KSC-06pd1299

KENNEDY SPACE CENTER, FLA. - On Launch Pad 39B, workers check one of the two trucks that move the rotating service structure (RSS). In preparation for the July 1 launch of Space Shuttle Discovery on mission STS-121, the RSS is being rolled away from the shuttle. The RSS provides protected access to the orbiter for changeout and servicing of payloads at the pad. The structure is supported by a rotating bridge that pivots about a vertical axis on the west side of the pad's flame trench. The hinge column rests on the pad surface and is braced to the fixed service structure. Support for the outer end of the bridge is provided by two eight-wheel, motor-driven trucks that move along circular twin rails installed flush with the pad surface. The track crosses the flame trench on a permanent bridge. The RSS is 102 feet long, 50 feet wide and 130 feet high. The structure has orbiter access platforms at five levels to provide access to the payload bay while the orbiter is being serviced in the RSS. Each platform has independent extendable planks that can be arranged to conform to a payload's configuration. This mission is the 115th shuttle flight and the 18th U.S. flight to the International Space Station. Photo credit: NASA/Kim Shiflett