Mobile Launcher Platform - Function

Function

Each MLP weighs 8,230,000 pounds (3,730,000 kg) unloaded and roughly 11,000,000 pounds (5,000,000 kg) with an unfueled Shuttle aboard, measures 160 feet (49 m) by 135 feet (41 m), and is 25 feet (7.6 m) high. It was carried by a crawler-transporter, which measures 131 feet (40 m) by 114 feet (35 m), and is 20 feet (6.1 m) high. Each crawler weighs about 6,000,000 pounds (3,000,000 kg) unloaded, has a maximum speed of about 1 mile (1.6 km) per hour loaded, and has a leveling system designed to keep the launch vehicle vertical while negotiating the 5 percent grade leading to the top of the launch pad. Two 2,750-horsepower (2,050 kW) diesel engines power each crawler.

Originally designated the "Mobile Launcher", the MLP was designed as part of NASA's strategy for vertical assembly and transport of space vehicles. Vertical assembly allows the preparation of the spacecraft in a ready-for-launch position, and avoids the additional step of lifting or craning a horizontally-assembled vehicle onto the launchpad (as the engineers of the Soviet space program chose to do).

The Mobile Launcher Platform was set atop six legs inside the massive Vehicle Assembly building. The Solid Rocket Boosters were mounted on top of the MLP. The External Tank was then lowered between the two boosters and attached to them. After that, the orbiter was lowered into position and attached to the External Tank. The Crawler-Transporter then carried the combined platform and vehicle to the launch site, and deposited them there together. Once the launch was completed, the crawler-transporter retrieved the empty MLP from the pad to be readied for its next use.