The fixed service structure is each pad's most prominent feature, standing 347 feet from ground level to the tip of the lightning mast. The lightning mast itself, 80 feet tall and made of fiberglass, supports a one-inch stainless steel cable that starts from an anchor 1,100 feet south of the fixed structure, angles up and over the mast, and then extends back down to a second anchor the same distance north. Below the lightning mast is a hammerhead crane used for pad hoisting operations.
Image to left: On Launch Pad 39A, a rescue team member and astronaut-suited worker approach landing in a slidewire basket reaching from the fixed service structure in the background during an emergency egress scenario. The four-hour exercise simulated normal launch countdown operations. It tested the team's rescue approaches on the fixed service structure, slidewire basket evacuation as well as communications and coordination. Credit: NASA/KSC
The fixed service structure is equipped with three swing arms that provide services or access to a shuttle on the pad. They are retracted when not in use. There are 12 floors on the FSS, positioned at 20-foot intervals. The first is located 27 feet above the pad surface. The structure also provides an emergency egress system for astronauts.
NASA's John F. Kennedy Space Center