(03/18/2002) -- STS-110 Mission Specialist Ellen Ochoa practices driving the M-113 armored personnel carrier, part of Terminal Countdown Demonstration Test activities. Accompanying her are fellow crew members Mission Specialist Rex Walheim (far left) and Pilot Stephen Frink (second from left). In front is the trainer. TCDT includes emergency egress training and a simulated launch countdown. The TCDT is held at KSC prior to each Space Shuttle flight. Scheduled for launch April 4, the 11-day mission will feature Shuttle Atlantis docking with the International Space Station (ISS) and delivering the S0 truss, the centerpiece-segment of the primary truss structure that will eventually extend over 300 feet