Themis.

About Themis

The Themis programme is an ongoing European Space Agency programme carried by prime contractor ArianeGroup, aiming to develop a prototype reusable rocket first stage and plans to conduct demonstration flights. The prototype rockets will also be called Themis. As of 2025, two prototypes are being developed: Themis 1-Engine Hop (T1H) and Themis 1-Engine Evolution (T1E). Later, a three-engine variant (T3) will be built. First flight test of the first vehicle (T1H) are expected to take place at Esrange in early 2026. Themis is expected to provide valuable information on the economic value of reusability for the European government space program and develop technologies for potential use on future European launch vehicles. Themis will be powered by the ESA's Prometheus rocket engine. Eventually, lessons learned with Themis's development will pave the way for developing the European reusable launchers Maia and Ariane Next. Themis is distinct from a similar project CALLISTO under development by CNES, DLR, and JAXA.