The plasma crystal experiments are among the most successful research projects on the International Space Station (ISS). The PKE-Nefedov plasma crystal laboratory was one of the first scientific research laboratories on the International Space Station (ISS). The PK-4 has been in operation in the Columbus module since 2014. More than 70 scientific publications confirm the knowledge gained from the experiments conducted over the last 15 years. The German Aerospace Center (Deutsches Zentrüm für Luft- und Raumfahrt; DLR) Complex Plasmas research group is gaining fundamental insights into, in particular, solid state and fluid physics, as well as applications in space physics, plasma physics, plasma technology and fusion research. At the end of November, the international project and research partners met at a comprehensive symposium at the DLR site in Oberpfaffenhofen to present the results of PK-4 so far and to plan future activities.
The ISS provides ideal conditions for the investigation of plasma crystals and complex plasmas. A plasma is an electrically charged gas, a bit like lightning, which rarely occurs on Earth. In contrast, 99 percent of the visible matter in space is in the plasma state. When dust particles or other microparticles are also contained in the ionised gas, these are highly charged and a 'complex plasma' is formed: In microgravity, the particles can spread freely in space and form ordered three-dimensional crystal structures. The particles behave similarly to atoms in a solid or liquid – with the advantage that each microparticle in the plasma can be observed individually and as if in slow motion. This provides a whole new insight into physics.
Using PK-4 records, researchers can follow how a solid object melts, how waves spread in fluids and how currents change at the atomic level. Complex plasma is a new aggregate state of soft matter, in addition to colloids, polymers, foams, gels, granular media or even liquid crystals – a realisation that microgravity results have brought to light for the first time.
Knowledge and technology transfer
Through technology transfer, plasma research also opens up completely new fields of application. The starting point is to develop and build – using the know-how from human spaceflight – miniaturised, user-friendly and at the same time highly efficient laboratories taking into account special safety aspects for astronauts. A special transfer from space to Earth has already been achieved by scientists (at the time, the Max Planck Institute for Extraterrestrial Physics (MPE), now DLR) with the production of a plasma source for medical use. With this, the first clinical study on the use of plasma for chronic wounds was conducted – a milestone for plasma medicine. This young, fast-growing research field combines knowledge from the fields of plasma microscopy, microbiology and medicine.
"After the successes achieved with plasma medicine at MPE, the research group at DLR is now working on new follow-up projects. The so-called cold atmospheric plasmas from the medical field can also be used for space travel – especially for the sterilisation of surfaces and components, such as those of the Mars Rovers, which are searching for life. The use of plasma could also make hygiene on board the ISS much easier in future," says Hubertus Thomas, Head of the DLR Complex Plasmas Research Group. The projects for the use of cold atmospheric plasmas are funded by the Bavarian Ministry of Economic Affairs and Media, Energy and Technology.
The current research project and plasma laboratory PK-4 on the ISS is a European-Russian cooperation with research partners around the world. Approximately 60 participants attended the PK-4 symposium in Oberpfaffenhofen: The DLR Complex Plasmas research group welcomed the international team of scientists with participants from the European space agency ESA - European Space Agency, the Russian space agency ROSCOSMOS, the US space agency NASA-NASA-National Science Foundation and the DLR Space Administration.
In a special guest speech, Cosmonaut Alexandr Samokutyaev also reported on his work on the ISS. In November 2014, together with colleague Elena Serova, the Russian installed the Plasma Crystal Laboratory and prepared for the first deployment: "Scientific experiments on the Space Station are very important and a core task for astronauts on board as they provide special insights for space travel and people on Earth. I am delighted to have been able to contribute with the PK-4 laboratory."
During the symposium, the specialist community also discussed and expanded the long-term PK-4 programme. Next year, three new series of experiments are planned in the Plasma Crystal Laboratory, which is to be operated on the ISS at least until 2019. "We are delighted that the highly successful PKE-Nefedov and PK-3 Plus experiments with PK-4 have enabled us to continue plasma crystal research on the ISS in the years to come. The symposium has once again demonstrated how diverse this research area is, and that German scientists are conducting research in an international environment," explains Thomas Driebe from DLR's Space Administration at the event.
In parallel with PK-4, the plasma researchers are already developing two novel plasma chambers, which form the scientific and technical connection to PK-4 and the previous PKE-Nefedov and PK-3 Plus projects. The experimental EKoPlasma set-up will be transferred to the ISS in 2020 and consists of a cylindrical 'Zyflex chamber' and a 12-surface 'Dodecahedron chamber'. These unique plasma chambers will enable the DLR research group to develop the research and application fields of complex plasmas further.
About the project
The PK-4 laboratory is a cooperation between the European Space Agency (ESA - European Space Agency) and the Russian space agency ROSKOSMOS. The Russian part, scientifically involved through the Joint Institute for High Temperatures (JIHT) at the Russian Academy of Sciences, is responsible for transporting the laboratory, transporting video data back to Earth and providing the crew time. The development of the PK-4 laboratory was also carried out in close contact with the JIHT. The experimental hardware is a proprietary development of the research group (at MPE) in cooperation with OHB System AG (formerly Kayser-Threde GmbH), which was also responsible for the PK-4 infrastructure. Additional financing for the project in Germany came from the DLR Space Administration and the Max Planck Society.