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

[Kabloona]

Ok, then how does helium released into oxygen create and explosion? Over pressure could rupture the tank, but that is not an explosion. AFAIK helium and oxygen are not combustible gases. Wouldn't it just rapidly vent without burning? And if it did, wouldn't we see a jet of burning gas coming out the side? What we do see is a ball of exploding gas on the side of the TE.

Even discarding the possibility of a ruptured COPV with flying fragments of carbon fiber/epoxy chunks and bits of metal liner flying around inside the LOX tank, an overpressure alone could well rupture the common bulkhead, very thoroughly mixing RP1 and LOX and destroying the stage; the specific ignition event is almost a formality at that point.

The only problem I see with this scenario is that, from the video, the size and behaviour of the LOX cloud escaping from the LOX vent during the filling process is not appreciably changed until the entire structure is well "ruptured".   Since filling was in progress (LOX in, GOX out) I would have expected we'd see the effect of any overpressure event in the LOX tank at the vent first, long (relatively speaking) before the explosion cloud.

(The above doesn't preclude the same COPV failure scenario in the RP-1 tank though)

One possible sequence of events that could be consistent with no observable change in LOX venting:

1. Helium system component ruptures, but leak rate of Helium is limited by the small diameter of the outlet line from the COPV, so the rate of change in LOX tank pressure is negligible compared to the speed of the next two steps, ie:
2. Shrapnel from the ruptured component pierces the common bulkhead...
3. LOX/RP-1 explosion ensues.

In this scenario, the initial "overpressure" event might have occurred inside the helium system itself, leading to component failure and bulkhead piercing/explosion before LOX ullage pressure had time to rise significantly.

Hmm...  but assuming the He in the COPVs is at a ridiculously high pressure, surely any release into the LOX tank, however small, would result in a large rate-of-change in LOX venting?

Not necessarily. The smaller the orifice, the slower the rate. And if the LOX tank was only, say, half-full at the time, that's a lot more ullage to pressurize. If the helium was venting through a 1/2" diameter COPV outlet into a half-filled LOX tank, I can imagine that pressurization rate being much lower than the speed of a fragment piercing the bulkhead and the resulting LOX/RP-1 explosion. Remember, SpaceX says the entire event took less than 100 msec.

[CyndyC]

Perhaps we can ease off the COPV talk for a bit. That's what I would call low hanging fruit. I think the issue is a little more nuanced than that.

As much as the COPV's are being beaten to death here, engineering logic says they're a primary suspect.

It's hard to imagine what other He component failure could overpressure the LOX tank in less than 100 msec, unless a smaller component failed and a metal fragment got propelled through the common bulkhead. I've never seen metal tubing fail at 6000 psi, but I imagine it could produce high-velocity shrapnel.

I have, however, seen a 1000 psi Helium line blow out and almost take someone's head off. I was working on my Masters thesis in a high-pressure solid propellant combustion lab. A friend and I were pressurizing a shock tube with Helium when one of the stainless steel Helium line fittings let loose, and a section of stainless tubing went ballistic and almost hit my fellow student in the head. Instead it dented the corrugated steel wall right next to him. We both went home pretty shaken. That accident gave me instant respect for the power of high pressure gases.

There is another way helium is used in the stages besides pressurizing the tanks, according to the Spaceflight101 FT page:

.....the combustion process that is sustained as LOX and RP-1 flow into the GG[gas generator]/[combustion]chamber once turbopumps spin up, initially using high-pressure helium for spin-up.

Does the helium for spinning up the turbopumps come from a COPV, or from a separate container?

[JamesH65]

There's a thought that's been going around in my head for the past three weeks about the two LOV events when it comes to the structural differences between S1 and S2... I call it simply, "what's the same, what's different"... S1 solid bird from launch to landing, S2 cantankerous... Why is this "if" there is so much commonality in materials, production technique, tooling, employees assembling them, handling and transportation, testing...etc?

Then the question Glen would be what happens during the integrated test that would cause two S2 failures, one in flight, one on the pad and are those unrelated?

Well, my career involvement in rocketry advanced as far as Estes Rockets, so take my thoughts with a grain of salt,

but, based on having built complex systems that sometimes get simplified because the customer didn't need EVERYTHING...

It would seem to me like S1 is like the absolute attention getter from an engineering perspective.  9 times as many engines, bigger tanks, more He systems, grid fins, landing legs, precision landing guidance, has to do re-entry and fly a gazillion times.  It's a complex beast and the best and the brightest engineering goes into that.

The S2 is a scaled down copy, 1 engine extended nozzle, small tanks, carries a tiny payload...  It's really boring by comparison.

I can easily picture a case where the senior engineer says, here, take this, it's validated on S1, it should work on S2, and the junior engineer does exactly that. 

I try to imagine simply the He fill system for S1 and compare it to the same system for S2.  Should be exactly the same, except, not as much He gets loaded, not as much plumbing, not as many COPVs.  Would it really be that the He process is the same in both cases, except S2 gets less He than S1?  Would the couplings be the same, the flow rates, the target load pressures, the expected COPV & plumbing temperatures, etc. etc.?

S2 is a totally different rocket than S1 albeit shares as many parts as possible with S1.  Sharing parts is good economics.  Do they share the same processes and do they have equal validation and oversight and QA?  Certainly your brightest engineers did the work on S1.  Did the same engineers do the work on S2?

In the fault tree analysis, is there a little box next to each item that says, "same as S1" and did that mean it didn't need the same analysis, design review that it got when it was defined for S1?

I don't claim any knowledge of the root cause, or even of the possible process failures that lead to it, but I know from personal experience, it's very easy to assume a working subsystem will work in a different context and end up being very surprised when it doesn't.

Or is it the case that S1 is overbuilt with increased structural margins for re-usability and S2 is pushing the minimal margins to extract maximum performance to make up for it...

This is the exact issue I've been getting at as well. Quality does not appear to be uniform .

But this is from the outside looking in.

If you are looking in from the outside, through blocked up windows, then really, you have NO idea of what is going on inside.

And yet your posts continue to claim things of which you have no knowledge whatsoever, I have more of an issue with extrapolating claims like this from no evidence than the issues themselves!

Your claims...

The struct issue wasn't the cause of CRS-7 despite that being stated as the cause by the engineers who designed and built the rocket and who had access to all the data.

That SpaceX has a quality control issue, despite having no knowledge of their quality control process.

That the same subsystem caused both accidents. Well, yes, the helium pressurization system, as whole could be regard as one subsystem. BUT, that subsystem contains a LOT of different parts, lots of sub-sub systems. Just like a car engine, it's one subsystem of the car, but a turbocharger failure would not be the same cause of engine destruction as a conrod failing. They are completely different failure modes. So to consider both accidents to have the same subsystem cause is ignoring the complexity of these subsystems. In the F9 accident cases, one was a strut failure, the other a issue with the helium pressurization. Completely different, and they should NOT be conflated, especially since SpaceX themselves  do not believe them to be linked.

You know who I believe? The engineers who designed it.

[FinalFrontier]

This is a very interesting article called, "Explosion Hazard from a Propellant-Tank Breach in Liquid Hydrogen-Oxygen Rockets:"

https://web.njit.edu/~muratov/hazards.pdf

Fig 13 lists possible scenarios and risks. I wonder how applicable it is to kerolox, but I figure the engineering risk assessment can inform people's guesses about the AMOS-6 incident. In particular, I wonder if cavitation and a shockwave from an exploding COPV could work as the sources of some of the types of combustion seen in the video.

Another user offered a theory on this in thread one I will try and repost it here later but basically the short answer is yes it can but it depends on exact conditions in the tank and propellant and how much potential energy you had at the failure pressure on the copv at the time.

Was it what I posted about focused shock detonation?
post#1156
https://forum.nasaspaceflight.com/index.php?topic=30981.1140

Yes sir appreciate it. Quite a few people have expanded on this and on various tests/results of COPV failures in our current thread as well, the point of all this being we have several possible ignition sources that could be caused by the COPV or other high pressure helium component failing inside the tank in and of itself.

[Jim]

Perhaps we can ease off the COPV talk for a bit. That's what I would call low hanging fruit. I think the issue is a little more nuanced than that.

As much as the COPV's are being beaten to death here, engineering logic says they're a primary suspect.

It's hard to imagine what other He component failure could overpressure the LOX tank in less than 100 msec, unless a smaller component failed and a metal fragment got propelled through the common bulkhead. I've never seen metal tubing fail at 6000 psi, but I imagine it could produce high-velocity shrapnel.

I have, however, seen a 1000 psi Helium line blow out and almost take someone's head off. I was working on my Masters thesis in a high-pressure solid propellant combustion lab. A friend and I were pressurizing a shock tube with Helium when one of the stainless steel Helium line fittings let loose, and a section of stainless tubing went ballistic and almost hit my fellow student in the head. Instead it dented the corrugated steel wall right next to him. We both went home pretty shaken. That accident gave me instant respect for the power of high pressure gases.

There is another way helium is used in the stages besides pressurizing the tanks, according to the Spaceflight101 FT page:

.....the combustion process that is sustained as LOX and RP-1 flow into the GG[gas generator]/[combustion]chamber once turbopumps spin up, initially using high-pressure helium for spin-up.

Does the helium for spinning up the turbopumps come from a COPV, or from a separate container?

And there are multiple COPV's with gases for different task.  The attitude control system nitrogen is one of them.  Same for engine spin system

[FinalFrontier]

Edited and broken down better.

You know who I believe? The engineers who designed it.

Your statement is akin to saying "I believe thiokol can't be wrong go ahead and launch because they designed it" during and after Challenger when they sat there with a known issue and denied they had a known issue until it was pulled kicking and screaming into the open. I can draw parallels with a multitude of other industrial disasters as well to show exactly how wrong this statement is, but I will forgo that. You don't know what you don't know.

Engineers are people not gods, they make mistakes all the time and they miss things, take it with a grain of salt if you want but I have been there to see it first hand. This is especially true when you are dealing with high energy and high stress systems like aerospace systems. The higher the temperatures, pressures, and kinetic and potential energies the more likely it is for things to go wrong and go wrong quickly and badly.

Note: Do not assume I am implying they are lying about this in some way or obfuscating things intentionally, I am only pointing out what should be obvious.

And a reminder, Elon Musk himself previously said complacency in operations and checkout from the top down was a contributing factor to CRS 7.
http://www.space.com/30013-spacex-complacent-rocket-explosion-musk.html

http://www.bloomberg.com/news/articles/2015-07-20/musk-says-spacex-failure-caused-by-strut-in-liquid-oxygen-tank


Have fun when that "conjecture" bites you in the ass when your MCT vehicle blows up and you find out the hard way your LES maybe didn't quite have enough Delta V. Musk himself has recognized it is an issue. With this said I have no idea what you are trying to argue here.

All of THAT said however, it is a very good thing that he recognized it was/is an issue this should help with solving the problem(s).

The struct issue wasn't the cause of CRS-7 despite that being stated as the cause by the engineers who designed and built the rocket and who had access to all the data.

Wrong. My speculation here is that it was not the only thing that failed and/or that the strut breaking free from the COPV sidewall as a result of an issue with that sidewall could create an identical failure mode in both observable failure and telemetry. Which it very well could since what actually failed was the helium lines not the COPV bottle, the pressure lines broke when the bottle was released, but initially were pinched shut by the violent upward buoyancy induced motion of the COPV after it broke loose. There is no way to know for sure whether the strut itself was the only thing that broke loose, that was my only actual conjecture here, but I have also pointed out, several times by the way, that it hardly matters what the exact failure was being that we are back here less than two years later with another lost vehicle that failed as a result of problems internal to the LOX tank on stage two. You are missing the forest through the trees here.

That the same subsystem caused both accidents. Well, yes, the helium pressurization system, as whole could be regard as one subsystem. BUT, that subsystem contains a LOT of different parts, lots of sub-sub systems. Just like a car engine, it's one subsystem of the car, but a turbocharger failure would not be the same cause of engine destruction as a conrod failing.

Forrest through the trees again. Either that or I did not adequately explain my point. My point is not the subsystem, my point is the structural element. The second stage LOX tank is built by a specific team on a specific area of the assembly floor and integrated/finished out in a similar fashion by other teams, point being however it, and the helium system within it, constitute one structural element of the vehicle. Engines, thrust frames, inter-stages, RP1 tanks, ect and so forth constitute other elements. SpaceX finishes out each of the elements individually and then integrates them on their assembly line, from which they are sent to McGregor for final testing. I do not know whether they test each major element individually or only after they are fully integrated stages (though we do know they test stage one and two separately or were at least prior to FT variant), but I would suspect they at least inspect+closeout each element prior to integrating each one into vehicle stages.

Therefore the actual issue here is one relating to production, testing, and closeout (or also potentially transportation of) the second stage or more specifically, if the issue occurred within the primary assembly facility at Hawthorne, within the LOX tank construction and closeout itself. Likewise it could also be testing conditions the LOX tank is subjected to at McGregor (and helium system) that affected it adversely (unknowingly) which did not affect the RP-1 tank in the same way. If that were the case the most likely reason would be temperature since the LOX is much colder.

But this is the key point, its a (big picture) quality issue with the second stage, or more narrowly a quality/(potentially design but again I think this is much less likely) issue with the stage 2 LOX tank itself.

This was and is my point the exact subsystem and failure mode are not relevant if the underlying reason for them is known to be quality/complacency issues, something Musk already acknowledged with regard to CRS 7.

That SpaceX has a quality control issue, despite having no knowledge of their quality control process.

Why do the rockets keep exploding if there is no quality control issue? Why do their rockets specifically keep exploding yet ULA India and ESA have all had successful flights this year? It's almost like its an issue specific to SpaceX or something 

And before you say apples to oranges you should look into the uses of COPV's on some of these other vehicles. F9FT definitely pushes the margins more than these from a design perspective, which is all the more reason why quality control should be a central concern within SpaceX at all times since you have a vehicle operating at much tougher margins.  Reuse-ability = more things that can go wrong, at least at this early stage, this includes the entire vehicle not just the first stage since it changes how much performance you need from both stages and how much prop you need on both. There is a reason why they are going to such lengths to use exotic propellants and very high pressure helium.

Completely different, and they should NOT be conflated, especially since SpaceX themselves  do not believe them to be linked.

Wrong. They said the specific failure mode of the two was not linked, not that the helium system was not linked or the second stage LOX tank or internal issues or any of the other factors. The only thing they have said is the specific failure mode is not the same, and that is easily determined. This also does not mean that the specific failure mode in this case did not in an unknown way contribute to the first failure, but again that is the only "conjecture" I offered up and again, is but one tree in the forest.

"But why throw this in then"?

Because my conjecture here is that SpaceX has alot less of an idea than they thought they did about what sort of dynamics occur in that tank during loading and launch. If this were not the case, I posit that the vehicle's would probably not keep blowing up.

If you are looking in from the outside, through blocked up windows, then really, you have NO idea of what is going on inside.

And yet your posts continue to claim things of which you have no knowledge whatsoever, I have more of an issue with extrapolating claims like this from no evidence than the issues themselves!

We have less of an idea for one, and second we have less of an idea with regard to specific failure mode. This does not apply to Macro issues for which we already have a well established set of facts namely, the rocket blew up again. There is no extrapolation whatsoever going on here, beyond your extrapolation of assuming what my point was while totally missing what my point was.

things of which you have no knowledge whatsoever

Read both thread's this is based entirely on data and facts already posted and presented by myself, others, and SpaceX itself. It once again remains only an opinion in totality but now I am repeating myself.

You have yet to offer any evidence to dispute these previously posted items while two blown vehicles and the CEO's own statements after the last one say otherwise.


All of this said I will finish this off by explaining why I am being so stubborn about this and why you should re-think what you are saying here. You should not be looking at the "big picture" issue(s) with regard to this failure and what it means for the future from the standpoint of "whatever broke is the only issue so fix that and it's good".

You should be looking at it from the standpoint of a current or prospective investor/entity wanting to launch payload and what you would want to see out of SpaceX internally if you have payloads on that manifest or want to have payloads on it in the future to assure your gear doesn't get blown up. What are they going to do differently (besides fix what broke)? What about mission assurance and flight rationale? Operation's and checkout? How did you (SpaceX) learn from this and what additional steps are you taking to prevent similar failures of the upper stage in the future for mission assurance?

Why? Because this is the only way private spaceflight is ever going to work. If you look at this from the standpoint of how we did spaceflight in the not so distant past, specific issues were fixed and culture changes occurred but we, the taxpayers, funded all of this. And even with all of this STS has two failures both of which had roots in lack of safety culture at the management level. Had this been private sector money, individuals, small entities, ect like you will need if you ever want to economically develop space and space access, what was done would not work at all.

I want to know why the same element of the vehicle fail's twice in less than 24 months across both the old and the "new and improved" variant and what they are going to do to fix it, not Shotwell telling us they plan on reflight within the next few months without even knowing what actually broke, why it broke, and why once again it was not caught.

And I can 100% guarantee you their customers are thinking the exact same thing right now.


PS:

None of this is intended as a personal attack and please don't take any of it as such. I enjoy debate and discussion but I also know it's very hard to tell mannerisms on an internet forum.

[Johnnyhinbos]

Please guys - while conducting your battles, please edit the quoted material for pertinent content only. Each post is becoming infinitely long as they are dragging along the entire conversation (which is getting longer and longer and longer and...). I know that after scrolling down more than three screens I give up and simply hit "back". Your actual point is never read...

[Space Ghost 1962]

FWIW think that much of this doesn't match what the operator/manufacturer/qualification/designer sees.

Expect that this will turn out to be manufacturing/QC/qualification issues related to their choice of extremely high pressure GHe, and that the smallest of fractures/leaks have interesting consequences given He properties, with interesting linkages to other systems.

Expect that the remedy will be a refinement of the existing design/operations, and that it will be extensively tested at McGregor provoking failures. Am certain they are sick to death of these issues with the pressurization system and will kill the issues with a comprehensive approach (why didn't they earlier is my issue with them).

Suggest radical redesign of F9US isn't in the cards. Extreme refinement of what goes into GHe pressurization is.

IMHO.

[Lars-J]

Please guys - while conducting your battles, please edit the quoted material for pertinent content only. Each post is becoming infinitely long as they are dragging along the entire conversation (which is getting longer and longer and longer and...). I know that after scrolling down more than three screens I give up and simply hit "back". Your actual point is never read...

Yep. Brevity is underrated. If you have a point to make, make it, don't write an essay on it.

[spacekid]

...My speculation here is that it was not the only thing that failed and/or that the strut breaking free from the COPV sidewall as a result of an issue with that sidewall could create an identical failure mode in both observable failure and telemetry. Which it very well could since what actually failed was the helium lines not the COPV bottle, the pressure lines broke when the bottle was released, but initially were pinched shut by the violent upward buoyancy induced motion of the COPV after it broke loose. There is no way to know for sure whether the strut itself was the only thing that broke loose, that was my only actual conjecture here, but I have also pointed out, several times by the way, that it hardly matters what the exact failure was being that we are back here less than two years later with another lost vehicle that failed as a result of problems internal to the LOX tank on stage two. ...

People should realize that after the CRS-7 failure last year, I'm not aware of any hardware that caused the accident (such as the failed strut or COPV) that was recovered. As a result, the only data they had was telemetry and video showing LOX spewing from the vehicle. Checking hardware on the ground they found some struts holding the COPV were below spec. The engineers made a plausible theory that matched the telemetry and video using below spec struts.

My comments would be that there could be alternative failure modes that would cause the same telemetry/video data. Once they determine root cause, they would/should verify that cause would not have caused the CRS-7 failure.

History has examples of accidents where investigators thought they found the cause but actually didn't (737 rudder issue).

[FinalFrontier]

...My speculation here is that it was not the only thing that failed and/or that the strut breaking free from the COPV sidewall as a result of an issue with that sidewall could create an identical failure mode in both observable failure and telemetry. Which it very well could since what actually failed was the helium lines not the COPV bottle, the pressure lines broke when the bottle was released, but initially were pinched shut by the violent upward buoyancy induced motion of the COPV after it broke loose. There is no way to know for sure whether the strut itself was the only thing that broke loose, that was my only actual conjecture here, but I have also pointed out, several times by the way, that it hardly matters what the exact failure was being that we are back here less than two years later with another lost vehicle that failed as a result of problems internal to the LOX tank on stage two. ...

People should realize that after the CRS-7 failure last year, I'm not aware of any hardware that caused the accident (such as the failed strut or COPV) that was recovered. As a result, the only data they had was telemetry and video showing LOX spewing from the vehicle. Checking hardware on the ground they found some struts holding the COPV were below spec. The engineers made a plausible theory that matched the telemetry and video using below spec struts.

My comments would be that there could be alternative failure modes that would cause the same telemetry/video data. Once they determine root cause, they would/should verify that cause would not have caused the CRS-7 failure.

History has examples of accidents where investigators thought they found the cause but actually didn't (737 rudder issue).

Bingo. Still happens to this day in the aviation industry all the time, though quite a bit less than it used during the 60-80s. Same for the maritime industry. Despite over a hundred years of innovations in safety and engineering, ships routinely still sink and in some cases with very little explanation (see MOL Comfort for a recent example of plausible theory).

FWIW think that much of this doesn't match what the operator/manufacturer/qualification/designer sees.

Expect that this will turn out to be manufacturing/QC/qualification issues related to their choice of extremely high pressure GHe, and that the smallest of fractures/leaks have interesting consequences given He properties, with interesting linkages to other systems.

Expect that the remedy will be a refinement of the existing design/operations, and that it will be extensively tested at McGregor provoking failures. Am certain they are sick to death of these issues with the pressurization system and will kill the issues with a comprehensive approach (why didn't they earlier is my issue with them).

Suggest radical redesign of F9US isn't in the cards. Extreme refinement of what goes into GHe pressurization is.

IMHO.

Basically, more or less this is the elephant we have been beating around in the room this entire time. But I can distill this a bit more.

CRS7 was blaimed on a strut failing. It was found that SpaceX was not independently testing, or not adequately so, these struts under flight conditions before they used them in the design of the vehicle, but instead trusted the ratings and tolerances the manufacturer of the struts said they could do. When they tested after the incident they found these tolerances were deficient or not always met by the actual material itself.

So what else didn't they test, or just develop flight rationale for based on circular assumptions?  This is what it means to have unknown unknowns and it doesn't matter how good you are at engineering you will always run into things like this for as long as humans continue to design the machines.

 
Another thing which has already been brought up but I would call attention back to from a complacency standpoint:

The entire point of a static fire test is to test that the vehicle is healthy before flight. So what happens if it isn't healthy and something breaks on the pad? The whole point of this was supposed to be to reduce risk to the payload and increase the chance of mission success. So why the heck did nobody at any point when this decision was made in the room say "jee maybe we are being counter-intuitive by changing what we do and mounting the payload for the static fire" ?  That is how I know they still have a complacency issue at least to some extent.


None of these are particularly "big deals" all of this, including what actually broke and caused this mess, is easy to fix, including whatever culture issues they may have.  Sticking to those fixes and not getting ahead of yourself in iterative design and pushing the limits on future vehicles, that is going to be the hard part.

[CyndyC]

Yep. Brevity is underrated. If you have a point to make, make it, don't write an essay on it.

Essays should be okay for people who can understand them. What I don't feel time to read here are Masters' theses.

[Space Ghost 1962]

None of these are particularly "big deals" all of this, including what actually broke and caused this mess, is easy to fix, including whatever culture issues they may have.  Sticking to those fixes and not getting ahead of yourself in iterative design and pushing the limits on future vehicles, that is going to be the hard part.

From my admittedly biased perspective, its a cultural issue. Conflict between agile development and classical "systems engineering".

My heretical (as received) suggestion was to do both and let them war for supremacy. Not well received.

Agile development has to have a complimentary "extreme pushback and accountability" foil to press up against. They need to overdo on the fine grained capture and assessment of vehicle function, assessment, operations and performance. They are getting there but they need to do so quicker/better. Less risk on operational systems/process.

In the same way ULA needs to adopt much more agile development and less dogmatic systems engineering.

And to complete this, OA needs to prove realism in both. BO is still to secretive for its own good.

[yokem55]

History has examples of accidents where investigators thought they found the cause but actually didn't (737 rudder issue).

Sorry for the OT, but for the record, the 737 rudder issue was not misdiagnosed. It was simply left unsolved (much to the consternation of the NTSB) a year or so after the Colorado Springs crash, and then took several years to nail down after the Pittsburgh crash when there was a close call reoccurrence that the pilot managed to stop in time. A big part of the delay was simply that while the rudder actuator misbehaving was a theory fairly early on after the Pittsburgh crash, the failure couldn't be reproduced with the actual flight hardware recovered from the crash until the exact same thermal conditions (cold actuator, hot hydraulic fluid) were also reproduced. This is not to say that everyone involved were angels - Boeing and the Pilot's union were really trying to not be stuck with the blame of two crashes. But the NTSB really deserves a lot of credit for getting to the bottom of that episode.

[mfck]

 ...

Another thing which has already been brought up but I would call attention back to from a complacency standpoint:

The entire point of a static fire test is to test that the vehicle is healthy before flight. So what happens if it isn't healthy and something breaks on the pad? The whole point of this was supposed to be to reduce risk to the payload and increase the chance of mission success

...

FWIW according to Jim the point of a static fire is to reduce schedule risk, not to reduce risk to a payload or increase mission success. He re-iterated this point on several occasions.

[Rocket Science]

I would just like to make a point about various opinions about SpaceX's approach to it's LVs. IIRC they stated that Falcon was designed from the onset to be a "human rated" vehicle, thus from my perspective one should hold their feet to the fire to the standards they set for themselves... 2017 is not that far away for there to be "unknown, unknowns" for a vehicle to begin tests with crew aboard IMHO... Years back I stated that "I would strap my back onto an Atlas V today" given the chance to fly. Nothing has changed my opinion so far...

[matthewkantar]

FWIW according to Jim the point of a static fire is to reduce schedule risk, not to reduce risk to a payload or increase mission success. He re-iterated this point on several occasions.

If I recall, Jim was referring to wet dress rehearsals for schedule assurance, not static fires, specifically for short launch window missions.

Matthew

[Roy_H]

Ok as I understand it if the root cause is helium rupture, 3 possibilities:
1) A fragment went through the common bulkhead into the RP1 tank mixing the two gases and creating a spark. If this was the scenario I would expect a more uniform explosion in all directions around the rocket.
2) A fragment went through the side of the tank and the aluminum was exposed leading to an aluminum/oxygen explosion.
3) The exploding helium tank ignited with its own carbon fiber overlay or aluminum inner tank reacting with the oxygen. Again I would have expected a more uniform explosion in all directions.

Is it possible to tell the composition of the burning materials by the color? Lithium-aluminum, vs, RP1, vs Carbon fiber and oxygen?

1st photo, an example of a "uniform" explosion, equal in all directions around the rocket.
2nd and 3rd frame before and after Falcon explosion.

[Rocket Science]

Ok as I understand it if the root cause is helium rupture, 3 possibilities:
1) A fragment went through the common bulkhead into the RP1 tank mixing the two gases and creating a spark. If this was the scenario I would expect a more uniform explosion in all directions around the rocket.
2) A fragment went through the side of the tank and the aluminum was exposed leading to an aluminum/oxygen explosion.
3) The exploding helium tank ignited with its own carbon fiber overlay or aluminum inner tank reacting with the oxygen. Again I would have expected a more uniform explosion in all directions.

Is it possible to tell the composition of the burning materials by the color? Lithium-aluminum, vs, RP1, vs Carbon fiber and oxygen?

1st photo, an example of a "uniform" explosion, equal in all directions around the rocket.
2nd and 3rd frame before and after Falcon explosion.

The spectra was discussed at length Roy in thread 1. I'll let those posters comment on it, or you can use the search function if you are interested...

[Jim]

Ok as I understand it if the root cause is helium rupture, 3 possibilities:
1) A fragment went through the common bulkhead into the RP1 tank mixing the two gases and creating a spark. If this was the scenario I would expect a more uniform explosion in all directions around the rocket.
2) A fragment went through the side of the tank and the aluminum was exposed leading to an aluminum/oxygen explosion.
3) The exploding helium tank ignited with its own carbon fiber overlay or aluminum inner tank reacting with the oxygen. Again I would have expected a more uniform explosion in all directions.

No, it was helium system and not just tanks.   

And lets just stop the exposed aluminum/aluminum fire.  That doesn't happen