Description of Driving Event:
Certification of Block II SSME Testing at 109% for Intact Abort Scenarios
Lesson(s) Learned:
The Block II engine will be certified for operation at 109% power level only for abort situations. Accordingly, the test program provides only limited cumulative test time at this thrust level.
Recommendation(s):
After completion of the current planned Block II certification test program, conduct a certification extension test program that will demonstrate the highest thrust level for safe continuous operation achievable by the Block II configuration. This program should attempt to achieve at least the 109% power level.
Evidence of Recurrence Control Effectiveness:
The Block II program was developed to "improve the safety, reliability, and robustness of the SSME" by providing lower operating temperatures, pressures, shaft speeds, and other critical parameters. An increase in operating power level from 104% to 104.5% will offset some of the weight gain of Block II. The Block II SSME was never intended to increase Space Shuttle ascent performance or increase payload capability to orbit. However, additional performance has been accepted for a few specific missions at the cost of some of the improved safety margin. There is a commitment that the ISS flights will provide 106% engine power level certification to achieve mandatory critical payloads to orbit. The Block II certification will also provide a 109% intact abort capability, which will allow the vehicle system to better optimize abort scenarios. Implementation recommendations for use of 109% throttle for intact aborts will be made by the Shuttle operations element once certification is complete.
Documents Related to Lesson:
N/A
Mission Directorate(s):
- Space Operations
- Exploration Systems
Additional Key Phrase(s):
- Aerospace Safety Advisory Panel
- Policy & Planning
- Safety & Mission Assurance
- Spacecraft
- Test & Verification
Additional Info:
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