Next Up After Glenn: An Orbital Erector Set

Weather permitting, tomorrow will see the safe conclusion to one of the most successful - and highly publicized - space shuttle missions ever.

Officials expect the 173,504 pound Discovery will touch down at Kennedy Space Center in Florida, as usual, as lightly as a ballerina. Dozens of experiments, from creating new medicines and materials to capturing new images of the sun's solar winds, will be completed and pored over for every minute detail. And the crew, including that poster boy of longevity, John Glenn, will disembark into a world where floating isn't the norm.

But Discovery's return to Earth also marks a crucial turning point for the American space program, as it leaves behind more than a decade of shuttle-led experimentation and embarks on the ambitious and risky International Space Station.

In two weeks, the United States and its 16 international partners will commence the first of 43 launches to build the largest and most complex scientific project in history, an enormous laboratory that could expand present knowledge of space and pave the way for a permanent human presence there. Success, experts say, depends as much on perfect launch missions and international cooperation as it does on maintaining the public's fascination with space.

"From now on the world's center of gravity on space missions is going to be the space station," says Keith Reiley, manager of the mission integration office at the Johnson Space Center in Houston. "I would hope that everybody accepts that space is a risky business," and that the road to the space station "will have its share of bumps."

Without a doubt, the biggest bump in the road is likely to be political and economic, rather than technological. Assembling the space station is expected to cost $21 billion; operating it for 10 years will cost another $10 billion.

All the US partners, including Russia, Japan, Canada, Brazil, and the 11 nations of the European Space Agency have agreed to contribute a combined $10 billion. But as the cost of the space station increases, US officials hope their partners will increase their allotments as well.

Because Russia appears to be teetering at the edge of the financial default, officials at the National Aeronautics and Space Administration (NASA) are coming up with contingency plans in the event that partner is unable to honor its commitment of money, hardware, and expertise.

"The question is, to what extent is this [space station] truly international?" says Larry Bell, director of the International Center for Space Architecture at the University of Houston. "Every country has to go to its coffers to ask for funding, but if one country can't deliver, then you can't jeopardize the whole program because of that."

James Van Laak, a deputy manager for space station operations in Houston, agrees that the big question about Russia is "Will they be there when you need them?"

"The space station will not be dead-ended if the Russians back out," he says. "I don't think we can do it for the same amount of money," but it will get done.

The first component, a "space tugboat" built by the Russians, is scheduled for launch Nov. 20 from the Baikonur space facility in Kazakstan. This control module will provide early propulsion, steering, and communications.

Two weeks later, the space shuttle Endeavour will be bringing a six-sided connecting module called Unity to join that Russian component.

By the time the station is completed in 2004, it will be 361 feet in length, as long as a football field, including the end zones.

The interior will have a volume equal to a Boeing 747 jumbo jet, with seven research laboratories: two US, one European, one Japanese, and three Russian.

OPERATING the space station will require a whole new set of skills, NASA officials say. For one thing, astronauts who stay aboard the space station will need to be prepared for the occasional malfunction and have the mechanical skills and gumption to fix it. Think of Bob Vila in zero gravity.

"It's not going to be like if your car stalls on the side of the road and you just call the tow truck," says Mr. Van Laak, holding a handsome handmade model of the planned space station. "We're going to need people with the mechanical skills to make things work."

In addition to mechanical skills, NASA is looking for a few good raconteurs, people with language ability and social skills who can deal with the long-term isolation of space. Some US astronauts aboard the Russian space station Mir simply clammed up after a few weeks, an unhealthy response for an operation dependent on communication.

"The isolation is always daunting to people," says Bonnie Dunbar, a five-time shuttle astronaut and acting deputy director for the space station's flight crew operations. "But there is no shortage of applications for the program. We can't turn them away."

Most NASA officials admit the future of human space exploration depends on maintaining the public's current interest, and willingness to see their tax dollars at work in space.

In addition, the public should be prepared for the inevitable malfunctions and delays that attend any mission of this size and complexity.

"There's an old Russian saying, 'Whatever doesn't kill you only makes you stronger,'" grins Van Laak. "Adversity will be good for us, because we will learn from our mistakes and improve."