1、Lessons Learned Entry: 0271Lesson Info:a71 Lesson Number: 0271a71 Lesson Date: 1993-07-07a71 Submitting Organization: JPLa71 Submitted by: P. W. SchaperSubject: Mars Observer Pressure Modulator Infrared Radiometer (PMIRR) Cooler Failure During Vibration Testing Abstract: A severe structural failure
2、occurred during flight acceptance vibration testing of the PMIRR radiative cooler. An erroneous assumption was made that the inherited design was acceptable despite a change in launch vehicle. Hold a complete and thorough design review for “inherited” flight hardware designs. Assure that inheritance
3、 is considered in the dynamic test model. Analyze interrelationships between modified and unmodified elements of flight hardware designs.Description of Driving Event: During flight acceptance vibration testing of the PMIRR radiative cooler assembly, a severe structural failure occurred. As a result
4、of this failure, the detectors and other internal elements of the cooler assembly were severely damaged.The PMIRR cooler assembly is a modification to a flight-proven design which had flown successfully as a part of the thematic mapper instrument for several years. Cost and schedule considerations h
5、ad dictated the choice of modifying an existing design over designing a custom cooler for the PMIRR instrument. An erroneous assumption was made that the inherited design was acceptable.Investigation into the event by a review board revealed that the failure was the result of the significant increas
6、e in vibration test levels required because of the change in launch vehicle for the PMIRR instrument. The thematic mapper had experienced much more benign launch environments and insufficient analysis of the failed component had taken place, particularly in the area, which was inherited from the ori
7、ginal design. It was also determined, however, that the original analysis of the unmodified component was flawed in that it assumed an incorrect value for allowable stress for the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-material and manufactu
8、ring processes used.This failure created a major cost and schedule impact to accommodate the reanalysis, rebuilding, and retesting of the cooler assembly.Reference(s): PFR #54605 PMIRR Failure Review Board ReportLesson(s) Learned: 1. Use of inherited designs does not preclude the necessity of perfor
9、ming in-depth analyses of all elements, whether redesigned or not, especially if environmental requirements change and are not identical to those for which inheritance is claimed.2. A dynamic test model for developmental testing can detect design flaws resulting from the use of inherited hardware an
10、d save more than its cost in terms of dollars and time.3. Weight reduction efforts and design changes of some elements of an assembly can adversely affect the behavior of unmodified elements.Recommendation(s): 1. A complete and thorough design review should be held for “inherited“ designs of flight
11、hardware. This review should examine changes in planned application, changes in design and plans for reanalysis and retest.2. Assure use of a dynamic test model for developmental testing of hardware designs based on “inheritance“.3. Perform an in-depth analysis of interrelationships between modified
12、 and unmodified elements of flight hardware designs.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Key Phrase(s): N/AAdditional Info: Approval Info: a71 Approval Date: 1991-03-28a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
