My advice for an aspiring astronaut is to really follow your passion. I mean, study something that interests you, but also qualifies you to apply. NASA recruits from a wide variety of backgrounds. I know people who have applied to be an astronaut who ask me, well should I do this or should I do that. And I said, you know, it doesn't matter. The basic requirements are you have to be in good health, and you have to have a good heart, I mean in a technical way, not to be a kind person, well that helps. Study something that you like and do well in it.

I was an eight-year-old kid when I watched the first Apollo Moon Landing way back in 1969 and there was something about that moment that really stuck in my head. I'd always been interested in space and flying and I was building model rockets and model airplanes, but something about that moment, I can remember like it was yesterday watching the Apollo Lunar Lander approach the surface of the Moon and then later watching Neil Armstrong and Buzz Aldrin take the first steps on the Moon, and something that day started the dream for me that, hey, I want to be like those guys.

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.

One day, people will be able to buy tickets to visit space.

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.

When Russians were having troubles, the Space Shuttle supported the Space Station Mir bringing up much needed supplies and replacements, critical spares, really. That they were able to keep their space station going for much longer than they would have without us. So, I think that shows the value of international cooperation.

If we're not able to launch our own people and operate our own spacecraft anymore then, you know, space - whether it should be or not, it's seen as like a harbinger of technology. If you can fly people into space, if you can operate into space, then you've got high technology and if you're the leader of that, then you're the leader in technology. If we lose that on a more or less permanent basis, or for a long period of time, my fear is that it will creep into the national psyche in all areas and we as a nation as a whole will kind of be diminished.