KENNEDY SPACE CENTER, FLA. - In the Crawler Transporter (CT) area, a worker offloads some of the new crawler shoes that arrived. In the background is one of the two CTs. The new shoes were manufactured by ME Global in Duluth, Minn. The CT transports the Mobile Launcher Platform, with the assembled Space Shuttle aboard, between the refurbishment area, the VAB and Launch Complex Pads 39A and 39B. The crawlers have 456 shoes, 57 per belt (8 belts in all). Each shoe weighs 2,200 pounds. The original shoes were manufactured for the Apollo Program. Cracks appeared in the shoes in recent years spurring a need for replacement. The new manufacturer, in Duluth, Minn., has improved the design for Return to Flight and use through the balance of the Space Shuttle Program. KSC-04pd2136

The Space Shuttle program was the United States government's manned launch vehicle program from 1981 to 2011, administered by NASA and officially beginning in 1972. The Space Shuttle system—composed of an orbiter launched with two reusable solid rocket boosters and a disposable external fuel tank— carried up to eight astronauts and up to 50,000 lb (23,000 kg) of payload into low Earth orbit (LEO). When its mission was complete, the orbiter would re-enter the Earth's atmosphere and lands as a glider. Although the concept had been explored since the late 1960s, the program formally commenced in 1972 and was the focus of NASA's manned operations after the final Apollo and Skylab flights in the mid-1970s. It started with the launch of the first shuttle Columbia on April 12, 1981, on STS-1. and finished with its last mission, STS-135 flown by Atlantis, in July 2011.