The Cold War had been concluded for less than a decade when NASA astronaut Bill Shepherd and two Russian cosmonauts, Sergei Krikalev and Yuri Gidzenko, crammed themselves into a Soyuz spacecraft and blasted into orbit on Halloween, 20 years ago.

Two days later their small spacecraft docked with the International Space Station, then a fraction of the size it is today. Their arrival would herald the beginning of what has since become 20 years of continuous habitation of the laboratory that NASA, leading an international partnership, would continue to build for another decade.

Born of a desire to smooth geopolitical tensions in the aftermath of the great conflict between the United States and Soviet Union, the space station partnership has more or less succeeded—the station has remained inhabited despite the space shuttle Columbia disaster in 2003, and later, nearly a decade of no US space transportation. NASA, Roscosmos, and the European, Japanese, and Canadian partners have been able to rely on one another.

Not that it has been easy. Tensions have existed from those very first moments on the station. Shepherd, who would serve as the first ISS commander over his more experienced cosmonaut counterparts, wanted to nickname the station “Alpha.” He had support for this from Krikalev, but some Russian space officials believed their earlier, Mir space station, had earned that honor. The new station, they believed, ought to be named “Beta.” NASA, too, had not signed off on this designation.

Nevertheless, Shepherd pressed ahead. He liked that Alpha was the first letter of the Greek alphabet, neither American nor Russian. So on the crew’s first day aboard the station, during a space-to-ground call with NASA Administrator Dan Goldin, Shepherd said over the public loop, “The first expedition on the space station requests permission to take the radio call sign Alpha.”

Goldin was not expecting this, and he spoke away from the microphone for a few moments, conferring with others on the ground. Then he came back and said the name “Station Alpha” was authorized for the duration of Shepherd’s nearly four-month expedition.

This suited the crew, and Shepherd replied, “Out, from Space Station Alpha.” Since then, more than five dozen other crews have rotated onto the International Space Station, most recently Expedition 63, which launched in mid-October. Always, in the two decades since, there have been at least two humans on board.

Days before the most recent launch to the space station from Kazakhstan, the mission’s NASA crew member, Kate Rubins, addressed this anniversary in the crew’s final pre-flight news conference.

“I think the International Space Station is one of the most incredible engineering achievements in human history,” she said. “It is quite a marvel to see such a giant machine that was built entirely by humans and flown off the surface of Earth still persists in space 20 years later.”

The station is unique in that no one has ever built such a large spacecraft in orbit, nor flown it so long. In that sense, it tests the limits of what is possible every day, and it is worth thinking about the achievements of the station. These go far beyond geopolitics and range from science to exploration to the commercialization of space. And yet there is growing concern that the space station may be retired before there is a replacement, soon ending our two-decades in orbit. Moreover, we could fritter away much of the value we have gained from such an outpost.

“This is critically important,” said NASA Administrator Jim Bridenstine about planning for a future in low-Earth orbit. “And it’s something that never gets funded.”

What station has done

The International Space Station has not been cheap. Depending on how one counts the beans—for example, how much of the space shuttle budget should be included, considering the shuttle was used almost exclusively to build ISS in the 2000s? NASA has spent between $100 billion and $150 billion to assemble and maintain the station since construction began nearly three decades ago. However, NASA, the nation, and the world has received a lot in return for their investment.

First of all, the International Space Station has lived up to its name. In addition to providing a valuable diplomatic link between Russia and the United States at a time of increasing tensions, the orbiting laboratory has opened space to much of the world.

NASA’s program manager for the station, Joel Montalbano, told Ars that the ISS had reached 108 countries over its lifetime, either through flying astronauts, conducting research that originated there, or through outreach events.

“We’ve been able to stay out of politics, and work on a physics-based philosophy,” he said. “It’s hard, and it’s challenging working with different cultures, and time changes. But it sets a good example for the rest of the world.”

Prior to the space station, NASA astronauts had mostly spent 10-day, or two-week increments in space during shuttle missions. Now, astronauts regularly fly six-month rotations. Scott Kelly has flown 11 months, while Peggy Whitson, Christina Koch, and Drew Morgan have all spent nine or more months in space. This allowed scientists and physicians on Earth to study how longer durations in microgravity affect human physiology.

The good news is that, as humans go beyond six months in space, scientists are not finding any big surprises or showstoppers. Montalbano said new actions needed to accommodate people on such missions are relatively straightforward—perhaps giving long-duration crew members an extra day off from time to time, and making sure their family members and loved ones back on Earth are being well taken care of. This type of research is essential before sending astronauts on longer missions deeper into the Solar System, to places such as Mars.

The space station is only now hitting its stride on scientific research, as well. The orbiting laboratory offers a resource very difficult to obtain on Earth: microgravity. For its first decade, little time was available for science, as much of the work on station was devoted to constructing and maintaining the facility. Then, after its substantial completion in 2010, the space shuttle stopped flying, so NASA was limited mostly to about two crew members on station at a time by Russian spacecraft.

The advent of the commercial crew program changes this. With each mission flown by SpaceX’s Crew Dragon vehicle, NASA will be able to send four people, instead of three. This fourth person’s time will be almost completely devoted to scientific research. This will allow the amount of “astronaut time” devoted to scientific research to double, from 35 hours per week to 70.

Finally, the station has provided a valuable platform for US companies to extend their reach into low-Earth orbit. SpaceX, Northrop Grumman, and Boeing have been able to develop cargo and crew transportation systems to orbit, stimulating their spaceflight activities. And companies such as Made in Space, Nanoracks, and a host of other firms have benefited from being able to test manufacturing and other activities in microgravity without having to go through the likely insurmountable hurdle of developing their own miniature space stations.

To the extent that commercial space is a rising industry in the United States, a lot of this activity can be traced in one way or another to the International Space Station.