ET repairs begin – inspections show less damage than feared

by Chris Bergin

NASA, United Space Alliance and Lockheed Martin engineers have completed an exhaustive overview of the main areas of damage sustained to Atlantis’ External Tank (ET-124) and are now begining to carrying out repairs.

A series of presentations acquired by this site downgrade areas of concern that do not meet “Post Build Acceptance Criteria” to around 1000 items.

**The most comprehensive collection of STS-117 onwards related presentions and mission documentation – not available anywhere else on the public net – are available to download on L2 **

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Related Notes and Presentations on L2, including: New FAWG Manifests – Post ET Damage. Daily Ops Reports. The NASA and Lockheed Martin notes on the ET damage (VAST), plus new images and many downloadable presentations. ET Manifest (Lockheed Martin) ET-117 Production Milestone Presentations, ‘through to’ STS-124 Baseline Mission Presentations, plus more, available to download on L2.

**Previous articles on the damage events: Article 1Article 2 – Article 3 – Article 4 – Article 5** Click for more screenshots of the damage.

**FREE 100mb video of the NASA ET Damage press briefing** – required to login to forum.

Those 1000 items are classified as crushed foam, caused by the freak hail storm late in February.

While some sanding and preparation work has already started on the top of the ET, the full process – from complete inspection, to repairs, to qualification and then rollout back to Pad 39A – is still believed to be a six week/45 day process, which would delay STS-117 from launching before May 11.

However, the most recent presentations do ‘sign off’ on some previous concerns, which in turn may reduce the timeline for repairs and possibly increase the chances of a late April launch target.

‘ET-124 experienced significant hail damage at Pad A. Damage consists of numerous sites (>1000) of crushed / damaged TPS (Thermal Protection System – Foam),’ noted a Lockheed Martin overview presentation on Thursday, backed up by similar update presentations on Friday. ‘Similar hail-induced damage occurred on ET-100 (<1000).’

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One of the first ‘hands on’ processes was the application of a red dye to the very top of the ET LOX section foam. However, the special mix did not work to plan, leading to a request for more supplies to be trucked over from the Michoud Assembly Facility (MAF) in New Orleans.

‘Found that the big bottles of dye that the mix is created form had not been opened in 10 years. There was no shelf life expiration issue, but the components were unacceptable (dried up),’ noted one presentation. ‘PRACA will be initiated to cover the discrepant material and we are currently getting more from mix components from MAF. New dye is currently being transported from MAF by truck.’

To inspect the tank – and carry out the repairs – several platforms were installed this week, including scaffolding. Most of these access points are now in place, although a couple of ‘remote’ areas won’t have access completed until next Monday.

The staggering amount of information gained by engineers show that NASA is utilizing a number of centers for the repair effort, including get-ahead tasks at MSFC (Marshall Space Flight Center) – who will aid the thermography effort.

‘Nose cone – Complete, No rejectable indications: 3 minor observations noted. Distorted fabric. No exposed, broken fibers, delaminations etc,’ added another encouraging presentation that was outlined to NASA’s PRCB (Program Requirements Control Board) meeting. ‘Thermography technique in work at MSFC. Plan to ship equipment to KSC Monday 3/11/07.

‘Intertank door – Complete, No rejectable indications. Ultrasonic Inspection is being staged for shipment for NDE next week. GH2 press line fairing – Complete, No rejectable indications. 2 minor observations. Ultrasonic Inspection is being staged for shipment for NDE next week.

‘LO2 Tank Ogive and Barrel TPS. Numerous defects were observed, but the density and severity is less than that observed in the pencil sharpened area. No areas were identified for possible BX-265 repair. Preliminarily expect PDL repairs, use-as-is and blend type repairs at this location.’

Also encouraging are repairs to Atlantis herself, with most of the tile damage – to the tip of her left wing – now repaired.

‘Identified 28 repairs on Orbiter TPS. Twenty are currently complete. Need to provide access to finish up the job,’ noted the most recent Shuttle Standup/Integration report.

Same applies for the observed damage to the Solid Rocket Boosters (SRBS), with the report adding: ‘SRB inspections are complete. Found very little damage attributed to hail. Engineering evaluation is in work on things they did find.’

The next key milestone with returning the tank back to flight status will be the evaluation of repair techniques on a test article at MAF. Should those repair efforts prove to be a success, those processes will be immediately translated on to ET-124, mitigating the possibility of a ‘bad repair’ on the tank.

Further articles will follow. Please refer to the live update pages on L2 (for NASA presentations, memos, emails and images) and on Atlantis’ section (open to all).

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