When I return through Earth’s atmosphere in my Soyuz I will have spent 193 days in space. My mission will have been the longest European space flight in history. Everything went well thanks to the thousands of people on ground that continuously keep an eye on us. Safety is number one priority in human space flight. Missions such as mine are inherently risky. In the last few weeks I started an experiment that looks at one of these risks: Altea Shield.

In brief: scientists are looking for a shield to protect astronauts during a long stay in space. The sun and other sources continuously send radiation into space. Some radiation such as radio waves are not harmful to humans. But particle radiation or ionising radiation with higher energies can be dangerous. Especially, if you are exposed to this type of radiation for a long time. NASA has even set a limit to how much accumulated radiation an astronaut can receive. If an astronaut gets near the limit, they are not allowed to fly another mission in space.

Bulletproof vest

The solution is not to keep people Earth-bound. In the long run we want to live for longer periods in space and travel further, to the Moon and to Mars. So it is better to develop an effective shield that stops the radiation as much as possible. On Earth this shield is our atmosphere. Condensation in the atmosphere absorbs almost all dangerous radiation, so we do not suffer from it in our

daily lives. On the International Space Station we do not have an atmosphere to protect us. The Altea Shield experiment will test different types of shields.

The procedures were complex. I had to hang large radiation sensors in the Station and connect them with cables. The cables float every which way: it looked like an Anaconda snake swimming around me. Altea Shield has six detectors that measure the radiation. For 40 to 60 days they will continuously measure space radiation that passes through the ISS and so reaches our bodies. On top of the detectors are walls made of polyethylene and kevlar, the same material that is used to make bulletproof vests. After testing we will know which material is better at keeping radiation away.

The search for the best space shield will continue in the coming years. Hanging water bags on the walls of space stations would be an obvious solution. Our atmosphere on Earth has taught us that water protects us against radiation very well. But water is heavy and expensive to launch in space. Once in space all that weight – as well as the weight of the ISS – must periodically be boosted so that the Space Station keeps its orbit. We are looking for a lighter material that can do the same job: protect people from space radiation. To be continued…