Nondestructive Evaluator for Polymer Ablatives (NEPAL)

Materials for thermal protection are required to protect structural components of missile launching systems, space vehicles during the re-entry stage, and solid rocket motors (SRMs). Polymer resins that have high char retention (e.g., phenolic resins) are the most common matrices in the composite materials for rigid thermal protection systems (TPSs) due to their tunable density, lower cost, and higher heat-shock resistance. One such application of the polymer TPS is in protection of missile launch systems from extremely hot exhaust gases. Missile launch systems integrated with a ship structures, such as the Mk 41 vertical launch system (VLS), need the rocket exhaust to be diverted vertically upwards through the plenum and the uptake. These sections are lined with ablative polymers of varying thicknesses to protect the structure from intense heat from rocket exhaust. The erosion of the ablative panels determines the life of the module structure. Currently, life prediction of these ablative materials are based on pre-determined in lab tests. However, as these multipurpose VLSs launch a variety of increasingly powerful rockets, the predetermined life estimations are inaccurate. A new non-destructive examination technique is needed for in situ determination of the remaining useful life of ablative lining.