Two months after I got out of test pilot school, I saw an advert that said NASA was recruiting more astronauts. The best job you could have as a test pilot was being an astronaut, so I volunteered.

No, I think most astronauts recognize that the space shuttle program is very high-risk, and are prepared for accidents.

There are several revenue streams that are near and present that could support a private space station, including in-space manufacturing, microgravity research, and tourism - for both individuals and sovereign nation astronauts - and in-space supply logistics.

Manned spaceflight has lost its glamour - understandably so, because it hardly seems inspiring, 40 years after Apollo, for astronauts merely to circle the Earth in the space shuttle and the International Space Station.

I think most astronauts are not risk takers. We take calculated risks for something that we think is worthwhile.

Astronauts have been stuck in low-Earth orbit, boldly going nowhere. American attempts to kick-start a new phase of lunar exploration have stalled amid the realisation that NASA's budget is too small for the job.

There are no wishy-washy astronauts. You don't get up there by being uncaring and blase. And whatever gave you the sense of tenacity and purpose to get that far in life is absolutely reaffirmed and deepened by the experience itself.

The photographs of space taken by our astronauts have been published all over the place. But the eye is a much more dynamic mechanism than any camera or pictures. It's a more exciting view in person than looking at the photographs. Of course, I personally am sick and tired of hearing people talk like that: I want to see it myself!

Our astronauts, when they go orbiting around the earth, they actually come back slightly younger than a twin that they would have on the planet Earth who was stationary. This is called the twin paradox.

Astronauts are very professional and when they're preparing for launch, they prepare for it as the most serious endeavor of our lives.

It's very dangerous to put astronauts on a moon base where there's radiation, solar flares and micro meteorites. It'd be much better to put robots on the moon and have them mentally connected to astronauts on the Earth.

We want to make sure we get living astronauts to the surface of Mars.

The images of Earth's delicate biosphere, contrasting with the sterile moonscape where the astronauts left their footsteps, have become iconic for environmentalists: these may indeed be the Apollo programme's most enduring legacy.

Before we had airplanes and astronauts, we really thought that there was an actual place beyond the clouds, somewhere over the rainbow. There was an actual place, and we could go above the clouds and find it there.

While we've taken seeds into space, and astronauts on the International Space Station have eaten lettuce they've grown, we haven't produced fruit in space, so we can't pollinate something.

The purpose of going to Mars is for humans to first begin to occupy, permanently, another planet in the solar system. The astronauts or pilgrims, whatever you might call them, are going to be very historically unique human beings.

So most astronauts getting ready to lift off are excited and very anxious and worried about that explosion - because if something goes wrong in the first seconds of launch, there's not very much you can do.

When many astronauts go to space, they see the insignificant size of the earth and vastness of space, and they become very religious, because they have seen the Signs of Allah.

I remember in 1967, when there was that terrible fire on NASA's Apollo 1 rocket that killed three astronauts, my father made pure oxygen and we lit this tiny cup and burned it. Suddenly, we had an unbelievable jet and a fire. You just could see exactly what had happened.

Sometimes astronauts feel a little ill or get minor scrapes. I trained as a crew medical officer to do basic treatment.

I am deeply grieved by the loss of the crew of Columbia. I express my sincere condolences to the families and friends of the astronauts. I believe that their names will remain as the bright sparkling stars in the universe and will light the way for those who will follow them on the difficult roads of space exploration.

The food isn't too bad. It's very different from the food that the astronauts ate in the very early days of the space program.

Ever since the environmental movement was sparked by photos of the whole Earth taken by astronauts onboard Apollo Lunar Modules, I've seen planetary exploration as an extension of a reverence and care for Earth.

Astronauts cannot pick their nicknames and can only get their nicknames from other astronauts. Any astronaut who tries to give himself a cool nickname will regret it by getting just the opposite from his astronaut friends.