Expander cycle demonstrator
Launcher studies have shown clearly the need for a versatile, high-performance, cryogenic upper stage engine capable of delivering payloads to all kinds of orbits, ranging from low Earth orbit to exploration missions in deep space.
In 2006, the Vinci engine entered a three-year expander cycle demonstrator project as part of ESA's Future Launchers Preparatory Programme, FLPP. It rapidly reached intensive hot-firing testing and achieved a comprehensive technical evaluation of the cryogenic expander cycle.
Functional description
The expander cycle offers two main comparative advantages: an integrated cycle, using the entire propellant flow efficiently, and the simplicity and robustness of the start-up transient, owing to a limited number of subsystems.
The turbines of the propellant pumps are powered by the main hydrogen flow after it has been expanded in the combustion chamber regenerative channels. Therefore, there is no need for a secondary combustion device to power the turbines with hot gas.
Main achievements
The project achieved the first cryogenic reignitions and closed-loop regulation in European rocket propulsion, and demonstrated Europe’s expertise in the high-pressure hydrogen expander cycle.
The overall technology readiness of the technical roadmap was harmonised to reach TRL 6, with some progress remaining to be made in combustion chamber design, pump suction demonstration, endurance demonstration, sequence optimisation, mass, composite nozzle thermal effects and turbine dynamic seals.
Perspectives
The expander demonstrator project was a step towards the next-generation cryogenic upper stage engine in Europe. The industrial teams gained enormous hands-on experience and knowledge, further developing skills and competencies.
The Ariane 6 Vinci engine’s design was chosen as the baseline propulsion for the Ariane 5 Mid-life Evolution (ME) project, which benefitted directly from the experience gained during engine tests and from the up-to-date engine documentation.
The demonstrator project also achieved the detailed technology readiness mapping of the cryogenic expander cycle engine, providing significant input for defining the specifications of future launchers.
