The European Space Agency (ESA) last week reached an important milestone in both rocketry and 3D printing. The BERTA engine, manufactured entirely by 3D printing, was successfully hot-fired for 560 seconds with a reference thrust of 2.45 kN.
The test firing, which took place at the DLR German Aerospace Center’s Lampoldshausen testing facility in Germany, takes the ESA a step closer to the practical utilisation of 3D-printing for engines designed for use in in-orbit transportation applications, microlaunchers and exploration spacecraft, such as lunar landers.
The thrust chamber was designed for 'storable propellants', called so because they can be stored in liquid form at room temperature. Rocket engines that are powered with storable propellants are easier to ignite and reignite on longer space missions.

ESA 3D printing
Preparing the thrust chamber demonstrator. Image: ESA
Developed by ArianeGroup for the ESA's Future Launchers Preparatory Programme the BERTA (Biergoler Raumtransportantrieb) combustion chamber helps to investigate flow and heat transfer phenomena on surfaces created by 3D printing, otherwise known as additive manufacturing.
Additive manufacturing is done by building up layer by layer, as opposed to the traditional process of cutting away extra material. Therefore, complex, optimised structures that are impossible to create using classical methods can be created using reduced amounts of material and energy.

ESA 3D thruster
Hot firing test at Lampholdshausen. Image: ArianeGroup / DLR
“3D-printing and qualifying parts for hot-firing and ultimately flight is a challenge, especially when dealing with fine, complicated structures, like the cooling channels of our demonstrator” said Wenzel Schoroth, propulsion engineer at ESA. “This hot-fire test is a way of demonstrating the effectiveness of our processes, as well as learning more about the flow phenomena within additively manufactured rocket engines.”
Further activities will look at the application of environmentally friendly propellants for larger engines delivering 5 kN of thrust. ESA is also developing additive manufacturing technology for larger engine demonstrators with cryogenic propellants.
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