In 2006, I became the fist American to be allowed to go visit their astronaut center in China in Beijing. I think that it makes sense for the U.S. to work with China in the future and I hope to see, if the political atmosphere between the United States and China allow for us to do more cooperation together, especially in the area of human space flight. I think in the same way that it's help improve the relations between the U.S. and Russia; it would help to improve the relations between the U.S. and China.

Of course, you'll have to meet the physical and psychological demands. A space walk takes a lot of energy.

The thing that you worry about your first flight or any flight is some kind of a problem coming up that is going to keep you from doing it. Whether it's being hit by a car, or getting in a bad accident, or coming down with some other medical disqualification. But once the boosters light, you're going.

Coming down under a parachute is quite different as well. You hit the ground pretty hard, but all the systems work very well to keep it from hurting, so it doesn't even hurt when you hit. It was a great experience to be able to do both.

We were trying to do as much science as we could because that was the main purpose of the international space station. But without the shuttle to bring up heavy laboratory equipment and bring back samples, we were limited by what we could do, but I was proud that we actually accomplished more science that was planned for the flight. And I got a chance to do two Russian spacewalks on that flight, I had become an expert in U.S. spacewalks and using U.S. suits and techniques, and this was a chance to put on a Russian Orlan suit and do two construction space flights outside of the space station.

My running ambition is to keep doing it until I'm way past the point where I have any business running. Just to keep doing it throughout my whole life—to stay fit and feel good.

It was in the back of my mind, even while I was going to school, but it wasn't until I was at university studying engineering that I thought, well what do I really want to do? And I kind of came back to that and I said, well the degrees I'm trying to get are going to qualify me to apply. And so, that's what I did after I finished my, or after I was getting my doctorates. That's when I first applied to NASA.