Some of the largest vehicles on earth are diesels. Earth-moving equipment, ocean liners, freight trains-all are diesel-powered. It should come as no surprise then that the largest self-propelled land vehicle in existence is powered by, you guessed it, diesel engines-a title the NASA Crawlers have held for 40 years.
There are actually two Crawlers, one nicknamed Hans, the other, Franz. Both Crawlers were designed by Bucyrus International and built for NASA by the Marion Power Shovel Co. The Crawlers were initially built during the days of the Apollo program and were delivered in 1965-they are now used to take the space shuttle and mobile launch platform to one of the two actual launch sites. The Crawlers are aptly named (Hans and Franz don't exactly sound very nimble), traveling at a maximum loaded speed of about 0.9 mph.
Let's talk about payload capacity for a second. Your new Chevy, Dodge, or Ford diesels come in at about a 4,000-6,000-pound payload capacity for whatever you're hauling. Unfortunately, the shuttle and launch pad combine for about 12.6 million pounds, leaving the family rig just a little bit short. The Crawlers were built to handle this massive problem, and the solution was equally massive. A Crawler weighs about 5.5 million pounds by itself, which is part of the reason it has to go so slowly. Even unloaded, its maximum speed is a blazing 2 mph. The platform on top of the Crawler where it connects to the launch pad is a 90-foot square (about the same size as the infield on a baseball field), and with the shuttle on top, the Crawler is more than 40 stories high-taller than most skyscrapers.
Everything is massive on the Crawler, and diesel powers it all. There are four diesels: two engines are used for jacking, steering, lighting, and ventilation and two are used for the drive system. Total horsepower comes in at more than 7,500 for all engines combined. The drive system is a combination of 16 electric motors, with two 2,750hp Alco diesel engines used to power four 1,000-kW generators. Two more 1,065hp diesels are used for jacking, steering, lighting and ventilation. Even with all that power on tap, it still only takes one person to drive.
The Crawler unloaded on a test run after receiving new "shoes." All 456 shoes (57 per track) were replaced with new ones in 2004. The Crawler moves along the Crawlerway (below), a specially made road system for the Crawlers to travel, so they don't sink into the ground. | 
The Crawler is making a turn with 18 million pounds of weight. From beginning to end, a turn like this on the way to the launch pad may take up to 25 minutes. |
Each track on the vehicle is 10 feet high, and the combined weight of all the shoes on just one track is 125,400 pounds. | |