CAPE CANAVERAL, Fla., — The International Space Station was a cramped, humid, puny three rooms when the first crew moved in. Twenty years and 241 visitors later, the complex has a lookout tower, three toilets, six sleeping compartments and 12 rooms, depending on how you count.

Monday marks two decades of a steady stream of people living there, according to AP. Astronauts from 19 countries have floated through the space station hatches, including many repeat visitors who arrived on shuttles for short-term construction work, and several tourists who paid their own way.

The first crew American Bill Shepherd and Russians Sergei Krikalev and Yuri Gidzenko blasted off from Kazakhstan on Oct. 31, 2000. Two days later, they swung open the space station doors, clasping their hands in unity.

Shepherd, a former Navy SEAL who served as the station commander, likened it to living on a ship at sea. The three spent most of their time coaxing equipment to work; balky systems made the place too warm. Conditions were primitive, compared with now.

Installations and repairs took hours at the new space station, versus minutes on the ground, Krikalev recalled. Each day seemed to have its own set of challenges, Shepherd said during a recent NASA panel discussion with his crewmates.

The space station has since morphed into a complex that's almost as long as a football field, with eight miles (13 kilometers) of electrical wiring, an acre of solar panels and three high-tech labs.

With the space station in place, two decades has seen that it was always occupied and there have always been humans in space. That legacy began on Halloween in 2000, when the first crew lifted off.

Three men boarded a Soyuz spacecraft at the Baikonur Cosmodrome in Kazakhstan for Expedition 1. Other crews had traveled into space to assemble the space station, but when the Expedition 1 crew arrived there on Nov. 2, they became the first official crew to live aboard the space station.

Although much of their four-month mission was spent getting the space station ready for many future crews to live (somewhat) comfortably, they also performed the first scientific experiment on the ISS.

Current Expedition 64 crewmembers Sergey Ryzhikov, Kate Rubins, and Sergey Kud-Sverchkov also spoke with NASA, reflecting on the anniversary and the 20 years of innovation since Expedition 1.

Working together

It may seem that it’d be difficult for America and Russia to work together, after the two countries had spent decades embattled in a space race. And yet, the American astronaut and the Russian cosmonauts worked together seamlessly. In fact, NASA was adamant on partnering with Russia. "It turned out to be an excellent partnership," said George Abbey, the former director of the Johnson Space Center.

Cosmonaut Krikalev recalled that the crew had difficulties in training, but none were in their interactions as friends. Instead, in working through the difficulties of figuring out the right training materials and the right simulations (because no one had ever done this before), the crewmembers felt that they began sharing a single brain.

One day, Shepherd met with hardware developers and asked a few questions. When Krikalev came to the meeting a little later, he repeated the same three to four questions. “We were just like, oh my god, they're sharing a brain now, these two," said Ginger Kerrick, who was the Russian training integration instructor for Expedition 1.

More than just learning to communicate, though, the Expedition 1 crew had to learn to think alike. Going into training, the US was behind Russia in terms of the theoretical knowledge of the system.

“They had less of a reliance on diagrams and documentation because the people teaching the classes were experts and knew that information inside and out,” Kerrick said. “Whereas on the US side, we were all starting up and so we were developing materials, and we didn’t have the expertise.”

In the end, the ISS team created a mixed system of training. Because they didn’t know what information they would need, they had to over-prepare, Krikalev said. Now, he notices that space station crews are able to learn only what they need, but at that time they needed to learn as much as possible.

Looking to the future

Expedition 1 prepared the ISS for crews to come and, in looking back, the space station’s current crew plans to celebrate 20 years of continuous habitation with a dinner much like the meals Shepherd, Krikalev, and Gidzenko enjoyed sharing together and a long look out at Earth.

In the recent future, the space station's capabilities will be tested when Crew-1 joins Expedition 64. In November, three NASA astronauts and one JAXA (Japan Aerospace Exploration Agency) astronaut will join Rubins, Ryzhikov, and Russian cosmonaut Sergey Kud-Sverchkov. This will mark not only the first time the ISS has housed seven people, but also the first time astronauts reach the space station via a commercial spacecraft, aboard the SpaceX Crew Dragon.

Twenty years after the first crew arrived, the ISS and the space agencies that run it continue to make history. — Agencies