Failure analysis of the Columbia space shuttle glass windshields

The silica glass windshields failed under brittle fracture conditions during the devastating destruction of the Columbia space shuttle. Macroscopic analysis and the use of a stereomicroscope on two fragments of the windows showed that each had one critical crack origin. The crack tips could be traced by the Wallner lines making up the mirror zones along the fracture surfaces of the samples. Particle impact zones along the fracture surfaces of the specimens implied that the windshields failed during breakup and were bombarded with debris during re-entry. X-ray photoelectron spectroscopy was used to identify the preexisting coatings found on the front and rear faces of the samples.