Space Shuttle Atlantis rolls out of the Vehicle Assembly Building to Launch Pad 39B via the crawler-transporter underneath.

Sitting on top of the mobile launcher platform, Space Shuttle Atlantis rolls out of the Vehicle Assembly Building to Launch Pad 39B via the crawler-transporter underneath. First motion was at 1:05 a.m. The slow speed of the crawler results in a 6-hour trek to the pad approximately 4 miles away. Atlantis' launch window begins Aug. 27 for an 11-day mission to the International Space Station. The STS-115 crew of six astronauts will continue construction of the station and install their cargo, the Port 3/4 truss segment with its two large solar arrays. Photo credit: NASA/Troy Cryder