helium bottle onto an Oxyliquit.
3. Supersonic compression wave follows, heating up the mixture of fine carbon and epoxy dust in LOX to a point of detonation
4. Detonation occurs throwing pieces of S2 into different directions
5. 60ms after that behind still burning fireball, the now open LOX tank disperses large cloud of vaporizing oxygen
6. At the same time pressure wave propagates down the LOX pressure vessel destroying common bulkhead
7. RP-1 flows down the scene and COPV submerged in RP-1 tank gets ripped from the tank breaking the tubing to pressure regulator
8. RP-1 tank's COPV gets propelled upwards by releasing helium from broken tubing
the rest is not worth describing.

Issues with this scenario:
1. Why didn't the back side or the whole circumference of S2 burst open due to sharp pressure wave
2. Why wasn't the payload lifted by pressure release into LOX
3. Why the epicenter of initial detonation SEEMS to be just at or outside the surface of S2
4. Why did the COPV fail in first place

Scenario 2: External FAE or oxuliquit initiated event
1. For unknown reasons FAE mixture occurs near the S2. Other option - due to long time stay in oxygen rich environment either rubber stops, some padding. grease, insulation or whatnot turns into oxyliquit)
2. Static discharge (btw highly unlikely in such wet weather) initiates the inadvertently created explosive
3. Explosion occurs, rising pressure just outside the S2 to ~400 psi and temperature 4,500 to 5,400 °F
4. Pressure wave propagates inside the S2 tearing the outer wall open in process and ripping He COPV from it's supports.
5. Pressure wave reflects back from inside wall of S2 and together with pressurized LOX throws He COPV out from S2 at mild speeds
6. LOX tank's COPV gets propelled upwards by releasing helium from broken tubing
7. At the same time pressure wave propagates down the LOX pressure vessel destroying common bulkhead
8. RP-1 flows down the scene and COPV submerged in RP-1 tank gets ripped from the tank breaking the tubing to pressure regulator

Issues with this scenario:
1. There's a wind out there, so FAE is difficult, but not impossible to form
2. Such a cloud of dispersed fuel should have been seen (although the actual fireball may have been a lot smaller when measured from images due to lit surroundings.
3. WTF formed the FAE mixture in first place.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/04/2016 08:51 pm
>
FAE's can also be nasty, hence the media tag of the "Poor mans atomic bomb" but these require both careful mixing of fuel and air and controlled ignition delay. I think they also like fuels with high flame or explosion propagation speeds and I don't think RP1 is very good at this.
>

Haven't spent much time around grain elevators or bins? No careful mixing there at all. Vapors will also blow without careful mixing, been there with poorly stored fuels.

Things you learn growing up on a farm.

An improvised explosive can be made using a tin of flour and a small dispersion charge. Old tech my uncle used as a vintage SO. The damnedest things can be bombs.
It seems unlikely to me that enough aerosol would collect upwind of the rocket, well above the umbilical cords, without some sort of obvious pressurized spray.  But I don't know how to estimate the size of the initial explosion nor how much RP-1/O2 aerosol it would take to generate it.

Here's a first pass at a way you might calculate it.  The example below, however is not proposed to be a calculation for this particular event.  It's only an approach to answering your question with examples.

You'll want a Stoichiometric solution that's ideal.  Perfect combustion of oxygen and fuel with no residuals.  That's the model for a fuel-air explosion.

Assume you have a cylinder that will contain your mixture that's 30 X 80 feet.

Calculate the volume of the cylinder which is 56,548 cubic feet.

Then at the standard atmospheric pressure, calculate how much free oxygen is in the volume.  A cubic foot of atmosphere will contain .04 kg of oxygen.

Then you need to know what your fuel stochiometrics are.  For kerosene which is close to RP1 you have to look it up or calculate it, but it looks like 2.56 kg of oxygen per kg of kerosene.

So to totally consume your oxygen, you need about 883 kg of kerosene.

Then you have to calculate the volume, and there are online calculators for that, which would come in at about 39 cubic feet or 261 gallons.

Create an aerosol from 261 gallons in 56,548 cubic feet and you'll have a massive fuel-air explosion.

In this scenario, a 261 gallon RP1 leak would have been pretty obvious and a 30 X 80 foot detonation core would have made a much more massive explosion.

What might be more realistic is an air-space cylinder of 3 x 10 feet.  In such a case, you'd need 1.3 gallons of kerosene, and you might have an explosion similar to what we observed.

A 2008 study concluded that a 1 kg of fuel-air explosive is equivalent to 5.3 kg of TNT.  So I guess to get to your final answer, figure how how much TNT it would take to create the event and divide by 5.3.  Alternatively 1 gallon of kerosene (6.8 kg) perfectly mixed would be equivalent to 36 kg of TNT

Problems of many are:
1.  How do you create the perfect aerosol?
2.  Can a 1.3 gallon leak go undetected?
3.  Would pure oxygen in the environment permit a decreased volume, and if so, what was the O2 content in that area?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/04/2016 08:56 pm
Issues with this scenario:
1. There's a wind out there, so FAE is difficult, but not impossible to form
2. Such a cloud of dispersed fuel should have been seen (although the actual fireball may have been a lot smaller when measured from images due to lit surroundings.
3. WTF formed the FAE mixture in first place.

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon), then gaseous release from that would be blown towards the vehicle, which would be consistent with the location of the explosion.

If that is not the case, rupture of the vehicle on the side facing the erector would have a similar effect.

If you flick quickly between any consecutive pairs of the 3 or 4 frames immediately prior to the explosion, there is some optical distortion around the area where the explosion occurred, which would be consistent with a rapid release of gas.

It would also be consistent with the sort of heat haze you'd expect in Florida.

Call it either way - I don't think we can get an answer without other camera angles (and probably access to SpaceX's telemetry data).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 09/04/2016 09:01 pm
I really do hope Elon Musk sees this discussion thread.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/04/2016 09:07 pm
Issues with this scenario:
1. There's a wind out there, so FAE is difficult, but not impossible to form
2. Such a cloud of dispersed fuel should have been seen (although the actual fireball may have been a lot smaller when measured from images due to lit surroundings.
3. WTF formed the FAE mixture in first place.

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon), then gaseous release from that would be blown towards the vehicle, which would be consistent with the location of the explosion.

...

Call it either way - I don't think we can get an answer without other camera angles (and probably access to SpaceX's telemetry data).

First of all - additional oxygen is NOT needed for FAE. The problem with the FAE scenario is that normally this environment there is fuel-deprived.

But I agree with you, that our chances to determine whether any of our scenarios have something to do with reality are effectively nil
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/04/2016 09:13 pm
Issues with this scenario:
1. There's a wind out there, so FAE is difficult, but not impossible to form
2. Such a cloud of dispersed fuel should have been seen (although the actual fireball may have been a lot smaller when measured from images due to lit surroundings.
3. WTF formed the FAE mixture in first place.

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon), then gaseous release from that would be blown towards the vehicle, which would be consistent with the location of the explosion.

...

Call it either way - I don't think we can get an answer without other camera angles (and probably access to SpaceX's telemetry data).

First of all - additional oxygen is NOT needed for FAE. The problem with the FAE scenario is that normally this environment there is fule-deprived.

But I agree with you, that our chances to determine whether any of our scenarios have something to do with reality are effectively nil
Especially when we're working off a few frames of 60 fps (16.67 ms resolution) video from a couple miles away. There is no smoking gun in the video.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/04/2016 09:21 pm
First of all - additional oxygen is NOT needed for FAE. The problem with the FAE scenario is that normally this environment there is fuel-deprived.

But I agree with you, that our chances to determine whether any of our scenarios have something to do with reality are effectively nil

Conversely, in a massively oxygen-rich environment, many things that aren't usually highly flammable become highly flammable.

And again, we don't have the data to call it. SpaceX may well do, by now...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gth871r on 09/04/2016 09:28 pm
I had a thought that someone who knows more than me might be able to shoot down.  Doesn't the rocket use a layer of cork as insulation?  If there was a leak of LOX somewhere (from the rocket or GSE doesn't matter) and that LOX dribbled down the outside of the tank and managed to soak into the cork that would be quite the hazardous thing to have wouldn't it?  If it ignited (which it probably would if you so much as looked at it the wrong way) wouldn't it burn with a bright intense flame just off to the side of the rocket for a very short while.  Just like we see in the video.  That heat right up against the thin aluminum skin could compromise the tank and the whole thing spills out from there.

Basically put this: https://www.youtube.com/watch?v=C0U4_k1iO6w

right next to a thin pressurized container.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/04/2016 10:00 pm
"Spacecom to recoup  $173m, plus interest, for destroyed satellite"


http://www.timesofisrael.com/spacecom-to-recoup-173m-plus-interest-for-destroyed-satellite/ (http://www.timesofisrael.com/spacecom-to-recoup-173m-plus-interest-for-destroyed-satellite/)

$205M +$50M (or a free launch) + $39M

Now, if they can stay in business...

Quote
The satellite’s owners, Space Communication, will receive over $173 million from IAI plus interest, which provided insurance for the device, a company official said.

According to Space Communication, also known as SpaceCom, the total sum from IAI is “approximately $205 million.”

Under the insurance policy, IAI will have to pay the amount “in under 60 days,” a spokesperson for the quasi-governmental firm said.

In addition, the Israeli company said it expects to receive either $50 million from SpaceX or “have the launch of a future satellite carried out under the existing agreement and with the payments that have [already] been made.”

Additional insurers are expected to pay SpaceCom an additional $39 million, the company said in a statement Saturday night.
This was noted earlier, but might need a reminder - SpaceCom was about to be sold to a Chinese buyer, contingent on successful Amos-6 launch. The deal is currently not happening, afaik.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rayleighscatter on 09/04/2016 10:07 pm
Just a quick note regarding the theories of origin based on the brightness of the fire/explosion.

Intensity doesn't correlate to origin, although on the surface that seems counter-intuitive. It simply indicates at what point the release of light energy is greatest. It's like the candle shown below, we know the wick is the source of ignition and the paraffin the source of fuel, but just based on the intensity of light we'd be led to believe the ignition is actually 2-3 inches above the candle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/04/2016 10:11 pm
The flash ignition is clearly to one side, but the collapse is symmetric and is unaccompanied by a noticeable, one-sided concussive force (the camera *is* very far away, granted).  If the failure was initiated externally, it's more likely to be via an externally applied over-pressurization, or something went ballistic through the tank walls.  I don't think an accelerated insulation fire is going to do that.  Of course, we've been surprised by cork before.  But I still think the smart money is on an internal failure.  Given the history of COPVs, I'm suspicious, and if there really is a mismatch in thermal expansion, the super-chilled LOX may be making a bad problem worse.

I am surprised that no statement has been made about postponing future launches (or did I miss that?).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/04/2016 10:14 pm
It isn't clear which system ariane V uses currently.
Here is a copv version.

http://www.sciencephoto.com/media/87925/view

A question I have as well for the industry folks. Does any other rocket put COPVs in the LOX tanks? If so, which one(s)?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AS-503 on 09/04/2016 10:26 pm
It isn't clear which system ariane V uses currently.
Here is a copv version.

http://www.sciencephoto.com/media/87925/view

A question I have as well for the industry folks. Does any other rocket put COPVs in the LOX tanks? If so, which one(s)?

Saturn V first stage (SI-C) had titanium helium bottles (granted not COPVs) in the LOX tank.
As others have mentioned this saves dry mass and increases He storage per volume.

On a side note, the COPVs inside the repeatedly tested returned booster now at SpaceX's Texas test facility surely have (by now) the most repeated cryo exposure to almost any other SpaceX COPV? Correct?
If so, should the COPVs in this stage be the most prone to failure if repeated cryo-loading is a significant failure mode?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/04/2016 10:41 pm
The flash ignition is clearly to one side, but the collapse is symmetric and is unaccompanied by a noticeable, one-sided concussive force (the camera *is* very far away, granted).  If the failure was initiated externally, it's more likely to be via an externally applied over-pressurization, or something went ballistic through the tank walls.  I don't think an accelerated insulation fire is going to do that.  Of course, we've been surprised by cork before.  But I still think the smart money is on an internal failure.  Given the history of COPVs, I'm suspicious, and if there really is a mismatch in thermal expansion, the super-chilled LOX may be making a bad problem worse.

I am surprised that no statement has been made about postponing future launches (or did I miss that?).

Well -- this bird was relatively well monitored, this being the FRR static firing.  You get all your flight readiness data from this countdown and static fire.

So, you would have to think that SpaceX has at least a starting-point theory about the cause of the anomaly.  It could even be that the launch team was seeing a particular parameter or system heading south a few seconds (or more) before the event, and simply had no way to back out of the situation.

We just don't know.

The one and only thing that leads me to believe we could be looking at some kind of GSE failure (though not necessarily an external explosion, again jury's out on that one) is that SpaceX, it seems to me, is acting rather like it believes the anomaly does not reflect an inherent design or manufacturing weakness in stage 2 as-is.  And I can imagine a few not-impossible of scenarios that could result in what saw happen that involve failures of propellant feed systems, helium feed systems and/or even hydraulic systems in the TEL.

Now, maybe SpaceX is acting this way after hard experience following CRS-7, and doesn't want anyone to think they are baffled by exploding second stages.  Maybe not.  If so, then the PR people have more control this time 'round than they did after CRS-7.  If not, then maybe they do pretty well know what happened, and at least have some ideas on how to keep it from happening again.

And maybe it's not a GSE problem, but a problem with pre-launch handling.  I do find it suspicious that the first initiation of the event appears to be very close to where stage 2 is supported while horizontal on what I've dubbed the soft cradle.  I am not insisting on a connection, here, but if that cradle supports the stage right at the common bulkhead location, and if there was some awkward drop (of even an inch or two) of the stage onto the cradle, surface inspection might not reveal a small crack that could propagate under cryogenic temps and pressurized conditions, especially across a common bulkhead with hundreds of degrees difference in temp across the bulkhead.

This could be one of those things where, sort of like Apollo 13, everyone knew there was an incident in processing, but inspections and Monte Carlo runs told them it shouldn't be a problem.  And when it actually becomes a problem, people shake their heads, beat themselves up over it for a few days, and then go on to fix whatever the error is.  With a better knowledge base than they had before.

Again, we don't know, and likely won't know where SpaceX's investigation is revealing for another week or more.  But if we hear something in the next three or four days, I bet it's something that validates the rocket itself and places the blame on bad processing or bad handling (or maybe even a broke-wide-open prop or helium feed line, in the realm of GSE issues).

We're sort of stuck waiting for more information from the people who actually have it... :(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Asmegin on 09/04/2016 10:46 pm
Someone posted this on reddit which I thought was interesting:

https://www.youtube.com/watch?v=tM-QlPAMLEc&feature=youtu.be&t=1m (https://www.youtube.com/watch?v=tM-QlPAMLEc&feature=youtu.be&t=1m)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AS-503 on 09/04/2016 10:49 pm
Someone posted this on reddit which I thought was interesting:

https://www.youtube.com/watch?v=tM-QlPAMLEc&feature=youtu.be&t=1m (https://www.youtube.com/watch?v=tM-QlPAMLEc&feature=youtu.be&t=1m)

Early Falcon 9 launches had various umbilical fires/explosions and in one instance had one of the cradle arms blown completely off. All after lift-off of course.

There have been multiple improvements to the TE since then.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/04/2016 10:59 pm
No cork on second stage
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dbavatar on 09/04/2016 11:48 pm
Is there a pressure relief valve almost exactly at the origin of the fire (if you believe the lens flare cross points to the right place)?

See venting during the JCSAT-16 static fire, which is exactly the same angle as the AMOS-6 video: https://www.youtube.com/watch?v=rK9Xz3ZqBG4&feature=youtu.be&t=2m18s
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jcopella on 09/04/2016 11:51 pm
The one and only thing that leads me to believe we could be looking at some kind of GSE failure (though not necessarily an external explosion, again jury's out on that one) is that SpaceX, it seems to me, is acting rather like it believes the anomaly does not reflect an inherent design or manufacturing weakness in stage 2 as-is.  And I can imagine a few not-impossible of scenarios that could result in what saw happen that involve failures of propellant feed systems, helium feed systems and/or even hydraulic systems in the TEL.

Hm, curious why you say this because their behavior so far makes me think just the opposite.

In the past when they've had an early indication of the cause of anomaly and it didn't imply a design flaw, Elon's been pretty forthcoming.

The longer they stay clammed up the more I think it's either a real head-scratcher or they've got a fairly deep-seated problem with the vehicle (or both).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 09/05/2016 12:37 am
So this was asked upthread a ways.
What do other vehicles use for helium bottles?
I noticed the atlas V uses helium bottles but I can't seem to find any info on their construction. They appear to be not inside of the tanks. Spaceflight101 just lists helium bottles. This diagram just shows their location for the rd180 and the rl10. The rl10 definitely isn't inside of a tank. Not sure about the lox tank for the rd180. Looks to be at the bottom of the lox tank.
http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf (http://www.ulalaunch.com/uploads/docs/Atlas500_Cutaway.pdf)

After looking into the topic over the past day, the Zenit launch vehicle, which appears to be the closest analog to the Falcon, uses titanium spheres for helium storage, submerged in the LOX tanks. Whether there are other materials in addition to titanium, such as some sort of overwrap, I have been unable to determine this. The Angara uses the same system.

I can not find another explicitly stated example of a launch vehicle which submerges COPV's in cryogenic Oxygen, although that doesn't mean there aren't any. From what I have found, vehicles which use COPV's for helium storage do not submerge them.


You might find more details with some digging into the Angara system.
http://forum.nasaspaceflight.com/index.php?topic=33141.msg1309883#msg1309883

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: laszlo on 09/05/2016 01:03 am
I really do hope Elon Musk sees this discussion thread.

Why?

He's got the telemetry, the wreckage, the engineers who designed it, the technicians who processed it. What useful thing could he possibly get from a bunch of amateurs with no access to the evidence speculating about something they don't understand (not for lack of education or intelligence, but from lack of access to the raw data - no insult intended to anyone posting in this thread). It may be entertaining, but it won't resolve the cause of the blast.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/05/2016 01:33 am
I really do hope Elon Musk sees this discussion thread.
I sure hope he ignores it and concentrates on the actual data he has in hand.

Am I the only one who read ZachS09's comment and took it for a bit of irony? :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/05/2016 01:36 am
I really do hope Elon Musk sees this discussion thread.
I sure hope he ignores it and concentrates on the actual data he has in hand.

Am I the only one who read ZachS09's comment and took it for a bit of irony? :)

I'm afraid so.   :-\
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 09/05/2016 01:36 am
3.  Original discussion thingee now dubbed an obvious COPV.  How does it blow out the side of the tank to the right, then end up shooting vertical centered on the tower, and loop to the left? Image 4  (produced by eeergo).  Also, if you measure it's size in early frames, you see that it's asymmetric and much larger than a COPV would be, unless it's headed towards the camera at an amazing speed or has become a pancake.


The trajectory has been concerning me as far as labelling it a COPV is concerned.

Your composite image shows it originating from a point to the right of the vehicle - for it to have been part of the vehicle, it would have had to deflect off the erector to change the trajectory, otherwise it would have headed towards the right of the frame.

I'm with your later comment that it's highly unlikely to be a COPV deflecting off the erector. Regardless of the elasticity of various components, there are two problems with that being the COPV:

(1) The odds of it hitting a part of the erector that deflected it would be very slight - firstly, it would have had to hit an outer upright exactly evenly, otherwise it would have ended up embedded within the lattice of the structure. Secondly, had it not bounced off an upright and gone into the frame of the erector, it wouldn't come out.  Thirdly, it would have had to pass through the clamping structure that holds the top of the vehicle - and that remained intact enough to hold the payload fairing for several seconds after.

(2) If you count the frames from the initial explosion to the point the object becomes visible flying out of the fireball, it's 20 (+/-1). Count forwards 20 frame from there and take a fix on the position and it's a couple of metres above the top of the fairing. That gives you an approximate distance travelled in the 20 frames after it becomes visible, so assuming a relatively constant velocity, the same distance back from the frame it was first visible should give you the approximate start point. (See attached image).

On that basis, it's unlikely this is a COPV (or anything else that was part of the vehicle). My guess would be this is part of the erector, liberated by the shockwave of the blast.

This image shows the emergence of the object frame by frame.  Also, using a 17' fairing size as reference, the object appears to have a longest dimension of about 5 feet.  If you look at the images to the left of where its appearance is obvious, it is obscuring parts of the tower several frames prior to your 20 frame point.

The COPV is about 22 inches in diameter and about 60 inches long.  Just for reference.


For us metric minded people that's around 55cm in diameter and about 1.5m in length.


See this thread for more..[/size]https://forum.nasaspaceflight.com/index.php?topic=36440.0 (https://forum.nasaspaceflight.com/index.php?topic=36440.0)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/05/2016 03:33 am
i read/skimmed that nasa copv doc. i though the most alarming section was about "stress ruptures" on page 8.

https://ston.jsc.nasa.gov/collections/trs/_techrep/SP-2011-573.pdf

Quote
4)
Stress Rupture of the Composite Overwrap. Fiber-wrapped composite vessels differ from
metal vessels in that they experience an effect known as stress rupture, or static fatigue.
Stress rupture is a situation in which the composite experiences degradation, as a function
of time. This degradation results in a sudden structural failure of the pressurized vessel’s
composite overwrap, resulting in the rapid release of the vessel’s contents and the stored
energy of the pressurized gas – possibly causing serious injury and damage to the surroundings.

“Stress rupture is a sudden failure mode for [COPVs] that can occur at normal
operating pressures and temperatures. This failure mode can occur while at stress
levels below ultimate strength for [an] extended time. The failure mechanism is com-
plex, not well understood, [and] difficult to accurately predict or detect prior to failure.
The location and mechanism of triggering damage causing sudden failure is highly
localized, but at a random location. This location and extent of local damage has not
been able to be [reliably] detected by current [NDE] techniques prior to catastrophic
failure. Pressure, duration of time at pressure, and temperature experienced contribute
to the degradation of the fiber and/or the fiber-matrix interface, particularly around
accumulations of fiber breaks, and these increase the probability of COPV stress rupture.”

also the appendix had a chart that also seemed frightening. it was labled "for probability concept illustration only", whatever that means.

im suspicious of copv, but ill go with "innocent until proven guilty".

my other leading suspicion is what ever line runs up the side of the RP1 tank above the umbilical. do we know if the lox fill line runs up through the center of the stage like S1? someone pointed out a few pages back that there is a relief valve in this area. wonder if the plumbing runs down from it?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/05/2016 03:55 am
So, if I'm reading that graph right,  say on the red line, there is a 1% chance of failure with 24 hours of use at 75% load on the composite overwrap. That means to improve the odds, you need to either reduce the time the vessel is loaded (less test time?), or reduce the load on the overwrap (thicker metal, lower pressure?).  Is that the right way to read that graph?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/05/2016 04:03 am
Just a quick note regarding the theories of origin based on the brightness of the fire/explosion.

Intensity doesn't correlate to origin, although on the surface that seems counter-intuitive. It simply indicates at what point the release of light energy is greatest. It's like the candle shown below, we know the wick is the source of ignition and the paraffin the source of fuel, but just based on the intensity of light we'd be led to believe the ignition is actually 2-3 inches above the candle.

It is my opinion that this analogy may be flawed. Some of the liquified paraffin is oxidizing at the wick, however there is not enough O2 to oxidize more than a fraction of it. You have liquid fuel but gaseous oxidizer. Not only that, the oxidizer is mixed with Nitrogen at a 22/78 ratio. As the burning paraffin releases heat and becomes hot gas, it rises carrying more unoxidized paraffin with it. This extra paraffin becomes gasified and more O2 is drawn in from the periphery of the heat plume. As more O2 comes into contact with the hot gasified paraffin (while in the presence of already oxidizing fuel and O2), more of the gasified paraffin has the oxidizer needed to burn. It is not just light being released a couple of inches above the wick. That actually is the place where most of the oxidization is taking place, because that is where more O2 becomes available.

In a rocket engine, you have pure O2 and fuel, in a ratio fairly close to balance (often slightly fuel rich to avoid corrosive nature of O2 rich exhaust gas). Much more of the combustion can take place at the point of fuel injection because all the needed oxidizer is also present. That is not the case with the candle. While some oxidization takes place beyond the edge of the nozzle, you are seeing the release of light from the hot and expanding gasses. In the candle plume, you really are seeing more oxidization taking place in the plume because O2 isn't reaching the fuel until that point. Even if you did not have liquid O2, but only placed this candle in a pure gaseous O2 environment, you would see it burn with exponentially more intensity as oxidizer would be able to reach the gasified paraffin sooner. Think about the Apollo 1 fire.

In any case, I would be careful not to draw too much comparison between what happens in a candle flame with what happened on this rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 04:03 am

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon),

There is no "if", it doesn't
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 04:05 am

In a rocket engine, you have pure O2 and fuel, in a ratio fairly close to balance (often slightly fuel rich to avoid corrosive nature of O2 rich exhaust gas)

There is no rocket engine in this case
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/05/2016 04:11 am

In a rocket engine, you have pure O2 and fuel, in a ratio fairly close to balance (often slightly fuel rich to avoid corrosive nature of O2 rich exhaust gas)

There is no rocket engine in this case

Yes, Jim. I know that. You may, however, have almost pure gaseous O2. We don't know. The example re. the rocket engine was only to show the flaw in what was being said about the plume above the candle.

If you have a pocket of gaseous O2 that is close to pure (lower percentage of N present), mixing with gaseous fuel, then get a static spark for ignition, the result is going to differ from the oxidization in a candle. That is my point. Thus my conclusion that while the candle does emit light, it does not do too much to illuminate this problem.  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 04:18 am

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon),

There is no "if", it doesn't

Sure looks like it does carry RP-1 but not the main flow to the F9 but to a vent/overpressure relief valve at the top of the strong back. Which suggests that if the joint in the "S" bend failed, it would vent some RP-1 to atmo.

As there is a LOX vent on the F9 2nd stage at about the same elevation, any leaked RP-1 and the vented LOX could be a fire source.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/05/2016 04:31 am

The flash started higher up on the stage.  Near the middle of it

Jim,
Looking at the closeup, it appears there is a load transference bracing structure internal to the main TEL that goes from the common bulkhead up to the cradle arms. It might even have some sort of pivot point about halfway in between. Likely meant to distribute the weight of payload and second stage while the vehicle is going from horizontal to vertical. Can you comment on that section of the TEL?

Then can you pinpoint the location of the COPV's in the LOX tank? Would the struts they are mounted on have their lower attach points anywhere near the common bulkhead?   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RonM on 09/05/2016 04:35 am

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon),

There is no "if", it doesn't

Sure looks like it does carry LOX but not the main flow to the F9 but to a vent/overpressure relief plus Dragon or sat umbilical at the top of the strong back. Which suggests that if the joint in the "S" bend failed, it would vent what ever was in the pipe to atmo.

As the pipe to the left seems to carry aircon to the top of the strong back, to feed either a Dragon or sat, this would suggest the "S" bend pipe carries LOX to the top of the strong back to feed either a Dragon or sat if needed.

No, the payloads don't need to be loaded with fuel or LOX when on the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 05:13 am

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon),

There is no "if", it doesn't

Sure looks like it does carry LOX but not the main flow to the F9 but to a vent/overpressure relief plus Dragon or sat umbilical at the top of the strong back. Which suggests that if the joint in the "S" bend failed, it would vent what ever was in the pipe to atmo.

As the pipe to the left seems to carry aircon to the top of the strong back, to feed either a Dragon or sat, this would suggest the "S" bend pipe carries LOX to the top of the strong back to feed either a Dragon or sat if needed.

No, the payloads don't need to be loaded with fuel or LOX when on the pad.

Would seem strongback fires have occurred before.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: shooter6947 on 09/05/2016 05:16 am

Would seem strongback fires have occurred before.

And, furthermore, that even when they impinge on the vehicle there is no effect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/05/2016 05:18 am

Would seem strongback fires have occurred before.

And, furthermore, that even when they impinge on the vehicle there is no effect.

In that particular case they did not.  We don't know what would happen with a larger LOX-induced fire.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 05:18 am

Would seem strongback fires have occurred before.

And, furthermore, that even when they impinge on the vehicle there is no effect.

When the strongback is fully retracted maybe no effect. Might just be a different result if the strongback is closely coupled to the F9 and occurs where the 2nd stage LOX tank vent is and the LOX tank is being vented (valve open).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/05/2016 05:30 am
I've read most of the comments in this thread.
Currently 2 plauseible scenarios stand out and both have their faults:

Scenario 1: COPV failure.
Goes like this:
1. COPV (carbon fiber on top of aluminium) fails for unknown reason (may be delamination, may be something else)
2. It is safe to say that when carbon fiber fails, it has tremendous energy stored in it (high tensile strength and stiffness combined). That makes us assume, that possibly helium COPV (at ~6000psi) fails like in https://www.youtube.com/watch?v=5UdVnO10J3U, and then carbon fiber and epoxy will be dispersed as a fine dust into LOX, thereby turning immediate vincinity of the helium bottle onto an Oxyliquit.
3. Supersonic compression wave follows, heating up the mixture of fine carbon and epoxy dust in LOX to a point of detonation
4. Detonation occurs throwing pieces of S2 into different directions
5. 60ms after that behind still burning fireball, the now open LOX tank disperses large cloud of vaporizing oxygen
6. At the same time pressure wave propagates down the LOX pressure vessel destroying common bulkhead
7. RP-1 flows down the scene and COPV submerged in RP-1 tank gets ripped from the tank breaking the tubing to pressure regulator
8. RP-1 tank's COPV gets propelled upwards by releasing helium from broken tubing
the rest is not worth describing.

Issues with this scenario:
1. Why didn't the back side or the whole circumference of S2 burst open due to sharp pressure wave
2. Why wasn't the payload lifted by pressure release into LOX
3. Why the epicenter of initial detonation SEEMS to be just at or outside the surface of S2
4. Why did the COPV fail in first place

Scenario 2: External FAE or oxuliquit initiated event
1. For unknown reasons FAE mixture occurs near the S2. Other option - due to long time stay in oxygen rich environment either rubber stops, some padding. grease, insulation or whatnot turns into oxyliquit)
2. Static discharge (btw highly unlikely in such wet weather) initiates the inadvertently created explosive
3. Explosion occurs, rising pressure just outside the S2 to ~400 psi and temperature 4,500 to 5,400 °F
4. Pressure wave propagates inside the S2 tearing the outer wall open in process and ripping He COPV from it's supports.
5. Pressure wave reflects back from inside wall of S2 and together with pressurized LOX throws He COPV out from S2 at mild speeds
6. LOX tank's COPV gets propelled upwards by releasing helium from broken tubing
7. At the same time pressure wave propagates down the LOX pressure vessel destroying common bulkhead
8. RP-1 flows down the scene and COPV submerged in RP-1 tank gets ripped from the tank breaking the tubing to pressure regulator

Issues with this scenario:
1. There's a wind out there, so FAE is difficult, but not impossible to form
2. Such a cloud of dispersed fuel should have been seen (although the actual fireball may have been a lot smaller when measured from images due to lit surroundings.
3. WTF formed the FAE mixture in first place.

The answer to 3 on scenario would be a leak in gse or in the quick disconnect fittings mounted in the s2 stage itself. Leak inside these fittings or around where the plumbing for them penetrates the tank would make more sense since gases and or fluids could potentially build up in a more meaningful amount here as opposed to a windblown cloud around the stage. If a leak or fire not totally internal to the stage initiated the failure I would expect it to be a problem with the qd fittings and tank plumbing where it penetrates.


However, having looked at this more I am starting to question the COPV failure idea as well. This event seems too energetic for that in terms of burning gases already being apparent as the stage is intially breaching. To me this says either fts related or somehow there was a sudden fast fire already inside the lox tank nano or mili seconds before it breached.

Still points to root cause being related to poor quality control on stage 2 and/or poor testing procedures. I am also beginning to question why they have been conducting static fire tests with the payloads already installed. In retrospect this seems to add uncessary risk since a selling point of this LV system is supposed to be that you can horizontally integrate or de-integrate the vehicle quite rapidly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 06:11 am
I've read most of the comments in this thread.
Currently 2 plauseible scenarios stand out and both have their faults:

Scenario 1: COPV failure.
Goes like this:
1. COPV (carbon fiber on top of aluminium) fails for unknown reason (may be delamination, may be something else)
2. It is safe to say that when carbon fiber fails, it has tremendous energy stored in it (high tensile strength and stiffness combined). That makes us assume, that possibly helium COPV (at ~6000psi) fails like in (see Youtube video in previous post), and then carbon fiber and epoxy will be dispersed as a fine dust into LOX, thereby turning immediate vincinity of the helium bottle onto an Oxyliquit.
3. Supersonic compression wave follows, heating up the mixture of fine carbon and epoxy dust in LOX to a point of detonation

4. Detonation occurs throwing pieces of S2 into different directions
5. 60ms after that behind still burning fireball, the now open LOX tank disperses large cloud of vaporizing oxygen
6. At the same time pressure wave propagates down the LOX pressure vessel destroying common bulkhead
7. RP-1 flows down the scene and COPV submerged in RP-1 tank gets ripped from the tank breaking the tubing to pressure regulator
8. RP-1 tank's COPV gets propelled upwards by releasing helium from broken tubing
the rest is not worth describing.

Issues with this scenario:
1. Why didn't the back side or the whole circumference of S2 burst open due to sharp pressure wave
2. Why wasn't the payload lifted by pressure release into LOX
3. Why the epicenter of initial detonation SEEMS to be just at or outside the surface of S2
4. Why did the COPV fail in first place

...
...

However, having looked at this more I am starting to question the COPV failure idea as well. This event seems too energetic for that in terms of burning gases already being apparent as the stage is intially breaching. To me this says either fts related or somehow there was a sudden fast fire already inside the lox tank nano or mili seconds before it breached.

...


Well, if you look carefully, then I propose a way, how the detonation initiated inside the tank. See points marked in bold.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/05/2016 06:48 am
The longer they stay clammed up the more I think it's either a real head-scratcher or they've got a fairly deep-seated problem with the vehicle (or both).
well, consider the calendar: we're in the middle of a 3-day weekend, and they know from last year's experience that RTF is not a sprint. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kolkmvd on 09/05/2016 07:18 am
Intensity doesn't correlate to origin, although on the surface that seems counter-intuitive. It simply indicates at what point the release of light energy is greatest. It's like the candle shown below, we know the wick is the source of ignition and the paraffin the source of fuel, but just based on the intensity of light we'd be led to believe the ignition is actually 2-3 inches above the candle.
Maybe not exactly as what you meant, but while the 'diffraction crosshairs' seems to point at the right 'edge' of the visible rocket, it may well be that the actual brightest part was slightly at the 'back' of the S2, invisible from camera standpoint. The liberated 'thingee' could origin from that side as well and not be flying straight up, but up and farther away from the camera.

I think Jim also suggested this in one of the earlier forum posts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/05/2016 07:23 am
So, if I'm reading that graph right,  say on the red line, there is a 1% chance of failure with 24 hours of use at 75% load on the composite overwrap. That means to improve the odds, you need to either reduce the time the vessel is loaded (less test time?), or reduce the load on the overwrap (thicker metal, lower pressure?).  Is that the right way to read that graph?

Yes, but note that time scale is a logarithm and the only data points were for a 50% chance of failure and for a day to a year failure chance you need to run it t 65% of ultimate tensile stress.

Most structures are run to a limit strength, either when it deforms or a safety factor.  AFAIK COPV run with SF of 2.35 or 2.5 IE 42% of failure level.

Watching a test of a COPV fail is quite spectacular but IRL how many of these have actually failed as the root cause of an accident?

The Shuttle had something like 50 tanks on board, many COPV's. AFAIK none of them failed in service.

Rupturing one usually causes a lot of trouble but then the root cause is not the COPV, it's what ruptured it in the first place.

Does anyone know of any operational failures of COPV? or high pressure vessels in general on LV's.  I'm sure there must have been a few in the last 60 yrs of spaceflight.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/05/2016 07:39 am
at 4 kelvin helium is liquid?

At 4 K and 23 bar, Helium is liquid and not supercritical. According to the attached pamphlet, Ariane V uses a liquid Helium tank for pressurisation, at 4.2 K. The liquid Helium would be heated by heat from the engine, where it would be used to pressurise the tanks. Not sure why that previous link said supercritical, but that is clearly incorrect, unless they somehow confused the liquid tank with the gaseous Helium tanks that are also used.

The critical point for Helium is at 5.2 K and 2.264 bar. Above that temperature and pressure, Helium is in a supercritical state, being neither liquid or gas. This means that at -207 C and a very high pressure, the Helium SpaceX is using is supercritical.

Note that the COPVs are located around the bottom of the LOX tank along the walls (so as the get maximum cooling since warmer LOX rises to the top). If one lets go, the explosion should initially expand through the path of least mass, which would be through the tank wall. This could be a jet of LOX/Aluminium/Carbon with perhaps maximum combustion occurring outside the tank wall. This might explain why the star effect looks to be outside the tank.

Another possible source of an explosion is a fuel (perhaps from contamination) and ignition source inside the tank. An example of that is the Apollo O2 tank explosion, where the fuel was teflon insulation and the ignition source the wires. There may be some electrical source within the tank that might be the cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 08:07 am
Another strongback fire caused by a RP-1 dump during the COTS1 mission.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 08:16 am
Is there a pressure relief valve almost exactly at the origin of the fire (if you believe the lens flare cross points to the right place)?

See venting during the JCSAT-16 static fire, which is exactly the same angle as the AMOS-6 video: https://www.youtube.com/watch?v=rK9Xz3ZqBG4&feature=youtu.be&t=2m18s

When the strongback is fully retracted maybe no effect. Might just be a different result if the strongback is closely coupled to the F9 and occurs where the 2nd stage LOX tank vent is and the LOX tank is being vented (valve open).

For the sake of neatness, here's the vent on the second stage, seen at the JCSAT16 static fire.

For the correlation (not causation!) list, this is about the height of the brightest point of the initial explosion.

Edit: -16 not -14
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 08:19 am
When the strongback is fully retracted maybe no effect. Might just be a different result if the strongback is closely coupled to the F9 and occurs where the 2nd stage LOX tank vent is and the LOX tank is being vented (valve open).

For the sake of neatness, here's the vent on the second stage, seen at the JCSAT14 static fire.

For the correlation (not causation!) list, this is about the height of the brightest point of the initial explosion.

Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 08:31 am
...
For the sake of neatness, here's the vent on the second stage, seen at the JCSAT14 static fire.

For the correlation (not causation!) list, this is about the height of the brightest point of the initial explosion.

Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

Looking at the mast, I would say that this structure provides enough wind shielding just near the rocket body for FAE mixture to form assuming:
1. There's long time spray of the whole structure with RP-1
2. Wind is not too strong
3. Part of the structure gets sprayed as well

But again - both scenarios are equally plausible and we do not have anything to incline towards neither one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/05/2016 08:36 am
Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

That is not what that is. That S bend is *above* the level of the second stage LOX umbilical. If you look at other photos, you'll see that that line goes onto the payload shroud, which means it cannot be RP1 or LOX. It's an air conditioning duct, as Jim said. 

IMHO, you're right on the Lox vent being close to that S bend.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 08:44 am
Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

That is not what that is. That S bend is *above* the level of the second stage LOX umbilical. If you look at other photos, you'll see that that line goes onto the payload shroud, which means it cannot be RP1 or LOX. It's an air conditioning duct, as Jim said. 

IMHO, you're right on the Lox vent being close to that S bend.

When I look at this picture:

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1366202;sess=14795

the tube is not connected to payload shroud in any ways.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: andy_l on 09/05/2016 09:01 am
So, if I'm reading that graph right,  say on the red line, there is a 1% chance of failure with 24 hours of use at 75% load on the composite overwrap. That means to improve the odds, you need to either reduce the time the vessel is loaded (less test time?), or reduce the load on the overwrap (thicker metal, lower pressure?).  Is that the right way to read that graph?

Worth also remembering that this data is for kevlar overwrap, whilst these particular tanks are carbon overwrap. The same article has to say about carbon overwrap:

Quote
For Kevlar® COPVs, the manufacturer can compute the stress rupture reliability using a Weibull model because a large, robust database exists. Un- fortunately, as of the writing of this paper, there is not a similar database for carbon. Two NASA independent stress rupture test programs are currently under way that should provide additional data availability in 2013 for analysis. Until that time, the NESC and JSC Engineering recommend that the carbon fiber strain remain at or below 50% of the ultimate strength. Based on industry- wide experience, the risk of stress rupture at a strain ratio of 50% is minimal for short-duration space missions.

Since we're now in 2016, presumably the empirical test data for carbon overwrap vessels is now available although I haven't managed to find it yet.

Cheers,


Andy
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/05/2016 09:05 am
When I look at this picture:

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1366202;sess=14795

the tube is not connected to payload shroud in any ways.
It goes to the very top of T/E, apparently to some equipment there and then umbilicals to the P/L.
It makes no sense to run RP-1 line up there, denoting it isn't.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/05/2016 09:40 am
Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

That is not what that is. That S bend is *above* the level of the second stage LOX umbilical. If you look at other photos, you'll see that that line goes onto the payload shroud, which means it cannot be RP1 or LOX. It's an air conditioning duct, as Jim said. 

IMHO, you're right on the Lox vent being close to that S bend.

When I look at this picture:

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1366202;sess=14795

the tube is not connected to payload shroud in any ways.

The payload in the pic is a Dragon. It is not a payload shroud, so no shroud AC duct attached. 

For a pic of that line (With the S in it) going into the Thiacom payload shroud, this link should work;
http://www.americaspace.com/wp-content/uploads/2014/01/1515011_694655020564843_986350026_n.jpg

That fact that line goes into a payload shroud means it cannot be RP1 (or for that matter, Lox).

Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 10:09 am
Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

That is not what that is. That S bend is *above* the level of the second stage LOX umbilical. If you look at other photos, you'll see that that line goes onto the payload shroud, which means it cannot be RP1 or LOX. It's an air conditioning duct, as Jim said. 

IMHO, you're right on the Lox vent being close to that S bend.

When I look at this picture:

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1366202;sess=14795

the tube is not connected to payload shroud in any ways.

The payload in the pic is a Dragon. It is not a payload shroud, so no shroud AC duct attached. 

For a pic of that line (With the S in it) going into the Thiacom payload shroud, this link should work;
http://www.americaspace.com/wp-content/uploads/2014/01/1515011_694655020564843_986350026_n.jpg

That fact that line goes into a payload shroud means it cannot be RP1 (or for that matter, Lox).

Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.

In this case, one plausible scenario is that this leaked hydrazine cloud gets connected to some rusty part of strongback and flashes (hydrazine autoignition temperature on rust is 24C)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 10:15 am
Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.

Ah, here we go again. The payload's fault. Anything but the vehicle.

Anything.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 10:19 am
Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.

Ah, here we go again. The payload's fault. Anything but the vehicle.

Anything.

No. It's more like "could we exclude Scenario 2 (FAE)?". The answer is that we couldn't. Both scenarios are plausible, though, Scenario 1 (COPV) seems more likely.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/05/2016 10:39 am
FWIW, I can't see how AMOS-6 could possibly be found to be the cause unless it had a high thrust/impulse kick stage that fired prematurely.

We're still making guesses and mostly in the dark but there are a few things that I think are incontrovertible at this time:

1) The explosion (imprecise terminology but I'm no expert) seems to have started on the upper TEL-side of the upper stage;

2) The payload seemed entirely intact until it fell into the fire at the base of the pad and subsequently its MPS prop tanks exploded, more likely to overheating than the impact (the second explosion);

3) The lower stage seems to have broken up top-to-bottom after the upper stage exploded (possibly the result of high-velocity debris from the initial event).

Conclusions are speculative at this point but I would at least hope that they are looking at the umbilical connections to the upper stage given that the event seems to have started at the tank wall/hull on the side the umbilicals are attached.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 10:39 am
Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.

Ah, here we go again. The payload's fault. Anything but the vehicle.

Anything.

No. It's more like "could we exclude Scenario 2 (FAE)?". The answer is that we couldn't. Both scenarios are plausible, though, Scenario 1 (COPV) seems more likely.

This one, where you postulate 2 separate failures and a fairly ludicrous hydrazine leak necessary to set up these FAE conditions (while at the same time the leak not being detected for hours and hours prior to the explosion) is stretching it IMHO and the scenario is nowhere near the level of plausibility of something causing overpressurization of a propellant tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/05/2016 10:44 am
In this case, one plausible scenario is that this leaked hydrazine cloud gets connected to some rusty part of strongback and flashes (hydrazine autoignition temperature on rust is 24C)

Interesting! That's 75F... and if those AC ducts are anything like commercial ones, those couplings at the S may well be steel, as well as (thanks to Florida humidity) have a spot of rust or two.

Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.

Ah, here we go again. The payload's fault. Anything but the vehicle.

Anything.

It's just as wrong to close off a hypothetical possibility because it isn't the vehicle as it is to close one off because it is. Rationally, it should make no difference.  (My personal prime suspect remains a 2nd stage COPV.)

Also, even if it was a hydrazine leak in AMOS, that does not get SpaceX off the hook - it might well be their fault due to a mistake in processing/handling of the payload.





Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/05/2016 10:51 am
Mostly agree with CJ.

Also, even if it was a hydrazine leak in AMOS, that does not get SpaceX off the hook - it might well be their fault due to a mistake in processing/handling of the payload.

It would get the Launcher off the hook and allow an early Return to flight, but that's wishful thinking right now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 10:56 am

the tube is not connected to payload shroud in any ways.

Which makes sense since there is no "payload shroud" in that picture.

Already noted before. Mybad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 11:06 am
In absence of any data on our part, any scenarios that require multiple failures (and the probability of chained failures drops off exponentially) like the above copious hydrazine leak on P/L *and* AC duct leak will inevitably look contrived.

Which reminds me, did anyone postulate the scenario of a strut failure on CRS-7 in the vast speculations on this forum?

My point is that complex failure mechanisms seem to be constructed here (for the apparent purpose of getting F9 off the hook) while there is probably a large number of single failure mechanisms we haven't even thought of.

Yes, theoretically, we as a forum community cannot exclude any of the more complex ones, but I feel Occam's razor probably has something to say about them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/05/2016 11:12 am
at 4 kelvin helium is liquid?

At 4 K and 23 bar, Helium is liquid and not supercritical. According to the attached pamphlet, Ariane V uses a liquid Helium tank for pressurisation, at 4.2 K. The liquid Helium would be heated by heat from the engine, where it would be used to pressurise the tanks. Not sure why that previous link said supercritical, but that is clearly incorrect, unless they somehow confused the liquid tank with the gaseous Helium tanks that are also used.

Wow. I did not realize Ariane 5 carried 168Kg of liquid Helium in the LOX tank. I know it's the pressurizing gas of choice but always thought keeping it liquid would be just too tough in a launch environment.

I think it's another testimony to how robust these structures are that none of them has ever failed in flight, given the massive (explosive) volume expansion that would take place if its insulation was punctured.

Sadly there is always a first time for everything and time will tell if this is that time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 11:21 am
Wow. I did not realize Ariane 5 carried 168Kg of liquid Helium in the LOX tank.

Are you sure it's located in the LOX tank? It doesn't look that way to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/05/2016 11:30 am
Just checked the Updates section and there was an SX press release from the 2nd. Interesting take aways were

They are looking at a period of 35-55 ms in time around the upper stage LOX tank across 3000 telemetry and video channels (although by now they should have started on site debris collection as well).

I'm fairly sure that would put it in explosion territory, as would the formation of any shock wave.

They state their 2nd FL launch pad is on schedule for being F9/FH ready by November. So Florida launches resume NET November 1st (Using Musk level optimism  :) ) unless they can repair this pad in less than 25 days.

I've no feel for how damaged the pad and TEL have been damaged. To a layman like me it looks really badly damaged with months of work to rebuild it but is it?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/05/2016 11:30 am

Obviously they will be looking at any changes in vehicle construction and procedures.
Is there any chance that just a procedural change could push past a material threshold that was uncomfortably close to disaster in prior launches but unrecognized?
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/05/2016 11:37 am
Wow. I did not realize Ariane 5 carried 168Kg of liquid Helium in the LOX tank.

Are you sure it's located in the LOX tank? It doesn't look that way to me.
Ooops. The pamphlet on the end of Steve's post said the LHe pressurizes the LOX tank. I conflated that with being in the LOX tank, which is where they are often put.

It's still pretty impressive. Each of the SSME's had something like a 300lb sphere to hold 40lbs of GHe. I'll note that being unmanned Ariane 5 has a higher g limit than the Shuttle, making it a significant piece of engineering.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 11:47 am
Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

That is not what that is. That S bend is *above* the level of the second stage LOX umbilical. If you look at other photos, you'll see that that line goes onto the payload shroud, which means it cannot be RP1 or LOX. It's an air conditioning duct, as Jim said. 

IMHO, you're right on the Lox vent being close to that S bend.

When I look at this picture:

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1366202;sess=14795

the tube is not connected to payload shroud in any ways.

Three tubes come up from the bottom. One stops where the 2ns stage umbilical attaches to the strongback. Two tubes continue up and run to the top of the strongback. Suggest the RP-1 goes to the top of the strongback as if needed the RP-1 can vent / dump from there. Of course the dumped RP-1 can cause problems.

Interesting the initial flash of the 2 events looks very similar. SlowMo video attached.

Fairly serious very top of the strongback vent is seen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/05/2016 11:59 am
In absence of any data on our part, any scenarios that require multiple failures (and the probability of chained failures drops off exponentially) like the above copious hydrazine leak on P/L *and* AC duct leak will inevitably look contrived.

Which reminds me, did anyone postulate the scenario of a strut failure on CRS-7 in the vast speculations on this forum?

My point is that complex failure mechanisms seem to be constructed here (for the apparent purpose of getting F9 off the hook) while there is probably a large number of single failure mechanisms we haven't even thought of.

Yes, theoretically, we as a forum community cannot exclude any of the more complex ones, but I feel Occam's razor probably has something to say about them.

Many aviation accidents were caused by multi point failures, not single point ones. But, to be clear, I'm not saying there was anything faulty with the AC ducting, just that it might have leaks (Very, very common for AC ductwork elsewhere, even with cleanrooms, because the positive pressurization inherent in ductwork makes tiny leaks irrelevant). Also, even with no leak, hydrazine in a duct would make for a capable FAE. It'd have to be a fast hydrazine leak, otherwise there would have been ample warning.

Also, to be clear, even if it was a hydrazine leak, how would that get SpaceX off the hook any more than a strut that didn't meet their spec did for CRX-7? Or for that matter, what's the difference between a GSE fault and a vehicle fault? It's all part of the same system, and that system includes payload care, processing, and handling. IMHO, clearing the F9 via blaming other aspects of the system (GSE, payload handling, etc) is about as useful as clearing the first stage via blaming the second stage (one is not much use without the other). 

Occam's Razor? If you're suggesting that indicates A COPV is a much more likely candidate, then I could not agree more. But more likely isn't the same thing as certain. And until we get more clues (I'm hoping for news Monday or Tuesday, but that's probably wishful thinking) there's not really much else we can do besides theorize.

 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: douglas100 on 09/05/2016 12:02 pm

Two tubes run to the top of the strongback. One stops where the 2ns stage umbilical attaches to the strongback. Suggest the RP-1 goes to the top of the strongback as if needed the RP-1 can vent / dump from there. Of course the dumped RP-1 can cause problems.

Suggest that this is totally wrong. Suggest that no RP-1 goes to the top of the strongback. Suggest that RP-1 is never "vented" it is drained (and filled) through the umbilical at the base of the second stage. Suggest that the fires seen on the strongback are by RP-1 draining from the disconnected umbilical which is set on fire by the exhaust of the engines as the vehicle rises.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/05/2016 12:17 pm
at 4 kelvin helium is liquid?

At 4 K and 23 bar, Helium is liquid and not supercritical. According to the attached pamphlet, Ariane V uses a liquid Helium tank for pressurisation, at 4.2 K. The liquid Helium would be heated by heat from the engine, where it would be used to pressurise the tanks. Not sure why that previous link said supercritical, but that is clearly incorrect, unless they somehow confused the liquid tank with the gaseous Helium tanks that are also used.

Wow. I did not realize Ariane 5 carried 168Kg of liquid Helium in the LOX tank. I know it's the pressurizing gas of choice but always thought keeping it liquid would be just too tough in a launch environment.

I think it's another testimony to how robust these structures are that none of them has ever failed in flight, given the massive (explosive) volume expansion that would take place if its insulation was punctured.

Sadly there is always a first time for everything and time will tell if this is that time.

If a liquid helium tank got punctured you would not have an explosion. Just more gaseous helium boiling off.
In my opinion the complications of liquid helium, Heating it, Insulating it, etc. Would out weigh the dangers of extreme pressure in a tank. Could also reduce weight of tank, location doesn't have to be in a fuel tank, might be a higher density. Haven't done the calculations of the density. 0.125g/cc for liquid. Haven't checked at what 5000 psi?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 12:24 pm

Two tubes run to the top of the strongback. One stops where the 2ns stage umbilical attaches to the strongback. Suggest the RP-1 goes to the top of the strongback as if needed the RP-1 can vent / dump from there. Of course the dumped RP-1 can cause problems.

Suggest that this is totally wrong. Suggest that no RP-1 goes to the top of the strongback. Suggest that RP-1 is never "vented" it is drained (and filled) through the umbilical at the base of the second stage. Suggest that the fires seen on the strongback are by RP-1 draining from the disconnected umbilical which is set on fire by the exhaust of the engines as the vehicle rises.

So what do we see venting sideways and falling down from the top of the strongback in the attached video? For sure it is not vented LOX.

Nice vent nozzle up there on the top of the strongback.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 12:30 pm
Launch pads do not vent combustible fluids freely into the atmosphere. LH2 powered vehicles have the boiled off GH2 siphoned off and burned off safely at a distance. RP-1 vehicles do not vent RP-1 because there is no reason to do so. Period.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 12:39 pm
Launch pads do not vent combustible fluids freely into the atmosphere. LH2 powered vehicles have the boiled off GH2 siphoned off and burned off safely at a distance. RP-1 vehicles do not vent RP-1 because there is no reason to do so. Period.

So what is vented to the right, falls down and is ignited in the video? Sure looks like RP-1 to me. Then I wonder why there is a vent on the very top of the strongback?

With respect, the video and the vent location suggest otherwise.

Please remember we are dealing with fluids chilled their max density point. So maybe super chilled RP-1, when it warms and expands a bit and may need to be vented.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Multivac on 09/05/2016 12:42 pm
After looking closely at various images of the strongback there seems to be a grill/mesh within the structure running up to and stopping near the S-bend. At first I couldn't think of what the purpose of this "mesh" is. Then I suddenly realised this "mesh" looks like a walkway. When the strongback is horizontal this walkway would provide easy access to umbilicals, etc.

Assuming this is a walkway, what would happen is a workman happened to have some contaminant on a boot (e.g. grease) and this was then exposed to a rich oxygen environment such as a LOX vent on S2?

Not implying anything, just asking.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 12:57 pm
Launch pads do not vent combustible fluids freely into the atmosphere. LH2 powered vehicles have the boiled off GH2 siphoned off and burned off safely at a distance. RP-1 vehicles do not vent RP-1 because there is no reason to do so. Period.

So what is vented to the right, falls down and is ignited in the video? Sure looks like RP-1 to me. Then I wonder why there is a vent on the very top of the strongback?

With respect, the video and the vent location suggest otherwise.

Please remember we are dealing with fluids chilled their max density point. So maybe super chilled RP-1, when it warms and expands a bit and may need to be vented.

Please stop. No sane person would ever vent RP-1 fumes into oxygen-rich environment near $300 mil vulnerable equipment full of dangerous flammables. In extreme "if", this could be some emergency vent, but I would be very surprised if it's that.

Please remove your "I have to prove my point" hat and wear "curios to what may be the actual likely reason" hat instead.

Super-chilled RP-1 is a viscous substance that is the least "excess venting" requiring flammable one can find.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: fthomassy on 09/05/2016 12:57 pm
Yes, but note that time scale is a logarithm and the only data points were for a 50% chance of failure and for a day to a year failure chance you need to run it t 65% of ultimate
You misread the plot. The points are the median values of many tests that failed within the yellow bands. So at 85% of rupture their could be more than 20 actual tests.

What the chart does not show is the effect of multiple cycles at a given load.  Holding at 40% rupture for 25 years is not what happens here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/05/2016 01:02 pm
So if it is a copv. Seems like people on this forum rate it better than 50%.
I like the description of the copv bursting through the side of o2 tank combined graphite and aluminum being the fuel, aluminum thereby giving the high brightness observed. What are the chances, location of FTS, being given a high enough shock to ignite it. Isn't necessary for the FTS to be ignited but is interesting from a combined effect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ames on 09/05/2016 01:08 pm
Yes, but note that time scale is a logarithm and the only data points were for a 50% chance of failure and for a day to a year failure chance you need to run it t 65% of ultimate
You misread the plot. The points are the median values of many tests that failed within the yellow bands. So at 85% of rupture the could be more than 20 actual tests.

What the chart does not show is the effect of multiple cycles at a given load.  Holding at 40% rupture for 25 years is not what happens here.

What makes you think that SpaceX have not run these tests; They tested a "great many" struts after CRS-7 and found some were well below spec.
There must be a reason why they did not conclude that the COPV was the cause. Probably because they tested the COPVs as well and found them good.

Ames

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 01:09 pm
Launch pads do not vent combustible fluids freely into the atmosphere. LH2 powered vehicles have the boiled off GH2 siphoned off and burned off safely at a distance. RP-1 vehicles do not vent RP-1 because there is no reason to do so. Period.

So what is vented to the right, falls down and is ignited in the video? Sure looks like RP-1 to me. Then I wonder why there is a vent on the very top of the strongback?

With respect, the video and the vent location suggest otherwise.

Please remember we are dealing with fluids chilled their max density point. So maybe super chilled RP-1, when it warms and expands a bit and may need to be vented.

Please stop. No sane person would ever vent RP-1 fumes into oxygen-rich environment near $300 mil vulnerable equipment full of dangerous flammables. In extreme "if", this could be some emergency vent, but I would be very surprised if it's that.

Please remove your "I have to prove my point" hat and wear "curios to what may be the actual likely reason" hat instead.

Super-chilled RP-1 is a viscous substance that is the least "excess venting" requiring flammable one can find.

Curious hat on.

So what was clearly vented from the top of the strongback, fell down until it found some heat and maybe LOX and caught fire? You can't avoid what the video clearly shows happened.

As far as I know vented LOX does not fall down as the vented white vapour does in the video. The only thing that I know of, that was on that strongback, that would form a heavy white vapour upon venting, fall down and then ignite is RP-1. What else can it be?

But yes you are right, it is nuts as can clearly be seen, when it is done, the RP-1 vapour falls down and ignites. Lucky for the F9 that the strong back was fully retracted and this fire and explosion did not damage the rising F9.

I do note the initial flash of the 2 events looks similar.

Different Dog, Same Leg Action?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 01:20 pm
So what was clearly vented from the top of the strongback, fell down until it found some heat and maybe LOX and caught fire? You can't avoid what the video clearly shows happened.

I agree that there *appears* to be a vent on the top of the strongback, although this could be a fitting to allow something to be pumped into the system when it is on the ground.

It would be useful if we knew what this was...

I'm not sure that whatever many have vented from the top of the strongback was whatever ignited - I would think a more likely candidate would be residual RP-1 from the fuelling line(s).

As far as I know vented LOX does not fall down as the vented white vapour does in the video. The only thing that I know of, that was on that strongback, that would form a heavy white vapour upon venting, fall down and then ignite is RP-1. What else can it be?

Oxygen is denser than air, (1.331kg/m³ v 1.205kg/m³) - and will be more so if the oxygen has been cooled.

As far as this particular explosion is concerned, if oxygen was liberated it would probably have been at pressure - which would have had more of an influence over initial distribution than relative densities (over the very short time frame we're looking at).

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 01:32 pm
Perhaps this nozzle in top is fire suppression head and the whole tube is for spraying rocket with fire suppression liquid, should there be RP-1 leak and develop fire. Then all that (mysterious tube, mysterious spray-nozzle) would make sense as well as the eventual purge from the tube (tube should be prefilled to enable quick reaction times).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: douglas100 on 09/05/2016 01:33 pm

I agree that there *appears* to be a vent on the top of the strongback, although this could be a fitting to allow something to be pumped into the system when it is on the ground.

It would be useful if we knew what this was...

It would. That would put this argument to bed. And you are right to emphasize "appears."

Quote
I'm not sure that whatever many have vented from the top of the strongback was whatever ignited - I would think a more likely candidate would be residual RP-1 from the fuelling line(s).

Agree. And I don't think it comes from the very top of the strongback either, but from about where the end of the disconnected RP-1 line would be swinging.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/05/2016 01:37 pm
To follow up a previous post.
A slight mis-adjustment of the top clamps allowed excess weight to be placed on the support fixture at the common bulkhead position. That caused a slight deformation of the tank body inward, after payload supports were removed and while vehicle was being raised to vertical. This was NOT enough to structurally damage the tank but WAS enough to crack a bolt holding one of the COPV's in place. Then the cryogenic cooling contracted the tank enough to shear the bolt completely. Other bolts and struts were strong enough to hold the COPV in place so that the unrestricted strut became a "dagger" that pierced the common bulkhead. Scraping as it pierced caused a spark that ignited the mixture around the hole.

Or not.       
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/05/2016 01:37 pm
Just a random thought that I haven't seen mentioned yet: the concept that the explosion could have been driven by nothing more than the combusion of LOX with *the tank itself*.

Aluminum alloys are generally LOX compatible.  *Generally*.  But it requires an intact oxide layer.  LOX is, for example, not compatible with freshly polished aluminum.  And once a burn begins, it's self-sustaining and very aggressive.

Any chance that there was a damaged or even never formed oxide layer inside?

Contamination also comes across as possibilities, because there's a lot of things considered incompatible with LOX - greases, lubricants, most solvents, most plastics, and on and on.  Most are not hypergolic, but they can go off with an ignition source, including mere impact.  LOX tanks must be clean, both on the vehicle end, the delivery end, and everything in-between.   But *not* cleaned to the point of removing the protective oxide layer shortly before filling.

Just some thoughts to add to the conversation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 01:48 pm
Perhaps this nozzle in top is fire suppression head and the whole tube is for spraying rocket with fire suppression liquid, should there be RP-1 leak and develop fire. Then all that (mysterious tube, mysterious spray-nozzle) would make sense as well as the eventual purge from the tube (tube should be prefilled to enable quick reaction times).

The "vent???" is pointed tangential to the F9 and not at the F9.

It would make sense to have a fire fighting system installed along the strongback.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 01:50 pm
To follow up a previous post.
A slight mis-adjustment of the top clamps allowed excess weight to be placed on the support fixture at the common bulkhead position. That caused a slight deformation of the tank body inward, after payload supports were removed and while vehicle was being raised to vertical. This was NOT enough to structurally damage the tank but WAS enough to crack a bolt holding one of the COPV's in place. Then the cryogenic cooling contracted the tank enough to shear the bolt completely. Other bolts and struts were strong enough to hold the COPV in place so that the unrestricted strut became a "dagger" that pierced the common bulkhead. Scraping as it pierced caused a spark that ignited the mixture around the hole.

Or not.     

I do not know, how Aluminium behaves in States, but in my country it mos likely will not throw a spark. When I was child, I tried to get spark out of Al by hitting it with hammer in several ways. No success.

I think that in order for Al to start combustion with superchilled LOX, it has to be:
1. Fine powder
2. There has to be high supersonic pressure wave
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: douglas100 on 09/05/2016 01:51 pm
@ Rei:  The oxide layer on aluminum tends to "heal" as soon as it's exposed to air. Atlas, Titan I, R-7, Zenit....they all had/have aluminum LOX tanks which tends to suggest that this isn't any problem.

Contamination might be a possibility, but I think that is way down the line. It would mean that there was something seriously wrong with SpaceX's processing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zardar on 09/05/2016 01:53 pm
Perhaps this nozzle in top is fire suppression head and the whole tube is for spraying rocket with fire suppression liquid, should there be RP-1 leak and develop fire. Then all that (mysterious tube, mysterious spray-nozzle) would make sense as well as the eventual purge from the tube (tube should be prefilled to enable quick reaction times).

The "vent???" is pointed tangential to the F9 and not at the F9.

It would make sense to have a fire fighting system installed along the strongback.

I think that 'vent' is used during the dragon late load, to supply clean air to the 'cabin'
http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg (http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg)


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 01:54 pm
Just a random thought that I haven't seen mentioned yet: the concept that the explosion could have been driven by nothing more than the combusion of LOX with *the tank itself*.

Aluminum alloys are generally LOX compatible.  *Generally*.  But it requires an intact oxide layer.  LOX is, for example, not compatible with freshly polished aluminum.  And once a burn begins, it's self-sustaining and very aggressive.

Any chance that there was a damaged or even never formed oxide layer inside?

Contamination also comes across as possibilities, because there's a lot of things considered incompatible with LOX - greases, lubricants, most solvents, most plastics, and on and on.  Most are not hypergolic, but they can go off with an ignition source, including mere impact.  LOX tanks must be clean, both on the vehicle end, the delivery end, and everything in-between.   But *not* cleaned to the point of removing the protective oxide layer shortly before filling.

Just some thoughts to add to the conversation.

Al-Oxygen fire is a possibility when oxide layer is continously removed like in moving mechanisms (turbopump or sometihg like this). In this environment, it would quickly reform.

Also, I would be very suprised if the tank would not be passivated with gaseous O2 before it even gets aseembled to rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 01:56 pm
Perhaps this nozzle in top is fire suppression head and the whole tube is for spraying rocket with fire suppression liquid, should there be RP-1 leak and develop fire. Then all that (mysterious tube, mysterious spray-nozzle) would make sense as well as the eventual purge from the tube (tube should be prefilled to enable quick reaction times).

The "vent???" is pointed tangential to the F9 and not at the F9.

It would make sense to have a fire fighting system installed along the strongback.

I think that 'vent' is used during the dragon late load, to supply clean air to the 'cabin'
http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg (http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg)

This one solves the matter with this tube. And again, Jim was right - no LOX, no RP-1 in there.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 02:03 pm
Perhaps this nozzle in top is fire suppression head and the whole tube is for spraying rocket with fire suppression liquid, should there be RP-1 leak and develop fire. Then all that (mysterious tube, mysterious spray-nozzle) would make sense as well as the eventual purge from the tube (tube should be prefilled to enable quick reaction times).

The "vent???" is pointed tangential to the F9 and not at the F9.

It would make sense to have a fire fighting system installed along the strongback.

I think that 'vent' is used during the dragon late load, to supply clean air to the 'cabin'
http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg (http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg)

Nice find ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 02:08 pm
This one solves the matter with this tube. And again, Jim was right - no LOX, no RP-1 in there.

Another useful photo showing the plumbing - note this is F9 1.1 and there are a few bits 'missing' from the erector compared to its most recent format.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 02:09 pm
Perhaps this nozzle in top is fire suppression head and the whole tube is for spraying rocket with fire suppression liquid, should there be RP-1 leak and develop fire. Then all that (mysterious tube, mysterious spray-nozzle) would make sense as well as the eventual purge from the tube (tube should be prefilled to enable quick reaction times).

The "vent???" is pointed tangential to the F9 and not at the F9.

It would make sense to have a fire fighting system installed along the strongback.

I think that 'vent' is used during the dragon late load, to supply clean air to the 'cabin'
http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg (http://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2016/04/spacex8-latecargoload-1024x683.jpg)

This one solves the matter with this tube. And again, Jim was right - no LOX, no RP-1 in there.

Yup solved.

Next the 2 strongback flashes and then the after burn that look like RP-1 buring due to the black smoke.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zardar on 09/05/2016 02:20 pm
A new theory:

One thing that surprised me was that the payload seemed to 'hold on' for quite a long time, given the destruction going on just below it.

Those clamps must be holding on really tightly?

But, there must be some means for the strongback to 'shrink' in conjunction with the rocket, when the chilled propellants are loaded? (IANARS, but it must get a few cm shorter, right?)

Looking at strongback photos, it looks like the top part is mechanically decoupled, to probably allow for this adjustment. (In fact, it looks like a meccano set in there, with all the rams and trusses)

But what if that decoupling failed, and the strongback didn't shrink correctly when the rocket was chilled? Would the stress on the S2 (in opposite to the usual flight stress) be enough to fracture something?

I'm sure the sensors would detect that, but by the time the rocket is partially filled, it might be too late to drain it to prevent damage?



(Edit- typo)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/05/2016 02:27 pm
@ Rei:  The oxide layer on aluminum tends to "heal" as soon as it's exposed to air.


Indeed.  But there are two aspects to that.

1) Air
2) Time

What gas is in the tank during transport / storage / erection?  Air, or something inert like nitrogen?  And how sure are we that due to the stress of erecting or loading the rocket that there was no damage to the oxide layer?

Quote
Atlas, Titan I, R-7, Zenit....they all had/have aluminum LOX tanks which tends to suggest that this isn't any problem.

It certainly suggests that it would not be a common problem - but not that we can rule it out, as each vehicle has its own  manufacture, transport, erection, etc properties.  It's also worthy of note that none of those rockets used densified LOX.  There's actually rather limited experience with it.

Quote
Contamination might be a possibility, but I think that is way down the line. It would mean that there was something seriously wrong with SpaceX's processing.

I agree.  I'm just presenting this possibility, to point out that the presence of combustion within the LOX tank does not inherently imply contact between the LOX and RP1.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 02:37 pm
This one solves the matter with this tube. And again, Jim was right - no LOX, no RP-1 in there.

Another useful photo showing the plumbing - note this is F9 1.1 and there are a few bits 'missing' from the erector compared to its most recent format.

Wonderful photo. Thanks.

Is the combined Aircon & LOX header unit, as per the attached, maybe "The Thingy" that shot up into the air from the strongback?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/05/2016 02:41 pm
@ Rei:  The oxide layer on aluminum tends to "heal" as soon as it's exposed to air.


Indeed.  But there are two aspects to that.

1) Air
2) Time

What gas is in the tank during transport / storage / erection?  Air, or something inert like nitrogen?  And how sure are we that due to the stress of erecting or loading the rocket that there was no damage to the oxide layer?

Quote
Atlas, Titan I, R-7, Zenit....they all had/have aluminum LOX tanks which tends to suggest that this isn't any problem.

It certainly suggests that it would not be a common problem - but not that we can rule it out, as each vehicle has its own  manufacture, transport, erection, etc properties.  It's also worthy of note that none of those rockets used densified LOX.  There's actually rather limited experience with it.

Quote
Contamination might be a possibility, but I think that is way down the line. It would mean that there was something seriously wrong with SpaceX's processing.

I agree.  I'm just presenting this possibility, to point out that the presence of combustion within the LOX tank does not inherently imply contact between the LOX and RP1.

That is just beyond unlikely:
1. Al tank holding supercooled LOX will NOT self-combust due to simple reasons - even if some patch of aluminium gets constantly scrubbed:
1.1. This Al oxide layer is one of the hardest substances known to man and does not come off easily
1.2. Any heat build-up before combustion will be absorbed by sheer mass of supercooled LOX and the point will NEVER reach combustion temperature
2. Densified LOX is probalby even less susceptible to causing Al-O2 fire due to general rule - lower temperature, slower reactions.
3. I have never heard about LOX containing Al tank to burst to fire without initiation. You have to enlarge specific surface considerably to make Al burn in LOX. AFAIK, you can even have Al slurry in LOX and it still won't autoignite. Although, it's a powerful explosive when actually excited.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 02:45 pm
Anyone have any history on how many cycles the second stage has gone though since manufacture?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 02:50 pm
Looking at strongback photos, it looks like the top part is mechanically decoupled, to probably allow for this adjustment.

If it's the section seen in the attached photographs, I think that was a change made when SpaceX transitioned from F9 1.1 to the slightly taller F9 FT.

I did wonder if this was if done because there was a difference between the heights of an F9 with Dragon vs an F9 with a fairing, but there are photographs of both payloads with both lengths of section.

Worth remembering that this strongback was presumably built for F9 1.0 and has been modified considerably to accommodate F9 FT.

Whether or not the slightly 'Heath Robinson' approach to design (compare it to the Vandenberg and Pad 39 TELs) has had any influence on the loss of this F9 will not doubt come out in due course.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/05/2016 02:54 pm
Anyone have any history on how many cycles the second stage has gone though since manufacture?
Not a number, but less than S1-024.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/05/2016 02:55 pm
Anyone have any history on how many cycles the second stage has gone though since manufacture?
Rough guess - this was the second prop load on the tankage. 1st for acceptance testing at McGregor, and then the static fire attempt.

Individual components have been tested more probably (the M1vac has had its own test cycle), but I'm thinking this was only the second all up loading test on the stage.

So I bet they have a group going over the test data from McGregor with a very fine tooth comb on top of the data from the incident.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Eric Hedman on 09/05/2016 02:57 pm
Here is the New York Times take on the impact of the Pad Failure:

http://www.nytimes.com/2016/09/05/business/spacexs-explosion-reverberates-across-space-satellite-and-telecom-industries.html?_r=0 (http://www.nytimes.com/2016/09/05/business/spacexs-explosion-reverberates-across-space-satellite-and-telecom-industries.html?_r=0)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/05/2016 02:58 pm
Hrmmm... Looks like there are two AC ducts; one in, one out? Is the S-bend is on the out (return) duct  and, hypothetically, there was a hydrazine leak in the payload, and if those AC ducts leak a bit (which normally would not be a problem due to positive pressurization... that S-bend, if a bit leaky, would put hypothetical hydrazine vapor in contact with the O2 being vented at about the area of the apparent locus of the event.

Ah, here we go again. The payload's fault. Anything but the vehicle.

Anything.
Making up ideas to "absolve" the vehicles is a smaller sin than overlooking possibilities because of that.

Any possibility that is compatible with the observed data should be looked at. If it turns out to be wrong (and this one most likely will) then nothing is lost.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FutureSpaceTourist on 09/05/2016 02:58 pm
Don't think this really qualifies for an update:

Quote
Peter B. de Selding ‏@pbdes 1h1 hour ago

Spacecom CEO David Pollack on how he learned his Amos-6 sat was under the smoke cloud from Cape Canaveral on Sept 1.
https://twitter.com/pbdes/status/772795118143303680 (https://twitter.com/pbdes/status/772795118143303680)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 02:59 pm
Anyone have any history on how many cycles the second stage has gone though since manufacture?
Rough guess - this was the second prop load on the tankage. 1st for acceptance testing at McGregor, and then the static fire attempt.
Thanks, that's all I would figure at this point as well unless they did more in Texas...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/05/2016 03:06 pm
This one solves the matter with this tube. And again, Jim was right - no LOX, no RP-1 in there.

Another useful photo showing the plumbing - note this is F9 1.1 and there are a few bits 'missing' from the erector compared to its most recent format.

Wonderful photo. Thanks.

Is the combined Aircon & LOX header unit, as per the attached, maybe "The Thingy" that shot up into the air from the strongback?

Um, again -- as I thought you agreed, no LOX and no RP-1 plumbing reaches up as far as the PL shroud.  So, where and how do you get the idea that there is some kind of unit that high on the TEL that intermixes LOX and air from the AC plumbing?

Since one of the things the AC system does is to flush air out of the PL fairing and replace it with gaseous nitrogen, obviously to mitigate fire risks within the fairing, I fail to see why you would ever be mixing a feed from the LOX fill system into the AC flows.  That would sort of be like having a complex system for filtering contaminants like lubricants out of the interiors of the engine turbopumps, but interpreting a specific pipe you can see on the outside of the turbopumps as feeding oil directly into the bearings.

In other words, not only is there no need to mix the LOX feeding system into the PL AC, adding more oxygen into the PL fairing it is actively what the AC system is trying to avoid.

I hate to say this, but as Jim (and others) who actually know what goes that far up the TEL have already pointed out, the only thing running up and down those conduits that go up to the PL shroud is air conditioning for the PL.  All RP-1 and LOX plumbing ends at the base of stage 2, well below your illustrative image, and well below where the initial flash was observed at the start of the anomaly.

The line you have labeled as a LOX line going up to what you have labeled as a combined LOX/AC header unit is, as again has been noted by people who have worked on those lines and who know and are not just speculating, is an AC return line.  Again, just to put the matter to rest, this is not a LOX line.  No LOX lines go farther up the TEL than the base of stage 2.

Now, if, say, the RP-1 umbilical that runs to the bottom of stage 2 were to have suffered a small leak that was located just such that it sprayed RP-1 in an invisible cloud up to the level of the LOX vents, near where the flash was seen, then maybe I could see a FAE event happening.  But it was a windy day...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/05/2016 03:14 pm
SpaceX, if they have tank pressure telemetry, would know for sure whether it was a COPV failure rupturing LOX and RP-1 tanks.

If it was, SpaceX would take a credibility hit: they did not properly fix a known problem.

If it wasn't a COPV failure, then there had to be another source of fuel outside vehicle. FAEs don't happen with only oxygen.

Almost the only plausible one is RP-1 leak in the fueling lines on the erector.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 03:22 pm
The line you have labeled as a LOX line going up to what you have labeled as a combined LOX/AC header unit is, as again has been noted by people who have worked on those lines and who know and are not just speculating, is an AC return line.  Again, just to put the matter to rest, this is not a LOX line.  No LOX lines go farther up the TEL than the base of stage 2.

Now, if, say, the RP-1 umbilical that runs to the bottom of stage 2 were to have suffered a small leak that was located just such that it sprayed RP-1 in an invisible cloud up to the level of the LOX vents, near where the flash was seen, then maybe I could see a FAE event happening.  But it was a windy day...

There are a couple of curious things about that pipe - see attached annotated image.

1. It appears to have a connection to the first stage

2. It ends, seemingly without any terminating connection (at a point in the strongback which is hinged, presumably for ease of construction / delivery).

I wonder if it's a duct within which pipes are run, rather than a single pipe?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: fthomassy on 09/05/2016 03:29 pm
AC for M1D-Vac?
edit: Vac
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: testguy on 09/05/2016 03:33 pm
Does anyone have an idea what data rate the 3000 channels of data were recording at?  I would assume some channels video and some GSE equipment would be low ( 30 to 100 Hz). 
Just trying to understand what kind of resolution Space X will see during the 30-35 miliseconds.  Got to believe SpaceX has all the digital data reviewed by now and have a good idea as to the source of the problem if not the reason.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/05/2016 03:35 pm
Quote
1. Al tank holding supercooled LOX will NOT self-combust due to simple reasons - even if some patch of aluminium gets constantly scrubbed:

"Constant" scrubbing is in no manner necessary.  As mentioned in the post you're responding to, formation of the oxide layer requires:

1) Air
2) Time

Even where air is present, it takes about three days to reach maximum thickness.  And lest you think I'm being ridiculous about the subject, I strongly recommend you read guidelines for handling LOX, which stress the importance of a full oxide layer being formed before filling an aluminum tank with LOX.

Quote
1.1. This Al oxide layer is one of the hardest substances known to man and does not come off easily

You clearly have never worked with aluminum.  Hit an aluminum pipe with a hammer.  Notice the shiny stuff?  You just removed the oxide layer.

Quote
1.2. Any heat build-up before combustion will be absorbed by sheer mass of supercooled LOX

I'm sorry, but I've personally watched aluminum burn in LOX.  If you don't believe me, take an aluminum can, fill it with LOX, drop a candle in it to get it going, and watch it go up in a brilliant shower of sparks.  You can probably find a video on Youtube of something similar.

Or, if you want something more scientific:

http://www.dtic.mil/dtic/tr/fulltext/u2/a229229.pdf

"Ignitions occurred in some specimens of all alloys during pressurized mechanical impact tests at MSFC ... attributed to test parameter variations that produce excessive local deformation leading to very high local temperatures in the specimens in the presence of oxygen in the absence of protective oxides."

Quote
2. Densified LOX is probalby even less susceptible to causing Al-O2 fire due to general rule - lower temperature, slower reactions

Conversely, reaction rates are also positively proportional to density.   Furthermore, you absolutely cannot generalize like that, particularly when you're talking about aluminum.  I've read a number of papers about the mechanics of aluminum combustion and it's a lot more complex than most combustion one encounters in rocketry, as at all scales the reaction rate is highly dependent on the behavior of how the oxide fractures and reforms during combustion.  Can you off the bat tell me at how the fracture behavior of the oxide layer changes as the temperature drops?
.
Quote
3. I have never heard about LOX containing Al tank to burst to fire without initiation ... AFAIK, you can even have Al slurry in LOX and it still won't autoignite.

I explicitly said "not hypergolic" and that an ignition energy source is required.

Re, the ignition of aluminum, you can find a nice summary here:

https://books.google.is/books?id=FgsKVot0WpQC&pg=PA338&lpg=PA338&dq=aluminum+LOX+tank+explosion+impact+-falcon+-apollo+-scrap&source=bl&ots=0f9Ny0UUJe&sig=MdDFBw3iS7-7tU5yi4WXIcPwOrU&hl=is&sa=X&ved=0ahUKEwjqu8CcxPjOAhXMI8AKHedUA-cQ6AEIVTAI#v=onepage&q=aluminum%20LOX%20tank%20explosion%20impact%20-falcon%20-apollo%20-scrap&f=false

Start reading at "Among the significant features of aluminum flammability are...".

In examples of vehicles actually brought down by LOX tank detonation without the presence of fuel, look at the X-1A and X-1D, both of which exploded during pressurization due to contamination with a grease used in the manufacture of their gaskets. 

To reiterate: LOX tanks must be clean - but still have their oxide layer intact when filled.  An ignition source is still needed, but it can occur from uneven deformation or heavy impact.  No, it's not a common source of explosion in rocketry.  But it is possible for combustion to occur in a LOX tank without the propellant having first come in contact with the LOX.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 03:36 pm

*IF* the pipe running through the s-bend in the extendable section of the erector carries LOX (and not aircon),

There is no "if", it doesn't

Sure looks like it does carry RP-1. 


No, it doen't.  There are multiple AC lines. The second stage get AC too



Would seem strongback fires have occurred before.


That is from the second stage umbilical
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/05/2016 03:42 pm
Does anyone have an idea what data rate the 3000 channels of data were recording at?  I would assume some channels video and some GSE equipment would be low ( 30 to 100 Hz). 
Just trying to understand what kind of resolution Space X will see during the 30-35 miliseconds.  Got to believe SpaceX has all the digital data reviewed by now and have a good idea as to the source of the problem if not the reason.

I would think SpaceX already has the data that illuminates what happened.  However, you're right, there is proximate cause and then there is root cause.

The data likely has shown them what the proximate cause was -- what was happening that made the rocket go boom.  As to what began the chain of events that led to the proximate cause, that's the item that will take longer to define. And that's what they need to get down to before they can even define their next steps in making the system safe to fly again.

The one thing I will say is this --it is not the exact same causation path that happened on CRS-7.  This was a sudden, abrupt failure, while CRS-7's overpressurization event occurred over a period of up to 10 seconds.  If this was an overpressurization event, it occurred far, far more rapidly.  So, people who are sitting back and dispensing their disgust about how SpaceX failed to fix the same problem that took down CRS-7 should just stop, since it's impossible that this could be the same problem.

It could possibly be a different problem in the same system, but it's not the same problem, has a different proximate cause, and almost certainly has a different root cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 03:42 pm
Just adjacent to that LOX vent is the "S" bend in the RP-1 supply pipe.

That is not what that is. That S bend is *above* the level of the second stage LOX umbilical. If you look at other photos, you'll see that that line goes onto the payload shroud, which means it cannot be RP1 or LOX. It's an air conditioning duct, as Jim said. 

IMHO, you're right on the Lox vent being close to that S bend.

When I look at this picture:

https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1366202;sess=14795

the tube is not connected to payload shroud in any ways.

Photo is of a Dragon mission, not applicable
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/05/2016 03:44 pm
There's an important detail, that a lot of us here (myself included) missed:

SpaceX gave costumers the choice to keep the satellite on the rocket for the test fire or not. Spacecom *chose* to keep it on top.

See: http://spacenews.com/qa-spacecom-ceo-it-took-a-minute-to-realize-the-guys-under-the-smoke-are-us/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 03:45 pm

In this case, one plausible scenario is that this leaked hydrazine cloud gets connected to some rusty part of strongback and flashes (hydrazine autoignition temperature on rust is 24C)

No, not plausible.  The fairing was intact.  As stated earlier in the thread.

Please read the whole thread, so we don't rehash discounted theories.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/05/2016 03:47 pm
Note in post 1349 how small the support fixture by the common bulkhead is. Note also the crescent connection between that structure and the upper clamps. It would make sense that these are small because they are only intended to support about 1/2 of stage 2. But also note it is right in the section that is the portion of the TEL that can be adjusted for height. Could it be that they simulated compressional loads properly but maybe underestimated the rotational load on those struts with a very heavy payload? (Could the Fairing have additional recovery system weight?)

Guessing at a list of things that might be different from prior launches.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 03:47 pm

Three tubes come up from the bottom. One stops where the 2ns stage umbilical attaches to the strongback. Two tubes continue up and run to the top of the strongback. Suggest the RP-1 goes to the top of the strongback as if needed the RP-1 can vent / dump from there. Of course the dumped RP-1 can cause problems.

Interesting the initial flash of the 2 events looks very similar. SlowMo video attached.

Fairly serious very top of the strongback vent is seen.

No, just stop.  It is an AC duct
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/05/2016 03:49 pm
If hydrazine was released from the satellite into the fairing, then flushed out by AC, it would end up in the very AC return line that many people are holding suspect.

Does that AC return duct go all the way down to ground, or does it vent the removed gases at some higher altitude?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 03:49 pm

Also, to be clear, even if it was a hydrazine leak, how would that get SpaceX off the hook any more than a strut


Because that would be the payload's fault and Spacex has no role in it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 03:52 pm
Note in post 1349 how small the support fixture by the common bulkhead is. Note also the crescent connection between that structure and the upper clamps. It would make sense that these are small because they are only intended to support about 1/2 of stage 2. But also note it is right in the section that is the portion of the TEL that can be adjusted for height. Could it be that they simulated compressional loads properly but maybe underestimated the rotational load on those struts with a very heavy payload? (Could the Fairing have additional recovery system weight?)

Guessing at a list of things that might be different from prior launches.

Things that are different: this one exploded on the pad, the others didn't ;)

The adjustable height / length bit of the structure was solely used - as far as I can tell - to modify the structure's height from F9 1.1 to F9 FT.

Bear in mind that the stages are very strong - strong enough to be trucked across the country, tested, launched and in the case of the first stage, landed. Those stresses are much more than being sat on the erector and taken vertical a couple of times.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 03:57 pm
If hydrazine was released from the satellite into the fairing, then flushed out by AC, it would end up in the very AC return line that many people are holding suspect.

Does that AC return duct go all the way down to ground, or does it vent the removed gases at some higher altitude?

There is no return duct.  It is a single pass system.  It vents out of the fairing near the bottom
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: testguy on 09/05/2016 04:08 pm
Does anyone have an idea what data rate the 3000 channels of data were recording at?  I would assume some channels video and some GSE equipment would be low ( 30 to 100 Hz). 
Just trying to understand what kind of resolution Space X will see during the 30-35 miliseconds.  Got to believe SpaceX has all the digital data reviewed by now and have a good idea as to the source of the problem if not the reason.

I would think SpaceX already has the data that illuminates what happened.  However, you're right, there is proximate cause and then there is root cause.

The data likely has shown them what the proximate cause was -- what was happening that made the rocket go boom.  As to what began the chain of events that led to the proximate cause, that's the item that will take longer to define. And that's what they need to get down to before they can even define their next steps in making the system safe to fly again.

The one thing I will say is this --it is not the exact same causation path that happened on CRS-7.  This was a sudden, abrupt failure, while CRS-7's overpressurization event occurred over a period of up to 10 seconds.  If this was an overpressurization event, it occurred far, far more rapidly.  So, people who are sitting back and dispensing their disgust about how SpaceX failed to fix the same problem that took down CRS-7 should just stop, since it's impossible that this could be the same problem.

It could possibly be a different problem in the same system, but it's not the same problem, has a different proximate cause, and almost certainly has a different root cause.

Agree with every thing you wrote.  I'm just trying to understand approximately how many data points they have for critical channels during that 30-35 miliseconds.  I have done enough failure investigations in my time to understand how important that information is along with the time to do each data scan. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/05/2016 04:11 pm


Bear in mind that the stages are very strong - strong enough to be trucked across the country, tested, launched and in the case of the first stage, landed. Those stresses are much more than being sat on the erector and taken vertical a couple of times.

And if your/their strength assumptions are in the slightest way wrong the vehicle goes boom -
- which it did.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 04:14 pm

Three tubes come up from the bottom. One stops where the 2ns stage umbilical attaches to the strongback. Two tubes continue up and run to the top of the strongback. Suggest the RP-1 goes to the top of the strongback as if needed the RP-1 can vent / dump from there. Of course the dumped RP-1 can cause problems.

Interesting the initial flash of the 2 events looks very similar. SlowMo video attached.

Fairly serious very top of the strongback vent is seen.

No, just stop.  It is an AC duct

The Yellow line ends at the bottom of the interstage and connects to one of the 2 shiny umbilical feeds that connect to the 2nd stage.

The Orange line does appear to be a A/C line.

The Green line connects to the other 2nd stage shiny umbilical that connects to the 2nd stage but doesn't appear to stop at the bottom of the interstage. It appears to continue to the top of the strongback.

Please show where the Green line stops being a supply line to the 2nd stage and becomes a return A/C duct as I can't see it. Maybe I should toss my engineering degree and 45 years of engineering experience.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/05/2016 04:16 pm
If hydrazine was released from the satellite into the fairing, then flushed out by AC, it would end up in the very AC return line that many people are holding suspect.

Does that AC return duct go all the way down to ground, or does it vent the removed gases at some higher altitude?

There is no return duct.  It is a single pass system.  It vents out of the fairing near the bottom

This surely looks like 2 separate ducts going into the fairing.
(http://i.imgur.com/24r2llc.jpg)

Edit: Oops. Big image.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/05/2016 04:20 pm
If hydrazine was released from the satellite into the fairing, then flushed out by AC, it would end up in the very AC return line that many people are holding suspect.

Does that AC return duct go all the way down to ground, or does it vent the removed gases at some higher altitude?

There is no return duct.  It is a single pass system.  It vents out of the fairing near the bottom

This surely looks like 2 separate ducts going into the fairing.
(http://i.imgur.com/24r2llc.jpg)

Edit: Oops. Big image.
Isn't that just one wound up to have leeway when the strong back moves back?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 04:23 pm


Bear in mind that the stages are very strong - strong enough to be trucked across the country, tested, launched and in the case of the first stage, landed. Those stresses are much more than being sat on the erector and taken vertical a couple of times.

And if your/their strength assumptions are in the slightest way wrong the vehicle goes boom -
- which it did.

Given the stresses the vehicle goes through in use, I think SpaceX's strength 'assumptions' would have to be a bit more wrong than the 'slightest way' for the vehicle to explode without warning on the pad because the strongback supports are set up wrong.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/05/2016 04:28 pm
If hydrazine was released from the satellite into the fairing, then flushed out by AC, it would end up in the very AC return line that many people are holding suspect.

Does that AC return duct go all the way down to ground, or does it vent the removed gases at some higher altitude?

There is no return duct.  It is a single pass system.  It vents out of the fairing near the bottom

This surely looks like 2 separate ducts going into the fairing.
[snip /]

Edit: Oops. Big image.
Isn't that just one wound up to have leeway when the strong back moves back?

No. Here is (the same? nope, this is Thaicom-6, other one is Thaicom-8) stage/fairing with the strongback partially retracted:
(http://www.satnews.com/images_upload/1083418300/52cb29836fc8f.png)

Still looks like 2 ducts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 04:32 pm
The Yellow line ends at the bottom of the interstage and connects to one of the 2 shiny umbilical feeds that connect to the 2nd stage.

The Orange line does appear to be a A/C line.

The Green line connects to the other 2nd stage shiny umbilical that connects to the 2nd stage but doesn't appear to stop at the bottom of the interstage. It appears to continue to the top of the strongback.

Please show where the Green line stops being a supply line to the 2nd stage and becomes a return A/C duct as I can't see it. Maybe I should toss my engineering degree and 45 years of engineering experience.

You may have missed my query about that duct, so attached again.

It does feed / join the feed to the first stage, but then comes to a end about halfway down the strongback - i.e. it can not be a supply from the ground.

The image you're using isn't thoroughly helpful as it doesn't show that the pipe marked in green doesn't go to the bottom of the erector.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/05/2016 04:33 pm
Still looks like 2 ducts.

Yea, you are right and I was wrong, there's another image upthread where you can clearly see the two ducts attached to the fairing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 04:35 pm
The left feed pipe to the 2nd stage umbilicals does stop at the bottom of the interstage but the right feed pipe does not stop at the bottom of the interstage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/05/2016 04:39 pm
In this case, one plausible scenario is that this leaked hydrazine cloud gets connected to some rusty part of strongback and flashes (hydrazine autoignition temperature on rust is 24C)

But it wasn't a fire.  It was a very neat and clean detonation, which subsided before the main fire erupted.

Any scenario that starts with internal mixing of RP1 and O2, I'd think, would result in a much much larger detonation, and it wouldn't subside - it would generate more mixing as it went, and it would also obliterate the payload.

If it was an internal event, it managed to burst the skin without shredding the stage, showed the detonation outside, ran its course, and then the shockwave destroyed the stage (which might have been weakened by the first event).

It all happens between the two critical frames of the youTube video...  The first shows nothing, not even deformation or spray, the second shows a detonation already many meters across.  30 ms is a long time in explosions... 



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/05/2016 04:41 pm
The Yellow line ends at the bottom of the interstage and connects to one of the 2 shiny umbilical feeds that connect to the 2nd stage.

The Orange line does appear to be a A/C line.

The Green line connects to the other 2nd stage shiny umbilical that connects to the 2nd stage but doesn't appear to stop at the bottom of the interstage. It appears to continue to the top of the strongback.

Please show where the Green line stops being a supply line to the 2nd stage and becomes a return A/C duct as I can't see it. Maybe I should toss my engineering degree and 45 years of engineering experience.

You may have missed my query about that duct, so attached again.

It does feed / join the feed to the first stage, but then comes to a end about halfway down the strongback - i.e. it can not be a supply from the ground.

The image you're using isn't thoroughly helpful as it doesn't show that the pipe marked in green doesn't go to the bottom of the erector.

If the Green pipe does not go to the ground then what does it feed into one of the 2 shiny umbilicals that connect to the 2nd stage?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/05/2016 04:42 pm


Given the stresses the vehicle goes through in use, I think SpaceX's strength 'assumptions' would have to be a bit more wrong than the 'slightest way' for the vehicle to explode without warning on the pad because the strongback supports are set up wrong.

But it could be strong in every possible direction & motion EXCEPT a pivot around that frighteningly tiny support fixture. It would have never been seen with non-payload static fires or even Dragon static fires and launches - they are not heavy enough, or present a long enough lever arm to have an effect. So just what, maybe 5 launches where they were close but dodged the bullet. Just like STS dodged the foam issue for 106 launches. How is this less likely than not testing COPV's enough to guarantee they won't explode?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 04:43 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/05/2016 04:45 pm
I'm still looking at at brittle fracture of material of either FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It is an event that happens very fast...

Note: this looks like a v1.0 second stage to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 04:47 pm
I'm still looking at at brittle fracture of material of either FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It is an event that happens very fast...

Note: this looks like a v1.0 second stage to me.
Yes, it's just for a reference point for my thoughts... Feel free to update the image...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/05/2016 04:54 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

Hmm, the bottom of that COPV mount you have circled in red does appear to be around the approximate centroid of the flash seen in the video.

I have no pet theory here, as amusing as it is to watch people with random backgrounds try to correct Jim and nitpick to support their own.  That said, I do wonder - personally - if the root cause of this might come down a handling mishap with S2 somewhere along the way days, weeks or even months ago, such as a jarred or dropped tank in the factory (say a jolt of 2" - 3" in placing on the cradle for transport or assembly jig, or the over-the-road transport truck having a minor collision along the route such as bumping a concrete post at a truck stop, running over a curb making a turn, etc)? Alternately, perhaps a bit of manufacturing re-work might have been required during assembly at one of the COPV mounts which was performed in a defective manner (something like that brought down an entire 747 full of people in Japan once) ... In other words, a seemingly minor event somewhere along the that seemed of no consequence but which eventually resulted in a major mishap.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 05:03 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

Hmm, the bottom of that COPV mount you have circled in red does appear to be around the approximate centroid of the flash seen in the video.

I have no pet theory here, as amusing as it is to watch people with random backgrounds try to correct Jim and nitpick to support their own.  That said, I do wonder - personally - if the root cause of this might come down a handling mishap with S2 somewhere along the way days, weeks or even months ago, such as jarred or dropped tank in the factory (say a jolt of 2" - 3" in placing on the cradle for transport or assembly jig, or the over-the-road transport truck having a minor collision along the route such as bumping a concrete post as a truck stop)? Alternately, perhaps a bit of manufacturing re-work might have been required during assembly at one of the COPV mounts which was performed in a defective manner (something like that brought down an entire 747 full of people in Japan once) ... In other words, a seemingly minor event somewhere along the that seemed of no consequence but which eventually resulted in a major mishap.
Yes, I agree Herb with that as well and could have produced a vibration or shock fatigue along the transport. I believe that Doug may have said thing along the same lines as well with the Apollo 13 LOX tank handling. Multiple causes including a bad material batch or start/stop FSW spot during manufacture could have revealed itself during erection and prop load temps, pressures and COPV upward strain.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/05/2016 05:09 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

You do realize the drawing your working from does not match reality in many ways...  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 05:16 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

You do realize the drawing your working from does not match reality in many ways...  ;)
Give me a side view cutaway please or I will reject your reality and replace it with my own... ;D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chrup4 on 09/05/2016 05:18 pm
Yes it happened to the Russians several times. The most famous one is probably the "Nedelin disaster" with an early ICBM, which resulted in a high number of fatalities too.

Note he said "total loss of the launch vehicle and payload prior to launch". The Nedelin Catastrophe shouldn't count since it was an ICBM test and didn't have anything but a dummy warhead aboard. Having said that, yes it did happen in the Soviet program a couple of times including the explosion of a Kosmos 3M booster in 1973 and the Plesetsk disaster in 1980.

I'm fairly sure that this had never happened in the US program prior to last Thursday since Atlas 9C didn't have the Able probe aboard it and the Atlas-Agena pad collapse in 1963 had a GAMBIT satellite that got destroyed, but it wasn't the one they were actually planning to launch.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 05:23 pm
But it could be strong in every possible direction & motion EXCEPT a pivot around that frighteningly tiny support fixture. It would have never been seen with non-payload static fires or even Dragon static fires and launches - they are not heavy enough, or present a long enough lever arm to have an effect. So just what, maybe 5 launches where they were close but dodged the bullet. Just like STS dodged the foam issue for 106 launches. How is this less likely than not testing COPV's enough to guarantee they won't explode?

That support is one of a pair - the second one is at the level of the 'claw' immediately under the fairings.

The pair of supports are mounted on a frame which appears to be pivoted at its centre - i.e. if the loading on one of the supports is disproportionate, it will give a little and the other one will be pressed against the stage.

No doubt someone could come up with a failure mode based on this ;)

Once the vehicle is located on the erector frame, there will be no unexpected forces. As far as I'm aware, the vehicle is lifted horizontally and lowered horizontally onto the erector, so I don't quite see how it can experience forces sufficient to damage it - unless it's been dropped or badly abused in transit.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chrup4 on 09/05/2016 05:26 pm
But it wasn't a fire.  It was a very neat and clean detonation, which subsided before the main fire erupted.

Any scenario that starts with internal mixing of RP1 and O2, I'd think, would result in a much much larger detonation, and it wouldn't subside - it would generate more mixing as it went, and it would also obliterate the payload.

Like for example Atlas 9C. The common bulkhead collapsed after the fire in the thrust section led to loss of tank support pressure, which caused the entire load of LOX to fall into the RP-1 tank, turn into explosive gel, and go off with an enormous bang, so powerful that it totally leveled the service structures on the pad and caved in the concrete launch stand.

The entire purpose of range safety destruct charges is to prevent this from happening--they split open the tanks and let the propellants spill out, minimizing mixing. At least on boosters with cryogenic propellants. On boosters with hypergols, the RSO system is designed to encourage propellant mixing so the toxic fuel cloud burns up as quickly as possible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 05:30 pm
But it could be strong in every possible direction & motion EXCEPT a pivot around that frighteningly tiny support fixture. It would have never been seen with non-payload static fires or even Dragon static fires and launches - they are not heavy enough, or present a long enough lever arm to have an effect. So just what, maybe 5 launches where they were close but dodged the bullet. Just like STS dodged the foam issue for 106 launches. How is this less likely than not testing COPV's enough to guarantee they won't explode?

That support is one of a pair - the second one is at the level of the 'claw' immediately under the fairings.

The pair of supports are mounted on a frame which appears to be pivoted at its centre - i.e. if the loading on one of the supports is disproportionate, it will give a little and the other one will be pressed against the stage.

No doubt someone could come up with a failure mode based on this ;)

Once the vehicle is located on the erector frame, there will be no unexpected forces. As far as I'm aware, the vehicle is lifted horizontally and lowered horizontally onto the erector, so I don't quite see how it can experience forces sufficient to damage it - unless it's been dropped or badly abused in transit.
We must always bear in mind that it could be an unfortunate combination of design, materials, forces, events, conditions and not a smoking gun...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/05/2016 05:35 pm
But it wasn't a fire.  It was a very neat and clean detonation, which subsided before the main fire erupted.

Any scenario that starts with internal mixing of RP1 and O2, I'd think, would result in a much much larger detonation, and it wouldn't subside - it would generate more mixing as it went, and it would also obliterate the payload.

If it was an internal event, it managed to burst the skin without shredding the stage, showed the detonation outside, ran its course, and then the shockwave destroyed the stage (which might have been weakened by the first event).

It all happens between the two critical frames of the youTube video...  The first shows nothing, not even deformation or spray, the second shows a detonation already many meters across.  30 ms is a long time in explosions...

I so agree with this statement... it needs reposting as the setup to mine....   ;)

My current thoughts on topic...  :P
Internal event where a high pressure He fitting burst violently... (not a COPV, a fitting)
Sending at least 3 'seen' fragments flying off at high speed... (prior postings of mine)
One of which reacted violently with going thru the AlLi skin producing the frame #1 detonation... "the flash"
Between the now rising pressure inside... the three holes (at least)... and the shockwave from the detonation...
S2 splits open and showers it's contents all over and the outcome is obvious to all... 

Just my latest... on topic...  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/05/2016 05:35 pm
For the sake of neatness, here's the vent on the second stage, seen at the JCSAT16 static fire.

For the correlation (not causation!) list, this is about the height of the brightest point of the initial explosion.

It would further not be surprising, and as explained at length using the candle as an example, that the largest/fastest initial burn happened near a source of gox.  It makes it more difficult to ascribe the point of ignition to the brightest point of the fire.  Ignition could have been elsewhere, but accelerated near the vent.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/05/2016 05:37 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

You do realize the drawing your working from does not match reality in many ways...  ;)
Give me a side view cutaway please or I will reject your reality and replace it with my own... ;D

LOL... Believe me when I say... I tried very hard to find one online...  ;D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 05:39 pm
So, I haven't had a chance to read every comment on the last 10 pages, but a friend of mine who worked Centaur for many years mentioned a theory I hadn't heard much in the first several dozen pages of this thread. His thought was that the failure could be due to a common bulkhead failure that wasn't driven by COPVs popping, but by something else such as ullage collapse. IIRC, someone mentioned somewhere that SpaceX was trying some new approaches for being able to give them longer hold-time with the subcooled propellants. It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead. Because the vehicle is constrained pretty strongly at the top and bottom, the outer walls might have been prevented from buckling, but the bulkhead could have buckled or flipped. Localized mixing would've created a shock sensitive enough mixture that the dynamics of the event could have provided its own initiation energy.

There's lots of possibilities how this could happen, but if it is the cause, it's not necessarily a rocket or a GSE/pad failure per se, but possibly an experiment gone horribly wrong. It would bode well for getting back to flight soon, but if true, may suggest that there are more risks to using highly subcooled propellants than initially thought.

Anyhow, figured I'd mention that one, since I think it's probably just as likely as a COPV/pressurization system related failure. And would fit in with the "not some stupid mistake SpaceX should've obviously not made, but something subtle about how they're pushing the envelope performance-wise".

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 05:39 pm

1.  The Green line connects to the other 2nd stage shiny umbilical that connects to the 2nd stage but doesn't appear to stop at the bottom of the interstage. It appears to continue to the top of the strongback.

2.  Please show where the Green line stops being a supply line to the 2nd stage and becomes a return A/C duct as I can't see it.

3.  Maybe I should toss my engineering degree and 45 years of engineering experience.

1.  It provides A/C to the second stage

2.  There is no such thing as an return A/C.  A/C on launch vehicles and spacecraft is a single pass with no return.  It is a purge.

3,  If it is not in the spaceflight industry, then yes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 05:40 pm

This surely looks like 2 separate ducts going into the fairing.


As you said, "going into".  There is no return
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 05:41 pm
The left feed pipe to the 2nd stage umbilicals does stop at the bottom of the interstage but the right feed pipe does not stop at the bottom of the interstage.

Green feeds A/C into the second stage

Again.  Just stop.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 05:41 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

You do realize the drawing your working from does not match reality in many ways...  ;)
Give me a side view cutaway please or I will reject your reality and replace it with my own... ;D

LOL... Believe me when I say... I tried very hard to find one online...  ;D
I'll just give Elon a call then... ;D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kraisee on 09/05/2016 05:42 pm
I believe the Green line is a Gaseous Nitrogen Purge Line to provide spark protection inside areas such as the Dragon's Trunk and the Interstage.

The Yellow line appears to be merely Conditioned Air, usually used for Fairings and the Dragon's cabin.

Both the GN2 and AC will simply vent out from small holes in the vehicle structure that are designed for the purpose (they are also used in flight to relieve pressure buildup as the atmo thins out).

I might have these two back-to-front, but Jim can probably correct me :)

The LOX and RP1 lines both stop at the same station (well below this area), where there is some equipment on the tower, and the umbilicals both connect at the bottom of the US/top of the Interstage.   I believe there is also a GN2 purge line on that umbilical.

In the video's of the COTS-1 flight you can see that umbilical venting a substantial amount of white gas during launch, and this is what caused the momentary fire ball around the tower during that flight. I'm still unsure what the specific fuel was on that occasion, but in such oxy-rich conditions it could have been virtually anything including paint, cork or even the metal structure itself.

Ross.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/05/2016 05:44 pm
I've got a pet theory, but before I embarass myself with it, I have a few questions.

How is the Common Bulkhead secured to the airframe? Is there a mechanical linkage that, given unspecified manufacturing/transport/handling errors, could create a pinhole leak in the RP1 tank?

Is the RP1 tank even under sufficent pressure, at the top of the tank, to produce an aerosol for an extended length of time? (from whenever RP1 loading allowed the leak to begin, until an ignition source caused our current disaster)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 05:44 pm
So, I haven't had a chance to read every comment on the last 10 pages, but a friend of mine who worked Centaur for many years mentioned a theory I hadn't heard much in the first several dozen pages of this thread. His thought was that the failure could be due to a common bulkhead failure that wasn't driven by COPVs popping, but by something else such as ullage collapse. IIRC, someone mentioned somewhere that SpaceX was trying some new approaches for being able to give them longer hold-time with the subcooled propellants. It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead. Because the vehicle is constrained pretty strongly at the top and bottom, the outer walls might have been prevented from buckling, but the bulkhead could have buckled or flipped. Localized mixing would've created a shock sensitive enough mixture that the dynamics of the event could have provided its own initiation energy.

There's lots of possibilities how this could happen, but if it is the cause, it's not necessarily a rocket or a GSE/pad failure per se, but possibly an experiment gone horribly wrong. It would bode well for getting back to flight soon, but if true, may suggest that there are more risks to using highly subcooled propellants than initially thought.

Anyhow, figured I'd mention that one, since I think it's probably just as likely as a COPV/pressurization system related failure. And would fit in with the "not some stupid mistake SpaceX should've obviously not made, but something subtle about how they're pushing the envelope performance-wise".

~Jon
Still pretty interesting Jon, Thanks! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 05:46 pm
At the point in the test T-8 minutes (during tanking).  All A/C purges would have changed over from conditioned air to conditioned GN2.  Both the fairing and second stage A/C purges.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kraisee on 09/05/2016 05:54 pm
So, I haven't had a chance to read every comment on the last 10 pages, but a friend of mine who worked Centaur for many years mentioned a theory I hadn't heard much in the first several dozen pages of this thread. His thought was that the failure could be due to a common bulkhead failure that wasn't driven by COPVs popping, but by something else such as ullage collapse. IIRC, someone mentioned somewhere that SpaceX was trying some new approaches for being able to give them longer hold-time with the subcooled propellants. It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead. Because the vehicle is constrained pretty strongly at the top and bottom, the outer walls might have been prevented from buckling, but the bulkhead could have buckled or flipped. Localized mixing would've created a shock sensitive enough mixture that the dynamics of the event could have provided its own initiation energy.
[SNIP]
~Jon

I heard a similar story from a retired seniour Boeing engineer, regarding (IIRC) one of Apollo-10's S-1C tank domes.   Apparently one of the massive 10m domes flipped inside caused by a stuck valve as they were draining the tank.   They repressurised the tank, got the dome to flip back again (apparently with an enormous "bang" you could hear from miles away), then put it through a full set of pressure tests, found it still met all of the criteria and decided not to replace it!   He said it flew with the same dome!   The story sounds barely plausible, but they were certainly a lot more steely eyed back in those days, so who really knows...   Maybe someone on here?

Ross.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/05/2016 05:58 pm
We must always bear in mind that it could be an unfortunate combination of design, materials, forces, events, conditions and not a smoking gun...

Indeed.

There's perhaps also a bit too much focus on the *exact* place the explosion started: yes, it's *probably* somewhere close to the upper stage COPVs, but if the explosion started outside the vehicle, the point of ignition will be as much the focus as the source of the substances consumed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 06:01 pm
It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead.

Pretty interesting theory, but could ullage collapse really happen that quickly that it wouldn't leave an obvious smoking gun in telemetry via a dropping pressure trend? I (naively) wouldn't think so.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ppb on 09/05/2016 06:02 pm
This has probably been asked before (please direct to the pertinent posts), but has any other launch vehicle immersed COPVs in LOX? All composite structures have delamination in the set of possible outcomes. It seems a LOX bath would only magnify this remote chance.

Sent from my LGLS885 using Tapatalk

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 06:12 pm
It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead.

Pretty interesting theory, but could ullage collapse really happen that quickly that it wouldn't leave an obvious smoking gun in telemetry via a dropping pressure trend? I (naively) wouldn't think so.

How do we know if there hasn't been a smoking gun in the telemetry? Even if SpaceX was reasonably sure they knew the problem, do you think they'd announce their findings before double and triple checking everything, and making sure the FAA, DoD, and NASA folks on their investigation panel were in agreement?

But yeah, while ullage collapse can happen quickly, it wouldn't be instantaneous, though it could be fairly quick.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 06:18 pm
How do we know if there hasn't been a smoking gun in the telemetry?

Granted, we don't know, but the press statement talking about a few tens of milliseconds of telemetry to me sounds like the anomaly had a rather quick onset.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 06:19 pm
How do we know if there hasn't been a smoking gun in the telemetry?

Granted, we don't know, but the press statement talking about a few tens of milliseconds of telemetry to me sounds like the anomaly had a rather quick onset.

True. Was just pointing out that even if the failure was due to mixing of LOX/RP-1 through a ruptured common bulkhead, that there were many possible explanations and COPVs only factor into some of them.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jimmy_C on 09/05/2016 06:45 pm
Here is a picture of the interior of a LOX tank (http://www.astronautinews.it/2015/07/26/un-supporto-difettoso-la-causa-della-perdita-del-falcon-9/) in the F9. Are the COPV those three black cylinders along the walls?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: feynmanrules on 09/05/2016 06:47 pm

So, I haven't had a chance to read every comment on the last 10 pages, but a friend of mine who worked Centaur for many years mentioned a theory I hadn't heard much in the first several dozen pages of this thread. His thought was that the failure could be due to a common bulkhead failure that wasn't driven by COPVs popping, but by something else such as ullage collapse. IIRC, someone mentioned somewhere that SpaceX was trying some new approaches for being able to give them longer hold-time with the subcooled propellants. It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead. Because the vehicle is constrained pretty strongly at the top and bottom, the outer walls might have been prevented from buckling, but the bulkhead could have buckled or flipped. Localized mixing would've created a shock sensitive enough mixture that the dynamics of the event could have provided its own initiation energy.

There's lots of possibilities how this could happen, but if it is the cause, it's not necessarily a rocket or a GSE/pad failure per se, but possibly an experiment gone horribly wrong. It would bode well for getting back to flight soon, but if true, may suggest that there are more risks to using highly subcooled propellants than initially thought.

Anyhow, figured I'd mention that one, since I think it's probably just as likely as a COPV/pressurization system related failure. And would fit in with the "not some stupid mistake SpaceX should've obviously not made, but something subtle about how they're pushing the envelope performance-wise".

~Jon

Interesting.  Regardless of whether it winds up being a design/manufacturing or gse/handling issue, I wonder if they'll take one of landed cores to experiment with tank-detank/static fires.   Customers love the benefits of spacex ambitions but hard to imagine them being cool w/pushing performance on production rockets w/300m sats and multi-year dev times attached.

Side note, at first I thought that this failure would be much easier for amateurs to diagnose since the video was so much better.   I don't think that any longer.  Very interesting to follow, learning lots of things from Jim and others here... maybe they'll prove me wrong.

Side note2, i notice that elon is tweeting less and shotwell wrote the official company response.   Some people have interpreted this bearish for id-ing root cause(s).  I wonder if since crs-7 was so recent I'd imagine they and their partners are confident in getting great resolution.   So less tweeting more patience into working the problem.  I do wonder how elon decides whether he's going to work on spx blow ups vs tsla issues.    I'm guessing spx since this is revenue stopping at the moment.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/05/2016 06:54 pm
It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead.

Ullage vent valves are unable to cope with this kind of scenario, check valves preventing letting ambient atmosphere in? AIUI prop loading was still underway so the tanks weren't flight pressurized.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/05/2016 07:00 pm
Here is a picture of the interior of a LOX tank (http://www.astronautinews.it/2015/07/26/un-supporto-difettoso-la-causa-della-perdita-del-falcon-9/) in the F9. Are the COPV those three black cylinders along the walls?

Yes... The 3 items are believed to be the He COPV's in S2...
Other flghts have shown 4 installed...
They are reported elsewhere to be about 17 inches in diameter and about 60 inches long...
Sources IIRC found in NSF here somewhere for all these items of note...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/05/2016 07:58 pm


 
Side note2, i notice that elon is tweeting less and shotwell wrote the official company response.   Some people have interpreted this bearish for id-ing root cause(s).  I wonder if since crs-7 was so recent I'd imagine they and their partners are confident in getting great resolution.   So less tweeting more patience into working the problem.  I do wonder how elon decides whether he's going to work on spx blow ups vs tsla issues.    I'm guessing spx since this is revenue stopping at the moment.
It may be more of a response to Tory Bruno's initial comments about 'not speculating about causes too soon' after the Orbital-6 anomaly. ¯\_(ツ)_/¯
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/05/2016 08:21 pm
I wouldn't read much into tweeting frequency, etc. They are doing this right with the initial comments (the standard - sorry for the customer, we'll get to the bottom of it, etc.). Then they set up a page on their official site for updates as and when they can provide them....which is useful.

Also remember any progress will be first communicated to their related teams, then to their customers (not least future customers) before anything is public....so there's going to be some process involved. It's only been a matter of days.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/05/2016 09:03 pm
I've read most of the comments in this thread.
Currently 2 plauseible scenarios stand out and both have their faults:

Scenario 1: COPV failure.
Goes like this:
1. COPV (carbon fiber on top of aluminium) fails for unknown reason (may be delamination, may be something else)
2. It is safe to say that when carbon fiber fails, it has tremendous energy stored in it (high tensile strength and stiffness combined). That makes us assume, that possibly helium COPV (at ~6000psi) fails like in (see Youtube video in previous post), and then carbon fiber and epoxy will be dispersed as a fine dust into LOX, thereby turning immediate vincinity of the helium bottle onto an Oxyliquit.
3. Supersonic compression wave follows, heating up the mixture of fine carbon and epoxy dust in LOX to a point of detonation

4. Detonation occurs throwing pieces of S2 into different directions
5. 60ms after that behind still burning fireball, the now open LOX tank disperses large cloud of vaporizing oxygen
6. At the same time pressure wave propagates down the LOX pressure vessel destroying common bulkhead
7. RP-1 flows down the scene and COPV submerged in RP-1 tank gets ripped from the tank breaking the tubing to pressure regulator
8. RP-1 tank's COPV gets propelled upwards by releasing helium from broken tubing
the rest is not worth describing.

Issues with this scenario:
1. Why didn't the back side or the whole circumference of S2 burst open due to sharp pressure wave
2. Why wasn't the payload lifted by pressure release into LOX
3. Why the epicenter of initial detonation SEEMS to be just at or outside the surface of S2
4. Why did the COPV fail in first place

...
...

However, having looked at this more I am starting to question the COPV failure idea as well. This event seems too energetic for that in terms of burning gases already being apparent as the stage is intially breaching. To me this says either fts related or somehow there was a sudden fast fire already inside the lox tank nano or mili seconds before it breached.

...


Well, if you look carefully, then I propose a way, how the detonation initiated inside the tank. See points marked in bold.

Yes I did see that and I do think this is a possible ignition source. Still not so sure though. Fwiw this would illustrate a clear reason why crs7 failed differently since the piping to the vessel failed first as a result of attachment point failure. This would explain the rupture and outgassing we saw in that failure without the fire we had in this failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/05/2016 09:11 pm
Wow. I did not realize Ariane 5 carried 168Kg of liquid Helium in the LOX tank.

Are you sure it's located in the LOX tank? It doesn't look that way to me.

Another point worth noting is that quite a few launch vehicles carry the helium supply in either engine bay voids or externally but not internally inside the liquid oxygen tanks. There are and have been some other LVs that do but this has also been a point of criticism regarding the design of F9 in the past. For reference the reason why F9 carries them internally is preformance driven.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/05/2016 09:24 pm
Does anyone have an idea what data rate the 3000 channels of data were recording at?  I would assume some channels video and some GSE equipment would be low ( 30 to 100 Hz). 
Just trying to understand what kind of resolution Space X will see during the 30-35 miliseconds.  Got to believe SpaceX has all the digital data reviewed by now and have a good idea as to the source of the problem if not the reason.

I would think SpaceX already has the data that illuminates what happened.  However, you're right, there is proximate cause and then there is root cause.

The data likely has shown them what the proximate cause was -- what was happening that made the rocket go boom.  As to what began the chain of events that led to the proximate cause, that's the item that will take longer to define. And that's what they need to get down to before they can even define their next steps in making the system safe to fly again.

The one thing I will say is this --it is not the exact same causation path that happened on CRS-7.  This was a sudden, abrupt failure, while CRS-7's overpressurization event occurred over a period of up to 10 seconds.  If this was an overpressurization event, it occurred far, far more rapidly.  So, people who are sitting back and dispensing their disgust about how SpaceX failed to fix the same problem that took down CRS-7 should just stop, since it's impossible that this could be the same problem.

It could possibly be a different problem in the same system, but it's not the same problem, has a different proximate cause, and almost certainly has a different root cause.

It is not only possible but almost 60% likely to have been a very similar problem with the same components. Failure mode differs because helium gas lines failed first in crs7 resulting in a "slower" overpressure as compared to a supersonic shockwave generated by a burst COPV bottle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 09:25 pm
It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead.

Pretty interesting theory, but could ullage collapse really happen that quickly that it wouldn't leave an obvious smoking gun in telemetry via a dropping pressure trend? I (naively) wouldn't think so.

How do we know if there hasn't been a smoking gun in the telemetry? Even if SpaceX was reasonably sure they knew the problem, do you think they'd announce their findings before double and triple checking everything, and making sure the FAA, DoD, and NASA folks on their investigation panel were in agreement?

But yeah, while ullage collapse can happen quickly, it wouldn't be instantaneous, though it could be fairly quick.

~Jon



I think my greatest concern is for those 3,000 channels of data... what was the data rate for each channel?  i.e. is tank pressure sampled every second, or every micro-second?  If this is a slow event that builds over seconds, most of those channels will be useful if only to say "not here."  If this is a fast event that builds then blows over 30-50 ms, only those data channels that sample and report within that window will be usable.

3,000 channels is a lot of data coming over how many networks at what speed with what packet priority?  Hopefully most of this came over a wired network at 1 GB or faster.  If it were the telemetry only, they're going have to be very lucky to see event data.  Hopefully its a mix of networks.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/05/2016 09:34 pm
Looking at the video, this really doesn't look to be an internal explosion.

     Maybe a burn off of the vented LOX, but not an internal blast.  However; we can't be certain of this until we can get some video from another angle.  An internal explosion would have lifted the payload clear of the tower as the upper stage unzipped and peeled away to the sides.

      I base this on other pad explosions I've seen in previous videos, as well as aircraft explosions of a similar nature.

      This looks like an uncontained explosion, that occurred from the tower or its near vicinity, that expanded into the side of the stage, rupturing it sideways, and then inhibiting the fuel and LOX.  As an uncontained explosion, both the initial and the rupture ignition, there wouldn't have been enough upwards force to shift the payload upwards to any sufficient distance.

      It should also be noted that such an internal explosion, would have forced the upper stage engine downwards to the first state's LOX tank, further adding fuel to the explosion, magnifying the over all explosive force helping to throw the payload at least several meters up and away from the tower.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/05/2016 09:36 pm
A question: How long do the telemetry systems stay alive? Would spacex still get telemetry from sensors in the S1 while S2 is already gone? Would they still get data from the fairing and the payload while it hung on the strongback?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/05/2016 09:36 pm

It is not only possible but almost 60% likely to have been a very similar problem with the same components.
58.72%, to be precise
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 09:41 pm
Does anyone have an idea what data rate the 3000 channels of data were recording at?  I would assume some channels video and some GSE equipment would be low ( 30 to 100 Hz). 
Just trying to understand what kind of resolution Space X will see during the 30-35 miliseconds.  Got to believe SpaceX has all the digital data reviewed by now and have a good idea as to the source of the problem if not the reason.

I would think SpaceX already has the data that illuminates what happened.  However, you're right, there is proximate cause and then there is root cause.

The data likely has shown them what the proximate cause was -- what was happening that made the rocket go boom.  As to what began the chain of events that led to the proximate cause, that's the item that will take longer to define. And that's what they need to get down to before they can even define their next steps in making the system safe to fly again.

The one thing I will say is this --it is not the exact same causation path that happened on CRS-7.  This was a sudden, abrupt failure, while CRS-7's overpressurization event occurred over a period of up to 10 seconds.  If this was an overpressurization event, it occurred far, far more rapidly.  So, people who are sitting back and dispensing their disgust about how SpaceX failed to fix the same problem that took down CRS-7 should just stop, since it's impossible that this could be the same problem.

It could possibly be a different problem in the same system, but it's not the same problem, has a different proximate cause, and almost certainly has a different root cause.

It is not only possible but almost 60% likely to have been a very similar problem with the same components. Failure mode differs because helium gas lines failed first in crs7 resulting in a "slower" overpressure as compared to a supersonic shockwave generated by a burst COPV bottle.

That's a lot more confident than I think we can be at this point. I think a COPV failure is one of the more likely failure sources, but far from the only credible cause of failure. I know this is hard for aerospace engineers, but humility is in order, especially with how little data we're working with here.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/05/2016 09:42 pm

It is not only possible but almost 60% likely to have been a very similar problem with the same components.
58.72%, to be precise
Yeah, but you're using metric percents.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 09:43 pm

It is not only possible but almost 60% likely to have been a very similar problem with the same components.
58.72%, to be precise

78.26% of statistics are made up on the spot. And 68.23% of those statistics are then defended vigorously when questioned...

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/05/2016 09:44 pm
A question: How long do the telemetry systems stay alive? Would spacex still get telemetry from sensors in the S1 while S2 is already gone? Would they still get data from the fairing and the payload while it hung on the strongback?
That depends on the physical data path the cabling takes and where exactly the explosion originated. If it originated from the umbilical, and they had a data line in the umbilical, they would have lost all the signal, all at once. If there was an alternate path (say through the interstage) then they would probably see further into the event. If the telemetry transmitters were active, then the sensitive paths would be he path from the sensors to the transmitter and avionics hardware on top of the upper stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 09:46 pm
Now for something completely different.

I was skimming parts of this book:   https://books.google.com/books?id=H9XKBQAAQBAJ

Its focus is on reducing the risk of industrial accidents.  There are several discussions about how to design HVAC and AC systems so they don't inadvertently detonate.  One minor tidbit just to spark an AC debate, don't mix water and aluminum shavings in a closed space.  You'll build up hydrogen gas... 

The book has lots of other examples of what not to do...

Does anyone know much about how the tower AC system was configured?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/05/2016 09:58 pm
So, I haven't had a chance to read every comment on the last 10 pages, but a friend of mine who worked Centaur for many years mentioned a theory I hadn't heard much in the first several dozen pages of this thread. His thought was that the failure could be due to a common bulkhead failure that wasn't driven by COPVs popping, but by something else such as ullage collapse. IIRC, someone mentioned somewhere that SpaceX was trying some new approaches for being able to give them longer hold-time with the subcooled propellants. It may be possible that something they did lead to ullage collapse in the S2 LOX tank (ie the cold GOX in the ullage is chilled enough by the subcooled LOX that it condenses, dropping the pressure enough to create a wrong-way pressure differential across the bulkhead. Because the vehicle is constrained pretty strongly at the top and bottom, the outer walls might have been prevented from buckling, but the bulkhead could have buckled or flipped. Localized mixing would've created a shock sensitive enough mixture that the dynamics of the event could have provided its own initiation energy.

This would require flipping bulkhead to lift against several meters worth of hydraulic pressure of LOX in LOX tank. Does not look likely to me. Also, if explosive mixture formed in the tanks (not outside of the tanks), the kaboom would be much more energetic, sending payload flying upwards.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/05/2016 10:00 pm
Looking at the video, this really doesn't look to be an internal explosion.

     Maybe a burn off of the vented LOX, but not an internal blast.  However; we can't be certain of this until we can get some video from another angle.  An internal explosion would have lifted the payload clear of the tower as the upper stage unzipped and peeled away to the sides.

      I base this on other pad explosions I've seen in previous videos, as well as aircraft explosions of a similar nature.

      This looks like an uncontained explosion, that occurred from the tower or its near vicinity, that expanded into the side of the stage, rupturing it sideways, and then inhibiting the fuel and LOX.  As an uncontained explosion, both the initial and the rupture ignition, there wouldn't have been enough upwards force to shift the payload upwards to any sufficient distance.

      It should also be noted that such an internal explosion, would have forced the upper stage engine downwards to the first state's LOX tank, further adding fuel to the explosion, magnifying the over all explosive force helping to throw the payload at least several meters up and away from the tower.

Just remember that the fuel and ox tanks can/will rupture at relatively low pressures. Once a tank wall blows out (at that relatively low pressure) which looks to me like what happened, there isn't any pressure left to push the payload up or the engine down.

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/05/2016 10:02 pm

It is not only possible but almost 60% likely to have been a very similar problem with the same components.
58.72%, to be precise

78.26% of statistics are made up on the spot. And 68.23% of those statistics are then defended vigorously when questioned...

~Jon


I agree with you 114.28%
About 50% of the time everyone on this site turns out to be wrong (me included)

 ;D

We will ultimately have to just wait and see. I don't expect to hear much until midweek or next week at the earliest. Still not able to rule out external fire, fts failure (my favorite secondary theory to be honest), or internal ignition by a source not related to COPV or other pressure systems.

What upsets me about all of this I guess, is the fact that it happened at all. Whatever this was it should have been caught before hand. Murphy's law is a SOB though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 10:06 pm

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Where Frame 0 is pre-event (USLaunchReport video)
Where Frame 1 is post-event,

I agree with you on Frame 2 forward.  However, not prior to Frame 2.

Frame 1 shows a "fast fire" moving at between 2,000 and 5,000 feet per second.  In the world I live in, 2,000 to 5,000 feet per second is called a detonation.

After Frame 2, it slows to 100-200 feet per second, and that's a deflagration, at least in the world I live in.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 10:10 pm
This would require flipping bulkhead to lift against several meters worth of hydraulic pressure of LOX in LOX tank. Does not look likely to me. Also, if explosive mixture formed in the tanks (not outside of the tanks), the kaboom would be much more energetic, sending payload flying upwards.

It depends strongly on how much propellant mixed. If only a little mixed before it was set-off, you could still see behavior similar to what we saw. I just have a hard time seeing any realistic source of an external explosion that was strong enough to shred the vehicle like that. Also, I would've expected to see the vehicle more a whole lot more under an external explosion. Maybe my baysplodey vehicle intuition isn't very good, but I still don't think there's been a credible explanation for where an external explosion could've come from.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 10:14 pm

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Where Frame 0 is pre-event (USLaunchReport video)
Where Frame 1 is post-event,

I agree with you on Frame 2 forward.  However, not prior to Frame 2.

Frame 1 shows a "fast fire" moving at between 2,000 and 5,000 feet per second.  In the world I live in, 2,000 to 5,000 feet per second is called a detonation.

After Frame 2, it slows to 100-200 feet per second, and that's a deflagration, at least in the world I live in.

But what people fail to realize is that a localized internal detonation need not have enough impulse to lift the fairing up against the probably heftily overbuilt strongback. If we're talking about a small pocket of mixed LOX/RP-1 right near the outer wall where the bulkhead attaches, you could see most of the energy going out the side wall.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 10:15 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/05/2016 10:23 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...
A tank losing pressure suddenly is VERY energetic. Obviously there was fire almost immediately since we don't see the tank burst until after we see fire. But I believe an over-pressurized LOX tank could easily provide enough energy to explain the small flying parts we see early on. There was an incident in McGregor a couple years ago with nitrogen tanks exploding and it was called an explosion. As far as we know there was no fire involved and thus no detonation.

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/05/2016 10:28 pm
Does anyone have an idea what data rate the 3000 channels of data were recording at?  I would assume some channels video and some GSE equipment would be low ( 30 to 100 Hz). 
Just trying to understand what kind of resolution Space X will see during the 30-35 miliseconds.  Got to believe SpaceX has all the digital data reviewed by now and have a good idea as to the source of the problem if not the reason.

I would think SpaceX already has the data that illuminates what happened.  However, you're right, there is proximate cause and then there is root cause.

The data likely has shown them what the proximate cause was -- what was happening that made the rocket go boom.  As to what began the chain of events that led to the proximate cause, that's the item that will take longer to define. And that's what they need to get down to before they can even define their next steps in making the system safe to fly again.

The one thing I will say is this --it is not the exact same causation path that happened on CRS-7.  This was a sudden, abrupt failure, while CRS-7's overpressurization event occurred over a period of up to 10 seconds.  If this was an overpressurization event, it occurred far, far more rapidly.  So, people who are sitting back and dispensing their disgust about how SpaceX failed to fix the same problem that took down CRS-7 should just stop, since it's impossible that this could be the same problem.

It could possibly be a different problem in the same system, but it's not the same problem, has a different proximate cause, and almost certainly has a different root cause.

It is not only possible but almost 60% likely to have been a very similar problem with the same components. Failure mode differs because helium gas lines failed first in crs7 resulting in a "slower" overpressure as compared to a supersonic shockwave generated by a burst COPV bottle.

That's a lot more confident than I think we can be at this point. I think a COPV failure is one of the more likely failure sources, but far from the only credible cause of failure. I know this is hard for aerospace engineers, but humility is in order, especially with how little data we're working with here.

~Jon

I know it's even harder for non-aerospace engineers speculating outside their areas of expertise. ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/05/2016 10:29 pm

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Where Frame 0 is pre-event (USLaunchReport video)
Where Frame 1 is post-event,

I agree with you on Frame 2 forward.  However, not prior to Frame 2.

Frame 1 shows a "fast fire" moving at between 2,000 and 5,000 feet per second.  In the world I live in, 2,000 to 5,000 feet per second is called a detonation.

After Frame 2, it slows to 100-200 feet per second, and that's a deflagration, at least in the world I live in.

But what people fail to realize is that a localized internal detonation need not have enough impulse to lift the fairing up against the probably heftily overbuilt strongback. If we're talking about a small pocket of mixed LOX/RP-1 right near the outer wall where the bulkhead attaches, you could see most of the energy going out the side wall.

~Jon


Jon, would you care to speculate on how such a pocket would occur?  Based on what we have seen so far, the pocket would be asymmetrical facing the camera (an exemplary example of Murphy in action if you ask me).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 10:30 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...
A tank losing pressure suddenly is VERY energetic. Obviously there was fire almost immediately since we don't see the tank burst until after we see fire. But I believe an over-pressurized LOX tank could easily provide enough energy to explain the small flying parts we see early on. There was an incident in McGregor a couple years ago with nitrogen tanks exploding and it was called an explosion. As far as we know there was no fire involved and thus no detonation.

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.
I'm speaking of parts being reported around outside the launch complex...

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/05/2016 10:31 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...

His "fast fire" was in reference to Dragon abort. It doesn't seem the initial detonation was big enough to have any effect on Dragon, just at it had no apparent effect on the payload, and the following "fast fire" which eventually resulted in the destruction of the payload, was slow enough for Dragon to abort away.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 10:34 pm

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Where Frame 0 is pre-event (USLaunchReport video)
Where Frame 1 is post-event,

I agree with you on Frame 2 forward.  However, not prior to Frame 2.

Frame 1 shows a "fast fire" moving at between 2,000 and 5,000 feet per second.  In the world I live in, 2,000 to 5,000 feet per second is called a detonation.

After Frame 2, it slows to 100-200 feet per second, and that's a deflagration, at least in the world I live in.

But what people fail to realize is that a localized internal detonation need not have enough impulse to lift the fairing up against the probably heftily overbuilt strongback. If we're talking about a small pocket of mixed LOX/RP-1 right near the outer wall where the bulkhead attaches, you could see most of the energy going out the side wall.

~Jon

I was responding to a different comment than yours, but to address yours.

I have a hydrodynamics text book I haven't looked at in many decades, but if I recall, you need to know the compressability of the fluid (LOX, densified, not stirred), the weight of that fluid above the original shock front, and the speed of that shock front, and the energy in that impulse.  Someone much younger than me could do the math.

But it kinda goes like this, if the detonation is in the tank, and at the top of the tank, a lot of the shock front would dissipate upwards into the payload and might jiggle it a bit or a lot.

BUT, if the detonation is in the tank, but further down the the tank, hydrodynamics will tell you how much of that shock front gets to the top of the tank and how much of the LOX is also moved which contributes to an upward jiggle, and the net effects will jiggle the payload less than if the detonation is at the top of the tank, depending of course on the mass of the displaced LOX that also impacts the payload.  Depending on the origin point, and the # of joules released, you could calculate whether the payload would move not at all, a little, or shoot off like a banshee.

I absolutely agree that an in-tank detonation doesn't require the payload to move an inch, but absent about 30 variables, the only data we have is when the smoke cleared, it was still there and toppling.  The video data clearly supports the assertion that if it moved in response to the event, it didn't move much.

As to where the detonation occurred.... well, go to Reddit for the easy answers.   Got any thoughts on my exploding air-conditioning system question.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 10:36 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...

His "fast fire" was in reference to Dragon abort. It doesn't seem the initial detonation was big enough to have any effect on Dragon, just at it had no apparent effect on the payload, and the following "fast fire" which eventually resulted in the destruction of the payload, was slow enough for Dragon to abort away.
Please don't take this as a snark, but the term "fast-fire" is meaningless in the world of physics that I teach...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 10:37 pm

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.

Here's my definition of detonation.

The event expansion rate moves faster than the local speed of sound.

Here's my definition of deflagration.

The event expansion rate moves slower than the local speed of sound.

Per my definition, Frame one is detonation.

Per my definition, after Frame one is deflagration.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/05/2016 10:38 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...
A tank losing pressure suddenly is VERY energetic. Obviously there was fire almost immediately since we don't see the tank burst until after we see fire. But I believe an over-pressurized LOX tank could easily provide enough energy to explain the small flying parts we see early on. There was an incident in McGregor a couple years ago with nitrogen tanks exploding and it was called an explosion. As far as we know there was no fire involved and thus no detonation.

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.
I'm speaking of parts being reported around outside the launch complex...
As am I. They were small, shoebox size pieces. It doesn't take much force if it is directed as in the case of a pressure explosion. The initial breach obviously covered a pretty small area since we see the initial explosion radiating in just one direction. It is the same principle behind canons and pressure cooker bombs. A little force allowed to build up and released all at once can have a lot of umph.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RonM on 09/05/2016 10:41 pm
If there was an initial detonation (supersonic speed) then shouldn't we have seen a shock wave, especially in the humid coastal air.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/05/2016 10:42 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...

His "fast fire" was in reference to Dragon abort. It doesn't seem the initial detonation was big enough to have any effect on Dragon, just at it had no apparent effect on the payload, and the following "fast fire" which eventually resulted in the destruction of the payload, was slow enough for Dragon to abort away.
Please don't take this as a snark, but the term "fast-fire" is meaningless in the world of physics that I teach...
His words, not mine. And almost certainly can be wholly replaced with the word "deflagration" without changing the intent or meaning of the tweet at all.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/05/2016 10:46 pm
Now for something completely different.

I was skimming parts of this book:   https://books.google.com/books?id=H9XKBQAAQBAJ

Its focus is on reducing the risk of industrial accidents.  There are several discussions about how to design HVAC and AC systems so they don't inadvertently detonate.  One minor tidbit just to spark an AC debate, don't mix water and aluminum shavings in a closed space.  You'll build up hydrogen gas... 

The book has lots of other examples of what not to do...

Does anyone know much about how the tower AC system was configured?

DoE paper on the aluminum dissociation water of water, releasing H2, and noting that NaCl promotes the reaction.

https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/aluminum_water_hydrogen.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 10:48 pm

Would they still get data from the fairing and the payload while it hung on the strongback?

What data would the fairing have?  Anyways, payload data goes through the second stage and its umbilical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/05/2016 10:48 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...
A tank losing pressure suddenly is VERY energetic. Obviously there was fire almost immediately since we don't see the tank burst until after we see fire. But I believe an over-pressurized LOX tank could easily provide enough energy to explain the small flying parts we see early on. There was an incident in McGregor a couple years ago with nitrogen tanks exploding and it was called an explosion. As far as we know there was no fire involved and thus no detonation.

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.
I'm speaking of parts being reported around outside the launch complex...
Can you confirm that these aren't very low ballistic coefficient items (foils, wraps, insulation, etc) that floated away on that huge thermal plume? I'd strongly suspect that anything found at 39A was this type of debris. Nothing in the video suggests that there was heavy or large debris flying more than a few hundred feet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 10:49 pm
If there was an initial detonation (supersonic speed) then shouldn't we have seen a shock wave, especially in the humid coastal air.

That is an EXCELLENT question.  Visible shock waves depend a lot on the moisture in the air.  As  the shock wave passes through, you can often see the shock wave propagation through moisture forming clouds along the shock front.  It sometimes is visible, and sometimes not.  With high speed photography of explosions you can often see diffraction occurring along the shock front as the refractive index of air changes under compression.  In this case, it's not high speed photography.  Nothing is obvious there either.

I looked for that in the video and saw no sign of a shock wave of that nature.

However, I did take a brief look at the venting oxygen clouds on S1, and you can see that they move down as if in response to a shock wave.  That's suggestive, but not definitive.

I'll take a more detailed look tomorrow and advise if there's further evidence of a shock front.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 10:49 pm
I still beg to disagree with Elon... It was an over-pressure event of an initial detonation followed by deflagration. I'm sure those on this site that saw it and heard it live would agree. The distance that parts flew would confirm the energy required...

His "fast fire" was in reference to Dragon abort. It doesn't seem the initial detonation was big enough to have any effect on Dragon, just at it had no apparent effect on the payload, and the following "fast fire" which eventually resulted in the destruction of the payload, was slow enough for Dragon to abort away.
Please don't take this as a snark, but the term "fast-fire" is meaningless in the world of physics that I teach...
His words, not mine. And almost certainly can be wholly replaced with the word "deflagration" without changing the intent or meaning of the tweet at all.
Yes, I know it was "his words", hence the "no snark" comment towards you! ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 10:50 pm
.

Does anyone know much about how the tower AC system was configured?

The system is located in a building west of the pad.  And it would not be the source of any combustibles.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 10:54 pm
If there was an initial detonation (supersonic speed) then shouldn't we have seen a shock wave, especially in the humid coastal air.
If you have multiple near simultaneous events Ron you will get wave interference and will be hard to discern without high speed cameras...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/05/2016 10:55 pm

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Where Frame 0 is pre-event (USLaunchReport video)
Where Frame 1 is post-event,

I agree with you on Frame 2 forward.  However, not prior to Frame 2.

Frame 1 shows a "fast fire" moving at between 2,000 and 5,000 feet per second.  In the world I live in, 2,000 to 5,000 feet per second is called a detonation.

After Frame 2, it slows to 100-200 feet per second, and that's a deflagration, at least in the world I live in.

But what people fail to realize is that a localized internal detonation need not have enough impulse to lift the fairing up against the probably heftily overbuilt strongback. If we're talking about a small pocket of mixed LOX/RP-1 right near the outer wall where the bulkhead attaches, you could see most of the energy going out the side wall.

~Jon


Jon, would you care to speculate on how such a pocket would occur?  Based on what we have seen so far, the pocket would be asymmetrical facing the camera (an exemplary example of Murphy in action if you ask me).

Some sort of localized structural failure of the common bulkhead, driven by one of the mechanisms under discussion (CB inversion driven by ullage collapse or some other mechanism, COPV failure, pressurization system failure, etc). A CB failure doesn't mean you get instantaneous mixing of all the LOX and RP-1, especially if the failure is fairly small.

Handwaving here, I just think the "if it was an internal explosion, it would have to be a big one that would pop the payload off" crowd is overstating their case.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/05/2016 10:55 pm
.

Does anyone know much about how the tower AC system was configured?

The system is located in a building west of the pad.  And it would not be the source of any combustibles.

Jim, you're some kind of wonderful.  :)  You're the only person I've ever known who can blow up one of my ideas in 21 words or less.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/05/2016 10:57 pm
.

Does anyone know much about how the tower AC system was configured?

The system is located in a building west of the pad.  And it would not be the source of any combustibles.

Jim, you're some kind of wonderful.  :)  You're the only person I've ever known who can blow up one of my ideas in 21 words or less.  :)

Two things.
It is a single pass system and it would be all GN2 at that time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/05/2016 11:05 pm

Despite appearances, this probably wasn't a "detonation." It was a "fast fire" as Elon said, and there is a world of difference. An internal pressure event followed by tank rupture and "fast fire" of LOX/RP-1 combustion appears consistent with what we saw.

Where Frame 0 is pre-event (USLaunchReport video)
Where Frame 1 is post-event,

I agree with you on Frame 2 forward.  However, not prior to Frame 2.

Frame 1 shows a "fast fire" moving at between 2,000 and 5,000 feet per second.  In the world I live in, 2,000 to 5,000 feet per second is called a detonation.

After Frame 2, it slows to 100-200 feet per second, and that's a deflagration, at least in the world I live in.

But what people fail to realize is that a localized internal detonation need not have enough impulse to lift the fairing up against the probably heftily overbuilt strongback. If we're talking about a small pocket of mixed LOX/RP-1 right near the outer wall where the bulkhead attaches, you could see most of the energy going out the side wall.

~Jon


Jon, would you care to speculate on how such a pocket would occur?  Based on what we have seen so far, the pocket would be asymmetrical facing the camera (an exemplary example of Murphy in action if you ask me).

Some sort of localized structural failure of the common bulkhead, driven by one of the mechanisms under discussion (CB inversion driven by ullage collapse or some other mechanism, COPV failure, pressurization system failure, etc). A CB failure doesn't mean you get instantaneous mixing of all the LOX and RP-1, especially if the failure is fairly small.

Handwaving here, I just think the "if it was an internal explosion, it would have to be a big one that would pop the payload off" crowd is overstating their case.

~Jon


Thanks Jon.  Do you think the plume from such an event would be visible for long?  Jiust wondering if there might be something visible in frame[0] since the USLaunchReport video seem to be facing where the plume would be originating from.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/05/2016 11:05 pm
If there was an initial detonation (supersonic speed) then shouldn't we have seen a shock wave, especially in the humid coastal air.

That image has nothing to do with humidity. Humidity has to do with Prandtl-Glauert singularities, that is condensation of air during the low pressure phase after shockwave passage. What your image shows is the high pressure leading edge of the shockwave refracting light since the pressure and density is increased sufficiently to alter the index of refraction of air. That phenomenon is affectionately called "the crack" if I'm not mistaken.

A shockwave has to be really powerful to display that kind of refraction and you obviously also need some kind of background to notice the light refraction. It's also very difficult to observe in normal speed video. Back in the days of atmospheric nuclear testing, smoke rockets were used to provide that reference background. Uniform grey sky like on Amos 6 doesn't cut it and it's questionable whether that "crack" would have even been seen in a video of the given resolution. Usually, powerful shockwaves are more trackable by the dust they raise as they sweep across.

I personally don't think this event produced a shockwave of that magnitude, such a thing would immediately tear apart the fairing and anything in the vicinity and would be much more obvious.

FWIW, the loudest bang that was heard was not the initial S2 explosion/detonation/"fast flame"/Pressure Release (TM) but rather the fuel-air mix detonation when the fireball with the released liquids falling down reached the ground and caused the propellants to mix well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/05/2016 11:09 pm
However, I did take a brief look at the venting oxygen clouds on S1, and you can see that they move down as if in response to a shock wave.  That's suggestive, but not definitive.

I suppose the key point there is that the stage was still venting O2 right up until the time of the "event" which kinda rules out a jammed LOX vent as being the cause of any tank overpressure.

To me this "event" has all the hallmarks of a tank internal rupture, cause as yet unknown, loss-of-containment, and subsequent ignition and has at least some commonality with the CRS accident (eg. both were associated with Stage 2) and for that reason I agree with Jon.  Presumably the SPX guys are poring over the data from this one *and* the CRS one to see if there is anything they've missed..  Let's hope they find something soon.


 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AS-503 on 09/05/2016 11:13 pm
I'm still looking at at brittle fracture of material of either the FSW at the common bulkhead or at the bottom COPV mount at the tank side wall. It could be cryro cycling or material dislocation. A failure in that area would cause RP-1/LOX mixing and the possible kinetic energy for ignition. It would an event that happens very fast...

Hmm, the bottom of that COPV mount you have circled in red does appear to be around the approximate centroid of the flash seen in the video.

I have no pet theory here, as amusing as it is to watch people with random backgrounds try to correct Jim and nitpick to support their own.  That said, I do wonder - personally - if the root cause of this might come down a handling mishap with S2 somewhere along the way days, weeks or even months ago, such as a jarred or dropped tank in the factory (say a jolt of 2" - 3" in placing on the cradle for transport or assembly jig, or the over-the-road transport truck having a minor collision along the route such as bumping a concrete post at a truck stop, running over a curb making a turn, etc)? Alternately, perhaps a bit of manufacturing re-work might have been required during assembly at one of the COPV mounts which was performed in a defective manner (something like that brought down an entire 747 full of people in Japan once) ... In other words, a seemingly minor event somewhere along the that seemed of no consequence but which eventually resulted in a major mishap.

Thanks for the quality post Herb.
Apollo 13 accident was ultimately caused by just such a "benign" handling incident quite some time before flight (over a year).

See page 8 of attached pdf.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Soleil_Deimos on 09/05/2016 11:17 pm
It may be interesting to note that at T-8:00 the MVAC hydraulics are pressurized and prepared for bleed. You can hear the call out on at least the last three technical streams. This is the only call out in regards to the second stage around this time, and according to the official statement the anomaly was about eight minutes before the engines would have fired. Since the MVAC uses RP-1 as hydraulic fluid, could this have been a leak somewhere in the hydraulic system?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 11:24 pm
Just to restate what I said over the last few days: after a localized material failure a "small vapor RP-1/LOX detonation" as "I" observed on the outside of the vehicle would be forced outward, essentially behaving as a "shaped charge" by it's energy wave being reflected off the prop in it's still liquid state and the tank structures themselves... After initiation, deflagration occurs... It's just a possible theory folks, not a fact in this case...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 11:35 pm
It may be interesting to note that at T-8:00 the MVAC hydraulics are pressurized and prepared for bleed. You can hear the call out on at least the last three technical streams. This is the only call out in regards to the second stage around this time, and according to the official statement the anomaly was about eight minutes before the engines would have fired. Since the MVAC uses RP-1 as hydraulic fluid, could this have been a leak somewhere in the hydraulic system?
Welcome to the forum! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/05/2016 11:39 pm

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.

Here's my definition of detonation.

The event expansion rate moves faster than the local speed of sound.

Here's my definition of deflagration.

The event expansion rate moves slower than the local speed of sound.

Per my definition, Frame one is detonation.

Per my definition, after Frame one is deflagration.

A simple overpressure inside the tank, with no combustion, that causes the tank to rupture will produce a supersonic shock wave. No detonation required for that. A bursting balloon will be a "detonation" by your definition.

So a "fast fire" combustion event that is initially contained inside the tank, which then ruptures, will produce a supersonic expansion of flaming combustion products, ie what we see in the first few frames.

Again, this is entirely consistent with a "fast fire" combustion inside the tank, which ruptures the tank and causes supersonic expansion of the hot gases. The "fast fire" then continues outside the tank as more LOX/RP-1 combust.

No detonation needed to explain what we saw, and I doubt we saw one. Overpressure and/or "fast fire" deflagration that begins inside the tank and ruptures it would produce what we saw and is easier to initiate than a detonation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/05/2016 11:54 pm

Detonation implies force applied by burning materials. In this case the force and the burning materials could be separate. Hopefully Elon knows more than us about the vehicle and the anomaly, so there is probably an explanation.

Here's my definition of detonation.

The event expansion rate moves faster than the local speed of sound.

Here's my definition of deflagration.

The event expansion rate moves slower than the local speed of sound.

Per my definition, Frame one is detonation.

Per my definition, after Frame one is deflagration.

A simple overpressure inside the tank, with no combustion, that causes the tank to rupture will produce a supersonic shock wave. No detonation required for that. A bursting balloon will be a "detonation" by your definition.

So a "fast fire" combustion event that is initially contained inside the tank, which then ruptures, will produce a supersonic expansion of flaming combustion products, ie what we see in the first few frames.

Again, this is entirely consistent with a "fast fire" combustion inside the tank, which ruptures the tank and causes supersonic expansion of the hot gases. The "fast fire" then continues outside the tank as more LOX/RP-1 combust.

No detonation needed to explain what we saw, and I doubt we saw one. Overpressure and/or "fast fire" that begins inside the tank and ruptures it would produce what we saw and is easier to initiate than a detonation.
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing, become vapor and then ignite? I'm trying to understand what you are saying...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/05/2016 11:59 pm
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation," just like there is no "detonation" going inside a normally operating M1D. That is a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 12:02 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/06/2016 12:08 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

I don't know what happened inside. Maybe a bulkhead leak/burst under a too-high pressure differential. Then internal "deflagration" followed by stage rupture. Or a COPV burst provided enough energy to intiate combustion of LOX with the overwrap material.

All I'm saying is that an internal "deflagration" could have caused what we saw in the video. It was not necessarily a "detonation" as was asserted upthread.

As a propulsion engineer I worked with solid propellants that could "deflagrate" (burn fast) and/or "detonate," and there is a technical difference, with a continuum between them, depending on how fast the deflagration proceeds. This is true also of the liquid-phase reactants involved here.

Seeing/hearing an event like this, observers may assume the event was the result of a "detonation," but not necessarily so.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 12:21 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

I don't know what happened inside. Maybe a bulkhead leak/burst under a too-high pressure differential. Then internal "deflagration" followed by stage rupture. Or a COPV burst provided enough energy to intiate combustion of LOX with the overwrap material.

All I'm saying is that an internal "deflagration" could have caused what we saw in the video. It was not necessarily a "detonation" as was asserted upthread.

As a propulsion engineer I worked with solid propellants that could "deflagrate" (burn fast) and/or "detonate," and there is a technical difference, with a continuum between them, depending on how fast the deflagration proceeds. This is true also of the liquid-phase reactants involved here.

In "explosions" like this, people may assume that high-speed combustion/explosion events must be the result of "detonation," and my example of the hydogen/oxygen balloon bursting shows that this is not necessarily true.
The problem with "words" that they generate imagery that can be unique for each individual and why in physics we stick to numbers...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/06/2016 12:26 am
Quote
The problem with "words" that they generate imagery specific for each individual and why in physics we stick to numbers...

And engineers working with energetic materials like propellants also have very specific definitions for words like "deflagration," "detonation," etc. Unfortunately, not all armchair rocket scientists have a firm grasp on those definitions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 12:41 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

The tanks are not at flight pressure during prop loading, which is when the klabooma happened.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 12:44 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

I don't know what happened inside. Maybe a bulkhead leak/burst under a too-high pressure differential. Then internal "deflagration" followed by stage rupture. Or a COPV burst provided enough energy to intiate combustion of LOX with the overwrap material.

All I'm saying is that an internal "deflagration" could have caused what we saw in the video. It was not necessarily a "detonation" as was asserted upthread.

As a propulsion engineer I worked with solid propellants that could "deflagrate" (burn fast) and/or "detonate," and there is a technical difference, with a continuum between them, depending on how fast the deflagration proceeds. This is true also of the liquid-phase reactants involved here.

Seeing/hearing an event like this, observers may assume the event was the result of a "detonation," and my earlier example of the hydogen/oxygen balloon bursting shows that this is not necessarily true.

My problem with internal deflagration is that the first visible signs would not be that flash followed by a decrease in magnitude - it would be an ever-increasing thing, as more propellant and oxidizer got in contact.

Somehow, within one frame (say 30 mSec if it happened right after the previous frame), we went from nothing to a bright structure about, what, 6 m tall?   Not quite supersonic in the "worst" case, but at least very close to it, and supersonic if it only took half a frame's time.

Then for a few frames it brightens up, diminishes, and then a secondary cloud of fluid appears, and everything catches fire and melts down.

So without speculating on what preceded the first external sign of trouble, my interpretation of what I see is a limited external explosion causing a shockwave, structural failure (maybe aided by a weakening caused by the root failure), and then the pressurized contents disperse and we have the big fire.

Faster video may tell a different tale of course.  Lots could have happened within those 30 mSec.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/06/2016 12:45 am
Someone tear down this theory:

A tiny leak in the RP1 tank at the common bulkhead (damaged rivet or something) aerosols RP1 on the upwind side of the rocket. Wind is continously blowing the aerosol away, limiting the FAE-ready cloud, and there was no ignition source.

Then at 8 minutes, the hydrolic sysems power up. Somehow, this introcuces an ignition source (static spark?) outside the tank, where there is not normally anything that matters.

Aerosol'd RP1 FAE-detonates, breaching the airframe at the common bulhead. RP1 and Lox ignite, and pour down the stage. First stage umbilicals are burned through, setting off thefirst stage as well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 12:47 am
Quote
The problem with "words" that they generate imagery specific for each individual and why in physics we stick to numbers...

And engineers working with energetic materials like propellants also have very specific definitions for words like "deflagration," "detonation," etc. Unfortunately, not all armchair rocket scientists have a firm grasp on those definitions.

Detonation and deflagarion are well defined. The biggest offender is "explosion", which is used to mean different things in different contexts, and you can't transfer.

A steam boiler can "explode". But the same level of event in the context of explosive would probably not count as an explosion.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 12:48 am
Quote
The problem with "words" that they generate imagery specific for each individual and why in physics we stick to numbers...

And engineers working with energetic materials like propellants also have very specific definitions for words like "deflagration," "detonation," etc. Unfortunately, not all armchair rocket scientists have a firm grasp on those definitions.
I'll take that one step further for each engineering discipline. For example; a combustion engineer in the automotive field, detonation would mean a specific event that what happening within the combustion chamber without a timed ignition spark...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/06/2016 12:55 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

I don't know what happened inside. Maybe a bulkhead leak/burst under a too-high pressure differential. Then internal "deflagration" followed by stage rupture. Or a COPV burst provided enough energy to intiate combustion of LOX with the overwrap material.

All I'm saying is that an internal "deflagration" could have caused what we saw in the video. It was not necessarily a "detonation" as was asserted upthread.

As a propulsion engineer I worked with solid propellants that could "deflagrate" (burn fast) and/or "detonate," and there is a technical difference, with a continuum between them, depending on how fast the deflagration proceeds. This is true also of the liquid-phase reactants involved here.

Seeing/hearing an event like this, observers may assume the event was the result of a "detonation," and my earlier example of the hydogen/oxygen balloon bursting shows that this is not necessarily true.

My problem with internal deflagration is that the first visible signs would not be that flash followed by a decrease in magnitude..l

Yes, an internal deflagration with a limited amount of fuel (say, COPV overwrap or some RP-1 from a bulkhead leak) combusting with LOX could produce exactly this phenomenon. The tank bursts suddenly with a bright flash and supersonic expansion, then the fireball grows more slowly and dims as the initial combustion products are consumed.

Quote
Then for a few frames it brightens up, diminishes, and then a secondary cloud of fluid appears, and everything catches fire and melts down.

Don't know why it brightens up again, maybe more fuel is becoming vaporized/atomized and available for combustion. But again, this isn't necessarily detonation. It's about how much fuel and oxidizer is in contact at any time in the event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 01:06 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

The tanks are not at flight pressure during prop loading, which is when the klabooma happened.
Do we have an exact point in the sequence yet? I haven't heard/read anything yet unless I missed it...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/06/2016 01:09 am
My problem with internal deflagration is that the first visible signs would not be that flash followed by a decrease in magnitude - it would be an ever-increasing thing, as more propellant and oxidizer got in contact.

Somehow, within one frame (say 30 mSec if it happened right after the previous frame), we went from nothing to a bright structure about, what, 6 m tall?   Not quite supersonic in the "worst" case, but at least very close to it, and supersonic if it only took half a frame's time.

Then for a few frames it brightens up, diminishes, and then a secondary cloud of fluid appears, and everything catches fire and melts down.

So without speculating on what preceded the first external sign of trouble, my interpretation of what I see is a limited external explosion causing a shockwave, structural failure (maybe aided by a weakening caused by the root failure), and then the pressurized contents disperse and we have the big fire.

Faster video may tell a different tale of course.  Lots could have happened within those 30 mSec.


That's what I see too.  No matter how I do the math, that first flash was outside the vehicle, and supersonic.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 01:19 am




Yes, an internal deflagration with a limited amount of fuel (say, COPV overwrap or some RP-1 from a bulkhead leak) combusting with LOX would produce exactly this phenomenon. The tank bursts suddenly with a bright flash and supersonic expansion, then the fireball grows more slowly and dims as the initial combustion products are consumed.

Quote
Then for a few frames it brightens up, diminishes, and then a secondary cloud of fluid appears, and everything catches fire and melts down.

Don't know why it brightens up again, maybe more fuel is becoming vaporized/atomized and available for combustion. But again, this isn't necessarily detonation. It's about how much fuel and oxidizer is in contact at any time in the event.

If there is already combustion going on, then as the outer tank fails due to the rising pressure, (all within 30 ms) the liquid inside would be forced out and burn without the first fire going out.

And, IMO, there would be very little structure standing, and lots of debris.

But if the internal event was cold, and still resulted in a limited release of combustibles, and they ignited outside...  then we're talking.

(Acknowledging that this kind of hand waved prediction is of low confidence... It's just playing with what little we've got to go on)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 01:20 am
Flight press starts at T-0:00:50 and tanks don't reach flight press until T-0:00:20

Correct timeline (http://spaceflight101.com/falcon-9-ft-countdown-timeline/):
Falcon 9 FT – Countdown Timeline
All Times Approximate.
Time   Event
L-15:00:00   Falcon 9 to Vertical
L-10:00:00   Countdown Initiation, Launch Vehicle Power-Up
L-6:00:00   First Weather Balloon Release
L-5:00:00   Launch Area Evacuation
L-4:45:00   Range Controllers on Station
L-4:35:00   Falcon 9 Attitude Control System N2 Loading
L-5:00:00   Launch Area Evacuation
L-2:45:00   Falcon 9 RF & Telemetry Checks
L-2:30:00   Falcon 9 Launch Vehicle Release System Test
L-2:25:00   TEA-TEB Bleed In
L-1:45:00   Comm & FTS Checks
L-1:40:00   Data Flow Tests with Downrange Tracking Stations
L-1:00:00   Weather Briefing
L-0:50:00   RF Link Checks
L-0:45:00   Pre-Load Hold Point, Propellant Polls
L-0:45:00   Blast Danger Area Clear, Roadblocks Established
L-0:45:00   Flight Control System Setup (Flight Software Loading)
L-0:45:00   Final Tank Chill-In
L-0:40:00   Ready for Prop Load
L-0:38:00   Launch Readiness Poll
L-0:36:00   Tanks vented for Prop Loading
T-0:35:00   Automated Countdown Sequence, Master Script Running
T-0:34:45   Launch Enable to Flight Mode
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
T-0:32:30   Confirm nominal Fuel Flow Rates
T-0:32:00   Latest Prop Flow Start
T-0:29:30   Stage 1 Helium Load
T-0:27:00   Spacecraft to Internal Power
T-0:25:30   Fuel Collector Pre-Valves Closed
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
T-0:13:00   Countdown Recycle Point
T-0:12:45   Merlin 1D & MVac BTV Activation
T-0:10:15   Grid Fin Pneumatics Secured
T-0:10:05   Boostback Hazards Disabled
T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
T-0:06:45   Stage 2 Helium Transition to Pipeline
T-0:06:35   MVac Hydraulics at Bleed Pressure
T-0:06:05   M1D Engines to TVC-Null Position
T-0:05:20   Flight Computers in Self-Alignment
T-0:05:20   Stage 1 Fuel Loading Complete
T-0:05:15   Launch Vehicle Heater Deactivation
T-0:05:00   Falcon 9 to Internal Power
T-0:05:00   Range Control Comm Check
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:50   Pressurization for Strongback Retract
T-0:04:40   Stage 2 TVC Bleed
T-0:04:30   Stage 2 RP-1 Bleed
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:20   Verify Good Self-Alignment
T-0:04:10   Strongback Cradles Opening
T-0:04:00   Vehicle Release Auto Sequence
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch
T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
T-0:02:35   Strongback Retraction Complete
T-0:02:05   Stage 2 LOX at Flight Level
T-0:02:00   Falcon 9 Transfer to Internal Power Complete
T-0:01:35   Flight Control to Self Alignment
T-0:01:30   Launch Director: Go for Launch
T-0:01:30   Final Engine Chilldown
T-0:01:25   Helium Loading Termination
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:30   HOLD Call for Abort
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:07   Pad Deck Water Deluge System Activation
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/06/2016 01:26 am




Yes, an internal deflagration with a limited amount of fuel (say, COPV overwrap or some RP-1 from a bulkhead leak) combusting with LOX would produce exactly this phenomenon. The tank bursts suddenly with a bright flash and supersonic expansion, then the fireball grows more slowly and dims as the initial combustion products are consumed.

Quote
Then for a few frames it brightens up, diminishes, and then a secondary cloud of fluid appears, and everything catches fire and melts down.

Don't know why it brightens up again, maybe more fuel is becoming vaporized/atomized and available for combustion. But again, this isn't necessarily detonation. It's about how much fuel and oxidizer is in contact at any time in the event.

If there is already combustion going on, then as the outer tank fails due to the rising pressure, (all within 30 ms) the liquid inside would be forced out and burn without the first fire going out.

And, IMO, there would be very little structure standing, and lots of debris.

But if the internal event was cold, and still resulted in a limited release of combustibles, and they ignited outside...  then we're talking.

(Acknowledging that this kind of hand waved prediction is of low confidence... It's just playing with what little we've got to go on)

Yup, many ways to slice and dice. I was only cautioning against what seems to me a premature assumption/conclusion (by others) that a "detonation" must have occurred.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 01:30 am
Flight press starts at T-0:00:50 and tanks don't reach flight press until T-0:00:20

Correct timeline (http://spaceflight101.com/falcon-9-ft-countdown-timeline/):
Falcon 9 FT – Countdown Timeline
All Times Approximate.
Time   Event
L-15:00:00   Falcon 9 to Vertical
L-10:00:00   Countdown Initiation, Launch Vehicle Power-Up
L-6:00:00   First Weather Balloon Release
L-5:00:00   Launch Area Evacuation
L-4:45:00   Range Controllers on Station
L-4:35:00   Falcon 9 Attitude Control System N2 Loading
L-5:00:00   Launch Area Evacuation
L-2:45:00   Falcon 9 RF & Telemetry Checks
L-2:30:00   Falcon 9 Launch Vehicle Release System Test
L-2:25:00   TEA-TEB Bleed In
L-1:45:00   Comm & FTS Checks
L-1:40:00   Data Flow Tests with Downrange Tracking Stations
L-1:00:00   Weather Briefing
L-0:50:00   RF Link Checks
L-0:45:00   Pre-Load Hold Point, Propellant Polls
L-0:45:00   Blast Danger Area Clear, Roadblocks Established
L-0:45:00   Flight Control System Setup (Flight Software Loading)
L-0:45:00   Final Tank Chill-In
L-0:40:00   Ready for Prop Load
L-0:38:00   Launch Readiness Poll
L-0:36:00   Tanks vented for Prop Loading
T-0:35:00   Automated Countdown Sequence, Master Script Running
T-0:34:45   Launch Enable to Flight Mode
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
T-0:32:30   Confirm nominal Fuel Flow Rates
T-0:32:00   Latest Prop Flow Start
T-0:29:30   Stage 1 Helium Load
T-0:27:00   Spacecraft to Internal Power
T-0:25:30   Fuel Collector Pre-Valves Closed
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
T-0:13:00   Countdown Recycle Point
T-0:12:45   Merlin 1D & MVac BTV Activation
T-0:10:15   Grid Fin Pneumatics Secured
T-0:10:05   Boostback Hazards Disabled
T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
T-0:06:45   Stage 2 Helium Transition to Pipeline
T-0:06:35   MVac Hydraulics at Bleed Pressure
T-0:06:05   M1D Engines to TVC-Null Position
T-0:05:20   Flight Computers in Self-Alignment
T-0:05:20   Stage 1 Fuel Loading Complete
T-0:05:15   Launch Vehicle Heater Deactivation
T-0:05:00   Falcon 9 to Internal Power
T-0:05:00   Range Control Comm Check
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:50   Pressurization for Strongback Retract
T-0:04:40   Stage 2 TVC Bleed
T-0:04:30   Stage 2 RP-1 Bleed
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:20   Verify Good Self-Alignment
T-0:04:10   Strongback Cradles Opening
T-0:04:00   Vehicle Release Auto Sequence
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch
T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
T-0:02:35   Strongback Retraction Complete
T-0:02:05   Stage 2 LOX at Flight Level
T-0:02:00   Falcon 9 Transfer to Internal Power Complete
T-0:01:35   Flight Control to Self Alignment
T-0:01:30   Launch Director: Go for Launch
T-0:01:30   Final Engine Chilldown
T-0:01:25   Helium Loading Termination
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:30   HOLD Call for Abort
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:07   Pad Deck Water Deluge System Activation
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF
My question is still "where" were we on the sequence when the event happened?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 01:34 am
According to SpaceX, the
Quote
anomaly took place about eight minutes in advance of a scheduled test firing of a Falcon 9 rocket.

Anyone know what fill level, temps, and pressures the 2nd stage COPVs would be at around 8 minutes? S2 helium load starts at 13:15 and finishes at 1:25, they might be less than 1/2 full at 8 minutes.

Is the helium loaded to S2 as liquid? The timeline lists "Liquid Helium Pumps"

Correct timeline (http://spaceflight101.com/falcon-9-ft-countdown-timeline/):
Falcon 9 FT – Countdown Timeline
...
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
...
T-0:29:30   Stage 1 Helium Load
...
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
...
T-0:10:00   Stage 2 Venting for LOX Fast Fill
...
T-0:09:15   Stage 1 Helium Topping
...
T-0:06:45   Stage 2 Helium Transition to Pipeline
...
T-0:02:40   Stage 1 LOX at Flight Level
...
T-0:02:05   Stage 2 LOX at Flight Level
...
T-0:01:25   Helium Loading Termination
...
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
...
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
...
[/quote]
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/06/2016 01:37 am
Flight press starts at T-0:00:50 and tanks don't reach flight press until T-0:00:20

Correct timeline (http://spaceflight101.com/falcon-9-ft-countdown-timeline/):
Falcon 9 FT – Countdown Timeline
All Times Approximate.
Time   Event
L-15:00:00   Falcon 9 to Vertical
L-10:00:00   Countdown Initiation, Launch Vehicle Power-Up
L-6:00:00   First Weather Balloon Release
L-5:00:00   Launch Area Evacuation
L-4:45:00   Range Controllers on Station
L-4:35:00   Falcon 9 Attitude Control System N2 Loading
L-5:00:00   Launch Area Evacuation
L-2:45:00   Falcon 9 RF & Telemetry Checks
L-2:30:00   Falcon 9 Launch Vehicle Release System Test
L-2:25:00   TEA-TEB Bleed In
L-1:45:00   Comm & FTS Checks
L-1:40:00   Data Flow Tests with Downrange Tracking Stations
L-1:00:00   Weather Briefing
L-0:50:00   RF Link Checks
L-0:45:00   Pre-Load Hold Point, Propellant Polls
L-0:45:00   Blast Danger Area Clear, Roadblocks Established
L-0:45:00   Flight Control System Setup (Flight Software Loading)
L-0:45:00   Final Tank Chill-In
L-0:40:00   Ready for Prop Load
L-0:38:00   Launch Readiness Poll
L-0:36:00   Tanks vented for Prop Loading
T-0:35:00   Automated Countdown Sequence, Master Script Running
T-0:34:45   Launch Enable to Flight Mode
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
T-0:32:30   Confirm nominal Fuel Flow Rates
T-0:32:00   Latest Prop Flow Start
T-0:29:30   Stage 1 Helium Load
T-0:27:00   Spacecraft to Internal Power
T-0:25:30   Fuel Collector Pre-Valves Closed
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
T-0:13:00   Countdown Recycle Point
T-0:12:45   Merlin 1D & MVac BTV Activation
T-0:10:15   Grid Fin Pneumatics Secured
T-0:10:05   Boostback Hazards Disabled
T-0:10:00   Stage 2 Venting for LOX Fast Fill
T-0:09:50   Flight Software Final Setups complete
T-0:09:45   TEA-TEB Ignition System Setup
T-0:09:45   Stage 2 Transmitter Re-Activation
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
T-0:06:45   Stage 2 Helium Transition to Pipeline
T-0:06:35   MVac Hydraulics at Bleed Pressure
T-0:06:05   M1D Engines to TVC-Null Position
T-0:05:20   Flight Computers in Self-Alignment
T-0:05:20   Stage 1 Fuel Loading Complete
T-0:05:15   Launch Vehicle Heater Deactivation
T-0:05:00   Falcon 9 to Internal Power
T-0:05:00   Range Control Comm Check
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:50   Pressurization for Strongback Retract
T-0:04:40   Stage 2 TVC Bleed
T-0:04:30   Stage 2 RP-1 Bleed
T-0:04:30   Stage 2 Thrust Vector Control Test
T-0:04:20   Verify Good Self-Alignment
T-0:04:10   Strongback Cradles Opening
T-0:04:00   Vehicle Release Auto Sequence
T-0:03:40   TEA-TEB Ignition System Auto Sequence
T-0:03:30   Strongback Retraction
T-0:03:25   Flight Termination System to Internal Power
T-0:03:15   FTS on Internal
T-0:03:05   Flight Termination System Armed, FTS Ready for Launch
T-0:02:55   Verify Good Mvac TVC
T-0:02:45   Fuel Trim Valve to Flight Position
T-0:02:40   Stage 1 LOX at Flight Level
T-0:02:40   FTS Countdown Sequence
T-0:02:35   Strongback Retraction Complete
T-0:02:05   Stage 2 LOX at Flight Level
T-0:02:00   Falcon 9 Transfer to Internal Power Complete
T-0:01:35   Flight Control to Self Alignment
T-0:01:30   Launch Director: Go for Launch
T-0:01:30   Final Engine Chilldown
T-0:01:25   Helium Loading Termination
T-0:01:20   Engine Purge
T-0:01:00   Flight Computer to start-up
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
T-0:00:50   First Stage Thrust Vector Actuator Test
T-0:00:30   HOLD Call for Abort
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
T-0:00:10   Latest VC Abort
T-0:00:07   Pad Deck Water Deluge System Activation
T-0:00:03   Merlin Engine Ignition
T-0:00:00   LIFTOFF
My question is still "where" were we on the sequence when the event happened?
The SpaceX statement said around T-8 minutes, so somewhere between Stage 1 Helium Topping and MVac Fuel Trim Valve Setup. I don't think that tells us anything useful since those things seem innocuous and there is a pretty big gap between those events. It does tell us that both LOX tanks were loading at the time and the RP-1 tank in the second stage was full.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 01:40 am
If S2 LOX loads linearly from 19:30 to 2:05 the LOX tank would be 65% full at 8:00. There are listed flow adjustments so that's probably not exact, but a reasonably good place to start. 35% is a lot of ullage space compared to a full tank at 3 to 5%
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John-H on 09/06/2016 01:44 am
What is the tank pressure while loading?  Doesn't it have to have some pressure to prevent the loaded tank from collapsing?

John
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 01:45 am
Ok, thanks to you both as earlier in this thread CBS reported 5 minutes or there about...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/06/2016 01:48 am
What is the tank pressure while loading?  Doesn't it have to have some pressure to prevent the loaded tank from collapsing?

John

No, the vehicle is structurally stable without pressure
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 01:52 am
What is the tank pressure while loading?  Doesn't it have to have some pressure to prevent the loaded tank from collapsing?

John

No, the vehicle is structurally stable without pressure
Jim, don't they do a nitrogen purge?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 01:53 am
What is the tank pressure while loading?  Doesn't it have to have some pressure to prevent the loaded tank from collapsing?

John

No, the vehicle is structurally stable without pressure

Do they use tank pressure to slow LOX boiloff? Or is filling the tanks as fast as possible more optimal?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 09/06/2016 02:46 am
It may be possible they need to have both tanks equal in pressure ( or one greater than the other) to keep the common bulkhead from inverting and asploding the rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/06/2016 03:08 am
What if there was a leak in the LN2 subcooling system, and LN2 was mixed into the lox? Would the LN2 cavitate in the pumps and piping? What about in the tank? Would the LN2 turn to gas in the tank? What would that do to the pressure levels in the tank? Dunno how such a scenario would fit into the incident if that's what happened, but what would that look like?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/06/2016 03:17 am
It's perhaps interesting to note that you're not going to get an ignition within either prop tank itself since it seems they mitigate against that by purging - so, looking at things outside the tanks:
 
The SpaceX statement said around T-8 minutes, so somewhere between Stage 1 Helium Topping and MVac Fuel Trim Valve Setup. I don't think that tells us anything useful since those things seem innocuous and there is a pretty big gap between those events. It does tell us that both LOX tanks were loading at the time and the RP-1 tank in the second stage was full.

What's the "MVac Fuel Trim Valve Setup" all about?  That's in Stage 2.. could a failure with it be the source of ignition??
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 09/06/2016 04:08 am
Borrowing Hartspace's Orbcomm photo again, just to the left and above his or her blue circle, and right where the flash occurred, is a huge electrical junction box on the TE. I've also attached an electrical diagram from page 39 of the Falcon User's Guide (http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf) (word description on page 38). I don't know how the precision of rocket grade electrical fault interruption compares to residential, but limits to the protection do exist.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/06/2016 04:16 am
There is no electrical fault interruption in that box
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 09/06/2016 04:17 am
There is no electrical fault interruption in that box

Then that can't be good  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: scanline on 09/06/2016 05:02 am
Hi folks.  I've needed the whole three day weekend to catch up, and great to find you all, btw!
I didn't see anything about what might be behind the rocket.  Could this be propellent falling behind it?
Image 1:  Green arrow shows dark material where it used to be brighter sky.  (easier to see in the video)
Image 2:  The plume falls on the far corner of the building.  This puts it behind the rocket, opposite the apparent location of the initial flash.
Image 3:  A few frames after 2.  Looks like a lot has fallen there.
Image 4:  My really rough sketch of where the plume might be.  The camera is about due South as close as I could line things up.  If there is stuff behind, it doesn't seem to go as far to the right, so I've made that line almost North-South and a bit to where the green arrow would put it.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/06/2016 05:32 am
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/06/2016 05:34 am
There is no electrical fault interruption in that box

Then that can't be good  :)

No need for it.  Most of the connects are data.  The power lines are controlled by the payload EGSE in the lower left of the diagram
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/06/2016 06:03 am
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.

Speaking from experience not to do with rockets; pure oxygen with a flammable  contaminant (ex: hydrocarbons) is a bad day looking for a time & place to happen, especially where pipes change direction which can cause local heating.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 06:19 am
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.

Speaking from experience not to do with rockets; pure oxygen with a flammable  contaminant (ex: hydrocarbons) is a bad day looking for a time & place to happen, especially where pipes change direction which can cause local heating.

If you had enough contaminants in LOX to initiate this event, the whole tank should have be gone in an instant. This is not what happened.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 07:14 am
Quote
Were the tanks not at flight pressure with helium? How could that support combustion without liquid prop mixing and then ignite? I'm trying to understand what you are saying...

What I'm saying is that LOX and RP-1 combusting is not necessarily a "detonation." It can be a "deflagration," or fast fire. There is a difference. People seem to be throwing around the word "detonation" without fully understanding what it actually means.
Oh, I agree with terminology use but you have me curious for the mechanism for a "fast-fire" in a single tank under flight pressure helium...

I don't know what happened inside. Maybe a bulkhead leak/burst under a too-high pressure differential. Then internal "deflagration" followed by stage rupture. Or a COPV burst provided enough energy to intiate combustion of LOX with the overwrap material.

All I'm saying is that an internal "deflagration" could have caused what we saw in the video. It was not necessarily a "detonation" as was asserted upthread.

As a propulsion engineer I worked with solid propellants that could "deflagrate" (burn fast) and/or "detonate," and there is a technical difference, with a continuum between them, depending on how fast the deflagration proceeds. This is true also of the liquid-phase reactants involved here.

Seeing/hearing an event like this, observers may assume the event was the result of a "detonation," and my earlier example of the hydogen/oxygen balloon bursting shows that this is not necessarily true.

My problem with internal deflagration is that the first visible signs would not be that flash followed by a decrease in magnitude - it would be an ever-increasing thing, as more propellant and oxidizer got in contact.

Somehow, within one frame (say 30 mSec if it happened right after the previous frame), we went from nothing to a bright structure about, what, 6 m tall?   Not quite supersonic in the "worst" case, but at least very close to it, and supersonic if it only took half a frame's time.

Then for a few frames it brightens up, diminishes, and then a secondary cloud of fluid appears, and everything catches fire and melts down.

So without speculating on what preceded the first external sign of trouble, my interpretation of what I see is a limited external explosion causing a shockwave, structural failure (maybe aided by a weakening caused by the root failure), and then the pressurized contents disperse and we have the big fire.

Faster video may tell a different tale of course.  Lots could have happened within those 30 mSec.

Considering that those same He COPV-s sometimes survive re-entry (see https://forum.nasaspaceflight.com/index.php?topic=36440.0), it is difficult to see how they will fail in mid-pressurization situation, when the He bottle is not actually full.

However IF they fail, then this results in enough carbon fiber, epoxy and aluminium dust and particles in order to turn the LOX into an explosive slurry. Following supersonic compression wave (due to high He pressure) will set this slurry off to a detonation. Not deflagration.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/06/2016 08:06 am
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.

Speaking from experience not to do with rockets; pure oxygen with a flammable  contaminant (ex: hydrocarbons) is a bad day looking for a time & place to happen, especially where pipes change direction which can cause local heating.

If you had enough contaminants in LOX to initiate this event, the whole tank should have be gone in an instant. This is not what happened.

Presumably contaminants don't just affect combustion. Could some materials be sensitive like the overwrapping of pressure vessels. Brainstorming further, how dry in terms of water ice particles does lox have to be - is it even possible to have ice contamination.
Apologies if this is annoying people, it's just that in the absence of new information about the event it is natural to think about external variables and the extent that they are understood. The vehicle is most likely the issue, or some transport handling
, from what informed people here have said.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 08:56 am
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.

Speaking from experience not to do with rockets; pure oxygen with a flammable  contaminant (ex: hydrocarbons) is a bad day looking for a time & place to happen, especially where pipes change direction which can cause local heating.

If you had enough contaminants in LOX to initiate this event, the whole tank should have be gone in an instant. This is not what happened.

Presumably contaminants don't just affect combustion. Could some materials be sensitive like the overwrapping of pressure vessels. Brainstorming further, how dry in terms of water ice particles does lox have to be - is it even possible to have ice contamination.
Apologies if this is annoying people, it's just that in the absence of new information about the event it is natural to think about external variables and the extent that they are understood. The vehicle is most likely the issue, or some transport handling
, from what informed people here have said.

By quick googling I found a few reports on LOX contamination:
1. STUDY OF LIQUID OXYGEN CONTAMINATION from 1961: http://www.dtic.mil/dtic/tr/fulltext/u2/272377.pdf
2. Ignition of Aluminum by Impact in LOX — Influence of Contaminants https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP12492S.htm

The first one is rather old and I did not notice any particularly agressive contaminants in the text. Yes, there may be combustibles (most importantly acetylene and methane), but I think that in purities used today this should not be an issue.

The second one I have no access to, but the name is interesting in this context. So, if anyone can access it, this would be interesting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/06/2016 09:10 am
COPV.

Lots of talk above and elsewhere that these are a prime consideration in the issue. Many people saying they have been problematical from the start.

AFAIK, there have been no issues with COPV's (ISTR something early on about SpaceX bringing manufacture of them in house, but that's it). The CRS-7 was a strut holding a COPV, not the COPV itself.

So why are so many people blaming the COPV with no evidence to support that blame?

Or have I missed a whole load of COPV issues that would indicate they are a likely cause  - someone said 60% likely above given previous issues- where does this number come from? I cannot see anything to support that claim. Just seems like made up number to me.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/06/2016 09:30 am
So why are so many people blaming the COPV with no evidence to support that blame?

People are looking for something that could trigger the pad anomaly.
With cold engines, there is a dearth of viable candidates.

Or have I missed a whole load of COPV issues that would indicate they are a likely cause  - someone said 60% likely above given previous issues- where does this number come from?

I think you missed the accurate probability: 58.72%.
The number is just made up.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/06/2016 09:46 am
Upthread, there's a discussion as to whether or not the initial fireball was supersonic. I looked at the vid frame by frame, and saw no sign of any shockwave. It then belatedly occurred to me that there might be an easy way to solve this, one way or another.

The speed of sound at 80F and 80% humidity at sea level works out to 1141.7 feet per second. The video is 60 frames per second. Therefor, the speed of sound should be 19 feet per frame.

The diameter of the F9 is 12 feet. Using that as a rough yardstick, a supersonic expansion would have to be more than one F9 diameter per frame.  It isn't.

As for the initial (first frame) appearance of the flash itself, I have a hard time accepting that, if it's an eruption from the LOX tank, that it's on the far right-hand edge against the TEL. If it was, how would it light up so much of the round rocket body? My guess is it's, from the camera's perspective, about halfway between the centerline and the righthand edge.

In the first frame, the light reflections seem to me to fit my guess for an origin point. For example, there's a grid fin on the lefthand edge that gets lit up in a way that implied direct lighting from the initial event. (I don't think it would, were the event on the opposite side of the F9). 

I've attached a grab of part of the first frame for reference. All credit to US launchreports.



 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 10:27 am
...

The diameter of the F9 is 12 feet. Using that as a rough yardstick, a supersonic expansion would have to be more than one F9 diameter per frame.  It isn't.

...

Fireball diameter is actually TWICE the diameter of the F9 there.

One odd thing, that puzzles me, is the leftmost shape of the initial fireball. I have in mind those 3 "tongues". This implies, that at least this part of the explosion front should probably be subsonic and parts of it's propagation should have been obstructed in some ways.

I should point out, that close to sonic wave propagation is complex and there may be transitions in both ways - from detonation to deflagration and the other way.
When there was FAE, then it may have started out as deflagration, then progressed temporarily as detonation in low supersonic and then outgassed (after it run out of oxygen in FAE mixture) as subsonic cloud.
When there was COPV, then I do not see how this could have started as subsonic event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/06/2016 10:35 am

Fireball diameter is actually TWICE the diameter of the F9 there.

One odd thing, that puzzles me, is the leftmost shape of the initial fireball. I have in mind those 3 "tongues". This implies, that at least this part of the explosion front should probably be subsonic and parts of it's propagation should have been obstructed in some ways.


No.

The middle "tongue" is the shape of the condensation cloud coming out of the LOX vent, reflecting (actually scattering) the light of the initial explosion. The shape above it is the same thing, it is the underside of the payload shroud lit up by the light of the initial explosion. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 10:43 am

Fireball diameter is actually TWICE the diameter of the F9 there.

One odd thing, that puzzles me, is the leftmost shape of the initial fireball. I have in mind those 3 "tongues". This implies, that at least this part of the explosion front should probably be subsonic and parts of it's propagation should have been obstructed in some ways.


No.

The middle "tongue" is the shape of the condensation cloud coming out of the LOX vent, reflecting (actually scattering) the light of the initial explosion. The shape above it is the same thing, it is the underside of the payload shroud lit up by the light of the initial explosion.

Well, Your're right. In addition, the blast runs radially, not diameter-wise from one edge to another. This requires the initial fireball to be twice the size for it to be supersonic. Meaning that it should have been:
1. About 37ft in diameter
2. Almost perfectly circular
3. Have clear edge

Which it is not.

However this all assumes that the event started in the next millisecond after last frame. Possible, but not probable.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 10:56 am
I'm looking at the longest dimension, the height.  It all appeared within those 30 ms.

It represents, to me, where fuel was present when detonation occurred.

That's why the irregular shape, and that is why it doesn't really grow, and then it diminishes, as the available fuel is consumed.

EDIT:

I agree it's "borderline supersonic" as stated above - depending on when within the 30 mSec it happened.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/06/2016 11:29 am

Fireball diameter is actually TWICE the diameter of the F9 there.

One odd thing, that puzzles me, is the leftmost shape of the initial fireball. I have in mind those 3 "tongues". This implies, that at least this part of the explosion front should probably be subsonic and parts of it's propagation should have been obstructed in some ways.


No.

The middle "tongue" is the shape of the condensation cloud coming out of the LOX vent, reflecting (actually scattering) the light of the initial explosion. The shape above it is the same thing, it is the underside of the payload shroud lit up by the light of the initial explosion.

Well, Your're right. In addition, the blast runs radially, not diameter-wise from one edge to another. This requires the initial fireball to be twice the size for it to be supersonic. Meaning that it should have been:
1. About 37ft in diameter
2. Almost perfectly circular
3. Have clear edge

Which it is not.

However this all assumes that the event started in the next millisecond after last frame. Possible, but not probable.
For what it's worth:

I had a co-worker at one of my former jobs have a look at this. This guy used to characterize explosive properties of industrial gases. After some measuring, separating reflection from actual fireball, performing calculations, and assuming the time between the two frames is indeed 30 milliseconds, he made the following remarks:

1. This only looks like an explosion IF it started in the last 3-to-6 milliseconds before the second frame, and then only if the explosion is in a gas.
2. If the explosive was solid in nature then it probably started within the timeframe of exposure of the frame itself (solid explosives have much higher explosive velocities than gases).
3. The shape of the visible fireball is hard to interpret given all the reflection involved. Reflective elements from the TEL, payload shroud, second stage structure and the vapour cloud surrounding the vehicle, do a good job obscuring the actual shape of the fireball, combined with the poor image quality.
4. That said, and compensating for said reflective elements, the shape of the fireball does not support the notion of an explosive detonation taking place; too irregular.
5. Given best-case expansion velocities, assuming gases as the combustion medium, this can best be classed as a near-explosive conflagration, not as a true explosive detonation. He literally said: "With regards to the expansion velocity of the fireball, the initial blast looks very much like what was witnessed when Challenger was destroyed. And that wasn't an explosion either."

Disclaimer:
OK, that was just a quick look by a guy familiar with explosive properties. But it is important to remember that above remarks are based on a single piece of poor quality footage only, and without having access to any other sources related to this incident. So please, don't pull any conclusions based on above remarks and observations. That would be silly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/06/2016 12:45 pm
[about COPV failure] However IF they fail, then this results in enough carbon fiber, epoxy and aluminium dust and particles in order to turn the LOX into an explosive slurry. Following supersonic compression wave (due to high He pressure) will set this slurry off to a detonation. Not deflagration.
Though a bursting COPV would be fast, it's not clear it could be supersonic in LOX.  The speed of sound in helium is about 970 m/s at room temperature (http://www.engineeringtoolbox.com/speed-sound-gases-d_1160.html).  Hence it will be about 500 m/s at cryogenic temperature.  This is as fast as the bubble from the busted COPV could expand.  The speed of sound in LOX is about 1000 m/s,  according to the NASA report "Sound Speed Measurements in Liquid Oxygen-Liquid Nitrogen Mixtures" (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19850026994.pdf). So not supersonic.

Also, at this point in the countdown, a burst COPV(or even all of them) won't rupture the tank from static overpressure alone (though they might from mechanical damage or shock).  The COPVs combined only contain enough gas to pressurize the tank once the helium is heated.  So without heating they can only fill something like 1/6 of the tank (depending on what temperature the Merlin heats them to).  Since the tank is not 5/6 full (they are loading it at this point in the countdown), even the release of all the helium should not overpressurize the tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 12:52 pm
[about COPV failure] However IF they fail, then this results in enough carbon fiber, epoxy and aluminium dust and particles in order to turn the LOX into an explosive slurry. Following supersonic compression wave (due to high He pressure) will set this slurry off to a detonation. Not deflagration.
Though a bursting COPV would be fast, it's not clear it could be supersonic in LOX.  The speed of sound in helium is about 970 m/s at room temperature (http://www.engineeringtoolbox.com/speed-sound-gases-d_1160.html).  Hence it will be about 500 m/s at cryogenic temperature.  This is as fast as the bubble from the busted COPV could expand.  The speed of sound in LOX is about 1000 m/s,  according to the NASA report "Sound Speed Measurements in Liquid Oxygen-Liquid Nitrogen Mixtures" (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19850026994.pdf). So not supersonic.

Also, at this point in the countdown, a burst COPV(or even all of them) won't rupture the tank from static overpressure alone (though they might from mechanical damage or shock).  The COPVs combined only contain enough gas to pressurize the tank once the helium is heated.  So without heating they can only fill something like 1/6 of the tank (depending on what temperature the Merlin heats them to).  Since the tank is not 5/6 full (they are loading it at this point in the countdown), even the release of all the helium should not overpressurize the tank.

What happens when this 500 m/s sonic compression wave hits the tank wall near the COPV together with the debris. I guess, there should be reflection first and then at the intersections interesting things may happen, which I wouldn't prognose as I'm not that familiar with hydro- and thermodynamics in case of compression wave reflection.

Another question is that you were referring to speed of sound in He at normal density (i.e. normal pressure). There, again, the gas was supercritical. I didn't find SoS measurements for supercritical He, but I found this: http://tinyurl.com/jl22vxx

Here the supercriticals conduct sound between 2-4 times faster than the same gas in normal density.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/06/2016 01:38 pm
@Woods170,

So, your contact's gut feeling is a tank rupture followed by the ignition of the escaping liquids on such a short time-frame that it seems instantaneous to the human eye and most types of camera? That brings us back to the possibility of a flaw in the tanks or plumbing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 01:38 pm
I was thinking of things in the sequence over a morning "cup of Joe"...

From SpaceX press release:
http://www.spacex.com/news/2016/09/01/anomaly-updates

"- Yesterday, at SpaceX's Launch Complex 40 at Cape Canaveral Air Force Station, an anomaly took place about eight minutes in advance of a scheduled test firing of a Falcon 9 rocket.

- The anomaly on the pad resulted in the loss of the vehicle."

One could read that "an anomaly took place about eight minutes" so it was noted and did they continue with the sequence or abort (back out)? I'm trying to reconcile what happened between eight minutes and the originally reported five minutes. I was following it as the event occurred and when Jim posted what happened, I just sat there blinking at the screen. I thought I read all the posts but might have missed something... Anyone?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 01:43 pm
...
Also, at this point in the countdown, a burst COPV(or even all of them) won't rupture the tank from static overpressure alone (though they might from mechanical damage or shock).  The COPVs combined only contain enough gas to pressurize the tank once the helium is heated.  So without heating they can only fill something like 1/6 of the tank (depending on what temperature the Merlin heats them to).  Since the tank is not 5/6 full (they are loading it at this point in the countdown), even the release of all the helium should not overpressurize the tank.

The tank is also venting LOX boiloff during prop load, so the vessel would not be bursting into a closed system. And helium load doesn't finish until about 6 minutes after this stage blew, so the COPVs were not fully filled.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/06/2016 01:53 pm
@Woods170,

So, your contact's gut feeling is a tank rupture followed by the ignition of the escaping liquids on such a short time-frame that it seems instantaneous to the human eye and most types of camera? That brings us back to the possibility of a flaw in the tanks or plumbing.
You either did not read or did not comprehend the disclaimer in my post.

Also, the guy did not pull any conclusions with regards to the failure mode. I only asked him to have a look at the fireball event from the footage. That's what he did, and nothing else.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/06/2016 02:15 pm
An interesting but probably pointless exercise.

I decided to see if anything could be learned about the flash timing between frames.  We all know the AGC of the camera will change that, but without knowing the camera model and settings at recording time, the AGC can be assumed to be reacting, but with unknown consequences.

Anyway, for your ponder pleasure, the histograms are attached.  I focused on what I think is the grid fin on the left of the F9 as the target for the histogram analysis.

This is in order of Frame 0 - everything's fine, to Frame 8.  FYI,  Frame 7 is when the maximum lens flair is visible.

Enjoy.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 02:18 pm
@Woods170,

So, your contact's gut feeling is a tank rupture followed by the ignition of the escaping liquids on such a short time-frame that it seems instantaneous to the human eye and most types of camera? That brings us back to the possibility of a flaw in the tanks or plumbing.
You either did not read or did not comprehend the disclaimer in my post.

Also, the guy did not pull any conclusions with regards to the failure mode. I only asked him to have a look at the fireball event from the footage. That's what he did, and nothing else.

The only conclusion, that can be made from this post, that you refer to (and some adjacent ones), is that it is highly unlikely, that this blast was a detonation. And also, that it's incredibly difficult to determine something from this low quality image (and distant sound). That's all.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: S.Paulissen on 09/06/2016 02:27 pm

The only conclusion, that can be made from this post (and some adjacent ones), that you refer to, is that it is highly unlikely, that this blast was a detonation. And also, that it's incredibly difficult to determine something from this low quality image (and distant sound). That's all.

Grammar is important.  I took it to men the opposite of what you intended.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/06/2016 02:36 pm
I was thinking of things in the sequence over a morning "cup of Joe"...

From SpaceX press release:
http://www.spacex.com/news/2016/09/01/anomaly-updates

"- Yesterday, at SpaceX's Launch Complex 40 at Cape Canaveral Air Force Station, an anomaly took place about eight minutes in advance of a scheduled test firing of a Falcon 9 rocket.

- The anomaly on the pad resulted in the loss of the vehicle."

One could read that "an anomaly took place about eight minutes" so it was noted and did they continue with the sequence or abort (back out)? I'm trying to reconcile what happened between eight minutes and the originally reported five minutes. I was following it as the event occurred and when Jim posted what happened, I just sat there blinking at the screen. I thought I read all the posts but might have missed something... Anyone?
There were early rumors of the event happening at T-3 and T-5.  I would not put a lot of stock in those rumors, they were anonomous and of the "I heard" variety.  It's certainly possible that they saw something in the data and were actively "aborting" the static fire but there is no evidence for it other than some speculation on this thread.  The same update from SpaceX says, " At the time of the loss, the launch vehicle was vertical and in the process of being fueled for the test."  So I don't think they were actively aborting.

This does not rule out a data anomaly and the loss being separated in time, but I don't think they were "aborting"  and I don't think we have any evidence that the events were separated in time.  *shrug*

Edit: Better words?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 02:47 pm
I was thinking of things in the sequence over a morning "cup of Joe"...

From SpaceX press release:
http://www.spacex.com/news/2016/09/01/anomaly-updates

"- Yesterday, at SpaceX's Launch Complex 40 at Cape Canaveral Air Force Station, an anomaly took place about eight minutes in advance of a scheduled test firing of a Falcon 9 rocket.

- The anomaly on the pad resulted in the loss of the vehicle."

One could read that "an anomaly took place about eight minutes" so it was noted and did they continue with the sequence or abort (back out)? I'm trying to reconcile what happened between eight minutes and the originally reported five minutes. I was following it as the event occurred and when Jim posted what happened, I just sat there blinking at the screen. I thought I read all the posts but might have missed something... Anyone?
There were early rumors of the event happening at T-3 and T-5.  I would not put a lot of stock in those rumors, they were anonomous and of the "I heard" variety.  It's certainly possible that they saw something in the data and were actively "aborting" the static fire but there is no evidence for it other than some speculation on this thread.  The same update from SpaceX says, " At the time of the loss, the launch vehicle was vertical and in the process of being fueled for the test."  So if they were already aware and aborting, they are being explicitly duplicitous.

This does not rule out a data anomaly and the loss being separated in time, but I don't think they were "aborting"  and I don't think we have any evidence that the events were separated in time.  *shrug*
Thanks for your feedback. So the way I could read it is that they just saw "a funny" and either aborted or not and continued to work it is possible... Or the funny had nothing to do with it and another failure took place or something in the back out occurred... Anyone else please feel free to chime in...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/06/2016 03:00 pm
Deleted some crap posts. Grammar back and forth isn't really a good idea on a fast moving thread. Please make sure your post adds materially to the discussion before posting. Thanks.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: testguy on 09/06/2016 04:27 pm
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.

Speaking from experience not to do with rockets; pure oxygen with a flammable  contaminant (ex: hydrocarbons) is a bad day looking for a time & place to happen, especially where pipes change direction which can cause local heating.

If you had enough contaminants in LOX to initiate this event, the whole tank should have be gone in an instant. This is not what happened.

Presumably contaminants don't just affect combustion. Could some materials be sensitive like the overwrapping of pressure vessels. Brainstorming further, how dry in terms of water ice particles does lox have to be - is it even possible to have ice contamination.
Apologies if this is annoying people, it's just that in the absence of new information about the event it is natural to think about external variables and the extent that they are understood. The vehicle is most likely the issue, or some transport handling
, from what informed people here have said.

By quick googling I found a few reports on LOX contamination:
1. STUDY OF LIQUID OXYGEN CONTAMINATION from 1961: http://www.dtic.mil/dtic/tr/fulltext/u2/272377.pdf
2. Ignition of Aluminum by Impact in LOX — Influence of Contaminants https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP12492S.htm

The first one is rather old and I did not notice any particularly agressive contaminants in the text. Yes, there may be combustibles (most importantly acetylene and methane), but I think that in purities used today this should not be an issue.

The second one I have no access to, but the name is interesting in this context. So, if anyone can access it, this would be interesting.

Here is a personal experience with oxygen contamination is a gaseous system.  I had a 2" isolation ball valve explode after being in service for many years.  The valve was last cycled 5 minutes prior to the incident and no oxygen flow was occurring (no delta P across the valve).  The failure was traced to comtaminated gaseous oxygen delivery from the supplier.  This was determined only after filters were installed on the fill lines and upon inspection revealed organics.  The suppliers investigation found their techs were failing to cap the the fill line from their factory to the delivery trucks.  Bugs were making a home in the line.  Just goes to show it can happen!
Needless to say there was extensive damage and required significant rework.  The fill filters are required to be inspected after EVERY delivery now.  A lesson learned.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 04:36 pm
I remember reading this years ago that the tank contamination concerns during Project Apollo was right down to the oils from a fingerprint...
http://history.nasa.gov/SP-4206/ch7.htm
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/06/2016 04:52 pm
Is spacex/nasa likely to have spectrum analysis? I good spectrum would indicate what metals were present in the initial flash. Do their cameras record colors in enough detail for this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/06/2016 04:56 pm
Is spacex/nasa likely to have spectrum analysis? I good spectrum would indicate what metals were present in the initial flash. Do their cameras record colors in enough detail for this?
Almost certainly not.  Digital or analog cameras are going to just record red/green/blue channels, not enough information for spectral analysis.  Even a film camera would just be recording those colors that the film emulsion responds to.  To get any decent spectrographic information they would have to had a camera capable of breaking down the specific spectrum of the light set up and pointed at the rocket before the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/06/2016 05:10 pm
So, here are a couple of things I've been wondering about, that I don't recall being discussed upthread.

First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

Well, the initial flash is so sudden that, if it was created by gasses escaping from the stage and flaring into combustion as soon as they escaped, you would think this would cause a propulsive effect on the stack at that point, right?  Equal to, or greater than, the force applied by an external explosion pushing against the stage, I would think.

And yet, the stack doesn't seem to move in response.  And whatever happened, physics would tend to require that the stack would respond to what seems obviously to be an explosive force happening on just one side of the vehicle.

So, we have one observation (notably from a very long lens non-professional camera, of less than perfect resolution and looking through a fair amount of heat haze) which seems to rule out both an internal and an external explosion.  Huh.

Logic would lead me to think that the problem is in the observation, not in the stack refusing to move in response to a sideways force.  The stack obviously moved and responded, just not in such a way that is easy to quantify from the one video we have.

The only real information that can constrain the amount of "push" on the vehicle will, I think, come from the Falcon's accelerometers, which I would hope were powered up and reporting information at the time of the anomaly.  I think this kind of data is likely helping SpaceX a lot in localizing the exact location of the initial force that was applied to the stack, and that ought to constrain the size and shape of the explosion.  (I find I have to use the term "explosion" in this context; please forgive me.  I don't intend to open a debate between detonation and deflagration...)

And speaking of the explosion, how sure are we that the first frame that shows the flash also includes in its field of view the actual origin point of the flash?  From looking at the shadows on the stack and the TEL from the flash, can we be certain that it began on the side or, from the camera's perspective, the front of the vehicle?  Could it have started on the opposite side of the stage, just out of view?

In this last, just curious if one reason the first image of the fireball seems to be so well-developed is that there could possibly have been a flash developing hidden behind the stage that began a horizontal unzipping that was in process for slightly more than the 1/30th of a second between Frame 0 and Frame 1.  An event that maybe would not have resulted in any visible change between frame -1 and frame 0?

Since some people are saying that a tank wall failure could have resulted in a very momentary spray of liquids flashing to gas before it ignited, if such a spray began during or before frame 0, hidden from direct view of the camera, is it absolutely certain such a thing would be visible?

Just tossing these out as thoughts... :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MikeAtkinson on 09/06/2016 05:11 pm
I had a co-worker at one of my former jobs have a look at this. This guy used to characterize explosive properties of industrial gases. After some measuring, separating reflection from actual fireball, performing calculations, and assuming the time between the two frames is indeed 30 milliseconds, he made the following remarks:
...

Would your co-worker be able to say how big the "explosion" was, in TNT equivalent or whatever is appropriate?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 05:19 pm
An explosion that can damage the skin would not move a fueled tank, not in a way that's visible in 3-4 frames...

Judo - CHOP!

It's concussion, not propulsion.

Watch any Bruce Lee movie...  By the time the guy is flying backwards, his bones are already broken...

Especially if the tank was already damaged from an internal event that is invisible to the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/06/2016 05:20 pm
....
So the way I could read it is that they just saw "a funny" and either aborted or not and continued to work it is possible... Or the funny had nothing to do with it and another failure took place or something in the back out occurred... Anyone else please feel free to chime in...
...

What 'funny'?, what 'abort'? Where do you get this from? Yes spacex said there was an anomaly, the anomaly was the 'explosion/fire/whatever you want to call it', we have not seen any info to suggest that anything else unexpected happened earlier in the timeline. (and Spacex also said that they are looking at 35-55ms of telemetry.)

/end of chime ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: S.Paulissen on 09/06/2016 05:22 pm
An explosion that can damage the skin would not move a fueled tank, not in a way that's visible in 3-4 frames...

Judo - CHOP!

It's concussion, not propulsion.

Watch any Bruce Lee movie...  By the time the guy is flying backwards, his bones are already broken...

Especially if the tank was already damaged from an internal event that is invisible to the camera.

My uninformed and entirely unsupported GUESS... is that a venting valve for the RP1 tank stuck shut, and the common bulkhead inverted leading to... everything we saw.  Highly unlikely.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/06/2016 05:29 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\

On edit...
As to movement... The rocket weighed several 100's of TONS at the moment of 'Flash'...  ???
Movement?... I think not much... that can be seen or even recorded...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/06/2016 05:30 pm
An explosion that can damage the skin would not move a fueled tank, not in a way that's visible in 3-4 frames...

Judo - CHOP!

It's concussion, not propulsion.

Watch any Bruce Lee movie...  By the time the guy is flying backwards, his bones are already broken...

Especially if the tank was already damaged from an internal event that is invisible to the camera.

My uninformed and entirely unsupported GUESS... is that a venting valve for the RP1 tank stuck shut, and the common bulkhead inverted leading to... everything we saw.  Highly unlikely.

So you (and apparently many others) think it's possible that they're pumping RP-1 with so much force that a stuck valve would blow the common bulkhead before any equipment on the ground noticed increasing pressure or just stopped pumping due to too much pressure?

The common bulkhead must be made of tin foil?

Disclaimer: I know nothing about rockets other than what's posted on these forums.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/06/2016 05:31 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

Well, the initial flash is so sudden that, if it was created by gasses escaping from the stage and flaring into combustion as soon as they escaped, you would think this would cause a propulsive effect on the stack at that point, right?  Equal to, or greater than, the force applied by an external explosion pushing against the stage, I would think.

And yet, the stack doesn't seem to move in response.  And whatever happened, physics would tend to require that the stack would respond to what seems obviously to be an explosive force happening on just one side of the vehicle.
Counterpoint- The Strongback is still attached to the rocket, dampening any horizontal motion with a structure specifically designed to dampen a less catastrophic horizontal motion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 05:36 pm
RP-1 finishes loading at 22 minutes before ignition, and does not boiloff or require much (if any) venting. What would cause a sudden buildup in pressure in the RP-1 tank 14 minutes after loading is complete?

http://spaceflight101.com/falcon-9-ft-countdown-timeline
Falcon 9 FT – Countdown Timeline
...
T-0:34:30   RP-1 Flow to both Stages
T-0:33:30   Stage 1 Liquid Oxygen Loading
...
T-0:29:30   Stage 1 Helium Load
...
T-0:25:00   All three Liquid Helium Pumps active
T-0:22:00   Stage 2 Fuel Loading Complete
T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:17:20   Stage 1 LOX Flowrate Adjustment for Stage 2 Fast Fill
T-0:13:15   Stage 2 Helium Loading
T-0:13:00   Stage 2 LOX Flow Adjustment for Helium Cryo Load
...
T-0:10:00   Stage 2 Venting for LOX Fast Fill
...
T-0:09:15   Stage 1 Helium Topping
...
T-0:06:45   Stage 2 Helium Transition to Pipeline
...
T-0:02:40   Stage 1 LOX at Flight Level
...
T-0:02:05   Stage 2 LOX at Flight Level
...
T-0:01:25   Helium Loading Termination
...
T-0:00:50   Stage 1, Stage 2 Pressurization for Flight
...
T-0:00:20   All Tanks at Flight Pressure
T-0:00:15   Arm Pyrotechnics
...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 05:38 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/06/2016 05:39 pm

Fireball diameter is actually TWICE the diameter of the F9 there.

One odd thing, that puzzles me, is the leftmost shape of the initial fireball. I have in mind those 3 "tongues". This implies, that at least this part of the explosion front should probably be subsonic and parts of it's propagation should have been obstructed in some ways.


No.

The middle "tongue" is the shape of the condensation cloud coming out of the LOX vent, reflecting (actually scattering) the light of the initial explosion. The shape above it is the same thing, it is the underside of the payload shroud lit up by the light of the initial explosion.

Well, Your're right. In addition, the blast runs radially, not diameter-wise from one edge to another. This requires the initial fireball to be twice the size for it to be supersonic. Meaning that it should have been:
1. About 37ft in diameter
2. Almost perfectly circular
3. Have clear edge

Which it is not.

However this all assumes that the event started in the next millisecond after last frame. Possible, but not probable.
For what it's worth:

I had a co-worker at one of my former jobs have a look at this. This guy used to characterize explosive properties of industrial gases. After some measuring, separating reflection from actual fireball, performing calculations, and assuming the time between the two frames is indeed 30 milliseconds, he made the following remarks:

1. This only looks like an explosion IF it started in the last 3-to-6 milliseconds before the second frame, and then only if the explosion is in a gas.
2. If the explosive was solid in nature then it probably started within the timeframe of exposure of the frame itself (solid explosives have much higher explosive velocities than gases).
3. The shape of the visible fireball is hard to interpret given all the reflection involved. Reflective elements from the TEL, payload shroud, second stage structure and the vapour cloud surrounding the vehicle, do a good job obscuring the actual shape of the fireball, combined with the poor image quality.
4. That said, and compensating for said reflective elements, the shape of the fireball does not support the notion of an explosive detonation taking place; too irregular.
5. Given best-case expansion velocities, assuming gases as the combustion medium, this can best be classed as a near-explosive conflagration, not as a true explosive detonation. He literally said: "With regards to the expansion velocity of the fireball, the initial blast looks very much like what was witnessed when Challenger was destroyed. And that wasn't an explosion either."

Disclaimer:
OK, that was just a quick look by a guy familiar with explosive properties. But it is important to remember that above remarks are based on a single piece of poor quality footage only, and without having access to any other sources related to this incident. So please, don't pull any conclusions based on above remarks and observations. That would be silly.

Musk stated that it was a fast fire, not an explosion since he stated that the crew escape system would have worked.

http://forum.nasaspaceflight.com/index.php?topic=40868.60
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/06/2016 05:43 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/06/2016 05:47 pm
I would not be surprised to find the root cause has something to do with the properties of sub-cooled LOX, as opposed to regular boiling-point LOX.  As many have pointed out, the US has not had a similar accident in about 50 years, a time span that includes many new generations of rockets.  So it would seem the needed precautions for regular LOX and RP-1 are well understood.  While it's certainly possible that SpaceX simply made some mistake, often the cause of an accident is some new material or procedure whose impact is not completely understood.  The likely candidate here is sub-cooled LOX (they also use cooled RP-1, but kerosene at these temperatures is used all the time by airplanes, outdoor tank farms, campers, and other uses). 

I have no specific suspect to relate this to the proximal cause.  Candidates could be the higher viscosity causing larger losses and higher stresses in the plumbing, the ability of sub-cooled LOX to condense oxygen or nitrogen from the air, or perhaps some mechanical property of some material that is different enough at sub-cooled temperatures.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: WHAP on 09/06/2016 05:51 pm

Musk stated that it was a fast fire, not an explosion since he stated that the crew escape system would have worked.

http://forum.nasaspaceflight.com/index.php?topic=40868.60

As has been discussed on this thread, the fast fire comment was taken to mean with respect to the crew escape system.  I'm not sure why that distinction was necessary.  It would be more impressive if the crew escape system could separate in the event of an "explosion".  Several posters have provided information based on the size of the plume and the frame rate of the video that shows this meets "accepted" definitions of an "explosion", and that "fast fire" is really not a typical term.  I'm no expert, but that loud BANG that occurs with the flash of light sure sounds like an explosion to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/06/2016 05:52 pm
I would not be surprised to find the root cause has something to do with the properties of sub-cooled LOX, as opposed to regular boiling-point LOX.  As many have pointed out, the US has not had a similar accident in about 50 years, a time span that includes many new generations of rockets.  So it would seem the needed precautions for regular LOX and RP-1 are well understood.  While it's certainly possible that SpaceX simply made some mistake, often the cause of an accident is some new material or procedure whose impact is not completely understood.  The likely candidate here is sub-cooled LOX (they also use cooled RP-1, but kerosene at these temperatures is used all the time by airplanes, outdoor tank farms, campers, and other uses). 

I have no specific suspect to relate this to the proximal cause.  Candidates could be the higher viscosity causing larger losses and higher stresses in the plumbing, the ability of sub-cooled LOX to condense oxygen or nitrogen from the air, or perhaps some mechanical property of some material that is different enough at sub-cooled temperatures.

Most upper stages use LH2 instead of RP-1, which has all the issues you just listed as being problematic with subcooled LOX, and then some. But LH2 stages don't seem to blow up often.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yg1968 on 09/06/2016 05:55 pm

Musk stated that it was a fast fire, not an explosion since he stated that the crew escape system would have worked.

http://forum.nasaspaceflight.com/index.php?topic=40868.60

As has been discussed on this thread, the fast fire comment was taken to mean with respect to the crew escape system.  I'm not sure why that distinction was necessary.  It would be more impressive if the crew escape system could separate in the event of an "explosion".  Several posters have provided information based on the size of the plume and the frame rate of the video that shows this meets "accepted" definitions of an "explosion", and that "fast fire" is really not a typical term.  I'm no expert, but that loud BANG that occurs with the flash of light sure sounds like an explosion to me.

I didn't read all of this thread. But I understood the fast fire tweet as indicating that it started off as a fire which means that they would have had time to trigger the escape system even if it was milliseconds.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/06/2016 05:59 pm

Musk stated that it was a fast fire, not an explosion since he stated that the crew escape system would have worked.

http://forum.nasaspaceflight.com/index.php?topic=40868.60

As has been discussed on this thread, the fast fire comment was taken to mean with respect to the crew escape system.  I'm not sure why that distinction was necessary.  It would be more impressive if the crew escape system could separate in the event of an "explosion".  Several posters have provided information based on the size of the plume and the frame rate of the video that shows this meets "accepted" definitions of an "explosion", and that "fast fire" is really not a typical term.  I'm no expert, but that loud BANG that occurs with the flash of light sure sounds like an explosion to me.

I didn't read all of this thread. But I understood the fast fire tweet as indicating that it started off as a fire which means that they would have had time to trigger the escape system even if it was milliseconds.

Either that, or that the initial event left even the fairing intact, and it would have had time to scoot.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dnavas on 09/06/2016 06:05 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

Well, I don't know if that was mine, but I do recall saying something similar in response to the idea that there was a fuel-air mix exploding up and down the stack 85' (or whatever height was being bandied about at the time).  It wasn't clear even then that we'd see something, but it seemed more likely to be projectile (either in or out).  Aside from the first frame, it seems that the "conflagration" was pretty symmetric, no?

I'd love to know what the two pieces exiting either side in those first few frames were.  :shrug:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: georgegassaway on 09/06/2016 06:14 pm
Musk says a lot of things “off the cuff”, that do not always turn out to be accurate.

It would seem to be more likely that the initial triggering event (whatever it was) was “explosive”, which then caused a chain of events which was non-explosive.

So his statement about a “Fast Fire” could be viable for 99.99+% of what happened after, but seemingly not for the initial event. He made this statement far too quick to likely have any real data to support a claim there was no explosion at any point whatsoever.  Yet some are hanging on his statement like it is etched in stone?

In a smaller scale, I think of it like using a blasting cap to set off a can of gasoline (a scenario not configured for a  fuel-air explosion).  The gasoline doesn’t “explode” (fast fire),  but the blasting cap does.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PreferToLurk on 09/06/2016 06:15 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...

The 60fps version is an interpolated up-conversion based on the original upload at 30fps.  If you are watching the video at 60fps and stepping through it frame by frame, just remember that every other frame was completely invented by an algorithm.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/06/2016 06:18 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...

The 60fps version is an interpolated up-conversion based on the original upload at 30fps.  If you are watching the video at 60fps and stepping through it frame by frame, just remember that every other frame was completely invented by an algorithm.
60FPS 1080p cameras are a thing and the source video could have been uploaded as such. Are you sure this was interpolated?

Edit - I don't think YouTube offers the 60fps option unless the original was uploaded as such. Perhaps US Launch Report uprated and interpolated it themselves, but there would be fairly obvious artifacts from that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/06/2016 06:29 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...

The 60fps version is an interpolated up-conversion based on the original upload at 30fps.  If you are watching the video at 60fps and stepping through it frame by frame, just remember that every other frame was completely invented by an algorithm.
60FPS 1080p cameras are a thing and the source video could have been uploaded as such. Are you sure this was interpolated?
Agreed... the file I reviewed was 1080P @ 60fps... My take was it WAS at the source file spec...  ???
Moving objects acted as they should frame to frame... (birds, fragments, etc)

PC I am on now does not have Google Chrome to duplicate my Saturday review...

On edit... posting I made Saturday...
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578168#msg1578168 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578168#msg1578168)
I later said my thinking was the pieces were fitting chunks... not COPV parts flying...
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578767#msg1578767 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1578767#msg1578767)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/06/2016 06:32 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...

The 60fps version is an interpolated up-conversion based on the original upload at 30fps.  If you are watching the video at 60fps and stepping through it frame by frame, just remember that every other frame was completely invented by an algorithm.
60FPS 1080p cameras are a thing and the source video could have been uploaded as such. Are you sure this was interpolated?
Agreed... the file I reviewed was 1080P @ 60fps... My take was it WAS the source file spec...  ???
Moving objects acted as they should frame to frame... (birds, fragments, etc)
It won't be the exact source file that was uploaded as YouTube often re-encodes the video for playback compatibility and bitrate  conformance, but it should be close.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/06/2016 06:40 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...

The 60fps version is an interpolated up-conversion based on the original upload at 30fps.  If you are watching the video at 60fps and stepping through it frame by frame, just remember that every other frame was completely invented by an algorithm.
60FPS 1080p cameras are a thing and the source video could have been uploaded as such. Are you sure this was interpolated?
Agreed... the file I reviewed was 1080P @ 60fps... My take was it WAS the source file spec...  ???
Moving objects acted as they should frame to frame... (birds, fragments, etc)
It won't be the exact source file that was uploaded as YouTube often re-encodes the video for playback compatibility and bitrate  conformance, but it should be close.
Agreed... I have uploaded 1080p 60fps drone and camcorder footage to YouTube in the past...
It usually makes a mess of the low res versions... But the top versions come out decent...

The file I had Saturday did have 60 frames per clock tick... confirmed that...
Also the Info for Geeks tab said as much... 1080p @ 60 fps
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/06/2016 06:46 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\
If so (I think the one I saw was 30 fps) then even more so...
I urge folks to Use the "gear icon" at YouTube and pull down the 1080P @60fps version and step thru it frame by frame using , and . buttons...  ;)
If that option is not shown... suggest use the Google Chrome Browser to solve that issue...

Just selecting 1080P doesn't guarantee 60fps (there's a 1080p 30fps version available, too). If you want to make sure you have the highest quality version, I recommend downloading with youtube-dl (http://rg3.github.io/youtube-dl/).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: matthewkantar on 09/06/2016 06:52 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://youtu.be/SQ8ZBPRiLXs

Enjoy, Matthew

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/06/2016 06:56 pm
Another minor hypothesis to shoot down.

The initial event occurred on the side of the tower/F9 closest to the camera.

Rationale:

There are multiple reflective bodies in the field of view, the oxy-globe, and 3 of the lightning towers, and some roof sections towards the bottom.

at Frame 0 as reference, note which parts of the towers and globe are reflecting.  Then toggle to Frame 1 and note the difference.

Compare that with Frame 20 or 30 or 40, and note which parts of the towers and globe are reflecting.

What I think I see is that a much larger portion of the rear towers and globe are illuminated as the event proceeds and surrounds the F9 completely, vs a much narrower illumination of the rear towers & globe at Frame 1.  To me that suggests that the event is partially obscured to the rear towers and globe by the F9 and its tower.


Does anyone have the ability to ray-trace cylinders & globes from different point source illuminations and see if you can duplicate the reflections based on where the source is?  I guess you'd also have to have a full 3-D model of the F9 and tower to get it right.

Does anyone know the radius of the globe and the top parts of the lightning towers?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/06/2016 07:07 pm
Another minor hypothesis to shoot down.

The initial event occurred on the side of the tower/F9 closest to the camera.

Rationale:

There are multiple reflective bodies in the field of view, the oxy-globe, and 3 of the lightning towers, and some roof sections towards the bottom.

at Frame 0 as reference, note which parts of the towers and globe are reflecting.  Then toggle to Frame 1 and note the difference.

Compare that with Frame 20 or 30 or 40, and note which parts of the towers and globe are reflecting.

What I think I see is that a much larger portion of the rear towers and globe are illuminated as the event proceeds and surrounds the F9 completely, vs a much narrower illumination of the rear towers & globe at Frame 1.  To me that suggests that the event is partially obscured to the rear towers and globe by the F9 and its tower.


Does anyone have the ability to ray-trace cylinders & globes from different point source illuminations and see if you can duplicate the reflections based on where the source is?  I guess you'd also have to have a full 3-D model of the F9 and tower to get it right.

Does anyone know the radius of the globe and the top parts of the lightning towers?

I noticed the same Saturday but did not mention at the time...  :)
The right hand tower top (the one a S1 COPV much later smacks into) was the brightest in Frame #1... my opinion...
Heck... it was smoking the most at one point in the melt down... (IR heating scorching the paint)
My take was... the flash was brightest at about the direction facing the camera or right of that...   ???
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/06/2016 07:12 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

OMG -- the top of the payload shroud moved forward and to the right...

da da DA!!!

:)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickyramjet on 09/06/2016 07:14 pm
I found a video from Youtube user Darkalarm (not great vid quality) showing the other side of the rocket during the "explosion".  I've read the entire thread and have not seen this posted.  There is a great deal of pixelation in this video, but if you watch carefully you can see the light from the ignition, and it's initially from the side facing away from this camera view.  Also, I watched the LOX venting at the moment of the first flash and could see no change.  This tells me there was no internal pressure change (enough to change the venting plume) at the moment of ignition.  I've watched many test fires and you can watch the venting clouds change at both engine ignition and at shutdown.  But, again, it's not great quality video, but may indicate something to some of the more knowledgeable folks on the forum.  link: https://www.youtube.com/watch?v=5gL00TQBfwI (https://www.youtube.com/watch?v=5gL00TQBfwI)
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/06/2016 07:20 pm
That appears to be the exact same video, mirrored left-to-right, with a slow motion interpolation applied that's mostly just amplifying compression artifacts.  I wouldn't give it any credence at all.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Eerie on 09/06/2016 07:20 pm
Question. If the separation between fuel and LOX in the second stage was compromised, and LOX started to flow into kerosene (or kerosene into LOX? which one is on top?) how long would it take until the thing exploded?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/06/2016 07:21 pm
That appears to be the exact same video, mirrored left-to-right, with a slow motion interpolation applied that's mostly just amplifying compression artifacts.  I wouldn't give it any credence at all.

What he said -- look at the flag on the payload fairing.  That video is worthless.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: testguy on 09/06/2016 07:47 pm
How important are contaminants in liquid oxygen? Presumably this is another variable compared to the test site.

Speaking from experience not to do with rockets; pure oxygen with a flammable  contaminant (ex: hydrocarbons) is a bad day looking for a time & place to happen, especially where pipes change direction which can cause local heating.

If you had enough contaminants in LOX to initiate this event, the whole tank should have be gone in an instant. This is not what happened.

Presumably contaminants don't just affect combustion. Could some materials be sensitive like the overwrapping of pressure vessels. Brainstorming further, how dry in terms of water ice particles does lox have to be - is it even possible to have ice contamination.
Apologies if this is annoying people, it's just that in the absence of new information about the event it is natural to think about external variables and the extent that they are understood. The vehicle is most likely the issue, or some transport handling
, from what informed people here have said.

By quick googling I found a few reports on LOX contamination:
1. STUDY OF LIQUID OXYGEN CONTAMINATION from 1961: http://www.dtic.mil/dtic/tr/fulltext/u2/272377.pdf
2. Ignition of Aluminum by Impact in LOX — Influence of Contaminants https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP12492S.htm

The first one is rather old and I did not notice any particularly agressive contaminants in the text. Yes, there may be combustibles (most importantly acetylene and methane), but I think that in purities used today this should not be an issue.

The second one I have no access to, but the name is interesting in this context. So, if anyone can access it, this would be interesting.

Here is a personal experience with oxygen contamination is a gaseous system.  I had a 2" isolation ball valve explode after being in service for many years.  The valve was last cycled 5 minutes prior to the incident and no oxygen flow was occurring (no delta P across the valve).  The failure was traced to comtaminated gaseous oxygen delivery from the supplier.  This was determined only after filters were installed on the fill lines and upon inspection revealed organics.  The suppliers investigation found their techs were failing to cap the the fill line from their factory to the delivery trucks.  Bugs were making a home in the line.  Just goes to show it can happen!
Needless to say there was extensive damage and required significant rework.  The fill filters are required to be inspected after EVERY delivery now.  A lesson learned.

I have no idea what the root cause of the incident is.  However, if I can relate one more situation dealing with unforgiving oxygen contamination that may help others.  Early in my career, I purchased an oxygen valve/actuator and paid the manufacturer to clean it for oxygen service.  It was received, packaged correctly and certified for oxygen service by the manufacturer.  Preliminary testing of the valve prior to putting it into service revealed it would not actuate.  Finally had to disassemble the valve and found it full of cutting oil and metal chips.  It was a disaster waiting to happen.  After that experience all oxygen cleaning and material compatibility verification was brought in house.  Another lesson learned.  Trust but verify.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/06/2016 07:49 pm
Some really interesting (as well as some not so good) work with the footage....although it makes me think we should have a whip round/collection for the USLaunchReport guys at some point, because without them having a camera on these static fires we'd have no footage (SpaceX had cameras on it, but for internal purposes).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 09/06/2016 07:50 pm
Another minor hypothesis to shoot down.

The initial event occurred on the side of the tower/F9 closest to the camera.

Rationale:

There are multiple reflective bodies in the field of view, the oxy-globe, and 3 of the lightning towers, and some roof sections towards the bottom.

at Frame 0 as reference, note which parts of the towers and globe are reflecting.  Then toggle to Frame 1 and note the difference.

Compare that with Frame 20 or 30 or 40, and note which parts of the towers and globe are reflecting.

What I think I see is that a much larger portion of the rear towers and globe are illuminated as the event proceeds and surrounds the F9 completely, vs a much narrower illumination of the rear towers & globe at Frame 1.  To me that suggests that the event is partially obscured to the rear towers and globe by the F9 and its tower.


Does anyone have the ability to ray-trace cylinders & globes from different point source illuminations and see if you can duplicate the reflections based on where the source is?  I guess you'd also have to have a full 3-D model of the F9 and tower to get it right.

Does anyone know the radius of the globe and the top parts of the lightning towers?

So far you have tracked every bug, bird, and square centimeter of debris within the ? number of miles between the event and the camera, and now you want us to start tracking every ray of light? To prove one of the few things that have been obvious from the beginning?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/06/2016 08:12 pm

So far you have tracked every bug, bird, and square centimeter of debris within the ? number of miles between the event and the camera, and now you want us to start tracking every ray of light? To prove one of the few things that have been obvious from the beginning?

Yes and I want a color comparison of the initial flash to rp1/lox exhaust and solid rocket motor with aluminum.  What does the color of the flash match for component materials....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 08:13 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

1. As this explosion is asymmetric, then the stack should move regardless if the explosion stards inside the LOX pressure vessel or outside. It's asymmetric and hence it moves the rocket
2. Besides that - analyze the part of the video before the event. There the rocket seems to wobble a little all the time. Reason being - this is extreme telephoto lens and hence the small atmospheric refraction differences make it move.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: daveglo on 09/06/2016 08:14 pm
Lots of interesting and entertaining speculation while we wait for facts from SpaceX.

So, here's my bit.  Can't find where anyone has talked about inadvertent activation of the flight termination system.  Rare, but it has happened before.  And Spacex has been talking about a new automatic FTS system.  Was that implemented yet? 

Everyone is focused on trying to mix fuel and lox, or overpressurization, to get to an explosion, but aren't there explosives attached right to the side of the stages?  The idea is to "unzip" the tanks upon activation, right?

Apologies in advance if I've missed this in prior discussions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/06/2016 08:26 pm
So, here's my bit.  Can't find where anyone has talked about inadvertent activation of the flight termination system.  Rare, but it has happened before.  And Spacex has been talking about a new automatic FTS system.  Was that implemented yet?

Anomaly occurred around T-8 minutes. Based on the Falcon 9 FT countdown the FTS system is not yet armed at that time.

T-0:03:05   Flight Termination System Armed, FTS Ready for Launch
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 09/06/2016 08:29 pm
Lots of interesting and entertaining speculation while we wait for facts from SpaceX.

So, here's my bit.  Can't find where anyone has talked about inadvertent activation of the flight termination system.  Rare, but it has happened before.  And Spacex has been talking about a new automatic FTS system.  Was that implemented yet? 

Everyone is focused on trying to mix fuel and lox, or overpressurization, to get to an explosion, but aren't there explosives attached right to the side of the stages?  The idea is to "unzip" the tanks upon activation, right?

Apologies in advance if I've missed this in prior discussions.

You can use the "Quick Search" box just above to search only this thread. FTS was brought up early on and has been discussed in detail. The FTS has been automated long enough to appear on the Falcon FT page on Spaceflight101.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: matthewkantar on 09/06/2016 08:32 pm
So, here's my bit.  Can't find where anyone has talked about inadvertent activation of the flight termination system.  Rare, but it has happened before.  And Spacex has been talking about a new automatic FTS system.  Was that implemented yet? 

This possibility is discussed at some length upthread. The failure would have to be in one charge of the FTS, not in the whole system, because of the localized nature of the initial flash. Furthermore as stated above, the charge would have to have detonated before it was armed. Highly unlikely.

Matthew
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kolkmvd on 09/06/2016 08:43 pm
Another minor hypothesis to shoot down.

The initial event occurred on the side of the tower/F9 closest to the camera.

Rationale:

There are multiple reflective bodies in the field of view, the oxy-globe, and 3 of the lightning towers, and some roof sections towards the bottom.
... i think this is also supported by the diffraction spikes being at the edge of the visible rocket, thus likely being 'behind' the rocket in the USLaunch vid
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/06/2016 08:45 pm
So far you have tracked every bug, bird, and square centimeter of debris within the ? number of miles between the event and the camera, and now you want us to start tracking every ray of light? To prove one of the few things that have been obvious from the beginning?

Um...it's called scientific investigation. It's what scientists do.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/06/2016 08:45 pm
I just thought of something.  Since this did not occur at launch or in flight, is the FAA really in charge of the investigation?  Or is it the Air Force, since it is a ground accident on their property.?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/06/2016 08:45 pm

So far you have tracked every bug, bird, and square centimeter of debris within the ? number of miles between the event and the camera, and now you want us to start tracking every ray of light? To prove one of the few things that have been obvious from the beginning?

Truthfully, I didn't track any birds or bugs.   I'm not suggesting we start tracking every ray of light, just some of them.  :)

Here's a reference to the type of model I had in mind.  :)  https://en.wikipedia.org/wiki/Ray_tracing_(graphics)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/06/2016 08:47 pm
Another minor hypothesis to shoot down.

The initial event occurred on the side of the tower/F9 closest to the camera.

Rationale:

There are multiple reflective bodies in the field of view, the oxy-globe, and 3 of the lightning towers, and some roof sections towards the bottom.
... i think this is also supported by the diffraction spikes being at the edge of the visible rocket, thus likely being 'behind' the rocket in the USLaunch vid

Just like to point out, I think it was "in front" not "behind".  :) 

Diffraction spikes to me are just lens imperfections that show up when you over-expose something.  They're often created inside the lens.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/06/2016 08:56 pm
1/60 = 0.01666666 or 16.66~ milliseconds per frame...
(@ 1080p 60fps original source posted to Utube)

I keep seeing 30 milliseconds and 1/30 sec mentioned in many posts...

Am I wrong in saying those numbers quoted are in error??...  :-\

On edit...
As to movement... The rocket weighed several 100's of TONS at the moment of 'Flash'...  ???
Movement?... I think not much... that can be seen or even recorded...

Well, let's settle this sonic issue once and for all. Let's make it "wooden and red" as they say in my place.

I'm a SI person, so forget me, when I start as metric.
I do not look up exact values for the temperature and humidity and pressure of the day as the difference is not important.

Speed of sound is somewhere between 340-347m/s
Time between frames is 0,0167 seconds
340 x 0,0167 = 5,678m = 18.63 ft rounded

From point of origination blast travels in both directions. Meaning that it starts from the center of sphere and travels to both sides simultaneously. That makes it 11,356m = 37.257ft as a maximum possible diameter of the fireball in deflagrating explosion assuming the event started immediately after the last frame.

Falcon 9 FT diameter is 3,66m = 12 ft. So, this stack should have been engulfed 3 times circumferentially. But in fact the oversaturated area on frame #1 is about 2 times the diameter of the rocket. Moreover, part of the oversaturated area is surrounded by fog and reflections making it seem larger than it really is.

Now, detonations do not come "in all shapes and sizes". They come in one shape only - a sphere unless something interrupts it. This means that the vertical dimension of the over-saturated area on the frame #1 is larger not due to detonation, but due to some other effect. Probably combination of fog diffusion of light and reflections between mast and the rocket body.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/06/2016 08:58 pm
I just thought of something.  Since this did not occur at launch or in flight, is the FAA really in charge of the investigation?  Or is it the Air Force, since it is a ground accident on their property.?

I kind of suspect that it would be both, as this is a launch vehicle intended to carry commercial payloads and, eventually, people.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JasonAW3 on 09/06/2016 09:06 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

OMG -- the top of the payload shroud moved forward and to the right...

da da DA!!!

:)

      But there was no upwards movement.  An internal explosion would have been, however briefly, contained within the structure, shown visible distortion of the skin of the stage, and thrown the payload upwards at least a few feet. 

      What it did was shift the payload shroud to one side.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/06/2016 09:11 pm
I just thought of something.  Since this did not occur at launch or in flight, is the FAA really in charge of the investigation?  Or is it the Air Force, since it is a ground accident on their property.?

It would be like a traffic accident, a fire in a building ... Property loss, aka casualty insurance.

However, the scope of AF interest would be that of a property owner, to the extent it affected AF interests/operations/liabilities/hazards. As covered in a lease agreement (likely). If base infrastructure were threatened, that would be sufficient.

Now, the FAA might still retain charge of an investigation under the launch license, under the concern that there was an intent with the test to launch, and that while not in flight or in process or launch, might inform on something that breached a duty leading up to launch, that could pose a greater threat to, say, public welfare.

Something that destroys a facility certainly gives that as a basis for action.

But because it would not be during an actual launch, there likely would be proscriptive limits to authority/action in/on this anomaly.

It could be why we are hearing little on this, because a comprehensive answer is desired (but not required) given the scale of the catastrophe. The optics are horrible ... it may look to many that people aren't doing their jobs, regardless of if they actually did.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/06/2016 09:14 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

Very clever approach.  I'm jealous that I didn't think of it.

It looks actually like it's moving to the right and dropping a bit.  I would interpret it as a structural collapse rather than motion imparted by an explosion, however defined.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/06/2016 09:15 pm
Just checked the Updates section and there was an SX press release from the 2nd. Interesting take aways
was

They state their 2nd FL launch pad is on schedule for being F9/FH ready by November. So Florida launches resume NET November 1st (Using Musk level optimism  :) ) unless they can repair this pad in less than 25 days.

I've no feel for how damaged the pad and TEL have been damaged. To a layman like me it looks really badly damaged with months of work to rebuild it but is it?
Oops. As someone reminded me, what about October?

So 56 days, not (as OP'd) 25 but could you really rebuild the pad and it's infrastructure in that time?

This being SX I'm quite sure all the plans, BOM's and supplier lists are on file and they could have started placing orders on the day it happened. A week or two for full site investigation then begin the teardown and rebuild?

I find it very hard to believe it will be back in working order before the other pad goes live.  :(

If so that just leaves the new pad carrying the load for any FL launches, which I'm guessing is most of the commercial ones.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/06/2016 09:15 pm
I just thought of something.  Since this did not occur at launch or in flight, is the FAA really in charge of the investigation?  Or is it the Air Force, since it is a ground accident on their property.?
Good point but I thought there was a lot of debate around this for commercial space flights with NASA pushing hard for jurisdiction but (IIRC) FAA getting it under their commercial spaceflight office.

I guess a similar question would be if say White Knight 2 crashed on take off from Edwards. Air Force for the runway or FAA as an experimental aircraft?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/06/2016 10:05 pm

So far you have tracked every bug, bird, and square centimeter of debris within the ? number of miles between the event and the camera, and now you want us to start tracking every ray of light? To prove one of the few things that have been obvious from the beginning?

Yes and I want a color comparison of the initial flash to rp1/lox exhaust and solid rocket motor with aluminum.  What does the color of the flash match for component materials....


If only they had a optical spectrometer recording the scene ...   Without having the camera make/model, lens make/model, settings at time of recording, etc., etc., etc. there wouldn't be any way to compare this video stream with any other with the same data available.  Worse, CCDs or CPDs these days?  Have lots of variability in precision which makes for great birthday party videos, but crappy instrumentation.  Plus, after demanding the camera to be placed in my clammy little hands, I'd want the original recorded media as well.  After a month of labor, unpaid????!!!!, I'd probably have to conclude, "don't know".  :(

The dynamic range on the youtube video is about 60% of what's possible.  At 8 bits per pixel per RGB channel, AFTER being mostly destroyed by MPEG or worse, almost half of the visible data really isn't available.  I've been trying to focus on the dynamics of the event, and assuming everything about the camera is worst case.  I would kill for a calibrated uncompressed 16 bit per channel video stream...

But, what you want is good stuff, albeit, unlikely to happen in this case.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/06/2016 10:14 pm
I just thought of something.  Since this did not occur at launch or in flight, is the FAA really in charge of the investigation?  Or is it the Air Force, since it is a ground accident on their property.?

I believe that the FAA/AST license encompasses pre-launch preparations, though when they deem that process begins eludes me.  But I'd bet they all claim authority over the wet-dress.

I know they tried to claim jurisdiction over Rotary twenty years ago, saying that we needed their approval to build our manufacturing facilities in Mojave, even before we had begun any licensing process.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/06/2016 10:33 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

Very clever approach.  I'm jealous that I didn't think of it.

It looks actually like it's moving to the right and dropping a bit.  I would interpret it as a structural collapse rather than motion imparted by an explosion, however defined.

Could be payload pivoting to the right as S2 moves left. (pivoting at the point of the TEL arms). Or right side of S2 collapsing before left side (and payload falling right as you said).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/06/2016 10:33 pm
OK, gang... using my geologic engineering background, i believe i have a plausible explanation of the *ploink* and rumble on the vid. YES is DOES COME FROM THE JUNKYARD!, but the explosion and subsequent fireball ARE to blame. Since the S1 is attached to the pad/ground, it transmits the pressure wave directly to the ground. This is why it registered on seismic equipment. since pressure waves travel much faster through the ground than in the compressible air, the transient noises in the video are caused by the explosion. The shock traveling through the ground will arrive to the microphone location before the sound traveling in the air. This shockwave/impulse caused something in the yard to tilt,rub,bang or rattle . Initial explosion shock arrival IS the *ploink* and fireball/collapse of the stack is the rattle. That should put everything to bed... what do you think Chris?

this will be for pressure or P-Wave impulses
since the coastal area of CCAFS is mostly unconsolidated sediment &  sand, one can use 1000 meters/sec as velocity.

Here's the study from 2011 by University of Florida regarding seismic energy propagation in FLA
http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

I'll let you have fun with the maths
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/06/2016 10:39 pm
OK, gang... using my geologic engineering background, i believe i have a plausible explanation of the *ploink* and rumble on the vid. YES is DOES COME FROM THE JUNKYARD!, but the explosion and subsequent fireball ARE to blame. Since the S1 is attached to the pad/ground, it transmits the pressure wave directly to the ground. This is why it registered on seismic equipment. since pressure waves travel much faster through the ground than in the compressible air, the transient noises in the video are caused by the explosion. The shock traveling through the ground will arrive to the microphone location before the sound traveling in the air. This shockwave/impulse caused something in the yard to tilt,rub,bang or rattle . Initial explosion shock arrival IS the *ploink* and fireball/collapse of the stack is the rattle. That should put everything to bed... what do you think Chris?

this will be for pressure or P-Wave impulses
since the coastal area of CCAFS is mostly unconsolidated sediment &  sand, one can use 1000 meters/sec as velocity.

Here's the study from 2011 by University of Florida regarding seismic energy propagation in FLA
http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

I'll let you have fun with the maths
I was checking for seismic data the a couple of days ago but could not locate a station for Florida. Perhaps you have better luck. I did find news of a quake offshore from Daytona beach on July 17th which was interesting...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ulm_atms on 09/06/2016 11:14 pm
I found this today while searching around.  Gives a great overview of oxygen in ALL forms....and many, many ways it can go boom.

http://www.hq.nasa.gov/office/codeq/doctree/canceled/1740151.pdf

Edit: I always misspell one word! :D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/06/2016 11:18 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

Very clever approach.  I'm jealous that I didn't think of it.

It looks actually like it's moving to the right and dropping a bit.  I would interpret it as a structural collapse rather than motion imparted by an explosion, however defined.

Could be payload pivoting to the right as S2 moves left. (pivoting at the point of the TEL arms). Or right side of S2 collapsing before left side (and payload falling right as you said).

To my eyes, the apparent movement down and right seems to be an illusion caused by the brightening illumination from the lower right.  Yes, the brightly lit area of the fairing is down and right of the original silhouette; but it’s because the top and left curves of the fairing body aren't illuminated and fade into the darker background (especially since the camera seems to change its exposure setting as the light brightens.)

So I don't think the payload moves at all.  Or maybe that's just my eyes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/06/2016 11:33 pm
First off, I recall someone (not sure who, there have been so many ideas tossed out) saying that they didn't feel this could be an external explosion, because they didn't see the stack move sideways in the first three or four frames after the initial fireball.  The point being made was that an external explosion capable of piercing the tank, especially at the common bulkhead, would first noticeably push the whole stack to the side.

I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.

https://www.youtube.com/watch?v=SQ8ZBPRiLXs

Enjoy, Matthew

Very clever approach.  I'm jealous that I didn't think of it.

It looks actually like it's moving to the right and dropping a bit.  I would interpret it as a structural collapse rather than motion imparted by an explosion, however defined.

Could be payload pivoting to the right as S2 moves left. (pivoting at the point of the TEL arms). Or right side of S2 collapsing before left side (and payload falling right as you said).
A thought I have wrt this video and the ensuing discussion is that

TL/DR the stack seems to move in the only direction it can - opposite to the erection movement.

Assuming that

the TEL at this point in countdown is locked in place relative to the pad;
the TEL is decoupled from the launch table (which actually bares the weight of the fueled stack);
the TEL provides only lateral support to the stack against wind gusts and such;
and assuming the erection axis is the only intended degree of freedom in the TEL;
and assuming the axis lock is not a very tough or particularly hard one (maybe even hydraulic only)     

it would seem that the apparent movement is along the path of least reaction force, i.e against the erection axis lock. Which would suggest that one can't infer the vector of the force that acts on the stack/TEL from apparent movement - no matter what the vector is, as long as it has a component aligned with the erection plane and the rest of the force is below the structural limit of the TEL, the TEL will move in that direction.

Edited for clarity
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bstrong on 09/06/2016 11:39 pm
An attempt to bring out some more detail in the suspect area of the strongback.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AnalogMan on 09/06/2016 11:52 pm
I just thought of something.  Since this did not occur at launch or in flight, is the FAA really in charge of the investigation?  Or is it the Air Force, since it is a ground accident on their property.?

I believe that the FAA/AST license encompasses pre-launch preparations, though when they deem that process begins eludes me.  But I'd bet they all claim authority over the wet-dress.

I know they tried to claim jurisdiction over Rotary twenty years ago, saying that we needed their approval to build our manufacturing facilities in Mojave, even before we had begun any licensing process.

The FAA license covers pre-flight operations as well as flight.  Specifically:

(b) “Pre-flight ground operations” shall mean SpaceX’s pre-flight preparations of the Falcon 9 launch vehicle at CCAFS, beginning with the arrival of the Falcon 9 Version 1.2 launch vehicle at CCAFS.

So I'm guessing they may well claim authority.

Copy of license LLS 14-090 Rev 2 attached.

---------

Edit to add this quote from the SpaceX release (my underline):

http://www.spacex.com/news/2016/09/01/anomaly-updates (http://www.spacex.com/news/2016/09/01/anomaly-updates)

"To identify the root cause of the anomaly, SpaceX began its investigation immediately after the loss, consistent with accident investigation plans prepared for such a contingency.  These plans include the preservation of all possible evidence and the assembly of an Accident Investigation Team, with oversight by the Federal Aviation Administration and participation by NASA, the United States Air Force and other industry experts."
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 12:26 am


A very good observation, young weed hopper, and one I thought about too.  Your observation is most credible, but...

The problem is locking the field of view which I didn't show in the image posted.  Granted long distance atmospheric distortion and such, and other things, there are multiple frames that show this.  I merged the two most obvious frames, but, there are others.  You are correct that the brightening is not uniform, and comes from the right to the left, which could create an optical illusion separate from actual motion, but, I looked at that over multiple frames and focused on finding the fairing irrespective of illumination, which is, as you suggest, the right thing to do, and concluded, IMHO, it actually rotates right and down.   If you have Photoshop, try selecting levels at various values to try to enhance the fairing.   You'll have to change the tolerance for each frame, since the illumination levels are changing frame to frame.

The original data is there to see.  RIP it and post please if you're sure I'm wrong.  :)

I welcome this debate and am willing to post multiple images, but the simple fact is as I see it, the fairing rotates towards the right and drops.

It doesn't go up ever in any mode I've looked at.

I still propose IMHO that the initial detonation is external to the F9, and in front of the tower facing the camera...  :) 

Elon's will be done.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/07/2016 01:20 am
5. Given best-case expansion velocities, assuming gases as the combustion medium, this can best be classed as a near-explosive conflagration, not as a true explosive detonation. He literally said: "With regards to the expansion velocity of the fireball, the initial blast looks very much like what was witnessed when Challenger was destroyed. And that wasn't an explosion either."
The National Fire Protection Association defines a detonation as "propagation of a combustion zone at a velocity greater than the speed of sound in the unreacted medium".  It defines an explosion as "the sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure. These high-pressure gases then do mechanical work such as moving, changing, or shattering nearby materials."

By the NFPA definition, I believe your friend is correct that this was not a "detonation", but it sure looked like an "explosion" by the NFPA definition. 

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FireJack on 09/07/2016 01:41 am
Is there any definitive proof that the center of the lens flair is in fact where the LOX fuel line is?

         I get the feeling that problem is going to be the use of the densified propellant. It could be that every time the falcon was loaded with the superchilled LOX there was a small chance that there would be an explosion and it was just a matter of time. I little bit of googling shows that a lot of people were concerned with the use of the new denser fuel.

My greatest fear is that the investigation shows that there are unresolvable issues with the densified fuel and spacex is ordered to stop using it. This would create all kinds of issues even assuming no changes need to be made to the rocket.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/07/2016 02:19 am


I can not parse the difference between a slow explosion and a fast fire, but the stack definitely moves. Pardon the crappy tech in this video, but it does illustrate the movement. All video credit to the dedicated folk at USLaunchReport for giving us something to chew on while we await word from the people with much more info and insight.


Wow - a new piece of evidence. And consistent with an external force pushing at the common bulkhead with the payload pivoting clockwise around the clamp.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: intrepidpursuit on 09/07/2016 02:22 am
Is there any definitive proof that the center of the lens flair is in fact where the LOX fuel line is?

         I get the feeling that problem is going to be the use of the densified propellant. It could be that every time the falcon was loaded with the superchilled LOX there was a small chance that there would be an explosion and it was just a matter of time. I little bit of googling shows that a lot of people were concerned with the use of the new denser fuel.

My greatest fear is that the investigation shows that there are unresolvable issues with the densified fuel and spacex is ordered to stop using it. This would create all kinds of issues even assuming no changes need to be made to the rocket.

Many rockets including Antares use subcooled fuel without issue. SpaceX was pushing it further, but it isn't complete uncharted territory.

The LOX fuel line is NOT at the center of the explosion. It goes in at the bottom of the stage through the interstage. The explosion was very near the center of the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/07/2016 02:33 am
Is there any definitive proof that the center of the lens flair is in fact where the LOX fuel line is?

The contrary seems more likely. From left to right, the Amos6 lens flare, the same point in the frame before the conflagration, the cross section from the Falcon 9 User's Guide v2.0, and the JCSAT14 static fire with the TE retracted, and no payload. The LOX fuel line is attached much lower than the epicentre.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AS-503 on 09/07/2016 03:04 am
Is there any definitive proof that the center of the lens flair is in fact where the LOX fuel line is?

The contrary seems more likely. From left to right, the Amos6 lens flare, the same point in the frame before the conflagration, the cross section from the Falcon 9 User's Guide v2.0, and the JCSAT14 static fire with the TE retracted, and no payload. The LOX fuel line is attached much lower than the epicentre.

With respect to the LOX to RP1 tank sizes. Your upper stage cutaway seems to show aprox. symmetric volumes between the two tanks. I thought there was about a 2:1 ratio of LOX to RP1 with both stages, such that the cutaway would show an aprox. 2:1 volume difference between the oxidizer (LOX) and the fuel (RP1).
Anyone know the specific cubic volume ratios for each stage?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FireJack on 09/07/2016 03:42 am
In the picture there seems to be some kind of structure running up the side of the second stage that ends around where the lox tank would start. This would seem to imply a failure of the lox lines.

  We really would need a much better view (even at hd the camera was a long way out on a humid day) and more detailed diagrams of the structures involved to make any realistic diagnosis.
Nothing to do but wait and hope it's nothing too bad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Cherokee43v6 on 09/07/2016 04:27 am


A very good observation, young weed hopper, and one I thought about too.  Your observation is most credible, but...

The problem is locking the field of view which I didn't show in the image posted.  Granted long distance atmospheric distortion and such, and other things, there are multiple frames that show this.  I merged the two most obvious frames, but, there are others.  You are correct that the brightening is not uniform, and comes from the right to the left, which could create an optical illusion separate from actual motion, but, I looked at that over multiple frames and focused on finding the fairing irrespective of illumination, which is, as you suggest, the right thing to do, and concluded, IMHO, it actually rotates right and down.   If you have Photoshop, try selecting levels at various values to try to enhance the fairing.   You'll have to change the tolerance for each frame, since the illumination levels are changing frame to frame.

The original data is there to see.  RIP it and post please if you're sure I'm wrong.  :)

I welcome this debate and am willing to post multiple images, but the simple fact is as I see it, the fairing rotates towards the right and drops.

It doesn't go up ever in any mode I've looked at.

I still propose IMHO that the initial detonation is external to the F9, and in front of the tower facing the camera...  :) 

Elon's will be done.  :)

Using the single frame advance (and many thanks to the person upthread who shared that trick for Youtube vids) I detect no motion on the part of the payload faring.  If you lay a ruler on the screen at the beginning, then as the light climbs the fairing, the only change is the background washout along the upper left curve.  The right edge remains absolutely clear and never shifts as the cloud climbs to obscure it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Helodriver on 09/07/2016 05:06 am
As of sunset September 6th, the strongback is still vertical as I photographed it.  No great details as its over 10.5 miles away in atmospheric wind and heat shimmer
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HIP2BSQRE on 09/07/2016 05:08 am
As of sunset September 6th, the strongback is still vertical as I photographed it.  No great details as its over 10.5 miles away in atmospheric wind and heat shimmer

What type of lens do you have to see something 10 miles away?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LtWigglesworth on 09/07/2016 05:57 am
As of sunset September 6th, the strongback is still vertical as I photographed it.  No great details as its over 10.5 miles away in atmospheric wind and heat shimmer

What type of lens do you have to see something 10 miles away?

Most probably a big one!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/07/2016 06:09 am
In the picture there seems to be some kind of structure running up the side of the second stage that ends around where the lox tank would start. This would seem to imply a failure of the lox lines.

LOX riser goes along the center axis of RP-1 tank. Still, it is one possible failure point. New subcooled LOX loading procedures strained the common bulkhead beyond what riser/bulkhead joint could handle? *arm waving disclaimer*
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/07/2016 07:05 am
When I thought about possible failure causes of COPV-s, one thing to note is, that as the temperature of this superchilled LOX is 66 K, nitrogen becomes solid at 63.15 K. Difference is less than 3 K, which is possibly inside the tolerances of the loading equipment.

On the other hand, as the COPV-s are produced at atmospheric pressure, there must be some air trapped in between the filaments. And although vacuum curing is possibly applied, not all of the air will be evacuated.

I do not know, what to make out of that. Although nitrogen density in solid mode is 0,25g/ml and liquid nitrogen is 0,8g/ml, this does not mean, that nitrogen expands like water as it solidifies. Fact is that when compressed, the density of nitrogen ice can become larger than water's. Meaning, that if nitrogen becomes solid, it does not excert any particularly large pressure on structures if it's trapped in somewhere there.

Just my food of thought to someone more qualified in such matters.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/07/2016 09:17 am

Using the single frame advance (and many thanks to the person upthread who shared that trick for Youtube vids) I detect no motion on the part of the payload faring.  If you lay a ruler on the screen at the beginning, then as the light climbs the fairing, the only change is the background washout along the upper left curve.  The right edge remains absolutely clear and never shifts as the cloud climbs to obscure it.

There are at least a couple of things going on here that I think are causing an optical illusion;

The brighter region advances preferentially along the right hand side of the rocket, making the right hand brighter than the left and giving the impression of movement to the right (the right side of the rocket becomes more dominant in your vision) - this creates a greater contrast which potentially affects retinal pre-processing and tricking your brain into seeing movement. A second thing is that the shape and movement of the cloud is such that it creates additional perception of movement to the right (because the cloud rises higher on the left first and then moves to the top left of the frame) -this effect would be mainly in the brain, and may be accentuated by the restricted shot - the cloud becomes totally dominant in the lower half of the frame and thus the brain has nothing to fix its perception of "stationary" against - typically the brain picks the largest thing, and that in this case is the cloud - and we know the cloud is not stationary (but your brain is stupid and doesn't know this!). just think when you're in a car and stationary and sometimes another car moves to the side of you and you think that you're rolling as a similar example. It's also related to the problems that VR has, because your eyes are saying you're not stationary and your ears are saying that you are stationary... but I digress.

Really if you want to see if it moves, the best thing is an outline of the whole thing and see if you observe any drift over that outline (you'd still have to be a bit careful of other optical effects, but it would be better than a single point consideration)

Eyes are a useful tool at times, but don't trust them! I have a lot of experience with the way that eyes work.

For reference, I work in medical optics related to production of medical devices and have some (but a relatively limited amount of) experience in retinal image processing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/07/2016 09:19 am
Some really interesting (as well as some not so good) work with the footage....although it makes me think we should have a whip round/collection for the USLaunchReport guys at some point, because without them having a camera on these static fires we'd have no footage (SpaceX had cameras on it, but for internal purposes).

I would be very glad if could you organize that for us. I know one can donate by contacting them directly on their web page, but I would like to see the money coming from the NSF user base as one donation. Almost all the footage we have from this incident is from US launch report. But that is not all they provided. In the past, they were one of the very few sources of high quality video of F9-S1 offloading from the Of Course I Still Love You as well as good quality video footage from road transported first stages on the cape. We have all gained so much from them, its time we give something back.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/07/2016 11:17 am
This is probably based on mistaken reporting and shouldn't be considered an update.   Various reports on financial channels state that Spacecom will be pursuing/expecting $50M from SpaceX and $200M from the satellite manufacturer.  Not sure why they're expecting to collect from the manufacturer.  Anyhow the implication is SpaceX isn't on the hook for the satellite costs.

http://arstechnica.com/science/2016/09/spacex-explosion-amos-6-satellite-owner-demands-50-million-dollars/

Also under the category: risk statements that make no sense to me - folks posted in this thread that SpaceX took unnecessary risks by running WDR with satellite onboard, however I don't see how the risk is any different than not running a WDR in the first place, which is the industry standard.   Also it's been stated that WDR are done to mitigate schedule risk, not launch risk.  That makes sense, but in hindsight we can see that a WDR done w/o the satellite onboard, would mitigate launch risk, regardless of SpaceX intentions (assuming this was a launch system fault and not a spacecraft fault)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 11:28 am
This is probably based on mistaken reporting and shouldn't be considered an update.   Various reports on financial channels state that Spacecom will be pursuing/expecting $50M from SpaceX and $200M from the satellite manufacturer.  Not sure why they're expecting to collect from the manufacturer.  Anyhow the implication is SpaceX isn't on the hook for the satellite costs.

http://arstechnica.com/science/2016/09/spacex-explosion-amos-6-satellite-owner-demands-50-million-dollars/

Details from Reuters: http://www.reuters.com/article/us-space-com-xinwei-group-idUSKCN11A0EF
It's all in the contract.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Ben the Space Brit on 09/07/2016 11:44 am
The issue is at least somewhat corporate-cultural, I think. Elon Musk has said that SpaceX's final goal is to make LEO flight as routine as airline flight. That means a minimal inter-flight cycle and I believe that WDRs with payload attached is part of this (get the rocket ready in the hanger and do everything you need on the pad before launch in one go).

Possibly this is an early warning that rocket technology is not yet mature enough to achieve this level of routine.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/07/2016 11:49 am
Why would the satellite manufacturer agree to refund unless their satellite somehow caused the incident?
Might be just venting hot air to impress the Chinese.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 11:55 am
Why would the satellite manufacturer agree to refund unless their satellite somehow caused the incident?
Might be just venting hot air to impress the Chinese.

We know that the payload was insured as marine cargo until the ignition for launch. I would think that the manufacturer signed this insurance policy and will pass the payout on to Spacecom.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 11:59 am
Are there any inside reports about the state of the investigation? I would assume that by now the investigators must have an idea what did not cause the anomaly.
There are some credible yet unsubstantiated rumours on reddit (https://www.reddit.com/r/spacex/comments/50rr9v/falcon_9_amos6_static_fire_anomaly_faq_summary/d7ci0b9)...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: StuffOfInterest on 09/07/2016 12:08 pm
As of sunset September 6th, the strongback is still vertical as I photographed it.  No great details as its over 10.5 miles away in atmospheric wind and heat shimmer

Sad photo to see but it does at least give one point for possible optimism.  Remembering that the TEL arm is in several pieces, it appears the lower section may be salvageable.  Everything in it will certainly have to be replaced but the frame itself may not be too bad.  I'd also exect the TEL base to not be too bad as that thing was designed to take direct rocket blast anyway.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/07/2016 12:11 pm
Why would the satellite manufacturer agree to refund unless their satellite somehow caused the incident?
Might be just venting hot air to impress the Chinese.

We know that the payload was insured as marine cargo until the ignition for launch. I would think that the manufacturer signed this insurance policy and will pass the payout on to Spacecom.

Exactly. http://www.globes.co.il/en/article-spacecom-to-claim-compensation-for-amos-6-from-iai-1001149933

Btw: The difference of the marine cargo to the usual insurance contract (the one that kicks in with the "intention to launch") is, that it will not compensate Spacecom for lost revenue of the satellite until replacement can be procured. It only compensates the satellite cost plus interest.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 12:14 pm


I don't see this as an optical illusion.  This is a composite of prior to the event and just before the fairing is obscured by the event.   Grey is the before.  I've cropped out most of the sky.  While the motion is optically illuminating from lower right to upper left, and that could produce the illusion you describe, the outline of the fairing you can see is still visible, and it's lower and tilted to the right. 

If you have the correct tools, you can cut out the before, rotate and drop it, and it's a perfect matchup for the after.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 12:17 pm
As of sunset September 6th, the strongback is still vertical as I photographed it.  No great details as its over 10.5 miles away in atmospheric wind and heat shimmer

So anyone care to speculate if that left-most lightning mast is scorched (it was probably downwind of the fire and smoke plume), just dirty, or just dark due to distance/lighting/photo processing? I understand the the masts are fiberglass, mounted on the steel tower bases.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/07/2016 12:26 pm


I don't see this as an optical illusion.  This is a composite of prior to the event and just before the fairing is obscured by the event.   Grey is the before.  I've cropped out most of the sky.  While the motion is optically illuminating from lower right to upper left, and that could produce the illusion you describe, the outline of the fairing you can see is still visible, and it's lower and tilted to the right. 

If you have the correct tools, you can cut out the before, rotate and drop it, and it's a perfect matchup for the after.

Could you, guys, elaborate, what difference does it make? Moved, moved a little, did not move at all - what conclusions will you make out of that?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 12:27 pm
So anyone care to speculate if that left-most lightning mast is scorched (it was probably downwind of the fire and smoke plume), just dirty, or just dark due to distance/lighting/photo processing? I understand the the masts are fiberglass, mounted on the steel tower bases.

Probably quite crispy:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/07/2016 12:33 pm

We know that the payload was insured as marine cargo until the ignition for launch. I would think that the manufacturer signed this insurance policy and will pass the payout on to Spacecom.

Thanks, that sounds plausible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/07/2016 12:37 pm
There appeared to be a venting near the point of the explosion. I've read every post but may have forgotten - Do we know what is venting there? Seems that all lox venting would be higher up on stage 2.

A sort of related question. What's in the COPV's before the helium load? Dry nitrogen? How does that substance/gas vent and where?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 12:39 pm
BTW, the question about the lightning masts gave me an idea.
There are three masts in the same frame:
* one is engulfed with fire from the explosion
* one gets so hot that it starts smoking
* one is only illuminated

Can this information be used to get some information about the direction of the initial main blast? I assume that the pad is exactly in the center of the four masts...

Minor correction: the leftmost mast in my screenshot is not a lightning masts but the strongback. The third mast that was visible before the anomaly is completely engulfed in fire and can't be seen at all.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 12:49 pm
And yet some more boring observations.

Attached you can see a subtraction between Frame 0 and Frame 1.  Essentially the differences.

This highlights the illumination changes to a degree.

A couple of thoughts.

1.  The fireball at this point extends past the tower on the right.
2.  If it extends past the body of the F9 on the left, it barely does so
3.  The illumination pattern on the fairing points to a very specific region on the tower, below at perhaps 315 degrees from the right bottom edge of the fairing.
4.  The grid fin on the left is being illuminated from above and to the right, and considering where it is on the F9, that illumination source must be many feet closer to the camera
5.  The illumination on the globe is very specular, almost like a point source... puzzling


Thoughts.... this looks like a elongated illumination source, more tall than wide, kinda like you'd see from a shop light.

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 01:00 pm


I don't see this as an optical illusion.  This is a composite of prior to the event and just before the fairing is obscured by the event.   Grey is the before.  I've cropped out most of the sky.  While the motion is optically illuminating from lower right to upper left, and that could produce the illusion you describe, the outline of the fairing you can see is still visible, and it's lower and tilted to the right. 

If you have the correct tools, you can cut out the before, rotate and drop it, and it's a perfect matchup for the after.

Could you, guys, elaborate, what difference does it make? Moved, moved a little, did not move at all - what conclusions will you make out of that?

Prior speculation states that if the explosion originated in the tank, then the fairing would have to move up.  That didn't happen.  That doesn't mean that it didn't happen in the tank, just that whatever happened had insufficient energy to move the fairing up.

Prior speculation states that the fairing didn't move.  It moved after a certain period of time, rotating right and down.  Why it moved that direction would be a different set of speculations.  Mine would be that S2's structure failed from the right to the left (no surprise) and the fairing fell in the direction it should have.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 01:09 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 01:11 pm
one other illumination tidbit.

If you look at the difference frame, you can see that the nearest edge of the strongback left of the hydrauic mounting points is illuminated.  Off hand that looks like it goes up and down.  Follow the taper upper right to lower left, and then the line down.

In order for that to be illuminated, the light source must extend some distance beyond that point which implies that the fireball must extend even closer to the camera than the edge of the strongback.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 01:19 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Jim, I obviously didn't state my question clearly.  This is the area that my question referred to.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 01:20 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Not clear if glennfish meant the T/E or lightning towers. If lightning tower, they're tubes with (I think, if they follow industry standards), a thick grounding conductor running their length to a deeply-driven grounding rod. If he's referring to the T/E, I think it's been well established that the only thing running up past the S2 umbilicals at the base of the stage would be conditioned air/N2 for payload purge, and hydraulics for the clamps. Is that a good summary, Jim?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 01:20 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Jim, I obviously didn't state my question clearly.  This is the area that my question referred to.


Still nothing
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/07/2016 01:36 pm


Still nothing

Jim,
Would this have been the first time this particular vehicle was lifted to vertical by the TEL?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 01:51 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Not clear if glennfish meant the T/E or lightning towers. If lightning tower, they're tubes with (I think, if they follow industry standards), a thick grounding conductor running their length to a deeply-driven grounding rod. If he's referring to the T/E, I think it's been well established that the only thing running up past the S2 umbilicals at the base of the stage would be conditioned air/N2 for payload purge, and hydraulics for the clamps. Is that a good summary, Jim?

yes
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 02:00 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Jim, I obviously didn't state my question clearly.  This is the area that my question referred to.


Umbilical catch net
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 02:13 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Not clear if glennfish meant the T/E or lightning towers. If lightning tower, they're tubes with (I think, if they follow industry standards), a thick grounding conductor running their length to a deeply-driven grounding rod. If he's referring to the T/E, I think it's been well established that the only thing running up past the S2 umbilicals at the base of the stage would be conditioned air/N2 for payload purge, and hydraulics for the clamps. Is that a good summary, Jim?

Did you say hydraulics for the clamps?  Any idea what the working fluid is in those hydraulics, and the capacity, and the working pressure?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/07/2016 02:22 pm
Are there any materials on the T/E in that area that could become sensitized after repeated exposure to low temperatures and liquid oxygen?  I'm reminded of the gasket explosions that destroyed several of the early X-planes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 02:56 pm
Are there any materials on the T/E in that area that could become sensitized after repeated exposure to low temperatures and liquid oxygen?  I'm reminded of the gasket explosions that destroyed several of the early X-planes.

Lessons learned long ago that are no longer repeated
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/07/2016 03:00 pm
Lessons learned long ago that are no longer repeated

Yes, but then again how many launch providers have their vehicle blow up during a tanking operation these days?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 03:02 pm
Lessons learned long ago that are no longer repeated

Yes, but then again how many launch providers have their vehicle blow up during a tanking operation these days?

Because they found a new way to do it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/07/2016 03:03 pm
For the sake of their reputation, I hope so.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/07/2016 03:04 pm
Ok assume for a second...

I think the copv failure fits the observations the best.
Copv blows apart.
Shrapnel of carbon fiber, plastic, aluminum holes the tank wall.
lox and shrapnel burn very brightly and explosively.
This scenario was posted previously by somebody else.

Second scenario however unlikely for a lot of reasons.
High speed bullet with or without explosive charge.
Holes tank.

How could we see the difference in this poor quality video.
How could spacex with high speed much better video tell the difference.
I think the telemetry would certainly tell the difference. Pressure curves should be tell tale along with sonic info.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/07/2016 03:06 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Not clear if glennfish meant the T/E or lightning towers. If lightning tower, they're tubes with (I think, if they follow industry standards), a thick grounding conductor running their length to a deeply-driven grounding rod. If he's referring to the T/E, I think it's been well established that the only thing running up past the S2 umbilicals at the base of the stage would be conditioned air/N2 for payload purge, and hydraulics for the clamps. Is that a good summary, Jim?

Did you say hydraulics for the clamps?  Any idea what the working fluid is in those hydraulics, and the capacity, and the working pressure?

Sanity check: how big was the initial blast?  How much hydraulic fluid would have been required for a blast of that size?  Now consider the speed of the initial blast.  The fuel and oxidizer would already have had to have been mixed.  Could such an enormous amount of hydraulic fluid have leaked without anyone noticing, let alone leaked and mixed with oxygen, all without blowing away in the wind?

I can't see how.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 03:18 pm
Lessons learned long ago that are no longer repeated

Yes, but then again how many launch providers have their vehicle blow up during a tanking operation these days?

Because they found a new way to do it.

Innovation!  8)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 03:21 pm
Okay -- from what Jim has said, the AC line running up to the payload fairing has no return, it just vents along vents in the fairing, and the one small side-conduit from the main conduit at the S1/S2 interface serves to provide GN2 to the interstage area, which, like the payload fairing, is flooded with nitrogen prior to launch to prevent any possible fires and clean out atmospheric contamination in that area, as well.

So, that means that, in my latest adaptation of the pic of an F9 on the pad, the conduit that runs up to the S-bend is the AC line.  So, the conduit to its left in this picture, which terminates in the padded boxes I had assumed was an AC filter complex, seems to be completely unconnected from the AC system.

Which begs the question, what is inside these padded boxes?  They are connected to the TEL and are the termination of the largest main conduit that reaches this far up the TEL.  They are also right around where the initial flash is seen.  They also show a number of different electrical connections, especially on some smaller panels attached to the whole complex on the camera-facing side of the TEL.  And there are three relatively small small pipe terminations below that appear to have orange cover booties on them that are visible below this complex, which could be liquid, gas or electrical terminations.

I've circled the whole complex I'm looking at in red.  The original image I'm working with circles the umbilicals feeding into the base of stage 2 in blue.

If an explosion occurred on the TEL, it would have started somewhere around this complex.

So, the obvious question is -- what the heck is actually inside this set of padded boxes on the TEL?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 03:26 pm

Are there any pipes/tubes running up and down on the side of the tower closest to the camera?  If so, does anyone know what's supposed to be in them?


Nothing, they are just lightning towers

Not clear if glennfish meant the T/E or lightning towers. If lightning tower, they're tubes with (I think, if they follow industry standards), a thick grounding conductor running their length to a deeply-driven grounding rod. If he's referring to the T/E, I think it's been well established that the only thing running up past the S2 umbilicals at the base of the stage would be conditioned air/N2 for payload purge, and hydraulics for the clamps. Is that a good summary, Jim?

Did you say hydraulics for the clamps?  Any idea what the working fluid is in those hydraulics, and the capacity, and the working pressure?

Sanity check: how big was the initial blast?  How much hydraulic fluid would have been required for a blast of that size?  Now consider the speed of the initial blast.  The fuel and oxidizer would already have had to have been mixed.  Could such an enormous amount of hydraulic fluid have leaked without anyone noticing, let alone leaked and mixed with oxygen, all without blowing away in the wind?

I can't see how.

Some approximations but not definitive answers. 

The horizontal dimension in Frame 1 is about 35 feet +-. 

That would be consistent with a TNT equivalent of 50-100 pounds

I'm not sure what the hydraulic fluid would be, but using kerosene as a surrogate that would be the equivalent of about 1.5-3 gallons perfectly mixed with air. 

It would require about 300 cubic feet of mixing space or a sphere about 8 feet in diameter.  Less if the oxygen level is higher.

In a UK directory of hydraulic explosions, there are cases of large mixing volumes very fast from small defects.  Working pressure of hydraulics can be very low (20+ PSI) to very high (5000+ PSI).  The higher the pressure, the faster the leak and more likely it would become an aerosol.

see comments on reply #  1259
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 03:33 pm
Thoughts.... this looks like a elongated illumination source, more tall than wide, kinda like you'd see from a shop light.

My tuppeneceworth on this is that we're looking at an explosion of vapour/gases in an oxygen-rich environment outside the vehicle.

Entirely possible that the upper stage tank/tanks was/were ruptured and discharging vapour, which was subsequently ignited by something on the erector.

Around 1/3 second after the first explosion, the upper stage tank(s) started to explode and beyond that point, it's merely narrative rather than anything that would help find a cause.

The 'problem' is that there's no indication of anything awry prior to the first frame showing the explosion.

(Incidentally, I'd agree that the top of the fairing moves slightly to the right around 1/2 second after the initial explosion. Given that the second explosion occurred just before this - which is probably a tank rupturing on the right side - that's unsurprising.)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 03:37 pm
So, that means that, in my latest adaptation of the pic of an F9 on the pad, the conduit that runs up to the S-bend is the AC line.  So, the conduit to its left in this picture, which terminates in the padded boxes I had assumed was an AC filter complex, seems to be completely unconnected from the AC system.

Which begs the question, what is inside these padded boxes?  They are connected to the TEL and are the termination of the largest main conduit that reaches this far up the TEL.  They are also right around where the initial flash is seen.  They also show a number of different electrical connections, especially on some smaller panels attached to the whole complex on the camera-facing side of the TEL.  And there are three relatively small small pipe terminations below that appear to have orange cover booties on them that are visible below this complex, which could be liquid, gas or electrical terminations.


You need to be looking at a more complete image of the erector which shows where the ducts come from / go to.

The AC line through the s-bend is going down, as far as I can tell - see attached: it's highlighted in green and comes to an end at the bottom of the image, where it's marked '2'.

I think Jim said the boxes on the left are part of the AC system?

The feed appears to be up the rearward duct of the pair running up the erector, through the white boxes and then back down via the pipe with the s-bend?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 03:45 pm
So, that means that, in my latest adaptation of the pic of an F9 on the pad, the conduit that runs up to the S-bend is the AC line.  So, the conduit to its left in this picture, which terminates in the padded boxes I had assumed was an AC filter complex, seems to be completely unconnected from the AC system.

Which begs the question, what is inside these padded boxes?  They are connected to the TEL and are the termination of the largest main conduit that reaches this far up the TEL.  They are also right around where the initial flash is seen.  They also show a number of different electrical connections, especially on some smaller panels attached to the whole complex on the camera-facing side of the TEL.  And there are three relatively small small pipe terminations below that appear to have orange cover booties on them that are visible below this complex, which could be liquid, gas or electrical terminations.

The AC line through the s-bend is going down, as far as I can tell - see attached: it's highlighted in green and comes to an end at the bottom of the image, where it's marked '2'.

I think Jim said the boxes on the left are part of the AC system?

The feed appears to be up the back of the erector, through the white boxes and then back down via the pipe with the s-bend?

That's why I'm asking.  The pictures we have don't let us track where the conduits all interact at the base of the TEL.  Since it's a no-return ventilation system, then you only need one conduit, but if the only -- or best -- place to locate a filter complex is up by stage 2, and you need to run the airstream through it, an up-down-up flow as you suggest might be the best kludge... er, excuse me, compromise, you could  come up with to do so.

However, I also recall two statements -- possibly both from Jim -- that seem contradictory.  One is that some of the flying debris after the initial flash is likely part of the AC filtering system.  The other is that the filtered GN2, and possibly the filtered air intake, for the AC system is provided from a location off the TEL, away from the pad.  Which made me think that all of the AC filtering, etc., is done off the TEL, and then led me to wonder what these padded boxes are for...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chewi on 09/07/2016 03:46 pm
Quote
Jeff Foust ‏@jeff_foust  (https://twitter.com/jeff_foust) · 5 minutes ago (https://twitter.com/jeff_foust/status/773546248339091456)

Here’s a closer look at SpaceX’s SLC-40 from earlier today.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 03:54 pm
I originally was looking internal to the vehicle and I posted my thoughts, so now I decided to think outside of the vehicle. The "exact" point in the sequence "has" been reported included that they were down to pressing for strongback retract. That system is dealing with extremely high pressures (there some experts are on here) and a component failure could fire a projectile at a high velocity piercing the vehicle and giving the appearance of an original confined external event. Energy, projectile, hydraulic fluid, LOX...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 03:58 pm
Quote
Jeff Foust ‏@jeff_foust  (https://twitter.com/jeff_foust) · 5 minutes ago (https://twitter.com/jeff_foust/status/773546248339091456)

Here’s a closer look at SpaceX’s SLC-40 from earlier today.

And that picture seems to show the padded boxes I've been asking about, albeit blackened, sitting relatively intact and still attached to the TEL structure.  While I suppose this could still be a source for an ignition event, it obviously didn't itself blow up in such a way that would deform and destroy the boxes, at least when viewed from the back of the TEL.

From this image, it also seems obvious that the various umbilicals that fed out from the TEL to the rocket are gone.  I'm beginning to wonder if the biggest thingie we saw flying away from the TEL might not have been a big piece of one of the PL fairing umbilicals...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 03:59 pm

That's why I'm asking.  The pictures we have don't let us track where the conduits all interact at the base of the TEL.  Since it's a no-return ventilation system, then you only need one conduit, but if the only -- or best -- place to locate a filter complex is up by stage 2, and you need to run the airstream through it, an up-down-up flow as you suggest might be the best kludge... er, excuse me, compromise, you could  come up with to do so.

However, I also recall two statements -- possibly both from Jim -- that seem contradictory.  One is that some of the flying debris after the initial flash is likely part of the AC filtering system.  The other is that the filtered GN2, and possibly the filtered air intake, for the AC system is provided from a location off the TEL, away from the pad.  Which made me think that all of the AC filtering, etc., is done off the TEL, and then led me to wonder what these padded boxes are for...

The duct with the s-bend definitely comes to an end about halfway up the erector, thus the feed to it must have come from the top.

There only appears to be one feed to the vehicle, which I presume is used to purge the interstage with GN2?

The other duct, which runs the full height of the stage and goes through the boxes, pretty much has to be the feed from the ground equipment, particularly if it's supplying GN2.

I'd imagine that the equipment on the erector is probably for pumping purposes because if the feed pumps are located a distance away from the erector, then flow may have become irregular by the time it reaches the payload / vehicle.

Add to that that the system is probably not perfectly sealed: even though it is under positive pressure, there may be the possibility that contamination could have got in, hence the need to re-filter it *just in case*.

As to why it goes up then down? That might be a legacy issue as this erector has been used with three different generations of F9, so it could be a modification? Or, it just fits better that way? Or it's considered more important to prioritise the feed to the payload fairing before the vehicle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 04:05 pm
Quote
Jeff Foust ‏@jeff_foust  (https://twitter.com/jeff_foust) · 5 minutes ago (https://twitter.com/jeff_foust/status/773546248339091456)

Here’s a closer look at SpaceX’s SLC-40 from earlier today.

Is there any information to be gleaned from the fact that only one lightning mast is charred? Obviously the "fast fire" did not spread in a circle centered around the vehicle. Am I wrong?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 04:08 pm
Quote
Jeff Foust ‏@jeff_foust  (https://twitter.com/jeff_foust) · 5 minutes ago (https://twitter.com/jeff_foust/status/773546248339091456)

Here’s a closer look at SpaceX’s SLC-40 from earlier today.

Is there any information to be gleaned from the fact that only one lightning mast is charred? Obviously the "fast fire" did not spread in a circle centered around the vehicle. Am I wrong?

Probably only that was the way the wind was blowing ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/07/2016 04:08 pm
From the latest pictures of the damaged T/E, the only part that appears to be conclusively missing are one or more of the white struts in the section just below the second stage cradle.  The loss of these struts seems to be what permitted the cradle to sag forward when the payload fell off.  Don't know if these were lost in the initial explosion or secondarily due to the fire.  Every other structural part of the T/E seems to be still there, just badly sooted.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 04:09 pm

So, the obvious question is -- what the heck is actually inside this set of padded boxes on the TEL?

Filters as I said.  There is another duct hidden behind the one with the s-curve

Both conditioned air and GN2 are supplied by ducts to the vehicle, there is switch over in the count.  The conditioned fluids are supplied to the base of the TEL and final filtering is done in the TEL.  The fans and cooling equipment are all in a building to the west of the pad.  There are no blowers or such on the TEL

As shown in an earlier photo, the duct with the s-curve is not used for the vehicle.  It supplies AC to the Dragon late load enclosure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 04:12 pm
Quote
Jeff Foust ‏@jeff_foust  (https://twitter.com/jeff_foust) · 5 minutes ago (https://twitter.com/jeff_foust/status/773546248339091456)

Here’s a closer look at SpaceX’s SLC-40 from earlier today.

Is there any information to be gleaned from the fact that only one lightning mast is charred? Obviously the "fast fire" did not spread in a circle centered around the vehicle. Am I wrong?

Probably only that was the way the wind was blowing ;)

Can the wind really influence a close to supersonic expansion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 04:16 pm
From the latest pictures of the damaged T/E, the only part that appears to be conclusively missing are one or more of the white struts in the section just below the second stage cradle.  The loss of these struts seems to be what permitted the cradle to sag forward when the payload fell off.  Don't know if these were lost in the initial explosion or secondarily due to the fire.  Every other structural part of the T/E seems to be still there, just badly sooted.

The damaged section is, I think, the bit where they extended the height of the erector to adapt it from F9 1.1 to F9 FT.

It has/had several struts I would think of as bottlescrews and several have failed, almost certainly collapsed by the weight of the payload.

As for the condition of the rest of the TEL, bear in mind it has been exposed to massive heat, which may have damaged it beyond repair. It may look as it the lower sections are not warped, but it might take a brave engineer to sign it off as reusable without a lot of very detailed examination

In reality it may be cheaper (and quicker) just to build a new one (okay, the base may well be okay, because that's designed to resist those sort of temperatures) - and I wouldn't be at all surprised if that process hasn't already been started. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mike_1179 on 09/07/2016 04:19 pm
Quote
Jeff Foust ‏@jeff_foust  (https://twitter.com/jeff_foust) · 5 minutes ago (https://twitter.com/jeff_foust/status/773546248339091456)

Here’s a closer look at SpaceX’s SLC-40 from earlier today.

Is there any information to be gleaned from the fact that only one lightning mast is charred? Obviously the "fast fire" did not spread in a circle centered around the vehicle. Am I wrong?

Probably only that was the way the wind was blowing ;)

Can the wind really influence a close to supersonic expansion?

Wind blew the billowing smoke and soot that way from the fire that burned for some time after the initiating event. That smoke and soot deposited on the tower or the flames were blown in that direction and they directly heated those surfaces more than the other towers.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mike_1179 on 09/07/2016 04:21 pm
From the latest pictures of the damaged T/E, the only part that appears to be conclusively missing are one or more of the white struts in the section just below the second stage cradle.  The loss of these struts seems to be what permitted the cradle to sag forward when the payload fell off.  Don't know if these were lost in the initial explosion or secondarily due to the fire.  Every other structural part of the T/E seems to be still there, just badly sooted.

The damaged section is, I think, the bit where they extended the height of the erector to adapt it from F9 1.1 to F9 FT.

It has/had several struts I would think of as bottlescrews and several have failed, almost certainly collapsed by the weight of the payload.

As for the condition of the rest of the TEL, bear in mind it has been exposed to massive heat, which may have damaged it beyond repair. It may look as it the lower sections are not warped, but it might take a brave engineer to sign it off as reusable without a lot of very detailed examination

In reality it may be cheaper (and quicker) just to build a new one (okay, the base may well be okay, because that's designed to resist those sort of temperatures) - and I wouldn't be at all surprised if that process hasn't already been started. 

What about all of the other stuff we can't see like the hold downs and the hydraulics for rotating the TEL up to vertical. There's a lot more than steel at the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 04:23 pm

Can the wind really influence a close to supersonic expansion?

I'm assuming that the top of that tower was damaged by the fires that followed the initial explosion.

It was certainly downwind of the fires; and the initial fires did reach that high. The tower is already charred when it's first visible above the flames about 30 seconds after the initial explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 04:26 pm
In reality it may be cheaper (and quicker) just to build a new one (okay, the base may well be okay, because that's designed to resist those sort of temperatures) - and I wouldn't be at all surprised if that process hasn't already been started. 

I don't think the base is meant nor designed to withstand an uncontrolled kerosene fire the lasted nearly as long as it did. The heat treatment of the steel, even if it wasn't all melted and sagged out of spec, will be completely ruined. I would not be surprised at all if LC-40 itself has to be rebuilt, possibly including part or all of the concrete hardstand.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 04:32 pm

I don't think the base is meant nor designed to withstand an uncontrolled kerosene fire the lasted nearly as long as it did. The heat treatment of the steel, even if it wasn't all melted and sagged out of spec, will be completely ruined. I would not be surprised at all if LC-40 itself has to be rebuilt, possibly including part or all of the concrete hardstand.

Wouldn't surprise me, either.

Quicker (and probably cheaper) to start work manufacturing new components now than to spend time and effort trying to salvage bits, examining them and then discovering they're wrecked.

Plus, it would probably be more sensible to install a TEL designed for F9 FT rather than re-creating something that's been repeatedly modified to deal with various developments of the vehicle.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/07/2016 04:41 pm
Ref Jeff Foust pic posted above...

The blackened lightning rod tube was on the upwind side, but facing the intense IR heat as the rocket burned down...
It was smoking very heavily when the fireball was at max intensity...
That same tower got smacked near it's base with (I believe) a S1 COPV liberated late in the event... (the lean)
I am surprised how black that one side got... crispy is a good term to use...  :o
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/07/2016 04:52 pm
Ref Jeff Foust pic posted above...

The blackened lightning rod tube was on the upwind side, but facing the intense IR heat as the rocket burned down...
It was smoking very heavily when the fireball was at max intensity...
That same tower got smacked near it's base with (I believe) a S1 COPV liberated late in the event... (the lean)
I am surprised how black that one side got... crispy is a good term to use...  :o
Burned, or just sooted? Maybe it just needs a scrub down like some other items is SpaceX inventory?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 05:03 pm
Thoughts.... this looks like a elongated illumination source, more tall than wide, kinda like you'd see from a shop light.

My tuppeneceworth on this is that we're looking at an explosion of vapour/gases in an oxygen-rich environment outside the vehicle.

Entirely possible that the upper stage tank/tanks was/were ruptured and discharging vapour, which was subsequently ignited by something on the erector.

Around 1/3 second after the first explosion, the upper stage tank(s) started to explode and beyond that point, it's merely narrative rather than anything that would help find a cause.

The 'problem' is that there's no indication of anything awry prior to the first frame showing the explosion.

(Incidentally, I'd agree that the top of the fairing moves slightly to the right around 1/2 second after the initial explosion. Given that the second explosion occurred just before this - which is probably a tank rupturing on the right side - that's unsurprising.)

I think there's a general misunderstanding of how little fuel is required for a FAE, and how fast a leak can release the required volume.

My estimates (provided elsewhere in this thread) suggest a 1.5 to 3 gallon leak would be required to create the initial event if perfectly mixed.  That's not a lot to see.  About .4 cubic feet of stuff as liquid, perhaps 300 cubic feet as vapour.

Further if it's a hydraulic system leak there are some online calculators that show how many cubic feet per minute go through a hole at certain temperature - pressures.

One calculator  http://www.tlv.com/global/TI/calculator/air-flow-rate-through-orifice.html

Plug in the allowable #s.  Set Units to SI, F, psi abs, psi abs, and mm.

Mine were 70 F,  3200 psig, 14 psig, 1 mm hole, discharge coefficient of .7

The answer is 57 cubic feet per minute or the requisite stuff is discharged in under 1/2 second.  Now this is airflow, not fuel, and fuel would go much slower than air, but the point is, it wouldn't take much or very long to get an FAE setup if this originated from a high-pressure hydraulic leak.

In that kind of scenario, we'd never see it in the available video, and the pressure loss in the hydraulic system might or might not be seen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scylla on 09/07/2016 05:05 pm
Some VERY clear, hi res pics of strongback and surrounding area.
Not sure of permissions, so just posting link.

https://imgur.com/a/se8bK
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/07/2016 05:07 pm
I wonder...

There's been a lot of speculation that the S-curve AC duct might have been the source of something. This has been counterpointed that it's ONLY an AC duct, and a this point in the countdown is only pushing gasious nitrogen.

However, supercooled LOX can freeze nitrogen and liquify oxygen.

Is there any posibility that the FAIRING got cold enough that the AC airturned liquid and flowed back through the pipe? Where it would get hung up on the S-curve and cause unspecified problems?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/07/2016 05:11 pm
Some VERY clear, hi res pics of strongback and surrounding area.
Not sure of permissions, so just posting link.

https://imgur.com/a/se8bK

Hmm, the strongback and all its constituent plumbing looks pretty intact in those pictures (considering what it went though)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/07/2016 05:14 pm
I believe the statement was made that there are COPV's in the RP1 tank in addition to the LOX tank. How would the initial gas (assuming gaseous nitrogen) be vented as they fill with helium? First I thought lines to the top of the tank to just vent into the tank's GN2 at the top of the tank. But could they have their own vent lines directly to the exterior since any overventing would only be helium venting?

 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chrisking0997 on 09/07/2016 05:17 pm
Ref Jeff Foust pic posted above...

The blackened lightning rod tube was on the upwind side, but facing the intense IR heat as the rocket burned down...
It was smoking very heavily when the fireball was at max intensity...
That same tower got smacked near it's base with (I believe) a S1 COPV liberated late in the event... (the lean)
I am surprised how black that one side got... crispy is a good term to use...  :o

Im confused about this "lean" that keeps coming up.  I dont see a lean.  Also, wasnt this tower on the downwind side (ie, smoke and flame blew into it)?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 05:19 pm
Anyone have a schematic of all the hydraulic lines on the strongback right up to the cradle? I've been trying to locate one....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 05:19 pm
Some VERY clear, hi res pics of strongback and surrounding area.
Not sure of permissions, so just posting link.

https://imgur.com/a/se8bK

Gotta admit, the damage looks a let less severe than I expected. Still don't know that I'd trust the remains of the T/E based on the heat flux, but overall it's not as bad I would have thought.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 05:20 pm
.  Also, wasnt this tower on the downwind side (ie, smoke and flame blew into it)?

As far as I recall, yes.

It's the one on the left in the USSpaceLaunch video and is obscured by flames and smoke very early on in the conflagration. When it first becomes visible about 30 seconds later, it's already blackened, presumably by the flames that engulfed it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 05:21 pm
Some VERY clear, hi res pics of strongback and surrounding area.
Not sure of permissions, so just posting link.

https://imgur.com/a/se8bK

Gotta admit, the damage looks a let less severe than I expected. Still don't know that I'd trust the remains of the T/E based on the heat flux, but overall it's not as bad I would have thought.
I'd look it over then scrap it...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 05:24 pm
Some VERY clear, hi res pics of strongback and surrounding area.
Not sure of permissions, so just posting link.

https://imgur.com/a/se8bK

Hmm, the strongback and all its constituent plumbing looks pretty intact in those pictures (considering what it went though)

Yes, but the most damaged area -- where the TEL bent -- is exactly where what I have called the "soft cradle", the small cradle that supports stage 2 right at its common bulkhead, was located -- and it doesn't appear to still be attached to the structure of the TEL.

Either (and most likely) that cradle broke off as the TEL bent under the weight of the payload and fairing, or -- and here's the great leap of intuition -- if a relatively small FAE kind of thing happened just behind that cradle, it could be that the cradle was ripped off in the initial flash and pushed hard into the side of the rocket, thus piercing the stage right at the common bulkhead and creating the structural failure that led to the complete LOV.

I guess I just find it interesting that the TEL didn't bend or show structural failure anywhere along where the massive deflagration occurred, but only shows structural failure right where that cradle was located, and the cradle is totally off the tower.  Yes, since that was where the initial flash occurred, you might expect that, but the fact remains that the one structural piece (not a conduit or other non-structural element) that departed the TEL at that location was that cradle...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/07/2016 05:25 pm
The HIF looks completely intact. The towers don't have any visible damage except the one charred fiberglass pole. The LOX sphere doesn't have any visible damage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Tonioroffo on 09/07/2016 05:26 pm
Don't try to check leaning towers on a photo.  Lenses have a lot of barrel and pincushion distortions.

Sent from my LG-D802 using Tapatalk

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 05:27 pm
So query: in those high-res photos on Imgur, what's the tangle hanging off the end of the T/E?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/07/2016 05:29 pm
So query: in those high-res photos on Imgur, what's the tangle hanging off the end of the T/E?

The remains of the umbilicals.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/07/2016 05:33 pm
It looks to me like it's actually what's left of the ducting (and associated wires) that used to connect to the payload fairing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scylla on 09/07/2016 05:34 pm
On the question, is one of the lightning towers leaning, look at the wires connecting the towers. All wires are intact and all wires have the same amount of sag. If a tower was leaning the sag between would change.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 05:37 pm

Yes, but the most damaged area -- where the TEL bent -- is exactly where what I have called the "soft cradle", the small cradle that supports stage 2 right at its common bulkhead, was located -- and it doesn't appear to still be attached to the structure of the TEL.

It's still there?

The cradle that supports the stage around the common bulkhead is part of a larger cradle with a second support at the top of the stage at the same height as the 'claw'.

Highlighted in green on the attached.

Edit: added 'before'. As far as I can tell, that cradle has two supports which hold the stage and it may well be pivoted to even the load between them when the stage is horizontal.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 05:38 pm
So query: in those high-res photos on Imgur, what's the tangle hanging off the end of the T/E?

The remains of the umbilicals.

Look at the full-size versions - that stuff (wires? tubing?) is hanging almost all the way down to the part of the T/E where it widens out toward the base. Seems as if whatever it is, it tore out with the vehicle as it collapsed, got pulled through and up the T/E tower and then back down until it just broke off at the end in the fire.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 05:44 pm
I'm trying to locate the hydraulic line that leads up to the cradle piston actuator, but the angle makes it a bit challenging...
I've been using this photo for reference of a "before"...
https://i.imgur.com/HxHowr6.jpg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 05:45 pm

Yes, but the most damaged area -- where the TEL bent -- is exactly where what I have called the "soft cradle", the small cradle that supports stage 2 right at its common bulkhead, was located -- and it doesn't appear to still be attached to the structure of the TEL.

It's still there?

The cradle that supports the stage around the common bulkhead is part of a larger cradle with a second support at the top of the stage at the same height as the 'claw'.

Highlighted in green on the attached.

Will add a 'before' when I can find one...

Please do, because yes, I see the structure that connects to the claw-arms (also only one of which is visible in this picture, though the other may be hidden) that support the stack right at the payload fairing adapter, but it seems to be open at the bottom.  The only structure I see at the bottom, where the smaller cradle was attached, is the background latticework of the far side of the TEL.  I don't see any sign of the small cradle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 05:48 pm
I wonder...

There's been a lot of speculation that the S-curve AC duct might have been the source of something. This has been counterpointed that it's ONLY an AC duct, and a this point in the countdown is only pushing gasious nitrogen.

However, supercooled LOX can freeze nitrogen and liquify oxygen.

Is there any posibility that the FAIRING got cold enough that the AC airturned liquid and flowed back through the pipe? Where it would get hung up on the S-curve and cause unspecified problems?

How would the faring get cold enough?  Could your house AC do that?  And wouldn't the spacecraft know that?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/07/2016 05:52 pm
Has this hole always been there?

Source image (https://i.imgur.com/cJEQpS1.jpg)

Furthermore, is it actually a hole?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/07/2016 05:55 pm

Yes, but the most damaged area -- where the TEL bent -- is exactly where what I have called the "soft cradle", the small cradle that supports stage 2 right at its common bulkhead, was located -- and it doesn't appear to still be attached to the structure of the TEL.

It's still there?

The cradle that supports the stage around the common bulkhead is part of a larger cradle with a second support at the top of the stage at the same height as the 'claw'.

Highlighted in green on the attached.

Will add a 'before' when I can find one...

Please do, because yes, I see the structure that connects to the claw-arms (also only one of which is visible in this picture, though the other may be hidden) that support the stack right at the payload fairing adapter, but it seems to be open at the bottom.  The only structure I see at the bottom, where the smaller cradle was attached, is the background latticework of the far side of the TEL.  I don't see any sign of the small cradle.

Working from this picture:

https://i.imgur.com/cJEQpS1.jpg

here's my attempt.  Movable clamp arms are in red, lower cradle structure in green.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 06:05 pm

Working from this picture:

https://i.imgur.com/cJEQpS1.jpg

here's my attempt.  Movable clamp arms are in red, lower cradle structure in green.

The movable clamps arms / claw are separate to the cradle structure.

The cradle structure comprises the mechanism that links the support cradle that supports the upper stage at the common bulkhead and also an (effectively) identical support cradle that sits at the same height as the claw.

The claw is only needed for holding the vehicle when the stage is vertical - the two support cradles which sit on the larger steel cradle have to be used to support the vehicle when it the erector is horizontal.

As far as I can figure out, by having this pair of supports on a pivoted cradle, they can move slightly and thus apply the same pressure to the vehicle as the cradle is self-equalising.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/07/2016 06:09 pm



Please do, because yes, I see the structure that connects to the claw-arms (also only one of which is visible in this picture, though the other may be hidden) that support the stack right at the payload fairing adapter, but it seems to be open at the bottom.  The only structure I see at the bottom, where the smaller cradle was attached, is the background latticework of the far side of the TEL.  I don't see any sign of the small cradle.

This is just the type of thing that might not be modeled correctly. They might have modeled a small explosion at that exact spot and concluded that the vehicle could withstand the pressure. What might have been missed is the momentum of the heavy payload causing a pendulum effect moving the S2 body away from that narrow lower support and the body then flexing back, stronger top section preventing any "give" at the bulkhead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 06:12 pm
Knew I'd seen a better photograph of the cradle: attached, with the frame and the pivot highlighted. The upper supports are at the same height as the claw, which is retracted in the photo.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 06:12 pm

This is just the type of thing that might not be modeled correctly. They might have modeled a small explosion

Why would they model any explosion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 06:15 pm
Knew I'd seen a better photograph of the cradle: attached, with the frame and the pivot highlighted. The upper supports are at the same height as the claw, which is retracted in the photo.
This is the one I posted before, if it's any use to you...
https://i.imgur.com/HxHowr6.jpg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 06:27 pm
Knew I'd seen a better photograph of the cradle: attached, with the frame and the pivot highlighted. The upper supports are at the same height as the claw.

I see what you're saying, and I totally agree that the cradle structure that connects the upper claw arms to the lower passive cradle (that doesn't wrap around the vehicle, it just serves as a support for the stage to lay on) is all connected, shows in green in the image you post, and does appear to be mostly on the TEL.

I wasn't talking about the entire structure to which the claw cradle at top, and the "soft cradle", which actually touches and supports the rocket, attach.  I was just talking about that arch of metal, with the little rubber tips and such, which support the second stage right at the common bulkhead when the stage is horizontal.  We're arguing semantics, in that you are rightly calling this entire large piece that connects the claws at top and the rubber-tipped rest at the bottom a cradle, while I'm just speaking of the rubber-tipped rest at the bottom of the piece that connects the two.

What I don't see in these post-event images is that actual curved rubber-tipped rest, circled in red in the steadfast image I've again detailed below that we've been looking at for a rough pre-accident TEL illustration.  I see the cradle assembly to which it was attached, and I see an angled bracket that did underlay and support the portion that actually came into contact with the rocket.  What I don't see is much if anything left of that arc-shaped cradle piece that actually cradled the rocket.  Especially the piece on the right side of the assembly, from the point of view of these new pictures.  It's hard to see, but a piece of the near-side part of that piece of the cradle might still be attached to the assembly, but the far side of it seems to be gone, just ripped off of what remains of the cradle assembly.

Which just happens to be exactly where the TEL bent, and where the initial flash was seen...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/07/2016 06:31 pm
What I don't see in these post-event images is that actual curved rubber-tipped rest, circled in red in the steadfast image I've again detailed below that we've been looking at for a rough pre-accident TEL illustration.

I'm fairly sure that those structures are still in place. The whole assembly is visible (https://i.imgur.com/BdezhQ7.jpg), albeit with poor lighting, in We Report Space's new picture album of SLC-40 (https://imgur.com/a/se8bK).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/07/2016 06:35 pm
So are the vents for the second stage lox tank visible in any of these photos?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: matthewkantar on 09/07/2016 06:39 pm
The TEL bent as a result of the support for the payload and fairing disappearing under them. The payload/fairing pivoted while bending the cradle until it fell. I believe all of the bending happened after the bulk of the rock confettied.

Enjoy, Matthew
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: StuffOfInterest on 09/07/2016 06:49 pm
The TEL bent as a result of the support for the payload and fairing disappearing under them. The payload/fairing pivoted while bending the cradle until it fell. I believe all of the bending happened after the bulk of the rock confettied.

Enjoy, Matthew

Also, if you look at the picture, that is where the connection is between two parts of the TEL tower.  Those bolts are going to be far weaker than the hard beams so it is only natural that it would have bent there when the arms were holding the entire payload with nothing underneath.  If those arms had been any stronger it probably would have taken the entire top of the TEL with it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 06:51 pm
The TEL bent as a result of the support for the payload and fairing disappearing under them. The payload/fairing pivoted while bending the cradle until it fell. I believe all of the bending happened after the bulk of the rock confettied.

Enjoy, Matthew

Which it is not designed to do.  The fairing actually fell on to the clamps
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 06:54 pm
What I don't see in these post-event images is that actual curved rubber-tipped rest, circled in red in the steadfast image I've again detailed below that we've been looking at for a rough pre-accident TEL illustration.

I'm fairly sure that those structures are still in place. The whole assembly is visible (https://i.imgur.com/BdezhQ7.jpg), albeit with poor lighting, in We Report Space's new picture album of SLC-40 (https://imgur.com/a/se8bK).

Yes, those are the pictures I have been looking at.  Because there seems to be a general reluctance to post any of them, I haven't been able to actually post a reference to what I'm seeing.

It actually is hard to tell if this is a perspective thing, or what.  I can see the near end of the cradle rest I've been discussing, and it does appear to still be attached to the TEL, again right at the plane where the TEL buckled.  There is then an angle bracket on the far, right side that has remained conformal to the rest of the TEL, i.e., has not collapsed along with the rest of the upper structure where the whole cradle assembly is located.  It appears that the entire cradle assembly is no longer centered in the TEL and that the far end of that cradle rest is on the other side of the angle bracket --which again, if it is a part of the cradle assembly, is not bent down like the rest of the assembly.

I can see what looks like about a third of the arc of the cradle rest going in from left, or near, end of that assembly, and then it stops.  I see no sign of the reciprocal cradle rest on the far, or right, side of the cradle rest.  It's either behind the angle bracket from this perspective (which would mean it's behind a piece of TEL structure that it was once in front of, from this angle) or it's entirely gone.

Again, while I find this suspicious, that point of the cradle rest is exactly where the initial flash seems to have been centered -- you would expect the maximum damage to the TEL at this point, and in fact, this is exactly where the TEL buckled, so yeah, it's arguably the point of max damage.  So, I'm not saying it must have caused the anomaly.  I'm just saying I don't think it's on the TEL anymore.

When/if we can post details from those images, I can show you what I mean...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/07/2016 06:56 pm


Why would they model any explosion?

Jim,
They wouldn't -  was just trying to say that if in some way they had tried to consider unlikely scenarios they still could have missed something. I'm not claiming any of this is likely, but whatever actually happened is going to turn out to be really weird.

 Can you tell us where the nitrogen in the RP1 tank goes as it fills? I would expect a purge line of some sort (to a reservoir? or completely down the TEL?) so no RP1 that got into the line would be accidentally released?

Edit: Just realized the COPV's could have preloaded Helium at 1 atmosphere.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 07:10 pm
Just a general comment -- while I don't discount the possibility that a COPV failure could have caused the anomaly, the whole feel of the discussion thus far is like a posse heading out to a hanging.  Some people have completely made up their minds, without any access to any data, that the COPVs must be at fault and so now SpaceX is screwed, since their design required the COPVs, used the way they are currently used.

I never liked posses.  They end up hanging innocent men a lot of times.

If a COPV is shown to have been the cause of the anomaly, fine, I will accept that.  But for now, I will go on record as saying that there are likely other possible causes, and it would not surprise me in the least if this had nothing whatsoever to do with the COPVs.

My own personal opinion is that there was some change to the fueling procedures, to try and support longer hold times after prop loading (as SpaceX announced they were going to be experimenting with on this flight), and the new fueling procedures led to an off-nominal situation that got out of control faster than anyone could react to.  But that's my own personal opinion, and it's based on the same lack of facts that we are all working with.  I only lean in this direction because, when this happened, I asked myself "What did they do differently this time than what they've done in the past?" and recalled the announced before-mentioned experimentation planned for managing the densified props over longer hold times.  You know, just tried to apply some logic to it, and came up with that question and answer.

Beyond that, I don't think it's appropriate to be convicting the COPVs before there is even a trial.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: EngineFan on 09/07/2016 07:20 pm
Absolutely. I can imagine the COPV's lawyer demanding they should be classed as innocent before proven guilty. ;)

I think because so much work was put into them after CRS-7, that would make them less likely to be the cause. Only thing that could catch us out on that is the COPV that failed during CRS-7 was due to a strut failing in flight.  Different scenario.

PS Long time listener, first time caller. Love this site and this thread shows why. What a community here!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/07/2016 07:26 pm
Kind of the same comment as above.

On one hand the focus on copv from previous failure.
The hydrostatic testing back at hawthorne
The static fire of stage 2 at mcgregor(without engine bell)
All the testing and the one thing not tested prior to this static fire.
GSE.

On the other hand the observations and suggestions of possible scenarios seems to me to point to the simplest and most probably culprit being a copv failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 07:27 pm
Anyone have a schematic of all the hydraulic lines on the strongback right up to the cradle? I've been trying to locate one....

If you're sniffing the same hound that I am, you don't need to trace the lines.  This looks like a self contained system.

The cradle uses a hydraulic piston to open & close on a hinge.
It's that black pipe with a silver piston sticking out of it.  You can see the extract and extend flow ports at each end of the black pipe.  The hoses feed into the pump below and towards the middle of the black pipe.

I "borrowed" these pics from other posters who were pointing out other things and highlighting those.

The first picture shows it extended.

The 2nd picture shows it extracted.

The 3rd picture shows it on the post-event tower, and you can see some of the hydraulic lines from the one on the other side.

I'd be very curious to know if the partially obscured one shows signs of a high-pressure leak.

Also, this looks a lot like a Bosh product, I'm not sure if they monitor the pressure in these.  They have a simple job, open or close.  They probably operate around 3,000 psi and there is no pre-charge or anything required.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 07:34 pm
Just a general comment -- while I don't discount the possibility that a COPV failure could have caused the anomaly, the whole feel of the discussion thus far is like a posse heading out to a hanging.  Some people have completely made up their minds, without any access to any data, that the COPVs must be at fault and so now SpaceX is screwed, since their design required the COPVs, used the way they are currently used.

I never liked posses.  They end up hanging innocent men a lot of times.

If a COPV is shown to have been the cause of the anomaly, fine, I will accept that.  But for now, I will go on record as saying that there are likely other possible causes, and it would not surprise me in the least if this had nothing whatsoever to do with the COPVs.

My own personal opinion is that there was some change to the fueling procedures, to try and support longer hold times after prop loading (as SpaceX announced they were going to be experimenting with on this flight), and the new fueling procedures led to an off-nominal situation that got out of control faster than anyone could react to.  But that's my own personal opinion, and it's based on the same lack of facts that we are all working with.  I only lean in this direction because, when this happened, I asked myself "What did they do differently this time than what they've done in the past?" and recalled the announced before-mentioned experimentation planned for managing the densified props over longer hold times.  You know, just tried to apply some logic to it, and came up with that question and answer.

Beyond that, I don't think it's appropriate to be convicting the COPVs before there is even a trial.

Oh come now, I'm not on that posse.  Right now I'm looking at the possibility that a hydraulic cylinder blew a gasket spewed a couple of gallons of hydraulic fluid in a second or so, thus creating a FAE.  The good news is that if I'm right, the post-event tower photos indicate that the evidence is hanging up there to be found, or not.

I jes don' hold to much with COPV failures.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 07:56 pm
Just a general comment -- while I don't discount the possibility that a COPV failure could have caused the anomaly, the whole feel of the discussion thus far is like a posse heading out to a hanging.  Some people have completely made up their minds, without any access to any data, that the COPVs must be at fault and so now SpaceX is screwed, since their design required the COPVs, used the way they are currently used.

I never liked posses.  They end up hanging innocent men a lot of times.

If a COPV is shown to have been the cause of the anomaly, fine, I will accept that.  But for now, I will go on record as saying that there are likely other possible causes, and it would not surprise me in the least if this had nothing whatsoever to do with the COPVs.

My own personal opinion is that there was some change to the fueling procedures, to try and support longer hold times after prop loading (as SpaceX announced they were going to be experimenting with on this flight), and the new fueling procedures led to an off-nominal situation that got out of control faster than anyone could react to.  But that's my own personal opinion, and it's based on the same lack of facts that we are all working with.  I only lean in this direction because, when this happened, I asked myself "What did they do differently this time than what they've done in the past?" and recalled the announced before-mentioned experimentation planned for managing the densified props over longer hold times.  You know, just tried to apply some logic to it, and came up with that question and answer.

Beyond that, I don't think it's appropriate to be convicting the COPVs before there is even a trial.

Oh come now, I'm not on that posse.  Right now I'm looking at the possibility that a hydraulic cylinder blew a gasket spewed a couple of gallons of hydraulic fluid in a second or so, thus creating a FAE.  The good news is that if I'm right, the post-event tower photos indicate that the evidence is hanging up there to be found, or not.

I jes don' hold to much with COPV failures.

Before you get too tightly wed to your theory, please remember two things: #1) we don't know what SpaceX uses for hydraulic fluid in the T/E and cradle mechs; #2) there are a number of well-understood hydraulic fluids in common aerospace usage that are not flammable.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/07/2016 07:58 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/07/2016 08:03 pm
I can attest to the mess ruptured hydraulic lines make. When the hoses on my tractor get around 3 y.o., one of them gets a pinhole and spews like crazy. I know it's time to just replace them all. I wonder whether they were changing these hoses on a regular basis. If so, how long between changes? Compared to LOV/LOPayload and destruction of the pad, it's a pretty inexpensive piece of preventative maintenance.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 08:04 pm

Before you get too tightly wed to your theory, please remember two things: #1) we don't know what SpaceX uses for hydraulic fluid in the T/E and cradle mechs; #2) there are a number of well-understood hydraulic fluids in common aerospace usage that are not flammable.

Well, I was going to put my first born child down as collateral on the bet, but you've dissuaded me.  :)

Both of your points are good ones.

If it's not the hydraulics, I'm pretty much out of ideas as to where to look for the initiating event.  Maybe I should take off my tin foil hat?

Does that cylinder look heavily corroded to you?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/07/2016 08:07 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.

It is a good practice of deductive logic. No one is claiming without doubt to have found a definitive solution, but it will be interesting to see how close this group is to the conclusion SpaceX draws. I also would not be surprised if they happen to be monitoring what's being said here, just for the sake of comparison.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Fan Boi on 09/07/2016 08:08 pm
To me the worst case scenario would be that a few months go by and they still don't know what the failure was. As long as they are able to determine the root cause and correct it, great! There is a reason the term "It isn't rocket science" is used to describe easy things, because rocket science isn't. They will find the root cause and move on, they are still young and still learning. Don't forget that there were no injuries or fatalities, hardware can be replaced. I stand behind them as much as I ever have.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/07/2016 08:09 pm
Hey monitoring a bunch of space nuts might give you an idea you would not normally think of. You know they are too deeply buried and we might think out of the box. (Waaay out of the box).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/07/2016 08:11 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.
Reddit user em-power (supposedly ex-SpaceX) says, that the investigation determined that the initial anomaly came from outside the vehicle.

Gesendet von meinem SM-T800 mit Tapatalk

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John Alan on 09/07/2016 08:13 pm

Before you get too tightly wed to your theory, please remember two things: #1) we don't know what SpaceX uses for hydraulic fluid in the T/E and cradle mechs; #2) there are a number of well-understood hydraulic fluids in common aerospace usage that are not flammable.

Well, I was going to put my first born child down as collateral on the bet, but you've dissuaded me.  :)

Both of your points are good ones.

If it's not the hydraulics, I'm pretty much out of ideas as to where to look for the initiating event.  Maybe I should take off my tin foil hat?

Does that cylinder look heavily corroded to you?

No... looks serviceable and I remind all that it was used to CLOSE the cradle before the rocket was stood up.
I'm assuming they looked for obvious leaks during the closing operation to verify ready to be used...

I took my Tin foil hat off this morning and decided not worth the struggle...  :P
It is whatever it is... (I still say He fitting broke near wall inside throwing chunks)...
Will stand down and wait for SpaceX to say what they find... THEN go from there...  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 08:17 pm

Oh come now, I'm not on that posse.  Right now I'm looking at the possibility that a hydraulic cylinder blew a gasket spewed a couple of gallons of hydraulic fluid in a second or so, thus creating a FAE.  The good news is that if I'm right, the post-event tower photos indicate that the evidence is hanging up there to be found, or not.

The hydraulic cylinder looks pretty basic, appears to be an unbalanced cylinder in that the rod doesn't come out of the back of it when it's retracted.

To operate it, it needs pressure. You feed hydraulic fluid into one side, it pushes the piston along and that pushes oil out of the other side.

If it isn't being operated, the pressure in it is very low - so it won't leak fluid.

Similarly the pipework won't hold any pressure unless the system is being operated.

The only pressure in the system will be - at least - beyond whatever valves operate that ram.

Given that was 8 minutes before the hot fire, the hydraulic system shouldn't have been in use, so there wouldn't have been pressure in the system - so there's not much chance of leaks; and even if there was, the pressure wouldn't be there to create a mist.


(For the record, I wouldn't expect a gasket to fail and cause that sort of issue - I'd suspect one of the joints on the pipework, probably where it's crimped to go into the fitting on the cylinder. Under use, that really would give you a very fine spray of hydraulic oil.)

(And yes, the cylinder is corroded - but it's mostly paint damage, unsurprising given the environment it exists in).



Addendum: *IF* those claw hydraulic cylinders are operated from a remote central pressure system (which presumably also operates the strongback retract); and *IF* that system is routed up the strongback; and *IF* the solenoid valves for the claw cylinders are near them; and *IF* the system is left idle and then pressurised about 8 minutes before hot fire; and *IF* there was a leak 'downstream' of the relevant solenoid; and *IF* that leak was somewhere around the common bulkhead; and *IF* the hydraulic fluid was inflammable - than all you'd need would be an ignition source and you'd have seen exactly what we did see.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 08:17 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.

Here's why I don't feel desperation.

There's some photo evidence to indicate that the initial event included a fireball that extended beyond the tower to the right, at least 15 feet, towards the camera, at least 20 feet, and not quite to the edge of the F9, < 15 feet.  The center of that cylinder is outside of the body of the F9.  If the center of that cylinder were inside the F9, then I'd blame the rocket, but it isn't.

So, absent official data, my question becomes, how do you create an explosion that starts outside of the body of the rocket?

Or is that desperation? :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/07/2016 08:26 pm
So here is a new one.

What if the rubber pads of the clamps (if they are indeed made of rubber or similar flamable material), became brittle in the cold, with the rubber forming crevasses that became drenched in liquid oxygen (e.g. condensed from air, as it is in contact with the cold wall of the oxygen tank) and then found an ignition source.

It would provide the basic components needed for an explosion: a fuel with a large surface area in intimate contact with an oxidizer. As a matter of fact, you could build a hybrid rocket motor using nothing but LOX and rubber as fuel. (Edit: It would also form a solid explosive, giving it the necessary oomph to penetrate the tank walls, unlike a gas explosion.)

This begs the question, why it never happened before.

One way is chance - it just happened to be the first time an ignition source was around. More plausible would be a new procedure to have longer retention times of the subcooled LOX on the pad, that some people mentioned. It would probably require lower temperatures than before, making condensation of oxygen on the outer tank surface more likely than before.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 08:33 pm
So, absent official data, my question becomes, how do you create an explosion that starts outside of the body of the rocket?

You have a rocket venting oxygen to create an oxygen-rich environment.

You introduce a fuel into it (which may be part of the structure of the vehicle or the erector, but you'd hope that whoever built them used materials that would resist catching fire too easily).

You introduce them to an ignition source. Boom.


Potentially there may have been an issue with more oxygen than before being vented, which could make fuel out of something that you mightn't have considered to be fuel - but SpaceX really must have thought about that one: rocket scientists know full well the horrific risks of oxygen-rich environments.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 08:35 pm


Addendum: *IF* those claw hydraulic cylinders are operated from a remote central pressure system (which presumably also operates the strongback retract); and *IF* that system is routed up the strongback; and *IF* the solenoid valves for the claw cylinders are near them; and *IF* the system is left idle and then pressurised about 8 minutes before hot fire; and *IF* there was a leak 'downstream' of the relevant solenoid; and *IF* that leak was somewhere around the common bulkhead; and *IF* the hydraulic fluid was inflammable - than all you'd need would be an ignition source and you'd have seen exactly what we did see.

I counted 7 IFs.  Let's go to Reddit and claim case closed.

I don't think the hydraulics come from a remote pressure system.  Usually there's a small reservoir near the pump and the pump looks like it's just below the main cylinder.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/07/2016 08:37 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.
Reddit user em-power (supposedly ex-SpaceX) says, that the investigation determined that the initial anomaly came from outside the vehicle.

The exact quote,

Link.... (https://www.reddit.com/r/spacex/comments/50rr9v/falcon_9_amos6_static_fire_anomaly_faq_summary/d7ci0b9)

Quote
em-power ex-SpaceX 22 points 14 hours ago

take this with a grain of salt, but i just spoke to one of the current spacex employees and according to him, the 'explosion' did originate from outside the rocket. they dont know yet exactly what caused it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 08:40 pm
So here is a new one.

What if the rubber pads of the clamps (if they are indeed made of rubber or similar flamable material), became brittle in the cold, with the rubber forming crevasses that became drenched in liquid oxygen (e.g. condensed from air, as it is in contact with the cold wall of the oxygen tank) and then found an ignition source.


Liquid oxygen is not going to form on the outside of the tank for two reasons

a.  The temperature differential from inside (going from aluminum through ice) is going to be below liquid oxygen formation temperature.  The temp difference between LOX boiling and supercooled is less than 25 degree C

B.  And if there was a risk of LOX forming, then they would have added insulation.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/07/2016 08:46 pm
So here is a new one.

What if the rubber pads of the clamps (if they are indeed made of rubber or similar flamable material), became brittle in the cold, with the rubber forming crevasses that became drenched in liquid oxygen (e.g. condensed from air, as it is in contact with the cold wall of the oxygen tank) and then found an ignition source.


Liquid oxygen is not going to form on the outside of the tank for two reasons

a.  The temperature differential from inside (going from aluminum through ice) is going to be below liquid oxygen formation temperature.  The temp difference between LOX boiling and supercooled is less than 25 degree C

B.  And if there was a risk of LOX forming, then they would have added insulation.

There would be no ice layer where the clamps are, so there could be "wet patches". But yes, it severely limits the amount of oxygen that could condensate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/07/2016 09:03 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.
Reddit user em-power (supposedly ex-SpaceX) says, that the investigation determined that the initial anomaly came from outside the vehicle.

The exact quote,

Link.... (https://www.reddit.com/r/spacex/comments/50rr9v/falcon_9_amos6_static_fire_anomaly_faq_summary/d7ci0b9)

Quote
em-power ex-SpaceX 22 points 14 hours ago

take this with a grain of salt, but i just spoke to one of the current spacex employees and according to him, the 'explosion' did originate from outside the rocket. they dont know yet exactly what caused it.
FWIW heard close to this, firsthand, as well. Be patient.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 09:08 pm
So here is a new one.

What if the rubber pads of the clamps (if they are indeed made of rubber or similar flamable material), became brittle in the cold, with the rubber forming crevasses that became drenched in liquid oxygen (e.g. condensed from air, as it is in contact with the cold wall of the oxygen tank) and then found an ignition source.


Liquid oxygen is not going to form on the outside of the tank for two reasons

a.  The temperature differential from inside (going from aluminum through ice) is going to be below liquid oxygen formation temperature.  The temp difference between LOX boiling and supercooled is less than 25 degree C

B.  And if there was a risk of LOX forming, then they would have added insulation.

There would be no ice layer where the clamps are, so there could be "wet patches". But yes, it severely limits the amount of oxygen that could condensate.

No.  The rubber pads would be insulators and nothing condenses
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/07/2016 09:09 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.
I agree and it bothers me. Spacex and this vehicle are things I care very much about and it's because of that that it bothers me. If you really are a "falcon hugger" let's call it , you should not be trying to find a failure mode that absolves the vehicle, you should be open to all possible failure modes particularly the most likely ones based on available information.


That being said will say this. I want to point out COPV is still only one possible explanation and I am finding as other users have found, some substantial issues with that as a failure mode.


The more I think about this the more the speed of this ignition bothers me. It happened extremely fast. I do think that an external fire can be ruled out but an external igniton source that somehow ignited fuel and LOX at or inside the tank side connections cannot be[/i].

I am also still looking for any available information regarding the placement of FTS charges on the second stage if any. Even though the system was not armed this does not mean it could not have failed in some way or received an eletrical discharge sufficient to detonate as the result of a failure.

I still think the problem was internal to the second stage lox tank but I am not as sure anymore as to the source of it and I really want to try and see where those charges are placed in relation to where we saw the first emergence of burning material.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 09:12 pm
I counted 7 IFs.  Let's go to Reddit and claim case closed.

I don't think the hydraulics come from a remote pressure system.  Usually there's a small reservoir near the pump and the pump looks like it's just below the main cylinder.

Not sure how good you are on hydraulics?

Yes, you need a pump to generate pressure.

The reservoir is generally a dump for hydraulic fluid at no pressure. The pump creates pressure, the fluid under pressure gets used for moving rams / motors and then the fluid is returned at low pressure to the reservoir, from where the pump picks it up, pressurises it and sends it round the system again.

If the pump is running and there's no demand for the fluid, pressure relief valves will dump the fluid directly back into the reservoir, where the pressure is lost.

In that sort of system, supply is under high pressure, return is effectively at no pressure.


So in this case, how do you generate hydraulic pressure locally?

Potentially a gas cylinder with a diaphragm across to the hydraulic fluid, but I'm not seeing that you could maintain that pressure at a steady level. Also, if it runs out of pressure, you need to lower the erector to recharge the pressure (unless it comes in from elsewhere, in which case just bring the hydraulic fluid in under pressure).

Put a diesel engine on the erector to drive a pump? No on several levels.

Put an electo-hydraulic pump on the erector? Possible, but there's an ignition risk that you'd prefer to avoid.

There has to be a pretty decent hydraulic system already in place to operate the cylinders that retract the erector, so just tap into that with a couple of big hoses that run up the structure. Pretty simple. I'd guess at a diesel motor in a bunker 50-100 yards away?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 09:13 pm
Yes the FTS is exonerated.  It is impossible for a stray signal to activate it.  In the SAFE mode, there is a physical block between the initiator and charge
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 09:15 pm
I counted 7 IFs.  Let's go to Reddit and claim case closed.

I don't think the hydraulics come from a remote pressure system.  Usually there's a small reservoir near the pump and the pump looks like it's just below the main cylinder.

Not sure how good you are on hydraulics?

Yes, you need a pump to generate pressure.

The reservoir is generally a dump for hydraulic fluid at no pressure. The pump creates pressure, the fluid under pressure gets used for moving rams / motors and then the fluid is returned at low pressure to the reservoir, from where the pump picks it up, pressurises it and sends it round the system again.

If the pump is running and there's no demand for the fluid, pressure relief valves will dump the fluid directly back into the reservoir, where the pressure is lost.

In that sort of system, supply is under high pressure, return is effectively at no pressure.


So in this case, how do you generate hydraulic pressure locally?

Potentially a gas cylinder with a diaphragm across to the hydraulic fluid, but I'm not seeing that you could maintain that pressure at a steady level. Also, if it runs out of pressure, you need to lower the erector to recharge the pressure (unless it comes in from elsewhere, in which case just bring the hydraulic fluid in under pressure).

Put a diesel engine on the erector to drive a pump? No on several levels.

Put an electo-hydraulic pump on the erector? Possible, but there's an ignition risk that you'd prefer to avoid.

There has to be a pretty decent hydraulic system already in place to operate the cylinders that retract the erector, so just tap into that with a couple of big hoses that run up the structure. Pretty simple. I'd guess at a diesel motor in a bunker 50-100 yards away?

Why hydraulic and not gas actuated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rerickson on 09/07/2016 09:22 pm
Basic question: Why does the F9 vent GOX so close to the vehicle and tower?
As I recall, the Shuttle ET vented GOX through a "beanie cap" into a pipe leading meters away. Granted that the ET was covered in foam (and a vent pipe must be free of stray organics!), but high O2 levels seem a risk.

P.S. Any notion of what the recent changes might have been, to allow longer holds with supercooled LOX?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 09:24 pm
Basic question: Why does the F9 vent GOX so close to the vehicle and tower?
As I recall, the Shuttle ET vented GOX through a "beanie cap" into a pipe leading meters away. Granted that the ET was covered in foam (and a vent pipe must be free of stray organics!), but high O2 levels seem a risk.

P.S. Any notion of what the recent changes might have been, to allow longer holds with supercooled LOX?

Because shuttle was the exception  and not the rule.   It is not needed. See every other launch vehicle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 09:26 pm
I counted 7 IFs.  Let's go to Reddit and claim case closed.

I don't think the hydraulics come from a remote pressure system.  Usually there's a small reservoir near the pump and the pump looks like it's just below the main cylinder.

Not sure how good you are on hydraulics?

Yes, you need a pump to generate pressure.

The reservoir is generally a dump for hydraulic fluid at no pressure. The pump creates pressure, the fluid under pressure gets used for moving rams / motors and then the fluid is returned at low pressure to the reservoir, from where the pump picks it up, pressurises it and sends it round the system again.

If the pump is running and there's no demand for the fluid, pressure relief valves will dump the fluid directly back into the reservoir, where the pressure is lost.

In that sort of system, supply is under high pressure, return is effectively at no pressure.


So in this case, how do you generate hydraulic pressure locally?

Potentially a gas cylinder with a diaphragm across to the hydraulic fluid, but I'm not seeing that you could maintain that pressure at a steady level. Also, if it runs out of pressure, you need to lower the erector to recharge the pressure (unless it comes in from elsewhere, in which case just bring the hydraulic fluid in under pressure).

Put a diesel engine on the erector to drive a pump? No on several levels.

Put an electo-hydraulic pump on the erector? Possible, but there's an ignition risk that you'd prefer to avoid.

There has to be a pretty decent hydraulic system already in place to operate the cylinders that retract the erector, so just tap into that with a couple of big hoses that run up the structure. Pretty simple. I'd guess at a diesel motor in a bunker 50-100 yards away?

Well as to how good I am, I own a tractor and a skid steer, both use hydraulics and so far I haven't severely injured myself.  I have been covered with hydraulic fluid...  That doesn't make me an expert, more of a practitioner in need of a shower.

on the attached photo.

1.  top left circle, extend supply connection
2.  top right circle, contract supply connection
3.  Middle circle, a box which is at least a valving system, and I inferred possibly a pump and reservoir out of view.
4.  However, what looks like a pipe (elongated blob) that may feed in and could be the feed from a pressure supply.  It does appear to come to a rude stop, or maybe feeds into another supply.

Hmm, if you are right about a remote pressure system, then I'll have to put my tinfoil hat back on.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/07/2016 09:27 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.
Reddit user em-power (supposedly ex-SpaceX) says, that the investigation determined that the initial anomaly came from outside the vehicle.

The exact quote,

Link.... (https://www.reddit.com/r/spacex/comments/50rr9v/falcon_9_amos6_static_fire_anomaly_faq_summary/d7ci0b9)

Quote
em-power ex-SpaceX 22 points 14 hours ago

take this with a grain of salt, but i just spoke to one of the current spacex employees and according to him, the 'explosion' did originate from outside the rocket. they dont know yet exactly what caused it.
FWIW heard close to this, firsthand, as well. Be patient.

Some people are born patient, some achieve patience, and some have patience thrust upon them.

Back to normal speculative mode:

Assuming the initial explosion was indeed outside, and assuming SpaceX still doesn't know what it was:

What internally-originated fault can fit those two speculative data points?

Can there be something as simple as a pin-hole RP1 leak from the rocket?  (assuming that pressurized RP1 was no longer present in the T/E)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 09:28 pm
Anyone have a schematic of all the hydraulic lines on the strongback right up to the cradle? I've been trying to locate one....

If you're sniffing the same hound that I am, you don't need to trace the lines.  This looks like a self contained system.

The cradle uses a hydraulic piston to open & close on a hinge.
It's that black pipe with a silver piston sticking out of it.  You can see the extract and extend flow ports at each end of the black pipe.  The hoses feed into the pump below and towards the middle of the black pipe.

I "borrowed" these pics from other posters who were pointing out other things and highlighting those.

The first picture shows it extended.

The 2nd picture shows it extracted.

The 3rd picture shows it on the post-event tower, and you can see some of the hydraulic lines from the one on the other side.

I'd be very curious to know if the partially obscured one shows signs of a high-pressure leak.

Also, this looks a lot like a Bosh product, I'm not sure if they monitor the pressure in these.  They have a simple job, open or close.  They probably operate around 3,000 psi and there is no pre-charge or anything required.
Thanks, I'm good with those pics. I was more specifically look for locations of hydraulic line couplers areas where one could fail (I agree about 3,000psi as well).
Just to confirm my theory, I went back to the video posted in the update thread and found my area of interest on the TEL continued to burn on its own well after all other fire had gone out as if under small pressure fed source...(I know it could have been damaged after as well)
https://www.youtube.com/watch?v=Yk4huQ3Iyhg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/07/2016 09:28 pm
Why hydraulic and not gas actuated.

I've not got any experience of gas-activated cylinders, so by default I look at something like this from a hydraulic point of view (something I spec up a couple of times most weeks).

Plus, the question assumed hydraulic actuation.

With a brief bit of thought, given the opportunity I'd prefer to fit a gas-actuated system in an installation like this. Mostly to avoid the potential of hydraulic fluid spraying around.

If this system is gas-actuated, that closes off a potential cause of failure.

Is this part of the system gas-actuated?

(If so, presumably the cylinders which raise and lower the erector are a conventional hydraulic system?)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 09:30 pm


Why hydraulic and not gas actuated.

Taking a queue from an earlier conversation.  I asked, "what's here" and someone said something like "Jim, it's just AC ducting and hydraulics isn't it."  You replied, "Yes".

So I went off on a wild goose chasing down how hydraulics makes things go boom.

I assume high-pressure nitrogen would be preferred...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 09:34 pm
Anyone have a schematic of all the hydraulic lines on the strongback right up to the cradle? I've been trying to locate one....

If you're sniffing the same hound that I am, you don't need to trace the lines.  This looks like a self contained system.

The cradle uses a hydraulic piston to open & close on a hinge.
It's that black pipe with a silver piston sticking out of it.  You can see the extract and extend flow ports at each end of the black pipe.  The hoses feed into the pump below and towards the middle of the black pipe.

I "borrowed" these pics from other posters who were pointing out other things and highlighting those.

The first picture shows it extended.

The 2nd picture shows it extracted.

The 3rd picture shows it on the post-event tower, and you can see some of the hydraulic lines from the one on the other side.

I'd be very curious to know if the partially obscured one shows signs of a high-pressure leak.

Also, this looks a lot like a Bosh product, I'm not sure if they monitor the pressure in these.  They have a simple job, open or close.  They probably operate around 3,000 psi and there is no pre-charge or anything required.
Thanks, I'm good with those pics. I was more specifically look for locations of hydraulic line couplers areas where one could fail (I agree about 3,000psi as well).
Just to confirm my theory, I went back to the video posted in the update thread and found my area of interest on the TEL continued to burn on its own well after all other fire had gone out as if under small pressure fed source...(I know it could have been damaged after as well)
https://www.youtube.com/watch?v=Yk4huQ3Iyhg

That would likely be the prop umbilicals, that contribute to burn like after every launch
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/07/2016 09:36 pm
Anyone have a schematic of all the hydraulic lines on the strongback right up to the cradle? I've been trying to locate one....

If you're sniffing the same hound that I am, you don't need to trace the lines.  This looks like a self contained system.

The cradle uses a hydraulic piston to open & close on a hinge.
It's that black pipe with a silver piston sticking out of it.  You can see the extract and extend flow ports at each end of the black pipe.  The hoses feed into the pump below and towards the middle of the black pipe.

I "borrowed" these pics from other posters who were pointing out other things and highlighting those.

The first picture shows it extended.

The 2nd picture shows it extracted.

The 3rd picture shows it on the post-event tower, and you can see some of the hydraulic lines from the one on the other side.

I'd be very curious to know if the partially obscured one shows signs of a high-pressure leak.

Also, this looks a lot like a Bosh product, I'm not sure if they monitor the pressure in these.  They have a simple job, open or close.  They probably operate around 3,000 psi and there is no pre-charge or anything required.
Thanks, I'm good with those pics. I was more specifically look for locations of hydraulic line couplers areas where one could fail (I agree about 3,000psi as well).
Just to confirm my theory, I went back to the video posted in the update thread and found my area of interest on the TEL continued to burn on its own well after all other fire had gone out as if under small pressure fed source...(I know it could have been damaged after as well)


That would likely be the prop umbilicals, that contribute to burn like after every launch
Thanks Jim for confirming my second thought...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/07/2016 09:58 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.

Here's why I don't feel desperation.

There's some photo evidence to indicate that the initial event included a fireball that extended beyond the tower to the right, at least 15 feet, towards the camera, at least 20 feet, and not quite to the edge of the F9, < 15 feet.  The center of that cylinder is outside of the body of the F9.  If the center of that cylinder were inside the F9, then I'd blame the rocket, but it isn't.

So, absent official data, my question becomes, how do you create an explosion that starts outside of the body of the rocket?

Or is that desperation? :)

My issue is that the source of ignition being outside the rocket does not mean the rocket itself is not at fault. There's a lot of stuff that indicates the source is outside, so I'm ok with that. The question I wonder is whether it is a leak in the rocket or the gse
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 10:09 pm

With a brief bit of thought, given the opportunity I'd prefer to fit a gas-actuated system in an installation like this. Mostly to avoid the potential of hydraulic fluid spraying around.

If this system is gas-actuated, that closes off a potential cause of failure.

Is this part of the system gas-actuated?


Hmmm,  Normally when someone suggests a stupid idea, someone who knows better comes back and says, "no it's not" or, "nothing there" or a gentle clarification that says "that's a nice idea but not in this case."

I think we're all in agreement that there shouldn't be hydraulic fluid running those pistons.

However, until I see a definitive "It's not", I'm going to keep that at the top of my irrationally derived suspect list.  :)

When you "spec" systems from time to time, in your catalog is there a part that looks like these?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/07/2016 10:09 pm
So do they replace umbilicals after every launch?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Karloss12 on 09/07/2016 10:27 pm
I recently witnessed a coleague with an Aluminium cup filled with liquid Nitrogen at -196°C.  A liquid quickly condensed on the outside surface of the cup and dripped onto the table.  This liquid was LOX condensed from the surrounding air with a condensation temperature of -186°C.  It was not LIN, as the surface was not cold enough to condense Notrogen at -196°C.

On the F9, if air is able to get to the surface of the 2nd stage LOX tank, then the super cooled temperature of the LOX in the tank would cause air (O2 and N2) to condence on the outside surface.  LIN would vaporise allot easier with a lower vaporising temperature, leaving a high concentration of LOX/GOX.

Is the LOX tank sealed in air tight insulation?  Can air get access to the surface of the aluminium surface of the LOX tank?

A high oxygen environment is one of three incredients for elevated risk of ignition.

I can't even guess what the fuel or the ignition method was.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 10:27 pm
There seems to be an awful lot of desperation for it to be anything but the rocket. It's one thing trying to figure out where the explosion occurred, since we can try to work on that with the information available, but another to deduce what caused the overall problem.

Here's why I don't feel desperation.

There's some photo evidence to indicate that the initial event included a fireball that extended beyond the tower to the right, at least 15 feet, towards the camera, at least 20 feet, and not quite to the edge of the F9, < 15 feet.  The center of that cylinder is outside of the body of the F9.  If the center of that cylinder were inside the F9, then I'd blame the rocket, but it isn't.

So, absent official data, my question becomes, how do you create an explosion that starts outside of the body of the rocket?

Or is that desperation? :)

My issue is that the source of ignition being outside the rocket does not mean the rocket itself is not at fault. There's a lot of stuff that indicates the source is outside, so I'm ok with that. The question I wonder is whether it is a leak in the rocket or the gse

The problem I personally have with a leak in the rocket is that, to me, this looks a lot like a fuel air explosion.  For the rocket to be the source, there would have to be an RP-1 leak which:
1.  spews about 3 gallons of fuel
2.  which turns into a vapor very fast (prevailing winds to the left)
3.  fills a volume of about 300 cubic feet and then finds a lit match.

Cold RP-1 is going to require a lot of heat to turn it into vapor, which suggests to me that a leak from the F9 tank is either massive (visible), or small, which puts most of the vapor to the left, away from where the center of the explosion seems to be.

If it were a fuel air explosion, granted that the wind is blowing from the right to left, the source of the fuel has to be to the right of the center of that cylinder, how much depends on how fast the fuel is released.  If it's something like RP-1 or hydraulic fluid, it can be above the centerline, again depending upon how fast the release is.

Others have stated that the RP-1 feed lines on the GSE are below the most likely center line of the explosion.

Others have stated that there shouldn't be hydraulic fluid in the system best placed to leak it, if it were there.

Somehow, we have to come up with the equivalent of 50 to 100 pounds of TNT exploding in a most unlikely place.

The rocket could absolutely be at fault, but if so, it's not clear how.  Of course, nothing else is obviously at fault either.  Perhaps we could simply declare that it didn't happen?  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: virnin on 09/07/2016 10:48 pm
I recently witnessed a coleague with an Aluminium cup filled with liquid Nitrogen at -196°C.  A liquid quickly condensed on the outside surface of the cup and dripped onto the table.  This liquid was LOX condensed from the surrounding air with a condensation temperature of -186°C.  It was not LIN, as the surface was not cold enough to condense Notrogen at -196°C.

On the F9, if air is able to get to the surface of the 2nd stage LOX tank, then the super cooled temperature of the LOX in the tank would cause air (O2 and N2) to condence on the outside surface.  LIN would vaporise allot easier with a lower vaporising temperature, leaving a high concentration of LOX/GOX.

Is the LOX tank sealed in air tight insulation?  Can air get access to the surface of the aluminium surface of the LOX tank?

A high oxygen environment is one of three incredients for elevated risk of ignition.

I can't even guess what the fuel or the ignition method was.

As pointed out much earlier in this thread, the ambient air was high in humidity.  As the LOX tank started to be filled and cooled down, the first thing to condense would be water vapor, forming frost then ice.  That ice would continue to thicken, completely insulating the O2/N2 in the air from the tank wall long before the Li/Al completely chilled to cryogenic temperatures.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 10:56 pm
I recently witnessed a coleague with an Aluminium cup filled with liquid Nitrogen at -196°C.  A liquid quickly condensed on the outside surface of the cup and dripped onto the table.  This liquid was LOX condensed from the surrounding air with a condensation temperature of -186°C.  It was not LIN, as the surface was not cold enough to condense Notrogen at -196°C.

On the F9, if air is able to get to the surface of the 2nd stage LOX tank, then the super cooled temperature of the LOX in the tank would cause air (O2 and N2) to condence on the outside surface.  LIN would vaporise allot easier with a lower vaporising temperature, leaving a high concentration of LOX/GOX.

Is the LOX tank sealed in air tight insulation?  Can air get access to the surface of the aluminium surface of the LOX tank?

A high oxygen environment is one of three ingredients for elevated risk of ignition.

I can't even guess what the fuel or the ignition method was.

As pointed out much earlier in this thread, the ambient air was high in humidity.  As the LOX tank started to be filled and cooled down, the first thing to condense would be water vapor, forming frost then ice.  That ice would continue to thicken, completely insulating the O2/N2 in the air from the tank wall long before the Li/Al completely chilled to cryogenic temperatures.

My first thought upon reading this was "Yes, unless something bumps against the skin of the LOX tank and knocks off a chunk of the ice layer after the tank skin has completely chilled."

My next thought was "Like that cradle piece that supports stage 2 under the common bulkhead when the rocket is horizontal."

That was followed by "It was a windy day.  I wonder how much the rocket and TEL move in wind gusts -- enough to knock that cradle against the skin of the stage hard enough to knock off some ice?"

I decided that documenting that short train of thought was a better way to explain this than trying to form it into something more formatted... :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 11:13 pm
I looked at difference subtraction frames sampling .5 second intervals prior to the event.  I saw a lot of birds and thermal optical effects but no indications of shedding ice and no changes in venting locations.

Doesn't mean it didn't happen... Just that the only public visual record doesn't support your idea.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/07/2016 11:15 pm
...
Assuming the initial explosion was indeed outside, and assuming SpaceX still doesn't know what it was:

What internally-originated fault can fit those two speculative data points?

Can there be something as simple as a pin-hole RP1 leak from the rocket?  (assuming that pressurized RP1 was no longer present in the T/E)

There is no pressurized RP1 in the rocket at T-8 minutes. The RP1 tanks aren't pressed until under 1 minute.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/07/2016 11:20 pm
...
Assuming the initial explosion was indeed outside, and assuming SpaceX still doesn't know what it was:

What internally-originated fault can fit those two speculative data points?

Can there be something as simple as a pin-hole RP1 leak from the rocket?  (assuming that pressurized RP1 was no longer present in the T/E)

There is no pressurized RP1 in the rocket at T-8 minutes. The RP1 tanks aren't pressed until under 1 minute.

If RP-1 is loading, though, the pressure in the fill umbilical, and particularly at the fill umbilical interface, has got to be high enough that a pinhole leak would produce a spray of material.  Of course, the closest prop umbilicals were down 10 feet from the original flash point, near the base of stage 2.  So, any FAE scenario would almost have to explain how an RP-1 leak could cause a flash 10 feet above the leak.

Again, though, we know that LOX load was in process; am I right in thinking that LOX and RP-1 load simultaneously?  Was RP-1 being loaded at the time of the anomaly, or just LOX?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IainMcClatchie on 09/07/2016 11:21 pm
I think the rightward and slightly downward motion of the fairing is a significant find.  That's actually quite a bit of motion, maybe 0.6 meters in about 1 second, or 1.2 m/s^2 acceleration at the tip, about 20 meters above the site of the initial flash.

I think this is consistent with the right wall of stage 2 rupturing while the wall was under significant axial compression, not axial tension.

When the stage is at the correct pressure, the walls are under axial tension.  So it seems to me that while the payload is moving, the ullage is well below nominal pressure, and my guess is that it is in the kerosene ullage, not the LOX ullage, because the flash happens around the level of the kerosene ullage.  Note that I'm not suggesting the ullage is below atmospheric pressure, but rather that the pressure is too low to support the nearly 100 tonnes of payload and LOX above it.  Supporting that load requires around 93 kPa above ambient.

The fairing motion happens after the flash, so I think that during a fair bit of the initial flamey bits, the stage is below nominal pressure.  To me, that says it's not an internal pressure vessel failure, which would have caused overpressure and pushed the payload to the left after a right wall rupture.  To me that's a big deal because until I saw that video I was pretty sure it was a pressure vessel problem.

So now my favorite theory is that there was a problem in the cradle that holds stage 2, perhaps during erection or chilldown.  My guess is that stage 2 got stressed in a way it can't tolerate.  This stress caused a slight buckle in the skin that wasn't noticed but reduced it's ultimate tensile strength.  Pressurizing the stage caused a rupture at the previously-buckled point, at a point low enough that kerosene and not ullage gas under a nominal ullage pressure was ejected forcibly from the tank.  I don't know what the ignition source was, but it must have been immediately proximate to the kerosene jet.  The tearing aluminum-lithium metal might have done it.

I also had some thoughts about that cradle holding stage 2.  It's got a difficult job.  While the stage is horizontal it's not too bad, the cradle just balances the load between the upper and lower clamps.  But when the stage rotates to vertical, the cradle must react to horizontal wind loads without reacting to the shrinkage of the rocket when cooled.  So there is some bearing that lets the cradle go up and down, but that system has to support the weight of the portion of the strongback that is rising and falling with the upper stage.  Otherwise, that weight is going to go into the rocket, but it's off center, so it's going to produce a torque.  That torque is going to produce a strong force on the lower clamp in the direction from the strongback to the rocket.  That force would tend to buckle the skin of the rocket inwards.

Notice that it's not enough to have hydraulic rams controlling the extension of the strongback top.  You have to actuate these rams to relieve any axial shear force between the cradle and rocket.  So you need some kind of servo loop.  If the servo loop pauses you harm the rocket.  So the root cause here could be a momentary loss of hydraulic pressure to the strongback temperature compensating hydraulics during chilldown of any of the propellant tanks.

One final thing: a jet of kerosene heading towards the camera would be hard to see.  It could develop for a frame or two before you'd notice.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/07/2016 11:22 pm
So here is a new one.

What if the rubber pads of the clamps (if they are indeed made of rubber or similar flamable material), became brittle in the cold, with the rubber forming crevasses that became drenched in liquid oxygen (e.g. condensed from air, as it is in contact with the cold wall of the oxygen tank) and then found an ignition source.


Liquid oxygen is not going to form on the outside of the tank for two reasons

a.  The temperature differential from inside (going from aluminum through ice) is going to be below liquid oxygen formation temperature.  The temp difference between LOX boiling and supercooled is less than 25 degree C

B.  And if there was a risk of LOX forming, then they would have added insulation.

After another post here:

I recently witnessed a coleague with an Aluminium cup filled with liquid Nitrogen at -196°C.  A liquid quickly condensed on the outside surface of the cup and dripped onto the table.  This liquid was LOX condensed from the surrounding air with a condensation temperature of -186°C.  It was not LIN, as the surface was not cold enough to condense Notrogen at -196°C.

Now I do see a serious problem with Jims point A.

There simply is no ice layer on the tank to begin with and no other insulation we'd have heard of. It would take some time for the ice layer to form and the tank would be uninsulated in the meantime. Usually, that cannot possibly be a problem. The LOX is filled in at boiling temperature anyway and there is never any chance at all to condense oxygen from the air.

With subcooled oxygen in the tank, there is a short window of opportunity for oxygen to condense - prior to any ice layer forming on the tank and insulating it.

No offence, Jim. But given that you instinctively took the possibility off the table, makes this something that may have been missed by the SpaceX engineers, precisely because I know you are very experienced in those things.

And Karloss12 shows us that the process does indeed it happen on the walls of an aluminum container containing a liquid that is even slightly warmer than the subcooled oxygen in the Falcon 9 tanks - which elevates this a bit above the level of mere speculation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/07/2016 11:29 pm

Now I do see a serious problem with Jims point A.

There simply is no ice layer on the tank to begin with and no other insulation we'd have heard of. It would take some time for the ice layer to form and the tank would be uninsulated in the meantime. Usually, that cannot possibly be a problem. The LOX is filled in at boiling temperature anyway and there is never any chance at all to condense oxygen from the air.

With subcooled oxygen in the tank, there is a short window of opportunity for oxygen to condense - prior to any ice layer forming on the tank and insulating it.


The cup analogy is really  not applicable.  There is big difference in thermal mass.  Ice should be forming during the chill down.   But then again, the  loading time is less than 30 minutes

But also, I should have said:

And if there was a risk of LOX forming, then they SHOULD have added insulation.  My point is that they would have analyzed this.  When liquid air forms on the outside and drains away, it is putting more heat into the tank
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tp1024 on 09/07/2016 11:43 pm

Now I do see a serious problem with Jims point A.

There simply is no ice layer on the tank to begin with and no other insulation we'd have heard of. It would take some time for the ice layer to form and the tank would be uninsulated in the meantime. Usually, that cannot possibly be a problem. The LOX is filled in at boiling temperature anyway and there is never any chance at all to condense oxygen from the air.

With subcooled oxygen in the tank, there is a short window of opportunity for oxygen to condense - prior to any ice layer forming on the tank and insulating it.


The cup analogy is really  not applicable.  There is big difference in thermal mass.  Ice should be forming during the chill down.   But then again, the  loading time is less than 30 minutes

But also, I should have said:

And if there was a risk of LOX forming, then they SHOULD have added insulation.  My point is that they would have analyzed this.  When liquid air forms on the outside and drains away, it is putting more heat into the tank

It's a new process. They may have analyzed it, came to a conclusion and missed a set of variables. Unlike others, they don't have the benefit of more than half a century of experience in rocketry plus even more in steel etc. where non-subcooled-LOX has been used, where all the stupid mistakes have already been made a dozen times or more.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 11:47 pm

Notice that it's not enough to have hydraulic rams controlling the extension of the strongback top.  You have to actuate these rams to relieve any axial shear force between the cradle and rocket.  So you need some kind of servo loop.  If the servo loop pauses you harm the rocket.  So the root cause here could be a momentary loss of hydraulic pressure to the strongback temperature compensating hydraulics during chilldown of any of the propellant tanks.


In response to just one of your comments, quoted above.  You assert that the hydraulics (which may or may not contain hydraulic fluid, that may or may not be flammable), must be constantly activated to maintain vehicle stability prior to launch.

Three questions:

1.  Is he right that there should be an ongoing pre-launch adjustment?
2.  Is that actually done?
3.  Are the hydraulics fluid or gas?

IF his assumption is correct, that could change the assumption that the hydraulics are at low PSI.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AJW on 09/07/2016 11:52 pm
What would the consequences be if tanks of something other than GN2 were either delivered or incorrectly connected before the flush?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/07/2016 11:56 pm
Again, though, we know that LOX load was in process; am I right in thinking that LOX and RP-1 load simultaneously?  Was RP-1 being loaded at the time of the anomaly, or just LOX?

No, Stage 2 RP1 load is complete at or near T-minus 22 minutes.

http://spaceflight101.com/falcon-9-ft-countdown-timeline/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/07/2016 11:58 pm

One final thing: a jet of kerosene heading towards the camera would be hard to see.  It could develop for a frame or two before you'd notice.

IMHO, I'd much rather see an aerosol than a jet.  I can make an explosion with an aerosol, but a jet is a flame thrower.  Absent significant pressure in the RP-1 tank, and I mean something on the order of 3000 psi, you won't get an explosion in one frame.  You'd end up with a Zozobra event, crowd pleasing and slow. Much slower than indicated by the video.  Cracking the tank maybe doubles the psi.  You need 1 or 2 orders of magnitude above that to make it go boom in 16 milliseconds.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 12:04 am
What would the consequences be if tanks of something other than GN2 were either delivered or incorrectly connected before the flush?

Someone would get fired.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: atsf90east on 09/08/2016 12:05 am
Basic question: Why does the F9 vent GOX so close to the vehicle and tower?
As I recall, the Shuttle ET vented GOX through a "beanie cap" into a pipe leading meters away. Granted that the ET was covered in foam (and a vent pipe must be free of stray organics!), but high O2 levels seem a risk.

P.S. Any notion of what the recent changes might have been, to allow longer holds with supercooled LOX?
The reason NASA used the "beanie cap" was that NASA did not want any ice accumulating on the surface of the ET, and subsequently shedding during flight and damaging the HRSI insulation tiles on the belly of the orbiters.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Okie_Steve on 09/08/2016 12:16 am
I've been pondering a couple of very thoughtful posts about what' was new/different this time and all the "fun" that can result from loss of ullage pressure and dome inversion etc. Thermo and Gas dynamic were not my best two subject in school and in any event that was back before rocks were invented so I have a physics question/ thought experiment  for anyone more current in those areas. Presumably the first LOX loaded into the tank boils/vents immediately as it hits the ambient temperature tank and then chills down from there due to convection as the LOX continues to load. Would it be within the realm of possibility to get to a point where the GOX reached a uniform temperature that slowly dropped until it went through a phase change "all at once"? And if so, how fast could such an event propagate? The now you see it, not you don't nature of the this putative scenario reminds me a bit of cavitation which as I recall causes quite high forces because of the suddenness of the collapse.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ulm_atms on 09/08/2016 12:24 am
The only issue with the aluminum cup demo is that, more then likely, it was indoors.  Inside an air conditioned room, the amount of water in the air is MUCH, MUCH lower then outside Florida in the middle of the summer.

For the cup, ice would form much slower around the cup giving the air next to the cup longer to chill and pull the oxygen out.  Outside in the Florida day, it would start forming almost instantly because the amount of water in the air. 

Inside

72 degree air with a dewpoint of 45 degrees (usual temp of the AC coils so that is what the AC system usually drops the dewpoint to due to condensation on the coils) gives a humidity of 40% and a water total of ~150 g/Kg in the air.

Outside

86 degree (today's temp at the cape) with a dewpoint of 71 degrees gives a humidity of 61% but with a water total of 636 g/Kg in the air.

I just can't see much to any LOX forming before it's coated with enough ice to keep that from happening and even if some fell off, it would ice back up quick with all the water in the air.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/08/2016 12:34 am
Per the great reddit user __Rocket__
Quote
I went through all the frames one by one (in the 60 fps video). Here's a quick list of what I found:

•   I reconstructed the origin path of 3 individual pieces flying around and they appear to have come from the 
        same 1mx1m area, about 1-2 meter below the common bulkhead (about 1-2 meters below the origin of the
        lens flare, visible in the second frame)
•   I agree that they look like aluminum tank skin: one of them in particular reflects back the light of the fire in
        one of the frames.
•   I reconstructed the various lens flares in the video. I don't think they pinpoint the origin of the detonation -   
        they are simply pointing to the geometric middle of the visible detonation plume, i.e. the lens flare origin
        doesn't have a true physical meaning. (The trajectories of the ejecta are more reliable and seem to point
        slightly below the lens flare center.)
•   I annotated the apparent movement of the nose cone and found that it's not real movement but the optical
        illusion created by a burning plume rising on the left side of the rocket - this illuminates part of the fairing
        that creates the appearance of it leaning towards the strongback. (Until the fairing is covered by the plume.)
•   The aperture of the camera appears to be unchanged for the first couple of frames - this can be verified
        from looking at the visible brightness of constant light sources, such as lighting.
•   Based on this the 'average illumination' of the fire can be seen on the bottom right spherical LOX tank, as   
        the fire gets reflected and shrunk. That point of light is the illumination: it clearly suggests a bright initial
        detonation followed by a fire that is ramping up.
•   (Later on the camera auto-shrinks its aperture as the fireball expands and its heat increases.)
•   Interestingly the frames themselves are showing a second peak in illumination, but this cannot be seen in         
        the reflection on the big spherical LOX tank. This is the 5th frame of the explosion in the video: this is the
        only frame that is showing two lens flares. It is possible that the plume of the first explosion is shadowing         
        the second one in the direction of the big spherical LOX tank, but the air is still clear towards the camera. So
        I believe there are 3 events altogether: the first detonation was very quick, the second one lasted 3-5
        frames, and the third one (structural disintegration) was the big fire everyone sees when watching the         
        video.
•   The shadows in the frame are all very interesting: for example in the first frame the shadow of the left side
        grid fin suggests that the first detonation happened over a volume that extended well beyond the rocket's
        diameter, in the direction of the camera. (This appears to support fuel/air mixture scenarios.)
•   The sharp shadow at the lower part of the rocket suggest either that the detonation also occurred within the
        strong-arm's volume, and the structure possibly shadowed the flash - or another possibility is that the water
        fog created by the first stage LOX tank is so thick that it stop the flash from penetrating further down.
•   The illumination of the fairing suggests a detonation volume that must also be extending away from the
        rocket in the rocket's direction.
•   The illumination of the strongback's middle region also gives an idea about how far the detonation plume
        must extend away from the strongback.
•   Ejecta analysis looks interesting too: much later in the video still unburnt LOX can be seen ejecting to the
        right, without having any fuel to burn - and turning into a white cloud as it freezes out moisture from the air.
        (It's cold LOX because it keeps going to the right, not rising up like hot gases do.)
        They appear to me to possibly be tank parts. They are curved, and appear to be venting a gas (or steaming
        if they are very cold.) One can be seen going past the payload, then deflecting off the TE and continuing up         
        with a good bit of energy. It can be followed all the way to the ground. Another piece can be seen on the left
        side. I found three pieces altogether. (I also found a fourth piece of shrapnel and reconstructed its
        trajectory, which pointed to a weird place - only to realize that it was a bird.)

I was going to download the video this weekend and do some analysis because I thought I was going to be home bound due to the hurricane, but it blew past, so I didn't have the chance. The thing I was most interested in is working from the original 60 fps video. Everyone seems to be using stills from 30 fps versions and missing intermediate frames.

Here's my conclusion based on that analysis:
•   I think the video supports an air/fuel detonation scenario: I just don't see how a COPV failure cold have
        reached all those places so quickly and created all those specific shadows - without also ejecting LOX
        through the strongback in the first frame. Also, LOX alone is not enough to create an initial large-volume
        detonation - fuel is also needed.
•   So I think the initially detonated mixture was necessarily fuel-rich: which supports a fuel leak (RP-1 or
        hydrazine) as the root cause, not a LOX leak.
•   The pressure wave of the air/fuel detonation pushed in the S2 tank skin at around the common bulkhead,
        which sheared the tank skin like a knife, rupturing both the LOX tank and the RP-1 tank.
•   The fuel-rich detonation died down after frame 1, because it consumed all oxygen from the air in the volume
        of detonation. The volume was still fuel-rich at this point
•   As the LOX exited from the now ruptured LOX tank it created the quick bright flash in frame 5 as it
        consumed all quick sources of fuel not consumed by the initial detonation. This kind of very bright flash is
        typical of LOX rupture: complete combustion of everything fuel.
•   This flash too dies down quickly, because now all sources of fuel are gone.
•   But now both the LOX and the RP-1 tanks are ruptured catastrophically, and the LOX is falling down into the
        RP-1 tank - which creates the real big explosion and the subsequent avalanche of deflagration.


This explanation seems to be about as good as we outsiders can do with the USLR video as the only primary (secondary?) source available currently. The main issue is that prop loading for S2 likely ended 12+ minutes before the explosion.

I am posting it here for all to read and critique, so please do poke holes in this speculative chain of events if you have any doubts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/08/2016 12:41 am
I think the rightward and slightly downward motion of the fairing is a significant find.  That's actually quite a bit of motion, maybe 0.6 meters in about 1 second, or 1.2 m/s^2 acceleration at the tip, about 20 meters above the site of the initial flash.

I think this is consistent with the right wall of stage 2 rupturing while the wall was under significant axial compression, not axial tension.

When the stage is at the correct pressure, the walls are under axial tension.  So it seems to me that while the payload is moving, the ullage is well below nominal pressure, and my guess is that it is in the kerosene ullage, not the LOX ullage, because the flash happens around the level of the kerosene ullage.  Note that I'm not suggesting the ullage is below atmospheric pressure, but rather that the pressure is too low to support the nearly 100 tonnes of payload and LOX above it.  Supporting that load requires around 93 kPa above ambient.

The fairing motion happens after the flash, so I think that during a fair bit of the initial flamey bits, the stage is below nominal pressure.  To me, that says it's not an internal pressure vessel failure, which would have caused overpressure and pushed the payload to the left after a right wall rupture.  To me that's a big deal because until I saw that video I was pretty sure it was a pressure vessel problem.

So now my favorite theory is that there was a problem in the cradle that holds stage 2, perhaps during erection or chilldown.  My guess is that stage 2 got stressed in a way it can't tolerate.  This stress caused a slight buckle in the skin that wasn't noticed but reduced it's ultimate tensile strength.  Pressurizing the stage caused a rupture at the previously-buckled point, at a point low enough that kerosene and not ullage gas under a nominal ullage pressure was ejected forcibly from the tank.  I don't know what the ignition source was, but it must have been immediately proximate to the kerosene jet.  The tearing aluminum-lithium metal might have done it.

I also had some thoughts about that cradle holding stage 2.  It's got a difficult job.  While the stage is horizontal it's not too bad, the cradle just balances the load between the upper and lower clamps.  But when the stage rotates to vertical, the cradle must react to horizontal wind loads without reacting to the shrinkage of the rocket when cooled.  So there is some bearing that lets the cradle go up and down, but that system has to support the weight of the portion of the strongback that is rising and falling with the upper stage.  Otherwise, that weight is going to go into the rocket, but it's off center, so it's going to produce a torque.  That torque is going to produce a strong force on the lower clamp in the direction from the strongback to the rocket.  That force would tend to buckle the skin of the rocket inwards.

Notice that it's not enough to have hydraulic rams controlling the extension of the strongback top.  You have to actuate these rams to relieve any axial shear force between the cradle and rocket.  So you need some kind of servo loop.  If the servo loop pauses you harm the rocket.  So the root cause here could be a momentary loss of hydraulic pressure to the strongback temperature compensating hydraulics during chilldown of any of the propellant tanks.

One final thing: a jet of kerosene heading towards the camera would be hard to see.  It could develop for a frame or two before you'd notice.

I've attempted to stabilize the image frame to frame.  There is so much motion just due to the Florida Humidity that it's impossible to tell if there is actually any motion at the fairing at all.  Again, credit to USLaunchReport.com...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 12:50 am
Hydrazine is not feasible.  It would have gone off in the fairing
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/08/2016 12:54 am
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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/08/2016 01:04 am
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 01:05 am
Jim, the flame fed fire is the above one with the arrow I'm talking about (hydraulic)? The lower one I take is an umbilical line with flame RP-1...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/08/2016 01:07 am
Hydrazine is not feasible.  It would have gone off in the fairing

Apologies if this is a bit of an odd question, but do we know the specific hydrazine compound that Amos-6 utilized? Monoprop is implied, so that points to hydrazine hydrate (I believe).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Maine1 on 09/08/2016 01:09 am
While viewing the video  I noticed that prior to 15 seconds of the anomaly (explosion) vapor is venting rather rapidly from the back (away from the rocket) of the T/E.  15 seconds prior to the anomaly it stops and vapor starts venting from the second stage.  This seems to correlate to an event on the countdown at T-10:00 of 'stage two venting for LOX fast fill'.  I know that Musk tweeted that the anomaly occurred at approximately T-8 minutes, but perhaps that was just an approximation.  If the anomaly occurred at  T-9:45 the closest event on the countdown is
TEA-TEB ignition setup.   I know what TEA-TEB is and why it is on the rocket, but no idea what 'ignition setup' means.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/08/2016 01:14 am
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.

IF a fuel-air explosive event occurred outside the vehicle, it would probably not be kerosene vapor but atomized droplets (essentially an aerosol), as might be sprayed under pressure through a very tiny leak. Not sure I underdetsand how that could happen at that point in the countdown if such an event did in fact occur involving kerosene.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 01:17 am
Hydrazine is not feasible.  It would have gone off in the fairing

Apologies if this is a bit of an odd question, but do we know the specific hydrazine compound that Amos-6 utilized? Monoprop is implied, so that points to hydrazine hydrate (I believe).

hydrazine hydrate is not a propellant.  Mono prop would be pure hydrazine.  But some biprops use it too.  The other is MMH.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/08/2016 01:19 am
FWIW, here are some edits of the We Report Space member's photos of the TE. Did my best to improve visibility.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/08/2016 01:23 am
Hydrazine is not feasible.  It would have gone off in the fairing

Apologies if this is a bit of an odd question, but do we know the specific hydrazine compound that Amos-6 utilized? Monoprop is implied, so that points to hydrazine hydrate (I believe).

hydrazine hydrate is not a propellant.  Mono prop would be pure hydrazine.  But some biprops use it too.  The other is MMH.

Much appreciated. Do you have any idea what prop Amos-6 was to use?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/08/2016 01:25 am
Hydrazine is not feasible.  It would have gone off in the fairing

Apologies if this is a bit of an odd question, but do we know the specific hydrazine compound that Amos-6 utilized? Monoprop is implied, so that points to hydrazine hydrate (I believe).

hydrazine hydrate is not a propellant.  Mono prop would be pure hydrazine.  But some biprops use it too.  The other is MMH.


Much appreciated. Do you have any idea what prop Amos-6 was to use?

MMH

See: http://www.space-propulsion.com/spacecraft-propulsion/apogee-motors/index.html
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/08/2016 01:26 am
FWIW, here are some edits of the We Report Space member's photos of the TE. Did my best to improve visibility.

So looking at the first of the two photos you've attached, I see that one of the umbilicals looks like it's superficially intact, hanging straight down. If you trace it up, it seems as if it's still attached to the large rectangular structure on the T/E in the center of the frame. At the bottom, however, there is a second, more slender umbilical that looks like it's not attached at the top. The photo isn't clear but it looks as if the large rectangular structure has a blackened hole in the center, where the second umbilical might have been attached.

Thoughts?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/08/2016 01:45 am
FWIW, here are some edits of the We Report Space member's photos of the TE. Did my best to improve visibility.

So looking at the first of the two photos you've attached, I see that one of the umbilicals looks like it's superficially intact, hanging straight down. If you trace it up, it seems as if it's still attached to the large rectangular structure on the T/E in the center of the frame. At the bottom, however, there is a second, more slender umbilical that looks like it's not attached at the top. The photo isn't clear but it looks as if the large rectangular structure has a blackened hole in the center, where the second umbilical might have been attached.

Thoughts?

To the diagram machine!

So I do see those two connected umbilicals and the rectangular frame where they attach. I also see three blackened holes. It is hard to tell if they were there before the mishap, I am currently looking for similar photos of the TE for reference.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/08/2016 01:45 am
While viewing the video  I noticed that prior to 15 seconds of the anomaly (explosion) vapor is venting rather rapidly from the back (away from the rocket) of the T/E.  15 seconds prior to the anomaly it stops and vapor starts venting from the second stage.  This seems to correlate to an event on the countdown at T-10:00 of 'stage two venting for LOX fast fill'.  I know that Musk tweeted that the anomaly occurred at approximately T-8 minutes, but perhaps that was just an approximation.  If the anomaly occurred at  T-9:45 the closest event on the countdown is
TEA-TEB ignition setup.   I know what TEA-TEB is and why it is on the rocket, but no idea what 'ignition setup' means.

I have noted occasional spurts of LOX venting from the TEL during the final 10 minutes several F9 counts, so I wouldn't let any sudden bursts of LOX venting convince you that there was something wrong with tank pressures.  That's the problem with a countdown process that includes several "interesting" events during the countdown -- it's hard to tell the routine from the out-of-nominal.

As for TEA/B -- yeah, there was some loaded in stage 2, and I can only imagine that "ignition setup" means that the first set of valves were opened, allowing the TEA/B starter fluid to move down to the level of the injector valves.  Though, as a caveat, I don't have anything like a schematic, here; there could be a redundant tank, and there could be redundant injectors, so "ignition setup" could apply to anything in the plumbing between the TEA/B tank(s) and injector(s).  It could also involve pressurization of TEA/B tanks, assuming their injectors are pressure-fed.

I have to doubt that the flash we saw was TEA/B combustion, though.  First, it will burst into flame as soon as it hits air, much less LOX venting, so I doubt it could accumulate long enough to generate a big enough flash; and second (and more important), the TEB portion (which is, I believe, the larger fraction of the mix) burns with a bright green color.  It's possible the color registration of the USLR video is bad, or didn't catch the color of the initial flash due to saturation, but I know I didn't see any green in that flash.  If I had, me and about a thousand other people here would be chorusing "TEA/B ignition!" starting about 10 seconds after the video was posted... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 01:52 am
and it was a static fire of the first stage, there would be no TEB/TEA Ops
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scylla on 09/08/2016 01:56 am
Just for reference.

An Uber-res photo of Thaicom and strongback vertical.

Photo Credit: John Kraus-AMERICASPACE.COM
https://photos.google.com/share/AF1QipNiF8NUr-BfOPZKJS0_9rA_Gn3dl5LAsITrB8HfPUb52IgMNu5uf4fNE_3I_iVuoQ/photo/AF1QipPpuaeuTrIf3IoNA9f_lqQgEJzo5Q73PZnwhDDw?key=ZW9EX2Rib3ktTklaU0pnanF0NFVGZWEyeVA3aDZR
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Norm38 on 09/08/2016 02:23 am
and it was a static fire of the first stage, there would be no TEB/TEA Ops

So the upper stage does not have TEA/TEB loaded for the static fire, only for actual launch?  That's a minor deviation from "test as you fly", but understandable given the nature of those chemicals.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 02:28 am
Don't know it is loaded or not, but if it is, they are not going to"play" with it during static fire
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Maine1 on 09/08/2016 02:32 am
Thanks Doug, Jim, That says it all, no reason to go further down the TEA/B path
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 03:00 am
...

The diameter of the F9 is 12 feet. Using that as a rough yardstick, a supersonic expansion would have to be more than one F9 diameter per frame.  It isn't.

...

Fireball diameter is actually TWICE the diameter of the F9 there.

One odd thing, that puzzles me, is the leftmost shape of the initial fireball. I have in mind those 3 "tongues". This implies, that at least this part of the explosion front should probably be subsonic and parts of it's propagation should have been obstructed in some ways.

I should point out, that close to sonic wave propagation is complex and there may be transitions in both ways - from detonation to deflagration and the other way.
When there was FAE, then it may have started out as deflagration, then progressed temporarily as detonation in low supersonic and then outgassed (after it run out of oxygen in FAE mixture) as subsonic cloud.
When there was COPV, then I do not see how this could have started as subsonic event.

just a suggestion to think about.

The image you have focused on and circled may be showing boil-off oxygen that has been vented prior to the detonation.

If you toggle between the pre-detonation and this frame, and then draw lines connecting the cloud components, you could make the case that the clouds have been shocked to new locations due to the detonation shock wave supersonic/subsonic/whatever.

I ran several traces of that and while it's an extremely weak hypothesis, you could argue that the upper cloud and the lower cloud that obscure part of the detonation were visible and existed in the pre-denonation frame, and were displaced in the frame you focus on.

If that is correct, tracing them back shows where the event occurred.  I have my candidate in mind, but it doesn't make sense, yet.  Like saying, "it originated from something that has no explosive potential, like a sock".

Anyway, look forward to your thoughts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/08/2016 05:27 am
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.

IF a fuel-air explosive event occurred outside the vehicle, it would probably not be kerosene vapor but atomized droplets (essentially an aerosol), as might be sprayed under pressure through a very tiny leak. Not sure I underdetsand how that could happen at that point in the countdown if such an event did in fact occur involving kerosene.
I would argue that such a leak would, without an ignition source, have been able to exist without any obvous sign, starting well before the explosion.
T-8:00, then, would be when some kind of ignition source was introduced to this already existing fuel-air mixture.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/08/2016 05:38 am
Did someone say the explosion was downwind from the rocket?

Could there have been a relatively stable vortex there, that kept fuel spray suspended for a while?  Maybe even helping with evaporation? 

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/08/2016 05:40 am
Thought it was the upwind side, opposite the direction the boiloff clouds were moving.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Elladan on 09/08/2016 05:57 am
While viewing the video  I noticed that prior to 15 seconds of the anomaly (explosion) vapor is venting rather rapidly from the back (away from the rocket) of the T/E.  15 seconds prior to the anomaly it stops and vapor starts venting from the second stage.

If you look closely, you can see that there's actually a cut in the video here, which was done as a fade (others have noted this before). It's a little hard to see because, other than the venting, nothing much changes and the vapor tends to fade naturally but in a visually distinct way.

This means that you can't really rely on the posted video for establishing a time sequence before the event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 07:08 am
I think the rightward and slightly downward motion of the fairing is a significant find.  That's actually quite a bit of motion, maybe 0.6 meters in about 1 second, or 1.2 m/s^2 acceleration at the tip, about 20 meters above the site of the initial flash.

I think this is consistent with the right wall of stage 2 rupturing while the wall was under significant axial compression, not axial tension.

When the stage is at the correct pressure, the walls are under axial tension.  So it seems to me that while the payload is moving, the ullage is well below nominal pressure, and my guess is that it is in the kerosene ullage, not the LOX ullage, because the flash happens around the level of the kerosene ullage.  Note that I'm not suggesting the ullage is below atmospheric pressure, but rather that the pressure is too low to support the nearly 100 tonnes of payload and LOX above it.  Supporting that load requires around 93 kPa above ambient.

The fairing motion happens after the flash, so I think that during a fair bit of the initial flamey bits, the stage is below nominal pressure.  To me, that says it's not an internal pressure vessel failure, which would have caused overpressure and pushed the payload to the left after a right wall rupture.  To me that's a big deal because until I saw that video I was pretty sure it was a pressure vessel problem.

So now my favorite theory is that there was a problem in the cradle that holds stage 2, perhaps during erection or chilldown.  My guess is that stage 2 got stressed in a way it can't tolerate.  This stress caused a slight buckle in the skin that wasn't noticed but reduced it's ultimate tensile strength.  Pressurizing the stage caused a rupture at the previously-buckled point, at a point low enough that kerosene and not ullage gas under a nominal ullage pressure was ejected forcibly from the tank.  I don't know what the ignition source was, but it must have been immediately proximate to the kerosene jet.  The tearing aluminum-lithium metal might have done it.

I also had some thoughts about that cradle holding stage 2.  It's got a difficult job.  While the stage is horizontal it's not too bad, the cradle just balances the load between the upper and lower clamps.  But when the stage rotates to vertical, the cradle must react to horizontal wind loads without reacting to the shrinkage of the rocket when cooled.  So there is some bearing that lets the cradle go up and down, but that system has to support the weight of the portion of the strongback that is rising and falling with the upper stage.  Otherwise, that weight is going to go into the rocket, but it's off center, so it's going to produce a torque.  That torque is going to produce a strong force on the lower clamp in the direction from the strongback to the rocket.  That force would tend to buckle the skin of the rocket inwards.

Notice that it's not enough to have hydraulic rams controlling the extension of the strongback top.  You have to actuate these rams to relieve any axial shear force between the cradle and rocket.  So you need some kind of servo loop.  If the servo loop pauses you harm the rocket.  So the root cause here could be a momentary loss of hydraulic pressure to the strongback temperature compensating hydraulics during chilldown of any of the propellant tanks.

One final thing: a jet of kerosene heading towards the camera would be hard to see.  It could develop for a frame or two before you'd notice.

For me, this theory is inconclusive for several reasons. Mainly because from this sole video you would not tell the difference between:
1. FAE near rocket, bursting LOX pressure vessel and ...
2. COPV fail near the wall of the pressure vessel, carbon dust ignition in LOX and burst the tank. This situation also forms final fireball outside the rocket due to the whole LOX mass flowing out quickly. Also, I think that Newton's 3rd law has some work to do here to move the stack.

One thing about common bulkhead. This should be able to tolerate all the force of the fully tanked and pressurized LOX even when the RP-1 tank is at 1atm. This is because it has to tolerate the stress of the same load in acceleration within 2-25G-s:

AFAIK, main load of the payload is carried by longitudinal rods embedded in circular ribs. Also tank skin bears part of the vertical load.

Considering that the rocket should be able to accelerate 10,886 kg (24,000 lb) at up to 25G-s, I do not see ANY way, how those clamps or any believable mechanism should be able to "buckle" the tank ina way, that it develops a leak. This is just beyond believable. Also if I would be F9 engineer, I would calculate different possible stresses near the clamps in following events:
1. Horizontal transportation
2. Going from horizontal to vertical
3. Cool-down during cryogenics loading in different extreme weather conditions (not only launch conditions)
4. etc.

I would also have added local strengthening at the region, where clamps attach, should the need be there.

Nothing I have seen this far makes me believe, that they didn't do that.

Also the notion, that I saw someone to post here, that "they do not have 50 years of other company's experience behind them" is just plain wrong. People, who work at Spacex, did not appear just from thin air. Guess, where they worked before! In Walmart?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Zardar on 09/08/2016 08:17 am
Is it correct that the thrust-vectoring on the M-Vac uses pressurised RP fuel during flight?

If so, is there a separate ground-side pressurised supply (and return) for the required fluids for the pre-launch  test of this system?

Is this another potential fuel source for the fireball?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 08:21 am
Is it correct that the thrust-vectoring on the M-Vac uses pressurised RP fuel during flight?

If so, is there a separate ground-side pressurised supply (and return) for the required fluids for the pre-launch  test of this system?

Is this another potential fuel source for the fireball?

AFAIK, some of the pressurised RP-1 from turbopump is just redirected for hydraulics. This system does not need to be pressurized before engines start running. Simply because before that, there's no thrust to vector :-)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/08/2016 08:29 am
This system does not need to be pressurized before engines start running. Simply because before that, there's no thrust to vector :-)

And what about MVac TVC checks prior to flight, known to have caused a scrub on at least one occasion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 08:34 am
This system does not need to be pressurized before engines start running. Simply because before that, there's no thrust to vector :-)

And what about MVac TVC checks prior to flight, known to have caused a scrub on at least one occasion?

Good point :-) Then it means, that the hydraulics line should be pressurized, there should be hydraulic accumulator for keeping pressure and there should be pressurized RP-1 supply. Now we are talking.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/08/2016 08:45 am
Yes the FTS is exonerated.  It is impossible for a stray signal to activate it.  In the SAFE mode, there is a physical block between the initiator and charge
Besides, as my former co-worker with knowledge of explosive characteristics pointed out: an inadvertant FTS detonation would not look anything like what was witnessed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 09:27 am
Yes the FTS is exonerated.  It is impossible for a stray signal to activate it.  In the SAFE mode, there is a physical block between the initiator and charge
Besides, as my former co-worker with knowledge of explosive characteristics pointed out: an inadvertant FTS detonation would not look anything like what was witnessed.

I agree. As FTS on F9FT has detcord installed (actually 2 detcords) along the tank, the actual activation of it should look like this:

https://www.youtube.com/watch?v=FU64SLmn60s

More about FTS here (although, it's ULA, there are many NASA standard parts there and I somehow believe, that this is the part, where innovation is not allowed): http://www.ulalaunch.com/uploads/docs/Published_Papers/Supporting_Technologies/
OrdnanceSafetyRequirementsforSpaceLaunchVehicles.pdf

F9 Grasshopper FTS activation video is this one:
https://www.youtube.com/embed/lnqjnxfjgUk
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/08/2016 10:24 am
As FTS on F9FT has detcord installed (actually 2 detcords) along the tank, the actual activation of it should look like this:

Source for this? I was under the impression that it was actually several shaped charges at discrete points.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/08/2016 10:27 am
I discussed a while back the combustion of aluminum tanks in LOX, both with and without contamination.  The short of it:

1) As a general rule, all common aluminum alloys are compatible with LOX and will not undergo combustion in normal conditions if they have their oxide layer.

2) Aluminum is not compatible with LOX if it does not have its oxide layer, and can combust (aggressively) if initiated, either thermally or by impact (it is, however, not hypergolic).

3) An oxide layer begins forming immediately after bare aluminum is exposed, but it takes about three days to reach maximum thickness (fastest in the beginning, slowing with time).  For bare aluminum to be present, it would have to be newly exposed (scratching, warping, shearing, aggressive cleaning) and either A) have been kept in an inert gas environment, or B) not have had sufficient time to reform (new damage).  Concerning B, the means which can expose aluminum also serve as a source of heating - for example, warping can lead to localized hot spots.

4) Due to the ease in which the oxide layer forms in air, more common incidents are contamination.  LOX is incompatible with a very wide range of organic compounds - tars, greases, solvents, paints, plastics, fuels, etc.  It's also incompatible with some metals, like titanium, which tend to burn aggressively when triggered by impact.  The presence of any such compound in LOX can lead to catastrophic failure, which then becomes further fueled by (very high energy) aluminum combustion.

5) More to the point, this has taken out craft before - most notably the X-1A and X-1D, whose tanks were contaminated by a chemical used in the manufacture of their gaskets.  And the stage in which they went off?  Why, pressurization, of course  ;)

To sum up: LOX tanks must be clean.  However, if aggressively cleaned to the point of removing the oxide layer, aluminum LOX tanks must be given time in a non-inert atmosphere.  Any damage to the aluminum through impact or mechanical action poses an ignition hazard, but it tends to need to be fairly significant; a mere impact without warping / abrasion / shearing / etc is not enough.  And lastly, it is critical that neither the tanks nor the LOX itself be contaminated with organic compounds.

All of this is for standard LOX.  I don't know what additional issues may come into play with densified LOX.  Honestly, I'm not sure if SpaceX even knows that either.  All sorts of additional gases can freeze out or liquify in densified LOX that can't in non-densified LOX, and the lower temperatures could make parts brittle, seals less effective, etc.  I hope their engineering was thorough before the switch over.  Part of me suspects that they missed something...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/08/2016 10:37 am
Attached you can see a subtraction between Frame 0 and Frame 1.  Essentially the differences.

Great work! Attached is an enhanced version. You can see the far off spherical LOX tank is quite illuminated, along with the top of a lightning tower. The bird that is passing by is seen as a bright spot near the middle tower. The gases that are moving or illuminated around the rocket can also be seen more clearly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/08/2016 10:41 am
Feynman's rubber ring, but supercooled? My gut feeling is that it is something to do with the supercooled LOX. It's really an area where they are entering new territory, though at this stage I have no idea whether it is GSE or the rocket itself that is the problem.

I'm curious though, if the explosion was external to the rocket and there were no flaws in the rocket, what would be required to actually penetrate it either via piping or via the shell of the rocket itself.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/08/2016 11:15 am
Some housekeeping and explained to help members - had to trim a couple of posts out. Reasons include:

1) There are now 101 versions of the video, some are really good work (such as the ones by members here), some really daft and using video tricks to see things that aren't there. Let's avoid the latter, especially when it results in five posts saying "that's crap and the music is wack". Trimmed that one out as it was crap. ;)

2) Quote members correctly. The last page had a lot of quotes, but just using the tag, so it was

Quote
and the claim is this happened
<---doesn't say who said it.

Quoting correctly shows who said it and clicks through to the original post.

Feynman's rubber ring, but supercooled?

See! ;D

A bad quote included as the "external" remark was actually an assumption made in a post on the day of the incident (after tracking it back). I tried to edit one back in but it was a messy post, so we have to remove bad posts like that or the chain becomes a mess of untraceable quotes.

3) Be careful with claims of "employees" saying things on social media etc. You can never be sure (externally from your own site) if people are pretending to be employees. This is a big investigation and you can be sure employees will not be talking openly about this. I can't stress how locked down things get during an investigation.

4) Of course there are rumors and that is also standard for such an incident. Got to be patient. Having a big chat and playing armchair engineer is fine - that's the internet, but don't step over the line past your own opinion or such (you know what I mean).

Let's keep the bar as high as is possible when we're working with incomplete data. Honestly, I think this is a great thread, so the housekeeping is aimed at keeping it that way.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 11:29 am
As FTS on F9FT has detcord installed (actually 2 detcords) along the tank, the actual activation of it should look like this:

Source for this? I was under the impression that it was actually several shaped charges at discrete points.

Not the best of sources, but here it is: http://space.stackexchange.com/questions/8762/does-the-falcon-9-v1-1-first-stage-have-an-explosive-flight-termination-system

However, cannot recall at the moment, from where I read about dual detcords. Perhaps from this ULA document by assuming, that the same rules are applied to everyone by NASA.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DMeader on 09/08/2016 11:33 am
5) More to the point, this has taken out craft before - most notably the X-1A and X-1D, whose tanks were contaminated by a chemical used in the manufacture of their gaskets.  And the stage in which they went off?  Why, pressurization, of course  ;)

That had nothing to do with combustion of aluminum. The LOX tanks in the X-craft were sealed with Ulmer leather gaskets, containing tricresyl phosphate, which became explosive when exposed to LOX. In fact, the propellant tanks were made of stainless steel.  When the gaskets were compressed between the tank flanges after assembly, the sealing compound containing TCP oozed out. Any mechanical shock was enough to cause it to detonate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/08/2016 12:00 pm
5) More to the point, this has taken out craft before - most notably the X-1A and X-1D, whose tanks were contaminated by a chemical used in the manufacture of their gaskets.  And the stage in which they went off?  Why, pressurization, of course  ;)

That had nothing to do with combustion of aluminum. The LOX tanks in the X-craft were sealed with Ulmer leather gaskets, containing tricresyl phosphate, which became explosive when exposed to LOX. In fact, the propellant tanks were made of stainless steel.  When the gaskets were compressed between the tank flanges after assembly, the sealing compound containing TCP oozed out. Any mechanical shock was enough to cause it to detonate.

Please re-read my post.  Point #5 was about contamination, not aluminum.  Aka, the source of the explosion, as you elaborate on, in the X-1A and X-1D.  Tricresyl phosphate is hardly alone in being capable of violent reactions with LOX; it's common among many organic compounds, which is why you don't store LOX in plastic containers.  Check any LOX compatibility guide if you have doubts about this.  Here's one for you:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010020209.pdf

"Organic materials should be avoided with both liquid and gaseous oxygen because of possibilities of explosions ... No compeltely compatible lubricants have been found ... Many organic and plastic materials exhibit impact sensitivity in LOX including (1) Synthetic elastomers and Thiokols (2) Cellulose-based papers (3) Silicone- and silicate-based oils and greases 4() Thermoplastics such as nylon and phenolics (5) Thermo-setting resins (phenolics, silicones, expoxies, etc) (6) Petroleum-based oils and greases"

I'd be glad to reference any other part of what I wrote as well.  For example, concerning in what conditions aluminum can ignite in LOX:

http://www.dtic.mil/dtic/tr/fulltext/u2/a229229.pdf

"Common to all ignitions in the Al alloys are these factors: (1) there must be sufficient localized deformation to promote localized specimen heating; (2) oxygen must be accessible; and (3) the oxide layer must be removed to expose the local heated area to oxygen."

Which is precisely what I wrote (they go into a lot more detail, which I summed up as well). 

Strangely, I've actually come across some people who don't believe that bulk aluminum can burn in LOX when given an ignition source.  To them, I just have to say:

https://www.youtube.com/watch?v=uPK_rSf1WUc&feature=youtu.be&t=26

Now, of course, that's nothing compared to what you'd experience in an actual large, enclosed pressure vessel.  But you can clearly see that even in this highly suboptimal situation, bulk aluminum in LOX most definitely can burn if given an ignition source.  And it's a very hot, energetic burn (aluminum-LOX-hydrocarbons has a significantly higher ISP than just LOX-hydrocarbons).  I ran into a report of an explosion in an LOX tanker truck a while back, triggered by an overheating pump.  If I recall correctly about 8 kilograms of aluminum was estimated to have burned away.  You don't have to burn anywhere near 8 kilograms to set in motion a CATO in a rocket.  And vertical is a much more vulnerable orientation to flame than horizontal.

(Ed: Okay, technically this wasn't a CATO, since there was no takeoff... unscheduled disassembly?)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 12:18 pm
As FTS on F9FT has detcord installed (actually 2 detcords) along the tank, the actual activation of it should look like this:

Source for this? I was under the impression that it was actually several shaped charges at discrete points.

It is cord
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 12:20 pm
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.

IF a fuel-air explosive event occurred outside the vehicle, it would probably not be kerosene vapor but atomized droplets (essentially an aerosol), as might be sprayed under pressure through a very tiny leak. Not sure I underdetsand how that could happen at that point in the countdown if such an event did in fact occur involving kerosene.
I would argue that such a leak would, without an ignition source, have been able to exist without any obvous sign, starting well before the explosion.
T-8:00, then, would be when some kind of ignition source was introduced to this already existing fuel-air mixture.

How?  The tank was not pressurized at the time
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/08/2016 01:07 pm
I think the rightward and slightly downward motion of the fairing is a significant find.  That's actually quite a bit of motion, maybe 0.6 meters in about 1 second, or 1.2 m/s^2 acceleration at the tip, about 20 meters above the site of the initial flash.

I think this is consistent with the right wall of stage 2 rupturing while the wall was under significant axial compression, not axial tension.

When the stage is at the correct pressure, the walls are under axial tension.  So it seems to me that while the payload is moving, the ullage is well below nominal pressure, and my guess is that it is in the kerosene ullage, not the LOX ullage, because the flash happens around the level of the kerosene ullage.  Note that I'm not suggesting the ullage is below atmospheric pressure, but rather that the pressure is too low to support the nearly 100 tonnes of payload and LOX above it.  Supporting that load requires around 93 kPa above ambient.

The fairing motion happens after the flash, so I think that during a fair bit of the initial flamey bits, the stage is below nominal pressure.  To me, that says it's not an internal pressure vessel failure, which would have caused overpressure and pushed the payload to the left after a right wall rupture.  To me that's a big deal because until I saw that video I was pretty sure it was a pressure vessel problem.

So now my favorite theory is that there was a problem in the cradle that holds stage 2, perhaps during erection or chilldown.  My guess is that stage 2 got stressed in a way it can't tolerate.  This stress caused a slight buckle in the skin that wasn't noticed but reduced it's ultimate tensile strength. Pressurizing the stage caused a rupture at the previously-buckled point, at a point low enough that kerosene and not ullage gas under a nominal ullage pressure was ejected forcibly from the tank.  I don't know what the ignition source was, but it must have been immediately proximate to the kerosene jet.  The tearing aluminum-lithium metal might have done it.
...

As Jim just said, the RP-1 tank isn't pressurized at T-8 minutes. Fuel load completes at 22 minutes and flight press starts at 50 seconds before liftoff. The vehicle does NOT need internal pressure for structural support; it is stable fully fueled but unpressurized, and in fact is in this condition for several minutes before every launch or static fire.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/08/2016 01:15 pm
This system does not need to be pressurized before engines start running. Simply because before that, there's no thrust to vector :-)

And what about MVac TVC checks prior to flight, known to have caused a scrub on at least one occasion?

Good point :-) Then it means, that the hydraulics line should be pressurized, there should be hydraulic accumulator for keeping pressure and there should be pressurized RP-1 supply. Now we are talking.

Relevant countdown events:

T-0:07:45   MVac Fuel Trim Valve Setup
T-0:07:30   Engine Chill Readiness
T-0:07:00   Engine Chilldown (Bleed Valves Open, both Stages
T-0:07:00   Spacecraft on Internal Power
T-0:06:45   Stage 2 Helium Transition to Pipeline
T-0:06:35   MVac Hydraulics at Bleed Pressure
T-0:06:05   M1D Engines to TVC-Null Position
T-0:05:20   Flight Computers in Self-Alignment
T-0:05:20   Stage 1 Fuel Loading Complete
T-0:05:15   Launch Vehicle Heater Deactivation
T-0:05:00   Falcon 9 to Internal Power
T-0:05:00   Range Control Comm Check
T-0:05:00   Second Stage Nitrogen Loading Termination
T-0:04:50   Pressurization for Strongback Retract
T-0:04:40   Stage 2 TVC Bleed
T-0:04:30   Stage 2 RP-1 Bleed
T-0:04:30   Stage 2 Thrust Vector Control Test
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 01:16 pm
...
How?  The tank was not pressurized at the time

Correct, but there's some confusion about whether the hydraulics system was pressurized and filled with RP-1, or not. If not, then how do they do pre-launch tests.

Edit:
T-0:06:35   MVac Hydraulics at Bleed Pressure
This is possibly the moment when hydraulic system is pressurized. Does that mean, that the pressurization was in progress at the time of incident? How do they pressurize the hydraulics without turbine running.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: king1999 on 09/08/2016 01:21 pm
Silence of SpaceX is deafening...  :o
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/08/2016 01:26 pm
What do you expect them to say at this point?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: starhawk92 on 09/08/2016 01:27 pm
Ok, armchair detectives, besides the obvious (LOX tank, lightning towers, engines), what can be effectively RULED OUT of the root cause at this point?

For example, clearly the bottom half of the rocket did not explode, what does that rule out?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/08/2016 01:28 pm
Ok, armchair detectives, besides the obvious (LOX tank, lightning towers, engines), what can be effectively RULED OUT of the root cause at this point?

For example, clearly the bottom half of the rocket did not explode, what does that rule out?

Well clearly it rules out everything in the first stage, and all the associated umbilicals to the first stage. But we knew that as soon as we'd seen video. Read the thread. The suspects are all well-talked out at this point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/08/2016 01:31 pm
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.

IF a fuel-air explosive event occurred outside the vehicle, it would probably not be kerosene vapor but atomized droplets (essentially an aerosol), as might be sprayed under pressure through a very tiny leak. Not sure I underdetsand how that could happen at that point in the countdown if such an event did in fact occur involving kerosene.
I would argue that such a leak would, without an ignition source, have been able to exist without any obvous sign, starting well before the explosion.
T-8:00, then, would be when some kind of ignition source was introduced to this already existing fuel-air mixture.

How?  The tank was not pressurized at the time


If the RP1 tank is full, it's pressurized at least by gravity (head pressure).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/08/2016 01:36 pm
Perhaps the best thing we can do is to start eliminating, based on lowest probability, what it couldn't be. Because, to be honest, I've been following this thread with great interest (as many no doubt are) and all the suggested scenarios seem to get MythBusted pretty easily.

So I'll start - again, a list of what it couldn't be and why it couldn't be.

- payload prop leaking: because fairing was intact when it toppled.

- FTS: because the system is mechanically isolated prior to arming, and it wasn't armed at time of event.

- pressurized RP-1 leak from S2 tank creating aerosol leading to FAE: because tank wasn't pressurized at time of event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/08/2016 01:39 pm
Silence of SpaceX is deafening...  :o

I find my productivity has gone down at work. You would think for the sake of the geek productivity of the world they would at least start dropping us some tidbits. This thread is addictive!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 01:40 pm
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.

IF a fuel-air explosive event occurred outside the vehicle, it would probably not be kerosene vapor but atomized droplets (essentially an aerosol), as might be sprayed under pressure through a very tiny leak. Not sure I underdetsand how that could happen at that point in the countdown if such an event did in fact occur involving kerosene.
I would argue that such a leak would, without an ignition source, have been able to exist without any obvous sign, starting well before the explosion.
T-8:00, then, would be when some kind of ignition source was introduced to this already existing fuel-air mixture.

How?  The tank was not pressurized at the time


If the RP1 tank is full, it's pressurized at least by gravity (head pressure).

Not nearly enough to produce a mist required for FAE to form.

My main speculative sources for pressurized RP-1 are hydraulic accumulators in MVac hydraulic scheme. Anyone knows wehere they are located? Only thing is that when MVac hydraulics are pressurized by spinning dry turbine during chilldown process, then the pressure is non-nominal to say the least. I do not know, how the hydraulics are pressurized, while turbine is not running.

Perhaps it is pressurized by filling the accumulators first to certain level and then injecting pressurized N2 to their gas bubbles.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 01:42 pm
Question for the Youtube video pros... Is there any way to watch a video in reverse not frame by frame, either slomo or normal speed?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/08/2016 01:45 pm
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup

anybody know what these events are? 9:30 and 7:45?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/08/2016 01:49 pm
Perhaps the best thing we can do is to start eliminating, based on lowest probability, what it couldn't be. Because, to be honest, I've been following this thread with great interest (as many no doubt are) and all the suggested scenarios seem to get MythBusted pretty easily.

So I'll start - again, a list of what it couldn't be and why it couldn't be.

- payload prop leaking: because fairing was intact when it toppled.

- FTS: because the system is mechanically isolated prior to arming, and it wasn't armed at time of event.

- pressurized RP-1 leak from S2 tank creating aerosol leading to FAE: because tank wasn't pressurized at time of event.

Also FTS doesn't look like that. By all accounts and including the short video of a cord going off upthread, it would first unzip the whole tank top to bottom and then explode.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/08/2016 01:50 pm
If the RP1 tank is full, it's pressurized at least by gravity (head pressure).

Not nearly enough to produce a mist required for FAE to form.

All you need for that is a large area covered with it, and time for evaporation.  I think this probability is lower than I initially did because the vapor is heavier than air and because of the wind at the time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 01:53 pm
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup

anybody know what these events are? 9:30 and 7:45?

Not absolutely sure, but:

T-0:09:30   M1D Trim Valve Cycling - trim valve is (if I remember correctly) for regulating incoming flow pressure to turbine. This is required because acceleration excerts force on fuel column and changes pressure. This valve is required to save the turbine from getting fuel with too much incoming pressure. Cycling means, that the valve is tested for extremes - goes full open, goes fully shut.
T-0:09:15   Stage 1 Helium Topping - self explanatory, isn't it - the start loadin He to Stage 1 COPV-s
T-0:07:45   MVac Fuel Trim Valve Setup - probably some kind of calibration event for the valve described above.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: clegg78 on 09/08/2016 01:55 pm
Silence of SpaceX is deafening...  :o

Fairly certain the last thing on SpaceX's mind right now is appeasing forums of conspiracy theorists and arm chair rocket scientists with half baked info.    This isn't a game, and truly in the big picture we don't even register on their radar.   I expect nothing less and nothing more than them to keep their heads down, find the problem and when ready communicate the minimum they need to reassure their customers/potential customers and save face where they can.

Jobs, businesses, and potential industries are in the balance.  I hope they take all the time they need, and am happy they see twitter isn't high on the list of  "customers" they need to be focused on.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Norm38 on 09/08/2016 02:18 pm
Ok, armchair detectives, besides the obvious (LOX tank, lightning towers, engines), what can be effectively RULED OUT of the root cause at this point?

For me the biggest things to be ruled out are all those that we would be considering if this failure had happened in flight, as with CRS-7.  Vibration, aerodynamic stress, g-forces, bending moments.  No engines running, M-Vac wasn't in chilldown.  We're looking for something that happened very fast, very quietly without any apparent outside mechanical force.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 02:29 pm
Ok, armchair detectives, besides the obvious (LOX tank, lightning towers, engines), what can be effectively RULED OUT of the root cause at this point?

For me the biggest things to be ruled out are all those that we would be considering if this failure had happened in flight, as with CRS-7.  Vibration, aerodynamic stress, g-forces, bending moments.  No engines running, M-Vac wasn't in chilldown.  We're looking for something that happened very fast, very quietly without any apparent outside mechanical force.
Hydraulic fitting... ;D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/08/2016 02:35 pm
Silence of SpaceX is deafening...  :o

Fairly certain the last thing on SpaceX's mind right now is appeasing forums of conspiracy theorists and arm chair rocket scientists with half baked info.    This isn't a game, and truly in the big picture we don't even register on their radar.   I expect nothing less and nothing more than them to keep their heads down, find the problem and when ready communicate the minimum they need to reassure their customers/potential customers and save face where they can.

Jobs, businesses, and potential industries are in the balance.  I hope they take all the time they need, and am happy they see twitter isn't high on the list of  "customers" they need to be focused on.

And how soon we forget...CRS-7 failure took (a mere) 3 weeks for SpaceX to release preliminary findings, and in the launch vehicle world even that is unusually fast. Other failure investigations (Taurus, Pegasus XL) have taken much longer. Expecting SpaceX to say anything this soon is unrealistic, unless the root cause is blindingly obvious, which it usually isn't.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kdhilliard on 09/08/2016 02:40 pm
Attached you can see a subtraction between Frame 0 and Frame 1.  Essentially the differences.

Great work! Attached is an enhanced version. You can see the far off spherical LOX tank is quite illuminated, along with the top of a lightning tower. The bird that is passing by is seen as a bright spot near the middle tower. The gases that are moving or illuminated around the rocket can also be seen more clearly.

Note that the bird (or bug) shows up brightly in this image not because it is illuminated but because it is moving rapidly across the field of view so that the subtraction between frames show a bright spot where the bug has cleared that spot in the sky.

~Kirk
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 02:45 pm
A stand down is also a good time to review all aspects of the vehicle, ground ops, procedures etc... If it takes longer to release information, so be it if it results in a more robust launch system...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/08/2016 02:48 pm
What kind of external analytical tools would normally be monitoring this? Obviously there would be cameras and sound, but would they have anything like a spectral analyser monitoring it or anything like that?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/08/2016 02:56 pm
And how soon we forget...CRS-7 failure took (a mere) 3 weeks for SpaceX to release preliminary findings, and in the launch vehicle world even that is unusually fast. Other failure investigations (Taurus, Pegasus XL) have taken much longer. Expecting SpaceX to say anything this soon is unrealistic, unless the root cause is blindingly obvious, which it usually isn't.
That's a good benchmark given the explosion was high up and out to sea, whereas here it's (literally) on their doorstep with lots of direct video and telemetry and a fairly tight timeframe to analyze.

I think we could have an announcement in a week, maybe two.



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 03:03 pm
Obviously there would be cameras and sound, but would they have anything like a spectral analyser monitoring it or anything like that?

There would be no need for such devices.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 03:09 pm
https://www.youtube.com/watch?v=7nL10C7FSbE

Shows that a direct flame does not ignite Jet-A, it needs to be an aerosol
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/08/2016 03:17 pm
Obviously there would be cameras and sound, but would they have anything like a spectral analyser monitoring it or anything like that?

There would be no need for such devices.

Why do you say that?  Do you not think knowing what is combusting in the initial phases of the explosion would be useful data?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/08/2016 03:24 pm
Obviously there would be cameras and sound, but would they have anything like a spectral analyser monitoring it or anything like that?

There would be no need for such devices.

They could certainly pick up buildup of materials in the air at an early stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RoboGoofers on 09/08/2016 03:31 pm
...LOx and Aluminum facts...

My question about this scenario is "OK, so unoxidized aluminum oxidizes rapidly in LOx, but what event caused the aluminum to be exposed? What caused the tank to be so severely bent that exposed enough raw aluminum to cause a runaway reaction?"

It's putting the cart before the horse. A successful launch hinges on them being able to load LOx into an aluminum tank; I'd assume they know the risks and the rocket passed their checks before being rolled out to the pad. If something messed up the LOx tank that much after raising it on the pad and the rocket didn't explode, they'd still have to have an investigation and delay a bunch of launches.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/08/2016 03:40 pm
...LOx and Aluminum facts...

My question about this scenario is "OK, so unoxidized aluminum oxidizes rapidly in LOx, but what event caused the aluminum to be exposed? What caused the tank to be so severely bent that exposed enough raw aluminum to cause a runaway reaction?"

It's putting the cart before the horse. A successful launch hinges on them being able to load LOx into an aluminum tank; I'd assume they know the risks and the rocket passed their checks before being rolled out to the pad. If something messed up the LOx tank that much after raising it on the pad and the rocket didn't explode, they'd still have to have an investigation and delay a bunch of launches.

would it have to be severely bent? cracking can expose relatively large surface area.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: starhawk92 on 09/08/2016 03:46 pm
Ok, armchair detectives, besides the obvious (LOX tank, lightning towers, engines), what can be effectively RULED OUT of the root cause at this point?

For example, clearly the bottom half of the rocket did not explode, what does that rule out?

Well clearly it rules out everything in the first stage, and all the associated umbilicals to the first stage. But we knew that as soon as we'd seen video. Read the thread. The suspects are all well-talked out at this point.

Yes, I've read the hundreds of COPV/not COPV messages.  And while people have narrowed to some favorites, it's also interesting to box in the problem with what it cannot be.  Like, can the strongback be eliminated?  Or parts of it?  It seems the fairing and the payload are eliminated as well.  Does that eliminate the systems connected to them?  What systems are monitored and would shut down the static fire if tripped -- aren't those also eliminated?  Like fuel pressure in the LOX pumps/hoses/tanks?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 03:56 pm
Obviously there would be cameras and sound, but would they have anything like a spectral analyser monitoring it or anything like that?

There would be no need for such devices.

Why do you say that?  Do you not think knowing what is combusting in the initial phases of the explosion would be useful data?

Because incidents like this are too infrequent to justify the need.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/08/2016 04:03 pm


Not nearly enough to produce a mist required for FAE to form.

My main speculative sources for pressurized RP-1 are hydraulic accumulators in MVac hydraulic scheme. Anyone knows wehere they are located? Only thing is that when MVac hydraulics are pressurized by spinning dry turbine during chilldown process, then the pressure is non-nominal to say the least. I do not know, how the hydraulics are pressurized, while turbine is not running.

Perhaps it is pressurized by filling the accumulators first to certain level and then injecting pressurized N2 to their gas bubbles.

Note that I'm not claiming a source fr the leak, whether the tank, hydralics, or anything else. Only that a leak could have been triggered earlier in the count without visible problems, which then made an otherwise "safe" accidental ignition source into the catastrophe we saw.

Basically pointing out a theory that fits with the "swiss cheese accident prevention" thingy pointed out earlier- Multiple independant failures, each safe on their own, that line up to cause problems.

In the same line... let say they slightly overpressured the keresene tank. It's not supposed to happen, but every bell curve has tails, and it's hardly catastrophic.
Lets assume there was a pinnhole leak in the RP tank- as long as its not at pressure, no problem. Even if it is, keep ignition sources away, and you're fine.
Getting an ignition source from warming up the hydrolics may involve a similar series of coincidences.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Spacedog49 on 09/08/2016 04:05 pm
Rocket Science

Most video editors have a reverse play connected with either the Speed or Duration effect. In Adobe Premiere the effect is Crtl+R. You can also speed up or slow down the action within the reversal effect. Make a copy of the original video in your editor timeline; Ctrl+C, Crtl+V. Select the copy and apply the reversal effect, Crtl+R. Set the Duration or Speed. This works in Premiere and Pinnacle. Instructions may also apply to Vegas. It's been a few years since I last used Vegas.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/08/2016 04:06 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/08/2016 04:07 pm

Yes, I've read the hundreds of COPV/not COPV messages.  And while people have narrowed to some favorites, it's also interesting to box in the problem with what it cannot be.  Like, can the strongback be eliminated?  Or parts of it?  It seems the fairing and the payload are eliminated as well.  Does that eliminate the systems connected to them?  What systems are monitored and would shut down the static fire if tripped -- aren't those also eliminated?  Like fuel pressure in the LOX pumps/hoses/tanks?

I doubt the strongback can be eliminated, in the same way the vehicle can't be eliminated.

Both have the potential to have provided the fuel and/or the oxidiser the caused the explosion.

Elon's comment "originated around the upper stage oxygen tank" can be read as "originated in the approximate area of the upper stage oxygen tank" or "originated outside the upper stage oxygen tank". It doesn't particularly help.

Thus, the equipment on the strongback must remain as much of a suspect as the vehicle is.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/08/2016 04:12 pm
My main speculative sources for pressurized RP-1 are hydraulic accumulators in MVac hydraulic scheme. Anyone knows wehere they are located? Only thing is that when MVac hydraulics are pressurized by spinning dry turbine during chilldown process, then the pressure is non-nominal to say the least. I do not know, how the hydraulics are pressurized, while turbine is not running.

Presumably any such venting would likely be into the interstage - which should by then be filled with GN2 supplied by the air-conditioning system, which is intended to prevent ignition in there?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 04:18 pm
Rocket Science

Most video editors have a reverse play connected with either the Speed or Duration effect. In Adobe Premiere the effect is Crtl+R. You can also speed up or slow down the action within the reversal effect. Make a copy of the original video in your editor timeline; Ctrl+C, Crtl+V. Select the copy and apply the reversal effect, Crtl+R. Set the Duration or Speed. This works in Premiere and Pinnacle. Instructions may also apply to Vegas. It's been a few years since I last used Vegas.   
Welcome to the forum! Great and informative first post for the "video sleuths" on here, thanks! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/08/2016 04:22 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?

I don't think anyone can tell Elon what to do! :) I'm sure they will provide an update when they have something they can share.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/08/2016 04:25 pm

I don't think anyone can tell Elon what to do! :) I'm sure they will provide an update when they have something they can share.
Can? I would say, want to share.... I read the silence as they don't have anything definite yet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/08/2016 04:30 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?

I don't think anyone can tell Elon what to do! :) I'm sure they will provide an update when they have something they can share.

I would put Shotwell as one of the few people that could tell Elon what to do without getting fired. 

It just isn't SpaceX, he was also supposed to do a big announcement on Tesla AutoPilot last week and he postponed until the end of last weekend but he has been silent since 9/1, kind of odd for Elon. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/08/2016 04:33 pm
One difference between the rocket and the T/E is that the rocket has identical controlled copies that can be used for tests, maybe even for a reproduction of the problem.

The T/E was a one-of-a-kind, and I don't know how you'd go about finding some fault that may not even be in the design documentation for the T/E.

I also suspect that the rocket is instrumented much better than the T/E.  A microphone can pick up something breaking just before the explosion, but I don't know if they have those on the T/E.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/08/2016 04:38 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?

He was also silent after the CRS-7 accident. So can we now say that he is "usually silent" after accidents, since this has been the case both times?

Can we also stop condescending, like he's a high school student who doesn't know when to shut up? SpaceX is in the middle of an extremely sensitive accident investigation, and he'll keep quiet about the details until they have a root cause nailed down, and have briefed customers, NASA and Air Force. Just like last time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 04:39 pm

Yes, I've read the hundreds of COPV/not COPV messages.  And while people have narrowed to some favorites, it's also interesting to box in the problem with what it cannot be.  Like, can the strongback be eliminated?  Or parts of it?  It seems the fairing and the payload are eliminated as well.  Does that eliminate the systems connected to them?  What systems are monitored and would shut down the static fire if tripped -- aren't those also eliminated?  Like fuel pressure in the LOX pumps/hoses/tanks?

I doubt the strongback can be eliminated, in the same way the vehicle can't be eliminated.

Both have the potential to have provided the fuel and/or the oxidiser the caused the explosion.

Elon's comment "originated around the upper stage oxygen tank" can be read as "originated in the approximate area of the upper stage oxygen tank" or "originated outside the upper stage oxygen tank". It doesn't particularly help.

Thus, the equipment on the strongback must remain as much of a suspect as the vehicle is.

Sort of the Sherlock Holmes approach to accident investigation?   :)

One way is to mask out everything that wasn't saturated in Frame 1, whatever remains is suspect.  Image below.

Another way is to trace known contours of the initial fireball, that part not impeded by structures.  Pink region on the same image.

Not sure if this is helpful or not to this kind of approach. My $0.0002 worth.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/08/2016 04:43 pm
You would think the pad has multiple microphones for triangulation.
Anybody know?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/08/2016 04:49 pm
You would think the pad has multiple microphones for triangulation.
Anybody know?

What would that provide that video doesn't?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 04:57 pm
You would think the pad has multiple microphones for triangulation.
Anybody know?

What would that provide that video doesn't?

3 time synchronized microphones being recorded at 20khz could localize the bang within about half an inch.

sound travels at 1125.33 feet/second

1125.33/20000 = 0.05 feet

1 microphone places it on a sphere
2 places it on a circle
3 places it at one of two points
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/08/2016 04:58 pm
possible non visible failure noises?
An event thats too fast for cameras would leave an audible trail.
Leaks of non visible gas(n2) would make sound but not be visible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gadgetmind on 09/08/2016 05:13 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?

And now I have a mental image of Elon wearing a Hanibal Lecter style mask and strapped to a wheely board. I'm not sure what else could keep him this quiet!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/08/2016 05:23 pm
Maybe the silence is that Elon is still recovering from Burning Man. He does frequent the event....

More seriously, chances of the internal LOX tank camera being on and recording at the time of the event? That would most likely in a few frames (35 ms) answer if a COPV burst. Just thinking, and unless SpaceX states if they have a recording, we will never know...

Edit: You know, on second though that would be a good question to pester SpaceX with....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/08/2016 05:40 pm
For some of the knowledgeable people here: Was there any GSE in use at SLC-40 that is industry standard enough that other launch providers would use it as well? I know SpaceX mostly customizes the pad, but I am just curious if other launch vehicles could be affected if the root is traced to something found at most/all launch pads (like tubing from supplier X or a valve from supplier Y).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/08/2016 05:46 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?

He was also silent after the CRS-7 accident. So can we now say that he is "usually silent" after accidents, since this has been the case both times?

Can we also stop condescending, like he's a high school student who doesn't know when to shut up? SpaceX is in the middle of an extremely sensitive accident investigation, and he'll keep quiet about the details until they have a root cause nailed down, and have briefed customers, NASA and Air Force. Just like last time.

The reference about leaning forward in twitter was taken directly from a comment that Shotwell made during a press call after the CRS-7 accident about Musk and Twitter. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/08/2016 05:53 pm
You would think the pad has multiple microphones for triangulation.
Anybody know?

What would that provide that video doesn't?

3 time synchronized microphones being recorded at 20khz could localize the bang within about half an inch.

sound travels at 1125.33 feet/second

1125.33/20000 = 0.05 feet

1 microphone places it on a sphere
2 places it on a circle
3 places it at one of two points

I'm quite aware of how triangulation works.  Here are some things to consider:

1) The speed of sound through a gaseous medium is only constant for constant temperature, constant constituency gas.  When you have temperature gradients or differences in makeup (dry air vs humid air vs pure oxygen, etc), the speed of sound will vary along the propagation path, which will lead to refraction of the sound waves and mislocation of the source of the sound.  In this case, you have a wide range of temperatures in your field of consideration as well as a wide range of constituencies.

2) The speed of wave propagation through a gaseous medium is only constant when the disturbance is small enough to discount nonlinear terms in the equations of motion, i.e., sound vs shock waves.  Shock wave propagation speed varies with its strength.

3) Syncing the microphones is itself not a terribly trivial task, though it is not insurmountable.

4) Reflections will confound efforts to triangulate properly.  Not every microphone will have a clear line of sight to the signal source.  Precisely locating the point source of a sound within the TEL structure, for example, has this issue.

5) Separating signal from noise is not an easy computational task.  Active pads have a number of sources of noise.  Determining what is meaningful and what isn't is tricky.

6) Even if you could triangulate the sound with centimeter-level accuracy, what do you then do with that information?  What would the use case be?  What can this get you that video and telemetry don't?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 05:54 pm
You would think the pad has multiple microphones for triangulation.
Anybody know?

Not for Engineering
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 05:59 pm
OK, gang... using my geologic engineering background, i believe i have a plausible explanation of the *ploink* and rumble on the vid. YES is DOES COME FROM THE JUNKYARD!, but the explosion and subsequent fireball ARE to blame. Since the S1 is attached to the pad/ground, it transmits the pressure wave directly to the ground. This is why it registered on seismic equipment. since pressure waves travel much faster through the ground than in the compressible air, the transient noises in the video are caused by the explosion. The shock traveling through the ground will arrive to the microphone location before the sound traveling in the air. This shockwave/impulse caused something in the yard to tilt,rub,bang or rattle . Initial explosion shock arrival IS the *ploink* and fireball/collapse of the stack is the rattle. That should put everything to bed... what do you think Chris?

this will be for pressure or P-Wave impulses
since the coastal area of CCAFS is mostly unconsolidated sediment &  sand, one can use 1000 meters/sec as velocity.

Here's the study from 2011 by University of Florida regarding seismic energy propagation in FLA
http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

I'll let you have fun with the maths


Well, It looks like you're right.

Below are the amplitude waveforms of the thunk that you suggest is coming through the ground vs. the one picked up by the microphones.

Waveforms are very similar.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: matthewkantar on 09/08/2016 06:11 pm
The idea of a problem with the second stage TVC hydraulics is compelling. Two problems with this:

1:If the anomaly took place when SpaceX says it did, at eight minutes, they were not yet messing around with the TVC system, tests of second stage TVC take place around 4:00 in the timelines I have seen.
2:The initial event does not seem to take place in the area of the TVC.

Am I correct?

Matthew
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rubtest on 09/08/2016 06:19 pm
for all the experts here :
Is it possible to make spectroscopic analysis from the Video of the AMOS-6 fire to deduct which material was
involved in the initial fast fire ?  we all assumed that the white color is oxygen or over saturation of the camera
but maybe more sensitive analysis can discover more ?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kansan52 on 09/08/2016 06:21 pm
The initial flash reminds me of arcing. Anything, even static, that could arc there?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/08/2016 06:24 pm
for all the experts here :
Is it possible to make spectroscopic analysis from the Video of the AMOS-6 fire to deduct which material was
involved in the initial fast fire ?  we all assumed that the white color is oxygen or over saturation of the camera
but maybe more sensitive analysis can discover more ?

As said earlier in the thread, no.  It is impossible to reconstruct a spectrum from three color channels.  That information is lost.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wolfpack on 09/08/2016 06:25 pm
Musk has been unusually silent on Twitter the past week.  I wonder if Shotwell told him he needs to stop leaning forward on incidents like this?

The fact is they have 2 Falcon 9's lost to 2nd stage failures. Whether or not these are common, we do not know. However, in either case, SpaceX has to be crystal clear on a) the fact that they are not common, and here's why or b) they are common, and here's why. Incontrovertible evidence. No more "this may be the problem". Root cause and rock solid proof thereof is the only thing that's going to get Falcon 9 back in good standing. Twitter just isn't the place to accomplish that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/08/2016 06:33 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 06:37 pm
for all the experts here :
Is it possible to make spectroscopic analysis from the Video of the AMOS-6 fire to deduct which material was
involved in the initial fast fire ?  we all assumed that the white color is oxygen or over saturation of the camera
but maybe more sensitive analysis can discover more ?

Short answer, no, not with this camera.

An ideal optical spectrometer uses a prism or diffraction grating which creates a rainbow with high precision which permits you to see emission or absorption lines.  Example:  http://alexpetty.com/content/images/2014/09/Figure-8--The-light-signature-of-Oxygen.png

Some of the cameras used in various space probes have filters that block all but narrow bands of light, and with these, you can take several pictures of the same scene using different filters and come up with a limited type of optical spectroscopy.

Examples:  http://www.iosoptics.com/images/band-pass-filter-large.jpg   and https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcReHhUeEPprsPIk3jjwchVr4slwFY1ltqT7MGJTrRkH6M5tZoWJ

This camera is designed to take photos that the eye can interpret as real and it will have pixels recording Red Green and Blue  that would look something like this:  http://www.buytelescopes.com/images/site2/product_copy/15628/6aa067dd-03a1-4d56-af73-fad4e5232de6.jpg

The net net is that a camera like this, and it probably only has 8 bits per color pixel to boot, is not going to be helpful in seeing any spectra.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 06:41 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?

That would have many
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: x15_fan on 09/08/2016 07:09 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?

I think it is pretty well established they have cameras on at least the lightening towers looking down on the F9/TEL. Also we know they have camera in the S2 LOX tank as well. Question is do they collect this feed all the time (I would think so) or are the data-link channels over subscribed so they can only get onboard video from some subset of camera at once? Whether that video is more illustrative is speculation. I have to imagine if the LOX tank cam was recording and goes from completely normal to black that tells you something right there. It was not a slow problem in the thank that worked its way out. It was quick regardless of the origin.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/08/2016 07:09 pm
The fact is they have 2 Falcon 9's lost to 2nd stage failures. Whether or not these are common, we do not know.

Sorry to be picky but... at the moment, the second stage is a strong candidate for being the cause of the problem, but the equipment on the erector could also have been at fault.

If it turns out that the second stage ruptured; and that caused the explosion, then there will be a strong suspicion that the fault with CRS7 was not properly identified - and that suspicion will remain even if SpaceX conclude that this had a different root cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 07:10 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/08/2016 07:16 pm
They would need a full spectrum camera for analysis which is not sop...
Small nit, but "hyper spectral" is the correct industry term. Camera's that have true hyper spectral sampling in all bands at the same time do not usually have the highest frame rate and resolution. They usually build up the images over time either with a slit and grating or narrow bandpass filtering (which can be filters or a double subtractive grating combo).

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 07:23 pm
They would need a full spectrum camera for analysis which is not sop...
Small nit, but "hyper spectral" is the correct industry term. Camera's that have true hyper spectral sampling in all bands at the same time do not usually have the highest frame rate and resolution. They usually build up the images over time either with a slit and grating or narrow bandpass filtering (which can be filters or a double subtractive grating combo).
Nits are good, but what I've used in the lab is this type...
http://www.spectralcameras.com/files/SisuCHEMA_brochure.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/08/2016 07:41 pm
Regarding SpaceX's silence, could we please not read too much into it? It's SOP (in aviation as well) to investigate first, then talk with customers, and then talk to the public. In that order.

As pointed out above, it took 3 weeks last time, and even that was usually fast for such an investigation. 

About the only clue the timeline might give us is that SpaceX did not uncover a 100% certain smoking gun (with 0 chance it could be something else) on day 1. Had they done so, it's possible it might have leaked by now. Possible, though far from certain.

It certainly seems like a very long time to us, but it's only been a week. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/08/2016 08:24 pm
They would need a full spectrum camera for analysis which is not sop...
Small nit, but "hyper spectral" is the correct industry term. Camera's that have true hyper spectral sampling in all bands at the same time do not usually have the highest frame rate and resolution. They usually build up the images over time either with a slit and grating or narrow bandpass filtering (which can be filters or a double subtractive grating combo).
Nits are good, but what I've used in the lab is this type...
http://www.spectralcameras.com/files/SisuCHEMA_brochure.pdf
Nice, a pushbroom, aka slit and grating. 1 cube every 7 seconds or so...  So getting back to why this isn't standard SOP for watching a vehicle, in 7 seconds the event had already progressed well past the point of data being interesting.

I use to do a bunch of spectroscopy work for a monochromator/spectrograph company. We had products that did both push broom for building up the cubes and double subtractive systems which could produce very narrow bandpass images and then build up a stack of the images at different wavelengths. Advantage of building up the stacks is you could take images of only the bands you are interested in. A fair number of the double subtractive systems ended up being used in Raman systems that where looking at low energy raman states very close to the laser lines (think metals). But I digress as we await word from SpaceX.

Still curious if they had the internal LOX tank camera turned on and what did it see...
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/08/2016 08:31 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?

Oh that's an absolute fact they had their own cameras on this.

PS to all: Looooong thread and things always tend to naturally wander as the conversation expands, but keep it on this topic (this vehicle's pad failure) and keep your posts useful. A lot of people are "reading" as opposed to posting and they are likely watching this as much as they would an update thread (given the update thread has no actual updates over recent days).

We've got lots and lots of other threads you can use for less specific stuff.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/08/2016 08:40 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...

You could do a lot with far simpler gear than that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/08/2016 08:45 pm
...

Still curious if they had the internal LOX tank camera turned on and what did it see...

Eee... Considering, that the internals of the LOX tank do not have good natural lighting conditions, I would bet, that only thing you see from this video is following:
1. Everything is normal
2. Everything is oversaturated
3. Everything is black as camera went offline
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/08/2016 08:50 pm
...

Still curious if they had the internal LOX tank camera turned on and what did it see...

Eee... Considering, that the internals of the LOX tank do not have good natural lighting conditions, I would bet, that only thing you see from this video is following:
1. Everything is normal
2. Everything is oversaturated
3. Everything is black as camera went offline

I go so far as to say the inside of the LOX tank has absolutely no natural lighting 8) But the artificial lighting for the camera might be enough to catch some anomalous events before the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 08:54 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...

You could do a lot with far simpler gear than that.
Yes, they could do a camera conversion..
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: hrissan on 09/08/2016 08:57 pm
Anyone brought attention to the weld between bottom of the LOX tank and the tube running inside RP tank?

What if LOX would slowly drip there. Assuming there is 10cm of free space left at the top of the RP tank after fueling, that is 0.6 cubic meters of GOX, or ~0.6 liters (0.5kg) of LOX.

LOX falling from the small hole could even turn a bit of RP solid and make a small pool of LOX on the top...

As there is a vent from the top of RP tank to atmosphere (can be seen during end of normal static fires videos, when it is opened after engines stop running to release pressure from RP tank), this LOX boiling in RP tank might get unnoticed...

~1kg of mixed propellants (not sure about ignition source though) might be enough to rip the tank skin apart.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Fan Boi on 09/08/2016 08:59 pm
Minor nit: This thread title is "SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD" but that makes it sound like the pad failed. How about (Failure on Launchpad) or (Failure on Pad).
Sorry, been refreshing this thread over and over all day...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 08:59 pm
Anyone brought attention to the weld between bottom of the LOX tank and the tube running inside RP tank?

What if LOX would slowly drip there. Assuming there is 10cm of free space left at the top of the RP tank after fueling, that is 0.6 cubic meters of GOX, or ~0.6 liters (0.5kg) of LOX.

LOX falling from the small hole could even turn a bit of RP solid and make a small pool of LOX on the top...

As there is a vent from the top of RP tank to atmosphere (can be seen during end of normal static fires videos, when it is opened after engines stop running to release pressure from RP tank), this LOX boiling in RP tank might get unnoticed...

~1kg of mixed propellants (not sure about ignition source though) might be enough to rip the tank skin apart.
I did, a zillion pages back... ;D Slight correction my weld comment was more about the circumference of the tank, so your area is new as far as I know...

Edit:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/08/2016 09:00 pm
...

Still curious if they had the internal LOX tank camera turned on and what did it see...

Eee... Considering, that the internals of the LOX tank do not have good natural lighting conditions, I would bet, that only thing you see from this video is following:
1. Everything is normal
2. Everything is oversaturated
3. Everything is black as camera went offline

I go so far as to say the inside of the LOX tank has absolutely no natural lighting 8) But the artificial lighting for the camera might be enough to catch some anomalous events before the explosion.

Does anybody remember when they did the first refire of landed booster. Can't remember which one. Musk tweeted something about thrust not quote right.
Did we ever find out what it was?
I always thought it might have been a camera was ingested. Small enough maybe to make it thru the turbine and not blow things up. I thought after that test fire we saw a lot less inside tank video.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/08/2016 09:42 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...

SOP is to have cameras that record events, not cameras that are to record catastrophic events.  You want to get indications if something is odd on the pad right now.  The cameras aren't there, and weren't assigned specific functions, based on the possibility that a rocket might explode, so we might want spectral analysis.  They are there to, for example, visually confirm that a valve has closed, or that the TEL has retracted the correct amount, before going on to the next item of the count.  Especially if  a sensor fails and you can't tell if the TEL has retracted from the sensors on it, for example.

Cameras are for monitoring current events, not for reconstructing catastrophic failures.  You don't go in assuming catastrophic failures...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 10:05 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...

SOP is to have cameras that record events, not cameras that are to record catastrophic events.  You want to get indications if something is odd on the pad right now.  The cameras aren't there, and weren't assigned specific functions, based on the possibility that a rocket might explode, so we might want spectral analysis.  They are there to, for example, visually confirm that a valve has closed, or that the TEL has retracted the correct amount, before going on to the next item of the count.  Especially if  a sensor fails and you can't tell if the TEL has retracted from the sensors on it, for example.

Cameras are for monitoring current events, not for reconstructing catastrophic failures.  You don't go in assuming catastrophic failures...

Just a thought.

I'd point out that in the beginning of rocketry, Von Braun painted black & white patterns on the V2 prototypes precisely so he could determine the causes of failures.  example:  https://blackcablondon.files.wordpress.com/2013/07/v2-rocket-launch.png

While today, we no longer put checkerboard patterns on rockets, since they don't usually spin out of control, the cameras are there for the same reason.

If a rocket successfully launches, no one reviews the video unless there was a specific pre-launch question.

On the other-hand, since the probability of failure is high, cameras are not there for PR, but for failure analysis, just in case.  It's cheap insurance.

The question here is, while there were many cameras present, were they turned on at this phase of the test count down?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 10:11 pm

While today, we no longer put checkerboard patterns on rockets, since they don't usually spin out of control, the cameras are there for the same reason.


No, it is because we can get reliable telemetry to get the roll rate data.   It has nothing to do with reliability. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/08/2016 10:19 pm
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...

SOP is to have cameras that record events, not cameras that are to record catastrophic events.  You want to get indications if something is odd on the pad right now.  The cameras aren't there, and weren't assigned specific functions, based on the possibility that a rocket might explode, so we might want spectral analysis.  They are there to, for example, visually confirm that a valve has closed, or that the TEL has retracted the correct amount, before going on to the next item of the count.  Especially if  a sensor fails and you can't tell if the TEL has retracted from the sensors on it, for example.

Cameras are for monitoring current events, not for reconstructing catastrophic failures.  You don't go in assuming catastrophic failures...
I don't get what you are saying to me Doug. My only comment was about having a highly specialized camera was not now part of norm video ops outside of the IR they use in addition to the standard video tracking camera...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/08/2016 10:23 pm

While today, we no longer put checkerboard patterns on rockets, since they don't usually spin out of control, the cameras are there for the same reason.


No, it is because we can get reliable telemetry to get the roll rate data.   It has nothing to do with reliability.

LOL, I have to watch my phrasing around you. :)

I didn't mean to suggest that roll rate was the reason for cameras, but that globally for all launches, there's a 5.8% failure rate, and cameras are a good means albeit not the only of determining why.

source:  http://space.stackexchange.com/questions/8566/what-is-the-success-failure-ratio-of-space-bound-rockets
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/08/2016 10:47 pm

While today, we no longer put checkerboard patterns on rockets, since they don't usually spin out of control, the cameras are there for the same reason.


No, it is because we can get reliable telemetry to get the roll rate data.   It has nothing to do with reliability.

LOL, I have to watch my phrasing around you. :)

I didn't mean to suggest that roll rate was the reason for cameras, but that globally for all launches, there's a 5.8% failure rate, and cameras are a good means albeit not the only of determining why.

source:  http://space.stackexchange.com/questions/8566/what-is-the-success-failure-ratio-of-space-bound-rockets


Not all failures occur within range of high-detail photography, especially if they're more than a few dozen miles down range and all you can see is a small portion of the vehicle, from one or two fairly close vantage points. Telemetry is vastly more important than imagery for operational space flight. In fact, it is a good bet that most aerospace engineers would rather use the same resources spent on imagery and use it instead for more and higher-data rate telemetry instead. Aerospace is far, far beyond roll patterns on interstages and fins for FMEA and post-loss investigation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/08/2016 11:47 pm
Question for Jim, PadRat, others who actually work on the hardware:

How does SpaceX know that the consumables that they receive from 3rd parties are not contaminated, and that all of the pumps and lines on the pad are clear of foreign matter besides what is meant to flow through them? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/08/2016 11:56 pm
Question for Jim, PadRat, others who actually work on the hardware:

How does SpaceX know that the consumables that they receive from 3rd parties are not contaminated, and that all of the pumps and lines on the pad are clear of foreign matter besides what is meant to flow through them? 

They come with certs, some are sampled/tested, some fluids use filters
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/09/2016 01:23 am
Can anyone suggest a frame averaging freeware download that permits image enhancement within a static image between selected frame #s?

I'm trying to figure out how to compare the static images prior to the static images just prior.

I'd kinda like to use an algorithm that allows one to average multiple frames for up-sampling.  The ones I've found in the astrophotography world do that, but they tend to take the whole video stream and don't allow me to stop prior to everything going south.

The idea is that the USLaunchReport video is of low resolution, but averaging with up-sampling would provide a higher resolution image, and then looking at the last few frames prior to Frame 1, you might be able to take the two composites, difference them, and maybe see something that may or may not have happened.

I've downloaded and tried about 6 apps from the astronomy folks but they don't permit range selection from Video, i.e. choose frames 200-300, upsample, save. 

ICE from MSFT has a great example, but it's not on the available list of processing options.

Ideas?  :)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/09/2016 01:28 am
That sounds like a great way to convince yourself that JPEG compression artifacts represent real events.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 01:37 am
Jim,

One theory that came up earlier was a pinhole leak in a hydraulics system leading to a fuel-air explosion. But that would seem to be a hazard for any LOX-based launch vehicle. Do you know if there are non-flammable hydraulic fluids, and is it typical for rocket companies to use those non-flammable hydraulic fluids in their launch site hydraulics (ie stuff that is going to be operating near venting GOX)?

I did a quick bit of googling, and it does look like there's a whole class of Flame Resistant Hydraulic Fluids, that are meant for use specifically in areas where they're operating near flame or other hazards, but do you know if it's standard practice to use those types of hydraulic fluid? Do you know if SpaceX does?

Just curious. Because if the hydraulic fluid they were using wasn't flammable, I'm back to wondering where they would've had a pressurized fuel source that could've created the Fuel Air Explosion that others are suggesting was the cause of the incident.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/09/2016 01:40 am
That sounds like a great way to convince yourself that JPEG compression artifacts represent real events.

LOL, except, I know all about artifacts, PM me and I'll email you one of my academic papers from 20 years ago.

I'm a wavelet boy at heart.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 01:45 am
Jim,

One theory that came up earlier was a pinhole leak in a hydraulics system leading to a fuel-air explosion. But that would seem to be a hazard for any LOX-based launch vehicle. Do you know if there are non-flammable hydraulic fluids, and is it typical for rocket companies to use those non-flammable hydraulic fluids in their launch site hydraulics (ie stuff that is going to be operating near venting GOX)?

I did a quick bit of googling, and it does look like there's a whole class of Flame Resistant Hydraulic Fluids, that are meant for use specifically in areas where they're operating near flame or other hazards, but do you know if it's standard practice to use those types of hydraulic fluid? Do you know if SpaceX does?

Just curious. Because if the hydraulic fluid they were using wasn't flammable, I'm back to wondering where they would've had a pressurized fuel source that could've created the Fuel Air Explosion that others are suggesting was the cause of the incident.

~Jon

One other question--if they were using a FRHF, do you know what type? It sounds like there are many options, but some of them might be more or less safe in an oxidizer rich environment. I have a hard time thinking that SpaceX wouldn't have looked into something like this, but it's worth asking.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/09/2016 01:57 am
Just curious regarding all the discussion about SpaceX having their own video of the failure: Is that an assumption or an established fact?
They would need a full spectrum camera for analysis which is not sop...

SOP is to have cameras that record events, not cameras that are to record catastrophic events.  You want to get indications if something is odd on the pad right now.  The cameras aren't there, and weren't assigned specific functions, based on the possibility that a rocket might explode, so we might want spectral analysis.  They are there to, for example, visually confirm that a valve has closed, or that the TEL has retracted the correct amount, before going on to the next item of the count.  Especially if  a sensor fails and you can't tell if the TEL has retracted from the sensors on it, for example.

Cameras are for monitoring current events, not for reconstructing catastrophic failures.  You don't go in assuming catastrophic failures...
I don't get what you are saying to me Doug. My only comment was about having a highly specialized camera was not now part of norm video ops outside of the IR they use in addition to the standard video tracking camera...

Yeah, sorry -- I usually take more time with my posts, but I was rushing to make a quick point during a break at work today.

All I was trying to say is that, under normal circumstances, the reason for having cameras is for monitoring items on the rocket and on the pad to visually verify status of various items.  Their purpose is not so much to gather data to be used in accident investigations, it is for the moment-to-moment verification of things you want to verify before you give your "go" to proceed with the count.

Yes, such data has been used in accident investigations in the past, and yes, it can be useful.  But accident investigation isn't their purpose, and therefore they aren't designed and implemented with accident investigation in mind.

It's sort of like the sensors on the rocket itself -- they are designed to provide performance data that lets you verify how the systems are working, and that you are ready for the next phase of the mission.  They are not designed with accident investigation in mind, either.  The way you can tell that is that SpaceX, as with most rockets as they gain maturity, has, I have read, been reducing the number of sensors in the rockets.  This saves a little weight, and is done because you just don't need strain gauges all over the place, you have now well-characterized all the performance data.

Now, since we all know that rockets can blow up, is it worthwhile to have a bunch of multi-spectral cameras watching them during launches and static fires?  I guess that depends on how likely you think it is that you will need that kind of data, both on any given launch or static fire, and even in the event of an accident investigation.

I think that in most circumstances, a multi-spectral camera will not be high up on the list of items you can use to prune your fault tree.  Since this is the first pad explosion in a heck of a long time, and the first in something like 50 years on a rocket that had not yet fired its engines, I'm pretty sure that very few people would have thought there was any likelihood of any kind of explosion eight minutes prior to planned engine ignition.  None of the activities that were in process at the time of this anomaly were considered likely to cause such an accident, so while it was a hazardous test (any test with propellant loading is considered hazardous), the likelihood of such a thing happening would have been thought, prior to last week, to be vanishingly small.

Even if you believe that a pad fallback case is possible and you want to use multi-spectral imagery to try and prune the fault tree for that kind of thing, you likely wouldn't start up the camera until closer to launch than eight minutes.  Again, it's been so long since a rocket blew up during prop loading that the possibility was, I believe, thought to be so low that no special data gathering that could support accident investigation was called for.

Now, since this event has happened, that means that people will be more aware and perhaps more interested in gathering data during prop loading, just in case.  And I'm not just talking about SpaceX.  It's perhaps opened up some eyes and reminded people that there is, indeed, a reason why tests of a fueled rocket are considered hazardous, and maybe any time you fuel a rocket, you ought to keep a close eye on it, just in case.

It's not been SOP not because there is no interest in gathering data during periods where you could have catastrophic failures, but more that prop loading and even static fires just haven't been considered very likely to be times when you are likely to have such failures.

Should they be in the future?  Maybe -- but it all comes down to trying to anticipate when you are most likely to get hit with such failures, and the best sensors to have deployed just in case.  And since catastrophic failures are hard to predict, both in timing and in causes, you end up prioritizing on the best data gathering for your development dollar.

Hard to say what changes might come out of this failure, though...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/09/2016 01:59 am
Tory Bruno weighs in on SpaceX's pad failure...

http://fortune.com/2016/09/08/spacex-grounded/

“It typically takes nine to 12 months for people to return to flight. That’s what the history is,” Tory Bruno, chief executive of United Launch Alliance, told Reuters.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 02:09 am
Tory Bruno weighs in on SpaceX's pad failure...

http://fortune.com/2016/09/08/spacex-grounded/

“It typically takes nine to 12 months for people to return to flight. That’s what the history is,” Tory Bruno, chief executive of United Launch Alliance, told Reuters.

I think they're reading more into what Bruno said than should be. He's just saying that without more details about what actually happened, the best you can do is look at historical trends for this type of accident recovery. He is right that this stuff has historically often take a long time, but he was not necessarily saying that he thinks it'll take a long time this time around.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/09/2016 02:10 am
All I was trying to say is that, under normal circumstances, the reason for having cameras is for monitoring items on the rocket and on the pad to visually verify status of various items.  Their purpose is not so much to gather data to be used in accident investigations, it is for the moment-to-moment verification of things you want to verify before you give your "go" to proceed with the count.

I don't buy that.  They and everyone else go to considerable effort to send many channels of telemetry data while the rocket is flying.  By then, it's too late to take any action, and there's no way to even get the rocket to change anything other than to destroy it.  The only logical reason to have all that detailed telemetry is for investigation of things going wrong.

Compared with putting all the sensors and wiring and transmitters and such on the rocket for telemetry, putting some cameras around the launch pad is trivial.  Cameras may have other purposes too, but I can't believe at least one of their main purposes isn't for investigation of anomalies.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Brovane on 09/09/2016 02:12 am
Tory Bruno weighs in on SpaceX's pad failure...

http://fortune.com/2016/09/08/spacex-grounded/

“It typically takes nine to 12 months for people to return to flight. That’s what the history is,” Tory Bruno, chief executive of United Launch Alliance, told Reuters.

So I wonder how he explains the RTF from CRS-7 taking 6-months.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Robotbeat on 09/09/2016 02:17 am
Russia just brushes the debris off the launch pad and launches again. Practically.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 02:21 am
Tory Bruno weighs in on SpaceX's pad failure...

http://fortune.com/2016/09/08/spacex-grounded/

“It typically takes nine to 12 months for people to return to flight. That’s what the history is,” Tory Bruno, chief executive of United Launch Alliance, told Reuters.

So I wonder how he explains the RTF from CRS-7 taking 6-months.

As I said above, I think you're reading too much into it. I think he was trying to say politely that he had no better idea than anyone else who's not at SpaceX, but here's what it has typically been in the past. Not "it can't go any faster than this" or "it's definitely going to take them a long time to figure this out", but more a "how on earth am I supposed to answer that question--here's what it's taken historically, but beyond that your guess is as good as mine".

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 02:23 am
Russia just brushes the debris off the launch pad and launches again. Practically.

Actually, they've had stand-downs for Proton failures. Maybe they could've brushed things off for military launches back during the USSR days, but paying customer typically like to see you prove you've fixed your rocket before they trust putting an expensive commsat on top for another roll of the dice.

I think someone from SpaceNews was pointing out that right now 2 of the 3 primary commercial satellite launchers (F9 and Proton) are stood down, and Ariane V is booked solid through the end of next year.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: alang on 09/09/2016 03:03 am
https://www.youtube.com/watch?v=7nL10C7FSbE

Shows that a direct flame does not ignite Jet-A, it needs to be an aerosol

Thanks Jim - also suggests how dangerous 'gasoline' is. I'm not sure I'd be sat down at a bench playing with a volatile liquid fuel.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/09/2016 03:31 am
What kind of external analytical tools would normally be monitoring this? Obviously there would be cameras and sound, but would they have anything like a spectral analyser monitoring it or anything like that?

Although the video spectral information may be lost with a three colour camera, the audio information could still be analysed after the fact. For example, here is a 1/3 octave analysis of the squeak heard after the initial explosion, but before the sound arrived via the atmosphere at the USLR camera. The fundamental tone is around 100 Hz, but there are harmonics above that frequency, e.g. at 400 Hz.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 03:49 am
Tory Bruno weighs in on SpaceX's pad failure...

http://fortune.com/2016/09/08/spacex-grounded/

“It typically takes nine to 12 months for people to return to flight. That’s what the history is,” Tory Bruno, chief executive of United Launch Alliance, told Reuters.

So I wonder how he explains the RTF from CRS-7 taking 6-months.

As I said above, I think you're reading too much into it. I think he was trying to say politely that he had no better idea than anyone else who's not at SpaceX, but here's what it has typically been in the past. Not "it can't go any faster than this" or "it's definitely going to take them a long time to figure this out", but more a "how on earth am I supposed to answer that question--here's what it's taken historically, but beyond that your guess is as good as mine".

~Jon

https://twitter.com/torybruno/status/774080155186757632

Tory: "Not what I said. I have no insider info and will not speculate. Described a study of historical industry failures."

IOW, media guy takes something out of context, tries to make it look controversial. Dog bites man, news at 11.

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: R7 on 09/09/2016 07:21 am
Anyone brought attention to the weld between bottom of the LOX tank and the tube running inside RP tank?

Contemplated that (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1579576#msg1579576) a while back, sudden failure in the riser/bulkhead joint.

Slow pinhole leak might be another way, turning LOX to GOX in the ullage as you described. That would significantly cool the ullage so if there are temperature sensors there they would have noticed early on.

Anyone know if there's any insulation in the common bulkhead? The riser must have otherwise its walls would turn RP-1 into goo.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: baskerbosse on 09/09/2016 07:29 am
Just out of curiosity,

I have heard SpaceX uses GoPro cameras for video feeds. Is this true?
Does anyone know where the GoPro cameras are located on the rocket?
Are they stock standard or modified?

Cheers,
Peter
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: 0Firefly on 09/09/2016 07:49 am
No good news from SpaceX on Twitter...

https://twitter.com/elonmusk/status/774150065166229504

Elon Musk:
Still working on the Falcon fireball investigation. Turning out to be the most difficult and complex failure we have ever had in 14 years.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 07:55 am
Elon:

"Still working on the Falcon fireball investigation. Important to note that this happened during a routine filling operation. Engines were not on and there was no apparent heat source. Turning out to be the most difficult and complex failure we have ever had in 14 years.. Support & advice from @NASA, @FAA, @AFPAA & others much appreciated. Please email any recordings of the event to [email protected]. Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else."

That sure sounds to me like they can't figure out the source of the fire. Based on other leaks it seems the know the fire started externally. They likely know the venting LOX ignited (hence trying to find the source of heat), but from what?

-- start of edit by Lar --
Here are the links to the tweets:
https://twitter.com/elonmusk/status/774150065166229504
Quote
Still working on the Falcon fireball investigation. Turning out to be the most difficult and complex failure we have ever had in 14 years.

https://twitter.com/elonmusk/status/774150289314029568
Quote
Important to note that this happened during a routine filling operation. Engines were not on and there was no apparent heat source.

https://twitter.com/elonmusk/status/774152037927792640
Quote
Support & advice from @NASA, @FAA, @AFPAA & others much appreciated. Please email any recordings of the event to [email protected].

https://twitter.com/elonmusk/status/774153847371501569
Quote
Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else.

Please note that the rules of evidence haven't been suspended for this thread. There is another thread to host more speculative discussion.    http://forum.nasaspaceflight.com/index.php?topic=41119.msg1581039#msg1581039

-- end edits by Lar --
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jarnis on 09/09/2016 07:58 am
Well, that's worrisome. I mean, if a week later they still apparently don't have a good candidate for the cause...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toastmastern on 09/09/2016 07:59 am
Just out of curiosity,

I have heard SpaceX uses GoPro cameras for video feeds. Is this true?
Does anyone know where the GoPro cameras are located on the rocket?
Are they stock standard or modified?

Cheers,
Peter

I've read somewhere that they started to make their own cameras a few years back, but before that I believe they used GoPro's yea
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DJPledger on 09/09/2016 08:02 am
Elon:

"Still working on the Falcon fireball investigation. Important to note that this happened during a routine filling operation. Engines were not on and there was no apparent heat source. Turning out to be the most difficult and complex failure we have ever had in 14 years.. Support & advice from @NASA, @FAA, @AFPAA & others much appreciated. Please email any recordings of the event to [email protected]. Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else."

That sure sounds to me like they can't figure out the source of the fire. Based on other leaks it seems the know the fire started externally. They likely know the venting LOX ignited (hence trying to find the source of heat), but from what?
Could the explosion been caused by a short circuit somewhere within the GSE? Short circuits can easily be powerful enough to cause a large explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:07 am
Could the explosion been caused by a short circuit somewhere within the GSE? Short circuits can easily be powerful enough to cause a large explosion.

I had earlier speculated this was the cause, but that's what he's saying, they haven't found a short, or an arc, or a spark, or anything else that could cause (what I think they believe to be) ignition of the venting LOX.

He further said they hadn't ruled out a drone or other impact. It's kind of crazy they're even thinking that direction in my opinion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:10 am
Well, that's worrisome. I mean, if a week later they still apparently don't have a good candidate for the cause...


With the thousands of telemetry channels and and video feeds they have, the fact that they not only don't have a likely candidate, but they don't have any candidate means at the very least the failure occurred in a place thought impossible to occur, and thus was unmonitored. Or it was external to the rocket and GSE and thus impossible to predict.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:12 am
Could the explosion been caused by a short circuit somewhere within the GSE? Short circuits can easily be powerful enough to cause a large explosion.

I had earlier speculated this was the cause, but that's what he's saying, they haven't found a short, or an arc, or a spark, or anything else that could cause (what I think they believe to be) ignition of the venting LOX.

He further said they hadn't ruled out a drone or other impact. It's kind of crazy they're even thinking that direction in my opinion.

Might I ask where he mentioned external impacts?

https://twitter.com/elonmusk/status/774155416976580608

and screen grab attached
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:13 am
Just out of curiosity,

I have heard SpaceX uses GoPro cameras for video feeds. Is this true?
Does anyone know where the GoPro cameras are located on the rocket?
Are they stock standard or modified?

Cheers,
Peter

I've read somewhere that they started to make their own cameras a few years back, but before that I believe they used GoPro's yea

This is correct, but AFAIK only for cameras on board the rocket. I believe they use commercial cameras on the droneships and GSE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DJPledger on 09/09/2016 08:13 am
Could the explosion been caused by a short circuit somewhere within the GSE? Short circuits can easily be powerful enough to cause a large explosion.

I had earlier speculated this was the cause, but that's what he's saying, they haven't found a short, or an arc, or a spark, or anything else that could cause (what I think they believe to be) ignition of the venting LOX.

He further said they hadn't ruled out a drone or other impact. It's kind of crazy they're even thinking that direction in my opinion.
Could there be the possibility that Amos-6 was sabotaged in some way? Some people on Twitter seem to think that foul play may have been at hand.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jakusb on 09/09/2016 08:14 am
Sounds like they worked through the fault tree and found nothing wrong and are left with more questions then answers.
As they intimately know their own rocket, I guess they particularly  could not figure out what would cause ignition from any of the possible elements in that part of the rocket/erector.
An failing tank, compartment or COPV would likely be visible before any form of ignition, would it not? Also such an event would/should clearly be visible in several of the 3000 telemetry channels.
Pretty worrisome they seem at a loss at this moment. Strange he reaches out to NASA via Twitter..
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/09/2016 08:18 am
Well, that's worrisome. I mean, if a week later they still apparently don't have a good candidate for the cause...


With the thousands of telemetry channels and and video feeds they have, the fact that they not only don't have a likely candidate, but they don't have any candidate means at the very least the failure occurred in a place thought impossible to occur, and thus was unmonitored. Or it was external to the rocket and GSE and thus impossible to predict.

Yep, it is actually quite a (potentially) positive thing for F9 as a system. GSE should also be heavily monitored, so that is also likely exempt as a causal factor.

All that is really left are highly unlikely and thus un-modeled or unpredicted eventualities. Also possible is a failure of the sensor network design, in the sense that a cause may have slipped unidentified through an accidental gap in vehicle and ground systems monitors. The likeliest cause is possibly some sort of extremely complex and/or improbable series of events that culminated in ignition, somehow.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:20 am
Could there be the possibility that Amos-6 was sabotaged in some way? Some people on Twitter seem to think that foul play may have been at hand.

Any time Israel is involved there will always be that train of thought - sometimes rightfully - but in this particular case I personally feel it's far more likely that if there is sabotage involved, it's targeted towards SpaceX rather than Spacecom.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jakusb on 09/09/2016 08:20 am
Could the explosion been caused by a short circuit somewhere within the GSE? Short circuits can easily be powerful enough to cause a large explosion.

I had earlier speculated this was the cause, but that's what he's saying, they haven't found a short, or an arc, or a spark, or anything else that could cause (what I think they believe to be) ignition of the venting LOX.

He further said they hadn't ruled out a drone or other impact. It's kind of crazy they're even thinking that direction in my opinion.
Could there be the possibility that Amos-6 was sabotaged in some way? Some people on Twitter seem to think that foul play may have been at hand.
Every incident has people claiming:
- terrorism
- ufo's
- black opps
- sabotage of any kind

Most of these claims are from people seeking attention or are trolling.

Of course with an investigation resulting in no answer, you will get at branches of fault tree that would normally be even ridiculous to consider. It seems we are getting to that stage now.
Drone, bullet, laser, anything external that does not show up on the video, but introduces heat near 2nd stage fuel valve.

Also any serious quality theorizing done on this forum on what could cause ignition is increasingly likely to potentially help SpaceX.  ;) (given they now openly reach out for any help)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/09/2016 08:22 am
Could there be the possibility that Amos-6 was sabotaged in some way? Some people on Twitter seem to think that foul play may have been at hand.

Any time Israel is involved there will always be that train of thought - sometimes rightfully - but in this particular case I personally feel it's far more likely that if there is sabotage involved, it's targeted towards SpaceX rather than Spacecom.

Also, as a rule, it is generally useful to invoke Occam's Razor in the context of most things analytical. In the sense of launch vehicle failures, this means avoiding the invocation of external actors before all other possible routes of failure have been ruled out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:23 am
Sounds like they worked through the fault tree and found nothing wrong and are left with more questions then answers.

Agreed.

As they intimately know their own rocket, I guess they particularly  could not figure out what would cause ignition from any of the possible elements in that part of the rocket/erector.

And let's not forget, due to the venting LOX and high pressure fuel lines, any possible source is looked for and engineered out of the equation - in theory. This isn't an overlooked area of rocket science.

An failing tank, compartment or COPV would likely be visible before any form of ignition, would it not? Also such an event would/should clearly be visible in several of the 3000 telemetry channels.

We all (most?) thought based on the video alone the ignition point was external to the rocket. They likely are more confident of that now, but until they've determined a cause they can't rule anything out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:25 am
Also, as a rule, it is generally useful to invoke Occam's Razor in the context of most things analytical. In the sense of launch vehicle failures, this means avoiding the invocation of external actors before all other possible routes of failure have been ruled out.

Of course, but it appears in this case they haven't found a cause in the rocket or GSE, which means they have to look externally.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jakusb on 09/09/2016 08:28 am
Any chance we have sound of that "quieter bang" Elon mentioned?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/09/2016 08:31 am
Any chance we have sound of that "quieter bang" Elon mentioned?

Attached below, two sounds, at 6 and 8 seconds. Unless he means a sound from a recording other than the USLR one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:32 am
Since Musk commented on the external impact theory, I'll give some thoughts. Based on my own armchair analysis of the video, I don't think the purported videos showing impact are true. Even for pro racing drones, they are moving too fast.

My next train of thought would be a bird shorting something. But they would have on video a bird in the area, even if not the short itself, I have to assume they have enough cameras around the area of ignition to see a bird around there.

Then for fun let's think about guns. Elon actually tweeted they heard a sound before the explosion they can't source. Let's say someone pulled off the road with a .50 cal. There are numerous spots within 2 miles, well within range of the gun. The first bang heard could in theory be the sound barrier being broken by the bullet.

Finally, there is the laser threat. Unlike the .50 cal, this would have to be corporate sabotage or nation state, but it is in theory possible.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/09/2016 08:32 am
Jim,

One theory that came up earlier was a pinhole leak in a hydraulics system leading to a fuel-air explosion. But that would seem to be a hazard for any LOX-based launch vehicle. Do you know if there are non-flammable hydraulic fluids, and is it typical for rocket companies to use those non-flammable hydraulic fluids in their launch site hydraulics (ie stuff that is going to be operating near venting GOX)?

1. I would be surprised if anyone has done any research on this, but from what I know of LOX (not as much as some..) I would imagine that pretty much any hydrocarbon-based fluid (RP-1 or Hydraulic Oil) atomised into a LOX cloud via a pinhole leak would be an accident waiting to happen.  If it happens to be a low-conductivity fluid like RP-1, simply spraying it from a pinhole can generate enough static electricity to ignite it if the spray happens to hit something conductive like the tower or the rocket itself.   They put ASA in jet fuel to help prevent this, but for various reasons I'm not sure they use ASA in RP-1.. it's up to the customer I suppose.

2. A pinhole leak in a LOX hose would physically blow it apart, so assuming they can find the umbilicals that should be a relatively easy one to rule in or out.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:34 am
Any chance we have sound of that "quieter bang" Elon mentioned?

Attached below, two sounds, at 6 and 8 seconds. Unless he means a sound from a recording other than the USLR one.

This is a good point, esp with regards to be (admittedly unlikely) .50 cal theory. If the first bang was recorded near the cameras away from the pad, then a gun is in play. If it was recorded on the pad, that likely eliminates a gun as a potential source.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:37 am
2. A pinhole leak in a LOX hose would physically blow it apart, so assuming they can find the umbilicals that should be a relatively easy one to rule in or out.

My interpretation is they know the location of the ignition, but not the source of the ignition. So they know it was outside the rocket, but that doesn't mean something inside the rocket didn't cause it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/09/2016 08:37 am
Also, as a rule, it is generally useful to invoke Occam's Razor in the context of most things analytical. In the sense of launch vehicle failures, this means avoiding the invocation of external actors before all other possible routes of failure have been ruled out.

Of course, but it appears in this case they haven't found a cause in the rocket or GSE, which means they have to look externally.

That is likely mostly true, agreed. They will most certainly continue exploring all possible avenues of failure through the vehicle and ground systems, SpaceX has probably only truly explored in depth all the likely sources of failure and will now branch out extensively into more extreme scenarios.

Regarding external sources of failure, I can simplify my intent: only invoke agency as a causal factor after all other possibilities have been ruled out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/09/2016 08:39 am
Since Musk commented on the external impact theory, I'll give some thoughts. Based on my own armchair analysis of the video, I don't think the purported videos showing impact are true. Even for pro racing drones, they are moving too fast.

My next train of thought would be a bird shorting something. But they would have on video a bird in the area, even if not the short itself, I have to assume they have enough cameras around the area of ignition to see a bird around there.

Then for fun let's think about guns. Elon actually tweeted they heard a sound before the explosion they can't source. Let's say someone pulled off the road with a .50 cal. There are numerous spots within 2 miles, well within range of the gun. The first bang heard could in theory be the sound barrier being broken by the bullet.

Finally, there is the laser threat. Unlike the .50 cal, this would have to be corporate sabotage or nation state, but it is in theory possible.

The thing about a bullet is that it would almost certainly be supersonic at the point of impact, meaning that the report would only be heard after (and likely several seconds after for a shot from a mile or more out).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccicchitelli on 09/09/2016 08:41 am
The thing about a bullet is that it would almost certainly be supersonic at the point of impact, meaning that the report would only be heard after (and likely several seconds after for a shot from a mile or more out).

Oh I know, but it depends on which video he's refering to: http://forum.nasaspaceflight.com/index.php?topic=30981.msg1580972#msg1580972
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ricmsmith on 09/09/2016 08:50 am
Any chance we have sound of that "quieter bang" Elon mentioned?

Attached below, two sounds, at 6 and 8 seconds. Unless he means a sound from a recording other than the USLR one.

This is a good point, esp with regards to be (admittedly unlikely) .50 cal theory. If the first bang was recorded near the cameras away from the pad, then a gun is in play. If it was recorded on the pad, that likely eliminates a gun as a potential source.

Neither of the noises on that recording sound like any kind of gun I've ever heard.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/09/2016 09:11 am
Elon:

Support & advice from @NASA, @FAA, @AFPAA & others much appreciated.

Will we see @FBI and @DHSgov in this list?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/09/2016 09:18 am
What failure modes would have been immediately obvious from telemetry data and can those be ruled out after Elons tweets (COPV, LOX condensing from air,...)?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/09/2016 09:24 am
IF they still have the S2 LOX tank camera, and the tank was not full, ISTM they could quickly rule out COPV's.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/09/2016 09:28 am
What failure modes would have been immediately obvious from telemetry data and can those be ruled out after Elons tweets (COPV, LOX condensing from air,...)?

After eight days of intensive examination on behalf of dozens or hundreds of highly knowledgeable engineers, it is very hard to say. Many, many things have likely been ruled out beyond reasonable doubt. This likely includes essentially every single obvious or readily apparent possibility, essentially every cause that would have generated data.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CJ on 09/09/2016 09:39 am
IMHO, the news from Musk means that causes which would be strongly indicated by instrumentation (Such as, I'm guessing, COPV - which until now was my personal top suspect) should have their odds lowered on the suspect list. 

Also IMHO, if SpaceX hasn't ruled anything out, it'd be unwise for us to do so (provided it's possible).

So, I'm going to go way the heck off the deep end here and speculate obnoxiously on the bang Musk mentioned; he's looking for recordings, and one possible use for those is triangulation. Just as one would do for, say, a gunshot. Could a rifle bullet (hitting S2 or the payload or the TLE) do what we've seen?

Edit to add: New tweet by Elon Musk, and this one does rule something out. He was asked if it was aliens, and he replied, "Nope, it wasn't me.". https://twitter.com/elonmusk/status/774154956739743750
Glad to see he still has his sense of humor during what must be a very trying time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/09/2016 09:52 am
Elon:

Support & advice from @NASA, @FAA, @AFPAA & others much appreciated.

Will we see @FBI and @DHSgov in this list?

That would be the thing to look out for if it goes down that road. I didn't hear of any increased security for the Atlas V launch yesterday, however.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/09/2016 09:57 am
Where are the batteries stored in F9 S2?.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: WBY1984 on 09/09/2016 10:01 am
Any chance we have sound of that "quieter bang" Elon mentioned?

Attached below, two sounds, at 6 and 8 seconds. Unless he means a sound from a recording other than the USLR one.

This is a good point, esp with regards to be (admittedly unlikely) .50 cal theory. If the first bang was recorded near the cameras away from the pad, then a gun is in play. If it was recorded on the pad, that likely eliminates a gun as a potential source.

Neither of the noises on that recording sound like any kind of gun I've ever heard.

Didn't someone on here yesterday posit that the first thump could've been sound transmitted through the ground, which would reach the microphone quicker than the pressure wave through the air?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/09/2016 10:01 am
>
So, I'm going to go way the heck off the deep end here and speculate obnoxiously on the bang Musk mentioned; he's looking for recordings, and one possible use for those is triangulation. Just as one would do for, say, a gunshot. Could a rifle bullet (hitting S2 or the payload or the TLE) do what we've seen?
>

Bullets hitting metal, especially steel, can make sparks. Some are solids, some have hardened cores or charges in them or can be rigged with either (in a hollow point. Don't ask.) A tuned rifle (ex: snipers 7.62 NATO, Lapua or Barrett - all commercially available) can put your eye out a mile away. 3.7m rocket? More, even without a targeting computer.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RedSky on 09/09/2016 10:02 am
Well, now that the bullet theory has been brought up, you don't need someone on land lurking nearby. Might as well go full conspiracy: Do they close off boating traffic offshore for a static test?  If not, someone should check if any Russian trawlers or small pleasure craft were "fishing" just offshore. Just joking, but at this point...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/09/2016 10:06 am
Well, now that the bullet theory has been brought up, you don't need someone on land lurking nearby. Might as well go full conspiracy: Do they close off boating traffic offshore for a static test?  If not, someone should check if any Russian trawlers or small pleasure craft were "fishing" just offshore. Just joking, but at this point...

Why would they need to use a firearm? Since we're playing full conspiracy, why not a small shaped charge with an incendiary mounted to an innocuous and easily missed spot on the strongback? The origin point of the explosion for this whole incident is perfectly positioned to shred the bulkhead separating the S2 fuel tanks and mix them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Giovanni DS on 09/09/2016 10:06 am
I would also consider something placed on the erector structure, no need of projectiles, a very small device could have been hidden there.

Is the erector routinely inspected for "extraneous devices"?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jakusb on 09/09/2016 10:15 am
Also this reply, make of it what you want.
Quote
AJ ‏@ashwin7002 34m34 minutes ago

@elonmusk @NASA @faa @AFPAA there are some videos on YouTube claiming something hit the rocket. Any reality there?
Quote
Elon Musk Verified account
‏@elonmusk:

@ashwin7002 @NASA @faa @AFPAA We have not ruled that out.

I guess many more branches on the fault tree are still open, varying in likelihood.
Elon confirming one is open, does not exclude any other... ;)
But it does imply many obvious ones are pretty much closed. As mentioned, likely all connected to telemetry.
Or they did find stuff in telemetry, but for now ruled it as other then root cause... Although also a possibility comes to mind that stuff is found in telemetry, even possible root cause, but something that should not escalate to this destruction... However, seems unlikely as Elon tends to be pretty open on such discoveries..
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lampyridae on 09/09/2016 10:20 am
Any chance we have sound of that "quieter bang" Elon mentioned?

Attached below, two sounds, at 6 and 8 seconds. Unless he means a sound from a recording other than the USLR one.

This is a good point, esp with regards to be (admittedly unlikely) .50 cal theory. If the first bang was recorded near the cameras away from the pad, then a gun is in play. If it was recorded on the pad, that likely eliminates a gun as a potential source.

Neither of the noises on that recording sound like any kind of gun I've ever heard.

Didn't someone on here yesterday posit that the first thump could've been sound transmitted through the ground, which would reach the microphone quicker than the pressure wave through the air?

No. Not even quarry blasts have this kind of audible ground "thump," although you may hear a rumble which is essentially dirt grinding against each other. Just because the ground vibrates doesn't mean it will transmit that back into the air as a sound wave. There are a large number of raypaths and different vibrational modes, so no. If I were SpaceX, I would be looking for nearby seismic data. If it were a source coupled to the ground, it would show up as a trace from a reasonable distance.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/09/2016 10:22 am
Also this reply, make of it what you want.
Quote
AJ ‏@ashwin7002 34m34 minutes ago

@elonmusk @NASA @faa @AFPAA there are some videos on YouTube claiming something hit the rocket. Any reality there?
Quote
Elon Musk Verified account
‏@elonmusk:

@ashwin7002 @NASA @faa @AFPAA We have not ruled that out.

This might just fit with a rumour coming from within SpaceX (days ago, but I refrained from posting because rumours are usually just that: rumours) that substantial parts of the fault tree focusing on F9 itself have been closed with parts focusing on GSE and external sources (meaning not the GSE and not the vehicle) still wide open.

If somehow the cause of this would be not associated with the vehicle, nor with the GSE, this could become real interesting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RedSky on 09/09/2016 10:25 am
The problem with some "device" on the erector is that requires either an inside job, or someone evading detection while sneaking onto a secure military base.  With those scenarios, there is a possibility of capture and exposure.  A boat offshore remains anonymous and can just slip away.  Who would like to get their commercial launch business back?  Who is hacking all sorts of sensitive US servers?   Sad to say, but this stuff just writes itself.  Which is why this sort of cause will be almost impossible to confirm.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/09/2016 10:38 am
Well, now that the bullet theory has been brought up, you don't need someone on land lurking nearby. Might as well go full conspiracy: Do they close off boating traffic offshore for a static test?  If not, someone should check if any Russian trawlers or small pleasure craft were "fishing" just offshore. Just joking, but at this point...

Why would they need to use a firearm?

With the proper firearm and ammunition, potentially effective from beyond the security zone.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/09/2016 10:59 am
How would a single shot with a gun disperse enough fuel AND oxidizer quickly enough to create such a big, immediate fireball? Wouldn't that disperse more of one fuel fist?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bynaus on 09/09/2016 11:05 am
How would a single shot with a gun disperse enough fuel AND oxidizer quickly enough to create such a big, immediate fireball? Wouldn't that disperse more of one fuel fist?

Or, one could ask the complement to that question: where and when would you shoot to intentionally blow up a rocket?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/09/2016 11:08 am
Didn't someone on here yesterday posit that the first thump could've been sound transmitted through the ground, which would reach the microphone quicker than the pressure wave through the air?

No. Not even quarry blasts have this kind of audible ground "thump," although you may hear a rumble which is essentially dirt grinding against each other. Just because the ground vibrates doesn't mean it will transmit that back into the air as a sound wave. There are a large number of raypaths and different vibrational modes, so no. If I were SpaceX, I would be looking for nearby seismic data. If it were a source coupled to the ground, it would show up as a trace from a reasonable distance.

Could it make a difference that the ground water table at the cape is very near the surface? The primary underground acoustic transmission could be by that water. If the water table vibrates at an audible frequency, why would the vibration not be transmitted to the air, even though attenuated considerably at the ground/air interface?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/09/2016 11:13 am
Can anyone suggest a frame averaging freeware download that permits image enhancement within a static image between selected frame #s?

Try using a video editor to slice out the footage you want to average and then use that with the astronomy software.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/09/2016 11:13 am
How would a single shot with a gun disperse enough fuel AND oxidizer quickly enough to create such a big, immediate fireball? Wouldn't that disperse more of one fuel fist?

Or, one could ask the complement to that question: where and when would you shoot to intentionally blow up a rocket?

Just to be clear: I didn't mean to say that you can't take out a rocket with a single gun shot with decent caliber or ammunition with a hit anywhere in the tankage, I just don't think it would look this way.
The initial fireball simply is too big and obviously fueled by fuel from S2, I personally don't yet believe the origin (important origin <> cause) of the incident was outside the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/09/2016 11:21 am
I dont know if mod action is required for this, but could someone interested in the sabotage/shooting hypothesis please start a new thread? The hypothesis cant be ruled out easily but I suggest this because the sabotage stuff has so much potential for all sorts of conspiracy theories that have no place in a technical analysis of this failure. Also, I dont do it myself because I dont want my name attached to it. Thank you.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul Adams on 09/09/2016 11:27 am
http://www.bbc.com/news/business-37316836
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/09/2016 11:33 am
I dont know if mod action is required for this, but could someone interested in the sabotage/shooting hypothesis please start a new thread? The hypothesis cant be ruled out easily but I suggest this because the sabotage stuff has so much potential for all sorts of conspiracy theories that have no place in a technical analysis of this failure. Also, I dont do it myself because I dont want my name attached to it. Thank you.

Seconded. This ought to be a technical, rational thread discussing and parsing through the failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/09/2016 11:36 am
Any chance we have sound of that "quieter bang" Elon mentioned?

Attached below, two sounds, at 6 and 8 seconds. Unless he means a sound from a recording other than the USLR one.

This is a good point, esp with regards to be (admittedly unlikely) .50 cal theory. If the first bang was recorded near the cameras away from the pad, then a gun is in play. If it was recorded on the pad, that likely eliminates a gun as a potential source.

Neither of the noises on that recording sound like any kind of gun I've ever heard.

Didn't someone on here yesterday posit that the first thump could've been sound transmitted through the ground, which would reach the microphone quicker than the pressure wave through the air?

No. Not even quarry blasts have this kind of audible ground "thump," although you may hear a rumble which is essentially dirt grinding against each other. Just because the ground vibrates doesn't mean it will transmit that back into the air as a sound wave. There are a large number of raypaths and different vibrational modes, so no. If I were SpaceX, I would be looking for nearby seismic data. If it were a source coupled to the ground, it would show up as a trace from a reasonable distance.

if the video was shot in a junk yard then the ground vibration would just have to vibrate a large metal object.

EDIT: I was kayaking on a river in portsmouth nh and they were driving piles. I got to a distance away where I could here the pile driver and also here the one before resonating on a buoy. The vibration traveling faster in the water was inaudible until it reached a large metal buoy which was making the sound.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: hrissan on 09/09/2016 11:41 am
The problem with some "device" on the erector is that requires either an inside job, or someone evading detection while sneaking onto a secure military base.  With those scenarios, there is a possibility of capture and exposure.  A boat offshore remains anonymous and can just slip away.  Who would like to get their commercial launch business back?  Who is hacking all sorts of sensitive US servers?   Sad to say, but this stuff just writes itself.  Which is why this sort of cause will be almost impossible to confirm.
SpaceX is no threat to state actors who can just wait for SpaceX to pave the path so they can copy the system if it proves economic.

Though we need a new thread for the conspiracy theories! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/09/2016 11:58 am
Has anybody done something as simple as hold up a diffraction grating in front of a cell phone and done a video of firecracker going off?
If the initial flash is small enough you might get useful spectra from it. Probably better at night.
You could then introduce various metals into the explosive and see the signature.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lampyridae on 09/09/2016 11:59 am
Didn't someone on here yesterday posit that the first thump could've been sound transmitted through the ground, which would reach the microphone quicker than the pressure wave through the air?

No. Not even quarry blasts have this kind of audible ground "thump," although you may hear a rumble which is essentially dirt grinding against each other. Just because the ground vibrates doesn't mean it will transmit that back into the air as a sound wave. There are a large number of raypaths and different vibrational modes, so no. If I were SpaceX, I would be looking for nearby seismic data. If it were a source coupled to the ground, it would show up as a trace from a reasonable distance.

Could it make a difference that the ground water table at the cape is very near the surface? The primary underground acoustic transmission could be by that water. If the water table vibrates at an audible frequency, why would the vibration not be transmitted to the air, even though attenuated considerably at the ground/air interface?

Water is a good conductor of sound but it couples compression waves to air terribly. You can hear things more clearly over water due to the temperature difference in the air refracting and focusing sound but that's about it.

if the video was shot in a junk yard then the ground vibration would just have to vibrate a large metal object.

EDIT: I was kayaking on a river in portsmouth nh and they were driving piles. I got to a distance away where I could here the pile driver and also here the one before resonating on a buoy. The vibration traveling faster in the water was inaudible until it reached a large metal buoy which was making the sound.

Water conducts pressure waves very well, but couples poorly to air. As for ground, you have to have a very precise set of conditions to get a drum or whatever to do the same. Ground transmission is made up of pressure waves, shear waves, ground roll and a whole bunch of other little modes as well.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Star One on 09/09/2016 11:59 am
A small drone perhaps some idiot trying to get a close up video, misjudges & slams it into the Falcon. Bang goes your launcher especially if it was one of the more pro models which are quite weighty.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GigaG on 09/09/2016 12:01 pm
If this was a hydrogen upper stage, such as an Atlas V or Delta IV, I would have suspected a clear-burning hydrogen fire (the first thump being ignition of hydrogen and eventually leading to the visible explosion in the upper stage.) But there is no such hydrogen or any clear-burning fuels on the Falcon 9.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/09/2016 12:06 pm
I dont know if mod action is required for this, but could someone interested in the sabotage/shooting hypothesis please start a new thread? The hypothesis cant be ruled out easily but I suggest this because the sabotage stuff has so much potential for all sorts of conspiracy theories that have no place in a technical analysis of this failure. Also, I dont do it myself because I dont want my name attached to it. Thank you.

Update thread for pure updates.

This discussion thread for technical and other discussion, from the rocket (which is not receiving any blame right now), the TE and GSE.

Wild Theories (which are NOT being ruled out, per Elon's comments, so don't complain about people asking about it....) here:
https://forum.nasaspaceflight.com/index.php?topic=41119.0
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/09/2016 12:09 pm
Jim,

One theory that came up earlier was a pinhole leak in a hydraulics system leading to a fuel-air explosion. But that would seem to be a hazard for any LOX-based launch vehicle. Do you know if there are non-flammable hydraulic fluids, and is it typical for rocket companies to use those non-flammable hydraulic fluids in their launch site hydraulics (ie stuff that is going to be operating near venting GOX)?

I did a quick bit of googling, and it does look like there's a whole class of Flame Resistant Hydraulic Fluids, that are meant for use specifically in areas where they're operating near flame or other hazards, but do you know if it's standard practice to use those types of hydraulic fluid? Do you know if SpaceX does?

Just curious. Because if the hydraulic fluid they were using wasn't flammable, I'm back to wondering where they would've had a pressurized fuel source that could've created the Fuel Air Explosion that others are suggesting was the cause of the incident.

~Jon

There are fire-resistant fluids.  One is even water.  The Dow family usually mixes glycol with water.  Glycol, however as an aerosol, would still ignite.

Not sure about the others.

If someone could affirmatively state that the clamp piston is gas operated, then we could shut down my favorite hypothesis.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/09/2016 12:12 pm
Elon:

"Still working on the Falcon fireball investigation. Important to note that this happened during a routine filling operation. Engines were not on and there was no apparent heat source. Turning out to be the most difficult and complex failure we have ever had in 14 years.. Support & advice from @NASA, @FAA, @AFPAA & others much appreciated. Please email any recordings of the event to [email protected]. Particularly trying to understand the quieter bang sound a few seconds before the fireball goes off. May come from rocket or something else."

That sure sounds to me like they can't figure out the source of the fire. Based on other leaks it seems the know the fire started externally. They likely know the venting LOX ignited (hence trying to find the source of heat), but from what?

uh oh...   this looks to me like, for the gazillion of cameras pointing at the rocket & pad, the only one that may have been turned on is the USLaunchReport camera...

If just one other camera had been on, a 3d reconstruction may have been possible.

Does anyone know when, during the countdown, the cameras are turned on?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 12:14 pm

Does anyone know when, during the countdown, the cameras are turned on?

They are always on
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/09/2016 12:20 pm
Has anybody done something as simple as hold up a diffraction grating in front of a cell phone and done a video of firecracker going off?
If the initial flash is small enough you might get useful spectra from it. Probably better at night.
You could then introduce various metals into the explosive and see the signature.

Yes, that works.  There is an open source project that will actually show you how to do this with cardboard and a CD or DVD (they work like diffraction gratings).  It also comes with calibration and analysis software for free.  It's not professional grade, but pretty darned good.

see:  https://publiclab.org/wiki/spectrometer
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JebK on 09/09/2016 12:39 pm

Does anyone know when, during the countdown, the cameras are turned on?

They are always on

But are they recording? 

If they had multiple recordings they would not be wondering if the noises heard before the initial explosion were coming from around the rocket or not.  If they already had good coverage they wouldn't be asking for the public to send in amateur video taken from miles away.



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: M.E.T. on 09/09/2016 12:44 pm

Does anyone know when, during the countdown, the cameras are turned on?

They are always on

But are they recording? 

If they had multiple recordings they would not be wondering if the noises heard before the initial explosion were coming from around the rocket or not.  If they already had good coverage they wouldn't be asking for the public to send in amateur video taken from miles away.

Maybe they're hoping some of the amateur video will include footage of the surrounding area, beyond the perimeter of the launch facility.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/09/2016 12:48 pm
if the video was shot in a junk yard then the ground vibration would just have to vibrate a large metal object.

EDIT: I was kayaking on a river in portsmouth nh and they were driving piles. I got to a distance away where I could here the pile driver and also here the one before resonating on a buoy. The vibration traveling faster in the water was inaudible until it reached a large metal buoy which was making the sound.

Water conducts pressure waves very well, but couples poorly to air. As for ground, you have to have a very precise set of conditions to get a drum or whatever to do the same. Ground transmission is made up of pressure waves, shear waves, ground roll and a whole bunch of other little modes as well.

Understood, you need a suitable transducer to couple the pressure waves to the air, like a loudspeaker. rsdavis9 gave an excellent example of one, a metal buoy floating on the air/water interface. If the 'quieter bang' Elon refers to is the 'metallic klunk' in the USLR recording, then why couldn't a large piece of metal in the junkyard be a similar transducer?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/09/2016 12:50 pm

Does anyone know when, during the countdown, the cameras are turned on?

They are always on

But are they recording? 

If they had multiple recordings they would not be wondering if the noises heard before the initial explosion were coming from around the rocket or not.  If they already had good coverage they wouldn't be asking for the public to send in amateur video taken from miles away.

Maybe they're hoping some of the amateur video will include footage of the surrounding area, beyond the perimeter of the launch facility.

Possible. Problem is that's going to be people filming family on the beach, etc. Very few people video static fires (and probably only the guys with the video we've seen). SpaceX teams have their own footage, but clearly they want more. And the other Cape assets - of which there are many - are not used for testing....only for launches.

They might get lucky with someone's home movie, so no harm in him asking.

They were still asking KSC guys to look out for debris this week too, as it spread over a large area.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 12:51 pm
Any object hitting the vehicle would be picked up by the same high speed accelerometers that were able to triangulate the strut failing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 12:52 pm

Possible. Problem is that's going to be people filming family on the beach, etc. Very few people video static fires (and probably only the guys with the video we've seen). SpaceX teams have their own footage, but clearly they want more. And the other Cape assets - of which there are many - are not used for testing....only for launches.


And Spacex asks that other assets be turned away during non launch times
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 12:53 pm

Does anyone know when, during the countdown, the cameras are turned on?

They are always on

But are they recording? 


They don't record sound
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/09/2016 12:56 pm

Does anyone know when, during the countdown, the cameras are turned on?

They are always on

But are they recording? 

If they had multiple recordings they would not be wondering if the noises heard before the initial explosion were coming from around the rocket or not.  If they already had good coverage they wouldn't be asking for the public to send in amateur video taken from miles away.

Maybe they were recording video, but not audio.  My system at my site has 19 cameras recording 24/7, but only two of them record audio.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/09/2016 01:18 pm
They don't record sound

So: Other recordings needed to triangulate that "quieter bang sound a few seconds before the fireball goes off"?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul Adams on 09/09/2016 01:29 pm
I don't know, I am simply asking; with the apparent cause being elusive, would they bring in FBI or other explosive experts to look at the damage on strongback in great detail to possibly provide additional information or clues?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/09/2016 01:39 pm
I dont know if mod action is required for this, but could someone interested in the sabotage/shooting hypothesis please start a new thread? The hypothesis cant be ruled out easily but I suggest this because the sabotage stuff has so much potential for all sorts of conspiracy theories that have no place in a technical analysis of this failure. Also, I dont do it myself because I dont want my name attached to it. Thank you.

Update thread for pure updates.

This discussion thread for technical and other discussion, from the rocket (which is not receiving any blame right now), the TE and GSE.

Wild Theories (which are NOT being ruled out, per Elon's comments, so don't complain about people asking about it....) here:
https://forum.nasaspaceflight.com/index.php?topic=41119.0

Bumping to remind people.....and will probably have to bump a few more times.

Three threads:
Updates.
Discussion.
Alternative Theories (which you should avoid if you have a problem with nonsense).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jcopella on 09/09/2016 01:53 pm
There is no good news in this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/09/2016 02:01 pm
How identical is the testing environment of stage 2 in Texas?  We know the engine has a different nozzle.  Does it fill through umbilicals?  If so, does it fast-fill at the last minute as at the Cape?  Does it use sub-cooled LOX? Do they fill the tanks all the way, or just enough for a 30 second test?  Do they do the pre-firing TVC test, or test the TVC during operation, or are they just testing  the engine?

I'm pretty sure they have not had a similar problem in Texas while testing second stages.  So the closer these tests are to the conditions during the accident, the more likely that the source is Florida, GSE, or T/E related.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mattstep on 09/09/2016 02:05 pm
They don't record sound

So: Other recordings needed to triangulate that "quieter bang sound a few seconds before the fireball goes off"?

Surely there must be dozens of security cameras recording sound scattered around the Cape?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey on 09/09/2016 02:06 pm
Most security cameras don't record sound.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/09/2016 02:12 pm
They don't record sound

So: Other recordings needed to triangulate that "quieter bang sound a few seconds before the fireball goes off"?

Surely there must be dozens of security cameras recording sound scattered around the Cape?

Just wondering why Elon asks for "any recordings of the event" on Twitter.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/09/2016 02:16 pm
I don't think musk was referring to the us launch recording sound before explosion. Unless they really don't have any better sound recordings?

Has anybody done the computation for sound in rock versus sound in air to see if it lines up with the thunk sound in the us launch video? The time delay for sound was what 12s. How much before the explosion was the thunk heard?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/09/2016 02:19 pm
I don't think musk was referring to the us launch recording sound before explosion. Unless they really don't have any better sound recordings?

Why not? It was the first (only?) video made public, has a very clear soundtrack, and the "precursor" sounds on it were noted both here and on Reddit by many observers.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Norm38 on 09/09/2016 02:19 pm
Any object hitting the vehicle would be picked up by the same high speed accelerometers that were able to triangulate the strut failing.

And the corollary to that is, that any failure event inside the vehicle (COPV, etc) would also have been picked up.  If they are closing off F9 fault trees as reported above, then they don't have any accelerometer data pointing to any mechanical event prior to the explosion.

So what do we know?  That apparently outside the vehicle, something caused venting LOX to ignite with something else, ignited by something that did not impart any mechanical force to the F9.  And also ignited with enough oomph to not just harmlessly flare off.
Yes there is venting LOX, but air is 20% oxygen already, and things do not just spontaneously combust.  There was a lot of fuel there from somewhere.  Where could fuel come from that telemetry would not detect?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/09/2016 02:19 pm
Falcon 9 FT is known for producing scary looking barfs of oxygen through its relief valve. I do not remember the same thing happening with previous (not supercooled LOX) version. Any chance this may be somehow related to what happened?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jaufgang on 09/09/2016 02:21 pm
They don't record sound

So: Other recordings needed to triangulate that "quieter bang sound a few seconds before the fireball goes off"?

Or maybe other recordings needed to first determine if that bang sound was local to that camera (wouldn't be heard on other recordings at all) or a loud sound from far away, potentially the pad or elsewhere.  I read some speculation upthread that the bang might have been something like a pop caused by thermal expansion in the morning sun of a metal barrel lying in the junkyard 4km away from the pad were the camera was placed.  Any recordings from another distant camera in a different location that might have picked up the same sound would rule out that possibility and indicate it was a very loud sound from somewhere far off.

If that's the case, then maybe they could try triangulation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 02:24 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...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/09/2016 02:25 pm
Falcon 9 FT is known for producing scary looking barfs of oxygen through its relief valve. I do not remember the same thing happening with previous (not supercooled LOX) version. Any chance this may be somehow related to what happened?

I remember one of the early static fire tests on an early F9 (pre v1.1 I believe and where they actually have a Cape camera live webcasting) where the F9 was venting a huge amount, to the point "the internet" thought there was something seriously amiss. But that was mainly due to weather conditions. So lots of venting, no big deal, is usually the call.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AnalogMan on 09/09/2016 02:26 pm
I don't think musk was referring to the us launch recording sound before explosion. Unless they really don't have any better sound recordings?

Has anybody done the computation for sound in rock versus sound in air to see if it lines up with the thunk sound in the us launch video? The time delay for sound was what 12s. How much before the explosion was the thunk heard?

Thunk happened ~5.25 seconds before main explosion started.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/09/2016 02:31 pm
I don't think musk was referring to the us launch recording sound before explosion. Unless they really don't have any better sound recordings?

Has anybody done the computation for sound in rock versus sound in air to see if it lines up with the thunk sound in the us launch video? The time delay for sound was what 12s. How much before the explosion was the thunk heard?

Thunk happened ~5.25 seconds before main explosion started.

That gives a wave propagation speed of about 700 m/s.  About twice the speed of propagation in air, about half the speed of propagation in water.  Not sure about propagation speed in swampy dirt.  Unless that "pre-thunk" can be corroborated by a recording from a different location, I'm not convinced it's not merely a coincidence.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: atsf90east on 09/09/2016 02:31 pm
Falcon 9 FT is known for producing scary looking barfs of oxygen through its relief valve. I do not remember the same thing happening with previous (not supercooled LOX) version. Any chance this may be somehow related to what happened?

This venting isn't unique, as shown by this photo from the Thaicom-8 launch on May 27.  My recollection is that the photo was taken at about T-4 minutes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/09/2016 02:32 pm
I don't think musk was referring to the us launch recording sound before explosion. Unless they really don't have any better sound recordings?

Has anybody done the computation for sound in rock versus sound in air to see if it lines up with the thunk sound in the us launch video? The time delay for sound was what 12s. How much before the explosion was the thunk heard?

Thunk happened ~5.25 seconds before main explosion started.

That gives a wave propagation speed of about 700 m/s.  About twice the speed of propagation in air, about half the speed of propagation in water.  Not sure about propagation speed in swampy dirt.  Unless that "pre-thunk" can be corroborated by a recording from a different location, I'm not convinced it's not merely a coincidence.

Discussed here:

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1579390#msg1579390

He estimates 1000 m/sec propagation speed for a seismic wave in that soil. The junkyard is about 4 km from the pad, so that would be a seismic wave travel time of about 4 seconds, vs 12 seconds in air.

Then the time delta would be 8 seconds for "ground vs air" wave speed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/09/2016 02:35 pm

Has anybody done the computation for sound in rock versus sound in air to see if it lines up with the thunk sound in the us launch video? The time delay for sound was what 12s. How much before the explosion was the thunk heard?

ok I just relistened to the video.
1:12 fireball
1:18 pop sound
1:24  big boom
Do I have those times right?
I'm sure it is upthread somewhere.
If these are the sounds them I get:

340m/s *12s = 4080 meters
4080/6000m/s=.68 seconds
in other words the p-wave should arrive about half a second after the visual explosion.
I used 6000m/s for p-wave in linestone.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/09/2016 02:37 pm

Has anybody done the computation for sound in rock versus sound in air to see if it lines up with the thunk sound in the us launch video? The time delay for sound was what 12s. How much before the explosion was the thunk heard?

ok I just relistened to the video.
1:12 fireball
1:18 pop sound
1:24  big boom
Do I have those times right?
I'm sure it is upthread somewhere.
If these are the sounds them I get:

340m/s *12s = 4080 meters
4080/6000m/s=.68 seconds
in other words the p-wave should arrive about half a second after the visual explosion.
I used 6000m/s for p-wave in linestone.

Wolfram66 got 1000 m/sec seismic wave speed in FL from this paper:

http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

Probably it's highly dependent on what you assume for local soil conditions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/09/2016 02:39 pm
Falcon 9 FT is known for producing scary looking barfs of oxygen through its relief valve. I do not remember the same thing happening with previous (not supercooled LOX) version. Any chance this may be somehow related to what happened?

This venting isn't unique, as shown by my photo from the Thaicom-8 launch on May 27.  My recollection was that I took this photo at about T-4 minutes.

There were moments when amount and trajectory of vented oxygen seemed to hint at LOX release (cloud hitting ground really fast and then expanding from there). I know this was pretty common with FL (supercooled LOX) version, but I do not remember this happening with previous F9. Just saying there may be correlation with these vent events that seem to be very violent and what happened on 9/1.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/09/2016 02:40 pm

Discussed here:

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1579390#msg1579390

He estimates 1000 m/sec propagation speed for a seismic wave in that soil. The junkyard is about 4 km from the pad, so that would be a seismic wave travel time of about 4 seconds, vs 12 seconds in air.

Then the time delta would be 8 seconds for "ground vs air" wave speed.

thanks you. I don't seem to have the forum search fu down yet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 03:30 pm

Surely there must be dozens of security cameras recording sound scattered around the Cape?

Each facility has its own and the facility owners are responsible for monitoring them.  There are not generic street corner type cameras on the Cape
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/09/2016 03:31 pm
They don't record sound

So: Other recordings needed to triangulate that "quieter bang sound a few seconds before the fireball goes off"?

Surely there must be dozens of security cameras recording sound scattered around the Cape?

Just wondering why Elon asks for "any recordings of the event" on Twitter.

Multiple angles and also if you have at least one more detector than you have sound source, then you can triangulate the signal and remove noise. A little more complex with echo but not much.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lar on 09/09/2016 03:36 pm
OK, we are going to try to use the new thread for the more wild and woolly stuff. Please try to use it too, don't make life harder for the mods. By the time you read this I should have moved a bunch of "was it a drone" stuff over there.

http://forum.nasaspaceflight.com/index.php?topic=41119

Thank you.

(guide I used: Drones, guns, sabotage, lasers... all that went in the more speculative thread. Info on sound propagation and calculations, questions about cameras, triangulation, the forensic process, stuff that is not speculative, stayed here .. If you think I missed one, or if you think I moved one that I shouldn't? report to mod)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: obi-wan on 09/09/2016 03:40 pm
Due to the lack of even a good theory on root cause, does that mean all test operations at MacGregor are on stand-down? It seems to me that the "long pole in the tent" isn't F9 return to flight, but getting far enough along in the system to get MacGregor back to work testing engines and stages.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ELinder on 09/09/2016 03:50 pm
Why does everyone automatically think bullets and such when thinking about what may have hit the vehicle or started the incident? I'd think it much more likely to be a sheared bolt head or nut popping under strain from the strongback or parts mounted to it. It would produce a noise and if it hit the right place, a spark and/or do more damage to start things off.

During development the launch vehicle has many strain gauges mounted, but what about the ground equipment? Any chance some of those may still be installed, such as those left over in the orbiter Columbia, that were recording data?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/09/2016 03:53 pm
USLaunchReport seems to have recordings of previous static tests, but they all start with strongback retracted. If you guys are reading this thread - is there any way you could upload longer versions that cover the same time range as last recording? It would be very interesting to compare and see if anything was different this time...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/09/2016 03:55 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?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science 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...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish 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.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: matthewkantar 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
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Multivac 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Pete 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tdenk on 09/09/2016 05:00 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
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Spacedog49 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.           
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish 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
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Fan Boi 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.

https://www.youtube.com/watch?v=HI-ENqgjQXM
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit 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 (https://en.wikibooks.org/wiki/Engineering_Acoustics/Outdoor_Sound_Propagation#Attenuation_by_atmospheric_absorption.5B5.5D_.5B6.5D_.5B7.5D).

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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos 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?"
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ellindsey 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?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MP99 on 09/09/2016 06:35 pm
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
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo 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.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/09/2016 06:40 pm
There is basically no way to re-enact something like this with any degree of accuracy. If a programmer wants to recreate something they have a backup or an image of both the program and the system at the time the issue occurred. Apart from a few potential write errors it is 99.9999999(as much as you want)% identical. For an entire rocket + GSE assembly you will be lucky to get it 95% identical. No two falcons are the same, the exact way a tube is swaying in the wind during fueling will not be the same, the exact humidity in the air and the subsequent reactions of the metal and LOX to that humidity will not be the same. Even if we set this up and run it a thousand times and find that every 100ish cycles we get a leak in X tube which could create a fuel-air mixture that leak could be in a completely different spot and give us a completely different idea of what could have happened. It isn't practically repeatable.

(To Rakaydos)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 06:41 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.

They all likely exploded
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mwfair on 09/09/2016 07:12 pm
regarding COPV
They all likely exploded
Due to heat weakening them?  If so they might look different than one that failed prior to the fire.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jongoff on 09/09/2016 07:14 pm
There are fire-resistant fluids.  One is even water.  The Dow family usually mixes glycol with water.  Glycol, however as an aerosol, would still ignite.

Yeah, I did some reading on this. But the glycol is mixed intimately with the water, so it would only ignite if enough of the water had boiled off. The whole point of FRFH's, according to the reading I did, is to make it much harder to create a fuel air explosion if they spring a leak in a hazardous environment. In fact the standard tests I was reading about for FRFH's is typically to create an aerosol and see if it will sustain flame. 

Now, admittedly, that's usually in normal air for the standard tests, but that was why I asked Jim about if it's standard practice to use FRFH fluids for launch stand hydraulics, and if so, what FRFH is typically used. And does anybody test them with a modified aerosol test that includes an oxygen elevated environment.

Quote
Not sure about the others.

If someone could affirmatively state that the clamp piston is gas operated, then we could shut down my favorite hypothesis.

That's the other possibility. I'm just skeptical that people would design hydraulics for use in a hazardous location (with oxygen and fire) without spending at least some time on picking a fluid that's as safe as possible for the application (gas or an appropriate FRFH that has been tested in a simulated environment).

~Jon
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 07:22 pm
Do you know if there are non-flammable hydraulic fluids, and is it typical for rocket companies to use those non-flammable hydraulic fluids in their launch site hydraulics (ie stuff that is going to be operating near venting GOX)?

Don't know.  Most of those systems would be further away like on Delta IV and Shuttle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/09/2016 07:29 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 (https://en.wikibooks.org/wiki/Engineering_Acoustics/Outdoor_Sound_Propagation#Attenuation_by_atmospheric_absorption.5B5.5D_.5B6.5D_.5B7.5D).

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.

I second to the opinion, that those "screek" and "clonk" must be local sounds.

However, I thought, that maybe there can be read out something from the echos. I seem to hear several echos of both, the initial event and the biggest bang, which even shook the camera. Measuring the time shift of those bangs and knowing the location of actual origin can give one two arcs, from which the reflected sound must have come from (assuming, that the microphone's location is known). Now, if there is a large building or forest wall or something else reflective on this arc, this should be the point from where the sound reflected. Now, this reflection can be compared to those anomalous sounds and see, if they had an echo and from where this should have come from.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/09/2016 07:29 pm
Quote
increasingly trying to understand sound heard prior to explosion

This is very telling. Points to one of two things:

Internal failure in the lox tank or GSE failure that rapidly overpressurized the tank or its internals.

FTS is ruled out (thanks for the info on this jim).

External fae is ruled out due to a variety of reasons though the wind is a big one.

Gse is not something I can completely rule out but it seems very unlikely, the system itself would probably fail first not the lox tank.

Payload as source is ruled out due to the payload not blowing up until after it fell off what was left of the TE and other aforementioned reasons regarding payload fuel.

Really IMHO only thing that fits in something within the lox tank. So COPV or other internal ignition+overpressure ignition not yet found.

My guess is the reason why it is so hard to pinpoint is because it happened extremely fast.

Still there are more questions now I think than we had before and not really any answers.


Here is the point though. The failure was in the LOX tank or very near to it in the second stage. I think this is almost 100% certain given spacex's own statements and the failure nature itself.

Second, to me this leads back to the original problem which brought down crs7: quality control.


Spacex is apparently learning the hard way they cannot keep doing things internally like a startup company. They need to seriously rethink their quality control program and how they test tankage components. They have been criticized by both other other industry figures and others for this in the recent past and have ignored the criticism as far more knowledgeable members on this site are no doubt aware.

Basically the short version, and I will preface this by saying that it's as I see it, is they need to get with the program already. Innovation is great but constantly changing component design and manufacture in the quest for efficiency is a recipe for these kinds of failures every time.

I suspect they will make real changes this time because the alternative will be losing contracts if this happens again.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ricmsmith on 09/09/2016 07:30 pm
Why are we talking about drones? We would have seen a drone on the video and SpaceX certainly would have seen it on on their pad cameras.

Because drones are the new favorite subject of the obsessively paranoid.

Personally I'm not being paranoid, there doesn't need to be any kind of conspiracy or deliberate action just someone stupid with a drone. Drones carry batteries, batteries can short or even explode. Plenty of people fly them far too close to airports, there have been many recorded near misses.

None of that has any practical basis in reality in this context.

Batteries burn (they "explode" in the sense of a pressure release and expansion, but there's no detonation) when you overcharge them, not in flight.  I've seen hundreds of crashes, some into concrete, some into steel, and I've only once seen a battery burn and that was a very extreme case.

It's perfectly legal to fly near airports with notification, in most cases.  The rule is "see and avoid" full-scale airplanes.  Controlled and/or restricted airspace is another matter and my understand is that CCAFs is restricted.

Ok, thanks. If it can't supply a source of ignition then that's it for that idea then.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 07:31 pm
They must be some fluid specs available from from the early Atlas and Titan hydraulic erector systems...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/09/2016 07:32 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.

Good work, almost there.
Now cut the spectrum image included to overlap the air transmitted vs ground transmitted waveforms.
The labeled "Animals reacting" is really the RUD in Progress of the stack collapse and impact of AMOS-6 + secondary Hydrazine detonation
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: FinalFrontier on 09/09/2016 07:43 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.

Good work, almost there.
Now cut the spectrum image included to overlap the air transmitted vs ground transmitted waveforms.
The labeled "Animals reacting" is really the RUD in Progress of the stack collapse and impact of AMOS-6 + secondary Hydrazine detonation


The inverted tank dome theory was mentioned earlier in this thread. For those knowledgeable on that failure mode and previous incidents on older vehicles I would ask if you guys think this is consistent with a dome inverting or otherwise failing in a not totally spontaneous way. Only other thing I can see making these would be either a valve cycling or failing to cycle properly or helium lines rupturing inside the tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wingarcher on 09/09/2016 07:49 pm
Maybe this was covered previously, if so, apologies.

What's the "standard" sampling rate for the sensors that are all over a rocket like this one?  It appears from the public Elon tweets that none of the telemetry shows anything unusual until it's all going haywire.

N
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/09/2016 07:50 pm
. . .  Any recordings from another distant camera in a different location that might have picked up the same sound would rule out that possibility and indicate it was a very loud sound from somewhere far off.

If that's the case, then maybe they could try triangulation.

Re: triangulation - if its possible to sync two or more audio tracks to within tens of ms, it should be possible to localize the source to within some 10s of feet, no?   SpaceX ought to have been able to do that.  Does that imply the sound came from an "expected" place - the area of the 2nd stage?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bob Shaw on 09/09/2016 07:52 pm
Has anyone listened to the video coverage earlier in the countdown, or even on different days, in order to get a feel for background noises and their likely  sources?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 08:06 pm
One thing I have seen personally explode with high energy was a reverse polarity automotive battery... This reminded me a bit of it. Falcon has her batteries, does the TEL and it's umbilicals have anything with such EMF potential if it was a polarity problem during power on?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jack Gray on 09/09/2016 08:10 pm
So Space X is requesting if you have audio, photos or videos of their anomaly last week to please send to them but wouldn't it also help if they presented what evidence they have so far like their own video? Don't know if it's some proprietary issue but just wondering.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 08:15 pm
. . .  Any recordings from another distant camera in a different location that might have picked up the same sound would rule out that possibility and indicate it was a very loud sound from somewhere far off.

If that's the case, then maybe they could try triangulation.

Re: triangulation - if its possible to sync two or more audio tracks to within tens of ms, it should be possible to localize the source to within some 10s of feet, no?   SpaceX ought to have been able to do that.  Does that imply the sound came from an "expected" place - the area of the 2nd stage?

What audio tracks?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 08:16 pm
Maybe this was covered previously, if so, apologies.

What's the "standard" sampling rate for the sensors that are all over a rocket like this one?  It appears from the public Elon tweets that none of the telemetry shows anything unusual until it's all going haywire.


Varies depending on the type of sensor and the need/use of the data
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/09/2016 08:29 pm
OK, gang... using my geologic engineering background, i believe i have a plausible explanation of the *ploink* and rumble on the vid. YES is DOES COME FROM THE JUNKYARD!, but the explosion and subsequent fireball ARE to blame. Since the S1 is attached to the pad/ground, it transmits the pressure wave directly to the ground. This is why it registered on seismic equipment. since pressure waves travel much faster through the ground than in the compressible air, the transient noises in the video are caused by the explosion. The shock traveling through the ground will arrive to the microphone location before the sound traveling in the air. This shockwave/impulse caused something in the yard to tilt,rub,bang or rattle . Initial explosion shock arrival IS the *ploink* and fireball/collapse of the stack is the rattle. That should put everything to bed... what do you think Chris?

this will be for pressure or P-Wave impulses
since the coastal area of CCAFS is mostly unconsolidated sediment &  sand, one can use 1000 meters/sec as velocity.

Here's the study from 2011 by University of Florida regarding seismic energy propagation in FLA
http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

I'll let you have fun with the maths

Working from another angle, the distance from the epicentre to the USLR camera is 4.34 kms.
If the speed of sound is 343.2 m/s, the sound should take 4340 / 343.2 = 12.64 seconds to arrive.

If I look at the audio in a waveform editor, I can mark the visible explosion at 13.467 - 12.64 = 0.836 seconds.
The first two events, the squeak and the clunk are at the 6.7 and 8.3 second marks, that is 5.864 and 7.464 after the explosion.

For the squeak to be ground transmitted, the velocity would be 4340 / 5.864 = 740.1 m/s.
For the clunk to be ground transmitted, the velocity would be 4340 / 7.464 = 581.46 m/s.

If 1000 m/s is the velocity of the pressure wave in the soil, then the sounds are not arriving quickly enough to be related to the explosion. Does anyone have a reason to suggest that the speed of transmission might be significantly less than 1000 m/s?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/09/2016 08:35 pm
So Space X is requesting if you have audio, photos or videos of their anomaly last week to please send to them but wouldn't it also help if they presented what evidence they have so far like their own video? Don't know if it some proprietary issue but just wondering.
You do have a point, the NFS community did an incredible reconstructing the first water landing for them. Hand over what audio files may exist and see if the NFS community can reconstruct it...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ap12 on 09/09/2016 08:36 pm
What is the likely sampling rate of oxygen and fuel tank pressure telemetry?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/09/2016 08:39 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.

Good work, almost there.
Now cut the spectrum image included to overlap the air transmitted vs ground transmitted waveforms.
The labeled "Animals reacting" is really the RUD in Progress of the stack collapse and impact of AMOS-6 + secondary Hydrazine detonation
This looks very convincing to me.  Quite a number of features line up here, enough to convince me that the "thumps before" are just fast-arriving versions of the main event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HankinNM on 09/09/2016 08:41 pm
It is beginning to look (to me) like Spacex may wind up doing a complete 'clean sheet' redesign of the second stage.  I think this is the 'hardest' problem they have ever run into, and they may not ever find a 'smoking gun' cause (I think it is already too late for that.)  Would reverting to 'non-chilled RP1 and LOX do anything to solve the problem  (I'm thinking Mr. Musk would pull his eyeteeth out before regressing to an earlier system/procedure)?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/09/2016 08:43 pm
If there are multiple microphones in the vehicle, they will have recorded an external event too, or at least its impact on the skin.

If the data was able to get out, it could tell them where the ignition was, and maybe even something about the shape of the exploding cloud.  It'll require some modeling, but I'm sure they're on it.

-------------

Here's a thought though.  The explosion happened on the upwind side.

What if there was a fuel leak, a spray, and it accumulated on the outside skin?  Maybe had time to wet a large area.

Contact with O2..  But don't know about ignition...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/09/2016 08:51 pm
OK, gang... using my geologic engineering background, i believe i have a plausible explanation of the *ploink* and rumble on the vid. YES is DOES COME FROM THE JUNKYARD!, but the explosion and subsequent fireball ARE to blame. Since the S1 is attached to the pad/ground, it transmits the pressure wave directly to the ground. This is why it registered on seismic equipment. since pressure waves travel much faster through the ground than in the compressible air, the transient noises in the video are caused by the explosion. The shock traveling through the ground will arrive to the microphone location before the sound traveling in the air. This shockwave/impulse caused something in the yard to tilt,rub,bang or rattle . Initial explosion shock arrival IS the *ploink* and fireball/collapse of the stack is the rattle. That should put everything to bed... what do you think Chris?

this will be for pressure or P-Wave impulses
since the coastal area of CCAFS is mostly unconsolidated sediment &  sand, one can use 1000 meters/sec as velocity.

Here's the study from 2011 by University of Florida regarding seismic energy propagation in FLA
http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

I'll let you have fun with the maths

Working from another angle, the distance from the epicentre to the USLR camera is 4.34 kms.
If the speed of sound is 343.2 m/s, the sound should take 4340 / 343.2 = 12.64 seconds to arrive.

If I look at the audio in a waveform editor, I can mark the visible explosion at 13.467 - 12.64 = 0.836 seconds.
The first two events, the squeak and the clunk are at the 6.7 and 8.3 second marks, that is 5.864 and 7.464 after the explosion.

For the squeak to be ground transmitted, the velocity would be 4340 / 5.864 = 740.1 m/s.
For the clunk to be ground transmitted, the velocity would be 4340 / 7.464 = 581.46 m/s.

If 1000 m/s is the velocity of the pressure wave in the soil, then the sounds are not arriving quickly enough to be related to the explosion. Does anyone have a reason to suggest that the speed of transmission might be significantly less than 1000 m/s?

Recalculate your numbers as though the sounds relate not to the initial flash and fireball but to the giant shockwave-inducing one once stage one finally bit the dust.  You'll get propagation speeds much closer to 1300 m/s.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/09/2016 08:56 pm
Here's one I don't think is in the list:

a leak, even a tiny one, in the S2 TEB system. It auto ignites in O2 at -20°C. Is it tanked on the ground or late loaded through the strongback?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/09/2016 09:05 pm
Shifting the spectrogram further back in time ALMOST but not exactly lines up...  What does this do to the speed calculations?  It also shows an earlier blip.  I need to listen to the audio to see if it's really related.

Edit:  I'm slightly convinced an offset of 6.725 seconds aligns two obvious sounds before the event with clicks during the event.  The initial sound is covered by a frog chirp.  I'll try to filter that out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: flyright on 09/09/2016 09:12 pm
Here's one I don't think is in the list:

a leak, even a tiny one, in the S2 TEB system. It auto ignites in O2 at -20°C. Is it tanked on the ground or late loaded through the strongback?

Not sure how the TEB is loaded, but wouldn't the evidence be a green flash?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/09/2016 09:15 pm
If it's stored at the bottom of S2 it should be covered by the interstage. How about it igniting the grid fin hydraulic fluid, or some other burn through scenario?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 09:22 pm
Here's one I don't think is in the list:

a leak, even a tiny one, in the S2 TEB system. It auto ignites in O2 at -20°C. Is it tanked on the ground or late loaded through the strongback?

I don't know but I would say on the ground in the hangar, because
a.  we don't see a container on the TEL for it.
b.  running a line from the ground all the way up the TEL to the second stage means a lot of fluid that would have to be purge out of the line after filling.  Maybe more than would be needed by the stage
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Googulator on 09/09/2016 09:23 pm
Grid fin hydraulic fluid is on S1, most likely an ignition there would destroy S1 first.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/09/2016 09:37 pm
It is beginning to look (to me) like Spacex may wind up doing a complete 'clean sheet' redesign of the second stage.  I think this is the 'hardest' problem they have ever run into, and they may not ever find a 'smoking gun' cause (I think it is already too late for that.)  Would reverting to 'non-chilled RP1 and LOX do anything to solve the problem  (I'm thinking Mr. Musk would pull his eyeteeth out before regressing to an earlier system/procedure)?
Re: clean sheet redesign of 2nd stage. Why? :
1. They don't know the root cause was in the second stage.
2. The first stage and second stage are as similar as two stages can be.  If the second stage did contain the root cause, why would the first stage be exempt from the same (undetermined) short coming?
3. If they don't know the root cause, they don't know how to avoid designing in the exact same mode of failure.

Re: densified propellent:
They don't know the root cause yet, what's the point of randomly changing things?

I don't know what they will do if they don't discover a root cause.  But they won't redesign the second stage just hoping that fixes the problem.  I guess at some point they'd double down on QA, GSE robustness safety, propellent purity, sensors, cameras and microphones.  The first steps hoping it doesn't happen again, the latter hoping if it does they'll get a definitive answer.  But that bleak possibility is months away.  There is still debris to collect, a TEL to disassemble and inspect, GSE to inspect and heads to scratch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/09/2016 09:44 pm
It is beginning to look (to me) like Spacex may wind up doing a complete 'clean sheet' redesign of the second stage.  I think this is the 'hardest' problem they have ever run into, and they may not ever find a 'smoking gun' cause (I think it is already too late for that.)  Would reverting to 'non-chilled RP1 and LOX do anything to solve the problem  (I'm thinking Mr. Musk would pull his eyeteeth out before regressing to an earlier system/procedure)?
Re: clean sheet redesign of 2nd stage. Why? :
1. They don't know the root cause was in the second stage.
2. The first stage and second stage are as similar as two stages can be.  If the second stage did contain the root cause, why would the first stage be exempt from the same (undetermined) short coming?
3. If they don't know the root cause, they don't know how to avoid designing in the exact same mode of failure.

Re: densified propellent:
They don't know the root cause yet, what's the point of randomly changing things?

I don't know what they will do if they don't discover a root cause.  But they won't redesign the second stage just hoping that fixes the problem.  I guess at some point they'd double down on QA, GSE robustness safety, propellent purity, sensors, cameras and microphones.  The first steps hoping it doesn't happen again, the latter hoping if it does they'll get a definitive answer.  But that bleak possibility is months away.  There is still debris to collect, a TEL to disassemble and inspect, GSE to inspect and heads to scratch.


I agree with mme.  People have been posting that the obvious failure trees have been closed off.  Also, the telemetry plus video (!) of the S2 tanks would be the first place everyone would have gone to.  They probably ruled out any obvious S2 failure modes before leaving the launch control centre!  I really respect the careful analysis of this forum in general and this thread specifically but i really have to wonder if folks still positing S2 redesign are simply trolling at this point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tdenk on 09/09/2016 09:46 pm
The second stage doesn't use densified propellant (?)

Thorsten
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/09/2016 09:50 pm
The second stage doesn't use densified propellant (?)

Thorsten

It does.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/09/2016 09:56 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.

Good work, almost there.
Now cut the spectrum image included to overlap the air transmitted vs ground transmitted waveforms.
The labeled "Animals reacting" is really the RUD in Progress of the stack collapse and impact of AMOS-6 + secondary Hydrazine detonation

Line up events starting with the *small unmarked sound almost at left edge.*  Now "First sound" and "Second Sound" IMO correlate with events after the "Initial Explosion".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/09/2016 09:57 pm
Shifting the spectrogram further back in time ALMOST but not exactly lines up...  What does this do to the speed calculations?  It also shows an earlier blip.  I need to listen to the audio to see if it's really related.

Not sure if you have the tools to do this, I'm not sure exactly how to do this either.

IF the clang and thunk are P & S waves, there is a chance that the camera is shaking at the same times, and not prior or after until the big 'un.


I tried focusing on two lights at the bottom during the clang and the thunk, thinking they wouldn't move unless the camera did, and boy was I wrong.  They're wobbling like mad because of other explosions at the same time that the clang and thump happen.  I'll try the tower next, but if you can synch the audio and video maybe you could look at shake and save me a mouse induced carpel tunnel event?  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/09/2016 10:04 pm
OK, gang... using my geologic engineering background, i believe i have a plausible explanation of the *ploink* and rumble on the vid. YES is DOES COME FROM THE JUNKYARD!, but the explosion and subsequent fireball ARE to blame. Since the S1 is attached to the pad/ground, it transmits the pressure wave directly to the ground. This is why it registered on seismic equipment. since pressure waves travel much faster through the ground than in the compressible air, the transient noises in the video are caused by the explosion. The shock traveling through the ground will arrive to the microphone location before the sound traveling in the air. This shockwave/impulse caused something in the yard to tilt,rub,bang or rattle . Initial explosion shock arrival IS the *ploink* and fireball/collapse of the stack is the rattle. That should put everything to bed... what do you think Chris?

this will be for pressure or P-Wave impulses
since the coastal area of CCAFS is mostly unconsolidated sediment &  sand, one can use 1000 meters/sec as velocity.

Here's the study from 2011 by University of Florida regarding seismic energy propagation in FLA
http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BDK75_977-01_rpt.pdf

I'll let you have fun with the maths

Working from another angle, the distance from the epicentre to the USLR camera is 4.34 kms.
If the speed of sound is 343.2 m/s, the sound should take 4340 / 343.2 = 12.64 seconds to arrive.

If I look at the audio in a waveform editor, I can mark the visible explosion at 13.467 - 12.64 = 0.836 seconds.
The first two events, the squeak and the clunk are at the 6.7 and 8.3 second marks, that is 5.864 and 7.464 after the explosion.

For the squeak to be ground transmitted, the velocity would be 4340 / 5.864 = 740.1 m/s.
For the clunk to be ground transmitted, the velocity would be 4340 / 7.464 = 581.46 m/s.

If 1000 m/s is the velocity of the pressure wave in the soil, then the sounds are not arriving quickly enough to be related to the explosion. Does anyone have a reason to suggest that the speed of transmission might be significantly less than 1000 m/s?

To answer your question, yes. speeds are not absolutes, they differ with density and mobility of the soil. 1000m/sec was given as general rule of thumb figure for surface propagation in FLA as stated in Attached pdf link.

The velocity for unconsolidated sand would be much slower than through solid limestone bedrock of FLA.
Even with limestone, you have to take into consideration the degree of jointing & fractures as well as voids (sinkholes & caves.) Since CCAFS is mostly unconsolidated sand and marshland, it may be significantly below the 1000m/sec in the study from UF i attached.

Think of hitting a pillow with a wood baseball bat vs hitting a concrete wall. the pitch of the sound differs because, a) energy is lost moving through void space (pillow) & propagation slows down due to movement of the particles. Hitting the concrete will give you a nice ping because the energy is transmitted more effectively.  on the micro-scale it's analogous to hitting croquet balls vs nerf balls .

Someone from NSF [Chris...etc] may drop UF Geology Dept or Geo-Physics dept a call to get feedback.
Don't know if local office of Army Corps of Engineers could also help?

 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/09/2016 10:13 pm
It's basically swampland. You're not going to get a surface wave, period.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickl on 09/09/2016 10:53 pm
I can appreciate that a surface wave would arrive before a wave traveling through the air, but would it actually make an audible sound?  I can see how it might shake the camera, but would the microphone pick it up? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/09/2016 11:05 pm
I can appreciate that a surface wave would arrive before a wave traveling through the air, but would it actually make an audible sound?  I can see how it might shake the camera, but would the microphone pick it up?
A microphone might not, but the junkyard the microphone is sitting in may react in ways a microphone can detect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 11:08 pm
Are any of the external "rocket cameras" located in the area of interest? If a battery caught fire or exploded in that oxygen rich environment...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/09/2016 11:11 pm
Are any of the external "rocket cameras" located in the area of interest? If a battery caught fire or exploded in that oxygen rich environment...


With electrical telemetry you don't need any cameras for that part of the fault tree...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 11:14 pm
Are any of the external "rocket cameras" located in the area of interest? If a battery caught fire or exploded in that oxygen rich environment...


With electrical telemetry you don't need any cameras for that part of the fault tree...
You misunderstood me, I'm talking about the one's mounted "on the rocket" to give us pretty videos from it as it launches...
https://www.youtube.com/watch?v=P79LmIOzwAM
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 11:14 pm
Are any of the external "rocket cameras" located in the area of interest? If a battery caught fire or exploded in that oxygen rich environment...

How long do you think it transmitted the video
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 11:21 pm
Are any of the external "rocket cameras" located in the area of interest? If a battery caught fire or exploded in that oxygen rich environment...

How long do you think it transmitted the video
I have no idea Jim, my only thought was about a battery failure or short. Your thoughts?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 11:23 pm
I doubt no more than one frame of vehicle cameras were on
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: djhopkins2 on 09/09/2016 11:25 pm
I had an interesting thought on how you might get LOX on the outside/bottom edge of the LOX tank, near the RP-1 tank vent without a leak.

At the sub chilled LOX temperatures that are present inside the tank, it is highly likely that you would actually get liquid oxygen condensing out of the surrounding air onto the rocket body.

This could also explain why this failure mode didn't crop up before... The sub-chilled LOX is a relatively new procedure and almost no one else has used it (might explain why they had a almost unheard of fueling failure). Combine that with changes in humidity and wind conditions and that could put a RP-1 plume and nearby liquid oxygen in the right place for a spark during LOX filling to ignite it.

Based on the approx. location of the start of the flame, the common bulkhead support cradle on the TE could possibly provide a location for a static discharge to occur near a suspected RP-1 tank vent and condensing O2.

It seems like a bit of a stretch but I remember making LOX on the outside of a pop can filled with LN2.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/09/2016 11:25 pm
I've been out of the loop all day today but when I raised my head, a little birdie indicated to me that part of the problem with this particular investigation is that SpaceX apparently housed some or all of their telemetry servers at or very close to the pad, and they were destroyed by the fire. I don't know how accurate this is, but given today's "cry for help" for external recordings and imagery of the failure, there may be some meat to it.

Make of this what you will. If true, I have to say, I would HATE to be the guy who approved that part of the launch CONOPS.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/09/2016 11:28 pm
I had an interesting thought on how you might get LOX on the outside/bottom edge of the LOX tank, near the RP-1 tank vent without a leak.

At the sub chilled LOX temperatures that are present inside the tank, it is highly likely that you would actually get liquid oxygen condensing out of the surrounding air onto the rocket body.

This could also explain why this failure mode didn't crop up before... The sub-chilled LOX is a relatively new procedure and almost no one else has used it (might explain why they had a almost unheard of fueling failure). Combine that with changes in humidity and wind conditions and that could put a RP-1 plume and nearby liquid oxygen in the right place for a spark during LOX filling to ignite it.

Based on the approx. location of the start of the flame, the common bulkhead support cradle on the TE could possibly provide a location for a static discharge to occur near a suspected RP-1 tank vent and condensing O2.

It seems like a bit of a stretch but I remember making LOX on the outside of a pop can filled with LN2.
Welcome to the forum! :) It's a long thread to read but I think I recall some making comments about static discharges as well. Have fun!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: djhopkins2 on 09/09/2016 11:29 pm
I looked into it and they are subchilling LOX to ~66.5K. The freezing point is 54.36 K and boiling point is 90.19 K and I believe Musk once said they were closer to freezing than boiling. I was reading this thread (https://forum.nasaspaceflight.com/index.php?topic=39072.0 (https://forum.nasaspaceflight.com/index.php?topic=39072.0)) and they bring up an interesting point.

Quote
    -340F is cold enough to liquify both Nitrogen and Oxygen in the atmosphere. I thought that was one of the big headaches of LH2 was that you had to deal with Liquid oxygen forming on the tanks and such. ~Jon

They also mention near the end of the thread some articles that describe frost as having pretty good insulating properties. However, this was soon after LOX loading commenced and there may not have been much time to form a thick frost layer. I've had liquid oxygen dripping off a LN2 container without much frost forming. LN2 has a boiling point of 77 K which is warmer than the LOX that SpaceX is using.

From another site (https://www.ccohs.ca/oshanswers/chemicals/cryogenic/cryogen1.html (https://www.ccohs.ca/oshanswers/chemicals/cryogenic/cryogen1.html)), it appears that this is a common safety concern

Quote
    Liquid hydrogen and liquid helium are both so cold that they can liquefy the air they contact. For example, liquid air can condense on a surface cooled by liquid hydrogen or helium. Nitrogen evaporates more rapidly than oxygen from the liquid air. This action leaves behind a liquid air mixture which, when evaporated, gives a high concentration of oxygen. This oxygen-enriched air now presents all of the same hazards as oxygen.

I Just found this video (https://www.youtube.com/watch?v=oL1mIxP4lwk (https://www.youtube.com/watch?v=oL1mIxP4lwk)) demonstrating the principle in open air with relatively warmer liquid nitrogen.

edit: English
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/09/2016 11:34 pm
There are posts on this earlier in the thread
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/09/2016 11:41 pm
Shifting the spectrogram further back in time ALMOST but not exactly lines up...  What does this do to the speed calculations?  It also shows an earlier blip.  I need to listen to the audio to see if it's really related.

Not sure if you have the tools to do this, I'm not sure exactly how to do this either.

IF the clang and thunk are P & S waves, there is a chance that the camera is shaking at the same times, and not prior or after until the big 'un.


I tried focusing on two lights at the bottom during the clang and the thunk, thinking they wouldn't move unless the camera did, and boy was I wrong.  They're wobbling like mad because of other explosions at the same time that the clang and thump happen.  I'll try the tower next, but if you can synch the audio and video maybe you could look at shake and save me a mouse induced carpel tunnel event?  :)

Here's the synced video.  I can't see anything happening...  Now I'm not sure which thread this should go in...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: djhopkins2 on 09/09/2016 11:42 pm
Welcome to the forum! :) It's a long thread to read but I think I recall some making comments about static discharges as well. Have fun!

I have seen quite some talk on how LOX generates a decent amount of static during flow. But the only way they had LOX getting outside the rocket at that location was with a break at the common bulkhead.

I wanted to add a possible mechanism by which LOX ends up outside the rocket near the common bulkhead support on the strongback (which is pretty much the apparent epicenter of the first sign of fire). There has also been talk of the RP-1 tank vent being near there. Add that to the fact that earlier launches, except for the last few, would have had warmer LOX (thus no LOX condensation) and you have a possible change that could have led to such a rare event, in rocket history, occurring.

At that rate, if the LOX on the outside of the tank came in contact with any organic matter (it wouldn't have to be RP-1). What do they use to prevent denting the common bulkhead with the TE support? Any sort of foam?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: djhopkins2 on 09/09/2016 11:44 pm
There are posts on this earlier in the thread

Being quite long, I hadn't read it in it's entirety. I'll see if I can find those.
Thanks  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: testguy on 09/09/2016 11:50 pm
Here's one I don't think is in the list:

a leak, even a tiny one, in the S2 TEB system. It auto ignites in O2 at -20°C. Is it tanked on the ground or late loaded through the strongback?

I don't know but I would say on the ground in the hangar, because
a.  we don't see a container on the TEL for it.
b.  running a line from the ground all the way up the TEL to the second stage means a lot of fluid that would have to be purge out of the line after filling.  Maybe more than would be needed by the stage
I have had lots of experience burning TEB in an oxygen environment.  Let's remember it is a fuel not an explosive.  The only flame you would get is until it is consumed.  The flame front will not propagate through the oxygen cloud unless some other fuel is present. 
Agree with Jim it is probably loaded on the ground and not from TEL.  TEB is not very energetic at ambient pressure.  It takes an inert pressurizent like GN2 to force in the line to get enough flow to get enough BTU's to do any good.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: demofsky on 09/10/2016 12:19 am
Something I don't recall being mentioned yet are stress fractures.  This could be caused by a number of of things including handling issues.  The thing about stress fractures is that they can act as a time bomb failing some time after the event that causes them.  For high pressure pipelines they could take months or years before failing.

One argument for a stress fracture is that the explosion occurred during LOX loading, with super cooled LOX providing the additional stress to cause the failure.   The actual failure could be quite small resulting in a plume of O2 being sprayed out prior to the ignition event.

I suppose this logic could also apply to chilled RP-1, providing the fuel required.  (LOX really isn't required here).

The only thing in favor of this is the timing with the metal walls of S-2 being stressed by the loading operations under way.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 12:22 am
Something I don't recall being mentioned yet are stress fractures.  This could be caused by a number of of things including handling issues.  The thing about stress fractures is that they can act as a time bomb failing some time after the event that causes them.  For high pressure pipelines they could take months or years before failing.

One argument for a stress fracture is that the explosion occurred during LOX loading, with super cooled LOX providing the additional stress to cause the failure.   The actual failure could be quite small resulting in a plume of O2 being sprayed out prior to the ignition event.

I suppose this logic could also apply to chilled RP-1, providing the fuel required.  (LOX really isn't required here).

The only thing in favor of this is the timing with the metal walls of S-2 being stressed by the loading operations under way.
Yes,  mentioned something similar at the common bulkhead, many pages back...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/10/2016 12:48 am
Any thought of condensed nitrogen getting trapped somewhere then boiling?  Do liquids like that have the same 'explosive' boiling behavior as water?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/10/2016 12:50 am
Shifting the spectrogram further back in time ALMOST but not exactly lines up...  What does this do to the speed calculations?  It also shows an earlier blip.  I need to listen to the audio to see if it's really related.

Not sure if you have the tools to do this, I'm not sure exactly how to do this either.

IF the clang and thunk are P & S waves, there is a chance that the camera is shaking at the same times, and not prior or after until the big 'un.


I tried focusing on two lights at the bottom during the clang and the thunk, thinking they wouldn't move unless the camera did, and boy was I wrong.  They're wobbling like mad because of other explosions at the same time that the clang and thump happen.  I'll try the tower next, but if you can synch the audio and video maybe you could look at shake and save me a mouse induced carpel tunnel event?  :)

Here's the synced video.  I can't see anything happening...  Now I'm not sure which thread this should go in...

I guess I should have said the "unsynched" audio, to look at if the camera shook when the possible P & S waves hit.  :)

I'm sorry, it's been along week for me.

The idea is, if the P & S waves are the sounds in your analysis,  WHEN they arrive, the camera may shake.  If it shakes, what ever it sees at the time, like 12 seconds into the explosion, might shake because P & S waves impart ground movement to things that are on the ground, like tripods and cameras.

My core question is, when those sounds arrive, does the camera shake?

Later, when the air-sound explosion arrives, the camera shakes like a banshee.  It's obvious then that the local environment is stability unfriendly.

But, if the camera shakes during the creak and thwap, that suggests possibly, that the sounds recorded are seismic, since seismic events include ground movement, which means tripods mounted on the ground would move, which means cameras focused on a fixed point would move, which means, we may or may not be able to confirm if those sounds are seismic, if the camera absolutely moves at the same time as the sounds arrive.

The camera is looking 12? seconds into the audio future at that point in time, so aside from everything else happening near the explosion, there is a tiny chance we can see non-local shockwave movement of things, during the creak and thump.  If we do, that's evidence for seismic sound transfer.  If we don't, it may simply mean it's acoustic, but the earth didn't move for the camera.

I focused on some lights near the ground in my attempt.  The lights at the time of the sounds went nuts because they were responding to local shock waves that the camera wouldn't hear for about 12 seconds.

May I please implore you to try this again?  You have the technology means in hand, obviously.  The result would be interesting.   :)

Please?  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: savuporo on 09/10/2016 12:51 am
Are any of the external "rocket cameras" located in the area of interest? If a battery caught fire or exploded in that oxygen rich environment...
Next up: all pad technicians get body cameras.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/10/2016 01:10 am
for the sound folks...
im still on the hunt for a nice geological map of the florida coast, but i did find some well data near the cape from usgs

http://pubs.usgs.gov/sir/2007/5207/pdf/v13figA1.pdf

well #W16226 aka BR1217
marked log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/BR1217_COMPOSITE_FMS_0_2713.tif
resistivity log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/BR1217_COMPOSITE_128_2713.tif
sonic log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/W-16226_BHCSONIC_100_2700.tif
neutron log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/W-16226_NEU_100_2700.tif
induction log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/W-16226_DI_SFL_100_2700.tif
temp/caliper log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/W-16226_CAL_FLTEMP_0_2692.las
temp/caliper/gamma ray log
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/BR1217_FLTEMP_CAL_GAM_83_1166.las
resistivity and density data
http://pubs.usgs.gov/ds/760/Downloads/FL/BREVARD/BR1217_CAL_GAM_NEU_DILL_BHCSONIC_128_2713.las
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/10/2016 01:33 am
Welcome to the forum! :) It's a long thread to read but I think I recall some making comments about static discharges as well. Have fun!

I have seen quite some talk on how LOX generates a decent amount of static during flow. But the only way they had LOX getting outside the rocket at that location was with a break at the common bulkhead.

I wanted to add a possible mechanism by which LOX ends up outside the rocket near the common bulkhead support on the strongback (which is pretty much the apparent epicenter of the first sign of fire). There has also been talk of the RP-1 tank vent being near there. Add that to the fact that earlier launches, except for the last few, would have had warmer LOX (thus no LOX condensation) and you have a possible change that could have led to such a rare event, in rocket history, occurring.

At that rate, if the LOX on the outside of the tank came in contact with any organic matter (it wouldn't have to be RP-1). What do they use to prevent denting the common bulkhead with the TE support? Any sort of foam?

Well, that would certainly change the meaning of "static fire".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/10/2016 01:40 am
here are some generalized cross section charts

http://pubs.usgs.gov/pp/1807/downloads/pp1807_plate21.pdf

http://pubs.usgs.gov/pp/1807/downloads/pp1807_plate19.pdf

http://pubs.usgs.gov/sir/2007/5207/pdf/v13plate01.pdf

and two big papers

http://ufdcimages.uflib.ufl.edu/UF/00/09/40/39/00001/SP50.pdf

http://www.nrc.gov/docs/ML1603/ML16034A497.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: leetdan on 09/10/2016 02:06 am
SpaceX apparently housed some or all of their telemetry servers at or very close to the pad, and they were destroyed by the fire.

Far be it from me to question your sources, but that doesn't jive even remotely with earlier statements. Telemetry being lost precludes telemetry being reviewed. If the supposed lost servers weren't hardened AND located close enough to burn in the aftermath, how would they not have been destroyed or at least damaged during a previous nominal launch?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/10/2016 02:15 am

Re: triangulation - if its possible to sync two or more audio tracks to within tens of ms, it should be possible to localize the source to within some 10s of feet, no?   SpaceX ought to have been able to do that.  Does that imply the sound came from an "expected" place - the area of the 2nd stage?

What audio tracks?

Huh.   It hadn't occurred to me that SpaceX might not have multiple video/audio recordings of the static fire.   That would be unfortunate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/10/2016 03:00 am
SpaceX apparently housed some or all of their telemetry servers at or very close to the pad, and they were destroyed by the fire.

Far be it from me to question your sources, but that doesn't jive even remotely with earlier statements. Telemetry being lost precludes telemetry being reviewed. If the supposed lost servers weren't hardened AND located close enough to burn in the aftermath, how would they not have been destroyed or at least damaged during a previous nominal launch?

I was surprised by this info too, that's why I said make of it what you will. I also don't know what public statements SpaceX has actually made that would contradict it. To what "earlier statements" do you refer?

As for the second half of the comment, it's quite possibly electronics are hardened against a 3 second static fire (or even a 2 minute static fire) but still unable to tolerate an extended-duration 1,000 degree-plus RP1 and/or hypergolic fire, impact with high-speed debris from a venting COPV, etc. SpaceX notably doesn't use old-fashioned blockhouses these days, you'll note. Most launch providers don't.

Anyway, I'm not wedded to this info - the person I got it from is far better placed than me to know what's going on in and around CCAFS right now, but you know,  there could be subtle misunderstandings on their part or in how it was explained to me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: winkhomewinkhome on 09/10/2016 03:05 am
***ARC FLASH**
I'm not sure if it has been noted here yet in the discussion - surprised if it hasn't been - when an electrical arc flash occurs it makes a "noise" - snap, crackle, pop, boom - as it were...

As always, for what it is worth!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 03:16 am

Re: triangulation - if its possible to sync two or more audio tracks to within tens of ms, it should be possible to localize the source to within some 10s of feet, no?   SpaceX ought to have been able to do that.  Does that imply the sound came from an "expected" place - the area of the 2nd stage?

What audio tracks?

Huh.   It hadn't occurred to me that SpaceX might not have multiple video/audio recordings of the static fire.   That would be unfortunate.

Audio is not used
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GeneBelcher on 09/10/2016 03:21 am

I was surprised by this info too, that's why I said make of it what you will. I also don't know what public statements SpaceX has actually made that would contradict it. To what "earlier statements" do you refer?

As for the second half of the comment, it's quite possibly electronics are hardened against a 3 second static fire (or even a 2 minute static fire) but still unable to tolerate an extended-duration 1,000 degree-plus RP1 and/or hypergolic fire, impact with high-speed debris from a venting COPV, etc. SpaceX notably doesn't use old-fashioned blockhouses these days, you'll note. Most launch providers don't.

Anyway, I'm not wedded to this info - the person I got it from is far better placed than me to know what's going on in and around CCAFS right now, but you know,  there could be subtle misunderstandings on their part or in how it was explained to me.

Not using blockhouses indicates to me that all the data is transmitted well away from the pad to servers, certainly not that they are using servers close enough to have been destroyed.

Also, one of Elon's tweets mentioned vehicle sensor data, indicating they have telemetry data.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 03:21 am
***ARC FLASH**
I'm not sure if it has been noted here yet in the discussion - surprised if it hasn't been - when an electrical arc flash occurs it makes a "noise" - snap, crackle, pop, boom - as it were...

As always, for what it is worth!

What voltages do you think are used on Launch vehicles?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/10/2016 03:30 am
It's basically swampland. You're not going to get a surface wave, period.
When I witnessed launches at KSC and the Cape, sometimes from less than 3 miles distant, I could feel the ground move beneath my feet before the sound of the launch arrived.  Isn't that a "surface wave"?

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Multivac on 09/10/2016 03:32 am
With regard to possible camera shake (or no shake) due to ground waves in the US Launch Report video...

I'm guessing the camera would be mounted on a decent tripod (or similar) and the lens used would be reasonably long. Most modern lenses especially long lenes incorporate "image stabilisation" or "vibration reduction".

IMHO I doubt the ground wages would be enough to shake to camera if image stabilisation was in use. I also think the the force of the sound waves through air would probably be enough to overwhelm any image stabilisation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/10/2016 03:39 am
***ARC FLASH**
I'm not sure if it has been noted here yet in the discussion - surprised if it hasn't been - when an electrical arc flash occurs it makes a "noise" - snap, crackle, pop, boom - as it were...

As always, for what it is worth!

What voltages do you think are used on Launch vehicles?

An ungrounded system can develop millions of volts of surface potential just from being in the wind.

I'm not saying this system is ungrounded, but if a ground failed or separated, a large potential could develop very quickly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/10/2016 04:04 am
***ARC FLASH**
I'm not sure if it has been noted here yet in the discussion - surprised if it hasn't been - when an electrical arc flash occurs it makes a "noise" - snap, crackle, pop, boom - as it were...

As always, for what it is worth!

What voltages do you think are used on Launch vehicles?

An ungrounded system can develop millions of volts of surface potential just from being in the wind.

I'm not saying this system is ungrounded, but if a ground failed or separated, a large potential could develop very quickly.

That requires particulates in the wind; dust, sand, dried sea spray etc. Was there any?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Adriano on 09/10/2016 04:09 am
An arc flash will only trigger an explosion or fire if there is a mixture of oxygen and combustible kerosene gasses. We now understand air oxygen will condense on the supercooled oxygen tank, hence an oxygen rich environment is unavoidable. But we can avoid kerosene gasses in the area by connecting a pipe to the vent of the kerosene tanks ending with a flare on top of the strong back, like it is normally done in refineries. Simple, effective and well tested...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/10/2016 04:37 am
Audio is not used

What about accelerometers?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: codefeenix on 09/10/2016 04:38 am
https://twitter.com/volcanoGlenn/status/774433349196779520

this guy says he has close seismic data (<1 mile away). can someone convince him to upload his data here?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Meltro on 09/10/2016 05:54 am

Re: triangulation - if its possible to sync two or more audio tracks to within tens of ms, it should be possible to localize the source to within some 10s of feet, no?   SpaceX ought to have been able to do that.  Does that imply the sound came from an "expected" place - the area of the 2nd stage?

What audio tracks?

Huh.   It hadn't occurred to me that SpaceX might not have multiple video/audio recordings of the static fire.   That would be unfortunate.

Audio is not used

Obviously not the pad cams but just confirming something I thought I remembered reading, wasn't it brought up in the last investigation that the accelerometers on the craft itself were sensitive enough to be able to reproduce sound?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Eyrie on 09/10/2016 07:21 am
Somebody PLEASE tell me there wasn't any Kapton insulated wiring on the TE or other GSE.
Kapton + salt atmosphere is bad news as the insulation cracks, causes shorts and catches fire. In an oxygen rich atmosphere near LOx vents likely to be worse.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Digitalchromakey on 09/10/2016 09:01 am
Earlier in this thread there were many posts regarding the large diameter duct with an ‘S’ bend in the upper section of the TEL.

It was established that this upper duct solely carried a/c for the payload/fairing which at a later stage in the launch sequence was transitioned to carrying gaseous purge nitrogen.

The payload’s hydrazine fuel is pre-loaded before the satellite is encased by the fairing.

Jim has pointed out that the fairing vents to the exterior and that there is no return path for nitrogen or a/c air.

However, the fairing must be pressurized somewhat above atmospheric pressure for the nitrogen purge system to work.

What is the possibility that some payload anomaly occurred where hydrazine fuel was accidentally discharged and somehow ended up coming out from the fairing then subsequently running down the side of S2 until it came into contact with the venting O2 at the point where an ignition occurred then leading to the LOV? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ciscosdad on 09/10/2016 10:36 am
From my understanding of Hydrazine's (actually MMH I believe) properties, it would certainly have carried the initial explosion immediately into the payload fairing, which was clearly uninvolved in the early sequence of events
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: guckyfan on 09/10/2016 10:40 am
From my understanding of Hydrazine's (actually MMH I believe) properties, it would certainly have carried the initial explosion immediately into the payload fairing, which was clearly uninvolved in the early sequence of events

The suggestion by digitalchromakey is not related to shooting if I understand him correctly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/10/2016 11:52 am

I was surprised by this info too, that's why I said make of it what you will. I also don't know what public statements SpaceX has actually made that would contradict it. To what "earlier statements" do you refer?

As for the second half of the comment, it's quite possibly electronics are hardened against a 3 second static fire (or even a 2 minute static fire) but still unable to tolerate an extended-duration 1,000 degree-plus RP1 and/or hypergolic fire, impact with high-speed debris from a venting COPV, etc. SpaceX notably doesn't use old-fashioned blockhouses these days, you'll note. Most launch providers don't.

Anyway, I'm not wedded to this info - the person I got it from is far better placed than me to know what's going on in and around CCAFS right now, but you know,  there could be subtle misunderstandings on their part or in how it was explained to me.

Not using blockhouses indicates to me that all the data is transmitted well away from the pad to servers, certainly not that they are using servers close enough to have been destroyed.

Also, one of Elon's tweets mentioned vehicle sensor data, indicating they have telemetry data.
I was thinking about this a lot last night, trying to hypothesize a system that would comport with this possible news. Imagine a very high bandwidth telemetry system - it will require a lot of signal bandwidth back to the storage system and then a relatively smaller bandwidth to the consoles of the folks working a mission. Remember, controllers only look at some of the data in realtime but can often focus in more closely on systems as necessary, pulling up some data and looking away from others on the fly as needed.

Now imagine a data system created by Silicon Valley types who think they have a more efficient way than running miles of high-data rate cabling back to launch control. Instead, limit the very high bandwidth runs from the vehicle down to a semi-hardened bunker near the pad then run a relatively "thin" set of data cables back to launch control to allow controllers to see what they want in realtime but store everything else for later download and analysis. "What could go wrong, right? Civilian rockets haven't blown up on the pad in 50+ years!" Remember, this system - whatever the details - was conceived before the Antares mishap when LC-40 was first converted.

Anyway, as I said I have no personal knowledge but thought it worth bringing up for discussion. I can imagine a data system architecture that lines up with the info - and even justification for such an architecture at the time it might have been created - but don't know if it's true. In fact we may never know unless a government investigation report is released that delineates difficulties experienced pursuing the investigation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/10/2016 12:02 pm
But then the Silicon Valley guys I know generally aren't afraid to transfer huge amounts of data around all the time. Actually I would be way less surprised to learn SpaceX transfers all data directly to Hawthorn before anyone even looks at it than to learn they store it locally somewhere
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/10/2016 12:21 pm

I was surprised by this info too, that's why I said make of it what you will. I also don't know what public statements SpaceX has actually made that would contradict it. To what "earlier statements" do you refer?

As for the second half of the comment, it's quite possibly electronics are hardened against a 3 second static fire (or even a 2 minute static fire) but still unable to tolerate an extended-duration 1,000 degree-plus RP1 and/or hypergolic fire, impact with high-speed debris from a venting COPV, etc. SpaceX notably doesn't use old-fashioned blockhouses these days, you'll note. Most launch providers don't.

Anyway, I'm not wedded to this info - the person I got it from is far better placed than me to know what's going on in and around CCAFS right now, but you know,  there could be subtle misunderstandings on their part or in how it was explained to me.

Not using blockhouses indicates to me that all the data is transmitted well away from the pad to servers, certainly not that they are using servers close enough to have been destroyed.

Also, one of Elon's tweets mentioned vehicle sensor data, indicating they have telemetry data.
I was thinking about this a lot last night, trying to hypothesize a system that would comport with this possible news. Imagine a very high bandwidth telemetry system - it will require a lot of signal bandwidth back to the storage system and then a relatively smaller bandwidth to the consoles of the folks working a mission. Remember, controllers only look at some of the data in realtime but can often focus in more closely on systems as necessary, pulling up some data and looking away from others on the fly as needed.

Now imagine a data system created by Silicon Valley types who think they have a more efficient way than running miles of high-data rate cabling back to launch control. Instead, limit the very high bandwidth runs from the vehicle down to a semi-hardened bunker near the pad then run a relatively "thin" set of data cables back to launch control to allow controllers to see what they want in realtime but store everything else for later download and analysis. "What could go wrong, right? Civilian rockets haven't blown up on the pad in 50+ years!" Remember, this system - whatever the details - was conceived before the Antares mishap when LC-40 was first converted.

Anyway, as I said I have no personal knowledge but thought it worth bringing up for discussion. I can imagine a data system architecture that lines up with the info - and even justification for such an architecture at the time it might have been created - but don't know if it's true. In fact we may never know unless a government investigation report is released that delineates difficulties experienced pursuing the investigation.
Bandwidth is cheap. CWDM Ethernet LX-4 provides 10Gbit/s per fibre. DWDM can achieve 1.6 Tbit/s per fibre with cheap of the shelf hardware. A cable contains multiple fibres (12).

Gesendet von meinem SM-T800 mit Tapatalk

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/10/2016 12:57 pm
Curious question on the servers wiped clean with burning RP-1 and LOX. Is it a flesh wound, or is it possible to send the remains out to one of those data recovery places? I know heat can do a number on drives. Curious if there is hope for the lost servers.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/10/2016 12:59 pm
Curious question on the servers wiped clean with burning RP-1 and LOX. Is it a flesh wound, or is it possible to send the remains out to one of those data recovery places? I know heat can do a number on drives. Curious if there is hope for the lost servers.
Got no clue, man. I passed along what I heard purely for the sake of discussion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/10/2016 01:07 pm
And yet another probably irrelevant image processing example.

Here we see a 10 frame sequence, the last frame on the right is frame 0.

The one to the left is Frame-1 minus frame 0,  Frame -2 minus frame -1, etc.  The differences of 9 frames leading to the last.

the range is maxed with no saturation.  Image upscaled X3.

There is no interpretation offered, it looks pretty, but I can't pull any meaning out of it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/10/2016 01:09 pm
Quote from: Herb Schaltegger
Got no clue, man. I passed along what I heard purely for the sake of discussion.

I get it, their are several things we don't know at this point. What data they have, what gse was lost or damaged, how bad the hydrazine contamination was, how big the cleanup will be, how much access they have to the pad...

For the historians like Ed, was this failure the largest hydrazine pad handling accident at the cape?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bbb_rocket on 09/10/2016 01:13 pm
Long time listener, first time caller. I have read all 2100+ messages so far in this board and I haven't heard this exact theory I'm about to put forth.

I call this the "slow slump" theory. Since the static fire is the first time the full stack was fully integrated and was being fueled, I propose that there was not necessarily a manufacturing flaw but a borderline tolerance flaw, along with a borderline tolerance mating of the strongback to the stack. As the RP1 was being loaded the rocket would be creaking and would be triggering sensors within the rocket, but the difference would be there would be an accumulation of borderline tolerance flaws that would cause the rocket to slowly "slump" along the side of the rocket facing the strongback and would have lead to a minor leak of the rocket near the top of RP1 stage 2 tank only when the tank was full (around the time of the anomaly occurred). This leak was minor enough  it would not have been observed easily on camera, but the RP1 was being atomized by LOX venting from S1 and carried up to be ignited by the oxygen rich venting on S2 until there was enough fuel to be ignited.

Sensor readings long before the anomaly would look different than prior static firings of the F9. The cause of the anomaly was a long running event while everyone is looking for a fast cascade of sensor reading, but culminated in the footage we have all seen in the video. The weak part of this theory is the ignition of this FAE event, but I'm postulating that given enough RP1, and oxidizer in this environment that any rust point on the strongback could have triggered the FAE, and subsequent LOV.

I'm just a curious armchair rocket sturgeon looking for answers like everyone else.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/10/2016 01:22 pm
Long time listener, first time caller. I have read all 2100+ messages so far in this board and I haven't heard this exact theory I'm about to put forth.

I call this the "slow slump" theory. Since the static fire is the first time the full stack was fully integrated and was being fueled, I propose that there was not necessarily a manufacturing flaw but a borderline tolerance flaw, along with a borderline tolerance mating of the strongback to the stack. As the RP1 was being loaded the rocket would be creaking and would be triggering sensors within the rocket, but the difference would be there would be an accumulation of borderline tolerance flaws that would cause the rocket to slowly "slump" along the side of the rocket facing the strongback and would have lead to a minor leak of the rocket near the top of RP1 stage 2 tank only when the tank was full (around the time of the anomaly occurred). This leak was minor enough  it would not have been observed easily on camera, but the RP1 was being atomized by LOX venting from S1 and carried up to be ignited by the oxygen rich venting on S2 until there was enough fuel to be ignited.

Sensor readings long before the anomaly would look different than prior static firings of the F9. The cause of the anomaly was a long running event while everyone is looking for a fast cascade of sensor reading, but culminated in the footage we have all seen in the video. The weak part of this theory is the ignition of this FAE event, but I'm postulating that given enough RP1, and oxidizer in this environment that any rust point on the strongback could have triggered the FAE, and subsequent LOV.

I'm just a curious armchair rocket sturgeon looking for answers like everyone else.

Well, that is a new idea.  :)  Been a while.... :)

Does your theory require S1 LOX to go up?  Couldn't the RP1 just come down and start evaporating?

Kerosine's vapor pressure is 0.5kPa at 20 degrees C.  Water, and beer, by comparison is 2.4.  It would, me thinks, take a long time to accumulate enough vapor, and the wind was blowing to the left...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: bbb_rocket on 09/10/2016 01:40 pm
Well, that is a new idea.  :)  Been a while.... :)

Does your theory require S1 LOX to go up?  Couldn't the RP1 just come down and start evaporating?

Kerosine's vapor pressure is 0.5kPa at 20 degrees C.  Water, and beer, by comparison is 2.4.  It would, me thinks, take a long time to accumulate enough vapor, and the wind was blowing to the left...

Unfortunately I'm not versed enough to work out the specifics of how LOX, and RP1 work that is why I'm proposing this theory for the experts to shoot down. But I believe a confluence of events between S1 and S2 and the conclusion of RP1 loading and the commencing of LOX loading that only occur at this specific point in the countdown triggered the event. It is also my understanding the wind was mild this date at LC40, if that is the case then the gathering of volatile cocktail of gases/ices on the exterior of the F9 would have made this event more possible.

I can do lots of hand waving in my ideas, but I'm a software engineer by trade but I'm trying to see logic flaws in how this event occurred.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 01:57 pm
We now understand air oxygen will condense on the supercooled oxygen tank.

We don't know if that occurred.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 01:59 pm

Obviously not the pad cams but just confirming something I thought I remembered reading, wasn't it brought up in the last investigation that the accelerometers on the craft itself were sensitive enough to be able to reproduce sound?


I brought that up long ago.  If something hit the vehicle, they would know from those.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 02:00 pm
Somebody PLEASE tell me there wasn't any Kapton insulated wiring on the TE or other GSE.
Kapton + salt atmosphere is bad news as the insulation cracks, causes shorts and catches fire. In an oxygen rich atmosphere near LOx vents likely to be worse.

Kapton is only used on spacecraft and not GSE
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 02:03 pm
Earlier in this thread there were many posts regarding the large diameter duct with an ‘S’ bend in the upper section of the TEL.

It was established that this upper duct solely carried a/c for the payload/fairing which at a later stage in the launch sequence was transitioned to carrying gaseous purge nitrogen.

The payload’s hydrazine fuel is pre-loaded before the satellite is encased by the fairing.

Jim has pointed out that the fairing vents to the exterior and that there is no return path for nitrogen or a/c air.

However, the fairing must be pressurized somewhat above atmospheric pressure for the nitrogen purge system to work.

What is the possibility that some payload anomaly occurred where hydrazine fuel was accidentally discharged and somehow ended up coming out from the fairing then subsequently running down the side of S2 until it came into contact with the venting O2 at the point where an ignition occurred then leading to the LOV? 


NO, as stated many times before that the fairing was intact.  Any leak would have ignited and gone up and into the fairing, blowing it up. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 02:09 pm
Ok, since yesterday I've been on my new fixation, the on board "gopro type" camera batteries (disclaimer: please note I said "type" no brand) I refer to these on board rocket cams.  Anyone familiar to the type of batteries and failure modes. (I've never owned one)... Some of these cameras are internal (interstage) and some external. Are the cameras on or in falcon powered by individual batteries or from a main(s). When are they charged in the sequence. They could still be off and charged or being charged from the TEL umbilicals. Some batteries will fail explosively and some will catch fire in normal air... Possibilities: from overcharge, short, reverse polarity, improper install, defect (who makes them) etc... Jim and I shared some brief comments yesterday, any other thoughts?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/10/2016 02:13 pm
If you accept musks statement that no obvious problems. And take that to mean nothing from the rocket initiated the event. And you discount all sabotage as highly unlikely. Then we are left with GSE and TEL. So I am now changing my opinion and thinking contamination is the most likely. I like the post up thread that said if you leave a cap off a lox line that bees could nest in there. The TEL is probably not as well inspected as the rocket so can contamination cause a self initiated event? I think upthread they said yes. The question is how close to the supposed center is a lox line and would the combination of foreign matter and lox be large enough to equal the initial explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 02:13 pm
There are two types of cameras.  Gopro, which stores the data and the telemetry cameras, which we can see live
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 02:21 pm
There are two types of cameras.  Gopro, which stores the data and the telemetry cameras, which we can see live
Thanks Jim, So we have the Gopros in the faring with their own batteries and the telemetry cameras off Falcon's mains which are located where on the second stage if publicly known?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/10/2016 02:24 pm
There are two types of cameras.  Gopro, which stores the data and the telemetry cameras, which we can see live
Thanks Jim, So we have the Gopros in the faring with their own batteries and the telemetry cameras off Falcon's mains which are located where on the second stage if publicly known?

The only 'go pro' cameras I know of in the second stage are on either side of the M1-vac and one on top of the second stage to view fairing sep and payload deploy. None near the apparent center of the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 02:26 pm
The only 'go pro' cameras I know of in the second stage are on either side of the M1-vac and one on top of the second stage to view fairing sep and payload deploy. None near the apparent center of the explosion.

Those aren't  go pro.  Go pro are self contained and data retrieved later.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 02:27 pm

For the historians like Ed, was this failure the largest hydrazine pad handling accident at the cape?

Shuttle and Titan had larger spills
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 02:31 pm
I'm looking at Falcon's user guide for battery locations for this. Since there are no pyros for stage sep only pneumatic/latches.

http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 02:48 pm
No joy on battery locations, but it did get me thinking about the "customer supplied cable 20ft." to pad junction box on the TEL (section 5.1) via the Catenary Umbililcal to S2 (image page 39)... Was that the case for this launch or was it supplied by SpaceX? Was it the first time it was powered on from the TEL junction box?
http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/10/2016 02:51 pm
From my understanding of Hydrazine's (actually MMH I believe) properties, it would certainly have carried the initial explosion immediately into the payload fairing, which was clearly uninvolved in the early sequence of events
Wouldn't the vents be somewhat one way? That and gravity might be enough to prevent it going internal to the fairing. Plus there would be no oxidizer in the fairing if only the "fuel" part was leaking.
The real problem with this is that you would have to believe in either a really slow leak initiated when the vehicle went vertical (too slow to measure) or an initiating event that would start a slightly faster leak closer to the incident.

So two questions: Would the payload have been monitored AT ALL during the static fire? Is Hydrazine hypergolic in oxygen enriched air? 

I don't think you would get such a bright flash nor an apparent fuel/ air explosion unless Hydrazine also evaporates rather quickly. Anyone know?
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 02:58 pm
1.  Wouldn't the vents be somewhat one way? That and gravity might be enough to prevent it going internal to the fairing.

2. Plus there would be no oxidizer in the fairing if only the "fuel" part was leaking.

3.  So two questions: Would the payload have been monitored AT ALL during the static fire?

4 Is Hydrazine hypergolic in oxygen enriched air? 


1.  No, they just have air blowing out them

2.  Not needed.  See below

3.  Yes,

4.  Hydrazine is a monopropellant, it needs no oxygen.  It reacts with many items.  Rust, dirt, foam, etc can set it off.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: woods170 on 09/10/2016 03:00 pm
Quote
increasingly trying to understand sound heard prior to explosion

This is very telling. Points to one of two things:

Internal failure in the lox tank or GSE failure that rapidly overpressurized the tank or its internals.

FTS is ruled out (thanks for the info on this jim).

External fae is ruled out due to a variety of reasons though the wind is a big one.

Gse is not something I can completely rule out but it seems very unlikely, the system itself would probably fail first not the lox tank.

Payload as source is ruled out due to the payload not blowing up until after it fell off what was left of the TE and other aforementioned reasons regarding payload fuel.

Really IMHO only thing that fits in something within the lox tank. So COPV or other internal ignition+overpressure ignition not yet found.

My guess is the reason why it is so hard to pinpoint is because it happened extremely fast.

Still there are more questions now I think than we had before and not really any answers.


Here is the point though. The failure was in the LOX tank or very near to it in the second stage. I think this is almost 100% certain given spacex's own statements and the failure nature itself.

Second, to me this leads back to the original problem which brought down crs7: quality control.


Spacex is apparently learning the hard way they cannot keep doing things internally like a startup company. They need to seriously rethink their quality control program and how they test tankage components. They have been criticized by both other other industry figures and others for this in the recent past and have ignored the criticism as far more knowledgeable members on this site are no doubt aware.

Basically the short version, and I will preface this by saying that it's as I see it, is they need to get with the program already. Innovation is great but constantly changing component design and manufacture in the quest for efficiency is a recipe for these kinds of failures every time.

I suspect they will make real changes this time because the alternative will be losing contracts if this happens again.


You just did that thing again that you are not supposed to do: pull conclusions based on little to no concrete information.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: launchwatcher on 09/10/2016 03:11 pm
Bandwidth is cheap. CWDM Ethernet LX-4 provides 10Gbit/s per fibre. DWDM can achieve 1.6 Tbit/s per fibre with cheap of the shelf hardware. A cable contains multiple fibres (12).
sure, but are they going to have optical links to the rocket?   If the link to the rocket is electrical they'll need some device near the pad to convert from electrical to optical.. and that may introduce some amount (microseconds to milliseconds) of buffering and packetization delay which would increase the amount of data lost over a system which merely repeated the signal a bit at a time...

Would not be surprised to see multiple 1000base-T twisted-pair gigabit ethernet links off the rocket (spec says max cable length ~100m) running to one or more ethernet switches on the pad (or even up on the TEL!) with an optical uplink off the pad.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 03:46 pm
Bandwidth is cheap. CWDM Ethernet LX-4 provides 10Gbit/s per fibre. DWDM can achieve 1.6 Tbit/s per fibre with cheap of the shelf hardware. A cable contains multiple fibres (12).
sure, but are they going to have optical links to the rocket?   If the link to the rocket is electrical they'll need some device near the pad to convert from electrical to optical.. and that may introduce some amount (microseconds to milliseconds) of buffering and packetization delay which would increase the amount of data lost over a system which merely repeated the signal a bit at a time...

Would not be surprised to see multiple 1000base-T twisted-pair gigabit ethernet links off the rocket (spec says max cable length ~100m) running to one or more ethernet switches on the pad (or even up on the TEL!) with an optical uplink off the pad.   


Fiber is used to go off the pad.

This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/10/2016 04:08 pm
Bandwidth is cheap. CWDM Ethernet LX-4 provides 10Gbit/s per fibre. DWDM can achieve 1.6 Tbit/s per fibre with cheap of the shelf hardware. A cable contains multiple fibres (12).
sure, but are they going to have optical links to the rocket?   If the link to the rocket is electrical they'll need some device near the pad to convert from electrical to optical.. and that may introduce some amount (microseconds to milliseconds) of buffering and packetization delay which would increase the amount of data lost over a system which merely repeated the signal a bit at a time...

Would not be surprised to see multiple 1000base-T twisted-pair gigabit ethernet links off the rocket (spec says max cable length ~100m) running to one or more ethernet switches on the pad (or even up on the TEL!) with an optical uplink off the pad.   


Fiber is used to go off the pad.

This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.
This might be an explanation for the supposedly lost telemetry. Maybe a few milliseconds worth of data was still in the (data) pipeline, when said pipeline got doused with LOX or burned to a crisp.
And this might well have been the most interesting data, because they were closest to the anomaly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/10/2016 04:14 pm

One small point - though GoPros _generally_ are used in the mode whereas the video is stored on the camera on a card, they _can_ also live stream the video via wifi or hardwire. Especially if the camera is powered externally. We do this at my aquarium regularly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/10/2016 04:29 pm
I don't think you're reading the same updates...

Quote
increasingly trying to understand sound heard prior to explosion

This is very telling. Points to one of two things:

Internal failure in the lox tank or GSE failure that rapidly overpressurized the tank or its internals.


The update said they're unable to pick up internal failure sounds prior to the explosion, and are interested in a sound that was heard externally.



FTS is ruled out (thanks for the info on this jim).


We've deemed FTS as an unlikely cause based on how it's supposed to work and common logic - not based on empirical evidence.  SpaceX probably ruled it out based on telemetry - there'd be evidence of it going off unexpectedly.  I haven't seen an FTS charge go off, but have seen detonator cords go off, and they don't look like that - but I haven't seen one go off next to a fuel tank...



External fae is ruled out due to a variety of reasons though the wind is a big one.


Actually, external FAE is very far from ruled out



Gse is not something I can completely rule out but it seems very unlikely, the system itself would probably fail first not the lox tank.


???



Payload as source is ruled out due to the payload not blowing up until after it fell off what was left of the TE and other aforementioned reasons regarding payload fuel.


This one you got right.



Really IMHO only thing that fits in something within the lox tank. So COPV or other internal ignition+overpressure ignition not yet found.


All these things take time and leave a mark in the telemetry.



My guess is the reason why it is so hard to pinpoint is because it happened extremely fast.

Still there are more questions now I think than we had before and not really any answers.


Here is the point though. The failure was in the LOX tank or very near to it in the second stage. I think this is almost 100% certain given spacex's own statements and the failure nature itself.

Second, to me this leads back to the original problem which brought down crs7: quality control.


Spacex is apparently learning the hard way they cannot keep doing things internally like a startup company. They need to seriously rethink their quality control program and how they test tankage components. They have been criticized by both other other industry figures and others for this in the recent past and have ignored the criticism as far more knowledgeable members on this site are no doubt aware.


That is a giant leap in logic.  The conclusion doesn't follow from anything above



Basically the short version, and I will preface this by saying that it's as I see it, is they need to get with the program already. Innovation is great but constantly changing component design and manufacture in the quest for efficiency is a recipe for these kinds of failures every time.

I suspect they will make real changes this time because the alternative will be losing contracts if this happens again.

You're entitled to your opinion, but you haven't connected it to any reality.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacekid on 09/10/2016 04:45 pm
Long time listener, first time caller. I have read all 2100+ messages so far in this board and I haven't heard this exact theory I'm about to put forth.

I call this the "slow slump" theory. Since the static fire is the first time the full stack was fully integrated and was being fueled, I propose that there was not necessarily a manufacturing flaw but a borderline tolerance flaw, along with a borderline tolerance mating of the strongback to the stack. As the RP1 was being loaded the rocket would be creaking and would be triggering sensors within the rocket, but the difference would be there would be an accumulation of borderline tolerance flaws that would cause the rocket to slowly "slump" along the side of the rocket facing the strongback and would have lead to a minor leak of the rocket near the top of RP1 stage 2 tank only when the tank was full (around the time of the anomaly occurred). This leak was minor enough  it would not have been observed easily on camera, but the RP1 was being atomized by LOX venting from S1 and carried up to be ignited by the oxygen rich venting on S2 until there was enough fuel to be ignited.

Sensor readings long before the anomaly would look different than prior static firings of the F9. The cause of the anomaly was a long running event while everyone is looking for a fast cascade of sensor reading, but culminated in the footage we have all seen in the video. The weak part of this theory is the ignition of this FAE event, but I'm postulating that given enough RP1, and oxidizer in this environment that any rust point on the strongback could have triggered the FAE, and subsequent LOV.

I'm just a curious armchair rocket sturgeon looking for answers like everyone else.

I'm thinking this is the way to look. It looks like a fuel air explosion. For that volume to develop, it seems like it  would take some time. And the way the wind is blowing, seems likely at least one part, fuel or O2 would come from the GSE and blow towards the vehicle. Perhaps fuel was sprayed out and began mixing with O2 by the rocket. Then a spark near the rocket/GSE interface occurred causing the accident.

Need to look in detail at the video a ways before the accident to see if anything different can be seen, especially around the GSE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HankinNM on 09/10/2016 04:55 pm
@MME-Thank you for setting me straight on this.  I guess that I do not have the 'stick-to-it-ivness' that most of you (and Mr. Musk) do.  I am interested in the final outcome of the investigation, and just got impatient, I guess.  I am trying not to be a 'troll', and have not noticed any 'complete S2 rebuild' posts except mine.  Patience is hard for me.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 04:56 pm
One of the things so small that pack a punch was this lithium ion battery explosion video from these guys with too much time on their hands for perspective... The second one is even better! I haven unable to find all the locations and type on Falcon S2 so far...
https://www.youtube.com/watch?v=bZ8IsMRFM5o
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 04:58 pm
Long time listener, first time caller. I have read all 2100+ messages so far in this board and I haven't heard this exact theory I'm about to put forth.

I call this the "slow slump" theory. Since the static fire is the first time the full stack was fully integrated and was being fueled, I propose that there was not necessarily a manufacturing flaw but a borderline tolerance flaw, along with a borderline tolerance mating of the strongback to the stack. As the RP1 was being loaded the rocket would be creaking and would be triggering sensors within the rocket, but the difference would be there would be an accumulation of borderline tolerance flaws that would cause the rocket to slowly "slump" along the side of the rocket facing the strongback and would have lead to a minor leak of the rocket near the top of RP1 stage 2 tank only when the tank was full (around the time of the anomaly occurred). This leak was minor enough  it would not have been observed easily on camera, but the RP1 was being atomized by LOX venting from S1 and carried up to be ignited by the oxygen rich venting on S2 until there was enough fuel to be ignited.

Sensor readings long before the anomaly would look different than prior static firings of the F9. The cause of the anomaly was a long running event while everyone is looking for a fast cascade of sensor reading, but culminated in the footage we have all seen in the video. The weak part of this theory is the ignition of this FAE event, but I'm postulating that given enough RP1, and oxidizer in this environment that any rust point on the strongback could have triggered the FAE, and subsequent LOV.

I'm just a curious armchair rocket sturgeon looking for answers like everyone else.

I'm thinking this is the way to look. It looks like a fuel air explosion. For that volume to develop, it seems like it  would take some time. And the way the wind is blowing, seems likely at least one part, fuel or O2 would come from the GSE and blow towards the vehicle. Perhaps fuel was sprayed out and began mixing with O2 by the rocket. Then a spark near the rocket/GSE interface occurred causing the accident.

Need to look in detail at the video a ways before the accident to see if anything different can be seen, especially around the GSE.
Welcome to the forum! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dbavatar on 09/10/2016 05:08 pm
This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/10/2016 05:27 pm
How about:

1. Support at the base of the rocket weakens on side facing TEL (this may correspond to the mysterious "thump/grind" sound)

2. Cradle at top of TEL begins carrying the weight of the loaded rocket, creating strain that the tanks aren't designed to deal with

3. Boom
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 05:33 pm
This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.

still packeting is good for losing data
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/10/2016 05:39 pm
Spacex is apparently learning the hard way they cannot keep doing things internally like a startup company. They need to seriously rethink their quality control program and how they test tankage components. They have been criticized by both other other industry figures and others for this in the recent past and have ignored the criticism as far more knowledgeable members on this site are no doubt aware.
Just a small point but AFAIK the struts were not "doing things internally." They were bought from a 3rd party, who I presume won't be supplying SX with anything else anytime soon.  :(

Your conclusion, that they cannot keep doing most things in house is not supported by actual facts.
Quote
Basically the short version, and I will preface this by saying that it's as I see it, is they need to get with the program already. Innovation is great but constantly changing component design and manufacture in the quest for efficiency is a recipe for these kinds of failures every time.
In fact it's an argument for bringing more in house as much as revamping their QC on externally made components. both of which I suspect they will consider doing, depending on the root cause analysis.
Quote
I suspect they will make real changes this time because the alternative will be losing contracts if this happens again.
Just to be clear IIRC SX said some of the struts they tested were 1/10 the design strength.

That's both a mfg flaw (I guess a botched heat treatment or wrong grade of starting material would be the simplest 1 stage way to do that, but I'm sure there are other, more complex failure paths ) and a failure in supplier QC to pick it up afterward.

The alternative is to scrap mfg testing, do all testing in house and activate penalty clauses if an excessive proportion of mfg supplied parts fails SX QC.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moskit on 09/10/2016 05:49 pm
still packeting is good for losing data

NASA seemed to also have concerns on SpaceX telemetry
https://forum.nasaspaceflight.com/index.php?topic=40621.msg1554985#msg1554985

SpaceX has about 3000 total channels, this was communicated by them on other occasions, so I suppose mentioning the number is just a generic way of saying "we have a lot of it" without specifying  more.

Discussion on how telemetry is done took place during CRS-7 event when Elon mentioned trying to reconstruct the last frame available. Some starting points should avoid rehashing:
https://forum.nasaspaceflight.com/index.php?topic=37476.msg1398608#msg1398608
https://forum.nasaspaceflight.com/index.php?topic=37954.msg1402048#msg1402048
https://forum.nasaspaceflight.com/index.php?topic=37476.msg1398972#msg1398972

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dbavatar on 09/10/2016 05:54 pm
still packeting is good for losing data
Packetization happens randomly between generation and storage, because everything has a buffer, that's the nature of being digital. Even serial UART's have buffers. It's just formally controlled in the link layer when using ethernet protocol. As long as the system is designed to control the maximum amount of data outstanding, it's fine. The only way to avoid the whole thing would be to go back to hard analog lines from every single sensor to recording medium, and no one wants to do that, or needs to if properly designed. Like I said, with 10Gbps ethernet you can send exactly 1 byte every 67ns. Of course if your source data was only 4 bits you've already packetized 2 samples!

TL;DR nothing wrong with using ethernet, assuming the engineers knew what they were doing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: savuporo on 09/10/2016 06:02 pm
This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket. .
Ethernet comes in a few versions. EtherCAT and Sercos and things like that have proven super reliable and robust for telemetry and realtime controls in industrial environments. I have no inkling if one of these is being used on GSE
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 06:16 pm

Ethernet comes in a few versions. EtherCAT and Sercos and things like that have proven super reliable and robust for telemetry and realtime controls in industrial environments. I have no inkling if one of these is being used on GSE

Those are used for accident reconstruction
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/10/2016 06:35 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 06:37 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?
Yes, many times... ;D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 06:42 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?

It would have happened at the beginning of the load.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/10/2016 06:43 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?
Yes, many times... ;D
Seems the simplest but suffers from location problems.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/10/2016 06:43 pm
And yet another probably irrelevant image processing example.

Here we see a 10 frame sequence, the last frame on the right is frame 0.

The one to the left is Frame-1 minus frame 0,  Frame -2 minus frame -1, etc.  The differences of 9 frames leading to the last.

the range is maxed with no saturation.  Image upscaled X3.

There is no interpretation offered, it looks pretty, but I can't pull any meaning out of it.

Considering the moire patterns you were getting along the length of the Falcon, I think what you invented here is a nice way to show how JPEG compression follows algorithms to create its artifacting... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MikeAtkinson on 09/10/2016 06:46 pm
No joy on battery locations, but it did get me thinking about the "customer supplied cable 20ft." to pad junction box on the TEL (section 5.1) via the Catenary Umbililcal to S2 (image page 39)... Was that the case for this launch or was it supplied by SpaceX? Was it the first time it was powered on from the TEL junction box?
http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf

The "customer supplied cable" could potentially be the source of the ignition, but it could not be the source of the fuel (in the order of 10kg) for the FAE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 06:55 pm
No joy on battery locations, but it did get me thinking about the "customer supplied cable 20ft." to pad junction box on the TEL (section 5.1) via the Catenary Umbililcal to S2 (image page 39)... Was that the case for this launch or was it supplied by SpaceX? Was it the first time it was powered on from the TEL junction box?
http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf

The "customer supplied cable" could potentially be the source of the ignition, but it could not be the source of the fuel (in the order of 10kg) for the FAE.

Both posts are wrong.  That cable is no where near the TEL or vehicle.  The pad junction box is in the bowels of the pad.  Those cables are labeled "customer rack harness" in figure 5.3.  All other cables are supplied by Spacex in 5.3.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/10/2016 07:02 pm
And yet another probably irrelevant image processing example.

Here we see a 10 frame sequence, the last frame on the right is frame 0.

The one to the left is Frame-1 minus frame 0,  Frame -2 minus frame -1, etc.  The differences of 9 frames leading to the last.

the range is maxed with no saturation.  Image upscaled X3.

There is no interpretation offered, it looks pretty, but I can't pull any meaning out of it.

Considering the moire patterns you were getting along the length of the Falcon, I think what you invented here is a nice way to show how JPEG compression follows algorithms to create its artifacting... ;)

LOL, depends on how extreme the compression setting is.  The range on the levels was 10% of the total available dynamic range.  That would be some extreme setting.  MPEG is usually defaulted to preserve level at the expense of detail, so your eye won't notice it s much, but then, no idea how the camera was set up, or what youtube did afterwards, so it could have gone bad fast.

I think that most of it actually is atmospherics drifting through the field of view between frames. 

Portions of individual frames literally dance around from the atmospherics.

Wish I knew a way to stabilize atmospherics without having a pre-existing model of the atmospherics.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Eerie on 09/10/2016 07:03 pm
Jim, do you have a hypothesis?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 07:04 pm
Jim, do you have a hypothesis?

A pressure/structure event
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/10/2016 07:09 pm
Jim, do you have a hypothesis?

A pressure/structure event
Without a trace in the telemetry?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Eerie on 09/10/2016 07:28 pm
Jim, do you have a hypothesis?

A pressure/structure event
Without a trace in the telemetry?


Maybe it happened so fast, telemetry missed the important part. I remember Jim criticizing the way SpaceX collect telemetry somewhere.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John-H on 09/10/2016 07:39 pm
When does the telemetry start? It was not a real flight, and 8 minutes before the start, so was everything turned on at the time?

John
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 07:49 pm
When does the telemetry start? It was not a real flight, and 8 minutes before the start, so was everything turned on at the time?


Telemetry starts when the vehicle is powered up.  It is not RF, it is hardline
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/10/2016 08:02 pm
Jim, do you have a hypothesis?

A pressure/structure event
Without a trace in the telemetry?

Who said there's no trace? No trace and telemetry not being conclusive are different things
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/10/2016 09:13 pm
Jim, do you have a hypothesis?

A pressure/structure event

Can pressure waves travel down pipes and then expand in vessels like down part full beer bottles? Or is there likely to be something structural stopping them?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Karloss12 on 09/10/2016 09:32 pm

Now I do see a serious problem with Jims point A.

There simply is no ice layer on the tank to begin with and no other insulation we'd have heard of. It would take some time for the ice layer to form and the tank would be uninsulated in the meantime. Usually, that cannot possibly be a problem. The LOX is filled in at boiling temperature anyway and there is never any chance at all to condense oxygen from the air.

With subcooled oxygen in the tank, there is a short window of opportunity for oxygen to condense - prior to any ice layer forming on the tank and insulating it.


The cup analogy is really  not applicable.  There is big difference in thermal mass.  Ice should be forming during the chill down.   But then again, the  loading time is less than 30 minutes

But also, I should have said:

And if there was a risk of LOX forming, then they SHOULD have added insulation.  My point is that they would have analyzed this.  When liquid air forms on the outside and drains away, it is putting more heat into the tank

My LIN in an Aluminium cup occurred outside on a reasonably humid warm summers day in Surrey, England.

It doesn't matter if the aluminium LOX container is a small cup or a large pressure vessel.  If it is suddenly filled with LIN or super chilled LOX, LOX will form on its surface and drip down and off the bottom on to whatever is below.  Even in very humid air, the dripping LOX may even wash away any ice crystals before they have a chance to make contact with and get stuck to the surface of the Aluminium.

However, if as Jim say, the Al/Li tank is pre chill down to say -150°C allowing an ice layer to form before LOX begins to be poured into the 2nd stage, then the surface of the ice will be to warm for LOX to form and drip.....however, during chill down fresh humid air will need to be forcibly convecting around the LOX tank.  If the pre chilled tank is simply sitting in stagnant air, all you get is the tiniest layer of ice on the surface surrounded by dehumidified air.  A constant flow of new humid air is required to build up the thickness of the layer of ice during pre-chill.  Free convection will likely not be good enough.

Insulating by ice build up on the surface sounds like a better option to insulation.  Insulation would need to be air tight and vacuumed, as it would quickly become a sponge soaked in LOX if it lost its air tightness.

With respect to LOX compatibility with Aluminium, a couple of decades ago, it was normal for LIN. LOX and LAR be stored in vacuum insulated storage tanks where the inner vessel was made of Aluminium or Stainless Steel.  However, there were a few instances of the Aluminium tanks spontaneously exploding for no reason when being filled with clean pure LOX.  As the LIN and LAR tanks weren't exploding, the industry made it standard to only fabricate Stainless Steel LOX storage vessels.

The air separation columns that distilled the Oxygen for use in the F9, were likely made of Aluminium.  During the air separation process, these columns have hundreds of litres of near pure LOX continuously trickling inside them splashing on top of and through Aluminium packing which is 0.25mm thick aluminium sheet.  There are probably a thousand such ASU plants around the world and this thin material never explodes.  It is always an aluminium plate fin heat exchanger that has 1mm parting sheets that spontaiously vaporises its self every couple of years.  They are assumed to explode due to getting a blockage and build up of solid CO2 and hydrocarbon impurities followed by an impingement of a foreign particle.

The LOX flowing into the F9 is already pureified of hydrocarbons and I can't imagine there is anything in the F9 2nd stage with such thin material and turbulent LOX flow.

If a COPV was the problem, then this would have been identified immediately.

If there was LOX dripping and vaporising, then the GOX sensor would have picked up elevated O2 levels.  Maybe an elevated O2 atmosphere is acceptable?  After chill down and the ice layer is formed, does the outside surface of the LOX tank have a slow continuous purge with GAN to prevent a high GOX atmosphere from forming at all?  This is standard for Cryogenic Air Separation Equipment.

Does the 2nd stage LOX tank have an outer skin with annulus space?  If SpaceX don't find the problem, then I predict they will introduce Nitrogen Purging around the LOX tank as a precaution.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/10/2016 09:44 pm

Now I do see a serious problem with Jims point A.

There simply is no ice layer on the tank to begin with and no other insulation we'd have heard of. It would take some time for the ice layer to form and the tank would be uninsulated in the meantime. Usually, that cannot possibly be a problem. The LOX is filled in at boiling temperature anyway and there is never any chance at all to condense oxygen from the air.

With subcooled oxygen in the tank, there is a short window of opportunity for oxygen to condense - prior to any ice layer forming on the tank and insulating it.


The cup analogy is really  not applicable.  There is big difference in thermal mass.  Ice should be forming during the chill down.   But then again, the  loading time is less than 30 minutes

But also, I should have said:

And if there was a risk of LOX forming, then they SHOULD have added insulation.  My point is that they would have analyzed this.  When liquid air forms on the outside and drains away, it is putting more heat into the tank

My LIN in an Aluminium cup occurred outside on a reasonably humid warm summers day in Surrey, England.

It doesn't matter if the aluminium LOX container is a small cup or a large pressure vessel.  If it is suddenly filled with LIN or super chilled LOX, LOX will form on its surface and drip down and off the bottom on to whatever is below.  Even in very humid air, the dripping LOX may even wash away any ice crystals before they have a chance to make contact with and get stuck to the surface of the Aluminium.

However, if as Jim say, the Al/Li tank is pre chill down to say -150°C allowing an ice layer to form before LOX begins to be poured into the 2nd stage, then the surface of the ice will be to warm for LOX to form and drip.....however, during chill down fresh humid air will need to be forcibly convecting around the LOX tank.  If the pre chilled tank is simply sitting in stagnant air, all you get is the tiniest layer of ice on the surface surrounded by dehumidified air.  A constant flow of new humid air is required to build up the thickness of the layer of ice during pre-chill.  Free convection will likely not be good enough.

Insulating by ice build up on the surface sounds like a better option to insulation.  Insulation would need to be air tight and vacuumed, as it would quickly become a sponge soaked in LOX if it lost its air tightness.

With respect to LOX compatibility with Aluminium, a couple of decades ago, it was normal for LIN. LOX and LAR be stored in vacuum insulated storage tanks where the inner vessel was made of Aluminium or Stainless Steel.  However, there were a few instances of the Aluminium tanks spontaneously exploding for no reason when being filled with clean pure LOX.  As the LIN and LAR tanks weren't exploding, the industry made it standard to only fabricate Stainless Steel LOX storage vessels.

The air separation columns that distilled the Oxygen for use in the F9, were likely made of Aluminium.  During the air separation process, these columns have hundreds of litres of near pure LOX continuously trickling inside them splashing on top of and through Aluminium packing which is 0.25mm thick aluminium sheet.  There are probably a thousand such ASU plants around the world and this thin material never explodes.  It is always an aluminium plate fin heat exchanger that has 1mm parting sheets that spontaiously vaporises its self every couple of years.  They are assumed to explode due to getting a blockage and build up of solid CO2 and hydrocarbon impurities followed by an impingement of a foreign particle.

The LOX flowing into the F9 is already pureified of hydrocarbons and I can't imagine there is anything in the F9 2nd stage with such thin material and turbulent LOX flow.

If a COPV was the problem, then this would have been identified immediately.

If there was LOX dripping and vaporising, then the GOX sensor would have picked up elevated O2 levels.  Maybe an elevated O2 atmosphere is acceptable?  After chill down and the ice layer is formed, does the outside surface of the LOX tank have a slow continuous purge with GAN to prevent a high GOX atmosphere from forming at all?  This is standard for Cryogenic Air Separation Equipment.

Does the 2nd stage LOX tank have an outer skin with annulus space?  If SpaceX don't find the problem, then I predict they will introduce Nitrogen Purging around the LOX tank as a precaution.
I have asked multiples times over the years if SpaceX performs a Nitrogen purge of all the tanks and lines and have never recieved an answer, perhaps this time?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/10/2016 09:48 pm
I've attempted to draw the internals of the second stage based both on the Falcon 9 User Manual
(http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf)
, and earlier diagram from 2008.
(http://selenianboondocks.com/wp-content/uploads/2008/11/s12-11.pdf)
There may be (are) more changes from 2008 to now then I've included in this drawing. 
All lengths are estimated from slightly blurry images.

Here's my drawing overlaid on the video...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/10/2016 09:53 pm
If the pre chilled tank is simply sitting in stagnant air, all you get is the tiniest layer of ice on the surface surrounded by dehumidified air.  A constant flow of new humid air is required to build up the thickness of the layer of ice during pre-chill.  Free convection will likely not be good enough.

From what I saw it was quite windy and very very humid on that day (tropical storm nearby).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gliderflyer on 09/10/2016 10:19 pm
There have been multiple times in Mojave when we would fill an uninsulated steel sphere with LN2. It would rapidly form an ice layer even in non-windy, low humidity conditions. The "ice" that forms is more like snow however, and is usually 1/4" to 3/8" thick. We wanted the LN2 to boil, so we would brush off the snow every few minutes. I don't remember liquid air ever forming; it would just start making more snow. I think the densified LOX on the Falcon 9 is warmer than LN2, so doubt air would condense on the outside.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/10/2016 10:59 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?

It would have happened at the beginning of the load.

Not if the contamination was inside the tank near the top.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Prober on 09/10/2016 11:23 pm
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.

I'm struggling with the fact that I've read that Kerosene vapors are heavier than air.


I'm struggling with something I thought i was  reading about a COPV inside the RP-1 tank?  On the face of it, might not be the best choice for a reusable launcher.  Any Certification papers around on this?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: deruch on 09/10/2016 11:44 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?

It would have happened at the beginning of the load.

Not if the contamination was inside the tank near the top.

Yeah, but the specific question he was responding to was about contamination in the LOX line (or maybe at the GSE/vehicle interface), and I assume propagating into the tank during LOX loading operations.  Jim's point was that in that scenario, the anomaly would be expected to occur at the beginning of the loading  This scenario is distinct from contamination having been in the tank prior to filling. 

That said, I'm not sure that the expectation would be all that different.  A good amount of the LOX that is loaded at the very beginning will boil off while the tank is chilling down.  So, you end up with quite a bit of GOX in the tank early in the fill operation and it is in contact with the contamination at the top of the tank.  Not sure I see much of a difference besides maybe the hydrodynamics of the LOX, but I'm not an expert.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/10/2016 11:48 pm
still packeting is good for losing data

NASA seemed to also have concerns on SpaceX telemetry
https://forum.nasaspaceflight.com/index.php?topic=40621.msg1554985#msg1554985

SpaceX has about 3000 total channels, this was communicated by them on other occasions, so I suppose mentioning the number is just a generic way of saying "we have a lot of it" without specifying  more.

Discussion on how telemetry is done took place during CRS-7 event when Elon mentioned trying to reconstruct the last frame available. Some starting points should avoid rehashing:
https://forum.nasaspaceflight.com/index.php?topic=37476.msg1398608#msg1398608
https://forum.nasaspaceflight.com/index.php?topic=37954.msg1402048#msg1402048
https://forum.nasaspaceflight.com/index.php?topic=37476.msg1398972#msg1398972

Thank you for this. Reference posts are always welcome for those of us who have failed to find information elsewhere on NSF (usually due to a lack of familiarity).

Nevertheless, the main conclusion I can derive from those past discussions of telemetry is that SpaceX very likely took the development of F9 FT to somewhat improve their telemetry system (if at all possible), both to account for whatever technical issues NASA's criticism arose from and to attempt to avoid the need for complex data reconstruction in the eventuality that future failures occurred.

This is of course nothing more than logical speculation, but it seems quite plausible that SpaceX took a serious look at their telemetry processes and likely made some minor to major revisions post-CRS-7.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 11:50 pm

Does the 2nd stage LOX tank have an outer skin with annulus space?  If SpaceX don't find the problem, then I predict they will introduce Nitrogen Purging around the LOX tank as a precaution.

No, the tank surface is the outer surfaces.  There is no need for purging.  Watch the video, there was wind
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/10/2016 11:51 pm
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?

It would have happened at the beginning of the load.

Not if the contamination was inside the tank near the top.

The tank was already filled once.  And what is the mechanism to make a tank dirty at the top?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Karloss12 on 09/10/2016 11:57 pm
If the pre chilled tank is simply sitting in stagnant air, all you get is the tiniest layer of ice on the surface surrounded by dehumidified air.  A constant flow of new humid air is required to build up the thickness of the layer of ice during pre-chill.  Free convection will likely not be good enough.

From what I saw it was quite windy and very very humid on that day (tropical storm nearby).

Yeah, there is no second skin, it is the wall of the LOX tank as well.  With chill down, LOX forming on the surface won't happen.

There was nothing complex happening at the time of the explosion.  Just LOX flowing through an oxygen cleaned pipe into a static oxygen cleaned LOX tank.  No moving parts or dynamic vibrations.  Around the world every day, road tankers fill their LOX storage tanks using quick connects with a person standing next to it and it never explodes.

If there was hydro carbon contamination inside the tank, there would need to be impingment or some sort of energy imput to cause ignition.  And then this ignition would have had to have had enough energy to cause the Al/Li shell to react with the LOX.

For the first few frames, what was the fuel?  I have assumed it was Aluminium and then after the first few frames the RP-1 tank ruptured and then the larger secondary LOX/RP-1 explosion starts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/11/2016 12:12 am
I've attempted to draw the internals of the second stage based both on the Falcon 9 User Manual
(http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf)
, and earlier diagram from 2008.
(http://selenianboondocks.com/wp-content/uploads/2008/11/s12-11.pdf)
There may be (are) more changes from 2008 to now then I've included in this drawing. 
All lengths are estimated from slightly blurry images.

Here's my drawing overlaid on the video...

Nice diagram. My desire now is to parse through possible connections between the local structures, what was likely to be happening around then
T-0:09:30   M1D Trim Valve Cycling
T-0:09:15   Stage 1 Helium Topping
T-0:07:45   MVac Fuel Trim Valve Setup
and the FAE that occurred in the vicinity of the interstage/MVac. Regarding the interstage, I am assuming that it is quite effectively sealed off from the environment outside of the vehicle. Can anyone verify or disprove this assumption?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gliderflyer on 09/11/2016 12:25 am
For the first few frames, what was the fuel?

The helium bottles are made out of carbon-epoxy, which burns quite aggressively in pure oxygen environments.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Karloss12 on 09/11/2016 12:33 am
For the first few frames, what was the fuel?

The helium bottles are made out of carbon-epoxy, which burns quite aggressively in pure oxygen environments.

Arrh, now I understand the COPV idea.  But the ignition method is still unknown and the telemetry would clearly show them rupturing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gliderflyer on 09/11/2016 12:56 am
For the first few frames, what was the fuel?

The helium bottles are made out of carbon-epoxy, which burns quite aggressively in pure oxygen environments.

Arrh, now I understand the COPV idea.  But the ignition method is still unknown and the telemetry would clearly show them rupturing.

Carbon materials soaked in LOX was once used as a mining explosive: https://en.wikipedia.org/wiki/Oxyliquit
It had a habit of just going off on its own, and ANFO was cheaper so people stopped using it. I don't know what data rate SpaceX records at, but I wonder if the COPV that was soaking in LOX could explode faster than the recording rate?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/11/2016 01:11 am
ISTM the same would apply to LOX condensing on S2, running down and wicking into the upper interstage outer composite layers & cork insulation. Lose a little paint and....
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 01:36 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/11/2016 02:06 am
It's basically swampland. You're not going to get a surface wave, period.
When I witnessed launches at KSC and the Cape, sometimes from less than 3 miles distant, I could feel the ground move beneath my feet before the sound of the launch arrived.  Isn't that a "surface wave"?

 - Ed Kyle

Not necessarily. A wind could retard the arrival of the launch sound. Also, the low frequency component can be "lensed" by the aquifer, where the same through the air might be dispersed. So you may be measuring different parts of the same longitudinal wave, depending on the "filter" of the medium.

Vandenberg launches seem different to me - the soil is dense enough that you can tell the ramp of ignition, and measure the difference in the same feature either path.

CCAFS/KSC launches may be different where you are, possibly due to effects of soil surcharging/other in certain areas than others. On the NASA Causeway for the MAVEN launch, there was absolutely no surface effect.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 02:53 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

One explanation is they think the reason points at someone else and they want to have outside data to back it up rather than just "Our internal data blames you!"
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 03:06 am
There have been multiple times in Mojave when we would fill an uninsulated steel sphere with LN2. It would rapidly form an ice layer even in non-windy, low humidity conditions. The "ice" that forms is more like snow however, and is usually 1/4" to 3/8" thick. We wanted the LN2 to boil, so we would brush off the snow every few minutes. I don't remember liquid air ever forming; it would just start making more snow. I think the densified LOX on the Falcon 9 is warmer than LN2, so doubt air would condense on the outside.

Depends on your setup. In college when I regularly transferred LN2 from the big dewar to the rolling dewar, the uninsulated copper transfer tube would frost/ice, then later condense liquid (presumably LOX, though unverified) from the air.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 03:40 am
1.  Wouldn't the vents be somewhat one way? That and gravity might be enough to prevent it going internal to the fairing.

2. Plus there would be no oxidizer in the fairing if only the "fuel" part was leaking.

3.  So two questions: Would the payload have been monitored AT ALL during the static fire?

4 Is Hydrazine hypergolic in oxygen enriched air? 


1.  No, they just have air blowing out them

2.  Not needed.  See below

3.  Yes,

4.  Hydrazine is a monopropellant, it needs no oxygen.  It reacts with many items.  Rust, dirt, foam, etc can set it off.

Yes, Hydrazine is a monopropellant. The problem with that line of thinking is that the payload didn't have hydrazine. It had UDMH (which, yes - is a hydrazine derivative, but not "hydrazine")

UDMH is much less likely to spontaneously decompose than straight hydrazine - that was one* big reason for developing Aerozine 50. Cut your hydrazine 50/50 with UDMH and you dramatically reduce your chances of spontaneous decomposition. You can even use it as a coolant.

Straight UDMH is even less reactive than the Aerozine blend. Still way more reactive than RP-1.

Neither Aerozine nor UDMH is used as a monopropellant.

And yes, I have actually worked with straight hydrazine. Grand total of about a liter, but that was exciting enough. I only needed about 5g of final product anyway.

*Another was freezing point depression, but that's not relevant to the topic at hand.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ciscosdad on 09/11/2016 04:02 am
I do NOT subscribe to the sabotage theories, but as outside interference has not yet been ruled out, perhaps they will need to borrow some techniques from aircraft crash investigation; ie microscopic examination of salvaged parts of the external hull for explosives residue and pitting from high velocity impact (implying high detonation velocity). Another would be partial reconstruction of the hull to demonstrate that the initial explosion was definitively outside the F9 (ie, the panels all buckled inwards). Would also allow higher precision in determining the initiation point.

This would  potentially eliminate some outside interference scenarios.

Having most of the pieces available for this sort of investigation will be useful, and finding a bullet hole would of course simplify things immensely!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/11/2016 04:03 am
SpaceX Explosion Reveals Hidden Opportunities In Space Investment (http://oilprice.com/Energy/Energy-General/SpaceX-Explosion-Reveals-Hidden-Opportunities-In-Space-Investment.html)

Quote from: Michael McDonald
The SpaceX explosion highlights a backend way to invest in the space...
... by investing in the launch insurance business.

Quote from: Michael McDonald
... Thus the loss of the rocket is a $250M plus hit – and that’s where the opportunity comes in. Such losses highlight the importance of risk mitigation through insurance – and the space insurance industry is one that investors can invest in.
... which profits from the sustained need for insurance.

Quote from: Michael McDonald
For SpaceX to have an insurance policy they must pay a premium to big name insurance companies like AIG, Allianz, AON, or XL Catlin. Last year there were $500 million in claims; double the premiums being paid.
... premium costs don't just gradually rise.

Quote from: Michael McDonald
... all it takes is 2 to 3 explosions a year for the insurance market to run into trouble – such problems can actually be a good thing. Typically, in catastrophe insurance markets, whether it is hurricanes or rocket explosions, a bad year leads to a good year. In bad years, some players exit the market, and everyone raises premium prices. That typically leads to a strong follow-up year in which the industry is more profitable thanks to higher prices.
... because the increased premiums stay with you for follow-on years.

Quote from: Michael McDonald
With an increase in annual launches there is a high likelihood of rocket explosions becoming even more numerous. These commercial space companies will feel a greater need to insure their rockets and their payloads, increasing the demand for insurance policies. By investing in insurers like AON or XL Catlin, companies that protect these rockets, investors can see a correlation between returns and development of the space industry, predominantly private.
... launch frequency means potential casualties must rise. Actually, the profitability of such insurance grows faster than the profitability of launches ... irrespective of success.

However, this does not bring down launch costs but increase them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: edkyle99 on 09/11/2016 04:13 am
I do NOT subscribe to the sabotage theories, but as outside interference has not yet been ruled out, perhaps they will need to borrow some techniques from aircraft crash investigation; ie microscopic examination of salvaged parts of the external hull for explosives residue and pitting from high velocity impact (implying high detonation velocity). Another would be partial reconstruction of the hull to demonstrate that the initial explosion was definitively outside the F9 (ie, the panels all buckled inwards). Would also allow higher precision in determining the initiation point.
...
Having most of the pieces available for this sort of investigation will be useful, and finding a bullet hole would of course simplify things immensely!
The problem is that aluminum and aluminum lithium melts at about 1,200 F or less.  This fire likely generated higher temperatures than that.  Much of the metal fuselage likely melted into silver blobs.

 - Ed Kyle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/11/2016 04:37 am
The T/E is still standing.

I think there will be residue of the initial burst, whatever it was, on the metal.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/11/2016 04:54 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DaveS on 09/11/2016 05:08 am
The T/E is still standing.
I'm not surprised. The hydraulics are probably destroyed so either they'll have to replace the entire hydraulic system for T/E or they'll have to rent some mobile cranes to manually rotate it back to a horizontal position.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DaveS on 09/11/2016 05:11 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
Yes, this is what has been plaguing me re: the sounds for a while now. There's no way to tell whether or not the sounds actually came from the pad or the vehicle. We do know for a fact that SpaceX do have at least one microphone at the pad, so if it didn't record the noises I seriously doubt that it came from either the pad or the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: tj on 09/11/2016 05:55 am

AMOS= Affordable Modular Optimized Satellite

AMOS-6
About 12k lbs wet mass and about 6-7k lbs dry mass

GTO to GEO: chemical propulsion; typically chemical propulsion uses about a 100 lb thrust bi-propellant engine burning hydrazine (monometylhydrazine) fuel and nitrogen tetroxide oxidizer.

Hall Effect electric thrusters for station keeping with maybe some backup hydrazine mono-propellant

I do not expect UDMH is the particular monopropellant used in AMOS-6 nor in most or all  sitcoms
The Space Shuttle maneuvering engine did not use UDMH

Monotmethyl hydrazine  CH3 (NH)NH2 is a good deal more volatile than UDMH


The TITAN LVs used f50% hydrazine and 50% UDMH (Aerozine 50) (one reason is a tad higher freezing point than the 2 deg C of hydrazine

Ariane 1 to Arian 4 75% UDMH and 25% hydrazine (UH25)

445-N 102 lb-force liquid apogee engine is a typical LAE GTO to GEO transfer orbit bi-propellant engine (Japan's IHI company is a supplier)

https://uppsagd.files.wordpress.com/2014/03/development-testing-of-a-new-bi-propellant-propulsion-subsystem-for-the-gmp-t-spacecraft.pdf
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IainMcClatchie on 09/11/2016 06:14 am
This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.

still packeting is good for losing data

Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.

There are link bit errors and switches dropping packets.  Serial lines aren't going to help reduce link bit error rate, that comes down to whatever technology you are using for transmission.  Raw serial lines do pass the glitchy data up to your software, so presumably you could do better error containment there.  Packet switched stuff will just dump the whole packet when there is a bit error, which potentially amplifies the underlying bit error rate. 

With gigabit ethernet over cat5, I found a consistent bit error rate of 3e-12.  With 10GbE over multimode fiber, I never saw a single bit error ever.  We ran a test for weeks, probably over a month (we forgot about it for a while), with an FPGA stuffing packets down the fiber with minimum interpacket gaps.  No errors.  That's better than 1e-16 BER!

Switches will not drop packets if they have enough bandwidth and buffering.  Timing problems are completely solved by having the sensors timestamp locally before sending data.  Latency for cheap off-the-shelf fiber 10GbE, as mentioned by dbavatar, is well under a microsecond.

10 GbE over fiber is so good (no ground loops!), so fast, so lightweight, and so cheap, you use 5 Gb/s of sensor bandwidth on each fiber and move to the next problem.  Separate differential serial lines for each sensor, by comparison, is a freaking nightmare.  I've seen bags of parallel coax thicker than my thigh... what a bulky, heavy pain in the ass.  You'll never end up instrumenting everything you should if you have to run all that cable.

I do think that packets over radio have a bit of an issue.  As I said, dumping the entire packet when one bit goes bad necessarily amplifies the effective error rate by the packet size in bits.  The straightforward packet implementation relies on resending to overcome any BER.  For a packet radio telemetry downlink, I'd want to use a redundant error correcting code below the packet level.  I don't know much about digital radio links, presumably something like this exists off the shelf.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/11/2016 07:39 am
"Ethernet is not a real time net because there's not even a guaranteed upper bound for latency" was a common refrain in industrial automation since 30 years ago when Ethernet ran on shared coax....

This gave rise to a bunch of other net types, and they all fell by the wayside as Ethernet became switched, and megabit, and gigabit...

F9 is a clean sheet design, and being able to get the last bit of data out is a design requirement for telemetry...j 

If they chose Ethernet, it's because current switches system are fast enough.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/11/2016 08:11 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
On reddit is a thread investigating the audio recording from the video. It seems that the camera had a stereo microphone. According to the redditor, the mystery sound came from a different direction than the explosion and is probably unrelated to the fireball.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/11/2016 08:49 am
In light of the appeal this is my $0.02 worth.

There are only two observable differences with this flight and any other.
1. The satellite
2. The wind and direction

There are no observable effects on the video to show any prior event. There is no ice cascade indicating any shock loads. The strange chirp noise could be, as others have pointed out, the explosion but through the ground. The frequency dispersion could make the odd noise. Might even be possible to reproduce.

The satellite and fairing is in all probability highly monitored, and probably like the video shows there are no indications of any events that would explain the situation.

I can also see why people are obsessed with an external projectile. It looks exactly right for that scenario. Except one problem, the wind. To hit that position, the strongback is in the way, it is also in a direction that experiences strong cross winds. Wind direction can be seen from the plume animations. However, the resulting explosion and the movement of the fairing to the south does look right for a point failure.

Now back to the wind. The discussions on oxygen condensation all show that the ice would form first. Yet there is one point this would not be true. This strong back is unique in having a pivoted cradle for the upper stage. This means the grabbers hold predominantly the far side of the cylinder. The pivoting cradle pushes on the near side, to the strongback. I have been unable to locate any hydraulics associated with this pivoting cradle from images or videos.

If gravity does its job, the cradle would push more on the upper support than the lower one. This would be countered by the grabbers. In an early video of the strongback retraction a previous Falcon 9 is seen to sway significantly. The grabbers must therefore have enough force to hold it. If they are slack the pivoting cradle will modulate its push, with the wind caused flexing, on the lower support. The wind direction is pushing the Falcon 9 away from the strongback. Every time the wind gusts the lower cradle would ease off the pressure and move up slightly. The pads on the grabbers are on the sides and the far side. How do they regulate the force, do they prioritise squashing it or pulling it back. These are also set while the rocket is horizontal but are used when it is vertical.

This arrangement could make sure the patches of tank were clear of ice and impart a varying, and sliding load to the skin.

There is also I believe a vent around that point for oxygen. The wind direction would carry the output to the rocket skin.

Was that enough to crack the skin exposing the fresh metal to oxygen and forming the initial fire. The rest is inevitable.

In this case there would be no indications on any sensors of any prior event.

If this is the case then the solution was also achieved in the event. The strongback was destroyed. The new designs do not have the same mechanism. They need to grab the Falcon 9 above the tanks with a grabber that has equal angle of pads around the cylinder.

Was it simply hugged too much, or too little.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MP99 on 09/11/2016 08:55 am


This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.

still packeting is good for losing data

Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.

There are link bit errors and switches dropping packets.  Serial lines aren't going to help reduce link bit error rate, that comes down to whatever technology you are using for transmission.  Raw serial lines do pass the glitchy data up to your software, so presumably you could do better error containment there.  Packet switched stuff will just dump the whole packet when there is a bit error, which potentially amplifies the underlying bit error rate. 

I believe Jim is simply saying that if you wait x ms to assemble a packet of data (packetise) before you transmit it, you will lose up to x ms of untransmitted data when an event occurs.

Cheers, Martin
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: savuporo on 09/11/2016 09:00 am
I believe Jim is simply saying that if you wait x ms to assemble a packet of data (packetise) before you transmit it, you will lose up to x ms of untransmitted data when an event occurs.
Packetization before transmitting is not really happening in hard-realtime industrial ethernet versions. Look up IEC 61158 / EtherCAT
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 09:36 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
Please don't take this as a snarky answer, but to say the cause "is" from coincidental ambient sounds is a little surprising from them this early in the investigation... Shuttle flew for thirty years and they were still discovering new things about her and retrospectively deemed it an "experimental" vehicle in an operational role... I was one of the many "so called foamologists" as was termed by the then NASA administrator Sean O'Keefe after the Columbia accident. Prior to the report, I had my physics student calculate the energy and forces of a strike from simple first principals would be enough to cause damage to RCC. The point I am making is to not go down the road of being in denial of the "fragility" of an experimental system with all the new processes they are using...
I really do hope they find the vehicle had no role in the event and still use the down time to review it objectively for possible improvements. If it was some GSE or something on the TEL the question would then be why it was allowed to happen? A nefarious action or "an act of god" are the only ways that they could relive themselves of any responsibility... Once again, my point is that it is just simply too soon from lessons learned...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/11/2016 10:24 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

I do NOT subscribe to the sabotage theories, but as outside interference has not yet been ruled out, perhaps they will need to borrow some techniques from aircraft crash investigation; ie microscopic examination of salvaged parts of the external hull for explosives residue and pitting from high velocity impact (implying high detonation velocity).

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.

Was it simply hugged too much, or too little.

These are all good points. If SpaceX does not have the telemetry data available to identify the root cause, then perhaps it will be necessary for them to re-create the environment in which the incident occurred. For example, set up a second stage in a suitably remote location. Provide an equivalent refuelling system, and equivalent loads, dummy or otherwise. Perform the fuel loading, multiple times. If necessary, overstress the stage while loading, and record the sounds it makes. Perhaps even shoot the stage to see what happens. Whatever it takes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/11/2016 11:18 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
Please don't take this as a snarky answer, but to say the cause "is" from coincidental ambient sounds is a little surprising from them this early in the investigation... Shuttle flew for thirty years and they were still discovering new things about her...

Not quite sure I understand your post. But it seems SpaceX hasn't yet concluded whether those precursor sounds *are* causal or unrelated, which is why they're asking for more audio. If I understand Elon's tweet, vehicle sensors (ie high freq accelerometers) didn't pick up the precursor sounds, which would suggest they didn't originate in the vehicle. But they are being extra cautious by asking for more audio in order to try to pinpoint where those sounds did come from. Which means, unlike the NASA shuttle foam debacle, they aren't making the mistake of ignoring evidence that could be overlooked or prematurely dismissed as unrelated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pippin on 09/11/2016 11:35 am
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
Bingo
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/11/2016 11:48 am
So nobody thinks contamination in the lox line could cause this type and magnitude explosion?

It would have happened at the beginning of the load.

Not if the contamination was inside the tank near the top.

Yeah, but the specific question he was responding to was about contamination in the LOX line (or maybe at the GSE/vehicle interface), and I assume propagating into the tank during LOX loading operations.  Jim's point was that in that scenario, the anomaly would be expected to occur at the beginning of the loading  This scenario is distinct from contamination having been in the tank prior to filling. 

That said, I'm not sure that the expectation would be all that different.  A good amount of the LOX that is loaded at the very beginning will boil off while the tank is chilling down.  So, you end up with quite a bit of GOX in the tank early in the fill operation and it is in contact with the contamination at the top of the tank.  Not sure I see much of a difference besides maybe the hydrodynamics of the LOX, but I'm not an expert.

What was in my mind when I reintroduced contamination was. Could contamination in a lox line take a while to ignite? Something hung up somewhere in the external plumbing that only ignites after high speed lox flow? I don't know enough about lox and contaminants to answer this question.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kalvill on 09/11/2016 12:20 pm
Is there any estimation how much fuel,lox,contamination... is needed for an initial ignition of the observed size (or needed size to  trigger the observed RUD)? I would expect such an amount estimation, say for fuel aerosol, would give some hints on the timing as it may need som time to build up. Any expert for a hint on this here?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/11/2016 12:27 pm
Is there any estimation how much fuel,lox,contamination... is needed for an initial ignition of the observed size (or needed size to  trigger the observed RUD)? I would expect such an amount estimation, say for fuel aerosol, would give some hints on the timing as it may need som time to build up. Any expert for a hint on this here?
I have seen somewhere on this thread of about a gallon of rp1 necessary for the initial explosion(that was for FAE).
Of course if a lox line explodes from contamination it takes what ever the tubing material is(Al?) with it.
My other problem with external lox line exploding is that the center of the initial explosion is not where the lox lines are.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 12:31 pm
MATLAB anyone?

I don't have a license, but this might yield interesting results:  https://sites.google.com/site/louyifei/research/turbulence
http://alumni.soe.ucsc.edu/~xzhu/doc/turbulence.html
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 12:54 pm

Yes, Hydrazine is a monopropellant. The problem with that line of thinking is that the payload didn't have hydrazine. It had UDMH (which, yes - is a hydrazine derivative, but not "hydrazine")


Neither UDMH or Aerozine 50 are not used by spacecraft.  It is a launch vehicle propellant.  MMH or Hydrazine is used in spacecraft for the  liquid apogee engine but hydrazine is use for attitude control thrusters

Neither UDMH or Aerozine 50 have been present at the Cape since the last Titan IV

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/11/2016 12:57 pm
This arrangement could make sure the patches of tank were clear of ice and impart a varying, and sliding load to the skin.

There is also I believe a vent around that point for oxygen. The wind direction would carry the output to the rocket skin.

Was that enough to crack the skin exposing the fresh metal to oxygen and forming the initial fire. The rest is inevitable.

Will such cracking result in the observed large and fast initial explosion? I doubt it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 01:02 pm
This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.

still packeting is good for losing data

Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.


No, my experience is with launch vehicle failures
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 01:04 pm

F9 is a clean sheet design, and being able to get the last bit of data out is a design requirement for telemetry...j 


Wrong, see CRS-7
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 01:05 pm
In light of the appeal this is my $0.02 worth.

There are only two observable differences with this flight and any other.
1. The satellite
2. The wind and direction



Spacex keeps changing the vehicle and GSE.  We don't know the other changes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/11/2016 01:11 pm
]

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.

still packeting is good for losing data
[/quote]

.....
10 GbE over fiber is so good (no ground loops!), so fast, so lightweight, and so cheap, you use 5 Gb/s of sensor bandwidth on each fiber and move to the next problem.  Separate differential serial lines for each sensor, by comparison, is a freaking nightmare.  I've seen bags of parallel coax thicker than my thigh... what a bulky, heavy pain in the ass.  You'll never end up instrumenting everything you should if you have to run all that cable.
....
[/quote]

Here is an opinion and a few guesses re Spacex telemetry. 

IMO SpaceX gets the same telemetry during this test as they do during flight. 

According to the  Falcon 9 User Guide:
Each stage has one 1.8Mbps PCM S-Band transmitter
Each stage has one FM/NTSC  S-Band transmitter

IMO the hardline data from the vehicle is exactly the same as what is transmitted during flight.  It's possible they have the transmitters running at the same time as the hardline. 

3000 channels of data sounds like a lot. But a channel might be 1 bit that is sampled once a second or a high frequency accelerometer sampled more than 20000 times a second. 

It will take a team of analysts weeks to digest and document nominal flight data from two 1.8Mbps data streams plus the payload and Dragon stuff. 

There is a minimum of buffering of data.  For things like accelerometers, data will be sampled, A-D converted and transmitted within a few microseconds.  For networked subsystems in the rocket that collect their own data, it will be delayed maybe a telemetry frame or two to collect it and sync it with the telemetry frames.  My guess is these delays would be no longer than 10- 20 millesecs.  I also suspect they have an overall telemetry frame that might be a second or longer that allows very low rate sampling for stuff like structure temperatures. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lee Jay on 09/11/2016 01:15 pm
This brings up an issue again.  ethernet is the wrong medium for telemetry within and coming off the rocket.  packetization means data can be lost in incidents such as this.  And timing can get screw up.  Serial data rules for these instances.

Loss is not a given on switched ethernet. Also the minimum frame time at 10Gbps is only 67 nanoseconds. At level, the amount of time it takes your operating system to finish an interrupt will be the driving factor in timing.

still packeting is good for losing data

Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.

There are link bit errors and switches dropping packets.  Serial lines aren't going to help reduce link bit error rate, that comes down to whatever technology you are using for transmission.  Raw serial lines do pass the glitchy data up to your software, so presumably you could do better error containment there.  Packet switched stuff will just dump the whole packet when there is a bit error, which potentially amplifies the underlying bit error rate. 

With gigabit ethernet over cat5, I found a consistent bit error rate of 3e-12.  With 10GbE over multimode fiber, I never saw a single bit error ever.  We ran a test for weeks, probably over a month (we forgot about it for a while), with an FPGA stuffing packets down the fiber with minimum interpacket gaps.  No errors.  That's better than 1e-16 BER!

Having run PCM and Ethernet for many years for data acquisition, I can tell you Ethernet is way more fragile on noisy channels.  Put it on a perfect channel and it's perfect.  Put it on a noisy radio channel, over low quality slip rings,  or on an electrical channel in a very noisy electrical environment and it fails 100 times as much as PCM.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Arb on 09/11/2016 01:29 pm
<Snip>
Now back to the wind. The discussions on oxygen condensation all show that the ice would form first. Yet there is one point this would not be true. This strong back is unique in having a pivoted cradle for the upper stage. This means the grabbers hold predominantly the far side of the cylinder. The pivoting cradle pushes on the near side, to the strongback. I have been unable to locate any hydraulics associated with this pivoting cradle from images or videos.

If gravity does its job, the cradle would push more on the upper support than the lower one. This would be countered by the grabbers. In an early video of the strongback retraction a previous Falcon 9 is seen to sway significantly. The grabbers must therefore have enough force to hold it. If they are slack the pivoting cradle will modulate its push, with the wind caused flexing, on the lower support. The wind direction is pushing the Falcon 9 away from the strongback. Every time the wind gusts the lower cradle would ease off the pressure and move up slightly. The pads on the grabbers are on the sides and the far side. How do they regulate the force, do they prioritise squashing it or pulling it back. These are also set while the rocket is horizontal but are used when it is vertical.

This arrangement could make sure the patches of tank were clear of ice and impart a varying, and sliding load to the skin.

There is also I believe a vent around that point for oxygen. The wind direction would carry the output to the rocket skin.

Was that enough to crack the skin exposing the fresh metal to oxygen and forming the initial fire. The rest is inevitable.

In this case there would be no indications on any sensors of any prior event.

If this is the case then the solution was also achieved in the event. The strongback was destroyed. The new designs do not have the same mechanism. They need to grab the Falcon 9 above the tanks with a grabber that has equal angle of pads around the cylinder.

Was it simply hugged too much, or too little.
A most interesting first post. Anyone able to refute it?

Edit: Prune quote.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 01:43 pm
<Snip>
Now back to the wind. The discussions on oxygen condensation all show that the ice would form first. Yet there is one point this would not be true. This strong back is unique in having a pivoted cradle for the upper stage. This means the grabbers hold predominantly the far side of the cylinder. The pivoting cradle pushes on the near side, to the strongback. I have been unable to locate any hydraulics associated with this pivoting cradle from images or videos.

If gravity does its job, the cradle would push more on the upper support than the lower one. This would be countered by the grabbers. In an early video of the strongback retraction a previous Falcon 9 is seen to sway significantly. The grabbers must therefore have enough force to hold it. If they are slack the pivoting cradle will modulate its push, with the wind caused flexing, on the lower support. The wind direction is pushing the Falcon 9 away from the strongback. Every time the wind gusts the lower cradle would ease off the pressure and move up slightly. The pads on the grabbers are on the sides and the far side. How do they regulate the force, do they prioritise squashing it or pulling it back. These are also set while the rocket is horizontal but are used when it is vertical.

This arrangement could make sure the patches of tank were clear of ice and impart a varying, and sliding load to the skin.

There is also I believe a vent around that point for oxygen. The wind direction would carry the output to the rocket skin.

Was that enough to crack the skin exposing the fresh metal to oxygen and forming the initial fire. The rest is inevitable.

In this case there would be no indications on any sensors of any prior event.

If this is the case then the solution was also achieved in the event. The strongback was destroyed. The new designs do not have the same mechanism. They need to grab the Falcon 9 above the tanks with a grabber that has equal angle of pads around the cylinder.

Was it simply hugged too much, or too little.
A most interesting first post. Anyone able to refute it?

Edit: Prune quote.

re the cradle, see Reply #1717 this thread.

clearly shows the hydraulics.  Later in that thread is a closeup.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 01:47 pm
The question that keeps replaying in my mind is why are the asking for sources of external events? That would mean they have decided that the vehicle is a sound design and played no responsibility in the mishap. Just thinking out loud on my keyboard...

Because different audio recordings taken from different distances/locations would help them determine whether the "precursor" sounds came from the rocket/pad, or were an artifact from near the camera.

Right now the only audio recording we have is the USLaunchReport video, and it's unclear whether the precursor sounds came from the rocket or from the junkyard where the camera was. If a different audio recording from another spot at the Cape also has the precursor sounds with the same time differential, that would suggest they came from the rocket/pad rather than the junkyard.
Please don't take this as a snarky answer, but to say the cause "is" from coincidental ambient sounds is a little surprising from them this early in the investigation... Shuttle flew for thirty years and they were still discovering new things about her...

Not quite sure I understand your post. But it seems SpaceX hasn't yet concluded whether those precursor sounds *are* causal or unrelated, which is why they're asking for more audio. If I understand Elon's tweet, vehicle sensors (ie high freq accelerometers) didn't pick up the precursor sounds, which would suggest they didn't originate in the vehicle. But they are being extra cautious by asking for more audio in order to try to pinpoint where those sounds did come from. Which means, unlike the NASA shuttle foam debacle, they aren't making the mistake of ignoring evidence that could be overlooked or prematurely dismissed as unrelated.
I have no problem with them looking for an additional data point "if" indeed that is what he means. As far as Shuttle was concerned, NASA folks are the same as the ones at SpaceX, as are us all. We are all humans, subject to biases, making mistakes and sometimes blinded by ambition...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 01:48 pm
Is there any estimation how much fuel,lox,contamination... is needed for an initial ignition of the observed size (or needed size to  trigger the observed RUD)? I would expect such an amount estimation, say for fuel aerosol, would give some hints on the timing as it may need som time to build up. Any expert for a hint on this here?
I have seen somewhere on this thread of about a gallon of rp1 necessary for the initial explosion(that was for FAE).
Of course if a lox line explodes from contamination it takes what ever the tubing material is(Al?) with it.
My other problem with external lox line exploding is that the center of the initial explosion is not where the lox lines are.

see these replies this thread

Reply #1259
Reply #1656
Reply #1677
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 02:06 pm

Yes, Hydrazine is a monopropellant. The problem with that line of thinking is that the payload didn't have hydrazine. It had UDMH (which, yes - is a hydrazine derivative, but not "hydrazine")


Neither UDMH or Aerozine 50 are not used by spacecraft.  It is a launch vehicle propellant.  MMH or Hydrazine is used in spacecraft for the  liquid apogee engine but hydrazine is use for attitude control thrusters

Neither UDMH or Aerozine 50 have been present at the Cape since the last Titan IV

Looks like I was wrong about UDMH on the payload, so I did some more digging. This is a reference to AMOS-6 using MMH for the propellant

http://spaceflight101.com/falcon-9-amos-6/amos-6-satellite/

I can't find any reference to MMH as a monopropellant. It is (like UDMH) notably more stable than straight hydrazine.

Flash point (in air) of -8C
Autoignition temperature of 196C
Flammable limits (in air) of 2.5-92%

Compare to UDMH

Flash point (in air) of -10C
Autoignition temperature of 248C
Flammable limits (in air) of 2-95%

Characteristics are quite similar.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 02:29 pm
Anyone with Windows and a fast connection and some free time care to help on a little image processing project?

see:  https://www.reddit.com/r/spacex/comments/528b1k/looped_video_70_frames_prefireball_with_a_couple/

MATLAB discussion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/11/2016 02:30 pm


re the cradle, see Reply #1717 this thread.

clearly shows the hydraulics.  Later in that thread is a closeup.

It shows the two large rams for the grabbers. I can find no other rams to control the pivoting cradle. The internship video has a good close up.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 02:40 pm
Do we have hard confirmation whether the fairing/payload was nitrogen purged? It is listed as an option in the F9 user's guide.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 02:48 pm
This arrangement could make sure the patches of tank were clear of ice and impart a varying, and sliding load to the skin.

There is also I believe a vent around that point for oxygen. The wind direction would carry the output to the rocket skin.

Was that enough to crack the skin exposing the fresh metal to oxygen and forming the initial fire. The rest is inevitable.

Will such cracking result in the observed large and fast initial explosion? I doubt it.

Some notes.

1. A tank full of densified LOX doesn't need to have a leak or vented oxygen in order for their to be a high oxygen concentration on the outside.  It's more than sufficient to liquefy air, and in the right conditions, a predominantly liquid oxygen mixture.  This is a risk that does not exist with boiling-point LOX.

2. What exactly do they paint with?  Most organics (with the exception of some fluorinated ones, which would be too expensive for paint) and silicone compounds are impact and heat sensitive when in contact with LOX. 

As a general rule one *strongly* tries to avoid air liquefaction around rockets.  Does SpaceX do anything at all to prevent it?

A note that if the actual problem was due to air liquefaction... there's no easy fix for this, at least not one that doesn't ruin performance. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jak Kennedy on 09/11/2016 02:49 pm
still packeting is good for losing data
Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.
No, my experience is with launch vehicle failures

So other launch vehicles have used packeting? What did the shuttle use?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 02:51 pm
Do we have hard confirmation whether the fairing/payload was nitrogen purged? It is listed as an option in the F9 user's guide.

The fairing AC is transition from air to GN2 for prop load.   The purge in the guide refer to a purge connected to the payload, which would be through a tube like an aquarium airline.  Comsat don't use purges like that, that is mostly for scientific spacecraft or ones with optics, with their various instruments.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 02:54 pm
still packeting is good for losing data
Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.
No, my experience is with launch vehicle failures

So other launch vehicles have used packeting? What did the shuttle use?

Shuttle existed long before ethernet
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 02:56 pm

1. A tank full of densitied LOX doesn't need to have a leak or vented oxygen in order for their to be a high oxygen concentration on the outside.  It's more than sufficient to liquefy air, and in the right conditions, a predominantly liquid oxygen mixture.  This is a risk that does not exist with boiling-point LOX.

2. What exactly do they paint with?  Most organics (with the exception of some fluorinated ones, which would be too expensive for paint) and silicone compounds are impact and heat sensitive when in contact with LOX. 

As a general rule one *strongly* tries to avoid air liquefaction around rockets.  Does SpaceX do anything at all to prevent it?

A note that if the actual problem was due to air liquefaction... there's no easy fix for this, at least not one that doesn't ruin performance. 

That isn't the problem.  There is ice on the stages.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 02:57 pm

clearly shows the hydraulics.  Later in that thread is a closeup.

We don't know if it is hydraulics, it could be pneumatics.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 02:57 pm

1. A tank full of densified LOX doesn't need to have a leak or vented oxygen in order for their to be a high oxygen concentration on the outside.  It's more than sufficient to liquefy air, and in the right conditions, a predominantly liquid oxygen mixture.  This is a risk that does not exist with boiling-point LOX.

2. What exactly do they paint with?  Most organics (with the exception of some fluorinated ones, which would be too expensive for paint) and silicone compounds are impact and heat sensitive when in contact with LOX. 

As a general rule one *strongly* tries to avoid air liquefaction around rockets.  Does SpaceX do anything at all to prevent it?

A note that if the actual problem was due to air liquefaction... there's no easy fix for this, at least not one that doesn't ruin performance. 

That isn't the problem.  There is ice on the stages.

Less Land (who brought up this particular topic) was arguing for conditions that could shed ice.  Which isn't a far-fetched concept.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 03:00 pm

Less Land (who brought up this particular topic) was arguing for conditions that could shed ice.  Which isn't a far-fetched concept.

it is farfetched.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 03:18 pm


re the cradle, see Reply #1717 this thread.

clearly shows the hydraulics.  Later in that thread is a closeup.

It shows the two large rams for the grabbers. I can find no other rams to control the pivoting cradle. The internship video has a good close up.
Welcome to the forum! :) I have looking for a few days now and only located the two rams as well...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/11/2016 03:25 pm
I think, in groping for answers, we have to be wary of "well, it couldn't have happened that way" thinking, to the point it blinds us to possibilities.

I recall that, at one point early in the Apollo 1 investigation, a parade of witnesses told the board all the ways in which the fire could not have started, each expanding on how their systems could not have been involved, until someone said they were thinking of asking Gus, Ed and Roger to testify.  To the shocked looks this garnered, he replied that since everyone was so positive that their systems could have had no causal relationship to the fire, that, if you listened to the testimony, it was obvious that the fire never happened!

The Challenger and Columbia investigation boards faced similar situations -- there was a huge amount of denial in each case of whole lines of investigation, including into the areas which ultimately yielded the actual causal chains of events.  Who can forget Feynman dunking an O-ring into a glass of icewater to demonstrate its temperature characteristics, or of crying foam-deniers after seeing the blasted RCC panel from the first foam impact test?  Each of these lines of investigation were strongly opposed by some of the board members, because they just couldn't believe, facts be hanged, that the actual causal events could possibly have caused the accidents in question.

The take-away here is that it's easy to get so far down the path of "well, that couldn't have happened" that you get yourself in the logical position of denying the observed facts.  And fact number one, that cannot be denied, is that the damned rocket blew up...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Digitalchromakey on 09/11/2016 03:27 pm

Yes, Hydrazine is a monopropellant. The problem with that line of thinking is that the payload didn't have hydrazine. It had UDMH (which, yes - is a hydrazine derivative, but not "hydrazine")


Neither UDMH or Aerozine 50 are not used by spacecraft.  It is a launch vehicle propellant.  MMH or Hydrazine is used in spacecraft for the  liquid apogee engine but hydrazine is use for attitude control thrusters

Neither UDMH or Aerozine 50 have been present at the Cape since the last Titan IV

Looks like I was wrong about UDMH on the payload, so I did some more digging. This is a reference to AMOS-6 using MMH for the propellant

http://spaceflight101.com/falcon-9-amos-6/amos-6-satellite/

I can't find any reference to MMH as a monopropellant. It is (like UDMH) notably more stable than straight hydrazine.

Flash point (in air) of -8C
Autoignition temperature of 196C
Flammable limits (in air) of 2.5-92%

Compare to UDMH

Flash point (in air) of -10C
Autoignition temperature of 248C
Flammable limits (in air) of 2-95%

Characteristics are quite similar.
The article you cite, plus other sources, state that AMOS-6 was equipped with an Airbus S400 Series Apogee motor which uses MMH and MON as Bipropellants.

The article further states that station keeping was to be achieved using a Thales Alenia Electric propulsion system, so there may well have been no separate pure Hydrazine loaded aboard to drive a monopropellant attitude control system.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 03:28 pm

The article further states that station keeping was to be achieved using a Thales Alenia Electric propulsion system, so there may well have been no separate pure Hydrazine loaded aboard to drive a monopropellant attitude control system.


Station keeping is not the same as attitude control
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 03:32 pm

Less Land (who brought up this particular topic) was arguing for conditions that could shed ice.  Which isn't a far-fetched concept.

it is farfetched.

The concept of ice shedding, off of smooth, freshly painted aluminum, on a substrate that's undergoing thermal expansion, uneven thermal expansion at that, and is a tall object subjected to time-varying wind and propellant loadings....  is far fetched?  In what world?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 03:33 pm
My suggestion to some of the new members is to read Wayne Hale's Blog on here...

http://forum.nasaspaceflight.com/index.php?topic=22791.0
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/11/2016 03:45 pm
still packeting is good for losing data
Disagree.  I concur with dbavatar.  Your experience may be based on a misbehaving link technology or oversubscribed switches.
No, my experience is with launch vehicle failures

So other launch vehicles have used packeting? What did the shuttle use?

Shuttle existed long before ethernet

Depends on your definition of long. Space shuttle design started in the early 70, 1972 was the launch date. First flight in 1981. Ethernet gestation was around the same time, at Xerox Parc, in 1973/4. First standard was 1983, although commercially introduced in 1980, before the first shuttle flight.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 03:49 pm
It's worth pointing out that the reason LH tanks need insulation and LOX tanks don't is precisely that: air liquefaction.  It's not simply "hydrogen is cold so it loses heat fast"; it's "hydrogen is cold enough to liquefy air which draws away heat *far* faster than would otherwise occur".  And "ice" isn't enough to protect it from air liquefaction, you need real insulation.

No, densified LOX is not as cold as hydrogen.  But it's still extremely cold - what, ~23C colder than boiling-point LOX?  The thermal conductivity of water ice is 2.2W/m², compared to typical foam insulations at around 0.03W/m² .  It's just not that good of an insulator.

And that's assuming it even stays on.  Or has sufficient time to form to a relevant thickness, when they're just starting loading.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/11/2016 03:55 pm

Less Land (who brought up this particular topic) was arguing for conditions that could shed ice.  Which isn't a far-fetched concept.

it is farfetched.

Could you explain? In normal conditions a tank would be covered in "snow". It just happens that one part is being rubbed clean by a pad. This I believe is a unique occurrence.

Further, I am only concerned with "observable" differences. There are many reasons that I am blind to and will not speculate about. Yet I have faith in SpaceX to know what they have changed, and investigate those first. If they appeal for explanations I assume they came up empty after the initial review of changes.

After changes the "unusual" is investigated next.

Looking back at the original video there is clearly a water vapour plume at 1.09. Yet at 1.10 there is a new plume below it down at the point of ignition that occurs at 1.11. After the initial blast the two plumes can be seen as separate reflecting areas and cause the odd shape to the reflecting cloud on the left side.

Why was the lower part of the tank not making a water vapour cloud earlier, and then why was a plume seen a second before the explosion? Yet the first stage was a constant vapour producer throughout. There will be wind flow issues due to the fairing but the place with the least obstruction (the turnbuckles) level with the bottom of the tank is producing no cloud.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/11/2016 04:01 pm
It's worth pointing out that the reason LH tanks need insulation and LOX tanks don't is precisely that: air liquefaction.  It's not simply "hydrogen is cold so it loses heat fast"; it's "hydrogen is cold enough to liquefy air which draws away heat *far* faster than would otherwise occur".  And "ice" isn't enough to protect it from air liquefaction, you need real insulation.

No, densified LOX is not as cold as hydrogen.  But it's still extremely cold - what, ~23C colder than boiling-point LOX?  The thermal conductivity of water ice is 2.2W/m², compared to typical foam insulations at around 0.03W/m² .  It's just not that good of an insulator.

And that's assuming it even stays on.  Or has sufficient time to form to a relevant thickness, when they're just starting loading.

Good point about ice coatings.  But I will note something from a book I'm currently re-reading, "Stages to Saturn," in a discussion of exactly this point.

When discussing the development of the J-2 engine, the author notes that, to a great extent, those early engine test setups not only expected ice to form around a myriad of LOX pipes and fittings, they welcomed it, because the ice made for a decent insulating layer and meant they didn't need to insulate these things.  But when they started working with LH2, they found that ice didn't form, air liquified.  And that liquified air would then drip down onto other pieces of the plumbing, causing problems.  And that the liquified air caused a much higher than desired heat loss into the LH2 plumbing.

This forced these engineers to develop a whole host of vacuum insulators to keep the LH2 plumbing dry and maintain correct thermal conditions.  Once the hurdle of developing a large number of vacuum insulation fittings had been cleared, they then started applying them to LOX plumbing and fittings, as well, because they afforded better thermal characteristics than the ice coatings did.

Every once in a while, the book you're reading directly applies to a seemingly unconnected discussion you find yourself in... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/11/2016 04:10 pm
I like ideas that have to do with the temperature, since the flight history of that configuration is much shorter.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Winston2016 on 09/11/2016 04:33 pm
OK, I've just slogged through the first 50 pages of this and decided to post this request for a general summary of what is known or suspected up to this point. My questions:

1. EXACTLY at what time in the countdown did this event occur? If this is not known, why isn't it?
2. WHERE is most likely location where the event initiated?
3. Is TEA-TAB for the second stage loaded prior to erection or while on the pad? I see mention of TEA-TAB in the countdown timeline.
3. Where are SpaceX pad cameras located?

Any other summaries beyond just those questions will be extremely welcome.

My thoughts: A mix of LOX/RP1 forms a high explosive gel. This was a cause of major problems (explosions) in early liquid fuel rocket engine development. Long ago I read of an incident where a fire truck had its tires or wheels blown off by driving over asphalt that had been saturated by a LOX tank or transport tanker leak, so it seems that these LOX explosive mixes are very sensitive to initiation to detonation (i.e., do not require a blasting cap). It was incredibly humid that day based upon the fog I see in the video. This would result in an unusual amount of ice fog and ice fog is a great source for static electrical charge buildups. I don't know what kind of defense against ice buildup they have on the LOX umbilical, but the fog would naturally lead to a greater tendency for ice buildup. If allowed, this would cause a greater force on the umbilical connection and would also result in greater static buildup.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 04:34 pm
I like ideas that have to do with the temperature, since the flight history of that configuration is much shorter.

Before this even happened, my though was "they are very brave to do static test in tropical storm conditions". Weather on this day was really bad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 04:52 pm
I like ideas that have to do with the temperature, since the flight history of that configuration is much shorter.

Before this even happened, my though was "they are very brave to do static test in tropical storm conditions". Weather on this day was really bad.
Might be interesting to look at the Field Mill data on that date and time...
http://catalog.data.gov/dataset/ksc-advanced-ground-based-field-mill-v1
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/11/2016 04:53 pm
Glenn Thompson posted the data from his infrasound station near the pad on Twitter:

https://twitter.com/volcanoglenn/status/774724624655519744
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 04:59 pm
Depends on your definition of long. Space shuttle design started in the early 70, 1972 was the launch date. First flight in 1981. Ethernet gestation was around the same time, at Xerox Parc, in 1973/4. First standard was 1983, although commercially introduced in 1980, before the first shuttle flight.


Long as in regular usage.  Airplanes didn't even use it for a long time.    Shuttle didn't even use it for PC's in the cabin until the later 90's.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 05:05 pm

Less Land (who brought up this particular topic) was arguing for conditions that could shed ice.  Which isn't a far-fetched concept.

it is farfetched.

The concept of ice shedding, off of smooth, freshly painted aluminum, on a substrate that's undergoing thermal expansion, uneven thermal expansion at that, and is a tall object subjected to time-varying wind and propellant loadings....  is far fetched?  In what world?


in the real world.   Lox outside the vehicle is not credible.   
Ice sheds all the time and is replaced by ice


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 05:23 pm
my standard dumb daily question.

Does anyone know what this is?

ref:  h ttps://www.youtube.com/watch?v=aUupk1uydRk
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 05:32 pm
Glenn Thompson posted the data from his infrasound station near the pad on Twitter:

https://twitter.com/volcanoglenn/status/774724624655519744

Assuming seismographs are located near the Lighthouse and assuming "U" on this chart represents the bang Musk was talking about, it is 4.5 seconds before explosion happens. Does it mean source of this bang  was a few hounded yards south of the pad?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/11/2016 05:46 pm
Glenn Thompson posted the data from his infrasound station near the pad on Twitter:

https://twitter.com/volcanoglenn/status/774724624655519744

Assuming seismographs are located near the Lighthouse and assuming "U" on this chart represents the bang Musk was talking about, it is 4.5 seconds before explosion happens. Does it mean source of this bang  was a few hounded yards south of the pad?

In that tweet he says the top three traces were from ultrasound sensors arranged in a triangle 0.87 mi from the pad.

The USLaunchReport video from a different location about 4 km away also has a roughly 4.5 second interval between the faint "precursor" pop/bang and the first big bang. So it's possible those are the same sounds. Then by triangulation, the same delta-T would suggest that the faint pop/bang did come from the rocket/pad area, same as the first big bang.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 05:51 pm
Glenn Thompson posted the data from his infrasound station near the pad on Twitter:

https://twitter.com/volcanoglenn/status/774724624655519744

Assuming seismographs are located near the Lighthouse and assuming "U" on this chart represents the bang Musk was talking about, it is 4.5 seconds before explosion happens. Does it mean source of this bang  was a few hounded yards south of the pad?

In that tweet he says the top three traces were from ultrasound sensors arranged in a triangle 0.87 mi from the pad. But only one of the (co-located) sensors shows the "U" artifact, so I'm not sure what we can conclude from it.

In this case the source of this bang is much closer to LC-40. If we knew exactly where these seismographs were located we could perform some crude triangulation to find two possible locations of this bang.

Edit - Glenn's tweet with seismographs recording successful SpaceX launch:
https://twitter.com/volcanoglenn/status/705511854127378432
We know exact launch time for that flight - can calculate a bunch of interesting values - speed of sound transferred via ground, typical seismograph response to engine start etc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: testguy on 09/11/2016 05:55 pm


1. EXACTLY at what time in the countdown did this event occur? If this is not known, why isn't it?
2. WHERE is most likely location where the event initiated?
3. Is TEA-TAB for the second stage loaded prior to erection or while on the pad? I see mention of TEA-TAB in the countdown timeline.
3. Where are SpaceX pad cameras located?


Item 3. TEA TEB.  I don't have first hand information on Space X's procedure.  However, what makes sense to me is to load it prior to S2 installation to Falcon in the horizontal mode.  That way the S2 TEA TEB container and associated plumbing could to checked for leaks.  When satisfied, pressurize the TEA TEB S2 container (pressure  vessel) to flight pressure and again checked for leaks and repair as necessary.  Again, when satisfied depressurize to ambient.  The next time it would be pressurized is during he countdown with S2 vertical and attached to S1.  This would be the easiest and safest way to go.

TEA TEB is not difficult to work with provided procedures are properly thought out and followed.  It is even shipped in DOT shipping containers by common carriers.  You just need to keep it away from oxidizers.  This is done by replacing air (oxygen) in all plumbing and containers with an inert gas such as GN2.  It becomes more hazardous when it is pressurized above ambient pressure because then it will form a jet if it is injected or from a leak.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/11/2016 05:56 pm
Glenn Thompson posted the data from his infrasound station near the pad on Twitter:

https://twitter.com/volcanoglenn/status/774724624655519744

Assuming seismographs are located near the Lighthouse and assuming "U" on this chart represents the bang Musk was talking about, it is 4.5 seconds before explosion happens. Does it mean source of this bang  was a few hounded yards south of the pad?

In that tweet he says the top three traces were from ultrasound sensors arranged in a triangle 0.87 mi from the pad. But only one of the (co-located) sensors shows the "U" artifact, so I'm not sure what we can conclude from it.

In this case the source of this bang is much closer to LC-40. If we knew exactly where these seismographs were located we could perform some crude triangulation to find two possible locations of this bang.

See my addition to original post above. A similar (roughly) 4.5 second differential exists in the USLaunchReport video, which means the faint precursor sound (if it is in fact the same sound) must have originated in the same area as the first big bang (or exactly one other "symmetrically opposite" point, which seems unlikely).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 06:11 pm
This arrangement could make sure the patches of tank were clear of ice and impart a varying, and sliding load to the skin.

There is also I believe a vent around that point for oxygen. The wind direction would carry the output to the rocket skin.

Was that enough to crack the skin exposing the fresh metal to oxygen and forming the initial fire. The rest is inevitable.

Will such cracking result in the observed large and fast initial explosion? I doubt it.

Some notes.

1. A tank full of densified LOX doesn't need to have a leak or vented oxygen in order for their to be a high oxygen concentration on the outside.  It's more than sufficient to liquefy air, and in the right conditions, a predominantly liquid oxygen mixture.  This is a risk that does not exist with boiling-point LOX.

2. What exactly do they paint with?  Most organics (with the exception of some fluorinated ones, which would be too expensive for paint) and silicone compounds are impact and heat sensitive when in contact with LOX. 

As a general rule one *strongly* tries to avoid air liquefaction around rockets.  Does SpaceX do anything at all to prevent it?

A note that if the actual problem was due to air liquefaction... there's no easy fix for this, at least not one that doesn't ruin performance.

Even if you have an air liquefaction problem (a position which I am not advocating) - the addition of around 0.5mm of insulating coating should slow heat transfer more than enough to go back to pure icemaking.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/11/2016 06:13 pm

Yes, Hydrazine is a monopropellant. The problem with that line of thinking is that the payload didn't have hydrazine. It had UDMH (which, yes - is a hydrazine derivative, but not "hydrazine")


Neither UDMH or Aerozine 50 are not used by spacecraft.  It is a launch vehicle propellant.  MMH or Hydrazine is used in spacecraft for the  liquid apogee engine but hydrazine is use for attitude control thrusters

Neither UDMH or Aerozine 50 have been present at the Cape since the last Titan IV

Looks like I was wrong about UDMH on the payload, so I did some more digging. This is a reference to AMOS-6 using MMH for the propellant

http://spaceflight101.com/falcon-9-amos-6/amos-6-satellite/

I can't find any reference to MMH as a monopropellant. It is (like UDMH) notably more stable than straight hydrazine.

Flash point (in air) of -8C
Autoignition temperature of 196C
Flammable limits (in air) of 2.5-92%

Compare to UDMH

Flash point (in air) of -10C
Autoignition temperature of 248C
Flammable limits (in air) of 2-95%

Characteristics are quite similar.
The article you cite, plus other sources, state that AMOS-6 was equipped with an Airbus S400 Series Apogee motor which uses MMH and MON as Bipropellants.

The article further states that station keeping was to be achieved using a Thales Alenia Electric propulsion system, so there may well have been no separate pure Hydrazine loaded aboard to drive a monopropellant attitude control system.

Well, for the "blame MMH leak" possibility, it doesn't really matter whether there was also pure hydrazine onboard.

Jim, thank you for the confirmation the inside of the fairing got a nitrogen purge.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 06:16 pm

1. Why?
2. The summary of the most likely sources mentioned so far by someone who HAS read the entire very long thread would be useful for everyone else.
3. A simple yes/no answer is all that question requires.
4. I'd certainly hope there's one in the umbilical area and some locations can be known through recollections of individuals who have watched their YouTube launch coverage. Anyone ever seen one from the umbilical area?


1.  Ask Spacex
2.  And we would have to do that for everybody that comes late to the party
3.  It is not known
4.  Spacex doesn't release close range camera views of the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Winston2016 on 09/11/2016 06:35 pm

1. Why?
2. The summary of the most likely sources mentioned so far by someone who HAS read the entire very long thread would be useful for everyone else.
3. A simple yes/no answer is all that question requires.
4. I'd certainly hope there's one in the umbilical area and some locations can be known through recollections of individuals who have watched their YouTube launch coverage. Anyone ever seen one from the umbilical area?


1.  Ask Spacex
2.  And we would have to do that for everybody that comes late to the party
3.  It is not known
4.  Spacex doesn't release close range camera views of the vehicle.

Well, then based upon that apparently permanent lack of public information, I'll leave all speculation to those who have that information.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jakusb on 09/11/2016 06:58 pm
(http://uploads.tapatalk-cdn.com/20160911/69fad97ab9681f6943e99f7bff5faa8a.jpg)
Not sure if I missed this being mentioned or discussed. Is this of any value? Can the source of the thump triangulated with this info?

Edit: just found it few posts back. Searched for seismic and found nothing. Should have searched for Thompson.
Mods: feel free to remove this post
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: john smith 19 on 09/11/2016 07:17 pm
Depends on your definition of long. Space shuttle design started in the early 70, 1972 was the launch date. First flight in 1981. Ethernet gestation was around the same time, at Xerox Parc, in 1973/4. First standard was 1983, although commercially introduced in 1980, before the first shuttle flight.


Long as in regular usage.  Airplanes didn't even use it for a long time.    Shuttle didn't even use it for PC's in the cabin until the later 90's.
IIRC the 3 stage solid Pegasus and Pegasus XL have used Ethernet for internal functions since their first launch.

I don't think it's ever been mentioned in any of their LOV investigations AFAIK.

For most people an 18-20 year usage history on a system is enough to make people feel quite comfortable about using it.

I'll note a couple of things.

The modern Ethernet standard is very different from the transformer coupled pure CSMA/CD free for all system Zerox/DEC/Internet introduced in the early 1970's. There is much more contention control. I will also not that it  it's 100-1000x faster than the straight 1553b standard or 5-200x faster  than the FO  based later version.

Data loss is a potential issue but the size of the Ethernet packets can be controlled and potential data loss traded off against packet overhead.

The other potential issue is items not being synchronized due to delays between when a channel is sampled and when it's sent. While Ethernet cannot supply a pure set of data values exactly when they happen (as a 3000 pin plug could) but the greater data rate would if necessary allow every channel to be time tagged.

In reality I suspect quite a few of those channels are events, essentially a time tag and a channel ID as and when necessary. A 4 byte entry can hold up to 4096 channel ID's and still time tag an even to the nearest 100 miliseconds in a 24 hour period.  While I could believe some events might need recording down to a millisecond to find out if some events have happened together (giving 17 minutes of range with 20 bits of time stamp, or over 49 hours with a 32 bit time stamp to the nearest millisecond.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 07:22 pm

IIRC the 3 stage solid Pegasus and Pegasus XL have used Ethernet for internal functions since their first launch.


Not a liquid vehicle with much more telemetry
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 08:23 pm
FWIW,  in response to my earlier MATLAB request, we managed to get the atmospheric turbulance out of the last 70 frames. 

Results here: https://www.youtube.com/watch?v=aUupk1uydRk

Description on how here:  https://www.reddit.com/r/spacex/comments/528b1k/looped_video_70_frames_prefireball_with_a_couple/d7i45o9

There will be an attempt to get more frames for about 20 seconds worth
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moskit on 09/11/2016 08:25 pm
The other potential issue is items not being synchronized due to delays between when a channel is sampled and when it's sent. While Ethernet cannot supply a pure set of data values exactly when they happen (as a 3000 pin plug could) but the greater data rate would if necessary allow every channel to be time tagged.
Modern Ethernet provides for precision timestamping, frequency and phase synchronisation down to 500ns (or even better in a small network). Developing these capabilities was required as Ethernet has become a de-facto (=cheap!) backhaul medium in mobile networks, especially with recent LTE-A introduction. This is all way beyond what was available 5-10 years ago, not to mention technology origins.

Nevertheless Ethernet or not is a secondary consideration, primary is how SpaceX wanted to perform the whole data multiplexing (delay/resilience/...).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/11/2016 08:38 pm
(http://uploads.tapatalk-cdn.com/20160911/69fad97ab9681f6943e99f7bff5faa8a.jpg)
Not sure if I missed this being mentioned or discussed. Is this of any value? Can the source of the thump triangulated with this info?

Edit: just found it few posts back. Searched for seismic and found nothing. Should have searched for Thompson.
Mods: feel free to remove this post

Here are the positions for Glenn Thompson's sensors:
https://www.google.com/maps/d/viewer?mid=17Tim56aFrQKtcF2KStP05hG9A3M

The one that recorded the blip before the main event is located NNE of the pad between SLC 40 and 41.

-C

Edit:  The data that I'm really interested in is the "pop" on the top channel at 13:07:11.
Edit 2: Corrected relative location of USF sensors to SLC-40
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 08:54 pm


Here are the positions for Glenn Thompson's sensors:
https://www.google.com/maps/d/viewer?mid=17Tim56aFrQKtcF2KStP05hG9A3M

The one that recorded the blip before the main event is located NNW of the pad between SLC 40 and 41.

-C

Edit:  The data that I'm really interested in is the "pop" on the top channel at 13:07:11.

I would love to know why only one of these three sensors registered the event. Tuned to different frequencies?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/11/2016 08:59 pm
The other potential issue is items not being synchronized due to delays between when a channel is sampled and when it's sent. While Ethernet cannot supply a pure set of data values exactly when they happen (as a 3000 pin plug could) but the greater data rate would if necessary allow every channel to be time tagged.
Modern Ethernet provides for precision timestamping, frequency and phase synchronisation down to 500ns (or even better in a small network). Developing these capabilities was required as Ethernet has become a de-facto (=cheap!) backhaul medium in mobile networks, especially with recent LTE-A introduction. This is all way beyond what was available 5-10 years ago, not to mention technology origins.

Nevertheless Ethernet or not is a secondary consideration, primary is how SpaceX wanted to perform the whole data multiplexing (delay/resilience/...).

With event propagation measured in maybe 1000 m/sec, and structural scale of 1 m, you're looking at 1 mSec desired latency.

That is a huge huge time for electronics, where you can package frames in uSecs.

The concern with "original" Ethernet was that you had multiple devices on a coax cable, and stochastic collision resolution, and so in principle a data packet may be held indefinitely before leaving the source.  Total bandwidth back then was 10 Mb/sec, which only applied in theory if one device was talking the whole time.

This is all history, however.  Applicable to vehicles that started development 20-30 years ago.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/11/2016 09:00 pm


Here are the positions for Glenn Thompson's sensors:
https://www.google.com/maps/d/viewer?mid=17Tim56aFrQKtcF2KStP05hG9A3M

The one that recorded the blip before the main event is located NNW of the pad between SLC 40 and 41.

-C

Edit:  The data that I'm really interested in is the "pop" on the top channel at 13:07:11.

I would love to know why only one of these three sensors registered the event. Tuned to different frequencies?

Ask Glenn Thomson.  @volcanoGlenn on Twitter.
BTW, all credit goes to Glenn for suggesting that his data might be useful.  I'm just the schmuck who saw his post and decided to help it rise above the background noise.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/11/2016 09:01 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 09:03 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)

This is amazing! Plus it seems to show the initial "bang" originated outside of the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/11/2016 09:05 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)



This might be my favorite post ever on NSF. #geekingOutOnDataAnalysis

Did USLR ever provide the exact coordinates for their camera?  We now know that Glenn's sensor picked up the thump at 28.574183, -80.5724.  If we know exactly where the USLR camera was, then we can see if the slight difference in arrival time for the thump intersects at the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/11/2016 09:09 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)



RDoc, do you mind if I cross-post your stacked graphs of the sonic and seismic data over on the FB @SpaceX group?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/11/2016 09:11 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)



RDoc, do you mind if I cross-post your stacked graphs of the sonic and seismic data over on the FB @SpaceX group?
Sure, anyone is free to use it as they wish.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/11/2016 09:22 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)

This is amazing! Plus it seems to show the initial "bang" originated outside of the pad.

Well, if his alignment is correct,  you'll note that the initial bang doesn't create much of a seismic signal, in which case, it doesn't tell us much about where the clang and thunk came from unless they came from the "debris hit the ground" phase with different P & S arrival times.  Which is possible since that occurs prior to the clang and thunk.

BUT, it would require recalculating the speed of sound in the ground.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 09:26 pm
This is the sound track from the video and the seismic data scaled and aligned as I personally think makes sense.  :)

This is amazing! Plus it seems to show the initial "bang" originated outside of the pad.

Well, if his alignment is correct,  you'll note that the initial bang doesn't create much of a seismic signal, in which case, it doesn't tell us much about where the clang and thunk came from unless they came from the "debris hit the ground" phase with different P & S arrival times.  Which is possible since that occurs prior to the clang and thunk.

BUT, it would require recalculating the speed of sound in the ground.

I guess you are right. Plus only one of three sensors registered this event. I believe all three sensors are identical to allow triangulation. Having only one sensor register something is strange.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/11/2016 09:32 pm
Keep in mind that assuming the speed in air and the speed in ground, while certainly different, are pretty constant over such a short period of time.

That means that the sequence of events and the interval between events is identical in both air and sound channels although they are offset from each other by an approximately constant interval IF they originate at one location.

For example, if I'm correct that the first major seismic event is the initial debris hitting the ground, which is what I mainly aligned on, note that there are seismic events that correspond to the fairing hitting the ground, exploding, and the payload exploding that all line up pretty well.

If the sound I identify as "Thump" corresponds to the seismic blip at about 3:07:11:30 on the top channel, it didn't originate at the rocket because the sound and seismic events don't align.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 09:34 pm
The other potential issue is items not being synchronized due to delays between when a channel is sampled and when it's sent. While Ethernet cannot supply a pure set of data values exactly when they happen (as a 3000 pin plug could) but the greater data rate would if necessary allow every channel to be time tagged.
Modern Ethernet provides for precision timestamping, frequency and phase synchronisation down to 500ns (or even better in a small network). Developing these capabilities was required as Ethernet has become a de-facto (=cheap!) backhaul medium in mobile networks, especially with recent LTE-A introduction. This is all way beyond what was available 5-10 years ago, not to mention technology origins.

Nevertheless Ethernet or not is a secondary consideration, primary is how SpaceX wanted to perform the whole data multiplexing (delay/resilience/...).

With event propagation measured in maybe 1000 m/sec, and structural scale of 1 m, you're looking at 1 mSec desired latency.

That is a huge huge time for electronics, where you can package frames in uSecs.

The concern with "original" Ethernet was that you had multiple devices on a coax cable, and stochastic collision resolution, and so in principle a data packet may be held indefinitely before leaving the source.  Total bandwidth back then was 10 Mb/sec, which only applied in theory if one device was talking the whole time.

This is all history, however.  Applicable to vehicles that started development 20-30 years ago.


A.  It is not history nor it is applicable to vehicle developed 20-30 years ago.  Most don't use ethernet

b.  Can't assume that F9 uses modern ethernet capabilities.  Same goes with assumptions about bandwidth

c.  And still does address that packets are always received serially.  Hence data can have holes when it is cut off. CRS-7 issue.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/11/2016 09:49 pm
To confirm the pivoting cradle is free to move, look at the technical webcast for CRS-8. Look at the internship video at 3:35 for a close up.

At 4:10, on the countdown clock for CRS-8, there is a close up. Look at the square sections behind the grabbers as they release. This is the top of the pivoting cradle. As the grabbers release the cradle falls forward while the strongback falls away.

What happens in high winds blowing the Falcon 9 away from the strongback?

The grabbers are not rigid so will allow the Falcon 9 to move away. If this movement is enough to allow the lower pivoting cradle to separate from the tank then all manner of mechanisms could occur.
1. For large gaps the snow would form behind the pad and then be crushed on the next sway.  This would form ice that is not thermally insulating. So the next sway would form more snow and then ice. A build up would occur. "Snow" can easily be 90% trapped air and compares well with good insulation. Ice is much worse. The pads pivot also. Would one end become thick with ice and create a point load?
2. Bouncing cold metals is just bad. Bouncing welds even more of a problem.
3. In a tiny gap situation the water would be condensed rapidly at the outer edges of the pad and only the dry air would get to the centre of the pad. The pad would provide insulation and wind shielding to lower the temperature behind its centre. This would lead to trapped condensation of oxygen plus repetitive loading/rubbing.

My experience is from corrosion of metals including aluminium in a sea environment. Similar situations occur with salt build up between moving items in a high sea spray environment. Same occurs with ice build up, but I make sure I never get any experience of that! Stainless tanks splitting after constant sloshing. Aluminium erosion by even the softest natural materials constantly rubbing. Crevice corrosion of stainless steel which is the opposite situation were damage is done due to oxygen starvation in narrow areas. All metals have to be treated fairly to gain their advantage. Any discontinuity in environment is always bad news.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 09:54 pm
No such mechanism was in work.  There is no play between the cradle and grabbers
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/11/2016 09:56 pm
To confirm the pivoting cradle is free to move, look at the technical webcast for CRS-8. Look at the internship video at 3:35 for a close up.

At 4:10, on the countdown clock for CRS-8, there is a close up. Look at the square sections behind the grabbers as they release. This is the top of the pivoting cradle. As the grabbers release the cradle falls forward while the strongback falls away.

What happens in high winds blowing the Falcon 9 away from the strongback?

The grabbers are not rigid so will allow the Falcon 9 to move away. If this movement is enough to allow the lower pivoting cradle to separate from the tank then all manner of mechanisms could occur.
1. For large gaps the snow would form behind the pad and then be crushed on the next sway.  This would form ice that is not thermally insulating. So the next sway would form more snow and then ice. A build up would occur. "Snow" can easily be 90% trapped air and compares well with good insulation. Ice is much worse. The pads pivot also. Would one end become thick with ice and create a point load?
2. Bouncing cold metals is just bad. Bouncing welds even more of a problem.
3. In a tiny gap situation the water would be condensed rapidly at the outer edges of the pad and only the dry air would get to the centre of the pad. The pad would provide insulation and wind shielding to lower the temperature behind its centre. This would lead to trapped condensation of oxygen plus repetitive loading/rubbing.

My experience is from corrosion of metals including aluminium in a sea environment. Similar situations occur with salt build up between moving items in a high sea spray environment. Same occurs with ice build up, but I make sure I never get any experience of that! Stainless tanks splitting after constant sloshing. Aluminium erosion by even the softest natural materials constantly rubbing. Crevice corrosion of stainless steel which is the opposite situation were damage is done due to oxygen starvation in narrow areas. All metals have to be treated fairly to gain their advantage. Any discontinuity in environment is always bad news.

First off, welcome to the forum!

Your highly informative post is most welcome, and you make some good points. Metals, especially those running up against the thin tolerances required for spaceflight, are most certainly less straightforwardly failure-proof than they may seem to those inexperienced in dealing with them.

Weather and environmental conditions are looking like they could potentially be quite the large factors in the mishap.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: volcanoGlenn on 09/11/2016 09:59 pm
Trying to register for this site. Craig, my seismic&infrasound station is 0.87 miles NNE of SLC-40 (you said NNW).

(http://uploads.tapatalk-cdn.com/20160911/69fad97ab9681f6943e99f7bff5faa8a.jpg)
Not sure if I missed this being mentioned or discussed. Is this of any value? Can the source of the thump triangulated with this info?

Edit: just found it few posts back. Searched for seismic and found nothing. Should have searched for Thompson.
Mods: feel free to remove this post

Here are the positions for Glenn Thompson's sensors:
https://www.google.com/maps/d/viewer?mid=17Tim56aFrQKtcF2KStP05hG9A3M

The one that recorded the blip before the main event is located NNW of the pad between SLC 40 and 41.

-C

Edit:  The data that I'm really interested in is the "pop" on the top channel at 13:07:11.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 10:07 pm
Welcome to the forum Glenn! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/11/2016 10:11 pm
Trying to register for this site. Craig, my seismic&infrasound station is 0.87 miles NNE of SLC-40 (you said NNW).

Glenn, welcome! And imidiately a question - why only one of three sensors would register the event you marked as U?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: martinc on 09/11/2016 10:11 pm
Hi

on the 70 frames slowdown link i notice what looks like a hole appear 3 or 4 seconds before the boom, does anyone else see this?
http://(https://s17.postimg.org/5n0e51sx7/spacex.jpg) (https://postimg.org/image/5n0e51sx7/)

Modified - no its not 3/4 seconds of course i'm slowing things down at lot, its very shortly before
and i also see a change in the 'fog' and things around it after this hole appears
yes, its unclear but the question is, is something happening here, or not..

Martin
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: craigcocca on 09/11/2016 10:12 pm
Trying to register for this site. Craig, my seismic&infrasound station is 0.87 miles NNE of SLC-40 (you said NNW).

(http://uploads.tapatalk-cdn.com/20160911/69fad97ab9681f6943e99f7bff5faa8a.jpg)
Not sure if I missed this being mentioned or discussed. Is this of any value? Can the source of the thump triangulated with this info?

Edit: just found it few posts back. Searched for seismic and found nothing. Should have searched for Thompson.
Mods: feel free to remove this post

Here are the positions for Glenn Thompson's sensors:
https://www.google.com/maps/d/viewer?mid=17Tim56aFrQKtcF2KStP05hG9A3M

The one that recorded the blip before the main event is located NNW of the pad between SLC 40 and 41.

-C

Edit:  The data that I'm really interested in is the "pop" on the top channel at 13:07:11.

Welcome Glenn.  I went back and fixed my original post to note that your infrasound sensor installation is located NNE of SLC-40 next to the Astronaut Beach House.  Just a simple typo on my part, unfortunately.

I'm going to let you take the conversation from here since you're the seismic/infrasound expert.  Welcome to the forum!

What's your take on the slight spacing between the "thump" and your channel 1 blip at 13:07:11 in post 2286 above?  Some have suggested that if all of the other significant events line up except for that one, that the "thump" can't be centered at the pad.  Is that your take on it?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacekid on 09/11/2016 10:13 pm
Long time listener, first time caller. I have read all 2100+ messages so far in this board and I haven't heard this exact theory I'm about to put forth.

I call this the "slow slump" theory. Since the static fire is the first time the full stack was fully integrated and was being fueled, I propose that there was not necessarily a manufacturing flaw but a borderline tolerance flaw, along with a borderline tolerance mating of the strongback to the stack. As the RP1 was being loaded the rocket would be creaking and would be triggering sensors within the rocket, but the difference would be there would be an accumulation of borderline tolerance flaws that would cause the rocket to slowly "slump" along the side of the rocket facing the strongback and would have lead to a minor leak of the rocket near the top of RP1 stage 2 tank only when the tank was full (around the time of the anomaly occurred). This leak was minor enough  it would not have been observed easily on camera, but the RP1 was being atomized by LOX venting from S1 and carried up to be ignited by the oxygen rich venting on S2 until there was enough fuel to be ignited.

Sensor readings long before the anomaly would look different than prior static firings of the F9. The cause of the anomaly was a long running event while everyone is looking for a fast cascade of sensor reading, but culminated in the footage we have all seen in the video. The weak part of this theory is the ignition of this FAE event, but I'm postulating that given enough RP1, and oxidizer in this environment that any rust point on the strongback could have triggered the FAE, and subsequent LOV.

I'm just a curious armchair rocket sturgeon looking for answers like everyone else.

I'm thinking this is the way to look. It looks like a fuel air explosion. For that volume to develop, it seems like it  would take some time. And the way the wind is blowing, seems likely at least one part, fuel or O2 would come from the GSE and blow towards the vehicle. Perhaps fuel was sprayed out and began mixing with O2 by the rocket. Then a spark near the rocket/GSE interface occurred causing the accident.

Need to look in detail at the video a ways before the accident to see if anything different can be seen, especially around the GSE.
Welcome to the forum! :)
Thanks! Been reading for a long time, finally registered.

I looked at the video a little bit further back before the explosion but couldn't see anything around the explosion origin like a fog.

In looking at the frame before and first explosion frame, I got the impression that the explosion originated in the strongback area.

I was wondering if someone has a chance with the first frame of the explosion, could you map it out and find the approximate center? The vehicle and strongback would distort it somewhat but the wind shouldn't have. If this has already been done, I'd appreciate where it might be in the thread.

I'm beginning to lean towards some contamination or some other event in the GSE LOX feed line or in the upper stage rocket feed line between the external connection and LOX tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Apollo-phill on 09/11/2016 10:13 pm
This is interesting read on " autoignition" with some refs to Lox/RP1

Wallace H. Boggs, "Autoignition -A Liquid Propellant Explosive Potential Limiting Phenomena" (April 1, 1976). The Space Congress®
Proceedings. Paper 6.
http://commons.erau.edu/space-congress-proceedings/proceedings-1976-13th/session-4/6
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/11/2016 10:21 pm
This is the frame before the explosion and the explosion frame and the two combined.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/11/2016 10:43 pm
Quote
Did USLR ever provide the exact coordinates for their camera?  We now know that Glenn's sensor picked up the thump at 28.574183, -80.5724.  If we know exactly where the USLR camera was, then we can see if the slight difference in arrival time for the thump intersects at the pad.

USLR camera position shown in this post:

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1576930#msg1576930

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1364818;sess=16902)

You should be able to find the coordinates on Google Earth.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: martinc on 09/11/2016 10:44 pm
i'm definately seeing something happen in the cloud/fog on the slowed down video

let me describe the events, first a 'hole' appears, which i'm not saying is a hole but that's what i'll refer to it as. it could be a hole blown in the cloud, a real hole, an artifact
you will easily see this on the slowed down vid by stepping through the youtube by hitting pause/play quickly and slowing down to 0.25 speed

next, there is the 'disruption', which happens very quickly, but not simultaneously with the appearance of the hole
its very quick and happens literally from one frame to the next, giving the appearance of a frame skip on the video
this would require an extremely high pressure force as it changes the dynamic of the cloud and is marked by the appearance of 4 dark spots

i've screen grabbed the before/after on the disruption, but you will need to see it on the video to judge its validity as these stills don't bring out the noticability of the change...

(https://s18.postimg.org/uj0b5m4t1/spacex2.jpg) (https://postimg.org/image/uj0b5m4t1/)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 10:45 pm
Hi

on the 70 frames slowdown link i notice what looks like a hole appear 3 or 4 seconds before the boom, does anyone else see this?
http://(https://s17.postimg.org/5n0e51sx7/spacex.jpg) (https://postimg.org/image/5n0e51sx7/)

Modified - no its not 3/4 seconds of course i'm slowing things down at lot, its very shortly before
and i also see a change in the 'fog' and things around it after this hole appears
yes, its unclear but the question is, is something happening here, or not..

Martin
I believe that may be the rubber bumper on the cradle being obscured on and off again by the gaseous oxygen... Anyone else?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dbavatar on 09/11/2016 11:18 pm
I haven't seen this mentioned yet, but with no smoking gun it would seem the next step would be to find the pieces that left the initial event, some at high rates of speed. The arc of the large piece that went up and over could easily be estimated, and to me it seemed like it escaped the initial S1 fire. It seemed like 2-3 other pieces were ejected at high speeds, although it's hard to tell if they're just birds.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/11/2016 11:21 pm
[
.....
The other potential issue is items not being synchronized due to delays between when a channel is sampled and when it's sent. While Ethernet cannot supply a pure set of data values exactly when they happen (as a 3000 pin plug could) but the greater data rate would if necessary allow every channel to be time tagged.

In reality I suspect quite a few of those channels are events, essentially a time tag and a channel ID as and when necessary. A 4 byte entry can hold up to 4096 channel ID's and still time tag an even to the nearest 100 miliseconds in a 24 hour period.  While I could believe some events might need recording down to a millisecond to find out if some events have happened together (giving 17 minutes of range with 20 bits of time stamp, or over 49 hours with a 32 bit time stamp to the nearest millisecond.

SpaceX may use ethernet inside the rocket for subsystem to subsystem communication.  I have no idea.  But PCM is entirely different.  You have to think simplicity.  Think of putting the 3000 channels in a 1.8Mbps stream - where you can take that stream on a RS-422 or similar channel and run it to an S-Band transmitter and have it duplicated on the ground.  The tlm is an unbroken, fixed rate stream, divided into fixed length frames each with sync word and a counter.   The frames themselves provide time information. Every (almost) bit of telemetry is at fixed preprogrammed locations so their exact (to a few microseconds) sampling time is known.  It's an interesting task designing these frames fitting in sensors with various sample rates.
Here is a link that describes PCM telemetery:
fhttp://www.storm.com/telemetry_tutorial/telemetry_tutorial.pdf (http://www.storm.com/telemetry_tutorial/telemetry_tutorial.pdf)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/11/2016 11:22 pm
Whatever the cause, it would be quite presumptive to act as if a group of a thousand or more exceptionally skilled engineers, managers, etc. - (goddamn hopefully) painfully familiar with the many lessons learned from the technical, systematic, and bureaucratic failures capable of allowing 14 astronauts to die - would be able to miss eventualities or make mistakes that would lead to failures of a launch vehicle, and do so to the extent that they were essentially caught off guard entirely, if it were not to some extent the case that spaceflight and rocketry were quite difficult endeavors.

No single sane person could deny that immense progress has been made in the reliability, technical prowess, and general efficacy of those endeavors. But acknowledging that is absolutely not the same thing as acknowledging that orbital spaceflight is something less than difficult, or that the fact that we have been engaging in it for many decades means anything when compared to actual examinations of the reliability of modern launch vehicles and thus the efficacy of modern aerospace engineering and materials science

My point is that however much you and I utterly loathe the saying that "Space is hard" (likely because those who use it seem to imply that it will be "hard" eternally), orbital spaceflight would indeed appear to be statistically more difficult than most any other comparably large engineering project. This is not in any sense to say that routinization of orbital spaceflight is impossible, but it would imply that we are not there yet, be that for technical inadequacy or something more slippery.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 11:23 pm

A substance that is a contact explosive with many organics at atmospheric pressures clearly is irrelevant to an investigation of an explosion.


correct.  Because there was no contact and no organics. 

There is no case for air liquefying on the outside of the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 11:28 pm

A substance that is a contact explosive with many organics at atmospheric pressures clearly is irrelevant to an investigation of an explosion.


correct.  Because there was no contact and no organics. 

There is no case for air liquefying on the outside of the vehicle.

Again: boldfaced assertion doesn't make it true.  You have a 23°C temperature differential to account for (about a tenth of the difference between the inside and the outside).  Your proposed "insulation" is 2,2W/m-K thermal conductivity.  You're proposing an amount equal to  seven thousandths of a millimeter of foam insulation, and claiming that it's enough to prevent a 23°C temperature differential.  Good to know that I can insulate my house with a practically invisibly small amount of insulation.

I'll reiterate: if you want to be dismissive, give an actual reason behind your argument.  Right now, your entire argument is built around, "because I say so".

As for "no organics" - even if there is no leak (which we don't know), and nothing on the strongback (which we don't know), we do know that the rocket is painted, and both silicone and organic-based paints are incompatible with LOX.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 11:30 pm

Again: boldfaced assertion doesn't make it true.  You have a 23°C temperature differential.  Your proposed "insulation" is 2,2W/m-K thermal conductivity.  You're proposing an amount equal to  seven thousandths of a millimeter of foam insulation, and claiming that it's enough to prevent a 23°C temperature differential.  Good to know that I can insulate my house with a practically invisibly small amount of insulation.

I'll reiterate: if you want to be dismissive, give an actual reason behind your argument.  Right now, your entire argument is built around, "because I say so".


I never said anything about proposed "insulation".

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 11:31 pm
I never said anything about proposed "insulation".

Then do explain what is to prevent the formation of LOX on the outside of the tank, given that the inside is significantly colder than the boiling point of oxygen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/11/2016 11:32 pm
Hi

on the 70 frames slowdown link i notice what looks like a hole appear 3 or 4 seconds before the boom, does anyone else see this?
http://(https://s17.postimg.org/5n0e51sx7/spacex.jpg) (https://postimg.org/image/5n0e51sx7/)

Modified - no its not 3/4 seconds of course i'm slowing things down at lot, its very shortly before
and i also see a change in the 'fog' and things around it after this hole appears
yes, its unclear but the question is, is something happening here, or not..

Martin
I believe that may be the rubber bumper on the cradle being obscured on and off again by the gaseous oxygen... Anyone else?

I'm gonna have to agree with you there. I looked at the original video at 1/4th speed, frame by frame, for about twenty minutes and could not find a hole appearing. I do believe that is the cradle being inconsistently obscured and revealed by the vented gaseous oxygen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 11:34 pm

Then do explain what is to prevent the formation of LOX on the outside of the tank, given that the inside is significantly colder than the boiling point of oxygen.



No, you provide the work that shows LOX IS forming on the outside.
You must know the thickness of the tank skin, the type of paint, the thickness of the paint and all other parameters.

Don't forgot that inside temp is not the temp of densified LOX since the tank is still chilling down.

Also, go back and look at previous launches and show where LOX is running down outside of the vehicle.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/11/2016 11:36 pm
i'm definately seeing something happen in the cloud/fog on the slowed down video

let me describe the events, first a 'hole' appears, which i'm not saying is a hole but that's what i'll refer to it as. it could be a hole blown in the cloud, a real hole, an artifact
you will easily see this on the slowed down vid by stepping through the youtube by hitting pause/play quickly and slowing down to 0.25 speed

next, there is the 'disruption', which happens very quickly, but not simultaneously with the appearance of the hole
its very quick and happens literally from one frame to the next, giving the appearance of a frame skip on the video
this would require an extremely high pressure force as it changes the dynamic of the cloud and is marked by the appearance of 4 dark spots

i've screen grabbed the before/after on the disruption, but you will need to see it on the video to judge its validity as these stills don't bring out the noticability of the change...

(https://s18.postimg.org/uj0b5m4t1/spacex2.jpg) (https://postimg.org/image/uj0b5m4t1/)

This does look interesting, could you timestamp and link the video(s) you found that in?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/11/2016 11:38 pm
I never said anything about proposed "insulation".

Then do explain what is to prevent the formation of LOX on the outside of the tank, given that the inside is significantly colder than the boiling point of oxygen.


No,
Again: boldfaced assertion doesn't make it true.  You have a 23°C temperature differential to account for (about a tenth of the difference between the inside and the outside). LOX.


No, you provide the work that shows LOX IS forming on the outside.

1. It's colder than the boiling point of oxygen.

And that's the entire work right there.  Either you think that there's some sort of insulation creating a significant temperature differential, or by the very definition of a boiling point, LOX will condense.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/11/2016 11:41 pm
I never said anything about proposed "insulation".

Then do explain what is to prevent the formation of LOX on the outside of the tank, given that the inside is significantly colder than the boiling point of oxygen.


No,
Again: boldfaced assertion doesn't make it true.  You have a 23°C temperature differential to account for (about a tenth of the difference between the inside and the outside). LOX.


No, you provide the work that shows LOX IS forming on the outside.
As a comment on external LOX - if there were such a layer, I'd expect it to be forming a vapor cloud where the LOX tank fill line was and not elsewhere. Having looked at closeup stills of the video for a too much time, I don't see anything like that.

I see some vapor around the vent height of the second stage and lots around the first stage, but that's about it. So, purely based on the video, I'm doubtful about LOX on the exterior of the second stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/11/2016 11:45 pm

1. It's colder than the boiling point of oxygen.

And that's the entire work right there.  Either you think that there's some sort of insulation creating a significant temperature differential, or by the very definition of a boiling point, LOX will condense.


Wrong.

Show the work that the exterior skin of the stage is below the boiling point of oxygen.

False assumption that the inside temp is the temp of densified LOX since the tank is still chilling down and hasn't reached equilibrium.   Also, the tank was not full yet.

Do you know thickness of the tank skin, the type of paint, the thickness of the paint and all other parameters?

It is your assertion, you have to provide the work.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/11/2016 11:59 pm
Hi

on the 70 frames slowdown link i notice what looks like a hole appear 3 or 4 seconds before the boom, does anyone else see this?
http://(https://s17.postimg.org/5n0e51sx7/spacex.jpg) (https://postimg.org/image/5n0e51sx7/)

Modified - no its not 3/4 seconds of course i'm slowing things down at lot, its very shortly before
and i also see a change in the 'fog' and things around it after this hole appears
yes, its unclear but the question is, is something happening here, or not..

Martin
I believe that may be the rubber bumper on the cradle being obscured on and off again by the gaseous oxygen... Anyone else?

I'm gonna have to agree with you there. I looked at the original video at 1/4th speed, frame by frame, for about twenty minutes and could not find a hole appearing. I do believe that is the cradle being inconsistently obscured and revealed by the vented gaseous oxygen.
Don't give up looking, we can always use new eyes and resources!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 12:09 am
He doesn't have to show his work because liquid air is not the issue.

Just move on.

To where? If it is solved then tell us. I hate wasting my time. Otherwise what areas do you suggest we explore?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/12/2016 12:09 am
Hi

on the 70 frames slowdown link i notice what looks like a hole appear 3 or 4 seconds before the boom, does anyone else see this?
http://(https://s17.postimg.org/5n0e51sx7/spacex.jpg) (https://postimg.org/image/5n0e51sx7/)

Modified - no its not 3/4 seconds of course i'm slowing things down at lot, its very shortly before
and i also see a change in the 'fog' and things around it after this hole appears
yes, its unclear but the question is, is something happening here, or not..

Martin
I believe that may be the rubber bumper on the cradle being obscured on and off again by the gaseous oxygen... Anyone else?

I'm gonna have to agree with you there. I looked at the original video at 1/4th speed, frame by frame, for about twenty minutes and could not find a hole appearing. I do believe that is the cradle being inconsistently obscured and revealed by the vented gaseous oxygen.
Don't give up looking, we can always use new eyes and resources!

Never fear, I'll most certainly continue observing so long as I have eyes that work reasonably well. :) Should have a good 50 years at least, barring major medical advances ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/12/2016 12:10 am
(This post was badly constructed, and we have no idea who it was responding to due to bad quoting. Please quote correctly. - Andy, Mod).


Then you're arguing that there is an effective insulation of relevance, something that you just denied.

The wall thickness is 4,7mm, paint unknown but let's just say 0,5mm, and let's use the previously mentioned ice thickness in this thread of 0,5mm.  Thermal conductivity is 205W/m-K for aluminum, about 0,4 for paints, and 2,2 for ice.  Net thermal conductivity is 1/(0,0047*205) + 1/(0,0005*0,4) + 1/(0,0005*2,2) = 6163 W/m-k.  Let's go with 70°K tank wall and 300°K external temp.  230K net temperature differential, boundary layer is 185°K, 115° boundary differential.  Heat flow is 709kW/m^2.

To go further than that requires a CFD run, or at least newton's law of cooling.  But when you have ~800W/m^2 as your baseline,. that's enough to liquefy  709kJ/s-m^2  / (1.01 Jk/kg-K - 230K) = 3,1kg/m^2-s of air (not counting enthalpy of formation, but it's well smaller than the energy to change the temperature in the case of air).  Tank diameter 3,66m, circumference *3,14=11,5m, oxygen tank length = ~6m, ~69m^2 = 211kg/s.  LOX burns with hydrocarbons at a slightly higher mass ratio of LOX to hydrocarbons as a general rule, so it's roughly equivalent to the combustion potential of dumping nearly 200 kilograms of fuel-air mixture of gasoline per second on the rocket.  Scale it down by whatever factors you want for assumed higher tank temperatures or LOX temperature stratification or whatnot, it's still a *lot* of potential energy.

You know very well that the thermal inertia of aluminum is tiny.

(note: I'm using LOX and air somewhat interchangeably here... technically N2 can liquefy as well, but the temperature differential strongly favors LOX predominating the mixture - nitrogen will boil off first, and any elevated-temperature skin for any reason may not liquefy N2 at all)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vaporcobra on 09/12/2016 12:15 am
Do try to keep the discussion civil and amicable, everybody. No need for terse or rude discourse.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 12:22 am

You know very well that the thermal inertia of aluminum is tiny.


Then why do they have chill down flows before fast fill.  What is venting during fill?  Boil off and that goes with your bad assumption of 70K



I have seen video of the tanks close up and saw no liquid on the exterior
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/12/2016 12:27 am
I've watch this clip all day, and can't see where I'm going wrong...
Frame #1 is T0 (no flame) (00:01:11:721)
Something appears on the right side at frame #3, which is very early in the event.  I tracked it out as far as I could and circled the object.  Some frames required filtering, which could just lead to image compression effects, but the object appears to be in the correct positions.
It appears to be coming towards the camera, and slowing down. (based on illumination and apparent size)
The solid two dots are projected guesses where the object should have been in the first two frames to end up where it is in frame #3.
In frame #2, the fire is to bright to spot it.
In frame #1, it's in what I would consider to be an interesting location...

Edit: Added video with no overlay.  Added Time
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 12:35 am
If people are going to point to stuff in video frames, please, please say what the time code of the frame is. I'd suggest using either the first frame with the explosion in it as the start point, or the start of the video itself.

min:sec:frame
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/12/2016 12:49 am
If people are going to point to stuff in video frames, please, please say what the time code of the frame is. I'd suggest using either the first frame with the explosion in it as the start point, or the start of the video itself.

min:sec:frame

Here is an anigif of the 5 frames leading up to the fast fire. They are at the following timestamps in the original USLR video:

1   00:01:11:671
2   00:01:11:688
3   00:01:11:704
4   00:01:11:721
5   00:01:11:738

Admittedly there are atmospheric artefacts to contend with, but it does seem to me that the cradle begins to tilt clockwise in frames 3 and 4.
Does anyone else see the same thing?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meberbs on 09/12/2016 01:42 am
...
Let's go with 70°K tank wall and 300°K external temp.  230K net temperature differential, boundary layer is 185°K, 115° boundary differential.
...

When you say boundary layer, I interpret that to mean air-tank wall boundary. Therefore by the second law of thermodynamics, no LOX outside the tank.

I realize that your split the difference method isn't particularly accurate, since you need to model the fluid flow, but it is a reasonable guess at the steady state that would result from the convection currents generated as air near the tank cools.

Anyway, modelling this is hard (CFD), but the experiment "what happens when a rocket tank filled with LOX is exposed to air" has been performed and we have people like Jim here with first hand knowledge of the results - no LOX forms outside the tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Andy USA on 09/12/2016 01:48 am
A reminder everyone needs to be civil and to correctly quote posts your responding to or they will be removed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: x15_fan on 09/12/2016 02:18 am
Ok, I've read through this thread over the last week or so and might have missed/forgotten some detail so forgive me. I was thinking as the RP-1 loading was complete by this point but previously under pressure to fill the tank. If there was some plumbing leak that sprayed/dripped RP-1 onto adjacent gear in the TEL, and that gear was warm, could it cause the RP-1 to slowly vaporize over time. This could happen until mixture was right and ignition source was found? Is there anything in the TEL that just gets warm to allow heating of the RP-1 in those 6 minutes? Seems like this is basic but don’t recall, please delete if duplicate.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomTX on 09/12/2016 02:27 am
Ok, I've read through this thread over the last week or so and might have missed/forgotten some detail so forgive me. I was thinking as the RP-1 loading was complete by this point but previously under pressure to fill the tank. If there was some plumbing leak that sprayed/dripped RP-1 onto adjacent gear in the TEL, and that gear was warm, could it cause the RP-1 to slowly vaporize over time. This could happen until mixture was right and ignition source was found? Is there anything in the TEL that just gets warm to allow heating of the RP-1 in those 6 minutes? Seems like this is basic but don’t recall, please delete if duplicate.

I find it implausible that ~10 kg of kerosene fully evaporated* in 6 minutes. It's just not that volatile.

I find it even more implausible that kerosene starting at -7C evaporated in 6 minutes without any visible sign.

Additionally, the initial deflagration looks quite wrong for an uncontrolled kerosene ignition. Too clean, too bright, no smoke/soot/partial burn anywhere.


*Or 100kg evaporated 10% and nobody saw the rest dripping/running down the TE. Or somewhere in between.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jyoung8607 on 09/12/2016 03:24 am
Additionally, the initial deflagration looks quite wrong for an uncontrolled kerosene ignition. Too clean, too bright, no smoke/soot/partial burn anywhere.

How about hydrogen? Hydrogen burns clean.

I'm fully willing to be told I'm nuts, but... it was a very humid day and frost would start building up quickly. What would happen if that frost managed to form an accidental circuit between some points (undefined for purposes of this question)? Could electrolysis break some of that frost into hydrogen and oxygen? And if that happened, could that rapidly building and layering frost start having a bunch of entrained hydrogen and oxygen bubbles, trapping much of it near its origin? And those bubbles might start to combine as gases form and expand within the ice layers.

My last physics class was a long time ago, so it's strongly possible I've made a basic mistake here. Just curious. I have no opinion on the ignition source, just trying to figure out the fuel.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/12/2016 03:55 am
Additionally, the initial deflagration looks quite wrong for an uncontrolled kerosene ignition. Too clean, too bright, no smoke/soot/partial burn anywhere.

How about hydrogen? Hydrogen burns clean.

I'm fully willing to be told I'm nuts, but... it was a very humid day and frost would start building up quickly. What would happen if that frost managed to form an accidental short-circuit between some points (undefined for purposes of this question)? Could electrolysis break some of that frost into hydrogen and oxygen? And if that happened, could that rapidly building and layering frost start having a bunch of entrained hydrogen and oxygen bubbles, trapping much of it near its origin? And those bubbles might start to combine as gases form and expand within the ice layers.

My last physics class was a long time ago, so it's strongly possible I've made a basic mistake here. Just curious. I have no opinion on the ignition source, just trying to figure out the fuel.
Ice from airborne water vapor is normally pretty pure water. Pure enough that it would take an enormous amount of power to generate enough hydrogen to make the explosion. 

Now the air near the ocean is a fair bit saltier. Salty enough for more efficient electrolysis?

In either case I think a big voltage dip would show in the power readings somewhere for there to be enough hydrogen, generated that fast (at most several minutes).

Interesting theory, and a new one I think, but I'd rate it pretty unlikely.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/12/2016 04:00 am
Additionally, the initial deflagration looks quite wrong for an uncontrolled kerosene ignition. Too clean, too bright, no smoke/soot/partial burn anywhere.

How about hydrogen? Hydrogen burns clean.

I'm fully willing to be told I'm nuts, but... it was a very humid day and frost would start building up quickly. What would happen if that frost managed to form an accidental circuit between some points (undefined for purposes of this question)? Could electrolysis break some of that frost into hydrogen and oxygen? And if that happened, could that rapidly building and layering frost start having a bunch of entrained hydrogen and oxygen bubbles, trapping much of it near its origin? And those bubbles might start to combine as gases form and expand within the ice layers.

My last physics class was a long time ago, so it's strongly possible I've made a basic mistake here. Just curious. I have no opinion on the ignition source, just trying to figure out the fuel.

The ice would just melt, not break apart into oxygen and hydrogen.  And even if it did somehow break apart into oxygen and hydrogen, the hydrogen would float up and away quite quickly.  Ever seen how fast a helium balloon floats up and away?  Hydrogen would float up and away even faster.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/12/2016 04:02 am
I've watch this clip all day, and can't see where I'm going wrong...
Frame #1 is T0 (no flame) (00:01:11:721)
Something appears on the right side at frame #3, which is very early in the event.  I tracked it out as far as I could and circled the object.  Some frames required filtering, which could just lead to image compression effects, but the object appears to be in the correct positions.
It appears to be coming towards the camera, and slowing down. (based on illumination and apparent size)
The solid two dots are projected guesses where the object should have been in the first two frames to end up where it is in frame #3.
In frame #2, the fire is to bright to spot it.
In frame #1, it's in what I would consider to be an interesting location...

Edit: Added video with no overlay.  Added Time

i think you're seeing two different objects. i think the darker object later on is a bird. i think you can see one or two birds fly diagnoly up and to the right from the lower left side of the rocket. might have been startled by the sound and took off from ground level. i think thats what i saw.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gliderflyer on 09/12/2016 04:24 am
With regards to the conversation about LOX condensing on the outside of the vehicle, I agree with Jim. He has a lot of experience with launch vehicles, so I generally take his statements as fact. Additionally, I have some experience working with both LOX and LN2. On several occasions I have worked with a steel sphere of LN2 that never formed liquid air on the outside, only snow. However, engineering is done with numbers not opinions, so I fired up Solidworks and made a model of the Falcon 9 tank skin.

I don't know the type or aluminum or the thickness, so for a first pass I used 6061 and Rei's thickness of 4.7mm, which seems to fit with the tank pressures I have heard of. An important distinction is that snow forms on the tanks, not ice. I found a thermal conductivity of 0.2 W/(m*k) for snow online (let me know if anyone finds a better value). In my experience, the snow layer is usually around .25" thick, but I used 1/8" to be conservative. I set the inside tank temperature to 70 K, and a convection load of 15 W/(m^2*K) at 300K for a ballpark for air. I left out the paint layer for simplicity.

From the attached pictures, you can see that the outer layer of snow is 114 K, which is too warm to condense LOX. This was just a quick and dirty sim that isn't perfect, but I think it is highly unlikely that air would condense on the outside of the tank. The snow will form first and prevent the air from liquefying.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Fractality on 09/12/2016 04:43 am
What would happen if that frost managed to form an accidental short-circuit between some points (undefined for purposes of this question)? Could electrolysis break some of that frost into hydrogen and oxygen? And if that happened, could that rapidly building and layering frost start having a bunch of entrained hydrogen and oxygen bubbles, trapping much of it near its origin? And those bubbles might start to combine as gases form and expand within the ice layers.

Frost doesn't conduct electricity well, so unlikely.  It's more interesting as a dielectric as far as catastrophic deflagrations are concerned .
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jyoung8607 on 09/12/2016 04:45 am
And even if it did somehow break apart into oxygen and hydrogen, the hydrogen would float up and away quite quickly.  Ever seen how fast a helium balloon floats up and away?  Hydrogen would float up and away even faster.
Sure, if it were immediately free to do so, but that's why I was thinking about trapped bubbles. And yes, hydrogen will find its way out of just about any container eventually, but on a much longer timescale than we're looking at.

I'm not married to this theory, but perhaps I should frame it a different way before I put it to bed:

We're looking for a fuel consistent with the first external bang. Hydrogen would be one candidate, but it's not native to the rocket. How could hydrogen get there? You can accidentally make it with electricity (which is definitely available) and water (which will invite itself to the party as frost, even if it melts later). Presence of salt to facilitate electrolysis is highly plausible near the ocean. We're currently struggling to identify how a FAE event got set up without a trace on the video we have, and electrolysis would be one way to invisibly build up a stock of invisible fuel.

That leaves questions: How much hydrogen would it take to generate the first bang? Is there any way that much hydrogen could have been trapped near the rocket somehow? That's when I thought of ice. After that, how much energy would you have to pour into electrolysis to get that much hydrogen? How long before that was the rocket cold enough to form frost? I don't know the answers to those.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/12/2016 05:02 am
And even if it did somehow break apart into oxygen and hydrogen, the hydrogen would float up and away quite quickly.  Ever seen how fast a helium balloon floats up and away?  Hydrogen would float up and away even faster.
Sure, if it were immediately free to do so, but that's why I was thinking about trapped bubbles. And yes, hydrogen will find its way out of just about any container eventually, but on a much longer timescale than we're looking at.

I'm not married to this theory, but perhaps I should frame it a different way before I put it to bed:

We're looking for a fuel consistent with the first external bang. Hydrogen would be one candidate, but it's not native to the rocket. How could hydrogen get there? You can accidentally make it with electricity (which is definitely available) and water (which will invite itself to the party as frost, even if it melts later). Presence of salt to facilitate electrolysis is highly plausible near the ocean. We're currently struggling to identify how a FAE event got set up without a trace on the video we have, and electrolysis would be one way to invisibly build up a stock of invisible fuel.

That leaves questions: How much hydrogen would it take to generate the first bang? Is there any way that much hydrogen could have been trapped near the rocket somehow? That's when I thought of ice. After that, how much energy would you have to pour into electrolysis to get that much hydrogen? How long before that was the rocket cold enough to form frost? I don't know the answers to those.

Frost doesn't form bubbles.  It forms crystals like snowflakes.  Like a whole bunch of interconnected snowflakes.  There are air gaps between the crystals, but the crystals don't form sheets, they form spires and branches.  The air and any other gas is free to move around between the crystals.

Anway, if you somehow had so much electricity flowing through frost to make hydrogen, it would melt the frost in that region.  Even if it had somehow formed bubbles, the bubbles would melt.

And even if somehow you had electricity accidentally flowing through frost somehow and forming hydrogen, the hydrogen production would be confined to a limited area around one electrode.  It wouldn't produce hydrogen over a wide area of frost where it could be trapped.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/12/2016 05:49 am
And even if it did somehow break apart into oxygen and hydrogen, the hydrogen would float up and away quite quickly.  Ever seen how fast a helium balloon floats up and away?  Hydrogen would float up and away even faster.
Sure, if it were immediately free to do so, but that's why I was thinking about trapped bubbles. And yes, hydrogen will find its way out of just about any container eventually, but on a much longer timescale than we're looking at.

I'm not married to this theory, but perhaps I should frame it a different way before I put it to bed:

We're looking for a fuel consistent with the first external bang. Hydrogen would be one candidate, but it's not native to the rocket. How could hydrogen get there? You can accidentally make it with electricity (which is definitely available) and water (which will invite itself to the party as frost, even if it melts later). Presence of salt to facilitate electrolysis is highly plausible near the ocean. We're currently struggling to identify how a FAE event got set up without a trace on the video we have, and electrolysis would be one way to invisibly build up a stock of invisible fuel.

That leaves questions: How much hydrogen would it take to generate the first bang? Is there any way that much hydrogen could have been trapped near the rocket somehow? That's when I thought of ice. After that, how much energy would you have to pour into electrolysis to get that much hydrogen? How long before that was the rocket cold enough to form frost? I don't know the answers to those.

I think, that you have not witnessed hydrogen explosions with oxygen. They do not resemble those yellow long burns, that we saw in this video, in any ways. Hydrogen, when mixed properly with oxygen, delivers very short and rapid bang with only small part of the core flame momentarily visible. Hydrogen burns with most of it's flame being invisible. And if someone will say Hindenburg, in this context, than visible flames there were caused by the skin, not the hydrogen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacefan80 on 09/12/2016 05:53 am

A substance that is a contact explosive with many organics at atmospheric pressures clearly is irrelevant to an investigation of an explosion.


correct.  Because there was no contact and no organics. 

There is no case for air liquefying on the outside of the vehicle.

Not supposed to be any organics in that area... but what about... bird poop.  The rocket had been exposed to the environment for a while.  In the small chance that LOx formed on the outside, and found some bird deposits...

I can't believe I just registered to post 'bird poop'.   ???
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ChrisWilson68 on 09/12/2016 06:13 am
Welcome to the forum!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: melee on 09/12/2016 06:42 am
Anyway, modelling this is hard (CFD), but the experiment "what happens when a rocket tank filled with LOX is exposed to air" has been performed and we have people like Jim here with first hand knowledge of the results - no LOX forms outside the tank.

Formation of liquid air has been reported at LN2 temperatures (https://www.freelists.org/post/arocket/Keeping-moisture-out-of-cryogenic-valves,7) (which subcooled LOX will certainly reach). Apparently this happens if an air-facing surface cools quickly enough that frost doesn't have enough time to form before it's washed away by liquid air. This may also be climate-dependent. I could see this happening at, say, a LOX valve, pipe, or inlet in some weather where it wouldn't in other conditions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kolkmvd on 09/12/2016 07:36 am
This is the frame before the explosion and the explosion frame and the two combined.

Regarding this picture, I can't find it upthread, but would it be possible somehow to discriminate between the saturation caused by the FAE itself and the saturation on the rocket / TE body? I feel the saturated part on the payload shroud and the lower S1, might be because of reflection, not of the actual FAE. Maybe by looking at the consecutive frames in the "aftermath" of the initial FAE. I tried to do it myself, but I failed to see a clear distinction between the two. However maybe some of the other brilliant mind on the forum can see ways to do this.

I think especially in moist conditions, the first flash may look larger than it was.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Katana on 09/12/2016 07:53 am
Anyway, modelling this is hard (CFD), but the experiment "what happens when a rocket tank filled with LOX is exposed to air" has been performed and we have people like Jim here with first hand knowledge of the results - no LOX forms outside the tank.

Formation of liquid air has been reported at LN2 temperatures (https://www.freelists.org/post/arocket/Keeping-moisture-out-of-cryogenic-valves,7) (which subcooled LOX will certainly reach). Apparently this happens if an air-facing surface cools quickly enough that frost doesn't have enough time to form before it's washed away by liquid air. This may also be climate-dependent. I could see this happening at, say, a LOX valve, pipe, or inlet in some weather where it wouldn't in other conditions.

Oxygen in air gaps of frost may liquify and form an oxygen rich slurry, even invisible inside frost.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 07:54 am
The snow will form first and prevent the air from liquefying.

In a perfect model, and a normal tank, there is absolutely no way to liquefy air.

But this is not the case with this tank. Take a simple example a hot metal insulated mug of tea. Wrap it in a blanket. The surface temperature on the outside of the mug rises. Take the blanket off and the normally cold mug wall will burn the skin.

The same happens for a tank but reversed. If a thick insulator is put on the outside of a tank the surface skin falls rapidly towards the tank inner temperature. The finite size of the insulator would mean there would be a distribution due to conduction through the skin. Forming only a central very cold spot.

Obviously this would not matter in a fixed state. But then introduce movement and intermittent gaps. The very cold point would be repetitively exposed to the atmosphere. The transient atmosphere could be a plume of dry vented oxygen. It could be a dry air flow from previously skin cooled air that has already lost its water. Air that has travelled across previously cleaned/compacted tank surface.

As an aside I disagree with the values used for thermal modelling. These are not conservative worst case values for ice. In reality snow is a wonderful insulator, but ice is a poor one. Ice is 2.22W/mK and rising as it gets colder than the freezing point. However, snow can be better than commercial structural insulation. The type of surface is all down to the method used to form the layer and the weather conditions. Windy weather compared to still weather will form different layers. Rainy weather is something else.

Then there are the "units" fixed to the outside of the tank permanently. These form an insulating layer also. The content of the gas inside those areas is unknown. But if it was dry purging air that could liquefy oxygen. I do not consider these as they are known designed items. However, they are discontinuities in the surface of the tank that makes it far from the situation of a basic thermal layer model of a tank. The whole tank did not explode instantly. The fault was very localised. Therefore no general linear 1D model will prove anything.

In this cold damp country we are obsessed with thermal insulation. Yet the practicalities are never addressed properly at the corners. We insulate the cavity of the walls and above the ceilings but ignore the inner wall skin projecting up into the cold roof space. It is always the edge or corner cases, that are beyond the linear models, that cause the problems.

So I am not looking for visible flows of LOX. I am looking at confined hidden insulated points of concentrated atmosphere where damage can occur and linear models do not apply. When I strike a match I do not strike the whole surface of the match head, instead it is concentrated point contacts on sand paper particles that cause the flame front to ignite the rest.

The only observable candidate, in the observable area, for unmodelled complex behaviour is the lower pads of the pivoting cradle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Katana on 09/12/2016 08:10 am
Yes, oxygen under snow.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pmonta on 09/12/2016 08:21 am
I'm wondering if cork insulation can be a fuel source if somehow it becomes saturated with LOX.  Is the cork at all permeable to gaseous oxygen? Might the boundary between cork and aluminum tank be cold enough to support the formation of a thin layer of LOX?  Then an ignition source, such as a spark, would have to somehow find that vulnerable patch.

On the other hand, I gather many vehicles use cork, so it must be possible to do so safely.  Just a thought.

Edit: after searching this thread more carefully, this has already been asked, and one reply stated that there is no cork on the second stage.  Perhaps the nearest source of carbon would be the composite interstage, then.

Edit 2: are any of the TEL S2 LOX lines insulated with cork?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chasm on 09/12/2016 08:27 am
How about a reversal of the insulation calculations?

What is the least amount of insulation that is needed to prevent the condensation of LOX out of air? (For both ice and snow case.) Worst case of course with the tank fully cooled down to densified LOX temperatures.



Video analysis.
One of the traps is GIGA. (garbage in garbage out) Because of the large distance and required long lens quality suffers.
Then the video went through at least 2, maybe 3 additional conversions. (camera file -> intermediate format(?) -> editor, saved for upload -> youtube conversion for distribution)

As far as I can tell everyone works with the YT files, nobody talking publicly has access to the camera files. Thus the fights about compression artifacts. Are the camera files better? Maybe not, but they are the best version available. They also remove doubts about cuts made in the YT version.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/12/2016 08:42 am
I can't believe I just registered to post 'bird poop'.   ???

Arno Penzias and Robert Wilson elegantly avoided mentioning such things by referring to a "white dielectric" instead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Quindar on 09/12/2016 09:37 am
To me the initial event resembles an impact initiation it is a small sharply focused event leading to the larger event with a slight delay.  Possibly something under pressure letting go producing a fragment that impacts with enough velocity to produce both a breach and the ignition source.  The event looks just like what you see on gun cameras when they shoot a vehicle containing volatile liquid that bright flash of the impact followed by the fireball.  Not suggesting a magic bullet but more like a part moving with some great volatility impacting something vulnerable and causing a very bad day and a lot of head scratching.  No more far fetched a theory than any other I have seen so far.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kolkmvd on 09/12/2016 10:21 am
Regarding LOX build-up vs "something else": in the first frame, a fragment is seen flying "to the right", which seems to be moving quite "fast". For me, the fragment seems expelled at the T=0 initial event. Would a LOX-fueled boom do that? At least the LOX must then have been confined in some box or thing that would 'blow up' or at least could create the power to expel parts.

Moreover, if indeed the fragment would be expelled at T=0, it would be worthwile finding it back. Also, while it is seen moving to the right, it could also be first reflected off the hull of the rocket. Or it could be there were more fragments, some moving "to the left", impacting the vehicle.

Edit: typo
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/12/2016 12:04 pm
Another imaging tidbit derived from something called Lucky Imaging.

The area I've circled seems to be a bit brighter than the general background behind the rocket.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/12/2016 12:16 pm
Hi

on the 70 frames slowdown link i notice what looks like a hole appear 3 or 4 seconds before the boom, does anyone else see this?
http://(https://s17.postimg.org/5n0e51sx7/spacex.jpg) (https://postimg.org/image/5n0e51sx7/)

Modified - no its not 3/4 seconds of course i'm slowing things down at lot, its very shortly before
and i also see a change in the 'fog' and things around it after this hole appears
yes, its unclear but the question is, is something happening here, or not..

Martin
I believe that may be the rubber bumper on the cradle being obscured on and off again by the gaseous oxygen... Anyone else?

Just a note on interpreting the images on that 70 frame turbulence removal.

There are EIGHT images per frame.

The bottom four are the range maxed differences between the frame above and the next frame.

The top left is the original.

The next to the right is the turbulence removal.

The next to the right is the turbulence removal with a slight deconvolution sharpening.

The right most one is the original with an overly aggressive deconvolution.  This one should not be used for interpretation purposes.  It was a test, and is too aggressive.  It's creating lots of unreal artifacts.

The two middle frames are probably the best for attempting to observe changes.

A further note, on the difference frames, a single large difference would have resulted in a single bright spot swamping out all the other differences.  All the difference frames have no single bright spot and seem to be indicative of various noise elements in the images and reconstructions.  The left most difference frames are illustrative of this in that the atmospheric distortions create exemplary dominant bright areas.  If there's a motion event associated with this, it's either small and subtle, or earlier in time than this 70 frame sample.  If it's small and subtle, the human eye may still find it, but be cautious.  There's lots of stuff happening in the image processing steps from camera to the time your eye looks at it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/12/2016 12:56 pm
Another imaging tidbit derived from something called Lucky Imaging.

The area I've circled seems to be a bit brighter than the general background behind the rocket.

I've just had a spooky thought. What if the "source of heat" was not local ... but 150 million km away, the Sun? Could the morning Sun reflect of various elements of the TEL and focus on a single spot? That bright area we see could be the Sun shining through a buildup of gaseous oxygen between the second stage and TEL. All we need now is a source of fuel, most likely from the TEL but perhaps also from the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/12/2016 01:00 pm
Attached is an image that shows where I think folks should concentrate if they believe that a visible event preceded the main show.

On the left is a compound image of the 70 turbulence stabilized frames, astrophotography technique.  In the middle is the difference between that image and the single last pre-event turbulence stabilized image.  On the right are the areas flagged, in yellow, where in my opinion, there are regions of interest.

Basically, the brighter the area in the difference map, the more it deviates from the normal.

We have a 1,200 frame turbulence removal in process, about 20 seconds worth, may be available tomorrow I'm told.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 01:07 pm
I'm wondering if cork insulation can be a fuel source if somehow it becomes saturated with LOX.  Is the cork at all permeable to gaseous oxygen? Might the boundary between cork and aluminum tank be cold enough to support the formation of a thin layer of LOX?  Then an ignition source, such as a spark, would have to somehow find that vulnerable patch.

On the other hand, I gather many vehicles use cork, so it must be possible to do so safely.  Just a thought.

Edit: after searching this thread more carefully, this has already been asked, and one reply stated that there is no cork on the second stage.  Perhaps the nearest source of carbon would be the composite interstage, then.

Edit 2: are any of the TEL S2 LOX lines insulated with cork?


No cork on stage 2
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/12/2016 01:12 pm
Anyway, modelling this is hard (CFD), but the experiment "what happens when a rocket tank filled with LOX is exposed to air" has been performed and we have people like Jim here with first hand knowledge of the results - no LOX forms outside the tank.

Formation of liquid air has been reported at LN2 temperatures (https://www.freelists.org/post/arocket/Keeping-moisture-out-of-cryogenic-valves,7) (which subcooled LOX will certainly reach). Apparently this happens if an air-facing surface cools quickly enough that frost doesn't have enough time to form before it's washed away by liquid air. This may also be climate-dependent. I could see this happening at, say, a LOX valve, pipe, or inlet in some weather where it wouldn't in other conditions.

From the above reference, there is a very interesting quote:
Quote
The reason why liquid-hydrogen tanks don't normally form a frost layer (and therefore need deliberately-provided insulation) is that the dripping liquid air usually washes the frost off before it can get established. Apparently you *can* get a frost layer on them if the initial conditions are just right. Maybe you're running into a milder version of the same thing, with the tank bottom sometimes getting too cold too fast and the frost layer not getting well started before the liquid air starts to show up.

So we know that at normal LOX temperatures (90K), you get only frost.   At LN2 (77K) temperatures, you get mostly frost, but sometimes LOX.  At normal LH2 temperatures (20K), you normally get LOX condensing, not frost, but you can sometimes get frost.

So what happens at 66K?  This looks mighty condition dependent, and as far as I know has never been formally studied.  You could argue (as Jim does) that the tank has to cool through 90K to get to 66K, and hence a frost layer will form first, and prevent LOX formation.   But fast fill means the sides are not in this state for long.  I'd take a very close look at this if I was on the investigation board.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 01:14 pm

The only observable candidate, in the observable area, for unmodelled complex behaviour is the lower pads of the pivoting cradle.

And nothing is happening there.  There is no movement between the pads and the vehicle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 01:16 pm
  But fast fill means the sides are not in this state for long.  I'd take a very close look at this if I was on the investigation board.

Look at past missions.  Is there liquid on the outside of the stages?

And if there was LOX forming one the vehicle, it isn't going to mix with anything on the TEL. It would stream down onto the fuel tank portion of the vehicle and evaporate.    It isn't going to contribute any more O2 to the environment than the GOX venting from the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 01:24 pm
  Perhaps the nearest source of carbon would be the composite interstage, then.


Too low for the explosion and it would evaporate before getting there
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 02:01 pm
No such mechanism was in work.  There is no play between the cradle and grabbers

I have taken your instructions and moved on. Assuming, also, your claim of no "play" in the cradle.

I will stick to the final cause which is the lower nearest pad on the pivoting cradle damaging the tank.
I will also stick to the initial cause which is the wind.
It is a purely mechanical scenario. All directions are with respect the USLaunchreport video

From the two pictures in post 1783 there seems to be a few pieces missing from the strongback
they are all missing from the nearest side. (far side in pictures) These include the horizontal beam
that attaches to the Falcon 9 nearside turnbuckle tops. Also a diagonal beam and the lower support
for the grabber arm and its diagonal.

So beams disappear yet a cat walk metal is left a little lacy. Two large diameter pipes remain.
Also what is described as the A/C filter unit is still basically recognisable. What was so
special about the beams?

I had initially assumed that the weight of the satellite had broken this section as it fell forward.
The first sighting after the blast has the whole section is already stable and fallen forward but still
holding on valiantly to the satellite.

The turnbuckle section is unsymmetrical with a clockwise (from above when upright) diagonals rising.
Now assume the wind gusted. The force on the fairing would pull the Falcon 9 away from the strongback.
This would put tension on the vertical turnbuckles away from the Falcon 9.

My assumption is that the nearest windward (right) side one snapped.

The wind is still blowing and the strength of the Falcon 9 limits the downwind direction motion.
Eventually it all starts to return to vertical as the gust dies. But there is now a missing turnbuckle.
The Falcon 9 holds up the strongback as it passes vertical. The grabbers work in reverse.
However, the nearest corner starts to dip ever so slightly putting all the weight on the Falcon 9 side nearest turnbuckles.
This breaks the horizontal and diagonal beams holding the nearside tops of the turnbuckle pair.

The Falcon 9 is now holding all the weight of the nearside of the top of the strongback.

The centre of weight is far to the windward direction. So the lower part of the pivoting cradle
puts horizontal force on the lower pivoting cradle pad. Because of the twist of the diagonal
turnbuckles the whole weight is on the nearside pad only.

The tank is ruptured. The blast occurs. The second stage disappears.

The video shows the top of the strongback moving to windward as the tank support
for the lower pad disappears in the explosion.

There is nothing to hold the strongback up, as it is now carrying the whole satellite.
The twist continues and the weight of the satellite (which is off centre) falls on the
nearside grabber which breaks off the lower supports.

It explains everything except the immediate ignition. It should have filled the air with
LOX as the rupture would be in the base of the tank. It is also the top of the RP1 tank.

Maybe it was leaking during the last second. Was that small extra plume at that level, the LOX
coming from a small rupture or crack. Was it instead falling into the lower tank displacing the RP1.
Finally, what struck the match? Was it just ripping fresh aluminium in oxygen.

Was the lack of visible prior movement simply due to the strength and mass of the Falcon 9 full of fuel.

So the difference to the other scenario is there was no bumping of the pad to cause
the rupture, just a large single force due to the strongback failing. The LOX was from the inside
but the initial fire was still the aluminium alloy.

However it is not a complicated scenario. So it does not fit the description.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacekid on 09/12/2016 02:23 pm
Regarding LOX build-up vs "something else": in the first frame, a fragment is seen flying "to the right", which seems to be moving quite "fast". For me, the fragment seems expelled at the T=0 initial event. Would a LOX-fueled boom do that? At least the LOX must then have been confined in some box or thing that would 'blow up' or at least could create the power to expel parts.

Moreover, if indeed the fragment would be expelled at T=0, it would be worthwile finding it back. Also, while it is seen moving to the right, it could also be first reflected off the hull of the rocket. Or it could be there were more fragments, some moving "to the left", impacting the vehicle.
I would expect that the initial fragment blown away from the initial explosion is located around the pad area. It probably got enveloped and mostly destroyed by the resultant explosion, but a survey of the GSE around the upper stage for hardware missing might identify it (assuming it came from the GSE which I think it did).

I would expect that SpaceX has or will be identifying and cataloging all items at the pad similar to a crime scene. Not only what's there is important but what should be there but isn't is also important.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 02:29 pm
Pad did not damage tank.
No turnbuckle snapped before the vehicle exploded.
Strong back did not fail before the vehicle exploded

The strong back is much, much more robust than the rocket.  It is there to protect the vehicle and provide more stiffness to the vehicle.  Vehicle movement is not going to damage the strong back.  The strong back also lifts the vehicle and cantilevered payload vertical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/12/2016 02:34 pm
I would expect that the initial fragment blown away from the initial explosion is located around the pad area. It probably got enveloped and mostly destroyed by the resultant explosion, but a survey of the GSE around the upper stage for hardware missing might identify it (assuming it came from the GSE which I think it did).

Mangled, roughed up, bent, torn, exposed to extreme heat, yes. But if landed outside of the raging RP-1 fire, it would not have been "destroyed". Beyond what have been consumed/melted in the fire that raged after the explosions the entire rocket still exists in smaller smaller pieces spread across a large area.  SpaceX still has a Falcon 9, some assembly required ;)

When you blast in a quarry the rock does not disappear, it just gets shattered and shifted around. You still need a front end loader to scoop it up and move it out of the quarry. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/12/2016 02:35 pm
There are three things required: a fuel, an oxidizer, and an ignition source.  It seems most of the folks posting theories are focusing on whichever of the three they like most and ignoring or wildly hand-waving about the rest.

Suppose there was lox-saturated frost on the rocket.  Then what?

Suppose the a hole is poked in the tank.  Then what?

Remember, all three have to occur either simultaneously or invisibly, since there was no prior indication before the explosion.

Further, (im)probabilities multiply.  So if you postulate a highly unlikely source for one of the three, it seems your burden is much higher for showing that the other two are quite likely/common.

To take an example, suppose that there is lox-saturated frost on the vehicle (unlikely, as direct observation of prior rockets hasn't evidenced it, but let's take this as the given).  If you want to say that the fuel source is the paint or the aluminum skin, it seems you should have the burden of showing that LOX-related incidents with painted rockets or aluminum tanks are likely and common.  But in fact LOX is carried in painted aluminum tanker trucks without incident every day.  And then you *also* have to show that there was a not-unlikely ignition source---and a powerful one, given that paint and aluminum are not exactly easy to ignite, and aluminum doesn't spark when it is mechanically deformed.  I don't think anyone has offered a plausible scenario there.

Let's try to make sure that all requirements of the explosion are addressed; that may trim down the number of wild theories.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 02:42 pm
Pad did not damage tank.
No turnbuckle snapped before the vehicle exploded.
Strong back did not collapse before the vehicle exploded

Thank you for succinctly stating what most of us who understand engineering have been trying to say. My posts yesterday explaining that aerospace structures are far more durable and strong than many of these "theories" require them to be were swept up in the "Cleanup on Aisle AMOS-6!" I suppose. Pity. I am rather proud of my word-smithing and hate to let a good technical rant get away.

At any rate, yes. Jim is right. People lately in this thread can't seem to separate discrete bits of basic science (LOX at 66K is cold!) from engineering (rocket stages are stronger than they look, and won't break when you lift them with a strongback).

As I said a few days ago, I personally have no pet theories but I feel very strongly this will be a complex set of causative factors involving the second stage - perhaps manufacturing re-work during assembly, perhaps a testing mishap at McGregor that wasn't noted or wasn't thought to be serious, perhaps even some improper alloys used in manufacturing once you trace the metallurgy back ... Figuring those things out - if they occurred or are relevant - could take months. And anything more obvious wouldn't have SpaceX asking for public help with imagery and recordings, either.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/12/2016 02:51 pm
Morning cup of Joe thought... Those  lower cradle bumpers against the sides of the stage have a pivot pin. Are they lubricated to stay free from binding? If they were lubricated and subject to a high pressure LOX vent blast, what would happen if the lube was inappropriate for a oxygen rich environment under pressure?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/12/2016 02:52 pm
Doesn't the partial pressure of GOX reduce it's condensation point considerably? The partial pressure of O2 in normal atmosphere is 21 kPa, which if I'm reading the phase diagram right reduces the vapor temperature by almost half of the temperature differential between subcooled and boiling LOX.

It's like a glass of water at room temperature: despite the fact that the outside of the glass is MUCH cooler than the boiling point of water, water vapor in the atmosphere does not condense because the partial pressure of water in a normal atmosphere is only a few kPa. The dew point of water varies with partial pressure, the condensation point of O2 should as well.

The aluminum-lithium skin might be insulation enough to prevent LOX formation even without ice buildup, as long as the sounding atmosphere is mostly nitrogen (i.e. the vented GOX doesn't comprise the majority of the local atmosphere for a long duration).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 02:53 pm
Morning cup of Joe thought... Those  lower cradle bumpers against the sides of the stage have a pivot pin. Are they lubricated to stay free from binding? If they were lubricated and subject to a high pressure LOX vent blast, what would happen if the lube was inappropriate for a oxygen rich environment under pressure?

A fire but not a blast
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/12/2016 02:54 pm

And nothing is happening there.  There is no movement between the pads and the vehicle

Jim,
Does the Vehicle shrink at all vertically when it cools? If it does, will the strongback and that support point move lower with it, or is it designed to slide?

I think the gusty winds blowing on the higher and wider payload could have caused the pivot cradle to do some things that even modelling a higher constant wind velocity might have missed, such as a resonance. And I could imagine the strongback creating some vortices where stagnant air could dry out due to declining temperature.

It almost doesn't matter. It seems to be turning into another Columbia incident where the unthinkable and supposedly impossible happens. I think all of us are hoping that something will nudge one of you knowledgeable guys to think "This can't possibly be the cause UNLESS some seemingly impossible event occurs - like liquid Oxygen dripping down the rocket" and then eventually finding that maybe, just maybe it COULD happen say one in 1000 times instead of never.       

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jacqmans on 09/12/2016 02:54 pm
Emergency management: A behind the scenes look on the Eastern Range

By Lt. Col. Greg Lindsey, 45th Mission Support Group commander Detachment 1, / Published September 08, 2016

CAPE CANAVERAL AIR FORCE STATION, Fla. -- 

Last week, the 45th Space Wing’s Incident Management Team responded to the Falcon 9 Static Test Fire anomaly on Space Launch Complex 40. The explosion occurred Sept. 1 at approximately 9:07 a.m. as many of us were just returning from our morning meetings. Minutes later I got the call … it’s the call no one wants to hear, but one for which we constantly train.

The call came over the safety net, followed by a call from the Fire Chief …“There’s been an explosion on Pad 40.” We immediately dispatched fire trucks to a staging position and began evacuating all nearby facilities.  Next step was to activate our Cape Canaveral Air Force Station Emergency Operations Center (EOC), a joint team comprised of military, government civilians and contracted personnel from across the 45th Space Wing. This team provides expertise in many critical functional areas so I manage the response phase of the operation.

Since the incident occurred during a planned hazardous operation, our customer, SpaceX, had coordinated with members of the 45th Security Forces Squadron to clear a predetermined safe zone known as a “Blast Danger Area” to prevent any injuries in the event that an anomaly would occur. Because the BDA had been established, my Pad Safety representative was able to verify that the BDA was clear prior to the start of the test which provided us with the good news that no one was injured within that safe zone. Security was able to immediately account for their security officers who formed the cordon of the BDA and so very quickly I was assured that we had 100 percent accountability with no injuries.  With that information, I knew that our team could focus on the situation at the pad, or so I thought.

As our team gathered in the EOC we conducted an initial briefing to establish a baseline of where each Emergency Support Function and Subject Matter Expert was in regards to their individual response efforts and where they could assist. The ESFs are functions such as the fire department, security, emergency management, and SMEs are representatives from each of our range users, Explosive Ordnance Disposal, Pad Safety and a host of others who contribute valuable insight to this dynamic response.

While you might think our immediate concern was the fires on the pad and their sources, my civil engineer representative informed me that during the explosion, the deluge system had been damaged and most of the water was being shot up into the air rather than being dispersed across the pad as designed. The SpaceX rep informed me that while the deluge wasn’t functioning optimally it was still helping to suppress the fire somewhat. That was fine except for one thing -- our 1.2 million gallon tank was being depleted at a rapid rate and there was no way to refill the tanks fast enough to sustain the output. If the tanks ran dry then the motors to the pumps would burn up, which would render the deluge system inoperable for other launch pads meaning our upcoming ULA launch might then be in danger.

Another issue I had to immediately consider were the many different high-pressure systems on the pad and whether or not they had been compromised and how to bring the pressures down if needed. Our team and I decided to take a multitask approach as we decided to send in our Initial Response Team to shut down the pumps and turn off one of the high-pressure systems that could be accessed from outside the perimeter of the launch pad.

No sooner had we accomplished the securing of the pumps when I was approached by another one of our range users who explained they were losing pressure on the chillers at a neighboring launch complex. Without those chillers the spacecraft for the next launch would be lost. Needless to say at this point I had to reestablish our priorities and get a team working on a way to get our IRT into Space Launch Complex 41 to allow access for technicians to enter in order to make the necessary repairs. 

As we were reviewing the plan, word came in from Pad 41 that all of the pressures were lost and technicians had to get to the spacecraft immediately. This is a situation when good working relationships with our counterparts at Kennedy Space Center came into play. We were able to coordinate with the KSC EOC for access through their roadblocks and get the required support to the spacecraft in plenty of time to not only save the spacecraft, but to keep the planned launch on schedule.

Perhaps the most dangerous part of our response was after the fires were out.  This is when it’s time to go in and clear the launch pad of any hazardous debris. Naturally, there may be pieces of jagged metal or broken blocks of concrete lying around, but there are also remnants of hazardous commodities as well as the possibility of unexploded ordnance on scene.  A team of trained Air Force experts consisting of EOD, Fire Department, and Environmental Health and Pad Safety personnel held the perimeter of the launch complex in order to assess the situation from a closer vantage point throughout the day. EOD Airmen are trained to detect, dispose and render safe any possible explosive threats while Environmental Health personnel continued to monitor the air quality to ensure it was safe for emergency responders and the general public. Fire department and range safety officials monitored the liquid holding tanks for flare ups and pressure issues.  Clearing the pad is extremely dangerous and requires careful planning by all of the members of the response team. EOD, environmental health, the fire department, pad safety and our SpaceX representatives were all instrumental in putting together a carefully orchestrated plan, which allowed each function to accomplish their task in a safe manner that allowed the next function to proceed in a much safer environment.

It’s also important to mention that all of these tasks were tackled by our response teams during almost constant lightning and tornado watches, followed by the pending Tropical Storm Hermine that was coming across Florida.  Managing a crisis is one thing, piling on significant weather events only added to the overall complexity of the entire day.

Because emergency response is so dangerous, there are times when we must be willing to think a little outside of the box. For example, valves needed to be shut down in order to make them safe. One course of action we considered was to use one of the robots operated by our EOD team. While we ultimately decided not to go that route it’s important to note how our team works through these scenarios to solve various problems that present themselves during such an incident. One suggestion we did pursue was one made by the EOC Manager – that we should explore the possibility of getting one of NASA’s Unmanned Aircraft Systems in the air. Once again, our KSC counterparts shared resources with us and were more than eager to support. I had the SpaceX rep meet them at the staging area with a map of the pad and suggested flight paths covering areas of particular concern to be filmed. It wasn’t too long after that first phone call until our incident commander was reviewing footage from the flight over the pad prior to the IRT, making its initial entry onto the pad itself.  This partnership of sharing resources between mission partners allowed us to quickly provide the IRT with a lot of visual details of what they would encounter at the pad and when in a dynamic situation like this, having a visual picture adds to our capability and strengthens our overall response timelines and efforts.

As darkness came, EOC members continued to monitor the situation throughout the night to ensure the safety of our personnel and the public.

It was a rewarding experience from the standpoint as an EOC Director to “sit in the seat” and be supported by so many highly-trained and skilled professionals. Responding to a contingency is never something we want to do, but it is good to know that when we have to, I have a team that can work through the chaos in a calm and calculated manner.  A team that sets priorities in a dynamic environment, accomplishing tasks while keeping our people and the public safe. 

This is a capability that you don’t want to have to use, but you’re glad is there.  Space is inherently dangerous … on this day we were faced with a difficult challenge, but one we were ready for. Moving forward, there will be some rebuilding that is necessary, but everyone went home safe to their families that night and woke up the next morning ready to go at it again.

Our range is comprised of the most knowledgeable, professional and committed personnel in the launch business today.  This is what makes our range unique and speaks to our commitment to providing assured access to space.

http://www.patrick.af.mil/News/Commentaries/Display/Article/938481/emergency-management-a-behind-the-scenes-look-on-the-eastern-range
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/12/2016 02:56 pm
I've just had a spooky thought. What if the "source of heat" was not local ... but 150 million km away, the Sun? Could the morning Sun reflect of various elements of the TEL and focus on a single spot? That bright area we see could be the Sun shining through a buildup of gaseous oxygen between the second stage and TEL. All we need now is a source of fuel, most likely from the TEL but perhaps also from the vehicle.

In the nominal operation, there absolutely must be no fuel on or near the rocket or TEL, nothing at all which can combust not only in ordinary air, but also in oxygen-enriched LOX boiloff plumes.

If there was fuel, _that_ is the problem. Not the ignition source.

It's impractical to eliminate all sources of ignition for such a situation, and SpaceX shouldn't try to debug that. They should figure out where did that fuel came from. Not how it ignited.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/12/2016 02:57 pm
Morning cup of Joe thought... Those  lower cradle bumpers against the sides of the stage have a pivot pin. Are they lubricated to stay free from binding? If they were lubricated and subject to a high pressure LOX vent blast, what would happen if the lube was inappropriate for a oxygen rich environment under pressure?

A fire but not a blast
Agreed, we would need a fuel mist in the mix somehow...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/12/2016 03:10 pm
Are "sniffers" used for any stage fuel leaks concentrations on the TEL (which I doubt) or is it just fuel line pressure and flow rate that's monitored?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/12/2016 03:14 pm
Pad did not damage tank.
No turnbuckle snapped before the vehicle exploded.
Strong back did not fail before the vehicle exploded

The strong back is much, much more robust than the rocket.  It is there to protect the vehicle and provide more stiffness to the vehicle.  Vehicle movement is not going to damage the strong back.  The strong back also lifts the vehicle and cantilevered payload vertical.

But Jim,
The vehicle is light and the raising operation is slow and smooth. No chance for any 'back-and-forth' motion to develop. The scenario described becomes even more likely if the support can slide because it could have pushed the RP1 tank inward at one point, had the rocket slide down and then it pushed at the common bulkhead or a bit higher which would bend the rocket upper portion away, thus opening the crack for the RP1. 

Yes, we are asking you to consider the impossible. Please don't be overly dismissive.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/12/2016 03:21 pm
There are three things required: a fuel, an oxidizer, and an ignition source.  It seems most of the folks posting theories are focusing on whichever of the three they like most and ignoring or wildly hand-waving about the rest.

Suppose there was lox-saturated frost on the rocket.  Then what?

Suppose the a hole is poked in the tank.  Then what?

Remember, all three have to occur either simultaneously or invisibly, since there was no prior indication before the explosion.

Further, (im)probabilities multiply.  So if you postulate a highly unlikely source for one of the three, it seems your burden is much higher for showing that the other two are quite likely/common.

To take an example, suppose that there is lox-saturated frost on the vehicle (unlikely, as direct observation of prior rockets hasn't evidenced it, but let's take this as the given).  If you want to say that the fuel source is the paint or the aluminum skin, it seems you should have the burden of showing that LOX-related incidents with painted rockets or aluminum tanks are likely and common.  But in fact LOX is carried in painted aluminum tanker trucks without incident every day.  And then you *also* have to show that there was a not-unlikely ignition source---and a powerful one, given that paint and aluminum are not exactly easy to ignite, and aluminum doesn't spark when it is mechanically deformed.  I don't think anyone has offered a plausible scenario there.

Let's try to make sure that all requirements of the explosion are addressed; that may trim down the number of wild theories.

I feel there are a few plausable minor explanations for fuel- the strongback hydraulics, the RP1 tank, the stage 2 gimbal hydrolics- that only need a few coincidences to happen.
Oxidiser is dead simple. Lox-Frost shouldnt even be nessisary for the fuel sources I feel are most likely. If a leak is under sufficent pressure to aerosolize the fuel, a FAE can develop with normal air.

The problem, I feel, is ignition source. There's no electrical events and no heat sources in that area, by design. Someone suggesed a one-in-a-million solar mirror ignition- while unlikely, it should be relatively simple (though not easy) to retroactively prove or disprove, as we've got a bazilion pictures of the erector.

I find that theory unlikely, but what ignition sources -are- plausable?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 03:22 pm
This is a refinement of the theory I posted in the wacky thread, but it seems at least as un-wacky as some of the ideas in this thread.  ::)

Based on the initial flash appearance and lack of damage to the left side of the stage initially, I'm proposing that the fire started outside the stage at the same height as the oxygen vents and that it wasn't a very energetic explosion. The stage, fairing and strong back didn't suffer very much blast damage at all, nor were there very many fragments thrown from it.

The mechanism I propose is that a small leak developed in the LOX line running down through the RP1 tank before the LOX loading started. RP1 was slowly leaking through this crack until the LOX started loading. At that point, the LOX started rapidly boiling in the pipe below the crack, streaming high velocity O2 up the pipe, pulling RP1 out of the crack by Bernoulli and atomizing it along with the RP1 that had already leaked into the pipe. Once the pipe chilled enough to freeze the RP1, the crack was sealed so the pressure drop due to loss of volume in the RP1 tank was below the noise in the pressure signal caused by the chilling of the RP1 tank due to the LOX filling on the common bulkhead.

The atomized RP1 froze into fine particles incorporating LOX either internally, in fine cracks or just surface wetting. They would float on the surface of the boiling LOX.

Initially a slug of LOX went into the RP1 tank due to it's density and immediately evaporated in the RP1 causing a slight increase in pressure that drove RP1 into the pipe. The increase in pressure in the RP1 tank could be very small, just enough to overcome a few meters of LOX head in the filling tank, so it may not be obvious in the pressure readings in the RP1 tank. RP1, liquid and solid, would float in LOX.

I'm further proposing that the LOX in the pipe and in the main tank was still boiling violently and that the agitation caused the RP1 as it thickened and froze to break up into small irregular particles, some of which had LOX either in internal bubbles or clinging to the surface due to wetting of irregular features or micro cracks.


These particles could be lofted into the LOX tank by the agitation of the boiling and out the vent where they'd form a cloud of fine frozen RP1 in the air around the vent, some with LOX on or in them. The video doesn't show it because it was mainly on the other side where the vents were and even there, fine particles wouldn't be very visible in the fog from the venting. Perhaps the wind blowing the fog around the tank also tended to concentrate the particle cloud between the strong back and the outside wall of the second stage. The initial flash also seemed to have a downward pointing tail that might be the particle cloud falling.

So the fuel was the fine particle cloud of frozen RP1, the oxidizer was the oxygen rich air in the venting stream, possibly with LOX on the particle surfaces or incorporated into their structure. It wouldn't take much RP1 I wouldn't think because of its high energy density if it has an oxidizer, about 10 times that of TNT.

The ignition source was a larger, more massive particle coated with LOX, propelled by a particularly energetic boiling event striking the vent itself hard enough to detonate. Mixtures of fuel and LOX are explosive and shock sensitive.

This then flashed out into the cloud of particles outside the rocket causing the initial explosion and that then blew back into the vent igniting the rest of the RP1 particles inside the LOX tank.

EDIT: attempt to answer Jim's objection to LOX pressurizing the RP1 tank. Italics are the additions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 03:24 pm

Jim,
Does the Vehicle shrink at all vertically when it cools? If it does, will the strongback and that support point move lower with it, or is it designed to slide?

I think the gusty winds blowing on the higher and wider payload could have caused the pivot cradle to do some things that even modelling a higher constant wind velocity might have missed, such as a resonance. And I could imagine the strongback creating some vortices where stagnant air could dry out due to declining temperature.

It almost doesn't matter. It seems to be turning into another Columbia incident where the unthinkable and supposedly impossible happens. I think all of us are hoping that something will nudge one of you knowledgeable guys to think "This can't possibly be the cause UNLESS some seemingly impossible event occurs - like liquid Oxygen dripping down the rocket" and then eventually finding that maybe, just maybe it COULD happen say one in 1000 times instead of never.       



Anything related to a mechanic failure would first show a breach in the vehicle followed by massive venting before the explosion.  See CRS
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 03:39 pm
All vehicle can flex and do flex in flight and on the pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/12/2016 03:42 pm

Jim,
Does the Vehicle shrink at all vertically when it cools? If it does, will the strongback and that support point move lower with it, or is it designed to slide?

I think the gusty winds blowing on the higher and wider payload could have caused the pivot cradle to do some things that even modelling a higher constant wind velocity might have missed, such as a resonance. And I could imagine the strongback creating some vortices where stagnant air could dry out due to declining temperature.

It almost doesn't matter. It seems to be turning into another Columbia incident where the unthinkable and supposedly impossible happens. I think all of us are hoping that something will nudge one of you knowledgeable guys to think "This can't possibly be the cause UNLESS some seemingly impossible event occurs - like liquid Oxygen dripping down the rocket" and then eventually finding that maybe, just maybe it COULD happen say one in 1000 times instead of never.       



Anything related to a mechanic failure would first show a breach in the vehicle followed by massive venting before the explosion.  See CRS

And would, I imagine, leave an unmistakable trace in the telemetry data, like bangs, groans and readings way outside the norm.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/12/2016 03:43 pm
The problem, I feel, is ignition source. There's no electrical events and no heat sources in that area, by design.

I disagree. The problem is the fuel, not ignition source.

Possible ignition sources: electrical wiring. Moving metal parts. Strongback has both.

Of course, SpaceX tries to reduce the possibilities for ignition sources there (as in: electrical insulation should be not damaged), but mainly it depends on not having PR-1 or something else combustible dripping there!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 03:44 pm

The mechanism I propose is that a small leak developed in the LOX line running down through the RP1 tank. Initially a slug of LOX went into the RP1 tank due to it's density and immediately evaporated in the RP1 causing a slight increase in pressure that drove RP1 into the pipe. The increase in pressure in the RP1 tank could be very small, just enough to overcome a few meters of LOX head in the filling tank, so it may not be obvious in the pressure readings in the RP1 tank. RP1, liquid and solid, would float in LOX.



The back and forth movement of fluid is not going to happen.  The pressure in the fuel tank is not going to overcome the pressure in the LOX line.

An increase of pressure to overcome a few meters of LOX head is going to be a few psi.  That is noticeable
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/12/2016 03:47 pm
What if it was a mechanical failure on the strongback which generated fast debris ("flying metal bolt") puncturing RP-1 tank or piping?

This explains everything. The "twang" sound, the RP-1 mist, the ignition source. No off-nominal telemetry before the event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/12/2016 03:48 pm
All vehicle can flex and do flex in flight and on the pad.

All STS external tanks shed foam but the foam cannot damage the Orbiter severely.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/12/2016 03:49 pm
What if it was a mechanical failure on the strongback which generated fast debris ("flying metal bolt") puncturing RP-1 tank or piping?

This explains everything. The "twang" sound, the RP-1 mist, the ignition source.
I believe that its been mentioned...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/12/2016 03:51 pm


And would, I imagine, leave an unmistakable trace in the telemetry data, like bangs, groans and readings way outside the norm.

Just as the ET foam left unmistakable marks on the orbiter. One groan is as good as another - until it isn't.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moskit on 09/12/2016 03:51 pm
Quote from: Stranger
hello,
"Негромкий инсульт" частной космонавтики

(don't shoot the translator, please transfer to "wacky" thread if this doesn't make sense)

Hypothesis in this (now deleted) post was approximately:
- SpaceX subcooled oxygen to increase mass by 15% (density 1140 kg/m3 goes up to 1300 kg/m3),
- transport of LOX requires certain maximum speed (? 2m/s ~= 7km/h) to avoid problems,
- to load larger mass of subcooled oxygen in required time, transfer speed might have been increased,
- due to LOX flow characteristics, a hydroshock could have happened in LOX supply line,
- if line is estimated at 100m length, 10cm diameter, it could have carried about 1t of LOX at about 3m/s ~= 11km/h,
- hydroshock would have converted this to energy (and heat?) rupturing LOX supply line, possibly also RP-1 supply line,
- "quiet bang" could have been sound of hydroshock.

If such hypothesis is true, oxygen plumbing would need to be redesigned for subcooled LOX.


There was more information and details in the original post, I could have also wrongly translated/understood something critical for the described idea.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 03:55 pm
Quote from: Stranger
hello,
"Негромкий инсульт" частной космонавтики

(don't shoot the translator, please transfer to "wacky" thread if this doesn't make sense)

Hypothesis in this (now deleted) post was approximately:
- SpaceX subcooled oxygen to increase mass by 15% (density 1140 kg/m3 goes up to 1300 kg/m3),
- transport of LOX requires certain maximum speed (? 2m/s ~= 7km/h) to avoid problems,
- to load larger mass of subcooled oxygen in required time, transfer speed might have been increased,
- due to LOX flow characteristics, a hydroshock could have happened in LOX supply line,
- if line is estimated at 100m length, 10cm diameter, it could have carried about 1t of LOX at about 3m/s ~= 11km/h,
- hydroshock would have converted this to energy (and heat?) rupturing LOX supply line, possibly also RP-1 supply line,
- "quiet bang" could have been sound of hydroshock.

If such hypothesis is true, oxygen plumbing would need to be redesigned for subcooled LOX.


There was more information and details in the original post, I could have also wrongly translated/understood something critical for the described idea.

It would be seen in telemetry and video
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 03:57 pm

The back and forth movement of fluid is not going to happen.  The pressure in the fuel tank is not going to overcome the pressure in the LOX line.

An increase of pressure to overcome a few meters of LOX head is going to be a few psi.  That is noticeable
It may have been a transient pressure increase if the leak was sealed by RP1 freezing at the break after some got into the line and then the stream of RP1 froze as the tank pressure decreased.

If the LOX in the fuel pipe were boiling it could also have drawn in RP1 by Bernoulli or cavitation.

I also wonder how much noise there is in the pressure readings in the RP1 tank while the LOX tank with a common bulkhead is chilling. This is far from a steady state.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/12/2016 03:57 pm
The problem, I feel, is ignition source. There's no electrical events and no heat sources in that area, by design.

I disagree. The problem is the fuel, not ignition source.

Possible ignition sources: electrical wiring. Moving metal parts. Strongback has both.

Of course, SpaceX tries to reduce the possibilities for ignition sources there (as in: electrical insulation should be not damaged), but mainly it depends on not having PR-1 or something else combustible dripping there!

Given that we're looking for "swiss cheese" failure modes, where individual minor failures are not problematic, both have to be the problem, I suppose.

So, bird picked at eletrical insulation for it's nest, pinhole leak in RP1 tank due to minor construction fault (edit: also, minor RP1 overpressure due to pumping error just barely within "acceptable" bounds), when the aerosol reaches the short, FAE goes off, shockwave  compresses rocketskin, shears both S2 tanks at common bulkhead.

Plausible?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacekid on 09/12/2016 03:58 pm
I would expect that the initial fragment blown away from the initial explosion is located around the pad area. It probably got enveloped and mostly destroyed by the resultant explosion, but a survey of the GSE around the upper stage for hardware missing might identify it (assuming it came from the GSE which I think it did).

Mangled, roughed up, bent, torn, exposed to extreme heat, yes. But if landed outside of the raging RP-1 fire, it would not have been "destroyed". Beyond what have been consumed/melted in the fire that raged after the explosions the entire rocket still exists in smaller smaller pieces spread across a large area.  SpaceX still has a Falcon 9, some assembly required ;)

When you blast in a quarry the rock does not disappear, it just gets shattered and shifted around. You still need a front end loader to scoop it up and move it out of the quarry.
My main concern would be if it were made of Aluminum, it could have melted in the fire.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 04:04 pm
All vehicle can flex and do flex in flight and on the pad.

So do oil tankers.  So do antenna masts. So does CRS-8 according to the technical webcast close up at 4:10.
I made no claim that they did not. All I claimed was a stack in a vertical position can support half of the top of a strongback while the other half is still attached. What it can not support is twisting and point contacts.

I maintain a slender aluminium structure that has stood for 44 years. It bends alarmingly, but still survives very high lateral loads partway and near the top. It does not even move for axial loads.

But you have completely discounted any strongback, contact points or mechanical failures. No visible external plumes to ignite.

The reason is now obvious. It is not an external observable event according to you. I am therefore puzzled why would SpaceX ask for third party coverage from the outside.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 04:08 pm

But you have completely discounted any strongback, contact points or mechanical failures. No visible external plumes to ignite.


Those would be seen in the video
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 04:09 pm

So, bird picked at eletrical insulation for it's nest,


The vehicle was only outside for less than 12 hours I believe and most of it at night.

And would be seen on video
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 04:10 pm
The back and forth movement of fluid is not going to happen.  The pressure in the fuel tank is not going to overcome the pressure in the LOX line.

An increase of pressure to overcome a few meters of LOX head is going to be a few psi.  That is noticeable
OK, another variant is that the leak was already in the LOX pipe running through the RP1 tank before the LOX loading was started. The RP1 was very slowly leaking into the pipe, then the LOX started loading and filling the pipe. That froze the RP1 at the leak, sealing the leak and preventing the RP1 tank pressure rise.

However, there were several kg of RP1 already in the pipe which was then filling with rapidly boiling LOX which created the particles needed for the theory conjecture.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: S.Paulissen on 09/12/2016 04:21 pm
The simplest single point failure would be LOX contamination from an unexpected source, IMO. *(this is an aside from the main point of this post)

I think the majority of these other ideas are highly improbable for many reasons including their blatant obviousness that they never could come to pass without notice before hand.  I think people need to stop trying to find a Rube Goldbergian cause including five separate sources.  Anomalies are generally simple, diagnosing them is the hard part because of incomplete data, not because the causes are too complex.  Maybe Jim will slap me down on this, and I'll edit.

I'm guilty of dropping my unsupported guess early in this thread, but the key difference between then and now is that we're too far along into this to be throwing out stuff that is easily dismiss-able from the known facts which were not available then.  In other words,  Focus on the most probable events and then rigorously vet them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickyramjet on 09/12/2016 04:22 pm

In the nominal operation, there absolutely must be no fuel on or near the rocket or TEL, nothing at all which can combust not only in ordinary air, but also in oxygen-enriched LOX boiloff plumes.

If there was fuel, _that_ is the problem. Not the ignition source.

It's impractical to eliminate all sources of ignition for such a situation, and SpaceX shouldn't try to debug that. They should figure out where did that fuel came from. Not how it ignited.


Sufficient fuel to cause the large initial blast could have come from the umbilical which carries LOX and RP1, which connects at the bottom of the RP1 tank.  In order for a fuel mist to reach the area of the initial blast there would have to be a pressure in the RP1 line for the mist to reach approximately the middle of the US, I guesstimate at about 18 feet.  RP1 has a density of 0.81 g/cm3, more if cooled.  To reach the 18 feet the RP1 pressure would need to be only about 7 psi.  SpaceX likes to do "rapid loading", so I think the pressure in the RP1 line was much higher, perhaps 50 or even 100 psi?  If there is a pin hole in the umbilical, or an improperly fitting connector where the umbilical attaches to the rocket, or some other scenario there could easily be a mist of RP1 (mixed with GOX) waiting for ignition.  And, there was a serious tropical storm passing north of the area that could easily induce a sufficient static charge.

The questions I have are:  Does anyone know the actual pumping pressure?  Is the pressure reduced to zero when the RP1 tank is full?  Is there a "full shutoff" valve inside the US?  (perhaps it closed quickly and caused a pressure spike)  Is the umbilical inspected and pressure tested after a launch?  Is it replaced after a launch?

How I came up with the numbers: I compared kerosene density with water.  Water has a density of 1 g/cm3 whereas kerosene has a density of .81.  A column of water 1 ft high gives a pressure of .43 psi, so kerosene would have a pressure of .35 lbs/ft.  I know my garden hose at 45psi easily shoots a stream of water 20 feet high.

There is a good chance my idea is full of holes, but I throw it there for everyone to chew on!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/12/2016 04:24 pm
The problem, I feel, is ignition source. There's no electrical events and no heat sources in that area, by design.

I disagree. The problem is the fuel, not ignition source.

Possible ignition sources: electrical wiring. Moving metal parts. Strongback has both.

Of course, SpaceX tries to reduce the possibilities for ignition sources there (as in: electrical insulation should be not damaged), but mainly it depends on not having PR-1 or something else combustible dripping there!

Given that we're looking for "swiss cheese" failure modes, where individual minor failures are not problematic, both have to be the problem, I suppose.

I don't think multiple failures are the only way for this failure to happen.

The off-nominal presence of RP-1 leak would be enough. It could be happening for minutes without visible effects (on video and in telemetry), waiting for a normally completely insignificant and harmless event, such as metal parts rubbing, setting it off.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 04:27 pm

But you have completely discounted any strongback, contact points or mechanical failures. No visible external plumes to ignite.


Those would be seen in the video

A cracked through beam would not show up until it was needed. This is one upright out of 4. The rest are not particularly elastic.  The movements necessary, based on your own idea that the support suffers no movements at all between the pads and the tanks would mean the distance moved to rupture the tank would be in mm. The video is MPEG coded and from a long distance where the pixel resolution is close to the size of a beam in the strongback. Nothing would possible be seen.

With a 4K camera you would need to be within 10m of the failure. The whole piece does not need to fall off to render it useless. A pad lifting would need the same distance. I use the same type of pads to hold up structures in windy conditions. No structure in this world worth having if it does not flex with its environment. We have a phrase over hear about building brick square buildings for toilets that can withstand anything. That is the only exception.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 04:29 pm

The off-nominal presence of RP-1 leak would be enough. It could be happening for minutes without visible effects (on video and in telemetry), waiting for a normally completely insignificant and harmless event, such as metal parts rubbing, setting it off.


RP-1 is not like gasoline.  A torch doesn't even light it

https://www.youtube.com/watch?v=7nL10C7FSbE
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 04:35 pm

A cracked through beam would not show up until it was needed. This is one upright out of 4. The rest are not particularly elastic. 



The fracture/collapse and subsequent rupture would be seen in the video before the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: starhawk92 on 09/12/2016 04:37 pm
I find it very challenging to believe that 3000 telemetry streams would not have detected 99.9% of the theories posted so far.

So, perhaps someone who has knowledge of the systems could answer this:
If the sound at -51 seconds is "within" the vehicle, is there any way it would not show in telemetry?  That is, something has to change, and if a piece is dislodged it has to fall.  And one of those events has to cause a change in the system state such that 51 seconds can elapse before an undetectable problem becomes an explosion.  What system is not monitored where this goes unnoticed by the people and computers monitoring the static fire?

In essense, does this not rule out the sound as coming from inside the vehicle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gotorah on 09/12/2016 04:45 pm

The off-nominal presence of RP-1 leak would be enough. It could be happening for minutes without visible effects (on video and in telemetry), waiting for a normally completely insignificant and harmless event, such as metal parts rubbing, setting it off.


RP-1 is not like gasoline.  A torch doesn't even light it

https://www.youtube.com/watch?v=7nL10C7FSbE
In the video, the fluid does not ignite  because he is careful to have it in a container with the fluid level well below the opening. Liquid propane burns the same way. a steel container can be lit and the flame will hover over the opening until the fuel is exhausted. Just don't tip it over or break the container.  Him doing that in a glass jar is very dangerous. If the heat broke the jar ?  ?  he would have to run like hell to escape it !
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/12/2016 04:53 pm
I believe SpaceX shines a laser some place on the 2nd stage to measure sway. Therefore they would have known if the rocket was moving out of a well defined tolerance.

Edit: Per catdlr's post below, the laser shines on the bottom of the interstage just above the grid fins.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: catdlr on 09/12/2016 05:03 pm
I believe SpaceX shines a laser some place on the 2nd stage to measure sway. Therefore they would have known if the rocket was moving out of a well defined tolerance.

Here at 20 seconds into this video.  Plus some nice close shots of the TE and LV.

https://youtu.be/o295V9Rqa8E?t=001

https://youtu.be/o295V9Rqa8E
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/12/2016 05:04 pm

The off-nominal presence of RP-1 leak would be enough. It could be happening for minutes without visible effects (on video and in telemetry), waiting for a normally completely insignificant and harmless event, such as metal parts rubbing, setting it off.


RP-1 is not like gasoline.  A torch doesn't even light it

Which is why I also posited an RP1 tank over-pressure approximately 1 standard deviation above the mean- not so rare to be remarked on, but enough that, with an undetected tank defect, would be enough to aerosolize a leak.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 05:23 pm

The off-nominal presence of RP-1 leak would be enough. It could be happening for minutes without visible effects (on video and in telemetry), waiting for a normally completely insignificant and harmless event, such as metal parts rubbing, setting it off.


RP-1 is not like gasoline.  A torch doesn't even light it

Which is why I also posited an RP1 tank over-pressure approximately 1 standard deviation above the mean- not so rare to be remarked on, but enough that, with an undetected tank defect, would be enough to aerosolize a leak.

First, per the many-times-posted F9 FT countdown flow, tanks were not at flight pressure. Second, do you know what the mean pressure of the RP1 tank would be? Third, do you know how well-controlled and repeatably pressure is maintained so that you can determine how large or small a single standard deviation is? Fourth, just how inaccurate and/or imprecise (*) do you think SpaceX's pressure transducers would have to be for them not to notice such deviance? Fifth, do you know enough about the S2 umbilicals to know if and where there might be check valves, cut-off valves and/or drains? Sixth, with tanks not yet at flight pressure, are you confident that SpaceX keeps GSE pressurized with RP1 to allow fuel to aerosolize though a leak? And even if so, I refer you back up to Nos. 2, 3 and 4 above.

(*) There is a difference between accuracy and precision. I'm just going to go ahead and assume (I know, I know ...) that anyone here who posits this kind of theory understands this difference.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 05:30 pm

A cracked through beam would not show up until it was needed. This is one upright out of 4. The rest are not particularly elastic. 



The fracture/collapse and subsequent rupture would be seen in the video before the explosion.

Again a cracked beam would not show up. A beam does not have to fall off to be useless. I have one beam broken here, it is 20mm out. Still standing in place.
There is no collapse in terms of visibility. Everything would still be in place but the structural integrity would be missing. The movement for failure is tiny when a point load is applied to a thin wall tank.
The rupture WAS visible as a huge fireball. The plumes going off down wind reflect the light. They are not the source of the light. The fireball is formed upwind of the vehicle. Which is just not sensible if it is caused by a plume igniting. It was windy.

I assume the opposite sequence. The fire was first or coincident with the rupture. The fire was the rupture.

It is clear that this is not normal, but it occurs. There is a report of two US fire fighters that were injured by aluminium regulators busting in flames.

I quote from www.astm.org: "The two aluminum regulator fires described above were not isolated. The U.S. Food and Drug Administration received 16 reports of other similar fires between 1993 and 1999 involving aluminum regulators attached to cylinder valves of portable oxygen cylinders. Considering the number of devices in clinical use, oxygen regulator fires are relatively rare; however, the consequences of these fires were quite serious."

Considering the massive number of uses of these cylinders 16 is 6 years is tiny. Now convert that to rocket launch frequency. Probability would state it would not have happened yet. But I think it did.

Similar stories in heat exchangers and full reports by EUROPEAN INDUSTRIAL GASES ASSOCIATION . Similar stories in dive bottles.

Absolute proof it does happen and it is rare. So it qualifies as a possibility. The issue here is that all these events have to have a trigger of contamination or rubbing. They do not occur on their own. The incidents involve people that are operating the equipment at the time. That means movement is a key requirement.

Hence my scenarios. A tank alone is safe. A tank being "abused" is not.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/12/2016 05:43 pm
Doesn't the partial pressure of GOX reduce it's condensation point considerably? The partial pressure of O2 in normal atmosphere is 21 kPa, which if I'm reading the phase diagram right reduces the vapor temperature by almost half of the temperature differential between subcooled and boiling LOX.

It's like a glass of water at room temperature: despite the fact that the outside of the glass is MUCH cooler than the boiling point of water, water vapor in the atmosphere does not condense because the partial pressure of water in a normal atmosphere is only a few kPa. The dew point of water varies with partial pressure, the condensation point of O2 should as well.

The aluminum-lithium skin might be insulation enough to prevent LOX formation even without ice buildup, as long as the sounding atmosphere is mostly nitrogen (i.e. the vented GOX doesn't comprise the majority of the local atmosphere for a long duration).
This is a very relevant point.  Thank you envy887! 

My trusty Kaye & Laby tables tell me that at 77.1 K the vapour pressure of LOX is 20 kPa, very close to the partial pressure of O2 in the sea-level atmosphere.  So (at sea-level) LOX could only condense  below about 77 K.  Between 77 K and 90.2 K it would evaporate faster than it condensed, even though it wouldn't boil. 

(The boiling point of LN2 - also at sea level - is 77.4 K, so if the LN2 is even one or two K below boiling, and in an uninsulated Al or Cu container, it could easily condense droplets of LOX on the outside, consistent with all the observations upthread.  You'd think that frost would form too, but as air approaches the cold container it cools too, and almost all the water vapour will be frozen out as mist, which will be carried away by downward convection.  The air that actually gets to touch the container will be very dry.  There won't be much frost to be "washed away by streams of LOX".  On the other hand, the frosty spherical steel LN2 tank also mentioned upthread was probably painted on the outside, and even a thin layer of paint would insulate well enough to give a temperature drop of a few K, enough to raise the outer surface above 77 K and prevent LOX condensation altogether.)

As Jim has made clear, even sub-cooled rockets are frosty, not dripping with LOX, because at the beginning of chilldown lots of moist air touches the rocket; the air hasn't yet had all the moisture squeezed out of it by cryo temperatures, and has lots of time to build up a thick frost layer, especially on the upwind side of the rocket.

However, I'm beginning to believe the LOX-soaked frost theory.  We should pull back and look at the wider context:

1)  This was a most unusual incident.  Nothing like it in 50 years.  What's new about this hardware?  Subcooled LOX.  (Not totally new, I know ... Antares, Soyuz ...)

2)  Out of all the places on the rocket, GSE etc where an anomaly might appear, this one appeared "around" a subcooled oxygen tank.  And judging from the video, on the upwind side.

So under what conditions could LOX form inside the frost layer?  Soaked in, not dripping down?  This part comes straight from a post a few hours upthread explaining cryopumping, which seems to have disappeared, or I'd quote it.  (Many apologies to its author, whose name I didn't note down before it disappeared.  It's a great idea.)  Suppose the frost layer is quite fluffy, and full of air spaces that connect to each other.  It's still a very good thermal insulator (the more air the better for that) but permeable to oxygen.  Then IF the paint/frost surface is below 77 K, LOX can condense there, sucking in more air, giving more LOX ... until the inner part of the frost layer is soaked in LOX.  (I should confess here that I don't know how well LOX soaks into snow; I don't know the relevant contact angle.  Can anyone here help?)  The soaked layer would thicken until its outer surface reached a part of the frost layer warmer than 77 K. It would be invisible from outside.

But how likely is it that the paint/frost surface would be below 77 K?  Using very rough numbers from here on ...  the Al tank is such a good conductor that we might as well assume 70 K for its outer surface, the Al/paint surface.  We might assume 273 K for the equilibrium frost/air surface.  Then the temperature drops for the limiting case are 7 K across the paint, and 196 K across the frost; so the frost would have to insulate at least 196/7 = 28 times better than the paint.  The thicker and fluffier the frost layer, the better it will insulate the structure beneath, the colder the paint will get, and the more likely LOX condensation becomes.  And the frost layer is likely to be thicker on the upwind side of the rocket.

Now I assume Spacex worked all this out when they were deciding on the thickness of the paint layer; it has to be a better insulator than 1/28th of the maximum plausible frost layer.  But on a humid day, with a tropical storm moving in, maybe the frost layer grew unusually thick and fluffy?

So this is my candidate for the oxidiser.  As for the fuel - the paint?  the tank Al?  And the ignition source could have been anything - mechanical shock, bird-poo ... as has been pointed out upthread, once you have fuel and oxidiser next to each other, an ignition source will always show up sooner or later.  Maybe the previous subcooled flights have just dodged the bullet.

What do people think?  Of course we must guard against bias, since if this is a contributory factor, it's easily fixed:  thicker paint, a bit less subcooling.  And we do want the fix to be easy.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/12/2016 05:48 pm
I don't believe your story on either the fuel or the ignition source, even if I grant your lox-frost theory for purposes of discussion.

After all, there is plenty of GOX around as well.  Why hasn't the paint burst into flames before?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/12/2016 05:55 pm
I don't believe your story on either the fuel or the ignition source, even if I grant your lox-frost theory for purposes of discussion.

After all, there is plenty of GOX around as well.  Why hasn't the paint burst into flames before?

Well, I was thinking of upthread stories like the LOX-soaked tarmac that exploded when a fire-truck drove over it.  That had never burst into flames before either, despite lots of GOX and hot sun.  I have to rely on people with more practical experience of LOX ignition than I have ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/12/2016 06:04 pm
I don't believe your story on either the fuel or the ignition source, even if I grant your lox-frost theory for purposes of discussion.

After all, there is plenty of GOX around as well.  Why hasn't the paint burst into flames before?

Well, I was thinking of upthread stories like the LOX-soaked tarmac that exploded when a fire-truck drove over it.  That had never burst into flames before either, despite lots of GOX and hot sun.  I have to rely on people with more practical experience of LOX ignition than I have ...
That's a LOX-soaked *hydrocarbon*. You're postulating LOX-soaked paint being a similar contact explosive... And even then you're missing the "heavy fire truck" part of the anecdote.  (Also it fails on account of explosive mass: 6" of asphalt vs a millimeter of paint).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 06:09 pm
I don't believe your story on either the fuel or the ignition source, even if I grant your lox-frost theory for purposes of discussion.

After all, there is plenty of GOX around as well.  Why hasn't the paint burst into flames before?

Well, I was thinking of upthread stories like the LOX-soaked tarmac that exploded when a fire-truck drove over it.  That had never burst into flames before either, despite lots of GOX and hot sun.  I have to rely on people with more practical experience of LOX ignition than I have ...
That's a LOX-soaked *hydrocarbon*. You're postulating LOX-soaked paint being a similar contact explosive... And even then you're missing the "heavy fire truck" part of the anecdote.  (Also it fails on account of explosive mass: 6" of asphalt vs a millimeter of paint).

And what's more, asphalt is typically porous, and on many modern surfaces, specifically DESIGNED to be to drain fluids through and off the surface, preventing ponding and thus hydroplaning. Painted aluminum aerostrures are no porous.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 06:11 pm
That's a LOX-soaked *hydrocarbon*. You're postulating LOX-soaked paint being a similar contact explosive... And even then you're missing the "heavy fire truck" part of the anecdote.  (Also it fails on account of explosive mass: 6" of asphalt vs a millimeter of paint).
Agreed. That's the genesis of my conjecture involving a frozen slush-like RP1/LOX chunk being propelled by the LOX boiling striking the edge of the vent being the ignition source.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 06:13 pm

 But on a humid day, with a tropical storm moving in, maybe the frost layer grew unusually thick and fluffy?


It was a standard Florida day.  The storm had no bearing on the weather.  It was no more humid or dryer, no more hotter or cooler, no more stiller or winder than a typical Florida day in the summer.

There is no fluffy frost or LOX on the side of the vehicle.  Look at previous launches

And again, if there was LOX it would evaporate upon running down the tank when it hits RP-1 temps
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DMeader on 09/12/2016 06:17 pm
One thing that strikes me as I read through these pages upon pages of theories, is how massively complex most of them are.  Veritable rube-goldberg-machine processes full of intricate things (hydrogen bubbles, LOX-soaked frost) that I guarantee that nobody who works a launch site has ever seen.  Even bird poop. While I have no idea what may have caused this accident, I'm willing to bet that it will end up being something much simpler that anything that has been considered. Occam's razor states that "Entities should not be multiplied unnecessarily." Multiplication on steroids has been going on here. Look for something simpler.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 06:17 pm
The rupture WAS visible as a huge fireball.

No, there would be fluid release before the flame.  See CRS-7

Search bleve. The fuel never gets out of the tank first. The heat finally melts the tank wall. In an aluminium alloy thin wall tank this is alarmingly quick. Look up the regulator fires on thick wall components. They were instant and had no fuel except the aluminium.

Once this initial event occurs the rest of the destruction is guaranteed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 06:25 pm

Search bleve.

Not applicable.  There is no boiling.  Again see photo below
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/12/2016 06:27 pm

The off-nominal presence of RP-1 leak would be enough. It could be happening for minutes without visible effects (on video and in telemetry), waiting for a normally completely insignificant and harmless event, such as metal parts rubbing, setting it off.


RP-1 is not like gasoline.  A torch doesn't even light it

Which is why I also posited an RP1 tank over-pressure approximately 1 standard deviation above the mean- not so rare to be remarked on, but enough that, with an undetected tank defect, would be enough to aerosolize a leak.

First, per the many-times-posted F9 FT countdown flow, tanks were not at flight pressure. Second, do you know what the mean pressure of the RP1 tank would be? Third, do you know how well-controlled and repeatably pressure is maintained so that you can determine how large or small a single standard deviation is? Fourth, just how inaccurate and/or imprecise (*) do you think SpaceX's pressure transducers would have to be for them not to notice such deviance? Fifth, do you know enough about the S2 umbilicals to know if and where there might be check valves, cut-off valves and/or drains? Sixth, with tanks not yet at flight pressure, are you confident that SpaceX keeps GSE pressurized with RP1 to allow fuel to aerosolize though a leak? And even if so, I refer you back up to Nos. 2, 3 and 4 above.

(*) There is a difference between accuracy and precision. I'm just going to go ahead and assume (I know, I know ...) that anyone here who posits this kind of theory understands this difference.
Tanks were not at flight pressure, but if the tank was slightly overfilled, there would be some purely internally generated pressure as subcooled Rp1 warmed up. Tanks would of course be designed to withstand this, for days on end, or it would be considered a fault. It would show up on the sensors, but be within tolerance. Because Acceptable Tolerance is a thing.

What would that pressure be? I do not know. What IS the expansion of subcooled RP1? Wound it be enough that a pinhole tank leak could cause aerosolization? That is my unproven assertion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 06:28 pm
The heat finally melts the tank wall. In an aluminium alloy thin wall tank this is alarmingly quick. Look up the regulator fires on thick wall components. They were instant and had no fuel except the aluminium.


There is no mechanism that burns the aluminum here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pmonta on 09/12/2016 06:30 pm
I'm wondering if cork insulation can be a fuel source if somehow it becomes saturated with LOX.  Is the cork at all permeable to gaseous oxygen? Might the boundary between cork and aluminum tank be cold enough to support the formation of a thin layer of LOX?  Then an ignition source, such as a spark, would have to somehow find that vulnerable patch.

On the other hand, I gather many vehicles use cork, so it must be possible to do so safely.  Just a thought.

Edit: after searching this thread more carefully, this has already been asked, and one reply stated that there is no cork on the second stage.  Perhaps the nearest source of carbon would be the composite interstage, then.

Edit 2: are any of the TEL S2 LOX lines insulated with cork?


No cork on stage 2

Any cork on the TEL in the vicinity of S2?  Are the TEL LOX lines insulated, and if so, with what?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 06:30 pm
The rupture WAS visible as a huge fireball.

No, there would be fluid release before the flame.  See CRS-7

Search bleve. The fuel never gets out of the tank first. The heat finally melts the tank wall. In an aluminium alloy thin wall tank this is alarmingly quick. Look up the regulator fires on thick wall components. They were instant and had no fuel except the aluminium.

Once this initial event occurs the rest of the destruction is guaranteed.

This is a frame of the CRS-7 failure just before the explosion showing some kind of precursor damage.
(http://images.spaceref.com/news/2015/explode.lrg.jpg)
If you look at the frame just before the explosion in the AMOS 6 case, there's no structural problem, nor any signs of external leakage.

Actually, it's not obvious to me that the CRS-7 second stage actually exploded other than by the internal pressure blowing it apart and aerodynamic forces. Was there a fire?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 06:30 pm
Tanks were not at flight pressure, but if the tank was slightly overfilled, there would be some purely internally generated pressure as subcooled Rp1 warmed up. Tanks would of course be designed to withstand this, for days on end, or it would be considered a fault. It would show up on the sensors, but be within tolerance. Because Acceptable Tolerance is a thing.

What would that pressure be? I do not know. What IS the expansion of subcooled RP1? Wound it be enough that a pinhole tank leak could cause aerosolization? That is my unproven assertion.

No, the tank is not closed.   It is still vented
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 06:33 pm

Any cork on the TEL in the vicinity of S2?  Are the TEL LOX lines insulated, and if so, with what?


Cork is not used on GSE.   
LOX lines are not the cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/12/2016 06:36 pm
I don't believe your story on either the fuel or the ignition source, even if I grant your lox-frost theory for purposes of discussion.

After all, there is plenty of GOX around as well.  Why hasn't the paint burst into flames before?

Well, I was thinking of upthread stories like the LOX-soaked tarmac that exploded when a fire-truck drove over it.  That had never burst into flames before either, despite lots of GOX and hot sun.  I have to rely on people with more practical experience of LOX ignition than I have ...
That's a LOX-soaked *hydrocarbon*. You're postulating LOX-soaked paint being a similar contact explosive... And even then you're missing the "heavy fire truck" part of the anecdote.  (Also it fails on account of explosive mass: 6" of asphalt vs a millimeter of paint).
Of course you're right that I have very little, or no, evidence for the paint as fuel, especially since I don't even know what kind of paint it is (can anyone here tell us that?)  That's why I wrote " ... the paint?  the tank Al?" so hesitantly.

I don't know what the fuel could have been, I'm just guessing at things likely to have been in contact with the hypothetical LOX-frost.  As for the " 6" of asphalt vs a millimeter of paint" point, is the quantity relevant?  If the conditions for ignition are present, can't a single flake of paint start the reaction, which will then spread to the rest of the paint and, especially, the Al?

Maybe the exploding tarmac was the wrong anecdote to use, it's just the one I remembered most clearly from those 122 pages ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Arb on 09/12/2016 06:36 pm
Tanks were not at flight pressure, but if the tank was slightly overfilled, there would be some purely internally generated pressure as subcooled Rp1 warmed up. Tanks would of course be designed to withstand this, for days on end, or it would be considered a fault. It would show up on the sensors, but be within tolerance. Because Acceptable Tolerance is a thing.

What would that pressure be? I do not know. What IS the expansion of subcooled RP1? Wound it be enough that a pinhole tank leak could cause aerosolization? That is my unproven assertion.

No, the tank is not closed.   It is still vented
There would however be head pressure if a postulated leak was low down on the tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/12/2016 06:40 pm
Tanks were not at flight pressure, but if the tank was slightly overfilled, there would be some purely internally generated pressure as subcooled Rp1 warmed up. Tanks would of course be designed to withstand this, for days on end, or it would be considered a fault. It would show up on the sensors, but be within tolerance. Because Acceptable Tolerance is a thing.

What would that pressure be? I do not know. What IS the expansion of subcooled RP1? Wound it be enough that a pinhole tank leak could cause aerosolization? That is my unproven assertion.

No, the tank is not closed.   It is still vented
There would however be head pressure if a postulated leak was low down on the tank.

Not one large enough to form a propellant mist, and that doesn't square with where the event took place.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jdeshetler on 09/12/2016 06:46 pm
This is a frame of the CRS-7 failure just before the explosion showing some kind of precursor damage.

You mean like this?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mike_1179 on 09/12/2016 06:47 pm
Thinking about structural failure - not a burning event that started this but a stage structural failure that led to propellant rupture and ignition.

The stage was test fired in McGregor at some point in its life, meaning it was loaded, pressurized and unloaded without failing. Trying to consider conditions which would be different at LC40 compared to McGregor.

Are stages inspected for cracks (ultrasound, dye penetration, critical crack length recording, etc) after test firing?
Are they inspected for cracks after transportation?
This stage had the payload on top for the static fire, are the tops of second stages loaded with a mass simulator during McGregor testing?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 06:48 pm
Not one large enough to form a propellant mist, and that doesn't square with where the event took place.
How about a stream of high velocity GOX formed by LOX boiling in the LOX pipe atomizing RP1 pulled into it by Bernoulli through a crack in the LOX pipe?

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/12/2016 06:52 pm

 But on a humid day, with a tropical storm moving in, maybe the frost layer grew unusually thick and fluffy?


It was a standard Florida day.  The storm had no bearing on the weather.  It was no more humid or dryer, no more hotter or cooler, no more stiller or winder than a typical Florida day in the summer.

There is no fluffy frost or LOX on the side of the vehicle.  Look at previous launches

And again, if there was LOX it would evaporate upon running down the tank when it hits RP-1 temps

I withdraw the "humid day" hypothesis.  Actually I was thinking even a normal Florida day might be more humid than normal for the other places SpaceX launch and test their rockets.  I wonder if they make a point of testing in different humidities?

As for the fluffy frost - I was thinking of the explanation for the white parts of the mostly-sooty returned stages.  Isn't that supposed to be because the soot coats the outside of the frost, which then melts away?

And as for the LOX running down as far as the RP-1 tanks, that's why I want to know about LOX/ice contact angles - can the LOX be held soaked into the frost by capillary forces?  Then it wouldn't be free to drip down.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SWGlassPit on 09/12/2016 06:54 pm
Not one large enough to form a propellant mist, and that doesn't square with where the event took place.
How about a stream of high velocity GOX formed by LOX boiling in the LOX pipe atomizing RP1 pulled into it by Bernoulli through a crack in the LOX pipe?

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)
The pressure differential in the LOX feedline would be in the wrong direction for that to happen.  If there were to be a leak, it would be into the RP-1 tank, not into the LOX feedline.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 06:59 pm
The pressure differential in the LOX feedline would be in the wrong direction for that to happen.  If there were to be a leak, it would be into the RP-1 tank, not into the LOX feedline.
I'm proposing that the leak started before the LOX was loaded and as the LOX started filling the feed line it was boiling and sending a stream of high velocity GOX up the line that pulled the RP1 into it and atomized it in addition to the RP1 that had already leaked into the pipe.

Once the LOX level reached the leak it was sealed by the RP1 in the tank freezing before the LOX head pressure exceeded the RP1 tank pressure. This isn't a steady state condition.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/12/2016 07:10 pm
Thinking about structural failure - not a burning event that started this but a stage structural failure that led to propellant rupture and ignition.

The stage was test fired in McGregor at some point in its life, meaning it was loaded, pressurized and unloaded without failing.

...



A bit of pedantry, but I don't believe it's possible to static fire a Merlin 1D Vac.

The upper stage is, iirc, fuelled at McGregor, but not fired.

But yes, the stage has gone through a fuelling cycle - so if there was anything obvious like a pinhole in the RP-1 tank, it would have noticed before it went to the Cape. Or indeed, before it left the factory.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/12/2016 07:13 pm
A bit of pedantry, but I don't believe it's possible to static fire a Merlin 1D Vac.

The upper stage is, iirc, fuelled at McGregor, but not fired.

https://www.youtube.com/watch?v=O90FROx8J3Y
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 07:23 pm

I'm proposing that the leak started before the LOX was loaded and as the LOX started filling the feed line it was boiling and sending a stream of high velocity GOX up the line that pulled the RP1 into it and atomized it in addition to the RP1 that had already leaked into the pipe.


No.  It needs too many miracles to happen in succession.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 07:29 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 07:34 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.

Why wouldn't the LOX have reacted violently to the hydrocarbon contamination immediately at the start of LOX load?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/12/2016 07:34 pm
There are three things required: a fuel, an oxidizer, and an ignition source.  It seems most of the folks posting theories are focusing on whichever of the three they like most and ignoring or wildly hand-waving about the rest.

Suppose there was lox-saturated frost on the rocket.  Then what?

Suppose the a hole is poked in the tank.  Then what?

Remember, all three have to occur either simultaneously or invisibly, since there was no prior indication before the explosion.

Further, (im)probabilities multiply.  So if you postulate a highly unlikely source for one of the three, it seems your burden is much higher for showing that the other two are quite likely/common.


I feel there are a few plausable minor explanations for fuel- the strongback hydraulics, the RP1 tank, the stage 2 gimbal hydrolics- that only need a few coincidences to happen.
Oxidiser is dead simple. Lox-Frost shouldnt even be nessisary for the fuel sources I feel are most likely. If a leak is under sufficent pressure to aerosolize the fuel, a FAE can develop with normal air.

The problem, I feel, is ignition source. There's no electrical events and no heat sources in that area, by design. Someone suggesed a one-in-a-million solar mirror ignition- while unlikely, it should be relatively simple (though not easy) to retroactively prove or disprove, as we've got a bazilion pictures of the erector.

I find that theory unlikely, but what ignition sources -are- plausable?

I agree with the initial quoted post.

Unless something remarkably strange has happened, we need oxidiser, fuel and an ignition source.

We have the oxidiser if the tank is venting - an oxygen-rich environment.

We potentially have the ignition source on the erector: there is part of the air conditioning system at the height the explosion was *probably* initiated.

Okay, it will be guarded against sparking but it's not beyond reasonable suspicion that there could be a bare wire shorting or a motor that's not shielded properly and that *could* be the source.

In any instance, an ignition source is potentially the easiest mistake to have been made: the TEL is a 'Heath Robinson' of a device, which has been modified for three iterations of launch vehicle and certainly isn't what you'd build if you had a clean start (see the ones at Vandenberg and Pad 39a for comparison).


The bit that bothers me is the fuel - I don't quite see where it's come from; and I'm not easily persuaded by (for example) strangely flammable paint that SpaceX didn't realise they were applying; and that then requires some strange circumstances of oxygen liquifying out of the air.


The hydraulic fluid is possibly a candidate, but only if the claw system uses hydraulics (not pneumatics); and if the fluid is not flammable (less likely).

The hypothetical hydraulic system has a few aspects which make it a candidate for me:

- the leak can be above the point of initiation of the explosion, allowing fluid to fall down beside the vehicle in the area where the initial explosion happened
- the leak can also be upwind of the vehicle, enabling ignition within the frame of the erector frame and an explosion which is centred between the vehicle and the strongback (which corresponds with what was seen)
- the hydraulic system is probably the highest pressure fluid on the pad, so a tiny leak in a hose or fitting (not uncommon unless pipes and fittings are tested / changed regularly) will almost inevitably cause a fine mist
- there is less likely to be telemetry watching hydraulic pressures (and if the system at the top of the strongback is fed from the high-volume system that raises and lowers the erector, any pressure drop would be negligible)


(By way of comparison, the RP-1 tank considered against these counts:
- the leak would be below the point of initiation of the explosion
- the leak would have to blow into the wind to find the ignition source and this plume would almost certainly have been visible
- pressure in the tank is unlikely to produce a fine enough vapour to ignite, although in an oxygen-rich environment, the bar may be set quite low on the vapour front
- telemetry should show any significant leaks

The one thing I might entertain is the connections / equipment on the strongback that provides the feed to the upper stage - these are a bit low to correspond with the apparent point of initiation of the explosion, but sufficient pressure might allow fine fuel to be be squirted upwards.)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/12/2016 07:40 pm
A bit of pedantry, but I don't believe it's possible to static fire a Merlin 1D Vac.

The upper stage is, iirc, fuelled at McGregor, but not fired.

https://www.youtube.com/watch?v=O90FROx8J3Y

Are they all static fired at McGregor, ie all the upper staged used for launches?

The understanding I had (which various people mention in this thread) is that the extended nozzle means the stage can not be tested.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 07:42 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.

Why wouldn't the LOX have reacted violently to the hydrocarbon contamination immediately at the start of LOX load?
Because there was no ignition source. You can mix LOX and hydrocarbon fuel and it won't go off spontaneously, it needs an ignition source or a shock. I'm suggesting that some of the frozen RP1 particles stuck together in the LOX tank to form a pellet of frozen RP1 and LOX with enough mass that when it was thrown by the boiling action at the top of the LOX tank it hit with enough energy to shock ignite itself.

https://en.wikipedia.org/wiki/Oxyliquit (https://en.wikipedia.org/wiki/Oxyliquit)

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/12/2016 07:47 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.
You mean, that the stage then vented a fuel-gox mix, ready to explode?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 07:52 pm

https://en.wikipedia.org/wiki/Oxyliquit (https://en.wikipedia.org/wiki/Oxyliquit)


Not applicable to RP-1
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 07:53 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.
You mean, that the stage then vented a fuel-gox mix, ready to explode?
Essentially. My conjecture is that the frozen RP1, either through mechanical agitation in the boiling LOX or because it was atomized by Bernoulli in the LOX pipe, was blown out the vent as a cloud of fine particles, some of which had LOX either incorporated internally or wetting the surface.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 07:53 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.

Why wouldn't the LOX have reacted violently to the hydrocarbon contamination immediately at the start of LOX load?
Because there was no ignition source. You can mix LOX and hydrocarbon fuel and it won't go off spontaneously, it needs an ignition source or a shock. I'm suggesting that some of the frozen RP1 particles stuck together in the LOX tank to form a pellet of frozen RP1 and LOX with enough mass that when it was thrown by the boiling action at the top of the LOX tank it hit with enough energy to shock ignite itself.



Those are the rest of the miracles.  I can tell you that it didn't happen that way
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 08:02 pm

https://en.wikipedia.org/wiki/Oxyliquit (https://en.wikipedia.org/wiki/Oxyliquit)


Not applicable to RP-1
Ah, but it is. There are a wide variety of such explosives using a lot of different types of fuel. Things like carbon black and charcoal I believe are used because they are less sensitive to detonation. Fuels that are more flammable are more dangerous and some will self detonate.

"Liquid oxygen plus ordinary fuels, hydrocarbons, and many other organic cmpd are powerful explosives. /Oxygen, liquid/"

from:
http://webwiser.nlm.nih.gov/getSubstanceData.do?substanceId=336&displaySubstanceName=Oxygen&STCCID=49%20043%2060&UNNAID=&selectedDataMenuItemID=7 (http://webwiser.nlm.nih.gov/getSubstanceData.do?substanceId=336&displaySubstanceName=Oxygen&STCCID=49%20043%2060&UNNAID=&selectedDataMenuItemID=7)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/12/2016 08:09 pm
Those are the rest of the miracles.  I can tell you that it didn't happen that way
Here are the steps:

1) Leak into the LOX line - improbable, but something improbable demonstrably happened.
2) LOX boiling in the line picking up the leaked RP1 and sucking in more. For a relatively small leak such as a crack, why wouldn't this be expected to happen?
3) LOX freezes the RP1 in the leak before the LOX pressure builds up enough to flow into the RP1 tank. How would this not happen? RP1 gets very viscous as it cools and freezes.
4) Frozen RP1 breaks up into fine particles. This I have no proof of and absent a cryogenic explosives lab have no way to test, but it doesn't seem impossible.
5) Cloud of particles goes out vent. If the particles were fine, why wouldn't they?
6) A clump of frozen RP1 mixed with LOX strikes a surface and ignites. The LOX comes from the LOX tank it's in, the explosion is expected and is one of the reasons people worry about not contaminating LOX.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mike_1179 on 09/12/2016 08:19 pm

The understanding I had (which various people mention in this thread) is that the extended nozzle means the stage can not be tested.

You can fire the engine without the nozzle extension and add it later.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/12/2016 08:19 pm
Those are the rest of the miracles.  I can tell you that it didn't happen that way
Here are the steps:

1) Leak into the LOX line - improbable, but something improbable demonstrably happened.
2) LOX boiling in the line picking up the leaked RP1 and sucking in more. For a relatively small leak such as a crack, why wouldn't this be expected to happen?
3) LOX freezes the RP1 in the leak before the LOX pressure builds up enough to flow into the RP1 tank. How would this not happen? RP1 gets very viscous as it cools and freezes.
4) Frozen RP1 breaks up into fine particles. This I have no proof of and absent a cryogenic explosives lab have no way to test, but it doesn't seem impossible.
5) Cloud of particles goes out vent. If the particles were fine, why wouldn't they?
6) A clump of frozen RP1 mixed with LOX strikes a surface and ignites. The LOX comes from the LOX tank it's in, the explosion is expected and is one of the reasons people worry about not contaminating LOX.
What happens to RP-1 in densified LOX? Does it freeze, dissolve, float, sink?

Consensus seems to be, that the initial fireball was a fuel-air explosion. If RP-1 leaked into the LOX tank and then vented with the GOX, all ingredients would be in place. It just needs a tiny spark for ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: speedevil on 09/12/2016 08:27 pm

What happens to RP-1 in densified LOX? Does it freeze, dissolve, float, sink?

Consensus seems to be, that the initial fireball was a fuel-air explosion. If RP-1 leaked into the LOX tank and then vented with the GOX, all ingredients would be in place. It just needs a tiny spark for ignition.

It will certainly either freeze or sink, unless it is in very, very small particles. The amount needed to 'mix' in the tank would be really quite large indeed. The pressure difference drives the plausible particle size. In order to get particles that will both stay in place without segregating, and volatalise with the oxygen spray - I suspect the pressure needed would be so high as to boil things at the jet site.

One thing that might change the situation is if there are any emulsifiers in the picture.
Does the strongback have any high pressure mustard pipes?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 08:44 pm
The empty weight is about 10 tonnes for the satellite, 25 tonnes for stage 1 and 4 tonnes for stage 2. The acceleration limits are 1 to 2 g. So that means the cradle is holding very little. It is certainly strong enough.

Also in horizontal transport the "rough" part has a support for the satellite directly. Further the tanks will be appropriately pressurized. Therefore the loads are quite comparable to other similar support situations outside the space industry.

When upright the whole lot is over 500 tonnes with 100 tonnes of second stage swaying around on the top of the 70m 12 foot tube. The distance of wobble, and speed, is easily seen on the CRS-8 video. Not anywhere near equivalent. With a fairing on top it would be more.

Certainly OK for normal operation, but this was not normal.

Can you explain the missing beams, broken off, as opposed to heated and distorted by a fireball? Why would a strut in compression by a simple 10 tonne weight break off. Why was one grabber only distorted? If it was all destroyed by the blast why was the blast selective between neighbouring struts and beams?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/12/2016 08:48 pm
Can you explain the missing beams, broken off, as opposed to heated and distorted by a fireball? Why would a strut in compression by a simple 10 tonne weight break off. Why was one grabber only distorted? If it was all destroyed by the blast why was the blast selective between neighbouring struts and beams?

Missing beams?

If you're referring to the collapsed section of the strongback, that's the weakest point - where what appears to be bottlescrews were used to enable the transition (expansion in height) from F9 1.1 to F9 FT.

Plus, it got bent when it had to hold the weight of the payload after the rocket had weakened it by exploding pretty much exactly at that point.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/12/2016 08:50 pm
Those are the rest of the miracles.  I can tell you that it didn't happen that way
Here are the steps:

1) Leak into the LOX line - improbable, but something improbable demonstrably happened.
2) LOX boiling in the line picking up the leaked RP1 and sucking in more. For a relatively small leak such as a crack, why wouldn't this be expected to happen?
3) LOX freezes the RP1 in the leak before the LOX pressure builds up enough to flow into the RP1 tank. How would this not happen? RP1 gets very viscous as it cools and freezes.
4) Frozen RP1 breaks up into fine particles. This I have no proof of and absent a cryogenic explosives lab have no way to test, but it doesn't seem impossible.
5) Cloud of particles goes out vent. If the particles were fine, why wouldn't they?
6) A clump of frozen RP1 mixed with LOX strikes a surface and ignites. The LOX comes from the LOX tank it's in, the explosion is expected and is one of the reasons people worry about not contaminating LOX.
What happens to RP-1 in densified LOX? Does it freeze, dissolve, float, sink?

Consensus seems to be, that the initial fireball was a fuel-air explosion. If RP-1 leaked into the LOX tank and then vented with the GOX, all ingredients would be in place. It just needs a tiny spark for ignition.

I don't see how one tubular pipe can leak into another.

Some sort of welding flaw in the area where the common bulkhead meets the tank wall(s)? Yes, quite possibly - but I'd still expect to see at least some evidence of the vehicle body failing prior to the explosion; and also there should have been some trace on the telemetry.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kaputnik on 09/12/2016 09:08 pm
Here are the steps:

1) Leak into the LOX line.

Going to stop you right there. How does something leak into a pressurised line?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/12/2016 09:10 pm
Here are the steps:

1) Leak into the LOX line.

Going to stop you right there. How does something leak into a pressurised line?

Aye, that too.

Just for sake of completeness, am I correct in thinking that that LOX and RP-1 pipes from the TEL to the vehicle are contained within an outer pipe that protects them from leakage / being crisped by the rocket exhaust as it launches?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/12/2016 09:21 pm
Those are the rest of the miracles.  I can tell you that it didn't happen that way
Here are the steps:

1) Leak into the LOX line - improbable, but something improbable demonstrably happened.
2) LOX boiling in the line picking up the leaked RP1 and sucking in more. For a relatively small leak such as a crack, why wouldn't this be expected to happen?
3) LOX freezes the RP1 in the leak before the LOX pressure builds up enough to flow into the RP1 tank. How would this not happen? RP1 gets very viscous as it cools and freezes.
4) Frozen RP1 breaks up into fine particles. This I have no proof of and absent a cryogenic explosives lab have no way to test, but it doesn't seem impossible.
5) Cloud of particles goes out vent. If the particles were fine, why wouldn't they?
6) A clump of frozen RP1 mixed with LOX strikes a surface and ignites. The LOX comes from the LOX tank it's in, the explosion is expected and is one of the reasons people worry about not contaminating LOX.
What happens to RP-1 in densified LOX? Does it freeze, dissolve, float, sink?

Consensus seems to be, that the initial fireball was a fuel-air explosion. If RP-1 leaked into the LOX tank and then vented with the GOX, all ingredients would be in place. It just needs a tiny spark for ignition.

I don't see how one tubular pipe can leak into another.

Some sort of welding flaw in the area where the common bulkhead meets the tank wall(s)? Yes, quite possibly - but I'd still expect to see at least some evidence of the vehicle body failing prior to the explosion; and also there should have been some trace on the telemetry.
And the other way around? LOX leaking into the RP-1 tank? The LOX would boil away and vent into the environment. Could it take enough fuel with it for the initial fuel-air explosion? The external walls would not be affected, it just needs the existing vents to escape.
Is this scenario possible? Could this be missed by the telemetry?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rickyramjet on 09/12/2016 09:24 pm
For those of you looking for an ignition source please consider the Hurricane that was passing through Florida to the north.  There were also many smaller t-storms spread all over.  A t-storm can be 30 or 40 miles away and induce significant voltages in wiring or metal structures, especially those that are 200 ft+ high.

Many years ago, 1973, in the Navy, we were anchored 2 miles offshore near Naples, Italy, for a medivac operation.  The CO wanted to send a radio message, but we had no luck.  I was ordered aloft to inspect the antennas at the top of the superstructure of the ship, about 120 feet high.  There was a lightning storm in the mountains, more than 30 miles distant.  Every time I saw a distant lightning strike in the mountains the entire top of the ship lit up with brilliant Elmo's Fire and my hair literally stood on end.  I got down below pretty darn quick.  Please google Elmo's Fire if you've not heard of it.  This is the reason NASA and the Range have restrictions on launches when there is t-storm activity or even just towering cumulus clouds.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/12/2016 09:29 pm
For those of you looking for an ignition source please consider the Hurricane that was passing through Florida to the north.  There were also many smaller t-storms spread all over.  A t-storm can be 30 or 40 miles away and induce significant voltages in wiring or metal structures, especially those that are 200 ft+ high.

Many years ago, 1973, in the Navy, we were anchored 2 miles offshore near Naples, Italy, for a medivac operation.  The CO wanted to send a radio message, but we had no luck.  I was ordered aloft to inspect the antennas at the top of the superstructure of the ship, about 120 feet high.  There was a lightning storm in the mountains, more than 30 miles distant.  Every time I saw a distant lightning strike in the mountains the entire top of the ship lit up with brilliant Elmo's Fire and my hair literally stood on end.  I got down below pretty darn quick.  Please google Elmo's Fire if you've not heard of it.  This is the reason NASA and the Range have restrictions on launches when there is t-storm activity or even just towering cumulus clouds.
Somebody posted the measurements from the field mills on the Cape.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: catdlr on 09/12/2016 09:32 pm
For those of you looking for an ignition source please consider the Hurricane that was passing through Florida to the north.  There were also many smaller t-storms spread all over.  A t-storm can be 30 or 40 miles away and induce significant voltages in wiring or metal structures, especially those that are 200 ft+ high.

Many years ago, 1973, in the Navy, we were anchored 2 miles offshore near Naples, Italy, for a medivac operation.  The CO wanted to send a radio message, but we had no luck.  I was ordered aloft to inspect the antennas at the top of the superstructure of the ship, about 120 feet high.  There was a lightning storm in the mountains, more than 30 miles distant.  Every time I saw a distant lightning strike in the mountains the entire top of the ship lit up with brilliant Elmo's Fire and my hair literally stood on end.  I got down below pretty darn quick.  Please google Elmo's Fire if you've not heard of it.  This is the reason NASA and the Range have restrictions on launches when there is t-storm activity or even just towering cumulus clouds.
Somebody posted the measurements from the field mills on the Cape.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582047#msg1582047
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 09:36 pm

Can you explain the missing beams, broken off, as opposed to heated and distorted by a fireball? Why would a strut in compression by a simple 10 tonne weight break off. Why was one grabber only distorted?


Because the payload and fairing were sitting on it, after the second stage disappeared.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/12/2016 09:50 pm
There are three things required: a fuel, an oxidizer, and an ignition source.  It seems most of the folks posting theories are focusing on whichever of the three they like most and ignoring or wildly hand-waving about the rest.

Suppose there was lox-saturated frost on the rocket.  Then what?

Suppose the a hole is poked in the tank.  Then what?

Remember, all three have to occur either simultaneously or invisibly, since there was no prior indication before the explosion.

Further, (im)probabilities multiply.  So if you postulate a highly unlikely source for one of the three, it seems your burden is much higher for showing that the other two are quite likely/common.


I feel there are a few plausable minor explanations for fuel- the strongback hydraulics, the RP1 tank, the stage 2 gimbal hydrolics- that only need a few coincidences to happen.
Oxidiser is dead simple. Lox-Frost shouldnt even be nessisary for the fuel sources I feel are most likely. If a leak is under sufficent pressure to aerosolize the fuel, a FAE can develop with normal air.

The problem, I feel, is ignition source. There's no electrical events and no heat sources in that area, by design. Someone suggesed a one-in-a-million solar mirror ignition- while unlikely, it should be relatively simple (though not easy) to retroactively prove or disprove, as we've got a bazilion pictures of the erector.

I find that theory unlikely, but what ignition sources -are- plausable?

I agree with the initial quoted post.

Unless something remarkably strange has happened, we need oxidiser, fuel and an ignition source.

We have the oxidiser if the tank is venting - an oxygen-rich environment.

We potentially have the ignition source on the erector: there is part of the air conditioning system at the height the explosion was *probably* initiated.

Okay, it will be guarded against sparking but it's not beyond reasonable suspicion that there could be a bare wire shorting or a motor that's not shielded properly and that *could* be the source.

In any instance, an ignition source is potentially the easiest mistake to have been made: the TEL is a 'Heath Robinson' of a device, which has been modified for three iterations of launch vehicle and certainly isn't what you'd build if you had a clean start (see the ones at Vandenberg and Pad 39a for comparison).


The bit that bothers me is the fuel - I don't quite see where it's come from; and I'm not easily persuaded by (for example) strangely flammable paint that SpaceX didn't realise they were applying; and that then requires some strange circumstances of oxygen liquifying out of the air.


The hydraulic fluid is possibly a candidate, but only if the claw system uses hydraulics (not pneumatics); and if the fluid is not flammable (less likely).

The hypothetical hydraulic system has a few aspects which make it a candidate for me:

- the leak can be above the point of initiation of the explosion, allowing fluid to fall down beside the vehicle in the area where the initial explosion happened
- the leak can also be upwind of the vehicle, enabling ignition within the frame of the erector frame and an explosion which is centred between the vehicle and the strongback (which corresponds with what was seen)
- the hydraulic system is probably the highest pressure fluid on the pad, so a tiny leak in a hose or fitting (not uncommon unless pipes and fittings are tested / changed regularly) will almost inevitably cause a fine mist
- there is less likely to be telemetry watching hydraulic pressures (and if the system at the top of the strongback is fed from the high-volume system that raises and lowers the erector, any pressure drop would be negligible)


(By way of comparison, the RP-1 tank considered against these counts:
- the leak would be below the point of initiation of the explosion
- the leak would have to blow into the wind to find the ignition source and this plume would almost certainly have been visible
- pressure in the tank is unlikely to produce a fine enough vapour to ignite, although in an oxygen-rich environment, the bar may be set quite low on the vapour front
- telemetry should show any significant leaks

The one thing I might entertain is the connections / equipment on the strongback that provides the feed to the upper stage - these are a bit low to correspond with the apparent point of initiation of the explosion, but sufficient pressure might allow fine fuel to be be squirted upwards.)

Just a thought for you based on your comments.

In post 2359 I show some image processing which shows "regions of interest".  If I take your hydraulic argument at face value, you could make the case that what's seen is two stream flows, one down the side of the TE/F9 and one on the opposite side of the TE.  The software could be picking up an aerosol plume which is otherwise not visible.  Or it could be picking up uncorrected atmospheric turbulence.  Or MPEG artifacts.

Just your thoughts?

We'll have better images over the net few days.  The "regions of interest" may change, may stay, may totally go away.

It's a lot of processing to do... If anyone would like to help out using one of the astrophotography image stackers, I've got a long shopping list of things to look at.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 09:56 pm
The discussion of FAE, hydraulic fluid and RP-1 spraying leaks and LOX on the outside of the vehicle is over.
SpaceX would have said something if they knew the source of the accident and now were just working on the cause.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 10:20 pm
Can you explain the missing beams, broken off, as opposed to heated and distorted by a fireball? Why would a strut in compression by a simple 10 tonne weight break off. Why was one grabber only distorted? If it was all destroyed by the blast why was the blast selective between neighbouring struts and beams?

Missing beams?

If you're referring to the collapsed section of the strongback, that's the weakest point - where what appears to be bottlescrews were used to enable the transition (expansion in height) from F9 1.1 to F9 FT.

Plus, it got bent when it had to hold the weight of the payload after the rocket had weakened it by exploding pretty much exactly at that point.

I tried to describe them earlier from the photos of the 1783? post. It is more than "bent". There is one bottle screw in the wrong direction completely. There are two welded beams missing. I think they are still up there but far from their associated welded joint. The bottle screw seems to still be upright but not supporting the structure that is now lower than its top end. The grabber beams that I thought also missing might be still there, but exactly in line with the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/12/2016 10:23 pm
By the way, this Q&A with Jim....*cough* I mean discussion thread ;) will move on to a new discussion thread when there's a milestone point in the investigation. This thread is technically too long - (over 100 pages, 480,000 views <--it's actually a lot more, but the forum runs out of fingers and toes when counting iPotato and tablet visits) - and there's always a danger of people joining mid-conversation and posting a question answered 20 pages previous.

Remember, we have the update thread for a quick view of what is solid news (things like Elon comments and so on) and the relief valve of the wacky thread for "I did some calculations on my Commodore 64..." so yeah, this is a long thread, but anyone wanting a quick view, read the update thread.

When there's a milestone point, likely via Elon, we'll go to a new thread....anything that has hit the spot from this thread could also be linked or copied over at that time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chasm on 09/12/2016 10:30 pm
The initial event -frame 1- is the fastest event, the rest is slower.

The initial event seems to happen between rocket and strongback. For various amounts of between. Could be adjacent to the rocket, which also means that it also could be shaded by the rocket.
At this point another perspective, say 90° offset would be nice. ;)

AS mentioned earlier, back to the basics.
In the good old fire triangle you need: fuel, oxidizer, heat.
Or more modern, the fire tetrahedron: fuel, oxidizer, heat, chain reaction.
Mixture is silent in both of them, and mixture is what will turn a gas fire into an explosion.

The speed of the initial event leads to the idea that a very fine fuel aerosol finds an ignition source.
Unfortunately for that idea the RP1 loading has been finished earlier and the tanks are not pressurized.
Another great source of fuel mist would be the hydraulics. They are in the area and a known risk. Because of that known risk there are directly to two objections: Are they using a normal oil instead of a safer alternative? Are this  actually hydraulics and not pneumatics?

Preview edit: Ok, that discussion is over.  :-X


There are no other obvious fuel sources that could be atomized and then ignited. Which leads everyone down the LOX route, increasing the amount of oxygen both makes fires much faster and many more things will burn...
It also leads to the the Helium/COPV route, high pressure, much stored energy.


Overall we miss heaps of details.
Are that hydraulics?
Where are the vents? GO2 and others. Rocket and strongback.
Where is electrical equipment that could be an ignition source?
Coming from the industrial world, are they using electrical gear that is intrinsically safe?
If so, is it still intrinsically safe in an oxygen enriched environment? - If oxygen enrichment can happen in the strongback area.
And much much more.
Perhaps most importantly we don't know what SpaceX has changed up in the loading/countdown process. Apparently they wanted to test something. But what, and did they actually do it.


If if if if and not a whole lot of autoritative answers. - Other than Jim.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: groundbound on 09/12/2016 10:52 pm

I don't see how one tubular pipe can leak into another.


Divine intervention would do it, which coincidentally seems to be the cause most often proposed all through this thread.

 :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ThereIWas3 on 09/12/2016 10:55 pm
I thought that SpaceX used RP1 as the hydraulic fluid, to not need another subsystem.   Or was that only on the F1?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 10:58 pm

Can you explain the missing beams, broken off, as opposed to heated and distorted by a fireball? Why would a strut in compression by a simple 10 tonne weight break off. Why was one grabber only distorted?


Because the payload and fairing were sitting on it, after the second stage disappeared.

Why would a 5 tonne satellite and fairing destroy all the turnbuckles and two welded beams? The same turnbuckles and beams, that lift it from horizontal along with a part of the dry weight of the Falcon 9. If they were so weak not to handle the offset when vertical, how did it get vertical?

I could see the grabbers distorting as they were outside their intended use. But the main connections in the strongback should have held. It means it was damaged at the turnbuckle area long before the fall. The initial blast does move the strongback and the fairing in the video. This would have been a twisting force. Did the blast break the strongback?

Or did the strongback fail first, and cause the blast.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 10:59 pm

Or did the strongback fail first, and cause the blast.

100% NO
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 11:03 pm

Why would a 5 tonne satellite and fairing destroy all the turnbuckles and two welded beams? The same turnbuckles and beams, that lift it from horizontal along with a part of the dry weight of the Falcon 9. If they were so weak not to handle the offset when vertical, how did it get vertical?

I could see the grabbers distorting as they were outside their intended use. But the main connections in the strongback should have held. It means it was damaged at the turnbuckle area long before the fall. The initial blast does move the strongback and the fairing in the video. This would have been a twisting force. Did the blast break the strongback?


Because of the blast and because the 10 tonne (satellite and fairing) dropped onto the grapper arms.  The cradle did not bend forward until after the blast.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 11:04 pm

Can you explain the missing beams, broken off, as opposed to heated and distorted by a fireball? Why would a strut in compression by a simple 10 tonne weight break off. Why was one grabber only distorted?


Because the payload and fairing were sitting on it, after the second stage disappeared.

Why would a 5 tonne satellite and fairing destroy all the turnbuckles and two welded beams?

Heat flux, blast wave and sudden shock from taking a load they're not designed to take at an angle the're not designed to take them. Seriously, have you ever analyzed a truss structure or any load-bearing system? A first-year Engineering Statics student can intuitively grasp that particular failure as an effect of the whole event, not a cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 11:16 pm

Heat flux, blast wave ...

That is my point. It was not the satellite.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 11:19 pm

Heat flux, blast wave ...

That is my point. It was not the satellite.

Absent the weight of the payload, those factors wouldn't have made any difference. That is everyone else's point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/12/2016 11:22 pm
The discussion of FAE, hydraulic fluid and RP-1 spraying leaks and LOX on the outside of the vehicle is over.
SpaceX would have said something if they knew the source of the accident and now were just working on the cause.

Granted that I have the authority to state a cause, equal to my ability to drill a hole through the earth... :)

But, seriously, we could use some help.

The software strategy we're employing should be able to identify physical structure changes near the diffraction limit of the camera & lens combination, less the MPEG destruction.  That means, if something changed on the 1-2 foot range, in the field of view of the camera, in the last 20 seconds prior to the event, we have a chance of seeing it.  That change could be motion related to parts, or plume related, or even one of the UFO theories.  IF there's a change at all.

Recap:  We've taken a state of the art atmospheric turbulence correction algorithm, and are running it through the last 1,200 frames of data.  The processing on that takes a long time.  It may finish tomorrow.

The approach assumes a static image and between multiple adjacent frames, calculates a most likely model of air turbulence effects for individual frames, and then corrects the distortion by trying to move pixels from where they are, to where they should have been.  The theory and math are in prior links.  It's smart enough to discriminate between real motion such as moving plumes and birds, from atmospheric distortion.  It's not perfect, but mathematically, it converges to a best fit.  If you've seen the 70 frame sampler posted earlier, you see the visual result.

However, that's the starting point, not the end point.

Given a group of frames, there are a gazillion other noise sources, including CCD voltage drift, uncorrected atmospheric disturbances, MPEG artifacts, and other nasty things that can still happen to the images.

That leads to the next step which we previewed in the 70 frame composite vs. the last frame difference map.

Astrophotography approaches use something called frame stacking to maximize towards the diffraction limit of the CCD/Lens combination given various assumptions on the types of distortion expected, or measured.  That's how folks routinely take a 100 or so pictures, each of which is blurry, and end up with an amazingly sharp (and accurate) single image.

The approach we're trying to take is to assume that for any given interval in the 20 seconds, (1200 frames), that interval can be stacked and compared with any other stacked interval.  If something visible happened during those 20 seconds, and it's visible within the diffraction limit of the camera and lens and MPEG, et al, differencing those stacked image sets, i.e. reducing our 1200 frames to 1 second or half second intervals, i.e. 30 or 60 frame stacks, will give us 20 to 40 frames to look at to see if anything changed given the limits of our process.

Needless to say, this takes a lot of compute power & time, and maybe it's pointless.

However, we could use some help on the stacking & differencing process.  We can provide a set of 1200 images in the next day or two, or the 70 that we have today, and you wonderful volunteers get to, download any of the many astrophysical stacking softwares, or create your own, and you could help create our 20 to 40 frames, and start the relatively mindless difference analysis, or choose alternative intervals or frame stack counts.  Or even expand upon this approach with a better one.

There are lots of variations, and the effort assumes that something might be visible, even though we have no clue what we're looking for.

So... anyone with the time, compute power, and the ability to learn and properly use stacking software?  We mean the kind that likes Point Spread Analysis, or Gaussian minimums (maximums in Europe), not the add and average type that professional photographers use.  :)

I guess PM me if you're game and we'll point you to the image files and an initial processing request.  Or publicly post your interest and I'll publicly post details on the next steps.

If we find something counter to expectations (boring low dynamic range differences), it will be a slightly bright region at a specific location.  The process won't say what's there, or what's happening, or what caused it to be there, merely that there's something there that maybe shouldn't be.  Then the arguments can begin again.  :)

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 11:24 pm

Heat flux, blast wave ...

That is my point. It was not the satellite.

Wrong, it was.  The satellite fell onto it
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 11:29 pm
  That means, if something changed on the 1-2 foot range, in the field of view of the camera, in the last 20 seconds prior to the event, we have a chance of seeing it.

All that would be a waste, because there is nothing to see since nothing changed and hence the problem that Spacex has

Spacex has many more cameras views.  There is no need to work on this one from this distance.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/12/2016 11:32 pm

Heat flux, blast wave ...

That is my point. It was not the satellite.

Absent the weight of the payload, those factors wouldn't have made any difference. That is everyone else's point.

Simply 5 tonnes extra and it was enough to tip the destructive balance. No, I do not see that. What I would concede is that the blast was offset and a twist was imparted on the structure through the motion of the base of the satellite/remaining stage 2 top. That, and the blast, could break off the beams, but it was not its weight.

The weight only bent the grabber.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 11:43 pm
It was closer to 10 tons and it fell.  There is an acceleration involved.
It broke a turnbuckle in compression
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/12/2016 11:46 pm
  That means, if something changed on the 1-2 foot range, in the field of view of the camera, in the last 20 seconds prior to the event, we have a chance of seeing it.

All that would be a waste, because there is nothing to see since nothing changed and hence the problem that Spacex has

Spacex has many more cameras views.  There is no need to work on this one from this distance.

Unless Spacex used this process on the many more camera views, they wouldn't know either.

I grant you your expertise in rockets.

Consider granting me mine in image processing?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/12/2016 11:49 pm

Heat flux, blast wave ...

That is my point. It was not the satellite.

Absent the weight of the payload, those factors wouldn't have made any difference. That is everyone else's point.

Simply 5 tonnes extra and it was enough to tip the destructive balance. No, I do not see that.

You really do not grasp truss design mechanics or load-paths do you?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/12/2016 11:49 pm
  That means, if something changed on the 1-2 foot range, in the field of view of the camera, in the last 20 seconds prior to the event, we have a chance of seeing it.

All that would be a waste, because there is nothing to see since nothing changed and hence the problem that Spacex has

Spacex has many more cameras views.  There is no need to work on this one from this distance.

Unless Spacex used this process on the many more camera views, they wouldn't know either.
.

Don't need it.  It is very obvious to see changes in close ups.

There is no more information to be obtained from this video, that can be obtained from closer views
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/12/2016 11:53 pm
There are three things required: a fuel, an oxidizer, and an ignition source.  It seems most of the folks posting theories are focusing on whichever of the three they like most and ignoring or wildly hand-waving about the rest.
I think this type of theorizing is useful.  Although there is plenty of oxidizer, there should be no fuel and no ignition source.   If one person can explain how there might be fuel (while ignoring the ignition part) and another can explain how an ignition source could arise (while ignoring how the fuel got there) it would represent significant progress.

It would be most unlikely that two separate and rare flaws would happen just on this mission.  To reduce the required coincidence down to one flaw, there are three possibilities.   The first, (a) is that some single flaw provided both fuel and an ignition source.  This seems most likely, but it apparently happened without clear signs from video or the the telemetry.  It's not obvious what this flaw might be.  Alternatively, perhaps one of these conditions is often (or always) violated.  Previous missions did not fail since the other is needed as well, but was not present.  In this case the safety margin was much less than thought, and only one additional problem could cause an explosion.  So perhaps:

(b) There has always (or often) been something flammable/explosive on the TE, umbilical, or rocket.  There has been no indication up until now since there was no source of ignition.  Or

(c) There has always (or often) been some potential ignition source.  However, since there was no fuel there was no indication.

Either of these, if shown, could reduce the puzzle to just one problem, which seems much more likely,  So speculation about how either could arise could be useful.

One alternative I've not seen addressed is a possibility for (c), an ignition source.  This might be static buildup from the flow of insulating liquid.  This is a  known problem  (http://www.machinerylubrication.com/Read/809/electrostatic-charge-hydraulic)that depends on flow rates, liquid properties, and so on.  Since both kerosene and LOX are insulating liquids, I'd assume this was already addressed in the existing art.  But sub-cooled LOX will have different properties, and SpaceX is pumping it at different rates, so maybe the old prevention techniques are insufficient.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/12/2016 11:56 pm
  That means, if something changed on the 1-2 foot range, in the field of view of the camera, in the last 20 seconds prior to the event, we have a chance of seeing it.

All that would be a waste, because there is nothing to see since nothing changed and hence the problem that Spacex has

Spacex has many more cameras views.  There is no need to work on this one from this distance.

Unless Spacex used this process on the many more camera views, they wouldn't know either.

Don't need it.  It is very obvious to see changes in close ups

Actually, I disagree.  Even with closeups, change is not always obvious.  Changes in luminance, distortion, refraction, are not things an untrained person is capable of seeing.  One reason image analysis exists and has a long storied history is because often times, things are not as they appear. 

Even if we are limited to a single horribly destroyed youtube video, the process we're working on applies to any recorded video stream.  The process looks for deltas.  It assumes, that whatever happened, didn't happen completely in 16 milliseconds.  Precursor elements, physical, refractive, reflective can be detected if you know how to process the images.  If everything happened soup to nuts in 16 milliseconds, then yes, it's pointless.  Otherwise, IMHO, not useless.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: seanpg71 on 09/12/2016 11:58 pm
No.  It needs too many miracles to happen in succession.
Not an especially strong argument.

The only fault I'm suggesting is a leak into the LOX line. After that, the stage has a situation of heavily hydrocarbon contaminated LOX which is an explosion waiting to happen.
You mean, that the stage then vented a fuel-gox mix, ready to explode?
Essentially. My conjecture is that the frozen RP1, either through mechanical agitation in the boiling LOX or because it was atomized by Bernoulli in the LOX pipe, was blown out the vent as a cloud of fine particles, some of which had LOX either incorporated internally or wetting the surface.

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582381#msg1582381)

I suppose that if you survive tanking with your rube goldberg small frozen blob of RP1 in you LOX tank, you might end up with something that looks a bit like CRS-7 once you start moving your LOX around for MVac chill-down.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Arch Admiral on 09/12/2016 11:59 pm
I think we need another sensible voice here besides Jim. Everyone else seems to be going off on weird tangents.

First, the explosion started at the junction of the S2 RP-1 and LOX tanks and the fireball burst outward on the WINDWARD side, adjoining the transporter/erector ("strongback"). The TEL is a thin lattice structure which would not stop the strong wind from scrubbing away the postulated leaking RP-1, etc. The only place that an explosive mixture of vapors could accumulate is in the turbulent eddy zone to LEEWARD of the booster (see the big external explosion that wrecked DC-X). The rapid dispersal of tank fragments further confirms that this was a internal explosion, not a DC-X type scenario.

Second, this type of accident is unknown in modern times with all other types of boosters, so we need to look for a unique feature of Falcon 9 which would fail in a unique way.

The glaringly obvious unique feature is the submerging of "composite" pressure vessels in supercooled liquid oxygen. British engineers call this material Carbon Reinforced Plastic (CRP) which is a more accurate description. Both the carbon fibers and the plastic/epoxy matrix are organic materials. The Falcon 9 design breaks a fundamental rule of rocket safety: no organic material must ever come in contact with LOX. As far as I know, every other modern rocket using CRP bottles for GHe or GN2 keeps them outside the propellant tanks. Those models using submerged tanks have stuck with titanium tanks.

The most famous case where this rule was broken was in 1951-53 when FOUR aircraft in the Bell X-1 and X-2 families blew up for no apparent reason. The LOX systems in these planes used LEATHER gaskets impregnated with WAX.

I don't know how Musk and his engineers convinced themselves that this configuration is safe. Possibly they put some inert coating on the outside of the bottles. But all the photos I have seen show them to be glossy black on the outside, like bare CRP.

Actually, we don't need actual combustion to explain the initial fireball. The He bottles are located right at the bottom of the LOX tank and a simple bursting of one would breach the common bulkhead and the outer skin at the same time.

Remember that the NASA investigators of the previous F9 S2 failure found photos of SpaceX assemblers STANDING on the He bottles - a great way to damage the outer surface after inspection.

You conspiracy buffs are now saying "Why didn't SpaceX already determine this from telemetry?" Granted that they actually have 3000 channels of telemetry and high-speed videos, I think they suffer from the same problem as the SpaceX amazing peoples on this thread - they are emotionally unable to admit that F9 has a fundamental design error that will require a long time to fix.

Look at the implications of this theory: All the first stages and second stages in production have to be redesigned and rebuilt. All the recovered first stages have to be rebuilt before they can be reused. I know I would have a hard time telling this to Elon if he were my boss.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/13/2016 12:17 am
I think we need another sensible voice here besides Jim. Everyone else seems to be going off on weird tangents.

First, the explosion started at the junction of the S2 RP-1 and LOX tanks and the fireball burst outward on the WINDWARD side, adjoining the transporter/erector ("strongback"). The TEL is a thin lattice structure which would not stop the strong wind from scrubbing away the postulated leaking RP-1, etc. The only place that an explosive mixture of vapors could accumulate is in the turbulent eddy zone to LEEWARD of the booster (see the big external explosion that wrecked DC-X). The rapid dispersal of tank fragments further confirms that this was a internal explosion, not a DC-X type scenario.

Second, this type of accident is unknown in modern times with all other types of boosters, so we need to look for a unique feature of Falcon 9 which would fail in a unique way.

The glaringly obvious unique feature is the submerging of "composite" pressure vessels in supercooled liquid oxygen. British engineers call this material Carbon Reinforced Plastic (CRP) which is a more accurate description. Both the carbon fibers and the plastic/epoxy matrix are organic materials. The Falcon 9 design breaks a fundamental rule of rocket safety: no organic material must ever come in contact with LOX. As far as I know, every other modern rocket using CRP bottles for GHe or GN2 keeps them outside the propellant tanks. Those models using submerged tanks have stuck with titanium tanks.

The most famous case where this rule was broken was in 1951-53 when FOUR aircraft in the Bell X-1 and X-2 families blew up for no apparent reason. The LOX systems in these planes used LEATHER gaskets impregnated with WAX.

I don't know how Musk and his engineers convinced themselves that this configuration is safe. Possibly they put some inert coating on the outside of the bottles. But all the photos I have seen show them to be glossy black on the outside, like bare CRP.

Actually, we don't need actual combustion to explain the initial fireball. The He bottles are located right at the bottom of the LOX tank and a simple bursting of one would breach the common bulkhead and the outer skin at the same time.

Remember that the NASA investigators of the previous F9 S2 failure found photos of SpaceX assemblers STANDING on the He bottles - a great way to damage the outer surface after inspection.

You conspiracy buffs are now saying "Why didn't SpaceX already determine this from telemetry?" Granted that they actually have 3000 channels of telemetry and high-speed videos, I think they suffer from the same problem as the SpaceX amazing peoples on this thread - they are emotionally unable to admit that F9 has a fundamental design error that will require a long time to fix.

Look at the implications of this theory: All the first stages and second stages in production have to be redesigned and rebuilt. All the recovered first stages have to be rebuilt before they can be reused. I know I would have a hard time telling this to Elon if he were my boss.

Especially if Elon, as Chief Designer, was the one who insisted on that approach in the first place.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/13/2016 12:23 am
Look at the implications of this theory: All the first stages and second stages in production have to be redesigned and rebuilt. All the recovered first stages have to be rebuilt before they can be reused. I know I would have a hard time telling this to Elon if he were my boss.
Then you have no business being on a failure board.  Would you rather explain to him why his NEXT rocket blew up, and then when the real problem comes out (as it eventually will) explain to him that you knew all along, and did not tell him?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/13/2016 12:25 am
It was closer to 10 tons and it fell.  There is an acceleration involved.
It broke a turnbuckle in compression

It was already grabbed at the top of the tank. It fell how far? Through a set of grabbers that you earlier were certain would allow no movement. The same set of grabbers that are still closed after the satellite had to fall off the top of them while at an angle that should have opened them instead if they were free to move.

The fall would be transmitted through a set of grabbers that are the only item observably bent. One grabber has not bent at all. Yet with that undamaged long flexing structure the forces instead are claimed to be transferred to a turnbuckle below which would at that point have been in alignment and destroyed by a downward axial force.

There are only two turnbuckles in compression by an offset weight of a satellite. The photo shows the one on the side with most damage intact and upright.

Nothing observable fits the description.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rakaydos on 09/13/2016 12:26 am
Tanks were not at flight pressure, but if the tank was slightly overfilled, there would be some purely internally generated pressure as subcooled Rp1 warmed up. Tanks would of course be designed to withstand this, for days on end, or it would be considered a fault. It would show up on the sensors, but be within tolerance. Because Acceptable Tolerance is a thing.

What would that pressure be? I do not know. What IS the expansion of subcooled RP1? Wound it be enough that a pinhole tank leak could cause aerosolization? That is my unproven assertion.

No, the tank is not closed.   It is still vented
Ok. Can you explain furthur where this vent would be on the Falcon 9?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: punder on 09/13/2016 12:29 am
.
.
.
Look at the implications of this theory: All the first stages and second stages in production have to be redesigned and rebuilt. All the recovered first stages have to be rebuilt before they can be reused. I know I would have a hard time telling this to Elon if he were my boss.

Especially if Elon, as Chief Designer, was the one who insisted on that approach in the first place.

This LOX-organics thing seems plausible. But I would question whether the SpaceX engineers involved in this part of the vehicle would a) fail to consider this in the first place, and b) fail to take it up the chain. I know from long experience that engineers never tire of telling other engineers, even their bosses, why they're wrong. AND the consequences of keeping your mouth shut are just too enormous. At this level you'd have to be crazy not to speak up.

And more: NASA and USAF have been all over the Falcon 9. Why didn't they balk at the composite He tanks?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 12:31 am

It was already grabbed at the top of the tank.

The top of the tank with fairing and payload would be shoved up some distance by the explosion before falling onto the one gripper.


 Through a set of grabbers that you earlier were certain would allow no movement.

Side to side movement.  Never said anything about vertical.  I would expect somebody on this forum to know that there is need to allow for vertical movement due to cryogenic contraction.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/13/2016 12:34 am
Everyone else seems to be going off on weird tangents.

Tanks have ruptured for many reason before. It causes a big cloud. What caused the ignition so instantly in this case?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/13/2016 12:36 am


Soup to nuts in 16 milliseconds?  That's fast... like amazingly fast.  Like re-write the history of exploding rockets...  but... I'm an imaging guru, not an exploding rocket guru.



The problem with an internal "soup to nuts in 16 mSec" event is that it would not cause a small bright flash that diminishes, and is followed by a much slower fire.

If something was able to do all that damage internally so quickly, it would follow that in the next 16 mSec, you'd have more LOX and propellant flying out and basically the event escalating.

Instead we see, very distinctly, a bright flash happening in frame 1, holding and diminishing for about 5 frames or so? and then the subsequent collapse (which could be a result of it, or the rest of the failure, happening in parallel).

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 12:36 am
I think we need another sensible voice here besides Jim. Everyone else seems to be going off on weird tangents.

First, the explosion started at the junction of the S2 RP-1 and LOX tanks and the fireball burst outward on the WINDWARD side, adjoining the transporter/erector ("strongback"). The TEL is a thin lattice structure which would not stop the strong wind from scrubbing away the postulated leaking RP-1, etc. The only place that an explosive mixture of vapors could accumulate is in the turbulent eddy zone to LEEWARD of the booster (see the big external explosion that wrecked DC-X). The rapid dispersal of tank fragments further confirms that this was a internal explosion, not a DC-X type scenario.

Second, this type of accident is unknown in modern times with all other types of boosters, so we need to look for a unique feature of Falcon 9 which would fail in a unique way.

The glaringly obvious unique feature is the submerging of "composite" pressure vessels in supercooled liquid oxygen. British engineers call this material Carbon Reinforced Plastic (CRP) which is a more accurate description. Both the carbon fibers and the plastic/epoxy matrix are organic materials. The Falcon 9 design breaks a fundamental rule of rocket safety: no organic material must ever come in contact with LOX. As far as I know, every other modern rocket using CRP bottles for GHe or GN2 keeps them outside the propellant tanks. Those models using submerged tanks have stuck with titanium tanks.

The LOX isn't supercooled, it's subcooled. There's a difference.

Titanium is also highly reactive with pure O2, particularly at the point of rupture in a failure.

The reactivity goes down with lower temperatures and pressures, so subcooled LOX is most likely less prone to autoignite contaminates than boiling LOX.

Quote
The most famous case where this rule was broken was in 1951-53 when FOUR aircraft in the Bell X-1 and X-2 families blew up for no apparent reason. The LOX systems in these planes used LEATHER gaskets impregnated with WAX.

I don't know how Musk and his engineers convinced themselves that this configuration is safe. Possibly they put some inert coating on the outside of the bottles. But all the photos I have seen show them to be glossy black on the outside, like bare CRP.

Most likely by testing. If they haven't tested a bursting COPV in a full LOX tank I would be a bit surprised. How many COPVs and tanking cycles as the F9 design been through with LOX? Hundreds of tanks? Thousands? They have flown 58 stages, each of which gets filled with 3 times before launch. That's 178 tanking cycles just on flight hardware, with on the order of 1,000 COPV cycles.

Quote

Actually, we don't need actual combustion to explain the initial fireball. The He bottles are located right at the bottom of the LOX tank and a simple bursting of one would breach the common bulkhead and the outer skin at the same time.

How can you be sure that a failed COPV would breach either the CB or outer wall or both? How can you be sure it would mix and explode with LOX?

Quote
Remember that the NASA investigators of the previous F9 S2 failure found photos of SpaceX assemblers STANDING on the He bottles - a great way to damage the outer surface after inspection.

You conspiracy buffs are now saying "Why didn't SpaceX already determine this from telemetry?" Granted that they actually have 3000 channels of telemetry and high-speed videos, I think they suffer from the same problem as the SpaceX amazing peoples on this thread - they are emotionally unable to admit that F9 has a fundamental design error that will require a long time to fix.

Look at the implications of this theory: All the first stages and second stages in production have to be redesigned and rebuilt. All the recovered first stages have to be rebuilt before they can be reused. I know I would have a hard time telling this to Elon if he were my boss.

What's the actual cause of the explosion? COPVs don't just burst while sitting half-full of liquid helium; they aren't hard to test for this - there were no dynamic loads. And they don't spontaneously combust when immersed in LOX.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/13/2016 12:39 am
I want to try something else...

In regular fuel-air explosion, you need to disperse the fuel very finely in "3D" to get a good burning mixture.

But here, we have LOX.

What if...  this is a surface phenomena, not a volume phenomena.

- It is very well coupled to the skin, so a much smaller amount of reactants might be able to damage the tank
- It might help with the wind conundrum.
- It will occur right on the wall, which kinda sorta maybe fits the video.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 12:40 am
One alternative I've not seen addressed is a possibility for (c), an ignition source.  This might be static buildup from the flow of insulating liquid.  This is a  known problem  (http://www.machinerylubrication.com/Read/809/electrostatic-charge-hydraulic)that depends on flow rates, liquid properties, and so on.  Since both kerosene and LOX are insulating liquids, I'd assume this was already addressed in the existing art.  But sub-cooled LOX will have different properties, and SpaceX is pumping it at different rates, so maybe the old prevention techniques are insufficient.

Well, it was raised by me some 1870-something posts back..

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917 (https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917)

..but thank you for raising it again.  8)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 12:43 am
One alternative I've not seen addressed is a possibility for (c), an ignition source.  This might be static buildup from the flow of insulating liquid.  This is a  known problem  (http://www.machinerylubrication.com/Read/809/electrostatic-charge-hydraulic)that depends on flow rates, liquid properties, and so on.  Since both kerosene and LOX are insulating liquids, I'd assume this was already addressed in the existing art.  But sub-cooled LOX will have different properties, and SpaceX is pumping it at different rates, so maybe the old prevention techniques are insufficient.

Well, it was raised by me some 1870-something posts back..

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917 (https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917)

..but thank you for raising it again.  8)

Did we establish how the second stage is grounded? The major points of contact (interstage, gripper pads) seem to be insulative.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/13/2016 12:48 am
One alternative I've not seen addressed is a possibility for (c), an ignition source.  This might be static buildup from the flow of insulating liquid.  This is a  known problem  (http://www.machinerylubrication.com/Read/809/electrostatic-charge-hydraulic)that depends on flow rates, liquid properties, and so on.  Since both kerosene and LOX are insulating liquids, I'd assume this was already addressed in the existing art.  But sub-cooled LOX will have different properties, and SpaceX is pumping it at different rates, so maybe the old prevention techniques are insufficient.

Well, it was raised by me some 1870-something posts back..

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917 (https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917)

..but thank you for raising it again.  8)

Did we establish how the second stage is grounded? The major points of contact (interstage, gripper pads) seem to be insulative.

Wouldn't there have to be a designed-in conductive path from the second stage thought the interstage to the first stage to keep all structure at the same potential during ascent?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 12:53 am
One alternative I've not seen addressed is a possibility for (c), an ignition source.  This might be static buildup from the flow of insulating liquid.  This is a  known problem  (http://www.machinerylubrication.com/Read/809/electrostatic-charge-hydraulic)that depends on flow rates, liquid properties, and so on.  Since both kerosene and LOX are insulating liquids, I'd assume this was already addressed in the existing art.  But sub-cooled LOX will have different properties, and SpaceX is pumping it at different rates, so maybe the old prevention techniques are insufficient.

Well, it was raised by me some 1870-something posts back..

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917 (https://forum.nasaspaceflight.com/index.php?topic=30981.msg1576917#msg1576917)

..but thank you for raising it again.  8)

Did we establish how the second stage is grounded? The major points of contact (interstage, gripper pads) seem to be insulative.

Wouldn't there have to be a designed-in conductive path from the second stage thought the interstage to the first stage to keep all structure at the same potential during ascent?

I would think so.. but it doesn't necessarily follow that the entire rocket is electrically bonded to the TEL - although it could be - and would have to be whilst fuelling, although that would presumably be done using the (conductive) umbilicals.


EDIT:  One thing I found interesting in those video frames posted was that the cloud of LOX from the vent did not appear to change at all until well after the initial bang, nor was it ignited by the initial bang (ie. the 'fire cloud' either wasn't fuel rich or wasn't going in that direction).  That's what makes me think this wasn't triggered by something within the LOX tank itself.
 
Does anyone know what the "MVac Fuel Trim Valve Setup" is all about??  That is the only thing I noted in the timeline posted that may have been happening at the time of the bang.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/13/2016 01:06 am

The top of the tank with fairing and payload would be shoved up some distance by the explosion before falling onto the one gripper. 


 Through a set of grabbers that you earlier were certain would allow no movement.

Side to side movement.  Never said anything about vertical.  I would expect somebody on this forum to know that there is need to allow for vertical movement due to cryogenic contraction.

It was shoved up now. But since the blast was clearly not concentric with the tank that would mean it would go the other way. It would also need to selectively retain an intact structural tank skin to allow it to come back down and impart the acceleration you say is required to crush the turnbuckle. It would also have to continue to sit there as the strongback turnbuckle areas collapsed.

As for the expansion that was immediately pointed out to you by a subsequent post by another when you claimed no movement could occur. Now we are told that these pads allow movement, but only in one direction. There could never be side to side movement at the lower pivot cradle pad anyway. That would require the Falcon 9 to twist. There was only up and down movement considered due to the pivot cradle.

Again nothing supports your claims.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/13/2016 01:07 am
I think we need another sensible voice here besides Jim. Everyone else seems to be going off on weird tangents.

I suspect there's quite a few longtime posters besides myself checking in on this thread, shaking our heads, and deciding not to wade into the "diverse" discussion. Not everyone is going off on tangents.

Not much substantive new information has been added to the discussion since the 2nd day after the accident, so there's not much new to discuss. Unfortunately, speculation has filled the void.

As for the supposition that composites in liquid oxygen might be the cause, I note that testing of composite compatibility in LOX was done as part of the X-33 program, although that says nothing about whether the tanks SpaceX used were of a compatible binder material. For the X-33, the intent was unlined LOX tanks, rather than COPV's submerged in LOX. Some more general info here:
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010020209.pdf

Relevant to this thread, Table 1 in that document (page 6) lists potential ignition sources. It's a longer list than I think most poster's appreciate - a lot of the discussion supposes scenarios where fuel and oxygen mix, but puzzle over ignition sources while ignoring, for example, the rupture they're positing as the cause of mixing as a possible ignition source. Obviously not all of these are relevant to Amos-6, and some seem redundant to a degree.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/13/2016 01:13 am
Some more notes to add to the LOX-soaked-frost theory in my post here:

However, I'm beginning to believe the LOX-soaked frost theory.  ...

1)  The Russian NK-33 family engines do use subcooled LOX (partly to cool the turbopump bearings better) but apparently not as low as 77 K.  According to Spaceflight101 at http://spaceflight101.com/spacerockets/soyuz-2-1v/   the N-1 cooled to 81 K, Antares-100 to 78 K and the current Soyuz 2-1v to 86 K.  Since these are all above 77 K, atmospheric LOX could never condense on the outside of their tanks, insulated or not.  Is it possible that the Antares-100 temperature of 78 K was chosen with this in mind?  Anybody know?  So there is not much industry experience with sub-77 LOX.

2)  There was talk of SpaceX experimenting with the timing of the fuelling process, perhaps to allow for future launch holds.  Do we know if they were doing that this time?  Since the temperature of the paint/frost surface depends on the thickness and fluffiness of the frost layer, and that in turn depends on timings and temperatures during chilldown, it's possible that the frost layer was different from usual this time.

3)  One thing in favour of the theory is that it's so easily testable in practice; a spare tank, some subcooled LOX, and a lot of days with different weather.  But of course SpaceX may already have done all that, have temperature sensors all over the outer skin, and measurements to show that the outer surface of the paint never gets down anywhere near 77 K.

I'm still open to all suggestions about fuel and ignition sources ... maybe something about the pads on the bottom of the pivoting cradle could cause ignition?  They’re in about the right place ...

There are three things required: a fuel, an oxidizer, and an ignition source.  It seems most of the folks posting theories are focusing on whichever of the three they like most and ignoring or wildly hand-waving about the rest.
Guilty as charged.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 01:15 am
...
Does anyone know what the "MVac Fuel Trim Valve Setup" is all about??  That is the only thing I noted in the timeline posted that may have been happening at the time of the bang.

It's testing/calibrating the servo motor driven propellent fine control valves on the 2nd stage:

The fuel-trim device consists of a servo-motor-controlled butterfly valve. To achieve the proper speed and torque, the design incorporates a planetary gearbox for a roughly 151:1 reduction ratio, plus additional gearing internal to the unit. The team qualified the components with a significant safety margin to protect against common-mode failure. The shaft of the motor interfaces with the valve directly to make fine adjustments. “The basic mixture ratio is given by the sizing of the tubes, and a small amount of the flow of each one gets trimmed out,” explains Frefel. “We only adjust a fraction of the whole fuel flow.”

http://www.micromo.com/applications/aerospace-defense/space-x-shuttle-launch

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/13/2016 01:18 am

Again nothing supports your claims.

An understanding of truss design and load-path analysis, basic physics and the US Launch Report video support his claims.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/13/2016 01:21 am

1)  The Russian NK-33 family engines do use subcooled LOX (partly to cool the turbopump bearings better) but apparently not as low as 77 K.  According to Spaceflight101 at http://spaceflight101.com/spacerockets/soyuz-2-1v/   the N-1 cooled to 81 K, Antares-100 to 78 K and the current Soyuz 2-1v to 86 K.  Since these are all above 77 K, atmospheric LOX could never condense on the outside of their tanks, insulated or not.  Is it possible that the Antares-100 temperature of 78 K was chosen with this in mind?  Anybody know?  So there is not much industry experience with sub-77 LOX.

77K is interesting because it's the temperature of LN2 at STP.  So temperatures near to, but just above, 77K are chosen because the allow the use of (cheap) LN2 to cool the LOX.  But the process is asymptotic as you approach the temperature of the coolant, which is why all previous systems left a generous margin between their target temperature and 77K, so the cooling process didn't take infinite time.

SpaceX got around this by lowering the pressure of the LN2 loop, so it boils a few degrees *below* 77K, and thus with the same margins between coolant and LOX temperatures they can get much closer to a 77K target.  But lowering the pressure makes the process more complicated.

Condensing atmosphere has nothing to do with it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 01:22 am
...
Does anyone know what the "MVac Fuel Trim Valve Setup" is all about??  That is the only thing I noted in the timeline posted that may have been happening at the time of the bang.

It's testing/calibrating the servo motor driven propellent fine control valves on the 2nd stage:

The fuel-trim device consists of a servo-motor-controlled butterfly valve. To achieve the proper speed and torque, the design incorporates a planetary gearbox for a roughly 151:1 reduction ratio, plus additional gearing internal to the unit. The team qualified the components with a significant safety margin to protect against common-mode failure. The shaft of the motor interfaces with the valve directly to make fine adjustments. “The basic mixture ratio is given by the sizing of the tubes, and a small amount of the flow of each one gets trimmed out,” explains Frefel. “We only adjust a fraction of the whole fuel flow.”

http://www.micromo.com/applications/aerospace-defense/space-x-shuttle-launch

Thanks for that.  Something else to add to the memory bank! :)

Where is was going with the enquiry was:  Is a short-circuit - or fuel leakage causing brittle-fracture, total failure and then short circuit - of this servo-valve assembly a possible cause here?  I've personally seen motorised cryogenic butterfly valves in industrial tank farms fail like this before (cheap ones on a Liquid Nitrogen system granted, but it did happen).
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/13/2016 01:24 am

Again nothing supports your claims.

An understanding of truss design and load-path analysis, basic physics and the US Launch Report video support his claims.


No design, or analysis, is needed as it is clearly claimed that the resulting failure is a turnbuckle in compression. So that leaves the video as the only evidence besides basic physics.

So what is the time index for the observable upward movement of the fairing? Or the index that shows it falling down onto the grabbers to crush the turnbuckle before the turnbuckle area is compromised.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 01:24 am

1.   It would also have to continue to sit there as the strongback turnbuckle areas collapsed.

2.  As for the expansion that was immediately pointed out to you by a subsequent post by another when you claimed no movement could occur. Now we are told that these pads allow movement, but only in one direction. There could never be side to side movement at the lower pivot cradle pad anyway. That would require the Falcon 9 to twist. There was only up and down movement considered due to the pivot cradle.

Again nothing supports your claims.

wrong. 

1.  It did sit there.  It was 8 seconds from the beginning of the explosion until the appearance of the fairing tipping over.

2.  The movement is the vehicle shrinking.  So the vehicle is sliding against the pads in the gripper and cradle.  The cradle pivot is not involved.   The cradle is for when the vehicle is horizontal.  Earlier strongback versions only had the gripper pads and the vehicle could not support the payload and fairing for long periods of time without supplemental support (crane and sling) while horizontal. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/13/2016 01:25 am

Thanks for that.  Something else to add to the memory bank! :)

Where is was going with the enquiry was:  Is a short-circuit - or fuel leakage causing brittle-fracture, total failure and then short circuit - of this servo-valve assembly a possible cause here?  I've personally seen motorised cryogenic butterfly valves in industrial tank farms fail like this before (cheap ones on a Liquid Nitrogen system granted, but it did happen).
The servo valves are much lower on the stage, near the Merlin.  The failure happened halfway up the tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 01:27 am
I want to try something else...

In regular fuel-air explosion, you need to disperse the fuel very finely in "3D" to get a good burning mixture.

But here, we have LOX.

What if...  this is a surface phenomena, not a volume phenomena.

- It is very well coupled to the skin, so a much smaller amount of reactants might be able to damage the tank
- It might help with the wind conundrum.
- It will occur right on the wall, which kinda sorta maybe fits the video.

You have to come up with the Stoichiometry of the fuel vs available oxygen.

If you assume RP1, Kerosine, Aluminum, bat guano, there is so much oxygen required to consume your fuel.

Deeper in this thread I provided the calculations for Kerosine, which is well studied.

I also provided an analysis of the frame 1 fireball.

Here's the basics:

1.  The frame 1 fireball is equivalent to 50-100 lb of tnt.  Analysis previously provided in this thread.
2.  If the detonation were FEA kerosine, that would have required .4 kg of kerosine.  Kerosine is not RP-1, but it's close.  It would have to be a perfect aerosol before the gremlin lit the match.  Analysis previously provided in this thread.
3.  Any other ignition source has to produce equivalent stoichiometry equivalent to 50-100 lb of tnt.  Aluminum and paint are not in the running. Nor is bird poop, iphones, lithium batteries, cork, seagulls, whatever.
4.  Frame 1 requires about 52 x 10^6 joules of energy to be consistent with that image.  Any hypothesis has to be able to produce this amount of energy.  Sherwin Williams is off the chart.  LOX, GOX, etc, is not a fuel.  You have to find a fuel that burns with that energy release in 16 milliseconds.  It doesn't matter if the oxygen is enriched, depleted, or drooling down the side of the rocket.  You need fuel that when combusted with air or enriched oxygen air, or dribbled by the nearest seagull or UFO, produces the requisite energy by BURNING the fuel.  IF you can't find the fuel, there is no explosion, and this never happened.

We have to find a means of producing 52 x 10^6 joules of energy, thereabouts, to identify the cause of this event.  My guesstimates are plus minus 50%


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 01:27 am

3)  One thing in favour of the theory is that it's so easily testable in practice; a spare tank, some subcooled LOX, and a lot of days with different weather.  But of course SpaceX may already have done all that, have temperature sensors all over the outer skin, and measurements to show that the outer surface of the paint never gets down anywhere near 77 K.

don't need to test it, just look at past missions.    No LOX soaked frost layer
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/13/2016 01:28 am
Actually, we don't need actual combustion to explain the initial fireball. The He bottles are located right at the bottom of the LOX tank and a simple bursting of one would breach the common bulkhead and the outer skin at the same time.

How can you be sure that a failed COPV would breach either the CB or outer wall or both? How can you be sure it would mix and explode with LOX?

I'm not the original poster, but keep in mind that SpaceX is on record as believing a COPV failure could cause a structural failure in CRS-7.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 01:33 am

Thanks for that.  Something else to add to the memory bank! :)

Where is was going with the enquiry was:  Is a short-circuit - or fuel leakage causing brittle-fracture, total failure and then short circuit - of this servo-valve assembly a possible cause here?  I've personally seen motorised cryogenic butterfly valves in industrial tank farms fail like this before (cheap ones on a Liquid Nitrogen system granted, but it did happen).

The servo valves are much lower on the stage, near the Merlin.  The failure happened halfway up the tank.

Oh well.. What else is halfway up the tank then?  Can't be too many things to rule out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 01:34 am
To start with, the LOX line I'm talking about is the line that runs from the LOX tank through the fuel tank to get to the engine. When the stage is being fueled, the pressure in both the LOX and RP1 tank is going to be very similar because they are separated by a common bulkhead.

RP1 will certainly float not sink in LOX, it is significantly less dense.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/13/2016 01:35 am
To start with, the LOX line I'm talking about is the line that runs from the LOX tank through the fuel tank to get to the engine. When the stage is being fueled, the pressure in both the LOX and RP1 tank is going to be very similar because they are separated by a common bulkhead.

RP1 will certainly float not sink in LOX, it is significantly less dense.

Remember, RP1 is loaded first, and then LOX. But neither tank is pressurized until late in the count after both tanks are full.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Less Land on 09/13/2016 01:37 am

1.   It would also have to continue to sit there as the strongback turnbuckle areas collapsed.

2.  As for the expansion that was immediately pointed out to you by a subsequent post by another when you claimed no movement could occur. Now we are told that these pads allow movement, but only in one direction. There could never be side to side movement at the lower pivot cradle pad anyway. That would require the Falcon 9 to twist. There was only up and down movement considered due to the pivot cradle.

Again nothing supports your claims.

wrong. 

1.  It did sit there.  It was 8 seconds from the beginning of the explosion until the appearance of the fairing tipping over.

2.  The movement is the vehicle shrinking.  So the vehicle is sliding against the pads in the gripper and cradle.  The cradle pivot is not involved.   The cradle is for when the vehicle is horizontal.  Earlier strongback versions only had the gripper pads and the vehicle could not support the payload and fairing for long periods of time without supplemental support (crane and sling) while horizontal.

1. I know it did sit there. That was my claim. How it did that, after your claim of it bouncing down onto two grabbers using the failed skin of an fully exploded tank wall to keep alignment is what I was countering. It sat there because it was always there, and was held there.

2. The cradle is not only for when the vehicle is horizontal otherwise they would have put the pads on the grabbers at the front and back. Not just the sides and the front. The video close up of the CRS-8 retract proves it is used when vertical.

Evidence shows the opposite of your claims.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 01:39 am
I want to try something else...

In regular fuel-air explosion, you need to disperse the fuel very finely in "3D" to get a good burning mixture.

But here, we have LOX.

What if...  this is a surface phenomena, not a volume phenomena.

- It is very well coupled to the skin, so a much smaller amount of reactants might be able to damage the tank
- It might help with the wind conundrum.
- It will occur right on the wall, which kinda sorta maybe fits the video.

You have to come up with the Stoichiometry of the fuel vs available oxygen.

If you assume RP1, Kerosine, Aluminum, bat guano, there is so much oxygen required to consume your fuel.

Deeper in this thread I provided the calculations for Kerosine, which is well studied.

I also provided an analysis of the frame 1 fireball.

Here's the basics:

1.  The frame 1 fireball is equivalent to 50-100 lb of tnt.  Analysis previously provided in this thread.
2.  If the detonation were FEA kerosine, that would have required .4 kg of kerosine.  Kerosine is not RP-1, but it's close.  It would have to be a perfect aerosol before the gremlin lit the match.  Analysis previously provided in this thread.
3.  Any other ignition source has to produce equivalent stoichiometry equivalent to 50-100 lb of tnt.  Aluminum and paint are not in the running. Nor is bird poop, iphones, lithium batteries, cork, seagulls, whatever.
4.  Frame 1 requires about 52 x 10^6 joules of energy to be consistent with that image.  Any hypothesis has to be able to produce this amount of energy.  Sherwin Williams is off the chart.  LOX, GOX, etc, is not a fuel.  You have to find a fuel that burns with that energy release in 16 milliseconds.  It doesn't matter if the oxygen is enriched, depleted, or drooling down the side of the rocket.  You need fuel that when combusted with air or enriched oxygen air, or dribbled by the nearest seagull or UFO, produces the requisite energy by BURNING the fuel.  IF you can't find the fuel, there is no explosion, and this never happened.

We have to find a means of producing 52 x 10^6 joules of energy, thereabouts, to identify the cause of this event.  My guesstimates are plus minus 50%
50 - 100 pounds of TNT!!!??? How did you arrive at anything near that number?

Have you ever seen even a pound of TNT explode? 50 to 100 pounds would have blown the entire second stage to bits.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/13/2016 01:40 am

3)  One thing in favour of the theory is that it's so easily testable in practice; a spare tank, some subcooled LOX, and a lot of days with different weather.  But of course SpaceX may already have done all that, have temperature sensors all over the outer skin, and measurements to show that the outer surface of the paint never gets down anywhere near 77 K.

don't need to test it, just look at past missions.    No LOX soaked frost layer

But isn't there always a frost layer (which explains the whiteness of the LOX-tank part of the sooty returned stages)?  And how would we know whether there was LOX soaked into it or not?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/13/2016 01:40 am

3)  One thing in favour of the theory is that it's so easily testable in practice; a spare tank, some subcooled LOX, and a lot of days with different weather.  But of course SpaceX may already have done all that, have temperature sensors all over the outer skin, and measurements to show that the outer surface of the paint never gets down anywhere near 77 K.

don't need to test it, just look at past missions.    No LOX soaked frost layer
With all due respect, the argument "In the ten previous trials, this effect never showed up" is evidence, but not sound engineering.  It could have been said in many, many previous failures, with respect to the cause that was eventually determined.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 01:41 am
I want to try something else...

In regular fuel-air explosion, you need to disperse the fuel very finely in "3D" to get a good burning mixture.

But here, we have LOX.

What if...  this is a surface phenomena, not a volume phenomena.

- It is very well coupled to the skin, so a much smaller amount of reactants might be able to damage the tank
- It might help with the wind conundrum.
- It will occur right on the wall, which kinda sorta maybe fits the video.

You have to come up with the Stoichiometry of the fuel vs available oxygen.

If you assume RP1, Kerosine, Aluminum, bat guano, there is so much oxygen required to consume your fuel.

Deeper in this thread I provided the calculations for Kerosine, which is well studied.

I also provided an analysis of the frame 1 fireball.

Here's the basics:

1.  The frame 1 fireball is equivalent to 50-100 lb of tnt.  Analysis previously provided in this thread.
2.  If the detonation were FEA kerosine, that would have required .4 kg of kerosine.  Kerosine is not RP-1, but it's close.  It would have to be a perfect aerosol before the gremlin lit the match.  Analysis previously provided in this thread.
3.  Any other ignition source has to produce equivalent stoichiometry equivalent to 50-100 lb of tnt.  Aluminum and paint are not in the running. Nor is bird poop, iphones, lithium batteries, cork, seagulls, whatever.
4.  Frame 1 requires about 52 x 10^6 joules of energy to be consistent with that image.  Any hypothesis has to be able to produce this amount of energy.  Sherwin Williams is off the chart.  LOX, GOX, etc, is not a fuel.  You have to find a fuel that burns with that energy release in 16 milliseconds.  It doesn't matter if the oxygen is enriched, depleted, or drooling down the side of the rocket.  You need fuel that when combusted with air or enriched oxygen air, or dribbled by the nearest seagull or UFO, produces the requisite energy by BURNING the fuel.  IF you can't find the fuel, there is no explosion, and this never happened.

We have to find a means of producing 52 x 10^6 joules of energy, thereabouts, to identify the cause of this event.  My guesstimates are plus minus 50%
50 - 100 pounds of TNT!!!??? How did you arrive at anything near that number?

Have you ever seen even a pound of TNT explode? 50 to 100 pounds would have blown the entire second stage to bits.

see my previous analysis in this thread.  It's all there
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 01:43 am
To start with, the LOX line I'm talking about is the line that runs from the LOX tank through the fuel tank to get to the engine. When the stage is being fueled, the pressure in both the LOX and RP1 tank is going to be very similar because they are separated by a common bulkhead.

RP1 will certainly float not sink in LOX, it is significantly less dense.

Remember, RP1 is loaded first, and then LOX. But neither tank is pressurized until late in the count after both tanks are full.
Precisely.
There's no pressure to prevent RP1 leaking from the full tank into the empty LOX line running through it before the LOX loading started.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 01:48 am
To start with, the LOX line I'm talking about is the line that runs from the LOX tank through the fuel tank to get to the engine. When the stage is being fueled, the pressure in both the LOX and RP1 tank is going to be very similar because they are separated by a common bulkhead.

RP1 will certainly float not sink in LOX, it is significantly less dense.

Remember, RP1 is loaded first, and then LOX. But neither tank is pressurized until late in the count after both tanks are full.
Precisely.
There's no pressure to prevent RP1 leaking from the full tank into the empty LOX line running through it before the LOX loading started.

Although I'm one who doesn't believe that's possible, for reasons discussed >1700 posts ago..

What if they inadvertently overfilled the RP1 tank and didn't notice?  Perhaps it's a closed system and the question is moot, but where do the fuel drains go??
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 01:48 am

Thanks for that.  Something else to add to the memory bank! :)

Where is was going with the enquiry was:  Is a short-circuit - or fuel leakage causing brittle-fracture, total failure and then short circuit - of this servo-valve assembly a possible cause here?  I've personally seen motorised cryogenic butterfly valves in industrial tank farms fail like this before (cheap ones on a Liquid Nitrogen system granted, but it did happen).

The servo valves are much lower on the stage, near the Merlin.  The failure happened halfway up the tank.

Oh well.. What else is halfway up the tank then?  Can't be too many things to rule out.

The trim valve, as it's name implies, only trims the flow. It is not the main propellent valving and doesn't work against full tank pressure, and AFAIK is not wet at this point in the count (i.e. it's downstream of the main valves).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/13/2016 01:51 am

Thanks for that.  Something else to add to the memory bank! :)

Where is was going with the enquiry was:  Is a short-circuit - or fuel leakage causing brittle-fracture, total failure and then short circuit - of this servo-valve assembly a possible cause here?  I've personally seen motorised cryogenic butterfly valves in industrial tank farms fail like this before (cheap ones on a Liquid Nitrogen system granted, but it did happen).

The servo valves are much lower on the stage, near the Merlin.  The failure happened halfway up the tank.

Oh well.. What else is halfway up the tank then?  Can't be too many things to rule out.

The trim valve, as it's name implies, only trims the flow. It is not the main propellent valving and doesn't work against full tank pressure, and AFAIK is not wet at this point in the count (i.e. it's downstream of the main valves).
I think Cameron's claim was that the servo might have overheated/shorted and started a fire.  But you're right, there would be little fuel for that fire at that point.  And my point was that the evidence of the fire would first show up near the engine/in the interstage, not halfway up the second stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: llanitedave on 09/13/2016 01:52 am
Credit where credit is due... threads like this are where Jim is at his best.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/13/2016 01:53 am
Folks, please be nice to Jim.  You've no idea how patient and accommodating he's being in responding to all of the theories here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 01:56 am

Thanks for that.  Something else to add to the memory bank! :)

Where is was going with the enquiry was:  Is a short-circuit - or fuel leakage causing brittle-fracture, total failure and then short circuit - of this servo-valve assembly a possible cause here?  I've personally seen motorised cryogenic butterfly valves in industrial tank farms fail like this before (cheap ones on a Liquid Nitrogen system granted, but it did happen).

The servo valves are much lower on the stage, near the Merlin.  The failure happened halfway up the tank.

Oh well.. What else is halfway up the tank then?  Can't be too many things to rule out.

The trim valve, as it's name implies, only trims the flow. It is not the main propellent valving and doesn't work against full tank pressure, and AFAIK is not wet at this point in the count (i.e. it's downstream of the main valves).

Ok.. but if you're right it just seems to me to be an odd time to test/cycle this valve (in the middle of LOX filling).  In an industrial setting you'd do this only after the valve(s) had chilled down to operating temperature and that would imply there's something in the vicinity to do the chillin' that ain't there otherwise?

...but as cscott points out, if the valve is nowhere near the ignition point, that can't be it, so we're looking for something else.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/13/2016 01:58 am
To start with, the LOX line I'm talking about is the line that runs from the LOX tank through the fuel tank to get to the engine. When the stage is being fueled, the pressure in both the LOX and RP1 tank is going to be very similar because they are separated by a common bulkhead.

RP1 will certainly float not sink in LOX, it is significantly less dense.

Remember, RP1 is loaded first, and then LOX. But neither tank is pressurized until late in the count after both tanks are full.
Precisely.
There's no pressure to prevent RP1 leaking from the full tank into the empty LOX line running through it before the LOX loading started.

Although I'm one who doesn't believe that's possible, for reasons discussed >1700 posts ago..

What if they inadvertently overfilled the RP1 tank and didn't notice?  Perhaps it's a closed system and the question is moot, but where do the fuel drains go??
 

Jim has indicated that the tanks remain vented to ambient pressure until they are pressurized late in the count. Drains, as I understand it, are back down the umbilicals into the GSE. Not exactly sure how the vents are designed but either fluid would flow out a vent (and should be visible in SpaceX's internal closeup imagery from the pad) or the GSE would register increased system pressure and load on the pumps (reduced RPM on the pump shaft, increased motor temp or current draw, decreased flow rate, increased pressure, whatever). But more to the point, RP1 load finishes fairly early in the count (T-22 minutes for S2), with plenty of time to notice and do something about it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 02:02 am
Actually, we don't need actual combustion to explain the initial fireball. The He bottles are located right at the bottom of the LOX tank and a simple bursting of one would breach the common bulkhead and the outer skin at the same time.

How can you be sure that a failed COPV would breach either the CB or outer wall or both? How can you be sure it would mix and explode with LOX?

I'm not the original poster, but keep in mind that SpaceX is on record as believing a COPV failure could cause a structural failure in CRS-7.

CRS-7 had a full COPV in a full LOX tank (<5% ullage) under flight loads at flight pressures and it didn't burst or ignite. This was a partially empty COPV in a partially empty LOX tank (>30% ullage) with no internal pressure and no dynamic loads, and it didn't just burst but also ignited, apparently in a few milliseconds and without warning.

It is far from obvious that a COPV failure would breach the tank under these circumstances. More evidence is needed to support that claim.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 02:03 am
Jim has indicated that the tanks remain vented to ambient pressure until they are pressurized late in the count. Drains, as I understand it, are back down the umbilicals into the GSE. Not exactly sure how the vents are designed but either fluid would flow out a vent (and should be visible in SpaceX's internal closeup imagery from the pad) or the GSE would register increased system pressure and load on the pumps (reduced RPM on the pump shaft, increased motor temp or current draw, decreased flow rate, increased pressure, whatever). But more to the point, RP1 load finishes fairly early in the count (T-22 minutes for S2), with plenty of time to notice and do something about it.

So there could (theoretically) be residual RP1 in the tank drain lines and umbilicals during LOX filling?? Interesting.

I wonder if they have any electrically-operated isolation valves on their RP1 drain lines anywhere near the location of the bang..
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 02:05 am
Jim has indicated that the tanks remain vented to ambient pressure until they are pressurized late in the count. Drains, as I understand it, are back down the umbilicals into the GSE. Not exactly sure how the vents are designed but either fluid would flow out a vent (and should be visible in SpaceX's internal closeup imagery from the pad) or the GSE would register increased system pressure and load on the pumps (reduced RPM on the pump shaft, increased motor temp or current draw, decreased flow rate, increased pressure, whatever). But more to the point, RP1 load finishes fairly early in the count (T-22 minutes for S2), with plenty of time to notice and do something about it.

So there could (theoretically) be residual RP1 in the tank drain lines and umbilicals during LOX filling?? Interesting.

I wonder if they have any electrically-operated isolation valves on their RP1 drain lines anywhere near the location of the bang..

The umbilicals connect to the interstage down by the Merlin. Also not particularly near the bang.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 02:15 am
Jim has indicated that the tanks remain vented to ambient pressure until they are pressurized late in the count. Drains, as I understand it, are back down the umbilicals into the GSE. Not exactly sure how the vents are designed but either fluid would flow out a vent (and should be visible in SpaceX's internal closeup imagery from the pad) or the GSE would register increased system pressure and load on the pumps (reduced RPM on the pump shaft, increased motor temp or current draw, decreased flow rate, increased pressure, whatever). But more to the point, RP1 load finishes fairly early in the count (T-22 minutes for S2), with plenty of time to notice and do something about it.

So there could (theoretically) be residual RP1 in the tank drain lines and umbilicals during LOX filling?? Interesting.

I wonder if they have any electrically-operated isolation valves on their RP1 drain lines anywhere near the location of the bang..

The umbilicals connect to the interstage down by the Merlin. Also not particularly near the bang.

Righto.  If you were going to isolate drain lines (I'm not saying they do this - I wouldn't know) you would, in industry anyways, normally do it as close to the source as possible ie. the top of the RP1 tank in this case.

..but if that ain't it, we need to keep crossing off the other possibilities.  There'll be some instrumentation there (I've seen an industrial pressure transmitter get fuel in it via a leaky diaphragm, but they probably use something more rocket-sciencey).  What else is up there??

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/13/2016 02:16 am

So there could (theoretically) be residual RP1 in the tank drain lines and umbilicals during LOX filling?? Interesting.


I don't think that necessarily follows. The tanks undoubtedly have check or isolation valves at their umbilical plates, and there may or may not be valves at the base of the tower and check valve/vents to allow the residuals to drain back down to the base of the T/E and out of the system I don't know, but I'd be very surprised if there was any significant volume of RP1 left in the system, let alone under any pressure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 02:30 am

So there could (theoretically) be residual RP1 in the tank drain lines and umbilicals during LOX filling?? Interesting.


I don't think that necessarily follows. The tanks undoubtedly have check or isolation valves at their umbilical plates, and there may or may not be valves at the base of the tower and check valve/vents to allow the residuals to drain back down to the base of the T/E and out of the system I don't know, but I'd be very surprised if there was any significant volume of RP1 left in the system, let alone under any pressure.

Sure.  ...but chasing down the fuel leak theory to it's ever-diminishing end, I'm only looking for enough RP1 at ambient pressure but in the wrong place to create the initial bang under the right conditions.  Whilst that doesn't need to be significant quantities, some small amount would still need to be heated to over 40degC to set it off: that would presumably be via electrical means.  Potential electrical sources include valves and instrumentation which presumably would become 'faulty' over some seconds and should thus have been noticed by the mission team.

But enough:  To me, COPV failure is still the most likely cause... but the 'how', where' and 'why' has yet to be explained almost 2,200 posts after it was raised as an option.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 02:36 am

1. I know it did sit there. That was my claim. How it did that, after your claim of it bouncing down onto two grabbers using the failed skin of an fully exploded tank wall to keep alignment is what I was countering. It sat there because it was always there, and was held there.

2. The cradle is not only for when the vehicle is horizontal otherwise they would have put the pads on the grabbers at the front and back. Not just the sides and the front. The video close up of the CRS-8 retract proves it is used when vertical.

Reality is not reflected in your posts.



1.  the grabbers do not see any vertical load in a nominal tanking or launch.  They do not support the fairing, they are only there for laterals.  In this case, the fairing and payload were "launched" by the explosion and were hung up on the grippers.   The grippers, cradle and strong all have parts failing from the load of the fairing, and the fairing falls off.

2.  There are bumpers on the back of the cradle and they are visible in the CRS-8 video.
Edit: and the attached photo.  The second stage is supported by the cradle at the forward dome interface and in the middle at the common bulkhead.   When the vehicle is vertical, the pads at the common bulkhead have no real purpose and the forward pads with the gripper pads keep the vehicle from moving laterally due to wind loads, and keeping the moment at the base of the vehicle to a minimum.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/13/2016 02:44 am
I think maybe we've all gotten so deeply into analyzing the US Launch Report video frame by frame that we lose a perspective -- of watching the dynamics of how the explosion progressed.

It has always appeared to me that, after the initial flash, you see a sort of horizontal unzipping of the second stage, right along the line of the common bulkhead.  It's not possible to see if the stage unzips the other way, on the other side of the rocket from our point of view, but it looks like, once the stage unzips, you get a cascade of RP-1 that starts to come down the side of the stack, but which is consumed after the first stage comes apart.

Now, run that backwards and forwards a few times.  The LOX escaping from the disintegrating LOX tank seems to be getting caught up in the fireball and carried upwards, while the RP-1 isn't nearly as completely consumed.  Doesn't that imply that 1), the stage 2 tanks couldn't have been ruptured much below the common bulkhead, or else a lot more of the RP-1 would have blown up into the fireball, leaving a lot less to cascade down, and 2) that whatever ruptured the tank most likely occurred exactly where it looks like -- right at, or just above, the common bulkhead, close to the point where the stage 2 rests on the cradle when horizontal.

And from the feeling of the motion (and this is entirely subjective, I admit), the initial flash looks to me to be slight toward the camera's point of view along the rocket than where it touches the TEL at that cradle.  This comes from the visual impression of where the flash began, and the first frame which displays the much larger fireball as it starts to proceed from right to left across the field of view.  So, while it's still non-obvious what caused the initial flash, it really appears to me that the fireball proceeds along the bulkhead as it opens up, and out of the bottom of the fireball you see RP-1 cascading down.  Which says a lot about how stage 2 unzipped, I think, which implies a rupture point at, or more likely just above, the common bulkhead...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/13/2016 02:49 am
Actually, we don't need actual combustion to explain the initial fireball. The He bottles are located right at the bottom of the LOX tank and a simple bursting of one would breach the common bulkhead and the outer skin at the same time.

How can you be sure that a failed COPV would breach either the CB or outer wall or both? How can you be sure it would mix and explode with LOX?

I'm not the original poster, but keep in mind that SpaceX is on record as believing a COPV failure could cause a structural failure in CRS-7.

CRS-7 had a full COPV in a full LOX tank (<5% ullage) under flight loads at flight pressures and it didn't burst or ignite. This was a partially empty COPV in a partially empty LOX tank (>30% ullage) with no internal pressure and no dynamic loads, and it didn't just burst but also ignited, apparently in a few milliseconds and without warning.

It is far from obvious that a COPV failure would breach the tank under these circumstances. More evidence is needed to support that claim.

Of course. My post is not in any way construed as proof of what happened.

But a COPV rupture causing subsequent failures does not seem to be out of the question. If it caused a rupture of the common bulkhead, then you have fuel and oxygen together, and as shown in post 2505, there were potential ignition sources.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/13/2016 02:52 am
  But fast fill means the sides are not in this state for long.  I'd take a very close look at this if I was on the investigation board.

Look at past missions.  Is there liquid on the outside of the stages?

And if there was LOX forming one the vehicle, it isn't going to mix with anything on the TEL. It would stream down onto the fuel tank portion of the vehicle and evaporate.    It isn't going to contribute any more O2 to the environment than the GOX venting from the vehicle.

could the strong back's supports where it touches the stage create a case where liquid accumulates on top of the pads that touch, and also perhaps wipe away small amounts of frost locally? would that be problematic?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 02:52 am
To start with, the LOX line I'm talking about is the line that runs from the LOX tank through the fuel tank to get to the engine. When the stage is being fueled, the pressure in both the LOX and RP1 tank is going to be very similar because they are separated by a common bulkhead.

RP1 will certainly float not sink in LOX, it is significantly less dense.

Remember, RP1 is loaded first, and then LOX. But neither tank is pressurized until late in the count after both tanks are full.
Precisely.
There's no pressure to prevent RP1 leaking from the full tank into the empty LOX line running through it before the LOX loading started.


Sorry but no

there are blanket pressures.  Yes, the tanks are vented but they are not vented to ambient.  the vent valves have a cracking pressure. 

And the LOX line is likely in another line for insulation

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 03:09 am

With all due respect, the argument "In the ten previous trials, this effect never showed up" is evidence, but not sound engineering.  It could have been said in many, many previous failures, with respect to the cause that was eventually determined.

This is not the Columbia scenario.

It is enough evidence since many launches were at night with worse, when the humidity is high and the wind still..    The wind was blowing for this one.

Also again, and if there were any LOX forming, it would drip down to the RP-1 tank and evaporate.




 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 03:12 am
And to all who think that the pads are wiping areas clear of ice. 
Stage 1 loading starts 14 minutes before the second stage.  It would have done most of the shrinking before LOX is onboard the second stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/13/2016 03:19 am
Attached is an image that shows where I think folks should concentrate if they believe that a visible event preceded the main show.

On the left is a compound image of the 70 turbulence stabilized frames, astrophotography technique.  In the middle is the difference between that image and the single last pre-event turbulence stabilized image.  On the right are the areas flagged, in yellow, where in my opinion, there are regions of interest.

Basically, the brighter the area in the difference map, the more it deviates from the normal.

We have a 1,200 frame turbulence removal in process, about 20 seconds worth, may be available tomorrow I'm told.

It appears that at least the three points of deviation on the left coincide with the cradle frame. So are you suggesting the cradle moved in the last frame before the fast fire?

Edit: If so, perhaps there is a design flaw with the cradle, especially when the rocket is vertical and subjected to transient loading from wind, e.g. vortex shedding. The lower pad is resting near the midpoint of the second stage, essentially creating a cantilever, and hence a stress concentrator. This effect is enhanced further when the grabber is engaged, because that pins the location of the top bulkhead. Because the cradle is also pinned, and the top pad is now fixed relative to the grabber, any flex in the rocket will be now concentrated at the lower pad. If the cradle extended to the base of the second stage, the lower pad could rest against the lower bulkhead, making the stage a pinned beam with far greater structural integrity.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/13/2016 03:19 am
If SpaceX didn't lose telemetry, then we're in crazy-land, right?  All the sane alternatives would have left a mark.

So - Collapsing bubbles as ignition mechanism?

I know the thermal mass is minuscule, but if the fluid is contaminated LOX, maybe that'll do it?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 03:25 am
Sorry but no

there are blanket pressures.  Yes, the tanks are vented but they are not vented to ambient.  the vent valves have a cracking pressure. 

And the LOX line is likely in another line for insulation
The issue with pressure isn't if it's at ambient, it's if there is a pressure differential between the RP1 tank and LOX line where the LOX line is at higher pressure than the RP1 tank before LOX loading starts, thereby preventing leaking of RP1 into the LOX line.

The construction of the LOX line is certainly a valid objection however. It must be insulated somehow, but I've not been able to find a description of how it's set up or what the coupling at the bottom RP1 bulkhead consists of. My conjecture does require a path for RP1 to get into the LOX tank which obviously is highly dependent on the exact design of that pipe. There could be other paths from below the RP1 surface into the LOX tank, but the LOX pipe is certainly the most obvious.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/13/2016 03:34 am
The issue with pressure isn't if it's at ambient, it's if there is a pressure differential between the RP1 tank and LOX line where the LOX line is at higher pressure than the RP1 tank before LOX loading starts, thereby preventing leaking of RP1 into the LOX line.

The construction of the LOX line is certainly a valid objection however. It must be insulated somehow, but I've not been able to find a description of how it's set up or what the coupling at the bottom RP1 bulkhead consists of. My conjecture does require a path for RP1 to get into the LOX tank which obviously is highly dependent on the exact design of that pipe. There could be other paths from below the RP1 surface into the LOX tank, but the LOX pipe is certainly the most obvious.

FWIW, RP1 getting into the LOX tank would rise to the top (away from the location of the bang), but be so chilled by the LOX such that you couldn't ignite it with a blowtorch.  OTOH, LOX getting into the RP1 tank could cause the RP1 tank to overfill, but they should notice that on their instrumentation.


...And that, I think, is the biggest problem with this entire conversation:  it seems no-one here has access to the detailed design of Stage 2 of the Falcon 9 (especially the bit between the two tanks) or, at least, if they do, they aren't letting on.  :-X

Despite the amazing efforts of all here, there is only so far you can go with any fault-tree analysis before you really DO need to know how the thing under observation is actually built.  ..after that, you're just guessing - and generating pages of circular discussion.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Gliderflyer on 09/13/2016 03:50 am
Sorry but no

there are blanket pressures.  Yes, the tanks are vented but they are not vented to ambient.  the vent valves have a cracking pressure. 

And the LOX line is likely in another line for insulation
The issue with pressure isn't if it's at ambient, it's if there is a pressure differential between the RP1 tank and LOX line where the LOX line is at higher pressure than the RP1 tank before LOX loading starts, thereby preventing leaking of RP1 into the LOX line.

The construction of the LOX line is certainly a valid objection however. It must be insulated somehow, but I've not been able to find a description of how it's set up or what the coupling at the bottom RP1 bulkhead consists of. My conjecture does require a path for RP1 to get into the LOX tank which obviously is highly dependent on the exact design of that pipe. There could be other paths from below the RP1 surface into the LOX tank, but the LOX pipe is certainly the most obvious.

Here is a picture of the first stage version: https://www.instagram.com/p/BJTVkzIjXUR/
The second stage line is apparently a shorter version of this. While a very artistic image, it isn't very descriptive. I guess it appears to be some form of vacuum jacket?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: northenarc on 09/13/2016 04:31 am
  Just a notion here, could this somehow be an effect of thermal shock on the COPV's or helium plumbing caused by the rapid fill cycle and subcooled LOX? I know everything is tested to these temperatures and lines are precooled and conditioned prior to LOX filling, but sub cooling and rapid fill together with COPV's is something that as far as I know has not been done before Falcon 9's recent history.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: iamlucky13 on 09/13/2016 05:37 am

FWIW, RP1 getting into the LOX tank would rise to the top (away from the location of the bang), but be so chilled by the LOX such that you couldn't ignite it with a blowtorch.

Are you sure? The teflon insulation that ignited inside the Apollo 13 cryo tank was pretty cold, too, but it only took a small amount of it warmed by the presumed short to ignite the rest of it. In air, the auto-ignition temperature of teflon is around 1000 deg. F, substantially higher than that of kerosense.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: yokem55 on 09/13/2016 07:08 am
I'm leaning more and more to the failed COPV scenario. The event happened, really, really fast. In 16 ms, the rocket went from sitting happily on the pad, to being enveloped by a fireball, and the simplest thing that could act that fast, that also makes sense is a COPV failure. All the various FAE theories that could happen that fast are really deficient in a fuel source that is both small enough to go unnoticed for several minutes leading up to the event, but large enough to make enough fuel to make the explosion. So my theory of the event:

I. During the tanking, as the lox filled the tank from the bottom up, one of the bottles near the TE side of the rocket let loose from thermal shock as the lox level rose up the bottle rapidly.

II. A burst near the top rocketed the bottle down towards common bulkhead. While the suddenly vented helium wouldn't be sufficient to burst the lox tank on its own due to the the amount of headroom available, the shredded carbon and epoxy exploding into the lox would provide more than enough fuel and energy to combust, and the gas from that combustion would have been sufficient to blow the side of the stage closest to the TE open. This blast is what we saw in "frame 1".

III. Shortly after that, the remains of the COPV and its mounting struts, aided by a shock wave of lox ahead of it impacted the common bulkhead popping its seam against the wall of the lox and RP1 tanks, allowing them to mix in a rather high energy environment.

IV. By that point there was too much fire coming out the top of the rocket instead of the bottom, and that was all she wrote...

I hope I'm wrong here, as if the COPV's are implicated, they'll be down for a year while they rework the helium storage system to something heavier but much less exciting.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/13/2016 07:11 am
OK, this is my theory:

1) A (possibly tiny) leak in the common bulkhead lets LOX into the RP1 tank
2) LOX boils away and takes some of the RP1 with it
3) The GOX-RP1 mix exits through the RP1 tank vent and forms a highly explosive cloud right were the initial explosion was observed.
4) Something (a tiny spark is enough) ignites the mixture and the rest is history

This would explain:

* no apparent breach of the hull before the explosion
* the sudden blast

Problems:
* Could this get past the telemetry?
* Could the postulated GOX-RP1 cloud form under the wind conditions?
* Could the boiling LOX carry enough RP1?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/13/2016 07:18 am
I'm leaning more and more to the failed COPV scenario. The event happened, really, really fast. In 16 ms, the rocket went from sitting happily on the pad, to being enveloped by a fireball, and the simplest thing that could act that fast, that also makes sense is a COPV failure.

Problems:
1) It appears that the initial blast originated outside the vehicle.
2) A failed COPV would be obvious in the telemetry.
3) Jim posted a picture from CRS-7. It shows a big cloud of LOX, not what appears to be a fuel-air explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/13/2016 07:31 am
Yeah :
CRS 7:
Tanks at flight pressure, overpressure causes LOX tank to burst, aerodynamic stress causes RP1 tank to disintegrate, huge cloud of mist , LOX and RP1, but no fire until the mess comes in contact with 1st stage exhaust.

AMOS6:
LOX tank half full, neither tank pressurized. Yet sudden big fireball around LOX tank? Thats so unlikely, even if any of the tanks had sprouted a leak it would more likely have created a waterfall style outpour. Since the lox is subcooled it wouldnt even turn gaseous on exit like pressurized boiling lox, it would just pour.

I think that alone points at an external event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Scotsh on 09/13/2016 08:51 am
Hello,

this has probably been asked before and i tried my best to search the thread, but didnt find anything to answer my question.

If this is a upper stage failure and it was a hot fire test (which is just testing the S1 booster), why was the upper stage fueled up? My guess it was fueled up or what exactly did combust there?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/13/2016 09:02 am
CRS 7:
Tanks at flight pressure, overpressure causes LOX tank to burst, aerodynamic stress causes RP1 tank to disintegrate, huge cloud of mist , LOX and RP1, but no fire until the mess comes in contact with 1st stage exhaust.

Emphasis mine. For all intents and purposes, the vehicle was out of the atmosphere by then. What had done the 2nd stage in was likely structural collapse due to 3G or so loading on the structure with the Dragon mass on top. The tanks are structurally stable at 1G but rely on flight pressurization for added stiffness.


AMOS6:
LOX tank half full, neither tank pressurized. Yet sudden big fireball around LOX tank? Thats so unlikely, even if any of the tanks had sprouted a leak it would more likely have created a waterfall style outpour. Since the lox is subcooled it wouldnt even turn gaseous on exit like pressurized boiling lox, it would just pour.

I think that alone points at an external event.

How does that preclude something internal like a COPV explosion, which are mounted near the tank walls and in the vicinity of the common bulkhead?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevinof on 09/13/2016 09:04 am
It's not so much a test as a dress rehearsal.  Both stages have already been tested in Texas but the idea of a pad test is to verify everything including the ground systems are all ok.

Yes they only fire the S1 engines but they are also testing the S2 fuel loading, pressures, venting, data feeds and a lot lot more.

Hello,

this has probably been asked before and i tried my best to search the thread, but didnt find anything to answer my question.

If this is a upper stage failure and it was a hot fire test (which is just testing the S1 booster), why was the upper stage fueled up? My guess it was fueled up or what exactly did combust there?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Pasander on 09/13/2016 10:32 am
My first post. Please be gentle..  :)

Does the umbilical for propellant feed to the upper stage provide both RP-1 and LOX?

If so...

Maybe the umbilical for the upper stage detached for some unknown reason. There would be pressure in the pipes feeding the propellants and quite possibly some back pressure (less than flight pressure) in the propellant tanks, too.

This would cause a spray/mist of RP-1 and LOX from the connection point. They would immediately mix and form a flammable cloud.

The connector separating would also provide a plausible ingition source, either by a mechanical or an electrical spark.

The resulting deflagaration would transition into a detonation almost instantly.

The detonation of a relatively large amount of material right next to the tanks would rupture them and everything would proceed downhill from there.

This all could happen in milliseconds, so it would not be readily evident in the video and it would also be difficult to tell the cause from the effect in the telemetry data.

But this scenario only "works" if the RP-1 and LOX feed lines are right next to each other.

Please shoot holes into this if you know something I don't, and sorry if this has been proposed earlier (quite many posts in this thread).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/13/2016 10:40 am
I've watched this video and the frames #0 - #3 also countless times so, that they've been burned to my retina already. I've convinced myself, that the initial blast originated in strongback. Not inside rocket, not on rocket body skin. Look at the attached image for approx location of initial bang. Here's why I think so:
1. Reflection on rocket body below is larger than above. There's at least is some reflection on payload fairing.
2. Those "claws" in left (frame #1) are streams of condensate, that scatter light. The same thing was possibly visible from the other side.
3. Also big part of the "flash" below is actually reflection from rocket body combined with condensate scattering
4. If the blast would have originated on rocket skin, we should not have seen those "claws". Also hints on the destruction of the S2 skin should have been visible

My take on what happened.
1. On umbilical connection with RP-1 main line, a pinhole leak developed
2. As the RP-1 is at least under pressure to reach the top of the tank (and then some to get realistic flowspeeds), then the jet should have reached at least the altitude of LOX tank on S2, giving us nice fountain, whose tip was directed towards leftmost corner of strongback near the rocket
3. The rocket is about 35pixels wide on the video. Thus, the stream to be visible, it should have had the width of at least half of a pixel (meaning approximately 2 in). In addition, the stream was hidden by the frame of the strongback
4. The stream wetted the strongback frame and the walkway (now standing vertical)
5. Heat transfer from surrounding air, strongback frame and walkway took subcooled RP-1 back to vaporization temperatures
6. Warm wind pushed the RP-1 fumes toward the rocket body
7. Downdraft near the rocket body made part of the fuel vapors sink downwards until diluted enough, so that this mixture won't catch fire anymore.
8. As of the point of ignition, I would point my finger towards electrical connections box up there, where either short or something else could have given the initial energy

After ignition:
1. Pressure ruptured both tanks, but first to arrive in scene was LOX, as the shockwave hit this tank first
2. Pressure wave pushed condensate cloud past the rocket (hence the whitish cloud is visible on left side, but barely visible on right side.
3. Arriving cold LOX should have suffocated the initial explosion if the strongback's structure would not have been wetted. Thus, it kept burning.
4. ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 11:47 am
Attached is an image that shows where I think folks should concentrate if they believe that a visible event preceded the main show.

On the left is a compound image of the 70 turbulence stabilized frames, astrophotography technique.  In the middle is the difference between that image and the single last pre-event turbulence stabilized image.  On the right are the areas flagged, in yellow, where in my opinion, there are regions of interest.

Basically, the brighter the area in the difference map, the more it deviates from the normal.

We have a 1,200 frame turbulence removal in process, about 20 seconds worth, may be available tomorrow I'm told.

It appears that at least the three points of deviation on the left coincide with the cradle frame. So are you suggesting the cradle moved in the last frame before the fast fire?

Edit: If so, perhaps there is a design flaw with the cradle, especially when the rocket is vertical and subjected to transient loading from wind, e.g. vortex shedding. The lower pad is resting near the midpoint of the second stage, essentially creating a cantilever, and hence a stress concentrator. This effect is enhanced further when the grabber is engaged, because that pins the location of the top bulkhead. Because the cradle is also pinned, and the top pad is now fixed relative to the grabber, any flex in the rocket will be now concentrated at the lower pad. If the cradle extended to the base of the second stage, the lower pad could rest against the lower bulkhead, making the stage a pinned beam with far greater structural integrity.

This type of processing can show differences in 5 ways at least.

1. Actual motion
2. Changes in luminance (i.e. more or less cloud)
3. Changes in chroma (i.e. color shift)
4. Errors in turbulence correction
5. Amplification of MPEG artifacts

We'll have more frames in a bit which will reduce 4 and 5.  As things stand with those 70 frames, 5 is largely gone, and 4 is mostly gone.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Digitalchromakey on 09/13/2016 11:59 am


Soup to nuts in 16 milliseconds?  That's fast... like amazingly fast.  Like re-write the history of exploding rockets...  but... I'm an imaging guru, not an exploding rocket guru.



The problem with an internal "soup to nuts in 16 mSec" event is that it would not cause a small bright flash that diminishes, and is followed by a much slower fire.

If something was able to do all that damage internally so quickly, it would follow that in the next 16 mSec, you'd have more LOX and propellant flying out and basically the event escalating.

Instead we see, very distinctly, a bright flash happening in frame 1, holding and diminishing for about 5 frames or so? and then the subsequent collapse (which could be a result of it, or the rest of the failure, happening in parallel).
This raises an interesting point, the video footage shows what happened, but effectively sampled every 16.7ms.

What is observed in the USLaunchReport video footage is nothing significantly unusual in one frame, then a sudden visible bright flash running almost all the way from the base of S2 up to the fairing, then leading to the subsequent 'slower darker' FAE blooming into a massive fireball.

The initial explosion is very bright and it's possible that video camera lens flare/overexposure makes the initial flash appear larger than it actually was.

Some posters have assumed that the center of the initial explosion must be at the geometric center of the first visible frame flash, which lies approximately at the boundary between the S2 RP1 and LOX tanks, however during the (up to 16.7ms) sampling interval, the flash could have started at the base of S2 then worked up tracing some extraneous fuel source, or vice-versa from the base of the fairing down.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/13/2016 12:04 pm

From the updates thread. An enhanced version of the image, to make it a bit brighter.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/13/2016 12:10 pm
Some posters have assumed that the center of the initial explosion must be at the geometric center of the first visible frame flash, which lies approximately at the boundary between the S2 RP1 and LOX tanks, however during the (up to 16.7ms) sampling interval, the flash could have started at the base of S2 then worked up tracing some extraneous fuel source, or vice-versa from the base of the fairing down.

I think there's also some merit in noting that there is a potentially a difference between the point of ignition and the location of the leak of the fuel for that initial burst (if indeed it was a leak).

It is possible that the ignition point is shown by that first frame; or the the ignition point was elsewhere and the image illustrates the point where the fuel being consumed was densest.

My suspicion is that the ignition source will have been something on the strongback: the air conditioning equipment is pretty much at that height - but is possibly upwind of any fuel.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/13/2016 12:11 pm
If Chris could get an updated quote from SpX about that (e.g., something as simple "we have 3,000 channels of telemetry at cadence 1kHz-1Hz and 15 cameras of 4K, 60 Hz video starting X hours prior to the incident"), it could be the basis for an interesting feature about telemetry and health monitoring of vehicles. 

There's a really interesting history of telemetry and accident reconstruction (reconstructing data from engine controllers recovered after 51-L, the MADS recovered on STS-107, and CRS 7 come to mind as well-known examples). 

Many thanks.

(PMing Chris is a good idea for a speedy response. He's at work during UTC work hours - Carl - Mod).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 12:17 pm


Soup to nuts in 16 milliseconds?  That's fast... like amazingly fast.  Like re-write the history of exploding rockets...  but... I'm an imaging guru, not an exploding rocket guru.



The problem with an internal "soup to nuts in 16 mSec" event is that it would not cause a small bright flash that diminishes, and is followed by a much slower fire.

If something was able to do all that damage internally so quickly, it would follow that in the next 16 mSec, you'd have more LOX and propellant flying out and basically the event escalating.

Instead we see, very distinctly, a bright flash happening in frame 1, holding and diminishing for about 5 frames or so? and then the subsequent collapse (which could be a result of it, or the rest of the failure, happening in parallel).
This raises an interesting point, the video footage shows what happened, but effectively sampled every 16.7ms.

What is observed in the USLaunchReport video footage is nothing significantly unusual in one frame, then a sudden visible bright flash running almost all the way from the base of S2 up to the fairing, then leading to the subsequent 'slower darker' FAE blooming into a massive fireball.

The initial explosion is very bright and it's possible that video camera lens flare/overexposure makes the initial flash appear larger than it actually was.

Some posters have assumed that the center of the initial explosion must be at the geometric center of the first visible frame flash, which lies approximately at the boundary between the S2 RP1 and LOX tanks, however during the (up to 16.7ms) sampling interval, the flash could have started at the base of S2 then worked up tracing some extraneous fuel source, or vice-versa from the base of the fairing down.

The fireball has a measurable boundary in some parts of that frame, not all, but some.  You can measure its probable width & height that way.  Try it.  Ignore the fully saturated areas, there's no data in those.  A good clue to size is to the right of the TE, where there's no structure or clouds to reflect anything.  Bright stuff there is not reflection, nor CCD artifact, nor lens flair.  It has structure.

Re the apparent shrinking... The event continues to expand during all relevant frames.  What gives the illusion of shrinking is gaseous material is obscuring parts of the fireball and about 5 frames in there's a lot of gaseous junk in the field of view.  If you measure the observable actual edges of the fireball, it's still expanding.

The event actually gets much brighter in the sense that the camera's AGC can't keep up with the intensity, which permits the flaring to become visible (which is inside the camera lens).  And by the way, the big Xs that everyone draws using the flair to pinpoint the center only works if the event is perfectly centered in the lens field of view.  As you move away from the center of the field of view, that beautiful X also moves.  Not knowing the lens, you can't say how much, but using the flair as any kind of geometric calculation is an error without knowing the lens and calculating how far the bright spots are from the center of the field of view.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/13/2016 12:26 pm


Soup to nuts in 16 milliseconds?  That's fast... like amazingly fast.  Like re-write the history of exploding rockets...  but... I'm an imaging guru, not an exploding rocket guru.



The problem with an internal "soup to nuts in 16 mSec" event is that it would not cause a small bright flash that diminishes, and is followed by a much slower fire.

If something was able to do all that damage internally so quickly, it would follow that in the next 16 mSec, you'd have more LOX and propellant flying out and basically the event escalating.

Instead we see, very distinctly, a bright flash happening in frame 1, holding and diminishing for about 5 frames or so? and then the subsequent collapse (which could be a result of it, or the rest of the failure, happening in parallel).
This raises an interesting point, the video footage shows what happened, but effectively sampled every 16.7ms.

What is observed in the USLaunchReport video footage is nothing significantly unusual in one frame, then a sudden visible bright flash running almost all the way from the base of S2 up to the fairing, then leading to the subsequent 'slower darker' FAE blooming into a massive fireball.

The initial explosion is very bright and it's possible that video camera lens flare/overexposure makes the initial flash appear larger than it actually was.

Some posters have assumed that the center of the initial explosion must be at the geometric center of the first visible frame flash, which lies approximately at the boundary between the S2 RP1 and LOX tanks, however during the (up to 16.7ms) sampling interval, the flash could have started at the base of S2 then worked up tracing some extraneous fuel source, or vice-versa from the base of the fairing down.

...

Re the apparent shrinking... The event continues to expand during all relevant frames.  What gives the illusion of shrinking is gaseous material is obscuring parts of the fireball and about 5 frames in there's a lot of gaseous junk in the field of view.  If you measure the observable actual edges of the fireball, it's still expanding.

...

Not true. If the fireball was in contact with this cloud of condensate, this should have been illuminated, assuming, that the fireball was still growing. This was not the case.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 12:29 pm


Soup to nuts in 16 milliseconds?  That's fast... like amazingly fast.  Like re-write the history of exploding rockets...  but... I'm an imaging guru, not an exploding rocket guru.



The problem with an internal "soup to nuts in 16 mSec" event is that it would not cause a small bright flash that diminishes, and is followed by a much slower fire.

If something was able to do all that damage internally so quickly, it would follow that in the next 16 mSec, you'd have more LOX and propellant flying out and basically the event escalating.

Instead we see, very distinctly, a bright flash happening in frame 1, holding and diminishing for about 5 frames or so? and then the subsequent collapse (which could be a result of it, or the rest of the failure, happening in parallel).
This raises an interesting point, the video footage shows what happened, but effectively sampled every 16.7ms.

What is observed in the USLaunchReport video footage is nothing significantly unusual in one frame, then a sudden visible bright flash running almost all the way from the base of S2 up to the fairing, then leading to the subsequent 'slower darker' FAE blooming into a massive fireball.

The initial explosion is very bright and it's possible that video camera lens flare/overexposure makes the initial flash appear larger than it actually was.

Some posters have assumed that the center of the initial explosion must be at the geometric center of the first visible frame flash, which lies approximately at the boundary between the S2 RP1 and LOX tanks, however during the (up to 16.7ms) sampling interval, the flash could have started at the base of S2 then worked up tracing some extraneous fuel source, or vice-versa from the base of the fairing down.

...

Re the apparent shrinking... The event continues to expand during all relevant frames.  What gives the illusion of shrinking is gaseous material is obscuring parts of the fireball and about 5 frames in there's a lot of gaseous junk in the field of view.  If you measure the observable actual edges of the fireball, it's still expanding.

...

Not true. If the fireball was in contact with this cloud of condensate, this should have been illuminated, assuming, that the fireball was still growing. This was not the case.

Show me a frame sequence with the fireball edges measured.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/13/2016 12:38 pm
I think it's not debatable that the initial flash died down for a few frames of the video before the main tank ruptures began the major fireball, as stage 2's tanks unzipped.

It seems to me we're seeing an external explosion and an initial cascade of LOX, that actually did nearly smother the fire due to blowing its fuel source away from the initial blast point.  Of course, it being LOX, as soon as any sufficient fuel source entered the mix (i.e., when the RP-1 tank ruptured), the fireball expanded again.

This would argue towards the LOX tank rupturing first, and then the RP-1 tank.  I believe this conclusion is reinforced by the observed cascade of unburned RP-1 coming down from the exploding second stage after the tanks were compromised.  Had both tanks come apart at the same time, as a tank wall failure at the common bulkhead would have done, the turbulence of the explosion would have mixed a lot more of the RP-1 into the fireball and resulted in little to no unburned RP-1 falling down along the sides of the rocket, I think...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/13/2016 12:56 pm
One idea that came to my mind - what if the explosion was caused by a litium-poly battery from one of S2 cameras? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/13/2016 12:57 pm
I think it's not debatable that the initial flash died down for a few frames of the video before the main tank ruptures began the major fireball, as stage 2's tanks unzipped.

It seems to me we're seeing an external explosion and an initial cascade of LOX, that actually did nearly smother the fire due to blowing its fuel source away from the initial blast point.  Of course, it being LOX, as soon as any sufficient fuel source entered the mix (i.e., when the RP-1 tank ruptured), the fireball expanded again.

This would argue towards the LOX tank rupturing first, and then the RP-1 tank.  I believe this conclusion is reinforced by the observed cascade of unburned RP-1 coming down from the exploding second stage after the tanks were compromised.  Had both tanks come apart at the same time, as a tank wall failure at the common bulkhead would have done, the turbulence of the explosion would have mixed a lot more of the RP-1 into the fireball and resulted in little to no unburned RP-1 falling down along the sides of the rocket, I think...

So, could I be right?
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1582920#msg1582920
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/13/2016 12:58 pm
Why would the cameras have separate batteries and why would they be placed in such an inherently cold environment like the skin of the tank at the bulkhead level?

IIRC, the 2nd stage downward-looking camera is near the interstage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/13/2016 01:00 pm
Question: is it possible to get a copy of the original, before-being-processed-by-Youtube video?

A lot of cameras record interlaced - top to bottom, every other row, then top to bottom, the in-between rows.  As a result, the in-between rows are read in slightly later.  Interlacing can be lost in video conversion; deinterlacing is commonly done to videos because modern monitors are progressive scan.  If the original was interlaced, it might be possible to get an in-between frame of the explosion, just at half the resolution.

There's also commonly an effect with cameras where data at the bottom of the frame is read out of the sensor slightly later than data at the top of the frame, but I can't see how that would be of any use here.  It's called "rolling shutter":

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

A good way to experience these effects is to drive along in a car filming something close off the side of the road, with as much zoom as you can without causing blur.  Aka, you want things to be going by very quickly.  If you pause a frame, you'll notice that everything looks bent in the frame due to the timeshift; a square object will look like a rhombus.  If the camera records interlaced, you'll notice that every other line seems out of whack.  It's relatively simple to split the interlacing into two separate half-res frames.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/13/2016 01:47 pm
My first post. Please be gentle..  :)

Does the umbilical for propellant feed to the upper stage provide both RP-1 and LOX?

If so...

Maybe the umbilical for the upper stage detached for some unknown reason. There would be pressure in the pipes feeding the propellants and quite possibly some back pressure (less than flight pressure) in the propellant tanks, too.

This would cause a spray/mist of RP-1 and LOX from the connection point. They would immediately mix and form a flammable cloud.

The connector separating would also provide a plausible ingition source, either by a mechanical or an electrical spark.

The resulting deflagaration would transition into a detonation almost instantly.

The detonation of a relatively large amount of material right next to the tanks would rupture them and everything would proceed downhill from there.

This all could happen in milliseconds, so it would not be readily evident in the video and it would also be difficult to tell the cause from the effect in the telemetry data.

But this scenario only "works" if the RP-1 and LOX feed lines are right next to each other.

Please shoot holes into this if you know something I don't, and sorry if this has been proposed earlier (quite many posts in this thread).
Welcome to the forum! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/13/2016 01:54 pm

Some posters have assumed that the center of the initial explosion must be at the geometric center of the first visible frame flash, which lies approximately at the boundary between the S2 RP1 and LOX tanks, however during the (up to 16.7ms) sampling interval, the flash could have started at the base of S2 then worked up tracing some extraneous fuel source, or vice-versa from the base of the fairing down.

most assumptions I have seen have based the ignition point at the crosshairs formed by the diffraction from the lens rather than geometric center (though this could just be the area with the optimal fuel/oxygen mix, too) one has to be really careful because of reflections etc to consider the geometrical center, particularly when the image is massively overexposed like this one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/13/2016 01:55 pm
TEL question: Do we know what was replaced on the TEL since the last launch (lines, cables) Was this the first time electrical power was fed through the cables and at how may Amps? Volts: 28DC?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:03 pm
OK, this is my theory:

1) A (possibly tiny) leak in the common bulkhead lets LOX into the RP1 tank
2) LOX boils away and takes some of the RP1 with it
3) The GOX-RP1 mix exits through the RP1 tank vent and forms a highly explosive cloud right were the initial explosion was observed.
4) Something (a tiny spark is enough) ignites the mixture and the rest is history

This would explain:

* no apparent breach of the hull before the explosion
* the sudden blast

Problems:
* Could this get past the telemetry?
* Could the postulated GOX-RP1 cloud form under the wind conditions?
* Could the boiling LOX carry enough RP1?
I don't believe there is a vent for the RP1 that would be normally exhausting on the pad. The LOX vent is needed because the LOX is boiling during filling.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/13/2016 02:06 pm
I don't believe there is a vent for the RP1 that would be normally exhausting on the pad. The LOX vent is needed because the LOX is boiling during filling.

There is a pressure relief valve like the one on the LOX tank. RP-1 tank is pressurized with helium and safing procedures after test firings and stage landing obviously require the ability to vent that pressurant gas.

1:10 - 1:16 into this video:

https://www.youtube.com/watch?v=LHqLz9ni0Bo
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/13/2016 02:07 pm
Followup: I think there's good evidence that it was interlaced, but that the interlacing has been filtered out.  See this:

https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg
(https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg)

That's from the highest res video I could download from Youtube, 1080p mp4.  Odd lines on the top, even lines on the bottom, split with:

ffmpeg -ss 71 -i video.mp4 -t 1 -vf il=d out-%04d.png

 Note that halfway through the odd lines there suddenly starts a chromatic abberation, which slowly diminishes as it continues downward.  The abberation continues along the even frames, top to bottom.  Yet the "image" in both the even and odd rows is identical.  It seems quite likely that the video was initially interlaced but has subsequently been deinterlaced during processing.  If so then there would be an additional recoverable frame as well as highly precise (sub-millisecond) timing on when the explosion began and at least the X coordinate in the frame of the ignition point.

If the original wasn't interlaced, I'd expect that the images from the even and odd rows would look almost identical.  They don't.  I can't think of a way that this result could be explained by compression artifacts, either.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 02:08 pm
My first post. Please be gentle..  :)

Does the umbilical for propellant feed to the upper stage provide both RP-1 and LOX?

If so...

Maybe the umbilical for the upper stage detached for some unknown reason. There would be pressure in the pipes feeding the propellants and quite possibly some back pressure (less than flight pressure) in the propellant tanks, too.

This would cause a spray/mist of RP-1 and LOX from the connection point. They would immediately mix and form a flammable cloud.

The connector separating would also provide a plausible ingition source, either by a mechanical or an electrical spark.

The resulting deflagaration would transition into a detonation almost instantly.

The detonation of a relatively large amount of material right next to the tanks would rupture them and everything would proceed downhill from there.

This all could happen in milliseconds, so it would not be readily evident in the video and it would also be difficult to tell the cause from the effect in the telemetry data.

But this scenario only "works" if the RP-1 and LOX feed lines are right next to each other.

Please shoot holes into this if you know something I don't, and sorry if this has been proposed earlier (quite many posts in this thread).

It is a common umbilical.
But disconnect would be visible on video and show up in telemetry
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jjyach on 09/13/2016 02:09 pm
Hi, long time lurker here, but I have a question.  I marked on the attached image a section of the second stage, near the Strongback.  What is this for/what does it contain?  I'm not sure if its structural or not, but it appears to connect down to the umbilical's at the base of the stage.  There also in some older factory images appears to be some sort of wiring through there too.  Does anyone know?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:09 pm
I've watched this video and the frames #0 - #3 also countless times so, that they've been burned to my retina already. I've convinced myself, that the initial blast originated in strongback. Not inside rocket, not on rocket body skin. Look at the attached image for approx location of initial bang. Here's why I think so:
1. Reflection on rocket body below is larger than above. There's at least is some reflection on payload fairing.
2. Those "claws" in left (frame #1) are streams of condensate, that scatter light. The same thing was possibly visible from the other side.
3. Also big part of the "flash" below is actually reflection from rocket body combined with condensate scattering
4. If the blast would have originated on rocket skin, we should not have seen those "claws". Also hints on the destruction of the S2 skin should have been visible

My take on what happened.
1. On umbilical connection with RP-1 main line, a pinhole leak developed
2. As the RP-1 is at least under pressure to reach the top of the tank (and then some to get realistic flowspeeds), then the jet should have reached at least the altitude of LOX tank on S2, giving us nice fountain, whose tip was directed towards leftmost corner of strongback near the rocket
3. The rocket is about 35pixels wide on the video. Thus, the stream to be visible, it should have had the width of at least half of a pixel (meaning approximately 2 in). In addition, the stream was hidden by the frame of the strongback
4. The stream wetted the strongback frame and the walkway (now standing vertical)
5. Heat transfer from surrounding air, strongback frame and walkway took subcooled RP-1 back to vaporization temperatures
6. Warm wind pushed the RP-1 fumes toward the rocket body
7. Downdraft near the rocket body made part of the fuel vapors sink downwards until diluted enough, so that this mixture won't catch fire anymore.
8. As of the point of ignition, I would point my finger towards electrical connections box up there, where either short or something else could have given the initial energy

After ignition:
1. Pressure ruptured both tanks, but first to arrive in scene was LOX, as the shockwave hit this tank first
2. Pressure wave pushed condensate cloud past the rocket (hence the whitish cloud is visible on left side, but barely visible on right side.
3. Arriving cold LOX should have suffocated the initial explosion if the strongback's structure would not have been wetted. Thus, it kept burning.
4. ...
One serious problem with this scenario is that RP1 vapor at anywhere near room temperature won't ignite and certainly won't explode even with an open flame. It's not at all like gasoline.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:14 pm
I don't believe there is a vent for the RP1 that would be normally exhausting on the pad. The LOX vent is needed because the LOX is boiling during filling.

There is a pressure relief valve like the one on the LOX tank. RP-1 tank is pressurized with helium and safing procedures after test firings and stage landing obviously require the ability to vent that pressurant gas.

Sure, but the proposal I was responding to was that there was an open vent on the RP1 tank that would allow a cloud of RP1 driven by evaporating leaked LOX to form outside the stage. The pressure relief valve wouldn't normally be open I don't believe. Obviously the LOX valve is open a lot during LOX loading to keep the pressure in the LOX tank under control due to boiling. There's nothing like that going on in the RP1 tank.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 02:18 pm
Hi, long time lurker here, but I have a question.  I marked on the attached image a section of the second stage, near the Strongback.  What is this for/what does it contain?  I'm not sure if its structural or not, but it appears to connect down to the umbilical's at the base of the stage.  There also in some older factory images appears to be some sort of wiring through there too.  Does anyone know?

That is cable tray.  Wire hardnesses that pass data, power and commands to and from the first stage and second stage engine section are underneath it.  There is likely also the FTS charges.  And there maybe is tubing for routing the helium from tanks in the stage.  Also, sensors heads for measuring propellant conditions.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/13/2016 02:20 pm
I don't believe there is a vent for the RP1 that would be normally exhausting on the pad. The LOX vent is needed because the LOX is boiling during filling.

There is a pressure relief valve like the one on the LOX tank. RP-1 tank is pressurized with helium and safing procedures after test firings and stage landing obviously require the ability to vent that pressurant gas.

Sure, but the proposal I was responding to was that there was an open vent on the RP1 tank that would allow a cloud of RP1 driven by evaporating leaked LOX to form outside the stage. The pressure relief valve wouldn't normally be open I don't believe. Obviously the LOX valve is open a lot during LOX loading to keep the pressure in the LOX tank under control due to boiling. There's nothing like that going on in the RP1 tank.

The fireball happened during fueling. If fuel gets in, the gas in the tank (Nitrogen??) has to get out. This would imply an open vent, I think.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/13/2016 02:20 pm
Question on the subject of possible COPV failure:

Suppose a bottle failed and being mounted to the wall of the tank you got LOX and COPV material flying out. It has been posted up thread several times that COPV material itself will burn nicely with LOX, and perhaps even supply an ignition source just by force of the rupture.

Question: Is it reasonable to assume that the failed COPV bottle by itself without any RP-1 would supply enough fuel to create a blast of the size seen in the initial frame(s)? (perhaps it depends on how the bottle breaks apart, does it break into a few large pieces? or is it instantly turned into a large mass of tiny particles?)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:26 pm
The fireball happened during fueling. If fuel gets in, the gas in the tank (Nitrogen??) has to get out. This would imply an open vent, I think.
Actually, it happened after fuel loading had completed and LOX loading had started but not finished.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/13/2016 02:32 pm
I've watched this video and the frames #0 - #3 also countless times so, that they've been burned to my retina already. I've convinced myself, that the initial blast originated in strongback. Not inside rocket, not on rocket body skin. Look at the attached image for approx location of initial bang. Here's why I think so:
1. Reflection on rocket body below is larger than above. There's at least is some reflection on payload fairing.
2. Those "claws" in left (frame #1) are streams of condensate, that scatter light. The same thing was possibly visible from the other side.
3. Also big part of the "flash" below is actually reflection from rocket body combined with condensate scattering
4. If the blast would have originated on rocket skin, we should not have seen those "claws". Also hints on the destruction of the S2 skin should have been visible

My take on what happened.
1. On umbilical connection with RP-1 main line, a pinhole leak developed
2. As the RP-1 is at least under pressure to reach the top of the tank (and then some to get realistic flowspeeds), then the jet should have reached at least the altitude of LOX tank on S2, giving us nice fountain, whose tip was directed towards leftmost corner of strongback near the rocket
3. The rocket is about 35pixels wide on the video. Thus, the stream to be visible, it should have had the width of at least half of a pixel (meaning approximately 2 in). In addition, the stream was hidden by the frame of the strongback
4. The stream wetted the strongback frame and the walkway (now standing vertical)
5. Heat transfer from surrounding air, strongback frame and walkway took subcooled RP-1 back to vaporization temperatures
6. Warm wind pushed the RP-1 fumes toward the rocket body
7. Downdraft near the rocket body made part of the fuel vapors sink downwards until diluted enough, so that this mixture won't catch fire anymore.
8. As of the point of ignition, I would point my finger towards electrical connections box up there, where either short or something else could have given the initial energy

After ignition:
1. Pressure ruptured both tanks, but first to arrive in scene was LOX, as the shockwave hit this tank first
2. Pressure wave pushed condensate cloud past the rocket (hence the whitish cloud is visible on left side, but barely visible on right side.
3. Arriving cold LOX should have suffocated the initial explosion if the strongback's structure would not have been wetted. Thus, it kept burning.
4. ...
One serious problem with this scenario is that RP1 vapor at anywhere near room temperature won't ignite and certainly won't explode even with an open flame. It's not at all like gasoline.

Sorry on posting in hurry, but here: http://www.aidic.it/aaas08/webpapers/43DiBenedetto.pdf they have plotted data also for temperatures below 45c, showing that it may be possible to initiate kerosene mixture in lower temperatures as well. Though, I'm currently unable to read this through and you can sink my ship easily.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/13/2016 02:33 pm
From update thread

From P.B. de Selding:

Quote
SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

https://twitter.com/pbdes/status/775702299402526720

That is a fast return and would indicate they have an idea what caused it or have narrowed it to not be the vehicle?

How do they go from 'we have no idea' to 'rtf in 3 months' in just a few days?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:35 pm
Question on the subject of possible COPV failure:

Suppose a bottle failed and being mounted to the wall of the tank you got LOX and COPV material flying out. It has been posted up thread several times that COPV material itself will burn nicely with LOX, and perhaps even supply an ignition source just by force of the rupture.

Question: Is it reasonable to assume that the failed COPV bottle by itself without any RP-1 would supply enough fuel to create a blast of the size seen in the initial frame(s)? (perhaps it depends on how the bottle breaks apart, does it break into a few large pieces? or is it instantly turned into a large mass of tiny particles?)
The pictures I've seen of COPV failures look more or less like this:
(http://abilitycomposites.com/wp-content/uploads/2015/06/tank-image.jpg)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:36 pm
From update thread

From P.B. de Selding:

Quote
SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

https://twitter.com/pbdes/status/775702299402526720

That is a fast return and would indicate they have an idea what caused it or have narrowed it to not be the vehicle?

How do they go from 'we have no idea' to 'rtf in 3 months' in just a few days?
They figured it out and it's an easy fix?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 02:37 pm
Question on the subject of possible COPV failure:

Suppose a bottle failed and being mounted to the wall of the tank you got LOX and COPV material flying out. It has been posted up thread several times that COPV material itself will burn nicely with LOX, and perhaps even supply an ignition source just by force of the rupture.

Question: Is it reasonable to assume that the failed COPV bottle by itself without any RP-1 would supply enough fuel to create a blast of the size seen in the initial frame(s)? (perhaps it depends on how the bottle breaks apart, does it break into a few large pieces? or is it instantly turned into a large mass of tiny particles?)

Depends on the type and cause of failure, and how much energy is stored in the vessel at the time. High energy overpressure failures can turn the resin matrix into dust and expose the massive surface area of all the winding fibers very quickly.

Low pressure spot failures or puncture failures would simply vent the helium into the LOX tank relatively slowly and with little debris.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 02:37 pm
Followup: I think there's good evidence that it was interlaced, but that the interlacing has been filtered out.  See this:

https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg
(https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg)

That's from the highest res video I could download from Youtube, 1080p mp4.  Odd lines on the top, even lines on the bottom, split with:

ffmpeg -ss 71 -i video.mp4 -t 1 -vf il=d out-%04d.png

 Note that halfway through the odd lines there suddenly starts a chromatic abberation, which slowly diminishes as it continues downward.  The abberation continues along the even frames, top to bottom.  Yet the "image" in both the even and odd rows is identical.  It seems quite likely that the video was initially interlaced but has subsequently been deinterlaced during processing.  If so then there would be an additional recoverable frame as well as highly precise (sub-millisecond) timing on when the explosion began and at least the X coordinate in the frame of the ignition point.

If the original wasn't interlaced, I'd expect that the images from the even and odd rows would look almost identical.  They don't.  I can't think of a way that this result could be explained by compression artifacts, either.

Someone earlier suggested that the 1080 was upsampled from the original of 720.  That might do it.

Do you see the same on the 720 version?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/13/2016 02:39 pm
How sure are we explosion happened on TEL side of the rocket around common bulkhead? I looked at the video and traced trajectories of 3 fast moving objects visible in first few frames and they all seem to come out from interstage area.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/13/2016 02:41 pm
Followup: I think there's good evidence that it was interlaced, but that the interlacing has been filtered out.  See this:

https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg
(https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg)

That's from the highest res video I could download from Youtube, 1080p mp4.  Odd lines on the top, even lines on the bottom, split with:

ffmpeg -ss 71 -i video.mp4 -t 1 -vf il=d out-%04d.png

 Note that halfway through the odd lines there suddenly starts a chromatic abberation, which slowly diminishes as it continues downward.  The abberation continues along the even frames, top to bottom.  Yet the "image" in both the even and odd rows is identical.  It seems quite likely that the video was initially interlaced but has subsequently been deinterlaced during processing.  If so then there would be an additional recoverable frame as well as highly precise (sub-millisecond) timing on when the explosion began and at least the X coordinate in the frame of the ignition point.

If the original wasn't interlaced, I'd expect that the images from the even and odd rows would look almost identical.  They don't.  I can't think of a way that this result could be explained by compression artifacts, either.

Someone earlier suggested that the 1080 was upsampled from the original of 720.  That might do it.

Do you see the same on the 720 version?

Yep, looks the same on the 720 version.  If it was deinterlaced, which IMHO seems likely, that was done before scaling.  After that, scaling will have no effect on any such artifacts.

I put in a request at US Launch Report for the raw video, if they have it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/13/2016 02:43 pm
Question on the subject of possible COPV failure:

Suppose a bottle failed and being mounted to the wall of the tank you got LOX and COPV material flying out. It has been posted up thread several times that COPV material itself will burn nicely with LOX, and perhaps even supply an ignition source just by force of the rupture.

Question: Is it reasonable to assume that the failed COPV bottle by itself without any RP-1 would supply enough fuel to create a blast of the size seen in the initial frame(s)? (perhaps it depends on how the bottle breaks apart, does it break into a few large pieces? or is it instantly turned into a large mass of tiny particles?)

Depends on the type and cause of failure, and how much energy is stored in the vessel at the time. High energy overpressure failures can turn the resin matrix into dust and expose the massive surface area of all the winding fibers very quickly.

Low pressure spot failures or puncture failures would simply vent the helium into the LOX tank relatively slowly and with little debris.

OK, lets go with a hypothetical worst case, can anyone answer the question if that is enough fuel for the initial visible blast?

(and for the record, considering they are now saying RTF in november, it's seems impossible for this to have been a COPV failure)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/13/2016 02:44 pm
How sure are we explosion happened on TEL side of the rocket around common bulkhead? I looked at the video and traced trajectories of 3 fast moving objects visible in first few frames and they all seem to come out from interstage area.
Interesting Marek, Could you post the link of which video you were watching and at what speed (normal?) you saw the objects...
Thanks
Rob
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herbie on 09/13/2016 02:45 pm
From update thread

From P.B. de Selding:

Quote
SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

https://twitter.com/pbdes/status/775702299402526720

That is a fast return and would indicate they have an idea what caused it or have narrowed it to not be the vehicle?

How do they go from 'we have no idea' to 'rtf in 3 months' in just a few days?
They figured it out and it's an easy fix?

Perhaps they finished a thorough examination of the TEL?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ugordan on 09/13/2016 02:45 pm
I put in a request at US Launch Report for the raw video, if they have it.

Their videos don't look deinterlaced to me, but they are known to use digital zoom on the camera *extensively* FWIW.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/13/2016 02:46 pm
How do they go from 'we have no idea' to 'rtf in 3 months' in just a few days?

'wtf' to 'rtf' in 3 months ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Earendil on 09/13/2016 02:49 pm
OK,

one serious flaw I see in all COPV scenarios is that COPV burst would clearly show on the telemetry.

In the CRS7 RUD, Elon tweeted about the sudden pressure drop in the first hours or so from the explosion.

So, as they are dealing with milliseconds of data, if the COPV would burst, they will see a pressure drop some milliseconds before the actual fire.. maybe also some other data I am not familiar with, but I am 99.99% sure, they would have known if it was that..

I would just forget about all the COPV speculations.. it would be too obvious for them to wonder about the reason for the RUD.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:53 pm
[OK, lets go with a hypothetical worst case, can anyone answer the question if that is enough fuel for the initial visible blast?

(and for the record, considering they are now saying RTF in november, it's seems impossible for this to have been a COPV failure)
I suspect we're well into flailing at a dead horse, but FWIW, I'm doubtful of an internal overpressure event such as a COPV failure simply because the initial flash was so fast and asymmetrical. There was no evidence of damage to the left side of the stage at the flash frame and no evidence of a wall failure before the flash frame. I'd expect an overpressure event to be more symmetrical and to first burst the wall, then ignite. If the ignition was inside the tank, I'd expect it to symmetrically blow out both sides.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 02:54 pm
OK,

one serious flaw I see in all COPV scenarios is that COPV burst would clearly show on the telemetry.

In the CRS7 RUD, Elon tweeted about the sudden pressure drop in the first hours or so from the explosion.

So, as they are dealing with milliseconds of data, if the COPV would burst, they will see a pressure drop some milliseconds before the actual fire.. maybe also some other data I am not familiar with, but I am 99.99% sure, they would have known if it was that..

I would just forget about all the COPV speculations.. it would be too obvious for them to wonder about the reason for the RUD.
In CRS-7 there wasn't a COPV failure, the COPV broke loose because of a strut failure and twisted and broke a helium line.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/13/2016 03:01 pm
Just one tiny problem with Ms. Shotwell's tweet -- I doubt they'll be launching from CCAFS (SLC-40) any time soon.  Much more likely from KSC (LC-39A), I would think... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Earendil on 09/13/2016 03:03 pm
OK,

one serious flaw I see in all COPV scenarios is that COPV burst would clearly show on the telemetry.

In the CRS7 RUD, Elon tweeted about the sudden pressure drop in the first hours or so from the explosion.

So, as they are dealing with milliseconds of data, if the COPV would burst, they will see a pressure drop some milliseconds before the actual fire.. maybe also some other data I am not familiar with, but I am 99.99% sure, they would have known if it was that..

I would just forget about all the COPV speculations.. it would be too obvious for them to wonder about the reason for the RUD.
In CRS-7 there wasn't a COPV failure, the COPV broke loose because of a strut failure and twisted and broke a helium line.

I am aware of that, nevertheless, .. overpressure due to some stuck valve or so, would show.. burst, would also show.. they would have know and said smth about it..

Then again, all my "expertise" on the subject comes from NSF and my own flow of logic :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/13/2016 03:04 pm
OK,

one serious flaw I see in all COPV scenarios is that COPV burst would clearly show on the telemetry.

In the CRS7 RUD, Elon tweeted about the sudden pressure drop in the first hours or so from the explosion.

So, as they are dealing with milliseconds of data, if the COPV would burst, they will see a pressure drop some milliseconds before the actual fire.. maybe also some other data I am not familiar with, but I am 99.99% sure, they would have known if it was that..

I would just forget about all the COPV speculations.. it would be too obvious for them to wonder about the reason for the RUD.

Sudden pressure increase in the LOX tank, followed by a pressure drop as the tank burst?

But - as has been said many times - in the absence of fuel (and probably an ignition source) - we would almost certainly have seen some sign of the LOX tank bursting before ignition (see CRS-7),

Plus, if there is a credible suggestion of RTF in November, that surely has to rule out major reworking of the vehicle?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 03:06 pm
[OK, lets go with a hypothetical worst case, can anyone answer the question if that is enough fuel for the initial visible blast?

(and for the record, considering they are now saying RTF in november, it's seems impossible for this to have been a COPV failure)
I suspect we're well into flailing at a dead horse, but FWIW, I'm doubtful of an internal overpressure event such as a COPV failure simply because the initial flash was so fast and asymmetrical. There was no evidence of damage to the left side of the stage at the flash frame and no evidence of a wall failure before the flash frame. I'd expect an overpressure event to be more symmetrical and to first burst the wall, then ignite. If the ignition was inside the tank, I'd expect it to symmetrically blow out both sides.

IF the COPV had a sudden, catastrophic high-energy over-pressure failure WITH rapid mixing and shock ignition of the resin matrix dust in LOX, then you would get exactly what the video shows. Several kg of epoxy would burn in a few milliseconds and the resulting shockwave of hot gasses (NOT cold helium shock from the initial COPV failure) would asymmetrically blow out the near side of the LOX tank with a large flare.

The part I cannot reconcile is how you get a high energy over-pressure failure while the tank is supposed to be in a low energy half-full state, without seeing the pressure rising on telemetry.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/13/2016 03:08 pm
Just one tiny problem with Ms. Shotwell's tweet -- I doubt they'll be launching from CCAFS (SLC-40) any time soon.  Much more likely from KSC (LC-39A), I would think... ;)

Shotwell didn't tweet anything. The tweet was secondhand from a statement.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/13/2016 03:13 pm
Just one tiny problem with Ms. Shotwell's tweet -- I doubt they'll be launching from CCAFS (SLC-40) any time soon.  Much more likely from KSC (LC-39A), I would think... ;)

Shotwell didn't tweet anything. The tweet was secondhand from a statement.

The second Tweet  (https://twitter.com/pbdes/status/775707555444252673) is very interesting. What can we conclude from unchanged insurance rates?

* The insurers already know the root cause and believe that the issue has been fixed
* It was not a vehicle issue
* ...?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kansan52 on 09/13/2016 03:24 pm
Someone upstream posted the answer may have come from examining the TEL (T/L). Is it ground level now? Maybe long lens photos from the ground or a drone camera but retracting and ground level examination could locate the point of ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kryten on 09/13/2016 03:25 pm
Quote
Peter B. de Selding ‏@pbdes  4m4 minutes ago
SpaceX's Shotwell: Nov return to flight is our best hope. We still haven't isolated the cause or whether its origin was rocket or ground.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 03:45 pm
Quote
Peter B. de Selding ‏@pbdes  4m4 minutes ago
SpaceX's Shotwell: Nov return to flight is our best hope. We still haven't isolated the cause or whether its origin was rocket or ground.
Well, it appears the horse is alive after all, resume the beating.  ::)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/13/2016 03:47 pm
Wow, that's an interesting set of Shotwell quotes in that series of tweets.  Goes from "we anticipate RTF in November, total down time three months" to (paraphrasing) "that's best-case, we still have no idea when we'll actually be able to fly."

Almost sounds like two different people being quoted under Shotwell's aegis -- one who thinks they've resolved the issue, and one who doesn't...   ???
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/13/2016 03:50 pm
I wonder....

Dragon 39A.
Iridium - Vandy.
SES - 39A or LC-40.
FH - 39A?

(Oh and there's SHERPA somewhere in the mix).

Probably the subject of a new thread at some point.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/13/2016 03:51 pm
From P.B. de Selding:

Quote
SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

https://twitter.com/pbdes/status/775702299402526720

That is a fast return and would indicate they have an idea what caused it or have narrowed it to not be the vehicle?

I hope so, but it's not certain.

If SpaceX after looking at all data just doesn't have enough information to have a reasonably suspect part of hardware, what are they to do? Stop launching "because we have an unknown unreliable hardware in our rocket"?

Of course not. Have a few blind hunches. Strengthen this strut, improve that insulation. Add a few RP-1 vapor sensors. Put more cameras around the pad, make sure they and their data would survive a similar accident. And back to work.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: BrightLight on 09/13/2016 03:51 pm
I wonder....

Dragon 39A.
Iridium - Vandy.
SES - 39A or LC-40.
FH - 39A?

(Oh and there's SHERPA somewhere in the mix).

Probably the subject of a new thread at some point.
https://twitter.com/pbdes
"SpaceX's Shotwell: Falcon Heavy wont launch this year, likely Q1 next year. Could be from Pad 39A or from VAFB, not sure."
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jack Gray on 09/13/2016 03:54 pm
Don't know if Selding is interviewing Shotwell or how he is getting his info as his tweets keep coming in sporadically:

Peter B. de Selding ‏@pbdes  3 minutes ago
SpaceX's Shotwell: Falcon Heavy wont launch this year, likely Q1 next year. Could be from Pad 39A or from VAFB, not sure.

 Peter B. de Selding ‏@pbdes  23 minutes ago
Shotwell: Not 100% certain if we'll launch from VAFB or CCAFS for next flight. Depends on customer. Both pads will be ready.

Peter B. de Selding ‏@pbdes  26 minutes ago
Shotwell: Will 'probably not' put payloads on next few static fires, but too easy to say, given Sept 1, that doing so is always bad idea.

 Peter B. de Selding ‏@pbdes  27 minutes ago
SpaceX's Shotwell: Nov return to flight is our best hope. We still haven't isolated the cause or whether its origin was rocket or ground.
 
 Peter B. de Selding ‏@pbdes  1 hour ago
SpaceX's Shotwell: We have been told that the Sept. 1 anomaly will not affect Falcon 9's insurance rates. So we expect no impact.

 Peter B. de Selding ‏@pbdes  1 hour ago
SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/13/2016 03:55 pm


Side to side movement.  Never said anything about vertical.  I would expect somebody on this forum to know that there is need to allow for vertical movement due to cryogenic contraction.

I knew that! Asked about it twice. How exactly is the vertical shrinkage of the vehicle handled by the strongback?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/13/2016 03:58 pm
Don't know if Selding is interviewing Shotwell or how he is getting his info as his tweets keep coming in sporadically:

Panel at World Satellite Business Week (see https://twitter.com/andreasmenn/status/775704776982011904)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Bubbinski on 09/13/2016 04:09 pm
Hmmm...Shotwell says they haven't isolated a cause or whether the issue was rocket or GSE but says "anticipating" a launch in Nov and then saying "best hope". Might they be getting at least some vital hints pointing to a resolution soon? Or might they be thinking of a test flight campaign without a payload to restore confidence and test improvements and theories?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 04:11 pm
Playing some more with the video I noticed that the sound of the initial flash is in the first frame with the flash, very slightly delayed, so there wasn't anything very loud going on in the previous frame.

This shows the audio from the frame before the flash and the flash frame.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/13/2016 04:13 pm

AMOS6:
LOX tank half full, neither tank pressurized. Yet sudden big fireball around LOX tank? Thats so unlikely, even if any of the tanks had sprouted a leak it would more likely have created a waterfall style outpour. Since the lox is subcooled it wouldnt even turn gaseous on exit like pressurized boiling lox, it would just pour.

I think that alone points at an external event.

How does that preclude something internal like a COPV explosion, which are mounted near the tank walls and in the vicinity of the common bulkhead?


I would claim that IF a COPV had failed, the either
- the LOX would not have ignited. With the available ullage space (>30% at the time of failure) and before helium topping took place, the pressure builtup would have been only moderate and it would be easily discernable on telemetry. This also would only explain a hole in the tank, not the "explosion" we saw.
- the LOX would have ignited (burning the COPV carbon dust). The localized high energy within the LOX tank would have set off both tank walls and other carbon elements in the tank (aka the rest of the COPVs) This would have detonated the entire 2nd stage LOX tank in a much more energetic explosion than what actually happened.

So either you'd have seen a much more benign failure mode or a much worse one.

But that's a mute point by now. Recent twitter information (return to flight in 3 month time, hinted on external cause, no change to F9 insurance rates, ...) is highly counter indicative to a failed COPV.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 04:15 pm

But that's a mute point by now. Recent twitter information (return to flight in 3 month time, hinted on external cause, no change to F9 insurance rates, ...) is highly counter indicative to a failed COPV.


No, the 3 months is a hope and there is no hint
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 04:16 pm


Side to side movement.  Never said anything about vertical.  I would expect somebody on this forum to know that there is need to allow for vertical movement due to cryogenic contraction.

I knew that! Asked about it twice. How exactly is the vertical shrinkage of the vehicle handled by the strongback?


The vehicle just slides in it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 04:17 pm
Add a few RP-1 vapor sensors.

No such things
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/13/2016 04:21 pm
Have a few blind hunches. Strengthen this strut, improve that insulation. Add a few RP-1 vapor sensors. Put more cameras around the pad, make sure they and their data would survive a similar accident. And back to work.

I would make them super high speed in multiple spectra, so that an analysis for the full spectrum can be made. I also would add seismographic, pressure, and sound recording instruments in multiple places to analyze any blast. Further, if they are close to having EDS ready for manned flights, I'd consider going ahead and putting EDS on unmanned flights for awhile.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/13/2016 04:24 pm
Add a few RP-1 vapor sensors.

No such things

It will have a characteristic absorption spectrum (or emission spectrum on a burn)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TomH on 09/13/2016 04:24 pm
Add a few RP-1 vapor sensors.

No such things

Maybe not stock on the shelf currently, but they should be easy to build.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: x15_fan on 09/13/2016 04:30 pm
Add a few RP-1 vapor sensors.

No such things

Maybe not stock on the shelf currently, but they should be easy to build.

This is a rather large and temperamental sensor...

https://en.wikipedia.org/wiki/Gas_chromatography%E2%80%93mass_spectrometry
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 04:31 pm
If we're talking about new sensors, does anyone know if SpaceX uses cameras similar to the NASA HiDyRS-X High Speed High Dynamic Range camera?

http://www.nasa.gov/feature/revolutionary-camera-recording-propulsion-data-completes-groundbreaking-test (http://www.nasa.gov/feature/revolutionary-camera-recording-propulsion-data-completes-groundbreaking-test)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/13/2016 04:32 pm


1.  It did sit there.  It was 8 seconds from the beginning of the explosion until the appearance of the fairing tipping over.

2.  The movement is the vehicle shrinking.  So the vehicle is sliding against the pads in the gripper and cradle.  The cradle pivot is not involved.   The cradle is for when the vehicle is horizontal.  Earlier strongback versions only had the gripper pads and the vehicle could not support the payload and fairing for long periods of time without supplemental support (crane and sling) while horizontal.
This is the type of factual information that helps reduce idle speculation, so thank you. But it gives rise to other what-ifs.
You say "The cradle is for when the vehicle is horizontal." Possibly the type of thinking that would reduce analysis of the gripper pads when the vehicle is VERTICAL.
For instance, (not claiming this is true) what if a paint imperfection had extra thickness just above the lower support? Might be warm enough to melt the accumulating frost then refreezing as ice. THEN the paint/ice dam breaks allowing very rapid dropping of the stage and going from a locally tensile condition to local compression? Might have even been strong enough to scrape the paint just above, exposing bare aluminum. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 04:34 pm
the last 20 seconds or so of the video, atmospheric turbulence removed, some additional deconvolution attempts.

No interpretation offered, yet.

https://www.youtube.com/watch?v=BFC4Imw0U0c

Working on getting the individual frames to a common place
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 04:41 pm

For instance, (not claiming this is true) what if a paint imperfection had extra thickness just above the lower support? Might be warm enough to melt the accumulating frost then refreezing as ice. THEN the paint/ice dam breaks allowing very rapid dropping of the stage and going from a locally tensile condition to local compression? Might have even been strong enough to scrape the paint just above, exposing bare aluminum. 

No.  It is a sliding interface.  They are just pads for lateral motion and not up and down
Just don't focus on this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/13/2016 04:42 pm

But that's a mute point by now. Recent twitter information (return to flight in 3 month time, hinted on external cause, no change to F9 insurance rates, ...) is highly counter indicative to a failed COPV.


No, the 3 months is a hope and there is no hint

My bad, I had missed one tweet.

The issue we have is, we don't know what causes SpaceX has been able to rule out by now.

Apparently they don't have the root cause yet, but I would still assume many of the "obvious" causes are ruled out by now with sufficiently high certainty.

Problem is no one tells us what they know has NOT been the cause, so we are still stuck speculating about everything.

We do know from CRS-7 that SpaceX has telemetry readings about Helium pressure. If the helium system pressure is still nominal after the tank wall has failed and LOX tank pressure dropped/spiked, SpaceX could be reasonably certain that the COPV were not to blame.

On the other hand if helium pressure did show an event at the same time, it would indicate that the helium system was involved (even if it doesn't give the exact failure mode or causality, but they couldn't rule it out anymore based on that alone)

And then there's the remote chance that they lost all telemetry before anything important showed up which has also been speculated but afair never confirmed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 05:01 pm
1300+ individual frames used to create the youtube video cited a few messages back.

www.greenerific.com/frames_v2_raw.zip

processing done by reddit user doersino

I'll disclose my typical masterful irrefutable conclusions in a day or 3... there's a lot of pixels to wander through.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/13/2016 05:03 pm


Which says a lot about how stage 2 unzipped, I think, which implies a rupture point at, or more likely just above, the common bulkhead...

Right where the lower support pads would be if the rocket had started to shrink down as the LOX was loaded. If the slide was unimpaired ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 05:14 pm


Right where the lower support pads would be if the rocket had started to shrink down as the LOX was loaded. If the slide was unimpaired ...

You are looking in the wrong place. 
They aren't going to be impaired
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OnWithTheShow on 09/13/2016 05:24 pm
Add a few RP-1 vapor sensors.

No such things

Maybe not stock on the shelf currently, but they should be easy to build.

What???? Sure there are.

See http://s7d9.scene7.com/is/content/minesafetyappliances/General%20Monitors%20Product%20Catalog-1

just for some of the many many flammable vapor detectors
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 05:25 pm
Nonsense. No to everything on that list.  Nice knee jerk reaction.

a.  better served by putting sensors on the vehicle
b.  Just need cameras with higher frame rate.  The multi spectra is a waste and not going to provide more data.  Just going to show what is already known.
b.  seismographic, pressure, and sound recording instruments are a waste.  Accidents happen in mostly in flight
c.  EDS doesn't do anything for accident reduction.  It uses existing sensors.
What Jim said is the thing, most accidents by far happen in flight.

It does seem both cheap and useful though to use high speed cameras, perhaps multiple ones set to different exposures to get inside bright events. There are 240 fps cameras available under $1K. External HDMI hard drive storage would obviously be needed as well, There'd be a LOT of data.

This might be interesting for amateurs to do actually. The engine plume might be really beautiful.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 05:30 pm
Add a few RP-1 vapor sensors.

No such things

Maybe not stock on the shelf currently, but they should be easy to build.

What???? Sure there are.

See http://s7d9.scene7.com/is/content/minesafetyappliances/General%20Monitors%20Product%20Catalog-1

just for some of the many many flammable vapor detectors

RP-1 specifically  and not just hydrocarbon. 
And the actual point is that it is not needed with RP-1.  The fumes are not explosive.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Karloss12 on 09/13/2016 05:33 pm
Don't know if Selding is interviewing Shotwell or how he is getting his info as his tweets keep coming in sporadically:

Peter B. de Selding ‏@pbdes  3 minutes ago
SpaceX's Shotwell: Falcon Heavy wont launch this year, likely Q1 next year. Could be from Pad 39A or from VAFB, not sure.

 Peter B. de Selding ‏@pbdes  23 minutes ago
Shotwell: Not 100% certain if we'll launch from VAFB or CCAFS for next flight. Depends on customer. Both pads will be ready.

Peter B. de Selding ‏@pbdes  26 minutes ago
Shotwell: Will 'probably not' put payloads on next few static fires, but too easy to say, given Sept 1, that doing so is always bad idea.

 Peter B. de Selding ‏@pbdes  27 minutes ago
SpaceX's Shotwell: Nov return to flight is our best hope. We still haven't isolated the cause or whether its origin was rocket or ground.
 
 Peter B. de Selding ‏@pbdes  1 hour ago
SpaceX's Shotwell: We have been told that the Sept. 1 anomaly will not affect Falcon 9's insurance rates. So we expect no impact.

 Peter B. de Selding ‏@pbdes  1 hour ago
SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

Sounds like they know which component went pop, but don't know why.....and possibly don't care why.  If they are having continuous confidence issues with the criminal component, maybe they are just going to replace it with something completely different, therefore there is no need for a long drawn out investigation.

Is the COPV temperamental enough to fit this hypothesis?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 05:36 pm

Sounds like they know which component went pop, but don't know why.....and possibly don't care why.  If they are having continuous confidence issues with the criminal component, maybe they are just going to replace it with something completely different, therefore there is no need for a long drawn out investigation.


No, she said they didn't know and the 3 months is a hope
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/13/2016 05:40 pm
..., most accidents by far happen in flight.


These measures are in place to capture the rare events, aka failures...

By your logic, most flights happen without an incident, so why use such sensors at all?

As for sensors to detect fumes, they are widely available and cheap, and generally you would not expect them to show much in open air, unless there's well, a fueling operation going on right near by...

RP-1 though should be mostly in aerosol form, not vapor form, and so you might need a slightly different sensor.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 05:55 pm

These measures are in place to capture the rare events, aka failures...

By your logic, most flights happen without an incident, so why use such sensors at all?


Because the same sensors provide a measure of mission success and are also used to operate the vehicle.

Surrounding the pad with various sensors is a wasted effort because most anomalies (not just accidents) happen in flight and on the vehicle. The pad sensors would just be more items to maintain, more overhead and for limited ROI.

Seismic sensors?  Come on, the location is known, it is at the pad
Sound sensors?  The vehicle has them already
Pressure ?  Yes, the vehicle exploded.  What else is it going to provide?
Multi spectra?  The constituents of the vehicle is know.  They are not looking for bombs
RP-1 sensor?  No vapors are not explosive.  Aerosol monitor, there is no such thing.  Anyways, use a camera to look for leaks. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/13/2016 06:18 pm
If sensors were there only to measure mission success, nobody would be worried about getting the data out within a milliSec....

The point is, failures happen, and are rare, and discounting ideas about sensors just because "failure is not expected there" is misguided.

Nobody ever expects the Spanish inquisition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 06:27 pm
If sensors were there only to measure mission success, nobody would be worried about getting the data out within a milliSec....


That is also a need for vehicle control.

And measuring mission success include accident investigations.  The sensors are not just there for the current mission, they are there for the next mission.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Spacedog49 on 09/13/2016 06:40 pm
If sensors were there only to measure mission success, nobody would be worried about getting the data out within a milliSec....

The point is, failures happen, and are rare, and discounting ideas about sensors just because "failure is not expected there" is misguided.

Nobody ever expects the Spanish inquisition.

If your sensor fails or is suspected of failure, it is the Spanish Inquisition according to NASA. I have personal knowledge. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OnWithTheShow on 09/13/2016 06:43 pm

RP-1 sensor?  No vapors are not explosive.  Aerosol monitor, there is no such thing.  Anyways, use a camera to look for leaks.

Im not sure if you are saying the absence of vapors is not explosive (true) or that kerosene vapors are not explosive (false). The explosive range of kerosene vapors is .7%-5% volume of air (a relatively narrow range as far as they go) and easily detectable by a sub $1000 air monitor.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/13/2016 06:44 pm
Add a few RP-1 vapor sensors.

No such things

Maybe not stock on the shelf currently, but they should be easy to build.

What???? Sure there are.

See http://s7d9.scene7.com/is/content/minesafetyappliances/General%20Monitors%20Product%20Catalog-1

just for some of the many many flammable vapor detectors

RP-1 specifically  and not just hydrocarbon. 
And the actual point is that it is not needed with RP-1.  The fumes are not explosive.

They shouldn't be there in significant quantities either
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/13/2016 06:47 pm
Let's combine several hypotheses together.  First, the start point seems at or near the support from the strongback.
Using the flare as a crosshair I get a point of origin just outside of the rocket, just above the strongback attachment.
From the picture in this post, there is a plastic support from the strongback that pushes against the rocket at just about the common bulkhead.  Suppose LOX does liquify from the air here (Jim thinks this unlikely, but the literature is full of references for this happening with LN2, and this is colder)  Also this looks like right at the bottom of the LOX tank, so it would be cold early in the fill sequence, and high enough so the LOX would not need to run over any warmer portions (and hence evaporate) before hitting the plastic bumper.

As CambrianEra has pointed out:
Hmm, let’s see the compatibility of various kind of rubber with oxygen:
Lots of stuff that is perfectly compatible with GOX is a hazard with LOX.  So if SpaceX was not expecting LOX here, the combination could be explosive.

Next, people have noted this contact point will slide as the vehicle cools:
Side to side movement.  Never said anything about vertical.  I would expect somebody on this forum to know that there is need to allow for vertical movement due to cryogenic contraction.
I knew that! Asked about it twice. How exactly is the vertical shrinkage of the vehicle handled by the strongback?
The vehicle just slides in it.
How much?  Assuming the stage one LOX tank is 30m tall, cools by 240K (306K->66K), coefficient of thermal expansion 22 microns/meter/K, we get a contraction of 15 cm.  So this point would be expected to be sliding at this point in the count, as the first stage tank fills.

I don't know about you, but I would not be enthusiastic about forcefully sliding a large chunk of LOX-soaked plastic across a surface while pressing on it.

Also, this lines up with the point indicated by the center of the lens flare.  It would also be very hard to tell if it was inside the rocket or outside, since it's right against the surface.   There would be no obvious signs on the telemetry that I can think of. And it would result in very fast secondary problems since it's directly against the fuel-LOX bulkhead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/13/2016 06:49 pm
If sensors were there only to measure mission success, nobody would be worried about getting the data out within a milliSec....

The point is, failures happen, and are rare, and discounting ideas about sensors just because "failure is not expected there" is misguided.

Nobody ever expects the Spanish inquisition.

If your sensor fails or is suspected of failure, it is the Spanish Inquisition according to NASA. I have personal knowledge.

:)

No doubt about sensors having a role in normal flight and in data monitoring....

Point was - when talking about sensors for identifying failures, the thinking of "we shouldn't put a sensor here since anomalies don't normally happen here" is not thought out.

You can't put sensors everywhere, but simply "usually doesn't happen here" is not a good guideline.  Failures don't usually happen in general...

This failure was unexpected.  You learn things from failures.   If you find yourself wishing that the T/E was more heavily instrumented, for example, then that's a lesson learned.

Widely spaced microphones on the launch site, to go with the multiple camera angles?  That won't bankrupt anyone. 

Fume sensors are fine, but at least in open air, their signal has a high variance.  It really depends on what the expected reading is, and what threshold is considered anomalous.  If they are too close, you'll always get either false positives or false negatives.  If there's enough gap, then yes.



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/13/2016 06:50 pm


The multi spectra is a waste and not going to provide more data.  Just going to show what is already known.


How do you know this in all cases?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/13/2016 07:21 pm

RP-1 sensor?  No vapors are not explosive.  Aerosol monitor, there is no such thing.  Anyways, use a camera to look for leaks.

Im not sure if you are saying the absence of vapors is not explosive (true) or that kerosene vapors are not explosive (false). The explosive range of kerosene vapors is .7%-5% volume of air (a relatively narrow range as far as they go) and easily detectable by a sub $1000 air monitor.
From wiki:
Quote
Because of the lack of light hydrocarbons, RP-1 has a high flash point, and is less of a fire hazard than gasoline/petrol or even some jet and diesel fuels.

RP-1 is a kerosene, but kerosene is not RP-1.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 07:34 pm

I don't know about you, but I would not be enthusiastic about forcefully sliding a large chunk of LOX-soaked plastic across a surface while pressing on it.


And what says it is pressing on it?

And as I pointed out, the first stage LOX loading starts 15 minutes or so before the second stage.  The first stage would have done most of the shrinking before the second stage even sees LOX on the inside and certainly before any forms on the outside (which it doesn't)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 07:37 pm

I don't know about you, but I would not be enthusiastic about forcefully sliding a large chunk of LOX-soaked plastic across a surface while pressing on it.

Lets list all the assumptions not backed by data

Forcefully sliding
Pressing
LOX
soaked
plastic
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 07:40 pm


The multi spectra is a waste and not going to provide more data.  Just going to show what is already known.


How do you know this in all cases?

The composition of the vehicles and materials are known. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 07:44 pm
Also this looks like right at the bottom of the LOX tank, so it would be cold early in the fill sequence, and high enough so the LOX would not need to run over any warmer portions (and hence evaporate) before hitting the plastic bumper.

No, it is at the common bulkhead interface (why would it be there) which would be would be warmer and evaporate the non existent LOX
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/13/2016 08:00 pm
So for the contamination theory.
Anybody know the composition of the following.
Lox lines: Al or stainless?
Umbilicals: ?

Also is there any strainers or check valves in the lox line near the second stage?
What do the connectors look like for the umbilicals to the rocket?
From the TEL to the umbilicals?
How do they work?
Like a quick connect hydraulic line? Basically o-ring, stainless ball for seal and little ball bearings to hold the coupling closed.
Do the umbilicals get replaced after being torched from the rocket on a launch?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Spacedog49 on 09/13/2016 08:01 pm
I applied Luma, Alpha, and Hue filters to the video and found two areas on the TEL that show change in their values. The top area is the payload A/C. The Luma /Alpha channels show activity throughout the video until 133 ms before the initial flash. At that time all Luma/Alpha activity concentrates in one small area.
The lower area is centered in the area of the initial flash. The Luma/Alpha activity in this area is intermittent. Under some filter combinations I get the impression of something escaping or flowing from one of the ducts. This could be a false artifact from the interplay of filters and video compression.
Something new to think about.
The quick RTFS could be the result of new evidence from the examination of the TEL.     
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/13/2016 08:13 pm
I'm be very skeptical about using the lens flare, or whatever the crossed lines of light are to pinpoint the ignition point or even the center of the explosion. Those only developed several frames after the initial flash and likely are pointing to the brightest part of the explosion the camera can see. There's no reason IMHO to assume that's where the explosion started.

Personally, I'm not convinced at all that the explosion started on the side of the vehicle the camera was viewing. It certainly flashed to the camera side, but it could well have started on the other side and blew around the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: speedevil on 09/13/2016 08:18 pm
Personally, I'm not convinced at all that the explosion started on the side of the vehicle the camera was viewing. It certainly flashed to the camera side, but it could well have started on the other side and blew around the stage.
The initial frame shows nothing, then the one after that shows a fireball that has expanded at nearly the speed of sound.
For it to have started at the back, and moved all the way round to completely encircle the front, would have taken it considerably supersonic, and caused a rather more energetic explosion. Some of the ligthning rods would also be differently illuminated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/13/2016 08:52 pm
Personally, I'm not convinced at all that the explosion started on the side of the vehicle the camera was viewing. It certainly flashed to the camera side, but it could well have started on the other side and blew around the stage.
The initial frame shows nothing, then the one after that shows a fireball that has expanded at nearly the speed of sound.
For it to have started at the back, and moved all the way round to completely encircle the front, would have taken it considerably supersonic, and caused a rather more energetic explosion. Some of the ligthning rods would also be differently illuminated.

The simple solution to this is that the explosion started within the frame of the TEL.

This isn't particularly surprising as the majority of possible ignition sources are located there (ignoring whether they are likely or not).


(Edit: for sake of clarity, I'm referring to ignition source, not the source of fuel. Oxidiser - I'm comfortable with this being the vent from the LOX tank).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/13/2016 09:47 pm
But not nescessarily the distribution of the elements involved in an incident like this.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/13/2016 10:21 pm
But not nescessarily the distribution of the elements involved in an incident like this.

Yes, it is know.  The safety packages for the rocket and spacecraft list the types and amounts of propellant, ordnance, power devices, batteries, structure, etc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 10:31 pm
I applied Luma, Alpha, and Hue filters to the video and found two areas on the TEL that show change in their values. The top area is the payload A/C. The Luma /Alpha channels show activity throughout the video until 133 ms before the initial flash. At that time all Luma/Alpha activity concentrates in one small area.
The lower area is centered in the area of the initial flash. The Luma/Alpha activity in this area is intermittent. Under some filter combinations I get the impression of something escaping or flowing from one of the ducts. This could be a false artifact from the interplay of filters and video compression.
Something new to think about.
The quick RTFS could be the result of new evidence from the examination of the TEL.     

What is a real world physics interpretation of Luma/Alpha activity?  Is it turning green, bright?   Did the AGC on the camera adjust to changing light levels?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Karloss12 on 09/13/2016 10:59 pm

Sounds like they know which component went pop, but don't know why.....and possibly don't care why.  If they are having continuous confidence issues with the criminal component, maybe they are just going to replace it with something completely different, therefore there is no need for a long drawn out investigation.


No, she said they didn't know and the 3 months is a hope

Take your Engineering hat off for just a moment Jim.

Shotwell doesn't just make random statements just because she feels like it.  It may not have contained specific Engineering info, however it was a strategic statement.

She only says that she doesn't know the cause and its origin.  She hasn't said that she doesn't know what specifically went pop.

I think she is aware of the specific component that failed and the non engineering "hope" statement is intended to allign the politians and decision makers for commencement of return the to launch strategy.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 11:01 pm
Difference analysis pass # 1.

This is an analysis comparing the first 11 seconds composite image content with the last second image composite content.   Technique explained previously in this thread.

The idea is:  Something changing over a long period of time, resulted in what seemed to happen in 16 milliseconds, and might be visible in the corrected image streams we have provided.

Interestingly, there is only one, I repeat one, dramatic change occurring in this initial (of many) image processing test.

Basically, we've composited 11 seconds worth of frames into one frame, skipped about 9 seconds, and composited the last second into one frame, and then looked at any significant differences.  (Don't do this at home without adult supervision)

The differences could be physical, luminosity, etc... the why list is prior in this thread as to possible causes, except causes 4 & 5 are extremely unlikely at this level of processing.

The one difference in this comparison (and there will be more comparisons) is red on the attached image.

So my standard daily question.  Exactly what is at the area identified in red?  It changed, whatever is there, more than any other changes  (factor of 5) in the frame comparison.  In the last 20 odd seconds prior to the event, would a change be expected where indicated?

This is not a diagnosis of failure or causes, it's a question initiated by a imaging change analysis process.  Your answers may help refine the process.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/13/2016 11:48 pm
My guess: the umbilical moved slightly.

That would account for a "large" image change, and would be expected with wind/completion of RP-1 loading/initiation of LOX loading/etc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/13/2016 11:59 pm
My guess: the umbilical moved slightly.

That would account for a "large" image change, and would be expected with wind/completion of RP-1 loading/initiation of LOX loading/etc.

Possible, but after I posted the image, I looked at our video stream.

Remember, it could be changes in luminance rather than a physical event.  The red area is extremely precise.  It not like +- x%.  That's exactly where the change occurs.

My irrefutable rock solid no one can doubt me interpretation is a bit different.

In the video stream, that region appears to grow light & dark over time.  It's consistent in behavior with the obvious venting seen to the left of the F9.

It could be the result of something venting a semi-opaque cloud to the right (above right, below right, unknown right).  The region appears to be between the F9 and the TE.  There should be no reason for there to be a change in luminosity, unless something is changing the luminosity.  The video doesn't show a physical motion as best as I can tell, i.e. a change in the physical structure of F9 and TE.  It does show luminosity changes.

Would there be an expected venting of any kind to the right of that area, keeping in mind the wind is blowing right to left?  Is there anything that could vent to the right of that area, unexpectedly?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/14/2016 12:00 am
Well, the area in red is the top of stage 1, at the very bottom of the interstage, from what I can tell.

What goes into the rocket, or interfaces between the TEL and the rocket, right there?  I doubt there is any fueling happening that high up on stage 1, so perhaps this is where the AC umbilical connects to the interstage?  I know per several things that have been posted throughout this thread that the AC system ventilates and purges both the payload fairing and the interstage.  Maybe this is where the AC umbilicals go into the interstage?

The LOX and RP-1 feed lines for stage 2 should be running right behind this area, though -- they reach up to the base of stage 2.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jjyach on 09/14/2016 12:12 am
Well, the area in red is the top of stage 1, at the very bottom of the interstage, from what I can tell.

What goes into the rocket, or interfaces between the TEL and the rocket, right there?  I doubt there is any fueling happening that high up on stage 1, so perhaps this is where the AC umbilical connects to the interstage?  I know per several things that have been posted throughout this thread that the AC system ventilates and purges both the payload fairing and the interstage.  Maybe this is where the AC umbilicals go into the interstage?

The LOX and RP-1 feed lines for stage 2 should be running right behind this area, though -- they reach up to the base of stage 2.

For sure there is the AC connection to the interstage there.  Jim can correct me if I am wrong, but I thought RP1 was loaded in the umbilical below the Lox (there at the interstage with the AC).

I believe there are 5 total umbilical lines[interstage through Stage2] (At least from the SES-9 launch) 1xRP1, 1xHe, 1xAC, 1XLox,1x(? power/data?)  Not certain what ones are below through
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 12:17 am
Well, the area in red is the top of stage 1, at the very bottom of the interstage, from what I can tell.

What goes into the rocket, or interfaces between the TEL and the rocket, right there?  I doubt there is any fueling happening that high up on stage 1, so perhaps this is where the AC umbilical connects to the interstage?  I know per several things that have been posted throughout this thread that the AC system ventilates and purges both the payload fairing and the interstage.  Maybe this is where the AC umbilicals go into the interstage?

The LOX and RP-1 feed lines for stage 2 should be running right behind this area, though -- they reach up to the base of stage 2.

For sure there is the AC connection to the interstage there.  Jim can correct me if I am wrong, but I thought RP1 was loaded in the umbilical below the Lox (there at the interstage with the AC).

I believe there are 5 total umbilical lines[interstage through Stage2] (At least from the SES-9 launch) 1xRP1, 1xHe, 1xAC, 1XLox,1x(? power/data?)  Not certain what ones are below through

repeating a question I asked of another comment:

Possible, but after I posted the image, I looked at our video stream.

Remember, it could be changes in luminance rather than a physical event.  The red area is extremely precise.  It not like +- x%.  That's exactly where the change occurs.

My irrefutable rock solid no one can doubt me interpretation is a bit different.

In the video stream, that region appears to grow light & dark over time.  It's consistent in behavior with the obvious venting seen to the left of the F9.

It could be the result of something venting a semi-opaque cloud to the right (above right, below right, unknown right).  The region appears to be between the F9 and the TE.  There should be no reason for there to be a change in luminosity, unless something is changing the luminosity.  The video doesn't show a physical motion as best as I can tell, i.e. a change in the physical structure of F9 and TE.  It does show luminosity changes.

Would there be an expected venting of any kind to the right of that area, keeping in mind the wind is blowing right to left?  Is there anything that could vent to the right of that area, unexpectedly?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/14/2016 12:22 am
Would there be an expected venting of any kind to the right of that area, keeping in mind the wind is blowing right to left?  Is there anything that could vent to the right of that area, unexpectedly?

- - - -

Please comment on my comment just before your comment.  :)  Please.  :)

Sorry, I got distracted and also failed to quote the post I was responding to.  My bad.

However, yeah -- thinking about it again and staring at the picture again, I think I was dead wrong.  The red spot is up near the top of the interstage, seeing as how it's just above the level of the grid fins.  And that would not only be where the AC vent goes in, but also where the LOX and RP-1 feeds go in.

So, yeah, the red spot would seem to be right around where he propellants were being loaded.  That could be significant.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jjyach on 09/14/2016 12:24 am
Well, the area in red is the top of stage 1, at the very bottom of the interstage, from what I can tell.

What goes into the rocket, or interfaces between the TEL and the rocket, right there?  I doubt there is any fueling happening that high up on stage 1, so perhaps this is where the AC umbilical connects to the interstage?  I know per several things that have been posted throughout this thread that the AC system ventilates and purges both the payload fairing and the interstage.  Maybe this is where the AC umbilicals go into the interstage?

The LOX and RP-1 feed lines for stage 2 should be running right behind this area, though -- they reach up to the base of stage 2.

For sure there is the AC connection to the interstage there.  Jim can correct me if I am wrong, but I thought RP1 was loaded in the umbilical below the Lox (there at the interstage with the AC).

I believe there are 5 total umbilical lines[interstage through Stage2] (At least from the SES-9 launch) 1xRP1, 1xHe, 1xAC, 1XLox,1x(? power/data?)  Not certain what ones are below through

repeating a question I asked of another comment:

Possible, but after I posted the image, I looked at our video stream.

Remember, it could be changes in luminance rather than a physical event.  The red area is extremely precise.  It not like +- x%.  That's exactly where the change occurs.

My irrefutable rock solid no one can doubt me interpretation is a bit different.

In the video stream, that region appears to grow light & dark over time.  It's consistent in behavior with the obvious venting seen to the left of the F9.

It could be the result of something venting a semi-opaque cloud to the right (above right, below right, unknown right).  The region appears to be between the F9 and the TE.  There should be no reason for there to be a change in luminosity, unless something is changing the luminosity.  The video doesn't show a physical motion as best as I can tell, i.e. a change in the physical structure of F9 and TE.  It does show luminosity changes.

Would there be an expected venting of any kind to the right of that area, keeping in mind the wind is blowing right to left?  Is there anything that could vent to the right of that area, unexpectedly?

Well if you look on the USLR video prior to the cut at 50 seconds it looks  like there is at the very least a LOx vent in the area.  I would highly doubt that they would vent anything else there (Except maybe He)  I have attached the SES-9 photo so you might look to see anything I missed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 12:54 am
Reference images for prior discussion re image delta.

FYI the third image from the left was the registration image.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 01:01 am
I don't know about you, but I would not be enthusiastic about forcefully sliding a large chunk of LOX-soaked plastic across a surface while pressing on it.
Lets list all the assumptions not backed by data

Forcefully sliding
Pressing
LOX
soaked
plastic
"Pressing" and "Forcefully sliding" - until the clamps let go, they are surely pressing on the far side of the rocket.  No way they would have an air gap and let the rocket rattle back and forth against the clamps - that would confuse the telemetry if nothing else.  So until the arms are opened, the rocket will be pressed into the pad on the erector.  And thermal contraction generates big forces, so it will slide despite being pushed against the rocket.

"Plastic" - there are black pads on the end of the arms that press against the rocket.  What are these made of, if not plastic?

"LOX-soaked"  This is indeed the most speculative part of the explanation.   However, there are many, many reports on the web of the dangers of liquid nitrogen temperature surfaces exposed to the air.  Here is one from MIT (http://chemistry.mit.edu/department-resources/environmental-health-safety/safety-notes/liquid-nitrogen).  Bold is in the original:
Quote
Systems including liquid nitrogen traps must never be opened to the atmosphere until the trap is removed from the coolant. Oxygen has a higher boiling point (-183 ƒC) than nitrogen (-196 ƒC), and will condense out of the atmosphere and collect in a liquid-nitrogen cooled vessel open to the air. Liquid oxygen forms highly explosive mixtures with many organic materials.
or here (https://www.ucd.ie/t4cms/UCD%20Liquid%20Nitrogen%20Safety%20Guide.pdf) (bold mine)
Quote
In some scenarios it is possible for containers holding liquid nitrogen to become sufficiently cooled so that the oxygen in the atmosphere condenses and forms liquid oxygen on the cooled surfaces. This can occur when vessels that are open to the atmosphere are cooled on the outside by liquid nitrogen thus allowing liquid oxygen to form on the inside of the vessel. Similarly pipe work cooled internally by liquid nitrogen can allow liquid oxygen to condense on the outside.
Note that in particular, the tendency of these surfaces to form frost does not always suppress the formation of LOX.

Will the outside of the rocket be less than 77K?  Yes, if the inside is at 66K.  The thermal conductivity of aluminum is about 205 w/m/k.  So to get an 11K drop across a 5 mm thickness you would need a heat flow of 205*11/0.005 = 451 kw/m^2.  No way you have that from condensing air, so the outside temp is less than 77K.

I completely agree that you have seen 10 launches or so that have used sub-cooled LOX, and have never seen this happen.  But I don't understand how you can be certain that it can't happen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/14/2016 01:03 am
So my standard daily question.  Exactly what is at the area identified in red?  It changed, whatever is there, more than any other changes  (factor of 5) in the frame comparison.  In the last 20 odd seconds prior to the event, would a change be expected where indicated?

If you go back to the original USLR video, you will see that the area identified is often completely obscured by dark venting. When not obscured, it is a bright area, so perhaps it should not be surprising that it changes more than any other area?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 01:06 am
So my standard daily question.  Exactly what is at the area identified in red?  It changed, whatever is there, more than any other changes  (factor of 5) in the frame comparison.  In the last 20 odd seconds prior to the event, would a change be expected where indicated?

If you go back to the original USLR video, you will see that the area identified is often completely obscured by dark venting. When not obscured, it is a bright area, so perhaps it should not be surprising that it changes more than any other area?

nice, but in this image sequence, it is not obscured.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/14/2016 01:08 am
I have attached the SES-9 photo so you might look to see anything I missed.

That photo reminds me of one other thing in that general vicinity: the stage separation latches - SpaceX doesn't like to use pyros and those are pneumatic, as I recall. I don't know details of how they are pressurized and actuated, however.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/14/2016 01:16 am
However, yeah -- thinking about it again and staring at the picture again, I think I was dead wrong.  The red spot is up near the top of the interstage, seeing as how it's just above the level of the grid fins.  And that would not only be where the AC vent goes in, but also where the LOX and RP-1 feeds go in.

So, yeah, the red spot would seem to be right around where he propellants were being loaded.  That could be significant.

It was pointed out around 741 posts ago that an RP1 pin-hole leak from the umbilical or connector could potentially trigger a FAE and even more so in an oxygen-rich environment.  After all, the umbilicals are flexible and could be subject to all kinds of abuse during loading and launch.

Anyone know if they keep the RP1 line pressurised during LOX loading - or is the RP1 umbilical drained and purged right after RP1 loading has finished?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/14/2016 01:33 am
I have attached the SES-9 photo so you might look to see anything I missed.

That photo reminds me of one other thing in that general vicinity: the stage separation latches - SpaceX doesn't like to use pyros and those are pneumatic, as I recall. I don't know details of how they are pressurized and actuated, however.
Helium pressure for pneumatic sep Herb...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/14/2016 01:41 am
I have attached the SES-9 photo so you might look to see anything I missed.

That photo reminds me of one other thing in that general vicinity: the stage separation latches - SpaceX doesn't like to use pyros and those are pneumatic, as I recall. I don't know details of how they are pressurized and actuated, however.
Helium pressure for pneumaic sep Herb...
.

Ah, more pressurized helium, then. Figured it would be that or N2. It probably makes sense that the latches themselves use the same fluid.  I wonder if ther might've been a failure in that system that affected the umbilicals nearby. Perhaps that might account for the sounds Elon's tweet referred to. Totally spitballing here, but if Glennfish's video analysis "red dot" is a real thing, it's another system in the general vicinity to think about a bit.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/14/2016 01:49 am
nice, but in this image sequence, it is not obscured.

Basically, we've composited 11 seconds worth of frames into one frame, skipped about 9 seconds, and composited the last second into one frame, and then looked at any significant differences.  (Don't do this at home without adult supervision)

On the USLR video, the fast fire starts at about 01:11. If I view the area identified in red for the 11 seconds from 00:50 to 01:01, it is never totally obscured, but it does vary in brightness, perhaps due to a small amount of venting. For the single second before the fire, it is relatively bright and steady. Your analysis does appear consistent with that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/14/2016 01:51 am
<snip>

Will the outside of the rocket be less than 77K?  Yes, if the inside is at 66K.  The thermal conductivity of aluminum is about 205 w/m/k.  So to get an 11K drop across a 5 mm thickness you would need a heat flow of 205*11/0.005 = 451 kw/m^2.  No way you have that from condensing air, so the outside temp is less than 77K.

<snip>

Surely this calculation would only apply if the outside of the rocket were unpainted Al?  But we know it's painted, and upthread I admitted complete ignorance about what kind of paint, and how thick (and how potentially explosive in contact with LOX ...).  Does anyone here know these details?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/14/2016 01:52 am
Difference analysis pass # 1.

This is an analysis comparing the first 11 seconds composite image content with the last second image composite content.   Technique explained previously in this thread.

The idea is:  Something changing over a long period of time, resulted in what seemed to happen in 16 milliseconds, and might be visible in the corrected image streams we have provided.

Interestingly, there is only one, I repeat one, dramatic change occurring in this initial (of many) image processing test.

Basically, we've composited 11 seconds worth of frames into one frame, skipped about 9 seconds, and composited the last second into one frame, and then looked at any significant differences.  (Don't do this at home without adult supervision)

The differences could be physical, luminosity, etc... the why list is prior in this thread as to possible causes, except causes 4 & 5 are extremely unlikely at this level of processing.

The one difference in this comparison (and there will be more comparisons) is red on the attached image.

So my standard daily question.  Exactly what is at the area identified in red?  It changed, whatever is there, more than any other changes  (factor of 5) in the frame comparison.  In the last 20 odd seconds prior to the event, would a change be expected where indicated?

This is not a diagnosis of failure or causes, it's a question initiated by a imaging change analysis process.  Your answers may help refine the process.
First off, I want to thank glennfish for all of this hard work in working with the very limited resources available to us.

Your red spot appears to be on the perimeter at the top of the interstage. One thing found in this area is the connection mechanism to the second stage. There are several attach points that are either explosively or pneumatically actuated in conjunction with the pusher mechanism. I know Elon is not a fan of the pyrotechnic release, but not 100% sure what it utilized here. Possible source of ignition?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/14/2016 01:56 am
Difference analysis pass # 1.

This is an analysis comparing the first 11 seconds composite image content with the last second image composite content.   Technique explained previously in this thread.

The idea is:  Something changing over a long period of time, resulted in what seemed to happen in 16 milliseconds, and might be visible in the corrected image streams we have provided.

Interestingly, there is only one, I repeat one, dramatic change occurring in this initial (of many) image processing test.

Basically, we've composited 11 seconds worth of frames into one frame, skipped about 9 seconds, and composited the last second into one frame, and then looked at any significant differences.  (Don't do this at home without adult supervision)

The differences could be physical, luminosity, etc... the why list is prior in this thread as to possible causes, except causes 4 & 5 are extremely unlikely at this level of processing.

The one difference in this comparison (and there will be more comparisons) is red on the attached image.

So my standard daily question.  Exactly what is at the area identified in red?  It changed, whatever is there, more than any other changes  (factor of 5) in the frame comparison.  In the last 20 odd seconds prior to the event, would a change be expected where indicated?

This is not a diagnosis of failure or causes, it's a question initiated by a imaging change analysis process.  Your answers may help refine the process.
First off, I want to thank glennfish for all of this hard work in working with the very limited resources available to us.

Your red spot appears to be on the perimeter at the top of the interstage. One thing found in this area is the connection mechanism to the second stage. There are several attach points that are either explosively or pneumatically actuated in conjunction with the pusher mechanism. I know Elon is not a fan of the pyrotechnic release, but not 100% sure what it utilized here. Possible source of ignition?
Helium to release the latches and Helium pneumatic pushers for assured stage separation...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/14/2016 02:12 am
Your red spot appears to be on the perimeter at the top of the interstage. One thing found in this area is the connection mechanism to the second stage. There are several attach points that are either explosively or pneumatically actuated in conjunction with the pusher mechanism. I know Elon is not a fan of the pyrotechnic release, but not 100% sure what it utilized here. Possible source of ignition?

Man, nobody reads the thread, even a few posts back. ;)

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1583462#msg1583462
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/14/2016 02:16 am
Your red spot appears to be on the perimeter at the top of the interstage. One thing found in this area is the connection mechanism to the second stage. There are several attach points that are either explosively or pneumatically actuated in conjunction with the pusher mechanism. I know Elon is not a fan of the pyrotechnic release, but not 100% sure what it utilized here. Possible source of ignition?

Man, nobody reads the thread, even a few posts back. ;)

https://forum.nasaspaceflight.com/index.php?topic=30981.msg1583462#msg1583462
Dang - sorry Herb. The issue is I read a thread, see something I want to comment on, quote it, reply and it gets dumped at the end of thread - skipping over the intervening posts. I try to skim forward to end of thread first, but man does this particular thread grow fast
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 02:30 am
I have attached the SES-9 photo so you might look to see anything I missed.

That photo reminds me of one other thing in that general vicinity: the stage separation latches - SpaceX doesn't like to use pyros and those are pneumatic, as I recall. I don't know details of how they are pressurized and actuated, however.
Helium pressure for pneumaic sep Herb...
.

Ah, more pressurized helium, then. Figured it would be that or N2. It probably makes sense that the latches themselves use the same fluid.  I wonder if ther might've been a failure in that system that affected the umbilicals nearby. Perhaps that might account for the sounds Elon's tweet referred to. Totally spitballing here, but if Glennfish's video analysis "red dot" is a real thing, it's another system in the general vicinity to think about a bit.

please save me a half hour of searching this thread.  At what points prior to Frame 0 did the sounds occur.  I can look at before/after image groups to that point in time.  If you want to same me more time, at 60 frames per second, with the last 3 frames in the database ignored from the download, which frame(s) in our data provided correspond to the clang and thunk.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/14/2016 02:36 am
First off, I want to thank glennfish for all of this hard work in working with the very limited resources available to us.

Your red spot appears to be on the perimeter at the top of the interstage. One thing found in this area is the connection mechanism to the second stage. There are several attach points that are either explosively or pneumatically actuated in conjunction with the pusher mechanism. I know Elon is not a fan of the pyrotechnic release, but not 100% sure what it utilized here. Possible source of ignition?

I'd like to second the thanks to glennfish for his efforts.

However I suspect the red spot is actually near the bottom of the interstage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jaufgang on 09/14/2016 02:40 am
My guess: the umbilical moved slightly.

That would account for a "large" image change, and would be expected with wind/completion of RP-1 loading/initiation of LOX loading/etc.

Possible, but after I posted the image, I looked at our video stream.

Remember, it could be changes in luminance rather than a physical event.  The red area is extremely precise.  It not like +- x%.  That's exactly where the change occurs.

My irrefutable rock solid no one can doubt me interpretation is a bit different.

In the video stream, that region appears to grow light & dark over time.  It's consistent in behavior with the obvious venting seen to the left of the F9.

It could be the result of something venting a semi-opaque cloud to the right (above right, below right, unknown right).  The region appears to be between the F9 and the TE.  There should be no reason for there to be a change in luminosity, unless something is changing the luminosity.  The video doesn't show a physical motion as best as I can tell, i.e. a change in the physical structure of F9 and TE.  It does show luminosity changes.

Would there be an expected venting of any kind to the right of that area, keeping in mind the wind is blowing right to left?  Is there anything that could vent to the right of that area, unexpectedly?

Might I suggest trying to establish a sort-of "control" measurement by running a similar "Difference Analysis" on other sets of frames?  This might provide a sanity check and indicate whether or not that red dot is truly indicative of something anomalous.

What if you take the 11 second composite and compare it with  a 1 second composite 10 seconds back or 20 seconds back?  Or better yet, does USLaunchReport have similar footage of previous launches or static test fires from the same vantage point and camera setup?  Maybe you could run a similar analysis on those at the same point in the countdown sequence and see whether or not you can produce similar results (red dot in that same location)?

If you can produce similar results in other video or frame intervals that didn't immediately precede the explosion, maybe you are just seeing the effect of something benign, such as an umbilical shifting in the wind.   If you run these control measurements and it only produces this red dot at that location in this one instance at this particular time, and you can't produce something similar elsewhere, then that could be a strong indication that you are on to something real and significant.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 02:49 am
<snip>
Will the outside of the rocket be less than 77K?  Yes, if the inside is at 66K.  The thermal conductivity of aluminum is about 205 w/m/k.  So to get an 11K drop across a 5 mm thickness you would need a heat flow of 205*11/0.005 = 451 kw/m^2.  No way you have that from condensing air, so the outside temp is less than 77K.
<snip>

Surely this calculation would only apply if the outside of the rocket were unpainted Al?  But we know it's painted, and upthread I admitted complete ignorance about what kind of paint, and how thick (and how potentially explosive in contact with LOX ...).  Does anyone here know these details?
Good point.  I ignored the paint since it's very thin, but it turns out that's a bad guess.  Assuming the paint is 0.1mm thick (since they don't want any extra mass), then it's 50x thinner than the aluminum.  But at least generic paint is a rotten thermal conductor -  this report (http://www.thefreelibrary.com/Special+heat+capacity+and+thermal+conductivity.-a0228354685) claims 0.17 w/m/K, or about 1000x worse than aluminum.   So even if it's only 1/50th as thick, it's still a 20x better insulator than the aluminum.  However, this would still need a flux of 20 kw/m^2 to maintain a delta-T of 11 degrees.   This online heat transfer calculator (http://www.efunda.com/formulae/heat_transfer/convection_forced/calc_lamflow_isothermalplate.cfm#calc) estimates heat transfer from a 70K plate in a 4 m/s wind to be about 2kw/m^2, so the surface will still be much closer to 66K than 77K.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 02:52 am
My guess: the umbilical moved slightly.

That would account for a "large" image change, and would be expected with wind/completion of RP-1 loading/initiation of LOX loading/etc.

Possible, but after I posted the image, I looked at our video stream.

Remember, it could be changes in luminance rather than a physical event.  The red area is extremely precise.  It not like +- x%.  That's exactly where the change occurs.

My irrefutable rock solid no one can doubt me interpretation is a bit different.

In the video stream, that region appears to grow light & dark over time.  It's consistent in behavior with the obvious venting seen to the left of the F9.

It could be the result of something venting a semi-opaque cloud to the right (above right, below right, unknown right).  The region appears to be between the F9 and the TE.  There should be no reason for there to be a change in luminosity, unless something is changing the luminosity.  The video doesn't show a physical motion as best as I can tell, i.e. a change in the physical structure of F9 and TE.  It does show luminosity changes.

Would there be an expected venting of any kind to the right of that area, keeping in mind the wind is blowing right to left?  Is there anything that could vent to the right of that area, unexpectedly?

Might I suggest trying to establish a sort-of "control" measurement by running a similar "Difference Analysis" on other sets of frames?  This might provide a sanity check and indicate whether or not that red dot is truly indicative of something anomalous.

What if you take the 11 second composite and compare it with  a 1 second composite 10 seconds back or 20 seconds back?  Or better yet, does USLaunchReport have similar footage of previous launches or static test fires from the same vantage point and camera setup?  Maybe you could run a similar analysis on those at the same point in the countdown sequence and see whether or not you can produce similar results (red dot in that same location)?

If you can produce similar results in other video or frame intervals that didn't immediately precede the explosion, maybe you are just seeing the effect of something benign, such as an umbilical shifting in the wind.   If you run these control measurements and it only produces this red dot at that location in this one instance at this particular time, and you can't produce something similar elsewhere, then that could be a strong indication that you are on to something real and significant.

Your suggestion is nuts on.  I have a processing scheme which looks at different intervals, in half second, full second, multi-second, etc intervals.

It takes time to do the processing.  On my dain bramaged PC, days to weeks.

The posted image group is the first one I tried, assuming that group had the most likelihood of showing if anything changed.  Now the trick is to define when and if that change is consistently there.

Mostly, I'm hoping Elon's interns are reading this thread and they can do the work.  I really have a day job, and analyzing SpaceX anomalies isn't on my top ten list of putting food on the table.

But, for those who have nothing better to do, I've provided all of the raw data for those who wish to process further.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul451 on 09/14/2016 03:25 am
Just so I've got the LOx-from-air scenario clear...

1. The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.

2. The condensation of oxygen must not have happened on the vastly longer first stage oxygen tanks during any of the horizontal test burns performed since SpaceX started working on subcooling LOx, such that no-one noticed the LOx dripping off and said "Hey do we have a LOx leak", and investigated the issue. Nor noticed on either stage in any previous vertical static-fire or launch.

3. Something must rub off the ice to expose the bare tank wall. So...

4. As the F9 shrinks due to the second stage LOx fill (but after shrinkage caused by the previous main stage LOx fill), the small support brace below the hydraulic/pneumatic grapples, resting against the reinforced area that rings the common bulkhead, must slide enough to scrape ice off that aforementioned reinforced area that rings the common bulkhead.

5. The thicker external skin of the ring around the common bulkhead must also be far enough below 90K for LOx to form faster than it evaporates.

6. The LOx forming on the newly exposed skin at the bottom of the common bulkhead ring must run... up?... to soak into the protective "plastic" pads of the support brace.

7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.

8. Something something then causes the below-90K "plastic" to catch fire.

9. ...causing our initial explosion.

[edit: "of"]
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ejb749 on 09/14/2016 04:00 am
The TE at pad 40 is the only one of the three that is not falcon heavy compatible. 
How many other differences are there to the other two TEs?
Are the other 2 TEs identical?
If they are significantly different to the one at pad 40, and the problem is external to the vehicle, it could be good news for RTF.
The TE at pad 40 had the most launches, and had been modified several times for each version of the Falcon 9.   Could that have contributed?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/14/2016 06:37 am
The TE at pad 40 is the only one of the three that is not falcon heavy compatible. 
How many other differences are there to the other two TEs?
Are the other 2 TEs identical?
If they are significantly different to the one at pad 40, and the problem is external to the vehicle, it could be good news for RTF.
The TE at pad 40 had the most launches, and had been modified several times for each version of the Falcon 9.   Could that have contributed?

If you view the CRS-8 technical webcast, at T-04:10 there is a closeup of the grippers being released and the strongback being retracted. The cradle can be seen to tilt forward as the grippers release, indicating that at least the top cradle pad was in contact with the second stage up to that point. Once the grippers have released, the rocket begins to sway, occasionally enough to bump the top pad. I've attached an edit of the technical broadcast below.

Vortex shedding has caused the destruction of several large chimneys in the past, for example at the Ferrybridge C power station. A turbulent vortex street can occur around chimneys, provided that the flow has a Reynolds number (Re) greater than 3.5 x 10^6, where Re = v * L / ν.

Similarly, a turbulent vortex street could occur around the Falcon 9 rocket. The minimum turbulent Re for the Falcon 9 is when the velocity of the wind v = 3.5 x 10^6 * 0.00001458 / 3.7 = 13.79 m/s. This is a 26.8 knot breeze, which is strong, but not inconceivable, especially at height. If a vortex street is established, there will be oscillating horizontal forces applied to the rocket. Because it is pinned at the base and the gripper by the much stronger and stiffer TE, the flexion mode (but hopefully not the amplitude) could be as shown below. This is especially likely if the frequency of the oscillations is near the resonant frequency of the rocket, which will change as the fuel is loaded.

In the Thaicom8 closeup of the second stage, both the top and bottom pads are seen to be in contact with the stage whilst the grippers are closed. The problem is that when the gripper is closed, it prevents movement of the upper pad towards the stage. The cradle itself is also pinned by the TE, so the lower pad can't move away from the stage. The fuselage is only millimetres thick, so even a small oscillation of the rocket could have a catastrophic effect at the point of contact, the lower pad. Although a breach in the stage near the common bulkhead may not explain how ignition occurred, it would explain what lead up to it.

I'm not completely sure which thread this theory belongs in, but any feedback would be appreciated. I'm also not sure if the cradles at the other pads are identical.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Spacedog49 on 09/14/2016 06:41 am
I applied Luma, Alpha, and Hue filters to the video and found two areas on the TEL that show change in their values. The top area is the payload A/C. The Luma /Alpha channels show activity throughout the video until 133 ms before the initial flash. At that time all Luma/Alpha activity concentrates in one small area.
The lower area is centered in the area of the initial flash. The Luma/Alpha activity in this area is intermittent. Under some filter combinations I get the impression of something escaping or flowing from one of the ducts. This could be a false artifact from the interplay of filters and video compression.
Something new to think about.
The quick RTFS could be the result of new evidence from the examination of the TEL.     


What is a real world physics interpretation of Luma/Alpha activity?  Is it turning green, bright?   Did the AGC on the camera adjust to changing light levels?

There is a change in brightness on the Green and Red channels. I require more information on the USRL camera to know the color weighted algorithm used to determine Luma. The brightness changes are pixel specific. The AGC changes occur during the explosion.     
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/14/2016 08:46 am
The TE at pad 40 is the only one of the three that is not falcon heavy compatible. 
How many other differences are there to the other two TEs?
Are the other 2 TEs identical?
If they are significantly different to the one at pad 40, and the problem is external to the vehicle, it could be good news for RTF.
The TE at pad 40 had the most launches, and had been modified several times for each version of the Falcon 9.   Could that have contributed?

The TE at pad 40 was built for F9 1.0, modified for F9 1.1 and modified again for F9 FT.

A lot of additional equipment has been added along the way, particularly at the top of the structure.

It very much has the look of something that has evolved rather than being designed that way.

The buckling at the top of the TE when the payload detached was at the point where the structure was extended to deal with the taller F9 FT first stage - hardly surprising given this was the weakest point of the structure.

The Vandenberg TE looks as if it's related to the LC40 TE and the new one at Pad 39 is very different.

Presumably there is a design for a TE for Boca Chica as well, which may be in build by now - although that could wellbe a clone of the Pad 39 TE.

I think there may be a reference up thread to the Pad 39 type TE (ie FH capable) being too large to fit into the building at LC40, so replacement may have to be a clean-sheet design (or indeed a partial rebuild if the lower section isn't heat damaged).

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/14/2016 08:51 am
I applied Luma, Alpha, and Hue filters to the video and found two areas on the TEL that show change in their values. The top area is the payload A/C. The Luma /Alpha channels show activity throughout the video until 133 ms before the initial flash. At that time all Luma/Alpha activity concentrates in one small area.
The lower area is centered in the area of the initial flash. The Luma/Alpha activity in this area is intermittent. Under some filter combinations I get the impression of something escaping or flowing from one of the ducts. This could be a false artifact from the interplay of filters and video compression.
Something new to think about.
The quick RTFS could be the result of new evidence from the examination of the TEL.     


What is a real world physics interpretation of Luma/Alpha activity?  Is it turning green, bright?   Did the AGC on the camera adjust to changing light levels?

There is a change in brightness on the Green and Red channels. I require more information on the USRL camera to know the color weighted algorithm used to determine Luma. The brightness changes are pixel specific. The AGC changes occur during the explosion.   

The pixels will have gone through a fair amount of processing before they get saved - debayers (converting the bayer array of pixels to YUV), black level, denoise, AGC, AWB and a load of other stuff. Then it gets compressed. Pixel level changes could be noise, or introduced by denoise. I'd be very wary about using imagery after all that processing. If the raw bayer images were available, that would be a better source, although I suspect they won't be - the storage and bandwidth requirements for raw 4k video at 60fps are prohibitive, and unlikely to be used for a static fire.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/14/2016 10:02 am
Well if you look on the USLR video prior to the cut at 50 seconds it looks  like there is at the very least a LOx vent in the area.  I would highly doubt that they would vent anything else there (Except maybe He)  I have attached the SES-9 photo so you might look to see anything I missed.

Here's the interstage area. You can see two vents on opposite sides half way up the interstage. These might be for venting GOX used to pre-chill the engine. Not sure if they are venting at T-8 minutes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/14/2016 10:14 am
I applied Luma, Alpha, and Hue filters to the video and found two areas on the TEL that show change in their values. The top area is the payload A/C. The Luma /Alpha channels show activity throughout the video until 133 ms before the initial flash. At that time all Luma/Alpha activity concentrates in one small area.
The lower area is centered in the area of the initial flash. The Luma/Alpha activity in this area is intermittent. Under some filter combinations I get the impression of something escaping or flowing from one of the ducts. This could be a false artifact from the interplay of filters and video compression.
Something new to think about.
The quick RTFS could be the result of new evidence from the examination of the TEL.     


What is a real world physics interpretation of Luma/Alpha activity?  Is it turning green, bright?   Did the AGC on the camera adjust to changing light levels?

There is a change in brightness on the Green and Red channels. I require more information on the USRL camera to know the color weighted algorithm used to determine Luma. The brightness changes are pixel specific. The AGC changes occur during the explosion.   

The pixels will have gone through a fair amount of processing before they get saved - debayers (converting the bayer array of pixels to YUV), black level, denoise, AGC, AWB and a load of other stuff. Then it gets compressed. Pixel level changes could be noise, or introduced by denoise. I'd be very wary about using imagery after all that processing. If the raw bayer images were available, that would be a better source, although I suspect they won't be - the storage and bandwidth requirements for raw 4k video at 60fps are prohibitive, and unlikely to be used for a static fire.

Still admiring the hard work and the determination of the video squeezing members, I second that sentiment. It would seem that that level of pixel witchcraft should either get a standalone thread or be discussed it the farfetched theories thread, else we are about to determine that the AMOS-6 anomaly has been caused by video compression deficiencies.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Multivac on 09/14/2016 10:46 am
I have attached the SES-9 photo so you might look to see anything I missed.

That photo reminds me of one other thing in that general vicinity: the stage separation latches - SpaceX doesn't like to use pyros and those are pneumatic, as I recall. I don't know details of how they are pressurized and actuated, however.
Helium pressure for pneumaic sep Herb...
.

Ah, more pressurized helium, then. Figured it would be that or N2. It probably makes sense that the latches themselves use the same fluid.  I wonder if ther might've been a failure in that system that affected the umbilicals nearby. Perhaps that might account for the sounds Elon's tweet referred to. Totally spitballing here, but if Glennfish's video analysis "red dot" is a real thing, it's another system in the general vicinity to think about a bit.

please save me a half hour of searching this thread.  At what points prior to Frame 0 did the sounds occur.  I can look at before/after image groups to that point in time.  If you want to same me more time, at 60 frames per second, with the last 3 frames in the database ignored from the download, which frame(s) in our data provided correspond to the clang and thunk.  :)

With regard to the sounds... We don't know for sure what sounds Elon was referring as there are several in the sound track from US Launch Alliance video, but IMHO there are two sounds of interest. That is assuming they are from the pad and not from some other direction completely. So far we don't have any information either way.

That said, assuming they are from the pad, then they occur at 1:06.5 and 1:07.5 in the video timeline.
(i.e. 1:18.64 and 1:19.64 video sound track).

Previous information on the sounds at:
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1581255#msg1581255 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1581255#msg1581255)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/14/2016 11:45 am
1. The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.

Yes.

Quote
2. The condensation of oxygen must not have happened on the vastly longer first stage oxygen tanks during any of the horizontal test burns performed since SpaceX started working on subcooling LOx, such that no-one noticed the LOx dripping off and said "Hey do we have a LOx leak", and investigated the issue. Nor noticed on either stage in any previous vertical static-fire or launch.

No.  Numerous alternatives exist, such as LOX/frost mixtures or a decision that the condensation was acceptable.

Quote
3. Something must rub off the ice to expose the bare tank wall.

No.  Frost is porous.  LOX cryopumps.  Furthermore, ice forms at a relatively limited rate, as water vapour is only a minor constituent of air.  And lastly, ice is not a perfect insulator.  Actually it's not that great of an insulator at all - 2,2W/m-K for dense ice, about a tenth as much for snow (not even as good as paint).  Foam insulation by contrast is about 0,03W/m-K.

Your requirement #4 is based on your assumption of #3.

Quote
5. The thicker external skin of the ring around the common bulkhead must also be far enough below 90K for LOx to form faster than it evaporates.

Which is not at all an unexpected scenario.

I'm not addressing #6 and #7, as I'm not involved in that specific scenario, only defending the argument of external LOX.

Quote
8. Something something then causes the below-90K "plastic" to catch fire.
9. ...causing our initial explosion.

LOX is incompatible with almost all organics (excepting fluoropolymers, to some extent), becoming shock sensitive, friction sensitive, heat sensitive and pressure sensitive, including ignition from bending due to localized hot spots.  The degree depends on the organic compound in question, but almost all organics are considered unsafe in contact with LOX.  LOX is  also sensitive to silicone.  It's furthermore sensitive to titanium and some other metals.

LOX deflagration with organic contaminants is not only possible, it's also brought down rockets in the past (X-1A and X-1D for examples).  I should add, the ignition source was "pressurization"

Do not underestimate LOX.  Don't get me wrong, it's nice in that unlike some oxidizers it can't undergo runaway thermal decomposition, it's not what you'd call "corrosive" compared to others,  and it's non-toxic.  As far as oxidizers go, it's pretty nice stuff.  But it's still an incredibly powerful oxidizer.  Things in contact with LOX are pretty much looking for an excuse to burn; they just need an initiation energy.  With things like steel and aluminum, the initiation energy is fairly high.  With organics, it's very low.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/14/2016 11:48 am
I should add that the accumulation of LOX and liquid air is nothing new to rocketry... that is, to hydrogen rocketry.  It's a  problem that must be controlled.  When air liquefies, it doesn't only draw heat away and boiloff the hydrogen; the problem isn't even just that it's very flammable.  It's also a problem because it likes to pool in those out-of-the-way locations like vent pipes and interstages, where it adds dead mass to the stage.  LH rockets often go through a period in the development stage of searching out places where LOX or liquid air is accumulating and adding more insulation or sealing things up better, since the insulation tends to be significantly lighter than accumulated liquid air.

When dealing with LH, it's normally liquid air, or at worst LOX-enriched liquid air, that accumulates, rather than a pure or near-pure LOX.  Even still, liquid air is also very volatile, despite the nitrogen dilutant.  With densified LOX, however, the LOX in the tank (assuming 67K) is only 10 degrees from the boiling point of nitrogen, while it's 23 degrees from the boiling point of oxygen.  Anything retarding heat flow can readily lead to a situation where predominantly or exclusively LOX will condense.  Likewise, nitrogen tends to boil off first when the mixture is evaporating.

Dealing with liquefaction is something kerolox rockets normally don't even have to consider.  But Falcon 9 isn't a simple kerolox rocket. 

As a demonstration, you may have missed it, but earlier in the thread someone linked a page where a person poured liquid nitrogen into an uninsulated stainless steel container. LOX formed on it and dripped down, collecting at the base before boiling off.  Stainless steel is a significantly worse heat conductor than aluminum.  The container was thicker than a Falcon 9's skin.  LN2 is ten degrees hotter than densified LOX.  Yes, air liquefaction is a concern.  That doesn't mean it caused the problem, but it is definitely something that must fall under consideration.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 11:54 am
Just so I've got the LOx-from-air scenario clear...

1. The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.
Technically, it's condensing faster than it's evaporating.  This is know to happen with LN2 (see references).  The outside is colder than LN2 (see calculations).  So yes.
Quote
2. The condensation of oxygen must not have happened on the vastly longer first stage oxygen tanks during any of the horizontal test burns performed since SpaceX started working on subcooling LOx, such that no-one noticed the LOx dripping off and said "Hey do we have a LOx leak", and investigated the issue. Nor noticed on either stage in any previous vertical static-fire or launch.
I'm sure that when SpaceX people noticed liquid on the outside of a sub-cooled surface, then knew it was condensed air.  It's in every cryo textbook and every university tract on dealing with cryo.  It was a known pain when dealing with liquid hydrogen.

On the other hand, it's normally no problem.  The LOX tank (both stages) is above the kerosene tank.  So LOX gets trapped in the frost and falls off, or runs down the tank, hits the fuel section, and evaporates into an already GOX rich environment.  No harm, no foul.

Quote
3. Something must rub off the ice to expose the bare tank wall. So...
No, depends on the conditions. Sometimes you get frost, sometimes a combination, and sometimes the liquid air prevents the frost formation.  See the references - they get LOX dripping off with no scraping of the ice required.
Quote
4. As the F9 shrinks due to the second stage LOx fill (but after shrinkage caused by the previous main stage LOx fill), the small support brace below the hydraulic/pneumatic grapples, resting against the reinforced area that rings of the common bulkhead, must slide enough to scrape ice off that aforementioned reinforced area that rings the common bulkhead.
As per references, scraping not required,  and the first stage LOX fill is not done until 2:40 before launch.  So the first stage is still shrinking at T-8:00.
Quote
5. The thicker external skin of the ring around the common bulkhead must also be far enough below 90K for LOx to form faster than it evaporates.
Yes.   The thicker aluminum at this point makes almost no difference, as the thermal conductivity is dominated by the paint.  See the calculations above.
Quote
6. The LOx forming on the newly exposed skin at the bottom of the common bulkhead ring must run... up?... to soak into the protective "plastic" pads of the support brace.
No, the LOX tank wall is above the common bulkhead.  If the "plastic" support thingy is located at the bulkhead, which makes mechanical sense and looks consistent with the picture, then LOX forming on the wall of the tank runs down onto the plastic support.
Quote
7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.
The surface of the plastic brace is pushed against a (painted) aluminum surface at well under 77K.  Plastic has a thermal conductivity orders of magnitude less than aluminum (epoxy, for example, is 0.35 w/m/K).  The pad is visible on photos, so cannot be too thin.  So a temperature gradient will form across the pad, with the rocket surface at close to 66K and the T/E surface at ambient.  But the rocket facing surface, and the first few mm of pad, will surely be cold enough to prevent the LOX from evaporating.
Quote
8. Something something then causes the below-90K "plastic" to catch fire.
LOX plus organics can be sensitive explosives.  And this would be scraping across the surface as the first stage fill completes.
Quote
9. ...causing our initial explosion.
Perhaps.  Could enough LOX condense in the time available?  What's the "plastic" made of?  SpaceX must have known of the possibility of LOX condensing, what countermeasures did they take?  We are all just guessing based on very limited data.  But this would explain the no-show on telemetry, the location of the fault, and the difficulty of telling inside from outside cause.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/14/2016 12:07 pm
I extracted snapshots of second stage from various SpaceX photos - these may be useful for you guys:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/14/2016 01:22 pm
<snip>
Will the outside of the rocket be less than 77K?  Yes, if the inside is at 66K.  The thermal conductivity of aluminum is about 205 w/m/k.  So to get an 11K drop across a 5 mm thickness you would need a heat flow of 205*11/0.005 = 451 kw/m^2.  No way you have that from condensing air, so the outside temp is less than 77K.
<snip>

Surely this calculation would only apply if the outside of the rocket were unpainted Al?  But we know it's painted, and upthread I admitted complete ignorance about what kind of paint, and how thick (and how potentially explosive in contact with LOX ...).  Does anyone here know these details?
Good point.  I ignored the paint since it's very thin, but it turns out that's a bad guess.  Assuming the paint is 0.1mm thick (since they don't want any extra mass), then it's 50x thinner than the aluminum.  But at least generic paint is a rotten thermal conductor -  this report (http://www.thefreelibrary.com/Special+heat+capacity+and+thermal+conductivity.-a0228354685) claims 0.17 w/m/K, or about 1000x worse than aluminum.   So even if it's only 1/50th as thick, it's still a 20x better insulator than the aluminum.  However, this would still need a flux of 20 kw/m^2 to maintain a delta-T of 11 degrees.   This online heat transfer calculator (http://www.efunda.com/formulae/heat_transfer/convection_forced/calc_lamflow_isothermalplate.cfm#calc) estimates heat transfer from a 70K plate in a 4 m/s wind to be about 2kw/m^2, so the surface will still be much closer to 66K than 77K.
Don't forget to account for the partial pressure of oxygen in the atmosphere.  It's not pure oxygen at STP.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/14/2016 01:35 pm
I extracted snapshots of second stage from various SpaceX photos - these may be useful for you guys:

Ta.  :) A few remarks, if I may. Some of this is guesswork, but I've spent enough time looking at TELs recently to be pretty confident...

1 - Probably Vandenberg, as the rams holding the claw look different / there isn't a lot of equipment at the top of the TEL / the sheeting isn't on the LC40 TEL

2, 3, 4 - LC40, probably after the changes made to adapt to F9 FT

5 - LC40, angle makes it difficult to see, but might be F9 1.1 era (bottle screws smaller) / also there seems to be not as much equipment at the top of the TEL

6 - LC 40, probably F9 FT

7 - ?!

8 - good image, appears to be F9 FT

9 - Vandenberg? - the background doesn't look like Florida / TEL hasn't got the pivoted cradle that LC40 has (with the support at the common bulkhead)

10 - Vandenberg

11 - good image, LC40 with F9 FT. The pivoted cradle is very visible.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/14/2016 01:41 pm
Just to clarify the change made to increase the height of the LC40 erector to change it from F9 1.1 to F9 FT, see the attached images which show the section of the strongback that was modified.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mr2828 on 09/14/2016 01:45 pm
Here's the interstage area. You can see two vents on opposite sides half way up the interstage. These might be for venting GOX used to pre-chill the engine. Not sure if they are venting at T-8 minutes.

I remember Jim mentioned many pages back that for any areas receiving A/C, they should have a small hole to allow the positive pressure to escape. Is there an A/C "vent" somewhere on the interstage? And if so, does that area face the T/E or is it pointed away?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 01:54 pm
I have attached the SES-9 photo so you might look to see anything I missed.

That photo reminds me of one other thing in that general vicinity: the stage separation latches - SpaceX doesn't like to use pyros and those are pneumatic, as I recall. I don't know details of how they are pressurized and actuated, however.
Helium pressure for pneumaic sep Herb...
.

Ah, more pressurized helium, then. Figured it would be that or N2. It probably makes sense that the latches themselves use the same fluid.  I wonder if ther might've been a failure in that system that affected the umbilicals nearby. Perhaps that might account for the sounds Elon's tweet referred to. Totally spitballing here, but if Glennfish's video analysis "red dot" is a real thing, it's another system in the general vicinity to think about a bit.

please save me a half hour of searching this thread.  At what points prior to Frame 0 did the sounds occur.  I can look at before/after image groups to that point in time.  If you want to same me more time, at 60 frames per second, with the last 3 frames in the database ignored from the download, which frame(s) in our data provided correspond to the clang and thunk.  :)

With regard to the sounds... We don't know for sure what sounds Elon was referring as there are several in the sound track from US Launch Alliance video, but IMHO there are two sounds of interest. That is assuming they are from the pad and not from some other direction completely. So far we don't have any information either way.

That said, assuming they are from the pad, then they occur at 1:06.5 and 1:07.5 in the video timeline.
(i.e. 1:18.64 and 1:19.64 video sound track).

Previous information on the sounds at:
http://forum.nasaspaceflight.com/index.php?topic=30981.msg1581255#msg1581255 (http://forum.nasaspaceflight.com/index.php?topic=30981.msg1581255#msg1581255)


Thanks, using your timings, here's the change maps:

pre-clang to post-clang
pre-thunk to post-thunk

No obvious changes visible above the noise.  1/2 second stacking per comparison pair.

frames 1003 to 973 : 5.5 to 5 seconds,
frames 1157 to 1183 : 2.5 to 3 seconds,
frames 1048 to 1078 : 3.75 to 4.25 seconds
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/14/2016 01:56 pm
This is actually pretty good video for seeing, where the GOX vents actually are and how they function:

https://www.youtube.com/watch?v=VX4LH0wn9Rs
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/14/2016 02:04 pm

If you go back to the original USLR video, you will see that the area identified is often completely obscured by dark venting. When not obscured, it is a bright area, so perhaps it should not be surprising that it changes more than any other area?

I think you may have missed the whole point of the analysis. The area identified had the recurring changes removed and only the differential change between the prior interval and the moments before the incident remain.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/14/2016 02:10 pm
<snip>
Will the outside of the rocket be less than 77K?  Yes, if the inside is at 66K.  The thermal conductivity of aluminum is about 205 w/m/k.  So to get an 11K drop across a 5 mm thickness you would need a heat flow of 205*11/0.005 = 451 kw/m^2.  No way you have that from condensing air, so the outside temp is less than 77K.
<snip>

Surely this calculation would only apply if the outside of the rocket were unpainted Al?  But we know it's painted, and upthread I admitted complete ignorance about what kind of paint, and how thick (and how potentially explosive in contact with LOX ...).  Does anyone here know these details?
Good point.  I ignored the paint since it's very thin, but it turns out that's a bad guess.  Assuming the paint is 0.1mm thick (since they don't want any extra mass), then it's 50x thinner than the aluminum.  But at least generic paint is a rotten thermal conductor -  this report (http://www.thefreelibrary.com/Special+heat+capacity+and+thermal+conductivity.-a0228354685) claims 0.17 w/m/K, or about 1000x worse than aluminum.   So even if it's only 1/50th as thick, it's still a 20x better insulator than the aluminum.  However, this would still need a flux of 20 kw/m^2 to maintain a delta-T of 11 degrees.   This online heat transfer calculator (http://www.efunda.com/formulae/heat_transfer/convection_forced/calc_lamflow_isothermalplate.cfm#calc) estimates heat transfer from a 70K plate in a 4 m/s wind to be about 2kw/m^2, so the surface will still be much closer to 66K than 77K.
Don't forget to account for the partial pressure of oxygen in the atmosphere.  It's not pure oxygen at STP.

Yes, and far upthread envy887 made this point too.  It happens that 77 K (as well as being LN2 bp) is also the temp at which LOX vapour pressure equals 20 kPa, the (sea-level) partial pressure of atmospheric O2.  So between 77 K and 90 K LOX will evaporate faster than it condenses, even though it doesn't boil.  Below 77 K condensation wins (at sea-level). 

Even more significantly, at 75 K the vapour pressure of LN2 equals 80 kPa, the partial pressure of N2 in the atmosphere.  Which means that between 75 and 77, LOX condenses while LN2 evaporates, and you will get pure LOX in your frost.

SpaceX seem to be the first to venture into this hazardous temperature range - the NK-33 family don't cool that far, because they rely on evaporating atmospheric-pressure LN2 to do the cooling.  According to Spaceflight101 at http://spaceflight101.com/spacerockets/soyuz-2-1v/   the N-1 cooled to 81 K, Antares-100 to 78 K and the current Soyuz 2-1v to 86 K.  Since these are all above 77 K, atmospheric LOX could never condense on the outside of their tanks, insulated or not.

On the other hand, LH2 rockets, as Rei says just upthread, got less dangerous liquid air because they were far below both 75 K and 77 K.

I think this temperature range, 75 to 77 K, is very significant.  If your paint surface is that cold you are essentially distilling pure LOX from the air.  And if it happens at the inside of the frost layer, cryopumping will quickly draw in more oxygen to build up the LOX.  From the estimated heat flux through tankwall and paint, and the latent heat of O2, we could estimate the speed of build-up ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/14/2016 02:24 pm
LOX condensation.

This is the first complete explanation of the initial burst. The only thing missing is what material the pads are made out of. I have heard rubber? Is that confirmed by somebody?

edit:
And by complete I mean: every complaint I can think of this scenario has an answer.
1. Why not in testing.
2. Location is perfect.
3. Why not before on a launch.
4. External.
5. Doesn't require a screw up somewhere by a worker.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/14/2016 02:31 pm
Just so I've got the LOx-from-air scenario clear...

1. The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.

2. The condensation of oxygen must not have happened on the vastly longer first stage oxygen tanks during any of the horizontal test burns performed since SpaceX started working on subcooling LOx, such that no-one noticed the LOx dripping off and said "Hey do we have a LOx leak", and investigated the issue. Nor noticed on either stage in any previous vertical static-fire or launch.

3. Something must rub off the ice to expose the bare tank wall. So...

4. As the F9 shrinks due to the second stage LOx fill (but after shrinkage caused by the previous main stage LOx fill), the small support brace below the hydraulic/pneumatic grapples, resting against the reinforced area that rings of the common bulkhead, must slide enough to scrape ice off that aforementioned reinforced area that rings the common bulkhead.

5. The thicker external skin of the ring around the common bulkhead must also be far enough below 90K for LOx to form faster than it evaporates.

6. The LOx forming on the newly exposed skin at the bottom of the common bulkhead ring must run... up?... to soak into the protective "plastic" pads of the support brace.

7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.

8. Something something then causes the below-90K "plastic" to catch fire.

9. ...causing our initial explosion.

1. Possible Frost GOX combo.

2. They do not use the strongback at any point in testing, There may never have been testing at McGregor of a combined 1st and second stage. (Does anyone know?) particularly there is no support bracing pad at McGregor.

3. The rocket is starting a second shrinkage due to Lox loading of stage 2. Confirmed by Jim to cause sliding. What if the stage 1 shrinkage was even a touch more than prior static fires, or a bit faster due to faster/colder load conditions as were surmised?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Fan Boi on 09/14/2016 02:43 pm
I want to suggest the possibility of using the MIT software mentioned in the video below. Anyone have access to it or know someone who might be able to run that footage through it? It takes very tiny movements and exaggerates them greatly, really cool actually. And it can be used after the footage has already been taken.

https://www.youtube.com/watch?v=3rWycBEHn3s
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/14/2016 02:46 pm

7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.


So is the fix as simple as replace the pads with something lox compatible?
Would woven fiberglass cloth be a good choice?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: whitelancer64 on 09/14/2016 02:54 pm

7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.


So is the fix as simple as replace the pads with something lox compatible?
Would woven fiberglass cloth be a good choice?

It might be better to add a layer of insulation around the LOX tank (or at critical areas). While everyone would hate to add weight to the 2nd stage, preventing LOX from forming in the first place may well be the better solution.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jet Black on 09/14/2016 02:59 pm
regarding the sounds, has anyone looked into roughly what the volume in dB would be required if we assume that it is from the rocket?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/14/2016 03:02 pm
Seems that people here are fixing a problem that has not been shown to even exist yet.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/14/2016 03:04 pm
Seems that people here are fixing a problem that has not been shown to even exist yet.

and may never be shown to exist!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/14/2016 03:07 pm
Seems that people here are fixing a problem that has not been shown to even exist yet.

and may never be shown to exist!

Well thinking about that.
Would the pads have to be missing from the TEL?
Could that be the proof?
Would a surface layer of the pads be enough to form the initial blast?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 03:13 pm
I want to suggest the possibility of using the MIT software mentioned in the video below. Anyone have access to it or know someone who might be able to run that footage through it? It takes very tiny movements and exaggerates them greatly, really cool actually. And it can be used after the footage has already been taken.

https://www.youtube.com/watch?v=3rWycBEHn3s

They have a web site where you can upload your own video and process and see the motion amplification.

Sign up for an account, login, upload your video, watch....

https://lambda.qrilab.com/site/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/14/2016 03:27 pm
Seems that people here are fixing a problem that has not been shown to even exist yet.

and may never be shown to exist!

Well thinking about that.
Would the pads have to be missing from the TEL?
Could that be the proof?
Would a surface layer of the pads be enough to form the initial blast?
It seems that, with all the post-incident imagery of LC40, it would be a simple thing to determine if the pads are still present, thus ruling out this scenario.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/14/2016 03:28 pm

7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.


So is the fix as simple as replace the pads with something lox compatible?
Would woven fiberglass cloth be a good choice?

It might be better to add a layer of insulation around the LOX tank (or at critical areas). While everyone would hate to add weight to the 2nd stage, preventing LOX from forming in the first place may well be the better solution.
Why is putting weight on the vehicle and not the GSE a good idea?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/14/2016 03:35 pm


LOX condensation.

This is the first complete explanation of the initial burst. The only thing missing is what material the pads are made out of. I have heard rubber? Is that confirmed by somebody?

If the pads are made of PFTE, there is no scenario here.

Even if the pads were made of an organic, I don't think there's been any credible ignition source shown.  Jim has pretty persuasively argued that there is no banging or bumping involved, and he has first hand experience, and there's no evidence for rocking or swaying from the video either.  Further, the magnitude and speed of the initial event seems incompatible with the amount and type of fuel proposed.

Also: would SpaceX continue to be baffled by the source if this were the answer?  They know exactly what the pads are made of, how they are cleaned, and what condition they are currently in.  Don't you think they would be quickly wrapping up this investigation if they saw the pads were made of a LOX-incompatible plastic, that one of the pads was unaccounted for, and there were witness marks on the cradle arms?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Fan Boi on 09/14/2016 03:35 pm
I want to suggest the possibility of using the MIT software mentioned in the video below. Anyone have access to it or know someone who might be able to run that footage through it? It takes very tiny movements and exaggerates them greatly, really cool actually. And it can be used after the footage has already been taken.

https://www.youtube.com/watch?v=3rWycBEHn3s

They have a web site where you can upload your own video and process and see the motion amplification.

Sign up for an account, login, upload your video, watch....

https://lambda.qrilab.com/site/

Nice! I created an account but I can't extract the video from youtube while at work, will have to do that from home. I also see that the MIT software can greatly exaggerate color differences too, can't wait to see what it shows of that failure. Hope someone reading this might do it and post the results, don't want to wait until tonight!
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 03:38 pm
Seems that people here are fixing a problem that has not been shown to even exist yet.
Perfectly true, but you might want to fix it anyway (unless your analysis can firmly prove it's impossible), even if it's not the cause of this particular mishap.

This is a pretty typical outcome from investigations - a bunch of things are uncovered that might cause problems, in addition to the one(s) that did.  These additional risks are typically fixed as well.   Working from memory here, but when they fixed the foam problem in the shuttle, they also fixed some explosive bolts whose pieces were not reliably captured, and a few other improvements.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/14/2016 03:42 pm



Also: would SpaceX continue to be baffled by the source if this were the answer?  They know exactly what the pads are made of, how they are cleaned, and what condition they are currently in.  Don't you think they would be quickly wrapping up this investigation if they saw the pads were made of a LOX-incompatible plastic, that one of the pads was unaccounted for, and there were witness marks on the cradle arms?

I was going to say in a previous comment but it appeared shotwell's comments were ambiguous.
I think shotwell's comments yesterday indicate they have a good idea of where the problem is but haven't conclusively proven it. And may never have hard proof. So they are now chasing down every other rare event that could be possible.

Anyways I looked and I am not good at reading photos so I couldn't tell if one or both pads were still there.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 03:44 pm

Good point.  I ignored the paint since it's very thin, but it turns out that's a bad guess.  Assuming the paint is 0.1mm thick (since they don't want any extra mass),

Wouldn't you think they have it thicker to act like an insulator?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 03:48 pm

1.  "Pressing" and "Forcefully sliding" - until the clamps let go, they are surely pressing on the far side of the rocket.  No way they would have an air gap and let the rocket rattle back and forth against the clamps - that would confuse the telemetry if nothing else.  So until the arms are opened, the rocket will be pressed into the pad on the erector. 

2.And thermal contraction generates big forces, so it will slide despite being pushed against the rocket.

1. They aren't clamping the vehicle tight.  It is just there to steady the vehicle.  It is not holding the vehicle.  It is like a boat bumper.

2.  What big forces?    Again, there is no clamping force.   

And it ignores this

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583334#msg1583334
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/14/2016 03:54 pm
Just thought of something:

Assume:
- lox has formed on the outside of the vehicle
- mechanical friction causes an ignition event where this lox touches the cradle pads - possibly with residue/dirt/bird-poop as a catalysator to decrease activation energy.( technically all you need is a single dust particle. Flower pollen,whatever)

This would not have needed to be an explosion strong enough to rupture the tank and/or reuired a lox-soaked plastic pad that obliterates.

All it needs is a localized spark strong enough to burn through the paint layer and aluminium passivation and start a chain reaction between aluminium and gaseous oxygen

This would still be very localized when a few milliseconds later it has burnt through the tank wall and allows the tank contents to add themselves to the equation.

The outside gox and organics wouldnt provide the energy for the initial explosion, merely the primer to ignite the tank wall

Or would that belong in the far fetched thread?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 03:55 pm

Vortex shedding has caused the destruction of several large chimneys in the past,

That is the reason the strong back is there and remains attached to the rocket so late into the count, is to prevent vortex shedding from damaging the vehicle.  The upper clamp points would be taking into account the natural frequency and modes of the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/14/2016 03:55 pm
For those looking at the interstage area, I just want to point out that at the top of S1 are the avionics and lithium ion batteries IIRC...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/14/2016 03:59 pm
A footnote to this recent post of mine, bringing in some effects of latent heat release ...


<nested quotes snipped>

Yes, and far upthread envy887 made this point too.  It happens that 77 K (as well as being LN2 bp) is also the temp at which LOX vapour pressure equals 20 kPa, the (sea-level) partial pressure of atmospheric O2.  So between 77 K and 90 K LOX will evaporate faster than it condenses, even though it doesn't boil.  Below 77 K condensation wins (at sea-level). 

Even more significantly, at 75 K the vapour pressure of LN2 equals 80 kPa, the partial pressure of N2 in the atmosphere.  Which means that between 75 and 77, LOX condenses while LN2 evaporates, and you will get pure LOX in your frost.

SpaceX seem to be the first to venture into this hazardous temperature range - the NK-33 family don't cool that far, because they rely on evaporating atmospheric-pressure LN2 to do the cooling.  According to Spaceflight101 at http://spaceflight101.com/spacerockets/soyuz-2-1v/   the N-1 cooled to 81 K, Antares-100 to 78 K and the current Soyuz 2-1v to 86 K.  Since these are all above 77 K, atmospheric LOX could never condense on the outside of their tanks, insulated or not.

On the other hand, LH2 rockets, as Rei says just upthread, got less dangerous liquid air because they were far below both 75 K and 77 K.

I think this temperature range, 75 to 77 K, is very significant.  If your paint surface is that cold you are essentially distilling pure LOX from the air.  And if it happens at the inside of the frost layer, cryopumping will quickly draw in more oxygen to build up the LOX.  From the estimated heat flux through tankwall and paint, and the latent heat of O2, we could estimate the speed of build-up ...

... and we need to take into account the effect of the release of latent heat by the LOX as it condenses (if it does).

Suppose for the sake of argument that in the absence of any condensation the outside of the paint layer would be, say, 70 K, just because of conduction and convection.  Now suppose condensation starts forming on the outside paint surface; at 70 K it'll be a mix of LOX and LN2.  This condensing gas will release latent heat, which will warm the top of the paint layer.  As it warms through 75 K it will stop condensing LN2, less latent heat will be released, and the warming will slow.  If it ever goes above 77 K, LOX condensation will stop too, and the top of the paint layer will cool again.  My point here is that the release of latent heat of condensation will act like a thermostat to keep the temperature within the dangerous 75 to 77 K range where the condensate is pure LOX.   

Of course we don't have enough data to model the size of this effect properly - we'd need the thermal capacity and conductivity of the paint, and the frost (we'd need to know how fluffy it typically is).   But there's no doubt about the direction of the effect - it will always push the temperature towards the 75 to 77 K range.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 04:05 pm

LOX is incompatible with almost all organics (excepting fluoropolymers, to some extent), .


Who wants to bet that the bumpers are made of a fluoropolymer called Teflon?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: whitelancer64 on 09/14/2016 04:06 pm

7. The protective "plastic" pads of the support brace, connected to the metal of the support brace, must also be far enough below 90K to prevent the soaking LOx from evaporating or just boiling away.


So is the fix as simple as replace the pads with something lox compatible?
Would woven fiberglass cloth be a good choice?

It might be better to add a layer of insulation around the LOX tank (or at critical areas). While everyone would hate to add weight to the 2nd stage, preventing LOX from forming in the first place may well be the better solution.
Why is putting weight on the vehicle and not the GSE a good idea?

If it's the GSE that the LOX is forming on, then insulate that. If it's forming on the tank, then the tank should be insulated. The idea being to prevent the LOX from forming at all.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 04:21 pm

a.  LOX does not form on the vehicle. (tank and paint thickness prevent it)  No need to go any further but to appease the LOX accusers
b.  The first bumper interface is at the common bulkhead attach weld.  Where warmer RP-1 is next to sub cooled LOX.  So temp on the surface is above LOX boiling point
c.  There is no sliding (contraction) while there is LOX in the second stage.  The first stage is loaded 15 minutes (or so) earlier.  The contraction (sliding) occurs in this period.
d.  The bumpers are made of LOX compatible material
e.  Spacex would have seen the LOX and come to this conclusion by now
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 04:28 pm


LOX condensation.

This is the first complete explanation of the initial burst. The only thing missing is what material the pads are made out of. I have heard rubber? Is that confirmed by somebody?

If the pads are made of PFTE, there is no scenario here.
This seems the first thing to check.  Combine LOX and a pad and if it's still safe, this is not the explanation.
Quote
Even if the pads were made of an organic, I don't think there's been any credible ignition source shown.  Jim has pretty persuasively argued that there is no banging or bumping involved, and he has first hand experience, and there's no evidence for rocking or swaying from the video either.  Further, the magnitude and speed of the initial event seems incompatible with the amount and type of fuel proposed.
The ignition source does not seem to be a huge obstacle.  Stuff combined with LOX is quite sensitive to mechanical shock, and the rocket is not still.  The first stage is still shrinking (it's not full until T-2:40), and the LOX will be boiling.  As Cernan says in "Last Man on the Moon", while going up the elevator "Every inch of the way, the rocket beside us hummed and vibrated.  Glasslike chunks of ice slid away as her cryogenic life-blood, liquid oxygen and liquid hydrogen, boiled and bubbled in her guts."    Whether or not you can get enough LOX-pad combo to explain the initial explosion required data we do not have.
Quote
Also: would SpaceX continue to be baffled by the source if this were the answer?  They know exactly what the pads are made of, how they are cleaned, and what condition they are currently in.  Don't you think they would be quickly wrapping up this investigation if they saw the pads were made of a LOX-incompatible plastic, that one of the pads was unaccounted for, and there were witness marks on the cradle arms?
This to me is the strongest objection - such an event should leave signs in the wreckage, and SpaceX would not be puzzled. I'd assume they must have examined the T/E by now, although this will presumable be easier and more thorough once they can lower it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/14/2016 04:32 pm
Hypothesis:

1.  A fly or similar insect is attracted by the white surface and sits down
2. Oxygen loading has started, the outside of the lox tank gets covered in frost. The insect freezes to death - and in place.
3. As oxygen fill rates ramp up, the temperature drops below 77K on the surface, under the ice. Liquid oxygen starts condensing.
4. The insect becomes immersed in a drop of liquid oxygen
5. As the stage shrinks further, the insect gets crushed between teflon pads and the tank wall
6. The insect ignites and combusts rapidly, burning a tiny black scorchmark into both teflon an tank paint, exposing the aluminium beneath to a few drops of liquid oxygen
7. The activation energy is just enough to start a sustained reaction between LOX and aluminium
8. The reaction spreads in 3 dimensions. Both on the surface and deeper into the tank wall.
9. In one tiny spot the tank wall is breached. The reaction can now spread along the inside of the tank wall where unlimited supplies of oxygen are available.
10. The energy release evaporates enough oxygen to form a shockwave that bursts the tank and sends the burning aluminium shards flying away as shrapnel.
11. The reaction stops consuming the aluminium since all burningmetal pieces have flown into regions with lower oxygen concentration, or burnt up. However a RUD is in progress as tank and bulkhead are breached
12. The oxygen and the RP1 start burning, big fireball
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/14/2016 04:34 pm
This to me is the strongest objection - such an event should leave signs in the wreckage, and SpaceX would not be puzzled. I'd assume they must have examined the T/E by now, although this will presumable be easier and more thorough once they can lower it.

That was my next question. Have they lowered it yet?
I think something conclusive will come out of having it lowered and thoroughly examined.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: whitelancer64 on 09/14/2016 04:48 pm
<snip>
Will the outside of the rocket be less than 77K?  Yes, if the inside is at 66K.  The thermal conductivity of aluminum is about 205 w/m/k.  So to get an 11K drop across a 5 mm thickness you would need a heat flow of 205*11/0.005 = 451 kw/m^2.  No way you have that from condensing air, so the outside temp is less than 77K.
<snip>

Surely this calculation would only apply if the outside of the rocket were unpainted Al?  But we know it's painted, and upthread I admitted complete ignorance about what kind of paint, and how thick (and how potentially explosive in contact with LOX ...).  Does anyone here know these details?
Good point.  I ignored the paint since it's very thin, but it turns out that's a bad guess.  Assuming the paint is 0.1mm thick (since they don't want any extra mass), then it's 50x thinner than the aluminum.  But at least generic paint is a rotten thermal conductor -  this report (http://www.thefreelibrary.com/Special+heat+capacity+and+thermal+conductivity.-a0228354685) claims 0.17 w/m/K, or about 1000x worse than aluminum.   So even if it's only 1/50th as thick, it's still a 20x better insulator than the aluminum.  However, this would still need a flux of 20 kw/m^2 to maintain a delta-T of 11 degrees.   This online heat transfer calculator (http://www.efunda.com/formulae/heat_transfer/convection_forced/calc_lamflow_isothermalplate.cfm#calc) estimates heat transfer from a 70K plate in a 4 m/s wind to be about 2kw/m^2, so the surface will still be much closer to 66K than 77K.

Jim, do you have numbers that say these estimates are incorrect?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 04:52 pm
just another puzzler to think about.

I was reviewing the turbulence removal output and realized that the software thinks it's removing atmospheric turbulence where there isn't anything really visible.  In fact it thinks it's removing turbulence in the enhanced portion of the image attached, between the highly visible upper and lower LOX/GOX clouds.

That implies that there's something that the algorithm thinks is drifting in the same way a turbulence region would drift, i.e. refractive index changes of some kind in a large area, highly correlated within and between frames.

So I looked at the only frame that seems capable of showing what's there, and stretched the hell out of it.

It seems to me that there is a slight cloud visible in the region between the upper & lower oxygen vent clouds.  Or maybe the CCDs started transferring charges between each-other in a cascade of illusory light level measurements.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DLK on 09/14/2016 04:54 pm
1. They aren't clamping the vehicle tight.  It is just there to steady the vehicle.  It is not holding the vehicle.  It is like a boat bumper.

Is it possible that something on the vehicle 'hung' or 'caught' on the strongback, interfering with its thermal contraction?
Would this go unnoticed during tanking?
I could see this causing mechanical stress on the hull.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/14/2016 04:56 pm
This to me is the strongest objection - such an event should leave signs in the wreckage, and SpaceX would not be puzzled. I'd assume they must have examined the T/E by now, although this will presumable be easier and more thorough once they can lower it.

That was my next question. Have they lowered it yet?
I think something conclusive will come out of having it lowered and thoroughly examined.
There are pictures posted which show they've had a crane up at the site for inspections.  I don't think they'll bring the T/E down until they've concluded their investigation, or ruled out the GSE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/14/2016 05:14 pm

and may never be shown to exist!

Well thinking about that.
Would the pads have to be missing from the TEL?
Could that be the proof?
Would a surface layer of the pads be enough to form the initial blast?

And may have acted as a "shaped charge" because of the metal frame it was in. Directing most of the force toward the vehicle just ABOVE the re-enforced portion of the stage because the rocket had shrunk and slid downwards.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 05:15 pm

The first stage is still shrinking (it's not full until T-2:40), and the LOX will be boiling. 


Most of the shrinking would have happened by second stage tanking.  The LOX is sub cooled, it is not boiling
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 05:17 pm

and may never be shown to exist!

Well thinking about that.
Would the pads have to be missing from the TEL?
Could that be the proof?
Would a surface layer of the pads be enough to form the initial blast?

And may have acted as a "shaped charge" because of the metal frame it was in. Directing most of the force toward the vehicle just ABOVE the re-enforced portion of the stage because the rocket had shrunk and slid downwards.

Really?  This is the rational thread. 
Here is the wacky thread. 
http://forum.nasaspaceflight.com/index.php?topic=41119.0

In fact, all the LOX and bumper talk should move there.    Too many things have to happen for this to be feasible
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DMeader on 09/14/2016 05:20 pm
Hypothesis:

1.  A fly or similar insect is attracted by the white surface and sits down

Please. Exploding flies?
Now you've just gone beyond silly.  We need the Monty Python Colonel here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/14/2016 05:50 pm
I wouldn't mind seeing the blast signature of an exploding Lithium Ion battery in the confined area of an interstage test... Just to compare to what we saw...

http://spacefellowship.com/news/art19992/preparations-for-first-falcon-9-launch.html
Test rig that looks something like this, you don't need the whole stack...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/14/2016 05:55 pm


Really?  This is the rational thread. 
Here is the wacky thread. 
http://forum.nasaspaceflight.com/index.php?topic=41119.0

In fact, all the LOX and bumper talk should move there.    Too many things have to happen for this to be feasible

Jim,
I will be happy to move there at the request Chris or other moderator.
No one, I believe, is saying that they know better than you. But in the 130 some odd pages, the idea has NOT been discounted to the point of impossibility. And no other competing suggestion takes into account the differences and potential differences that made this instance unique. The people "in the know" such as yourself seem to agree that handling the extra-sub-cooled LOX is new territory in handling launch vehicles.  If not some weird interaction verging on the impossible, then WHAT?

Our objection I think, is, as of today, in your view, the Falcon would not have exploded.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul451 on 09/14/2016 05:57 pm
... and we need to take into account the effect of the release of latent heat by the LOX as it condenses (if it does).

You also need to take into account the effect of the release of latent heat by the water that is also freezing out.

Hence...

My point here is that the release of latent heat of condensation will act like a thermostat [...]

...by your own argument, the external temperature of the skin cannot ever fall below 77K. Water vapour in that humid Florida wind will act like a thermometer, continually raising the temperature until the rate of ice formation slows.


This would still be very localized when a few milliseconds later it has burnt through the tank wall [...]

A few milliseconds? Of a solid aluminium fire?


1. The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.
Technically, it's condensing faster than it's evaporating.  This is know to happen with LN2 (see references).  The outside is colder than LN2 (see calculations).

Much earlier in the thread, several people modelled the flow of heat and showed that the external temperature wouldn't fall below the critical 77K. Even the smallest amount of water-ice frost will prevent LOx condensation, even ignoring the heat of condensation of that frost.

Hence someone else (I'm too lazy to go hunting) suggested that the frost itself would insulate the skin, allowing the skin to subcool under the ice, if the ice fell away, it would briefly expose sub-77K skin to the air.

That led to the suggestion that the cradle pads could have scraped away the ice as the vehicle condensed, which led to the idea that the pads themselves (soaked in LOx) could have also provided the fuel for the initial blast.

My response was to try to show the failure to think through the contradictions in that idea. Amongst other things, if the pads scrape the ice away from the tank, exposing skin below the pads to allow LOx condensation, how did the pads become "soaked" in the LOx that is forming below them?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 06:02 pm

Our objection I think, is, as of today, in your view, the Falcon would not have exploded.


No, my view is that incident had nothing to do with pads or LOX forming.
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/14/2016 06:08 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Widow of F9-20 on 09/14/2016 06:10 pm
This to me is the strongest objection - such an event should leave signs in the wreckage, and SpaceX would not be puzzled. I'd assume they must have examined the T/E by now, although this will presumable be easier and more thorough once they can lower it.

That was my next question. Have they lowered it yet?
I think something conclusive will come out of having it lowered and thoroughly examined.

Soon. Safety rules for lowering a damaged structure is also a consideration.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: John-H on 09/14/2016 06:15 pm
The grabber does not crush the tank, so there is probably a gap or at least a loose fit between the bumper pad and the tank. If there is a small gap, it will be below LOX condensation temperature, since the pad acts as an insulator. Air will go in and LOX will condense in the space
If the wind is rattling the rocket even slightly, the gap will bang shut and a few drops of LOX will be squirted around. It only takes a bit of dirt or  sand to scrape the paint off the aluminum and create a bare surface and some activation energy.
There would be a flash  and just enough of a bang to get things started.

If it didn't happen this way, it is still a possible scenario that needs to be addressed.

John
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 06:18 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.

I mean the temp of the helium as it exits
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 06:21 pm
it will be below LOX condensation temperature,

Based on what?

It only takes a bit of dirt or  sand to scrape the paint


why is there dirt or sand on them and how thick do you think the paint is?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/14/2016 06:24 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.

I mean the temp of the helium as it exits

Joule-Thomson effect.  It gets warm.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NaN on 09/14/2016 06:25 pm
I wouldn't mind seeing the blast signature of an exploding Lithium Ion battery in the confined area of an interstage test... Just to compare to what we saw...

Problem with this as a cause is that the characteristics of Li-Ion batteries are very well known. They would certainly have them electrically and thermally protected, and should be instrumented as well, since they are known to do bad things when abused.
While we don't have enough information to rule them out and such a test would be interesting, I think SpaceX would already have identified it if this were the cause.

Edit to add: also at this point in the countdown, batteries would be fully charged for some time and just on trickle. They do not tend to have problems in this state.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 06:31 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.

I mean the temp of the helium as it exits

Joule-Thomson effect.  It gets warm.

Will it get hot?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/14/2016 06:32 pm


No, my view is that incident had nothing to do with pads or LOX forming.
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?

OK - so go with it. Are you saying a Helium fitting or pipe broke? what then? into the RP1 or LOX tank?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: HMXHMX on 09/14/2016 06:38 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.

I mean the temp of the helium as it exits

Joule-Thomson effect.  It gets warm.

Will it get hot?

As with all such questions, the answer is...it depends.  On the hole size, location, edge geometry of the crack or pinhole, etc.  Could be a real science project trying to prove.

Myself, I tend towards an explanation that involved a helium system failure (COPV or line failure) that generates debris with sufficient energy to puncture the common bulkhead and allow LOX to drain into the RP1 tank ullage.  I don't worry much about ignition, since I follow the "ignition is always free" rule of investigation.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/14/2016 06:41 pm
Interesting what a LOX hydrocarbon flash looks like. Attachment 1.
On the left is LOX and Oil.
On the right are 2 F9 strongback fires which appear to look very similar to the image on the left.

In the area of the recent F9 flash there are 14 hydraulic connectors. If one was leaking?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul451 on 09/14/2016 06:47 pm
It only takes a bit of dirt or  sand to scrape the paint off the aluminum and create a bare surface and some activation energy.

The cradle being pointed to exists to support the F9 while it is horizontal on the TEL and being moved from the assembly building to the launch pad. Ie, the dry mass of the entire stage is resting and rubbing on those pads during transport. The same parts are also used at other steps in manufacture, transport and integration to support and move the stage around.

The part of the vehicle that the pads rest on were designed with that in mind. (That's why the cradle is aligned with the common bulkhead, rather than on the tank walls. Not only is it much stronger than the tank walls, but it's amenable to reinforcing.)

If that doesn't noticeably and routinely damage the paintwork, the vastly lower force from the vehicle swaying in the breeze is not going to. Specs of dirt, flies, pollen, dielectric bird deposits, regardless.

[I just want people to look at their wild theorising in the broader context of how the vehicle is handled. The F9 doesn't just magically appear, vertical, at the launch pad, waiting for the slightest bump to cause it to explode. It's intended to go through a bunch of handling and movement. To offer these things as an explanation for the explosion, you need to explain how the forces involved differ from everything else the vehicle does. By contrast, note the proffered explanation for the CRS-7 loss: A bracket that was an order-of-magnitude below design strength, holding a He-tank under full LOx buoyancy, at 3g's additional head-pressure.]
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Paul451 on 09/14/2016 06:50 pm
In the area of the recent F9 flash there are 14 hydraulic connectors. If one was leaking?

Traveller, I don't think those lines you've marked are part of the hydraulics. I believe they are the cables that connect the umbilicals to the counter-weight pipe that hangs further down the TEL.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 06:53 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.

I mean the temp of the helium as it exits

Joule-Thomson effect.  It gets warm.

Will it get hot?

As with all such questions, the answer is...it depends.  On the hole size, location, edge geometry of the crack or pinhole, etc.  Could be a real science project trying to prove.


I knew it would get warm but like you said it depends.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mike_1179 on 09/14/2016 06:57 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.

I mean the temp of the helium as it exits

Joule-Thomson effect.  It gets warm.

Will it get hot?

Quoting an old thread. I vaguely remembered reading this discussion years ago

As the broken part was failing, helium would be expanding from the high-pressure tanks to the low pressure of the atmosphere, but this doesn't seem to explain the result, since the Joule-Thomson coefficient of helium is only around .065 degrees K/atm, so going from 6000 psi to atmospheric pressure should only heat it up about 27 degrees C or K.

So, if the ambient temperature is ~75 degrees F, then it wouldn't get any hotter than ~125 degrees F.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/14/2016 07:02 pm
a.  LOX does not form on the vehicle. (tank and paint thickness prevent it)  No need to go any further but to appease the LOX accusers

Ha!  I indignantly reject the labels of LOX-hoaxer and LOX-accuser.  The polite term for us is "LOX-frosters".

Here is the calculation that convinces me that LOX condensation is possible.  It's based on my post back around page 121 , but with actual numbers for conductivities.

First, can we agree that a layer of frost, of some unspecified thickness, does form on the outside of the LOX tanks when they’re full or filling?  After all, there is enough left to stop the white parts of the returned stages getting sooted-up, and there must be more before the launch vibrations shake it off. It starts forming when filling chilldown begins, no cryo temps yet, so starts like ordinary fridge-frost and then thickens to form an insulating blanket.

I contend that the temperature of the paint/frost surface depends crucially on the thickness and fluffiness of this frost layer, which I guess to be more or less like dry snow.  After all, if you wrapped the rocket in a perfectly insulating blanket, the outside of the paint on the LOX tank would quickly fall to the temperature of the LOX inside.  The question is, how thin can this blanket be made before that temperature rises above 77 K?

As for numbers, LouScheffer in #2694 gives a thermal conductivity of 0.17 W/m/K for generic paint.  Wikipedia's "List of thermal conductivities" gives 0.05, 0.11, and 0.25 W/m/K for "dry snow".  So as a first approximation, we might take the conductivities of paint and frost to be about equal.

Then with the same very rough numbers I've used in an earlier post: 

tank Al/paint surface:  70 K
paint/frost surface:  77 K for the limiting case
frost/air surface:  273 K

delta-T across paint:  7 K
delta-T across frost:  196 K

Assuming equal thermal conductivities, the frost will have to be 196/7 = 28 times thicker than the paint.  If the frost is thicker than this, the paint/frost surface will be colder than 77 K.

How realistic is "28 times thicker"?  Well, say 1 mm for quite thick paint; then the frost would have to be thicker than 28 mm.  Isn't this quite realistic? about an inch?  (Obviously my numbers could easily be out by a factor of 2 or more, but we are still talking about inches.)

But then of course the inch of frost has to be fluffy and porous enough for O2 to diffuse in through it to the paint surface and condense there.  Isn't this quite plausible?  Once the condensation starts, cryopumping will pull in more air quite forcefully. 

From the outside, there would be no visible sign of the LOX under the frost.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 07:03 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.
I mean the temp of the helium as it exits
It will rise due to the Joule-Thomson effect, but this seems too small to be any problem.  From the paper "The Joule-Thomson Effect in Helium", by J. R. Roebuck and H. Osterberg (http://journals.aps.org/pr/abstract/10.1103/PhysRev.43.60) the effect is about 0.06 degrees C/atm of pressure drop.  So if the pressure drop is 500 atm (a very high helium pressure) the rise in temperature is 30 degrees C.  This does not seem to be enough to add any significant problem to the pressure spike, mechanical damage, etc. that the bursting tank already causes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/14/2016 07:29 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.
I mean the temp of the helium as it exits
It will rise due to the Joule-Thomson effect, but this seems too small to be any problem.  From the paper "The Joule-Thomson Effect in Helium", by J. R. Roebuck and H. Osterberg (http://journals.aps.org/pr/abstract/10.1103/PhysRev.43.60) the effect is about 0.06 degrees C/atm of pressure drop.  So if the pressure drop is 500 atm (a very high helium pressure) the rise in temperature is 30 degrees C.  This does not seem to be enough to add any significant problem to the pressure spike, mechanical damage, etc. that the bursting tank already causes.

Plus the thermal inertia of the cold LOX.

Plus, how did this supposed event manage to form a large ball, practically at the speed of sound, within 16-30 mSec out side of the tank, without signs of the tank bursting?

I agree that the pressurized He tanks are a tempting source of energy in an environment that is otherwise supposed to be benign, but I think the key here is "supposed to be".

So far, nobody has put forward an explanation that fits what we saw.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/14/2016 07:31 pm
Joule-Thomson effect here does not seem significant.

However, its possible that the shards of a fractured line in or near the stage could penetrate with friction enough to ignite aluminum in an oxygen rich environment. What argues against this is the metal is too thin to guarantee ignition, and for various reasons could quench. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/14/2016 07:36 pm

No, my view is that incident had nothing to do with pads or LOX forming.
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
A problem with this is that there appears to be no evidence on telemetry.   From  videos of scuba tank ruptures (https://www.youtube.com/watch?v=f-xmaPSZ6GM), it takes a tank many seconds to empty through a hole.  In addition, this won't overpressurize the tank unless the ullage is quite small, which it is not at this stage of loading.

For a COPV failure to not be obvious on telemetry, I think it would have to a catastrophic failure, not a mere hole.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DanielW on 09/14/2016 07:46 pm
What happens to high pressure (2000-4000 psi) Helium at 77k or 280k when released through a small diameter tube?
It shards at the end. Unless you reinforce it.
I mean the temp of the helium as it exits
It will rise due to the Joule-Thomson effect, but this seems too small to be any problem.  From the paper "The Joule-Thomson Effect in Helium", by J. R. Roebuck and H. Osterberg (http://journals.aps.org/pr/abstract/10.1103/PhysRev.43.60) the effect is about 0.06 degrees C/atm of pressure drop.  So if the pressure drop is 500 atm (a very high helium pressure) the rise in temperature is 30 degrees C.  This does not seem to be enough to add any significant problem to the pressure spike, mechanical damage, etc. that the bursting tank already causes.

This is the first I have heard of the coefficient inversion so probably a good thing I ended up programming instead of engineering.

I would be curious where the outlet starts within the COPV. If the initial orifice with the pressure drop is relatively internal to the helium then any escaping helium could heat the remaining helium starting a feedback cycle that might not show up as a pressure drop allowing the bottle to get warmer and warmer.

However, now that my understanding of expanding gases is turned on end I question myself in assuming more heat pressurizes helium. :-p
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Space Ghost 1962 on 09/14/2016 07:53 pm
The feedback effect is limited. Also, this is at a lower temperature than the effect typically goes down to. The only remaining issue is how much the pressure differential (due to the high psi) and the nature of the transient (duration/flow) were to be unstable/chaotic.

The hard part about that is such a short duration high flow event has an unlikely failure mechanism, like improper manufacturing/installation/qualification/test.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/14/2016 08:03 pm

1.  Plus the thermal inertia of the cold LOX.

2.  Plus, how did this supposed event manage to form a large ball, practically at the speed of sound, within 16-30 mSec out side of the tank, without signs of the tank bursting?

3.  I agree that the pressurized He tanks are a tempting source of energy in an environment that is otherwise supposed to be benign, but I think the key here is "supposed to be".



1.  Doesn't play into it.
2.  What ball or tank?
3.  I am thinking plumbing and not tanks and some of the lines have to be on the exterior of the vehicle.
4.  The first flash was outside the vehicle per the video. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mfck on 09/14/2016 08:12 pm
Expanding helium flow hitting the S2 skin, preventing both - formation of snow and oxidation of aluminium?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: hpras on 09/14/2016 08:15 pm
OK, my shot.  He feed line to COPV bursts, starts fragmenting shrapnel, Punctures tank somewhere near the common bulkhead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jaufgang on 09/14/2016 08:21 pm
I wouldn't mind seeing the blast signature of an exploding Lithium Ion battery in the confined area of an interstage test... Just to compare to what we saw...

Problem with this as a cause is that the characteristics of Li-Ion batteries are very well known. They would certainly have them electrically and thermally protected, and should be instrumented as well, since they are known to do bad things when abused.
While we don't have enough information to rule them out and such a test would be interesting, I think SpaceX would already have identified it if this were the cause.

Yeah...  In addition to rocket science, Elon apparently knows a thing or two about Li-Ion batteries. Don't forget that his other hobby is building fast cars with batteries and revolutionizing the manufacturing Li-Ion batteries on a global scale.  He no doubt has an impressive percentage of the worlds top Li-Ion experts on his payroll.

If there was any reason to believe that an exploding battery might be somehow implicated in this event, his accident investigation team would certainly have that base covered. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/14/2016 08:25 pm
I wouldn't mind seeing the blast signature of an exploding Lithium Ion battery in the confined area of an interstage test... Just to compare to what we saw...

Problem with this as a cause is that the characteristics of Li-Ion batteries are very well known. They would certainly have them electrically and thermally protected, and should be instrumented as well, since they are known to do bad things when abused.
While we don't have enough information to rule them out and such a test would be interesting, I think SpaceX would already have identified it if this were the cause.

Edit to add: also at this point in the countdown, batteries would be fully charged for some time and just on trickle. They do not tend to have problems in this state.
If we know everything about them, then the questions are why do seem surprised when we see a problem come up in commercial products, aviation and automotive application? They also have the stored energy for an explosion and I don't know the types of telemetry on them nor their state at the time... What else is in the interstage area have that much potential explosive energy?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/14/2016 08:33 pm
I wouldn't mind seeing the blast signature of an exploding Lithium Ion battery in the confined area of an interstage test... Just to compare to what we saw...

Problem with this as a cause is that the characteristics of Li-Ion batteries are very well known. They would certainly have them electrically and thermally protected, and should be instrumented as well, since they are known to do bad things when abused.
While we don't have enough information to rule them out and such a test would be interesting, I think SpaceX would already have identified it if this were the cause.

Yeah...  In addition to rocket science, Elon apparently knows a thing or two about Li-Ion batteries. Don't forget that his other hobby is building fast cars with batteries and revolutionizing the manufacturing Li-Ion batteries on a global scale.  He no doubt has an impressive percentage of the worlds top Li-Ion experts on his payroll.

If there was any reason to believe that an exploding battery might be somehow implicated in this event, his accident investigation team would certainly have that base covered.
So what's your point? Top experts that design cars that burn to the ground, rockets that blow-up on the pad and inflight. Perhaps you should take them down from your "god-like" worship of them and that they are mere mortals that can fail like the rest of us…
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: atsf90east on 09/14/2016 08:36 pm
Quote
Yeah...  In addition to rocket science, Elon apparently knows a thing or two about Li-Ion batteries. Don't forget that his other hobby is building fast cars with batteries and revolutionizing the manufacturing Li-Ion batteries on a global scale.  He no doubt has an impressive percentage of the worlds top Li-Ion experts on his payroll.

If there was any reason to believe that an exploding battery might be somehow implicated in this event, his accident investigation team would certainly have that base covered. 

If the Lithium Ion batteries turn out to be the culprit, how would they be contained?  If they were placed in a stainless steel "vault" as was done on the Boeing 787 Dreamliner, a pressure relief tube run to the outside of the interstage would be required to vent the combustion gasses overboard in the event of a thermal runaway.  The escaping gasses might be hot enough to ignite a oxygen rich vapor cloud when the Falcon 9 is still on the Pad.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wes_wilson on 09/14/2016 08:43 pm

1.  Plus the thermal inertia of the cold LOX.

2.  Plus, how did this supposed event manage to form a large ball, practically at the speed of sound, within 16-30 mSec out side of the tank, without signs of the tank bursting?

3.  I agree that the pressurized He tanks are a tempting source of energy in an environment that is otherwise supposed to be benign, but I think the key here is "supposed to be".



1.  Doesn't play into it.
2.  What ball or tank?
3.  I am thinking plumbing and not tanks and some of the lines have to be on the exterior of the vehicle.
4.  The first flash was outside the vehicle per the video.

Does He, Lox, Rp1 get loaded through connections from the strongback that are in close proximity to each other?  Falcon 9 User guide says He is at a pressure of around 6K psi.  If the lines were in proximity could a leak in an He line have acted as a jet cutter releasing fuel & oxidizer? 

Not sure you can jet cut at that low a pressure but it looks like there's clearly some homebrew CNC systems cutting at 12K psi. 



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Nigeluna on 09/14/2016 09:57 pm
Reading this thread (while watching the paralympics) leads me to think there are two factors here that are in danger of being missed. Factor one is the mystery of the dog in the night and factor 2 is the remarkably short timescale of the active event.

The dog in the night refers to a highly instrumented vehicle, fueled but not yet at flight pressures etc and effectively inert, that apparently is overwhelmed by disaster before the monitoring systems can detect onset. The dog didn't bark it seems. Were it to be a simple case of COPV or other pressure/battery failure surely the instrumentation would have seen this, especially after last June. Something might have been missed but this is most improbable. Also there is no high or low explosive on the second stage or strongback AFAIK apart from the FTS and possibly batteries.

Mind you this Strongback/Falcon (all models) has probably been used a few dozen times now without problems (apparently) as each vehicle has been run through twice! The strongback seems to have little instrumentation but can be built to solid engineering standards rather than aerospace weights.

The remarkably short timescale refers to the fireball development over about 30mS of video (or is it 16mS with interlacing). If a structural failure of the strongback occurred at 1G then the falling item may travel about 4"/10cm after 30mS. Cameras should have seen this and on its own this would not generate an energetic event. If this came from internal to the vehicle one would have expected instrumentation to have detected precursor events. If there were precursor events only on the strongback or at the strongback/vehicle interface then the vehicle instrumentation may not have detected it or seen something very garbled by a complex transmission path. I don't know what data rates such vehicles use, and from Jim's comments this may limit recovery of the last data points, Depending on where sensors are, once an explosion has occurred one could imagine sensors saying they were perfectly happy as the fireball was about to eat them. Even so this would chatacterize the fireball but may not say why it happened.

It is difficult to see where the energetic material/source came from. It may be that there are two things happening IMHO. The second was the fireball and seems to happen on about two percent of vehicle fuelings - but what was the energy source? The first or precursor event may be some failure mode that permits the generation of an unplanned energetic material. Unless there is a sufficiency of such, and a means of initiating release of that energy, this would not be a problem and may never be seen. The LOX/hydrocarbon gel if inadvertently mixed seems one possibility historically. Unless or until such a feature reveals itself by going bang one may never suspect it exists.

SpaceX are going to have their work cut out here. It may be some consolation that, if they didn't do static firings of the complete vehicle before launch, they may not have seen this before flight 70 (say) and that could be carrying people!

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/14/2016 10:56 pm

If you go back to the original USLR video, you will see that the area identified is often completely obscured by dark venting. When not obscured, it is a bright area, so perhaps it should not be surprising that it changes more than any other area?

I think you may have missed the whole point of the analysis. The area identified had the recurring changes removed and only the differential change between the prior interval and the moments before the incident remain.

In the video stream, that region appears to grow light & dark over time.  It's consistent in behavior with the obvious venting seen to the left of the F9.

So did the area identified have the recurring changes removed or averaged?

Basically, we've composited 11 seconds worth of frames into one frame, skipped about 9 seconds, and composited the last second into one frame, and then looked at any significant differences.  (Don't do this at home without adult supervision)

If composited means averaged, then the last second, which remains relatively bright, will have a higher luminosity at the 'red spot'.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/14/2016 11:12 pm
Vortex shedding has caused the destruction of several large chimneys in the past,

That is the reason the strong back is there and remains attached to the rocket so late into the count, is to prevent vortex shedding from damaging the vehicle.  The upper clamp points would be taking into account the natural frequency and modes of the vehicle.

When the Falcon 9 strongback was first designed, there was no cradle, so there was only one upper clamp point. The introduction of the cradle changed the design to give better support when the rocket is horizontal. My point is that change could have introduced an issue when the rocket is vertical, and wind speed even briefly exceeds 13.8 m/s. The amplitude of the movement need only be millimetres, and so may not be visible on camera. The frequency of any oscillation could be deeply subsonic, and also may not have been detected.

Edit: It may be that this sort of event could only occur when the rocket has a particular natural frequency, i.e. for a particular fuel load.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/14/2016 11:25 pm
An addendum to this recent post, bringing heat flux and latent heat into the model:

a.  LOX does not form on the vehicle. (tank and paint thickness prevent it)  No need to go any further but to appease the LOX accusers

Ha!  I indignantly reject the labels of LOX-hoaxer and LOX-accuser.  The polite term for us is "LOX-frosters".

Here is the calculation that convinces me that LOX condensation is possible.  It's based on my post back around page 121 , but with actual numbers for conductivities.

First, can we agree that a layer of frost, of some unspecified thickness, does form on the outside of the LOX tanks when they’re full or filling?  After all, there is enough left to stop the white parts of the returned stages getting sooted-up, and there must be more before the launch vibrations shake it off. It starts forming when filling chilldown begins, no cryo temps yet, so starts like ordinary fridge-frost and then thickens to form an insulating blanket.

I contend that the temperature of the paint/frost surface depends crucially on the thickness and fluffiness of this frost layer, which I guess to be more or less like dry snow.  After all, if you wrapped the rocket in a perfectly insulating blanket, the outside of the paint on the LOX tank would quickly fall to the temperature of the LOX inside.  The question is, how thin can this blanket be made before that temperature rises above 77 K?

As for numbers, LouScheffer in #2694 gives a thermal conductivity of 0.17 W/m/K for generic paint.  Wikipedia's "List of thermal conductivities" gives 0.05, 0.11, and 0.25 W/m/K for "dry snow".  So as a first approximation, we might take the conductivities of paint and frost to be about equal.

Then with the same very rough numbers I've used in an earlier post: 

tank Al/paint surface:  70 K
paint/frost surface:  77 K for the limiting case
frost/air surface:  273 K

delta-T across paint:  7 K
delta-T across frost:  196 K

Assuming equal thermal conductivities, the frost will have to be 196/7 = 28 times thicker than the paint.  If the frost is thicker than this, the paint/frost surface will be colder than 77 K.

How realistic is "28 times thicker"?  Well, say 1 mm for quite thick paint; then the frost would have to be thicker than 28 mm.  Isn't this quite realistic? about an inch?  (Obviously my numbers could easily be out by a factor of 2 or more, but we are still talking about inches.)

But then of course the inch of frost has to be fluffy and porous enough for O2 to diffuse in through it to the paint surface and condense there.  Isn't this quite plausible?  Once the condensation starts, cryopumping will pull in more air quite forcefully. 

From the outside, there would be no visible sign of the LOX under the frost.
In the 1 mm paint + 28 mm frost model above, which completely ignored the latent heat released by the (hypothetical) condensing LOX, the heat flux through paint and frost together was about:

0.17 x 203 / 0.029 = 1200 W/sq.m

The paint heat flux equalled the frost heat flux, as there was no heat source at their boundary.

But do these crude models allow a realistic extra heat flux through the paint to take the latent heat released at the paint/frost boundary by the (hypothetical) condensing LOX and dump it into the tank LOX?  Here's a slightly more accurate model in which the paint has a steeper thermal gradient than the frost (which is about the same as before, for simplicity).

tank LOX/tank Al surface:  66 K
tank Al/paint surface:  66 K
paint/frost surface:  76 K for typical LOX condensation
frost/air surface:  273 K

delta-T across Al tank wall:  0 K  because Al conducts heat 500x better than paint or frost
delta-T across paint:  10 K
delta-T across frost:  197 K

The heat flux through the frost is still about 1200 W/sq.m, but the heat flux through the paint (still assumed 1 mm thick) is now:

0.17 x 10 / 0.001 = 1700 W/sq.m

So with its delta-T increased from 7 K to 10 K the paint can carry away an extra 1700 - 1200 = 500 W/sq.m of latent heat released at the paint/frost boundary.  This is enough to condense 500 / 213000 = 0.0023 kg of LOX every second for each square metre of tank wall, about 1 kg every 7 minutes.  This would be soaked into something like 10 kg of frost (per sq.m of tank wall), probably still invisible from outside.

I know I've ignored specific heat.  The heat extracted from the O2 as it cools by 200 K on its way in through the pores in the frost is about the same as the heat released when it condenses (if it does). The frost will act like a heat exchanger and mess up the neat linear temperature gradients.  This could easily change the results by a factor of 2 or so.  All I'm trying to do is show that all the quantities are of the right order of magnitude; the LOX-frost idea is not inherently absurd.  It is at least consistent with the laws of physics.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/14/2016 11:27 pm

1.  Plus the thermal inertia of the cold LOX.

2.  Plus, how did this supposed event manage to form a large ball, practically at the speed of sound, within 16-30 mSec out side of the tank, without signs of the tank bursting?

3.  I agree that the pressurized He tanks are a tempting source of energy in an environment that is otherwise supposed to be benign, but I think the key here is "supposed to be".



1.  Doesn't play into it.
2.  What ball or tank?
3.  I am thinking plumbing and not tanks and some of the lines have to be on the exterior of the vehicle.
4.  The first flash was outside the vehicle per the video.

Now that's an interesting set of comments.

Let's take an assumption.   A helium line feed at 5,000 PSI near (+- 5 feet?) an RP1 line feed that has ambient RP1 liquid just sort of sitting there at any temperature.  (Question, once the fueling is complete, is the feed line drained, or is it simply relieved of pumping pressure?)

Pretend the helium line feed ruptures.  The pieces of the feed will travel at between 400 and 900 ft/second (barrel pressure and projectile velocity in gun systems calculator, google it).  The gas speed will be much higher, depending on the calculator de jour and other unknowns.

If the rupture is directional, it not only ruptures the RP1 line, but also creates an RP1 aerosol (and probably has enough frictional energy for ignition by the stray parts),  Creating an aerosol of .4 kg of RP1 and , if I'm reading this right, creates and ignites a 15 ft column of vapor in 16 milliseconds.  1 frame time from  rupture to detonation.  If the rupture occurs somewhere in frame 0, we can't see it because it's too fast.   If the (sorry Jim, I know you said no more FAE discussions) FAE occurs near the beginning of the Frame 1 capture, it's too late to see what happened in Frame 0, because, well, it's obscured by a fireball saturating the camera.

As far as monitoring goes, Spacex actually sees the HE line pressure drop, but the drop may only be visible after the event has occurred, and easily attributed to being caused by the event, rather than the cause of the event.  To see the HE event, they would have to be sampling the HE line  at near 1 millisecond intervals.

OK, back to my regularly scheduled program.  Anyone want to buy a few kilos of organic potatoes?  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/15/2016 12:01 am

Let's take an assumption.   A helium line feed at 5,000 PSI near (+- 5 feet?) an RP1 line feed that has ambient RP1 liquid just sort of sitting there at any temperature.  (Question, once the fueling is complete, is the feed line drained, or is it simply relieved of pumping pressure?)

Pretend the helium line feed ruptures.  The pieces of the feed will travel at between 400 and 900 ft/second (barrel pressure and projectile velocity in gun systems calculator, google it).  The gas speed will be much higher, depending on the calculator de jour and other unknowns.

Yeah, I mentioned something along those lines abut 23 hours ago ...

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583473#msg1583473

...  though I didn't detail the specifics; in fact, internal helium lines in the interstage are actually near some potentially vulnerable bits, not just the umbilicals: the S2 MVac and associated hydraulics, the bottom of the S2 RP1 tank, power and data lines for sensors and engine control systems; similar avionics in the interstage for S1 guidance and landing, etc.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 12:05 am

Let's take an assumption.   A helium line feed at 5,000 PSI near (+- 5 feet?) an RP1 line feed that has ambient RP1 liquid just sort of sitting there at any temperature.  (Question, once the fueling is complete, is the feed line drained, or is it simply relieved of pumping pressure?)

Pretend the helium line feed ruptures.  The pieces of the feed will travel at between 400 and 900 ft/second (barrel pressure and projectile velocity in gun systems calculator, google it).  The gas speed will be much higher, depending on the calculator de jour and other unknowns.

Yeah, I mentioned something along those lines abut 23 hours ago ...

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583473#msg1583473

...  though I didn't detail the specifics; in fact, internal helium lines in the interstage are actually near some potentially vulnerable bits, not just the umbilicals: the S2 MVac and associated hydraulics, the bottom of the S2 RP1 tank, power and data lines for sensors and engine control systems; similar avionics in the interstage for S1 guidance and landing, etc.

Interesting, but how about EXTERNAL feed lines.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: baskerbosse on 09/15/2016 12:55 am

Yeah, I mentioned something along those lines abut 23 hours ago ...

http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583473#msg1583473

...  though I didn't detail the specifics; in fact, internal helium lines in the interstage are actually near some potentially vulnerable bits, not just the umbilicals: the S2 MVac and associated hydraulics, the bottom of the S2 RP1 tank, power and data lines for sensors and engine control systems; similar avionics in the interstage for S1 guidance and landing, etc.

..isn't there TEA-TEB plumbing/vessel around there as well? ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/15/2016 01:27 am



..isn't there TEA-TEB plumbing/vessel around there as well? ...

No.  TEA-TEB is loaded in the HIF, I'm told.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/15/2016 02:20 am
The problem with assuming that frost has a thermal conductivity of snow rather than ice: that means it's extremely porous.  Which means that liquid air / LOX will readily cryopump through it.

If you want to posit something that would block air from reaching the tank wall, you need to posit solid ice with almost no pore space.  Cryopumping occurs through even very small gaps because liquefying air creates a partial vacuum, providing a strong pressure gradient pulling more air in.  Cryopumping means you also ruin the R-value / K-value of the frost, since air is actively being pulled through it.

Cryopumping would of course stop if you had a LOX-soaked slush on the side of the tank.  But that would not exactly be a safe situation.  With hydrogen, liquefied air usually runs off (and if you're unlucky, pools somewhere on the rocket), usually forming fast enough to take some or all of the frost with it.  At densified-LOX temperatures, however, I don't know what the behavior would be.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/15/2016 02:58 am
Jim,

Would a helium leak through a small pipe take more than 30 ms to cause structural damage?   And didn't SpaceX imply in a public statement that 3000 channels of telemetry showed no signs of that within 30 ms of ignition?

Though having the lox tank full, and ulage  at its lowest volume, would be the worst case for time to damage from aleakn He leak.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 04:19 am
The amplitude of the movement need only be millimetres, and so may not be visible on camera. The frequency of any oscillation could be deeply subsonic, and also may not have been detected.


Launch vehicles are not that delicate.   They can flex more than millimetres and the frequency would be low.   And accelerometers would detect the movement and frequency.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/15/2016 05:07 am
The amplitude of the movement need only be millimetres, and so may not be visible on camera. The frequency of any oscillation could be deeply subsonic, and also may not have been detected.


Launch vehicles are not that delicate.   They can flex more than millimetres and the frequency would be low.   And accelerometers would detect the movement and frequency.

Yes, the vehicle can flex, but the lower pad can't. That's the problem, if the vehicle flexes towards it, the pad will puncture the fuselage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: baskerbosse on 09/15/2016 05:21 am



..isn't there TEA-TEB plumbing/vessel around there as well? ...

No.  TEA-TEB is loaded in the HIF, I'm told.

Suspected that.

-Where is it located once onboard?
Is there an external connector like on S1?
Plumbing to Combustion chamber/gas generator?(must confess I do not know how the ignition works)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Steven Pietrobon on 09/15/2016 06:16 am
Some possible locations of explosion located near the edge of common bulkhead near the TE:

1) COPV
2) Cradle pads if made from non-safe material
3) Umbilical lines (carries various electrical and Helium pressure lines)
4) TE umbilical catching mats if made from non-safe material

Sources of oxidiser

1) O2 in air
2) GOX from tank vents
3) LOX if tank surface below 77 K

Sources of ignition

1) Sudden COPV failure
2) Electrical wires in umbilical
3) Sunlight concentration from TE

What are the conditions like in the umbilical tunnel? This is an enclosed space. Could LOX form inside the tunnel?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/15/2016 07:37 am
Is it possible that the initial explosion took out the data connection between the second stage sensors and the ground? That way any measurements of precursor events might not reach the ground hence the difficulties to explain what happened?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MikeAtkinson on 09/15/2016 08:33 am
Let's take an assumption.   A helium line feed at 5,000 PSI near (+- 5 feet?) an RP1 line feed that has ambient RP1 liquid just sort of sitting there at any temperature.  (Question, once the fueling is complete, is the feed line drained, or is it simply relieved of pumping pressure?)

Pretend the helium line feed ruptures.  The pieces of the feed will travel at between 400 and 900 ft/second (barrel pressure and projectile velocity in gun systems calculator, google it).  The gas speed will be much higher, depending on the calculator de jour and other unknowns.

If the rupture is directional, it not only ruptures the RP1 line, but also creates an RP1 aerosol (and probably has enough frictional energy for ignition by the stray parts),  Creating an aerosol of .4 kg of RP1 and , if I'm reading this right, creates and ignites a 15 ft column of vapor in 16 milliseconds.  1 frame time from  rupture to detonation.  If the rupture occurs somewhere in frame 0, we can't see it because it's too fast.   If the (sorry Jim, I know you said no more FAE discussions) FAE occurs near the beginning of the Frame 1 capture, it's too late to see what happened in Frame 0, because, well, it's obscured by a fireball saturating the camera.

As far as monitoring goes, Spacex actually sees the HE line pressure drop, but the drop may only be visible after the event has occurred, and easily attributed to being caused by the event, rather than the cause of the event.  To see the HE event, they would have to be sampling the HE line  at near 1 millisecond intervals.

OK, back to my regularly scheduled program.  Anyone want to buy a few kilos of organic potatoes?  :)

From the video there seems to be a dark dense fragment which flies up and to the right. It seems to be about 15-20 cm in diameter and follows a ballistic trajectory, gradually slowing down and dropping sightly from a straight line. The interesting thing about this fragment is that it seems to originate from below the "explosion", but still goes upwards.

http://forum.nasaspaceflight.com/index.php?topic=40157.msg1583295#msg1583295

If this is not a bird or bug (and what is presumably a bird follows a similar trajectory starting at the bottom left corner in frame 13), then it is a prime candidate for what could rupture the fuel line.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 08:34 am
In the area of the recent F9 flash there are 14 hydraulic connectors. If one was leaking?

Traveller, I don't think those lines you've marked are part of the hydraulics. I believe they are the cables that connect the umbilicals to the counter-weight pipe that hangs further down the TEL.

They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/15/2016 08:52 am
They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

Ah, that's what they are - saw the bent pipes in the one of the 'after' images and wondered.

Presumably the bending is the result of the top of the strongback collapsing; and in turn their condition implies that those are steel pipes of a relatively small diameter, which reinforces the supposition that they're hydraulics pipes.

They are in a location that's consistent with the start of the explosion; and they are under sufficient pressure that a leak would result in vapour.

The fundamental question would be whether or not the fluid used is explosive in an oxygen-rich environment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GoferThrottleUp on 09/15/2016 10:10 am
They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

Ah, that's what they are - saw the bent pipes in the one of the 'after' images and wondered.

Presumably the bending is the result of the top of the strongback collapsing; and in turn their condition implies that those are steel pipes of a relatively small diameter, which reinforces the supposition that they're hydraulics pipes.

They are in a location that's consistent with the start of the explosion; and they are under sufficient pressure that a leak would result in vapour.

The fundamental question would be whether or not the fluid used is explosive in an oxygen-rich environment.

I like your idea but Jim has ruled out flammable hydraulic fluid in a previous post.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/15/2016 10:32 am
How about this. Has anybody every gotten there finger or tongue frozen to a aluminum pole in the winter?
If the pads had water on them and then that froze. The pads would not be inclined to slide when the vehicle shrinks. The adhesion can be quite strong. Actually enough to rip the material frozen instead of break the ice. So we would have a large sudden snap of material/ice and then that would create a sizable impact that could ignite our lox/"something not lox safe" mixture. The snap and ring of the tank could also be the sound that elon is looking for. One pad could have let go first and then the second one letting go set off the explosion.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 11:15 am
Let's take an assumption.   A helium line feed at 5,000 PSI near (+- 5 feet?) an RP1 line feed that has ambient RP1 liquid just sort of sitting there at any temperature.  (Question, once the fueling is complete, is the feed line drained, or is it simply relieved of pumping pressure?)

Pretend the helium line feed ruptures.  The pieces of the feed will travel at between 400 and 900 ft/second (barrel pressure and projectile velocity in gun systems calculator, google it).  The gas speed will be much higher, depending on the calculator de jour and other unknowns.

If the rupture is directional, it not only ruptures the RP1 line, but also creates an RP1 aerosol (and probably has enough frictional energy for ignition by the stray parts),  Creating an aerosol of .4 kg of RP1 and , if I'm reading this right, creates and ignites a 15 ft column of vapor in 16 milliseconds.  1 frame time from  rupture to detonation.  If the rupture occurs somewhere in frame 0, we can't see it because it's too fast.   If the (sorry Jim, I know you said no more FAE discussions) FAE occurs near the beginning of the Frame 1 capture, it's too late to see what happened in Frame 0, because, well, it's obscured by a fireball saturating the camera.

As far as monitoring goes, Spacex actually sees the HE line pressure drop, but the drop may only be visible after the event has occurred, and easily attributed to being caused by the event, rather than the cause of the event.  To see the HE event, they would have to be sampling the HE line  at near 1 millisecond intervals.

OK, back to my regularly scheduled program.  Anyone want to buy a few kilos of organic potatoes?  :)

From the video there seems to be a dark dense fragment which flies up and to the right. It seems to be about 15-20 cm in diameter and follows a ballistic trajectory, gradually slowing down and dropping sightly from a straight line. The interesting thing about this fragment is that it seems to originate from below the "explosion", but still goes upwards.

http://forum.nasaspaceflight.com/index.php?topic=40157.msg1583295#msg1583295

If this is not a bird or bug (and what is presumably a bird follows a similar trajectory starting at the bottom left corner in frame 13), then it is a prime candidate for what could rupture the fuel line.

It's a bird.  You can trace it back to the left side of the event on the same trajectory.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 11:39 am
They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

Ah, that's what they are - saw the bent pipes in the one of the 'after' images and wondered.

Presumably the bending is the result of the top of the strongback collapsing; and in turn their condition implies that those are steel pipes of a relatively small diameter, which reinforces the supposition that they're hydraulics pipes.

They are in a location that's consistent with the start of the explosion; and they are under sufficient pressure that a leak would result in vapour.

The fundamental question would be whether or not the fluid used is explosive in an oxygen-rich environment.

I like your idea but Jim has ruled out flammable hydraulic fluid in a previous post.

In the attached dual images, the flash on the right is the 1st frame of a LOX & Oil flash. On the left is the 1st frame of the F9 flash. As the central colour and the 2 fringing colours appear to match each other, just maybe the initial F9 flash was a LOX and Oil flash.

Then add in there were 14 in-line hydraulic connectors, to support the F9 FT TEL extension and that those 14 connectors are where the centre of the initial F9 flash occurred.

Found a shot of Amos6, clearly showing the hydraulic line joiners where the 1st flash occurred.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/15/2016 11:48 am
The amplitude of the movement need only be millimetres, and so may not be visible on camera. The frequency of any oscillation could be deeply subsonic, and also may not have been detected.


Launch vehicles are not that delicate.   They can flex more than millimetres and the frequency would be low.   And accelerometers would detect the movement and frequency.

Yes, the vehicle can flex, but the lower pad can't. That's the problem, if the vehicle flexes towards it, the pad will puncture the fuselage.

The "lower pad" rests on a visibly-reinforced portion of S2 right where the common bulkhead exists inside the stage. It's probably the strongest portion of S2 aside from the thrust structure at the bottom of the RP1 tank. I've made this point several times over the last two weeks, but rockets just aren't that fragile and the designers aren't complete nincompoops when it comes to designing their support equipment.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/15/2016 11:49 am
How about this. Has anybody every gotten there finger or tongue frozen to a aluminum pole in the winter?


If your tongue was a Teflon or other fluorocarbon elastomer pad, it wouldn't stick.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 12:02 pm
They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

Ah, that's what they are - saw the bent pipes in the one of the 'after' images and wondered.

Presumably the bending is the result of the top of the strongback collapsing; and in turn their condition implies that those are steel pipes of a relatively small diameter, which reinforces the supposition that they're hydraulics pipes.

They are in a location that's consistent with the start of the explosion; and they are under sufficient pressure that a leak would result in vapour.

The fundamental question would be whether or not the fluid used is explosive in an oxygen-rich environment.

I like your idea but Jim has ruled out flammable hydraulic fluid in a previous post.

In the attached dual images, the flash on the right is the 1st frame of a LOX & Oil flash. On the left is the 1st frame of the F9 flash. As the central colour and the 2 fringing colours appear to match each other, just maybe the initial F9 flash was a LOX and Oil flash.

Then add in there were 14 in-line hydraulic connectors, to support the F9 FT TEL extension and that those 14 connectors are where the centre of the initial F9 flash occurred.

Found a shot of Amos6, clearly showing the hydraulic line joiners where the 1st flash occurred.

Traveler...  LTNS  :)

Attached is a representative photo from a stream of 1,307 we processed to remove air turbulence.

Taking the 1st 10 seconds into a single stacked image, skipping 9 seconds, then stacking the last second, there was one exactly one clear difference region circled in the attached representative image.

Interpreted to be nothing more than an air-gap between the TE and F9, exactly where are your upper and lower circles WRT to that air gap?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 12:59 pm
Traveler...  LTNS  :)

Attached is a representative photo from a stream of 1,307 we processed to remove air turbulence.

Taking the 1st 10 seconds into a single stacked image, skipping 9 seconds, then stacking the last second, there was one exactly one clear difference region circled in the attached representative image.

Interpreted to be nothing more than an air-gap between the TE and F9, exactly where are your upper and lower circles WRT to that air gap?

As attached. The 14 hydraulic line jointing connectors are where the centre of what looks like a LOX & Oil flash occurred.

If one of the 14 joints failed and it was spraying hydraulic fluid and/or vapour into the air, I doubt you would see that on the images. That is until it mixed with enough venting LOX to ignite.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/15/2016 01:12 pm
They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

Ah, that's what they are - saw the bent pipes in the one of the 'after' images and wondered.

Presumably the bending is the result of the top of the strongback collapsing; and in turn their condition implies that those are steel pipes of a relatively small diameter, which reinforces the supposition that they're hydraulics pipes.

They are in a location that's consistent with the start of the explosion; and they are under sufficient pressure that a leak would result in vapour.

The fundamental question would be whether or not the fluid used is explosive in an oxygen-rich environment.

I like your idea but Jim has ruled out flammable hydraulic fluid in a previous post.


I'm not sure it was unambiguous:


clearly shows the hydraulics.  Later in that thread is a closeup.

We don't know if it is hydraulics, it could be pneumatics.


My point of view (on the basis that those are indeed hydraulic feed pipes in those images):

The rams that raise and lower the strongback will be hydraulic.

There would be a lot of sense in powering the claw rams on the strongback with hydraulic fluid from the same system - the pressure is already there and it's just a case of teeing lines off

(Okay, the pump - presumably remote - might need to be powered up to enable the claws to be operated at a different time to the strongback, but usually these events are very close together in the countdown anyway).

There's also an advantage in using the one hydraulic system in that there doesn't need to be additional equipment on the strongback - ie a pump which constitutes another potential point of failure (and indeed a potential ignition source).

Similarly, it should be possible to put the operating solenoids for each hydraulic pipe at ground level, so they're easily accessible and also remove the amount of electrical equipment (and hence ignition risk) from the strongback.

However... because the erector has been modified several times (F9 1.0 to F9 1.1 to F9 FT), the lines on the strongback have been extended, probably twice. That may be why the pipes in the image have got what appears to be connectors on them, ie they were used to graft in longer pipes.

I keep coming back to the thought that the way in which the TEL has been built may have a lot to do with the failure: it's been modified repeatedly, when perhaps a complete rebuilt was required once SpaceX arrived at the F9 FT design?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 01:13 pm
if the vehicle flexes towards it, the pad will puncture the fuselage.

No, it won't.  It is not point load, it is spread out by the pad.  And it is at the common bulkhead joint and not a tank side.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 01:14 pm
Traveler...  LTNS  :)

Attached is a representative photo from a stream of 1,307 we processed to remove air turbulence.

Taking the 1st 10 seconds into a single stacked image, skipping 9 seconds, then stacking the last second, there was one exactly one clear difference region circled in the attached representative image.

Interpreted to be nothing more than an air-gap between the TE and F9, exactly where are your upper and lower circles WRT to that air gap?

As attached. The 14 hydraulic line jointing connectors are where the centre of what looks like a LOX & Oil flash occurred.

If one of the 14 joints failed and it was spraying hydraulic fluid and/or vapour into the air, I doubt you would see that on the images. That is until it mixed with enough venting LOX to ignite.

There just isn't enough detail in what we have to see anything obvious.  Perhaps cloud like behavior in the difference map area of interest.  Nothing obvious in your area of interest.

https://www.youtube.com/watch?v=rV1DJzFLI9c
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 01:16 pm
]

 They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

A.  Why would they be under pressure at that time?
b.  why would there be 7 lines for only two actuators?
c.  The leak would be seen on other cameras
d.  How do you know they are hydraulic lines and not He and GN2 lines?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 01:24 pm
The Strongback was replaced for V1.1 and modified for FT.  The V1.0 strongback was discarded.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 01:46 pm

c.  The leak would be seen on other cameras


much as still it's my favorite theory, here's a real example.  Things are much slower and far more visible than my favorite theory requires, and this is with a non-flame retardant hydraulic fluid.

https://www.youtube.com/watch?v=QgJX8x99t5E
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/15/2016 01:48 pm
]

 They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

A.  Why would they be under pressure at that time?
b.  why would there be 7 lines for only two actuators?
c.  The leak would be seen on other cameras
d.  How do you know they are hydraulic lines and not He and GN2 lines?

*On the basis that these are indeed hydraulic pipes*

A - Depends where the solenoids valves that switch them on and off are. If they're at the top of the strongback (contradicting myself!) then there would be pressure there. There would be some sense in having the valves near to the rams, as it would remove lag / pressure issues from the system.

B - From memory, there are another two rams up there somewhere? - but that may be an earlier version of the TEL. Four rams would give 8 pipes (minimum, could be 12 depending how they're plumbed, but they look to me like they've only got 2 pipes each). Potentially there may be something else up there that is hydraulically actuated?

C - Yes, but we don't have access to them.

D - we don't.

The Strongback was replaced for V1.1 and modified for FT.  The V1.0 strongback was discarded.

That would explain why the top section looks so different in the various iterations.

Was the *entire* frame discarded or did they retain the lowest 1/3? - that looks to be of a slightly different construction and there's a relatively obvious joint.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 01:53 pm

c.  The leak would be seen on other cameras


much as still it's my favorite theory, here's a real example.  Things are much slower and far more visible than my favorite theory requires, and this is with a non-flame retardant hydraulic fluid.


The aerosoled fluid did not burn
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 01:54 pm

Was the *entire* frame discarded

Yes
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 01:55 pm

C - Yes, but we don't have access to them.


But Spacex does and they would have seen a leak
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kolkmvd on 09/15/2016 01:55 pm
Glenn, great work on the video.

I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel, the red and green being saturated. The center of the initial saturated area actually has a hole in the blue channel. This questions me: how comes? Does not look like a vapor cloud to me, but probably the part was obscured by some thing on the TEL?

Actually, I think you can make an educated guess about the size of that initial *kaboom* by following the development of the cloud.

I couldn't find any mention of this upthread, but I think it was already noticed that the "light-emitting body" in frame T=0 must have been smaller than the TEL, because its back is not illuminated
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/15/2016 02:05 pm

c.  The leak would be seen on other cameras


much as still it's my favorite theory, here's a real example.  Things are much slower and far more visible than my favorite theory requires, and this is with a non-flame retardant hydraulic fluid.


The aerosoled fluid did not burn

Pardon me if I'm mistaken, but wasn't the issue of a potential hydraulic leak brought up as a potential fuel source in the event of a leak of GOX, leak of LOX, condensation of LOX, or other O2-concentrating event (surrounding a tank full of LOX with a GOX headspace, pipes full of LOX, and all of the LOX in question lower than the boiling point of O2)?

If that was the hypothesis - again, please correct me if I'm wrong - then what's the relevance of hydraulic fluid not immediately bursting into flame in normal air?  "Aerosolized mists of hydrocarbons" and "high concentrations of oxygen" are not famous for playing nicely.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jgoldader on 09/15/2016 02:08 pm


I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel, the red and green being saturated. The center of the initial saturated area actually has a hole in the blue channel. This questions me: how comes? Does not look like a vapor cloud to me, but probably the part was obscured by some thing on the TEL?

Is it possible that the ADC converter in the camera "rolled over" and went negative at the brightest point?  Astronomical-grade CCD imagers will sometimes do this.  If that "dark spot" is at the center of the diffraction "X", then it could actually mark the brightest spot, rolled over.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rocketguy11 on 09/15/2016 02:10 pm
First time poster...  I'm not sure if I've seen this scenario so I apologize if it's already been mentioned.  The Titan II silo accident in 1980 was caused by FOD dropped down into the silo (in that case a large socket) which bounced and pierced the skin creating an aerosol.  The resultant explosion took out the entire missile and silo:
http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543
Note that those were hypergolic propellants...  In the SpaceX case, a large piece of FOD could have fallen off the strongback due to the high wind, bounced off one of the strongback beams and hit the skin of the fuel tank and created a pinhole leak.  Hydrostatic pressure in the tank would be sufficient to generate an aerosol that would then mix with the vented LOX.  Still need an ignition source though.  Also you would think a camera would catch it but it wouldn't take much of an object to cause damage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 02:11 pm
Glenn, great work on the video.

I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel, the red and green being saturated. The center of the initial saturated area actually has a hole in the blue channel. This questions me: how comes? Does not look like a vapor cloud to me, but probably the part was obscured by some thing on the TEL?

Actually, I think you can make an educated guess about the size of that initial *kaboom* by following the development of the cloud.

I couldn't find any mention of this upthread, but I think it was already noticed that the "light-emitting body" in frame T=0 must have been smaller than the TEL, because its back is not illuminated

Oxygen has some strong absorption lines in the blue side of the visible spectrum but even more in the red & green portions.  It's possible your blue channel is picking up an uncombusted oxygen cloud in the foreground.  However, the cloud is more likely water vapor condensing to cloud form.   That absorption spectrum looks like a much better fit to your data.

If you try to trace the clouds back one frame, they kinda look like a shock front, which if true, would support your guess about tracing back the origin.  I tried, but failed, perhaps if you follow the blue, you might succeed.

If you trace my comments in this thread, you'll see some guesstimates about the energy required for this event based on speed and diameter of the edge of the fireball/cloud.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 02:27 pm

c.  The leak would be seen on other cameras


much as still it's my favorite theory, here's a real example.  Things are much slower and far more visible than my favorite theory requires, and this is with a non-flame retardant hydraulic fluid.


The aerosoled fluid did not burn

Well actually part of it did, about 6,000 milliseconds later than my favorite theory requires, and it was a very slow deflagration to boot with an excellent ignition source available.  I guess this real world example doesn't support the hydraulic mist theory very well...  :'(
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/15/2016 02:33 pm
They are not counter-weight wires. They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.

Ah, that's what they are - saw the bent pipes in the one of the 'after' images and wondered.

Presumably the bending is the result of the top of the strongback collapsing; and in turn their condition implies that those are steel pipes of a relatively small diameter, which reinforces the supposition that they're hydraulics pipes.

They are in a location that's consistent with the start of the explosion; and they are under sufficient pressure that a leak would result in vapour.

The fundamental question would be whether or not the fluid used is explosive in an oxygen-rich environment.

I like your idea but Jim has ruled out flammable hydraulic fluid in a previous post.
Welcome to the forum! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 02:35 pm
This is not the 1st TEL flash and then fire event that was triggered by LOX coming into contact with the something on the TEL:

https://youtu.be/tM-QlPAMLEc?t=62

Hit phase and then single frame it using the  < & > keys.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/15/2016 02:35 pm
First time poster...  I'm not sure if I've seen this scenario so I apologize if it's already been mentioned.  The Titan II silo accident in 1980 was caused by FOD dropped down into the silo (in that case a large socket) which bounced and pierced the skin creating an aerosol.  The resultant explosion took out the entire missile and silo:
http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543
Note that those were hypergolic propellants...  In the SpaceX case, a large piece of FOD could have fallen off the strongback due to the high wind, bounced off one of the strongback beams and hit the skin of the fuel tank and created a pinhole leak.  Hydrostatic pressure in the tank would be sufficient to generate an aerosol that would then mix with the vented LOX.  Still need an ignition source though.  Also you would think a camera would catch it but it wouldn't take much of an object to cause damage.
Anther new guy, welcome to the forum! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 02:39 pm


I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel, the red and green being saturated. The center of the initial saturated area actually has a hole in the blue channel. This questions me: how comes? Does not look like a vapor cloud to me, but probably the part was obscured by some thing on the TEL?

Is it possible that the ADC converter in the camera "rolled over" and went negative at the brightest point?  Astronomical-grade CCD imagers will sometimes do this.  If that "dark spot" is at the center of the diffraction "X", then it could actually mark the brightest spot, rolled over.

The "diffraction X" cannot be used to identify the brightest spot of anything.

A perfect lens where the brightest spot is exactly in the center of the field of view maybe, if the internals of the lens barrel where the reflections occur to create the X, are symmetric, then yes, it might point to the brightest spot in the field of view.

HOWEVER, as that spot moves away from the center of the field of view, the X will move away from the brightest spot because the reflections inside the lens are now asymmetric.  You'll still see the X, but it's no longer going to be over the brightest spot.

re:  CCDs / ADCs.   CCDs that are saturated may start bleeding voltage to adjacent CCD cells, which expands the saturation range and may lead to linear streaking during readout.

I haven't seen an ADC in production in 20 years that will flip bits on saturation.  Usually, at the end of the integration time, the ADC has reached its maximum voltage on the ladder, and it can't go anywhere, neither higher or lower.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/15/2016 02:50 pm

No, it won't.  It is not point load, it is spread out by the pad.  And it is at the common bulkhead joint and not a tank side.
Jim.
About how wide would you estimate the "common bulkhead joint" to be? How wide is the pad and how much in total would you estimate the vehicle would shrink?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/15/2016 02:51 pm
The TE at pad 40 is the only one of the three that is not falcon heavy compatible. 
How many other differences are there to the other two TEs?
Are the other 2 TEs identical?
If they are significantly different to the one at pad 40, and the problem is external to the vehicle, it could be good news for RTF.
The TE at pad 40 had the most launches, and had been modified several times for each version of the Falcon 9.   Could that have contributed?

If you view the CRS-8 technical webcast, at T-04:10 there is a closeup of the grippers being released and the strongback being retracted. The cradle can be seen to tilt forward as the grippers release, indicating that at least the top cradle pad was in contact with the second stage up to that point. Once the grippers have released, the rocket begins to sway, occasionally enough to bump the top pad. I've attached an edit of the technical broadcast below.

Vortex shedding has caused the destruction of several large chimneys in the past, for example at the Ferrybridge C power station. A turbulent vortex street can occur around chimneys, provided that the flow has a Reynolds number (Re) greater than 3.5 x 10^6, where Re = v * L / ν.

Similarly, a turbulent vortex street could occur around the Falcon 9 rocket. The minimum turbulent Re for the Falcon 9 is when the velocity of the wind v = 3.5 x 10^6 * 0.00001458 / 3.7 = 13.79 m/s. This is a 26.8 knot breeze, which is strong, but not inconceivable, especially at height. If a vortex street is established, there will be oscillating horizontal forces applied to the rocket. Because it is pinned at the base and the gripper by the much stronger and stiffer TE, the flexion mode (but hopefully not the amplitude) could be as shown below. This is especially likely if the frequency of the oscillations is near the resonant frequency of the rocket, which will change as the fuel is loaded.

In the Thaicom8 closeup of the second stage, both the top and bottom pads are seen to be in contact with the stage whilst the grippers are closed. The problem is that when the gripper is closed, it prevents movement of the upper pad towards the stage. The cradle itself is also pinned by the TE, so the lower pad can't move away from the stage. The fuselage is only millimetres thick, so even a small oscillation of the rocket could have a catastrophic effect at the point of contact, the lower pad. Although a breach in the stage near the common bulkhead may not explain how ignition occurred, it would explain what lead up to it.

I'm not completely sure which thread this theory belongs in, but any feedback would be appreciated. I'm also not sure if the cradles at the other pads are identical.
One issue I see with this theory is that the wind is blowing right to left (more or less) in the video. Therefore the round body of the rocket is in the lee of the TEL, thereby disrupting and partially blocking air flow to the rocket
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/15/2016 03:02 pm



The "lower pad" rests on a visibly-reinforced portion of S2 right where the common bulkhead exists inside the stage. It's probably the strongest portion of S2 aside from the thrust structure at the bottom of the RP1 tank. I've made this point several times over the last two weeks, but rockets just aren't that fragile and the designers aren't complete nincompoops when it comes to designing their support equipment.


"the designers aren't complete nincompoops"
Please Herb,
This is just a strawman. Nobody thinks or says this. Many, I think, are trying to just hypothesize a scenario where out of a thousand decisions maybe one was just a bit off.  Off enough so that most times this would not happen. But due to wear, the environment (such as rust), slightly changed procedures that wouldn't appear to change anything, whatever, a new set of unique circumstances occurred. Clearly this was the case.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/15/2016 03:07 pm

c.  The leak would be seen on other cameras


much as still it's my favorite theory, here's a real example.  Things are much slower and far more visible than my favorite theory requires, and this is with a non-flame retardant hydraulic fluid.


The aerosoled fluid did not burn

Well actually part of it did, about 6,000 milliseconds later than my favorite theory requires, and it was a very slow deflagration to boot with an excellent ignition source available.  I guess this real world example doesn't support the hydraulic mist theory very well...  :'(

Perhaps you missed Rei's post a few posts back: That video is in regular air, the situation could hypothetically be very different if you also happen to have a high concentration of oxygen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:10 pm
Glenn, great work on the video.

I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel, the red and green being saturated. The center of the initial saturated area actually has a hole in the blue channel. This questions me: how comes? Does not look like a vapor cloud to me, but probably the part was obscured by some thing on the TEL?

Actually, I think you can make an educated guess about the size of that initial *kaboom* by following the development of the cloud.

I couldn't find any mention of this upthread, but I think it was already noticed that the "light-emitting body" in frame T=0 must have been smaller than the TEL, because its back is not illuminated

It would seem there is something going on in the centre of the fireball and that something is just above the S2 cradle and to the left of the 14 hydraulic line joints.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/15/2016 03:12 pm



The "lower pad" rests on a visibly-reinforced portion of S2 right where the common bulkhead exists inside the stage. It's probably the strongest portion of S2 aside from the thrust structure at the bottom of the RP1 tank. I've made this point several times over the last two weeks, but rockets just aren't that fragile and the designers aren't complete nincompoops when it comes to designing their support equipment.


"the designers aren't complete nincompoops"
Please Herb,
This is just a strawman. Nobody thinks or says this.

Postulating a theory that puts a load-bearing support on the strongback at a point that would push it up against the thin wall of an empty tank while it's carrying a cantilevered load of many tons would require the designers of the GSE to be nincompoops. Or worse.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/15/2016 03:14 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:15 pm

c.  The leak would be seen on other cameras


much as still it's my favorite theory, here's a real example.  Things are much slower and far more visible than my favorite theory requires, and this is with a non-flame retardant hydraulic fluid.


The aerosoled fluid did not burn

Pardon me if I'm mistaken, but wasn't the issue of a potential hydraulic leak brought up as a potential fuel source in the event of a leak of GOX, leak of LOX, condensation of LOX, or other O2-concentrating event (surrounding a tank full of LOX with a GOX headspace, pipes full of LOX, and all of the LOX in question lower than the boiling point of O2)?

If that was the hypothesis - again, please correct me if I'm wrong - then what's the relevance of hydraulic fluid not immediately bursting into flame in normal air?  "Aerosolized mists of hydrocarbons" and "high concentrations of oxygen" are not famous for playing nicely.

That is two failures. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/15/2016 03:16 pm

One issue I see with this theory is that the wind is blowing right to left (more or less) in the video. Therefore the round body of the rocket is in the lee of the TEL, thereby disrupting and partially blocking air flow to the rocket
Nice wide Payload fairing up there catching a lot of wind. The Pivot would likely be the upper support pads.
Add a little resonance and who knows?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:22 pm
This is not the 1st TEL flash and then fire event that was triggered by LOX coming into contact with the something on the TEL:

https://www.youtube.com/watch?v=tM-QlPAMLEc?t=62

Hit phase and then single frame it using the  < & > keys.

No, that was not LOX related.  It was RP-1
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:26 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:26 pm

One issue I see with this theory is that the wind is blowing right to left (more or less) in the video. Therefore the round body of the rocket is in the lee of the TEL, thereby disrupting and partially blocking air flow to the rocket
Nice wide Payload fairing up there catching a lot of wind. The Pivot would likely be the upper support pads.
Add a little resonance and who knows?

Spacex knows.   They designed the TEL and grippers specifically to prevent this.  That is why it is released late into the count
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:27 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

You mean gas lines
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 03:27 pm

It would seem there is something going on in the centre of the fireball and that something is just above the S2 cradle and to the left of the 14 hydraulic line joints.

Well that's a new processing method to me.  Exactly what did you do here?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:28 pm
This is not the 1st TEL flash and then fire event that was triggered by LOX coming into contact with the something on the TEL:

https://www.youtube.com/watch?v=tM-QlPAMLEc?t=62

Hit phase and then single frame it using the  < & > keys.

No, that was not LOX related.  It was RP-1

RP-1 was dumped from the top of the TEL, fell down and then ignited?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/15/2016 03:28 pm
That is two failures.

Either two failures or one failure plus one oversight.

Which is pretty much the description of how accidents happen.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:30 pm

It would seem there is something going on in the centre of the fireball and that something is just above the S2 cradle and to the left of the 14 hydraulic line joints.

Well that's a new processing method to me.  Exactly what did you do here?

Set Gamma = 0 on the RBG image and did a vertical interlace with the frame just before the bang.

Nice package that re-pixelates as you zoom in;
http://stereo.jpn.org/eng/stphmkr/
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/15/2016 03:34 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

i think what youve got marked as 6 and 7 are one large line?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:34 pm
This is not the 1st TEL flash and then fire event that was triggered by LOX coming into contact with the something on the TEL:

https://www.youtube.com/watch?v=tM-QlPAMLEc?t=62

Hit phase and then single frame it using the  < & > keys.

No, that was not LOX related.  It was RP-1

RP-1 was dumped from the top of the TEL, fell down and then ignited?

From the second stage umbilical
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:36 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

You mean gas lines

So ALL the 7 lines are GAS lines?

SpX uses gas pressurised actuators and not hydraulic pressurised actuators on that portion of the TEL?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/15/2016 03:37 pm


Postulating a theory that puts a load-bearing support on the strongback at a point that would push it up against the thin wall of an empty tank while it's carrying a cantilevered load of many tons would require the designers of the GSE to be nincompoops. Or worse.

Your words: "carrying a cantilevered load of many tons" And maybe this is the beginning of the incident. Load was expected to be spread across the TOP and bottom supports. One slight misalignment. Rocker pivot doesn't rock, who knows? Then you raise it to vertical with just six supports? Those bottom ones rather narrow? Certainly narrower than the top.
Something in this mess has to be "unthinkable". Astonishingly quick. A two part scenario.
Something strange enough that it would get past some of the smartest designers and engineers there are. So no, you have it backwards. We KNOW they would have worked the issues that make sense. That only leaves the issues that don't make sense. (with our extremely limited knowledge).   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/15/2016 03:42 pm
If that was the hypothesis - again, please correct me if I'm wrong - then what's the relevance of hydraulic fluid not immediately bursting into flame in normal air?  "Aerosolized mists of hydrocarbons" and "high concentrations of oxygen" are not famous for playing nicely.

That is two failures. 
Not by the standard of accident investigation.   From  the National Fire Protection Association (http://www.nfpa.org/Assets/files/AboutTheCodes/61/61_A2016_CMD-AGR_SD_SRStatements.pdf), " always assume an ignition source is present unless we can prove one cannot exist".  So one failure (hydrauic fluid leak) and one contributing factor (should have used hydraulic fluid that is non-flammable even in high oxygen environments).   Of course if SpaceX used a completely non-flammable fluid such as water, all these arguments are moot. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:43 pm
This is not the 1st TEL flash and then fire event that was triggered by LOX coming into contact with the something on the TEL:

https://www.youtube.com/watch?v=tM-QlPAMLEc?t=62

Hit phase and then single frame it using the  < & > keys.

No, that was not LOX related.  It was RP-1

RP-1 was dumped from the top of the TEL, fell down and then ignited?

From the second stage umbilical

So what was ignited on the TEL was RP-1 vented / dumped from the rising F9? The vent / dump occurred after liftoff and the umbilicales were well released.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:45 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

You mean gas lines

So ALL the 7 lines are GAS lines?

SpX uses gas pressurised actuators and not hydraulic pressurised actuators on that portion of the TEL?
No, I am not stating that.  I am stating that you are making an assumption based on no supporting  data and there are better explaination for those lines.

The vehicle needs He and GN2 of different pressures and that is the likely purpose of those lines.  Seven makes no sense for hydraulics.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 03:51 pm


Postulating a theory that puts a load-bearing support on the strongback at a point that would push it up against the thin wall of an empty tank while it's carrying a cantilevered load of many tons would require the designers of the GSE to be nincompoops. Or worse.

Your words: "carrying a cantilevered load of many tons" And maybe this is the beginning of the incident. Load was expected to be spread across the TOP and bottom supports. One slight misalignment. Rocker pivot doesn't rock, who knows? Then you raise it to vertical with just six supports? Those bottom ones rather narrow? Certainly narrower than the top.
Something in this mess has to be "unthinkable". Astonishingly quick. A two part scenario.
Something strange enough that it would get past some of the smartest designers and engineers there are. So no, you have it backwards. We KNOW they would have worked the issues that make sense. That only leaves the issues that don't make sense. (with our extremely limited knowledge).

This isn't an issue.  This isn't close to being a cause.  The TEL did not damage the vehicle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 03:57 pm
The center of the initial saturated area actually has a hole in the blue channel.

Now a couple of other things to think about.

BLUE is going to usually be more in focus than Red or Green.  Shorter wavelengths.

Also,  my eyes may be deceiving me by now, but taking your thought and running with it.  There is a chance that the initial shockwave is visible in the blue channel for some number of frames.  Can you do your own independent magic and see if you agree, and if so, at which frame does it hit the "nearest" tower?

Does anyone know how far the tower is from the F9?  about?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 03:58 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

You mean gas lines

So ALL the 7 lines are GAS lines?

SpX uses gas pressurised actuators and not hydraulic pressurised actuators on that portion of the TEL?
No, I am not stating that.  I am stating that you are making an assumption based on no supporting  data and there are better explaination for those lines.

The vehicle needs He and GN2 of different pressures and that is the likely purpose of those lines.  Seven makes no sense for hydraulics.

There are 7 lines. You can count them.

Why say they are GAS lines when you apparently don't know for sure?

BTW those lines are running well above the S1 & S2 umbilical feed points, so how would those lines feed He & GN2 to the vehicle?

You can see that a few lines do run into the upper payload umbilical section but the others do not.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/15/2016 04:11 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

i think what youve got marked as 6 and 7 are one large line?

i think the left most line is also smaller than the rest.

1 small, 3 medium, 1 large, 1 X-large

you can see where the L and XL make a turn to the left. easier to see there.

edit: or maybe youre right about the right side... 1 small, 3 medium, 1 large, 1 large, 1 small
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/15/2016 04:16 pm
4 hydraulic lines.  One supply, one return each for the grippers.  One line for Helium.  One line for Nitrogen.  Everyone's right?

Not saying if the lines are actually hydraulic instead of pneumatic, or that they used flammable fluid.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/15/2016 04:19 pm

One issue I see with this theory is that the wind is blowing right to left (more or less) in the video. Therefore the round body of the rocket is in the lee of the TEL, thereby disrupting and partially blocking air flow to the rocket
Nice wide Payload fairing up there catching a lot of wind. The Pivot would likely be the upper support pads.
Add a little resonance and who knows?
1. The rocket is chock full of accelerometers.  SpaceX knows how much the rocket is moving and if a resonance is occurring.
2. The same accelerometers would tell them if the second stage hit the pad especially with enough force to puncture a tank.
3. They have multiple cameras on this and all 8 previous launches with densified propellent.  They would have reviewed the film by now and noticed if the rocket shrank enough for the pad to be offset from the common bulkhead.

It seems unlikely to be the cause and unlikely that SpaceX would not figured it out if it was.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/15/2016 04:21 pm
Question about resonance and natural frequency.  Would anyone at SpaceX (or any rocket manufacturer for that matter) have done modal analysis with the rocket partially filled with boiling liquids in them with a strong crosswind blowing through the TEL?  Seems this is a fairly "transient" state and hard to model.  Therefore the designers may have made the engineering decision that the analysis time wasn't worth it since the actual time is so "short".  So they concentrated on the full and empty analysis.

I guess I'm suggesting some time of missed harmonic type of failure mode.  Fairly "out there" granted.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 04:26 pm
Not really hard to model.  And it would be too short of a time frame to cause damage.  The tanks fill fast.   And as I posted videos, Launch vehicles do flex.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/15/2016 04:31 pm
Not really hard to model.  And it would be too short of a time frame to cause damage.  The tanks fill fast.   And as I posted videos, Launch vehicles do flex.

Clearly rockets flex, not in dispute.  But what about harmonics in this particular loading case?  Are you saying engineers have never overlooked, poorly modeled, or just got harmonics wrong?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/15/2016 04:33 pm
Not really hard to model.  And it would be too short of a time frame to cause damage.  The tanks fill fast.   And as I posted videos, Launch vehicles do flex.

Clearly rockets flex, not in dispute.  But what about harmonics in this particular case?  Are you saying engineers have never overlooked, poorly modeled, or just got harmonics wrong?
The rocket is has accelerometers.  SpaceX should have actual data on how much the rocket was swaying, if it was resonating and if it smacked into the TEL.  Even if they lost all telemetry on impact and the impact wasn't transmitted they should have the data showing the increasing amplitude of the "sway."
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/15/2016 04:34 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

You mean gas lines

So ALL the 7 lines are GAS lines?

SpX uses gas pressurised actuators and not hydraulic pressurised actuators on that portion of the TEL?
No, I am not stating that.  I am stating that you are making an assumption based on no supporting  data and there are better explaination for those lines.

The vehicle needs He and GN2 of different pressures and that is the likely purpose of those lines.  Seven makes no sense for hydraulics.

6 feed lines under pressure (three devices which can be operated in two directions) and one return line back to the tank, which wouldn't be under much pressure.

Depends on how the hydraulic devices are operated - albeit the rams operating the claw look to me like they work on a feed and return rather than two feeds and one return.

But yes, in this instance 7 doesn't make a lot of sense - assuming it is indeed 7 hydraulic lines, which is a matter of some debate.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/15/2016 04:35 pm
Not really hard to model.  And it would be too short of a time frame to cause damage.  The tanks fill fast.   And as I posted videos, Launch vehicles do flex.

Clearly rockets flex, not in dispute.  But what about harmonics in this particular case?  Are you saying engineers have never overlooked, poorly modeled, or just got harmonics wrong?
The rocket is has accelerometers.  SpaceX should have actual data on how much the rocket was swaying, if it was resonating and if it smacked into the TEL.  Even if they lost all telemetry on impact and the impact wasn't transmitted they should have the data showing the increasing amplitude of the "sway."

It wouldn't have to hit anything, just vibrate in just the wrong way and crack the weld at the common bulkhead.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 04:47 pm
Not really hard to model.  And it would be too short of a time frame to cause damage.  The tanks fill fast.   And as I posted videos, Launch vehicles do flex.

Clearly rockets flex, not in dispute.  But what about harmonics in this particular loading case?  Are you saying engineers have never overlooked, poorly modeled, or just got harmonics wrong?

Fatigue is the failure mode in harmonics and the timeframe for going from empty to full is on the order of a half hour.  Too quick for the vehicle to be in a resonance and shake itself apart.  It would pass right through the resonance in seconds at the flow rates they use.  And resonance is not going to be a buzz, it would long mode for vortex shedding.  Anyways, this would be seen on vehicle sensors
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 04:48 pm
What three devices? There are on two clamps
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 04:50 pm
Not really hard to model.  And it would be too short of a time frame to cause damage.  The tanks fill fast.   And as I posted videos, Launch vehicles do flex.

Clearly rockets flex, not in dispute.  But what about harmonics in this particular case?  Are you saying engineers have never overlooked, poorly modeled, or just got harmonics wrong?
The rocket is has accelerometers.  SpaceX should have actual data on how much the rocket was swaying, if it was resonating and if it smacked into the TEL.  Even if they lost all telemetry on impact and the impact wasn't transmitted they should have the data showing the increasing amplitude of the "sway."

It wouldn't have to hit anything, just vibrate in just the wrong way and crack the weld at the common bulkhead.

It isn't vibrate as in Buzz, it is only going to flex as in the videos
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Lars-J on 09/15/2016 04:55 pm
The center of the initial saturated area actually has a hole in the blue channel.

Now a couple of other things to think about.

BLUE is going to usually be more in focus than Red or Green.  Shorter wavelengths.

Also,  my eyes may be deceiving me by now, but taking your thought and running with it.  There is a chance that the initial shockwave is visible in the blue channel for some number of frames.  Can you do your own independent magic and see if you agree, and if so, at which frame does it hit the "nearest" tower?

This is heavily compressed video, with different ratios of data for each channel. You are reading too much into very limited data. This is the equivalent of zooming in to a highly compressed JPEG and thinking that you are seeing something that is likely just an artifact of data compression.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 04:56 pm
<snip>
I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel <snip>

Given the choice of red pill or blue, the blue is the better choice.

Thought I'd look at what you're looking at and see if there was anything interesting.

There is something rather bizarre here, attached animated gif, I think.

There is a cloud at the bottom right of the fireball that seems to grow over the first few frames.  No surprise.

However, if this is condensed water vapor or LOX or GOX, just where the heck did it come from so early in this sequence?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/15/2016 04:57 pm
What three devices? There are on two clamps

Not three devices on this TEL, but 7 pipes would be applicable under different circumstances.

I qualified the comment with the observation that the rams on the claw have only two pipes going to then; and that 7 pipes doesn't make sense in this instance ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/15/2016 05:02 pm

2. The same accelerometers would tell them if the second stage hit the pad especially with enough force to puncture a tank.

It seems unlikely to be the cause and unlikely that SpaceX would not figured it out if it was.

I don't think it requires the support pad to puncture the tank. That is likely ruled out by the timing. But it MIGHT have deformed it just enough to get the pad stuck while it was trying to slide. Ice/LOX dam? As Jim stated, it MUST slide.
Say one side sticks but not the other, Could that develop enough force to snap a turnbuckle support? That snapping could be the flash. If at the top connector, it may have forced the turnbuckle towards the tank wall and THAT's what punctured the tank.


Can a static charge be built up on the painted surface?

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 05:02 pm
The center of the initial saturated area actually has a hole in the blue channel.

Now a couple of other things to think about.

BLUE is going to usually be more in focus than Red or Green.  Shorter wavelengths.

Also,  my eyes may be deceiving me by now, but taking your thought and running with it.  There is a chance that the initial shockwave is visible in the blue channel for some number of frames.  Can you do your own independent magic and see if you agree, and if so, at which frame does it hit the "nearest" tower?

This is heavily compressed video, with different ratios of data for each channel. You are reading too much into very limited data. This is the equivalent of zooming in to a highly compressed JPEG and thinking that you are seeing something that is likely just an artifact of data compression.

:) I think not.  :)  I really kinda sorta know what a compression artifact is.  I was using wavelets to reduce artifacts long before most of you folks ever heard of GIF files.  I have a colleague who was on the committee that drafted the first JPEG standard and she was simply appalled that the industry took the example in the appendix and defined it as the standard.  JPEG does not have to create the types of artifacts we all know & love.  The appendix example, however, does, and hence that's our standard these days.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: TheTraveller on 09/15/2016 05:04 pm
im only counting 6 of these lines? 4 small ones, 1 medium, 1 larger?

See below.

i think what youve got marked as 6 and 7 are one large line?

i think the left most line is also smaller than the rest.

1 small, 3 medium, 1 large, 1 X-large

you can see where the L and XL make a turn to the left. easier to see there.

edit: or maybe youre right about the right side... 1 small, 3 medium, 1 large, 1 large, 1 small

As per the joints. 6 joints, 7 lines.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/15/2016 05:09 pm

The rocket is has accelerometers.  SpaceX should have actual data on how much the rocket was swaying, if it was resonating and if it smacked into the TEL.  Even if they lost all telemetry on impact and the impact wasn't transmitted they should have the data showing the increasing amplitude of the "sway."

Maybe not so much "sway"ing, as much as vibrating like a tuning fork. Compressing the frost layer, into an ice/lox ridge just above the common bulkhead line. where it might be colder than expected.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: LouScheffer on 09/15/2016 05:34 pm
They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.
A.  Why would they be under pressure at that time?
b.  why would there be 7 lines for only two actuators?
c.  The leak would be seen on other cameras
d.  How do you know they are hydraulic lines and not He and GN2 lines?
(a) At least one line should be under pressure to keep the claw closed.
(b) and (d). There must be at least 2 hydraulic lines going to the top of the erector to run the claw.  Maybe not all 7 are hydraulic.
(c) Small hydraulic leaks are well known (https://www.gates.com/~/media/files/gates/industrial/fluid-power/manuals/gates_fluid_power_ebook.pdf) for being nearly invisible, even at close range. (Often leading to injuries where the hydraulic fluid is injected into a worker's hand, even through gloves.)  A quite substantial leak might take place without being seen on camera, especially as any camera viewing the back of the T/E would be fairly far away.

Leaking hydraulics are also known to cause explosions if they are not using water based fluid.  From the same document:
Quote
With the exception of those comprised primarily of water, all hydraulic fluids are flammable when exposed to the proper conditions. Leaking pressurized hydraulic fluids may develop a mist or fine spray that can flash or explode upon contact with a source of ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 05:37 pm

The rocket is has accelerometers.  SpaceX should have actual data on how much the rocket was swaying, if it was resonating and if it smacked into the TEL.  Even if they lost all telemetry on impact and the impact wasn't transmitted they should have the data showing the increasing amplitude of the "sway."

Maybe not so much "sway"ing, as much as vibrating like a tuning fork. Compressing the frost layer, into an ice/lox ridge just above the common bulkhead line. where it might be colder than expected.

No, that not a mode for the structure of this vehicle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/15/2016 05:42 pm
In so far as looking at what can create an aerosol cloud outside the vehicle, at least the basic ingredients of "Helium leak" and "some flammable in the rocket" are there.

Perhaps not in the main storage tanks, but in the fill lines, since some fueling activity was happening at the time.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Helodriver on 09/15/2016 05:44 pm
They are hydraulic lines that have been cut and extended. Note the 14 in line connectors at each end of the extension section. You can see them toasted in the attached. See if you can count 7 lines as in the original image.
A.  Why would they be under pressure at that time?
b.  why would there be 7 lines for only two actuators?
c.  The leak would be seen on other cameras
d.  How do you know they are hydraulic lines and not He and GN2 lines?
(a) At least one line should be under pressure to keep the claw closed.
(b) and (d). There must be at least 2 hydraulic lines going to the top of the erector to run the claw.  Maybe not all 7 are hydraulic.
(c) Small hydraulic leaks are well known (https://www.gates.com/~/media/files/gates/industrial/fluid-power/manuals/gates_fluid_power_ebook.pdf) for being nearly invisible, even at close range. (Often leading to injuries where the hydraulic fluid is injected into a worker's hand, even through gloves.)  A quite substantial leak might take place without being seen on camera, especially as any camera viewing the back of the T/E would be fairly far away.

Leaking hydraulics are also known to cause explosions if they are not using water based fluid.  From the same document:
Quote
With the exception of those comprised primarily of water, all hydraulic fluids are flammable when exposed to the proper conditions. Leaking pressurized hydraulic fluids may develop a mist or fine spray that can flash or explode upon contact with a source of ignition.

I observed a 3000 psi hydraulic leak inside a helicopter I was flying some years back, within seconds half the cabin was filled with fine foglike mist. This from a cracked fitting on a line less than 1/2 inch in diameter. Outside in bright sun and from a distance the leak would have been easy to miss.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: joncz on 09/15/2016 05:49 pm
First time poster...  I'm not sure if I've seen this scenario so I apologize if it's already been mentioned.  The Titan II silo accident in 1980 was caused by FOD dropped down into the silo (in that case a large socket) which bounced and pierced the skin creating an aerosol.  The resultant explosion took out the entire missile and silo:
http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543
Note that those were hypergolic propellants...  In the SpaceX case, a large piece of FOD could have fallen off the strongback due to the high wind, bounced off one of the strongback beams and hit the skin of the fuel tank and created a pinhole leak.  Hydrostatic pressure in the tank would be sufficient to generate an aerosol that would then mix with the vented LOX.  Still need an ignition source though.  Also you would think a camera would catch it but it wouldn't take much of an object to cause damage.

The puncture in the Titan didn't aerosolize the hypergolics.  The socket punctures the skin of the stage (Titan II was a balloon).  The hypergolic poured out of the stage for some time (there were, IIRC, two attempts to enter the silo and stop the leakage).  The hypergolics ended up pooling in the bottom of the silo and when the stage lost structure due to loss of pressure, the collapse burst the other hypergolic tank and you had a explosive mix in the bottom of the silo - essentially a cannon shot that blew the blast doors off the silo and the warhead quite some distance away.

Reference - Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety, Eric Schlosser

Edit: misspelling
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mn on 09/15/2016 06:10 pm
....
I observed a 3000 psi hydraulic leak inside a helicopter I was flying some years back, within seconds half the cabin was filled with fine foglike mist. This from a cracked fitting on a line less than 1/2 inch in diameter. Outside in bright sun and from a distance the leak would have been easy to miss.

And boy are we glad that mist didn't ignite  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/15/2016 07:17 pm
(a) At least one line should be under pressure to keep the claw closed.

I think it's a bigger version of a type of ram I'm very familiar with.

Essentially, as long as there are non-return valves on the pipes to the ram, the claw will remain closed without pressure (other than the residual pressure in the fluid).

For the ram to be forced open, the piston inside has to be pushed (or pulled) by a force (such as trying to pull the rocket out of the claw) and the easiest way for it to move is to push the hydraulic fluid with it.

If there's a non-return valve (or something like a solenoid valve) in that pipe, the fluid can't flow, so the ram stays put.

The exception to this is massive overloading (probably shock loading) which damages the seals around the piston, but (i) that's certainly not happened here; (ii) even if it did happen, the amount of movement will be slight; and (iii) something would probably burst elsewhere first (I'm not suggesting this has happened in this instance!).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: mme on 09/15/2016 07:28 pm

The rocket is has accelerometers.  SpaceX should have actual data on how much the rocket was swaying, if it was resonating and if it smacked into the TEL.  Even if they lost all telemetry on impact and the impact wasn't transmitted they should have the data showing the increasing amplitude of the "sway."

Maybe not so much "sway"ing, as much as vibrating like a tuning fork. Compressing the frost layer, into an ice/lox ridge just above the common bulkhead line. where it might be colder than expected.
Wires "buzz" because they have a small diameter and the frequency of the vortex shedding is inversely proportional to the diameter (and proportional to the wind velocity).  I'm pretty sure to get the 3.6 m F9 body or the 5.2 m fairing to buzz would require unrealistic winds.  The input frequency from any wind that would actually exist at ground level would induce a sway, not a buzz.  And a buzz would imply tiny movements anyway.

I am not an aerospace engineer, just a code-monkey, so I'm going to bow out.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Hyperloop on 09/15/2016 07:34 pm
Followup: I think there's good evidence that it was interlaced, but that the interlacing has been filtered out.  See this:

https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg
(https://c7.staticflickr.com/9/8324/29619459086_d5c8623e19_z.jpg)

That's from the highest res video I could download from Youtube, 1080p mp4.  Odd lines on the top, even lines on the bottom, split with:

ffmpeg -ss 71 -i video.mp4 -t 1 -vf il=d out-%04d.png

 Note that halfway through the odd lines there suddenly starts a chromatic abberation, which slowly diminishes as it continues downward.  The abberation continues along the even frames, top to bottom.  Yet the "image" in both the even and odd rows is identical.  It seems quite likely that the video was initially interlaced but has subsequently been deinterlaced during processing.  If so then there would be an additional recoverable frame as well as highly precise (sub-millisecond) timing on when the explosion began and at least the X coordinate in the frame of the ignition point.

If the original wasn't interlaced, I'd expect that the images from the even and odd rows would look almost identical.  They don't.  I can't think of a way that this result could be explained by compression artifacts, either.

Someone earlier suggested that the 1080 was upsampled from the original of 720.  That might do it.

Do you see the same on the 720 version?

720 Only comes in a progressive flavor, not interlaced.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: JamesH65 on 09/15/2016 07:39 pm
The center of the initial saturated area actually has a hole in the blue channel.

Now a couple of other things to think about.

BLUE is going to usually be more in focus than Red or Green.  Shorter wavelengths.

Also,  my eyes may be deceiving me by now, but taking your thought and running with it.  There is a chance that the initial shockwave is visible in the blue channel for some number of frames.  Can you do your own independent magic and see if you agree, and if so, at which frame does it hit the "nearest" tower?

This is heavily compressed video, with different ratios of data for each channel. You are reading too much into very limited data. This is the equivalent of zooming in to a highly compressed JPEG and thinking that you are seeing something that is likely just an artifact of data compression.

:) I think not.  :)  I really kinda sorta know what a compression artifact is.  I was using wavelets to reduce artifacts long before most of you folks ever heard of GIF files.  I have a colleague who was on the committee that drafted the first JPEG standard and she was simply appalled that the industry took the example in the appendix and defined it as the standard.  JPEG does not have to create the types of artifacts we all know & love.  The appendix example, however, does, and hence that's our standard these days.

H264, which I suspect this was recorded with, doesn't use wavelets.

And the sensor in the camera will record all three colour channels at the same time, blue won't be 'earlier'. Note the CCD's are in effect black and white, and there is a RGB bayer filter  that cuts out unwanted colours for each pixel. There are twice as many green pixels as red or blue, so green is a better channel for detail, if the bayer data (raw) were available. Once it's debayered, and all the image processing pipeline has had its evil way, the individual pixels are entirely untrustworthy. Debayering (depending on the algorithm) causes fringing, the slightest movement of either the camera or the subject is likely to cause weird fringing changes at the pixel level. Don't trust them.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/15/2016 07:54 pm
heres a picture from vandy tel, i thought this area was interesting. looks like a couple valves near the top of the interstage.

https://i.imgur.com/HQC5qKa.jpg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 07:56 pm
The center of the initial saturated area actually has a hole in the blue channel.

Now a couple of other things to think about.

BLUE is going to usually be more in focus than Red or Green.  Shorter wavelengths.

Also,  my eyes may be deceiving me by now, but taking your thought and running with it.  There is a chance that the initial shockwave is visible in the blue channel for some number of frames.  Can you do your own independent magic and see if you agree, and if so, at which frame does it hit the "nearest" tower?

This is heavily compressed video, with different ratios of data for each channel. You are reading too much into very limited data. This is the equivalent of zooming in to a highly compressed JPEG and thinking that you are seeing something that is likely just an artifact of data compression.

:) I think not.  :)  I really kinda sorta know what a compression artifact is.  I was using wavelets to reduce artifacts long before most of you folks ever heard of GIF files.  I have a colleague who was on the committee that drafted the first JPEG standard and she was simply appalled that the industry took the example in the appendix and defined it as the standard.  JPEG does not have to create the types of artifacts we all know & love.  The appendix example, however, does, and hence that's our standard these days.

H264, which I suspect this was recorded with, doesn't use wavelets.

And the sensor in the camera will record all three colour channels at the same time, blue won't be 'earlier'. Note the CCD's are in effect black and white, and there is a RGB bayer filter  that cuts out unwanted colours for each pixel. There are twice as many green pixels as red or blue, so green is a better channel for detail, if the bayer data (raw) were available. Once it's debayered, and all the image processing pipeline has had its evil way, the individual pixels are entirely untrustworthy. Debayering (depending on the algorithm) causes fringing, the slightest movement of either the camera or the subject is likely to cause weird fringing changes at the pixel level. Don't trust them.

There is no commercial camera that I am aware of that uses wavelets.  H264 is most likely.

Blue isn't earlier, it's just shorter wavelength, but it may show features different than red or green, if there's an object that emits or absorbs more blue than red/green.  Further the between cell blooming is less which often increases actual resolution.

FYI, I'm so old, that once upon a time I had to get custom fab for our own 1k X 1k CCD because there weren't any commercially available.  We had to move lots of data over 9600 baud modems and looked into every compression algorithm known and theorized.  We had a "zero" artifact requirement since our image data was literally used for life & death decisions.

I'm well aware of how camera technology compromises imaging.

Depending on the compression employed, i.e. best basis wavelets, pixels are not inherently untrustworthy, depends on how much compression you really need.

Commercial camera products?  I would say that any 16x16 jpeg block is a reasonable representation of what was in that block, and the pixels themselves may be ok if there's no contrast in the block... sometimes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kolkmvd on 09/15/2016 07:58 pm
There is a cloud at the bottom right of the fireball that seems to grow over the first few frames.  No surprise.

However, if this is condensed water vapor or LOX or GOX, just where the heck did it come from so early in this sequence?
Sorry, I can't get what you're pointing at? Can you annotate the image?

I think if you look at frame 2 and 3 in the blue (where vapor was formed), you can get a rough idea how the initial deflagation developed. With that in mind, i think we're able to see what part of the frame 1 flash (frame 0 being the intact f9) is the light reflected off the f9/tel and what not. For me, it looks like it never extended up to the fairings, neither below the interstage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 08:10 pm
There is a cloud at the bottom right of the fireball that seems to grow over the first few frames.  No surprise.

However, if this is condensed water vapor or LOX or GOX, just where the heck did it come from so early in this sequence?
Sorry, I can't get what you're pointing at? Can you annotate the image?

I think if you look at frame 2 and 3 in the blue (where vapor was formed), you can get a rough idea how the initial deflagation developed. With that in mind, i think we're able to see what part of the frame 1 flash (frame 0 being the intact f9) is the light reflected off the f9/tel and what not. For me, it looks like it never extended up to the fairings, neither below the interstage.

I tend to agree.  You can't see the flash/reflection boundary up or down, but you can see boundaries left & right.  I'm assuming it's not spherical but cylindrical because the trajectories of stuff thrown out don't seem to converge on a nice sphere.  Can you share your imaging results?  Here's a crop showing the bizarre cloud location.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dorkmo on 09/15/2016 08:34 pm
in this picture you can see the hoses from the cylinders go to some sort of mounting plate, where i assume they switch to pipe. it looks like what may be an electrical conduit passes behind this area but i dont think its related. you can also see what looks like a doudle redundant sensor setup to confirm the claws are open. ?

http://spaceflightnow.com/wp-content/uploads/2015/01/10904397_10155398957535131_6988152543507651642_o.jpg
http://www.spaceflightinsider.com/wp-content/uploads/2015/04/1124-spacex_falcon_9_crs6-jason_rhian.jpg
https://i.imgur.com/E5S0Fla.jpg
http://spaceflight101.com/dragon-spx9/wp-content/uploads/sites/98/2016/07/CnmLA8zW8AAaONn.jpg-large.jpg
http://www.spacex.com/sites/spacex/files/orbcomm_l-1_vertical.jpg
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/15/2016 09:02 pm
But it MIGHT have deformed it just enough to get the pad stuck while it was trying to slide. Ice/LOX dam? As Jim stated, it MUST slide.
Say one side sticks but not the other, Could that develop enough force to snap a turnbuckle support? That snapping could be the flash. If at the top connector, it may have forced the turnbuckle towards the tank wall and THAT's what punctured the tank.


No, it wouldn't deform.  That would be see on sensor.  There is no ice dam.  It isn't that type of ice.
The incident had nothing to do with this pads.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NaN on 09/15/2016 09:57 pm
(trimmed)

I'm well aware of how camera technology compromises imaging.

Depending on the compression employed, i.e. best basis wavelets, pixels are not inherently untrustworthy, depends on how much compression you really need.

Commercial camera products?  I would say that any 16x16 jpeg block is a reasonable representation of what was in that block, and the pixels themselves may be ok if there's no contrast in the block... sometimes.

Are you still using video sourced from YouTube? Wouldn't it have been transcoded at least one additional time after the camera's initial encoding, with unknown settings?
Add in the fact that there is only one source in the public domain, and it gets much more difficult to extract anything with confidence (ie, are you seeing a deceptive lighting effect that, while not an artifact, wouldn't show up from a different angle)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/15/2016 10:03 pm
The camera most likely didn't have a ccd but a cmos detector. Not impossible that it's ccd but extremely rare in commercial cameras. Also absorption of oxygen is narrow band, the light source is broad band, like the pixel filter. Oxygen absorption is not enough to make a difference. However most glasses have less throughout in blue than in red or green. Might be the reason why blue is less overexposed. Pure speculation here though.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/15/2016 10:12 pm
<snip>
I've been looking at the actual initial 'deflagation', after T=0 and found there is quite a lot to see in the Blue channel <snip>

Given the choice of red pill or blue, the blue is the better choice.

Thought I'd look at what you're looking at and see if there was anything interesting.

There is something rather bizarre here, attached animated gif, I think.

There is a cloud at the bottom right of the fireball that seems to grow over the first few frames.  No surprise.

However, if this is condensed water vapor or LOX or GOX, just where the heck did it come from so early in this sequence?

http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1370346;sess=49969 (http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30981.0;attach=1370346;sess=49969)

This is a really good demonstration. Can someone explain from Frame 0 [pre-explosion] to frame1 how the tongue of flame that extends downward and around the S1 section of the Falcon. it is not just a reflection and can not be RP-1 in a few milliseconds. The GIF sequence demonstrates that in frames 2-3-4 the expansion of the fireball and the discontinuation of the tongue extending down the stage.

Is it possible that the initiation event occurred down below the Grid-Fins and traveled up to the location of the venting GOX on the S2? I can't account for the long section of flame below the point of explosion at the middle bumper common bulkhead section.  watching this GIF cycle to me it looks similar to re-lighting a candle by igniting the fumes from the wick as shown here.
https://www.youtube.com/watch?v=C5eTn5d0cvg (https://www.youtube.com/watch?v=C5eTn5d0cvg)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Hyperloop on 09/15/2016 10:22 pm
The camera most likely didn't have a ccd but a close detector. Not impossible that it's ccd but extremely rare in commercial cameras. Also absorption of oxygen is narrow band, the light source is broad band, like the pixel filter. Oxygen absorption is not enough to make a difference. However most glasses have less throughout in blue than in red or green. Might be the reason why blue is less overexposed. Pure speculation here though.

Been in videography/film for 10+ years and I've never heard of a "close detector" could you elaborate?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/15/2016 10:24 pm
Ohh autocorrection on mobile phone... I meant cmos. Sorry. I correct the post.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/15/2016 10:29 pm
This involves GOX and LOX, but this is what it looks like as the Gif cycles

https://www.youtube.com/watch?v=oAdkxRz1L-c (https://www.youtube.com/watch?v=oAdkxRz1L-c)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Hyperloop on 09/15/2016 10:41 pm
Ohh autocorrection on mobile phone... I meant cmos. Sorry. I correct the post.

Ahhhhh, that makes so much more sense now!  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 10:48 pm

Can someone explain from Frame 0 [pre-explosion] to frame1 how the tongue of flame that extends downward and around the S1 section of the Falcon. it is not just a reflection and can not be RP-1 in a few milliseconds. The GIF sequence demonstrates that in frames 2-3-4 the expansion of the fireball and the discontinuation of the tongue extending down the stage.

Is it possible that the initiation event occurred down below the Grid-Fins and traveled up to the location of the venting GOX on the S2? I can't account for the long section of flame below the point of explosion at the middle bumper common bulkhead section.  watching this GIF cycle to me it looks similar to re-lighting a candle by igniting the fumes from the wick as shown here.
https://www.youtube.com/watch?v=C5eTn5d0cvg (https://www.youtube.com/watch?v=C5eTn5d0cvg)

The simple answer is, a proper image analysis of a single video with no other sources, with full access to engineering data available prior to the event will take time, so unless SPACEX folks have a slam dunk with their data set, no.

Given the single video source that we have, assuming I have to do the work, and fortunately there are others out there looking at variations, unless SPACEX announces a solution, the data we have, which is fundamentally crap, will take weeks to disentangle.  There's a lot there, and a lot pending for analysis, but sadly, it's kinda like the Zapruder film as captured on a VCR on a CBS special.  A few generations removed from what's real.

To your specific questions: Preliminary analysis suggests that the Frame 1 image holds saturation data consistent with both a detonation (fast fire, argue elsewhere) and a reflection component.   Previously in this thread I've provided evidence that the reflection component points to specific areas of illumination which would be the fireball, but however interpreted, the camera data available shows a mix of actual fireball and reflection which overlap because the camera was saturated irrespective of the source.  Except for right and left boundaries of the fireball, it's almost impossible to discern the vertical dimensions of the fireball.  Trajectory analysis suggests (not definitively) that the frame 1 fireball was taller than wider, i.e. 35 feet wide, perhaps 85 feet tall, but, perhaps not.  The tongue extending down the stage is probably reflection, IMHO, but it could be actual detonation.  And using the word detonation is also suspect although I believe, and will post, evidence of supersonic shock wave later, if my computer stops crashing.

As to the initial event occurring below the grid fins, the analysis I've done suggests not.  The difference analysis I've done shows a suspect region above the grid fins prior to the event, but well below everyone's, including mine, assessment of the center point of the event, but absolutely no one has stepped forward saying, "that's where I planted the bomb, how did you find it."  Something happened during the 22 seconds I've subjected to serious imaging analysis above the grid fins, but nothing beyond a possible cloud event shows in the video.  I emphasis cloud, because the image stabilizing technique we used isn't perfect and I've posted prior videos that show, while at a gross level, things are copacetic, the algorithm, screwed up on the finer details needed for interpretation.  As usual, blame the programmer.

As for your relighting candle video, things in the available video are happening an order of magnitude+ faster than with your candle.  Elon may call this a fast fire, but, IMHO an event that obliterates a 35 X 85 foot area in 16 milliseconds, which is my best estimate,  to me is defined as a detonation (others disagree).  Your candle model has to speed up a lot to be consistent with this video, albeit, the chemistry & physics may be relevant.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NaN on 09/15/2016 10:52 pm

Are you still using video sourced from YouTube? Wouldn't it have been transcoded at least one additional time after the camera's initial encoding, with unknown settings?
Add in the fact that there is only one source in the public domain, and it gets much more difficult to extract anything with confidence (ie, are you seeing a deceptive lighting effect that, while not an artifact, wouldn't show up from a different angle)

sigh

You are sighing because you've already answered this multiple times, or because it's an exceedingly stupid question? I've generally kept up with the thread from the beginning, but when it grows 5 pages in the course of an evening out, it's impossible to keep up with everything.
Please help me out with a pointer. I've searched and not found it.

edit: all I can find is this nondefinitive statement
Even if we are limited to a single horribly destroyed youtube video
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 10:59 pm
The camera most likely didn't have a ccd but a cmos detector. Not impossible that it's ccd but extremely rare in commercial cameras. Also absorption of oxygen is narrow band, the light source is broad band, like the pixel filter. Oxygen absorption is not enough to make a difference. However most glasses have less throughout in blue than in red or green. Might be the reason why blue is less overexposed. Pure speculation here though.

how about a CPD?

Someone has to make friends with the USLR folks.  Shall we do a gofundme to buy the raw video and an ask me anything session?  Calling Chris Bergin.  Can we make them an offer they can't refuse, or shall we wait for SPACEX to send out their conclusion?  :)

They were fantastic in posting what they normally post and I'm sure provided the raw data to SPACEX.

For this forum, all we have is a youtube video.  For folks like me, it's like, well, it's painful.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/15/2016 11:09 pm

Are you still using video sourced from YouTube? Wouldn't it have been transcoded at least one additional time after the camera's initial encoding, with unknown settings?
Add in the fact that there is only one source in the public domain, and it gets much more difficult to extract anything with confidence (ie, are you seeing a deceptive lighting effect that, while not an artifact, wouldn't show up from a different angle)

sigh

You are sighing because you've already answered this multiple times, or because it's an exceedingly stupid question? I've generally kept up with the thread from the beginning, but when it grows 5 pages in the course of an evening out, it's impossible to keep up with everything.
Please help me out with a pointer. I've searched and not found it.

I'm sorry, it's been a long week.  I apologize if that was interpreted in a demeaning way. 

Absolutely the video was transcoded too many ways, from the CCD, to the ADC, to the MPEG DSP, to the actual recording, and then from the actual recording to youtube.  Lord knows how many bits flipped along the way, plus if it was a CPD instead of a CCD things would have been even stranger.

Yes, you're absolutely right that the image content on the youtube video is like, difficult.

As for extracting things with confidence, in spite of all of that butchering of the raw data, the techniques I and others have applied actually can find a degree of real content in the video.  Unfortunately, any video analysis that relies on the value of a single pixel, or in this case, a range of 16x16 pixels, is suspect.

The astrophotography techniques after atmospheric correction techniques are supposed to bring us to the diffraction limit of the lens, but in a recent video posted here, which is as good as it gets, we're still on the order of 1 pixel +- 6.

That's really bad.  Kinda like we have about 3 foot resolution when we think we see 6 inch resolution. 

The sigh was based on the fact that I know exactly what I'm dealing with, and you only identified a small subset of the problems, which are sadly, 1/3 of the ones I'm trying to deal with in my processing models. 

I apologize for my brief comment.  Yours was valid, and I was sighing because it's not only valid, but you missed some of the issues as well.

The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/15/2016 11:54 pm
Yes, the vehicle can flex, but the lower pad can't. That's the problem, if the vehicle flexes towards it, the pad will puncture the fuselage.

The "lower pad" rests on a visibly-reinforced portion of S2 right where the common bulkhead exists inside the stage. It's probably the strongest portion of S2 aside from the thrust structure at the bottom of the RP1 tank. I've made this point several times over the last two weeks, but rockets just aren't that fragile and the designers aren't complete nincompoops when it comes to designing their support equipment.

if the vehicle flexes towards it, the pad will puncture the fuselage.

No, it won't.  It is not point load, it is spread out by the pad.  And it is at the common bulkhead joint and not a tank side.

I've never said it is a point load, or just the side of a tank. Nor would I ever suggest the designers are any sort of nincompoops.

The scenario I'm attempting to discuss is not a simple static load problem. It is dynamic, and subject to a set of conditions that won't be replicated on every flight. For example, of the 8 FT launches so far, 2 were Dragon missions, and not all of the others had the payload fairing in place for the static fire. JCSAT-14 and 16 didn't, but SES-9 and Thaicom-8 did, I'm not sure about the other 2.

One relevant aspect of the payload fairing is it's diameter. The minimum turbulent Re for the formation of a vortex street is 3.5 * 10^6. The velocity for that Re and a diameter of 5.2m is v = 3.5 * 10^6 * 0.00001458 / 5.2 = 9.8 m/s, or about 19 knots. For a cylinder with a smooth surface, and the same Re, the Strouhal number peaks at 0.47. The frequency of vortex shedding can be calculated from those values:

f = St * V / D = 0.47 * 3.7 / 9.8 = 0.177 Hz

The oscillations lead to two forces on the cylinder, lift and drag. The oscillations in lift force occur at the vortex shedding frequency and oscillations in drag force occur at twice the vortex shedding frequency. So, for the fairing, shedding leads to forces oscillating at 0.177 and 0.354 Hz.

Another relevant aspect of the payload is that its position is only pinned by the strongback grabbers at the top of the second stage, when they are closed. In that configuration, the rocket could be modelled as having the second mode of flexion of a cantilever beam, especially if the height of the grabbers is the same as the node of the mode shape. I've done some rough estimates of the second natural frequency of a fully loaded F9, and it comes out around fn2 = 0.723 Hz. I suspect damping and fuel slosh could push this number lower, but if anyone has a better estimate, that would be helpful. Importantly, the natural frequency shifts downwards as fuel is loaded, so the shedding forces might only match or be a low order harmonic at a particular point in the loading cycle.

So, for flex induced by vortex shedding from the fairing to be a significant issue, here are some of the pre-conditions:

1. The payload and fairing are attached.
2. The wind speed is 9.8m/s.
3. The grabber is closed.
4. The fuel load is such that the natural frequency matches the shedding forces.
5. The position of the grabbers matches the node of the mode shape.
6. The cradle (and hence the lower pad) is fixed in position by the grabber and the pin joint on the strongback, which is vastly stiffer and stronger than the rocket.

If the lower pad of the cradle was not rigid, the risk would be mitigated. If all of the conditions were met, the onset of a significant flex could be quite sudden, and may not register on accelerometers as anything other than a step function at the same time as the start of the fast fire. Anyway, I'm just trying to suggest a possible mode of failure. I'm not saying other modes aren't valid, and it may well turn that an unexpected combination of events is the real answer.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: NaN on 09/15/2016 11:59 pm

Are you still using video sourced from YouTube? Wouldn't it have been transcoded at least one additional time after the camera's initial encoding, with unknown settings?
Add in the fact that there is only one source in the public domain, and it gets much more difficult to extract anything with confidence (ie, are you seeing a deceptive lighting effect that, while not an artifact, wouldn't show up from a different angle)

sigh

You are sighing because you've already answered this multiple times, or because it's an exceedingly stupid question? I've generally kept up with the thread from the beginning, but when it grows 5 pages in the course of an evening out, it's impossible to keep up with everything.
Please help me out with a pointer. I've searched and not found it.

I'm sorry, it's been a long week.  I apologize if that was interpreted in a demeaning way. 

Absolutely the video was transcoded too many ways, from the CCD, to the ADC, to the MPEG DSP, to the actual recording, and then from the actual recording to youtube.  Lord knows how many bits flipped along the way, plus if it was a CPD instead of a CCD things would have been even stranger.

Yes, you're absolutely right that the image content on the youtube video is like, difficult.

As for extracting things with confidence, in spite of all of that butchering of the raw data, the techniques I and others have applied actually can find a degree of real content in the video.  Unfortunately, any video analysis that relies on the value of a single pixel, or in this case, a range of 16x16 pixels, is suspect.

The astrophotography techniques after atmospheric correction techniques are supposed to bring us to the diffraction limit of the lens, but in a recent video posted here, which is as good as it gets, we're still on the order of 1 pixel +- 6.

That's really bad.  Kinda like we have about 3 foot resolution when we think we see 6 inch resolution. 

The sigh was based on the fact that I know exactly what I'm dealing with, and you only identified a small subset of the problems, which are sadly, 1/3 of the ones I'm trying to deal with in my processing models. 

I apologize for my brief comment.  Yours was valid, and I was sighing because it's not only valid, but you missed some of the issues as well.

The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.

Thank you for the detailed response - and I agree. This is technically very interesting to me, given that I know just enough about video compression and analysis to know that I wouldn't attempt to do what you are doing, as it's far too easy to see things that aren't there. I'm glad you have the expertise to avoid those traps.
We can dream that we'll be gifted with additional data, but given that SpaceX themselves still hadn't concluded if it was internal or external with all of their data and resources, the deck is stacked against us.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/16/2016 01:12 am
... and we need to take into account the effect of the release of latent heat by the LOX as it condenses (if it does).

You also need to take into account the effect of the release of latent heat by the water that is also freezing out.

Hence...

My point here is that the release of latent heat of condensation will act like a thermostat [...]

...by your own argument, the external temperature of the skin cannot ever fall below 77K. Water vapour in that humid Florida wind will act like a thermometer, continually raising the temperature until the rate of ice formation slows.


This would still be very localized when a few milliseconds later it has burnt through the tank wall [...]

A few milliseconds? Of a solid aluminium fire?


1. The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.
Technically, it's condensing faster than it's evaporating.  This is know to happen with LN2 (see references).  The outside is colder than LN2 (see calculations).

Much earlier in the thread, several people modelled the flow of heat and showed that the external temperature wouldn't fall below the critical 77K. Even the smallest amount of water-ice frost will prevent LOx condensation, even ignoring the heat of condensation of that frost.

Hence someone else (I'm too lazy to go hunting) suggested that the frost itself would insulate the skin, allowing the skin to subcool under the ice, if the ice fell away, it would briefly expose sub-77K skin to the air.

That led to the suggestion that the cradle pads could have scraped away the ice as the vehicle condensed, which led to the idea that the pads themselves (soaked in LOx) could have also provided the fuel for the initial blast.

My response was to try to show the failure to think through the contradictions in that idea. Amongst other things, if the pads scrape the ice away from the tank, exposing skin below the pads to allow LOx condensation, how did the pads become "soaked" in the LOx that is forming below them?


Point by point:

Quote
You also need to take into account the effect of the release of latent heat by the water that is also freezing out.     ...by your own argument, the external temperature of the skin cannot ever fall below 77K. Water vapour in that humid Florida wind will act like a thermometer, continually raising the temperature until the rate of ice formation slows.
Surely 273 K?  But yes, the outside of the frost layer will never go below 273 K in humid air for that reason.  If the rocket cools, and the outside of the frost cools with it, more water vapour will freeze onto the outside of the frost layer, warming it and thickening it (insulating the rocket better) until a new equilibrium is reached with a colder rocket and a thicker frost blanket.  But all this happens on the outside of the frost, while the LOX condensation happens (if it does) on the inside next to the paint, which is why the LOX-frost theory relies on the frost having enough air-spaces inside it to allow O2 to diffuse in as far as the paint.

Quote
The outside of the tank must be far enough below 90K to prevent condensing LOx from evaporating.
True.  The limiting temperature is 77 K, at which the vapour pressure of LOX equals 20 kPa, the partial pressure of O2 in the atmosphere.  (It's pure coincidence that this is also the boiling point of LN2.)

Quote
Much earlier in the thread, several people modelled the flow of heat and showed that the external temperature wouldn't fall below the critical 77K.
If you mean LouScheffer at #2694, he wasn't taking the frost into account.

Quote
Even the smallest amount of water-ice frost will prevent LOx condensation, even ignoring the heat of condensation of that frost.
This isn't true if O2 can diffuse in through the frost.  Of course if the "frost" is a continuous layer of glassy ice, the outside of it will be at 273 K (for the reason above), and you'd be right, LOX condensation couldn't happen (and you'd have to knock or scrape the ice off to expose a sub-77 surface to the air).  But the frost that forms on cryo equipment is not glassy flawless ice.  It's more like compacted dry snow, and is very far from airtight.

Quote
Hence someone else (I'm too lazy to go hunting) suggested that the frost itself would insulate the skin, allowing the skin to subcool under the ice
That might have been me, among others.  My analysis of the thermal gradients and heat flows is here:
It's long.  Click on the link to see it.

Quote
That led to the suggestion that the cradle pads could have scraped away the ice as the vehicle condensed, which led to the idea that the pads themselves (soaked in LOx) could have also provided the fuel for the initial blast.
I think the cradle-pads are irrelevant.  No scraping is necessary to make the LOX, and there is a much better source of fuel right next to the LOX; the Al tank-wall, only the paint-thickness away.

As for ignition sources, "organic contamination" has been mentioned many times upthread, including bird-poop and bugs on the paint surface.  I think this is entirely plausible.  The windward painted surface could easily have all those, plus greasy thumbprints, droplets of oil, and all kinds of plant debris blown on the wind.  Who bothers to scrub down the outside of a rocket?  It never mattered before.  The LOX inside the rocket is carefully contained in surgically clean metal.  The condensed LOX outside is in intimate contact with anything that happened to be on the paint and is now trapped under the frost layer.

If one of these bits of organic matter does act as an initiator and ignite with the LOX, it doesn't need to be very big.  It doesn't have to make the paint explode or even set it on fire; all it has to do is scorch a tiny area of paint, weaken it and open one small crack through the thickness of the paint down to the Al tank wall.  Then everything depends on the oxide layer on that metal.  If that is breached, the LOX will start to react with the unprotected Al underneath.  Even a few grams of condensed LOX will be enough to burn a few grams of Al and make a hole in the tank wall.  And then ...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rocketguy11 on 09/16/2016 01:44 am
First time poster...  I'm not sure if I've seen this scenario so I apologize if it's already been mentioned.  The Titan II silo accident in 1980 was caused by FOD dropped down into the silo (in that case a large socket) which bounced and pierced the skin creating an aerosol.  The resultant explosion took out the entire missile and silo:
http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543
Note that those were hypergolic propellants...  In the SpaceX case, a large piece of FOD could have fallen off the strongback due to the high wind, bounced off one of the strongback beams and hit the skin of the fuel tank and created a pinhole leak.  Hydrostatic pressure in the tank would be sufficient to generate an aerosol that would then mix with the vented LOX.  Still need an ignition source though.  Also you would think a camera would catch it but it wouldn't take much of an object to cause damage.

The puncture in the Titan didn't aerosolize the hypergolics.  The socket punctures the skin of the stage (Titan II was a balloon).  The hypergolic poured out of the stage for some time (there were, IIRC, two attempts to enter the silo and stop the leakage).  The hypergolics ended up pooling in the bottom of the silo and when the stage lost structure due to loss of pressure, the collapse burst the other hypergolic tank and you had a explosive mix in the bottom of the silo - essentially a cannon shot that blew the blast doors off the silo and the warhead quite some distance away.

Reference - Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety, Eric Schlosser

Edit: misspelling

We were both close on this one - Here is the text from Titan II, A History of  Cold War Missile Program, David K. Stumpf:
"As he swing it up into operating position, the 8.75-pound socket separated from the ratchet at waist-high level, fell onto the Level 2 platform, bounced once onto the rubber boot between the platform edge and the missile airframe, and before either technician could grab it, pushed through the boot, and fell approximately 80 feet.  The socket hit on the thrust mount ring, then bounced upward and toward the missile, puncturing the Stage I fuel tank skin.  Both technicians watched as a stream of white liquid poured out of the missile.  There was now quite obviously a fuel leak in Stage I.  In 35 to 40 seconds, a noticable could of Aerozine 50 vapor had reached Level 5 of the launch duct, approximately 30 feet below them."
...
"Most Probable Explosion Scenario
...
The fuel sprayed out of the tank due to normal tank pressure, vaporizing rapidly.  Decomposition and oxidization of the Aerozine 50 was accelerated by contaminants, metallic oxides, and acoustical batting on the launch duct wall, which had a large surface area that promoted catalytic degradation, probably resulting in numerous small fires.  These events heated the launch duct, causing pressure increases in the other three missile propellant tanks. ... Fuel vapor concentrations reached explosive levels in the launch duct. ... Numerous electrical motors and other potential ignition sources were present in the silo equipment area.  Ignition was probably electrical and a vapor fire propagated into the launch duct, resulting in an explosion as the fuel vapors ignited.  The explosion and resulting overpressure ruptured the Stage I oxidizer aft dome, dumping the oxidizer into the ruptured Stage I fuel tank.  The resulting hypergolic reaction generated the major in-silo explosion."

Original reference cited by Stumpf is "Investigation of Scenarios and Sequence of Events for the Titan II Complex 374-7Explosion", Report of Missile Accident Investigation: Major Missile Accident, 18 and 19 September 1980, of Titan II Complex 374-7, AFHRA, Maxwell AFB, Alabama

This obviously isn't the exact same scenario as the SpaceX situation but my only point is that a small skin puncture can create an vapor cloud.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 01:51 am

This obviously isn't the exact same scenario as the SpaceX situation but my only point is that a small skin puncture can create an vapor cloud.

Still not applicable analogy.  RP-1 doesn't form a vapor cloud
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 02:06 am
  Of course if the "frost" is a continuous layer of glassy ice, the outside of it will be at 273 K (for the reason above), and you'd be right, LOX condensation couldn't happen

And it doesn't, that is the reality.  There have been past missions with higher and lower humidity.

If one of these bits of organic matter does act as an initiator and ignite with the LOX,

And this fails.    The organic matter is the fuel, there still has to be initiator to cause ignition.  Just sitting there does not make it burn.  Thumb prints only burned when impacted
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GerryB on 09/16/2016 04:26 am
I found an interesting Air Force Propulsion Laboratory document (http://dtic.mil/dtic/tr/fulltext/u2/665121.pdf) describing the fire, detonation, and autoignition criteria of various hydraulic fluid mists, including dependency on GOX concentration. Page 55 shows an especially interesting graph. Mineral oil mists (the most common hydraulic fluid) are very flammable at oxygen partial pressures > 0.3 atm, but the autoignition temperatures are off the bottom of the graph and it's not possible to extrapolate whether it could spontaneously ignite or still need an initiator.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: dror on 09/16/2016 04:48 am

This obviously isn't the exact same scenario as the SpaceX situation but my only point is that a small skin puncture can create an vapor cloud.

Still not applicable analogy.  RP-1 doesn't form a vapor cloud

But can it create an aerosol cloud ?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CameronD on 09/16/2016 05:10 am

This obviously isn't the exact same scenario as the SpaceX situation but my only point is that a small skin puncture can create an vapor cloud.

Still not applicable analogy.  RP-1 doesn't form a vapor cloud

But can it create an aerosol cloud ?

From a small leak under high pressure, it certainly can.. and if the release rates happen to be higher than ~10m/s, the possibility of the cloud/spray being ignited through static discharge to any surrounding conductive surface not at the same potential is high enough that if it happened on an industrial site, you'd run first and ask for help later...

The issue here though is that RP-1 fuelling was complete already.

 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GoferThrottleUp on 09/16/2016 05:58 am
I found an interesting Air Force Propulsion Laboratory document (http://dtic.mil/dtic/tr/fulltext/u2/665121.pdf) describing the fire, detonation, and autoignition criteria of various hydraulic fluid mists, including dependency on GOX concentration. Page 55 shows an especially interesting graph. Mineral oil mists (the most common hydraulic fluid) are very flammable at oxygen partial pressures > 0.3 atm, but the autoignition temperatures are off the bottom of the graph and it's not possible to extrapolate whether it could spontaneously ignite or still need an initiator.

Hi there, another newbie. Also see this somewhat dated investigation into how flame-resistant hydraulic fluid can ignite.

http://www.fire.tc.faa.gov/pdf/tn90-19.pdf

I have to admit that in every failure scenario discussed so far in this thread, there seems to be an equal number of 'for' and 'against' opinions; some more authoritive than others. All I can say is I am firmly on the 'its not the vehicle' side merely because I want it to be so.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/16/2016 07:11 am
I would propose setting up a shared google doc, wiki or similar colaboration page so we could collect together each theory , why they would be plausible, and what speaks against them. Reading back in this thread is becoming increasingly unfeasible, especially as arguments pop up repeatedly and you try to find a previous answer in the hundreds of pages. We had some real gemstones of posts but you need to dig deeply.
As it gets harder to keep oversight were running in circles
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: moralec on 09/16/2016 08:26 am
I would propose setting up a shared google doc, wiki or similar colaboration page so we could collect together each theory , why they would be plausible, and what speaks against them. Reading back in this thread is becoming increasingly unfeasible, especially as arguments pop up repeatedly and you try to find a previous answer in the hundreds of pages. We had some real gemstones of posts but you need to dig deeply.
As it gets harder to keep oversight were running in circles

If the issue is this thread being unmanageable, it's better to have stand alone threads for specific hypothesis (those that are getting a lot of traction and serious numeric analysis) . Chris should be the judge to that.

We did the wiki thing for the CRS-3 video analysis and worked very well  to coordinate that task. We were however,  a small number of contributors. For something more ambitious it's going to requiere a lot of housekeeping.


Sent from my iPhone using Tapatalk
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Pasander on 09/16/2016 10:25 am
Elon may call this a fast fire, but, IMHO an event that obliterates a 35 X 85 foot area in 16 milliseconds, which is my best estimate,  to me is defined as a detonation (others disagree)

Well, I agree with you. As per my first ever post I still think most likely scenario is that a RP-1+LOX detonation happened somewhere outside but near the vehicle.

My credentials for saying this may be a bit weak, but I consider myself a somewhat proficient amateur pyrotechnician and earlier in my life I made my own detonating explosives, even synthesizing the primary explosives for my own DIY electric igniters. And I blew up things A LOT!

The first apparent event on the USLR video seems pretty darn sudden and energetic to be anything else than a detonation of a mixture of RP-1 and LOX. By Occam's Razor it seems the most likely explanation. There's RP-1, there's LOX, and whatever caused them to mix in the first place is also a plausible ignition source. We also know mixtures of LOX and hydrocarbons are detonable, and AFAIK they can undergo deflagaration to detonation transition.

Now, I'm just waiting for SpaceX to release their investigation report to see if I'm right!  ;)

PS. I'm quite sure SpaceX knows by now WHAT happened. They may not know exactly WHY it happened..
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/16/2016 11:14 am
PS. I'm quite sure SpaceX knows by now WHAT happened. They may not know exactly WHY it happened..

Last information from Shotwell was, that they didn't even know, whether it was the F9 or something else. This was on 09/13.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/16/2016 11:36 am
Quote
Quote
Even the smallest amount of water-ice frost will prevent LOx condensation, even ignoring the heat of condensation of that frost.

This isn't true if O2 can diffuse in through the frost.  Of course if the "frost" is a continuous layer of glassy ice, the outside of it will be at 273 K (for the reason above), and you'd be right, LOX condensation couldn't happen (and you'd have to knock or scrape the ice off to expose a sub-77 surface to the air).  But the frost that forms on cryo equipment is not glassy flawless ice.  It's more like compacted dry snow, and is very far from airtight.

More to the point, it's worse than that.  Air liquefaction means cryopumping; it creates a partial vacuum, drawing in more air to replace it.  It literally sucks air up to the cold surface, through whatever may be in the way.  Not only putting air back in contact with the cold surface, but also ruining the insulator's R value.

A low porosity/high density ice (which will eventually form) could prevent cryopumping.  But not only does it take time to form, but it's also not a good insulator.

With LH, air usually liquefies fast enough to wash off the frost.  But at densified LOX temperatures?  Beats me.  How many experts do you think there are in the world on the behavior of air at the surface of uninsulated tanks of densified LOX?  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/16/2016 12:52 pm

Are you still using video sourced from YouTube? Wouldn't it have been transcoded at least one additional time after the camera's initial encoding, with unknown settings?
Add in the fact that there is only one source in the public domain, and it gets much more difficult to extract anything with confidence (ie, are you seeing a deceptive lighting effect that, while not an artifact, wouldn't show up from a different angle)

sigh

You are sighing because you've already answered this multiple times, or because it's an exceedingly stupid question? I've generally kept up with the thread from the beginning, but when it grows 5 pages in the course of an evening out, it's impossible to keep up with everything.
Please help me out with a pointer. I've searched and not found it.

I'm sorry, it's been a long week.  I apologize if that was interpreted in a demeaning way. 

Absolutely the video was transcoded too many ways, from the CCD, to the ADC, to the MPEG DSP, to the actual recording, and then from the actual recording to youtube.  Lord knows how many bits flipped along the way, plus if it was a CPD instead of a CCD things would have been even stranger.

Yes, you're absolutely right that the image content on the youtube video is like, difficult.

As for extracting things with confidence, in spite of all of that butchering of the raw data, the techniques I and others have applied actually can find a degree of real content in the video.  Unfortunately, any video analysis that relies on the value of a single pixel, or in this case, a range of 16x16 pixels, is suspect.

The astrophotography techniques after atmospheric correction techniques are supposed to bring us to the diffraction limit of the lens, but in a recent video posted here, which is as good as it gets, we're still on the order of 1 pixel +- 6.

That's really bad.  Kinda like we have about 3 foot resolution when we think we see 6 inch resolution. 

The sigh was based on the fact that I know exactly what I'm dealing with, and you only identified a small subset of the problems, which are sadly, 1/3 of the ones I'm trying to deal with in my processing models. 

I apologize for my brief comment.  Yours was valid, and I was sighing because it's not only valid, but you missed some of the issues as well.

The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.
Good effort, your earned a break while we all wait! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/16/2016 01:02 pm
  Of course if the "frost" is a continuous layer of glassy ice, the outside of it will be at 273 K (for the reason above), and you'd be right, LOX condensation couldn't happen

And it doesn't, that is the reality.  There have been past missions with higher and lower humidity.

If one of these bits of organic matter does act as an initiator and ignite with the LOX,

And this fails.    The organic matter is the fuel, there still has to be initiator to cause ignition.  Just sitting there does not make it burn.  Thumb prints only burned when impacted

Don't these two points work against each other?  Granted, the initiating events may be very rare.    But Murphy's Law guarantees that one will show up eventually.  If your rocket is in a state where an impact on a thumbprint will blow it up, it will blow up some day.

This is why I don't think your first point is sound.  The fact that they haven't blown up before may have been just good luck, the absence of an initiator.  For all we know, they may all have had LOX-frost and organic matter - how would we see that from outside? And would it show up in telemetry?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herb Schaltegger on 09/16/2016 01:05 pm

This is why I don't think your first point is sound.  The fact that they haven't blown up before may have been just good luck, the absence of an initiator.  For all we know, they may all have had LOX-frost and organic matter - how would we see that from outside? And would it show up in telemetry?


Seriously? All you folks hanging your hats on "LOX frost" need to get a grip on reality. Even rocket is touched by technicians during servicing and close-out, they have bugs land on them, birds poop on them, they fly through clouds of insects on ascent ... This is simply not a serious issue.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Pasander on 09/16/2016 01:11 pm
PS. I'm quite sure SpaceX knows by now WHAT happened. They may not know exactly WHY it happened..

Last information from Shotwell was, that they didn't even know, whether it was the F9 or something else. This was on 09/13.

But she said this incident doesn't affect the insurance rates for F9 launches. Maybe I'm jumping to conclusions but I think that means there's nothing wrong with the launch vehicle. (Also, the "anomaly" didn't really seem to initiate from within the rocket.)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/16/2016 01:20 pm
...
The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.

USLaunchReport accepts support over at their youtube channel. I made a donation along with a request to share the original video recording with the NSF community.

If the original video file would be useful, I suggest a concerted effort by NSF members to provide support to them and echo the request for the video.

The youtube channel is here: https://www.youtube.com/channel/UC5hWqb0u1eKgYmVryCEyJYA/featured
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/16/2016 01:42 pm
Here's a picture for review.

Steps:
  1.  removal of atmospheric turbulence
  2.  stacking 60 frames in the last second before the event
  3.  stacking 60 frames in the second before
  4.  subtracting the frames to get a difference frame
  5.  examination of any pixels that are way outside the distribution of the difference histogram

There is one pixel in this sequence that passes the above.

It's probably noise, and it is smaller by at least a factor of 3 than the theoretical best resolution of the camera after having massaged all the bits.

It's probably totally irrelevant, but, here it is, for what it's worth.

Blue line pointing to red dot.

Followed by the histogram showing where it is on the histogram.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/16/2016 01:43 pm
...
The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.

USLaunchReport accepts support over at their youtube channel. I made a donation along with a request to share the original video recording with the NSF community.

If the original video file would be useful, I suggest a concerted effort by NSF members to provide support to them and echo the request for the video.

The youtube channel is here: https://www.youtube.com/channel/UC5hWqb0u1eKgYmVryCEyJYA/featured
It's great that you did that, but I recall Chris saying something about organizing something through NSF membership. Perhaps he can update us! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/16/2016 01:54 pm
...
The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.

USLaunchReport accepts support over at their youtube channel. I made a donation along with a request to share the original video recording with the NSF community.

If the original video file would be useful, I suggest a concerted effort by NSF members to provide support to them and echo the request for the video.

The youtube channel is here: https://www.youtube.com/channel/UC5hWqb0u1eKgYmVryCEyJYA/featured
It's great that you did that, but I recall Chris saying something about organizing something through NSF membership. Perhaps he can update us! :)

I got tired of waiting around for Chris 8) Plus they are worth supporting anyway, they do a great job with getting videos that nobody else publishes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/16/2016 01:55 pm
PS. I'm quite sure SpaceX knows by now WHAT happened. They may not know exactly WHY it happened..

Last information from Shotwell was, that they didn't even know, whether it was the F9 or something else. This was on 09/13.

But she said this incident doesn't affect the insurance rates for F9 launches. Maybe I'm jumping to conclusions but I think that means there's nothing wrong with the launch vehicle. (Also, the "anomaly" didn't really seem to initiate from within the rocket.)
I think "not affecting the rates" is just a combination of two things: 1) the failure rate still matches the insurance companies' internal estimate of falcon failure rates---which may be higher than spacex thinks it should be, but the insurance adjusters are saying they've done a good job, and 2) the launch insurance didn't actually pay out on this incident---reports are that the "marine transport insurance" was on the hook, since the cargo hadn't "launched" yet.

Further, future marine transport insurance contracts might be more carefully worded to exclude coverage of static fire.  Although the base rates of neither the marine transport insurance nor the launch insurance would increase, you'd then need to purchase a separate "static fire insurance" (or rider) if you wanted to attach payload for the static fire, and that *would* cost extra.

I don't think anyone was implying that the cause was known, especially at the early point at which the statement was made.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/16/2016 02:03 pm
So, for flex induced by vortex shedding from the fairing to be a significant issue, here are some of the pre-conditions:

1. The payload and fairing are attached.
2. The wind speed is 9.8m/s.
3. The grabber is closed.
4. The fuel load is such that the natural frequency matches the shedding forces.
5. The position of the grabbers matches the node of the mode shape.
6. The cradle (and hence the lower pad) is fixed in position by the grabber and the pin joint on the strongback, which is vastly stiffer and stronger than the rocket.

That's a long (and therefore unlikely) set of preconditions!  Further, if the rocket is *designed to flex* (as Jim has stated), the result is still: nothing.  A bit of a sway, observable on telemetry.

So, for the fairing, shedding leads to forces oscillating at 0.177 and 0.354 Hz.
[...]
If all of the conditions were met, the onset of a significant flex could be quite sudden, and may not register on accelerometers as anything other than a step function at the same time as the start of the fast fire.
By your own math, it would take *at least* three seconds to reach maximum deflection.  That's order of magnitudes slower than the event is seen to develop, and would be incredibly obvious from the accelerometer data on the stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/16/2016 02:03 pm


Seriously? All you folks hanging your hats on "LOX frost" need to get a grip on reality. Even rocket is touched by technicians during servicing and close-out, they have bugs land on them, birds poop on them, they fly through clouds of insects on ascent ... This is simply not a serious issue.

Yes, seriously. There may be only be about eight (4 static fires, 4 launches) where this combination of heavy payload, somewhat modified TEL and sub-cooled oxygen have come together in this configuration.  Or about 14 if you count all F9-FT campaigns. We have a seriously fast initiating event that MAY require highly unlikely preconditions. It's either unanticipated vehicle interactions with rapidly changing states of being (can't think of a word for this) or something more like CRS-7 where a part or parts was sub-specification even with all the inspections and prior testing.
Is there another option?


 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/16/2016 02:08 pm

This is why I don't think your first point is sound.  The fact that they haven't blown up before may have been just good luck, the absence of an initiator.  For all we know, they may all have had LOX-frost and organic matter - how would we see that from outside? And would it show up in telemetry?


Seriously? All you folks hanging your hats on "LOX frost" need to get a grip on reality. Even rocket is touched by technicians during servicing and close-out, they have bugs land on them, birds poop on them, they fly through clouds of insects on ascent ... This is simply not a serious issue.

So we're agreed that all rockets have miscellaneous organic matter on their outside paintwork. It just never mattered before, because no rocket before F9 FT ever subcooled below 77 K.

Since we agree that the organic matter is a certainty, I'll amend my last sentence to:
"For all we know, they may all have had LOX-frost - how would we see that from outside? And would it show up in telemetry?"
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/16/2016 02:12 pm
Is there another option?

A plumbing failure in the high pressure helium supply, as Herb and Jim have been repeatedly suggesting.

Folks with far fetched theories need to judge them by that bar.  Your theory needs to be at least as likely than "a helium line fractured and sent a high energy fragment through the stage".

Now, that's not to say that theory is certain, and it would take a lot of work to *prove* exactly what happened to the satisfaction of the FAA, customers, NASA, etc.  But IMNSHO that theory should be the "reasonableness" threshold by which other theories are judged.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: whitelancer64 on 09/16/2016 02:29 pm


Is there another option?

A plumbing failure in the high pressure helium supply, as Herb and Jim have been repeatedly suggesting.

Folks with far fetched theories need to judge them by that bar.  Your theory needs to be likely than, "a helium line fractured and sent a high energy fragment through the stage".

Now, that's not to say that theory is certain, and it would take a lot of work to *prove* exactly what happened to the satisfaction of the FAA, customers, NASA, etc.  But IMNSHO that theory should be the "reasonableness" threshold by which other theories are judged.

Trouble is, a helium line break should show up clearly in telemetry. Even if the cause of the break is much more tricky to figure out, the fact of the break initiating the failure should be broadly evident, not something Elon Musk would describe as "the most difficult and complex failure we have ever had in 14 years."

So the cause should be something "difficult and complex." It follows from what we know this isn't something relatively straightforward.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rei on 09/16/2016 02:31 pm
"For all we know, they may all have had LOX-frost - how would we see that from outside?

How good are you at seeing half-centimeter droplets of a nearly transparent liquid in blurry zoomed-in video footage behind clouds of fog?  ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/16/2016 02:43 pm


Is there another option?

A plumbing failure in the high pressure helium supply, as Herb and Jim have been repeatedly suggesting.

Folks with far fetched theories need to judge them by that bar.  Your theory needs to be likely than, "a helium line fractured and sent a high energy fragment through the stage".

Now, that's not to say that theory is certain, and it would take a lot of work to *prove* exactly what happened to the satisfaction of the FAA, customers, NASA, etc.  But IMNSHO that theory should be the "reasonableness" threshold by which other theories are judged.

Trouble is, a helium line break should show up clearly in telemetry. Even if the cause of the break is much more tricky to figure out, the fact of the break initiating the failure should be broadly evident, not something Elon Musk would describe as "the most difficult and complex failure we have ever had in 14 years."

So the cause should be something "difficult and complex." It follows from what we know this isn't something relatively straightforward.
No.  This search for unicorns is maddening.

There may well have been a drop in He pressures visible on telemetry.  It would still involve a lot of work to figure out whether this was the *root cause* or just a consequence of some other failure.  Herb has also indicated that the rumor is that some GSE-related telemetry was lost in the subsequent fire, which could also complicate the investigation.

Don't confuse "hard to prove" with "extremely unlikely chain of events".

The cause may in the end be extremely simple---as was the CRS-7 fault ("a weak strut").  In the CRS-7 case it still took them weeks to test thousands of other struts before they could reproduce the failure to their satisfaction. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/16/2016 02:44 pm
Trouble is, a helium line break should show up clearly in telemetry. Even if the cause of the break is much more tricky to figure out, the fact of the break initiating the failure should be broadly evident, not something Elon Musk would describe as "the most difficult and complex failure we have ever had in 14 years."

We don't really know how much SpaceX knows at the moment. When Elon says "most difficult and complex failure", he may be talking about the root cause, while the proximal cause is already known.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 03:05 pm

So we're agreed that all rockets have miscellaneous organic matter on their outside paintwork. It just never mattered before, because no rocket before F9 FT ever subcooled below 77 K.

And it still doesn't matter.  No, rocket has outside surfaces below 77k.  The numbers provided here are not verified.


"For all we know, they may all have had LOX-frost - how would we see that from outside?

With a camera, and that is why it is not the reason.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/16/2016 03:16 pm
Now that's interesting.  The trajectory of one of the debris passes right through the object containing the delta pixel identified on my previous post.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: SLC on 09/16/2016 03:19 pm
Is there another option?

A plumbing failure in the high pressure helium supply, as Herb and Jim have been repeatedly suggesting.

Folks with far fetched theories need to judge them by that bar.  Your theory needs to be at least as likely than "a helium line fractured and sent a high energy fragment through the stage".

Now, that's not to say that theory is certain, and it would take a lot of work to *prove* exactly what happened to the satisfaction of the FAA, customers, NASA, etc.  But IMNSHO that theory should be the "reasonableness" threshold by which other theories are judged.

So if we use the high-pressure helium fracture theory as a benchmark ... here are some background considerations which might be relevant:

1)  This was a most unusual incident.  Nothing like it in 50 years, in any other rocket.  What's new about the F9 FT design?  LOX subcooled  below 77 K.

2)  Out of all the places  where an "anomaly" might occur, this one appeared "around" a subcooled oxygen tank.  And judging from the video, on the upwind side (where I think frost would be thicker, and therefore the underlying paint surface better insulated and so colder).

3)  The point in the countdown at which the anomaly happened.  This is really puzzling - the rocket was hardly doing anything, just filling and cooling.  Almost all the mechanical parts were under much less than their design stresses.  This points to the cause being something to do with cooling, not mechanical stress.  And something that would quietly and invisibly build up a stock of energy somewhere it shouldn't have been (the chemical energy of the condensed LOX a paint-thickness away from the the Al).

4)  Why on this particular test?  This is admittedly a very speculative point, but were SpaceX experimenting with the filling and cooling procedure and timings?  If they were, the frost layer could have been different from usual in some way.

On the other hand, isn't helium plumbing quite well understood and reliable in general?  Matching the previous  points:

1)  Innovation.  Is the helium plumbing on F9 FT very different from other rockets?

2)  Location of anomaly - OK, I concede the helium is where the LOX is. 

3)  Point in countdown.  Surely the He system was not particularly stressed at the time?

4)  (Speculative)  Were SpaceX doing anything unusual with the He pressurization that day?

None of these considerations are very decisive.  But they do shade the probabilities.  The main argument has to be in the calculations, which just upthread I've tried to provide for LOX-frost.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 03:25 pm

This was a most unusual incident.  Nothing like it in 50 years, in any other rocket.  What's new about the F9 FT design?  LOX subcooled  below 77 K.


There is a lot more.

Longer tanks
more instrumentation for the subcooled LOX
I think there was some rework done with all gas systems (not just He) due to CRS-7
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/16/2016 03:31 pm
On the other hand, isn't helium plumbing quite well understood and reliable in general?

It's worth noting here that if this is a helium issue, it wouldn't be the first one for SpaceX, and NASA wasn't entirely satisfied with their investigation of the previous COPV failure on CRS-7. This wouldn't be that unprecedented. That's why I think it's the best current theory. It explains why there was no visible ignition on the tapes, explains the location, and has precedent within this launch vehicle's own history.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 03:38 pm

1.  The footage that "we" have.  Since SLC asked about how would "we" see it.  If you have something that's not blurry and zoomed in that you can share with the forum, I'm sure it would be greatly appreciated  :)

2. Indeed it was - visible for miles and miles away.

3.  I don't think people seeing a massive fireball erupt is in doubt here.  You seem to be positing a slow burn triggering a far larger one.  Is LOX famous for slow burns?


1.  Look at past missions
2.  Wrong, That wasn't the ignition source.  I am talking about the impact or energy that started the fingerprint or bird crap on fire. That event would be seen.
3.  No that is the secondary effect.  the flash from the fingerprint or bird crap on fire, would be seen before the stage erupted.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jpo234 on 09/16/2016 03:38 pm
On the other hand, isn't helium plumbing quite well understood and reliable in general?

It's worth noting here that if this is a helium issue, it wouldn't be the first one for SpaceX, and NASA wasn't entirely satisfied with their investigation of the previous COPV failure on CRS-7. This wouldn't be that unprecedented. That's why I think it's the best current theory. It explains why there was no visible ignition on the tapes, explains the location, and has precedent within this launch vehicle's own history.

Gwynne Shotwell said: "We still haven't isolated the cause or whether its origin was rocket or ground."
I just can't believe that a failure in the helium system (COPV or pipes) would be so hard to find. Not the root cause, just "This thingamajig blew up." or even "Something blew up inside the vehicle".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/16/2016 03:41 pm
Does anyone know the routing of the helium load lines from the umbilical connector to the COPVs? Do they run up the outside of the fuel and LOX tanks, then enter the LOX tank near the COPVs? Or do they run through the LOX center feed line through the fuel tank?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/16/2016 03:45 pm
Gwynne Shotwell said: "We still haven't isolated the cause or whether its origin was rocket or ground."
I just can't believe that a failure in the helium system (COPV or pipes) would be so hard to find. Not the root cause, just "This thingamajig blew up." or even "Something blew up inside the vehicle".

See my earlier post: Shotwell and Elon may be talking about a root cause, whereas they are being interpreted as talking about a proximal cause. For all we know they could already be aware of an overpressurization event in the LOX tank caused by a helium tank or line rupture, and are instead currently having a difficult time a root cause that led to the helium system failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Herbie on 09/16/2016 03:55 pm
Does anyone know the routing of the helium load lines from the umbilical connector to the COPVs? Do they run up the outside of the fuel and LOX tanks, then enter the LOX tank near the COPVs? Or do they run through the LOX center feed line through the fuel tank?

How is telemetry routed? Does it fail over to wireless transmission if the hard connection is lost?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/16/2016 04:24 pm
One major difference between LH2 stages and the F9 second stage is just how long the highly cryogenic propellant is in the tank, giving it time to cool its surroundings. See below the timeline entries for LH2 loading of Centaur/DCSS courtesy of Spaceflight 101

01:50   Centaur LH2 Loading
01:45:00   DCSS LH2 Topping

Centaur begins loading an hour and 50 minutes before launch, DCSS is already nearly finished at 1 hour 45 minutes before launch. See Falcon below

T-0:19:30   Stage 2 Liquid Oxygen Loading
T-0:02:05   Stage 2 LOX at Flight Level

From the first drop of LOX to fueling complete is only 17 minutes. In order for LOX condensation to be the issue a roughly half-filled LOX tank had to have chilled the outside below 77k in less than 12 minutes (19:30 start of fueling, ~8 min anomaly).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Mike_1179 on 09/16/2016 04:30 pm
Does the LOX for engine chill-down come from the LOX tank or is it supplied directly from GSE?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moderas on 09/16/2016 04:38 pm
Does the LOX for engine chill-down come from the LOX tank or is it supplied directly from GSE?

I don't have a source so I can't say 100%, but MVac chills in flight using on board LOX so it seems to me it would be unnecessary complication to have extra plumbing for a GSE supported chill before launch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: robert_d on 09/16/2016 04:40 pm

I would like to plead, that these frost theories be kept, but not here, instead in the wacky theory thread.

Up to the mods, of course, but until then ** NO **

There is enough credible evidence including sub-cooled LOX, and the exterior flash. And the likelihood that any interior cause would be in the telemetry.
Some plausible math and history of Hydrogen stages.
There is NO evidence that every inch of the vehicle is even monitored full time. They might have cameras switch angles occasionally looking at this position because NOTHING EVER HAPPENS HERE.

To Jim's point -  Damaging foam was not a "real thing" IN PEOPLES MINDS until it was. LOX infused frost may not be a real thing IN PEOPLES MINDS right now. Proof Later? Likely not. But to be so dismissive?
Relax.
 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacekid on 09/16/2016 04:57 pm
Now that's interesting.  The trajectory of one of the debris passes right through the object containing the delta pixel identified on my previous post.
Do you know the time between when the pixel change occurred and when the object was at that point?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 05:05 pm

To Jim's point -  Damaging foam was not a "real thing" IN PEOPLES MINDS until it was. LOX infused frost may not be a real thing IN PEOPLES MINDS right now. Proof Later? Likely not. But to be so dismissive?
Relax.
 

Wrong, there is no correlation with Columbia foam and nonexistent LOX.  There was evidence ignored in Columbia.  There is no such evidence in this case.

LOX infused frost has just as much evidence as lone gunman, a small ordnance device, and many other things.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rsdavis9 on 09/16/2016 05:05 pm
I cant find the post right now but it said helium line rupture fits the location.
I can't see how an external helium line fits the location of the event.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/16/2016 05:13 pm
Now that's interesting.  The trajectory of one of the debris passes right through the object containing the delta pixel identified on my previous post.
Do you know the time between when the pixel change occurred and when the object was at that point?

With this technique, the pixel change occurred during the last second prior to Frame1.  Frame1 being defined as the first image of the event, in the USLR video, at 1.11.755 

The object first appears  at 1.11.788, 33 miliseconds later
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: whitelancer64 on 09/16/2016 05:15 pm

To Jim's point -  Damaging foam was not a "real thing" IN PEOPLES MINDS until it was. LOX infused frost may not be a real thing IN PEOPLES MINDS right now. Proof Later? Likely not. But to be so dismissive?
Relax.
 

Wrong, there is no correlation with Columbia foam and nonexistent LOX.  There was evidence ignored in Columbia.  There is no such evidence in this case.

LOX infused frost has just as much evidence as lone gunman, a small ordnance device, and many other things.

Yet you seem unable to refute it. Where's your calculations that show LOX buildup cannot occur?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DMeader on 09/16/2016 05:23 pm
This "LOX-soaked frost" thing seriously needs to either go to the "wacky theories" thread or go away altogether. To the best of my knowledge it has never been observed to happen. Continuing with it is doing nothing beyond muddying the waters here.

Considering the clouds of venting GOX swirling around the vehicle, I'd submit that is as oxygen-rich an environment as would be needed granted a source of fuel and ignition.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RonM on 09/16/2016 05:23 pm

To Jim's point -  Damaging foam was not a "real thing" IN PEOPLES MINDS until it was. LOX infused frost may not be a real thing IN PEOPLES MINDS right now. Proof Later? Likely not. But to be so dismissive?
Relax.
 

Wrong, there is no correlation with Columbia foam and nonexistent LOX.  There was evidence ignored in Columbia.  There is no such evidence in this case.

LOX infused frost has just as much evidence as lone gunman, a small ordnance device, and many other things.

Yet you seem unable to refute it. Where's your calculations that show LOX buildup cannot occur?

You got that backwards. Where is the proof that LOX buildup did occur.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/16/2016 05:25 pm
...
The simple fact is, that video is all we have, and it sucks, and it takes a lot of work to jam every possible bit back to where it belongs, and that, sigh, will never happen with that video.

USLaunchReport accepts support over at their youtube channel. I made a donation along with a request to share the original video recording with the NSF community.

If the original video file would be useful, I suggest a concerted effort by NSF members to provide support to them and echo the request for the video.

The youtube channel is here: https://www.youtube.com/channel/UC5hWqb0u1eKgYmVryCEyJYA/featured
It's great that you did that, but I recall Chris saying something about organizing something through NSF membership. Perhaps he can update us! :)

I got tired of waiting around for Chris 8) Plus they are worth supporting anyway, they do a great job with getting videos that nobody else publishes.

My bad, been way too busy. If someone makes the approach and gets a response out of them, make the offer on behalf of NSF, a good link to donate towards and let me know via PM. I'll start a thread. If they can offer a better file, great. If not, no problem, the original point was thanks to them actually filming static fires etc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/16/2016 05:27 pm
I cant find the post right now but it said helium line rupture fits the location.
I can't see how an external helium line fits the location of the event.

As far as I'm aware, the only hypothesis that's been floated in here is an internal helium rupture. Then again, this thread's getting rather long so it's a bit hard to keep track of things anymore.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Chris Bergin on 09/16/2016 05:52 pm
LOX frosty stuff moved to the wild thread. Sorry, but that one was going around in circles and annoying folk (per the report to mods, etc).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:03 pm
One last thought on the rocket swaying or vibrating theory.  The more I think about it, the less I like this idea anyway.  But with that being said the logic used here to shoot it down was that accelerometers would have seen it, and SpaceX would have said so.  And that rockets flex, and are designed to do so, etc.  Yes, clearly.  So the sway/vibration was seen, SpaceX though it was within tolerance (maybe on the high side, maybe not) so it doesn't raise any flags.  But what if their tolerances were dead wrong.  Or what if tolerances stacked up in such a way between the TEL and Rocket, or something that was supposed to move or vice versa unexpectedly failed, such that "normal/acceptable" movements now became an issue?
 

It would be visible in pad videos.  Did you see the onboard camera view of the rocket flexing?  The flex was on the order of feet and not inches and the vehicle skin crinkled and uncrinkled.

Ever heard of the term rate gyro package on launch vehicles?   Not those in the main guidance system but a package installed on the side of the booster (can't be interior because the location is usually on a prop tank).   What this package does is measure the attitude and rates of the vehicle at that location which the guidance system compares with its gyros at its location.   They are different because the vehicle flexes from wind and thrust vehicle control.  The guidance system uses this information to adjust the control gains, so that it doesn't chase its tail all over the sky.

Edited:

Additionally, the F9 has another guidance system for the first stage (don't know where it is located), so between the three groups of gyros, the motion of the vehicle would be pretty well known.  And the structural sensors would pick up any failures.  Same with the video.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 06:08 pm
One last thought on the rocket swaying or vibrating theory.  The more I think about it, the less I like this idea anyway.  But with that being said the logic used here to shoot it down was that accelerometers would have seen it, and SpaceX would have said so.  And that rockets flex, and are designed to do so, etc.  Yes, clearly.  So the sway/vibration was seen, SpaceX though it was within tolerance (maybe on the high side, maybe not) so it doesn't raise any flags.  But what if their tolerances were dead wrong.  Or what if tolerances stacked up in such a way between the TEL and Rocket, or something that was supposed to move or vice versa unexpectedly failed, such that "normal/acceptable" movements now became an issue?
 

It would be visible in pad videos.  Did you see the onboard camera view of the rocket flexing?  The flex was on the order of feet and not inches and the vehicle skin crinkled and uncrinkled.

Ever heard of the term rate gyro package on launch vehicles?   Not those in the main guidance system but a package installed on the side of the booster (can't be interior because the location is usually on a prop tank).   What this package does is measure the attitude and rates of the vehicle at that location which the guidance system compares with its gyros at its location.   They are different because the vehicle flexes from wind and thrust vehicle control.  The guidance system uses this information to adjust the control gains, so that it doesn't chase its tail all over the sky.

Yes, this is exactly my point.  SpaceX knows exactly how/where/when/how much the rocket moved.  Everything is within those tolerances.  What if their tolerances are wrong?

Upon your edit:
Wouldn't these same sensors (along with the He pressure gauges) also pick up a failure in the He system.  That triangulation is how they got their failure mode past time.  What failure would not have been picked up by these sensors and cameras?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:13 pm
What if their tolerances are wrong?

Did you see the flex video?
During the development of launch vehicles, there are structural tests that verify that the vehicle can take the loads it will see.  And one of the reasons for flight instrumentation is to make sure the loads are within limits.

Read the additional paragraph to the original post.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 06:21 pm
What if their tolerances are wrong?

Did you see the flex video?
During the development of launch vehicles, there are structural tests that verify that the vehicle can take the loads it will see.  And one of the reasons for flight instrumentation is to make sure the loads are within limits.

Read the additional paragraph to the original post.

Was that flex test done while a partial load of sub cooled LOX was being loaded in a strong wind?  By the way I have not seen any reports of the actual wind speed direction or speed or how that relates to past experience and launch/tanking go-no go conditions.  Apologies if I missed that.

I don't want to continually knock on you.  Clearly you know your stuff.

Could you please lay out your hypothesis (you have mentioned the He system multiple times) for this failure and please include why that would not come up in testing, or show up in telemetry.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:22 pm

Wouldn't these same sensors (along with the He pressure gauges) also pick up a failure in the He system. 

Structural failures have signatures and are not that quick.  Movement and strains can be seen before a failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 06:24 pm

Wouldn't these same sensors (along with the He pressure gauges) also pick up a failure in the He system. 

Structural failures have signatures and are not that quick.  Movement and strains can be seen before a failure.

Yes, clearly.  So why haven't they pin pointed the failure yet? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:31 pm

1.  Was that flex test done wile a partial load of sub cooled LOX was being loaded in a strong wind?  By the way I have not seen any reports of the actual wind speed direction or speed or how that relates to past experience and launch/tanking go-no go conditions.  Apologies if I missed that.

2.  Could you please lay out your hypothesis (you have mentioned the He system multiple times) for this failure and please include why that would not come up in testing, or show up in telemetry.

1.  It is not needed. 
a.  Vortex shedding  was shown to be  a low frequency for this vehicle.  Hence, the movement that would cause loads that would cause parts to fail would be visible many ways.
b.  The propellant level and temp have no bearing on the matter. 

2.  At the beginning, I just said it was likely related to some kind of pressure event.  Later I may have said even more likely in the helium system.  I am only going by the event and not providing a timeline. 

By the imagery available, it happen by the strong back and that is also where the stage wiring/tubing tunnel  and umbilical are located.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:32 pm

Wouldn't these same sensors (along with the He pressure gauges) also pick up a failure in the He system. 

Structural failures have signatures and are not that quick.  Movement and strains can be seen before a failure.

Yes, clearly.  So why haven't they pin pointed the failure yet? 
Bursts (which are not the same as structure failures) can happen faster
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 06:45 pm

1.  Was that flex test done wile a partial load of sub cooled LOX was being loaded in a strong wind?  By the way I have not seen any reports of the actual wind speed direction or speed or how that relates to past experience and launch/tanking go-no go conditions.  Apologies if I missed that.

2.  Could you please lay out your hypothesis (you have mentioned the He system multiple times) for this failure and please include why that would not come up in testing, or show up in telemetry.

1.  It is not needed. 
a.  Vortex shedding  was shown to be  a low frequency for this vehicle.  Hence, the movement that would cause loads that would cause parts to fail would be visible many ways.
b.  The propellant level and temp have no bearing on the matter. 

2.  At the beginning, I just said it was likely related to some kind of pressure event.  Later I may have said even more likely in the helium system.  I am only going by the event and not providing a timeline. 

By the imagery available, it happen by the strong back and that is also where the stage wiring/tubing tunnel  and umbilical are located.

So temperature and fluid/pressure damping/stiffinging have no effects on rockets?

What pressure event would not have been picked up by the rocket's telemetry?  And how would such a pressure event be catastrophic happening internal to a partially filled vessel?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/16/2016 06:48 pm
So temperature and fluid/pressure damping/stiffinging have no effects on rockets?

What pressure event would not have been picked up by the rocket's telemetry?  And how would such a pressure event be catastrophic happening internal to a partially filled vessel?

The problem with arguments like this is you have to justify why they only affect the Falcon 9 when they should otherwise be equal factors in literally dozens of other launch vehicles that have never experienced this kind of failure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 06:52 pm
So temperature and fluid/pressure damping/stiffinging have no effects on rockets?

What pressure event would not have been picked up by the rocket's telemetry?  And how would such a pressure event be catastrophic happening internal to a partially filled vessel?

The problem with arguments like this is you have to justify why they only affect the Falcon 9 when they should otherwise be equal factors in literally dozens of other launch vehicles that have never experienced this kind of failure.

They do affect everything.  But perhaps SpaceX missed an off nominal corner case in their analysis.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Toast on 09/16/2016 06:53 pm
What pressure event would not have been picked up by the rocket's telemetry?

Let's be clear: We don't know what has and has not been picked up by the rocket's telemetry. That's the biggest reason that a lot of these failure analysis threads end up with conclusions that miss the mark by a wide margin when the investigation results are released--we (obviously) don't have as much info as those inside the actual investigation. Based on Musk and Shotwell's statements, some people assume that there's no sign of pressure problems on the telemetry, but neither of them have ever said that.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:55 pm

So temperature and fluid/pressure damping/stiffinging have no effects on rockets?


Whether the vehicle is warm and empty or cold and full, the driving force is not going to change.   The vehicle response will be, where as it would flex more when it is warm and empty.  As the vehicle gains weight, the wind had less and less affect on the vehicle and hence less force.  The changes in material properties are bounded by the full and empty case.
Having a partially filled tank with cryogens doesn't mean one part is brittle and the other flexible.  There is no abrupt change in material properties between the upper and lower part of the tank

It isn't going to create a condition that overloads the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 06:56 pm

They do affect everything.  But perhaps SpaceX missed an off nominal corner case in their analysis.

There is no corner case here
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 06:59 pm
What pressure event would not have been picked up by the rocket's telemetry?

Let's be clear: We don't know what has and has not been picked up by the rocket's telemetry. That's the biggest reason that a lot of these failure analysis threads end up with conclusions that miss the mark by a wide margin when the investigation results are released--we (obviously) don't have as much info as those inside the actual investigation. Based on Musk and Shotwell's statements, some people assume that there's no sign of pressure problems on the telemetry, but neither of them have ever said that.

Ding ding ding, we have a winner...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 07:01 pm

They do affect everything.  But perhaps SpaceX missed an off nominal corner case in their analysis.

There is no corner case here

So there was no pad anomaly then, clearly.

I'm going to bow out now and just watch again for a while
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 07:14 pm

They do affect everything.  But perhaps SpaceX missed an off nominal corner case in their analysis.

There is no corner case here

So there was no pad anomaly then, clearly.

I'm going to bow out now and just watch again for a while

There are other corner cases in other places.

But explain how there can be a corner case in your example.  How is the vehicle's response to exterior forces is not enveloped by the prelaunch empty and full cases. And in-flight full and empty cases where the vehicle sees loads much greater than any prelaunch
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/16/2016 07:32 pm
Don't remember seeing this so far:

Ignition source:  S-Band telemetry and video antennas.  Small patch antennas (a few inches in diameter - a printed pattern on something like a circuit board) will be on the skin of the rocket near the avionics. 

IMO, at this point in countdown, S-Band transmitters should be powered up.  (Launch vehicle I know powered up S-Band transmitters about one hour before launch. 

Stage 2 has two S-Band transmitters of not insignificant power.  20Watt telemetry and 10 Watt video.
Our 30 watt transmitter required 145 watts of DC power.  RF power was enough to burn up RF relays if switched while power was on.  Personnel had to clear the area during transmitter operation unless antenna hoods were in place)  SpaceX transmitters are near microwave oven frequencies and it's pretty clear you can ignite something with a microwave oven ( oven 2460 MHz  -- Space X 2213.5 MHz and 2251.5 MHz).  Way back, I remember UHF power in the 10-50 watt range burning up circuit boards if you did something stupid.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: chuck34 on 09/16/2016 07:42 pm

They do affect everything.  But perhaps SpaceX missed an off nominal corner case in their analysis.

There is no corner case here

So there was no pad anomaly then, clearly.

I'm going to bow out now and just watch again for a while

There are other corner cases in other places.

But explain how there can be a corner case in your example.  How is the vehicle's response to exterior forces is not enveloped by the prelaunch empty and full cases. And in-flight full and empty cases where the vehicle sees loads much greater than any prelaunch

Lots of corner cases everywhere.  I'm not willing to throw any out.

Two glaring examples of differences between flight and pad operations.  A giant clamp a few meters above the apparent failure, and a support pad right at the apparent failure
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/16/2016 08:23 pm
What would happen if helium or nitrogen quick connect bursts in S2 quick connect plate? I found photo of S2's quick connect plate - looks like kerosene, LOX, helium, nitrogen and electric connections are next to each other - any debris could puncture these, create LOX/kerosene aerosol + provide ignition source. I know quick connect plates have been used for a long time and I am not aware of any previous incidents (except of hydrogen leaks in Space Shuttle), but it feels like a good root cause - used many times (potential for micro cracks), subjected to extreme environments.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 08:32 pm
Two glaring examples of differences between flight and pad operations.  A giant clamp a few meters above the apparent failure, and a support pad right at the apparent failure

Not so "glaring"

Those reduce the flexing and reduce loads. They protect the vehicle. They were added because of analysis and testing.   Delta IV doesn't have such a clamp.  Falcon 9 V1.0 didn't have a pad.  So they saw something in testing and analysis that says that vehicle needed them.  So you are saying they put them on the strong back without considerations for damage they can cause to the vehicle.  Like designing safety harness with spiked anchors to keep the harness from sliding off the user.

And again, any motion that would cause the pads or clamps to damage the vehicle would be seen.  There isn't going to be a steady force pushing on the vehicle into the pads.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jimvela on 09/16/2016 08:46 pm
OK, After staying well away form this thread I'll wander in with a question and a bit of discussion.

Question- Is the payload powered up at around the time in the hotfire when this event happened?

Background about the question:  One item that is unique for every launch of every rocket is the wire harnesses from S2 or fairing down the pad.  They are unique at each launch because the harnesses are destroyed on launch, and because each payload is different from the others.

On other launchers with payloads that I've worked, we check those harnesses out long before day of launch (and in fact do checks of those things way before we ever get to the pad). 

The flow with a F9 launch compresses those timelines greatly.  What happens if there was an undetected wiring error in those harnesses?  In my view this opens up a bunch of branches in the fault tree.   Aside from providing potential ignition sources close to the vehicle, an electrical fault in a J-box could take out other GSE systems and could explain loss of telemetry and perhaps even cause malfunctions in systems that could lead to an overpressure event...


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/16/2016 08:52 pm
OK, After staying well away form this thread I'll wander in with a question and a bit of discussion.

Question- Is the payload powered up at around the time in the hotfire when this event happened?

Background about the question:  One item that is unique for every launch of every rocket is the wire harnesses from S2 or fairing down the pad.  They are unique at each launch because the harnesses are destroyed on launch, and because each payload is different from the others.

On other launchers with payloads that I've worked, we check those harnesses out long before day of launch (and in fact do checks of those things way before we ever get to the pad). 

The flow with a F9 launch compresses those timelines greatly.  What happens if there was an undetected wiring error in those harnesses?  In my view this opens up a bunch of branches in the fault tree.   Aside from providing potential ignition sources close to the vehicle, an electrical fault in a J-box could take out other GSE systems and could explain loss of telemetry and perhaps even cause malfunctions in systems that could lead to an overpressure event...
I asked a similar question about the customer supplied harness and if that was the case in this test...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ww2planes1 on 09/16/2016 09:09 pm
Replying from my phone... Let's see if this comes out OK...

Question- Is the payload powered up at around the time in the hotfire when this event happened?

Probably.  They would likely have taken advantage of the time to run a countdown rehearsal in parallel.

The flow with a F9 launch compresses those timelines greatly.  What happens if there was an undetected wiring error in those harnesses?  In my view this opens up a bunch of branches in the fault tree.   Aside from providing potential ignition sources close to the vehicle, an electrical fault in a J-box could take out other GSE systems and could explain loss of telemetry and perhaps even cause malfunctions in systems that could lead to an overpressure event...

Those harnesses (for the payload) should be isolated from the rocket harness and would probably have been tested by the satellite manufacturer as part of an interface check.  I don't think those checks would take long, and even with the compressed schedule.  It's not something I would see the customer/manufacturer giving up.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: jimvela on 09/16/2016 09:28 pm
I asked a similar question about the customer supplied harness and if that was the case in this test...

The Catenary Quick Disconnect Jbox on that TE appears to me to be located right at the apparent point of ignition of the flash that initiated the event...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/16/2016 09:35 pm
I asked a similar question about the customer supplied harness and if that was the case in this test...

The Catenary Quick Disconnect Jbox on that TE appears to me to be located right at the apparent point of ignition of the flash that initiated the event...
Yes, that's what I posted at the time however; Jim stated that it is not where it appears in the Falcon users guide if I understood him correctly. So I left it there...
Post#2146
http://forum.nasaspaceflight.com/index.php?topic=30981.2140
Post#2173
http://forum.nasaspaceflight.com/index.php?topic=30981.2160
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: cscott on 09/16/2016 09:36 pm
Both the s band antennas and the payload junction box appear to be sources of ignition without associated fuel or oxider theories.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/16/2016 09:42 pm
OK, After staying well away form this thread I'll wander in with a question and a bit of discussion.

Question- Is the payload powered up at around the time in the hotfire when this event happened?

Background about the question:  One item that is unique for every launch of every rocket is the wire harnesses from S2 or fairing down the pad.  They are unique at each launch because the harnesses are destroyed on launch, and because each payload is different from the others.

On other launchers with payloads that I've worked, we check those harnesses out long before day of launch (and in fact do checks of those things way before we ever get to the pad). 

The flow with a F9 launch compresses those timelines greatly.  What happens if there was an undetected wiring error in those harnesses?  In my view this opens up a bunch of branches in the fault tree.   Aside from providing potential ignition sources close to the vehicle, an electrical fault in a J-box could take out other GSE systems and could explain loss of telemetry and perhaps even cause malfunctions in systems that could lead to an overpressure event...

I agree.  Lot of potential for problems.  I would bet on the spacecraft being powered up.  These unique cables that reside on the vehicle are probably checked out with some kind of one-time 'simulator' such as a patch board etc., not the real thing.  Spacecraft people will do their own checks before hooking up to make sure no gross problem, but this has to be kind of minimal.  It's been claimed here voltages are in the range of 28V, but I'm pretty sure this doesn't apply to the spacecraft where it may be over a hundred.

Whatever the SC GSE is doing will NOT be in SpaceX telemetry.  (IMO, but pretty sure.)
Edit:
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 09:52 pm
No, spacecraft are around 32 volts
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/16/2016 10:27 pm
No, spacecraft are around 32 volts
My memory is says different - for some spacecraft.  I think we even had to requalify some connectors.  I'm referring to large geo comm satellites.  I'll check my sources and get back.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/16/2016 10:38 pm
What would happen if helium or nitrogen quick connect bursts in S2 quick connect plate?

Well my last hypothetical required helium rupture because it has the highest PSI to play with.  My model said it had to be within 5 feet.  Your photo suggests it's less than 5 feet.  The pending issue on that hypothesis is there has to be RP1 remaining in the line, even if not under pressure.  My FAE model requires .4kg of RP1, more or less, which leads to the next question, how big is the RP1 line, and how many feet of line have to be converted to vapour to provide .4 kg of RP1?  Don't worry about the ignition source, Murphy provided.

:)

FWIW  have a new set of delta videos coming.  Not sure if they show squat or not. It's a stacking delta video, for those few who wander the halls of imaging entropy.  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: PDJennings on 09/16/2016 10:44 pm
No, spacecraft are around 32 volts
My memory is says different - for some spacecraft.  I think we even had to requalify some connectors.  I'm referring to large geo comm satellites.  I'll check my sources and get back.

Communications satellites can have a low power bus at around 28 (28-32) volts, and a high power bus used by the payload at around 100 volts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/16/2016 10:49 pm
I'll ask again... How many Amps?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: psionedge on 09/16/2016 11:25 pm
I'll ask again... How many Amps?
At launch? Not that many. You likely only have your vehicle computer, T&C components, and thermal system on. Maybe a GPS receiver as well. Payload, momentum wheels wouldn't be operating.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/16/2016 11:30 pm
I'll ask again... How many Amps?
At launch? Not that many. You likely only have your vehicle computer, T&C components, and thermal system on. Maybe a GPS receiver as well. Payload, momentum wheels wouldn't be operating.
Thanks, but I'm really looking for the "max current" from to TEL to the LV at any given time in the sequence...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/16/2016 11:47 pm
No, spacecraft are around 32 volts
My memory is says different - for some spacecraft.  I think we even had to requalify some connectors.  I'm referring to large geo comm satellites.  I'll check my sources and get back.

It is a standard for all spacecraft
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/17/2016 12:00 am
I'll ask again... How many Amps?
At launch? Not that many. You likely only have your vehicle computer, T&C components, and thermal system on. Maybe a GPS receiver as well. Payload, momentum wheels wouldn't be operating.

Actually, when the spacecraft is internal, There is only Data
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/17/2016 12:02 am
I'll ask again... How many Amps?
At launch? Not that many. You likely only have your vehicle computer, T&C components, and thermal system on. Maybe a GPS receiver as well. Payload, momentum wheels wouldn't be operating.
Thanks, but I'm really looking for the "max current" from to TEL to the LV at any given time in the sequence...

Amps are limited by the number of conductors
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: virnin on 09/17/2016 12:26 am
One last thought on the rocket swaying or vibrating theory.  The more I think about it, the less I like this idea anyway.  But with that being said the logic used here to shoot it down was that accelerometers would have seen it, and SpaceX would have said so.  And that rockets flex, and are designed to do so, etc.  Yes, clearly.  So the sway/vibration was seen, SpaceX though it was within tolerance (maybe on the high side, maybe not) so it doesn't raise any flags.  But what if their tolerances were dead wrong.  Or what if tolerances stacked up in such a way between the TEL and Rocket, or something that was supposed to move or vice versa unexpectedly failed, such that "normal/acceptable" movements now became an issue?
 

It would be visible in pad videos.  Did you see the onboard camera view of the rocket flexing?  The flex was on the order of feet and not inches and the vehicle skin crinkled and uncrinkled.

Ever heard of the term rate gyro package on launch vehicles?   Not those in the main guidance system but a package installed on the side of the booster (can't be interior because the location is usually on a prop tank).   What this package does is measure the attitude and rates of the vehicle at that location which the guidance system compares with its gyros at its location.   They are different because the vehicle flexes from wind and thrust vehicle control.  The guidance system uses this information to adjust the control gains, so that it doesn't chase its tail all over the sky.

Yes, this is exactly my point.  SpaceX knows exactly how/where/when/how much the rocket moved.  Everything is within those tolerances.  What if their tolerances are wrong?

Upon your edit:
Wouldn't these same sensors (along with the He pressure gauges) also pick up a failure in the He system.  That triangulation is how they got their failure mode past time.  What failure would not have been picked up by these sensors and cameras?

Keep in mind that while the TEL is horizontal, transporting rocket and payload from HIF to pad, the entire weight is on the pads, including dynamic loads from any subtle imperfections in the roadway.  The force those pads exert on the rocket structure during transport would dwarf anything that could be developed by vortex shedding or run-away harmonics.  IMHO, neither the TEL nor it's pads should be candidates for damaging the structure, especially to the point of rupturing the skin.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/17/2016 12:47 am
I'll ask again... How many Amps?
At launch? Not that many. You likely only have your vehicle computer, T&C components, and thermal system on. Maybe a GPS receiver as well. Payload, momentum wheels wouldn't be operating.

Payload battery charging also.  But this can be stopped sometime prior to launch.

For the rocket, you're forgetting all the transmitters.  These take a lot of 28V DC power.  A 30W S-Band transmitter may need 145 Watts.   5+ Amps or so.    You also have to remember there may have long wires and a large voltage drop for the power - so you can get momentary voltage surges (50V?) if you lose a large load.

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GoferThrottleUp on 09/17/2016 12:52 am
Keep in mind that while the TEL is horizontal, transporting rocket and payload from HIF to pad, the entire weight is on the pads, including dynamic loads from any subtle imperfections in the roadway.  The force those pads exert on the rocket structure during transport would dwarf anything that could be developed by vortex shedding or run-away harmonics.  IMHO, neither the TEL nor it's pads should be candidates for damaging the structure, especially to the point of rupturing the skin.

I think there is some sort of support strap that carries the weight of the rocket when it is horizontal. You can see it in some of the photos



Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: johnx98374 on 09/17/2016 01:34 am
No, spacecraft are around 32 volts
My memory is says different - for some spacecraft.  I think we even had to requalify some connectors.  I'm referring to large geo comm satellites.  I'll check my sources and get back.

It is a standard for all spacecraft

Proton User Guide says GSE to spacecraft wiring limited to 100 V. 
Sea Launch User Guide says customer limited to 150V and 58 Amps until launch. 
Delta !V User Guide says 11A and 126 VDC max.

Edited typos and removed personal reference.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: pogo661 on 09/17/2016 01:37 am
Now that's interesting.  The trajectory of one of the debris passes right through the object containing the delta pixel identified on my previous post.

Ha, the grassy knoll.   Well played.   
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GerryB on 09/17/2016 01:47 am
A nice photo of the SpaceX strongback on Kwajalein in 2006 shows the base of the Falcon 1's strongback and the plumbing leading up from it.  (http://www.delong.com/WebPhotos/Kwajalein-2006-11/large-47.html)There are three thick pipes, one especially well thermally insulated (so it's probably for LOX). There are also 3 comparatively thin metal tubes paralleling the main pipes. Electrical conduits? Hydraulic lines?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/17/2016 01:52 am
No, spacecraft are around 32 volts
My memory is says different - for some spacecraft.  I think we even had to requalify some connectors.  I'm referring to large geo comm satellites.  I'll check my sources and get back.

It is a standard for all spacecraft

Proton User Guide says GSE to spacecraft wiring limited to 100 V. 
Sea Launch User Guide says customer limited to 150V and 58 Amps until launch. 
Delta !V User Guide says 11A and 126 VDC max.

I think our case was similar.  High voltage capability was added sometime after our program started.  Test equipment had to be upgraded to test the cables.
Thanks, wish we had similar info for Falcon...

Edit:Typo
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/17/2016 02:00 am
Keep in mind that while the TEL is horizontal, transporting rocket and payload from HIF to pad, the entire weight is on the pads, including dynamic loads from any subtle imperfections in the roadway.  The force those pads exert on the rocket structure during transport would dwarf anything that could be developed by vortex shedding or run-away harmonics.  IMHO, neither the TEL nor it's pads should be candidates for damaging the structure, especially to the point of rupturing the skin.

I think there is some sort of support strap that carries the weight of the rocket when it is horizontal. You can see it in some of the photos

I believe that was replaced by the cantilever-style support cradle, with the claw at the top and small cradle at the bottom, for F9 v1.1 and beyond.  At least on the SLC-40 TEL.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ctillier on 09/17/2016 03:37 am
I started off in the wild & wacky thread, but I actually think my idea may not belong there after all (presumptuous, perhaps)

My scenario, with apologies if it has already been debunked:

RP-1 tank is full, but still at ambient pressure with relief vent open (assumes existence of said vent valve -- there must be one to safe the stage after payload separation.)
During LOX filling, a little bit of LOX somehow leaks into the RP-1 tank (assumes unknown manufacturing defect-- a bad weld, thermal shock, who knows)
Leaking LOX is warmed by RP-1, boils and vaporizes (even after freezing RP-1 locally into blobs of wax) and starts to vigorously agitate contents of RP-1 tank.  Surface of RP-1 inside the tank is roiled by GOX bubbles, creating small droplets of RP-1 aerosol (much like air bubbles in a Jacuzzi will create tiny suspended water droplets) in an enriched oxygen atmosphere, filling the ullage space.  None of this is visible in external camera imagery or in telemetry, since the RP-1 tank remains vented at ambient pressure during second stage tanking operations.  All temperatures and pressures are green, and any accelerometers register the normal signature of tanking.  Since GOX is being generated in the RP-1 tank, the RP-1 aerosol mixture is chased out of the RP-1 tank through the relief vent(s), at a height roughly coincident with the top of the RP-1 tank, and wafts outside the vehicle.  Eventually, the plume finds an ignition source in the nearby TEL systems and detonates.

This does not involve any vapors.  It does not involve strange sources of fuels-- the obvious fuel is RP-1.  It does not involve cyrogenic effects related to cooled LOX.  It would not show up in telemetry until the explosion.  It is set off outside the vehicle.  It would plausibly occur only during LOX tanking.

Any fatal flaws here?  In the other thread it was claimed the RP-1 tank wouldn't be vented to ambient air...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GerryB on 09/17/2016 04:05 am
A nice photo of the SpaceX strongback on Kwajalein in 2006 shows the base of the Falcon 1's strongback and the plumbing leading up from it.  (http://www.delong.com/WebPhotos/Kwajalein-2006-11/large-47.html)There are three thick pipes, one especially well thermally insulated (so it's probably for LOX). There are also 3 comparatively thin metal tubes paralleling the main pipes. Electrical conduits? Hydraulic lines?
Another picture shows the three thinner  lines are carrying gaseous nitrogen (http://www.delong.com/WebPhotos/Kwajalein-2006-11/large-53.html). They may be similar to the 6 unidentified lines (https://forum.nasaspaceflight.com/index.php?topic=30981.msg1584378#msg1584378) on the  SLC-40 strongback.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: liometopum on 09/17/2016 05:38 am
The image on the left is the first explosion frame, drawn using the X of light.
The next explosion frame produced a brighter, and wider X. The image on the right is that second frame, with the lines of the X outlining the wider lines of the X.

It appears the explosion started at the X in the first frame, and them moved upwards along that pipe that I have an oval around.

1. Can someone tell me what the X on the first image is marking? What is that?

2. And what is that vertical pipe that is in the center of the oval? What is in it?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/17/2016 05:56 am
I started off in the wild & wacky thread, but I actually think my idea may not belong there after all (presumptuous, perhaps)

My scenario, with apologies if it has already been debunked:

RP-1 tank is full, but still at ambient pressure with relief vent open (assumes existence of said vent valve -- there must be one to safe the stage after payload separation.)
During LOX filling, a little bit of LOX somehow leaks into the RP-1 tank (assumes unknown manufacturing defect-- a bad weld, thermal shock, who knows)
Leaking LOX is warmed by RP-1, boils and vaporizes (even after freezing RP-1 locally into blobs of wax) and starts to vigorously agitate contents of RP-1 tank.  Surface of RP-1 inside the tank is roiled by GOX bubbles, creating small droplets of RP-1 aerosol (much like air bubbles in a Jacuzzi will create tiny suspended water droplets) in an enriched oxygen atmosphere, filling the ullage space.  None of this is visible in external camera imagery or in telemetry, since the RP-1 tank remains vented at ambient pressure during second stage tanking operations.  All temperatures and pressures are green, and any accelerometers register the normal signature of tanking.  Since GOX is being generated in the RP-1 tank, the RP-1 aerosol mixture is chased out of the RP-1 tank through the relief vent(s), at a height roughly coincident with the top of the RP-1 tank, and wafts outside the vehicle.  Eventually, the plume finds an ignition source in the nearby TEL systems and detonates.

This does not involve any vapors.  It does not involve strange sources of fuels-- the obvious fuel is RP-1.  It does not involve cyrogenic effects related to cooled LOX.  It would not show up in telemetry until the explosion.  It is set off outside the vehicle.  It would plausibly occur only during LOX tanking.

Any fatal flaws here?  In the other thread it was claimed the RP-1 tank wouldn't be vented to ambient air...

Me like it.  There can also be some variants on that, once you go down this road. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ZachS09 on 09/17/2016 06:05 am
To be honest, I'm actually NOT looking forward to the Return To Flight Falcon 9 mission this November because I believe that by the time November comes, SpaceX still would not have found the root cause of the September 1 explosion.

And, in addition, I can visualize the RTF Falcon 9 mission exploding again after launch.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: OneSpeed on 09/17/2016 08:11 am
So, for flex induced by vortex shedding from the fairing to be a significant issue, here are some of the pre-conditions:

1. The payload and fairing are attached.
2. The wind speed is 9.8m/s.
3. The grabber is closed.
4. The fuel load is such that the natural frequency matches the shedding forces.
5. The position of the grabbers matches the node of the mode shape.
6. The cradle (and hence the lower pad) is fixed in position by the grabber and the pin joint on the strongback, which is vastly stiffer and stronger than the rocket.

That's a long (and therefore unlikely) set of preconditions!  Further, if the rocket is *designed to flex* (as Jim has stated), the result is still: nothing.  A bit of a sway, observable on telemetry.

Yes, it is a long list. My point was that this scenario is not likely to occur with every launch. It may never have occurred. At the absolute most, it has occurred once.
If the rocket sways against a fixed object, the result will not be nothing.

So, for the fairing, shedding leads to forces oscillating at 0.177 and 0.354 Hz.
[...]
If all of the conditions were met, the onset of a significant flex could be quite sudden, and may not register on accelerometers as anything other than a step function at the same time as the start of the fast fire.
By your own math, it would take *at least* three seconds to reach maximum deflection.  That's order of magnitudes slower than the event is seen to develop, and would be incredibly obvious from the accelerometer data on the stage.

Firstly, maximum deflection is reached one quarter of the way through a sinusiod, so certainly less than a second. Secondly, when a vortex is shed in a turbulent stream, the forces generated will not be a smooth sinusiod. They can be extremely abrupt, i.e. a step function.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/17/2016 08:53 am
I started off in the wild & wacky thread, but I actually think my idea may not belong there after all (presumptuous, perhaps)

My scenario, with apologies if it has already been debunked:

RP-1 tank is full, but still at ambient pressure with relief vent open (assumes existence of said vent valve -- there must be one to safe the stage after payload separation.)
During LOX filling, a little bit of LOX somehow leaks into the RP-1 tank (assumes unknown manufacturing defect-- a bad weld, thermal shock, who knows)
Leaking LOX is warmed by RP-1, boils and vaporizes (even after freezing RP-1 locally into blobs of wax) and starts to vigorously agitate contents of RP-1 tank.  Surface of RP-1 inside the tank is roiled by GOX bubbles, creating small droplets of RP-1 aerosol (much like air bubbles in a Jacuzzi will create tiny suspended water droplets) in an enriched oxygen atmosphere, filling the ullage space.  None of this is visible in external camera imagery or in telemetry, since the RP-1 tank remains vented at ambient pressure during second stage tanking operations.  All temperatures and pressures are green, and any accelerometers register the normal signature of tanking.  Since GOX is being generated in the RP-1 tank, the RP-1 aerosol mixture is chased out of the RP-1 tank through the relief vent(s), at a height roughly coincident with the top of the RP-1 tank, and wafts outside the vehicle.  Eventually, the plume finds an ignition source in the nearby TEL systems and detonates.

This does not involve any vapors.  It does not involve strange sources of fuels-- the obvious fuel is RP-1.  It does not involve cyrogenic effects related to cooled LOX.  It would not show up in telemetry until the explosion.  It is set off outside the vehicle.  It would plausibly occur only during LOX tanking.

Any fatal flaws here?  In the other thread it was claimed the RP-1 tank wouldn't be vented to ambient air...

I like it as well. At least it fits all information we have so far and does not require much magic. However, the stage was tested at McGregor. If there was a leak from the LOX to the fuel tank, shouldnt that have made a big-bada-boom at the test already?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Stranger on 09/17/2016 09:41 am
why SpaceX silent?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kevin-rf on 09/17/2016 10:36 am

I like it as well. At least it fits all information we have so far and does not require much magic. However, the stage was tested at McGregor. If there was a leak from the LOX to the fuel tank, shouldnt that have made a big-bada-boom at the test already?

Is the second stage tested in McGregor, or just the first? Can't really hot fire a second stage, and there is is no need to stack it when testing the first stage.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Barrie on 09/17/2016 10:39 am
why SpaceX silent?

They are working the problem, not working the crowd  :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RDoc on 09/17/2016 10:42 am
I started off in the wild & wacky thread, but I actually think my idea may not belong there after all (presumptuous, perhaps)

My scenario, with apologies if it has already been debunked:

RP-1 tank is full, but still at ambient pressure with relief vent open (assumes existence of said vent valve -- there must be one to safe the stage after payload separation.)
During LOX filling, a little bit of LOX somehow leaks into the RP-1 tank (assumes unknown manufacturing defect-- a bad weld, thermal shock, who knows)
Leaking LOX is warmed by RP-1, boils and vaporizes (even after freezing RP-1 locally into blobs of wax) and starts to vigorously agitate contents of RP-1 tank.  Surface of RP-1 inside the tank is roiled by GOX bubbles, creating small droplets of RP-1 aerosol (much like air bubbles in a Jacuzzi will create tiny suspended water droplets) in an enriched oxygen atmosphere, filling the ullage space.  None of this is visible in external camera imagery or in telemetry, since the RP-1 tank remains vented at ambient pressure during second stage tanking operations.  All temperatures and pressures are green, and any accelerometers register the normal signature of tanking.  Since GOX is being generated in the RP-1 tank, the RP-1 aerosol mixture is chased out of the RP-1 tank through the relief vent(s), at a height roughly coincident with the top of the RP-1 tank, and wafts outside the vehicle.  Eventually, the plume finds an ignition source in the nearby TEL systems and detonates.

This does not involve any vapors.  It does not involve strange sources of fuels-- the obvious fuel is RP-1.  It does not involve cyrogenic effects related to cooled LOX.  It would not show up in telemetry until the explosion.  It is set off outside the vehicle.  It would plausibly occur only during LOX tanking.

Any fatal flaws here?  In the other thread it was claimed the RP-1 tank wouldn't be vented to ambient air...
This assumes that the RP1 tank is at ambient pressure and has an open relief valve. That seems very unlikely to me.

What pressure would the valve be relieving? The RP1 isn't going to be boiling off as the LOX is during loading. Certainly there is a relief valve for use in case of a scrub and the need to lower the tank from flight pressure. However, I'm pretty sure that both the RP1 and LOX tanks are pressurized above ambient during loading. They can't be at very different pressure since the common bulkhead would have to withstand any difference.

To get any particles outside, there would have to be a pressure increase inside the tank which would show up on the pressure monitors. Even if there were an open vent, it's not like the top of the tank is open, it's a small valve. To get significant flow, there has to be a pressure difference.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: vanoord on 09/17/2016 12:42 pm

1. Can someone tell me what the X on the first image is marking? What is that?

2. And what is that vertical pipe that is in the center of the oval? What is in it?

1. Not a lot, but that is around the height of the LOX/RP-1 tanks common bulkhead.

2. It's not a pipe, it's the frame for the cradle that supports the top of the vehicle.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/17/2016 12:49 pm
So, for flex induced by vortex shedding from the fairing to be a significant issue, here are some of the pre-conditions:

1. The payload and fairing are attached.
2. The wind speed is 9.8m/s.
3. The grabber is closed.
4. The fuel load is such that the natural frequency matches the shedding forces.
5. The position of the grabbers matches the node of the mode shape.
6. The cradle (and hence the lower pad) is fixed in position by the grabber and the pin joint on the strongback, which is vastly stiffer and stronger than the rocket.

That's a long (and therefore unlikely) set of preconditions!  Further, if the rocket is *designed to flex* (as Jim has stated), the result is still: nothing.  A bit of a sway, observable on telemetry.

Yes, it is a long list. My point was that this scenario is not likely to occur with every launch. It may never have occurred. At the absolute most, it has occurred once.
If the rocket sways against a fixed object, the result will not be nothing.

So, for the fairing, shedding leads to forces oscillating at 0.177 and 0.354 Hz.
[...]
If all of the conditions were met, the onset of a significant flex could be quite sudden, and may not register on accelerometers as anything other than a step function at the same time as the start of the fast fire.
By your own math, it would take *at least* three seconds to reach maximum deflection.  That's order of magnitudes slower than the event is seen to develop, and would be incredibly obvious from the accelerometer data on the stage.

Firstly, maximum deflection is reached one quarter of the way through a sinusiod, so certainly less than a second. Secondly, when a vortex is shed in a turbulent stream, the forces generated will not be a smooth sinusiod. They can be extremely abrupt, i.e. a step function.

A.  Still would be see visually and in the data
b.  Movement is not going to be greater than the empty vehicle
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/17/2016 12:57 pm

4. The fuel load is such that the natural frequency matches the shedding forces.
5. The position of the grabbers matches the node of the mode shape.


Both are not viable.  The whole point of the grabbers is to prevent this.   They are not needed as part of erecting the vehicle.  They are specifically there to protect against movement and loads from vortex shedding.  They are only released in the last minutes before launch and in delay or scrub, the strongback and grabbers are re-engaged within minutes. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/17/2016 12:57 pm
why SpaceX silent?
Welcome to the forum! :) I'm going to venture a guess that they still aren't 100% sure of the cause, so they're not ready to release anything other than they are working on it...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: docmordrid on 09/17/2016 01:01 pm
why SpaceX silent?
Welcome to the forum! :) I'm going to venture a guess that they still aren't 100% sure of the cause, so they're not ready to release anything other than they are working on it...

Or, they do have a handle on it and are presenting the boards findings to their customers and other partners before publication.

Coin flip.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/17/2016 01:03 pm
The image on the left is the first explosion frame, drawn using the X of light.
The next explosion frame produced a brighter, and wider X. The image on the right is that second frame, with the lines of the X outlining the wider lines of the X.

It appears the explosion started at the X in the first frame, and them moved upwards along that pipe that I have an oval around.

1. Can someone tell me what the X on the first image is marking? What is that?

2. And what is that vertical pipe that is in the center of the oval? What is in it?
Another new guy, welcome to the forum! :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/17/2016 01:19 pm
We don't have to come up with a lot of theories about RP1 mixing in the air to explain the fireball. I remember a long time ago where a military jet fighter was demonstrating a roll low over the water at the Toronto Ex. In one frame the tip of the wing hit a wavelet of water. In the next frame the aircraft cartwheeled 270° and in the next frame the whole aircraft was not visible at all due to the large fireball. This plane was travelling at over 400mph so there was no opportunity for gasses to accumulate around the craft.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/17/2016 01:33 pm
We don't have to come up with a lot of theories about RP1 mixing in the air to explain the fireball. I remember a long time ago where a military jet fighter was demonstrating a roll low over the water at the Toronto Ex. In one frame the tip of the wing hit a wavelet of water. In the next frame the aircraft cartwheeled 270° and in the next frame the whole aircraft was not visible at all due to the large fireball. This plane was travelling at over 400mph so there was no opportunity for gasses to accumulate around the craft.
I don't recall that crash Roy, do you remember what year it was? By your description of a cartwheel, if it ripped open a wing tank the rotating fuel would aerosolize and travel via inertia relatively along the aircraft... Do I have what you saw right?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: speedevil on 09/17/2016 01:41 pm
We don't have to come up with a lot of theories about RP1 mixing in the air to explain the fireball. I remember a long time ago where a military jet fighter was demonstrating a roll low over the water at the Toronto Ex. In one frame the tip of the wing hit a wavelet of water. In the next frame the aircraft cartwheeled 270° and in the next frame the whole aircraft was not visible at all due to the large fireball. This plane was travelling at over 400mph so there was no opportunity for gasses to accumulate around the craft.
Err - no.
At 400MPH, 200m/s, each kilo of fuel has 20kJ of energy.
If all is used to atomise the kerosene, and assuming it has a surface tension similar to Nonane, that is 22mN/m.
This can be rewritten as 22mJ/m^2. Or, it is enough to atomise the litre of kerosene so it has a surface area of 20000/0.022 = a million square meters.

This is enough to be easily submicron.
(it is dramatically more complex than this, and much will be slowed by drag) However, droplets will be very, very small.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/17/2016 02:02 pm
I started off in the wild & wacky thread, but I actually think my idea may not belong there after all (presumptuous, perhaps)

My scenario, with apologies if it has already been debunked:

RP-1 tank is full, but still at ambient pressure with relief vent open (assumes existence of said vent valve -- there must be one to safe the stage after payload separation.)
During LOX filling, a little bit of LOX somehow leaks into the RP-1 tank (assumes unknown manufacturing defect-- a bad weld, thermal shock, who knows)
Leaking LOX is warmed by RP-1, boils and vaporizes (even after freezing RP-1 locally into blobs of wax) and starts to vigorously agitate contents of RP-1 tank.  Surface of RP-1 inside the tank is roiled by GOX bubbles, creating small droplets of RP-1 aerosol (much like air bubbles in a Jacuzzi will create tiny suspended water droplets) in an enriched oxygen atmosphere, filling the ullage space.  None of this is visible in external camera imagery or in telemetry, since the RP-1 tank remains vented at ambient pressure during second stage tanking operations.  All temperatures and pressures are green, and any accelerometers register the normal signature of tanking.  Since GOX is being generated in the RP-1 tank, the RP-1 aerosol mixture is chased out of the RP-1 tank through the relief vent(s), at a height roughly coincident with the top of the RP-1 tank, and wafts outside the vehicle.  Eventually, the plume finds an ignition source in the nearby TEL systems and detonates.

This does not involve any vapors.  It does not involve strange sources of fuels-- the obvious fuel is RP-1.  It does not involve cyrogenic effects related to cooled LOX.  It would not show up in telemetry until the explosion.  It is set off outside the vehicle.  It would plausibly occur only during LOX tanking.

Any fatal flaws here?  In the other thread it was claimed the RP-1 tank wouldn't be vented to ambient air...

I like it as well. At least it fits all information we have so far and does not require much magic. However, the stage was tested at McGregor. If there was a leak from the LOX to the fuel tank, shouldnt that have made a big-bada-boom at the test already?
Maybe it did, but didn't ignite, since there was no T/E..

Or the leak is new or intermittent...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/17/2016 02:05 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 6cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

Edit: correction by envy887 below the expansion is out by a factor of ten. 6cm instead of 60. 5cm according to his reduced temperature difference.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/17/2016 02:15 pm
We don't have to come up with a lot of theories about RP1 mixing in the air to explain the fireball. I remember a long time ago where a military jet fighter was demonstrating a roll low over the water at the Toronto Ex. In one frame the tip of the wing hit a wavelet of water. In the next frame the aircraft cartwheeled 270° and in the next frame the whole aircraft was not visible at all due to the large fireball. This plane was travelling at over 400mph so there was no opportunity for gasses to accumulate around the craft.
I don't recall that crash Roy, do you remember what year it was? By your description of a cartwheel, if it ripped open a wing tank the rotating fuel would aerosolize and travel via inertia relatively along the aircraft... Do I have what you saw right?
That may well have been the case, although not obvious as the plane in the second frame having rotated 270° appeared completely intact. Very fuzzy on the year about 1980 give or take several years.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/17/2016 02:30 pm
Well, I've pretty much beat the USLR video to death at this point.

I could walk into a court room and comfortably declare that in my opinion this video holds no solid evidence of any changes that were a visible precursor to the event.

It's been a fun and educational exercise and required cooperation from several other persons to get to this point.

To me, a summary of the negative results are shown on the video below.

What you are looking at is a video of a moving average of the difference frames, stacked 10 per frame.  These are the bottom six difference groups where differences are adjacent frames only.  The contrast has been stretched so the differences become visible.  If you have the means, further contrast stretching makes some of the clouds more visible.  Keep in mind, in the last 10 frames, the stack count is 9, then 8, then 7, so you will perceive brightening, but be careful about drawing conclusions in those last 10 frames.  Those frames were independently stacked in groups of 1 or 2 or 3, and those results are essentially the same.  The upload to youtube may have added some MPEG artifacts that aren't in the original 16 bit grey scale uncompressed processing.

While there are some interesting and statistically significant changes, none of those changes relate to any actual physical motion of any part of the F9 or TE as seen by the original video.  There are areas of clouds that occur to the left of the F9, and some to the right, but these clouds are slow events and from other discussions, appear to be normal clouding events.  There are statistical outliers that show in 1 second adjacent stacks, but these are no longer visible when compared to non-adjacent 1 second stacks, i.e. they're noise. 

There is one possible exception, but not significantly above the noise levels, i.e. in the 1 SD range.  In the last half dozen frames, towards the center of each delta frame there is a diagonal lower left to upper right structure which appears to show a delta in the last few frames, but I wouldn't make a strong case for that.  It's possible, but not well supported by the raw data.

If you find this video exciting, I can upload another which uses 50 frame stacks.  It will thrill you at an 80% lower level.

Maybe your eyes can see more than mine, but absent another video source, I'm sure you'll all be grateful that I'm done with this approach.  I think I'll go to the wild & whacky thread for a while and invent ways to detonate clouds of water vapor.


https://www.youtube.com/watch?v=t4iCR6tbW0Q
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/17/2016 02:35 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

You dropped a decimal place somewhere. 0.000022 [m/m-K] *11.3 [m] * 200 [K] = 0.00498 [m] or about 5 cm.     
That's less than 0.5% strain, and commercial Al-Li alloys exhibit a minimum of 12% tensile strain before fracture, at 77 K temps.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Barrie on 09/17/2016 02:40 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

You dropped a decimal place somewhere. 0.000022 [m/m-K] *11.3 [m] * 200 [K] = 0.00498 [m] or about 5 cm.     
That's less than 0.5% strain, and commercial Al-Li alloys exhibit a minimum of 12% tensile strain before fracture, at 77 K temps.

I thought the RP-1 was also sub-cooled, and loaded before LOX, so the temperature difference won't be that big either.

Edit: oops! As you say, you have already taken that into account in your calc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/17/2016 02:47 pm
We don't have to come up with a lot of theories about RP1 mixing in the air to explain the fireball. I remember a long time ago where a military jet fighter was demonstrating a roll low over the water at the Toronto Ex. In one frame the tip of the wing hit a wavelet of water. In the next frame the aircraft cartwheeled 270° and in the next frame the whole aircraft was not visible at all due to the large fireball. This plane was travelling at over 400mph so there was no opportunity for gasses to accumulate around the craft.
I don't recall that crash Roy, do you remember what year it was? By your description of a cartwheel, if it ripped open a wing tank the rotating fuel would aerosolize and travel via inertia relatively along the aircraft... Do I have what you saw right?
That may well have been the case, although not obvious as the plane in the second frame having rotated 270° appeared completely intact. Very fuzzy on the year about 1980 give or take several years.
Thanks Roy, I had been going to the Ex airshow since the late 60's, good times! I tried to go all three days back then. After the Snowbirds and Nimrod accidents my wife didn't want to go with me anymore. Those were a couple of sad days... :'( The 80's had a few good shows out in Hamilton and London as well! 8)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/17/2016 02:50 pm
I like it as well. At least it fits all information we have so far and does not require much magic. However, the stage was tested at McGregor. If there was a leak from the LOX to the fuel tank, shouldnt that have made a big-bada-boom at the test already?
Maybe it did, but didn't ignite, since there was no T/E..

Or the leak is new or intermittent...

Well this entire theory hinges on the fact that there is some kind of relieve valve to ambient. As has been pointed out by RDoc and liked by Jim, which indicates to me that there is no valve to ambient.

This assumes that the RP1 tank is at ambient pressure and has an open relief valve. That seems very unlikely to me.

They need to get air/gas out the RP1 tank somehow or there would be no way to get the fuel into the tank in the first place. But that might go through an exit tube that does not vent to ambient. Jim, how is this done on other launch vehicles? How is the gas that must be present while tanking is removed?

Also, it must be a 2-way valve since (presumably N2) is flowing back when de-tanking. Or are they pressurizing the RP1 and LOX tank with Helium during the de-tanking procedure?

Anyway, many questions but not much food for an explosion unless there is some valve to the outside world from the RP1 tank. And that has been de-bunked.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: envy887 on 09/17/2016 02:53 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

You dropped a decimal place somewhere. 0.000022 [m/m-K] *11.3 [m] * 200 [K] = 0.00498 [m] or about 5 cm.     
That's less than 0.5% strain, and commercial Al-Li alloys exhibit a minimum of 12% tensile strain before fracture, at 77 K temps.

I thought the RP-1 was also sub-cooled, and loaded before LOX, so the temperature diffference won't be that big either.

I accounted for that with the 200 K (instead of 240 K) temp differential. RP-1 is at about -8 C, LOX at about -208 C
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/17/2016 03:03 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

You dropped a decimal place somewhere. 0.000022 [m/m-K] *11.3 [m] * 200 [K] = 0.00498 [m] or about 5 cm.     
That's less than 0.5% strain, and commercial Al-Li alloys exhibit a minimum of 12% tensile strain before fracture, at 77 K temps.

Thanks for pointing out my error, and that other piece of critical information, expansion before fracture.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/17/2016 03:06 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

You dropped a decimal place somewhere. 0.000022 [m/m-K] *11.3 [m] * 200 [K] = 0.00498 [m] or about 5 cm.     
That's less than 0.5% strain, and commercial Al-Li alloys exhibit a minimum of 12% tensile strain before fracture, at 77 K temps.

I thought the RP-1 was also sub-cooled, and loaded before LOX, so the temperature diffference won't be that big either.

I believe the RP1 tank is not filled to the top, so the top of the tank could be considerably warmer than the liquid portion below. However this is a moot point as explained by envy881.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/17/2016 03:26 pm
I started off in the wild & wacky thread, but I actually think my idea may not belong there after all (presumptuous, perhaps)

My scenario, with apologies if it has already been debunked:

RP-1 tank is full, but still at ambient pressure with relief vent open (assumes existence of said vent valve -- there must be one to safe the stage after payload separation.)
During LOX filling, a little bit of LOX somehow leaks into the RP-1 tank (assumes unknown manufacturing defect-- a bad weld, thermal shock, who knows)
Leaking LOX is warmed by RP-1, boils and vaporizes (even after freezing RP-1 locally into blobs of wax) and starts to vigorously agitate contents of RP-1 tank.  Surface of RP-1 inside the tank is roiled by GOX bubbles, creating small droplets of RP-1 aerosol (much like air bubbles in a Jacuzzi will create tiny suspended water droplets) in an enriched oxygen atmosphere, filling the ullage space.  None of this is visible in external camera imagery or in telemetry, since the RP-1 tank remains vented at ambient pressure during second stage tanking operations.  All temperatures and pressures are green, and any accelerometers register the normal signature of tanking.  Since GOX is being generated in the RP-1 tank, the RP-1 aerosol mixture is chased out of the RP-1 tank through the relief vent(s), at a height roughly coincident with the top of the RP-1 tank, and wafts outside the vehicle.  Eventually, the plume finds an ignition source in the nearby TEL systems and detonates.

This does not involve any vapors.  It does not involve strange sources of fuels-- the obvious fuel is RP-1.  It does not involve cyrogenic effects related to cooled LOX.  It would not show up in telemetry until the explosion.  It is set off outside the vehicle.  It would plausibly occur only during LOX tanking.

Any fatal flaws here?  In the other thread it was claimed the RP-1 tank wouldn't be vented to ambient air...

I like it as well. At least it fits all information we have so far and does not require much magic. However, the stage was tested at McGregor. If there was a leak from the LOX to the fuel tank, shouldnt that have made a big-bada-boom at the test already?
Maybe it did, but didn't ignite, since there was no T/E..

Or the leak is new or intermittent...

Of course an O2 sensor in the RP1 tank (put there to confirm purging, for example) would put a damper on this theory...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Stan-1967 on 09/17/2016 03:54 pm

Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

Roy-H...do you think this failure mechanism could originate on electroplated parts,  either on the the pad/erector or inside the rocket?  Electroplating cycles usually start off by removing all surface oxides,  then proceed to deposit the metal.  If the electroplated metal fails or cracks, it will expose the oxide free base metal.   The electroplated metal will also mismatch CTE's with the base metal, so as these parts undergo temperature cycling, internal stress can rise dramatically,  and failure can be catastrophic.   I have personally heard nickel plated parts fail when stressed to the point of adhesion failure to the base metal.  It can be quite loud.  It also can produce a shower of metal flakes. If this type of failure happened around GOX or LOX,  it could be quite reactive.   When applying this to the pad equipment, I think of hydraulic Pistons & such,  when applied to the rocket I have little personal knowledge of material selection.   Struts maybe? 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: rockets4life97 on 09/17/2016 04:24 pm
I think it goes without saying that if SpaceX hasn't figured out the cause by November than the RTF won't be in November.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Roy_H on 09/17/2016 04:32 pm

Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

Roy-H...do you think this failure mechanism could originate on electroplated parts,  either on the the pad/erector or inside the rocket?  Electroplating cycles usually start off by removing all surface oxides,  then proceed to deposit the metal.  If the electroplated metal fails or cracks, it will expose the oxide free base metal.   The electroplated metal will also mismatch CTE's with the base metal, so as these parts undergo temperature cycling, internal stress can rise dramatically,  and failure can be catastrophic.   I have personally heard nickel plated parts fail when stressed to the point of adhesion failure to the base metal.  It can be quite loud.  It also can produce a shower of metal flakes. If this type of failure happened around GOX or LOX,  it could be quite reactive.   When applying this to the pad equipment, I think of hydraulic Pistons & such,  when applied to the rocket I have little personal knowledge of material selection.   Struts maybe?

As I do not work in the industry, I have no knowledge, but I have not read anything that would make me believe there is any electro-plating done on the tanks. Even if the struts were electro-plated (which I doubt), they would be at uniform temperature and not experience the stress I envisioned.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Stan-1967 on 09/17/2016 06:36 pm
As I do not work in the industry, I have no knowledge, but I have not read anything that would make me believe there is any electro-plating done on the tanks. Even if the struts were electro-plated (which I doubt), they would be at uniform temperature and not experience the stress I envisioned.

I agree that the tanks themselves would not have any electroplating. ( way too big, and not functional purpose ) I do think that a part inside the tank, like a strut, if electroplated, would NOT be in equilibrium if immersed in LOX or a part outside the rocket on the pad/erector exposed to very cold conditions would be NOT in equilibrium.  The CTE mismatch of the electroplated coating vs. the base metal is the source of stress buildup. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/17/2016 06:40 pm
There is no electroplating.  Passivation is what is done, if needed.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Stan-1967 on 09/17/2016 06:48 pm
There is no electroplating.  Passivation is what is done, if needed.

I agree passivation is what makes sense as a functional coating on anything like a stainless steel (Chrome containing) alloy.  I thought the struts were more like Invar, ( nickel-iron ) for low CTE.   Passivation is not as straight forward on those types of metals.  If you know that there is no plating on anything inside the tanks, it puts that question to bed.


Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: wtrix on 09/17/2016 07:25 pm
Well, I've pretty much beat the USLR video to death at this point.

I could walk into a court room and comfortably declare that in my opinion this video holds no solid evidence of any changes that were a visible precursor to the event.

It's been a fun and educational exercise and required cooperation from several other persons to get to this point.

To me, a summary of the negative results are shown on the video below.

What you are looking at is a video of a moving average of the difference frames, stacked 10 per frame.  These are the bottom six difference groups where differences are adjacent frames only.  The contrast has been stretched so the differences become visible.  If you have the means, further contrast stretching makes some of the clouds more visible.  Keep in mind, in the last 10 frames, the stack count is 9, then 8, then 7, so you will perceive brightening, but be careful about drawing conclusions in those last 10 frames.  Those frames were independently stacked in groups of 1 or 2 or 3, and those results are essentially the same.  The upload to youtube may have added some MPEG artifacts that aren't in the original 16 bit grey scale uncompressed processing.

While there are some interesting and statistically significant changes, none of those changes relate to any actual physical motion of any part of the F9 or TE as seen by the original video.  There are areas of clouds that occur to the left of the F9, and some to the right, but these clouds are slow events and from other discussions, appear to be normal clouding events.  There are statistical outliers that show in 1 second adjacent stacks, but these are no longer visible when compared to non-adjacent 1 second stacks, i.e. they're noise. 

There is one possible exception, but not significantly above the noise levels, i.e. in the 1 SD range.  In the last half dozen frames, towards the center of each delta frame there is a diagonal lower left to upper right structure which appears to show a delta in the last few frames, but I wouldn't make a strong case for that.  It's possible, but not well supported by the raw data.

If you find this video exciting, I can upload another which uses 50 frame stacks.  It will thrill you at an 80% lower level.

Maybe your eyes can see more than mine, but absent another video source, I'm sure you'll all be grateful that I'm done with this approach.  I think I'll go to the wild & whacky thread for a while and invent ways to detonate clouds of water vapor.


https://www.youtube.com/watch?v=t4iCR6tbW0Q

I'll bow to the ground for the work you have accomplished. Simply astonishing.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Stranger on 09/17/2016 08:08 pm
why SpaceX silent?
Welcome to the forum! :) I'm going to venture a guess that they still aren't 100% sure of the cause, so they're not ready to release anything other than they are working on it...
Thank you!
what some data about 3,000 telemetry channels?
rise in temperature, pressure drop, etc.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/17/2016 08:59 pm
why SpaceX silent?
Welcome to the forum! :) I'm going to venture a guess that they still aren't 100% sure of the cause, so they're not ready to release anything other than they are working on it...
Thank you!
what some data about 3,000 telemetry channels?
rise in temperature, pressure drop, etc.

I don't need telemetry to tell you that both have happened :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: MarekCyzio on 09/17/2016 09:15 pm
Is there any definitive proof that the center of the lens flair is in fact where the LOX fuel line is?

         I get the feeling that problem is going to be the use of the densified propellant. It could be that every time the falcon was loaded with the superchilled LOX there was a small chance that there would be an explosion and it was just a matter of time. I little bit of googling shows that a lot of people were concerned with the use of the new denser fuel.

My greatest fear is that the investigation shows that there are unresolvable issues with the densified fuel and spacex is ordered to stop using it. This would create all kinds of issues even assuming no changes need to be made to the rocket.

Many rockets including Antares use subcooled fuel without issue. SpaceX was pushing it further, but it isn't complete uncharted territory.

The LOX fuel line is NOT at the center of the explosion. It goes in at the bottom of the stage through the interstage. The explosion was very near the center of the stage.

Are you sure about that? I reviewed all photos as well as diagrams and it seems that two pipes that go into interstage are only used for nitrogen purge. All S2 connections including kerosene, LOX, helium, nitrogen + data/power go through a single quick disconnect plate. But I may be wrong, so please provide some evidence to your claim :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/17/2016 09:27 pm
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/17/2016 10:12 pm
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/17/2016 10:27 pm
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?

With all due respect, as I've posted twice previously, the "diffraction flares" are internal lens barrel reflections.  They point to the center of the putative "X" if and only if the lens and the light source are at the center of the field of view and all of the internals of the lens are symmetric, which is unlikely if this is a zoom lens.

Since the brightest illumination is offset from the center of the field of view, the "diffraction flares" are pointing to a location different from the brightest point.  How much offset requires knowing the lens, having the lens, testing the lens, and calculating the "flare" deviation as the source drifts from the center of the field of view.

If the the "flare" analysis points to the area identified, then I assure you, the brightest point is not there.  It's probably someplace to the right, but without knowing or testing the lens, all I can be sure of is the flare "X" probably doesn't point to the brightest spot, which is most likely to the right of the "X", but could be left depending on the element count in the lens, and where the reflections occur in the lens barrel.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: RotoSequence on 09/17/2016 11:16 pm
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?

With all due respect, as I've posted twice previously, the "diffraction flares" are internal lens barrel reflections.  They point to the center of the putative "X" if and only if the lens and the light source are at the center of the field of view and all of the internals of the lens are symmetric, which is unlikely if this is a zoom lens.

Since the brightest illumination is offset from the center of the field of view, the "diffraction flares" are pointing to a location different from the brightest point.  How much offset requires knowing the lens, having the lens, testing the lens, and calculating the "flare" deviation as the source drifts from the center of the field of view.

If the the "flare" analysis points to the area identified, then I assure you, the brightest point is not there.  It's probably someplace to the right, but without knowing or testing the lens, all I can be sure of is the flare "X" probably doesn't point to the brightest spot, which is most likely to the right of the "X", but could be left depending on the element count in the lens, and where the reflections occur in the lens barrel.

Apologies. I'm not very good at recalling everything that's happened or all of the well made points in this thread.  :-[
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/17/2016 11:20 pm
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?

With all due respect, as I've posted twice previously, the "diffraction flares" are internal lens barrel reflections.  They point to the center of the putative "X" if and only if the lens and the light source are at the center of the field of view and all of the internals of the lens are symmetric, which is unlikely if this is a zoom lens.

Since the brightest illumination is offset from the center of the field of view, the "diffraction flares" are pointing to a location different from the brightest point.  How much offset requires knowing the lens, having the lens, testing the lens, and calculating the "flare" deviation as the source drifts from the center of the field of view.

If the the "flare" analysis points to the area identified, then I assure you, the brightest point is not there.  It's probably someplace to the right, but without knowing or testing the lens, all I can be sure of is the flare "X" probably doesn't point to the brightest spot, which is most likely to the right of the "X", but could be left depending on the element count in the lens, and where the reflections occur in the lens barrel.

Apologies. I'm not very good at recalling everything that's happened or all of the well made points in this thread.  :-[

No worries.  If optics were intuitive, Newton would have only been an alchemist.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/18/2016 12:00 am
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?

With all due respect, as I've posted twice previously, the "diffraction flares" are internal lens barrel reflections.  They point to the center of the putative "X" if and only if the lens and the light source are at the center of the field of view and all of the internals of the lens are symmetric, which is unlikely if this is a zoom lens.

Since the brightest illumination is offset from the center of the field of view, the "diffraction flares" are pointing to a location different from the brightest point.  How much offset requires knowing the lens, having the lens, testing the lens, and calculating the "flare" deviation as the source drifts from the center of the field of view.

If the the "flare" analysis points to the area identified, then I assure you, the brightest point is not there.  It's probably someplace to the right, but without knowing or testing the lens, all I can be sure of is the flare "X" probably doesn't point to the brightest spot, which is most likely to the right of the "X", but could be left depending on the element count in the lens, and where the reflections occur in the lens barrel.

Here is a starry photo made through a _refractor_ telescope (Skywatcher Esprit-100). As you see, there _are_ diffraction spikes, and they _are_ centered on each star.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Stranger on 09/18/2016 12:13 am
Quote
Thank you!
what some data about 3,000 telemetry channels?
rise in temperature, pressure drop, etc.

I don't need telemetry to tell you that both have happened :)
Oh, please tell us :)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: DMeader on 09/18/2016 12:14 am
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?

With all due respect, as I've posted twice previously, the "diffraction flares" are internal lens barrel reflections.  They point to the center of the putative "X" if and only if the lens and the light source are at the center of the field of view and all of the internals of the lens are symmetric, which is unlikely if this is a zoom lens.

Since the brightest illumination is offset from the center of the field of view, the "diffraction flares" are pointing to a location different from the brightest point.  How much offset requires knowing the lens, having the lens, testing the lens, and calculating the "flare" deviation as the source drifts from the center of the field of view.

If the the "flare" analysis points to the area identified, then I assure you, the brightest point is not there.  It's probably someplace to the right, but without knowing or testing the lens, all I can be sure of is the flare "X" probably doesn't point to the brightest spot, which is most likely to the right of the "X", but could be left depending on the element count in the lens, and where the reflections occur in the lens barrel.

Here is a starry photo made through a _refractor_ telescope (Skywatcher Esprit-100). As you see, there _are_ diffraction spikes, and they _are_ centered on each star.
.

Probably a because the telescope has the higher quality symmetrical optics he was referring to. Also a much simpler optical path (how many elements, how well aligned) than the zoom that was used to shoot the video.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AncientU on 09/18/2016 12:25 am
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/18/2016 12:45 am
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

Guys/Gals  go have your debate.  This video's X doesn't point to the "brightest spot" which is probably a diffuse "brightest spot".   Show me the math that converges the X to a single point.  There is math for that.

I'll watch your debate and intervene if someone goes totally whacko.

Meanwhile I'm posting on the whacko thread.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: meekGee on 09/18/2016 01:05 am
Quote
Thank you!
what some data about 3,000 telemetry channels?
rise in temperature, pressure drop, etc.

I don't need telemetry to tell you that both have happened :)
Oh, please tell us :)
Well, there was a rise in temperature and there was a loss of pressure.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: ccdengr on 09/18/2016 01:09 am
Here is a starry photo made through a _refractor_ telescope (Skywatcher Esprit-100). As you see, there _are_ diffraction spikes, and they _are_ centered on each star.
Probably from the non-circularly-symmetric iris in the camera.  The telescope is mostly likely circularly symmetric and cannot form spikes.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: watermod on 09/18/2016 11:23 am
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

Guys/Gals  go have your debate.  This video's X doesn't point to the "brightest spot" which is probably a diffuse "brightest spot".   Show me the math that converges the X to a single point.  There is math for that.

I'll watch your debate and intervene if someone goes totally whacko.

Meanwhile I'm posting on the whacko thread.
This is why I think they need some non-lens non-image based IR based sensing across the pad and erector.   One good way is with the STTR I suggested they look at.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/18/2016 11:50 am
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

In this particular case, it's a refractor scope, not a reflector.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GoferThrottleUp on 09/18/2016 12:17 pm
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

In this particular case, it's a refractor scope, not a reflector.

spikes will also occur in any optical system where the elements are not perfectly aligned axially - in the real world this means everything with more than one lens. Mechanical zoom lenses in particular will exhibit spikes, and it is true that the nexus of the spikes is only marginally related to the point of max brightness. Considering the source of the imagery to hand, it would be unwise to place to much emphasis on a purely geometric interpretation.

Added later - It been 40 years since I studied optics, and I just realised I mis-remembered this. Should have googled it first I guess. More correctly, its a non-circular aperture that causes diffraction spikes and while misaligned optics will give you an asymmetrical light path, in most cases its the iris of the camera that is principally to blame. Sorry folks, in future I will check my facts.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/18/2016 12:45 pm

This is why I think they need some non-lens non-image based IR based sensing across the pad and erector.   One good way is with the STTR I suggested they look at.

No, needed.  There are other camera views, that provide the info needed.  This isn't LH2 vehicle, no need to look for invisible fires. 
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/18/2016 03:39 pm
In the thousands and thousands of posts in this thread, I don't think the following pieces have been put together in quite this way, so let me pull a few objective facts together and add a single speculation, and see if y'all think they go together:

First, the upper stage cradling system on the TEL at SLC-40 supported some of the weight of the rocket, while horizontal and during erection to vertical, through the upper stage structure.  Since it would usually be considered a strong point in the upper stage structure, the cradle supports the upper stage right where the common bulkhead is located within the stage.  This was likely done on purpose.  I mean, if you asked an engineer where the strongest point on the second stage was, where stress from supporting its weight would be most effectively distributed through the rest of the stage's structure, I can well imagine that the place where the internal bulkhead is located would be stronger, structurally, than the tank skin above or below the bulkhead.

So, some stresses are transmitted through the second stage right at that bulkhead location.  Which, per the US Launch Report video, seems to be where the initial event occurred.

So far, just objective facts, no speculation.

Now, the speculation:

Suppose one small section of the weld attaching the common bulkhead to the inner tank walls was weak or faulty.  This assumption posits that SpaceX does not inspect every single weld on every single vehicle.

A below-standard weld right where the stage distributes stresses through the rest of the stage structure would itself be stressed as the vehicle is handled, transported on the TEL, and erected from horizontal to vertical.  Perhaps this weakened the weld further.

Finally, the loading of sub-cooled LOX caused the metal to shrink slightly, and even though the stage had been cryo-loaded before, this time, after additional stresses of actually being supported on the TEL, the shrinkage stressed the weld even further.  Even though the LOX tank was not yet pressurized, during LOX load it went through possibly greater stress than during pressurization.

The weld snapped near the end of LOX loading, right where the highest level of stress had been transmitted through the vehicle through normal handling, i.e., having the stage's weight supported through the stage structure and through the TEL cradle.  This is exactly at the location where we saw the initial flash.

The weld failure exposed a fresh-cut aluminum-lithium edge, which is reactive in LOX, and the shock wave generated by the weld failure provided all the remaining energy needed to start the metal on fire, right along the weld line connecting the common bulkhead to the tank skin.  The skin adjacent to the failed weld lost structural integrity very, very quickly, and a fireball from the initial ignition found a much easier expansion path through air than it had through LOX within the tank, accounting for its initial supersonic expansion -- it was being driven not only by the energy of the initial fire, but also by the resistance of the less-compressible LOX on the other side of the fire from the air outside of the brand-new hole in the tank skin.  It was also driven by the fast release of combustion gasses through what was initially a very small hole in the tank skin.

The initial flash expressed the fast fire of the tank skin, fed by the LOX behind it.  As regular air crept in and LOX immersion was replaced by air and combustion gasses, the rate of combustion of the tank skin slowed, and the fire receded, accounting for the very bright initial flash and its subsequent dimming.

Right about the time the initial flash began to fade, the tank rupture extended both up and down the length of the stage, and began to liberate RP-1 from below the common bulkhead.  This provided a more plentiful, and much more easily combustible, fuel for the fire than the tank skin, and so the fire went Off To The Races, completing the destruction of the upper stage and throwing fiery shrapnel through the upper bulkheads of stage 1, leading to its destruction.  This also accounts for the observed cascade of fiery RP-1 seen flowing down along the side of the rocket just before the first stage unzipped itself -- the upper stage tanks ruptured and some of the RP-1 was set on fire, but much more slowly than the stuff that immediately mixed and combusted with the liberated LOX.

So, one weld, perhaps just barely out of spec, at a location where we know the bulkhead is welded in and where normal handling stresses would distribute stress through the stage, could account for all of the observed events.

Yes, this would be a significant issue for SpaceX -- if a bad weld got through the inspection process, they will have to address some serious process issues before NASA and the FAA will look favorably on an RTF.  Which is why I don't care for the theory all that much.  But -- it does explain the observed facts...
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/18/2016 04:11 pm
Gee Doug, it only took 74 pages for you to agree... ;D
http://forum.nasaspaceflight.com/index.php?topic=30981.1380
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/18/2016 04:18 pm
Gee Doug, it only took 74 pages for you to agree... ;D
http://forum.nasaspaceflight.com/index.php?topic=30981.1380

Yeah, well, you were still flogging the COPVs at that point, as well.  I was trying to come up with a more likely single-point failure that arose out of a single root cause, rather than adding two or more main failure modes together... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/18/2016 04:28 pm
Gee Doug, it only took 74 pages for you to agree... ;D
http://forum.nasaspaceflight.com/index.php?topic=30981.1380

Yeah, well, you were still flogging the COPVs at that point, as well.  I was trying to come up with a more likely single-point failure that arose out of a single root cause, rather than adding two or more main failure modes together... ;)
Not me... It was the FSW at the Common Bulkhead or the mount not the COPV itself... I'm  still a "Weldologist"... ;D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CyndyC on 09/18/2016 10:38 pm
Suppose one small section of the weld attaching the common bulkhead to the inner tank walls was weak or faulty.  This assumption posits that SpaceX does not inspect every single weld on every single vehicle.

I would like to posit that SpaceX inspects every single weld on every single vehicle, and/or that no welds were weak or faulty. From page 10 of the User's Guide (http://www.spacex.com/sites/spacex/files/falcon_9_users_guide_rev_2.0.pdf), "Tanks are manufactured using friction stir welding—the highest strength and most reliable welding technique available."

Friction stir welding was explained and demonstrated on The Science Channel just last night, during "NASA's Rocket to Mars", episode 1 from season 2 of the "Impossible Engineering" series. NASA is using friction stir welding on Orion, and I think it was said NASA also pioneered the method. Instead of using high heat and melting the metal, friction is used to "plasticize" the metal which forms "seamless" welds.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/18/2016 10:41 pm

I would like to posit that SpaceX inspects every single weld on every single vehicle, and/or that no welds were weak or faulty.

Same words apply to every launch vehicle since day one.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/18/2016 11:02 pm

The weld failure exposed a fresh-cut aluminum-lithium edge, which is reactive in LOX, and the shock wave generated by the weld failure provided all the remaining energy needed to start the metal on fire, right along the weld line connecting the common bulkhead to the tank skin. 

I really hate to disagree with a fellow Minnesotan, but I must.

First, I looked through a number of NASA technical reports on the flammability of various AL-LI alloys.  The results basically concluded that they were very expensive but had about 10 X lower flammability ratings than pure aluminum.  The testing was in LOX environments and specific tests to determine how to burn the metal in LOX.  AL-LI was rated as better than stainless steel and considered an ideal tank material, albeit not recommended for turbo pumps and other environments where friction could raise the temperature to the melting point, which was the flash point.

Granted that a weld failure could generate the 1kC plus temperature required for AL-LI alloy burn initiation, the burn rates were extremely slow, measured in fractions of feet per second.  While disconcerting and fatal for the studied mission configurations, they were well below the 1k fps conflagration indicated in the video.

Finally, to purport that the energy dump of the fracture was sufficient to be the initiator detonation, that's cool, but you have to have a structural failure consistent with a 16 ms event.  My best guess says that event required the equivalent to 50 to 100 pounds of TNT. At 4 megajouls per kg, were talking about a minimum of 88 megajoules of energy release from a crack.

All this has to happen in 16 milliseconds.

I really have a hard time swallowing that, even after a Jucy Lucy at Matts and 2 pints of Coors.

I can't offer a better theory, but this one to me, fails the sniff test.

Going for the 3rd pint now.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: kraisee on 09/18/2016 11:06 pm
They thoroughly inspect every FSW join in-situ on the welding machine, using various ultrasonic systems that have been developed specifically for FSW.   They've been doing so since they started, back on the Falcon 1's.

By now they are arguably one of the most experienced companies in the world with such techniques and I find it very hard to believe they made that sort of mistake.

Any theoretical damage to the US structure is IMHO, far more likely to have occurred after the tank left the factory.

I personally think the 75-77K oxygen frost buildup on the exterior is a more likely cause.   Or an internal COPV/Helium system failure - maybe.

Ross.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/18/2016 11:08 pm
They thoroughly inspect every FSW join in-situ on the welding machine, using various ultrasonic systems that have been developed specifically for FSW.   They've been doing so since they started, back on the Falcon 1's.   By now are arguably one of the most experienced companies in the world with such techniques.


Not really, there are many with the same or more.  There were earlier adopters of the technique still in work.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: GerryB on 09/19/2016 02:22 am
The weld failure exposed a fresh-cut aluminum-lithium edge, which is reactive in LOX, and the shock wave generated by the weld failure provided all the remaining energy needed to start the metal on fire, right along the weld line connecting the common bulkhead to the tank skin. 

The initial flash expressed the fast fire of the tank skin, fed by the LOX behind it.  As regular air crept in and LOX immersion was replaced by air and combustion gasses, the rate of combustion of the tank skin slowed, and the fire receded, accounting for the very bright initial flash and its subsequent dimming.

I am very supportive of the idea a weld being a feasable initial tank failure point, no matter how many inspections or tests were made. I like your justifications of the extreme joint stresses (in multiple, repeated, varying loads and extreme temperature changes).

The "exterior flash is burning tank Al, propelled by internal LOX+Al detonation" part of your hypothesis isn't supported by Aluminum's behavior nor the actual video we've over-studied so much. Aluminum sheets and tubes in pure LOX can be ignited and cause shock waves, (https://books.google.com/books?id=rmhPj4lDWHcC&pg=PA192&lpg=PA192&dq=aluminum+tubing+in+liquid+oxygen&source=bl&ots=3rZc8So_WS&sig=_GnuuEBFhEVnofP8WXZ2m86YYdA&hl=en&sa=X&ved=0ahUKEwjpo53fqprPAhVN-2MKHUoNA0wQ6AEIKTAC#v=onepage&q=aluminum%20tubing%20in%20liquid%20oxygen&f=false) but the reaction is self-dampening mostly by the heat transport of the LOX itself.  Such an internal event could certainly cause a pressure wave and further cascading failures, but it would not create a 5+ meter fireball of detonated aluminum at hypersonic  speeds.
The reference also discusses the LOX+solid Al reaction is dependent on having not even minute contamination of the LOX. Unless the LOX is 99.9999% (not even 99.9!) pure, the contaminants (usually Ar and N) tend to significantly interfere with the reaction propogation. Of course maybe the F9's LOX is ultra pure for reasons of rocket combustion.. I don't know.

But I think your weld story is quite reasonable in explaining a small shock, extending the crack or failure, perhaps invisible to eye,  that could have created a small pressurized leak in the RP1 bulkhead or wall. It was that leak that accumulated an RP1 aerosol mixing with vented GOX that later (perhaps several seconds later) detonated.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: oldAtlas_Eguy on 09/19/2016 02:37 am

I would like to posit that SpaceX inspects every single weld on every single vehicle, and/or that no welds were weak or faulty.

Same words apply to every launch vehicle since day one.
A point of trivia for the welding calibration and inspection and in support of it being done frome day one is that the standard procedure for doing the spot welds on the Atlas (this is the Atlas al la 1956 incarnation) that prior to usage of the spot welder two stainless steel test coupons one for each sheet associated with its specific source role id oriented in the exact way that the welding is to be done are welded together and then this coupon goes off to the lab to be x-rayed and then sliced through the weld to inspect the metal microscopically for proper welding. So I doubt that SpaceX is less diligent than what was done for ICBMs mass produced in the 100+ quantities over just a few years prior to the 1960s.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: liometopum on 09/19/2016 03:26 am
Quote
Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

I googled part of that sentence:

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Johnnyhinbos on 09/19/2016 03:39 am
I think perhaps it's a good time to remember that SpaceX routinely rotates first stages with two cranes, picking up the stage from the very ends. We've all seen it many times, both at McGregor and at Port Canaveral. I know the issue happened on the second stage, but folks keep coming back to the (artificially) perceived frailty of these rockets. They aren't. At all.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: liometopum on 09/19/2016 03:57 am
Quote
Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #3055 on: 09/18/2016 12:00 AM »
LikeQuote
Quote from: glennfish on 09/17/2016 10:27 PM
Quote from: RotoSequence on 09/17/2016 10:12 PM
Quote from: glennfish on 09/17/2016 09:27 PM
In answer to a PM about the "possible" change that doesn't meet my definition of statistically significant.  I've circled it in the cropped image below.

Aren't those spots the exact centers of two of the initial diffraction flares?

With all due respect, as I've posted twice previously, the "diffraction flares" are internal lens barrel reflections.  They point to the center of the putative "X" if and only if the lens and the light source are at the center of the field of view and all of the internals of the lens are symmetric, which is unlikely if this is a zoom lens.

Since the brightest illumination is offset from the center of the field of view, the "diffraction flares" are pointing to a location different from the brightest point.  How much offset requires knowing the lens, having the lens, testing the lens, and calculating the "flare" deviation as the source drifts from the center of the field of view.

If the the "flare" analysis points to the area identified, then I assure you, the brightest point is not there.  It's probably someplace to the right, but without knowing or testing the lens, all I can be sure of is the flare "X" probably doesn't point to the brightest spot, which is most likely to the right of the "X", but could be left depending on the element count in the lens, and where the reflections occur in the lens barrel.

Here is a starry photo made through a _refractor_ telescope (Skywatcher Esprit-100). As you see, there _are_ diffraction spikes, and they _are_ centered on each star.

The first three explosion frames show X's. The centers of those X's are clustered, the first X along the right edge of the rocket, and the other two further over, to the right and above, the initial point. 
The X's mark the brightest spot on the images.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: liometopum on 09/19/2016 04:46 am
Additionally, on frame 2, notice how that bulge, on the center, right edge of the fireball, is ejected out further than the rest of the fireball.

Its height is very close to the center of the X's. Remember the X on explosion frame one (EF1) is slightly lower than the X on EF2, as is this bulge.

This may represent ejection from the presumed point of the EF1 explosion, the X in frame one, that is at the right edge of the F9, and slightly lower than the X in this frame.

And no debris is present, also supporting that the explosion was at the exterior surface of the rocket, at the point of the X on EF1.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IainMcClatchie on 09/19/2016 05:54 am
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

This is generally correct.  A four vane spider produces four diffraction spikes.  A three or six vane spider produces six diffraction spikes.

Guys/Gals  go have your debate.  This video's X doesn't point to the "brightest spot" which is probably a diffuse "brightest spot".   Show me the math that converges the X to a single point.  There is math for that.

There is indeed.

[Switch into camera geek mode.  I design these things for a living.]

The point spread function is the light pattern you get on the sensor from a single point of incoming light, like a star.  Any image you get will be the point spread function convolved with the incoming pattern of light.

The dominant terms of the point spread function are related to a Fourier transform of the aperture.  From the Wikipedia page on Fraunhofer Diffraction (http://"https://en.wikipedia.org/wiki/Fraunhofer_diffraction"), here is the PSF of a rectangular aperture (By Epzcaw - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15782478).  Generally speaking, deviations of the aperture away from circular lead to spikes.  This rectangular aperture has a very large deviation and so very strong spikes.
(https://upload.wikimedia.org/wikipedia/commons/1/18/Rectangular_diffraction.jpg)

It is possible to also have contributions to the PSF from internal reflections inside the lens.  I have screwed up lenses to have these defects in the past.  You'll get faint rainbows, ellipsoid, and mushroom shaped artifacts, and the effect will vary tremendously with the position on the focal plane.  The Xs in the video we're looking at are not these kind of artifacts.  The spikes from aperture imperfections, on the other hand, are generally consistent across the image.

Apertures in refractive camera and video lenses are often noncircular because the aperture stop blades cannot be shaped to maintain a circular aperture at all possible settings.  They compromise and get it close in most cases.

So here's the kicker: the aperture spikes are generally circularly symmetrical.  That means the center of those X's are indeed the brightest spots in the image.  For off-center bright spots in a wide angle lens, there can be some distortion, but we don't have those effects here.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Digitalchromakey on 09/19/2016 10:03 am
Additionally, on frame 2, notice how that bulge, on the center, right edge of the fireball, is ejected out further than the rest of the fireball.

Its height is very close to the center of the X's. Remember the X on explosion frame one (EF1) is slightly lower than the X on EF2, as is this bulge.

This may represent ejection from the presumed point of the EF1 explosion, the X in frame one, that is at the right edge of the F9, and slightly lower than the X in this frame.

And no debris is present, also supporting that the explosion was at the exterior surface of the rocket, at the point of the X on EF1.
The video recording only represents 16.7ms samples of what actually happened, so the apparent center of the explosion may well not be the actual starting/ignition point of the explosion, just the center of the bulk of the fuel for the initial FAE.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: gospacex on 09/19/2016 10:42 am
I personally think the 75-77K oxygen frost buildup on the exterior is a more likely cause.

Oxygen does not explode by itself. It needs fuel. What was the fuel?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacekid on 09/19/2016 11:55 am
And no debris is present, also supporting that the explosion was at the exterior surface of the rocket, at the point of the X on EF1.
Good point.

I think the explosion pierced the side of the upper stage beginning its demise but it didn't obliterate it, another sign of how strong these rockets are.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: photonic on 09/19/2016 11:58 am

[...]

The point spread function is the light pattern you get on the sensor from a single point of incoming light, like a star.  Any image you get will be the point spread function convolved with the incoming pattern of light.

[...]

So here's the kicker: the aperture spikes are generally circularly symmetrical.  That means the center of those X's are indeed the brightest spots in the image.  For off-center bright spots in a wide angle lens, there can be some distortion, but we don't have those effects here.

[Amateur space geek, but working in optics for the last 15 years] I can confirm this story: unless there is something realy funny going on, every strong point-like source in an image will look to be convolved with the point-spread-function of the imaging system. This means that e.g. in case of a telescope, you will see diffraction spikes centered around each star, see the various images here: https://en.wikipedia.org/wiki/Diffraction_spike.

This means that the center of the X should likely point to the brightest spot in the scene.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: starhawk92 on 09/19/2016 12:50 pm
. . . . and see if *y'all* think . . . .

Sorry Doug, it's just hard to take seriously a Minnesotean who writes Southern.  I'm pretty sure everyone here knows the correct way to say that in 'Sotean is " . . . and see if yousguys think . . . . ".
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Rocket Science on 09/19/2016 12:51 pm
When I have been speaking of a failure at at FSW at the common bulkhead or at the base of a COPV mount nearby at the tank wall all may seem normal during a NDE. The weld itself can be fine but a surrounding material may fail or the weld interface itself...
http://www.worldcat.org/title/proceedings-of-the-1st-international-joint-symposium-on-joining-and-welding-osaka-japan-6-8-november-2013/oclc/890090103

Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: liometopum on 09/19/2016 02:21 pm
Quote
Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
« Reply #3082 on: Today at 10:03 AM »

The video recording only represents 16.7ms samples of what actually happened, so the apparent center of the explosion may well not be the actual starting/ignition point of the explosion, just the center of the bulk of the fuel for the initial FAE.

So, if I get this correctly, you are saying the X marks where the bulk of the fuel was, and not necessarily the point where the blast started.

For sure it marks the bulk of the fuel in each frame, as that is the point of greatest light output.

But the explosion started DURING the first time interval, so that frame's explosion represents something less than that shown in successive frames, meaning the first explosion frame is even closer to the source of the problem than a normal frame would suggest. 

It takes LOX to make this first explosion step go so quickly. If the explosion started somewhere else, where would it get the LOX to flash?

This first X is on the surface of the rocket. An explosion interior would show debris flying outwards, and we don't see that. If the explosion started off the rocket, there is no LOX. 

Close examination of the "bulge-on-the-bulge" shows it too may have 'launched' from the point of that first X, on the rocket surface. That is, we are seeing the emergence of the effect of the start of the blast. In this image, I have overlaid the X's from the first two frames (red X is first explosion frame), and the bulge-on-the-bulge, on the last, pre-explosion, frame. The circle is the location of the bulge-on-the-bulge in explosion frame 2. It looks like it blew out almost horizontally, with just a slight upward angle, that became more pronounced as the explosion continued.

I'd like to propose that the bulge-on-the-bulge may be a critical and separate piece of evidence to determine the starting point of the blast. I'd encourage some of you to analyze this, better than I can.





Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Jim on 09/19/2016 02:45 pm
just the center of the bulk of the fuel for the initial FAE.

what FAE?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: CorvusCorax on 09/19/2016 03:45 pm
There's only a limited number of possible energy source combinations for the "fire" in the fireball:

Solid fuel, solid oxidizer ( an explosive charge, like in flight abort sys or solid rocket boosters orullage rockets, i think this has been ruled out)

Solid fuel, liquid oxydizer ( like lox burning the aluminium tank wall or a blown to dust COPV in liquid oxygen)

Solid fuel gaseous oxydizer ( not fast enough for this kinda flash, unless oxydizer under pressure, is it?  Edit: wrong, it could be in a "dust explosion" like in a flour silo. That situation even comes with static charge as builtin ignition source)

Liquid fuel, solid oxydizer (combo imho N/A but for sake of completeness)

Liquid fuel liquid oxydizer ( would have to be pre mixed or very rapidly mixing for this kinda flash i think)

Liquid fuel , gaseous oxydizer ( imho would have to be pre- mixed or very rapidly mixing for this kind of flash - also called FAE under some circumstances)

Gaseous fuel, solid oxydizer (??? I cant even come up with one)
Gaseous fuel, liquid oxydizer ( i dont think there any flammable gases anywhere near the TE or rocket)
Gaseous fuel, gaseous oxydizer ( unless a RP1 or hydraulic fluid overheated and boiled, but that should show on sensors wayyyybefore)

Which do you think are we seeing in the frame 0 flash? Based on shape, speed size and colour of flash?

Edit: or maybe more important,can combos be ruled out from the flash?

 (please disregard the likeliness of availability of those constituents for that answer thats supposed to be separate. I want to avoid a "hmm looks like solidcharge but that cant be so i say something else" self censorship. )
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Moskit on 09/19/2016 04:46 pm
There's only a limited number of possible energy source combinations for the "fire" in the fireball:

Thank you for posting the list!

Let's keep in mind that SpaceX seems to know (based on their tweets) where fuel and oxidizer came from (which we don't) and were puzzled just by the source of heat (for ignition).
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Comga on 09/19/2016 05:26 pm
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

Guys/Gals  go have your debate.  This video's X doesn't point to the "brightest spot" which is probably a diffuse "brightest spot".   Show me the math that converges the X to a single point.  There is math for that.

I'll watch your debate and intervene if someone goes totally whacko.

Meanwhile I'm posting on the whacko thread.

Optics is my profession.
The diffraction spike should cross at the point of maximum brightness.
They are not reflections from the lens barrel.  (Those would be "ghosts" and look different.)
The two spikes indicate to linear "obstructions", either spiders or aperture blades in front of or within the "lens", or even photographing through a window screen. 
The existence of "spiders" is not common for lenses, but they could have used a telescope with spiders.  We could ask.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/19/2016 05:35 pm

The weld failure exposed a fresh-cut aluminum-lithium edge, which is reactive in LOX, and the shock wave generated by the weld failure provided all the remaining energy needed to start the metal on fire, right along the weld line connecting the common bulkhead to the tank skin. 

I really hate to disagree with a fellow Minnesotan, but I must.

First, I looked through a number of NASA technical reports on the flammability of various AL-LI alloys.  The results basically concluded that they were very expensive but had about 10 X lower flammability ratings than pure aluminum.  The testing was in LOX environments and specific tests to determine how to burn the metal in LOX.  AL-LI was rated as better than stainless steel and considered an ideal tank material, albeit not recommended for turbo pumps and other environments where friction could raise the temperature to the melting point, which was the flash point.

Granted that a weld failure could generate the 1kC plus temperature required for AL-LI alloy burn initiation, the burn rates were extremely slow, measured in fractions of feet per second.  While disconcerting and fatal for the studied mission configurations, they were well below the 1k fps conflagration indicated in the video.

Finally, to purport that the energy dump of the fracture was sufficient to be the initiator detonation, that's cool, but you have to have a structural failure consistent with a 16 ms event.  My best guess says that event required the equivalent to 50 to 100 pounds of TNT. At 4 megajouls per kg, were talking about a minimum of 88 megajoules of energy release from a crack.

All this has to happen in 16 milliseconds.

I really have a hard time swallowing that, even after a Jucy Lucy at Matts and 2 pints of Coors.

I can't offer a better theory, but this one to me, fails the sniff test.

Going for the 3rd pint now.

I'm doing something I rarely do, especially in this thread -- I'm responding to a post when there are lots of posts, a page or two (in my set-up, at 100 posts a page) after it.  Because it's such a good post.

First, thanks for the good numerical analysis of the energy required to generate the initial flash, and the burning characteristics of the Al-Li alloys.  I will say that you're sort of connecting the initial event to the first visible flash -- the fire could have been burning along a failed weld for a second or two, building up combustion products and generating a pressure wave into the LOX, along with a possible bounce-back pressure wave, before the fire burned through the tank wall.  So, initiating energy in terms of the original fire may not be directly related to the energy seen in the flash.  Some things could have added to that energy, including the rapid decompression of the combustion products through the hole in the tank.

The biggest thing to respond to is the point where I used a really big weasel-word phrase -- where I said that my scenario posited that SpaceX doesn't inspect every weld, or at the best missed a bad weld in their inspection process.  I qualified the theory with that phrase because that was what I thought was the weak point of the theory.

Now, error-prone human beings are making these things, and such things like bad welds have passed inspections before.  But, especially with FSW (and yes, I've seen the same "Impossible Engineering" episode y'all did about SLS, which incidentally makes it sound like NASA invented FSW just for assembly of SLS... ;) ), I would think that the weld quality is intrinsically higher, that bad welds are less likely, and inspections would have a higher probability of catching them if they did occur.

As I said, I wasn't in love with the theory, for a variety of reasons, especially that it would require conditions occurring that ought to have been obvious in the telemetry.  For example, if a bad weld snapped, the vibration it would create likely would have shown up in the accelerometer data.  And any combustion lasting for more than a few milliseconds inside the LOX tank ought to have shown up in the pressure readings in the tank.  These kinds of telemetry indications would seem to conclusively prove that the problem originated inside of stage 2.

Seeing as how SpaceX, at last announcement, weren't sure if the initiating event happened inside or outside of the rocket, you'd think that rules out any event inside the tank that took more than a few milliseconds from initiation to tank wall failure.  And I can't convince myself that my little theory would have happened in that short of a timeframe.

But, hey, it was a sequence of events that could have resulted in what we saw, and since it has to be expressed in the complete absence of any of the detailed data available to SpaceX, I figured it was just as good as any of the other speculation I'm hearing, and doesn't (for example) depend on the generation of explosive LOX-soaked frost for the first time in 60 years of launching rockets filled with LOX... ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: the_other_Doug on 09/19/2016 05:42 pm
. . . . and see if *y'all* think . . . .

Sorry Doug, it's just hard to take seriously a Minnesotean who writes Southern.  I'm pretty sure everyone here knows the correct way to say that in 'Sotean is " . . . and see if yousguys think . . . . ".

My family is originally from places like Houston and southern Indiana -- I come by it legitimately.  Also, I am a transplanted Illinoisan, though I have been living in Mpls for more than 20 years.  I now regularly use the terms "y'all" and "oof-da!" in the same sentence, eh?  :D
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: feynmanrules on 09/19/2016 06:20 pm
While some of the commentary on this thread has been covered in this video, it hasn't been put together in such a comprehensive way to my knowledge.

It's interesting because he syncs up the audio with the video and points out that there is a pop and what definitely sounds like a metal screech/groan 5 seconds before the explosion.   he then postulates (similar to jim's best guess at least as I understand) that it's most likely an he COPV breaking through the barrier between two tanks in s2.   he also briefly empathizes w/difficulty noticed by many here re:extracting info from frames preceding the deflagration.

Detailed analysis of Spacex Rocket Explosion (https://www.youtube.com/watch?v=EhdQPaABFK0)

(via: peter de selding https://twitter.com/pbdes)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: liometopum on 09/19/2016 06:42 pm
What software did Mason use in his "Detailed Analysis ... " video?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Semmel on 09/19/2016 07:24 pm
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

Guys/Gals  go have your debate.  This video's X doesn't point to the "brightest spot" which is probably a diffuse "brightest spot".   Show me the math that converges the X to a single point.  There is math for that.

I'll watch your debate and intervene if someone goes totally whacko.

Meanwhile I'm posting on the whacko thread.

Optics is my profession.
The diffraction spike should cross at the point of maximum brightness.
They are not reflections from the lens barrel.  (Those would be "ghosts" and look different.)
The two spikes indicate to linear "obstructions", either spiders or aperture blades in front of or within the "lens", or even photographing through a window screen. 
The existence of "spiders" is not common for lenses, but they could have used a telescope with spiders.  We could ask.

Comga, I am not an optical engineer (but I could ask one tomorrow, I am on a astronomy workshop and have access to about 5 or so). Could the diffraction cross come from something like a lens hood?

https://en.wikipedia.org/wiki/File:Five_lens_hoods.JPG

A ghost would actually pretty helpful because it would likely not be overexposed. Unfortunately, US Launch Report seems to have used good gear ;)
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Kabloona on 09/19/2016 07:35 pm
What software did Mason use in his "Detailed Analysis ... " video?

Comments on the YouTube video say it was  Sony Vegas Pro.

It's interesting because he syncs up the audio with the video and points out that there is a pop and what definitely sounds like a metal screech/groan 5 seconds before the explosion. 

Those "precursor" sounds were noted here shortly after the USLR video was first made public, and have been discussed extensively upthread.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Comga on 09/19/2016 07:37 pm
Diffraction spikes are caused by the spider suspending the secondary mirror in a telescope.
Symmetrical pairs of spikes indicate the spider is a symmetrical four-vane assembly.

Guys/Gals  go have your debate.  This video's X doesn't point to the "brightest spot" which is probably a diffuse "brightest spot".   Show me the math that converges the X to a single point.  There is math for that.

I'll watch your debate and intervene if someone goes totally whacko.

Meanwhile I'm posting on the whacko thread.

Optics is my profession.
The diffraction spike should cross at the point of maximum brightness.
They are not reflections from the lens barrel.  (Those would be "ghosts" and look different.)
The two spikes indicate to linear "obstructions", either spiders or aperture blades in front of or within the "lens", or even photographing through a window screen. 
The existence of "spiders" is not common for lenses, but they could have used a telescope with spiders.  We could ask.

Comga, I am not an optical engineer (but I could ask one tomorrow, I am on a astronomy workshop and have access to about 5 or so). Could the diffraction cross come from something like a lens hood?

https://en.wikipedia.org/wiki/File:Five_lens_hoods.JPG

A ghost would actually pretty helpful because it would likely not be overexposed. Unfortunately, US Launch Report seems to have used good gear ;)

Lens hoods are designed to NOT vignette (or stick into and obstruct) the aperture while coming as close as practical given the precision, or imprecision, of manufacturing, mounting, and adjusting them. However, if a lens hood was rotated out of proper alignment, it could vignette with the tilted "X" pattern of the diffraction spikes, but their curved edges suggests that is not the cause of the spikes.  (Search "curved secondary spider" to see how curves are used to suppress diffraction spikes.)

Ghosts are rarely helpful.   ;D  They are generally just blobs, shaped like the aperture if anything.

edit: typo
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: Wolfram66 on 09/19/2016 08:01 pm
While some of the commentary on this thread has been covered in this video, it hasn't been put together in such a comprehensive way to my knowledge.

It's interesting because he syncs up the audio with the video and points out that there is a pop and what definitely sounds like a metal screech/groan 5 seconds before the explosion.   he then postulates (similar to jim's best guess at least as I understand) that it's most likely an he COPV breaking through the barrier between two tanks in s2.   he also briefly empathizes w/difficulty noticed by many here re:extracting info from frames preceding the deflagration.

Detailed analysis of Spacex Rocket Explosion (https://www.youtube.com/watch?v=EhdQPaABFK0)

(via: peter de selding https://twitter.com/pbdes)

can anyone explain the line or tongue of flame extending down the S1 in the Frame1 image[first frame to show explosion]. it can't be RP1 and cant be just a reflection of GOX vapor.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/19/2016 08:12 pm

can anyone explain the line or tongue of flame extending down the S1 in the Frame1 image[first frame to show explosion]. it can't be RP1 and cant be just a reflection of GOX vapor.


Previous discussion this thread with someone who was looking at the separate RGB channels.  It's most visible in the blue.

It's very consistent with a water vapor cloud absorption spectrum between the fireball and the camera.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: AJW on 09/19/2016 08:40 pm
I heard a story about FSW at SpX where there was a problem with the FSW tool tip.  Apologies that this is vague and I am just retelling my understanding of the circumstance. 

The automated FSW process completed, external visual inspection looked fine since it was already a tight fit.   Turned out that the FSW tip wasn't contacting the internal surface properly, so the system went through the motions, but no FSW had actually occurred.   The process was changed to add additional inspections following each weld, including inspection of the tip.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/19/2016 09:07 pm
Additionally, on frame 2, notice how that bulge, on the center, right edge of the fireball, is ejected out further than the rest of the fireball.

Its height is very close to the center of the X's. Remember the X on explosion frame one (EF1) is slightly lower than the X on EF2, as is this bulge.

This may represent ejection from the presumed point of the EF1 explosion, the X in frame one, that is at the right edge of the F9, and slightly lower than the X in this frame.

And no debris is present, also supporting that the explosion was at the exterior surface of the rocket, at the point of the X on EF1.

To me, that looks a lot like frame 5.  Where did you get this video image?  On the USLR video, that bird is on that position on frame 5.

Debris are visible in Frame 2,3,4, and two on frame 5
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: glennfish on 09/19/2016 09:31 pm
On the X.


Let's get some specific agreement on some numbers here if we're going to say this is evidence.

Inclusive of  frames1 thru frames5 here's what I see.

The flares are +- 56 degrees.

On a video image size of 1920 by 1080, the width of each flare is approximately 30 pixels.

Pre-event flares are visible on the lights on the ground on the bottom of the frame.  What are the angles on those?

What #s do you come up with?

In drawing a line for an X, what are your criteria for selecting a start and end point?
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: spacejulien on 09/19/2016 09:35 pm
Way back about 100 pages or so I presented my theory, but nobody commented on it. Maybe this time I will get some feedback. SpaceX has the unique super-cooled LOX. This means there is little prior experience or documentation. Metal expands or contracts with temperature. The rocket empty may have been slightly hotter than usual in the hot Florida sun, but I don't point this out as most likely cause, just say'n. The LOX tank gets filled chilling the bottom of the tank creating a large temperature difference between it and the top of the RP1 tank just below. Super cooled LOX at -210°C and top of RP1 at least +30°C so a difference of about 240°C. Expansion coefficient of aluminum is 22.2x10^-6 m/°K for a circumference of 3.6m*pi = 11.3m is therefore 60cm by my calculations. I think that will create a huge amount of stress at the LOX/RP1 joint. The bang heard before the explosion could be the tank cracking open. However, this in itself does not explain the fire. Somewhere upthread it is explained that LOX in contact with freshly exposed aluminum will spontaneously ignite. If the crack propagated into the LOX tank and opened up then LOX would escape through the crack and explode.

You dropped a decimal place somewhere. 0.000022 [m/m-K] *11.3 [m] * 200 [K] = 0.00498 [m] or about 5 cm.     
That's less than 0.5% strain, and commercial Al-Li alloys exhibit a minimum of 12% tensile strain before fracture, at 77 K temps.

I thought the RP-1 was also sub-cooled, and loaded before LOX, so the temperature diffference won't be that big either.

I believe the RP1 tank is not filled to the top, so the top of the tank could be considerably warmer than the liquid portion below. However this is a moot point as explained by envy881.

Thermal mismatch of a cylindrical container is calculated radially. With the radius of 1.8m the radial shrink of the filled LOx tank would be 22.2x10^-6 m/°K *1.8 m * 200 K = 0.0095 m = 9.5 mm (0.4 inch roughly). This is no big deal.

Under flight ullage pressures of about 2.5 to 3.5 bars rocket tanks radially extend by similar amounts:
A tank barrel section is dimensioned by p * r = sigma/ju * t = E * eps * t . With:
p = pressure
r = tank radius
sigma = stress
ju = ultimate factor of safety (assumed 1.5)
t = wall thickness
E = Young's modulus
eps = elongation
Use the middle and right side and set stress sigma to ultimate limit Rm: E*eps = Rm/ju .
Solving for eps: eps=Rm/ju/E = 600 MPa / (1.5 * 80000 MPa) = 0.005 = 0.5% .
Radial expansion is thus eps * r = 0.005 * 1800 mm = 9 mm

Under such thermal mismatch the tank just assumes an S-shape (in the longitudinal section) to accommodate the different radii.
Ok, I have seen shitty designs with stringer stiffening that prohibit the S-shape and such design has stress concentrations at the onset of these stringers which are thus prone to excessive yielding or even crack initiation. But as all designs are thoroughly analysed and optimised they usually don't make it into the final product. And if they do then it's because the analyses have shown them to be bearable.

I've seen tanks attached to stiff ambient temperature CFRP skirts via a 200 mm metallic skirt, enough for the tank to shrink and the CFRP to maintain its radius and the skirt doing the S-shape.

All this talk about subcooled LOx lets people forget that we're launching rockets with liquid Hydrogen @ 20 K since decades. Thermal mismatch included.
Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
Post by: IainMcClatchie on 09/20/2016 12:25 am
Here's spacejulien's s-curve.
(https://dl.dropboxusercontent.com/u/84857707/Cold%20Stage2%20tank.png)

The left image shows the temperature profile, the right image shows the deformation (times 20).  Ideally this would have been all one image but I just banged it out and this was easier.  You have to kind of eyeball the vertical shrinkage between the two.  The cut lines show the levels to which I filled the tanks with LOX (top) and kerosene (bottom).  Note that the kerosene is in contact with the bottom of the intertank bulkhead.

I didn't put any stringers in, they would greatly increase the strains and add local strain concentrations.  I don't know what the stringer design is, and the guys designing this thing are using the same analysis I am, so they'll have optimized that issue already.

Some things that I didn't expect:
  • The S curve happens below the spot on the tank where the S curve is, in the equithermal part of the tank wall.
  • The bottom of the kerosene tank gets pushed up by the strains on the tank above it.
  • When LOX and kerosene touch opposite sides of a thin plate of AlLi, LOX wins, utterly.  The kerosene might actually freeze solid, but if it doesn't the convection coefficient of liquid kerosene getting a bit more dense from cooling is nothing like the convection coefficient of LOX boiling on contact.  The metal wall is driven under the LOX boiling temperature, at which point the LOX switches to all-liquid convection.

  • Does anyone know if the kerosene actually does contact the bottom of the LOX dome, and if so, do they have some insulation on it to prevent the kerosene from forming wax on the bottom of that dome?  It seems like you could easily grow several cm of wax, which would be heavy and unusable as fuel.

    Another thing I learned is that the stringer design is going to be complicated by the thermal loads of reentry, when the level of the LOX and kerosene is changing and a significant amount of heat comes in the side.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: mn on 09/20/2016 12:47 am
    just the center of the bulk of the fuel for the initial FAE.

    what FAE?

    I see a fireball. We know that needs fuel and air. (You can argue that technically it was not an explosion but that is semantics at this point).

    So if this is not a FAE what would you call it?

    You can argue that it was not the 'initial event' but I don't see how you can argue against a FAE
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: ejb749 on 09/20/2016 01:03 am
    Here's spacejulien's s-curve.
    ...

    The left image shows the temperature profile, the right image shows the deformation (times 20).  Ideally this would have been all one image but I just banged it out and this was easier.  You have to kind of eyeball the vertical shrinkage between the two.  The cut lines show the levels to which I filled the tanks with LOX (top) and kerosene (bottom).  Note that the kerosene is in contact with the bottom of the intertank bulkhead.

    I didn't put any stringers in, they would greatly increase the strains and add local strain concentrations.  I don't know what the stringer design is, and the guys designing this thing are using the same analysis I am, so they'll have optimized that issue already.

    Some things that I didn't expect:
  • The S curve happens below the spot on the tank where the S curve is, in the equithermal part of the tank wall.
  • The bottom of the kerosene tank gets pushed up by the strains on the tank above it.
  • When LOX and kerosene touch opposite sides of a thin plate of AlLi, LOX wins, utterly.  The kerosene might actually freeze solid, but if it doesn't the convection coefficient of liquid kerosene getting a bit more dense from cooling is nothing like the convection coefficient of LOX boiling on contact.  The metal wall is driven under the LOX boiling temperature, at which point the LOX switches to all-liquid convection.

  • Does anyone know if the kerosene actually does contact the bottom of the LOX dome, and if so, do they have some insulation on it to prevent the kerosene from forming wax on the bottom of that dome?  It seems like you could easily grow several cm of wax, which would be heavy and unusable as fuel.

    Another thing I learned is that the stringer design is going to be complicated by the thermal loads of reentry, when the level of the LOX and kerosene is changing and a significant amount of heat comes in the side.

    What would happen if the LOX is partially filled, and there was a pause for some reason, and then filling resumed.  The tank deflection could take a different path from the un-deformed shape to fully deformed shape then if the filling was continuous.   The bottom would contract more during the 'soak' time and reach it's fully deformed shape sooner.   Could an unexpected intermediate shape cause extra stress somewhere?  ... and maybe a 'pop' sound?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: kolkmvd on 09/20/2016 09:42 am
    can anyone explain the line or tongue of flame extending down the S1 in the Frame1 image[first frame to show explosion]. it can't be RP1 and cant be just a reflection of GOX vapor.
    Why do you think it can't be just a reflection? For me it actually does, because this 'tongue' is visible in many frames of the explosion and its brightness follows the brightness of the actual *kaboom* up at S2 level.  It also does not develop or consumes GOX.

    Previous discussion this thread with someone who was looking at the separate RGB channels.  It's most visible in the blue.
    It's very consistent with a water vapor cloud absorption spectrum between the fireball and the camera.
    So you mean it's GOX reflection?

    The picture below has the brightness of the my-guess-for-reflection parts decreased.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: IainMcClatchie on 09/20/2016 10:32 am
    LOX boiling moves heat at an incredible rate.  AlLi conducts pretty well.  My guess is that the "cold soak" time for that tank to get to statis is on the order of minutes, all all of that is in the portion of the tank skin between the LOX and the bulkhead.  Time to statis for the wall in contact with LOX is seconds.

    It's interesting to think about the change of shape of the tank as it fills with LOX.  First though, without a significant heat source at the top (freezing water?) note that the top of the LOX tank is just going to go to something close to LOX temperature, as heat flows down the tank walls into the LOX.

    I don't have any good pictures of the stringers, but in this pic, it looks like they aren't continuous.
    (http://i.imgur.com/LS8VwKF.jpg)

    In this pic, it looks like the stringer shape might actually be a spring, which should allow some radial deflection of the wall with respect to the reinforcing ring.
    (http://images.inc.com/uploaded_files/image/feature-118-Elon-Musk-SpaceX-pop_7027.jpg)

    So maybe the S moves along the tank as it cools down, and that's just allowed by the stringer design.  Buckling being the catastrophic failure process that it is, you'd think that springiness would tend to increase the tendency to buckle, as springs have small response to the first little bit of deflection.  So I'm not super confident that stringer cross section is supposed to spring.

    I'm also a bit shocked to see that the rings are in four sections held together by bolted bridge plates.  That's great for adjustability, but those bolts have to be dissimilar to their nuts or you'd get galling.  Because they are dissimilar metals, it seems you'd automatically get a voltage across the union, and if LOX or Kerosene acts as an electrolyte at all, you've got a battery.  I'd also be curious if there is any iron in that hardware, as I've heard iron and LOX are bad together.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/20/2016 12:31 pm
    just the center of the bulk of the fuel for the initial FAE.

    what FAE?

    I see a fireball. We know that needs fuel and air. (You can argue that technically it was not an explosion but that is semantics at this point).

    So if this is not a FAE what would you call it?

    You can argue that it was not the 'initial event' but I don't see how you can argue against a FAE

    A fireball is not an FAE and there is nothing that shows that it is an FAE
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/20/2016 12:34 pm

    I'm also a bit shocked to see that the rings are in four sections held together by bolted bridge plates. 

    Bolts?  How about rivets?

    I'd also be curious if there is any iron in that hardware, as I've heard iron and LOX are bad together.

    There isn't going to be iron in there.  Give them the benefit of doubt on that level of detail
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: ejb749 on 09/20/2016 02:16 pm
    Here's another inside shot.  I see what Nasa means by people working inside the tank!  Look at all the tools and junk!

    (http://php.scripts.psu.edu/dept/sspl/uploads/News/Falcon9tank.jpg)

    and here's a little more info...
    http://selenianboondocks.com/2006/10/spacex-comstac-briefing/ (http://selenianboondocks.com/2006/10/spacex-comstac-briefing/)
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Kabloona on 09/20/2016 02:57 pm
    just the center of the bulk of the fuel for the initial FAE.

    what FAE?

    I see a fireball. We know that needs fuel and air. (You can argue that technically it was not an explosion but that is semantics at this point).

    So if this is not a FAE what would you call it?

    You can argue that it was not the 'initial event' but I don't see how you can argue against a FAE

    You can argue against an FAE if the combustion event began inside the stage with LOX meeting RP-1. The analysis video posted upthread by feynmanrules shows the center of the fireball lining up with the LOX/RP-1 bulkhead, which could have failed internally.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: liometopum on 09/20/2016 03:33 pm
    In the previous explosion, after launch... that spot where the explosion appears to start,  is that at the same place, the common bulkhead, that this explosion appears to start?

    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/20/2016 03:49 pm
    In the previous explosion, after launch... that spot where the explosion appears to start,  is that at the same place, the common bulkhead, that this explosion appears to start?


    no
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: MARSATTACK on 09/20/2016 06:02 pm
    Speaking of second stage common bulkhead, would an explosion occur if the lox and fuel were to mix following its  failure?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cambrianera on 09/20/2016 06:06 pm
    Stringers should be only in first stage RP-1 tank: likely no stringers in LOX tank nor in second stage.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: wtrix on 09/20/2016 07:00 pm
    Stringers should be only in first stage RP-1 tank: likely no stringers in LOX tank nor in second stage.

    Where you take this information from. Maybe there are less stringers there, but for tank integrity, they are incredibly good. You forget that even the second stage has to be able to carry ~11 metric tons under 30G acceleration. That's difficult to do with bare 4,5mm LiAl skin. Don't you find?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/20/2016 07:07 pm
    Speaking of second stage common bulkhead, would an explosion occur if the lox and fuel were to mix following its  failure?

    See the last sentence

    http://forum.nasaspaceflight.com/index.php?topic=30981.msg1583824#msg1583824
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: rsdavis9 on 09/20/2016 07:17 pm
    Stringers should be only in first stage RP-1 tank: likely no stringers in LOX tank nor in second stage.

    Where you take this information from. Maybe there are less stringers there, but for tank integrity, they are incredibly good. You forget that even the second stage has to be able to carry ~11 metric tons under 30G acceleration. That's difficult to do with bare 4,5mm LiAl skin. Don't you find?

    spacex web site user guide:

    first stage:
    LOX tank – monococque; Fuel tank – skin and stringer
    second stage:
    LOX tank – monococque; Fuel tanks – skin and stringer

    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: georgegassaway on 09/20/2016 07:19 pm
    Stringers should be only in first stage RP-1 tank: likely no stringers in LOX tank nor in second stage.

    Where you take this information from. Maybe there are less stringers there, but for tank integrity, they are incredibly good. You forget that even the second stage has to be able to carry ~11 metric tons under 30G acceleration.

    THIRTY G acceleration? 

    Don't you mean something more like three?

    Max thrust of Mvac of 210,000 pounds, and a 24,000 pound payload would be about 8.75 TWR.  But that is ignoring the mass of the 2nd stage (let's go with near-empty mass just before shutdown). Also, the Mvac can throttle down to about 39%. So include 2nd stage mass (near-empty), and 39% throttle-down and it would be right around 3 G's. 
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: CyndyC on 09/20/2016 07:34 pm

    can anyone explain the line or tongue of flame extending down the S1 in the Frame1 image[first frame to show explosion]. it can't be RP1 and cant be just a reflection of GOX vapor.

    Previous discussion this thread with someone who was looking at the separate RGB channels.  It's most visible in the blue. It's very consistent with a water vapor cloud absorption spectrum between the fireball and the camera.

    The "tongue of flame" or "water vapor cloud" can't be off at some distance between the fireball and the camera, because the lower portion of the tail is behind a vertical bar of the TEL, so it's right next to the rocket.

    What might be even more enlightening, not only about this observation but compared to everything that has been observed so far, is that the curve is most visible in the blue channel, and what's blue besides reflections of the sky is the blue of a flame, indicating the hottest and most oxygen rich portion, hotter than white.

    Full disclosure I'm going to try the power of suggestion here. First, you might want to light a candle and remind yourself how rarely you pay attention to any part of the flame other than the white tip, that a closer look reveals a hint of blue at the base, and above the blue is a translucent grayish core that remains inside the white of the flame.

    Next, you might want to view the "1/250x Speed" slow motion video on You Tube, and freeze it at the 34 second mark. If you have a Roku or Google Chromecast and can watch it on a large screen TV, even better.

    https://www.youtube.com/watch?v=HXqG-R8O39g

    You might see the same features I'm seeing if you view the full anomaly as a flame of a candle, all the way down to the middle of the diagonal brace of the TEL, which extends to the left at the lower half of the 1st stage. There would be the blue and hottest part, and the origin or closer to it, not at the attention grabbing fireball. What also can be considered are the blue flames given by Bunsen burners, gas range tops, and propane torches, all fed by gases much further below.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cambrianera on 09/20/2016 07:37 pm
    Stringers should be only in first stage RP-1 tank: likely no stringers in LOX tank nor in second stage.

    Where you take this information from. Maybe there are less stringers there, but for tank integrity, they are incredibly good. You forget that even the second stage has to be able to carry ~11 metric tons under 30G acceleration. That's difficult to do with bare 4,5mm LiAl skin. Don't you find?

    Load during flight is carried by pressurization.
    Stringers on RP-1 tank are needed only to stabilize the skin without pressurization (factory & hangar handling, transport) due to the mass of octaweb inducing a bending moment.
    Some shorter stringers would be used as attachment points.
    Lot of pictures in old threads, like these:
    http://forum.nasaspaceflight.com/index.php?topic=28882.msg916693#msg916693

    Most updated info is what rsdavis9 posted...
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: wtrix on 09/20/2016 08:02 pm
    Stringers should be only in first stage RP-1 tank: likely no stringers in LOX tank nor in second stage.

    Where you take this information from. Maybe there are less stringers there, but for tank integrity, they are incredibly good. You forget that even the second stage has to be able to carry ~11 metric tons under 30G acceleration.

    THIRTY G acceleration? 

    Don't you mean something more like three?

    Max thrust of Mvac of 210,000 pounds, and a 24,000 pound payload would be about 8.75 TWR.  But that is ignoring the mass of the 2nd stage (let's go with near-empty mass just before shutdown). Also, the Mvac can throttle down to about 39%. So include 2nd stage mass (near-empty), and 39% throttle-down and it would be right around 3 G's.

    Mybad. Saw somewhere a graph extending to 30G-s, which is not true.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: glennfish on 09/20/2016 09:15 pm

    can anyone explain the line or tongue of flame extending down the S1 in the Frame1 image[first frame to show explosion]. it can't be RP1 and cant be just a reflection of GOX vapor.

    Previous discussion this thread with someone who was looking at the separate RGB channels.  It's most visible in the blue. It's very consistent with a water vapor cloud absorption spectrum between the fireball and the camera.

    The "tongue of flame" or "water vapor cloud" can't be off at some distance between the fireball and the camera, because the lower portion of the tail is behind a vertical bar of the TEL, so it's right next to the rocket.

    What might be even more enlightening, not only about this observation but compared to everything that has been observed so far, is that the curve is most visible in the blue channel, and what's blue besides reflections of the sky is the blue of a flame, indicating the hottest and most oxygen rich portion, hotter than white.

    Full disclosure I'm going to try the power of suggestion here. First, you might want to light a candle and remind yourself how rarely you pay attention to any part of the flame other than the white tip, that a closer look reveals a hint of blue at the base, and above the blue is a translucent grayish core that remains inside the white of the flame.

    Next, you might want to view the "1/250x Speed" slow motion video on You Tube, and freeze it at the 34 second mark. If you have a Roku or Google Chromecast and can watch it on a large screen TV, even better.

    https://www.youtube.com/watch?v=HXqG-R8O39g

    You might see the same features I'm seeing if you view the full anomaly as a flame of a candle, all the way down to the middle of the diagonal brace of the TEL, which extends to the left at the lower half of the 1st stage. There would be the blue and hottest part, and the origin or closer to it, not at the attention grabbing fireball. What also can be considered are the blue flames given by Bunsen burners, gas range tops, and propane torches, all fed by gases much further below.

    I'll give you a different interpretation, keeping in mind we don't have a 3d reconstruction to tell where anything is in the foreground or background.

    If you examine the pre-event frame and look at clouding events, there are large ones to the left, and some partially obscuring the F9 body, and some venting between the F9 and the TE.  The fact that they are visible strongly suggest water vapor clouds from venting GOX at low temperatures.

    Now, if you imagine an explosion, what happens is that the shock wave tends to move stuff away from the center of the explosion.  If some of that water vapor were between the camera and the center of the detonation, the shock wave would push that water vapor towards the camera.  That water vapor could still be a cloud in that frame and it could still be in front of the fireball, albeit slightly behind the shock wave.

    see example of a shock wave moving clouds at 1:41 in this clip

    https://www.youtube.com/watch?v=p0xY69kUtdU
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: glennfish on 09/20/2016 10:22 pm
    What might be even more enlightening, not only about this observation but compared to everything that has been observed so far, is that the curve is most visible in the blue channel, and what's blue besides reflections of the sky is the blue of a flame, indicating the hottest and most oxygen rich portion, hotter than white.

    Full disclosure I'm going to try the power of suggestion here. First, you might want to light a candle and remind yourself how rarely you pay attention to any part of the flame other than the white tip, that a closer look reveals a hint of blue at the base, and above the blue is a translucent grayish core that remains inside the white of the flame.


    You might see the same features I'm seeing if you view the full anomaly as a flame of a candle, all the way down to the middle of the diagonal brace of the TEL, which extends to the left at the lower half of the 1st stage. There would be the blue and hottest part, and the origin or closer to it, not at the attention grabbing fireball. What also can be considered are the blue flames given by Bunsen burners, gas range tops, and propane torches, all fed by gases much further below.

    I totally missed something in your comment.

    In the BLUE channel, the cloud is darker, not brighter.  That means, less blue is coming through, not more.  In the red and green channels, it's mostly bright, a tad less in the green, and not at all in the red.

    There is structure visible in the blue channel, wipe out on the red, and barely something maybe there in the green.

    Essentially, it's brightest in the red channel, slightly less bright in the green, and clearly not as bright in the blue.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: SLC on 09/20/2016 11:19 pm
    An interesting article from The Space Review on "Non-Launch Mishaps", just to keep us busy while we wait for SpaceX to say something ...

    http://www.thespacereview.com/article/3064/1
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: CyndyC on 09/21/2016 12:27 am
    I totally missed something in your comment.

    In the BLUE channel, the cloud is darker, not brighter.  That means, less blue is coming through, not more.  In the red and green channels, it's mostly bright, a tad less in the green, and not at all in the red.

    There is structure visible in the blue channel, wipe out on the red, and barely something maybe there in the green.

    Essentially, it's brightest in the red channel, slightly less bright in the green, and clearly not as bright in the blue.

    Ok, thanks for clarifying that part, but I'm still inclined to look further down since a specific cause has not been found further up.

    A large apartment complex fire I worked back in my Red Cross days had an extremely odd cause that I recalled in association with my analysis here. A resident had backed into his parking space, and when he started up his car again, heat and sparks from his exhaust ignited the parched grass in front of his building. The trail of flame that resulted traveled across 20-30 feet of lawn and did considerable damage to his building and others next to it.

    It isn't obvious right away, but the entire length of the left side of the rocket is lit up almost as instantaneously as above.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: IainMcClatchie on 09/21/2016 12:46 am
    Why would the shorter kerosene tanks have stringers but the longer LOX tanks have none?

    And why would the first stage kerosene tank have stringers when the shorter second stage LOX tank has none?

    Is it that the rocket is moved with the kerosene tanks unpressurized and the LOX tanks pressurized?

    Or is it that the LOX tanks, due to the larger pressure changes they see, can't use stringers, and so use thicker skin sections?  I have also read the 4.5 mm thick spec for the Falcon's skins, and I don't believe it.  Because that skin is fabricated in barrels, it would be just too easy to make each barrel section a different thickness.  Because the stresses seen at each section are different, the weight savings available are significant.

    Now let me flip that argument around.  Although the LOX tank sees the largest temperature changes from inert to fully fuelled, the kerosene tank sees the largest temperature differentials while sitting fuelled on the pad.  So in the simulation I did, essentially all the temperature-induced strain (which wasn't much, since I had no stringers) was in the kerosene tank.

    The stringers in that tank from 2006 appear to be continuous, rather than divided into sections as in the pictures I posted.  I wonder what they are using now?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: glennfish on 09/21/2016 12:57 am
    I totally missed something in your comment.

    In the BLUE channel, the cloud is darker, not brighter.  That means, less blue is coming through, not more.  In the red and green channels, it's mostly bright, a tad less in the green, and not at all in the red.

    There is structure visible in the blue channel, wipe out on the red, and barely something maybe there in the green.

    Essentially, it's brightest in the red channel, slightly less bright in the green, and clearly not as bright in the blue.

    Ok, thanks for clarifying that part, but I'm still inclined to look further down since a specific cause has not been found further up.

    A large apartment complex fire I worked back in my Red Cross days had an extremely odd cause that I recalled in association with my analysis here. A resident had backed into his parking space, and when he started up his car again, heat and sparks from his exhaust ignited the parched grass in front of his building. The flame that resulted traveled across 20-30 feet of lawn and did considerable damage to his building and others next to it.

    It isn't obvious right away, but the entire length of the left side of the rocket is lit up almost as instantaneously as above.

    Strictly speaking under my rules of image interpretation, the left side of the rocket is illuminated from a fire ball that extends beyond the rocket towards the camera.  Previously in this thread I note the illumination changes on things like the grid fin and the payload fairing indicating that a lot of the fireball content is towards the camera extending far forward of the F9 AND TE.

    As to why, or how far, the USLR video doesn't have sufficient data to suggest the distance.   Lots of good data is washed out from pixel saturation.

    I gently advise you look at my previous posts.

    This wasn't even close to an automotive fire as you described.  It was extremely fast.   If I had no prior knowledge of the content,  I'd declare a number of military grade devices that could do this, but absent various militias with access, all I can be sure of is that the only photographic record in the public domain says, prior to the detonation, everything was copacetic.  Afterwards, you have your choice of conflagration mechanisms.

    The cloud you refer to is a water vapor cloud being blown towards the camera.

    I will bet your first born child against mine on that.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/21/2016 01:22 am
    1.  Why would the shorter kerosene tanks have stringers but the longer LOX tanks have none?

    2. And why would the first stage kerosene tank have stringers when the shorter second stage LOX tank has none?

    3. Is it that the rocket is moved with the kerosene tanks unpressurized and the LOX tanks pressurized?


    4.  Because that skin is fabricated in barrels, it would be just too easy to make each barrel section a different thickness.  Because the stresses seen at each section are different, the weight savings available are significant.


    1.  They both do

    2.  they both do.

    3 Neither, they are pressurized for flight.

    4.  No.
    a.  The weight saving would be minimal
    b.  The costs would increase
    c.  also welding two different thicknesses would cause issues.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: dorkmo on 09/21/2016 02:36 am
    1.  Why would the shorter kerosene tanks have stringers but the longer LOX tanks have none?

    2. And why would the first stage kerosene tank have stringers when the shorter second stage LOX tank has none?

    3. Is it that the rocket is moved with the kerosene tanks unpressurized and the LOX tanks pressurized?


    4.  Because that skin is fabricated in barrels, it would be just too easy to make each barrel section a different thickness.  Because the stresses seen at each section are different, the weight savings available are significant.


    1.  They both do

    2.  they both do.

    3 Neither, they are pressurized for flight.

    4.  No.
    a.  The weight saving would be minimal
    b.  The costs would increase
    c.  also welding two different thicknesses would cause issues.

    i think in the areas not near the edges they mill some thickness of the second stage tanks.

    https://www.flickr.com/photos/spacex/23779742713/

    https://www.instagram.com/p/BDgfxVeF8TW/

    https://www.facebook.com/SpaceX/photos/a.10150303260090131.563831.353851465130/10154725227190131/?type=3&theater
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: GerryB on 09/21/2016 02:58 am
    Fodder for "cracks in LOX tank" theories. During STS-133 (https://en.wikipedia.org/wiki/STS-133) fueling, the shuttle's external LOX tank had multiple significant cracks caused by the thermal stress of LOX loading. The stresses were known and well modeled, but the failure was actually in imperfect heat treating of a batch of internal Al/Li stringers, (http://www.cbsnews.com/network/news/space/home/spacenews/files/ad71f2f20c5a6a6998966aac915dab86-140.html) reducing their strength far below design and expectation.

    That tank loading failure had a simulaneous minor but beyond-flight-limit gaseous H2 leak due to a poorly fitting umbilical connector. The 20,000 ppm leak was detected by GSE sensors.

    The post-mission final report from NASA.  (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120014466.pdf)
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: JamesH65 on 09/21/2016 08:23 am
    What might be even more enlightening, not only about this observation but compared to everything that has been observed so far, is that the curve is most visible in the blue channel, and what's blue besides reflections of the sky is the blue of a flame, indicating the hottest and most oxygen rich portion, hotter than white.

    Full disclosure I'm going to try the power of suggestion here. First, you might want to light a candle and remind yourself how rarely you pay attention to any part of the flame other than the white tip, that a closer look reveals a hint of blue at the base, and above the blue is a translucent grayish core that remains inside the white of the flame.


    You might see the same features I'm seeing if you view the full anomaly as a flame of a candle, all the way down to the middle of the diagonal brace of the TEL, which extends to the left at the lower half of the 1st stage. There would be the blue and hottest part, and the origin or closer to it, not at the attention grabbing fireball. What also can be considered are the blue flames given by Bunsen burners, gas range tops, and propane torches, all fed by gases much further below.

    I totally missed something in your comment.

    In the BLUE channel, the cloud is darker, not brighter.  That means, less blue is coming through, not more.  In the red and green channels, it's mostly bright, a tad less in the green, and not at all in the red.

    There is structure visible in the blue channel, wipe out on the red, and barely something maybe there in the green.

    Essentially, it's brightest in the red channel, slightly less bright in the green, and clearly not as bright in the blue.

    I'd be wary about comparing colour channel brightnesses. It depends on the sensitivity of the sensor to those colours which is determined by the colour mask, assuming it's a bayer sensor. Without knowing that (and it might be possible to find it out if we know the make and model of camera ), making judgements might be foolish. It also depends on the processing when converting from bayer to RGB, probably via YUV on the way.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: kolkmvd on 09/21/2016 09:57 am
    I'd be wary about comparing colour channel brightnesses. It depends on the sensitivity of the sensor to those colours which is determined by the colour mask, assuming it's a bayer sensor. Without knowing that (and it might be possible to find it out if we know the make and model of camera ), making judgements might be foolish. It also depends on the processing when converting from bayer to RGB, probably via YUV on the way.

    Yes, fully agree. But because the blue channel appeared to have become less saturated, it still yields extra info. You can also see the AGC of the camera already kicking in the following frames.

    You could compensate for that, so that the development of the fireball vs reflection can be followed more accurate.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Pasander on 09/21/2016 11:16 am
    After wathing the 1/250 speed video at 0.25 speed a few times I think the initial explosion/detonation might have happened just inside the vehicle. The expanding fireball means there were a relative large amount of RP-1 and LOX mixed from the get-go. While a sufficiently large explosion just outside the vehicle might explain this ("carving" RP-1 and LOX out of the tanks by the expanding reaction gases) I now tend to think an explosion/detonation inside might be a better fit for what I'm seeing.

    You may note in the first few frames (of the USLR video) how the LOX/vapor cloud starts expanding slightly downwards. The fireball seems also directed very slightly downwards. This could be explained by the bulk of the LOX (~1.23 g/ml subcooled, more dense than water) directing the expanding gases and other materials sideways and slightly downward. After the first few frames the bulk mass of LOX and RP-1 start to react so the rest of the video tells little about what actually happened.

    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    Slightly off-topic (but perhaps also slightly relevant), here's a video I made this spring: http://www.liveleak.com/view?i=093_1460939734 (http://www.liveleak.com/view?i=093_1460939734)  An explosion/fireball effect

    I had there about 100g of pyrotechnic material (flash powder) surrounded by a mixture of 3 liters of fuel oil and 2 liters of gasoline (~1.3 gallons of flammable liquids). So, you see how a little bit of something can make a great show..
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/21/2016 11:40 am
    Fodder for "cracks in LOX tank" theories. During STS-133 (https://en.wikipedia.org/wiki/STS-133) fueling, the shuttle's external LOX tank had multiple significant cracks caused by the thermal stress of LOX loading. The stresses were known and well modeled, but the failure was actually in imperfect heat treating of a batch of internal Al/Li stringers, (http://www.cbsnews.com/network/news/space/home/spacenews/files/ad71f2f20c5a6a6998966aac915dab86-140.html) reducing their strength far below design and expectation.

    That tank loading failure had a simulaneous minor but beyond-flight-limit gaseous H2 leak due to a poorly fitting umbilical connector. The 20,000 ppm leak was detected by GSE sensors.

    The post-mission final report from NASA.  (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120014466.pdf)

    The stringers were not on the LOX tank, they were on the intertank
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Kabloona on 09/21/2016 02:55 pm
    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    I think you may have answered your own question. If the common bulkhead ruptured internally, the combustion event started inside the stage and didn't become visible until the tank wall(s) burst. In that scenario, you'd expect a very sudden appearance of a large fireball. One moment it's not there, next moment it is. Compare to a video of a hydrogen balloon being exploded.

    Telemetry may already have told that story; you seem to be assuming it hasn't. The question is, if that was in fact the story, what was the root cause. They may know it was an internal failure from telemetry but not yet be able to pinpoint a root cause.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: spacekid on 09/21/2016 03:06 pm
    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    I think you may have answered your own question. If the common bulkhead ruptured internally, the combustion event started inside the stage and didn't become visible until the tank wall(s) burst. In that scenario, you'd expect a very sudden appearance of a large fireball. One moment it's not there, next moment it is. Compare to a video of a hydrogen balloon being exploded.

    Telemetry may already have told that story; you seem to be assuming it hasn't. The question is, if that was in fact the story, what was the root cause. They may know it was an internal failure from telemetry but not yet be able to pinpoint a root cause.
    SpaceX is saying that they expect only a 3 month delay. If there was a problem with the rocket, especially a tank failure, the delay would be longer than 3 months. I would think 9 to 18 months. To me, a 3 month delay tells me they believe it was an external explosion but they don't have definitive evidence or root cause yet.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Herb Schaltegger on 09/21/2016 03:10 pm
    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    I think you may have answered your own question. If the common bulkhead ruptured internally, the combustion event started inside the stage and didn't become visible until the tank wall(s) burst. In that scenario, you'd expect a very sudden appearance of a large fireball. One moment it's not there, next moment it is. Compare to a video of a hydrogen balloon being exploded.

    Telemetry may already have told that story; you seem to be assuming it hasn't. The question is, if that was in fact the story, what was the root cause. They may know it was an internal failure from telemetry but not yet be able to pinpoint a root cause.
    SpaceX is saying that they expect only a 3 month delay. If there was a problem with the rocket, especially a tank failure, the delay would be longer than 3 months. I would think 9 to 18 months. To me, a 3 month delay tells me they believe it was an external explosion but they don't have definitive evidence or root cause yet.

    Ms. Shotwell's statement was only a best-case scenario. I have heard from more than one source that RTF will not be this year.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: mfck on 09/21/2016 06:13 pm
    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    I think you may have answered your own question. If the common bulkhead ruptured internally, the combustion event started inside the stage and didn't become visible until the tank wall(s) burst. In that scenario, you'd expect a very sudden appearance of a large fireball. One moment it's not there, next moment it is. Compare to a video of a hydrogen balloon being exploded.

    Telemetry may already have told that story; you seem to be assuming it hasn't. The question is, if that was in fact the story, what was the root cause. They may know it was an internal failure from telemetry but not yet be able to pinpoint a root cause.
    SpaceX is saying that they expect only a 3 month delay. If there was a problem with the rocket, especially a tank failure, the delay would be longer than 3 months. I would think 9 to 18 months. To me, a 3 month delay tells me they believe it was an external explosion but they don't have definitive evidence or root cause yet.

    Ms. Shotwell's statement was only a best-case scenario. I have heard from more than one source that RTF will not be this year.
    Was that SpaceX, NASA or 3rd party source?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cambrianera on 09/21/2016 06:24 pm
    Why would the shorter kerosene tanks have stringers but the longer LOX tanks have none?
    Because the RP-1 tank (when horizontal and unpressurized) takes the greatest part of the load of octaweb and engines.

    And why would the first stage kerosene tank have stringers when the shorter second stage LOX tank has none?
    Because it is shorter and carries no loads during handling and transport .

    Is it that the rocket is moved with the kerosene tanks unpressurized and the LOX tanks pressurized?
    Both pressurized for flight, unpressurized for handling and likely partially pressurized for road transport.

    Or is it that the LOX tanks, due to the larger pressure changes they see, can't use stringers, and so use thicker skin sections?  I have also read the 4.5 mm thick spec for the Falcon's skins, and I don't believe it.  Because that skin is fabricated in barrels, it would be just too easy to make each barrel section a different thickness.  Because the stresses seen at each section are different, the weight savings available are significant.
    See Jim and dorkmo. FSW has to be carefully adjusted for thickness variations

    The stringers in that tank from 2006 appear to be continuous, rather than divided into sections as in the pictures I posted.  I wonder what they are using now?
    Stringers are friction stir welded during preparation of barrels.
    F9 v1.0 had 2m barrels (and lot of joints on stringers), F9v1.1 has 6m barrels (and 6m stringer sections inside).
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: DaveS on 09/21/2016 06:32 pm
    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    I think you may have answered your own question. If the common bulkhead ruptured internally, the combustion event started inside the stage and didn't become visible until the tank wall(s) burst. In that scenario, you'd expect a very sudden appearance of a large fireball. One moment it's not there, next moment it is. Compare to a video of a hydrogen balloon being exploded.

    Telemetry may already have told that story; you seem to be assuming it hasn't. The question is, if that was in fact the story, what was the root cause. They may know it was an internal failure from telemetry but not yet be able to pinpoint a root cause.
    SpaceX is saying that they expect only a 3 month delay. If there was a problem with the rocket, especially a tank failure, the delay would be longer than 3 months. I would think 9 to 18 months. To me, a 3 month delay tells me they believe it was an external explosion but they don't have definitive evidence or root cause yet.

    Ms. Shotwell's statement was only a best-case scenario. I have heard from more than one source that RTF will not be this year.
    This is very true. I remember back in 2003 when the Columbia accident investigation was still very much underway that NASA initially projected a RTF time frame of October of the same year. So SpaceX isn't alone in setting "too-optimistic" RTF time frames.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: mn on 09/21/2016 06:56 pm
    My take on all this is that the LOX tank might have ruptured into the RP-1 tank. It would almost certainly form an explosive cloud and an ignition source could be there, too. What I don't really understand is how all of this can happen so quickly, within a single frame of video. (It could have happened a little earlier, just not evident on the video, but wouldn't the telemetry then tell the story?)

    I think you may have answered your own question. If the common bulkhead ruptured internally, the combustion event started inside the stage and didn't become visible until the tank wall(s) burst. In that scenario, you'd expect a very sudden appearance of a large fireball. One moment it's not there, next moment it is. Compare to a video of a hydrogen balloon being exploded.

    Telemetry may already have told that story; you seem to be assuming it hasn't. The question is, if that was in fact the story, what was the root cause. They may know it was an internal failure from telemetry but not yet be able to pinpoint a root cause.

    SpaceX has said that they are working with 35-55ms of telemetry (http://forum.nasaspaceflight.com/index.php?topic=40868.msg1577618#msg1577618 (http://forum.nasaspaceflight.com/index.php?topic=40868.msg1577618#msg1577618)). We can assume that means 55ms from first atypical reading to end of telemetry. When the telemetry ends relative to the visible fire is anyone's guess, I don't think they have said publicly.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: mme on 09/21/2016 07:26 pm
    ...
    SpaceX is saying that they expect only a 3 month delay. If there was a problem with the rocket, especially a tank failure, the delay would be longer than 3 months. I would think 9 to 18 months. To me, a 3 month delay tells me they believe it was an external explosion but they don't have definitive evidence or root cause yet.
    Ms. Shotwell's statement was only a best-case scenario. I have heard from more than one source that RTF will not be this year.
    This is very true. I remember back in 2003 when the Columbia accident investigation was still very much underway that NASA initially projected a RTF time frame of October of the same year. So SpaceX isn't alone in setting "too-optimistic" RTF time frames.
    Shotwell was very clear that they still did not know the root cause and that November was best case.  Secondary sources were less clear and then people started drawing conclusions from what a November RTF "implied."  It implies that people should really find the primary source of any quote. :)
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: spacekid on 09/21/2016 07:43 pm
    ...
    SpaceX is saying that they expect only a 3 month delay. If there was a problem with the rocket, especially a tank failure, the delay would be longer than 3 months. I would think 9 to 18 months. To me, a 3 month delay tells me they believe it was an external explosion but they don't have definitive evidence or root cause yet.
    Ms. Shotwell's statement was only a best-case scenario. I have heard from more than one source that RTF will not be this year.
    This is very true. I remember back in 2003 when the Columbia accident investigation was still very much underway that NASA initially projected a RTF time frame of October of the same year. So SpaceX isn't alone in setting "too-optimistic" RTF time frames.
    Shotwell was very clear that they still did not know the root cause and that November was best case.  Secondary sources were less clear and then people started drawing conclusions from what a November RTF "implied."  It implies that people should really find the primary source of any quote. :)
    SpaceNews quotes her as saying “We’re anticipating getting back to flight, being down for about three months, so getting back to flight November, the November timeframe,”. Anticipate can be defined as "To see as a probable occurrence; expect". Seems rather definitive to me.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: CorvusCorax on 09/21/2016 07:55 pm
    Even if she had said it and meant it like that, that has to be taken with a gram of salt so early in a failure investigation. Assumtions can shift faster than a collapsing stack as new insight is gained.

    Basically that 3 month timespan would imply that nothing is technically wrong with the rockets already manufactured and also no jard to change things at the remaining pads equipment, aka that the risk of boom could be mitigated by a mere procedure change, for example in tanking sequence

    If anything ends up having to be changed on rockets, 3 months is impossible, even if just gnd equipment needs changing it'dbe tough. Sometimes the fault analysis and search for root cause alone can take 3 month.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cscott on 09/21/2016 08:30 pm


    [Photo of Elon standing inside LOX tank]

    What are all of those projections into the LOX tank in your picture?  Too many to be sensors, and we're told there are no stringers so they can't be stringer mount points.  Not big enough to be anti-swirl vanes.  Too regular to be ad-hoc mount points for COPVs/etc.  I'm out of ideas!
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: whitelancer64 on 09/21/2016 08:35 pm


    [Photo of Elon standing inside LOX tank]

    What are all of those projections into the LOX tank in your picture?  Too many to be sensors, and we're told there are no stringers so they can't be stringer mount points.  Not big enough to be anti-swirl vanes.  Too regular to be ad-hoc mount points for COPVs/etc.  I'm out of ideas!

    Mount points for slosh baffles?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: rsdavis9 on 09/21/2016 08:38 pm
    Are those the copv struts we can see in the distance?

    Are all these mount points welded? It looks like it. I can't see a bolt head.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: whitelancer64 on 09/21/2016 08:47 pm
    Are those the copv struts we can see in the distance?

    Are all these mount points welded? It looks like it. I can't see a bolt head.

    Keep in mind that the picture is from 2008, this is the Falcon 9 v1.0

    http://www.upenn.edu/gazette/1108/feature4_1.html

    *edit* added link
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: rsdavis9 on 09/21/2016 08:50 pm


    [Photo of Elon standing inside LOX tank]

    What are all of those projections into the LOX tank in your picture?  Too many to be sensors, and we're told there are no stringers so they can't be stringer mount points.  Not big enough to be anti-swirl vanes.  Too regular to be ad-hoc mount points for COPVs/etc.  I'm out of ideas!

    Who said no stringers?

    spacex user guide said monocoque for the lox tanks.

    Quote
    Monocoque (/ˈmɒnəˌkɒk, -ˌkoʊk/), also structural skin, is a structural system where loads are supported through an object's external skin, similar to an egg shell. The word monocoque is a French term for "single shell" or (of boats) "single hull".[1] A true monocoque carries both tensile and compressive forces within the skin and can be recognised by the absence of a load carrying internal frame.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Rocket Science on 09/21/2016 08:51 pm
    Are those the copv struts we can see in the distance?

    Are all these mount points welded? It looks like it. I can't see a bolt head.
    Those look like the COPV mount points and the FSW common bulkhead that I have been mentioning in the thread. The interface on the common bulkhead looks like a FSW lap joint that can pass a NDE and can still experience a failure in the paper I cited...
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Jim on 09/21/2016 08:51 pm
    https://www.youtube.com/watch?v=PPnCKK1isMI

    Falcon 9 LOX tank cam
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cambrianera on 09/21/2016 08:53 pm
    Are those the copv struts we can see in the distance?

    Are all these mount points welded? It looks like it. I can't see a bolt head.

    Mounts are FSW, same as stringers.
    Mounts are likely for slosh baffles, as seen in 2nd stage lox tank.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: jpo234 on 09/22/2016 03:22 pm
    Any new whispers from inside the investigation?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: iamlucky13 on 09/22/2016 06:13 pm
    I'm not sure if there's a better thread for this - ULA wrote a letter to the Air Force discussing price vs. reliability and risk tolerance of a contract, and requesting a 60 day extension on a current bid deadline so more can be known about the failure.

    https://www.washingtonpost.com/business/economy/boeing-lockheed-venture-raises-spacex-explosion-in-fight-over-pentagon-contract/2016/09/21/b6907fa8-7f7e-11e6-9070-5c4905bf40dc_story.html

    Nothing surprising - ULA arguing their strengths.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: kevin-rf on 09/22/2016 06:20 pm
    Any new whispers from inside the investigation?
    It's not yet Friday ;)

    *based on always releasing bad news on a Friday, and good news on a Monday
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: jpo234 on 09/22/2016 06:27 pm
    Any new whispers from inside the investigation?
    It's not yet Friday ;)

    *based on always releasing bad news on a Friday, and good news on a Monday
    That's for public companies that have stock prices to protect.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: LM13 on 09/22/2016 07:06 pm
    Any new whispers from inside the investigation?
    It's not yet Friday ;)

    *based on always releasing bad news on a Friday, and good news on a Monday

    After CRS-7, Musk announced a root cause roughly three weeks later, on Monday, July 20. 

    Based on that precedent, I was guessing that they'd announce a failure cause either today (three weeks after the failure), or this coming Monday (in keeping with their "announce bad news on Monday" precedent), or in a brief statement at IAC. 
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Kabloona on 09/22/2016 07:12 pm
    Any new whispers from inside the investigation?
    It's not yet Friday ;)

    *based on always releasing bad news on a Friday, and good news on a Monday

    After CRS-7, Musk announced a root cause roughly three weeks later, on Monday, July 20. 

    Based on that precedent, I was guessing that they'd announce a failure cause either today (three weeks after the failure), or this coming Monday (in keeping with their "announce bad news on Monday" precedent), or in a brief statement at IAC.

    Just remember Elon said this is their "most complex ever" anomaly, ie more difficult than CRS-7. So don't hold your breath.

    Quote
    Still working on the Falcon fireball investigation. Turning out to be the most difficult and complex failure we have ever had in 14 years.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: garidan on 09/22/2016 07:59 pm
    I wonder if it could be useful to setup a new second-stage-only on a temporary lower structure, in a safe place in case of a successful recreated explosion, with a rebuilt lower supply tower and try to replicate the situation, testing the possible root causes they can test, or simply looking at dozens others fill and empty sequences of LOX in the second stage. The second stage would be equipped with more sensors, and so the exterior.
    They don't need to light the engines, so McGregor is not needed nor it has to be at risk.
    If at a loss, after weeks of testing all day long and analyzing data, they could try to damage on purpose some structures and see if this actually lend to a potentially explosive situation.
    I mean, initial conditions of the accident are not all replicable and known, but if nothing else, testing many times trying to fail again can help to understand by experiment.
    They have the money and workforce to do this in parallel to what they are already doing.
    They have to be sure to find a reasonable root cause, and be quick to exit this impasse.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cscott on 09/22/2016 08:04 pm
    You might want to look for pictures of McGregor to see if your suggestion is being followed.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: mme on 09/22/2016 08:38 pm
    ...
    Shotwell was very clear that they still did not know the root cause and that November was best case.  Secondary sources were less clear and then people started drawing conclusions from what a November RTF "implied."  It implies that people should really find the primary source of any quote. :)
    SpaceNews quotes her as saying “We’re anticipating getting back to flight, being down for about three months, so getting back to flight November, the November timeframe,”. Anticipate can be defined as "To see as a probable occurrence; expect". Seems rather definitive to me.
    Sorry to belabor the point, SpaceNews is a secondary source.  If you follow anything closely enough you will discover that people are misquoted/partially quoted all the time.  I'm not implying ill intent, it's just another example of the the telephone game (https://en.wikipedia.org/wiki/Chinese_whispers).

    I watched the entire presentation (which unfortunately I can not find now or I'd pass on the link.)  Here are a couple of live tweets from the same talk, the second one clarifying the first:

    https://twitter.com/pbdes/status/775702299402526720
    Quote
    Peter B. de Selding
    ‏@pbdes
    SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

    (I really wish I could find the video.  I'm pretty sure she  said 39A, not CCAFS.)

    https://twitter.com/pbdes/status/775715783498428416
    Quote
    Peter B. de Selding
    ‏@pbdes
    SpaceX's Shotwell: Nov return to flight is our best hope. We still haven't isolated the cause or whether its origin was rocket or ground.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: garidan on 09/22/2016 08:56 pm
    https://www.youtube.com/watch?v=xYs2h1ek6HM&feature=youtu.be
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: TomH on 09/22/2016 09:56 pm
    I wonder if it could be useful to setup a new second-stage-only on a temporary lower structure, in a safe place in case of a successful recreated explosion, with a rebuilt lower supply tower and try to replicate the situation, testing the possible root causes they can test, or simply looking at dozens others fill and empty sequences of LOX in the second stage. The second stage would be equipped with more sensors, and so the exterior.
    They don't need to light the engines, so McGregor is not needed nor it has to be at risk.
    If at a loss, after weeks of testing all day long and analyzing data, they could try to damage on purpose some structures and see if this actually lend to a potentially explosive situation.
    I mean, initial conditions of the accident are not all replicable and known, but if nothing else, testing many times trying to fail again can help to understand by experiment.
    They have the money and workforce to do this in parallel to what they are already doing.
    They have to be sure to find a reasonable root cause, and be quick to exit this impasse.

    I have been thinking the same thing. So far, this has been an exercise in deduction. Scientific methodology combines hypothesis, deduction, induction, controlled experimentation, observation, defined dependent and independent variables, multiple trials, peer review and much more.

    https://en.wikipedia.org/wiki/Models_of_scientific_inquiry
    https://en.wikipedia.org/wiki/Hypothetico-deductive_model
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Space Ghost 1962 on 09/22/2016 10:32 pm
    Too many variables. Too much a shot in the dark. Too hard to convince of a causal chain of events.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: pogo661 on 09/23/2016 02:02 am
    Does SpaceX have a place they can try to recreate this failure, that they can afford to lose if they do?  Seems like it would take a long time to build a high fidelity test stand that replicated the gse, what with cryogenic pumps, air conditioning, etc.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Lee Jay on 09/23/2016 02:11 am
    McGregor.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: cscott on 09/23/2016 02:19 am
    It's like folks aren't listening.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: mfck on 09/23/2016 02:46 am
    It's like folks aren't listening.
    Imagined the thread broadcast as audio...
    Rich idea, had to share.


    Sorry.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Pete on 09/23/2016 03:39 am
    It's like folks aren't listening.
    Imagined the thread broadcast as audio...
    Rich idea, had to share.


    Sorry.

    It would be something like a Monty Python sketch, as narrated by Mr Bean, with side-comments by Larry Curly and Moe
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: TomH on 09/23/2016 03:47 am
    Too many variables. Too much a shot in the dark. Too hard to convince of a causal chain of events.

    I don't think a complete replica is necessary. Nevertheless, if analysis of the available data from this incident does not reveal a cause, controlled experimentation and testing may absolutely become necessary.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: RoboGoofers on 09/23/2016 02:57 pm
    I wonder if it could be useful to setup a new second-stage-only on a temporary lower structure, in a safe place in case of a successful recreated explosion, with a rebuilt lower supply tower and try to replicate the situation, testing the possible root causes they can test, or simply looking at dozens others fill and empty sequences of LOX in the second stage. The second stage would be equipped with more sensors, and so the exterior.
    They don't need to light the engines, so McGregor is not needed nor it has to be at risk.
    If at a loss, after weeks of testing all day long and analyzing data, they could try to damage on purpose some structures and see if this actually lend to a potentially explosive situation.
    I mean, initial conditions of the accident are not all replicable and known, but if nothing else, testing many times trying to fail again can help to understand by experiment.
    They have the money and workforce to do this in parallel to what they are already doing.
    They have to be sure to find a reasonable root cause, and be quick to exit this impasse.

    If you look at it another way, they've been doing this since their first F9 launch: they set up the rocket, fill and empty it, test fire it, and then just for good measure, put a payload on it and send it to orbit. Since this last one failed, they can use the data recovered to figure out why the previous ones didn't blow up.

    in other words, it could take a long time for a test article to explode like this. or it may never explode like this. or it may explode in a completely different way. if your car breaks down, you don't drive around another car until it also breaks down and then assume that the first car also had the exact same problem. Even if they both have a flat tire, one could be manufacturing defects and the other could be a puncture. The extra data is only going to get in the way.

    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: garidan on 09/23/2016 03:33 pm
    If you look at it another way, they've been doing this since their first F9 launch: they set up the rocket, fill and empty it, test fire it, and then just for good measure, put a payload on it and send it to orbit. Since this last one failed, they can use the data recovered to figure out why the previous ones didn't blow up.

    in other words, it could take a long time for a test article to explode like this. or it may never explode like this. or it may explode in a completely different way. if your car breaks down, you don't drive around another car until it also breaks down and then assume that the first car also had the exact same problem. Even if they both have a flat tire, one could be manufacturing defects and the other could be a puncture. The extra data is only going to get in the way.

    I disagree. Falcon 9 FT is a different rocket from previous versions, expecially concerning the fuel loading phase and temperature, so not so much useful previous data. We now know something went wrong. Was it LOX and contamination? Test. Was it LOX and exposed Al ? Test. Was there a mixture of RP1 and LOX, a COPV, oxygen ice forming? Test what-if scenarios, measure and gain data, try to fail and see how big and different it happens. Then reconsider everything. There are many use cases and combination of adverse factors ? Sure, but if by the data you have you cannot understand what went wrong, you need more data. And it's better to get data by tests than by another burst up payload.
    Too much and unplanned data is spam, but modeling and simulation cannot be the only tools you have. And even a month earlier in finding a root cause is worth the effort, even more if SpaceX ends into no clear answer.

    As for McGregor, I don't know if there are redundant test stands for second stages, I just meant one thing is to have a test stand you hope and plan to not damage, another thing is to have a test stand you are happy to destroy, perhaps more than one time :-)
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: spacekid on 09/23/2016 04:00 pm
    If you look at it another way, they've been doing this since their first F9 launch: they set up the rocket, fill and empty it, test fire it, and then just for good measure, put a payload on it and send it to orbit. Since this last one failed, they can use the data recovered to figure out why the previous ones didn't blow up.

    in other words, it could take a long time for a test article to explode like this. or it may never explode like this. or it may explode in a completely different way. if your car breaks down, you don't drive around another car until it also breaks down and then assume that the first car also had the exact same problem. Even if they both have a flat tire, one could be manufacturing defects and the other could be a puncture. The extra data is only going to get in the way.

    I disagree. Falcon 9 FT is a different rocket from previous versions, expecially concerning the fuel loading phase and temperature, so not so much useful previous data. We now know something went wrong. Was it LOX and contamination? Test. Was it LOX and exposed Al ? Test. Was there a mixture of RP1 and LOX, a COPV, oxygen ice forming? Test what-if scenarios, measure and gain data, try to fail and see how big and different it happens. Then reconsider everything. There are many use cases and combination of adverse factors ? Sure, but if by the data you have you cannot understand what went wrong, you need more data. And it's better to get data by tests than by another burst up payload.
    Too much and unplanned data is spam, but modeling and simulation cannot be the only tools you have. And even a month earlier in finding a root cause is worth the effort, even more if SpaceX ends into no clear answer.

    As for McGregor, I don't know if there are redundant test stands for second stages, I just meant one thing is to have a test stand you hope and plan to not damage, another thing is to have a test stand you are happy to destroy, perhaps more than one time :-)
    The primary things to investigate are assuming O2 was readily present (and the initial explosion was outside the vehicle), how did the fuel become present and what ignighted it. Those 2 things could be tested without a rocket or only part of the rocket such as the interface panel.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: ThereIWas3 on 09/23/2016 04:52 pm
    Is the construction of the F9 2nd stage largely different from the first stage other than the number of engines?  For example, does the first stage use those same sort of immersed helium bottles that were the problem before?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: The_Ronin on 09/23/2016 05:00 pm
    I know we generally are not supposed to talk about what is on /r/SpaceX here but they have a thread about COPV harmonics being the root cause.  That would be a bad thing, I think.

    How much performance/density would they lose if they moved the COPV tanks outside of the tank?
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Herb Schaltegger on 09/23/2016 05:04 pm
    I know we generally are not supposed to talk about what is on /r/SpaceX here but they have a thread about COPV harmonics being the root cause.  That would be a bad thing, I think.

    How much performance/density would they lose if they moved the COPV tanks outside of the tank?

    IF that is indeed the case, harmonics per se isn't the problem - resonance is. And resonant frequency is easy to change in a system. Those tiny lead weights around the rim of your wheels? Those are there to provide a counteracting mass to damp out resonance in your spinning wheels. So, IF the problem is a harmonic resonance in the COPV tanks (e.eg., vibrations set up in response to rapidly loading propellants, THEN the solution is equally-simple. Add a tiny bit of mass, or simply change the physical arrangement of whatever part was oscillating, to damp the vibration and prevent the resonance.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: wannamoonbase on 09/23/2016 05:09 pm
    Herb is exactly right, not a complicated thing to correct. 

    Seems like a very unlikely failure but it was a strange accident, who knows.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Ixian77 on 09/23/2016 05:14 pm
    While watching the USSpace video for the umpteenth time, and looking for something completely different, found something compelling to me.

    Watch the video from the :40s mark to the event and note the strong venting from LOX vent, starting about :48s mark.  The vent stream looks to strongly vent towards the TEL until the event. Re-watching the video looking at this, it seems to me it leads to the event.

    Then looking the the countdown timeline:

    T-10:00 LOX venting for fast fill.

    Best I can tell from reading this entire thread is that the event occurred around the T-8:00 mark.
    Since there is only appx. 22s of this stronger venting until the event, could this venting indicate an experiment by SpaceX in 'accelerated fast fill'.

    It is known that SpaceX are trying to trim time out of the countdown sequence. Perhaps SpaceX have a vent fan installed in the LOX vent line and actively vent the GOX from the tank, allowing the pumps to fill faster and  decrease filling time. Perhaps this process could be stepped-up with a varying speed fan in the vent line. High speed on the vent fan plus filling pumps running at top speed equals 'optimal fast fill'.
    Maybe you trim 3-5 minutes from the 17 minute current filling rate.

    Whether the above tank filling experiment occurred or not, this 22s vent stream may have created the densest, coldest, purest cloud of GOX SpaceX have seen in the previous 14 attempts with dLOX.

    Ambient  weather conditions, on this otherwise normal Florida summer day, create an area of lower pressure below the umbilical, between the rocket and the TEL. The previous appx. nine minutes of LOX tank filling have this area colder and filled with  GOX. SpaceX are prepared for this, of course, but this day something has changed.

    This day the GOX cloud causes an electrical arc somewhere in the TEL.
    One possibility could be the pump motor/step-up transformer for the pneumatic system that pressurize the grabber arms.
    The arc flash accounts for the initial bright light. The arcing reaches the umbilicals, or anywhere else around the rocket/TEL, even the cradling pads (throwing those guys a bone, even though they are in exile).
    This arcing liberates material into the pure GOX cloud, very fast FAE.

    The pressure wave from this event impacts S2, generating a pressure wave that travels trough the RP--1 tank, the CB, and the partially filled LOX tank.

    The RP-1 tank and CB may have withstood the pressure of this event had the rocket not been held by the gripper arms.
    The effect on the partially filled LOX tank of this wave could have been catastrophic.

    How would a tank partially filled with dLOX react to this wave?

    Rapidly UN-densing?

    That could cause the LOX to try to rapidly fill the remaining volume of the tank, rushing upward and rebounding down through the tank, rupturing the tank horizontally across  the CB.
    That could account for the witnessed nature of the S2 failure.

    Solution could be simple. Strong fan on TEL, pointing at the GOX vent.
    Motor setting: 11.

     
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: Kaputnik on 09/23/2016 05:20 pm
    Those tiny lead weights around the rim of your wheels? Those are there to provide a counteracting mass to damp out resonance in your spinning wheels.

    Interesting- I had always presumed that it was much simpler than that, to put the CG of the wheel in the middle.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: eriblo on 09/23/2016 05:25 pm
    While watching the USSpace video for the umpteenth time, and looking for something completely different, found something compelling to me.

    Watch the video from the :40s mark to the event and note the strong venting from LOX vent, starting about :48s mark.  The vent stream looks to strongly vent towards the TEL until the event. Re-watching the video looking at this, it seems to me it leads to the event.

    Then looking the the countdown timeline:

    T-10:00 LOX venting for fast fill.

    Best I can tell from reading this entire thread is that the event occurred around the T-8:00 mark.
    Since there is only appx. 22s of this stronger venting until the event, could this venting indicate an experiment by SpaceX in 'accelerated fast fill'.

    [...]
    Note that the video is edited, with a cut at :50 s (22 s before the explosion), so we have no way of knowing the timeline before that...
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: docmordrid on 09/23/2016 05:29 pm
    Those tiny lead weights around the rim of your wheels? Those are there to provide a counteracting mass to damp out resonance in your spinning wheels.

    Interesting- I had always presumed that it was much simpler than that, to put the CG of the wheel in the middle.

    Both balance and reaction forces which could produce wobble, hence weights on the inward and outward sides of the rim.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD
    Post by: philw1776 on 09/23/2016 05:30 pm
    I know we generally are not supposed to talk about what is on /r/SpaceX here but they have a thread about COPV harmonics being the root cause.  That would be a bad thing, I think.

    How much performance/density would they lose if they moved the COPV tanks outside of the tank?

    IF that is indeed the case, harmonics per se isn't the problem - resonance is. And resonant frequency is easy to change in a system. Those tiny lead weights around the rim of your wheels? Those are there to provide a counteracting mass to damp out resonance in your spinning wheels. So, IF the problem is a harmonic resonance in the COPV tanks (e.eg., vibrations set up in response to rapidly loading propellants, THEN the solution is equally-simple. Add a tiny bit of mass, or simply change the physical arrangement of whatever part was oscillating, to damp the vibration and prevent the resonance.

    If so, they will analyze to ensure that any and all other possible resonance modes and harmonics are also dampened and not inadvertantly amplified by a fix.  But knowing the cause is key to the battle.  Hope they now know.
    Title: Re: SpaceX Falcon 9 - AMOS-6 - (Pad Failure) - DISCUSSION THREAD (1)
    Post by: Chris Bergin on 09/23/2016 06:36 pm
    The Friday update is a good jump off point into Thread 2, as this one is way too long to keep up with.

    Thread 2:
    http://forum.nasaspaceflight.com/index.php?topic=41252.0

    (I'll fill out the opening post).