1、Lessons Learned Entry: 0370Lesson Info:a71 Lesson Number: 0370a71 Lesson Date: 1995-01-24a71 Submitting Organization: JPLa71 Submitted by: R.K. MallisSubject: DDM Power Supply Failure Abstract: A power supply failure in the Drop Dynamics Module may not have occurred if the payload had been designed
2、to JPL D-1489, “Payload Classification Product Assurance Provisions.” Design and test to standards consistent with the class of payload.This lesson is probably obsolete as D-1489 has been withdrawn and there are no longer payload classes. Description of Driving Event: The Drop Dynamics Module (DDM)
3、is a Class C experiment which is flown on the Shuttle (STS). On its first flight, one of the set of seven commercial power supplies used by the DDM failed when an internal short caused the main circuit breaker to trip. Repeated attempts to energize the system were unsuccessful and an in-flight work-
4、around was accomplished by the JPL payload specialist. Although the location of the failure was known, failure analysis did not determine the cause since the internal damage to the two failed transistors precluded a reconstruction of the event. Circuit analysis did indicate an over-stressed design.
5、However, this condition had not prevented several hundred power supply turn-ons prior to the failure and several thousand turn-ons of the set of power supplies. In addition, the work-around solution to the power supply failure was to rewire the configuration such that two of the remaining power supp
6、lies would assume the load of the failed power supply. Those two power supplies successfully picked up the extra load. Since this failure occurred after launch, the possibility of a vibration-induced failure cannot be disregarded. The DDM was designed and implemented prior to the release of JPL docu
7、ment D-1489 (Flight Project Document FPO 600-3), entitled “Payload Classification Product Assurance Provisions.“ This document provides a description of the principal product assurance elements and the specific provisions which are to be applied as a function of payload class.Provided by IHSNot for
8、ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Keyword(s): ReliabilityLesson(s) Learned: Experiences such as the DDM power supply failure reinforce the need for design and testing to standards consistent with the class of payload.Recommendation(s): For payloads
9、 of a specified class (particularly those using commercial equipment), one should ensure that the provisions of JPL document D-1489 are met with respect to reviews, problem failure accountability, parts selection, materials and processes, environmental testing, quality assurance, and commercial equi
10、pment qualification.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Parts Materials & Processesa71 Payloadsa71 Safety & Mission Assurancea71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo r
11、eproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1986-12-12a71 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-,-,-
