Over the next few years, Gatens and her team ran experiments on different life-support concepts and did their best to keep up with the constant design changes for the station. By 1993 NASA engineers had blown through billions of dollars on engineering studies, and the station had gone through seven major redesigns. That year the entire program avoided being canceled in Congress by a single vote. The life-support system that Gatens spent nearly a decade working on would never be used for Freedom. But it would find new life aboard the International Space Station, the Clinton administration’s proposal that salvaged the program by sharing the cost among more than a dozen nations.
“NASA has been very open about the fact that in order to do exploration beyond low earth orbit, you have to have a platform there to test systems and get experience,” says Michael Suffredini, the cofounder and CEO of Axiom Space, a company that is poised to build the world’s first commercial space station.
“It's been an exciting program to work on, through the roller-coaster early phase to seeing it complete and the research starting to bear fruit,” says Gatens, who is now the acting director of the International Space Station. “And we’re continuing to expand its capability, not only for commercial use but for exploration use. It’s been a great program.”The first modules of the ISS—a Russian cargo module called Zarya and a US module called Unity that serves as the station’s dining room—were launched in 1998 . Less than two years later, the fledgling ISS would receive its first visitors. On the morning of October 31, 2000, NASA astronaut Bill Shepherd and the Russian cosmonauts Sergei Krikalev and Yuri Gidzenko blasted off from Russia’s Baikonur cosmodrome on a two-day journey to the station. Their arrival on November 2 kicked off a four-and-a-half-month stay and marked the beginning of an uninterrupted human presence in low earth orbit that continues to this day.
Over the past two decades, more than 240 people from 19 countries have visited the ISS. Not only did these astronauts finish building the station, but they have also conducted pioneering science experiments that have changed our understanding of biology , physics , and chemistry . When they’re not busy playing music or taking mind-blowing photos of Earth , they’ve helped lay the foundation for a bustling economy in low earth orbit . And now that NASA has turned its sights on establishing a long-term human presence on the moon and Mars, astronauts on the ISS are testing the technologies that will make it happen.
Much of the space station’s first decade in orbit was dedicated to building it into the sprawling laboratory that it is today. When the first crew arrived in 2000, the ISS consisted of just three modules. (Zvezda, a Russian life-support module, was added just a few months before the trio’s arrival.) Since then it has grown to be more than a football field long and now consists of 16. The ISS has housed up to 13 people at once, although typically there are only three to six crew members on board. The last major modules—the panoramic cupola viewport and the US Tranquility node, a life-support system that generates oxygen and recycles water—were added to the ISS in 2011, which marked the beginning of the space station’s “utilization period,” during which the focus of its occupants was primarily on experimentation and station upkeep.