Commander Rick Husband has just one other spaceflight under his belt and already he's flying as commander. That's a rarity.
"I think a lot of it has to do with being in the right place at the right time, for starters," says Husband, 45, an Air Force colonel from Amarillo, Texas.
The former test pilot was selected as an astronaut in 1994 on his fourth try. He made up his mind as a child that that was what he was going to do with his life.
"It's been pretty much a lifelong dream and just a thrill to be able to get to actually live it out," he says.
Another lifelong passion: singing.
Husband, a baritone, has been singing in church choirs for years. He used to sing in barbershop quartets, back during his school days.
Pilot William McCool says one of the most nerve-racking parts of training for this scientific research mission was learning to draw blood -- from others.
Columbia's two pilots are exempted from invasive medical tests in orbit, like blood draws. That means he and his commander have to draw blood from their crewmates.
McCool felt bad practicing on NASA volunteers.
"I didn't want to inflict pain," he recalls. "We weren't really gathering science, so everything that they were going through was for my benefit, and I guess I felt bad a little bit."
The 41-year-old Navy commander, a father of three sons, graduated second in his 1983 class at the Naval Academy. He went on to test pilot school and became an astronaut in 1996. This is his first spaceflight.
McCool grew up in Lubbock, Texas.
Payload commander Michael Anderson loves flying, both in aircraft and spacecraft, but he dislikes being launched.
It's the risk factor. "There's always that unknown," he says.
Anderson, 43, the son of an Air Force man, grew up on military bases.
"I was always fascinated by science-fiction shows, shows like 'Star Trek' and 'Lost in +Space+,"' he says. "And going out of your house and looking up and seeing jets fly by, that seemed like another very exciting thing to do. So I knew I wanted to fly airplanes, and I knew I wanted to do something really exciting, and I always had a natural interest in science.
"So it all kind of came together at a very young age, and I thought being an astronaut would be the perfect job."
Anderson was flying for the Air Force when NASA chose him in 1994 as one of only a handful of black astronauts. He traveled to Russia's Mir space station in 1998.
He is now a lieutenant colonel and in charge of Columbia's dozens of science experiments. His home is Spokane, Wash.
When Kalpana Chawla emigrated to the United States from India in the 1980s, she wanted to design aircraft. The space program was the furthest thing from her mind.
"That would be too far-fetched," says the 41-year-old engineer. But "one thing led to another," and she was chosen as an astronaut in 1994 after working at NASA's Ames Research Center and Overset Methods Inc. in Northern California.
On her only other spaceflight, in 1996, Chawla made a pair of mistakes that sent a science satellite tumbling out of control. Two other astronauts had to go out on a spacewalk to capture it.
"I stopped thinking about it after trying to figure out what are the lessons learned, and there are so many," she says. "After I had basically sorted that out, I figured it's time to really look at the future and not at the past."
She realizes some may see this flight as her chance to redeem herself.
David Brown is a Navy novelty: He's both a pilot and a doctor. He's also probably the only NASA astronaut to have worked as a circus performer.
Brown was a varsity gymnast at the College of William and Mary when he got a phone call one day: Would he like to join the circus? So during the summer of 1976, he was an acrobat, tumbler, stilt walker and 7-foot unicycle rider.
"What I really learned from that, and transfers directly to what I'm doing on this crew, is kind of the team work and the safety and the staying focused, even at the end of a long day when you're tired and you're doing some things that may have some risk to them."
He joined the Navy after his medical internship and went on to fly the A-6E Intruder and F-18. His current rank is captain.
NASA chose him as an astronaut in 1996. This is his first spaceflight; he will help with all the experiments.
Brown, 46, is taking up a flag from Yorktown High School in Arlington, Va., his alma mater, that another graduate took up Mount Everest. "I'm going to get it a little bit higher up, but I won't have to walk as far to get it there."
Laurel Clark, a Navy physician who worked undersea, likens the numerous launch delays to a marathon in which the finish line keeps moving out five miles.
"You've got to slow back down and maintain a pace," she says.
The 41-year-old Clark was a diving medical officer aboard submarines and then a naval flight surgeon. She became an astronaut in 1996.
Her family, including her 8-year-old son, worry sometimes about her being an astronaut. But she tells everyone "what an aggressive safety program we have."
"To me, there's a lot of different things that we do during life that could potentially harm us and I choose not to stop doing those things," she notes. "They've all come to accept that it's what I want to do."
She will help with Columbia's science experiments, which should have flown almost two years ago.
Her home is Racine, Wis.
Ilan Ramon, a colonel in Israel's air force, is the first Israeli to be launched into space.
"For Israel and for the Jewish community, it's something beyond being in space," he says. "It's a very symbolic mission."
His mother and grandmother survived the Auschwitz death camp, and his father was a Zionist who fought for Israel's statehood alongside his own father. The astronaut also fought for his country, in the Yom Kippur War in 1973 and the Lebanon War in 1982.
"I was born in Israel as an Israeli, so I'm kind of a dream fulfillment for all this last-century generation," he says.
Ramon, 48, served as a fighter pilot during the 1970s, 1980s and early 1990s, flying F-16s and F-4s. He was promoted in 1994 to lead Israel's department of operational requirement for weapon development and acquisition. He was selected as his country's first astronaut in 1997 and moved to Houston in 1998 to train for a shuttle flight.
He and his wife, Rona, have four children and call Tel Aviv home.