Lessons Learned from the Space Shuttle Engine Hydrogen Flow Control Valve Poppet Breakage

摘要

During ascent of OV-105 during the STS-126 mission, a Main Propulsion System (MPS) engine hydrogen flow control valve (FCV) appeared to transition from the low towards the high flow position without being commanded. The other two valves compensated for the additional flow as expected, and there was no impact to the mission. After landing, an x-ray on the vehicle indicated the cause was a broken poppet. The valve was removed from the system and sent to the vendor for teardown and evaluation. Both the vehicle pressurization system and the valve piece parts were inspected for clues as to the breakage, but no out of print condition, material non-conformance, or evidence of particle impact were found.