STS-133: PRCB baseline outlines processing and mission for Discovery

by Chris Gebhardt

As pre-launch processing continues for Discovery’s STS-131 mission, pre-flight planning continues for what is – at this time – the final manifested flight of the Shuttle Program, STS-133. Discovery will be flying with ELC-4 (ExPRESS Logistics Carrier -4) and the PMM (Permanent Multi-purpose Module), as outlined in the latest Program Requirements Control Board (PRCB) mission baseline overview. 

Mission-Specific Updates:

In all, STS-133 is baselined as a 8+1+2 day mission with 0 (zero) primary EVAs (spacewalks), one (1) ISS-based contingency EVA, and two (2) Shuttle-based contingency EVAs (in case the ET umbilical doors fail to close after ET/Orbiter separation and/or in case the payload bay doors cannot be closed by computer command and require manual closure at the end of the mission). It is also highly likely the mission will be reduced to four crew members.

For STS-133, Discovery will fly with 4 Cryo tank sets and 5 GN2 (gaseous nitrogen) tanks – as noted in the 92 page baseline presentation, available to download on L2.

In terms of STS-133 turnaround and preparation efforts, Discovery is scheduled to land at the Kennedy Space Center at the completion of the STS-131 mission on the night of April 15.

Should Discovery’s 131 mission actually land at the Kennedy Space Center, the vehicle will be towed off the SLF (Shuttle Landing Facility) about 4-hours after landing and into OPF-3 (Orbiter Processing Facility Bay 3) for immediate post-flight deservicing ahead of flow turnaround operations for STS-133.

Should landing occur at the contingency landing site in California, Discovery will be towed off the runway to the Mate/Demate Device (MDD) where post-flight deservicing and ferry flight preparations would occur.

After approximately one week of servicing and preparations, Discovery (with aerodynamic tailcone assembly attached) will be hoisted atop one of two Shuttle Carrier Aircrafts (SCAs) and ferried back to the Kennedy Space Center for flow turnaround operations.

Under nominal conditions (i.e. a KSC landing for STS-131 and no change to the STS-133 baselined launch date), Discovery will spend 104 days inside her OPF undergoing final inspections, modifications, and calibrations for the STS-133 flight.

SRB (Solid Rocket Booster) stacking will then begin on June 9 on MLP-2 after the scheduled launch of Atlantis/STS-132 from that MLP in mid-May.

In all, SRB stacking is baselined for 23-days with 16-days worth of contingency. This rather large contingency margin could go some way toward alleviating potential schedule concerns with any slip to the STS-132 launch date as NASA managers are currently evaluating the potential need to slip the 132 launch date into June due to possible delays to that mission’s LON flight: STS-134 with AMS.

In addition to SRB stacking operations, Discovery’s External Tank (ET-138) will arrive On Dock at the Kennedy Space Center on July 5 ahead of a July 20 or 22 mating to the SRB stack.

Following the completion of SRB closeout and ET/SRB mating operations, Discovery will rollover to the VAB for mating with her ET/SRB stack on August 9 for her 39th and final flight.

After a week of mating and interface checkouts, Discovery and the STS-133 stack will rollout to Launch Pad 39A on August 16 for 22+9-contingency+1-holiday days worth of pad processing.

If all goes to plan, the STS-133/ULF-6 (Utilization and Logistics Flight 6) flight will liftoff on the 134th and final Space Shuttle mission on September 16, 2010 at ~11:57a.m. EDT, with a nominal End of Mission landing on September 24.

According to the LSFR document, Discovery’s End of Mission (EOM) landing is planned for the Kennedy Space Center, FL – apparently confirming that, as for now, Discovery’s landing will not take place in California with a follow-up cross-country farewell tour of various NASA centers during a ferry flight back to KSC.

Discovery Vehicle Modifications for STS-131:

For STS-133, several modifications will be made to Discovery as part of a weight savings and increased safety effort to allow for maximum payload upmass on the ELC-4 and PMM payloads.

Among these modifications will be the removal of a 5th PRSD (Power Reactant Storage Distribution) tank set, the completion of all “red” OMDP (Orbiter Maintenance Down Period) requirements, and five modifications.

The first of these modifications pertains to the re-flight of the Boundary Layer Transition (BLT) DTO (Detail/Dedicated Test Objective).

“Re-flight of protuberance tile and associated thermocouple instrumentation” from STS-131 will be undertaken on STS-133.

There is the potential to increase the height of the protuberance instead of simply re-flying the same protuberance, but a frim decision has yet to be made.

“Potential for protuberance height increase from the 0.35″ height being flown on STS-131 – pending evaluation and analysis of STS-131 performance flight data.”

The second modification mentioned in the LSFR document for STS-133 also relates to the Boundary Layer Transition DTO, this time in terms of a catalytic coating applied to the surface of one downstream DTO tile.

“Re-flight of catalytic coating applied to one tile in BLT DTO region of influence would require shelf life extension of existing lot of catalytic coating material or production of new lot of catalytic coating (age life limited) and reapplication to selected tile,” notes the LSFR presentation.

Additional modifications for Discovery include the completion of Wing Leading Edge Spar “Sneak Flow” protection.

Designed to “limit allowable plume flow to 50 percent across the flow restrictor,” the Wing Leading Edge (WLE) Spar “Sneak Flow” Protection modification would increase the overall WLE panel damage tolerance by “adding a flow restrictor.”

Currently, all WLE panels on Discovery, less Left Hand panels 2-4, have been modified to date.

Completion of the modification would allow Left Hand WLE panels 2-4 to fly with the same damage resistance as the other WLE panels on Discovery; however, completion of the modification would take up valuable time in Discovery’s already short OPF flow toward STS-133 and would thus have to be balanced accordingly to prevent the OPF turnaround flow from impacting the mating and pad flow cycle as currently planned.

Similarly, the fourth modification also deals with the WLE panels, specifically Left Hand panels 2-4. For this modification, the lower Wing Leading Edge Carrier Panel Horse Collar Gap Filler was redesigned to an “enhanced design with additional sleeving.”

To date, this modification has already been carried out on all WLE panels except Left Hand panels 2-4. Completion of the mod would bring Left Hand WLE panels 2-4 into alignment with the remaining 41 WLE panels.

The final, baselined modification for Discovery relates to a connector saver redesign for the Left OMS Pod and Ku Band antenna.

“Connector Saver mod provides proper interfacial seal and wavy washer engagement retention force to reduce risk of inadvertent demate during use,” states the LSFR presentation.

This modification has already been carried out on other systems onboard Discovery, with only the Left Hand OMS Pod and Ku Band antenna remaining.

In addition to these baselined mods, one potential modification also exists for Discovery. This modification pertains to the Main Engine Ignition (MEI) Acoustic sensors.

“MEI Acoustic Sensor Filter Mod. Completion of MADS low pass in-line filter installation for MEI acoustic sensors (microphones) in the Left Hand OMS pod stinger,” notes the LSFR document.

This modification consists of “re-routing existing coax cable from the acoustic sensor to the new in-line filter mounted with a saddle clamp, and routing a new cable from the filter to the micro-WIS box.” The existing coax route is to the filter, not the micro-WIS.

In all, the LSFR notes that portions of this modification could be complete prior to STS-131. As such, all work regarding this modification that will be performed during the flow toward STS-133 will be documented at the Delta LSFR.

L2 members : Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4500 gbs in size

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