Mobile launch platform

The Mobile Launcher Platform (MLP) is one of three two-story structures used by NASA at the Kennedy Space Center to support the Space Shuttle stack throughout the build-up and launch process: during assembly at the Vehicle Assembly Building (VAB), while being transported to Launch Pads 39A and B, and as the vehicle's launch platform. NASA's three MLPs were originally constructed for the Apollo program to launch the Saturn V rockets in the 1960s and 1970s, and remained in service through the end of the shuttle program in 2011 with alterations.

The MLP was constructed for transporting and launching the Saturn V rocket for the Apollo program lunar landing missions of the 1960s and 1970s. Each MLP originally had a single exhaust vent for the Saturn V's engines. The MLPs also featured a 120 m (380 ft) Launch Umbilical Tower (LUT) with nine arms that permitted servicing of the vehicle on the launch pad, and swung away from it at launch. For Skylab and Apollo-Soyuz, MLP No. 1 was modified with a pedestal (called "the milkstool") that allowed the shorter Saturn IB rocket to use the Saturn V tower and service arms, and Saturn V Ground Support Equipment (GSE) was removed or de-activated and Saturn IB GSE equipment was installed.

After the Apollo program, the launcher platforms were modified for the Space Shuttle (Space Transport System). The umbilical towers from Mobile Launchers 2 and 3 were removed. Portions of these tower structures were erected at the two launch pads, 39A and 39B. These permanent structures are now known as the Fixed Service Structures (FSS). The umbilical tower from Mobile Launcher 1 (which was the platform used for the most significant Apollo missions) was taken apart and stored in the Kennedy Space Center's industrial area. Efforts to preserve it in the 1990s failed, however, for lack of funding and it was scrapped.

In addition to removal of the umbilical towers, each Shuttle-era MLP was extensively reconfigured with the addition of two Tail Service Masts, one on either side of the Main Engine exhaust vent. These 9.4 m (31 ft) masts contained the feed lines through which liquid hydrogen (LH₂) and liquid oxygen (LOX) were loaded into the shuttle's external fuel tank, as well as electrical hookups and flares that were used to burn off any ambient hydrogen vapors at the launch site immediately prior to Main Engine start.

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