The preferred architecture is that of the Falcon 9 rocket (a reusable first stage landing vertically with a common engine model for the two stages) while using an engine burning a mixture of liquid methane and liquid oxygen.
More specifically, the two programmes were named "SALTO (reuSable strAtegic space Launcher Technologies & Operations) and ENLIGHTEN (European iNitiative for Low cost, Innovative & Green High Thrust Engine) projects," respectively.
[3] In May 2022, the "French Economy Minister Bruno Le Maire said SALTO and ENLIGHTEN would be operational by 2026", and ArianeGroup stated that the target date was achievable.
[3][needs update] As of May 2022[update], the SALTO project intended to carry out an initial flight test of a single rocket stage by mid-2024, using a Themis prototype first stage to validate the landing phase of the design.
The density of liquid methane is higher than hydrogen, which allows a mass reduction in the tank structure.