1、Lessons Learned Entry: 1839Lesson Info:a71 Lesson Number: 1839a71 Lesson Date: 2006-7-30a71 Submitting Organization: LARCa71 Submitted by: Sudha Natarajana71 POC Name: Scott Hilla71 POC Email: Scott.a.hillnasa.gova71 POC Phone: 757-864-7029Subject: Laser Beam Expander Optics (BEO) Structural Failure
2、 Abstract: During the unit level vibration testing of the BEO of the LIDAR instrument of CALIPSO Satellite, the composite structure spider legs supporting the BEO secondary mirrors failed catastrophically. After the initial analysis of the BEO, several small design changes to the structure were made
3、, each of which was so minor, with so little impact on the overall design margin, that the structural analysis was not updated. However, the combined effects of these modifications consumed all design margin, leading to failure during qualification testing.Description of Driving Event: During the un
4、it level vibration testing of the BEO of the LIDAR instrument of CALIPSO Satellite, the composite structure spider legs supporting the BEO secondary mirrors failed catastrophically. After the initial analysis of the BEO, several small design changes to the structure were made, each of which was so m
5、inor, with so little impact on the overall design margin, that the structural analysis was not updated. However, the combined effects of these modifications consumed all design margins, leading to failure during qualification testing. Loss of all flight hardware, plus increased cost, schedule and ri
6、sk: (1) To save cost and schedule, the original two flight BEOs were vibrated together (mounted on the same shaker plate) . Both units failed in the same manner, so the failure destroyed both flight BEOs. There were no flight spares of the structure. (2) To save cost and schedule, the flight optics”
7、the most expensive and longest lead-time Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-components of the assemblies”were vibrated as an integral part of the structures1; when the structures failed, both sets of flight optics were also destroyed. Th
8、ere was only one set of spare optics. (3) To minimize the cost and schedule impact of the recovery, the risk was accepted of redesigning and rebuilding the BEOs in parallel with the Payload-level qualification testing, such that the BEOs were not tested as an integral part of the Payload until Satel
9、lite-level testing; this risk acceptance paid off and very little schedule was lost. Lesson(s) Learned: Lack of rigor in the change process lead to degraded margin in the structural design of BEO. While conservative design margins may allow an acceptable risk in not repeating an analysis, never unde
10、restimate the combined impact of more than one minor change. When assessing the risks in combining or bypassing tests, be sure to consider the impact of a systematic failure affecting all hardware. Recommendation(s): If the consequences of a failure are high, structural elements should first be mech
11、anically tested using mass models of attached hardware. Fight spares should be tested separately. Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Space OperationsAdditional Key Phrase(s): a71 Systems Engineering and Analysis.a71 Engineerin
12、g Design (Phase C/D).a71 Integration and TestingAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Project: CALIPSOApproval Info: a71 Approval Date: 2008-04-28a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
