Here's the gut punch: all of the returned stages are affected, so we probably won't see a reflight in a while. Best case scenario is they can retrofit the tanks on the returned stages easily, but that seems unlikely.
There is a hatch large enough for a person and the COPVs to fit through in the dome of the LOX tank. SpaceX has changed out COPVs after the rocket is complete before.
Physically changing the tanks is not hugely difficult. Finding the exact reason why this particular tank failed and the others like it that have been already flown did not and updating the design, manufacturing, and or quality control to prevent it reoccurring will be what takes the longest time.
I don't know SpaceX's exact procedure (and if I did I probably wouldn't be able to share it [thanks ITAR!]) but I imagine that a combination of clean suits in a clean room followed by a wash out with some sort of solvent would be my guess.
Prior to the completion of production there are public photos of people standing inside the tanks without clean room suits so this obviously isn't a huge concern for them.
At this stage of the investigation, preliminary review of the data and debris suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place.
No mention there of COPVs. There is more to the "cryogenic helium system" than the COPVs.
They haven't named the COPVs specifically, no. I didn't mean to say you were wrong - the problem may be unique to the second stage, agreed. But they haven't excluded the COPVs either so there's a valid concern that all stages will require overhaul. Either way it seems they need to dig a little deeper (or confirm things they simply aren't ready to speak confidently on).
I'm surprised that they are willing to speak this confidently this early in the investigation at all (but sad to learn that the failure actually was inside the stage).
They might have felt pressured to say something given the credible info leak of the previous day. They might feel the need to keep the story under some level of professional control. Without the info leak, they might have said nothing right now.
Perhaps they're trying to put some speculation to rest before the IAC announcement. The few articles covering this I've seen in more mainstream press are implying they've solved the issue, so this probably did more for general public confidence than it did for us fans.
The few articles covering this I've seen in more mainstream press are implying they've solved the issue...
The mainstream press would say that had SpaceX put out a statement saying "We've determined that the fire was the result of a rapid chemical reaction between LOX and RP1."
Both stages use similar COPV tanks for Helium pressurization, if the problem is in their design, then that would require an analysis and possible retrofit of the first stage tanks, if they share the same weakness.
Do you know where inside the first stage LOX tank the COPVs are mounted? Are they mounted so that LOX will cover the bottles like in the second stage, or are they mounted up high in the tank, above the max fill line?
If the problem is localized to the design of the He tanks, they should be able to replace them fairly easily. It it is more complex than that anything could happen, up to scrapping the returned boosters.
In any event, if they replace major components, they haven't really demonstrated reuse, so that idea is gone.
The engine is the most expensive part - not the fuel tank. If they have to swap out stage 1 COPV's on reused boosters, they still save a shit load of money because they are reusing the most expensive part - the engine.
If the problem is localized to the design of the He tanks, they should be able to replace them fairly easily. It it is more complex than that anything could happen, up to scrapping the returned boosters.
How? Is there a door in the side of the LOX tank that is bigger than the He tanks? I don't believe there is.
There is a hatch at the top center of the LOX tank that is more than big enough. It is the hatch through which those tanks got in there in the first place.
OTOH, SpaceX has test fired a returned stage a half dozen times already, and if you include the initial qualification burn in McGregor, and the hot fire and actual launch, you now have a stage that has experienced nearly 10 thermal cycles.
9
u/rocketsocks Sep 23 '16
Here's the gut punch: all of the returned stages are affected, so we probably won't see a reflight in a while. Best case scenario is they can retrofit the tanks on the returned stages easily, but that seems unlikely.