STS-126 working Display Processor issue – STS-125 de-stack preps

by Chris Bergin

Engineers are working a connection issue with an Integrated Display Processor on Endeavour, which is currently a constraint to moving into the S0007 Launch Countdown.  Meanwhile, Atlantis will be de-stacked from ET-127, before being rolled back to her Orbiter Processing Facility (OPF) next week.

Processing at Pad 39A is proceeding to plan for the November 14 launch date, though the “CRT2 MEDS 1553 bus error” – which was observed during power-up last Friday – will need to be resolved before next week’s launch countdown begins.

“On the vehicle processing side, the payload bay doors were closed for flight last week,” noted an “8th Floor” review of STS-126’s processing on L2. “On Friday, during vehicle power up, CRT2 MEDS 1553 bus error was annunciated by IDP2. Initial troubleshooting was inconclusive. Further engineering evaluation will be required.”

This highly technical issue relates to the Integrated Display Processor 2’s poor – or ratty – connection to its particular display with the MIL-STD-1553B databus. This could lead to the loss of the display during flight.

“New IPR to DPS (Data Processing System) during vehicle power up last Friday,” added processing information this week on L2. “The IPR was for CRT2 MEDS 1553 bus error annunciated by IDP2.

“This was no constraint to continued power up operations. The constraint is to S0007 (Launch Countdown).”

Apart from this new problem, processing has been relatively issue-free – as the complex ballet of pre-S0007 operations are carried out on the shuttle.

“S0044 Launch Countdown Phase Simulation was completed yesterday. Time Code Generator (TCG) countdown time test was successfully completed yesterday,” noted Tuesday processing information. “S1287 Aft closeouts for launch continue.”

“S0007.100 Launch countdown preparations began yesterday. S1005/1006 LOX/LH2 Dew point and conditioning checks are scheduled for today. S5009 Ordnance installation and connections are scheduled to begin tomorrow.”

Meanwhile, Atlantis will be de-mated from ET-127 – on what is currently a flexible schedule – now the STS-125 mission has been delayed until at least May, 2009. She will be rolled back – on her wheels (as opposed to on the Orbiter Transport System) – early next week.

ET-127 – which is currently undergoing repairs – will now be used by Discovery for February’s STS-119 mission to the International Space Station (ISS).

“The plan is to demate OV104/Atlantis from the STS-125 stack and use that stack to support STS-119/15A with OV103/Discovery,” added the 8th Floor overview on Monday. “Orbiter demate is targeted for later this week. The STS-119/15A mission is scheduled to launch NET February 12th.

“Call to stations for OV-104 Atlantis de-mate from the external tank (S0030) is currently scheduled for 1600hrs Friday 11/7/08. OV-104 will roll back to OPF Bay-1 on Sunday 11/9/08. The landing gear will be extended and the Orbiter will roll back on wheels. This will allow maintenance in Bay-1 to be completed by Saturday 11/8/08.”

However, Tuesday processing information points to the de-stack taking place next Monday, as engineers evaluate the most viable schedule of events for sending Atlantis back to her OPF.

“S0030 Orbiter/ET de-mate operations are scheduled as follows: Orbiter/ET de-mate pre-ops are scheduled to begin tomorrow and complete Friday. Orbiter Sling build-up is scheduled for Friday. Orbiter/ET de-mate is scheduled to begin on Monday (11/10).”

Engineers have started repairs on ET-127 – following three impacts by a steel rod that liberated from a weather protection sheet around the orbiter’s FRCS (Forward Reaction Control System), ahead of rollback from Pad 39A.

“LH2 Tank Foam Damage: Removed loose foam. Red dye and sand complete. Kaman readings In-Work,” added Tuesday processing information, with confirmation that no damage was observed on Atlantis herself.

“The Impact Analysis Team was requested to run an impact analysis of the rod to the RCC panels on the wing leading edge similar to a launch day potential ice impact analysis,” added a separate note.

“Based on the mass of the rod and the distance it would have fallen, no detectable damage is predicted. Surface defects would not be detectable by this analysis. Therefore, the RCC panels were visually inspected and no surface defects or damages were found.”

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.

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