STS-124 gains extra margin for May 31 launch target

by Chris Bergin

The orbiter fleet remains in great shape ahead of STS-124 and STS-125, with only the External Tanks continuing to be the critical item in the schedule.

Fine work by engineers in the Vehicle Assembly Building (VAB) has protected STS-124’s schedule through ET/SRB (Solid Rocket Booster) mating over the weekend, so much so that Discovery may be able to rollover and rollout a day ahead of schedule.

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**LIVE updates on Discovery STS-124 Processing**

STS-124 Latest:

Discovery herself is ready to roll out of the ‘barn’ – leading to some her engineering team finding themselves moved into the adjacent Orbiter Processing Facilities (OPFs), in order to aid processing work on Atlantis and Endeavour.

‘In OPF, have taken quite a bit of the resources off to work OV-104 (Atlantis) and OV-105 (Endeavour),’ noted the latest Integrated Flow Status report. ‘On TPS (Thermal Protection System), have no cavities. Total cavity count on this flow was 217. There still is TPS work, but no tile bonds left to do.

‘Schedule is to do weight and C.G. (Center of Gravity) on April 18. Get the OTS (Orbiter Transport System) in on April 21 and be ready to roll on April 28. If this has to be pulled in, there is available margin to do that.’

Other work schedule for this week includes MLG (Main Landing Gear)/NLG (Nose Landing Gear) resistance measurements on Wednesday. Final tire pressurization for flight on Thursday, and the disconnecting of the T-0 umbilicals, also on Thursday.

Tracking April 28 as the rollover date places rollout to Pad 39A one week later – and right on track to make the May 31 launch date. However, there is a possibility that the current flow allows for an additional day to be gained for the pad flow, thanks mainly to the issue free mating operations over the weekend.

‘The critical path is the ET. This weekend got the ET mate complete; gets us a little ahead of schedule. If we do stay on this path, will try to get the orbiter over there early and get out of the VAB early. That will get us another day at the pad.’

Another engineering effort is also heading towards completion – this time with the concrete slope at Pad 39A, which had suffered erosion damage.

As noted in a previous article, damage to the concrete was spotted after the launch of Endeavour on STS-123. Initially it was believed to have been caused by the new water deluge system, but that has since been cleared as the cause.

‘Had some erosion underneath the pad slope, underneath the concrete. That repair work took place this weekend. No issues with completing this before rollout,’ confirmed the latest Shuttle Stand-up/Integration report.


Atlantis remains in the midst of processing for the final servicing mission to the Hubble Space Telescope, which is classed as an October 6 NET (No Earlier Than) launch target as a best case scenario – based on the projected delivery dates of ET-127 and ET-129 – the latter required for the LON-400 (Launch On Need) rescue mission via Endeavour.

Work is concentrated on repairing her TPS, post flight from STS-122, and the successful installation of the replacement radiator flex hose – after the previous hose flexed into an Omega shaped bend during payload bay door closure both pre-launch and ahead of re-entry.

‘In OPF, have 167 total cavities on tile; 34 are complete with 123 left to do. The chin panel is back up. We’re doing step and gap measurements,’ noted the Stand-up. ‘Air data probes are stowed for flight, so that IPR (Interim Problem Report) is behind us. Last week, completed the ET push test.’

“On radiator retract hose, will be doing PLBD cycles on OV-105 this week,” added the Orbiter Project Office. “There is a fair chance that we will go into an omega bend with the forward starboard hose. Building up a box, and may just change this out proactively this flow no matter what happens, since we have a relatively long flow.”

While next month will see the beginning of SRB stacking in the VAB’s High Bay 3, preparations are also continuing on the booster stack for Endeavour’s flight, a sign of the continuous processing milestones that are carried out several flights in advance.

“Have one delivery that will be done Tuesday for STS-126, the right aft. This is a good milestone because we will have both afts delivered to RPSF (Rotation Processing and Surge Facility) for their ops for STS-126.”

ET Latest:

Engineers at the Michoud Assembly Facility (MAF) in New Orleans are continuing to push ahead with work on the two tanks that are causing the delay in the 2008 manifest, with the majority of workers involved with production on ET-127 and ET-129.

ET-127: Making progress on the tank. Electrical harness and routing is in work on the LOX tank, and on the LOX dome to the intertank. Our mast is installed on the H2 tank, and we are getting ready to put the manhole covers on. On the length of the H2 tank, are in the process of working through the LO2 feedline installation.

“IFR (Ice Frost Ramp) uppers are being installed. Longeron trims and sprays are in process. Have proficiencies being started for bipod sprays,” noted the latest from Lockheed Martin/MAF.

“ET-129: IFR applications in progress on the LOX tank. On H2 tank, IFR base trims are proceeding well. Have first of five no-win trim and base applications completed. Working through the final aft hardware completion activities. Expect the aft cross beam to be ready to be installed on the tank later this week.”

Interestingly, managers have noted that discussions with MAF last week confirmed that the amount of post-Columbia modifications to the tanks may have “gone too far.”

This is not an excuse to reduce the amount of work that is being carried out on the tanks, as documentation showed shuttle managers were looking at the full range of modifications that have been proposed since Return To Flight for some time. Recently this resulted in some of the modifications being dropped, based on updated flight history.

“(Went to) MAF last Thursday and Friday and had some good discussions,” noted System Engineering and Integration (SE&I). “The intent is to look at some areas in production of the tanks that we may have gone too far in how we do the process controls implemented during Return to Flight.

“SE&I will look at maybe changing the debris zones on the tank, which would give some relief in the process controls. The intent is not to change the risk on the tank, but to take advantage of all the things learned during Return to Flight in our modeling of the risk and doing the risk assessment, as well as the performance of the tank.”

This will likely aid the tank schedule downstream, which is already looking healthy, mainly in part to the recent delays in the launch manifest.

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