Germany provides the first scientific experiment onboard the ISS - the PKE-3 Plus: phase transitions in plasma crystals
The German Aerospace Center (DLR) has had pioneering experiments onboard the International Space Station (ISS) since the very beginning. Indeed, scientific research activities onboard the station got underway in February 2001 with a German experiment, which is still running as part of a German-Russian collaboration.
Sergej Krikalev onboard the International Space Station ISS
The PKE plasma crystal experiment was designed to study low-temperature plasmas. Small particles are added to an ionised gas (plasma) of free electrons, ions and neutral gas, causing them to be electrostatically charged. This results in interactions between the particles. In certain conditions, these particles form geometric shapes known as plasma crystals, a state of matter that was first discovered in 1994.
The force of gravity has little effect on a conventional plasma. But because the mass of the microparticles introduced to the plasma is billions of times greater than that of the electrons and ions, a complex plasma reacts sensitively to gravity by depositing its particles. The plasma crystal is vertically compressed and the three-dimensional lattice is limited to just a few layers. Large three-dimensional structures can only be studied without distortion in zero gravity. Scientists are most interested in the autonomous processes that take place inside plasma crystals, and these can only be studied in weightless conditions.
PKE-3 Plus is a continuation of the scientific testing and usage of the German-developed equipment which has been onboard the ISS since January 2006. The experiment on phase transitions in complex plasmas is being carried out in several stages. First of all Thomas Reiter will prepare the PK-3 Plus equipment for operation. He will then initiate the automatic process and check periodically on what is happening in the plasma chamber on a monitor. By agreement with the scientists on Earth, manual interventions can also be made where necessary or where this would significantly improve the experiment. All experimental data is stored automatically before the astronauts send it back to Earth for analysis in the form of interchangeable hard disks.
Complex plasmas are commonly found in nature. For example, they occur in interstellar molecular clouds, planetary ring systems such as the Saturn system, and comet tails. In plasma technology they are often encountered in the form of 'dusty' plasmas. In addition to their importance in fundamental research (in fluid physics, solid-state physics and astrophysics), complex plasmas could also have practical long-term applications. These might include adding coatings to electronic microchips, the production of solar cells and flat screens, plasma medicine or biotechnology.
Coordinators: G. Morfill (Max Planck Institute, Garching) and V. Molotkov (RAdW, Moskow)