Every day, we get a little bit closer to the kind of expertise and the kind of experience we're going to need to go there. I'd love to be the guy walking on Mars.

We're going to be focusing our science on things that will take us farther and longer into space. For many of those experiments, the crew members are human guinea pigs, which is fine; that's part of my job. I don't mind being a human guinea pig.

I never made a career decision based solely on my desire to be an astronaut. I attended the Naval Academy because I wanted to be a Navy pilot. I majored in math because math had always come pretty easily to me and I liked it.

After assembly complete, when we have a larger crew on orbit, a more complex vehicle, more laboratories and more robot arms, maybe we'll have room for specialists. But right now we don't.

I think it's going to be a very important, unique data set in terms of measuring the behavior of your lower body in space and trying to figure out what we can do to preserve bone and muscle density.

There weren't any astronauts until I was about 10. Yuri Gagarin went into space right around my 10th birthday.

It took me a long time to get selected as an astronaut. In fact, I applied for 20 years before I was selected.