1、Lessons Learned Entry: 0367Lesson Info:a71 Lesson Number: 0367a71 Lesson Date: 1995-01-13a71 Submitting Organization: JPLa71 Submitted by: J.E. KochSubject: Pyro Multiple Event Indication Abstract: A Voyager post-fire squib short resulted in anomalous spacecraft telemetry signals. Design initiation
2、and sensing circuits to prevent sneak paths. Recognize post-fire squib shorts as a “normal” occurrence to be taken into consideration when designing squib activation or sensing circuits.Description of Driving Event: The Voyager Spacecraft utilized a super-zip separation band initiated by a Pyro Swit
3、ching Unit (PSU) for separation from the launch vehicle. Initiation of either of the two redundant Mild Detonating Fuses (MDF) in the super-zip separation band would cause separation, while detonation of both MDFs could rupture the tube containing the MDFs and probably contaminate the spacecraft. Te
4、lemetry from both Voyagers 1 and 2 indicated that both MDFs received current from the PSU. Current to the secondary MDF should have occurred only if the primary MDF failed to cause separation from the launch vehicle. The anomalous telemetry signal indicating a current to the secondary MDF was traced
5、 to a primary detonator post-fire short to the spacecraft frame which resulted in a reverse current through the PSUs sensing circuit caused by a noise decoupling RC network between the PSU common and the spacecraft frame. The anomaly was reproduced in the laboratory thus verifying that the secondary
6、 MDF did not detonate.Lesson(s) Learned: Post-fire squib shorts can result in anomalous spacecraft telemetry signals.Recommendation(s): 1. Initiation and sensing circuits must be designed and analyzed with great care to prevent sneak Provided by IHSNot for ResaleNo reproduction or networking permitt
7、ed without license from IHS-,-,-paths which permit unwanted current flows. This is especially true in sensing circuits which could result in anomalous telemetry indications.2. Post-fire squib shorts must be recognized by the design engineer as a “normal“ occurrence and should be taken into considera
8、tion when designing squib activation or sensing circuits.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Energetic Materials - Explosive/Propellant/Pyrotechnica71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1986-09-11a71 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-,-,-
