Shuttle: each time it rises, NASA gains new confidence
At the space shuttle mission control center, the flight insignia of astronauts Joe Engle and Richard Truly has been hung on the wall along with those from the many orbital and lunar missions the center has previously guided.
This time there was a difference. It is the second such insignia for a single spacecraft, and many more are expected to follow.
Columbia's second sojourn ended at Edwards Air Force Base, Calif., on a sun-cracked lake bed under a blue sky spread with clouds as feathery as angel hair.
Its mission - highly successful in spite of a premature end due to a malfunctioning fuel cell - symbolizes the end of the era of use-it-once, throw-it-away manned spacecraft. Already the shuttle team is looking ahead to Columbia's third mission. At this writing, it was uncertain when that would take place. Sometime in March was suggested as a likely time.
Among the results that most pleased NASA officials:
* Tile performance. The protective tiles, which plagued the space shuttle's first flight, performed substantially better this time around. Although six tiles on the spacecraft's body were blistered by the heat of reentry, none fell off as they did last April. ''The famous tile problem,'' says one NASA official, ''is getting better.''
* Experiment data. Despite the shortened trip, two experiments - an imaging radar for mapping geological formations on Earth and an infrared sensor - wound up with ''more data takes than anticipated,'' said a pleased Don Puddy, National Aeronautics and Space Administration flight director. In addition, he said, NASA believed ''good data'' was obtained from the Ocean Color Experiment, which sights patches of color in the globe's seas. This could help locate schools of commercial fish or define polluted areas.
* Exercise of Columbia's ''robot'' arm. The Canadian-made device, which in the future may be used to pluck satellites from Columbia's cargo hold and place them in space, ''performed superbly well,'' said flight director Puddy. The two astronauts conducted several flexing exercises with the so-called ''remote manipulator system.''
Some of the secondary tests that were skipped when the mission was cut from an anticipated 5 days, 4 hours to 2 days, 6 hours will be conducted on the next flight. These include exploring the reception and transmission patterns of the spacecraft's radio antennas, which can be done on any flight.
Winds gusting as high as 18 knots prevented the astronauts from a planned landing in a cross wind - an experiment of particular interest to flight officials. But astronauts Engle and Truly did test the shuttle's automatic landing system - unlike the astronauts aboard the Columbia's first voyage, who glided the craft down entirely under manual control.
As noted by L. Michael Weeks, acting associate administrator for the Space Transportation System at NASA, 90 to 95 percent and perhaps more of Columbia's past mission objectives were accomplished.
Picking up the jargon of an engineer, Mr. Weeks explained that the shuttle team is on a fast ''learning curve.'' This is illustrated by the way the oil filter problem that had postponed the launch was resolved.
The launch date slipped from Nov. 4 to Nov. 12 when lubricating oil from one of three auxiliary power units (APUs) was suspected of being contaminated. These units power the spacecraft's hydraulic systems, which move the rudder, elevons, and other control services, and lower the landing gear.
The suspect oil was removed along with the oil filter and put through a ground simulation of a full mission's use. This showed that the contamination problem cleared up as the oil warmed and the crystallized material causing the problem redissolved.
Weeks said they probably could have flown the mission with that oil and had no problem. Shuttle managers now know they have sound, reliable equipment in those APUs. This adds to their experience and confidence in operating the spacecraft, which Joe Engel called a ''good solid bird.''
Gaining this kind of confidence is what the series of shuttle flight tests is all about. The mission curtailment was due not so much to the fact that one of Columbia's three fuel cells had to be shut down as to lack of experience in operating with only the remaining two.
Gene Kranz, deputy director of flight operations, explained: ''From the standpoint of a flight operator looking at the shuttle, I think that as an overall flight system . . . the architecture is magnificent. I think part of our conservatism, however, at this stage in the flight test program, is because we as ground operators and as crewmen have yet to learn to use that system to a 100 percent effectiveness.
''And it's basically giving the confidence to use what I call the defense in depth or the capability to absorb damage and keep going on. . . . And that's a process that takes a lot of engineering judgment and the kind of experience we're getting here.''
Indeed, the two remaining fuel cells likely would have been quite adequate for the full five-day mission. Flight director Puddy emphasized that ''there was every likelihood that you could have gone ahead and continued to fly. . . .''
He added: ''However, based on our concern primarily for the dramatic change in flight procedures you would have to go to should you lose another fuel cell . . . and based on the decision that we had accomplished such a high percentage of our objectives . . . there appeared to be no future for taking the risk of continuing . . . .''
The fuel cells are considered to be highly reliable. The loss of one took the mission team by surprise. That faulty unit now will be thoroughly studied to eliminate whatever caused its failure. Meanwhile, Christopher C. Kraft, director of the Johnson Space Center, says he continues to think three fuel cell units provide adequate redundancy for the shuttle because, basically, they are reliable.
This suggests that, on future missions, were a fuel cell unit to fail with important mission objectives not yet accomplished, flight controllers could let the shuttle remain in orbit with confidence.