Author Topic: SpaceX Falcon 9 v1.1 - SpX-7/CRS-7 DRAGON FAILURE - Discussion Thread 2  (Read 564339 times)

Online Chris Bergin

Discussion Thread 2 for the Falcon 9 v1.1 mission with the CRS-7 Dragon, now in post-failure discussion.

Resources:

SpaceX News Articles from 2006 (Including numerous exclusive Elon interviews):
http://forum.nasaspaceflight.com/index.php?topic=21862.0

SpaceX News Articles (Recent):
http://www.nasaspaceflight.com/tag/spacex/

SpaceX Dragon Articles:
http://www.nasaspaceflight.com/tag/dragon/

=--=

Articles for CRS-7:

Static Fire:
http://www.nasaspaceflight.com/2015/06/spacex-static-fire-falcon-9-crs7-mission/

Launch and Failure:
http://www.nasaspaceflight.com/2015/06/falcon-9-crs-7-dragon-commute-orbit/

Post Failure Status:
http://www.nasaspaceflight.com/2015/07/spacex-working-falcon-9-diagnosis-treatment/

=--=

SpaceX GENERAL Forum Section:
http://forum.nasaspaceflight.com/index.php?board=45.0 - please use this for general questions NOT specific to this mission.

SpaceX MISSIONS Forum Section:
http://forum.nasaspaceflight.com/index.php?board=55.0 - this section is for everything specific to SpaceX missions.


CRS-7 UPDATES thread (UPDATES only, discussion belongs here)
http://forum.nasaspaceflight.com/index.php?topic=37739.0

CRS-7 There and back again party thread
http://forum.nasaspaceflight.com/index.php?topic=37749.0

L2 SpaceX Section:
http://forum.nasaspaceflight.com/index.php?topic=24469.0
« Last Edit: 07/30/2015 04:38 PM by Chris Bergin »

Offline Kabloona

  • Senior Member
  • *****
  • Posts: 4321
  • Velocitas Eradico
  • Fortress of Solitude
  • Liked: 2554
  • Likes Given: 529
I'm finding It disconcerting that we haven't heard from SpaceX in a while....I know they're working the analysis and it could take time...lots of time if the root cause is not readily forthcoming..and that's the part that is really bothering me....no news, not even a"we're getting close", or " we're on the trail and it's all coming together.."....nothing.....

...it's waaaay too quiet out there....

Really?  How you doing with Orbital/ATK/Aerojet?

Fair point.....although from my perspective, there is a lot more riding on SpaceX resolving this quickly because of any possible impact to their HSF program...

Especially for HSF, we should hope they reach a *correct* conclusion rather than merely a quick one.
« Last Edit: 07/04/2015 02:20 AM by Kabloona »

Online Chris Bergin

Latest article:
http://www.nasaspaceflight.com/2015/07/spacex-working-falcon-9-diagnosis-treatment/

Aimed at the news site audience, so covered some background here with the angle of how they recovered from Falcon 1's early life and moved into F9 - and evolved it. Then into the failure and used some of the amazing work the guys are producing in L2 (we've gif'ed some of it for the article).

Steered clear of a lot of the speculation, but went into a bit with the area Elon's referenced.

Tried to balance objectivity, with some positivity by covering how they've recovered before, avoided "OMG, rocket went boom!" as much as I've avoided "It's SpaceX, it was a successful RUD!"

Hopefully it works.

Offline johnx98374

  • Member
  • Posts: 94
  • USA
  • Liked: 67
  • Likes Given: 40
The discussions and speculation here has been intense...I've thoroughly enjoyed it.....but....

I'm finding It disconcerting that we haven't heard from SpaceX in a while....I know they're working the analysis and it could take time...lots of time if the root cause is not readily forthcoming..and that's the part that is really bothering me....no news, not even a"we're getting close", or " we're on the trail and it's all coming together.."....nothing.....

...it's waaaay too quiet out there....

Don't be impatient.  The ink on the failure investigation plan is probably not even dry yet.  At this stage they're  probably just gathering data, telemetry, production and QA records and  figuring out a budget and charge numbers. This could take months unless there is clear evidence of something simple and unambiguous.

Offline kraisee

  • Expert
  • Senior Member
  • *****
  • Posts: 10483
  • Liked: 415
  • Likes Given: 19
And the LOX tank is cryo, so how do you maintain there's no insulating liner? Something has to insulate the LOX tank, doesn't it?

The LOX is stored directly in the aluminum tank.

Part of the outside of the stage has cork insulation covering it, but that is not a liner.

The rest of the tank is just allowed to form a thin layer of ice, because it acts as a pretty good insulator and it falls off during launch.

Ross.

Ross, I want to be clear that I'm not asking about an internal tank liner, but about an external insulating liner

I agree with you Jim.

I think the difference originated because I've always used the term "liner" to represent bonded internal structures that are usually included as a chemically protective layer, or as a structural base (such as metal liners inside most COPV's).

I'm just more used to using the term 'layer' for things like insulation that is attached to the exterior.   Its just a difference in terminology, but we're on the same page now! :)

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32440
  • Cape Canaveral Spaceport
  • Liked: 11186
  • Likes Given: 331
A few friends who work at JSC have told me that Gerst has gone from his "everything will be fine" of Sunday to wanting a full-blown NASA-led investigation. That might be just to preempt a congressional investigation. But you're right; the silence is deafening.

Anyone else at NASA getting the same vibes?

No, that is just nonsense since NASA has no authority to lead the investigation.  The friends don't know how things work.  It was a commercial launch and hence  It is a Spacex led investigation with the FAA as the lead gov agency.  NASA also has a rep and it is from LSP vs the ISS program since they have the rocket expertise even though ISS has the contract. 

Congress also has no authority either.  The only thing it can investigate is NASA's contracting mechanism and management of the contract.

There is no need for any updates until there are updates to be given

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 12935
    • Space Launch Report
  • Liked: 3994
  • Likes Given: 759
I'm happy Mr. Musk provided his initial information, but I'm not expecting any more.  ITAR and whatnot.

Look, it has already been more than eight months since Antares blew apart, and we still don't know why and Antares is still probably a year from launching again. 

I would like to be optimistic and say "a few months" until Falcon 9 flies again, but I'm not so sure it will be that easy.  Antares gets to fly again because it is dropping the old engines (who's failure cause still isn't known) entirely.  Falcon 9 will have to be fixed from the inside out, and that can only happen if a certain cause can be determined.

 - Ed Kyle
« Last Edit: 07/04/2015 02:37 AM by edkyle99 »

Offline jimhillhouse

  • Member
  • Posts: 58
  • Liked: 8
  • Likes Given: 3
A few friends who work at JSC have told me that Gerst has gone from his "everything will be fine" of Sunday to wanting a full-blown NASA-led investigation. That might be just to preempt a congressional investigation. But you're right; the silence is deafening.

Anyone else at NASA getting the same vibes?

No, that is just nonsense since NASA has no authority to lead the investigation.  The friends don't know how things work.  It was a commercial launch and hence  It is a Spacex led investigation with the FAA as the lead gov agency.  NASA also has a rep and it is from LSP vs the ISS program since they have the rocket expertise even though ISS has the contract. 

Congress also has no authority either.  The only thing it can investigate is NASA's contracting mechanism and management of the contract.

There is no need for any updates until there are updates to be given

NASA will be the one to approve SpaceX's resumption of CRS launches, manifesting of ISS cargo, and ISS rendezvous.

So if NASA wants to conduct its own mishap investigation, SoaceX will either cooperate or face the consequences.

Offline QuantumG

  • Senior Member
  • *****
  • Posts: 8671
  • Australia
  • Liked: 3596
  • Likes Given: 846
No, that is just nonsense since NASA has no authority to lead the investigation.

NASA will be the one to approve SpaceX's resumption of CRS launches, manifesting of ISS cargo, and ISS rendezvous.

So if NASA wants to conduct its own mishap investigation, SoaceX will either cooperate or face the consequences.

For once I agree with Jim. NASA doesn't make decisions to do things that aren't in the book. If Gerst wants to do his own investigation he'll have to do it through back channels.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32440
  • Cape Canaveral Spaceport
  • Liked: 11186
  • Likes Given: 331

NASA will be the one to approve SpaceX's resumption of CRS launches, manifesting of ISS cargo, and ISS rendezvous.

So if NASA wants to conduct its own mishap investigation, SoaceX will either cooperate or face the consequences.

Quite the opposite, NASA has no authority or jurisdiction here and it would be facing the consequences.  NASA has no leverage.  It bought a commercial launch, it has to follow the rules.  Also, Spacex can ignore NASA and still perform its commercial launches.  NAXSA would be shooting itself in the foot since it needs ISS logistics missions.

That aside, NASA isn't going  to conduct its own mishap investigation no matter what your JSC friends say.   Did NASA doing that for Antares mishap? Why should Spacex be any different?  There is no need for a NASA one.  NASA gets all the data for every Falcon 9 launch.  NASA can already see what Spacex sees (or even a little more a since NASA is better at reconstructing data). 

Offline cleonard

  • Full Member
  • **
  • Posts: 211
  • Liked: 32
  • Likes Given: 0
Well it seems like we now have a some indication that the failure has only a short signature in the telemetry on the order of a few seconds or less.  Perhaps quite a bit less. 

Ever since I saw the failure on live TV I been of the opinion that it was some pressurant issue.  As has been said on several occasions that COPV's have many different failure modes.  I don't think that a complete sudden failure is an option.  If a COPV lets go it happens fast compared to one second.  Really only single digit milliseconds and I can't see how it would not lead to a more spectacular failure then what we saw.   

COPV's can fail in leaking type mode as well and the high pressure plumbing can fail resulting in leak.  If the leak is of a sufficient rate it can overwhelm the tank pressure relief system and cause an over pressure tank failure.  I'm not talking a dripping faucet type of leak.  More like a leak that can be measured in cubic meters per second.    Everything we now know really seems to point at this type of scenario.

For more on COPV characteristics, I found this nice COPV primer document from NASA.  It's a nice overview.  The shuttle had 24 of them.   http://ston.jsc.nasa.gov/collections/trs/_techrep/SP-2011-573.pdf

Now the above says little as to what caused the failure.  I sure don't know what caused it, but there is one area that has not been brought up.  The life cycle loads on the vehicle structure do not only consist of flight loads.  The rocket is transported several thousand miles from where is it built in California, to a stop in Texas for live firing, and then on to Florida.  Most of the road surfaces in the US interstate system are in decent shape, but not all.   There is a significant chance that the vehicle is subject to what must be significant loads from say a pot hole.  It's also a side load and that is totally different from the flight loads.

That said I can't imagine that SpaceX doesn't gather accelerometer data of some type while the vehicle is being transported.
 
« Last Edit: 07/04/2015 07:07 AM by cleonard »

Offline gospacex

  • Senior Member
  • *****
  • Posts: 3028
  • Liked: 537
  • Likes Given: 604
It's not a given that the cause will be pinpointed. What then?

Common sense says that the most suspect hardware would need to be beefed up (say, COPVs with higher safety margin and/or more conservative design), more/better sensors, telemetry bandwidth substantially increased, and fly again.

Offline tj

  • Member
  • Posts: 40
  • Liked: 15
  • Likes Given: 0
Spacecraft Tank Pressures-Typical
Hydrazine: 150 PSI at lift off
Oxidizde: 250 PSK at lift off
Helium used for repress of Hydrazine & Oxidizer at launch: 4500 PSI typ
Soon after SV separation Helium Tank is activated
Hydrazine and Oxidizer Pressure at 300 PSI

Tanks are required to be qualified to 50 x 0 to 450 PSI (for Hydrazine and Ox)
Then, after that, they are required to not burst at 600 PSI

Helium tank no-burst pressure: 9000 psi.

Plumbing and valves: similar design/qual regime.

Now just manufacture, test, install, operate  the flight units as good as the qual unit

For SpaceX, if a helium bottle is inside the LOX tank, what is its pressure:
Did this helium tank rupture, causing LOX tank to rupture.

Did SpaceX actually test the tanks as they were used in flight (i.e. test-like-you-fly)
We shall see.

Offline Damon Hill

  • Veteran
  • Full Member
  • ****
  • Posts: 556
  • Auburn, WA
  • Liked: 81
  • Likes Given: 151
Being pump-fed, helium pressurant is really for ullage and structural stiffness--the stage will fold up under flight loads if there's a sudden loss of pressure and non-compressible liquid as seemed to happen.

I have doubts that the COPVs could outright burst, but I'm wondering if flight vibrations could loosen one; are there mechanical fasteners or welds?  SpaceX should have plenty of data on structural loads and vibrations.

At any rate, I'm sure SpaceX is just as surprised and dismayed as anyone at this unforeseen failure.

Offline miiser

  • Member
  • Posts: 11
  • Liked: 11
  • Likes Given: 5
People have been looking at various LOX tank pressure scenarios involving He bottles, LOX plumbing, etc.  But could this be simply a structural failure of the LOX tank, with nominal tank pressure beforehand? (whether related or unrelated to the rumored liner cracking issue)  This would seem to fit all the data, and from what I've heard this cargo was especially heavy.  The vehicle was at or near MAXQ.  If the LOX tank wall simply buckled inward and collapsed, I would expect to see pretty much exactly what we've seen.  (Visualize a very heavy person standing on an unopened can of soda.)  I would expect there to be a brief and rapid increase in pressure as the tank volume decreased, with LOX gushing out the vents for a fraction of a second (one or two frames of video).  Then the tank would rupture, and you'd have the LOX squirting out everywhere.  The Dragon would almost immediately dump off the top as a result of the buckling, as was observed.  Following LOX tank collapse, the remaining vehicle would pancake and banana peel predictably from aerodynamic and g forces.

From what I've heard Musk say, SpaceX's tank fabrication method is "innovative".  And innovative is where the unknown/unpredicted failures often occur.  Could be an unseen manufacturing defect, or just that all the previous flights were near failure and this one was just a little bit over the edge.  And I suspect that one of the reasons some of the other launch providers moved away from pressure stabilized tanks in their current models was that there may have been concerns over the thin walls behaving dynamically in a difficult-to-predict fashion and being considered a risk.

I can't think of any reason why it couldn't have been simple structural failure.
« Last Edit: 07/04/2015 11:00 AM by miiser »

Offline Hauerg

  • Full Member
  • ****
  • Posts: 745
  • Berndorf, Austria
  • Liked: 351
  • Likes Given: 1125
It was nowhere near MaxQ.

Offline Im_Utrecht

  • Member
  • Posts: 20
  • Utrecht, Earth
  • Liked: 3
  • Likes Given: 12
I remember that with the launch of the first Falcon v1.1 Elon Musk said that he was afraid of bending.
Could this have played a role  ?

Offline miiser

  • Member
  • Posts: 11
  • Liked: 11
  • Likes Given: 5
It was nowhere near MaxQ.

While you are correct that MAXQ was reached 50 seconds or so earlier, you are incorrect that it was "nowhere near MaxQ" in terms of the magnitude of force.  The load doesn't max out and then go immediately to zero afterwards.  It's a very gradual drop off.  Acceleration and speed increase as the atmosphere thins and the propellant weight decreases, so they tend to balance each other out, but the atmosphere would still be pretty thick at this point in the flight.  The load would still be pretty near MAXQ.
« Last Edit: 07/04/2015 12:05 PM by miiser »

Offline miiser

  • Member
  • Posts: 11
  • Liked: 11
  • Likes Given: 5
I remember that with the launch of the first Falcon v1.1 Elon Musk said that he was afraid of bending.
Could this have played a role  ?

Certainly, bending/torque would contribute to the buckling load on the wall.

I also notice that, right before failure, the ring of condensation vapor around the Dragon became asymmetric, with a sort of bump on top.  Possibly the vehicle is beginning to flex abnormally at this point in time with the wall starting to buckle on one side.  But this could be nothing/optical effects.
« Last Edit: 07/04/2015 11:34 AM by miiser »

Offline kevinof

  • Full Member
  • ****
  • Posts: 642
  • Antibes
  • Liked: 428
  • Likes Given: 489
I remember that with the launch of the first Falcon v1.1 Elon Musk said that he was afraid of bending.
Could this have played a role  ?

Certainly, bending/torque would contribute to the buckling load on the wall.

I also notice that, right before failure, the ring of condensation vapor around the Dragon became asymmetric, with a sort of bump on top.  Possibly the vehicle is beginning to flex abnormally at this point in time with the wall starting to buckle on one side.  But this could be nothing/optical effects.

When Musk mentioned bending I think he was referring to the first stage due to fact that it was long and slender. The issue with this flight appeared to be in S2 and S1 displayed no signs of bending and in fact kept trying to fly even after S2 started to go away.

Tags: