Orbiter Summit updates fleet status – Tank schedule remains tight

by Chris Bergin

A summit between NASA and United Space Alliance’s (USA) Orbiter departments has concluded with a review of the current – albeit few and far between – issues with the fleet, highlighted by the APU leaks that have been observed on recent flights.

Meanwhile, the opportunity to advance the STS-125 launch date ahead of October 8 appears to have been lost, with the Michoud Assembly Facility (MAF) noting their shipping dates are slipping to the right again – despite a huge effort taking place in New Orleans.

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External Processing Latest:

Managers were hoping to launch Atlantis a few days prior to the scheduled October 8 launch date, in order to add flexibility for the launch of Endeavour on STS-126. The timeline remains tight due to only a month separating the two launch dates, and a Beta Cutout that begins on November 25.

To allow for this advancement – to be decided at a management meeting next week – was based on a shipping date of July 8 for ET-127 (STS-125), and August 2 for ET-129 (STS-400/STS-126). At one point, ET-127 was within July 6, but this has since slipped again to July 11.

‘Critical path is getting out of intertank, getting door on, completing composite nosecone installation, and completing both aft interface TPS (Thermal Protection System( sprays, pours, and trims. That allows them to go into all systems. Along this pathway, are now out of intertank and will be going up today with intertank access door. Nose cone is mounted,’ noted MAF’s latest processing report on L2.

‘Working a fastener issue with one of the fasteners that goes around the vent louver opening. All closeout sprays and pour/trim activities are in work on aft interface hardware; pacing item is on minus Y vertical strut to get the spray/trim done by the SRB cable so can go into L systems there. Finishing up a few LO2 feedline attach closeout repairs.’

The effort in New Orleans should not be underestimated, with a full 24/7 effort continuing on this tank to avoid it slipping past July 11. This includes – and not for the first time – the workforce processing the tank throughout a holiday. Notably, July 11 is still a huge advancement on one of the previous dates, which was closer to August.

‘Will be working three shifts this Friday, Saturday, and Sunday. Projecting ET completion on July 10, with shipment on July 11. (Shuttle manager John) Shannon appreciates everyone’s hard work to have ET-127 out early.’

ET-127’s transport – the Pegasus Barge being pulled by the Freedom Star (following its replacement with the Liberty Star) – is set to arrive at MAF on Friday evening.

‘Freedom Star is with Pegasus under tow and is about 200 miles off of Tampa Bay, FL. It’s on schedule to deliver the barge to MAF Friday evening.

‘On Liberty Star, confirmed that cylinder 1 has low compression. Have team coming in to work on the motor next week. Expect to have Liberty Star up and running next week.’

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ET-129 is about to be moved into its next phase of production, but remains well outside of the Aug 2 required shipping date for STS-125 advancement, and also outside of the August 5 date – which is the timeline for supporting an October 8th launch of STS-125.

‘Harness routing continues to be critical path. LO2 harnesses and tubings are in hand. Started with tubing installations down the hydrogen tank. About 75 percent done with routing harnesses across the cross beam,’ added MAF on the progress of ET-129.

‘All LOX feedline flange closeouts are in work. Got into LOX feedline attach closeouts. Manhole cover is installed and torqued. Will do TPS closeouts when get to Building 420. Feedline faring is installed and mounted. Began routing camera harnesses inside intertank. Still not inside the August 5 shipment date, but are working to pull this in.’

Updates were also provided for the next three tanks, which all appear to be in good shape.

Orbiter Summit/APU:

Expansive notes from the Orbiter Summit (on L2) outlined numerous subjects of interest relating to the three orbiters, including confirmation that the Quick Disconnects (Q/Ds) on all APUs will be changedout.

Each orbiter has three APUs – which produces pressure for the orbiter’s hydraulic system that controls the vehicle’s wing flaps, rudder, body flap and landing gear, among other elements of the vehicle.

Leaks have been observed on recent flights, most notably with Endeavour’s APU 1 Fuel Tank – which was noted as suffering from decaying tank pressure (tank outlet pressure transducers) at a rate of around 4 psi/day.

‘APU QD leak: On two recent flights, had problems with small GN2 leak. During flight, can’t tell whether it’s GN2 or hydrazine. Spend a lot of time worrying about this during flight,’ the notes added. ‘Always have good rationale showing that it is nitrogen.

‘Found a leaky Q/D when vehicle came back this time. Showed that it leaked under cold conditions and didn’t leak when it was warmer. Agreed to change out all APU Q/Ds, so won’t have this problem again.

‘Folks will continue to investigate root cause and determine why they were leaking. Will also look at potential for a heater mod to keep Q/Ds warm to prevent leakage.’

Leaking APUs are only an issue if they leak Hydrazine, as opposed to Nitrogen (GN2). At the time a leak was observed on Endeavour’s APU 1, flight history was used, which showed the Q/D was a leading candidate on the fault tree.

Listed were STS-65’s processing flow and STS-72 post flight, which observed the Q/D cavity as ‘wetted’. The most serious event was on STS-9, which was documented as an ‘Entry/Landing Fire’ – after injector stem leaks on Columbia caught fire during landing. However, this was only discovered in post flight processing.

As part of the evaluations, a physics based analysis was required to help differentiate between a Hydrazine Leak and a GN2 Leak, due to the limited ability to distinguish between the two leakage media on orbit.

Rudder Speed Brake (RSB) clips/tabs:

A new item of interest of late has been the RSB clips or tabs, one of which liberated in the final few days of STS-124’s flight. Discussions have been taking place on short and long term plans to mitigate such a liberation from occurring again – even though they hold no specific requirement during flight.

‘Discussed rudder speed brake clips during OPO (Orbiter Project Office) Tech Tag-up. Forward plan for OV-104/STS-125 is to replace 3 clips (13 discrepant parts total),’ noted the latest Shuttle/Stand-up/Integration report. ‘Based on schedule, best plan is to replace these clips and fly.

‘Will take all parts that had anomalies during inspections off and replace them for STS-125. Doing a better inspection now (previously they were visual inspections). Will add tactile inspections to ensure have good well bonds in short term, which was done on OV-104 and OV-105.’

As previously noted, the long-term plan involves the possibility that the clips don’t even need to be on the vehicle – which would allow for their removal from the fleet. Evaluations should be complete in time for the launch of Endeavour on STS-126 this November.

‘Have long term plan to look at thermal analysis to see if can fly without having clips in place. Hoping to have this in place for STS-126. So, OV-105 team will await decision pending thermal analysis.

‘In meantime, will continue to build new clips. Looking at transport, only risk in flight would be pre-flight when do air surface slew at the pad during T-5 count. There is a small possibility that they could liberate a clip in that timeframe.

‘Will work to ensure there is no transport to vehicle if the clip was to fall down into the flame trench. Loads are higher in flight, so most likely panels are liberating during ascent (are contained during ascent). Will have a small risk posture discussion for STS-125 for this. And, hopefully will have a long term plan to remove clips or look at a redesign.’

‘On OV-104/STS-125, building replacements for the rudder speed brake thermal barriers,’ noted USA Logistics. ‘Are in negotiations with a certified special processor trying to get them to work this weekend to do the heat treat. Tracking this as yellow against the need date. In worst case, will be a couple days off on schedule.’

STS-125 Processing Latest:

Good news has been forthcoming on the 10R RCC (Reinforced Carbon Carbon) panel on Atlantis’ right wing, following what appears to be a successful fit of a replacement panel that has been donated by Discovery.

‘Completed fit check on 10R RCC. That was the panel received from OV-103. Plan is to begin installation for flight on Monday,’ noted USA Ground Operations, on L2. ‘Will ensure paperwork is changed as far as Program directives go. Doing final aero surface positioning today. Working preps for crew equipment interface test which is scheduled for next weekend.’

A panel was initially donated by Endeavour, but this proved to be troublesome during the fit check. Discovery will now require a new panel, which is being shipped from Lockheed Martin in January.

‘RCC 10R panel: It looks like step and gap there is good and is the best posture to fly in. Re-shot the thermography on the ship. Received data that was very consistent with what they took when this panel was on OV-103. Means data is consistent, and there isn’t anything anomalous going on.

‘Have known for a long time that when take T-seals off, that you can get different or higher readings. When began this thermography, NDE (Non Destructive Evaluation) team recommended that every T-seal be removed every flow to obtain data because receive the best results this way. This isn’t possible from a flow perspective.

‘Will go off and look at data and understand what it means. Think will be in good posture for flight. Will discuss doing thermography off of the ship (whether it’s reasonable to pull the panel, take it over to the bench, collect any more data, install it for flight, and catch paperwork later). There is a directive that specifies taking OV-105 10R panel and putting it on OV-104. They will follow-up with this.’

STS-400/STS-126 Processing Latest:

Endeavour’s main element of interest continues to be on the Left Hand External Tank Door motor, as previously reported. This will be changed out, as per latest notes.

‘LH ET door actuator on OV-105 has a strange signature that looks like the brakes are slipping,’ noted USA Orbiter. ‘As soon as receive a spare (available in a month), will change this out.’

The other area of evaluation that has taken place this week relates to the four radiator retract hoses that carry freon coolant to the orbiter’s radiators on orbit.

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All of the orbiters have been suffering from kinks to various hoses during payload bay door closure on orbit and during closure pre-flight.

A test was preformed on Endeavour this week, known as a door cycle, to see if the problem would reoccur. However, all four hoses retracted without issue.

‘OV-105 radiator retract hoses. Wanted to perform door cycles to ensure they went back into the box. (Previously) had a problem with C-bend on one of those hoses. Performed door cycles, and hoses retracted into the box normally. Gives them good flight rationale for upcoming flight.

‘Forward hose showed potential for C-bend, but it didn’t have any evidence of C-bend. Aft hose had very significant braid damage which was acceptable for one flight. Preliminary data showed that damage did not go down into box.

‘Means damage wasn’t induced during cycles on-ground or in-flight. Need to go off and understand this, but the hose is good for one flight. Will discuss R&R’ing of both hoses during next OV-105 flow.

‘They are in good shape for this flight. Continuing with securing. Opening up rudder speed brake today in preparation for the spring tab change outs.’

Endeavour’s other recent milestone saw all three of her Space Shuttle Main Engines (SSMEs) installed for her upcoming STS-400 role and primary STS-126 mission.

‘Completed engine installation into OV-105/STS-126 on Monday and Tuesday this week, and are securing from this,’ noted Pratt & Whitney Rocketdyne. ‘Should get into interface leak checks the middle of next week.’

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