Life in space isn't easy, Tim knows because he had to go through six years of training before his trip to the International Space Station. One of the most daunting moments of a mission is when you head outside on your first space walk. Tim visits the European Space Agency HQ in Cologne, meeting up with Rosemary Coogan a trainee astronaut. Using the latest cutting-edge virtual reality technology, Tim gives Rosemary a lesson on how to survive, when you're floating 400 kilometers above the earth.

But even when you're inside the space station, life is totally different. Dealing with being weightless as you float around can be fun, but everything around you floats too. We see how Tim prepares his specially designed space food: everything from pizza to strawberry shortbreads. And there's something you really don't want floating around your living quarters… so going to the loo in space is much more complicated. Then there's the weekly Saturday morning clean up that includes two hours of vacuuming.

But the biggest strain on your body is the forces experienced when you're launched into space. Tim visits the RAF Centre of Aviation Medicine in Lincolnshire, where he meets space medicine doctor Joseph Britton. Tim undergoes a G-Force test that all astronauts dread, he is spun around in a capsule, replicating the forces as a rocket accelerates to ten times the speed of a bullet. All this training will be essential if we are to realise our dream of building a home on the moon and Mars.

It's said that the first person to walk on Mars has already been born. And to see the challenges of such an audacious mission, Tim travels to the US to meet Kai Staats. Housed under 6000 panes of glass, Biosphere 2 in Arizona is the world's largest enclosed ecological habitat: there's a forest and a coral reef, and people like Kai are working out how we take all this with us to survive on Mars.