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Orion Heat Shield Bond Quality Inspection: Complete Inspection System

The NASA Orion space capsule must survive the rigors of atmospheric reentry; therefore, the heat shield must be inspected before launch. The nature of the thermal protective material that makes it perform so well also makes it difficult to inspect nondestructively. Other techniques are capable of detecting air voids, but the kissing unbond—that is, an unbond with zero thickness—cannot easily be detected. In previous work, the authors described the evolution of a customized pulse-echo ultrasonic inspection technique capable of detecting voids and kissing unbonds both in a laboratory environment and on the actual heat shield. The technique was capable of inspecting 90% of the heat shield where the heat shield is mostly flat. In the current paper, the technique is completed to inspect the most challenging last 10% of the heat shield, which includes regions of large curvature such that the echo may not return to the transducer. The paper describes the justification of using phased array and the implementation for data acquisition, data reconstruction, and analysis of generated C-scans. Additionally, results are discussed showing the ability of the new system to detect unbonds on a strongly curved specimen.

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