JF Mezei wrote:
On 2021-01-16 17:55, Jeff Findley wrote:
Today's SLS Green Run test ended prematurely. It was supposed to fire
for something like 8 minutes to simulate a full duration burn on an
actual flight. It only got to something like a minute and 20 seconds
when it shutdown. Wane Hayle tweeted that he heard "MCF" (Major
Component Failure) called out.

I heard something like "DCT anomaly".

~50 seconds in: "MCF" callout (Major Component Failure)

A few seconds later: "Copy that, but we’re still running, we’ve still
got four good engines, right?"
"Yeah, copy that"

~67 seconds in: *Either* "TVC violation" or "TCC violation" is called
out.

A few seconds later: Engines are clearly in shutdown sequence.

So either "Thrust Vector Control" hardware failure or "Test Commit
Criteria" violation - which could be anything including "the engines
are shutting down for some reason".

I initially heard it as TVC since it happened JUST as they started
gimballing the engines which would use the TVC hardware.. but when
some claimed it was TCC I listened again and it could be either, I
don't think it's possible to distinguish those two in that
circumstance.


Press conference at 19:30 Saturday (Eastern).

It mentioned some FID (Failure ID) callouts preceding the MCF for
Engine 4 and that it was the "engine controller" that commanded the
shutdown. SPN don't mention the TVC/TCC callout which hints it might
have been TCC, not TVC (but not proof).

They also say they MAY decided that this is sufficient testing.

Wasn't it this test some were trying to skip in an effort to reduce
delays? I'd say it's proven exactly why it was necessary.

Either way remember that they said the same about the need to retest
the Boeing Starliner on it's "immediately afterwards" press conferance
so I wouldn't put too much stock in that.

Apparently a re-test would take at least a month to prepare, not
counting any changes or fixes but those might be able to be done in
parallel.

They also mentioned a flash at the thermal blankets near engine 4 just
as they initiated the engine gimballing around the time the shutdown
started, and that the only damage they've found so far is on the
thermal blanket there.

As SPN notes they have a number of other engines if they decide to
swap out engine 4 (and send it back to refurbishing) or they might
decide it's repairable.

It's much too early for anything really substantive.

https://spaceflightnow.com/2021/01/1...t-test-firing/
https://old.reddit.com/r/SpaceXLoung...ch_system_hot/