Astronauts cannot pick their nicknames and can only get their nicknames from other astronauts. Any astronaut who tries to give himself a cool nickname will regret it by getting just the opposite from his astronaut friends.

Astronauts cannot pick their nicknames and can only get their nicknames from other astronauts. Any astronaut who tries to give himself a cool nickname will regret it by getting just the opposite from his astronaut friends.

The hardest thing for me as an astronaut was to improve my swimming skills.

Viewing our planet was so compelling. Words like beautiful and awesome just don't do it justice. I felt that I was looking at a paradise. I was looking at heaven. I can't imagine any place being more beautiful than our planet and how lucky we are to be able to live here.

I was the first person to tweet from space, but now every astronaut tweets from space and does Instagram and Snapchat and Face - they have Facebook going. I think it's more of a personal relationship they have with space now. They see it as more obtainable than me watching my superhero Neil Armstrong and Buzz Aldrin walking on the moon. It's like, there's no way I can do that.

I think most astronauts are not risk takers. We take calculated risks for something that we think is worthwhile.

I applied to be an astronaut four times. I was rejected three times before I was accepted. So, it's about that, not - following your dream and not giving up.