A recent European rocket engine, dubbed Greta, has successfully completed its first hot-fire test campaign, marking a significant step forward in sustainable space propulsion. Developed by ArianeGroup for the European Space Agency (ESA), Greta demonstrated stable operations, including controlled shutdowns and multiple restarts, at a test facility in Trauen, Germany. The engine’s development focuses on a 5 kN thrust class, designed for reliable re-ignition – a crucial capability for various space missions.
The Greta project is part of ESA’s Future Launchers Preparatory Programme (FLPP), and represents a shift towards more environmentally friendly rocket propellants. Unlike traditional engines that often rely on monomethyl hydrazine, Greta utilizes a combination of hydrogen peroxide and ethanol. This alternative propellant mix offers a lower carbon footprint, addressing growing concerns about the environmental impact of space travel. The successful test campaign, which ran from July to November 2025, saw the engine fire continuously for over 40 seconds at a time, according to the ESA.
The engine’s design incorporates innovative manufacturing techniques. Greta’s 30-cm high combustion chamber is constructed using a laser melting process, building up layers of metal powder. This allows for the creation of complex internal structures, such as intricate cooling channels, that would be difficult to achieve with conventional methods. These channels are positioned close to the chamber wall, which experiences temperatures exceeding 2,000°C during combustion, ensuring efficient heat management.
The testing phase utilized a newly developed, low-cost, and versatile mobile test stand equipped with instruments to measure critical data like pressure and temperature. This data will be instrumental in further optimizing the engine’s performance. ArianeGroup, based in Ottobrunn, Germany, is the prime contractor for the Greta project, which was supported by a €3 million contract aimed at advancing knowledge in hydrogen peroxide engine technology.
Potential Applications for the Greta Engine
The versatility of the Greta engine opens up possibilities for a range of space applications. ESA highlights its potential use in lunar landers, providing a reliable and restartable propulsion system for descending to and ascending from the lunar surface. The engine could be integrated into kick stages, such as Astris, which is currently under development as an add-on for Europe’s Ariane 6 rocket. Astris is designed to provide additional propulsion for deploying satellites into specific orbits.
On February 6, 2026, a new phase of the Greta project commenced with ArianeGroup, focusing on refining the engine design for flight readiness. This next stage will involve collaboration with several subcontractors: Safran Aero Boosters in Belgium, the Institute of Aviation in Poland, and InPraise Systems from the Czech Republic, who will contribute to the development of a flight-like motor design. ArianeGroup is leading the effort to incorporate lessons learned from the initial test campaign and previous function.
The next evolution of Greta is slated for testing on the same mobile test bench in Trauen at the end of 2027. This continued development underscores Europe’s commitment to advancing sustainable and reliable space propulsion technologies. The Greta engine represents a significant step towards a greener future for space exploration, offering a viable alternative to traditional, less environmentally friendly rocket engines.
The successful completion of the initial test campaign and the launch of the next development phase demonstrate the ongoing progress of the Greta project. As the engine moves closer to flight readiness, it promises to play a crucial role in enabling future lunar missions and enhancing the capabilities of European launch systems.
Readers interested in following the Greta project’s progress can find updates on the European Space Agency website and through ArianeGroup’s official channels. The next major milestone is scheduled for the end of 2027, when the refined engine will undergo further testing in Trauen, Germany.
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