Hitos: A high-temperature optical fibre-based sensor system for space structures

Space vehicles intended for transport applications like launchers, reusable modules, ATV's and manned capsules demand increasing complexity and quality levels to face the growing market needs. With the goal to achieve a more reliable and affordable access to space, ESA started in 1999 the Future Launchers Technology Programme (FLTP) focused on the development of technologies related with re-usability of launchers and coordination of national efforts. Since then, the technologies applied to Health Monitoring Systems (HMS) for vehicle structures were strongly promoted as a fundamental tool to achieve an effective cost reduction without compromise of safety. To achieve the implementation of a reliable and effective Health Monitoring system, a broad range of sensors have to be distributed along the structure to measure different flight parameters like thermal profile, pressure and friction, strain etc. The goal of the HiTOS project was to propose a substitute of conventional temperature (thermocouples) and strain (strain gauges) sensors, thanks to the new generation of Optical Fibre-based sensors arising from an evolution of conventional Fibre Bragg Gratings: The so called Regenerated Fibre Bragg Gratings or rFBG. Along this contribution, the optical fibre temperature and strain sensors based in Bragg Gratings are introduced, and the different advantages and drawbacks are discussed for the specific case of structural monitoring in a Space vehicle. Experimental tests over a complete demonstration set-up are described together with the relevant results.