Phoebus is a European Space Agency (ESA) project together with ArianeGroup and MT Aerospace. It aims to assess the feasibility and benefits of replacing the metallic tanks on ESA’s Ariane 6 upper stage with carbon-fibre reinforced-plastic tanks. While this lightweight material offers the possibility of saving several tonnes of mass, such an approach has never been implemented before and presents significant technical challenges.

The central core of ESA’s Ariane 6 rocket runs on liquid oxygen and liquid hydrogen, two very different molecules, so the Phoebus project is developing and producing two versions of the same carbon fibre tank concept. This article focusses on progress made on the liquid oxygen tanks, more news on the Phoebus project is linked at the end of this article.

Liquid oxygen is cooled and stored to –180 °C, a highly reactive and possibly corrosive propellant. Phoebus has already proved it is possible to use carbon fibre tanks for liquid oxygen storage: small demonstration ‘bottle’ tanks have shown that even without a protective liner, carbon-fibre reinforced-plastic can hold oxygen in liquid form without leaking nor reacting.