NASA’s giant crawler transporter gets an overhaul
By David Szondy
September 9, 2012
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In a world where the latest smartphone is obsolete before you’ve figured out how to set the ringtones, there’s something satisfying about seeing a piece of technology that hits the sweet spot so perfectly that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.