1、Lessons Learned Entry: 1319Lesson Info:a71 Lesson Number: 1319a71 Lesson Date: 2003-01-13a71 Submitting Organization: MSFCa71 Submitted by: C. DelanoSubject: International Space Station (ISS) Program/Microgravity Science Glovebox (MSG)/Solidification Using a Baffled Sample Ampoule (SUBSA) Investigat
2、ion Eurotherm Controller Anomaly Description of Driving Event: During a materials science investigation process run within the MSG on-board ISS on 7/23/02, the SUBSA Eurotherm Controller (Zone 1) on the Process Control Module (PCM) would not take a command to raise the Thermal chamber main heater se
3、tpoint above 825 degrees C.Files were uplinked to query setpoint limits in the Eurotherm Controller; a local Mod Bus setpoint limit of 825C was found and confirmed why the anomaly occurred.SUBSAs Investigation Control Software (ICS) was reconfigured to route Zone 1 setpoint temperature commands to M
4、od Bus 160 instead of Mod Bus 24 in the Eurotherm Controller. The Mod Bus 160 command address does not have a local setpoint limit. The desired setpoint of 845 degrees C was properly configured.After these steps, no further problems were encountered prior to the completion of all on-board experiment
5、 processing.Lesson(s) Learned: During ground testing, a SUBSA Ground Unit Thermal Chamber temperature of about 820 C with qualification Sample Ampoule assemblies (SUBSA-GD1, SUBSA-Q3, and SUBSA-Q4) was sufficient to melt all of the sample charge (approx. 37mm) + about 4mm of the samples seed. This m
6、et the SUBSA Principal Investigators desire to melt about 2mm into the seed. However, during SUBSAs on-orbit experiment, the flight heater unit temperature of 820 C did not melt into the seed.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-To melt fu
7、rther into the seed, SUBSA tried to issue a setpoint change command to increase the Thermal Chambers temperature. The Eurotherm 2408 Controller that controls the Thermal Chambers temperature would not accept any setpoint change commands above 825 C. Therefore, the SUBSA Thermal Chamber hot zone temp
8、erature did not reach the commanded setpoint that is required to achieve the desired science result of melting 2mm into the sample material seed.Overall, the problems experienced with the SUBSA flight hardware and flight software can be directly attributed to programmatic budget and schedule constra
9、ints which resulted in inadequate run-time using flight software with flight hardware end items as well as last minute software loads and/or changes to flight software after shipment to KSC for pre-launch processing.Recommendation(s): NASA must not allow programmatic constraints/limitations in cost
10、schedule drive compromise into a thorough risk assessment and testing program.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Policy & Planninga71 Research & Developm
11、enta71 Risk Management/Assessmenta71 Test & VerificationAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 2003-01-21a71 Approval Name: Lisa Boninea71 Approval Organization: MSFCa71 Approval Phone Number: 256-544-2544Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
