Manufacture of photonic Thermal Protection Systems for NASA spacecraft BSc thesis, MSc thesis Motivation: Space vehicles have to withstand great heat exposures during atmospheric entries. With velocities that can reach 45,000 km/h, the radiation flux emitted by the gas shock layer can represent over 50% of the total incoming heat flux in the most extreme cases. Current thermal protection systems are focused on managing the convective and conductive heat fluxes reaching spacecraft. However, the protection against the radiative component has not been tackled yet and is critical for future planetary landings. Methodology: The goal of this project is to add a reflective function to state-of-the-art heat shield composites, namely Phenolic Impregnated Carbon Ablators (PICA) [1]. Our approach consists in synthesizing 1D and 3D photonic crystals, which display reflection band gaps, shaped as micro modules. The integration of such modules in the composite will be tuned to preserve its intrinsic thermal and mechanical properties. Testing under simulated atmospheric entry conditions will then be performed, characterizing the final product as an optically active thermal protection system. More specifically, this ETH-NASA agreement [2] comprehends the following subprojects: synthesis of 1D and 3D micrometric photonic structures; study of their reflectance in composites; reflectance enhancement of the carbon foam; assembly and characterization of PICA. Depending on the subproject, SEM, EDX, XRD, mechanical tests, reflectance and density/porosity measurements will be used as characterization techniques. If you are motivated, please contact us to know more about the available projects.

Figure: (a) Space Shuttle heat shield ceramic tiles (nasa.gov); (b, c) PICA micrographs [1]; reflective platelets under (d) light and (e) electron microscopy [3] displaying interference color; (f) reflective platelets composite; (g) modified carbon fibers; (h) representation of Orion’s reentry into Earth’s atmosphere (nasa.gov); (i) reentry test (spacex.com); (j) post-test PICA sample [4]. Contact information: Erik Poloni (Complex Materials) – erik.poloni@mat.ethz.ch Florian Bouville (Complex Materials) – florian.bouville@mat.ethz.ch References [1] Agrawal et al., J. Spacecr. Rockets 50, 735–741 (2013). [2] http://photonicna.ethz.ch/partners/index-partners.html [3] Pfaff & Reynders, Chem. Rev. 99, 1963–1981 (1999). [4] Milos & Chen, J. Spacecr. Rockets 47, 2009 (2010).