When Robyn Gatens was hired by NASA in 1985, the agency had just announced plans for a space station called Freedom, and the young chemical engineer had been tapped to help solve one of its biggest technological challenges. NASA engineers had plenty of experience keeping astronauts alive in space for a few days or weeks at a time, but the new space station was meant to be permanently occupied. That meant designing life-support systems that would provide crews with breathable air and drinkable water for years on end. It was a daunting problem, and it was up to Gatens and her colleagues to solve it.
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.
“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.
A few years before, Congress had designated the US portion of the ISS as the newest addition to the country’s national laboratories, which would be responsible for handling all non-NASA microgravity research. In 2011, NASA officials selected the nonprofit Center for Advancement of Science in Space to manage the laboratory, which has been responsible for shepherding hundreds of experiments from researchers at American universities and companies. The lab collaborates with the National Science Foundation and the National Institutes of Health to select those experiments and flies about 50 every year.
“We have this awesome model of a public-private partnership on this station that lends itself to organizations other than NASA who are doing things in microgravity that may not relate to space exploration,” says Ken Shields, the chief operation officer of the ISS National Laboratory. “In developing these partnerships, we now have companies that are able to do technology research and development on the station in a rapid way and apply the results.”
The ISS National Lab handles experiments in both basic and applied science. Out of the hundreds of inquiries received every year, the lab can fly only a few dozen payloads that fall into a few broad categories of interest, such as remote sensing or life sciences. While an earthbound national lab like Lawrence Livermore or Argonne might have thousands of employees, the ISS National Lab has only a handful of NASA crew members. “We are extremely reliant upon the astronauts to execute the experiments,” says Michael Roberts, the acting chief scientist of the ISS National Laboratory. He says the limited time of the astronauts, who are also tasked with carrying out NASA’s own experiments and taking care of the station, creates all sorts of unique challenges that aren’t faced by other national labs. Just getting the experiments into their hands is fraught with logistical difficulties. “It's not an easy prospect to take an experiment, package it up, put it on a rocket, launch it to a remote destination, have it transferred over, have it activated, have it shut down, collected, and sent back,” Roberts says.
A science or technology payload on the ISS could involve anything from creating fireballs to growing barley for beer, but NASA administrators have singled out a few core areas that they think are the most promising for R&D in low earth orbit. Manufacturing in microgravity, for instance, has advantages for making exotic materials like a fragile type of glass that could dramatically improve the performance of undersea cables. But arguably the most exciting applications are in the medical field; experiments with organs on a chip could eventually eradicate animal testing and expedite drug discovery. The microgravity environment could be harnessed to grow 3D cell-tissue models, called organoids, that will be useful for studying a variety of human diseases.
Last year, Valentina Fossati, a researcher at the New York Stem Cell Foundation, sent a few organoids to the ISS in order to study key cellular mechanisms in Parkinson’s disease and multiple sclerosis in microgravity. Fossati is particularly interested in the role that microglia, nervous-system cells that are involved in the process of neuroinflammation, play in these diseases. Microglia are extremely sensitive to their environment, so studying how they behave in the absence of gravity is critical to getting a better understanding of their role in neurodegenerative diseases. “It’s really about disease modeling and trying to understand what is happening in the brain,” says Fossati. “What I’m trying to re-create in a dish is how the neurons die. The absence of gravity would very likely change what happens between the cells.” Although Fossati’s research is ultimately about treating people on Earth, it could also help improve astronaut health by revealing the ways that long stays in microgravity affect our brain cells.
In addition to helping humans back on Earth, the ISS has also proven to be an invaluable research lab for studying the effects of the space environment on the body. Extended stays in microgravity can wreak havoc on bone and muscle tissue, and there are risks associated with long-term exposure to the high radiation environment of deep space. Without the ISS, researchers wouldn’t be able to study these issues, which will be critical to keeping astronauts safe when they venture back to the moon and finally on to Mars.
“I’ve been involved with life-support systems for my whole career, and the ISS is a critical test bed for that,” says Gatens. For example, on a Mars mission, NASA will have to send spares of critical components along with the crew to ensure safety even if a part fails. But without a test bed to study the failure rates of these components, the agency would likely have taken up valuable cargo space and wasted the mission’s budget flying more spares than necessary out of an abundance of caution. “If we had tried to do a mission to Mars back when we first flew the ISS, we would have had so much uncertainty around failures,” Gatens says. “Through the experience we've gained on ISS we have been able to reduce the number of spares it would take us to successfully execute a trip to Mars by several times.”
Gatens says the ISS has also been critical for stoking interest in low earth orbit from private companies. Last year, NASA went to the Nasdaq stock exchange to declare the ISS “open for business,” and its focus on fostering commercial projects in the lab is starting to pay off. NASA has relied on private companies like Nanoracks to develop and operate equipment for scientific payloads for years, but it's beginning to attract clientele whose primary business has nothing to do with space. Earlier this year, for example, executives for the cosmetics company Estee Lauder signed a contract with NASA to host a photo shoot on the station for an advertisement for skin cream. Next year, Axiom Space, which is developing the world’s first commercial space station, will fly Tom Cruise and three other private astronauts to the station to film a movie.
The ISS has been doing laps around Earth for so long that it can be easy to take this remarkable experiment in technology and international cooperation for granted. More than a quarter of the world’s population has never known a time when there wasn’t a human in space. Even without all of the advances in science, technology, and medicine it’s made possible, that alone is an incredible achievement. The space station probably won’t be around for another 20 years—and it wasn’t meant to be. It was always envisioned as a stepping stone in the human exploration of other worlds. Monday will mark 20 years since astronauts opened its hatch for the first time. But the adventure is just beginning.