Minutes From 2 July ART Meeting 1:
The Tracker ART met 2 July via telecom. The review process has been segmented into three fundamental steps:
1. Understand the failure, data available, analysis results, probable cause's)
2. Review & concur on likely cause's), review candidate corrective actions
3. Review selected corrective action plan, evaluate associated risks & mitigations
The objective of the first meeting was to focus on Step 1. Robert Johnson reviewed the sequence of events related to the Tracker Pre-engineering-Model Proto-Flight Tower-Module Testing as documented in LAT-TD-00793.
The ART requested additional information on available test data (LAT-TD-00788) and results from insert pull out tests. Significant discussion occurred with respect to manufacturing processes associated with the carbon-carbon material as well as design practices associated with the use of inserts and design load path redundancy.
The ART also questioned whether we were sure that the AMES Test facility provided the expected input for each test. The tracker Team has reviewed the test set-up and it is understood that the Test environment was as expected.
The ART questioned whether a Stress Factor of 2.1 was appropriate for the selected material, this question will be reviewed again as part of the corrective action recommendations
The ART concluded that the ability to analytically reproduce the failure scenario during the test(s) was unlikely due to the unknowns in structure condition during the failure for the first test (as screws backed out) and the going in structural integrity of the Pre-Engineering Model for the second test due to the known crack. In addition, it was agreed that no further information could be extracted from the existing test data.
The ART is considering a recommendation for further analysis by HYTEC to evaluate Tracker Load paths with various non-participating inserts. The concern is that industry experience indicates that tolerance build-ups can result in one or more attach points not carrying the expected load resulting in increased loads at other points, this may have been a contributing factor in the failure.
The ART members are requested to email any summary concerns, issues, comments from this first meeting to Dick Horn for inclusion in the ART report.
The ART concluded that the primary objectives of the meeting were satisfied with respect to understanding the failure and data available. The next meeting will be focused on probably/likely cause(s) and review of candidate corrective actions.
ART-1: Provide ART with test result data from Vibration Tests (LAT-TD-00788) - Horn Closed (See Attachment)
ART-2: Provide ART results of insert pull out tests - Johnson - Open (ECD NLT 8 July)
ART-3: Provide ART the properties for the carbon-carbon material - Johnson - Open (ECD NLT 8 July)
ART-4: Provide a recommendation for design practice and analysis cases for redundant load path considerations - Rodini - Open (ECD NLT 8 July)
Please provide any corrections to these minutes and Action Item responses to Dick Horn