Cryogenic performance of a novel design of all-composite propellant tank with anti-leakage capability

In this study we developed a lightweight cryogenic propellant tank using carbon fiber-reinforced composite materials, which have significantly higher strength-to-weight ratio compared to metals. To further reduce weight, we utilized a collapsible mandrel assembly to manufacture a one-piece tank shell without a metal liner. The tank shell layers were laid up on the outer surfaces of the total assembly including the composite mandrel assembly and the bosses. The mandrel segments in the tank were separated and extracted through the boss opening after autoclave cure. New design concepts were implemented to prevent leakage in cryogenic environments. The bosses were also made of the composite materials to eliminate thermal expansion difference between the bosses and the co-bonded composite layers of the tank shell at cryogenic temperatures. Additionally, anti-leakage composite layers were applied to some areas of the inner surfaces of the tank to block potential leak paths between the bosses and the tank shell. More detailed descriptions about these were presented in the main text. We manufactured two scaled-down all-composite tanks and conducted a series of ambient and cryogenic pressure tests to validate our all-composite tank design. The results demonstrated a sufficient margin of safety against bursting and anti-leakage capabilities even in cryogenic environments. Our research efforts can contribute to weight reduction of space launchers and lunar landers, which can directly lead to noticeable increase of the payload.