This is the 32nd in an exclusive series of 50 articles, one published each day until July 20, exploring the 50th anniversary of the first-ever Moon landing. You can check out 50 Days to the Moon here every day.
One of the unsung heroes of the race to the Moon in the 1960s is an Earthbound behemoth that crunched along over crushed rock and never got going more than one mph.
Yet that creation—one of the lower-tech and lower-glamour elements of Apollo—has turned out to be so well-designed that it is one of the few major pieces of Apollo technology still in routine use for spaceflight.
This was NASA’s crawler-transporter, the tractor that carried the entire Saturn 5 rocket and its launch tower from the building where the rocket was assembled to the beachside launch pads.
The crawler, as it was typically called, solved an almost unimaginable problem in a way that is still hard to believe: it picked up a fully assembled Saturn V rocket that weighed 500,000 pounds, and its launch tower that weighed 11 million pounds, and it carried them 3.5 miles over a roadway out to the launch pad.
It was like picking up and moving a 44-story skyscraper—without toppling or even jarring it—almost four miles.
NASA had considered all kinds of means of getting its rocket from the point where it was assembled to the launch pad, including canals and rails. But when NASA officials saw the power and stability of big earth-moving equipment in mines in the early 1960s, they were persuaded that a tractor-like vehicle—with lots of high-tech adaptations—was a much better answer.
The result was labeled at the time as the largest “road vehicle” ever built. But among the special elements, the crawler needs its own, specially engineered roadway.
Here’s how the crawler works:
It has a perfectly level platform—a flat top—that is bigger than a baseball diamond, 131 feet by 114 feet.
That platform is built atop a vast infrastructure of steel support. At each corner are mounted a pair of tractor treads that look like those you’d find on a tank or a bulldozer—except much larger. Each tractor assembly is twice as high as a person; each individual tread of those tracks weighs a ton, and each tractor assembly has 71 of them.
The crawler can be driven either forward or backward: it has a glass-encased cab, with complete controls, facing in each direction. The crawler would drive into the Vehicle Assembly Building, the vast 50-story-tall building in which the stages of the Apollo rockets were assembled (and in which the space shuttles and their launch rockets were also assembled).
The crawler would carefully tuck in under the Saturn rocket and its launch platform and lift them up off their support pylons. The crawler had elaborate systems for keeping the rocket completely level, even during the 5º climb from the VAB to the launch pads.
The crawler itself—without any rocket on top—weighs 5.5 million pounds. It not only has its muscular support structure and its tractor treads but also two diesel engines to move the whole contraption, each the scale of a diesel locomotive. The crawler is reported to have a top speed of two miles per hour, but with its Apollo rocket on board, it moved out to the pad at about eight-tenths of a mile an hour, or about one foot a second. It took most of a day to get the Saturn 5 out to the pad, and the crawler had a crew of 20 to 30 people, half on-board tending to the vehicle’s engines and leveling machinery and the other half walking alongside to make sure nothing unusual was happening. The crawler uses 165 gallons of diesel fuel to go a mile, which is to say, it goes 32 feet on a gallon of fuel.
The roadway from the VAB to the two Apollo launchpads required as much advanced attention and construction as the crawler itself. It had to be able to handle a vehicle and its load that together totaled almost 18 million pounds. The ground had been engineered down almost 30 feet: six feet of roadbed, including almost three feet of crushed stone; and, below that, 24 feet further down, the ground had been settled and compressed. The crawler’s treads grind the top layer of rock in its path into powder.
The crawler formally debuted on May 25, 1966, the fifth anniversary of John F. Kennedy’s speech rallying Americans to go to the Moon. That was the first time it shouldered a full load, a mock-up version of the Saturn V and the full launch tower assembly.
The moment was considered significant enough that 500 officials from NASA, the federal government, and its contractors gathered at Cape Kennedy for the occasion, including rocket pioneer Wernher von Braun, who engineered the Saturn V; Robert Gilruth, the head of Houston’s Manned Spacecraft Center; and Robert Seamans, the second-in-command of NASA. (The Orlando Sentinel ran a story in advance saying rumors that President Lyndon Johnson would attend the rollout were not true.)
Another 4,500 people came just to watch the rollout of one of the strangest vehicles ever created.
NASA deputy chief Seamans, an MIT-trained engineer, was deeply skeptical of the crawler, which had had some problems during its final engineering and testing. “Today,” he said, “we’ll see if we have a good idea.” When the crawler’s diesel motors roared to life, the crowd cheered, but Seamans cautioned, “Wait until it actually moves.” Move it did, at its stately pace.
The crawlers were the work of the Marion Power Shovel Company, of Marion, Ohio, and NASA bought two identical vehicles. They have been refurbished over the years, and they are one of the few pieces of Apollo-era equipment that has been easily adapted to the post-Apollo era. They’ve been in service for more than 50 years. They moved not only every Apollo rocket to the pad but also every space shuttle. At least one of the two is being updated for use in moving NASA’s new Space Launch System (SLS) heavy-lift rocket to the launch pad, if and when it is finished and ready for use. Its twin remains in commission, moving smaller rockets to the pad.
The Orlando Sentinel reported Sunday that the crawlers have logged 5,000 miles taking America’s spaceships to their launch pads. Each spaceflight, with Apollo capsules reaching 25,000 mph and covering a half-million miles or more to the Moon, has started with a trip of 3.5 miles, run at slightly less than 1 mph.
Charles Fishman, who has written for Fast Company since its inception, has spent the past four years researching and writing One Giant Leap, his New York Times best-selling book about how it took 400,000 people, 20,000 companies, and one federal government to get 27 people to the Moon. (You can order it here.)
For each of the next 50 days, we’ll be posting a new story from Fishman—one you’ve likely never heard before—about the first effort to get to the Moon that illuminates both the historical effort and the current ones. New posts will appear here daily as well as be distributed via Fast Company’s social media. (Follow along at #50DaysToTheMoon).