Final liftoff to end U.S. space shuttle era

Space shuttle Atlantis was set to rocket off its seaside launch pad in Florida on Friday on the final flight in the 30-year U.S. shuttle program.
Liftoff was set for 11:26 a.m. EDT (1526 GMT), but as many as 750,000 tourists who have flooded into the Cape Canaveral area may have to stay for the weekend to catch a final glimpse of a shuttle vaulting into orbit.
Meteorologists on Thursday said there was a 70% chance the launch would be delayed by rain, clouds and thunderstorms.
"It's just our typical tropical stuff," NASA's Shuttle Launch Weather Officer told reporters on Thursday morning.
Conditions were expected to improve on Saturday, but even then forecasters saw only a 60% chance of acceptable weather.
Atlantis and its four-person crew will be carrying food and other supplies critical to the International Space Station.
The 12-day mission to the orbital research outpost 354 km above Earth is among the most routine of any of the 134 that preceded it.
It is seen as a key insurance policy, however, in case commercial delivery firms hired to resupply the station starting next year run into problems with their new rockets.
Space Exploration Technologies, or SpaceX, which is owned by Internet entrepreneur Elon Musk, successfully tested its Dragon capsule in orbit last December and hopes to make it to the space station in a second test flight later this year.
The other compact cargo hauler, being developed by aerospace company Orbital Sciences Corp, has yet to make its official debut.
With the space shuttles retiring, the station and its six-member live-aboard crew will need regular supply runs from both companies, in addition to deliveries from Russian, European and Japanese spacecraft.
NASA has been steadily building the $100 bln station over the last 11 years. Completing it was the primary reason the United States decided to fix the shuttles and resume flying after the 2003 Columbia disaster.
With the space station assembly complete, the United States wants to use the $4 bln or so it has been spending each year to maintain and operate NASA's three space shuttles to develop new spacecraft that can travel beyond the station's near-Earth orbit, where the shuttles cannot go.