As part of the European REXUS (Rocket Experiments for University Students) program, a sounding rocket was launched from the Esrange Space Center in northern Sweden on 11 March 2025. On board was an experiment from TU Berlin, which is investigating fuel tanks produced using additive manufacturing for space applications. The student team from the Berlin space club BEARS e.V. had successfully applied to take part in REXUS, a program sponsored by the German Aerospace Center (DLR) and the Swedish Space Agency SNSA.
“We are very happy that the launch went so smoothly, after all we have been working on the mission for almost two years,” says Matteo Grube, Master’s student of aerospace engineering. “Now it’s time to evaluate the measurement data during weightlessness. That will keep us busy for a while yet.”
The aim of the experiment was to investigate the behavior of propellants in microgravity-like conditions. Liquid propellants behave differently in space than under gravity, as they do not automatically flow to the lowest point of a tank. Propellant management devices (PMDs) are used to control fuel distribution. These traditionally consist of metal sheets or hollow profiles that prevent the liquid from floating freely and enable a uniform supply to the propulsion system. The TU Berlin team has now tested six different PMD designs that were produced exclusively using 3D printing.
“Until now, welded-in metal sheets or hollow profiles have provided a remedy,” explains Grube. “We now wanted to test various new designs for the PMDs that can only be produced using additive manufacturing processes.”
During the two-minute weightlessness test, the tanks were filled with water mixed with a fluorescent substance to make the behavior of the liquid visible. Six cameras documented the experiments, while the tanks were made of transparent Plexiglas to allow optimal observation. The research runs under the project name WOBBLE2 (“Weightless Observation of Fluid Behavior with Berlin Liquid Guidance Experiment”), which refers to the team’s earlier approaches that have already been proposed for other space programs.
Research into 3D-printed PMDs could lead to more efficient fuel tanks in satellites and spacecraft in the long term. The use of additive manufacturing allows complex structures that would be difficult to realize with conventional manufacturing methods. Metallic 3D printing in particular opens up new design possibilities for lightweight yet stable structures. It is only in recent years that this technology has become established in the aerospace industry, with selective laser melting being used to manufacture high-performance components.
“We are very pleased that so many students from the team have now been able to fly to the Esrange Space Center rocket base,” says Benedict Grefen from the Department of Astronautics at TU Berlin, who supervises the student team and was the initiator of the project. “We received several travel grants from the Society of Friends of TU Berlin, including for a preparatory meeting in Kiruna last year.”
The project would not have been possible without external support. In addition to funding from TU Berlin, the team received financial support from the Society of Friends of TU Berlin, which made several trips to the Esrange Space Center possible. Technical support came from APWORKS GmbH for metal 3D printing and from Sensirion AG, which provided sensors. The experiment was also successfully implemented thanks to additional funding for travel and material costs. The data obtained will now be analyzed in the coming months in order to evaluate the efficiency and functionality of the tested designs.
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