Twin columns of fire propel Space Shuttle Atlantis into a blue sky after liftoff from Launch Pad 39B.

Twin columns of fire propel Space Shuttle Atlantis into a clear blue sky after liftoff from Launch Pad 39B. At left is the fixed service structure, topped by the lightning mast. Clouds of smoke and steam nearly obscure the pad. Atlantis is heading for a rendezvous with the International Space Station on mission STS-115. Liftoff was on-time at 11:14:55 a.m. EDT. After several launch attempts were scrubbed due to weather and technical concerns, this launch was executed perfectly. Mission STS-115 is the 116th space shuttle flight, the 27th flight for orbiter Atlantis, and the 19th U.S. flight to the International Space Station. During the mission, Atlantis' astronauts will deliver and install the 17.5-ton, bus-sized P3/P4 integrated truss segment on the station. The girder-like truss includes a set of giant solar arrays, batteries and associated electronics and will provide one-fourth of the total power-generation capability for the completed station. STS-115 is scheduled to last 11 days with a planned landing at KSC