The shuttle Discovery's astronauts will test three, not four, tile and wing leading edge repair techniques during the first post-Columbia shuttle flight in May, NASA officials clarified today.

Shuttle program manager William Parsons told CBS News that one proposed technique, the so-called overlay tile repair, will not be demonstrated by Discovery's crew because of safety issues.

The technique calls for fixing damaged heat-shield tiles by filling in voids with insulation and then covering the area with a heat-resistant sheet that would be held in place by drywall-type bolts screwed directly into the surrounding tile.

One option debated during a lengthy meeting Thursday at the Johnson Space Center was for the Discovery astronauts to demonstrate the overlay technique in the shuttle's crew cabin. Asked to clarify the results of the meeting, Parsons said today that concern about fine tile particles that could be released into the cabin air supply ruled out an overlay demonstration.

"So we have decided to carry the overlay and tools up but not pull them out and do a demonstration," he said. "The repair technique is so straight forward that we do not believe the demo is really necessary. We may pull them out and show them, who knows, but we won't demo."

The astronauts will, however, test a leading edge repair technique using a plug-like patch that would be inserted into a hole in a leading edge panel and held in place by an expansion bolt. They also will stage a spacewalk to test two other rudimetary repair techniques as reported Thursday.

In one, astronauts Stephen Robinson and Soichi Noguchi will test a leading edge crack repair technique and in the other, they will coat deliberately damaged tiles with a material that should increase their ability to reject heat.

Engineers, meanwhile, are still assessing whether additional robot arm inspections will be required to look for signs of actual damage.

If significant additional inspections ultimately are required after Discovery docks with the international space station, the repair demonstration spacewalk could be elminated because of scheduling conflicts. But shuttle managers are hopeful that will not be required.