1、Lessons Learned Entry: 0397Lesson Info:a71 Lesson Number: 0397a71 Lesson Date: 1995-06-07a71 Submitting Organization: JPLa71 Submitted by: G. ErvinSubject: Viking Spacecraft Anomalous Power Turn-On Abstract: While on the launch pad, Viking experienced an anomalous power turn-on that resulted in a to
2、tal discharge of the spacecraft batteries. Failure analysis had not detected that discrete failure of a relay located in support equipment could have caused the problem. All interfaces with the spacecraft should be subject to failure mode analysis, status indicators or alarms should be used, and the
3、 spacecraft should not be left unattended unless periodic monitoring is conducted.Description of Driving Event: While on the launch pad, a Viking Spacecraft experienced an anomalous power turn-on during a period when the spacecraft was unattended. The power turn-on resulted in a total discharge of t
4、he spacecraft batteries. The most probable cause was induced current resulting from local lightning strikes on the seven miles of cable between the support equipment located in Building AO and in the Launch Complex Trailer at the launch pad. Spacecraft internal power “ON“ is accomplished by energizi
5、ng a motorized switch in the spacecraft, which then connects the spacecraft batteries to the power bus. The induced current caused a relay located in the support equipment to connect an emergency battery to the spacecraft motorized switch, which then initiated the power turn-on. Analysis conducted d
6、uring the investigation disclosed that a possible discrete failure of the relay would have caused the same problem. This failure analysis was not performed prior to the incident. After the deep discharge, the Viking Spacecraft batteries were no longer flight certified and had to be replaced at a con
7、siderable expenditure of resources.Lesson(s) Learned: 1. Failure mode analysis can disclose potential fault scenarios and indicate prudent preventive action.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2. Periodic monitoring of spacecraft can prov
8、ide detection of anomalous conditions.Recommendation(s): 1. All interfaces with the spacecraft should be subject to failure mode analysis.2. Since it is difficult to anticipate all failure modes, use should be made of indicators or alarms to provide verification of operational performance or mode st
9、atus.3. The spacecraft should not be left unattended unless periodic monitoring is conducted. The periods to be used and the parameters to be monitored should be based on an analysis of the conditions under which the spacecraft is left unattended.Evidence of Recurrence Control Effectiveness: N/ADocu
10、ments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Ground Operationsa71 Safety & Mission Assurancea71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1996-01-26a71 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-,-,-
