KENNEDY SPACE CENTER, FLA. - After rollback of the rotating service structure (RSS) on Launch Pad 39B, Space Shuttle Discovery stands bathed in spotlights. Beneath the shuttle is the mobile launcher platform, which spans the flame trench below. The flame deflector system includes an inverted, V-shaped steel structure that receives and deflects the flames from the orbiter main engines on one side; the opposite side deflects the flames from the solid rocket boosters. 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 perm