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NASA’s giant crawler transporter gets an overhaul


September 9, 2012

NASA's massive crawler - at the time it entered service, it was the largest land vehicle on Earth (Image: NASA)

NASA's massive crawler - at the time it entered service, it was the largest land vehicle on Earth (Image: NASA)

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NASA’s giant crawler transporter that carried the Apollo missions and the Space Shuttles to the launch pad is getting an upgrade. In service since the mid-1960s, the 2,495 tonne (2,750 ton) vehicle is receiving new engines and other improvements that will allow it to carry the future Space Launch System (SLS) rockets due to enter service in 2017.

In a world where the latest smartphone is obsolete before you’ve figured out how to set the ringtones, there’s something satisfying about seeing a piece of technology that hits the sweet spot so perfectly that there’s no reason to replace it. Despite being over half a century old, B-52s are still on active duty and it isn’t unusual to walk through a high-tech factory and see some ancient machine from the 1930s at work because nothing better has been invented.

So it is at the Kennedy Space Center where the crawler transporters that carry rockets between the Vehicle Assembly Building (VAB) and the launch pads at Launch Complex 39. In the 47 years that the crawler transporters “Hans” and “Franz” have been at work, they’ve rolled out every Apollo, Skylab and Apollo Soyuz mission and all the Shuttle missions. They’ve traveled more than 3,400 miles (5,500 km) and are on the national register. You’d expect to see them in a museum by now all cleaned up and with a neat little plaque. Instead, they’re still in service and one of the crawlers is now undergoing an upgrade to allow it to handle giant rockets well into the next decade.

Delivered in 1965, the two crawlers were needed because the weather in Florida is so appalling. Previously, rockets had been built right on the launch pad. That worked in dry, sunny New Mexico where the V2s were tested, but Florida is wet, humid and prone to hurricanes, so the Apollo launch vehicles had to be assembled and prepared in the VAB and then rolled out to the pad.

Moving up to 6,360 metric ton (7,000 short ton) of Saturn V rocket and launching platform up to four miles (6.43 km) safely isn’t easy. It requires a machine of unprecedented size capable of withstanding insane punishment and yet remain utterly stable.

Built by Marion Power Shovel Company of Marion, Ohio, the crawlers are 131 feet (39.92 m) long, 113 feet (34.44 m) wide and stand 20-26 feet (6.09-7.92 m) high. Weighing in at 2,495 tonne (2,750 ton) unladen, they required a specially designed road to handle the weight and ensure that no sparks (which don't go well with rocket fuel) are generated as the metal treads roll over it. These giant treads are made of 456 steel shoes 7.5 feet (2.28 m) long, 1.5 feet (0.45 m) wide and weigh 0.9 tonne (1.1 ton each.

In all, this makes the crawlers the world’s largest self-powered land vehicle and at the time it entered service, it was the largest land vehicle on Earth.

The crawlers run on 16 traction motors, powered by four 1,341 bhp (1,000 kW) generators driven by two 2,750 bhp (2,050 kW) V16 Alco diesel engines. That sounds like the crawlers should go like a stabbed rat, but in fact, they take six hours to go from the Vehicle Assembly Building to pad at a maximum speed of one mile per hour (1.6 kph) loaded or two miles per hour (3.2 kph) unloaded. Those six hours are always nerve wracking for the NASA technicians because during that time the giant, very delicate rockets are exposed to rain, wind and even lightning.

They may be powerful, but they aren’t cheap to run. Not that you’d expect them to be at a price tag of US$14 million each in 1965. According to NASA statistics, they gulp down diesel fuel at a rate of 125.7 gallons per mile (295.6 liters per kilometer) – that’s 42 feet per gallon (3.38 meters per liter).

Despite their great size, the controls of the crawlers are actually extremely precise. They uses a laser guidance system and hydraulic controls and jacks designed to keep a skyscraper-sized rocket stable to within ten minutes of arc.

The current upgrades are the first the crawlers have had since 2003. After completion, the Crawler 2 will increase its current lifting capacity, set during the Shuttle program, from 5,443 tonne (6,000 ton) to 8,164 tonne (9,000 ton). New 1,500 kilowatt power diesel engines, built by Cummins Engines in Minnesota, were delivered last December to replace the old Apollo era ones. Work began in February this year with 20 technicians on the job and required the VAB’s massive overhead crane to swap the engines.

Along with the engines, the crawler will receive 16 higher-capacity jacking cylinders, new roller bushings and roller shafts, plus upgraded electrical power system components. In addition they will get cable replacements and driver cab controls as well as new electrical control systems, programmable logic controller modernization, new instrumentation systems, a new belt pin lubrication system, new hydraulic valves and hydraulic tubing replacements.

With all that, it’s a bit of a shame that these stalwart machines have to play second fiddle to the space rockets they transport.

Sources: NASA, Transportation Nation

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past. All articles by David Szondy


They are electric. The crawler is a series hybrid, like a Chevy Volt. The engines are just generators....

Chris Maresca

Although they are technical marvels why don't they just use rails? I don't mean your standard 2 pair rails but maybe 10 spread out or whatever is required to carry the load. I'm not a big fan of threaded vehicles because of their high price and maintenance costs.


I was hoping the replacement engines would be green electric or fuel cell engines. Space travel has always served as the springboard for cutting edge technology.


that thing is a LONG way short of being the heaviest self-propelled vehicle.

the Krupp earth mover is 45,000 Tons (so 20 times as heavy).


"World’s largest self-powered land vehicle" ? at measly 2500 tons ;) ? Bucket-wheel excavator reach around 14000 tons, or to be precise in the case of the Bagger 293, 14200 tons.


thk, The power necessary to move the weight of a fully loaded cargo freighter can not be met at this time with a fuel cell or a straight battery powered motor. If you had really read the article you would have found that they use electric motors to move the tracks. Anything other than a diesel generator will have to produce kilowatts of power. Short of putting a nuclear reactor in the crawlers we have nothing today that will supply that amount of power.

Doug Doyle

@thk - Space travel hasn't been the springboard for cutting edge technology for about 30 years.

Why else do you think that the latest, greatest phone is simply a redesigned case with more off the shelf components crammed into it and more software written to take advantage of existing technology?

The unfortunate truth is that people (in general) no longer care about the space program nor look to it for any kind of inspiration.


This needs a HHO kit to get better fuel usage

Allen Clarke

"-You didn't built that!" Roads and bridges built that thing, not NASA...

Edgar Castelo

"at the time it entered service, it the largest land vehicle on Earth" For all those confused about it's size. And yes in the 1960's it was the largest. At that time even the largest Bucket Wheel loader was only tipping the scales at 550 tones.

Beisswenger Design

So NASA now builds the Cummins diesel generator sets ?


If they also improved the fuel footage, then the upgrades count as eco-modding.

Gregg Eshelman
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