NASA and contractor engineers/managers have met to evaluate the latest data and presentations relating to the repair of ET-124 – which was damaged by a hail storm last month.
The meeting evaluated the problems related to the non-standard repairs required on the tank, and the subsequent timeline of returning the stack to flight status – although a new launch date wasn’t decided, and won’t be until April 10 when a final decision will be taken on if to fly with ET-124 or swap to ET-117.
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Article during the Summit from this morning – confirmed post media call:
While most documentation currently points to the NET (No Earlier Than) May 11 launch target, information that is being presented to the summit points towards the requirement for more data, before a new schedule can be confidently produced. However, the opportunity to launch in April isn’t possible – as reported by this site two weeks ago.
‘On Wednesday, they will discuss ET repair efforts,’ summarized shuttle manager Wayne Hale’s notes on the latest stand-up/integration report. ‘Other projects affected by hail should attend and summarize where we are.
‘At the PRCB (Program Control Requirements Board), (we) will have detailed review of the appropriation of the baseline plan as if were going to use ET-124, with on the order of 45 days of repair work in VAB, and proceeding to launch sometime in early May. A series of TIMs (Technical Interchange Meetings) have provided the preliminary technical discussion on the repair techniques.
NASA administrator Mike Griffin and assistant administrator Bill Gerstenmaier called for the senior management level review of ET-124 repairs, for the purpose of finalizing the approach for STS-117, with the options ranging from proceeding with repairs – currently being carried out on the tank, or to swap with ET-117 – which is set to arrive at KSC next month. A tank swap – classed as unlikely at this stage – would delay STS-117 to June.
‘We are faced with the discussion of whether will we be able to repair this tank,’ added Hale’s notes. ‘Will we get to a point where we can repair the tank and make the launch window, or do we need to move to the next tank when it arrives at KSC, take ET-124 offline, do longer duration repairs, and proceed to a late June launch window?
‘The launch window is still in work. This will be part of the discussion with the senior level management. Really have to get story together to present to senior level management.’
Hopes that the data would be complete to the point where a definitive plan was available for a new launch date decision was dismissed by a NASA HQ memo, which noted: ‘The repair work is proceeding on the STS-117 external tank. There will be a briefing today to senior agency management, to discuss the forward work plan. There will be no decisions made on the new launch date during this meeting.’
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Also, a series of presentations that are being viewed by today’s summit point to a range of opinions on whether ET-124 is repairable to the level required for safe flight.
‘There will be a repair risk impact to STS-117, the extent of which is yet to be determined,’ claimed the Repair Risk Assessment Summary presentation. ‘Conditional probabilities (risk level as a function of time) are calculated for repairs because of the unknown release time. The failure mechanism(s) have not been determined to the point of accurately characterizing the release time or amount of debris liberated
‘The highest repair risk is from repairs made to the LO2 tank. The greater the mass and release rate, the higher the risk. Depending on the mass size, a single release from the LO2 tank can have very high risk level if the repair liberates at the worst possible time.’
Another presentation, NASA Engineering and Safety Center (NESC)’s STS-117 Hail Damage Repair Assessment Project Status, called for more tests to be carried out on ET-124, for the purpose of confirming non-standard repairs can be completed successfully.
‘Recommendations: Perform additional crushed foam testing on panels with simulated hail damage. Use (special) panels sprayed with foam thickness representative of high damage area away from the nose cone BX-265 repair
‘Impact panels in such a manner as to simulate STS-117 hail damage. Inspect and repair panels using the same techniques, processes and criteria. Expose panels to hot gas ascent heating conditions to assess the potential for foam loss.’
NASA is hosting a media call this evening to discuss the status of the repair and assessment effort, although at this stage – with the meeting still ongoing – it appears managers will note they need to continue their assessments.
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