Preliminary tests for an intelligent thermal protection system for space vehicles

Re-entry in planetary atmospheres is one of the most challenging environments to be faced by an aerospace structure. Presently space agencies are studying and developing programs to reduce launch costs by developing a new generation reusable launch vehicles. In fact a significant portion Of the launch cost, for those vehicles, is represented by maintenance, non destructive testing and personnel involved in round operations. For instance NASA and Lockeed Martin are leading the VentureStar program, where the real time health monitoring is considered an important aspect, while ESA has now finished a preliminary analysis for different reusable launch vehicle configurations. Fiber optic sensors which can be embedded into structural components can provide an efficient means for fast and reliable structural health monitoring In this paper the possibility of embedding fiber optic sensors into materials subjected to particularly critical thermal treatments is verified. Several specimens of metal alloys and carbide based powders with embedded optical fibers have been prepared by the high pressure high velocity oxy fuel technique. The tests have proven the feasibility of the embedding with the above mentioned technology which exposes the fibers to quite a severe environment during the deposition. Micrographic analysis and optical transmission tests have been carried out on the sprayed specimens.