Some 220 miles above Earth orbits the biggest test of international spaceflight cooperation. It has a Russian and American crew. Its components were built on four continents. It has endured a Perils of Pauline history that might have terminated the project were it not that 15 other countries had signed on to the project through binding agreements.
But now, as spacefaring countries on both sides of the Atlantic look to extend humanity's presence to the moon, and eventually beyond, the space station's model of cooperation may have run its course.
The moon and, perhaps later, Mars efforts are slated to occur in incremental steps over decades, defying the single-project model that has been the space station's hallmark. Any new team effort will require a new approach by the United States, in particular, since its potential partners have grown more capable and less satisfied with what they see as their "subcontractor" roles.
Indeed, much has changed since 1984, when President Reagan called on Western allies to join in building a space station in response to the effort by the Soviet Union. The cold war ended, allowing the US and Russia to work together. Meanwhile, China joined the manned spaceflight club, and reportedly is looking at future manned lunar missions. Japan and India initiated moon and Mars exploration programs of their own. And Europe has launched its own Aurora program to reach the moon and beyond.
Thus, nations can pick partners with manned spaceflight experience in ways they couldn't during the cold war, when the US National Aeronautics and Space Administration was the only free-world option. Because their visions for human space exploration overlap, they probably will team up, experts say.
"This is inherently a global effort," says Lori Garver, former NASA associate administrator. "This is humanity's vision."
The alternative could be a new space race that no nation can sustain. Rough estimates for President Bush's vision for space exploration run as high as $100 billion over the life of the program - although no one knows for sure because it proceeds on a "go as you pay" basis, and new technologies or unforeseen stumbling blocks could dramatically change the equation.
Beyond questions of space- exploration costs are broader issues of how the US achieves its strategic goals, according to Joan Johnson-Freese, who heads the department of national- security studies at the US Naval War College in Newport, R.I. "We need to show we are a leader - the kind you want to work with." By joining with other nations in shaping a long-term manned-spaceflight effort, instead of merely asking other nations to sign on to Washington's project, she says, "we can shape the space activities of other countries, rather than have them going off and doing things we don't want them doing."
Placing cooperation on a more equal footing also could help sustain public support for a long-term effort, she adds. "I work a lot with European space officials, and they tell me: If you think it's hard to get support for your space program, try doing it when the public perceives that you only play a supporting role."
The International Space Station shows the benefits and potential pitfalls of cooperation, analysts say.
The international nature of the partnership, in which allies committed to building key components, helped see it through tough budget times variously experienced by its 16 partners. And the inclusion of Russia in 1993 has been the program's savior since the Columbia disaster, Ms. Garver points out. When the Russians joined - a move that was highly criticized and very expensive - it meant that the station's orbit had to be changed to make it accessible to rockets launched from the Baikonur cosmodrome in Kazakhstan. Without Russia's crew-exchange and resupply missions since the Columbia accident, the station would be empty.
"People complain that we need an independent means of getting into space instead of having to rely on the Russians" if there's a gap between the shuttle's retirement and the deployment of a US crew-exploration vehicle to replace it, Garver says. "I appreciate that we're getting there at all."
Bill Clinton, who as President brought the Russians in unilaterally for strategic reasons and for their expertise in building and operating space stations, ordered a downsizing of the station - one of many redesigns over the years as costs ballooned far beyond initial estimates. The redesigns have raised nagging questions about Washington's commitment to long-term cooperative projects, analysts say.
For example, the station is destined for downsizing yet again as NASA administrator Michael Griffin implements the president's vision for space exploration. And the deadline for retiring the shuttle by 2010 is firm, regardless of the station's construction status. One potential victim of these decisions: The station's centrifuge module, a Japanese lab designed for biological experiments.
The partners are expecting word this month on how a pared-down schedule of shuttle flights will affect construction. The change would mark the second shift in less than a year for the space station's construction timeline. After nearly two decades participating in the program, Europe and Japan have yet to see any of the space station's once-touted benefits.
Beyond broad issues of the stability of international projects lie concerns about technology transfer, notes Ray Williamson, a research professor at George Washington University's Space Policy Institute. Two items - the International Traffic in Arms Regulation (ITAR) and the Iran Nonproliferation Act (INA) - threaten to stymie closer ties on space projects. The ITAR classifies satellites and their parts as "munitions," subjecting them to tight controls. As a result, Europe is said to be looking for other partners in what was to be a joint US-European Mars Rover project. Next year, after a US-Russian agreement on transportation to and from the space station expires, provisions of the INA would prevent US astronauts from using Russian spacecraft to reach the space station. "ITAR is a real impediment, and it's getting worse in some ways," he says. "The Iran act is a real showstopper as well."
In June, Secretary of State Condoleezza Rice and Dr. Griffin sent a letter to Congress asking lawmakers to amend the INA, which may happen, experts say. It's less clear if adjustments will be made to ITAR.
The US is entering uncharted territory, but one rife with opportunities for new forms of cooperation, some observers say.
"We're talking about a science-and- technology program with a 50-year time horizon," says Charles Kennel, coauthor of a 2004 report on space cooperation and now director of the Scripps Institution of Oceanography in La Jolla, Calif. While China is new to manned spaceflight, "by the time these plans start to unfold, the Chinese are going to be a major player on the human spaceflight scene.... International human-spaceflight initiatives can't be managed in a top-down way anymore."
Among the report's recommendations: All space-exploring nations that want to contribute to the overall goals of human exploration form a group to coordinate the efforts. The group would meet once a year to discuss their programs, make sure their efforts dovetail with those of other members, and find ways to share resources or undertake joint projects.
"We've done this all the time in the science world; now it's time to do it in the human-spaceflight world," Dr. Kennel says. NASA and European Space Agency comet missions provide a small example, he notes. While NASA last week smashed a comet, ESA's Rosetta mission is en route for the next step - placing a lander on a comet's core. Both agencies also cooperated on the Cassini-Huygens mission, where an ESA probe landed on Saturn's moon Titan earlier this year.
Another example is the Committee on Earth Observing Satellites, a global steering committee on which Kennel sat during his tenure as an associate administrator at NASA heading the agency's Mission to Planet Earth program. The committee consists of representatives from 18 to 20 countries that have Earth-observing programs. They meet to work out nonbinding agreements that help coordinate programs, set up common standards for handling data, and exchange information about future projects.
Such a path for human spaceflight would allow countries to dip into a bigger toolbox of cooperative approaches - from pursuing projects to guarantee human access to space, such as the proposed Russian "Clipper" project that is drawing interest from Europe and Japan, to an approach more like a space station, where each contribution depends on the success of others. The value of some redundancy is evident in Russia's current trips with crew and cargo to the space station.
"If this is an eventual goal of the human race to do it, if it's a global goal, and you agree to those basic principles and make some incremental contribution to the overall goal, then you can be a member of the club" and share its benefits, Kennel says.
United States: President Bush's plan aims to return humans to the moon by 2020 and, perhaps eventually, to Mars.
Russia: After reorganizing its space agency, the country is now emphasizing robot over manned missions.
Europe: Its Aurora program envisions unmanned and manned missions aimed at putting humans on Mars by 2030.
China: With the Shenzhou 5 in 2003, China joined the US and Russia as the only nations to launch humans into space. It has talked about more manned missions, a possible space station, and unmanned missions to the moon.
Japan and India: Their space programs emphasize unmanned missions only.