REG NASA-LLIS-6150-2012 Lessons Learned - Hydrogen Venting Potential Explosive Hazard.pdf

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1、Public Lessons Learned Entry: 6150 Lesson Info: Lesson Number: 6150 Lesson Date: 2010-11-1 Submitting Organization: MSFC Submitted by: Kristen Kinder Subject: Hydrogen Venting Potential Explosive Hazard Abstract: Passive pressure relief features can not adequately control the concentration of leakin

2、g gas. Description of Driving Event: In the Space Shuttle Program, hydrogen gas vented from the External Tank (ET) hydrogen tank to the facility flare stack through the ET Vent Arm System when the ET vent valve was opened. If hydrogen leaked at the ET/ground interface, the system was designed so tha

3、t hydrogen would leak into the purged Ground Umbilical Carrier Plate (GUCP) cavity, and then out into the atmosphere through the 5-inch slit in the refrigerator gasket. If the concentration in the GUCP cavity was above 40,000 ppm in the interface cavity, a Launch Commit Criteria (LCC) violation occu

4、rred, necessitating a launch scrub even though the ET vent valve was closed for tank pressurization. Lesson(s) Learned: Reliance on a passive slit in the refrigerator gasket to relieve the build up of hydrogen at a sensitive place on the launch vehicle creates a condition that reduces the probabilit

5、y of launch. A simple piping fix could reduce this risk if the lower cavity where leaking hydrogen gas can accumulate were designed to purge residual hydrogen to well below the critical level. This would prevent the condition where hydrogen in the GUCP cavity causes a launch scrub. Recommendation(s)

6、: 1. For future designs that vent hydrogen from vehicle to a facility flare stack, plumb the potential leaking hydrogen in the interface cavity back into the same system that sends the gas to the facility flare stack. 2. Do not assume passive pressure relief features can adequately control the conce

7、ntration of leaking gas, especially if the feature was designed to relieve pressure, and not maintain specific levels of gas concentration. Evidence of Recurrence Control Effectiveness: N/A Documents Related to Lesson: N/A Mission Directorate(s): Exploration Systems Space Operations Additional Key P

8、hrase(s): 1.Spacecraft Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1.Flight Operations 1.Vehicle concepts 1.Level II/III requirements definition 1.Launch Systems 1.Propulsion 1.Cryogenic Systems 1.Launch Vehicle Additional Info: Project: Shuttle / New Launch Vehicle Approval Info: Approval Date: 2012-03-16 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-