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.

In the 19th Century people were looking for the Northwest Passage. Ships were lost and brave people were killed, but that doesn't mean we never went back to that part of the world again, and I consider it the same in space exploration.

We would like to carry out 100 percent, or maybe more, of our scientific program; I would like to devote some of my spare time toward extra scientific work.

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.

If I wasn't doing this kind of exploration, I'd like to be doing some other kind of exploration. It might be more risky, or less risky, but, in the business of exploration, risk is part of the territory.

It so happened that my goals kind of matched my career progression toward becoming an astronaut.

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.