Astronaut safety: Research by GSI and FAIR for the best protection from space radiation
It’s light, solid and could play an important role in future space missions into the depths of space: lithium hydride, a salt-like chemical compound of lithium and hydrogen. Crucial indications for the possible suitability of lithium hydride as a shielding material against cosmic radiation have now been found by research partners in Germany and Italy. The international team including the scientists Marco Durante, Christoph Schuy, Felix Horst and Uli Weber from the Department of Biophysics at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt as well as other partners has published its findings in the “Radiation Research” journal.
Protecting people in space from cosmic radiation is a major challenge for space exploration. Harmful effects of space radiation pose a serious health risk to astronauts, especially in future long-term missions. Such radiation effects must be considered and minimized both in the design phase of spaceships and in mission planning. The weight that can be taken on board a spacecraft is yet another limiting factor. New materials which offer an improved shielding performance and lighter weight are in demand. That’s especially true when it comes to deep-space missions where radiation is even more intense than in the near-Earth orbit.
The international team of scientists has been working together in this area. Aside from the GSI Helmholtzzentrum the researchers are from the Institute of Medical Physics and Radiation Protection at the the Mittelhessen University of Applied Sciences in Giessen, from the Trento Institute for Fundamental Physics and Applications (TIFPA) in Povo, the Physics Department at the University of Trento in Povo, the Department of Applied Science and Technology at the Politecnico di Torino in Turin as well as from the Physics and Chemistry Departments and NIS (Center for Nanostructured Interfaces and Surfaces) at the University of Torino in Turin. Thales Alenia Space in Turin is also a part of the team. The company manages for the European Space Agency ESA the ROSSINI project for the optimization of radiation protection for astronauts, a long-term joint research project by ESA and GSI.
The team’s objective: to identify suitable shielding materials which are better than the well-proven standard solution hard polyethylene which is currently used for radiation protection on Earth, for example, or in the sleeping areas of the near-Earth International Space Station ISS . Due to the high hydrogen content of hydrides, lithium hydride was chosen as a promising starting point for further studies.
The investigations were carried out mainly at the accelerator facility on the GSI and FAIR campus in Darmstadt where particle radiation which is prevalent in outer space can be generated and made available for experiments. In its experiments, the research team evaluated the shielding performance of lithium hydride among other things using measurements with high-energy carbon rays. Accurate data could also be provided for benchmarking Monte Carlo simulations. Such simulations are used for risk estimation in studies without particle accelerators to obtain a statistical overview of radiation effects.
The recently published studies suggest that lithium hydride might be a good candidate as a shielding material. The Head of the GSI Department of Biophysics, Professor Marco Durante, summarizes: “Initial experimental results suggest that lithium hydride is appropriate in improving radiation protection for people over a long-term space mission.” Lithium hydride could therefore be an effective strategy in protecting people when it comes to long-term exploration of the solar system. “It could be the right material to go to Mars.”
Dr. Christoph Schuy, experiment supervisor, also considers the lithium hydride compounds to be promising. However, the researchers and engineers still have a number of tasks ahead of them, such as the precise determination of neutron production cross sections at high energies or the safe coating of the material.
While it offers a glimpse into the future, additional experiments at higher energies and with heavier ions are needed to fully assess the shielding ability of lithium hydride and other promising lithium compounds. The potential emergence of secondary radiation must also be investigated as well as a possible secondary benefit of shielding material such as in lithium-hydride-based batteries in spacecraft. Professor Durante explains: "We now have to test complex, realistic structures that simulate the real spacecraft walls, including lithium hydride. These tests started in February as part of the FAIR Phase 0 experimental program and are funded by the ESA-ROSSINI3 project".
ESA and GSI have been working together successfully on several research projects for years. At the future FAIR Accelerator Center which is currently being built at GSI, these possibilities will be considerably expanded upon: FAIR will facilitate experiments with an even wider range of particle energies and intensities and can simulate the composition of cosmic radiation more accurately than any other accelerator facility. ESA and FAIR agreed to work closer together and signed a collaborative agreement on cosmic radiation research just over a year ago. (BP)