1、Lessons Learned Entry: 2045Lesson Info:a71 Lesson Number: 2045a71 Lesson Date: 2009-5-11a71 Submitted by: Michael Bella71 POC Name: Michael Hagopiana71 POC Email: michael.hagopian-1nasa.gova71 POC Phone: 301-286-6732Subject: Failure of Pyrotechnic Operated Valves with Dual Initiators Abstract: Four
2、spacecraft propulsion system pyrovalve no-fire failures were investigated by the NESC (NASA Engineering and Safety Center). In all four cases, a normally closed pyrovalve failed to actuate during tests in which simultaneous firing of dual initiators failed to ignite the booster charge. Timing of red
3、undant initiator firings is crucial for reliable operation of pyrovalves. Dual simultaneous firing ( 10 microseconds skew) is not as robust as a single firing and should be avoided.Description of Driving Event: Four spacecraft propulsion system pyrovalve “no-fire“ failures were investigated by the N
4、ESC (NASA Engineering and Safety Center). In all four cases, a normally closed pyrovalve failed to actuate during tests in which simultaneous firing of dual initiators failed to ignite the booster charge. In each failure, a common aluminum Y-shaped PCA (Y-PCA) manufactured by CONAX was used to mecha
5、nically accommodate the two initiators and to direct the individual output products of each initiator towards the booster charge. Booster charge ignition is intended to generate sufficient pressure to actuate the pyrovalve. Testing of both single and dual initiators revealed important design charact
6、eristics affecting pyrovalve device performance. They include Primer Chamber Assembly (PCA) geometry and material properties, as well as operational effects on combustion product flow, and resulting energy transfer to the booster.Lesson(s) Learned: Provided by IHSNot for ResaleNo reproduction or net
7、working permitted without license from IHS-,-,-The CONAX PCA design has evolved slowly over time undergoing incremental changes to correct known issues. These piecewise changes were verified by limited test, without a full understanding of the overall system impact or effect on margins. Adequate sys
8、tem performance margins may be adversely affected in existing or future systems incorporating a pyrovalve actuated by simultaneous firing of dual initiators. The primary finding from this investigation is that dual simultaneous firing ( 10 microseconds skew) is not as robust as a single firing and s
9、hould be avoided.Recommendation(s): When close sequential firing of the redundant initiator is necessary, the NESC recommends the skew time between initiator firings should ideally be longer than the flow duration for single fire. Thus the NESC recommendation that use of the device should be constra
10、ined to single fire operation (or dual with skew greater than 2 milliseconds) to ensure robustness of booster ignition. The NESC has forwarded this finding, and others related to critical PCA parameters and device qualification issues, to projects using the current design. In addition, the NESC cont
11、ributed to a new stainless steel PCA design activity initiated by the Mars Science Laboratory project.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: CONAX Y-PCA Booster Anomaly Investigation Report NESC Document Number RP-08-111 NASA Technical Memorandum (TM) Number TM
12、-2008-215548 Click here to download document. Mission Directorate(s): N/AAdditional Key Phrase(s): a71 Additional Categories.Energetic Materials - Explosive/Propellant/Pyrotechnica71 Additional Categories.Hardwarea71 Additional Categories.SpacecraftProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Approval Info: a71 Approval Date: 2009-05-11a71 Approval Name: mbella71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
