High winds, which had threatened to postpone Monday's liftoff, abated in time for flight managers to clear Atlantis for blastoff. NASA had planned to dispatch Atlantis last week, but called off the launch when a hydrogen line burst open as the shuttle was being fueled for blastoff. The cracked weld was patched over the weekend, clearing the way for Monday's launch.
"It looks like we've got a good vehicle for you to ride today," shuttle launch director Mike Leinbach told the Atlantis crew shortly before blastoff. "It's time for you guys to take a ride."
Launch was delayed a few minutes by a software glitch, but at 4:44 p.m. the shuttle soared off its seaside launch pad, tearing through light patches of clouds as it sailed on twin pillars of flame and smoke out over the Atlantic Ocean.
The journey to the International Space Station and its three-man resident crew will take two days. Station commander Yury Onufrienko -- a Russian cosmonaut -- and NASA astronauts Dan Bursch and Carl Walz are the fourth crew to live aboard the station. They are scheduled to return to Earth in June after a six-month mission.
The station crew will host the shuttle squad for a quartet of spacewalks to attach a new 44-foot-long, 15-foot diameter exterior truss segment on top of the U.S. laboratory Destiny. The 14-ton segment, which provides structural support as well as communications, cooling and electrical connections, is the first of 11 segments that NASA plans to add to the station over the next two years.
The truss was designed to serve as the spinal column for the growing orbital complex, which eventually will include laboratories built by the Japanese, European and Russian space agencies, as well as three more sets of solar array panels to provide electrical power.
"We call it a structural segment, but it's really quite a bit more than that," said flight engineer and robot arm operator Ellen Ochoa. "If you get close to (the truss) you realize that it's covered with equipment. It has computers, it has fluid lines, miles of cable, almost 1,000 electrical connections. It's really quite a bit more than what we normally refer to it as."
The truss also will serve as a track for a mobile transporter, part of which is being delivered to the station by the Atlantis crew. The transporter will enable the station's robot arm to be moved around to different parts along the outside of the station.
Ochoa, who is making her fourth flight, will board the space station to use its beefier robotic crane to lift the truss out of the shuttle's payload bay and position it on top of the Destiny laboratory.
"Currently, the space station is in kind of two dimensions right now," said astronaut Steven Smith, one of the four spacewalkers aboard Atlantis.
The station extends forward and up, he explained in a prelaunch interview. With the new truss segment, the outpost will begin expanding to the left and right.
"It is really a structural backbone for building the station ... and to make it even more valuable in terms of a research facility. ... To do more research, we need more power. And the way we will do that is to put our truss on, followed by other truss sections, and those truss sections will include more solar arrays, for example, to provide more power," Smith said.
Smith, who is making his fourth spaceflight, is partnered with rookie astronaut Rex Walheim for two of the four spacewalks planned during Atlantis' flight. Crewmates Jerry Ross, who is flying for an unprecedented seventh time and rookie Lee Morin, are scheduled to conduct the other two outings.
Atlantis' crew is headed by three-time flier Michael Bloomfield. His co-pilot is rookie flier Stephen Frick.
The mission is NASA's second this year and the 109th since shuttle flights began in 1981.