One shoe, or link, from the treads of the Crawler-Transporter represents the massive tracked vehicles built in 1965 to move Apollo-Saturn rockets and the Space Shuttle 3.5 miles from the Vehicle Assembly Building to the launch pad at Kennedy Space Center between 1966 and 2011. Powered by two 2,750-horsepower diesel engines, the two crawler-transporters moved on four double-tracked tread belts, each containing 57 shoes like this one. Each shoe weighed approximately 1,984 pounds. The crawler-transporters traveled at 1 mile per hour when loaded and 2 miles per hour when unloaded. Nicknamed Hans and Franz, they covered more than 3,400 miles during their careers, about the driving distance from Miami to Seattle.