Technical Challenges on Coatings for European Space Missions

The European Space Agency (ESA) as Europe’s gateway to space faces continuously challenges driven by its mission requirements. Those requirements encompass among others extreme temperature and radiation challenges – from cryogenic temperatures encountered during exploratory missions to hot temperatures encountered during launcher, entry, descent and landing missions. In this paper several specific examples will be shown where special coatings play a central role to master those challenges and to enable our space missions.

One set of examples will include two future ESA inner planetary missions, one named Solar Orbiter, the other one named BepiColombo. The latter is a collaboration with the Japan Aerospace Exploration Agency (JAXA) and is aimed at orbiting the planet Mercury. A challenging mission orbit with high heat loads coming from the approximately 450°C hot sub solar point of Mercury is a specific challenge. External materials are expected to reach up to about 550°C while irradiated with a UV/VUV intensity up to 13 times higher than in earth orbit. Examples showing the performed ground testing simulating up to 25000 esh for those missions will be shown.

Another (completely different) example will be given on one common conversion coating currently used on ESA spacecraft which is Alodine 1200; a commercial product that is hexavalent chromium-based. However, due to the environmental impact of hexavalent chromium and recent EU regulations enforcing the prohibition of the use of certain hazardous substances, there is a great need for hexavalent chromium-free anti-corrosion coatings.

ESA has partnered with the National Aeronautics and Space Administration (NASA) Technology Evaluation for Environmental Risk Mitigation (TEERM) for this project. In this paper results on the aluminium alloys 2024, 6061 and 7075 used as substrates, in combination with identified possible alternatives for hexavalent chromium-free surface treatments will be presented. Testing efforts include Salt spray resistance, damp heat and thermal cycling.