Chris Hadfield: You come back in pretty good shape, plus I did space walks on my second flight which are really physical.
The life of an astronaut or a cosmonaut is extremely varied and complex and part of it is, during a space flight is, re-entering into the atmosphere and as you come into the air and it slows you down you can have a force that is many times the normal force of gravity on your body, four times is a typical level but it can easily be eight times or even more. Eight times your own weight pushing you down and you need to be able to understand how that feels on your body and whether you’re going to be able to work in that environment, and this centrifuge here is I think the largest human-rated centrifuge in the world. It’s eighteen metres, it can put eighteen times the force of gravity on your body, something that is very uncomfortable. But typically with the Soyuz we don’t pull more than eight or nine maximum and so that’s what we fly in the centrifuge. And when I was a CF-18 pilot, a fighter pilot, and when we’d pull back on the stick you could get eight or nine times the force of gravity. And so I’ve ridden in centrifuges before, but the purpose of this one is to truly understand and be ready for the environment that we’re going to see when we return to the earth from space.