STS-120 Commander Pamela Melroy is ready for her turn at driving practice in the armored personnel carrier.

STS-120 Commander Pamela Melroy is ready for her turn at driving practice in the M-113 armored personnel carrier. The M-113 is part of emergency exit procedures from Launch Pad 39A. The training is part of terminal countdown demonstration test, or TCDT, activities the crew is undertaking at NASA's Kennedy Space Center. The TCDT also includes equipment familiarization and a simulated launch countdown. Mission STS-120, which will carry the Italian-built U.S. Node 2 to the International Space Station, is targeted for launch on Oct. 23. Photo credit: NASA/Kim Shiflett