STS-117 crew arrives at KSC – Atlantis hoping to clear RCC issue

by Chris Bergin

The seven man crew that are set to launch with Shuttle Atlantis on Friday have arrived at the Kennedy Space Center in Florida.

Meanwhile, Shuttle managers have been ironing out the remaining issues on Atlantis ahead of the milestone L-2 day meeting. Several processing IPRs (In Process Reviews) have been closed out, although an issue with an area of wing leading edge RCC is gaining the bulk of discussions.

**The most comprehensive collection of STS-117 onwards related presentions and mission documentation, plus expansive daily processing documentation and updates are available to download on L2 ** Including all FRR documentation and presentations. All processing content and quotes from the article below orginate from L2’s STS-117 Special Section.

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Commander Frederic Sturckow, Pilot Lee Archambault, Mission Specialists Steven Swanson, John ‘Daniel’ Olivas, Patrick Forrester, James Reilly and Expedition 15 replacement Clayton Anderson flew into Florida in their fleet of T-38 planes late on Monday.

The four astronauts that will be riding Atlantis from the flight deck started their day by carrying out a final pre-launch simulation, spending four hours practicing Ascent and Abort procedures with the mission control team in Houston. All seven then made the 900 mile trip to KSC, where they were greeted by members of the media.

STS-117 was set to fly earlier in the year, before a freak hail storm damaged the top of External Tank ET-124, causing the rollback to the VAB (Vehicle Assembly Building) for repairs.

‘As you know, we had a little bit of a setback,’ said Sturckow. ‘We flew by the launch pad on our way here and (Atlantis) looks great. We’ve spent a long time training for this mission.’

Pad processing for Atlantis continues to proceed smoothly, as STS-117 heads towards the start of S0007 launch countdown procedures.

Several IPRs were noted on the latest processing update (Monday), including a MPS (Main Propulsion System) Engine 2 Reg A Helium Outlet Pressure Spike, which caused the control logic to safe the system and bled the pressure down, which in turn caused a master alarm to occur.

‘This pressure fluctuation is not uncommon and happens during FRTs (Flight Readiness Test) on a regular basis.. It will be closed as an explained condition,’ noted the processing report.

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Such issues are not unusual for the hugely complex vehicle during the pad flow, with the most important element being the continued on-schedule timeline towards launch, which remains the case.

‘Finished aft closeout on vehicle at pad and did aft confidence checks Sunday,’ noted the latest integration report on Monday, which added that the two-stage pressurization of the Composite Overwrap Pressure Vessels (COPVs) went to plan, despite some media over-reaction to what was a standard safety memo.

‘S0007 preps are in work with call to stations scheduled 20:30 Tuesday. Will open payload bay doors today and charge payload batteries and close doors tomorrow.’

The report noted 105 ‘constraints’ which are being ticked off by system engineering, with only a handful requiring further attention, or are in the process of being closed out.

‘On aft thrust structure strain gages, have 5 of 12 not working,’ was one example in the integration report. ‘Changed batteries, but still don’t work. Plan to leave these as are.’

The main area of conversation relates to RCC coating on Atlantis’ wing’s leading edge. However, this too is expected to be closed out at the L-2 day meeting.

‘There was a significant open item regarding RCC concerns that will be closed at the L-2 MMT (Mission Management Team),’ noted NASA information.

‘The NESC (NASA Engineering and Safety Center) raised a relatively recent concern with RCC coating spalling near wing leading edge T-seals, which could expose the substrate to oxidation and burn through during entry. This phenomena has only been seen three times in program history, twice on RCC panels post flight (with no burn through) and once on the nose cap after heat treating in an autoclave.

‘Thermography shows some promise for detecting this problem before the coating spalls. This concern was heightened based on post-flight inspection of OV-103 (Discovery) after STS-114 when thermography detected one of these areas adjacent to the groove along the 8R T-seal, although the coating had not yet spalled.

‘The Orbiter Project Office (OPO) has evaluated the concern and has flight rationale for all but a very narrow area just inside the T-seal to panel groove (or joggle as OPO referred to it). OPO and the NESC have an action to review thermographic data taken from OV-104’s RCC and identify any areas of concern.’

That thermographic review will take place at the L-2 MMT, and NASA won’t be taking any chances, should the resulting review find that there is a risk with the RCC – which would lead to another rollback of the vehicle for the replacement of the RCC in question. That, however, would be in a worse case scenario.

‘The direction from the FRR (Flight Readiness Review) is that any data that shows an area that is considered to have a high probability of spalling and creating an entry risk will invalidate the flight rationale and require a roll back to replace the suspect RCC,’ added the information.

‘It is possible that there will be some inconclusive areas since the thermography is still a new and uncertified method of assessing RCC for this problem. In those cases, the FRR board agreed that the planned FD2 (Flight Day 2) inspections will, by design, detect any entry critical surface damage on the RCC.

‘Coating that has not spalled before MECO (Main Engine Cut Off) is not expected to be at risk of coming off until after peak heating since there are no significant mechanical loads on the leading edge surface until lower in the atmosphere.

‘Inconclusive data in some area would be factored into the Damage Assessment Team’s focused inspection deliberations during the flight. However, it was clear that focused inspections of these areas will not form the basis for flight rationale to clear this concern.’

Confidence is high, however, that the RCC will be cleared by the thermography data, with the United Space Alliance noting on their processing information: ‘Looked with NESC folks at results of LASS line scan technique for evaluating thermography data. Set intensity amplitude based on what see in thermography data for 8R problem.

‘Tripped that limit on five panels, but thermograpy scans from pre-STS-115 (panels were just refurbished) were no different. Confident nothing wrong with panels. Will discuss at Tuesday and at L-2.’

Once this issue is closed out, Atlantis is expected to head towards the rollback of the RSS (Rotating Service Structure) and tanking with a clean bill of health, as NASA move ever closer to what they hope will be the first of four missions in 2007.

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