TEXUS 51 was launched into space from the Esrange Space Center near Kiruna in northern Sweden on 23 April 2015 at 09:35 CEST. The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) research rocket carried four German biology and materials science experiments to an altitude of 259 kilometres. During the nearly 20 minute research flight, the experiments were under microgravity conditions for approximately six minutes. The payloads were then returned to the ground by parachute.
One of the experiments on board is ParSiWal; its goal is to improve the quality and efficiency of solar cells. It does this by determining the critical incorporation rate of particles during the directional solidification of solar silicon in space. Researchers at the Fraunhofer Institute for Integrated Systems and Device Technology (Institut für Integrierte Systeme und Bauelementetechnologie; IISB) in Erlangen, the University of Freiburg and the University of Bayreuth have been studying the unwanted incorporation of silicon carbide particles that can occur during the crystallisation of silicon. In the industrial production of silicon solar cells for photovoltaics, silicon carbide particles impede the mechanical processing of the product and reduce the efficiency of solar cells. Therefore, the incorporation of these particles in the silicon crystal needs to be prevented. For this reason, the researchers want to understand through experimentation what mechanisms are responsible for this process. Microgravity is an important prerequisite for the experiments since gravity has a significantly influence on the flow of molten materials.
In the FOKUS experiment, a 'frequency comb' – a special laser developed by the Max Planck Institute of Quantum Optics in Munich – is being tested for its suitability for use in space. At the core of a frequency comb is a pulsed laser that generates a range of optical frequencies. In the future, this technology is expected to be used in precision spectroscopy, such as in the investigation of trace gases in the atmosphere, or in the development of new, extremely accurate atomic clocks for research missions or navigation.
Many astronauts suffer from infections during their lengthy stays in space. The reasons for these disruptions to the human immune system in microgravity are being investigated by a group of scientists from the University of Magdeburg in the SITI-2 experiment (Signal transduction in Immune system cells in microgravity). This involves exposing cell structures to microgravity on the TEXUS-51 flight, where gene activity in the immune system is analysed using modern DNA chip technology. If the scientists' suspicions are confirmed, and specific molecules in the cell membrane are responsible for the disruptions, these discoveries could lead to new approaches in the long-term fight against diseases.
In the TRACE-3 materials science experiment (Transition from columnar to equiaxed solidification in a transparent model alloy), conducted by the ACCESS research centre in Aachen, scientists are analysing the processes and structures that play a part in the solidification of metal alloys. They are investigating this using a mixture of organic substances that solidifies in a similar way to liquid metal. The solidification process can then be observed directly, since the alloy is transparent. The data acquired is expected to improve industrial casting processes.
TEXUS dual campaign – two rockets in one week
TEXUS-52 is scheduled for launch on 27 April 2015, carrying three more experiments by German scientists. With the newly developed Flumias experiment, a special optical microscope – a confocal laser scanning microscope (CLSM) – will be used on a TEXUS flight for the first time. This instrument enables live biological samples to be studied over an extended period of time. This is done by capturing three-dimensional, high-resolution (spatially and temporally) fluorescence microscopy images, a technique known as live cell imaging. With this method, three working groups from the Universities of Stuttgart-Hohenheim and Magdeburg are aiming to provide evidence of the effects of microgravity on the structure and dynamics of the cytoskeleton in human immune, nerve and thyroid carcinoma cells. This research forms the basis for further investigations into health maintenance for astronauts in space and of patients on Earth. Additional biological sample studies using Flumias are planned for later TEXUS flights.
In the OASIS-TEX (Optical Analysis of Smectic Islands in Space – Thermocapillary Experiments) project, researchers at the University of Magdeburg and the University of Colorado are investigating the properties of liquid crystal layers. Liquid crystals are used in the manufacture of display devices, in medicine, cosmetics and in the manufacture of detergents. From these, films with a uniform thickness of a few nanometres (two to three molecules thick) to several microns (approximately 1000 molecules) can be created. Curved in shape, these films can be visualised as particularly stable soap bubbles. They have interesting structural and dynamic properties, making them ideal models for basic research on physical properties such as the interaction between molecules.
In tandem with NASA, the OASIS experiment is expected to be carried out on the ISS in due course. The TEXUS-52 flight is being used as a general test. In doing so, two important scientific questions can be addressed; in the first experiment area, special flows in a film surface, known as Marangoni flows, are generated through differences in temperature. The scientists are hoping to discover how the structure of the individual molecules affects macroscopic flow behaviour. In the second experiment, a liquid cylinder is generated between two pistons that are drifting apart and stretched to the point where it spontaneously collapses into individual droplets. The aim is to study the effect of the crystalline arrangement of the molecules of the liquid crystal in this process, in comparison to a ‘normal’ liquid.
The extent to which certain plankton organisms are suitable as a component in future bioregenerative life support systems in space stations or other extreme environments is being investigated in the Daphnia experiment by scientists from the University of Bayreuth. One important model organism for this research is the Daphnia fresh water flea. However, little is known about the effect of gravity or microgravity on the behaviour and physiology of these creatures. Hence, it is important to first examine these effects in short flights, such as TEXUS, before the organisms can be used in life support systems in space. Furthermore, the researchers hope to learn about the various gravity-sensitive biological systems that have developed in the course of evolution. For this reason, the researchers will be analysing the swimming behaviour of the animals and also carrying out molecular experiments to examine the effect of microgravity at the genetic level.
In the entire TEXUS programme, some 300 scientific experiments have been carried out since 1977, 70 percent of which have been under contract to DLR and 30 percent as part of a collaboration with the European Space Agency (ESA). DLR has once again counted on Airbus Defence and Space in Bremen for the launch preparations and carrying out the TEXUS 51/52 dual campaign. Also involved are OHB Systems, based in Munich, and the DLR mobile rocket base (MORABA) in Oberpfaffenhofen. The two-stage VSB-30 rocket was developed in collaboration with the Brazilian space organisations CTA (Centro Técnico Aerospacial) and IAE (Instituto de Aeronáutica e Espaço), MORABA and Swedish space organisation SSC.