Space shuttle Orbiter waits patiently to fly -- in reality

The reusable space shuttle -- the key to the next phase of space operations for the United States -- sits proudly on its launching pad. But with a wide range of tests still facing the craft, a firm launch date, at this writing, had yet to be set.

This is not to say that the outlook for the much-delayed shuttle is bleak. National Aeronautics and Space Administration engineers believe they have solved the three major obstacles that have stood in the way of the multibillion-dollar project. Astronauts John Young and Robert Crippen are ready to go -- indeed, after two years of delays, they complain they are if anything overtrained.

However, the mimeographed 1981 calendars in offices throughout the sprawling Florida space complex reflect more faith than realism with their message, "We WILL launch in March." Roland Raab, a NASA spokesman who has one of those calendars in his office, conceded its message was quite optimistic.

"If we work full force, 24 hours a day, seven days a week, encounter no delays and no weather problems, we still might make it," he said. "That's like if you bought a bicycle for Christmas and never had put one together before. The directions say you can put it together in 30 minutes. What's the chance of it really taking that long? We don't really have a launch date."

After five days of testing, work is already four days behind schedule, he said, and the long list of tests showing on a flow chart in his office indicated the possibilities of further delays.

"There's no room for delay, bad weather, or breaking a piece of equipment if we're going to meet that March deadline," he said. "there's very little money in our budget for spare parts, so if anything breaks, we'll have to build a new one. If we find a major piece of equipment won't work the way it's designed, then they have to go back to the drawing boards."

While they cannot pin an exact launch date, NASA engineers believe they have come up with solutions to the three technological problems that are unique to this project.

Perhaps the one that has gained the most publicity lately has been the complex thermal protection system that will stop the spacecraft from burning up when it reenters the atmosphere.

On past generations of spacecraft, heat protection was not a problem. The area exposed to intense heat on Gemini and Apollo capsules was small, and engineers did not care if heatshields on those craft disintegrated during reentry because the capsules were not going to be reused.

But the space shuttle Orbiter is designed to be reused 100 times before it is discarded, and the area on it that will be exposed to heat up to 3,000 degrees F. during reentry is large.

The shuttle's thermal protection system is complex. On the nose and wingtips , where the heat will be most intense, engineers have designed a three dimensional carbon weave covering that is held together with an epoxy resin. That shield can withstand temperatures up to 3,500 degrees F.

For much of the bottom of the craft, where temperatures will still be high, engineers have developed a new insulation material out of a silica fiber base that has a thin, black silica ceramic coating. This insulation, which weighs and looks much like styrofoam, can withstand heat up to 2,300 degrees F., and engineers believe it eventually will be used extensively in industry.

The same insulation, covered with a white silica ceramic coating, has been put on parts of the craft where temperatures should not exceed 1,200 degrees F., and a felt insulation covers the rest of the vehicle.

That silica fiber insulation is cut into small tiles, and 31,000 of them -- each a different size and thickness -- cover 75 percent of the Orbiter. During part of the 20,000 hours of wind tunnel tests the aircraft underwent, some of the tiles flew off, and engineers feared that if even a few of the tiles fell away during liftoff, the Orbiter could be destroyed during reentry.

All of the 31,000 tiles were removed, and engineers decided to put a layer of felt between the tiles and the spacecraft's aluminum body. That felt, which gives the tiles more flexibility when under stress, is attached to the Orbiter and tiles with a rubber cement.

"This new system of tiles is like a skin," Raab said. "Each tile has different forces acting on it, and each one responds in a different way. The possibility of one of them falling off is practically nil. They're designed to have 125 percent of the strength required for the most rigorous flight. If they make it through the launch, we're home free."

While insulation problems have gotten the most publicity lately, mechanical problems within the newly designed engines put the project back two years, NASA officials say.

A Saturn rocket, which propelled the Apollo missions into space, was designed to burn 2 1/2 minutes and then it was discarded. A space shuttle engine will burn for nine minutes on each of 55 flights before it is overhauled and used for 55 more. It runs at a much higher pressure than older rocket designs, and the difference between temperatures within the engine is greater than any engine has ever experienced before.

Major delays occurred, Raab said, because problems with the engine's design were not discovered until late in the craft's development.

"Most of the delay was due to lack of money," he said. "If we had had more money in the beginning of the project, it would have allowed more early testing that would have discovered the engine's problems sooner."

NASA had asked Congress for $12.8 billion to develop the shuttle, but received only $5.15 billion, Raab said. The project has been hampered by short money ever since.

The third system unique to the space shuttle's design is the computer network built on board. Old spacecraft had one computer. When it failed, the pilots took over.

On board the Orbiter will be five computers -- four active and one standby. The pilot will never directly control anything. He will push a command, and the four computers will "vote" whether to allow it. If they all agree, the command is sent to the instrument.

If one of them disagrees, the other three will analyze the dissenter to find if it is mal- functioning. If they determine it is, they will turn it off. If at least one of the computers work, the spacecraft nearly flies itself. But if all five of them should fail, then the Orbiter is lost because the astronauts cannot fly it by themselves.

Young and Crippen's first trip in a space shuttle will be a low-key, 55-hour flight that will test the craft's equipment during launch and landing and its ability to operate its payload bay doors at altitudes up to 170 miles. Not until its fourth trip will it actually do the task for which it is designed: carrying satellites high enough where they can be launched to their final destinations.

The shuttle eventually will take over much of the work that individual rockets now have to do. Up to four satellites will be loaded into its 60-by-15 foot cargo hold and blasted about 170 miles into space. There astronauts will open the shuttle's bay doors, activate a mechanical arm that will lift out a satellite and its booster rocket, and position it for take off.

The astronauts will maneuver the shuttle away from the satellite, and it will be blasted to its designated orbit as much as 22,000 miles higher.

What the shuttle accomplishes, NASA officials say, is to eliminate the need for a costly expendable rocket to shoot every satellite through its first two stages into space. With the demand for communications, weather and military satellites growing steadily, they say, the shuttle should eventually be able to pay for itself.

But first, the craft has to be taken through those crucial test flights.