Space Shuttle Discovery sustained “an average amount of tile damage,” Wayne Hale, the NASA space shuttle program manager, said.

NASA was watching closely during and after the July 4 launch of Discovery on a mission to the International Space Station (ISS), to see whether foam insulation would break free from the Discovery external fuel tank and hit the orbiter vehicle, causing damage.

After Discovery landed, several NASA leaders who inspected it found it exceptionally “clean” and free from visible damage. There also seemed to be loss of only small pieces of foam insulation.

But a more thorough and time-consuming post-mission inspection of the orbiter did show some damage, though certainly nothing exceptional.

“We did not see any of the worse-than-average foam [insulation] release, and we did not see any worse than average tile damage,” Hale said in a news briefing. There was merely “an average amount of foam loss, an average amount of tile damage” to the Discovery orbiter vehicle, he said.

As for assessments just after Discovery landed that it seemed undamaged, Hale said, “Of course it looks great. If it didn’t look great, that would be horrible,” if damage was so extensive it was visible in a casual inspection.

Hale’s advice: “Beware of first reports” about the condition of a returning shuttle.

A formal review Friday to assess all the post-flight inspections of Discovery presented the true picture, he said.

The damage issue is critical, as shown by the mission of the Space Shuttle Columbia. Foam insulation broke free from the fuel tank and hit the leading edge of a Columbia orbiter wing, puncturing it. Later, the searing hot gases in reentry blasted inside the wing, causing structural failure and loss of the orbiter and crew on Feb. 1, 2003.

That’s why NASA wanted to launch Discovery this year in daylight, so cameras could capture any foam loss or other problems. While relatively little foam loss was seen, thanks to fuel tank and insulation redesigns, and the foam loss occurred at a point in flight where it wasn’t dangerous, that’s no guarantee there can’t be a problem when Space Shuttle Atlantis lifts off, Hale said.

The brilliant performance of Discovery “is one flight,” and not a guarantee of performance on future shuttle missions such as the Atlantis flight, he said.

Further improvements still need to be made in the design of external fuel tanks, such as in the ice frost ramps, where titanium may be used to shield the foam so that it doesn’t break loose during launches, Hale said. That potential fix, however, would first have to be proven in a wind tunnel test.

Another solution to the problem of potential damage to an orbiter is to repair it once it reaches orbit, such as during a docking with the ISS.

This, however, won’t become a routine procedure, Hale predicted, saying such an emergency measure would be unlikely to be certified for common use. Further, “I hope we never have to use” repairs, he said, meaning he hopes that no shuttle ever incurs substantial damage.

Even though Discovery came through its mission with no major damage, Hale said, “We continue to be vigilant about any damage that might occur to our thermal protection system” on the shuttle that protects it during each fiery reentry.

At some point, later this year, NASA may be sufficiently confident in the shuttle fixes that it will begin performing shuttle launches in the dark, briefers indicated.

Hale and other NASA briefers also covered other issues during a series of briefings.

With Atlantis poised for a launch in a window beginning Sunday, Aug. 27 and running into September, and the Russian spacecraft Soyuz set to blast off Sept. 14 to 18 on a mission to the ISS, there could be as few as two days between Atlantis undocking from the space station and Soyuz arriving.

This is one of a series of up to 18 U.S. shuttle flights to be launched by 2010, before the space shuttle fleet retires. It would be difficult to launch any more missions than the 16 plus two extra flights now foreseen, because suppliers of components for the fleet are preparing to shut down operations at some point, Hale said.

“If we need a couple more flights, it would be very difficult” to do so, he said.

All flights are needed to complete construction of the ISS, which will roughly double in size from its present configuration. But one briefer, Mike Suffradini, ISS manager, said he has “a high degree of confidence that we will be successful” and fly all the shuttle missions now scheduled before the shuttles are retired.

As for speculation that NASA will propose deep cuts in its science experiments budget so as to provide funds for the vision of manned missions o the moon, Mars and beyond, he discounted those rumors.

At this point, “We have not made any plans to make any reductions anywhere,” he said.

President Bush won’t move until February to hand Congress his proposal for the federal government budget for the fiscal year ending Sept. 30, 2008, which would include funds for NASA.