CAPE CANAVERAL, Fla. -- Shuttle Columbia's planned move to the launch pad Wednesday was postponed for a day or two after an Apollo-era crawler-transporter broke down in the doorway of Kennedy Space Center's mammoth Vehicle Assembly Building.
The mechanical failure, however, is not expected to delay the shuttle's planned Feb. 28 launch on a Hubble Space Telescope servicing mission.
"We've got plenty of contingency time in our launch processing schedule, so there will be no impact to the launch if we get to the pad in the next couple of days," said KSC spokesman Bruce Buckingham.
Built in the mid-1960s to haul Saturn 5 moon rockets to the launch pad, the diesel-powered transporter began inching its way out of the 52-story assembly building about 7:48 a.m. EST (1148 GMT).
But then a steering mechanism on one of the transporter's double-tracked crawlers began acting erratically, prompting engineers to halt the planned 3.5-mile (5.6-kilometer) move.
With a mobile launch platform and a fully assembled shuttle sitting atop it, the transporter was left stranded -- at least temporarily -- partway in and partway out of one of the assembly building's four giant doorways."I've got to admit it. We're actually stuck," Buckingham said.
Engineers think a steering system sensor or actuator might have failed. The tank-like truck on the right front end of the transporter, consequently, failed to align itself properly for the move.
If that indeed is the case, a spare sensor or actuator will be installed on the transporter and Columbia will begin making its way to KSC's launch pad 39A early Thursday.
If the problem proves a bit more difficult to solve, a second transporter will be moved into place and Columbia's rollout to the launch pad will be tentatively scheduled for Friday.
Measuring 131 feet (40 meters) long and 114 feet (34.5 meters) wide, the transporters are made up of a large, flat metal top deck with four double-tracked trucks at each of its corners.
Two 2,750-horsepower diesel engines drive four 1,000-kilowatt generators that provide electrical power to 16 traction motors. The motors turn the double-tracked trucks, propelling the transporter along at a top speed of two mph (3.2 kilometers per hour).
Contractor drivers operate the vehicle from inside a control cab located on the right front corner of the top deck of the transporter.
Standard operating procedure calls for a transporter to be driven into place beneath a mobile launch platform once a fully assembled shuttle is mounted atop it and checked out.
The transporter jacks the launch platform up off of its pedestals and then begins a six-hour trek out to the launch pad. In this case, the operation was halted before the transporter could move more than 100 feet (30.3 meters).
Despite their age, NASA has had relatively few problems with its two crawler transporters, which have traveled a combined 3,400 miles (5,440 kilometers) -- or about the distance between Miami and Seattle -- since the mid-1960s.
"They're generally very trustworthy vehicles," Buckingham said.
"The irony," added Jack King, a spokesman for NASA shuttle contractor United Space Alliance, "is that they were only built to go 100 miles (160 kilometers) for the Apollo program."
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