Weight savings requirements for the High Speed Civil Transport (HSCT) engine nozzle have motivated development of polymer matrix composite (PMC) and ceramic matrix composite (CMC) structural concepts for the nozzle secondary air ejector door. Initial trade studies of these concepts resulted in synthesis of a PMC sandwich door concept with CMC thermal protection system (TPS) as a promising candidate for further development. Thermal and structural analyses of this concept have been performed to permit a weight comparison with a baseline metallic door concept. A manufacturing plan has been developed to highlight producibility issues and support parametric cost estimating efforts. The final results show that the composite door concept has a modest weight advantage and a distinct cost disadvantage relative to the metallic concept. Risk mitigation and design recommendations have been developed to make the composite concept more attractive for future HSCT engine nozzle development efforts.