1、Lessons Learned Entry: 1358Lesson Info:a71 Lesson Number: 1358a71 Lesson Date: 2003-07a71 Submitting Organization: JPLa71 Submitted by: Eric Sunada, David OberhettingerSubject: Current Limitation is Necessary for All Uses of Power Supplies (2002) Description of Driving Event: Non-flight test heaters
2、 located on each of the three non-flight, inert TIRS (Transverse Impulse Rocket System) motors were powered during system thermal test of the Mars Exploration Rover (MER 1) to accelerate return of the test chamber to ambient conditions. Post-test inspection of the TIRS assembly revealed that the hea
3、ters had burned through the heater Kapton insulation (Figure 1) and severely damaged the surrounding flight MLI (multi layer insulation) blanket (Figure 2) on all three units. The failure was caused by the lack of a current limit specification on the controlling GSE (ground support equipment) power
4、supplies. Test temperature sensors were located 4-5 inches from the heater; this was too far away to detect the high temperature due to the low thermal conductance of the TIRS motor case.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-refer to D desc
5、riptionDThe only flight hardware damaged by the test heater failures were the three flight TIRS MLI thermal blankets. These were refabricated because failure to correct the damage might have been mission catastrophic. References1. JPL Problem/Failure Report No. Z78893, December 30, 2002.2. Eric Suna
6、da, “Inert TIRS Motor Test Heater Failures during System Thermal Test 1,“ JPL internal memorandum 353/ES/02-047.MER, December 26, 2002.Additional Key Words: system test, integration and test, ATLO, overheating, test-induced failure, test damage, overtest, overtemperature, current-limiting, excess cu
7、rrent, thermal-vacuum test, T-V test, heat transfer Lesson(s) Learned: 1. Adhere to the JPL and industry best practice of explicitly current limiting all power supplies.2. For low thermal conductivity applications like the TIRS motors, a test thermocouple should also be placed directly on or immedia
8、tely adjacent to the heater.3. Extreme caution must be exercised in the use of heaters on test components to accelerate thermal vacuum test warm up.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Recommendation(s): (see Lessons above) Evidence of Rec
9、urrence Control Effectiveness: Preventive Action Notice No. Z82153 was opened by JPL on October 15, 2003. The measure taken to implement Laboratory-wide corrective action on the above recommendations was updating the JPL System Thermal Testing Standard (JPL D-22011) to provide safeguards against bur
10、n-through. This corrective action is presently under independent assessment.Documents Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Space Operationsa71 Aeronautics Researcha71 Aeronautics ResearchAdditional Key Phrase(s): a71 Flight Equipmenta71 Ground Equipmenta71 Ground
11、Operationsa71 Hardwarea71 Payloadsa71 Safety & Mission Assurancea71 Spacecrafta71 Test & Verificationa71 Test Articlea71 Test FacilityAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2003-29a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
