The idea of an orbiting space station somewhere between our terrestrial home and the rest of the cosmos has long been tantalizing. As long ago as 1869, the writer Edward Everett Hale proposed a floating station of sorts --a navigational beacon for space-going ships -- in his book, The Brick Moon.

In the years following the human advent into space, scientists have worked to perfect the concept of the Space Station and build their research outpost on-high. In a sense, the International Space Station is the culmination of efforts spanning 20 years:

• Diagram of the Salyut 4

  Salyut.The world's first space station, the Salyut, was launched by the Soviets in April 1971. About 9 feet in diameter and 50 feet long, this small work station could accommodate three astronauts. The first crew -- Georgi Dobrovolsky, Vladislav Volkov, and Viktor Patsayev -- lived aboard this floating lab for 23 days. But they were killed during their return to Earth, when air leaked out of a faulty valve in the Soyuz capsule transporting them home. No one else would ever live or work aboard the Salyut, because it fell back into the Earth's atmosphere six months after its launch.

• A close-up view of the Skylab space station cluster photographed against a black sky background from the Skylab 3 command module.

  Skylab. The American space station was carried to low-earth orbit aboard one of Wernher von Braun's Saturn V rockets in May of 1973. Loaded with valuable scientific cargo, including medical experiments and a solar telescope array capable of observing the Sun, Space Lab managed to stay aloft longer than Salyut. After a few early problems --repaired by American astronauts in a series of historic space walks-- Skylab was home to working astronauts who lived in space for as long as 84 days at a time. From 1974 on, however, it remained empty, and finally crashed back to Earth five years later, in 1979.

• Mir Docking Module View of Mir U.S. astronaut Jerry Linenger and Mir 23 Commander Vasily Tsibliev conducting a successful five-hour spacewalk.

  Mir. Though the notorious Mir (Russian for "Peace") is today a symbol of ramshackle obsolescence, it was a state-of-the-art accomplishment in 1986, when it was launched. It is aboard the Mir that scientists first started collecting data on the impact of long-term life in space and developing protocols for low-gravity research; it is aboard the Mir that nations refined the models for collaboration that will fuel humanity's joint journey through space in the years to come.

  Even in its old-age, Mir continues to contribute to the cause. As the station deteriorates, NASA and its partners are learning from the problems. Faulty cooling pumps, fire, and collision aboard the Mir have all become object lessons for ISS engineers, who can learn from mistakes and use them to endow the ISS with components and technology superior to that of space stations that have come before.

The next generation space lab, the International Space Station, was first conceived, in grand fashion, by NASA engineers in the form of an expensive and elaborate system known as Freedom. Too costly to fly by the US government, Freedom was scaled back; but ultimately, because its US designers could not cut costs enough, other nations were invited to join in. Canada, Japan, and the nine European Space Agency nations committed first, and then Russia followed suit. Although the late arrival of the Russian Space Agency (RSA) caused a few bumps in the road, it has, as the sponosr of MIR, provided the ISS project with tremendous experience in long-term human space flight.

"The Russians came into the program a little late in the game," says Kelle Pido, an engineer in NASA's International Partners Office, which helps ensure that the partner agencies are working well together. "We'd been going at it a few years and we already had a set of standards amongst ourselves, and now Russia comes in with an existing space program and tried and true standards of their own, and really challenging us on the way we do a lot of things. I think it's really been for the better. The crew has come out with much better equipment and accommodations aboard the station."

Cosmic Collaborators: Astronaut Terrence W. Wilcutt, pilot and cosmonaut Valeri G. Korzun, Mir-22 commander are seen here transferring the Contingency Water Container (CWC).

The beginnings of the new station are, naturally, tied to the end of the old. Phase I of International Space Station is the Shuttle-Mir project currently underway, in which NASA astronauts live and work aboard Mir, training with their Russian colleagues at the Star City facility outside Moscow. In March 1995, astronaut Norm Thagard joined the crew of Mir. Three months later, the shuttle Atlantis docked with Mir -- the first time an American vessel had docked with the station -- to retrieve him. Since March 1996, there has been a continuous NASA presence on Mir.

Already, the program has allowed the Russian and American agencies to get to know each other -- something that is crucial if the International Space Station can succeed. After all, ISS is a tremendous logistical operation to be built through more than 40 launches by a number of different vehicles, including the American space shuttle, the Russian Soyuz craft, and launchers from the other space agencies as well. Phase I has provided vital information for this operation, says Sergei Krikalev, the cosmonaut who has done two stints abour Mir, been a crew member of a shuttle flight, and most recently, been named Flight Engineer of the first ISS crew. "Primary control of the first part of our flight will come from Mission Control in Moscow," Krikalev explains. "Then it will be transferred to Mission Control in Houston." Cooperation is important, he emphasizes, and "it's something that we've already learned how to do."