A risk-assessment methodology for the Space-Shuttle external-tank welds

This paper presents a simulation model designed to evaluate the risk involved in deleting preproof test x-ray inspection of some welds on the Space Shuttle external tank (ET). The simulation model combines engineering and statistical models to evaluate the risk of a weld leak or burst during proof test and flight. Results of the model show that the risk due to the deletion of x-ray inspections is relatively high. This suggests that deleting the x-ray inspection would be a step in the wrong direction since the cost of failure during proof testing could be extremely high. Although this study addresses a weld inspection issue on the ET, the models developed can be applicable to other situations where weld risk assessment is needed