NASA engineers yesterday found an apparent manufacturing flaw in a part of one of the boosters to be used on the next shuttle flight and are trying to determine whether the problem will affect the tentative August launch date.

An improved "nondestructive testing" technique that involves ultrasonic scanning revealed a welding irregularity in one of two aft skirts at Kennedy Space Center for the flight of the shuttle Discovery, according to Russell Bardos, director of propulsion for the National Aeronautics and Space Administration.

Inspections in recent days had turned up flaws in two of six booster aft skirts in NASA's inventory, prompting engineers to reinspect, using the new technique, the two skirts scheduled for the next launch.

"We're seeing more {flaws} because we're looking harder," Bardos said.

Improved techniques likely will uncover problems that may have existed in flight hardware in the past but had no ill effects, he added. "But because of the more-conservative position we're taking, it leads us to analyze these more carefully." David Winterhalter, director of systems engineering and analysis, said the review should be complete in a day or so.

"It's the nature of the business that we're in that we'll find things that need to be improved," he said.

The aft skirt is a cone-shaped segment that covers the booster's steering nozzle and provides support for the shuttle as it sits on the launch pad. It is manufactured by USBI Inc. and McDonnell Douglas.

The options, depending on severity of the flaw, are to use the aft skirt as is, to repair it or to replace it, Bardos said. "The {faulty} weld is in a low-stress area, and this is good. But it requires some calculations" to assess how to deal with it.

NASA officials have said they hope to set a new launch date this week.