The sweltering Texas sun fills the airy campus of the Johnson Space Center with what feels like a heavy tropical mist. Meanwhile, in building 9A and others, astronauts are busy training.

These men and women spend time in virtual reality gear, full-motion space vehicle mock-ups and high-speed airplanes, all designed to prepare them to go into outer space.

A few, like space veteran Michael Foale, are planning to blast into space this October, not on a space shuttle, but on a Soyuz rocket, the 300-ton workhorse of the Russian space program. His crew's destination is the International Space Station, the world's only orbiting vehicle where humans can live and work in space.

It is a mission unlike any Mr. Foale has taken before: ?One of the more interesting aspects of our flight is we don't know really how we are going to come home. Some people may say you're unwise taking a one-way trip to space, but we always have the Soyuz vehicle that we launch on to return in. We have that available to us throughout our mission.?

A space shuttle was originally scheduled to return Mr. Foale and his colleague, cosmonaut Alexander Kaleri, to earth after their six-month mission on the orbiting outpost. However, the return flight was thrown into question after the February disintegration of the Space Shuttle Columbia that killed all seven astronauts on board. Columbia was only about 15 minutes away from touchdown when it shattered into tens of thousands of pieces. The accident grounded the space shuttle fleet.

NASA could still send a shuttle to bring the crew back home if it is able to implement recommendations of the board investigating the Columbia disaster.

After the tragedy, some observers questioned the risk of human exploration of space. But Mr. Foale says it would have been a mistake to suspend human presence aboard the 240-mile-high space station while NASA recovered from the loss of Columbia: ?For us not to step up and continue in space for me is really not an option. We need to show perseverance in our goals and dreams in maintaining a human presence in space. Now that we have a space station there, we need to develop it and we need to use it.?

Mr. Foale says that the space station partners immediately offered help after Columbia and its crew were lost. Their actions illustrated the strength and adaptability of international cooperation:

?No sooner had Columbia had its terrible tragedy, two days later the Russians launched a progress rocket. It was kind of unnoticed because we were so shocked, but it was a significant thing. The Russian partner maintained its stalwart support of the space station and was reliable and continued to do what it said it was going to do; that is, supply the station. Our international partners stepped forward and said, how can we pay for Soyuz missions to help get Americans and Russians to the station to maintain our joint interest and investment in the space station

While on board, Mr. Foale and Cosmonaut Kaleri will carry out numerous experiments, including one using ultrasound technology to study what happens to their hearts and lungs after long periods in zero gravity. Mr. Foale says NASA's advancement of ultrasound technology is now helping doctors in hospitals on earth to quickly determine injuries.

Mr. Kaleri, who has spent over one year in space, agrees that a lot of the discoveries made there improve life for everyone. This is one of the reasons he risks flying into space. ?For me, it is better to have a risky mission to help all the people on the earth than to have a risk by myself.?

A third crew member is Pedro Duque, a Spaniard with the European Space Agency. He says the risks of space flight are something astronauts accept when they take the job. However, Columbia's loss was personally very difficult. He had trained with three of the seven astronauts who perished.

Mr. Duque says their deaths, as painful as they were, will lead to improvements: ?We have the sensation that every time something happens there is no doubt that everything becomes a little safer. Of course, that brings a little bit more to your mind the fact that space flight is risky and we have to be aware of the choice we made at some point in our lives. We're still going, and we have faith in the engineers and ground processing teams that will put the Soyuz rocket together, fuel it and launch it into space.?

These three men are the only ones scheduled to travel into space this year. Astronaut Michael Foale says it's a long wait to go into space, and the recent disaster can make it longer:

?Every astronaut, in my experience has dreamt or wanted to be an astronaut since childhood. These are men and women who have wanted to do this for so long that I think waiting another two or three years, maybe five or even 10 years to fly in space is still worth it for them. We have seen a terrible tragedy this year. I saw a tragedy when I was trying to become an astronaut and we were in the first class after Challenger, we knew we wouldn't fly soon. When one wants to become an astronaut and one sees how dangerous flying in space can be, it doesn't change one's outlook on why they want to do this.?

Even before the Columbia tragedy, NASA had to reduce the number of crew members on the space station because of budget cuts.

Given these realities, astronaut Ronald Garan knows it may be a while before he straps into a space vehicle bound for outer space. He is one of a third of the nearly 150 NASA astronauts who have not yet flown. Despite being earth-bound, he looks forward to going where perhaps no one has gone before:

?I would like to see us as a nation getting back to launching vehicles as soon as possible. But I really feel that when I joined NASA, it was really a rewarding experience to be part of the team; that is, part of the space program. Even though, if it's five or 10 or 15 years before I can fly, in those years I will be contributing to the overall effort for space exploration. We need to go beyond. The International Space Station is a stepping stone for us to go beyond. The things that we learn in terms of long duration space flight will help us go back to the moon or even to Mars.?

Mr. Garan and many of the space program's employees are ready to make changes to improve the space shuttle's safety. He says it is important to remember the space shuttle is an incredibly complex vehicle and that NASA has a way of making really difficult things look easy.

?The Columbia accident investigation board has done a wonderful job, and a lot of hours and people are going through the details of what exactly happened and how we are going to fix it so it does not happen again,? says Mr. Gran. ?Those recommendations are going to be accomplished, and we are going to come out of the other end of this. However, we are not going to be able to take out all of the risk. That level of risk is what we accept as being astronauts. It comes with the job and you understand that.?

Over 400 people from more than 30 countries followed Yuri Gagarin and Alan Shepard's first ventures into space. As the true explorers of our time, astronauts will continue to take the risk of flying beyond the bounds of planet earth in the name of progress for all humanity.