With the looming station blocking her view, Ivins then will rely on TV cameras as she attempts a daring bit of orbital baton twirling, flipping the $1.4 billion lab so it can be so it can be mounted atop the 13-story outpost.

And if problems crop up, the degree of difficulty will increase exponentially, threatening to halt a near-global project that involves 100,000 people from 16 nations on four continents.

"I wake up at night in a cold sweat thinking about this," said Ivins, one of NASA's most accomplished astronauts with four shuttle flights already under her extra small belt.

"My job will get incredibly difficult if everything is not working right - unbelievably hard," she said. "It is doable. But it is ugly."

Coming on the heels of a three-week delay to address dangerous solid-fuel rocket booster problems, Ivins and the Atlantis crew now are scheduled to blast off from Kennedy Space Center Wednesday with the U.S. Destiny lab in tow.

The intended scientific heart of the station, Destiny is a crucial linchpin that will enable an intricately orchestrated outpost assembly sequence to continue and other research facilities from Europe and Japan to be added to the complex.

"There is no way around it," said Atlantis mission specialist Tom Jones. "You've got to get the lab up to the station in order to expand it."

The complex job, however, is easier said than done.