Despite a dead fuel cell, the space shuttle Columbia came through its abbreviated second flight with such flying colors that it would require no other maintenance except refueling and the replacement of the fuel cell to be reflown again.

"The vehicle looks superb, so much better than it did after flight one last April that we could press on and fly it again," shuttle orbital test manager Donald K. (Deke) Slayton said at a news conference here today. ". . . Damage to the bird is minimal compared to what we'd seen after the first test flight."

Good as this news was to shuttle managers, it was tempered by the fact that the spacecraft is still plagued by so many nagging mechanical and computer troubles that the time it takes to get the shuttle ready again for flight is growing longer instead of shorter.

Shuttle managers used to talk of turnaround time of two weeks between flights. Now, said shuttle launch operations director George F. Page in an interview, "We'll never see a two-week turnaround in my lifetime. At best, I think we're talking about reaching a turnaround time of between five and eight weeks."

As uncertain as the long-term picture looks, the immediate effect of the second flight made shuttle managers optimistic that many of the problems can be worked out. Slayton said Columbia lost no tiles on its second flight and suffered damage to no more than a dozen of the more than 31,000 tiles that cover the shuttle's fuselage to protect it from the heat of reentry. Slayton said that even the damaged tiles continued to protect Columbia's fuselage from the heat of friction with the Earth's atmosphere during the return flight.

In contrast, after Columbia's first trip last April, more than a dozen tiles were missing and almost 400 were damaged badly enough to be replaced.

"Looking at it today," Page said, "I thought the bird looked so good that we were going through a curing process from the reentry heat that made the whole tile system work better."

The reason for the improvement, Slayton and Page explained, was that shuttle managers made changes in launch procedures and toughened up some tiles in vulnerable positions on the shuttle.

Even though the flight of astronauts Joe Henry Engle and Richard H. Truly was cut short by more than half because of a dead fuel cell, Slayton insisted that Engle and Truly worked so hard the two days they were in orbit that they did 90 percent of what they had set out to do.

"We accomplished so many of our flight objectives that I envision a minimum tuning on the next flight to catch up," Slayton said. "If we got everything that we were shooting for on the second flight, then our third flight will just be an expansion of that."

The next flight of Columbia is scheduled for mid-March, two months late because of the countdown problems that delayed the first flight from March to April and the second flight from September to November.

The next flight is planned to be a seven-day flight that will be flown at a steeper and faster liftoff and a steeper and faster reentry to test how Columbia performs in ever more demanding circumstances. While the crew for the next flight has not been announced, it is believed Columbia will be flown the third time by astronauts Jack Lousma and Gordon Fullerton. Lousma flew in space before on Skylab; Fullerton has not flown in space, though he served as copilot on some of the shuttle's landing tests when it was dropped off the back of a Boeing 747 here at Edwards Air Force Base four years ago.

One reason flight directors refused to allow Columbia to fly on with two of its three fuel cells was that shuttle managers desperately wanted information about Columbia's reentry into the atmosphere that they did not get on the first flight. During reentry on the first flight, when the shuttle underwent maximum heating at an altitude of 400,000 feet, something happened that erased all the data being recorded by heat sensors along the fuselage.

"In my opinion, 50 percent of the data we wanted from this flight was entry data," Slayton said. "If we had lost an additional fuel cell we would have lost all that."

Slayton explained that if Columbia returned to earth on one fuel cell, the astronauts would not have had enough electricity to bring Columbia home to a safe landing and keep the instruments like the heat sensors running. The sensors that collect data on how the fuselage heated up during reentry are among those instruments not needed at landing. Had they been turned off, shuttle managers still would not have the vital information they need on how Columbia behaves during reentry even though the shuttle had made two test flights.

What concerns shuttle managers the most now is not the next two flights of their test program but the nagging difficulties they have been having in getting Columbia ready for a subsequent flight. The space shuttle has now lifted off twice from Cape Canaveral but has gone through four launch countdowns to make those two flights.

The two countdowns that had to be stopped minutes before liftoff have cost the shuttle program almost $100 million and weeks in delay that now threaten to postpone the shuttle's first operational flight, which is scheduled for next September.