1、Public Lessons Learned Entry: 6456 Lesson Info: Lesson Number: 6456 Lesson Date: 2011-6-29 Submitting Organization: KSC Submitted by: Matthew Craycraft Subject: Atmospheric Revitalization and Pressure Control System (ARPCS) Abstract: This lesson learned provides a summary of ground operations lesson
2、s learned for the Space Shuttle Atmospheric Revitalization and Pressure Control System compiled in June 2011. Lessons learned topics covered include: composite overwrap pressure vessel stress rupture failure mode, O2/N2 flow sensor problems, ground support equipment pressure distribution unit calibr
3、ation, negative pressure relief valve failure to reseat, fire bottle quantity verification, test requirements, latching valves and position indication, and cabin leak checks. Description of Driving Event: The recommendations that follow are relative to ARPCS processing problems. At the start of the
4、Shuttle Program, certification for composite overwrapped pressure vessels (COPVs) was based on an age life tanks assumed leak before burst, and reliability assumed to be greater than 0.9999 (less than 1 in 10,000 failures). The Johnson Space Center (JSC) initiated a test program to verify age on Kev
5、lar overwrap. In 2004-2005, mid-life re-certification was performed. The NASA Engineering and Safety Center (NESC) found errors in the calculation of the stress ratio based on the Lawrence Livermore National Laboratorys (LLNL) COPV test program. In 2005-2006, a study to assess true reliability of CO
6、PVs in the Orbiter fleet began. Space Shuttle Columbias tanks (found intact) were dissected, inspected, and tested to gain data points. White Sands Test Facility (WSTF) performed an accelerated life test on a 40-inch Orbital Maneuvering System (OMS) tank deemed to be the worst in the fleet. In 1989-
7、1990, flow sensor problems (biased, drifting, failed sensors) in O2/N2 flowmeters became more evident. In the early 2000s, approximately 50 percent of the sensors were unreliable. Lesson(s) Learned: See recommendations Recommendation(s): 1. If COPV concerns warrant it, consider a local clear of the
8、Processing Facility when pressurizing above 33 percent of design burst (1633 psig)requires two clears: initial servicing and final flight top-off post-sampling. Do not exceed 110 degrees Fahrenheit (tank Operations and Maintenance Requirements Specification Document (OMRSD) limit is 170 degrees Fahr
9、enheit). 2. Upgrade failing sensors and pursue alternate technology. 3. Flowmeters should be designed to allow in-place calibration. 4. Post-clean and lubricate the seat in the Negative Pressure Relief Valve (NPRV); do not inspect the valve seat at every flow, only during full testing of the valve;
10、and include a leak check of the secondary seal cover. 5. Install quantity gaging system to verify fluid level for fire bottles not easily accessible. 6. Line Replaceable Unit (LRU) retest requirements should be driven by criticality and likelihood of failure. 7. Requirements should be tightest at ac
11、ceptance test plan level (acceptance testing versus Operational Maintenance Requirements and Specifications Document (OMRSD) versus Launch Commit Criteria versus Flight Rules) with the largest margin for flight rules. 8. Design of valves should incorporate position indication telemetry. 9. Develop a
12、 bell jar tester to validate feed-through connector integrity as a precursor to the cabin leak check. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: Atmospheric Revitalization and Pressure Control System TIM-Presentation-June 2011 Mission Directorate(s): Exploration S
13、ystems Space Operations Additional Key Phrase(s): Additional Categories.Test & Verification Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Categories.Ground Equipment Additional Categories.Ground Operations Additional Categories.Pressure
14、Vessels Safety and Mission Assurance.Early requirements and standards definition Systems Engineering and Analysis.Long term sustainability and maintenance planning Additional Categories.Fire Protection Additional Info: Project: Space Shuttle Approval Info: Approval Date: 2012-09-28 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
