A record heat wave here may delay space shuttle Discovery's return flight to Cape Canaveral atop a Boeing 747.

"The way this heat looks now, we will not ferry out until Sunday at the earliest, even though we'd be ready to go on Saturday," shuttle recovery manager Fritz Widick said today at a news conference. The last few days' 100-plus-degree temperatures were to blame, he said, and more such heat was predicted.

Widick explained that temperatures of less than 90 degrees are needed for the Boeing 747 to achieve enough lift to get the 100-ton spaceliner into the air. He said higher temperatures reduce the air's density, making it difficult for the 747 to clear the runway and gain altitude.

Widick said that the arrival at the Kennedy Space Center may even be later because if the plane has to refuel, it will do so at Altus Air Force Base in Oklahoma where temperatures also have been above 100.

Widick said Discovery apparently came through its six-day maiden space flight in the best shape of all 12 shuttle flights. Discovery lost no heat-resistant tiles on liftoff or during reentry and suffered damage to no more than three or four tiles near the landing gear doors.

"The tiles are in better shape than any of the previous flights," Widick said. "We've always seen broken tiles near the landing gear doors, so I guess that's something we have to expect on every flight."

As on almost all shuttle missions, the landing gear brakes suffered some damage, but much less than in the past. Washers are missing from each side of Discovery's disc brakes, and one washer on the port side was crushed. The brake assemblies have been removed and sent back to a manufacturing plant in Akron for analysis and rebuilding.

The right landing gear strut was about three inches lower than the left strut, meaning that something may have broken off on touchdown. Widick said the struts will be examined more thoroughly when Discovery reaches the Kennedy Space Center.

"This may be the explanation of why commander [Henry W.] Hartsfield landed a little off the center stripe when he touched down on Wednesday," Widick said. "Of course, you'll have to ask him to fill you in on that."

Inspection of the two vent nozzles just behind the cabin on the port side of the shuttle showed no damage from the ice that formed around them in the flight's last days. Widick said he had no explanation as to why the blocks of ice had built up, requiring the astronauts to use the ship's robot arm to knock the ice loose before returning to earth on Wednesday.

"There are heaters in there to keep those lines from freezing," Widick said. "We're going to have to look at that, and we may have to do something to change things so we don't have that problem again."