A new European rocket engine, dubbed Greta, has successfully completed a hot-fire test campaign, marking a significant step towards more sustainable and versatile space propulsion. Developed by ArianeGroup for the European Space Agency (ESA), the engine demonstrated stable operations, controlled shutdowns, and multiple restarts during testing at ArianeGroup’s Trauen site in Germany.
The Greta project focuses on a 5 kN thrust class engine designed for restartability, a crucial capability for missions requiring precise orbital adjustments. Unlike many traditional rocket engines in this thrust range that rely on monomethyl hydrazine – a highly toxic propellant – Greta utilizes a combination of hydrogen peroxide and ethanol, offering a more environmentally friendly alternative with a lower carbon footprint. This focus on sustainable propellants aligns with growing efforts to reduce the environmental impact of space travel.
The recent test campaign, conducted between July and November 2025, involved multiple ignitions and sustained firing periods exceeding 40 seconds. These tests were performed on a newly developed, low-cost, and versatile mobile test stand equipped with instruments to measure critical parameters like pressure and temperature, providing valuable data for engine optimization. The engine’s combustion chamber, measuring 30 centimeters in height, was manufactured using laser melting production techniques – a process where metal powders are fused together layer by layer, enabling the creation of complex internal cooling channels crucial for withstanding temperatures exceeding 2000°C during combustion.
Innovative Manufacturing and Cooling
The employ of laser melting allows for the creation of intricate geometries that would be difficult to achieve with conventional manufacturing methods. Specifically, Greta’s cooling system utilizes these complex channels to circulate fluid as close as possible to the combustion chamber wall, effectively dissipating heat and protecting the engine from damage. This advanced cooling technique is essential for reliable and repeated engine operation.
Future Applications and Development
ArianeGroup, based in Ottobrunn, Germany, is the prime contractor for the Greta project. The completed test campaign was part of a €3 million contract aimed at expanding knowledge in the design and operation of hydrogen peroxide-fueled engines within this thrust class. Potential applications for Greta include powering lunar landers and serving as a kick stage for larger rockets, such as the Astris stage currently under development for Europe’s Ariane 6 launch vehicle, as noted by the European Space Agency.
On February 6, 2026, ArianeGroup initiated the next phase of the Greta project, focusing on refining the engine design for flight readiness. This next stage will involve collaboration with subcontractors including Safran Aero Boosters in Belgium, the Institute of Aviation in Poland, and InPraise Systems from the Czech Republic, who will contribute to the production of flight-like motor components. The evolved Greta engine is slated for testing on the same mobile test bench in Trauen by the end of 2027.
This development comes as the European space industry continues to innovate in propulsion technologies. Just last year, Starion celebrated the successful launch of the Copernicus Sentinel-2C satellite, highlighting the ongoing commitment to Earth observation and space infrastructure, as reported by Starion Group. The advancements in engine technology, like those demonstrated by Greta, are crucial for enabling future missions and maintaining Europe’s position in the global space landscape.
The Greta engine represents a significant step towards greener and more flexible space propulsion systems. With ongoing development and testing, this innovative engine promises to play a key role in future lunar missions and enhance the capabilities of European launch vehicles. Share your thoughts on the future of sustainable space travel in the comments below.
