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GLS

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IMO, that's probably debris or for some reason the bleed valve solenoid didn't fully open...
Did a quick check of the pumbing and the bleed valves (both LH2 and LOX) aren't solenoids, but are in fact pressure actuated valves, feed pressure to open from a single solenoid. So if the solenoid didn't open, the LOX bleed would also suffer, which doesn't appear to be the case. So that leaves the LH2 bleed valve not opening... which would be picked up by the engine controller.
Interesting situation... :unsure:
 

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The more I look at this, the more convinced I am that there is debris somewhere, or inside the bleed line or somewhere inside the "main" fuel lines of the engine... which means delay of several days or weeks.
Christmas launch bets?
 

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Apparently; they have a plan, that would bring the engine temp down before the window expires. We'll see
 

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Thunder Chicken

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But if it is debris, I don't think they can tell where it is, so they risk a pad abort and engine damage. So they would still not go anywhere and look like idiots in the process.

My bet is another month.
The engine bleed problem doesn't sound good. They were able to do this during the wet dress rehearsal, right? I assumed they went through all the pre-chill activities as part of that test, but maybe not?
 

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The engine bleed problem doesn't sound good. They were able to do this during the wet dress rehearsal, right? I assumed they went through all the pre-chill activities as part of that test, but maybe not?
From what I heard, they didn´t came as far down the "checklist" as during this countdown during the wet dress rehearsal, so maybe that is why they didn´t catch the #3 issue.
 

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I didn't know this (or had forgotten it), but it uses actual (used) SSMEs. Would have been a good idea if only the thing didn't end up so costly. We're talking engines that are decades old, and have been sitting around for mostly a decade after the Shuttles stopped flying. I sure hope they did their homework right on material aging etc. One of them literally flew on the Shuttle-Mir mission. I wouldn't be surprised if it's that one having the issues
 

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I didn't know this (or had forgotten it), but it uses actual (used) SSMEs. Would have been a good idea if only the thing didn't end up so costly. We're talking engines that are decades old, and have been sitting around for mostly a decade after the Shuttles stopped flying. I sure hope they did their homework right on material aging etc. One of them literally flew on the Shuttle-Mir mission. I wouldn't be surprised if it's that one having the issues

The thermal conditioning of the engines was also the cause for a number of launch aborts during the STS era. Its not unknown or unexpected, such things can happen.
 

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I didn't know this (or had forgotten it), but it uses actual (used) SSMEs. Would have been a good idea if only the thing didn't end up so costly. We're talking engines that are decades old, and have been sitting around for mostly a decade after the Shuttles stopped flying. I sure hope they did their homework right on material aging etc. One of them literally flew on the Shuttle-Mir mission. I wouldn't be surprised if it's that one having the issues
Each of the engines have been inspected multiple times and even acceptance test fired. Also, they were fired again during the Core Stage Green Run test campaign at Stennis Space Center last year with no issues.
 

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From what I heard, they didn´t came as far down the "checklist" as during this countdown during the wet dress rehearsal, so maybe that is why they didn´t catch the #3 issue.
They took it to T-0:39 during wet dress rehearsal, but it's not clear to me that they actually did all the items. It seems it was all they could do to just get fuel in the tanks.
 
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GLS

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So here is a diagram of the engine*, coloured in MS Paint, to illustrate the issue:
1661777894835.png
*) just the fuel side as the whole thing is too big for the forum

The LH2 comes into the engine at the top left thru the Low-Pressure Fuel TurboPump, and flows down the left side (thick dark blue line) into the High-Pressure Fuel TurboPump and thru the Main Fuel Valve, at the lower right corner, and then to the Main Combustion Chamber, Nozzle and ultimately into the Preburners.

During tanking, the MFV is closed and LH2 is allowed in the engine up until it to cool the pumps and ducts. To keep cooling these parts, a LH2 flow is maintained by opening the Fuel Bleed Valve, just upstream of the MFV, which "bleeds" LH2 from the engine back up to the LH2 manifold outside the engines (vertical thin dark blue line).
If the FBV opened, and there is a position sensor there and no mention of a valve position issue, then IMO they are not getting the flow because either the thick or the thin blue line is partially obstructed. It's also possible that the bleed line got accidentally bent while workers where inside the engine compartment since the last tanking, but I think that would not go unnoticed. Another possibility is the flow from the other 3 engines was so much that it reduced the flow from this engine, but I think that was put to bed when they closed the Prevalves in those engines, effectively stopping their bleed flow (they can't control the Bleed valves directly), and nothing changed in the affected engine.

So my bet is rollback and engine swap.
 
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