REG NASA-LLIS-6142-2012 Lessons Learned - Don抰 Purge Engine Hydrogen Lines With Helium If The Engines Cannot Tolerate Consume Any Amount Of Helium.pdf

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1、Public Lessons Learned Entry: 6142 Lesson Info: Lesson Number: 6142 Lesson Date: 2010-11-1 Submitting Organization: MSFC Submitted by: Kristen Kinder Subject: Dont Purge Engine Hydrogen Lines With Helium If The Engines Cannot Tolerate/Consume Any Amount Of Helium Description of Driving Event: In the

2、 Space Shuttle Program, helium was used to purge the hydrogen fill and drain line to assist in removing liquid hydrogen from between the inboard and outboard fill and drain valves prior to launch. Testing at Marshall Space Flight Center (MSFC) has shown that helium vapor is present between these two

3、 valves prior to launch. In the event the inboard valve was to not close completely (or if the relief valve were to relieve), helium would be ingested into the engines. The Space Shuttle Main Engines have not been proven to tolerate helium ingestion above the specification level, and the concern is

4、for a potential pump over-speed and catastrophic engine failure. Lesson(s) Learned: In main propulsion systems, the liquid propellant feed systems that are external to the engine, common potential failure modes of valves can impact the safety of engine operation by allowing incompatible or unwanted

5、purge gases to be ingested in the feed line. Purge substances that are not intended for use in the combustion processes internal to the engine act differently than the intended propellants under engine operating conditions, and may cause catastrophic engine failure. Testing for tolerable levels of p

6、urge substances is recommended. Recommendation(s): For future liquid engine and feed system designs where purging of liquid hydrogen engine feed systems are required, design using one of these options: 1. Purge the line with a commodity the engines can ingest (gaseous hydrogen) (Alternative Design S

7、olution), or 2. Certify the engines for the potential ingestion of this commodity (helium) (Validation of Design; Certification) or 3. Turn on the purge after the outboard Fill and Drain (F&D) valve closes to eliminate the possibility of ingesting the unwanted substance. (Operational Sequence modifi

8、cation) Some of the above recommendations are an operational process change based on the design configuration of this specific system. The principles of this lesson should be applied to any design regardless of configuration.) Evidence of Recurrence Control Effectiveness: N/A Documents Related to Le

9、sson: N/A Mission Directorate(s): Exploration Systems Space Operations Additional Key Phrase(s): 1.Cryogenic Systems 1.Flight Operations 1.Vehicle concepts Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1.Level II/III requirements definition 1.Launch Systems 1.Propulsion 1.Launch Vehicle 1.Spacecraft Additional Info: Project: Shuttle / New Launch Vehicle Approval Info: Approval Date: 2012-03-19 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-