Prometheus: Europe’s reusable rocket engine fires at Germany’s upgraded P5 test bench

On Thursday, October 29, 2026, an engine and a test bench were tested at the same time at Lampoldshausen in Germany. The European Space Agency’s (ESA) reusable Prometheus engine completed several hot-fire tests (runs with real combustion) at the P5 test bench, which had been upgraded to feed methane engines. ESA announced on Friday, November 6 that the tests proved that both the upgraded bench and the engine’s new manufacturing techniques work.

Prometheus is a low-cost engine that burns liquid oxygen and liquid methane. It was designed to fit various reusable rocket stages, to relight in flight and to be used on many flights. Its power is similar to that of the Vulcain 2.1, the largest European engine in service today, which powers the Ariane 6. ESA supports the programme through its Future Launchers Preparatory Programme, with ArianeGroup as prime contractor, and the first engine is used on Themis, ESA’s reusable rocket demonstrator.

Why methane

The choice of methane has specific reasons. It does not need to be chilled as much as liquid hydrogen, allows operation without expensive helium, and sealing is easier to achieve. It performs better than kerosene and leaves no soot, a problem for engines that must be reused. That lowers the cost of both the engine and the rocket.

A chamber built by cold spray

The second test concerned the combustion chamber. The new Prometheus chamber was built by cold gas spray, an additive manufacturing method, that is, “printing” parts from metal powder: the powder is fired at high speed onto the chamber body and bonds firmly to its surface. Such techniques cut production time, simplify the making of complex parts and reduce cost. The project’s goal is for the engine to be produced faster and to cost ten times less than the previous generation of 1,200 kN (kilonewton, a unit of thrust) engines. Four Prometheus engines are planned to be built in succession.

In the tests the engine showed something else as well: it achieved multiple restarts without a high-pressure start-up system, relying only on its inlet pressures. ESA calls this a European first for an engine of this class. Repeated ignitions have a history: on June 20, 2025, at ArianeGroup’s PF20 test bench in Vernon, France, a second engine achieved four successive ignitions, also a European first for this type of engine. Prometheus tests had begun in 2022 at the same French site.

The P5 bench

P5 is owned by ESA and operated by the German Aerospace Center (DLR). It is one of the largest cryogenic propulsion test facilities in Europe, that is, for engines using liquefied propellants kept at extremely low temperatures. It was built for the Ariane 5 development programme and has qualified the Vulcain engines of the Ariane family, as well as the entire upper stage of the Ariane 6. Prometheus is the first engine fired there with liquid oxygen and liquid methane. The upgrade allows a quick return to oxygen and hydrogen feed, so P5 can go on testing liquid-hydrogen engines.

“Repeated engine starts and lower manufacturing costs are crucial to increasing launcher supply and diversifying Europe’s access to space,” said ESA’s Director of Space Transportation Geraldine Naja. “Prometheus validated key technologies and inaugurated the bench’s new capability to run on methane, so that more European engines can be tested and prove their worth, thanks to the outstanding work of all the teams in Germany and France.”

The next step is an improved version of the engine, the “Mark 2”, whose first test phase will take place at ArianeGroup’s test centre in Vernon. France, Germany, Sweden, Belgium, the Netherlands and Switzerland take part in the programme, with ArianeGroup, GKN Aerospace, Safran Aero Boosters and APP as the main partners.

ESA is moving in parallel on other European space projects. In late October it ordered four more second-generation Galileo satellites, while at the European student rocketry challenge the White Noise team of the National Technical University of Athens won two awards.