Inside NASA's Vehicle Assembly Building Space Shuttle Discovery stretches as it waits for rollout to Launch Pad 39B.

Inside NASA's Vehicle Assembly Building, Space Shuttle Discovery stretches high above the floor as it waits for rollout to Launch Pad 39B. The shuttle sits on a mobile launcher platform atop the crawler-transporter. The rollout is an important step before launch of Discovery on mission STS-121 to the International Space Station. Discovery's launch is targeted for July 1 in a launch window that extends to July 19. During the 12-day mission, Discovery's crew will test new hardware and techniques to improve shuttle safety, as well as deliver supplies and make repairs to the station. Photo credit: NASA/Jack Pfaller