CAPE CANAVERAL, Fla., Aug. 12 (UPI) -- While space shuttle technicians wrap up repairs on shuttle Atlantis' propulsion system, another equipment problem threatens NASA's plans to resume flights in September.
Workers have found cracked bearings in the massive Apollo-era crawler transporters that taxi the shuttles to the launch pad, NASA said Monday.
The bearings are in 20-inch-wide cylinders that lift the shuttle and its launch platform. The devices weigh almost 6 tons and keep the spaceship level during the climb to the launch pad. Each cylinder, which can be extended up to about 6 feet, has two bearings, one at the top and one at the bottom.
Technicians had removed two of 16 cylinders for maintenance and discovered cracks in three of the four bearings, said Kennedy Space Center spokesman George Diller.
Additional inspections showed of the crawler's 32 bearings, 15 are cracked. The finding prompted NASA to inspect its other crawler transporter, which turned out to have at least 13 cracked bearings.
"It's fairly significant on some of them," said Diller. "Some are no longer really operating as bearings."
Although the bearings, made of a steel derivative, are original equipment from the 1960s Apollo era, engineers are not convinced age is a factor in the cracks.
"There may be something else going on," Diller said.
Damage to some bearings is so extensive that repairing them is not likely an option. NASA has eight spare bearings in its storeroom and can manufacture additional bearings if needed. Although the original vendor still is in business, NASA is not expecting any additional bearings to be found as the components were a one-of-a-kind, special order.
"We don't think they have any more," said Diller.
How quickly one of the transporters can be repaired is under review. NASA had planned to move Atlantis from its assembly hangar to the launch pad at the end of August or early September.
The flight would be NASA's first since the space shuttles were grounded to repair tiny cracks in their fuel flow liners. The cracks have been welded and the orbiter's main engines were scheduled to be installed this week.
The crawler transporters are 5.5-million pound, 131-foot long tractors that originally were built to carry NASA's massive Saturn rockets to the launch pad for missions to the moon. The transporters were modified in the 1970s for the space shuttle program.