William Oefelein left and Mark Polansky head for the slidewire baskets part of the emergency egress system.

On the 195-foot level of the fixed service structure on Launch Pad 39B, STS-116 Pilot William Oefelein (left) and Commander Mark Polansky head for the slidewire baskets, part of the emergency egress system. They and other crew members are practicing the procedure to get off the pad that are part of the prelaunch preparations known as terminal countdown demonstration test. The TCDT includes a simulated launch countdown and payload familiarization. The STS-116 mission is No. 20 to the International Space Station and construction flight 12A.1. The mission payload is the SPACEHAB module, the P5 integrated truss structure and other key components. Launch is scheduled for no earlier than Dec. 7. Photo credit: NASA/Kim Shiflett