The 31st German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) parabolic flight campaign ended successfully on 9 March 2018. Twelve experiments in the fields of human physiology, biology, physics, technology testing and materials science took place on board the A310 ZERO-G, dealing with investigations into the birth of stars, plasma physics, the behaviour of molten materials in zero gravity and blood circulation in the human body, amongst other things. The campaign took place in Bordeaux, where the company Novespace, which conducts parabolic flight campaigns on behalf of the DLR Space Administration, is based. "The experiments remain exciting, even after 18 years of research on parabolic flights, as many participants are breaking new scientific or technological ground in their questions," said Katrin Stang, Programme Manager for DLR's parabolic flights.
CIMON – an astronaut assistance system for the ISS
Among the experiments on board the current parabolic flight campaign was the future astronaut-assistance system CIMON, which will be used on the International Space Station (ISS). CIMON is mobile, equipped with artificial intelligence and is designed to support and take some of the load off astronauts in their everyday tasks. The aim of the parabolic flight test was to test the basic properties of CIMON in microgravity. In particular, its spatial orientation, navigation and manoeuvring were tested, in order to be optimally prepared for deployment on the ISS – in permanent microgravity. Christian Karrasch, CIMON Project Manager at the DLR Space Administration, was on board and is satisfied with the results of the parabolic flight. "CIMON has demonstrated that it can manoeuvre safely in microgravity, and passed all the tests with flying colours – we are really looking forward to its first deployment on the ISS."
The birth of stars in a parabolic flight experiment
How are stars born? The INKA (unstable protoplanetary bodies in a low-pressure wind tunnel) experiment performed by scientists from the Faculty of Physics at the University of Duisburg-Essen addressed this question. Sand dunes migrate when the wind removes particles from one side, which are then deposited by gravity on the downwind side. Indeed, what would happen without gravity? The dunes would simply break up in a cloud of sand grains.
Similar situations are conceivable during the formation of planets, in which loosely linked particles the size of sand grains form a body a kilometre or so in size with very little gravity of its own – a planetesimal. To discover the conditions under which such bodies are stable, scientists observed a sample made of particles one millimetre in diameter in a low-pressure wind tunnel, in which the pressure and wind speed could be varied. The wind tunnel was simultaneously on a centrifuge, in order to simulate different levels of planetesimal gravity (planetesimal size).
Plasma crystals – a phenomenon that only occurs in microgravity
Complex plasmas are electrically conductive gases – similar to those used in fluorescent tubes – into which 'dust particles', also referred to as microparticles, are introduced. The microparticles, with a diameter of up to ten microns, receive a strong negative charge in a plasma chamber due to electron attachment and are made to float using electric fields. As a result of this charge, the electrostatic interaction between the microparticles is very strong, so that new, scientifically interesting phenomena can occur, such as the formation of a plasma crystal – a regular arrangement of microparticles in the plasma.
In their parabolic flight experiment, scientists from Justus Liebig University in Gießen wanted to investigate the electrorheological properties of the liquid phase in complex plasmas. In addition to this basic research, complex plasmas are also ideal for use as modelling systems for other areas, such as crystallography, the physics and technology of liquids and gases, as well as nanotechnology. Since 2014, this experimental system has had a 'duplicate' in the PK-4 facility on the ISS, in order to facilitate longer-term research under microgravity.
The design of new materials through unique research opportunities
Like the PK-4, the DLR TEMPUS facility for researching melting in microgravity has a twin on the ISS. In the TEMPUS experiments, liquids can be examined in unique ways; metals and alloys can be positioned and melted using electromagnetic fields. In this way, the molten material is not contaminated through contact with another material, such as a crucible. In microgravity there are no disruptive convective flows in the molten material, as would occur under normal gravitation.
The measurements performed by scientists from DLR and various universities are focusing on new findings concerning the thermophysical properties of materials, such as density, viscosity, electrical conductivity and thermal expansion. These results form the basis of model calculations for technical processes in the design of new materials. In the 31st DLR parabolic flight campaign, a new thermal imaging camera was used. "The thermal imaging camera has allowed us for the first time to observe TEMPUS samples at temperatures below 600 degrees Celsius," explained Julianna Schmitz from the DLR Institute of Materials Physics in Space in Cologne. "This expands our research capabilities and allows us to study metals that melt at low temperatures. We are very pleased with the results."
Human microcirculation in microgravity
Microcirculation is the blood flow in the smallest vessels in the human body. It has great significance for the human organism as an important blood reservoir, and affects blood pressure, promotes heat exchange and transports oxygen and vital nutrients to cells. Researchers at the University Hospital of Düsseldorf have examined changes in microcirculation in microgravity on a parabolic flight using a special manual microscope the size of a smartphone that takes measurements under the tongue. The findings from the parabolic flight could help in the development of new diagnostic alternatives, in order to identify people at an increased risk of circulatory problems and thus prevent them in good time. The flight safety of astronauts and jet pilots, for example, could also be significantly improved in this way.