Shuttle and Station Missions

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Sure Footing
A KSC worker uses a forklift to offload the newly arrived crawler shoes to a staging area. When Space Shuttle Discovery rolls to the pad next year, the trip is guaranteed to be on firm ground. That's because the Crawler Transporters used to carry the Space Shuttles to the launch pads are being overhauled, including the installation of new tread shoes.

"The Crawler Transporters are going to be in great shape for Return to Flight," said Mark Hamilton, NASA Crawler Transporter systems engineer at Kennedy Space Center in Florida.

Image to right: A KSC worker uses a forklift to move the recently arrived crawler shoes to the staging area. Credit: NASA

The job of NASA's two Crawlers is to transfer the Space Shuttle from the Vehicle Assembly Building (VAB) to the launch pad. The VAB is where an orbiter, external fuel tank and two Solid Rocket Boosters are assembled into one immense unit and readied for flight. From the VAB, the Crawler rolls the Space Shuttle down the rocky, 3-mile-long crawlerway to its seaside launch position.

Each of the monstrous Crawlers has eight tank-like tread belts that move it along at a speed of up to 1 mile an hour when carrying a Space Shuttle. The individual belts have 57 shoes, for a total of 456 shoes per crawler. A single shoe measures 7.5 feet long, 1.5 feet wide and weighs in at a whopping 1 ton!

NASA decided to replace the shoes after inspections late last year revealed cracks forming in the Crawler shoes. Most of the shoes were originally installed in 1965 and have helped launch every Apollo and Space Shuttle mission in history. After nearly 40 years of flawless service, the old shoes are being retired to make way for the latest model.

The new shoes were forged by ME Global Manufacturing of Duluth, Minn. Once ready to ship, groups of 20 shoes were loaded onto trucks for the 1,700-mile trek to KSC. The number of shoes transported at one time had to be limited to 20 so that their mammoth weight wouldn't tear up the highways on the way down.

In addition to receiving new shoes, the Crawlers are also getting other equipment overhauls and replacements. The gear-and-roller systems that drive the track belts are undergoing refurbishment to ensure they are ready to roll when the time comes to make a trip to the pad. The motor control systems are also being upgraded with new wiring to ensure that nothing short-circuits a Crawler's journey. Also, the replacement of Crawler components continues with the installation of new driver cabs, mufflers, radiators and ventilation systems.

In 2005, NASA plans to roll Space Shuttle Discovery out to launch pad 39B when absolutely sure the vehicle is ready to perform its mission. It's the sort of confidence secured by hard work, attention to detail, and the solid steps of 456 shoes.
Charlie Plain
NASA's John F. Kennedy Space Center