It's been more than two years since the last shuttle, Columbia, disintegrated in the skies above Texas, killing all seven astronauts.
Now NASA, which has already delayed the Discovery flight twice, says it's ready again to go uphill. That's their expression for the extremely dangerous and risky blastoff into space -- uphill.
The pressure's on, but you wouldn't know it from talking to the confident commander of the Discovery, a veteran astronaut, who's married with two young children.
Her name is Eileen Collins, and as Correspondent Dan Rather reported last spring, she seems to have no fear of flying.
But 60 Minutes II was surprised to learn that Collins is afraid of roller coasters.
"How am I supposed to believe that when you ride the fire on the Shuttle?" asks Rather.
"I tried last summer. I stood in line for 20 minutes, got all the way up to the top, took a look at what I was gonna get on, and I turned around and went right back down," says Collins, laughing.
Go figure why someone who's afraid of roller coasters feels comfortable on the shuttle, rocketing into space with 77-million horsepower, able to fly from Los Angeles to New York in just 10 minutes.
But Commander Collins says she is ready to fly. She's been training in a $100-million shuttle simulator, which looks and feels just like the real thing. She invited 60 Minutes II to go along for the trip uphill.
After we strapped in, the entire simulator tilted back to mimic the real shuttle cockpit on the launch pad. Astronauts say it can be uncomfortable, even painful, lying on their backs for several hours, waiting for the final countdown.
Everything shook as we accelerated from zero to 120 in under 10 seconds, from zero to a 1,000 miles per hour in just one minute.
"Six thousand feet right now, 7,000. 8,000. There's 10,000 feet. We're 400 knots right now," says Collins. "You're actually 100 knots by the time you clear the tower -- 100 miles an hour. Now we're going Mach One. We just broke the speed of sound."
In just two minutes, we burned through two million pounds of fuel. "My stomach feels like it's in my throat," says Rather.
Collins became an astronaut in 1991, five years after the Challenger exploded shortly after liftoff, killing seven astronauts. She had her own close call in 1999, when she became the first female commander on a shuttle flight. The flight started with a dramatic malfunction, all because of one frayed wire.
"It was rubbing against the top of a screw, and rubbed through the insulation, and caused a temporary loss of power," says Collins. "We lost two main engine controllers. Little did we know we also had fuel leaking out of one of our main engines. We actually ran out of gas."
Backup systems and computers saved the shuttle then, and it made it safely into orbit. Four years later, a catastrophe hit. That same shuttle, the Columbia, broke apart and disintegrated, trying to return to earth after 16 days in space. Seven astronauts died.
Why take the risk again?
"Well, first of all, I love my job. And I think back to when I was a teenager, you know, I started to get interested in flying when I was a teenager. And I picked it up at age 20," says Collins. "And I started flying and I loved it. So, I joined the Air Force at a time when women were just accepted into Air Force flying. This was 1978. And became a pilot, and I said, 'Hey, this is something I can do.'"
Collins became a flight instructor in the Air Force and rose to the rank of colonel before retiring. The Discovery mission will be her fourth in space.
Is the shuttle safe to fly now? "Well, the shuttle is certainly safe to fly, and I certainly would not get on the shuttle if I didn't think it were safe," says Collins.
For the next mission, Collins will be relying again on the rocket scientists and specialists on the ground in mission control. For weeks, they've also been practicing computer simulations: liftoffs, docking with the international space station, space walks, and re-entries.
The man in charge in Mission Control is Flight Director Paul Hill. What's the riskiest part of the mission?
"If you had to pick one, going uphill, no question," says Hill. "Powered flight, 7 million pounds of fire. Controlling that fire as it comes out of the back end of the spaceship going uphill. Ten minutes later, we've gone from zero to 17,500 miles an hour. That's a scary proposition."
Is he worried? "We're worried, but we're always worried," says Hill. "There are things in space flight that can kill the crew."
"It's a dangerous line of work," says Rather.
"You bet," says Hill. "It's just as dangerous today as it was before the accident."
Collins says she has to live with that danger, and so does her family. She says her husband, a commercial airline pilot, understands. But it's been harder explaining it to her two children.
Do they know about the Challenger? Do they know about Columbia?
"About six weeks before the Columbia accident, I told my daughter," says Collins. "My daughter was 7 at the time. I told her about Challenger. … She didn't know about it. And I told her about the accident."
"I had a book. I showed her a picture of the crew. I showed her a picture of the explosion," adds Collins. "And I said, 'You know, I want you to hear this from me. I don't want somebody at school to tell you about it. And I want you to know that the shuttle is very safe and this accident is not gonna happen again.' And then, two months later, the Columbia accident happened."