EOS: Additive Manufacturing Safer and More Economical with Additive Manufacturing
In cooperation with EOS, the Ariane Group has succeeded in producing a thermally and mechanically highly durable injection head for the future consisting of only one single component. Compared to casting and machining the throughput time for additive production is heavily reduced.
Space missions usually involve investments of several hundred million euros. Their success often depends on the function of a few components. Space companies call these components "Mission Critical". Therefore, specialists continuously optimize the installed components and their functions. Above all, they must be robust and must work reliably under the most adverse conditions. Reducing the number of components is a valuable contribution to space missions. It simplifies production, minimizes measuring and testing efforts and reduces the probability of failure considerably. This could, for instance, be achieved in the case of an injection head, by using an all-in-one design (AiO).
In order to develop and build the future Ariane 6 carrier rocket, the European Space Agency (ESA) has awarded a contract to the joint venture of the Airbus Group and the French Safran Group, today's Ariane Group. As of 2025, this rocket is to provide Europeans with a cost-effective, internationally competitive connection to space. Since public subsidies are no longer required, the manufacturer is trying to reduce costs in the development and construction of the rocket. The company focuses on the upper stage engine that propels the rocket after leaving earth orbit.
A rocket engine has to withstand tremendous forces and extreme conditions. Therefore, the engine must work extremely reliably and precisely. The injection head is one of the central elements of the engine. It injects the fuel mixture into the combustion chamber. Manufactured in a conventional way, it consists of 248 components. These components are manufactured in a variety of production processes and then assembled. The processing steps, including casting, soldering, welding and drilling, create weak points that can pose a risk under extreme loads. In addition, the many processing steps are time-consuming and complex. In conventional production, for example, more than 8,000 cross holes are drilled in copper sleeves for the injection elements. The sleeves must then be screwed together accurately with 122 injection elements. Only in this way can the injection element properly mix the hydrogen with the oxygen.
With regard to risk management, a functionally integrated component is easier to assess. All components that used to be individually manufactured and assembled are manufactured as a single component. This also reduces the number of previously required processing steps and thus shortens the production time. This approach is extremely economical and therefore also meets the commercial requirements of the manufacturer.
Fulfilled Requirements with Additive Processes
Meanwhile, it has been possible to manufacture the injection heads as a single component and integrate all functions. To this end, rocket manufacturer Ariane Group used EOS' additive processes. Steffen Beyer, Head of Production Technology Materials & Processes at Ariane Group, says: "The production of the injection head as a single component can only be realized with EOS technology," and he adds: "Only additive manufacturing can combine functional integration, lightweight construction, design simplification and the reduction of throughput times in a single component".
The injection head is still made of a heat- and corrosion-resistant nickel-based alloy (EOS Nickel Alloy IN718). It is characterized by very good tensile, fatigue, creep and breaking strength at elevated temperatures. It therefore made sense to continue using this material. "Following our successful development of the component, the focus was on cost-effectiveness," reports Dr.-Ing. Fabian Riss, Production Technology Materials & Processes. The manufacturer Ariane Group had specified a significant reduction in throughput times and unit costs. In a step-by-step process, the first components were produced on an EOS M 290 machine.
The process was then scaled to the larger EOS M 400-4 additive manufacturing system, which produced the injection head at up to four times the speed because it had four lasers working in parallel. "Scaling the construction process to the highly productive EOS M 400-4 system was an important step for us in advancing the industrialization and competitiveness of the Ariane 6 project. “Thanks to the experience and industry knowledge of the EOS colleagues, the cooperation was very fruitful. The result speaks for itself and proves the great performance of the team," explains Dr. Steffen Beyer.
While casting and machining used to take more than three months, the throughput time for additive production on the EOS M 290 machine was reduced to 133 hours. On the EOS M400-1 additive manufacturing system with only one laser, it took 65 hours, with four parallel lasers (EOS M 400-4) the injection head was completed in only 35 hours.
Lighter Yet More Stable
With this technology, the Ariane Group fulfilled all the requirements. Instead of 248 components, the injection head now consists of only one component. It fulfils the same functions and can be manufactured much faster and more economically. EOS's powder-bed-based, industrial 3D printing technology made it possible, among other things, to print the 122 injection nozzles, the base plate, the front plate and the distribution dome as an integral component with the corresponding supply connectors for the fuels hydrogen and oxygen. The significantly higher productivity of the multi-laser system EOS M 400-4 compared to single-laser systems (EOS M290) reduced the construction time to less than a third, the costs sank to half.
The project team achieved further successes. By simplifying the design and thanks to improved material properties compared to casting, the additive manufacturing process produces components with the same robustness and strength and with significantly thinner walls. This makes it about 25 % lighter than before. This aspect carries a lot of "weighty" for a rocket to be transported into space.
The experts at the rocket manufacturer see an additional advantage in the fact that additive manufacturing processes can significantly accelerate innovation cycles. Structural optimizations, design changes and the production of test components in the development phase can be brought directly from the CAD data to the production process without time-consuming tool production. While it used to take about six months to complete a component, it now only takes a few days. This enables the space specialists to optimize and test components in significantly shorter cycles. In addition, with additive manufacturing they are part of and monitor the entire production chain themselves. Above all, this creates confidence in the quality of the components produced.
This article was first published by Schweizer MaschinenMarkt