Updates SpaceX Falcon 9 F5 CRS SpX-2 through CRS SpX-12 Updates

[GLS]

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IMO, the RSO sent the destruct command probably just an attempt to detonate the charges to make the debris recovery safer. I can't think of any other reason they would be "so late". Also, I doubt there was an accidental detonation because the charges only go off, I'm 99% sure, via coded command from the RSO console and there's no break-wire backup or anything. So, I'm super confident that the Air Force isn't at fault here.

 

[RCO]

I think it's more a case of, "why'd it take so long for them to hit the FTS?"

I don't find it particularly strange that Flight Safety didn't destruct the vehicle in the 10 seconds or so during which the vehicle was leaking LOX and beginning to disintegrate, as it would not be immediately clear to someone watching all the video and telemetry in real time that the vehicle had catastrophically failed until the final disintegration occurred. Flight Safety's main goal is to prevent the vehicle from leaving the planned corridor, which has been cleared of people below it and has minimal risk to life and property. As long as the vehicle is still going in the right direction, they are in no hurry to destroy it. The main goal of the destruct is to render the vehicle non propulsive and to burn or disperse the remaining propellant. So the destruct system just shuts the engines down and opens the propellant tanks up, hopefully igniting them as well. They mostly just don't want a disabled vehicle flying uncontrollably into a populated area. I do think it's a little strange that the FTS was activated at 70 seconds after the failure rather than, let's say, 10 or 15 seconds after the disintegration. But this is not a safety concern, as the vehicle remained on course and never threatened to leave the safety zone. As someone else mentioned, I think the only reason they bother sending the destruct signal after the disintegration is to make sure the destruct charge itself does not reach the land intact. This is just standard procedure, although in this particular case I think there is very little chance of the destruct charge reaching the ground intact. I noticed that in Range Safety's warning notice to the public, they told people to not touch any debris and to not use a cell phone near it. I suppose the cell phone warning is because there is a concern that the RF energy could somehow trigger a destruct charge (or separation bolt or such) to explode. Although, again, I believe this is just a CYA standard practice, not a realistic hazard.

 

[Linguofreak]

There we disagree... The Shuttle was never unsafe. It had really bad safety to no safety in situations in which Soyuz for example excels. And excels in safety in situations in which Soyuz looks bad.

Is there any part of a Soyuz launch in which a failure of the launch vehicle will guarantee a loss of the crew? The Shuttle had no survivability at all for any catastrophic failure during the SRB burn, which was probably the phase of flight where catastrophic failures were most likely. For Soyuz, a catastrophic failure of the first stage would almost certainly be survivable for the crew.

Just looking at the disadvantages of a launcher makes you often forget, that it also had advantages - the chance to survive a failure after SRB SEP was for example much higher in the Shuttle than in a Soyuz at the same flight conditions.

What exact failure mode and cause of crew death are we talking about here, and how would the Shuttle do better?

 

[RisingFury]

I'm a little worried that SpaceX hasn't posted any updates yet. They figured out the tank pressure problem quickly, but then silence.

I'm not suggesting anything's wrong. But given how mouthy the company usually is, even about its failed first stage landing attempts, I'm worried that they haven't found anything at all yet.

 

[Andy44]

The Shuttle had no survivability at all for any catastrophic failure during the SRB burn, which was probably the phase of flight where catastrophic failures were most likely.

Says who? Before the Challenger accident it was believed that the most probable failure mode was an SSME failure; had Challenger been operated properly the SSME would still be perceived as the most dangerous component of the system due to its complexity and moving parts. The SSME blew up on the test stand during development in fact.

The spectacular nature of the Challenger accident has made SRBs a source of fear for everyone who has seen the film, but the fact is that the SRBs are quite safe and reliable, especially after the redesign.

 

[MaverickSawyer]

I'm a little worried that SpaceX hasn't posted any updates yet. They figured out the tank pressure problem quickly, but then silence.

I'm not suggesting anything's wrong. But given how mouthy the company usually is, even about its failed first stage landing attempts, I'm worried that they haven't found anything at all yet.

Well, from the sound of it, the last few seconds of telemetry are pretty garbled. It may be taking them a while to make sure they're actually able to use it in the investigation. Otherwise... They've got zero leads or evidence to go on.

 

[RCO]

I'm a little worried that SpaceX hasn't posted any updates yet. They figured out the tank pressure problem quickly, but then silence.

I'm not suggesting anything's wrong. But given how mouthy the company usually is, even about its failed first stage landing attempts, I'm worried that they haven't found anything at all yet.

I'm not at all surprised. SpaceX is mouthy about their successes. But in the past, SpaceX has been very close mouthed and cagey about failures, releasing very little information to the public. The exception is R&D type failures, such as 1st stage recovery, in which failure is expected and the publicity regarding innovative R&D helps engage the public and generate excitement and political capital for the company. The justification in the past for their silence has been "export law", but I think the real reason is they don't want their competitors getting the information and using it as leverage in contract competitions.

I'm sure SpaceX knows a lot more than they're telling us. We never got a detailed technical explanation regarding the previous Merlin engine failure, and I doubt we'll ever get a detailed technical explanation of this failure.

The biggest concern for SpaceX supporters should be if this turns out to be some kind of poor quality discipline issue (i.e. Challenger disaster). If it's a culture/process issue, it puts a big question mark on the future of manned flight and high value heavy lift DoD missions.

People in this forum keep discussing whether or not "man rated" is a real thing or not. For sure, all the launch providers have had systemic/process/quality issues in the past. But I think the biggest perceived concern over whether SpaceX is ready for the big leagues has to do with whether or not they've developed the disciplined culture required for high reliability. This culture is not easy to develop or maintain, and it took LM/Boeing/ULA a long time to get to where they are reliability wise. It's not simply a matter of being technically proficient and innovative.

If this is just a technical issue which was not easily predictable, it's much easier for SpaceX to move forward.

 

[Linguofreak]

Says who? Before the Challenger accident it was believed that the most probable failure mode was an SSME failure; had Challenger been operated properly the SSME would still be perceived as the most dangerous component of the system due to its complexity and moving parts. The SSME blew up on the test stand during development in fact.

And that's another thing: had an SSME actually blown up in flight, it would have been an LOCV at any stage of launch. A tower-and-capsule rocket concentrates all the stuff that's likely to fail catastrophically downwind of the spacecraft and puts only low-energy maneuvering rockets on the spacecraft itself. The spacecraft is also much more durable and less likely to be ripped apart by aerodynamic forces if separated from the stack in an uncontrolled fashion.

The Shuttle had its high energy stuff onboard and alongside the orbiter, and the orbiter was almost certain to be incapable of a controlled landing after an uncontrolled separation. Even an Apollo 13 style failure on orbit would likely have been unsurvivable for the orbiter (or for the crew without a rescue shuttle) because the "command module" and "service module" equivalent parts were not separated, so such a failure would likely have rendered reentry unsafe.

The spectacular nature of the Challenger accident has made SRBs a source of fear for everyone who has seen the film, but the fact is that the SRBs are quite safe and reliable, especially after the redesign.

Even the problem they experienced on the Challenger flight would not have resulted in an LOCV if the leak had not impinged on the ET. (Though as I understand it, it would have necessitated an abort).

But a tower-and-capsule rocket with the exact same boosters Challenger flew with would not have killed its crew in the exact same failure scenario that Challenger experienced. Such a rocket would not have needed to rely on the perfect functionality of the launch vehicle to ensure crew survival.

 

[Andy44]

And that's another thing: had an SSME actually blown up in flight, it would have been an LOCV at any stage of launch. A tower-and-capsule rocket concentrates all the stuff that's likely to fail catastrophically downwind of the spacecraft and puts only low-energy maneuvering rockets on the spacecraft itself. The spacecraft is also much more durable and less likely to be ripped apart by aerodynamic forces if separated from the stack in an uncontrolled fashion.

The Shuttle had its high energy stuff onboard and alongside the orbiter, and the orbiter was almost certain to be incapable of a controlled landing after an uncontrolled separation. Even an Apollo 13 style failure on orbit would likely have been unsurvivable for the orbiter (or for the crew without a rescue shuttle) because the "command module" and "service module" equivalent parts were not separated, so such a failure would likely have rendered reentry unsafe.



Even the problem they experienced on the Challenger flight would not have resulted in an LOCV if the leak had not impinged on the ET. (Though as I understand it, it would have necessitated an abort).

But a tower-and-capsule rocket with the exact same boosters Challenger flew with would not have killed its crew in the exact same failure scenario that Challenger experienced. Such a rocket would not have needed to rely on the perfect functionality of the launch vehicle to ensure crew survival.

All true. The key for ensuring crew survival on an STS-type system is to make the likelihood of failure low enough to live with the potential consequences. This is done by following procedures and checklists rigorously, as opposed to a more tolerant capsule system which relies on inherent design. Both systems are safe enough when all the rules are followed, and both are still scary dangerous compared to most other modes of travel.

 

[Cairan]

Here's an SSME-related close call we seldom discuss... https://www.youtube.com/watch?v=0Rz82mf01Yo

 

[Thunder Chicken]

Even the oxidizer line of the rocket engine does not have the diameter to permit such massive emissions of LOX. And the chill-down line that branches off the main LOX line usually (again, I have no knowledge of the piping in a Falcon 9 rocket), will be much smaller. So, by the observed cloud, this is already wrong. Also we had no smaller emission of LOX before the tank failed completely.

Also, such a breaking pipe would not instantly result in a structural failure of the second stage and would not get observed as "counter-intuitive overpressure event"

Good point - the "overpressure" terminology suggests something else happening than a simple failure of a line or weld during normal chilldown.

The 2nd stage O2 tank is pressurized with helium during the chilldown of the engine lines. The helium tank pressure must necessarily be much higher than the nominal pressurized o2 tank pressure, so some regulation system must be used to step down the pressure. What if that system were to fail? Is the helium tank pressure enough to rupture the o2 tank if it were introduced unregulated?

 

[MaverickSawyer]

Good point - the "overpressure" terminology suggests something else happening than a simple failure of a line or weld during normal chilldown.

The 2nd stage O2 tank is pressurized with helium during the chilldown of the engine lines. The helium tank pressure must necessarily be much higher than the nominal pressurized o2 tank pressure, so some regulation system must be used to step down the pressure. What if that system were to fail? Is the helium tank pressure enough to rupture the o2 tank if it were introduced unregulated?

Oh, definitely. Especially if it all dumps at once.

 

[Linguofreak]

All true. The key for ensuring crew survival on an STS-type system is to make the likelihood of failure low enough to live with the potential consequences. This is done by following procedures and checklists rigorously, as opposed to a more tolerant capsule system which relies on inherent design.

I quite frankly doubt that you can get the likelihood of failure low enough on a spaceplane if it's not a full SSTO vehicle (certainly not with the spaceplane side-mounted, it has to be top-mounted if it's feasible as a non-SSTO at all). Safety aside, I doubt that wings are actually cost-effective unless you're able to do not only SSTO, but horizontal takeoff.

 

[hellotoall]

Second stage is 2/3 oxi. on top and 1/3 fuel on bottom. Separated by one dome. As mentioned in my previous post there are radial and circumferential baffles to prevent sloshing. the dome separating fuel from the oxidizer has insulation on it make sure only the smallest amount of fuel freezes - when its cold it turns to a gel like substance and its needs to be liquid to not clog the sump. The oxidizer tank portion has helium bottles hung from bracketry. All skin and dome are friction sit welded. Depending on concentricity of the parts, final thickness may vary slightly. They are almost unique on every rocket. no two tanks would have the same thicknesses in all the same places. The fuel tank dome is the outer dome and holds the motor and control equipment. All in all pretty simple. I dont want to repeat my previous post.

The brief part of man rating that i can recall were different safety factors on structural analysis. 1.25 factor for not-man rated and maybe 1.5 to 2.0 on man rated equipment and possible other factors beyond my knowledge in terms of materials and propogation of failure - so you can see it generally results in a heavier rocket.

 

[RCO]

I'll stick my neck out and make my prediction for the root cause of the failure. The LOX tank pressure relief vent valve gets stuck closed, and then as the engine chilldown proceeds (plus declining external atmospheric pressure and tank heating), LOX tank gauge pressure gradually rises until the vent valve is forced open. The vent valve then gets stuck open and pressure in the tank drops to the point that the tank is no longer structurally stable. Collapse, breach, and disintegration ensues. Root cause is a sticky vent valve, possibly due to ice.

 

[RisingFury]

Quite a specific prediction. We'll see if it holds - that is if SpaceX releases the cause of the failure to the public

 

[RCO]

Quite a specific prediction. We'll see if it holds - that is if SpaceX releases the cause of the failure to the public

It is! Although I think some of the other suggestions, such as He bottle explosion or engine LOX plumbing breakage are also reasonably likely. Vent valve is just my best guess.

I suppose the public data release will depend on whether the information is perceived as a net marketing plus or minus, and whether the information might be used against them by their competitors and detractors. In the case of the Merlin engine failure, all we got for a long time was "engine anomaly and controlled shutoff". They eventually admitted it was a breach, but never gave any details on the root cause, such as a bad weld, etc.

If this failure is a minor technical detail that can probably be recovered from in 6 months or less, I think we may get some good information. If it's a cultural/process/quality issue or a major technical design flaw, with broader implications, I doubt we'll get much.

 

[Urwumpe]

Good point - the "overpressure" terminology suggests something else happening than a simple failure of a line or weld during normal chilldown.

The 2nd stage O2 tank is pressurized with helium during the chilldown of the engine lines. The helium tank pressure must necessarily be much higher than the nominal pressurized o2 tank pressure, so some regulation system must be used to step down the pressure. What if that system were to fail? Is the helium tank pressure enough to rupture the o2 tank if it were introduced unregulated?

Lets say it so: In the worst case, easily. Would a gas bottle in the tank burst due to manufacturing faults (which can always happen), you would also have shrapnel flying around in the tank, which can easily punch through the thin walls.

Also, you would have a very short time from first indication of a problem (overpressure event) to structural failure, about like observed. There are a few other branches in the failure tree thinkable, which would be very similar and which would only be a difference in the time between overpressure event and structural failure.

But simply a gas valve on a helium bottle stuck open would not be enough. Would multiple gas bottles stuck open, yes, that could overwhelm the vent system and pop the tank at its weakest location (tank dome welds usually)


But for any slow failure, remember that there had been almost no visible warning before massive amounts of LOX got released and got released at pretty constant rate for quite a time. So, the tank did not just explode completely, releasing all LOX in fractions of a second into the air stream and atomize it. There must have been a hole, much larger than the usual piping because of the much higher mass flow rates.

If the hole was on the forward tank dome, the inflow of LOX into the trunk of the Dragon could result in separation of either the Dragon capsule from the trunk or the whole spacecraft from the second stage.

Maybe the helium bottles also worked fine and simply opened automatically to keep the tank pressure constant whole the contents of the tank vented out through the hole. At one point, the hole will have grown larger and the tank pressure have dropped so far, that the tank itself will no longer resist aerodynamic forces and a rapid aerodynamic destruction sets in from above. Maybe something also triggered the FTS from inside. I am not sure there, but I would place my bets on the second explosion coming from the FTS.

But what is the root cause? A helium bottle? Maybe. But there could also be manufacturing faults, a falling IDA, etc. All could result in a "counter-intuitive overpressure event" as final anomaly in the telemetry.

I doubt that SpaceX will find an exact root cause there, even with 3000 values telemetered. But maybe they and NASA can limit the cause to 3-4 possible components of the stage.

 

[RCO]

Also, you would have a very short time from first indication of a problem (overpressure event) to structural failure, about like observed.

We don't have any information regarding the time from the overpressure starting to the time of the observed failure, so how can you say that a particular model matches what was observed? I assume SpaceX has this information, but they're not sharing it.

All we know is when the O2 cloud appeared. And once this occurred, we can assume that there was a pretty sizable breach or leak somewhere, and pressure in the LOX tank was rapidly declining until collapse occurred or structural damage was severe enough that hypersonic air flow was able to enter the tank.

But we have no information to indicate when the overpressure occurred and whether it was a slow, gradual build up or a sudden, violent one.

 

[hellotoall]

I keepp thinking. If it happened past max q, maybe its likely a fatigue issue or manufacturing defect in.the upper lox portion. Any structural breakaway is going take a piece of the tank wall with it as everything is attached to the wall. It was prob more sudden as you migh think if gasses were escaping for a while then it might perturb the trajectory??? and show up sooner on telemetry or onboard cams. The tank would be pretty full of lox with only a small space for ullage gases. I think upper tank dome failure or bottle mount failure and then aero forces acting on.opening did the rest. As no one was onboard its funnto speculate .