The Shuttle Crawler Transporter

Explanation: NASA's Crawler-Transporters are the largest tracked vehicles in existence. Although the crawlers pack over 5,000 horsepower , their top speed is less than two kilometers per hour when fully loaded. Eleven people are needed to drive a single crawler. Diesel fuel mileage is about 350 liters per kilometer (less than 0.007 miles per gallon). The crawler 's function is to move NASA's space shuttles -- complete with launch platforms -- from the Assembly Building to the Launch Pad at Kennedy Space Center in Florida , USA . Two of these massive machines have operated since the Apollo era and have now crawled over 4,000 kilometers, all the while keeping their contents perfectly upright. In this picture a crawler transports the shuttle Columbia to the pad prior to its March 1st launch on the latest Hubble Space Telelescope Servicing Mission .