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#80
by
mkirk
on 06 Sep, 2006 11:20
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Here is a detailed diagram that shows where the Fuel Cells are located.
http://www.spaceflight.nasa.gov/shuttle/reference/sodb/2-9cl.pdfI have also attached another diagram of the fuel cell location.
Also the coolant pump is essential for the operation of the fuel cell, whithout it the cell will overheat in a matter of minutes when under normal load. So if the problem is with the pump - which would be indicative of the anomalous currents - then you have to changeout the fuel cell.
To answer someone else's question, you must have three good cells to launch!!!!! If a fuel cell fails while in orbit than you are MDF (minimum duration flight) and have to land on flight day 5 or 6.
Mark Kirkman
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#81
by
Jim
on 06 Sep, 2006 11:38
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Svetoslav - 6/9/2006 6:28 AM
I think that flying as-is good. The fuel cell is not out completely as we have phase B and C. Neither A is completely out. Atlantis could launch even with two cells if that one fails completely.
The phases have nothing to do with the power coming out of the fuel cell (not the same phases as Apollo 13, those were buses). Anyways, rules are no launch unless 3 fuel cells are working
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#82
by
Chris Bergin
on 06 Sep, 2006 11:41
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0730 CDT (one hour's time) Fault tree review with OPO
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#83
by
Jim
on 06 Sep, 2006 11:43
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Wubbo - 6/9/2006 5:38 AM
Does anyone have any pointers to background docs, or information on how these multiple phases are used and how a flight could happen with one phase unavailable?
Apologies if this is a dumb question, or the wrong place to ask. I've just recently joined the NSF site and am still trying to 'grok' it all.
GJ
The phases are not same as the buses that the fuel cells are tied to. The many of the electrical motors on the Orbiter run on 3 phase AC power. There are inverters tie to the fuel cells to provide 3 phase 400 Hz AC power through out the orbiter. The motor in the coolant pump is missing a phase, which indicates probably an open circuit
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#84
by
mkirk
on 06 Sep, 2006 11:45
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A word about the currents:
The coolant pump is a motor and requires 3 phases of AC to work properly (although 2 phases may or may not work in some cases). The higher currents on that phase (A of AC1) may indicate that the pump is the problem. They will likley take the pump off line and see if the indications on AC1 change...this will help narrow down the origin of the problem.
I am only guessing but I think the pump is the problem and that will require a changeout of the fuel cell.
Mark Kirkman
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#85
by
Jonesy STS
on 06 Sep, 2006 11:52
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Thanks for all the info Mark etc. Best on the net.
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#86
by
gordo
on 06 Sep, 2006 11:58
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In Laymans terms; think of each fuel cell as 3 fuel cells in one. The problem here lies in 1/9th of the system, but certain equipment needs each of the 3 different phases to run correctly.
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#87
by
joncz
on 06 Sep, 2006 12:01
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From:
http://www-pao.ksc.nasa.gov/kscpao/status/stsstat/1995/aug/8-31-95s.htmSTS-69 SCRUB ANNOUNCEMENT
August 31, 1995
5:30 a.m.
Mission managers scrubbed today's scheduled launch of Space Shuttle
Endeavour and mission STS-69 due to the failure of one of the orbiter's
three fuel cells. The scrub was called at about 3:30 a.m., prior to
commencing tanking operations, during normal fuel cell activation.
Fuel cells provide electricity to the orbiter while in space. Mission
rules state that all three fuel cells must be up and operational prior
to launch. Managers have indicated the fuel cell will be removed and
replaced, effectively postponing the launch about a week.
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#88
by
Gerald Richling
on 06 Sep, 2006 12:06
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Hello! Murphy's Law is now strictly enforced! It is very likely that Atlantis will be rolled back to VAB, demated and swap out the fuel cell. If NASA keeps daylight only launch restriction in place, the launch of STS-115 will not occur until February 19, 2007 when next extended daylight launch opportunies opens up. If NASA relaxes this daylight restriction, permitting night launches, Lauch will likely occur perhaps in mid October, 2006. Frustrating, isn't it?
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#89
by
Chris Bergin
on 06 Sep, 2006 12:15
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Gerald Richling - 6/9/2006 12:53 PM
If NASA relaxes this daylight restriction, permitting night launches, Lauch will likely occur perhaps in mid October, 2006. Frustrating, isn't it?
If NASA relaxes that restriction, there's an opportunity on September 24 (start of window). We published the document on L2 and there's a specific slide published on here showing this.
Most of your post was inaccurate.
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#90
by
kneecaps
on 06 Sep, 2006 12:17
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I seems to me that the cause of concern is if the coolant pump on FC1 is good or not. This does not have anything directly to do with power coming from the fuel cell as Jim says...But and its a big but....if the coolant pump fails then you have no fuel cell.
The question will be, are the anomalous currents on Phase A of AC1 indicative of a critical problem with the coolant pump. I think we may find out soon.
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#91
by
mkirk
on 06 Sep, 2006 12:20
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gordo - 6/9/2006 6:45 AM
In Laymans terms; think of each fuel cell as 3 fuel cells in one. The problem here lies in 1/9th of the system, but certain equipment needs each of the 3 different phases to run correctly.
I think you are confusing substacks with 3 phase AC power.
Motorized devices on the orbiter such as pumps, fans, drive units for the vent doors, payload bay doors, ET doors etc...require multiphase operation from the AC busses. In some cases you can loose a single phase and still retain operation of the particular motor - this is certainly not ideal.
AC power comes from the inverters which take the DC power produced by the fuel cells and distributed through the Main Busses and coverts it to AC. Main Bus A powers AC1, Main B AC2, and Main C AC3. Each AC bus is powered by 3 inverters (i.e. 3 phases).
Mark Kirkman
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#92
by
Jim
on 06 Sep, 2006 12:22
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Edit:
Mark beat me to the answer and his was better
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#93
by
mkirk
on 06 Sep, 2006 12:24
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kneecaps - 6/9/2006 7:04 AM
I seems to me that the cause of concern is if the coolant pump on FC1 is good or not. This does not have anything directly to do with power coming from the fuel cell as Jim says...But and its a big but....if the coolant pump fails then you have no fuel cell.
The question will be, are the anomalous currents on Phase A of AC1 indicative of a critical problem with the coolant pump. I think we may find out soon.
More specifically the question is what is causing the short...the suspect is the coolant pump on that fuel cell. The fault tree analysis that will be conducted in about 20 minutes will look at all of the possible causes of the "off nominal readings" on AC1 - all 3 phases showed off nominal readings starting with the spike in phase A.
The MMT meets at 1 eastern to review the forward plan.
I personally think we are screwed when it comes to launching during this 3 day period!!
Mark Kirkman
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#94
by
joncz
on 06 Sep, 2006 12:29
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Gerald Richling - 6/9/2006 7:53 AM
...
It is very likely that Atlantis will be rolled back to VAB, demated and swap out the fuel cell.
My post immediately before yours suggested the R&R can be and has been done at the pad (the trusses may have to be removed, however). And given the potential for a Sep 24th window with relaxed lighting requirements I would expect that, barring weather forcing a rollback, is what they would plan to do.
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#95
by
Chris Bergin
on 06 Sep, 2006 12:50
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#96
by
nathan.moeller
on 06 Sep, 2006 12:55
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Shame. Oh well better safe than sorry. Don't want another STS-83 that's for sure. Any other word from the engineering community on what might be done to fix the problem?
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#97
by
rdale
on 06 Sep, 2006 13:03
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Nathan - if you scroll back you'll see a MMT meeting is planned for noon, after that we'll know what they will do to fix the problem. If someone does find additional info, you can rest assured that it will be posted here.
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#98
by
rosbif73
on 06 Sep, 2006 13:03
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If any heads roll due to this being related to the lightning strike, the vultures are waiting...
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#99
by
DaveS
on 06 Sep, 2006 13:10
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rdale - 6/9/2006 2:50 PM
Nathan - if you scroll back you'll see a MMT meeting is planned for noon,
Actually it's noon CDT, 1 pm EDT.
