Texus-46's flight to the weightless world

"The launch was very smooth, all systems functioned perfectly and luckily the weather cooperated, too," said Antonio Verga, ESA's sounding rocket project manager. "We had some problems during the preparation of experiments last week and some adverse weather, but finally we were able to launch the rocket. According to preliminary analysis, the scientific results are very good."

"The fuselage of the rocket housing the experiments has been hoisted back to Esrange by helicopter and the de-integration work of the experiments has been already completed showing excellent conditions of the experiment modules," said Martin Zell, Head of Research Operations Department of the Directorate of Human Spaceflight.

The Texus flights are conducted by ESA's Directorate of Human Spaceflight in cooperation with the German Aerospace Centre, DLR. The research is performed as part of the 'European programme for Life and Physical sciences and applications using the International Space Station' (ELIPS).

A space centre in the north

The Esrange centre, located in northern Sweden, well above the polar circle, is owned by the Swedish space authorities and operated by the Swedish Space Corporation. It is one of the few active rocket-launching stations in mainland Europe. The relatively small rockets reach altitudes of up to 750 km, falling back some 70 km northwest of the launch pad. Texus-46 climbed to 252 km. These flights are optimal for short-duration research, either for in situ measurements and sample collection in the upper atmosphere and in space, or for flying experiments that require weightless conditions.

ESA uses sounding rockets mainly for microgravity research; Texus is currently the most flown. Almost 5 m long and weighing nearly 400 kg, Texus is boosted by a Brazilian two-stage VSB-30 rocket and includes a German video and telemetry/telecommand module. The well-proven recovery system, nosecone and ring adapters complete the payload, on this occasion alongside two scientific experiments.

The burning issue of nitrogen oxides

One of the experiments was housed in the 1.2 m-long, 103 kg cylindrical Japanese Combustion Module (JCM), from the Japan Aerospace Exploration Agency (JAXA), with ESA participation. JCM studied the combustion properties of a partially premixed spray of fuel droplets, expected to be almost perfectly spherical in microgravity.

Besides studying how the flame propagated, it aimed to determine the production rate of nitrogen oxides as a function of temperature. They are directly harmful to humans (affecting the respiratory system), are responsible for acid rain, and cause smog in cities.

A better understanding of nitrogen oxide emissions and the high-temperature combustion processes will be used to improve the efficiency of liquid-fuelled gas turbines by increasing the temperature of the burning process.

Metal alloys in levitation

The other experiment module, 1.8 m long and weighing 177.3 kg, carried a 'frequent flyer': an electromagnetic levitator (EML) that melts together two metal samples held in place by a pair of powerful magnets to prevent contact with the crucible walls. The magnetic coils generating the strong electromagnetic field not only liquefy the alloys by induction, but also keep the molten metal drop centred between the magnets. Jointly developed by ESA and DLR, EML was making its third flight and working with a sample from each agency.

During the 6-minute flight, the experimenters remotely commanded the melting and observed the behaviour. The first sample was a special steel alloy with superior mechanical strength, ductility and wear-resistance. During the final moments of weightlessness, it was chill-cooled.

The experiment aimed to increase our understanding of continuous casting processes of steel -- a material that remains crucial in the industrial production of components in the automotive industry, medical implants, and power production for coatings and further alloy refinement.

The second sample, an alloy of palladium and silicon, was heated to 1300°C. The molten specimen was then subjected to electromagnetic impulses to make it warp and oscillate. Accurately measuring the fading oscillation will help to determine the viscosity and the surface tension of the sample with very high accuracy. The 'eutectic' alloy is one of the best binary metallic glass formers and the measurements on Texus-46 will serve to validate existing numerical methods.