A model thermal protection system (TPS) was designed by bonding ceramic porous tiles to 2.2 and 3.5 mm thick 2124-T351 aluminum alloy plates. One of the goals of the present work was to investigate the potential of detecting simulated defects using guided waves. Simulated defects consisted of cracks, voids and delaminations at the tile-substrate interface. Cracks and voids were introduced into the porous tiles during the fabrication of the TPS. Delamination was created by cutting the gluing tape between the tile and the aluminum substrate. Guided wave propagation studies were conducted using the pitch-catch approach, while changing the angle of strike and the frequency of the transducer excitation to generate the appropriate guided wave mode. The receiver was placed at a distance so that only the guided waves were received during the immersion experiment. The delamination defect could be conclusively detected, however the presence of the imperfect bond between the tiles and the substrate interfered with the detection of the simulated cracks and voids in the porous tiles.