With the support of the European Space Agency, German aerospace company MT Aerospace has developed a unique design for a small-scale rocket fuel tank made of a carbon-fibre reinforced plastic. The tank can hold liquid hydrogen and oxygen without leaking and without the use of a metal liner.
By excluding metal, the novel fuel tank is much lighter. It also requires fewer parts to assemble and is a faster, cheaper alternative to other fuel tank designs, according to the ESA. Any way to reduce weight on a spacecraft is a boon, since more fuel is needed to launch heavier objects into orbit and beyond.
“This is a tremendous step forward. We have found a very specific carbon composite and processing method that will allow us to consider new architectures and combinations of functions for rocket upper stages which are not possible using metal,” Kate Underhill, a project manager in the Future Launchers Preparatory Program at the ESA, said in an agency news release.
The upper stages of rockets are important for high-altitude and in-space propulsion; switching the upper stage from aluminium to a carbon composite could yield an extra 2 tons of payload capacity, according to Daniel Neuenschwander, the director of space transportation for the ESA.
The new carbon-fibre reinforced plastic design was put through cryogenic stress tests, to see how the tank would fare in holding propellants chilled to -253˚C (-423.4 Fahrenheit). “Metal is leak-tight. To recreate the same property with carbon composite required a complex weave of black carbon fibre and a special resin. The material resisted cryogenic temperatures, pressure cycles and reactive substances over a number of separate tests,” Underhill said.
Ultimately, data from tests of the innovative design will be applied to the final look of the ESA’s Phoebus upper stage rocket for the Ariane 6 launcher. Phoebus will have nearly 3.66 m-wide hydrogen and oxygen tanks made of carbon-fibre reinforced plastic, and the material will also be applied to the interface between the tanks and the upper stage’s outer layer. Phoebus will be tested with cryogenic fluids in 2023, according to the ESA.
This team isn’t the only one trying out unconventional materials for spacecraft. Engineers in Finland have built and tested a wooden satellite prototype that they say will be a proof-of-concept for future nano-satellites with few to no metal components.