The fluidic and electrical operations of these test cryogenic tanks and ground equipment have been validated ahead of time to de-risk hot firing tests with the Prometheus engine under integration on the same test bench.

“This is an exciting time. In the next step for Themis, we will combine two key building blocks for the future of space transportation systems in Europe. Both are developed within ESA’s Future Launchers Preparatory Programme. Themis, ESA’s flagship reusable first stage vehicle and Prometheus, its next-generation low-cost reusable engine,” said Yann Tincelin, Space Transportation Systems Project Engineer at ESA.

Prometheus is an ultra-low-cost engine built extensively through additive layer manufacturing. This has reduced the estimated cost of production by a factor of ten compared to Ariane 5’s core stage Vulcain engine. It features variable thrust and multiple ignitions and is therefore suitable for core and upper rocket stages.

The fuel used for Prometheus is liquid oxygen–methane which is highly efficient, allows standardisation and operational simplicity. Methane propellant is also widely available and easy to handle which will minimise ground operations before and after flight. 

Prometheus technologies are likely to be incorporated in improvements made to rocket engines currently in operation.

European industry steps ahead

In parallel to the ongoing activities for ground hot firing tests, Themis flight demonstrators are also under preparation. A European ecosystem of industry partners is forging ahead to develop and manufacture components.

Flight version steel cryogenic tanks are being manufactured. Low-cost optimised thrust vector actuation systems for Prometheus are being designed. The landing legs system has entered its final design stage before manufacture. All these enabling building blocks will come together for integration on the Themis flight demonstrator for low-altitude hop-tests in Kiruna, Sweden.

Meanwhile, the final design of ‘Launch complex 3’ at Kiruna Esrange Space Center has been reviewed by the Swedish Space Center and ArianeGroup, to prepare for the first Themis hop-tests in Sweden in 2023.

This incremental progress is built on early evaluation at each intermediate step with focus first on technical de-risking of Prometheus integration into a fully operational stage, then on flights increasingly representative of operational launch vehicles.

The final steps will be flights from Europe’s Spaceport in French Guiana in 2025 to demonstrate ascent to high altitude, reentry, landing, refurbishment and reuse, with an integrated Themis demonstrator equipped with three Prometheus engines and all the required subsystems for enabling stage recovery.

Quelle: ESA

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Update: 21.09.2025

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Themis stands on the launch pad

In brief

• The first model of ESA’s reusable rocket demonstrator Themis is standing on its own legs at its launch pad in Kiruna, Sweden.
• Themis is set to be the first European demonstration of a full-scale vertical take-off and landing rocket element that uses cryogenic propulsion.
• This is the first time the rocket stage demonstrator has had its four legs installed, now the demonstrator is fully assembled.

In-depth

The first model of the European Space Agency’s (ESA) reusable rocket demonstrator Themis is standing at its launch pad in Kiruna, Sweden.

Themis is investigating technologies to demonstrate rocket stage recovery and reuse. The first vehicle model – called T1H for Themis-1 engine-Hop – arrived at the Esrange Space Center over the summer, with its landing legs shipped separately. The legs are now installed, and T1H is standing tall.

Themis is set to be the first European demonstration of a full-scale vertical take-off and landing rocket element that uses cryogenic propulsion.

T1H is 30 m tall standing on its legs and 3.5 m wide, holding the necessary technologies for the low-altitude take-off and landing tests it is set to perform. Themis uses the Prometheus engine, almost as powerful as the Ariane 6 rocket’s main engine – but Prometheus can restart in flight and throttle its thrust to ensure a soft and safe landing.

Themis was transported by truck over 3000 km from the ArianeGroup integration building in Les Mureaux, France, to the Swedish Space Corporation’s Esrange Space Center in the north of Sweden.

After final check at a Kiruna assembly building, Themis was moved to the pad in August and hoisted onto a tool to allow the swift assembly of its four legs. This is the first time the rocket stage demonstrator has had its four legs installed, now the demonstrator is fully assembled and ready for its wet dress-rehearsal preparing for a first flight.

Themis, the first European reusable main stage’s full-scale demonstrator, was developed by ESA’s future Space Transportation preparation programme, with ArianeGroup as prime contractor and multiple European industrial partners. Themis’s first flight campaign with T1H, will be realised in the scope of Horizon Europe project Salto, funded by the European Union. The Salto project is responding to the EU Space Research and Innovation Programme and is implemented by 25 consortium partners from 12 European Union countries.

Quelle: ESA