Cape Canaveral, Fla. ? With the entire space shuttle fleet grounded this summer by fuel-line cracks, NASA said Friday it would weld the flawed plumbing and aim for a late-September launch.

Space shuttle program manager Ron Dittemore said NASA had assembled “a Super Bowl of welders” from across the country for the unprecedented job, which will begin next week on shuttle Atlantis. The hope is to launch Atlantis on a belated space station construction mission as early as Sept. 28.

Dittemore said the welding would require more precision than typical hard-hat work.

NASA decided to bump Atlantis ahead of Columbia’s scientific research mission with the first Israeli astronaut, because of the space station’s more pressing needs. Endeavour will follow Atlantis to the station as early as Nov. 2. Columbia, which should have been in orbit right now, will not fly until the end of November at the earliest.

Shuttle flights were halted earlier this summer after 11 hairline cracks no longer than three-tenths of an inch were found in the hydrogen-fuel lines of all four spaceships. The cracks were in the metal liners and are thought to have been there for years and perhaps decades.

NASA still is not sure exactly how or when the cracking occurred. But Dittemore said it was clear that the intense roar and vibration of the main engines, or the effect of the fuel, contributed to the problem.

The cracks, for now, are not considered dangerous. But engineers fear the cracks might grow and then splinter into shrapnel that could get sucked into an engine with catastrophic consequences.

Before deciding on welding, NASA reviewed other repair options and even evaluated whether the cracks needed to be fixed at all.

NASA will test-fire spare engines to try to solve the mystery of the cracks and determine whether the welding will keep the fuel lines intact for the next 20 years.

“We feel confident about our knowledge of the crack itself and our ability to repair it, but we’re not as confident about what that smoking gun is,” Dittemore said. “It’s going to take us a little bit of detective work to figure that out.”