• The Prometheus® and Themis demonstrator programs have made significant progress during the summer at ArianeGroup’s Vernon site.
• Following the first ignition campaign of the Prometheus^® engine on the Themis reusable stage demonstrator in June 2023, testing has continued regularly. The latest test, on October 20, ignited and ran the Prometheus® engine for 30 seconds.
• These tests of a complete stage running on liquid oxygen and liquid bio-methane are essential in order to develop the technological building blocks needed for Europe’s future reusable space launchers.
• At the same time, the roadmap for the Themis demonstrator is being followed in order to prepare for the flight tests. The Themis tanks are currently undergoing a series of tests to validate the flight subassemblies. The landing legs also underwent their first deployment tests. Finally, the major component parts of the vehicle have been received.
• The Prometheus® and Themis demonstrators are European Space Agency (ESA) programs for the development of reuse technologies in Europe, for which ArianeGroup is lead contractor.

The Prometheus® and Themis demonstrator programs made significant progress over the course of the summer. The firing test campaign for the Prometheus® engine on the Themis reusable stage demonstrator notably continued on a regular basis on ArianeGroup’s Vernon (France) site.

On June 22, ArianeGroup completed the first ignition campaign of Prometheus® on Themis, carried out with the support of the “France Relance”⁽¹⁾ recovery fund. During the last test in that campaign, the engine ran for a period of 12 seconds.

A second test carried out on September 23 completes the initial phase of the contract with the European Space Agency (ESA).

Then, a further firing test was conducted on October 20 with ignition and operation of the Prometheus® engine for 30 seconds followed by a re-ignition.

The aim now is to test operation of the engine throughout its thrust envelope during the coming months. The engine’s ability to vary its thrust is essential for the Themis stage to be able to return to Earth.

In parallel, the Themis reusable stage demonstrator roadmap is continuing. The ArianeGroup teams are now entering the first flight preparation phase. The next steps will validate the Prometheus® engine for the Themis flight envelope, prior to the flight tests in Kiruna, Sweden.

With regard to the Themis stage itself, significant progress was made in a number of key areas over the course of the summer.

The major parts of the vehicle have arrived at Vernon, notably the Multi-Engine Bay (MEB), a structure built by SABCA (Belgium) that will accommodate the three Prometheus® engines, and the Flight Control Bay (FCB) built by APCO Technologies (Switzerland), which will mainly accommodate the avionic equipment.

The Themis landing legs have also undergone their first deployment tests. These legs, built by Almatech (Switzerland), are scaled to support the stage’s return to Earth.

The Themis tanks are currently undergoing a series of tests in Vernon, in order to validate the flight subassemblies. The structure comprising the two tanks with a common base is a major component of the vehicle. This campaign comprises several filling tests with liquid oxygen (-183°C) and liquid methane (-160°C). The success of these tests is a crucial step in validating the utilization and behavior of the tanks prior to the flight tests.

All of these tests carried out in Vernon are covered by the development contracts for the Prometheus® and Themis demonstrators awarded to ArianeGroup by ESA. Once the various test campaigns have been successfully completed, the Themis stage will be integrated at ArianeGroup’s Les Mureaux site near Paris and readied for the flight tests.

The demonstrator will then be sent to Sweden for hop tests to be conducted at the Esrange Space Center in Kiruna, as part of the European Union’s SALTO (Horizon Europe) project.