The Mobile Launcher Platform is a two-story steel structure which provides a transportable launch base for the Space Shuttle. First used in the Apollo/Saturn program, the Platforms underwent modifications for the Shuttle.
The main body of each Platform is 25 feet (7.6 meters) high, 160 feet (49 meters) long, and 135 feet (41 meters) wide. At their parking sites north of the Vehicle Assembly Building, in the Vehicle Assembly Building high bays and at the launch pads, the Mobile Launcher Platforms rest on six pedestals 22 feet (6.7 meters) high.
Unloaded, a Platform weighs about 8.23 million pounds (3.73 million kilograms). With an unfueled Shuttle aboard, it weighs about 11 million pounds (5 million kilograms).
The main body of the Platform provides three openings – two for the exhaust of the solid rocket boosters and one for the main engines exhaust.
There are two large devices called Tail Service Masts, one on each side of the main engines exhaust hole. The masts provide several umbilical connections to the orbiter, including a liquid-oxygen line through one and a liquid-hydrogen line through another. These cryogenic propellants feed into the external tank from the pad tanks via these connections. At launch, the umbilicals pull away from the orbiter and retract into the Masts, where protective hoods rotate closed to shield them from the exhaust flames. Each Tail Service Mast assembly is 15 feet (4.6 meters) long, 9 feet (2.7 meters) wide, and rises 31 feet (9.4 meters) above the Platform deck.
Other umbilicals carry helium and nitrogen, as well as ground electrical power and communications links.
Eight attach posts, four on the aft skirt of each SRB, support and hold the Space Shuttle on the Mobile Launcher Platform. These posts fit on counterpart posts located in the Platform’s two solid rocket booster support wells. The space vehicle disconnects from the Platform by explosive nuts which release the giant studs linking the solid rocket attach posts with the Platform support posts.
Each Mobile Launcher Platform has two inner levels containing electrical, test and propellant-loading equipment.
