"We have that in the plan. We just need the budget to do that."

Almost three years after the station's first two building blocks were launched and linked in orbit, NASA is facing an anticipated $4.8 billion station cost overrun. Shelved as a result: Plans for a U.S. dormitory and an American crew rescue ship.

Those components are crucial to expanding the station's crew capacity from three to six or seven -- a complement considered essential to adequately staffing station labs and conducting a strong research program.

At least two crewmembers are needed to keep station systems running, and once European and Japanese laboratories are added to the outpost, additional staff will be required to perform science experiments.

What's more, either the American rescue craft or additional Russian Soyuz lifeboats would be needed to provide an expanded crew with a way to abandon ship in an emergency. A single Soyuz now remains parked at the station at all times, but the craft can only accommodate three.

The projected cost overrun has prompted NASA to draw up plans for a scaled back station that includes neither the American-made dorm nor the U.S. rescue ship.

NASA and its global partners, however, are attempting to forge barter agreements that would enable a habitation module and a rescue ship to be built within existing U.S. cost caps.

And while it's unclear whether that effort will bear fruit, NASA officials are quick to note that progress on the project over the past 13 months has been nothing short of remarkable.

"This has been probably one of the most dynamic and one of the most amazing periods we've had in human spaceflight," said senior NASA station manager Bill Gerstenmaier.

"I think what history will say is that during this period, the space station program grew at a pace that nobody expected," added Helms. "I know that was the plan, but the fact that the plan actually came off the way it was planned, I think, actually surprised everybody."

A joint effort of 16 space agencies in the U.S., Russia, Europe, Japan, Canada and Brazil, the $60 billion station construction project kicked off with the late 1998 launches of a Russian space tug and an American docking module.

Outpost assembly then came to a standstill for almost two years as cash-strapped Russia struggled to build and launch the station's current crew quarters.

The long-awaited July 2000 launch of that module, however, kicked off a fast-paced flurry of missions considered as complex as any staged as part of NASA's Apollo moon landing project.

First, the bus-sized crew module was outfitted during a September 2000 shuttle mission, and then the first piece of the station's central truss was erected the next month.

The first full-time resident crew boarded the outpost in November 2000, and a $600 million U.S. electric power tower was added in December 2000.

The $1.4 billion U.S. Destiny laboratory was delivered in February, and the station's second resident crew - w-hich included Helms and Voss -- replaced its inaugural tenants in March.

A month later, a $600 million Canadian robot arm was mounted on the outpost, and then in June, the first phase of station construction was capped with the addition of a $164 million airlock.

Coupled together, the robot arm and the airlock will enable spacewalking assembly and maintenance work to be carried out without a visiting shuttle present, providing station crews with an unprecedented level of self-sufficiency.

So in the span of a year, the once-vacant station sprouted from a relatively small two-roomer to a 17-story orbital research complex that has the same amount of habitable space as a standard American three-bedroom house.

Now equal in mass to Russia's former space station Mir, the outpost weighs 132 tons and stretches 171 feet (52 meters) from end to end. Perpendicular to that core are massive American solar wings that stretch 240 feet (73 meters) from tip to tip.

And with the exception of some computer problems and start-up glitches with the station's Canadian crane, the rapid expansion largely came off without a hitch.

"Quite frankly, we anticipated we would run into some problems along the way and are amazed that everything has worked out so well," said NASA shuttle program manager Ron Dittemore.

Added senior NASA station manager Jim Van Laak: "To see all of these pieces function near perfectly, I think, strains one's ability to comprehend it."

The next stage of construction will begin in September with the launch of a Russian docking compartment that will double as an auxiliary airlock.

The station's third full-time crew, which took command of the outpost earlier this month, will outfit the new segment during a trio of subsequent spacewalks.

Coming up early next year: The start of a string of U.S. assembly missions aimed at raising the rest of the station's central truss, a 10-piece skeletal backbone that eventually will stretch 356 feet (108 meters) from end to end -- or about the length of a football field.

Three additional U.S. electric power towers and their associated solar wings then will be mounted at either end of the truss, paving the way for the launches of Japanese and European science laboratories in 2004 and 2005, respectively.

Dittemore said the upcoming assembly flights are expected to be every bit as complex as those that have been carried out to date.

"The challenges aren't going to ease up," he said. "We're flying mission after mission that include spacewalks, rendezvous and docking, and intricate robotic (arm) maneuvers - the elements of space exploration that really get your pulse going."

Exactly how the station will be completed, and whether the outpost will ever be equipped to house an expanded crew, remains to be seen.

NASA and the Italian Space Agency are trying to hammer out a barter agreement that would call for an existing Italian cargo carrier to be converted into an orbital dormitory. The conversion of an American connecting node also is under consideration.

The European Space Agency is being asked to increase its financial participation in the development of a rescue ship. A second option: Purchasing additional Russian Soyuz so that two of the craft could routinely be kept at the complex to accommodate a crew of six.

The ongoing negotiations will continue over the next several weeks, and a decision on which options to pursue isn't expected until after the U.S. Congress finalizes NASA's budget for 2002.

"We're kind of waiting to see what our budget will be," said Gerstenmaier. "So it's a little early, but we're doing all the 'what-if' planning to be prepared."

The crew now on the station, meanwhile, is carrying out a suite of 50 U.S. and Russian science experiments, but Helms said that existing outpost facilities already are equipped to do even more research.

"The only limiting factor at this point seems to be the number of humans that are up there. So if we can expand the space station to accomplish the objective of increasing the manpower, we can get a lot more done," she said. "And that's something we all should be reaching for."