Crawler-transporter #2 in a December 2004 road test after track shoe replacement.
Manufacturer Marion Power Shovel
Engine Two 2,750 horsepower (2,050 kW) V16 Alco diesel engines. Two 1,006 horsepower (750 kW) generators, driven by two 1,065 horsepower (794 kW) engines, are used for jacking, steering, lighting, and ventilating.
Transmission 16 traction motors, powered by four 1,341 horsepower (1,000 kW) generators
Length 131 ft
Width 114 ft
Height Adjustable, 20 to 26 ft (6.1 to 7.9 m)
Curb weight 2,721 tonnes (2,721,000 kg; 6,000,000 lb)

The crawler-transporters are a pair of tracked vehicles used to transport spacecraft from NASA's Vehicle Assembly Building (VAB) along the Crawlerway to Launch Complex 39. They were originally used to transport the Saturn IB and Saturn V rockets during the Apollo, Skylab and Apollo–Soyuz programs. They were then used to transport Space Shuttles from 1981 to 2011. The crawler-transporters carry vehicles on the Mobile Launcher Platform, and after each launch return to the pad to take the platform back to the VAB.[1]

The two crawler-transporters were designed and built by Marion Power Shovel (now Bucyrus International) using components designed and built by Rockwell International at a cost of US$14 million each.[citation needed] They are the largest self powered land vehicles in the world. When they were built, they were the largest tracked vehicles in the world, a title later taken by the German Bagger 288 excavator.[2][3]



The crawler-transporter carrying the Ares I-X on its test flight

The crawler-transporter has a mass of 2,721 tonnes (2,721,000 kg; 6,000,000 lb) and has eight tracks, two on each corner.[2] Each track has 57 shoes, and each shoe weighs 1,984 pounds (900 kg). The vehicle measures 131 by 114 feet (40 by 35 m). The height from ground level to the platform is adjustable from 20 to 26 ft (6.1 to 7.9 m), and each side can be raised and lowered independently of the other. The crawler uses a laser guidance system and a leveling system to keep the Mobile Launcher Platform level within 10 minutes of arc (about 1 foot (30 cm) at the top of the Saturn V), while moving up the 5% grade to the launch site.[4] A separate laser docking system provides pinpoint accuracy when the crawler-transporter and Mobile Launch Platform are positioned in the VAB or at the launch pad.[5] A team of nearly 30 engineers, technicians and drivers operate the vehicle.[6]

A crawler-transporter carrying Discovery travels the ramp to Launch Pad 39B. The vehicle's back end can be raised, keeping the Shuttle and the MLP level.

The crawler has 16 traction motors, powered by four 1,341 horsepower (1,000 kW) generators, in turn driven by two 2,750 horsepower (2,050 kW) V16 Alco diesel engines. Two 1,006 horsepower (750 kW) generators, driven by two 1,065 horsepower (794 kW) engines, are used for jacking, steering, lighting, and ventilating. Two 201 horsepower (150 kW) generators are also available to power the Mobile Launcher Platform. The crawler's tanks hold 5,000 U.S. gallons (19,000 l; 4,200 imp gal) of diesel fuel, and it burns 125.7 US gal/mi (296 l/km; 104.7 imp gal/mi).[2]

The crawler is controlled from two control cabs located at either end of the vehicle, and travels along the 3.5 miles (5.6 km) crawlerway at a maximum speed of 1 mile per hour (1.6 km/h) loaded, or 2 miles per hour (3.2 km/h) unloaded. The average trip time from the VAB along the Crawlerway to Launch Complex 39 is about five hours.[2] Each crawlerway is 7 ft (2 m) deep and covered with Alabama and Tennessee river rock for its low friction properties to reduce the possibility of sparks. In 2000, NASA unearthed and restored an Apollo-era segment of the crawlerway to provide access to a high-bay building in order to provide protection from a hurricane.[7]

Kennedy Space Center has been using the same two crawlers, nicknamed "Hans" and "Franz" for the bodybuilding characters,[3] since their initial delivery in 1965. In their lifetime, they have traveled more than 3,400 miles (5,500 km), about the same driving distance as Miami to Seattle.[6]

The crawlers were overhauled in 2003 with upgrades to the Motor Control Center, which houses the switchgear and electrical controls of all of major systems onboard, a new engine and pump ventilation system and new diesel engine radiators, and replacement of the two driver cabs on each vehicle (one on each end).[6] NASA had planned to use the crawlers for the Constellation program after the Space Shuttle was retired in 2011; due to their age and need to support the heavier Ares V and its launch tower, NASA planned to modify the crawler's engines. With the cancellation of the Constellation program, the fate of the crawlers is unknown.[citation needed]

Cultural references

In a season three episode of Dirty Jobs, host Mike Rowe helps workers maintain a crawler-transporter. Rowe also takes the transporter for a short drive.[8]

The crawler is also featured in the 2011 motion picture, Transformers: Dark of the Moon.

In the Fallout 3 add on pack Broken Steel the fictional US government survivors, The Enclave, have a mobile base built on and into a heavily modified crawler.


Crawlerway junction at the LC-39 observation gantry. The right track leads to pad LC-39A (pictured with the Space Shuttle Endeavour), while the left track leads to pad LC-39B.


External links

Wikimedia Foundation. 2010.

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