CNES projects library

October 20, 2023


Prometheus is a very-low-cost engine that will run on methane, marking a significant break with today’s technologies. The first hot-fire tests were conducted in 2022 and the engine is scheduled to enter service by 2030.

Europe’s Ariane launcher has been powered since 1996 by the Vulcain engine. By 2030, a new engine called Prometheus (Precursor Reusable Oxygen METHane cost Effective propUlsion System) will be picking up the baton. Reusable up to five times and capable of delivering variable thrust up to 120 tonnes, Prometheus will burn oxygen and methane in place of oxygen and hydrogen.

Among methane’s many advantages as a rocket fuel, it is cheaper, easier to handle and remains liquid at almost the same temperature as oxygen. Six times denser than hydrogen, methane will also enable more-compact rocket stages, making them easier to recover for reuse. CNES is also looking at producing methane from biomass at the Guiana Space Centre.

From an economic perspective, Prometheus is aiming to reduce production costs tenfold with respect to the Vulcain engine—which has a unit cost of €1 million—thanks to a different architecture, extensive use of 3D printing and a production rate of 50 engines per year. From a schedule perspective, the goal is to equip the lower (with the Themis demonstrator) and upper stages of Europe’s future range of launchers—from micro-launchers to a new version of Ariane—by 2030.

Prometheus was conceived and designed by CNES and ArianeGroup between 2015 and 2017. Responsibility for the programme was handed over to the European Space Agency (ESA) at the Ministerial Conference in Lucerne in December 2016. ESA has tasked ArianeGroup with developing Prometheus and CNES is supporting the agency on project oversight, notably as Project Technical Officer on the joint ESA/CNES team. CNES is also participating as industry partner to pool the best talents and experience with a view to pushing the limits of disruptive innovation for the Prometheus project.

The first engine tests are being conducted at the Vernon facility on the THEMIS-1G test platform developed with funding from the government stimulus plan and under a CNES contract. The first full hot-fire test of the first M1 engine was completed on 22 June 2023.