Prometheus reusable rocket engine reaches new development milestone with hot-fire test on DLR's P5 test bench

On 29 October 2026, the Prometheus reusable rocket engine reached a new development milestone with the validation of its operation integrated with the P5 test bench owned by the European Space Agency (ESA) and operated by the German Aerospace Center (DLR) at Lampoldshausen, Germany.

This success on the DLR's P5 test bench represents a key step in the engine's development.

"Reusability is more important than ever in space transportation. The success of these new tests on the Prometheus reusable rocket engine is a key step forward for ArianeGroup and for Europe," said Philippe Clar, Head of Space Transportation Programmes at ArianeGroup. "This new campaign demonstrates the ability of our teams in France and Germany, working with our partners, to develop solutions that meet market needs and break new ground, with the aim of giving Europe sovereign capabilities in reusable space technologies."

Reflecting the spirit of innovation behind the Prometheus programme, the test also demonstrated the engine's ability to start without a starter system. This is a first in Europe for a gas-generator-cycle engine in the 100-tonne thrust class.

The campaign also included the first test of a key engine component manufactured using a new 3D-printing process known as Cold Gas Spray (CGS). This is the first combustion chamber to be manufactured using the process, in which metal powder is sprayed at high speed onto a component and bonds firmly to the surface. Additive manufacturing, or 3D printing, is central to the Prometheus programme. By redesigning its production processes, ArianeGroup uses 3D printing extensively. This helps shorten production times, simplify the manufacture of complex components and reduce costs.

The campaign also validated the German Aerospace Centre's (DLR) P5 test bench for long-duration hot-fire testing with liquid oxygen and methane (methalox).

The campaign marks another step in the ongoing development of the Prometheus reusable rocket engine. The next campaign will test an improved version of the engine known as Mark 2 and will take place at ArianeGroup's Vernon test centre.

Prometheus is a reusable rocket engine being developed by ArianeGroup as prime contractor on behalf of the European Space Agency (ESA). Designed to power future European launchers, this variable-thrust engine in the 100–120-tonne thrust class runs on liquid methane (LCH₄) and liquid oxygen (LOX).