Mobile Launcher Platform 2 or MLP-2, formerly Mobile Launcher 2 or ML-2 is one of three Mobile Launcher Platforms used at Kennedy Space Center Launch Complex 39. During the late 1960s and early 1970s, it was used for Saturn V and Saturn INT-21 launches, and was subsequently used by the Space Shuttle.
Mobile Launcher Platform 2 Wikipedia
MLP-2 was originally constructed in 1964 as a Mobile Launcher for the Saturn V rocket, and was designated ML-2, or LUT-2. It was built by Ingalls Iron Works. The swing arms, which were constructed by Hayes International were added at a later date.
Following completion, ML-2 was used for the unmanned Apollo 6 mission, followed by three manned Apollo launches; Apollo 9, Apollo 12 and Apollo 14. It was subsequently used for the launch of Skylab on a Saturn INT-21 in 1973.
Following the launch of Skylab, ML-2 was the second of the Mobile Launchers to be converted for use by the Space Shuttle. The Launch Umbilical Tower was dismantled and placed into storage, and the base of the launch platform was modified to accommodate the locations of engines on the Shuttle. The platform was redesignated MLP-2.
In total, MLP-2 has been used for forty four Shuttle launches, starting in 1983. All of the orbiters except Columbia made their maiden flights from MLP-2. It was also the launch site for the ill-fated STS-51L mission, when Space Shuttle Challenger disintegrated shortly after launch, killing all seven crew.