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Measuring without gravity


On Friday, April 7, 2017, the research rocket MAXUS-9 successfully launched from the Esrange rocket launch site near Kiruna in northern Sweden. After 12 minutes of weightlessness, the scientific payload landed safely using a parachute. Five scientific experiments were carried out during the unmanned flight, three of them under German management. The Bundesanstalt für Materialforschung und -prüfung (BAM) played a key role in one of the experiments.

Material science phenomena in metal melts under weightlessness

The experiment was conducted within the framework of the "In situ X-ray monitoring of advanced metallurgical processes under microgravity and terrestrial conditions (XRMON)" project funded by the European Space Agency (ESA). Together with their research partners, BAM is investigating materials science phenomena in metal melts under weightlessness. The aim is to obtain knowledge about metallurgical processes in metal melts in situ using X-ray radiography.

"It is important to exclude the disturbing factor 'gravity' because diffusion coefficient reference data can only be measured without this influence. In the experiment we observed very clearly how diffusion occurred without any disturbance", says Dr. Axel Griesche from BAM's Component Safety Department.

Axel Griesche is co-initiator of the project and is cooperating with researchers and industrial partners from six European countries. The scientists expect the results of the experiment will provide detailed insights into the fundamentals of solidification processes in metal alloys. These findings can be used to improve models that today's simulation programs use, for example, for the prediction of microstructure formation during solidification.

Scientists watch processes live on monitors

In the XRMON-Diff2 experiment during the rocket flight of MAXUS-9, the scientists from BAM and the German Aerospace Centre (DLR) could observe how metal melts were mixed "purely diffusively" without the disturbing influence of buoyancy convection in real time. Buoyancy convection occurs in gases and liquids under the influence of gravity: light molecules rise upwards, heavy ones sink downwards. The scientific challenge in the experiment was to observe diffusion, i.e. mixing, without the influence of buoyancy convection. The scientists observed the process live on monitors in the control centre. The measurements were carried out on molten germanium-silicon and aluminium-titanium alloys.

MAXUS-9 started almost exactly seven years after its predecessor, MAXUS-8. Many European partners are now involved as in previous missions: ESA finances the rocket and the experimental modules, Airbus DS is responsible for the overall project management, and the Swedish Space Corporation (SSC) runs the rocket launch site. Industrial partners from all over Europe are also involved.

Other experiments during the rocket flight included the investigation of the influence of gravity or weightlessness on micro-organisms, on the propagation of flames in fuels and on the solidification of titanium-aluminium alloys.

Source: Bundesanstalt für Materialforschung und-prüfung (BAM)