1、Lessons Learned Entry: 0041Lesson Info:a71 Lesson Number: 0041a71 Lesson Date: 1991-11-25a71 Submitting Organization: KSCa71 Submitted by: David PenningtonSubject: Emergency Power-Down Procedures for Multiple Fuel Cells; Fuel Cell Helium Ingestion; Crew Module Fire Alarm and/or Electrical Component
2、Activations; Vehicle Data Down Link Description of Driving Event: Fuel cells are connected to the orbiter power busses via a motorized switch. OMI emergency procedures for powering down fuel cells assume redundant ground power is connected to the orbiter and calls for only one disconnect sequence fu
3、el cell 1, 2, then 3. The power to disconnect the FC is delivered through the same busses they are being disconnected from. During a multiple fc failure (i.e. FC 2 & 3) with no ground power connected, the OMI requires FC 1 to be disconnected first. Since FC 1 was the only one operating correctly and
4、 suppling the busses with power, switching it off first removed the power needed to disconnect the rest.Lesson(s) Learned: 1. When emergency power-down procedures are being performed, ensure that an operating bus is the last one disconnected.2. Failure to maintain GSE helium pressure below vehicle r
5、eactant pressure when fuel cells are operating may result in FC degradation or failure.3. Orbiter fire alarm and electrical components operate intermittently and erroneously when main bus voltage is lower than minimum required.4. Vehicle data to the firing room is lost when fuel cell power down sequ
6、ences are initiated with no vehicle ground power applied.Recommendation(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Configure operations and GSE design to minimize times when fuel cells are operating without redundant ground power.2. Insti
7、tute a positive means of isolating the vehicle from GSE supplied fluids, by GSE design or procedural means.3. Instruct orbiter integrity clerks (OIC), electrical techs/space craft operators and operations personnel to monitor main bus voltage and alert test team upon occurrence of low voltage.4. Imp
8、lement an obvious flag/color change on the data display indicating data has stopped updating. Maintain ground power to vehicle whenever possible.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Space Operationsa71 Exploration SystemsAdditio
9、nal Key Phrase(s): a71 Configuration Managementa71 Energetic Materials - Explosive/Propellant/Pyrotechnica71 Energya71 Ground Operationsa71 Ground Equipmenta71 Hardwarea71 Launch VehicleAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1994-06-01a71 Approval Name: James G. Klinea71 Approval Organization: KSC/HEIa71 Approval Phone Number: 407-867-7614Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
