The European Space Agency (ESA) and ArianeGroup have completed the first round of testing for their jointly developed new rocket engine, Greta, validating its stable operation capability. The engine's combustion chamber is manufactured using metal 3D printing, enabling structural designs difficult to achieve with conventional processes. Testing took place from July to November 2025 in Trauen, Germany. The Greta combustion chamber is a 30 cm tall laser powder bed fusion (LPBF) formed part with complex cooling channels directly integrated into the wall interior. The coolant circulates just millimeters from the combustion zone, withstanding combustion temperatures exceeding 2000°C. The propellant has been switched to a hydrogen peroxide and ethanol blend, replacing the previously widely used hydrazine-based propellants. Testing included continuous combustion exceeding 40 seconds, multiple restarts, and shutdown conditions, all of which performed stably. The next phase will invest approximately 3 million euros, partnering with Safran Aero Boosters, the Aviation Institute, and InPraise Systems, to advance the prototype toward a flight-ready engine. This case elevates the value of LPBF for aerospace hot-section components to a new level: integrated forming of cooling channels and structure means designs no longer accommodate manufacturing constraints but are driven by functional requirements. For the metal powder supply chain, the requirements for powder sphericity, oxygen content, and batch consistency in combustion-chamber-grade LPBF parts will tighten further as such projects move from prototypes to flight parts. Value for powder buyers: (1) Pay attention to batch stability and oxygen content metrics of superalloy powders for LPBF; aerospace combustion chamber orders tolerate far less powder inconsistency than general industrial parts; (2) Proactively evaluate supply sources for fine-particle-size, high-sphericity powders; forming 30 cm-class thin-walled complex channels places high demands on powder flowability; (3) Confirm powder reuse cycles and performance degradation data with suppliers; flight-part certification typically requires complete powder lifecycle records.