Almost everything I do when I approach an operational problem comes from the time I've been in space. It's a way of organizing your thoughts. We use problem-solving; what we call "what-if-ing." What if this happened? What would we do? We go over plan B, C, D, E, F, and whatever else, depending on the criticality of what we're doing. This kind of thing can be applied almost everywhere, even at home.

I am definitely a little more nervous for my colleagues when I'm working at mission control than I am myself, on the shuttle.

Will we go explore? Absolutely. That's what humans have been doing since we left the caves in Ethiopia. Why? Because this is part of our nature. We're curious. We want to push the envelope. That will never stop. We will see people on Mars, hopefully in our lifetime. My hope is that the endeavour is so large, so complex, so technically challenging, so demanding and so uplifting, that it will be done with a consortium of nations. I hope the people who do set foot on Mars will do so for all mankind, and not just one nation in particular.

The prerequisite that people have a scientific or engineering degree or a medical degree limits the number of female astronauts. Right now, still, we have about 20 per cent of people who have that prerequisite who are female. So hey, girls: Embrace the very fun career of science and technology. Look at computer science. That's what I did.

I always call myself a space construction worker. We were only the second mission ever to go to the space station. There was nothing on board. We brought the first three tons of equipment, including some of the Imax camera stuff. We literally switched the light on to the station and walked in. It was an assembly mission.

The one thing we can't really train for is weightlessness, real weightlessness. It's a ton of fun. It's pure Newtonian physics. You push in one direction, you go in the opposite direction with an equal force.

Some people will always be volunteers to explore, and it is, in my mind, a privilege.