Pre-launch propellant servicing – known as S0024 Operations – has been halted, as engineers check into an issue relating to Discovery’s GPCs (General Purpose Computers).
Meanwhile, International Space Station (ISS) managers are currently “go” for Discovery’s arrival next month during STS-124, pending assurances that the on-going Soyuz investigation results in confirmation of “a solid rescue vehicle for the crew.
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The GPCs ‘split’ 2-1-1 this morning, with a MDM (Multiplexer/Demultiplexer) card (FA2) to be changed out – hopefully correcting the issue. Engineers are optimistic the issue does not relate to a data bus problem – which would hold the potential of a rollback.
As the SSP (Space Shuttle Program) Flight Readiness Review (FRR) continues today and tomorrow, engineers have been out at the pad carrying out S0024 operations.
‘Pre-launch propellant servicing picked up with call to stations at 23:00 (local) Sunday night and continues through Wednesday,’ noted Tuesday processing information.
However, later on Tuesday morning’s shift, engineers observed the GPC ‘split’, occurring first with GPC 4 and then GPC 2 – which is an off-nominal condition for the orbiter.
Should the problem be pinpointed to the faulty card, or even a GPC, both can be swapped out at the pad. However, if the issue is with the data bus, then the stack may have to be rolled back for corrective action.
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As of Tuesday afternoon, engineers believe the problem is specific to MDM FA2, as opposed to the data bus, with R&R and re-testing to confirm their findings.
‘S0024 stopped. Faulty MDM FA2 to be R&Rd,’ noted a processing flash on L2. However, the report already sounded optimistic on the expected conclusion to troubleshooting, adding, ‘will not impact launch.’
Late on Tuesday, information noted the forward plan of removing and replacing the MDM, along with re-testing, will take two days.
Wednesday morning: The decision on carrying out the R&R process required approval from the noon PRCB (Program Requirements Control Board) meeting, which has now been granted.
Meanwhile, SRB (Solid Rocket Booster) Hydraulic Power Unit (HPU) hydrazine loading has been completed out at Launch Pad 39A, with OMS (Orbital Manoeuvring System)/RCS (Reaction Control System) oxidizer propellant loading, FRCS (Forward Reaction Control System) oxidizer system purges and QD (Quick Disconnect) leak checks also completed.
‘OMS/RCS fuel loading is scheduled to pick up first shift today,’ noted Tuesday processing information. S1287, Orbiter aft closeouts are scheduled to begin on Wednesday.’
ISS Preparations for STS-124:
With the launch just over two weeks away, teams on the ground are finalizing their preparations to support the mission which will see the installation of the JEM/KIBO laboratory for the Japanese Space Agency. This includes preparation work on the International Space Station (ISS), ahead of Discovery’s arrival next month.
‘STS-123/1J preparation: The ground team and Expedition crew is working hard to get prepared for the 1J/STS-124 mission,’ added acquired information.
‘This includes prepack for return items, Robotics checkouts and moving the Mobile Transporter (MT) to the 1J position (scheduled for May 12th), checking out the Common Berthing Mechanism (CBM) that will be used for KIBO attach, conferences between the 1J crew and Exp 17 crew, etc. All is going well so far.’
‘1J/STS-124 SORR: The Station Ops Readiness Review was held on May 6th. As you might imagine, the Japanese contingent was both very proud of the outstanding efforts of their design, integration, and ops teams to be ready for flight, and very excited to finally be at the point of launch.
“As you all know, we are starting to draw near completion of the key elements of ISS assembly after this mission. The only major elements remaining are the JEM/KIBO external porch facility, the S6 truss and solar arrays to be flown on 15A, possibly Node 3 as a habitation module, and a number of flights to preposition spares for the post shuttle retirement period.”
Interestingly, the recent issue with Soyuz TMA-11’s ballistic re-entry – the second such re-entry in a row for the Russian vehicle – is continuing to cause a level of concern for NASA’s plans.
It appears that NASA has to be satisfied with level of progress made at the on-going investigation for the purpose of being confident they have a back-up rescue plan in the highly unlikely event of an emergency evacuation on the station, combined with a serious problem for Discovery – to the point she was unable to carry out the evacuation.
“One of the major topics of discussion revolved around the last two Soyuz entry profiles/ballistic entries,” noted information created on Monday. “We are working hard with our Russian colleagues to ensure that we have a solid rescue vehicle for the crew.
“After closing out some open actions and paper, and pending resolution of the Soyuz investigation, all members of the board recommended GO for launch.”