SCRUB: STS-115: Launch Day - September 8

#60 by DaveS on 08 Sep, 2006 08:58
Chris, how about posting some of the ECO sensor trouble shooting charts on L2 here?
#61 by Svetoslav on 08 Sep, 2006 09:00
Theoretically, the shuttle may launch with this, but it's a little dangerous, because if there's a premature engine cutoff, this could lead to a disaster.
As for me, I als oappologise for being suspicious.
#62 by psloss on 08 Sep, 2006 09:01
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Svetoslav - 8/9/2006 4:47 AM

Theoretically, the shuttle may launch with this, but it's a little dangerous, because if there's a premature engine cutoff, this could lead to a disaster.
That's pure speculation without more details.
#63 by DaveS on 08 Sep, 2006 09:01
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Svetoslav - 8/9/2006 10:47 AM

Theoretically, the shuttle may launch with this, but it's a little dangerous, because if there's a premature engine cutoff, this could lead to a disaster.
It has failed "wet", not "dry" needed for a pre-mature MECO.
#64 by DaveS on 08 Sep, 2006 09:02
T-3 hours and holding for 3 hours.
#65 by neo on 08 Sep, 2006 09:09
Reminder please: did STS-114 and/or STS-121 involve an LCC waiver for specific ECO failure/s?
#66 by just-nick on 08 Sep, 2006 09:10
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DaveS - 8/9/2006 1:48 AM

Quote
Svetoslav - 8/9/2006 10:47 AM

Theoretically, the shuttle may launch with this, but it's a little dangerous, because if there's a premature engine cutoff, this could lead to a disaster.
It has failed "wet", not "dry" needed for a pre-mature MECO.

Actually, I think the whole "job" of the sensor is to trigger an early but controlled MECO if you run into premature depletion (STS-93 again, right?). The alternative -- which would happen if two sensors failed wet -- is that the tank drains out while the SSME's are running happily along. Result is sudden overspeed, failed turbines, and bits of hot metal flying apart.

So fail dry = chance of MECO at some odd, early point. Fail wet = chance of self-destructing SSME's if you burn too much fuel.
#67 by DaveS on 08 Sep, 2006 09:10
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neo - 8/9/2006 10:56 AM

Reminder please: did STS-114 and/or STS-121 involve an LCC waiver for specific ECO failure/s?
114: They had one ready, but never used it as all ECO sensors worked nominally throughout the July 26 countdown.
121: Not sure.
#68 by Chris Bergin on 08 Sep, 2006 09:10
Answering a few questions here.

No LCC waiver for this type of ECO fail.

Point Sensor Box is being troubleshooted.

Will be a scrub if no solution.
#69 by HKS on 08 Sep, 2006 09:11
For those on L2, I have bumped a thread from a PRCB regarding 3 of 4 ECO LCC
#70 by Chris Bergin on 08 Sep, 2006 09:17
Talk of a scrub.

All four LH2 ECO sensors indicating DRY right now as part of the normal switchout.

For the previous 50 minutes, LH2 ECO 3 is showing WET.

Tanking is proceeding as normal while the troubleshooting takes place.
#71 by psloss on 08 Sep, 2006 09:18
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just-nick - 8/9/2006 4:57 AM

Actually, I think the whole "job" of the sensor is to trigger an early but controlled MECO if you run into premature depletion (STS-93 again, right?). The alternative -- which would happen if two sensors failed wet -- is that the tank drains out while the SSME's are running happily along. Result is sudden overspeed, failed turbines, and bits of hot metal flying apart.

So fail dry = chance of MECO at some odd, early point. Fail wet = chance of self-destructing SSME's if you burn too much fuel.
The system is biased to the oxygen side, and I'm not sure the sensor data is used until some point after liftoff.

The issue with depletion is having all those moving parts running without fuel.
#72 by Chris Bergin on 08 Sep, 2006 09:22
Internal loop:

Talk on OIS 232 About ECO Sensor (-------)
They are seeing an ECO point box sensor funny. LH2 Sensor #3 failure. They said that Wayne Hale accepted for STS-114 a scenario where they would be NO GO today, but try the next time and if it repeats, they would be GO. The idea to is watch that the sensors go dry when they drain the tank. They said these sensors and boxes had gone through a full ATP.
#73 by psloss on 08 Sep, 2006 09:23
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Chris Bergin - 8/9/2006 5:04 AM

Talk of a scrub.

All four LH2 ECO sensors indicating DRY right now as part of the normal switchout.

For the previous 50 minutes, LH2 ECO 3 is showing WET.

Tanking is proceeding as normal while the troubleshooting takes place.
Not sure I follow the behavior of the problem reading...are you saying that the indication has changed back and forth from what's expected? (Sometimes WET when it should indicate DRY, but also sometimes DRY when it should indicate DRY?) That sounds different than the behavior from the first STS-114 launch attempt.
#74 by Chris Bergin on 08 Sep, 2006 09:26
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DaveS - 8/9/2006 9:45 AM

Chris, how about posting some of the ECO sensor trouble shooting charts on L2 here?

Dave, go for it. Take what you want off L2. You have my permission.
#75 by Chris Bergin on 08 Sep, 2006 09:26
Pressing on with filling ET (======)
Pressing on. Management will talk the LLCO sensor. Some might want to go with 3 of 4, but Wayne Hale only agreed to that after the 24 hour trouble shooting. More to come.
#76 by Chris Bergin on 08 Sep, 2006 09:27
A number of problems...

LH2 Circ Pump voltage low (----)
The primary voltage on PhA is 109 - one bit toggle (109 is the ICD lower limit), with PhB and PhC at 110. The potentiometer will be switched over. The secondary is good at 115, 117, 117 volts.
#77 by Shuttle Man on 08 Sep, 2006 09:30
They are sending a team out to the pad (during replenish) to take a look at whatever they can. Lots of problems being recorded.
#78 by psloss on 08 Sep, 2006 09:35
Sure looks like this news isn't going to break except places like this until live commentary at the bottom of the hour...still no report anywhere else that I can see...
#79 by rfoshaug on 08 Sep, 2006 09:36
I haven't seen anything on this on other spaceflight related internet sites. This just shows why nasaspaceflight.com is the best site for up-to-date info! Excellent work and a big thanks to Chris and his sources.

I was wondering - it seems that for this launch and the previous two launches, the ECO sensors have been the talking point of the launch day, and they've caused quite a few headaches for NASA. Has this always been the case through the Space Shuttle program, os is this a "new" issue, and if so - why? There was some talk about a bad batch of sensors, but if this is a sensor from that batch, I'd believe NASA would have known that a long time ago and been prepared for a possible ECO sensor failure.

I also think it could be wise if NASA would just continue with the countdown even if they decide to scrub, just to check if other sensors and systems need replacing before the next launch attempt.