Germany is one of the most important nations conducting scientific research on board the ISS, particularly in the field of research under space conditions (life and physical sciences) in which around 40 percent of the projects selected in a Europe-wide contest originated with German research institutes.
Having won the international best science contest, around 100 German projects are now waiting to be realised. Pursuing the goals of the DLR Space Agency's Research under Space Conditions programme, these projects define concrete research objectives for the next few years.
Compared to the experiments conducted in the early phase of ISS utilisation, Columbus will offer a considerably wider range of research options in the years to come. Next to experiments in gravitational biology, scientists are beginning to concentrate on radiation and astrobiology projects. The new devices that will be mounted on the external platforms of Columbus offer excellent opportunities in this respect. As it is now possible for astronauts to stay on the ISS for prolonged periods, it is not surprising that research in space medicine should focus on investigating the attenuation of muscles and bones. In addition, these studies as well as those in radiation and astrobiology will contribute greatly to the preparation of future long-range astronaut missions to the Moon or other destinations.
Ever since evolution began, gravity has been playing a crucial role for all organisms. For many years, researchers have been trying to answer the question of how organisms perceive gravity and respond to this stimulus, i.e. how plants can distinguish between up and down, and why roots and shoots grow in the right direction. Scientists have already wrested many secrets from nature. Thus, they discovered that roots contain heavy particles which shift when the direction of gravity changes. Moreover, they were able to show that the cytoskeleton and a variety of messenger substances are involved in the process as well. Yet they have been unable so far to establish the exact sequence of steps from gravity perception to plant response. This is where the BIOLAB and other experiments on Columbus will begin searching for answers to that question with modern molecular biology methods.
The MATROSHKA experiment, measuring radiation both inside and outside the ISS
Both the intensity and the composition of space radiation vary greatly. This being so, further measurements are planned to improve our ability to assess the risk of radiation exposure. Applying its many years of expertise in this field, the DLR Institute of Aerospace Medicine will continue its measurements inside and outside the ISS in the years to come. Analysing the biological impact of cosmic radiation may be even more important than measuring its intensity and composition. Matroshka, a sophisticated phantom dummy that simulates the human upper torso with all its organs, has been giving good results in the past. At present, it is employed inside the ISS to measure the radiation field there, but it will be moved outside again in the course of 2008.
In astrobiology, a new chapter will be opened as well. Alongside Columbus, the Expose-EuTEF system will arrive on the ISS. Next to comparative radiation dosimetry, the system will be used to expose a variety of organisms to the extreme environmental conditions of space and investigate their ability to survive. Theses studies serve to explore the origin, evolution and spread of life and, by the same token, to answer the question of how the spores of life might have arrived on Earth in the dim and distant past.
In the field of space medicine, the German experiments conducted on the ISS will focus for some years on the metabolism of muscles and bones. Following the principle of integrative physiology, a holistic view of human beings and the interplay between their various systems and organs, scientists will study the interaction between bones and muscles on the one hand and the cardiovascular, metabolic, immune, and hormonal-regulation systems on the other. Experiments aim at understanding the attenuation of muscles and bones and developing suitable countermeasures from which not only astronauts but also the people on Earth stand to benefit.
Objectives of physical research
About 90 percent of all metallic and semi-conducting materials are produced by metallurgic melt processes. To optimise existing technologies or develop new ones from scratch, researchers need to know more and more about the details of all processes involved. Today, designing materials produced by melting calls for efficient computer simulation programmes to circumvent industrial-scale pilot tests that are expensive in terms of both energy and time. Weightlessness eliminates spurious forces that may act on a melt, such as convection and the sedimentation of components that differ in density. These are crucial advantages in studying the interaction between solidification conditions and the structure and properties of the resultant materials. Another objective will be to considerably enhance the precision with which the thermophysical properties of reactive metal melts can be established by measuring them in suspension, i.e. in a containerless process. The research activities that will be conducted by the ESA Materials Science Lab on the ISS will concentrate on melts that are relevant to the industry.
Fluid and gas physics permeates many applications on which gravity has a major impact. Basic studies on the ISS will investigate fluid flows within a geometry that will enable fuel to be transported by capillary forces in a new generation of satellite tanks. Whenever a jet is fired, an adequate supply of fuel must be available at the injection nozzle. This being so, experiments will have to be conducted in weightlessness to establish the limits at which flows become unstable. On Earth, hydrostatic fluid pressure prevents precise measurements.
Another project will address flows in a spherical gap. This geophysical model simulates flow processes in the liquid outer core of the Earth by replacing the central force of our planet with an artificial gravitational field in a spherical gap. What is interesting to scientists in this context is the flow patterns that arise. The top-down bias that is inevitable in terrestrial laboratories can be avoided only in weightlessness. This experiment is the first scheduled for the Fluid Sciences Lab of Columbus.
By studying the combustion of droplets and sprays, researchers intend to analyse ignition mechanisms so as to improve combustion processes for liquid fuels under high pressure. They aim to lower the pollutant emissions of gas turbines and aircraft engines by reducing the richness of fuel-air mixtures as far as possible without affecting efficiency. Weightlessness greatly assists in exploring the basic mechanisms of combustion without interference. So far, related experiments have been conducted on the Bremen drop tower, but once the American Combustion Integrated Rack has been commissioned on the ISS, new opportunities for experimenting and cooperating will open up.
In recent years, the physics Nobel Prize has been repeatedly awarded for discoveries relating to quantum phenomena. Investigators of the Bose-Einstein condensation succeeded in cooling gas atoms far enough for them to lose their individuality and appear as matter waves. Laboratory tests have shown that a laser will work with such matter waves instead of light waves. At the moment, attempts are being made at the Bremen drop tower to generate ultra-frigid gas atoms in weightlessness so as to reduce their temperature even further. On the ISS, physicists plan to study ultra-frigid atoms systematically in the long term in order to obtain an even better insight into the world of quantums.
One major field of research on the ISS is based on the discovery of plasma crystals made in 1994 by scientists working at the Max Planck Institute for Extraterrestrial Physics. The research programme on the ISS, which has been running for more than six years now in cooperation with Russia, will be extended into the next decade because of its great scientific yield. The data obtained so far from space experiments yielded new fundamental insights and discoveries.
Far from being an exotic subject of research, plasmas enriched with particles appear frequently in nature (the rings of Saturn, the tails of comets) as well as in terrestrial plasma technology (manufacture of chips and solar cells). The equipment required to open up yet another field of research that deals with fundamental interactions between particles will be available on the ISS by the end of the decade. In this case, research aims at simulating elementary processes in the birth of planets - the agglomeration of cosmic dust - as well as in the formation of clouds in the atmosphere (aerosol growth).