Columbia survives second trip in better shape than first

America's space shuttle Columbia survived its second journey into space in better shape than it survived its first mission last April. A quick external check of the spacecraft at the Dryden Flight Research Center in California revealed only minor, superficial damage to the heat-shielding tiles. Loss of some of these had caused concern after the first mission.

In short, according to Donald K. (Deke) Slayton, orbital flight test manager, Columbia ''looks superb . . . considerably better than it did after flight one. . . . There is some limited damage there, but it's minimal compared to what we've seen previously.''

This, plus the lack of indication of any major internal problems with the spacecraft, helps build the confidence of shuttle managers that Columbia can go on to the 100 mission life for which it is designed.

George F. Page, shuttle operations director, says that doesn't mean that every piece on the shuttle will fly 100 missions without changes, ''but I will say that the tile system looks very promising.'' He speculates that the tiles may be ''going through a curing process'' due to the heat of reentry from orbit. This may enhance their ability to survive.

There is one minor mystery. About half a dozen tiles had their upper portions sheared off. The cause of this will have to be identified. But Mr. Page adds that he, too, is impressed with the good condition of the spacecraft.

Now Columbia is being readied for its trip back to Cape Canaveral where it will be prepared for its third mission, scheduled to run seven days. Although no specific launch date has yet been set, Page says mid-March, give or take a week, is a likely time. He warns that this quick turnaround assumes there will be no major problem discovered when the faulty fuel cell is examined. Loss of that cell forced curtailment of Columbia's second mission.

At this stage neither he nor Deke Slayton anticipates such trouble. They both note that fuel cells have been one of the more reliable types of spacecraft hardware, going back to past Apollo and Gemini programs. They expect the present problem to be sorted out relatively easily.

Slayton also says he would have had no qualms about continuing Columbia's second mission on only two of the three fuel cells. Even if one of those were also to fail, astronauts could land the craft safely.

However, Slayton explains, half of the mission objectives involved gathering different types of data about reentry and landing. Those data could not have been taken with only one fuel cell because of the need to conserve power for vital spacecraft functions. Hence the decision to bring Columbia back early and not risk the loss of reentry data.

Part of those data concerned the performance of the autopilot system. The astronauts exercised this system for part of their landing approach. This is only the beginning of tests that Slayton says, hopefully, will demonstrate a fully automatic landing capability in many kinds of weather.

''We're trying to develop a machine that has basically a zero (visibility) capability,'' says Slayton. ''And with that capability we can land in any kind of weather.'' He notes that this will not include violent storms.

Meanwhile, other members of the shuttle launch team are carefully inspecting Pad A at Cape Canaveral's Launch Complex 39. They want to find ways to further cut down damage both to the pad and to the spacecraft as its rockets ignite.

Last April, Columbia sustained some damage from flying debris and from shock-wave pressure reflected up toward the spacecraft when the solid rocket boosters were fired. An enhanced system to suppress such excess pressure, using jets and blankets of water, appears to have worked, cutting the overpressures by about 75 percent.

Tying down everything that looked as though it could come lose and hardening more of the pad structure reduced damage to the pad itself and probably helped Columbia's tiles survive better this time, Page says. Some of the minor damage to the tiles may have been caused by pieces of protective material that were put over parts of the pad structure. This material burned off as expected during the launch.

Shuttle officials, pleased with Columbia's performance, are looking for ways to enhance the survivability of what they consider to be a 100-mission spacecraft.