CAPE CANAVERAL, Fla. - After rollback of the rotating service structure, or RSS, on Launch Pad 39A at NASA's Kennedy Space Center in Florida, space shuttle Discovery is closer to launch on the STS-128 mission. On either side of the engine nozzles are the tail masts, which provide several umbilical connections to the orbiter, including a liquid-oxygen line through one and a liquid-hydrogen line through another.