Eplus3D partnered with the student-led UCL Rocket team from University College London (UCL) to design, 3D print, and test a regeneratively cooled, bipropellant rocket engine for the Race 2 Space 2025 competition in the UK. The team is one of six UCL Racing (UCLR) teams with the university’s Mechanical Engineering department, and Eplus is the technical manufacturing partner for the Excelsior engine project, offering DfAM consultations and using LPBF at its German facility to print the engine’s injector components and thrust chamber out of AlSi10Mg on the EP-M400S quad-laser printer. There were several technical challenges the team faced, including tight dimensional tolerances, coaxial swirl injector elements, and 58 internal coolant channels in the design, which required advanced manufacturing capabilities. The material had to balance mechanical strength, density, thermal conductivity, and machinability, and a robust cooling strategy was needed so the material wouldn’t fail, was temperatures in the combustion chamber are upwards of 2,500 K. Finally, a fast and cost-efficient manufacturing process was needed for this student project and its limited timeframe.
To achieve fine internal channel resolution and smooth surfaces, a 60 µm layer thickness was used for printing, and AlSi10Mg was selected because of its roughly 165 W/m·K thermal conductivity after stress relief, which allowed for rapid heat transfer to the coolant in the interior channels. Thanks to Eplus3D’s DfAM experience, the students optimized the design for printability, fabricating it as two integrated assemblies to reduce part count and assembly complexity. The regeneratively cooled Excelsior engine successfully withstood three hot-fire tests at Airborne Engineering Ltd. for the Race 2 Space 2025 competition, and achieved its target thrust of 5kN. The team ranked fourth in the Nitrous Bipropellant category, and out of 17 engines, the Excelsior was one of only eight to survive all hot-fire tests. As Eplus3D concluded, this project showed “that advanced LPBF in AlSi10Mg can produce high-performance regeneratively cooled rocket engines within the constraints of a university project. By combining innovative design, optimised manufacturing, and rigorous testing, the collaboration between Eplus3D and UCL Rocket shows how additive manufacturing can accelerate aerospace propulsion development.
