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#140
by
edkyle99
on 06 Sep, 2006 15:05
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Chris Bergin - 6/9/2006 9:02 AM
Update:
OPO Telecon with vendors (mdwright)
- A spare pump or qual pump will be cut up to get a better understanding of the pump design. In particular, the interest is in whether or not the phase windings are isolated from one another.
- Several scenarios for a short
- Thermal equilibrium is reached in about 26-30 minutes - Worst case next failure could result in motor controller shutdown during ascent
Right. When you loose a phase on a three-phase motor, or have an internal short on one of the winding sets of a three-phase motor, the motor can overheat, which leads to progressive insulation failure, which causes more short circuits. This pump motor might be running now with an internal short that is not bad enough to trip a circuit breaker, but it probably won't run for very long this way before the failure progresses.
- Ed Kyle
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#141
by
Chris Bergin
on 06 Sep, 2006 15:10
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Chris Bergin - 6/9/2006 3:50 PM
They've restarted the fuel cell. Waiting for results (will be a document - which have to go on L2 - as per source instructions).
Second graph now on L2. Certainly has different graph appearance. I'll try and get permission to post the two different graphs here.
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#142
by
Chris Bergin
on 06 Sep, 2006 15:11
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Outline notes from sources:
09/06/06 07:29:01 CET FC/PRSD STS-115 Coolant Pump Anomaly (-----)
STS-115 Fuel Cell Startup
Flow-thru and pulse purges were nominal. FC 1 activation was at 249:01:23:28 GMT (pumps on). At 249:01:34:55 GMT the H2 pump motor status experienced a step increase from 0.48 to 0.64 vdc. This corresponded to a spike in the AC 1 phase A current from 4.32 to 5.20 amps (0.10 second duration), followed by a decrease to 3.76 amp. Phase B current increased 0.2 amps and phase C current increased 0.10 amp. These values remained relatively stable for the remainder of the fuel cell startup. The heatup continued nominally, achieving the ready-for-load status in 25 m 21 s. Due to a concern that the coolant pump may be operating on only two phases, the connection of fuel cell 1 to main bus A was delayed. The H2 pump motor status measurement indicated that the H2 pump was still operating on all three phases. The decision was made to connect fuel cell 1 to the bus and continue with the startup for fuel cells 2 and 3. The startup for these two fuel cells was nominal.
A troubleshooting plan was discussed to determine a way to see if the coolant pump was indeed operating on only AC1 phases B and C. One option was to open either the phase B or phase C circuit breaker. The fuel cell coolant pump can operate on two phases but not on only one. If the coolant pump delta pressure indication would go off then that would verify that phase A was not feeding the coolant pump. The other option was to shutdown the fuel cell and observe the drop in the AC1 phase currents. The decision was made to shutdown the fuel cell rather than intentionally stopping a pump while the fuel cell was running.
Fuel cell 1 was removed from the bus at 249:05:42:18 GMT. The stop command was issued at 249:05:45:21 GMT (pumps off). Phases B and C decreased about one amp while phase A decreased only 0.3 amps, verifying that phase A was not powering the coolant pump. The fuel cell start command (pumps on) was issued at 249:05:47:56 GMT. The AC1 phase currents all returned to the values that they were prior to the shutdown. The AC1 startup transient appeared nominal, and the measurement returned to a value of 0.64 vdc. The FC 1 water conductivity sensor self-test circuit energized at startup, verifying that AC 1 phase A was active. Fuel cell 1 was reconnected to main bus A at 249:05:50:09 GMT. All fuel cell parameters were nominal. In order to proceed with the countdown, the fuel cell high load calibration was performed, beginning at 249:06:46:00 GMT, and lasting for about 48 minutes. Again, all fuel cell parameters were nominal. The fuel cell loads were brought back down to typical prelaunch steady state values.
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#143
by
mkirk
on 06 Sep, 2006 15:12
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Chris Bergin - 6/9/2006 9:50 AM
They've restarted the fuel cell. Waiting for results (will be a document - which have to go on L2 - as per source instructions).
deleted to read Chris' post.
Mark Kirkman
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#144
by
gordo
on 06 Sep, 2006 15:13
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----- called with a question from Wayne regarding any other equipment that has not been checked out/fired up in several years. Fuel Cell 1 had not been fully activated in 3 years..
Pretty shocking state of affairs that kit has not been fully run up and checked out. Big Management oversight there IMO.
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#145
by
rdale
on 06 Sep, 2006 15:15
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astrobrian - 6/9/2006 10:45 AM
From the discussion here it is leaning towards replacement more than a fly as is. In that case I would think RSS rollback would be the next step would it not?
Exactly. But since it's still in the discussion stage, and the MMT doesn't meet until 1pm, would it make sense to roll back the RSS tomorrow and completely wipe out this launch window before reaching a verdict?
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#146
by
Chris Bergin
on 06 Sep, 2006 15:16
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Equipment checkouts continued (------)
Boeing Console is trying to gather information on the subsystems. Email was sent and messages left for (deleted) to try to get the GFE story.
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#147
by
just-nick
on 06 Sep, 2006 15:17
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gordo - 6/9/2006 8:00 AM
----- called with a question from Wayne regarding any other equipment that has not been checked out/fired up in several years. Fuel Cell 1 had not been fully activated in 3 years..
Pretty shocking state of affairs that kit has not been fully run up and checked out. Big Management oversight there IMO.
Second that -- it seems reasonable to do a dry run (well, perhaps a wet run) and get power to/from all the systems for a vehicle that hasn't flow in years. Sometime before reaching the "if we don't fly today we don't fly for months" point that shuttles always seem to be at. I'm surprised that such power up activities aren't part of launch rehersals, actually.
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#148
by
edkyle99
on 06 Sep, 2006 15:24
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Chris Bergin - 6/9/2006 9:58 AM
Outline notes from sources:
09/06/06 07:29:01 CET FC/PRSD STS-115 Coolant Pump Anomaly (--------)
STS-115 Fuel Cell Startup
Flow-thru and pulse purges were nominal. FC 1 activation was at 249:01:23:28 GMT (pumps on). At 249:01:34:55 GMT the H2 pump motor status experienced a step increase from 0.48 to 0.64 vdc. This corresponded to a spike in the AC 1 phase A current from 4.32 to 5.20 amps (0.10 second duration), followed by a decrease to 3.76 amp. Phase B current increased 0.2 amps and phase C current increased 0.10 amp. These values remained relatively stable for the remainder of the fuel cell startup. The heatup continued nominally, achieving the ready-for-load status in 25 m 21 s. Due to a concern that the coolant pump may be operating on only two phases, the connection of fuel cell 1 to main bus A was delayed. The H2 pump motor status measurement indicated that the H2 pump was still operating on all three phases. The decision was made to connect fuel cell 1 to the bus and continue with the startup for fuel cells 2 and 3. The startup for these two fuel cells was nominal.
A troubleshooting plan was discussed to determine a way to see if the coolant pump was indeed operating on only AC1 phases B and C. One option was to open either the phase B or phase C circuit breaker. The fuel cell coolant pump can operate on two phases but not on only one. If the coolant pump delta pressure indication would go off then that would verify that phase A was not feeding the coolant pump. The other option was to shutdown the fuel cell and observe the drop in the AC1 phase currents. The decision was made to shutdown the fuel cell rather than intentionally stopping a pump while the fuel cell was running.
Fuel cell 1 was removed from the bus at 249:05:42:18 GMT. The stop command was issued at 249:05:45:21 GMT (pumps off). Phases B and C decreased about one amp while phase A decreased only 0.3 amps, verifying that phase A was not powering the coolant pump. The fuel cell start command (pumps on) was issued at 249:05:47:56 GMT. The AC1 phase currents all returned to the values that they were prior to the shutdown. The AC1 startup transient appeared nominal, and the measurement returned to a value of 0.64 vdc. The FC 1 water conductivity sensor self-test circuit energized at startup, verifying that AC 1 phase A was active. Fuel cell 1 was reconnected to main bus A at 249:05:50:09 GMT. All fuel cell parameters were nominal. In order to proceed with the countdown, the fuel cell high load calibration was performed, beginning at 249:06:46:00 GMT, and lasting for about 48 minutes. Again, all fuel cell parameters were nominal. The fuel cell loads were brought back down to typical prelaunch steady state values.
Puzzling that the thing started back up normally. How could the pump motor have stopped drawing current on one phase after the first startup, but then started drawing current normally again when restarted? Is pump motor power fed through a motor controller or by dedicated circuit breakers, etc.? Something must have tripped or opened up the Phase A circuit feeding just the pump motor during the initial startup. It is the "something" that is obviously of concern.
- Ed Kyle
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#149
by
astrobrian
on 06 Sep, 2006 15:25
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I always thought that was what the TCDT did. (a dry run)
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#150
by
Svetoslav
on 06 Sep, 2006 15:27
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So, is Cell 1 working as expected?
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#151
by
DaveS
on 06 Sep, 2006 15:30
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astrobrian - 6/9/2006 5:12 PM
I always thought that was what the TCDT did. (a dry run)
Nope. The RSS is in place around the orbiter during the TCDT.
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#152
by
spaceshuttle
on 06 Sep, 2006 15:35
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so is the launch postponed for tomorrow...
let me rephrase: is the next launch date known, or do we have to wait for a briefing?
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#153
by
edkyle99
on 06 Sep, 2006 15:36
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Svetoslav - 6/9/2006 10:14 AM
So, is Cell 1 working as expected?
It looks like Fuel Cell 1 restarted normally, but they will have to completely understand why the fuel cell pump motor lost a phase during the initial startup - and have to be able to prove to themselves that it won't recur. I don't know how you could "prove" that a transient, which is often a sign that a bigger failure is pending, won't recur.
- Ed Kyle
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#154
by
rdale
on 06 Sep, 2006 15:38
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"so is the launch postponed for tomorrow..."
If you read the posts in this very thread you will see that a fuel cell problem has resulted in a 24-hr delay while they troubleshoot.
"is the next launch date known"
For now, it's tomorrow.
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#155
by
Svetoslav
on 06 Sep, 2006 15:39
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Sometimes NASA amazes me with the decisions! Why did they have to scrap Atlantis knowing that Discovery is older than Atlantis? They should scrap Discovery, and keep Atlantis alive
As for the fuel cell, if it's performing OK, I see no reason to have more delays.
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#156
by
astrobrian
on 06 Sep, 2006 15:40
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For now tomorrow, for sure probably during the presser here in a couple hours
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#157
by
DaveS
on 06 Sep, 2006 15:41
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spaceshuttle - 6/9/2006 5:22 PM
so is the launch postponed for tomorrow...
let me rephrase: is the next launch date known, or do we have to wait for a briefing?
Not known at this time. MMT still have to meet at 1 pm EDT and make their decision.
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#158
by
gordo
on 06 Sep, 2006 15:43
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Svetoslav - 6/9/2006 4:26 PM
As for the fuel cell, if it's performing OK, I see no reason to have more delays.
It was a lack of imagination that caused the Columbia accident, you have to imagine everything that could go wrong, before you say its working. At the moments its nominal but it wasn't last night and they don't fully know why.
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#159
by
psloss
on 06 Sep, 2006 15:43
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Svetoslav - 6/9/2006 11:26 AM
Sometimes NASA amazes me with the decisions! Why did they have to scrap Atlantis knowing that Discovery is older than Atlantis? They should scrap Discovery, and keep Atlantis alive
As for the fuel cell, if it's performing OK, I see no reason to have more delays.
Well apparently you don't understand WHY Atlantis is going to be retired after five more flights.
As for the fuel cell, how do you know it's working OK?
