Mobile Launcher Platform

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An MLP being carried by a Crawler-Transporter.

The Mobile Launcher Platform or MLP is a two-story structure used by NASA, along with the Crawler-Transporter, to transport the Space Shuttle stack from the Vehicle Assembly Building (VAB) to either Launch Pad 39-A or 39-B at the Kennedy Space Center, as well as serve as the vehicle's launch platform.

[edit] Description

Each MLP, of which NASA currently has three, is a two story rectangular structure that were originally constructed for the use of transporting the large Saturn V rocket for the Apollo lunar landing missions of the 1960s and 1970s. Each MLP originally had a launch umbilical tower with the familiar swing arms that moved away from the Saturn V at launch. For Skylab and Apollo-Soyuz, one of the MLPs was slightly modified with the so-called "milkstool" pedestal that allowed the shorter Saturn IB rocket to use the Saturn V tower.

After Apollo, two of the three MLPs were modified for support of the Space Shuttle in the 1970s (the third was modified and first used on STS-32). Each Shuttle-era MLP had the Apollo umbilical tower removed (these were later placed at the launchpads themselves as the so-called "Fixed Service Structure" or FSS) and reconfigured with the addition of twin Tail Service Masts on either side of the Main Engine exhaust vent, which contain liquid hydrogen (LH₂) and liquid oxygen (LOX) "T-0" disconnects (where LH₂ and LOX are loaded into the shuttle, as well as electrical hookups and flares that are used to burn off any ambient hydrogen vapors immediately prior to Main Engine start. Two additional holes for the SRBs were also added(the SSMEs used the original Saturn IB/Saturn V exhaust vent). Towers, known as "rain birds," for the water suppression system were also added, with the system being modified after STS-1 when acoustic loads damaged most of the Shuttle's TPS during liftoff.

Water is released onto the mobile launcher platform on Launch Pad 39A at the start of a rare sound suppression system test in 2004. During launch, 300,000 gallons are poured onto the pad in only 20 seconds.

The Space Shuttle assembly is held to the MLP through the use of eight attach posts, also called "hold-down bolts", four on the aft skirt of each Solid Rocket Booster. Immediately before SRB ignition, frangible nuts attached to the top of these bolts are detonated, releasing the assembly from the platform.

Each MLP weighs 9.25 million pounds and measures 160 feet by 135 feet (49 meters by 41 meters), and is 25 feet (7.6 meters) high. A MLP is carried from the Vehicle Assembly Building to the launch pad atop a Crawler-Transporter.

[edit] New Mobile Launcher Platforms

With the announcement by NASA to replace the Space Shuttle with the Orion spacecraft and the Ares I crew-launched vehicle and the Ares V cargo launch vehicle, NASA will construct, as part of the infrastructure improvements to LC-39, three new light-weight MLPs that will support the new Ares I rocket and its launch umbilical tower, which altogether will weigh about 9.5 million lbs. This will allow NASA to use the current Crawler-Transporter vehicles until their replacements are constructed to support the heavier Ares V rocket and its launch support tower^{[citation needed]}. The Ares V rocket will use the existing Shuttle MLPs, but modified and strengthened to support the heavier weight of the vehicle and its support tower.