Perhaps you have seen it in movies like Armaggedon or The Martian but training to become an astronaut is physically demanding, emotionally draining, and mentally exhausting. And that's just the beginning.
Here are some photos from the training that Tim Peake and his teammates underwent at the European Space Agency:
Check out more photos on the Guardian.
(Images credit: Vittorio Crobu/ESA)
so that part of the underwater training they won't have to deal with