Space Shuttle Atlantis rockets into the blue sky above Launch Pad 39A after liftoff.

Space Shuttle Atlantis rockets into the blue sky above Launch Pad 39A after liftoff. Beneath Atlantis' main engines are blue cones of light, known as shock or mach diamonds. They are a formation of shock waves in the exhaust plume of an aerospace propulsion system. Liftoff of Atlantis on mission STS-117 to the International Space Station was on time at 7:38:04 p.m. EDT. The shuttle is delivering a new segment to the starboard side of the International Space Station's backbone, known as the truss. Three spacewalks are planned to install the S3/S4 truss segment, deploy a set of solar arrays and prepare them for operation. STS-117 is the 118th space shuttle flight, the 21st flight to the station, the 28th flight for Atlantis and the first of four flights planned for 2007. Photo Credit: NASA/Tony Gray & Don Kight