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 FLPP. It rapidly reached intensive hot-firing testing and achieved a comprehensive technical evaluation of the cryogenic expander cycle. Improvement and harmonisation of the technology readiness level is now being performed.

Functional description

Expander cycle demonstrator

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 has 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.


The expander demonstrator project is a step towards the next-generation cryogenic upper stage engine in Europe. The industrial teams have gained enormous hands-on experience and knowledge, further developing skills and competencies.

The cryogenic expander cycle engine is at the crossroads of several preparatory programmes. The Vinci engine’s current design was chosen as the baseline propulsion for the Ariane 5 Mid-life Evolution (ME) project, which benefits directly from the experience gained during engine tests and from the up-to-date engine documentation.

The demonstrator project has also achieved the detailed technology readiness mapping of the cryogenic expander cycle engine, providing significant input for defining the specifications of future launchers.

Last update: 30 October 2012

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