Crystallographic oxide phase identification of char deposits obtained from space shuttle Columbia window debris

Char deposits on recovered fragments of space shuttle Columbia windowpanes were analyzed to further understand the events that occurred during orbiter reentry and breakup. The TEM analysis demonstrated that oxides of aluminum and titanium mixed with silicon oxides to preserve a history of thermal conditions to which portions of the vehicle were exposed. The presence of Ti during the beginning of the deposition process, along with the thermodynamic phase precipitation upon cool down, indicated that temperatures well above the Ti melt point were experienced. The stratified observations implied that additional exothermic reactions, expectedly metal combustion of a Ti–6Al–4V structure, had to occur for oxide formation. Results are significant for aerospace vehicles, where thermal protection system (TPS) breaches could cause material originally designed for substructural applications to be in direct path with reentry plasma.