1、Lessons Learned Entry: 0289Lesson Info:a71 Lesson Number: 0289a71 Lesson Date: 1993-07-13a71 Submitting Organization: JPLa71 Submitted by: B. Wagoner / D. SevillaSubject: Magellan In-Flight Solar Array Deployment Indication Abstract: Although shuttle astronauts observed Magellan solar panel deployme
2、nt, a microswitch failed to provide a “panels-latched” indication. Ensure that telemetry transducers measure the desired function- not just a related function. Microswitch design should account for the need for overtravel in the actuation stroke. Perform a FMECA early in the spacecraft life cycle.De
3、scription of Driving Event: During the launch sequence of the Magellan spacecraft, the two solar panels were observed by the space shuttle astronauts to have deployed, but the “panels-latched“ telemetry indication was not transmitted. The deployment mechanism Failure Mode Effects and Criticality Ana
4、lysis (FMECA) had identified the potential for latching indication problems, therefore in the planned launch sequence the panels were rotated such that the subsequent Inertial Upper Stage (IUS) burn would drive the panels toward the latched position.Analysis has shown that the anomaly was due to the
5、 combination of marginal microswitch actuation stroke and zero-g effects on the solar array hinge mechanism. This combination caused one or both of the series-wired microswitches to fail to close. During the IUS burn, a small shift of the panels resulted in microswitch closure and provided the prope
6、r telemetry indication.Except for the time spent addressing the initial concern, the anomaly did not impact the Magellan mission.Reference(s):PFR #52230IOM 3524-90-503, From D. Sevilla to B. Wagoner, dated November 5, 1990Provided by IHSNot for ResaleNo reproduction or networking permitted without l
7、icense from IHS-,-,-Lesson(s) Learned: 1. Microswitches on Magellan were mounted such that they would detect the position of the solar panels (as opposed to the status of the latching mechanism). As a result, they were just a position indicator and not a “panels latched“ indicator.2. A marginal micr
8、oswitch actuation stroke plus zero-g effects can result in failure of the microswitch to close.3. Failure Mode Effects and Criticality Analysis (FMECA) is a worthwhile activity and can result in problem workarounds being built into flight sequences ahead of time.Recommendation(s): 1. Care should be
9、taken in deciding where to mount telemetry transducers to assure that the desired function is actually being measured, and not just a related function.2. All applications of microswitches should take into account the need for overtravel in the actuation stroke.3. Perform a Failure Mode Effects and C
10、riticality Analysis (FMECA) early in the spacecraft life cycle, and involve the cognizant design personnel.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 ScienceAdditional Key Phrase(s): a71 Flight Equipmenta71 Safety & Mission Assurancea
11、71 SpacecraftAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1991-07-11a71 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-,-,-
