New materials and related fabrication processes for hot structures on RLV'S

The next generation of Reusable Launch Vehicles (RLV's) will implement the substitution of traditional blunt bodies with new aerodynamic configurations characterized by slender profiles with sharp leading edges. The main advantage of this redesign of hypersonic space vehicle is represented by enhanced maneuverability and improved cross range capability and consequently increased mission safety, In addition the reduction of wave drag in the ascent phase will reduce the costs of the payload deployment. The real possibility to adopt sharp profiles is strictly related to the selection and availability of materials with suitable performance. In fact at hypersonic speeds, sharp edges of slender configurations reach values of the surface temperatures much higher than any temperature allowable by traditional thermal protection system (TPS) and more the geometrical radius of curvature decreases, more the heat flux at leading edge increases. Recent research and developments of a new class of materials named Ultra High Temperature Ceramics (UHTC) seems to offer the right chance to fabricate hot structures for RLV's applications which can withstand temperatures above 2000°C. This paper deals with a new process technology based on the employment of zirconium diborides ceramic matrix composites that appropriately modified and reinforced can be considered, as our previous numerical investigation showed, very promising candidate materials for the fabrication of hot structures of slender bodies such as nose cap, wing leading edges, etc. The materials developed in the frame of a consistent scientific collaboration coordinated by CIRA, and involving Centre Sviluppo Materiali SpA (CSM) and University of Rome "La Sapienza", have been thermally and mechanically characterized in order to assess their applicability to a specific space mission requirements. Copyright © 2003 by the International Astronautical Federation. All rights reserved.