1、Lessons Learned Entry: 1035Lesson Info:a71 Lesson Number: 1035a71 Lesson Date: 2001-08-17a71 Submitting Organization: WSTFa71 Submitted by: Regor SaulsberrySubject: Mars 2001 Risk Reduction Testing, Pyrovalve Description of Driving Event: A new low blow-by pyrovalve was used in place of a high blow-
2、by pyrovalve primarily to avoid the possibility of a pyrotechnic-induced propellant explosion in a newly designed propulsion system. During blow-by testing of the new valves, one valve did not cycle when commanded. Failure analysis indicated that both initiators and the booster had fired, yet the va
3、lve did not cycle. Further investigation indicated that the booster charge was expelled from the Primer Chamber Assembly down into the ram bore. This prevented the booster can surface from opening properly (petaling) and some of the booster energy was diverted to expanding the booster can rather tha
4、n fully transmitting the energy to the ram. As a result, the diminished energy transferred to the ram was inadequate to shear the tube section that opened the valve. The valve manufacturer improved booster retention by increasing an aluminum retention ring diameter to be slightly larger than the ram
5、 bore and improved the potting between the booster and housing. This improved valve configuration was then procured by the program and evaluated by typical lot acceptance testing.Subsequent testing and analysis indicated that the potting bond was not consistent, and that the booster retention ring c
6、ould possibly deform, allowing displacement of the booster into the ram bore. The risk of a flight valve failing was low but still unacceptable to the project because the vehicle did not have redundant pyrovalves.The retention washer material was changed to a high strength stainless steel and the ou
7、tside diameter was further increased. The potting process was also improved to form a better gas seal. Testing indicated the reliability risk had been successfully mitigated.Lesson(s) Learned: When focusing on fixing one hardware problem, be careful to identify and eliminate other hardware Provided
8、by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-problems which may be created by the change. Additionally, be careful to fully test every hardware change to qualify the system and ensure something has not been missed. In this scenario, new hardware was used t
9、o eliminate a known hazard but it introduced other unanticipated risks. Changing from the previous high blow-by valve to a new low blow-by valve did mitigate the risk of a pyrotechnically induced propellant explosion upon ignition. However, an increased operational reliability risk was introduced be
10、cause the new valve did not have an extensive operational history. The risks were initially missed, but were ultimately identified through thorough testing and necessary modifications were made.Recommendation(s): 1. When focusing on fixing one hardware problem, be careful to identify and eliminate o
11、ther hardware problems which may be created by the change.2. Fully test every hardware change to qualify the system and ensure something has not been missed.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics
12、 ResearchAdditional Key Phrase(s): a71 Energetic Materials - Explosive/Propellant/Pyrotechnica71 Flight Equipmenta71 Hardwarea71 Parts Materials & Processesa71 Risk Management/Assessmenta71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2001-12-06a71 Approval Name: Jan Jungewaeltera71 Approval Organization: WSTFa71 Approval Phone Number: 505-524-5161Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
