This study involves the development of a non-contact automatic method of measuring both the thickness and profile of nonconductive coatings applied to metallic substrates. A new system which uniquely combines two fundamental measurement techniques—eddy current position sensing, and laser optical triangulation—was designed. This Automated Coating Inspection System has been developed to replace manual inspection of the Thermal Protection System (TPS) on the External Tank (ET) of the Space Shuttle. The ET is a disposable fuel tank, 155 feet long and 28 feet in diameter. A coating of Spray on Foam Insulation (SOFI) is applied to the outer aluminum surface of the tank for both cryogenic insulation and aerodynamic heating protection. The inspection of the SOFI on the ET is used as an example for presenting a comparison between manual and the proposed automated inspection method.
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