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 leaks accurately under these extreme cryogenic conditions.
Initial 60-litre demonstrator tanks have already proven CFRP's ability to hold liquid hydrogen without leakage. Building on this milestone, engineers are now constructing a larger 2,600-litre prototype tank measuring two metres in diameter. The inner pressure vessel was completed at MT Aerospace in Augsburg, Germany in September 2025, with full production due for completion in December. ArianeGroup will oversee the upcoming testing phase, including design and setup of the specialized test facility.
Testing will begin in April 2026 at ArianeGroup's Trauen site in Germany, where the hydrogen-filled tank will be gradually pressurized and cooled to operational extremes. The goal is to approach the cracking point without complete structural failure, enabling engineers to precisely map the onset of material stress. Multiple test cycles will generate data on pressure, temperature, and strain, helping refine designs for future lightweight cryogenic tanks.
Phoebus operates under ESA's Future Launchers Preparatory Programme (FLPP), which funds early-stage innovations for next-generation launch systems. By investing in high-risk, high-reward technologies such as CFRP cryogenic tanks, FLPP aims to reduce the development risks for Europe's future space transportation infrastructure.
Related Links
Future space transportation at ESA
Rocket Science News at Space-Travel.Com
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