News Changes to the SpaceX BFR rocket.

Urwumpe said:
I think its a bad luck event even with massive venting and can't be prevented at all, because the cause is a rupture of both oxygen and fuel pipes, possibly caused of a hard engine shutdown. Even if only a fraction of the propellant leaks out, as soon as it find a helpful ignition source, the volume of the leaked propellant goes up. And worse: This isn't even the root cause. The engine shutdown might be caused be a single pipe failing in flight, making the other fail on resulting emergency shutdown and causing a fluid hammer in the other pipe. Or since its really hard to detect a broken pipe near the engine early enough to trigger the shutdown in time, SpaceX could have had a massive turbine overspeed by a pump running dry, blowing up the whole powerhead of the Raptor engine.

Large Blowout panels might be a solution to prevent the worst, but this costs structural integrity or mass increase, also only less than half of the circumference is available, the rest is covered by the heatshield = Its impossible to isolate engines completely from shrapnel AND provide enough venting capacity without "simply" ejecting the whole engine backwards (against the residual thrust, while staying onboard during lateral maneuvers)
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And I suppose even if it doesn't catch fire, the leak alone could have you fall short of orbit anyway. From the telemetry, CH4 dropped pretty quickly.

I think it was SN11 though which had something similar. Fire from a leak cooked the engine, and as soon as it relit for the flip, it had a hard start and the engine took out the whole ship. Here it seems like they failed one by one, but maybe there's enough containment or they didn't fail destructively. It still isn't clear to me what even caused it to blow, FTS or the fire, but apparently timestamps from the explosion videos put it some 3 minutes after they lost comms.

They must be really hoping Raptor 3 is the godsend they mean it to be in terms of containment, because if there's one recurring issue in this program it's engine leaks. SN11, the first booster, now this one. The fire suppression probably won't be too complicated to add, but it's still a suboptimal bandaid.
 
Looking at the Starship telemetry on the video stream:

7:40 MET the first sea level Raptor drops out.
7:58 MET video cuts to external view showing fire coming out of aft flap hinge.
8:04 MET another sea level Raptor and a vacuum Raptor drop out at the same time.
8:18 MET another vacuum Raptor drops out.
8:24 MET last sea level Raptor drops out.
8:25 MET Loss of telemetry updates. Velocity stops increasing, but shows last vacuum Raptor still functioning.

From ~ 8:00 MET on the CH4 tank level started dropping a lot faster than the LOX. At loss of telemetry the CH4 tank level was about 1/3rd of the LOX tank level.

I wonder if they had an N-1 style cascade of failures and leaks that lead to the RUD.
 
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Thunder Chicken said:
I wonder if they had an N-1 style cascade of failures and leaks that lead to the RUD.
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Yes, I agree with you. I also think the progressive nature of the "anomaly" is very similar to the failure modes of the N-1. But we should include there, that the fire likely burned the cables to the engines as well, causing short circuits and loss of signals that might produce confusing telemetry states, especially for us who can't analyse the full telemetry and know nothing about the signal paths, which would enable us to tell what the reported states in the telemetry actually really mean about the state of the vessel.

And we don't know, if SpaceX used fire-proof cable insulations like mandatory in modern aircraft, or cheaper material like Kapton to keep the costs down.
 
A little consideration inspired by insomnia. I have a hard time believing that Superheavy, which probably has an overall dry mass in excess of 250 tons, has to jettison the hotstaging ring in order to reenter successfully.
 
K_Jameson said:
A little consideration inspired by insomnia. I have a hard time believing that Superheavy, which probably has an overall dry mass in excess of 250 tons, has to jettison the hotstaging ring in order to reenter successfully.
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So they jettison it for show?
 
The hot stage ring question still seems a bit unanswered. The official explanation is very vague and maybe doesn't add up too well, unless we're just missing key info. Worth mentioning though the ring is documented (FAA) as being some 12 t, which is 5% of the booster's dry mass (assuming 250 t).

One good line of speculation was around the LOX landing tank: They design it in the context of the initial boosters, but then rapidly add a ring, extra engine shielding, ice filtration and the CO2 system. The centre three Raptors will be drawing propellant directly from the landing tank during the landing burn, so it shouldn't just be a matter of keeping extra reserves in the mains. The problem with this and why I no longer quite think it works, is B15 (set for Flight 8) was the first out of the factory with a visibly expanded landing tank, but there's good indication this was retrofitted onto the past few boosters.

Even if the landing tank is good now, what about supply for the middle ring of 10? Judging from the remaining frost lines after catch, it seems the main tanks are coming back with quite a bit left (seen estimates of a few hundred). That may be to do with engine-out reserves and whatever other reasons, but how much would the ring eat into those reserves really?

Another possibility is aerodynamics, there's some indication, although based on quite literal shadows on gridfins, that the ring may have been ripped off during Flight 3 on booster descent. Flight 3 was the first booster to make it back down, but Flight 2 will have already planned for no jettison too. Would they not have figured out until bringing it back that the booster was then too heavy to return? There's always the possibility though that jettisoning isn't strictly necessary unless going back to the tower, and Flight 4 was just the demonstration before having to do it for sure on Flight 5.
 
diogom said:
Another possibility is aerodynamics, there's some indication, although based on quite literal shadows on gridfins, that the ring may have been ripped off during Flight 3 on booster descent. Flight 3 was the first booster to make it back down, but Flight 2 will have already planned for no jettison too. Would they not have figured out until bringing it back that the booster was then too heavy to return? There's always the possibility though that jettisoning isn't strictly necessary unless going back to the tower, and Flight 4 was just the demonstration before having to do it for sure on Flight 5.
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It could also be that the ring moves the COG position to much forward for a safe landing. If the stage is usually just a very heavy engine section and empty tanks, it would behave close to a shuttlecock while falling back to earth. A heavy hot staging ring could make it less stable in flight, requiring more force to control attitude and make the gridfins less effective. Also, since all stages/vehicles of the project are massively overweight by now, shedding as much mass as possible could also be a compensation.
 
I would say, the information policy of SpaceX is subpar on handling the fallout of their testing strategy....
Kaine said she’s grown wary of SpaceX’s response to the ordeal and the Starship program in general. She said she’s not interested in keeping any of the debris she collected. Her goal is to keep the roadways and beaches she frequents clean and free of dangerous materials.

“You need to come pick this up,” Kaine said of SpaceX. “And my concern has grown on a larger level about these launches, because now that I’m reading about it — there’s such limited information out there.”
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I expected something like that. :D
 
Just heard: "issue", "transition", "state machine".


Been there, done that :ROFLMAO:
 
I am still not really getting comfy with talk like "We keep pushing the boundaries of the booster..." shouldn't it at least work ok-ish once, before you start pushing for higher goals?
 
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