For the last several years and culminating in six months in orbit next year, I've been training for my third space flight. This one is almost in a category completely different than the previous two, specifically to live in on the space station for six months, to command a space ship and to fly a new rocket ship.

Careers, like rockets, don't always take off on time. The trick is to always keep the engine running.

My vision is for a fully reusable rocket transport system between Earth and Mars that is able to re-fuel on Mars - this is very important - so you don't have to carry the return fuel when you go there.

Once you get into space, you can really unleash a lot of creativity, but the launch itself? I have been through all of the creative ways, and believe me, chemical rockets are the best.

I've always been interested in the idea of space exploration. When I was younger it was just a dream, but the theory of rockets being able to travel through space was very much alive. I found it very exciting.

My parents grew up during the space race, and I think they imagined the future would be us living on moon bases and everyone has rocket shoes.

The years of space flight since the orbiting of Sputnik I back in 1957 had produced many fascinating results, but they had also brought a realization of the many problems that surrounded the use of rockets for space flight.

It seems that 'rocket scientist' is a job category that's here for the long haul, like 'mortician.' But all this activity masks an important point: rockets are not a terribly efficient way to lift things into space.

If you're at Kennedy Space Center, the closest you're going to get to a rocket going off is like three and a half miles.

Space travel is the only technology that is more dangerous and more expensive now than it was in its first year. Fifty years after Yuri Gagarin, the space shuttle ended up being more dangerous and more expensive to fly than those first throwaway rockets, even though large portions of it were reusable. It's absurd.

Reusable rockets promise much easier testing because you should usually get them back, and you can debug as you go rather than having to get everything perfect the first time.

Whether solid rockets are more or less likely to fail than liquid-fuel rockets is debatable. More serious, though, is that when they do fail, it's usually violent and spectacular.

If you're going to go to the moon, you don't shoot the rocket right at the moon. You have to go at it obliquely.

The Orion capsule uses an escape system quite like that of the Apollo spacecraft in the 1960s and 70s: an 'escape tower' containing a solid-fuel rocket that will pull it up and away from Ares I in a pinch.

Rocket scientists agree that we have about reached the limit of our ability to travel in space using chemical rockets. To achieve anything near the speed of light we will need a new energy source and a new propellant. Nuclear fission is not an option.

I'm never going to go to Mars, but I've helped inspire, thank goodness, the people who built the rockets and sent our photographic equipment off to Mars.

Growing up in the '60s and early '70s, with the space flight and the Apollo program, I always loved planes. I always loved rockets and I always loved space travel.

From the moment of using rocket devices, a great new era will begin in astronomy: the epoch of the more intensive study of the firmament.

When you launch in a rocket, you're not really flying that rocket. You're just sort of hanging on.

During launch, the outside of the rocket is covered in a protective fairing, so we couldn't see outside, but as soon as that was jettisoned, my first view of the earth was over the Pacific Ocean, which was this wonderful deep blue, with clouds just over the top, and sunlight streaming in through the window.

One of the things that we can say with confidence is that we will have much lighter, much stronger materials, and this will reduce the cost of air flight, and the cost of rockets.

Rocket science is tough, and rockets have a way of failing.

Sometimes people wonder why aeroplanes are so cheap and rockets are so expensive. Even the most superficial comparison shows one obvious difference: aeroplane engines use outside air to burn their fuel, while rockets have to carry their own oxidisers along.

I certainly remember building model rockets. It was fun to watch the rocket blast into the air, suspenseful to wonder if the parachute would open to bring the rocket safely back.