We call it the United States space shuttle. And legally, that's exactly what it is. But in a practical sense, it also belongs to a number of other nations as well - to Canada and 10 of the 12 members of the European Space Agency.
They are contributing nearly $1 billion worth of hardware and effort to the shuttle project.
The second mission of the Columbia - which was in the final hours of the launch countdown at this writing - promises to open a new era of cooperative manned spaceflight.
For one thing, it will begin the flight testing of a many-jointed mechanical arm supplied by Canada at a cost of $100 million (Canadian) and seven-year development effort. Along with the arm in Columbia's payload bay is a group of scientific experiments mounted on a special instrument pallet. This pallet is a forerunner of a somewhat larger version that will be part of the European Spacelab complex.
Developed over the past six years at an estimated cost equivalent to $833 million, and scheduled to go aloft in mid-1983, Spacelab is a chamber that fits in a shuttle's cargo bay. It will provide a ''shirt-sleeve'' working environment for scientists, allowing both European and American specialists to work with instruments mounted outside Spacelab on the pallet. Besides integrating the instruments with the shuttle and Spacelab systems, the pallet supplies the instruments with electric power and other services.
International cooperation in space, of course, is not new. Both US and Soviet spacecraft have carried other nations' equipment. The Soviet Union has also taken guest cosmonauts from other countries into orbit. And there was the historic, but one-of-a-kind, joint US-Soviet orbital flight.
Now Columbia is initiating something quite different. This cooperation is conceived hopefully as a long-term partnership.
It is rooted in agreements reached in 1973 and 1974 following invitations from then President Richard Nixon and the US National Aeronautics and Space Administration (NASA). At that time, mutual benefits were envisioned. The US would draw on wider, more varied expertise and share some of the staggering costs of space flight. Other nations would share in leading space enterprises they couldn't tackle on their own and would develop new competence in high technology.
This remains the main payoff for them. Although NASA will buy three more mechanical arms from Canada, the $74 million (Canadian) to be paid hardly recoups Canada's costs. But Canada has developed a valuable product for which it sees uses in mining, oil recovery, and nuclear power plant work. It may also have a worthwhile export item.
The European Space Agency (ESA), for its part, sees a new doorway opening for its members in space. The first operational Spacelab is scheduled for the sixth shuttle mission in mid-1983 with one European and one US specialist on board. Commenting on this, ESA says, ''Thus, in 1983, Europe will join the nations which already have a manned space program and will, in this way, stay in the forefront of space research during the next decade.''
ESA will, of course, also have vigorous projects of its own. At a time when NASA wonders if budget cuts will force it virtually to abandon unmanned space research, ESA is preparing to send a probe to Halley's comet and contemplates a mission to Mars. Europe also is thinking of developing a more powerful version of its Ariane launching rocket and going after the business of launching commercial satellites in direct competition with the shuttle.
The partnership with the US hasn't been easy. Delays with the shuttle's development and design changes forced by US budget restraints have added to Spacelab costs.
Meanwhile, a parallel partnership in unmanned space research has gone sour. NASA has unilaterally backed out of agreements to the dismay and the cost of the Europeans. The worst incident has been cancellation of the US half of what was the International Solar Polar Mission to send twin spacecraft - one US and one European - to study the sun's polar regions. This was after ESA had spent the equivalent of about $100 million on the project, some 62 to 65 percent of its allotted program funds.
This has raised apprehensions about US good faith, even in the shuttle program.
As do their US counterparts, ESA officials pin high hopes on the shuttle as their best chance to open a productive new space frontier. Manfred Fuchs of Erno Raumfahrttechnik GMBH in West Germany, Spacelab's prime contractor, has summed it up by saying: ''Columbia is America's dream. If that dream doesn't work, ours won't either.''