One of the things, and the most exciting, actually definitely the most exciting thing is, having children. You know, I didn't have children before. I had been married only a year before my space station mission, so having three-year-olds is a whole new experience and that's the new adventure. It may sound funny because people have kids every day, but having your own kids, having my own kids, was as fundamentally, or maybe even more fundamentally life changing then even flying in space.

If you think about the energy that a rocket engine has to put out and all the fuel and you're sitting on top of like a bomb. And on the Space Shuttle, that big orange tank is filled with liquid hydrogen and liquid oxygen, the white cell rocket boosters on the sides are filled with solid propellant. There's a lot of energy in all those chemicals there and you've got to control it in a way so it doesn't explode. So, there's a lot of plumbing, a lot of valving, a lot of control systems, and it's a very complicated thing. So, how do you bring the price of that down?

What keeps me up at night? Probably most, thinking about the future for my kids. It sounds kind of funny, but not so much what they're going to do, but how as a parent, how my wife and I as parents, how best we should prepare them for the world. And I know everybody does this, I think everybody stays up at night thinking about the best thing for their kids, and astronauts are no different.

I attended a big human space flight conference in Beijing and I was going as myself. And really, there weren't any NASA astronauts there, I was the only so-called American Astronaut there. We had astronauts from most of the other countries, certainly from Russia, from France, from Japan, several other countries, but it was a little bit odd because here we are at an international gathering of a lot of astronauts and I'm talking about somewhere upwards of 30 or so astronauts, and I'm the only American. And I wasn't even there in an official capacity.

We were doing something called telemedicine, where we were using the ultrasound. One interesting application of this ultrasound is the possibility that you could possibly use it to measure critical bone areas during a long space mission and track if you're losing bone in these areas. On Earth, when they check you for bone loss, you get in this big machine. It's the size of a room and it's got a platform with an x-ray that scans your whole body and in critical areas and it takes a while and it just wouldn't be practical to have a machine like that in space.

On the mission I brought a flag from China, I brought the stone sculpture from Hong Kong, and I brought a scroll from Taiwan. And what I wanted to do is, because as I was going up and I am this Chinese-American, I wanted to represent Chinese people from the major population centers around the world where there are a lot of Chinese people. And so, I wanted to bring something from each of those places and so it really wasn't a political thing and I hope people saw it that way. I was born here, I was raised in the U.S., and I'm an American first, but also very proud of my heritage.

I'm Chinese-American, of course, and so it's very interesting to see China actually launch their own astronauts, becoming the third nation, following the United States and Russia, to do so.