Thomas Marshburn

We have to be plumbers, electricians, construction engineers, or workers, on the space station, but at the same time running a laboratory, being scientists, being the best laboratory assistants we can be. It's all in a bundle; it's very exciting, it's a lot of fun.

When we're on the space station, we orbit the Earth 16 times per day, which means we're constantly moving to and away from the sun. From light to shadow, the temperature swings by 300 degrees. Of course we're protected by the gear we wear, but you can definitely feel this temperature change.

In 2009 I went up on the space shuttle. I was in space for 16 days and docked at the space station for 11 days. The entire crew did five space walks, of which I was involved with three of them. When you're doing a space walk, you always have a buddy with you. It's a very dangerous environment when you're doing a space walk.

Then there was the challenge to keep doing better and better, to fly the best test flight that anybody had ever flown. That led to my being recognized as one of the more experienced test pilots, and that led to the astronaut business.