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.

Richard Branson is probably the most visible of the private commercial space guys, and what is venture, Virgin Galactic is about is sub orbital flight. That is, you'll see a spacecraft that looks more or less like an airplane and it will fly into space, but only spend about 15 minutes. It'll go up in a parabolic arc and then fall back down, and so the customers on that flight will only get about five minutes of weightlessness. They'll get to glimpse the horizon of the Earth, take a look at it before just before they start coming back down into the atmosphere.

That was in 1994, July, 1994, and I can remember that like it was yesterday too because it was the culmination of a childhood dream to finally be laying on the launch pad inside a space shuttle and getting ready to be launched into space. The impression of going into a space shuttle is that it looks like a brand new simulator. We spend so many hours inside a simulator that everything is very familiar. Every switch, the seats, the way things work, but the vehicle, the actual spacecraft looks brand new because it hasn't been used nearly as much as the simulators.

I loved flying as much as I thought I would and continue to fly aircraft.

Space is very unforgiving business

I had done everything I could do as an astronaut, and we have a long line of inexperienced astronauts waiting for their first missions, and so my role really should be to step aside and help them prepare for their missions, rather than to try to get another mission.

One of my challenges was to try to photograph the Great Wall of China. And I did actually take some photos, but it was hard to discern the wall with the naked eye.