English: Atlantis rockets into the blue sky above Launch Pad 39A after liftoff on the STS-117 mission. Beneath Atlantis' main engines are blue cones of light, known as shock or mach diamonds, which are a formation of shock waves in the exhaust plume of an aerospace propulsion system. The shuttle delivered a new segment to the starboard side of the International Space Station's backbone, known as the truss, during this mission in 2007. During three spacewalks station and shuttle crew installed the S3/S4 truss segment, deployed a set of solar arrays and prepared them for operation. STS-117 was the 118th space shuttle flight, the 21st flight to the station and the 28th flight for Atlantis.