Phoebus project advances composite hydrogen tank testing for Ariane 6

The European Space Agency (ESA), in collaboration with ArianeGroup and MT Aerospace, is progressing with the Phoebus project to explore replacing metallic cryogenic tanks on the Ariane 6 upper stage with carbon-fibre reinforced-plastic (CFRP) tanks. The initiative could reduce launch mass by several tonnes, but introduces complex challenges in maintaining integrity at extreme cryogenic conditions.

Hydrogen, the smallest molecule in the Universe, must be cooled to - 253 C for use as rocket fuel, posing a major materials challenge. Carbon composites typically become brittle and prone to microcracking at such low temperatures. The Phoebus team therefore had to devise new methods not only for tank design but also for measuring hydrogen leakage rates-since no existing equipment could detect le