1、Lessons Learned Entry: 0305Lesson Info:a71 Lesson Number: 0305a71 Lesson Date: 1993-09-01a71 Submitting Organization: JPLa71 Submitted by: B. WagonerSubject: Galileo Retro Propulsion Module (RPM) Flow Decay Problem Abstract: To reduce costs, the Mars Observer propulsion and other subsystems followed
2、 design practices more common to earth-orbiting satellites than to planetary missions. Consider contractor experience in bipropellant spacecraft propulsion system design in source selection. To manage risk on one-of-a-kind developments, assure thorough technical oversight of contractors with limited
3、 experience in the design of interplanetary spacecraft.Description of Driving Event: When the Galileo launch date was delayed from 1986 to 1989 with an increase in mission duration from four to eight years, the RPM design was re-evaluated. It was determined that a significant risk existed of in-flig
4、ht loss of propulsion capability over the extended mission due to oxidizer flow decay. Flow decay is due to blockage of small oxidizer flow passages and filters by the accumulation of contamination products caused by interaction between the stainless steel lines and components with the nitrogen tetr
5、oxide oxidizer.Replacement of most of the stainless steel oxidizer feed system with titanium has alleviated the concern.Lesson(s) Learned: Contaminants created by the interaction of stainless steel lines and components with nitrogen tetroxide oxidizer can result in the blockage of small oxidizer flo
6、w passages and filters.Recommendation(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. The use of stainless steel components in combination with nitrogen tetroxide should be eliminated where obstruction in small passages may occur.2. Projects o
7、f long mission duration that use nitrogen tetroxide oxidizer systems and cannot avoid the use of stainless steel should develop a mechanism to predict flow decay hazard conditions.3. Oxidizers should be purified immediately before loading to minimize contamination products.Evidence of Recurrence Con
8、trol Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Parts Materials & Processesa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1988-04-07a71 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-,-,-
