LOX test rig for rocket fuel tanks made of CFRP
Together with MT Aerospace, Grasse Zur Composite Testing has developed a test rig for LOX („liquid oxygen“) testing. The main goal of the Phoebus project is to increase the payload performance of the launcher by more than two tonnes by reducing the mass of the upper stage through a new design and lighter materials. At the same time, Phoebus also aims to reduce production costs.
Carbon-fibre reinforced plastic (CFRP) materials, or carbon composites, allow new architectures and combinations of functions otherwise not possible using metallic materials. CFRP is lightweight and dark in appearance and will be used for the cryogenic propellant tanks as well as primary and secondary structures of Phoebus, hence the name ‘black’ upper stage. Furthermore, their manufacturing process allows for an integrated layout that results in fewer parts compared to a comparable metallic configuration, thereby reducing production and assembly costs.
With the help of the test rig developed by Grasse Zur Composite Testing, the CFRP tanks are cooled down to approx. -180 °C. The CFRP tanks are then subjected to an internal pressure via a fully remote-controlled system. Four independently switched impact pendulums realise the application of impacts on the upper and lower end cap of the tank („boss“). The tests, which were carried out at an open-air test site in Germany, show that lightweight, carbon fibre reinforced plastic is strong enough to replace metal used in upper-stage rocket structures. This is an important milestone in Europe for the development of a prototype of a highly-optimised ‘black’ upper stage, Phoebus, a joint initiative by MT Aerospace and ArianeGroup, funded by ESA’s Future Launchers Preparatory Programme.