European Space Agency programme to develop a prototype reusable rocket first stage
TheThemis programme is an ongoingEuropean Space Agency programme carried by prime contractorArianeGroup, aiming to develop a prototypereusable rocketfirst stage and plans to conduct demonstration flights. The prototype rockets will also be calledThemis. As of 2025, two prototypes are being developed:Themis 1-Engine Hop (T1H) andThemis 1-Engine Evolution (T1E). Later, a three-engine variant (T3) will be built.[1][2] First flight test of the first vehicle (T1H) are expected to take place atEsrange in early 2026.[3] 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.[4][5] Themis will be powered by the ESA'sPrometheus rocket engine.[4] Eventually, lessons learned withThemis's development will pave the way for developing the European reusable launchersMaia[6] andAriane Next.[7] Themis is distinct from a similar projectCALLISTO under development byCNES,DLR, andJAXA.[8][9]
On 15 December 2020, ESA signed a contract worth €33 million with ArianeGroup in France for the "Themis Initial Phase". This first phase of theThemis programme involves development of the flight vehicle technologies and test bench andstatic fire demonstrations inVernon, France. It also includes the preparation of the ground infrastructure at theEsrange Space Center inKiruna,Sweden, for the first hop tests and any associated flight vehicle modifications.[10][11][12] Two possible landing sites have been mentioned in discussions surrounding the project:[11] the formerDiamant launch complex, which will be used for the flight testing phase[13] and the Ariane 5 launch complex, which will become available after the transition from theAriane 5 toAriane 6. The estimated program timeline, as of December 2020[update], expected low-altitude hop tests in 2022 and a fullflight envelope test in 2025.[14] In November 2024, ESA has awarded a contract toArianeGroup to build a secondThemis demonstrator (T1E)[6] and announced that testing of theThemis main systems has been completed and the assembly of the first demonstrator was underway.[15]
In December 2021, ESA completed a series of tanking tests on the steel propellant tanks for Themis.[16] On 22 June 2023, the first hot-fire test of thePrometheus engine, as a part of theThemis first stage demonstrator, was successfully conducted in Vernon, France.[17] Landing leg testing began in July 2024.[18]ArianeGroup has brought the main elements ofThemis T1H together for the first time during a full-fit check inLes Mureaux, France in December 2024.[1]Themis T1H integration was completed at Les Mureaux in June 2025. The vehicle was packed and prepared for shipment[19] and on 27 June 2025, it arrived at theEsrange spaceport in Sweden.[20][21] In September 2025,Themis T1H had its four landing legs installed and ESA shared a photo of the vehicle standing at its launch pad atEsrange.[22][23]
