US shuttle Atlantis speeded toward the International Space Station Saturday after a successful lift-off on the final mission for the 25-year-old spacecraft.
The shuttle blasted off from Cape Canaveral, Florida into a clear blue sky on Friday afternoon.
Several minutes after the launch, Atlantis's twin white solid rocket boosters were separated and dropped into the Atlantic Ocean.
The shuttle's three engines propelled the vehicle on its eight-and-a-half-minute climb to orbit, assisted by the two orbital maneuvering system engines.
"Launch was just phenomenal," said associate NASA administrator Bill Gerstenmaier during a postlaunch news conference.
The 32nd and final voyage for Atlantis, first launched in 1985, will take the astronauts to the orbiting space research facility, delivering an integrated cargo carrier and a Russian-built mini research module.
Before it gets there, the shuttle may have to dodge a piece of space debris that NASA is tracking, Gerstenmaier said.
"I think the maneuver will be on Sunday if we determine we need to do it," he said.
Just before liftoff, launch director Mike Leinbach wished the Atlantis crew "good luck and goodspeed," encouraging them to "have a little fun up there."
Based on current plans, the Atlantis launch is one of the last three missions of NASA's shuttle program, which is due to be mothballed at the end of the year.
After this mission, only two more shuttle launches remain, one in September for Discovery and the final blast off for Endeavour in November.
Early Friday the shuttle's external tank was filled with over 500,000 gallons (two million liters) of liquid oxygen and liquid hydrogen in an operation lasting some two hours, NASA said.
In a poignant moment for NASA as the US space agency counts down towards the end of an era in human spaceflight, Atlantis will be retired upon its safe return home after a quarter-century career.
During a 12-day mission largely spent moored to the ISS, Atlantis and the crew will deliver over 12 tonnes of equipment, as astronauts seek to complete the 100-billion-dollar orbiting outpost.
"Twelve days, three (spacewalks), tons of robotics.... We're putting on spares that make us feel good about the long-term sustainability of the ISS, replacing batteries that have been up there for a while, and docking a Russian-built ISS module," said space shuttle program manager John Shannon.
"This flight has a little bit of everything, and it's been a great preparation for the team."
President Barack Obama effectively abandoned in February plans by his predecessor George W. Bush to send astronauts back to the moon by 2020 and perhaps on to Mars.
Constrained by soaring deficits, Obama submitted a budget to Congress that encouraged NASA to focus instead on developing commercial transport alternatives to ferry astronauts to the ISS after the shuttle program ends.
Nonetheless, Obama set a bold new course in April for the future of US space travel, laying out a vision to send American astronauts into Mars orbit by the mid-2030s.
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