Replaying the Fracture Process of a Failed Space Shuttle Orbiter Thruster
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In order to rationalize the continued safe-flight of the Space Shuttle Orbiter fleet, root cause was urgently sought for the explosive failure of a Space Shuttle Orbiter reaction control system thruster that occurred on the test stand. To confirm the postulated failure scenario, the direction of crack propagation in the fuel chamber wall had to be determined. It was also necessary to determine if any of the failed thruster injector materials had been embrittled over time. Conventional fractography could not provide conclusive answers, but a quantitative 3D analysis of the topographies of the opposing fracture surfaces was able to reconstruct the entire fracture process and thereby confirm root cause. The work shows how a failure event can be replayed through fracture surface topography analysis, FRASTA, and how information on load conditions, relative crack growth rates, and fracture mechanics parameters may be extracted from fracture surfaces.
KeywordsFailure mechanism Quantitative fractography Failure analysis Explosion Cracking behavior
Assisted by many of their NASA colleagues, Darren Cone of the NASA White Sands Test Facility, Las Cruces, NM, and Erica Worthy, Bud Castner, James Martinez, Joseph Durning, and Shayne Westover of the NASA Johnson Space Center, Houston, TX analyzed the thruster failure and successfully determined root cause and contributing factors. The authors are grateful for their helpful comments on the draft of this manuscript. Bob Piascik, leader of the NESC Materials Technical Discipline Team, saw the potential of FRASTA in this failure analysis investigation and arranged for financial support.
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