Millimeter Wave Detection of Localized Anomalies in the Space Shuttle External Fuel Tank Insulating Foam and Acreage Heat Tiles

Undesired manufactured or in-service produced anomalies in the form of voids in the SOFI and unbonds in the heat tiles can significantly reduce their designed effectiveness. Additionally, unbonds in the heat tiles may cause their complete separation from the fuselage exposing it to extreme heat. Millimeter wave NDT methods are viable candidate for life-cycle inspection of the SOFI and the acreage heat tiles of the Space Shuttle fleet. The results of these investigations described in this paper clearly showed the utility of these methods for detecting localized anomalies in thick SOFI and acreage heat tiles. These methods are fast and robust and the systems used to produce these images are small, real-time and provide a significant amount of useful information about the nature of an anomaly (e.g., size, location, etc.) without the need for complex image processing. This investigation is currently ongoing and additional results will be provided in the final paper