STS-124: RSS retracted to reveal Discovery

by Chris Bergin

Shuttle Discovery continues to have no issues that are a constraint to launch, as she looks ahead to the opening STS-124 launch attempt on Saturday.

Several new IPRs (Interim Problem Reports) have been filed on Friday, though this is normal for S0007 (Launch Countdown) operations, as the vehicle is moved through L-1 preparations. The Rotating Service Structure (RSS) has now been retracted.

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The next key event is the tanking operations for External Tank (ET-128) on Saturday morning. So far, no issues are being reported with the vehicle that would delay either operation from proceeding as scheduled.

‘Orbiter and SRB PIC resistance tests are complete,’ noted the latest S0007 information on L2. ‘PRSD (Power Reactant Storage and Distributation) cryo load is complete, OMBUU (Orbiter Mid Body Umbilical Unit) is disconnected, and the flight doors are installed. Avionics checkout is complete

‘SSME (Space Shuttle Main Engine) final preparations and TSM (Tail Service Mast) securing activities are in work this morning. Comm activation is planned for 1500. RSS retraction is planned for 2030.’

The only IPR from Thursday – relating to the approach lights on Runway 15 at the Shuttle Landing Facility (SLF) – which held a constraint to launch when coming out of the T-9 minute hold, has been now been cleared.

‘Update to IPR taken by Integration. At the SLF, Rwy 15 approach lights are intermittent and not holding intensity,’ added L2 information. ‘Repairs are complete and lighting is back to normal operations following two transformers being changed out and the repair of a splice.’

Also cleared for flight was an issue relating to interference on an Orbiter Instrumentation Systems (OIS) channel, following a changeout of a faulty cable.

‘Update to IPR taken by Integration for an intermittent squeal on OIS Channel 232. Indyne indicated that the problem was in a faulty Range Random Switch that impeded a proper software load. Repair is complete following the cable change out and the software reload.’

Of the new issues reported by engineers working on the vehicle during this S0007 phase, all IPRs have been troubleshooted, or cleared as a ‘known/explained condition’ of the hardware.

‘New IPR: Ox fill valve microswitch out of adjustment position indicator . Preplan procedure was run and the valve were adjusted to proper tolerance. IPR to close as explained condition.

‘New IPR TSM drain valve out of adjustment. Preplan procedure was run and the valve were adjusted to proper tolerance. IPR to close as explained condition.

‘New IPR: Detected TSM vent valve position didn’t pickup closed indication as it should. Indicator was mechanically adjusted, and cycled multiple times. Valve position indicator now functions properly. Removed from the S0007 constraints list.

‘New IPR: Replenish Valve did not cycle on backup during pre-loading test cycles. Valve did operate correctly during testing on primary. It appears that the problem is on the pneumatic side, as the valve did show current when commanded.

‘Troubleshooting found a broken connector. It has been replaced and (related department) reports that the valve is working.’

As pre-empted in Thursday processing information, a communication issue with a unit on the WLE (Wing Leading Edge) instrumentation has received a ‘deferral’ – which means it will be worked on after Discovery arrives back home at the end of STS-124.

‘Additional communication attempts from the flight deck were attempted by sending a request to unit 1056 for diagnostics and to change its mode to ‘idle’ (instead of a full reset). No communication was established. (Paperwork) will be processed for deferral.’

Other tasks upcoming for overnight includes the filling of the pad sound suppression system water tank. Power up the master events controllers. Power up space shuttle main engine controllers and load with flight software – all due around 3am local.

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On the weather front, STS-124 has a great opportunity to launch on Saturday, with only a 20 percent chance of unacceptable weather at the time of launch.

‘Synoptic Discussion: A high pressure ridge is located north of Florida, and east-south-easterly flow is prevalent over Kennedy Space Center (KSC),’ noted the latest USAF weather report. Weather will be similar on launch day.

‘Isolated coastal showers may be in the area during the morning hours, but a sea breeze will develop in the afternoon, clearing the coast and causing showers to move inland. With this weather pattern, weather is favorable for launch, with only a slight concern for anvils returning toward the east coast from inland thunderstorms. Our primary concern for launch is anvils moving toward KSC from the northwest.

‘Sunday, a trough moves into North Florida causing more potential for thunderstorms northwest of KSC, and an increased chance for anvils to threaten the area. Monday, the trough progresses closer to the Central Florida area. The ridge shifts to the south of KSC, and the sea breeze convergence and associated showers and thunderstorm will be lingering near the east coast of Central Florida.

‘Due to the threat of showers and thunderstorms in the vicinity, the 48-hour delay probability of KSC weather prohibiting launch increased to 60 percent.’

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