CAPE CANAVERAL, Fla. - When the space shuttle Atlantis landed on Thursday, you can bet former astronaut Tom Jones was watching.

The four-time shuttle flyer, U.S. Air Force pilot and planetary scientist attended NASA's last shuttle launch - Discovery's July 4th liftoff from NASA's Kennedy Space Center (KSC) - and is no stranger to the risks of human spaceflight after his 11-year astronaut career. But as long as the effort pushes humanity into new frontiers and science realms, the crewed exploration of space is a worthy endeavor, Jones has said.

Jones flew three science missions aboard NASA space shuttles between 1994 and 1996, and helped deliver the U.S.-built Destiny laboratory to the International Space Station (ISS) during the Atlantis shuttle's STS-98 mission in 2001.

In his book Sky Walking: An Astronaut's Memoir, Jones details his orbital exploits and took time to answer some questions on his experience and NASA's plans for the space shuttle program.

SPACE.com: You're a veteran of four space shuttle flights, three spacewalks and one launch pad abort during your astronaut career. NASA has now launched its third orbiter flight since the Columbia accident. How do you view the risks of human spaceflight?

I was probably na?ve at first of how I calculated the risks. I believed we had minimized it to the absolutely lowest level possible and the people involved were so good that I didn't have a lot to worry about.

On the catastrophic problem of foam, I was right in there with the program managers assessing it as a non-issue. Now, I think the important thing is that when an astronaut straps into the space shuttle, or the Crew Exploration Vehicle, they need to know on an ethically honest basis that what they're attempting is worth the benefit of what they'll get out of this mission.

Looking at where NASA is now as the agency returns to flight, is it worth the risk?

If it's just to maintain human spaceflight for the U.S. and not go anywhere, with no increase to our knowledge base or attempt at some really tough exploration, I don't think it's worth it. [But] clear, ambitious goals are, perhaps that means going back to the Moon, or visiting near-Earth asteroids, which has a planetary protection role.

It's clear from Sky Walking that you are a very spiritual person and that your faith is important to you? How did that factor into your work as an astronaut?

I don't think it changed me dramatically. I just know that having my faith, and having support spiritually from my friends...that kind of support was essential. If you lay the entire burden and the pressure of the mission on your own shoulders, I think you're making it really tough on yourself.

Human beings are social and they need that support from their comrades, both in a technical and spiritual way. So I just felt that I not only had a spiritual connection with my crewmates, but I had hundreds of other people praying for me, and I believe that makes a difference in how you approach the work and your confidence level.

NASA's STS-121 shuttle mission, and more recently the STS-115 spaceflight, reopened the door on ISS construction, and you helped deliver the U.S. Destiny lab during STS-98 aboard Atlantis in 2001. Is the station what you expected it would be by now?

I expected that by 2006 it would be farther along, I thought it would be fully crewed by now with crews of six, and that all the labs would be up there, and of course so did NASA. And, of course, the Columbia accident kicked the chocks out from under those plans.

There are seven astronaut families, nine really counting those of the ISS Expedition 13 crew, watching closely as their loved ones fly in space, something your own family is quite familiar with. How vital is that family support for astronauts and why did you include it in Sky Walking?

I couldn't have done these missions with without their support, and I think that's true of every astronaut's career.

I just don't know how my wife Liz got through those four flights. I had the focus of the mission and the reward of actually getting to do the work in an incredibly exotic and beautiful place. She got all the stress and didn't get any reward, and that's a generous gift.

You already had two young children when you launched on your first spaceflight, how did you explain the risks of your astronaut job to them?

They were eight and five the first time I flew and 15 and 12 by the end, and more aware of the risks. They went from very giddy young children just taking snapshots [of launches] to the knowledge a few years later that they could lose their dad.

I told them that this was important, this is what astronauts do for their country. I think they took heart from that, if I was committed to it that it was alright. I think after four flights, having put my family through that ringer, it was time not to do one more time. It was very much a family decision.

In Sky Walking, you describe NASA's early partnership with Russia's Federal Space Agency during the construction of the International Space Station. Were those early ISS days more difficult than they should have been?

I guess I wasn't expecting them to be easy, but in the early 1990s I thought it would be easier. As a Cold Warrior, the suspicion was there that the Russian thing was purely political. But I learned a lot along the way.

I worked with cosmonauts, learned their capabilities and, as we know, since Columbia they've kept the space station going. I really had a conversion because I felt that we couldn't really afford to blow the space station...that this is our only chance to get this right.

The Russian element, as difficult as it was to digest in the beginning, proved essential, I think, to the credibility of the whole enterprise in the long run.

Is NASA at a similar crossroads now as it reaches back to the Moon and on toward Mars? That it has to get the station right to pursue NASA's vision?

I don't think the space station has to be on the critical path to get to the Moon or beyond to Mars. But it will be a lot more difficult if we ignore the opportunity that the space station offers.

NASA is in this very difficult transition of transferring from one flight vehicle to another. They haven't done that since the '70s and I think all of those lessons have to be relearned. It's probably the biggest challenge that NASA has faced after the Apollo Moon landings and you can't do it on a shoestring.

When you look back on your astronaut career, what - if anything - has been left unfinished?

I think that my hopes for my astronaut class were that we'd go to the Moon, but it didn't come to pass. But we got to work on a fantastic challenge and it took me to my limit. I think there are going to be other people who want to go to their limits to do some exploration out at the Moon and I believe we should go to the asteroids after that.

You can learn more about Jones' experiences in space at his website: www.astronauttomjones.com.