Service Structure

A service structure (supply tower or launch tower) is a structure constructed on a launch pad to facilitate fueling, loading cargo and crew into the spacecraft. A supply tower also usually includes an elevator which allows maintenance and crew access. Immediately before ignition of the rocket's motors all connections between the tower and the craft are severed and the bridges over which these connections pass often quickly swing away to prevent damage to the structure or vehicle. In contrast with launch towers, service structure towers do not guide rockets as they lift off.

Service structures generally consist of fixed components and mobile ones. The structures at Kennedy Space Center Launch Complex 39 pads include a rotating service structure that is moved in place around the shuttle stack for period of time that the space craft sits on the pad prior to launch, usually several weeks. That structure is rotated back out of the way several hours prior to the launch while the fixed service structure remains in place at all times. Unmanned and manned rockets such as the Delta, Saturn V also used fixed and mobile service structure configurations with the mobile portion moved away from the vehicle several hours before launch. The Saturn's "fixed service structure", however, was formally called the launch umbilical tower (LUT) and was fixed to a Mobile Launcher Platform.

Similarly, Soviet designed service structures such those at the Baikonur Cosmodrome stand while servicing the vehicle the entire structure falls away at launch time.

• Launch at Baikonur Cosmodrome Site No. 1

• Saturn V with fixed (left) and mobile (right) service structures