The last time no representative of the human race was in space Bill Clinton was in his final year in the White House, Vladimir Putin was in the first year of his quarter-century reign, the New England Patriots had yet to win any of their six eventual Super Bowl titles, and Taylor Swift was turning 11. It was the fall of 2000 and the American space shuttle was between missions, as was the Russian Soyuz spacecraft, meaning every member of the human species was on the planet. On Oct. 31, however, all that changed when American astronaut William Shepherd and Russian cosmonauts Yuri Gidzenko and Sergei Krikalev blasted off aboard a Soyuz rocket, arrived in orbit, and began a two-day chase of the unoccupied International Space Station (ISS), at last arriving and climbing aboard on Nov. 2.
Since that day, the ISS, which is reaching its 25th anniversary, has put some magnificent achievements on the board. It has been continuously occupied by a rotating cast of over 280 astronauts and cosmonauts from 26 countries who have lived and worked and sweated and slept and made space their home for assignments that have sometimes seen them spending a year or more off of the planet. In that time, according to NASA, they have conducted more than 4,000 scientific investigations resulting in 4,400 published papers, including 361 in 2024 alone.
The ISS has “come into its own as a very sophisticated scientific laboratory,” says retired NASA astronaut Scott Kelly, who famously spent a year in space aboard the station in 2015 and 2016.
“We’ve been able to have an international partnership in science that is the longest running in history and with documented returns,” says Henry Hertzfeld, research professor of international affairs at George Washington University’s Elliott School of International Affairs, and the former director of the school’s Space Policy Institute.
But the aging station—which faces abandonment and deorbiting in 2030—is raising a lot of questions too, not the least being whether it has been worth all of the time, labor, and not insignificantly, money needed to build it and maintain it over two and a half decades of service. Have those returns Hertzfeld speaks of led to any actual benefits on Earth? Has our time aloft taught us more about how to live and operate in space? Could our efforts and revenue have been better spent on a robustly funded return to the moon and later journeys to Mars?
NASA, no surprise, sees the station as a win, and is only too happy to tout the benefits it has produced. In zero-g, convection, sedimentation, and the downward tug of gravity are eliminated, allowing astronauts to grow better protein crystals for use in drug development; 3D-print living tissue that could eventually be used for transplants; study the effect of chemotherapy drugs on cancer cells—which grow more aggressively in weightlessness, producing actionable results faster; and more.
“I did the first DNA sequencing in space,” says retired NASA astronaut Kate Rubins. Who served two rotations aboard the station for a cumulative 300-plus days aloft. “We’re learning things about regenerative medicine and stem cell therapies that [will be] medical therapies for patients back on Earth.”
Pure research, of course, is not applied research and insiders admit it could be a long time before the therapies Rubins speaks of ever reach the patients. “I’m not sure if you asked the average American what kind of science has been done on the International Space Station that will improve your life in any meaningful way, I don’t think they can answer that,” says Kelly. “Perhaps in the future some of that research will be turned into something that’s more understandable.”
Sticker shock
That vague payoff tomorrow for hard cash and hard labor spent today has always dogged the space station enterprise. For more than 40 years, what is now known as the ISS has been a sinkhole for money. It was in 1984 that President Ronald Reagan first directed NASA to build a permanently occupied space station, then known as Freedom. The estimated cost was $8 billion. In 1993, after the fall of the Soviet Union, President Clinton changed the station from an all-NASA enterprise to one that gathered in the Russians as well as 13 other partner nations, including Canada, Japan, and members of the European Space Agency. The modest ISS that the crew of Shepherd, Gidzenko, and Krikalev first visited in 2000 was nothing compared to the behemoth it is today. Back then, the entire vehicle consisted of just three habitable modules. That has more than quintupled to 16 modules providing more living space than a six-bedroom home, with two bathrooms, a gym, six sleeping pods and a cupola that provides a 360-degree view of the Earth below. If the one-million-pound spacecraft with its vast array of solar wings were brought down to the ground, it would more than cover a football field.
That kind of orbiting infrastructure does not come cheap. Over the years, the most commonly cited figure for the cost of the station has been $100 billion. But nobody pretends that number is reliable.
“I was putting $100 billion on my Air Force OPR [officer performance report] 10 years ago,” says retired astronaut—and now Texas U.S. Senate candidate—Terry Virts, who served two tours of duty aboard the station, once as commander, for a total of seven months in space. From 2013 to 2023, however, NASA has spent an additional $3 billion annually to maintain the station. In 2024 and 2025 the figure jumped to over $4 billion, though that funding was shared by other space agency operations, including NASA’s program to develop commercial use of low-Earth orbit by private companies. And none of this money includes what other partner nations pay per year on upkeep of their modules and the care, feeding, and training of crews, ballooning the overall cost further.
“I bet it’s been over 200 [billion dollars], maybe 250,” says Virts. That’s an opinion analysts echo.
The station’s dizzying sticker price has meant not just balance sheet costs but opportunity costs. It took the NASA of the 1960s just eight years to go from a single popgun suborbital flight in 1961 to the surface of the moon in 1969. The NASA of today, meantime, has been slow-walking its effort to return to the moon and later go to Mars since 2004, when President George W. Bush first announced the program. Most of the problems have not been the space agency’s fault. In 2010, President Barack Obama canceled Bush’s moon-Mars initiative, only to revive work shortly after on the heavylift booster and the crew craft that will be needed for the missions, when lawmakers from space states like Texas and Florida pushed back. Even then, NASA has suffered from years of flat funding that have kept the program moving at a creep. The fact that a cash-poor NASA is trying to juggle two human space flight programs—the station and moon-Mars—only exacerbates the funding problem. Reaching the moon 56 years ago meant a monomaniacal focus on that one goal, not the split attention—and split budgets—of maintaining a permanent presence in low-Earth orbit while simultaneously trying to reach another world.
Pascale Ehrenfreund, research professor of space policy and international affairs at George Washington University’s Space Policy Institute has a generally positive view of the ISS but does suggest that NASA has not kept its eye on the ball when it comes to the moon. “There has not been this openness in order to build a cislunar economy, to inhabit the moon and later on to Mars,” she says. “The mindset was not yet there.”
Three missions for one station
If the space station is going to be judged, it can’t be on the basis of just one test, but three—the engineering, the science, and the politics. Of those, engineering is perhaps the most impressive. There is no overstating how remarkable it is that the ISS exists at all. Building the outpost required 42 assembly missions, from 1998 to 2011 at a construction site 250 miles above the Earth moving at a speed of five miles per second. Modules were built on opposite sides of the world—the U.S., Russia, Europe, Japan—and yet they fit together in orbit at airtight tolerances of fractions of a millimeter. No astronauts or cosmonauts were injured or killed on the worksite, and though the Columbia disaster took place in 2003, during the construction period, that crew’s mission was entirely science-based and did not include a visit to the station.
Photoillustration by TIME (Source image: NASA Johnson, 2021)
“The idea that we’ve been able to build this million-plus-pound structure in space while flying at 17,500 miles an hour in a vacuum—with all the space walks we’ve done, all the hazardous operations, the launches, the landings—and we haven’t lost one person, even seriously injured somebody,” says Kelly. “I think it really gave us an opportunity to refine our space-faring skills.”
Those skills could pay dividends down the line, not only in helping us master the job of designing and manufacturing space infrastructure—in Earth orbit and later on the moon or Mars—but also in practicing the acrobatics of extensive spacewalking necessary to perform the assembly work. Building the station, says Rubins, gave crews and designers an “understanding of how to do multiple spacewalks of very extended duration, [There have been] massive improvements in spacesuit technology. We wouldn’t have learned that without the ISS. It’s readily translatable to [walking] on the surface of the moon in one-sixth gravity.”
With the station down to its last five years of service, multiple private companies—including Long Beach, Calif.-based Vast; Kent, Wash.-based Blue Origin; and Houston-based Axiom Space—are working to build brand new commercial follow-on stations which, they hope, will take the place of the deorbited ISS and lead to a thriving low-Earth-orbit economy. All of them will be beneficiaries of the construction lessons learned by ISS designers and astronauts—and NASA is lending a hand with the Commercial Low-Earth Orbit Development Program, intended to ease the transition from the public to the private sector.
“We’re seeing a booming space industry,” says retired astronaut Mike Massimino, who flew two shuttle missions and, during his time aloft, performed four spacewalks. “I think it’s leading us to commercial space stations. There are a lot of people putting in some big money.”
Orbiting Laboratory
The science work that will be done aboard the commercial stations was also pioneered aboard the ISS. Protein crystals grow larger and more uniformly in the absence of gravity, and crew members on the station are taking advantage of this fact to study and develop new drugs. Most promising is work being done with the cancer drug Keytruda, with astronauts helping Big Pharma develop a form of the drug that can be injected quickly and easily at a doctor’s office rather than being administered by a slow intravenous drip in a clinic. The Food and Drug Administration approved the drug in September. Space station crews are also partnering with LambdaVision to manufacture artificial retinas in orbit that can be used to treat patients losing their vision to such conditions as retinitis pigmentosa.
“Through nine missions to the International Space Station, we’ve leveraged the unique environment of microgravity to manufacture artificial retinas,” says Nicole Wagner, CEO of LambdaVision. “Our continued efforts on the ISS will advance a therapy to restore vision … and pave the way for future space-based biomanufacturing.’
And then there is the research on the astronauts themselves that could have knock-on effects both for helping crews stay healthier on long-duration deep space missions, and also provide new clues to the riddle of aging—and perhaps slow it down. “What happens with the human body in space is actually an accelerated form of aging,” says Rubins. “You have things like osteoporosis, arterial stiffness, vestibular disorders, and orthostatic intolerance. When I landed from space I had to be carried out of the capsule and went about my first few days on Earth looking like a 90-year-old.”
In 1998, John Glenn—a U.S. Senator and the first American to orbit the Earth, in 1962—returned to space aboard the shuttle Discovery at age 77. Much of his work involved serving as a guinea pig for medical experiments investigating how his naturally aging body reacted to being in space. In general, Glenn’s performance on fitness and vital signs tests was equivalent to or even better than that of his younger crewmates, but there were exceptions. Muscles tend to atrophy in space since they are not working against gravity, and Glenn’s did not rebound as quickly as those of the rest of the crew once he returned to Earth. He also experienced sleep disturbances in space—a pattern consistent with older people even in a one-g environment.
Kelly’s year in space was also heavily medically-based, with NASA researchers comparing his health and physical changes before, during, and after the mission with that of his identical twin brother, Mark Kelly—also a NASA astronaut and now a U.S. Senator. Among the findings: Scott’s telomeres—the cuffs that protect the end of chromosomes like an aglet protects a shoelace—grew shorter faster than Mark’s. Telomeres naturally shorten as people age, but Scott’s exceeded the typical rate. Researchers also found that Scott’s body mass decreased by 7% during flight, while Mark’s stayed stable on the ground.
“There’s so much that is on the horizon that NASA will continue to do for the next five years of the space station,” says Rubins, “and we have commercial space stations that I think will scale this.”
What the commercial stations won’t be able to replicate as well will be the soft-power dividends of the ISS. American astronauts have, for years now, been flying to the ISS aboard Russian Soyuz spacecraft, and, since 2022, Russian cosmonauts have been flying aboard America’s SpaceX Crew Dragon ships. While Russia’s ISS modules are at one end of the station and the American modules are at the other, the crews work, eat, and socialize as one—a camaraderie that may currently be absent in Moscow-Washington relations, but that transcends political differences in space.
In 2015, during Kelly’s year on the station, Russian troops intervened in the Syrian civil war in support of dictator Bashar al-Assad—a move that the U.S. strongly opposed. There was fighting on Earth, but friendship aloft.
“I remember talking to [cosmonaut] Sergey Volkov,” Kelly says, “and there was a big concern that [the U.S. and Russia] could get into a hot conflict. Despite flying with people I would once have considered my enemy, we were talking about it in a very abstract way, almost like we weren’t talking about the United States and Russia. At that moment, what was most important to us was our ability to work together, our support for each other, our being able to trust these Russians with our lives, literally, and them, likewise to trust us.”
“The most important return on the station was the international relations we’ve built,” says Virts.
Even the rest of us, who aren’t aboard the station, benefit from this soft-power halo. The ISS is the third brightest object in the night sky—after the moon and Venus—and is readily visible to 8.2 billion people, and that has an impact.
“It is clearly something that demonstrates that we are a major global power,” says Rubins, “and we can work with other major global powers to do something positive for humanity.”
Not that station relations have always been entirely chummy; sometimes the cosmic carrot can turn into a stick. From 2011, when the last shuttle flew, to 2020, when the first Crew Dragon took astronauts to space, the U.S. was without a way to get crews to the station, and had to rely on the Russian Soyuz for a lift—a service Russia provided at a cost that eventually exceeded $90 million per seat. In 2014, after Russia seized Crimea, President Obama imposed sanctions on the individuals and groups responsible for the aggression. Shortly after, Russian Deputy Prime Minister Dmitry Rogozin tweeted: “After analyzing the sanctions against our space industry, I suggest the USA bring their astronauts to the ISS using a trampoline.”
More recently, Kelly believes that Russia’s egregious behavior in launching the larger war on Ukraine is reason enough to throw them off the station entirely—a move that he acknowledges would be impossible since astronauts and cosmonauts rely on Russia’s uncrewed Progress supply vehicle to stabilize and orient the station.
“We have no ability to kick Russia out of the club,” he says, “which I would have liked to have done. I would have been a proponent for that.”
But Russia’s not going anywhere and nor are any of the other partner nations in the five years of life the ISS has left to it. The decision to spend so much treasure—both in actual capital and human capital—on a low-Earth-orbit platform was made long ago, and it will only be after all of the science done aboard the station has seeped into the pharmaceutical, manufacturing, and biomedical economies that we will know whether the bet we made was the right one. A more-focused, Apollo-like sprint to the moon and Mars would surely have made for banner headlines and grand parades that have not been accorded the station. But the engineering that made the ISS possible and the science and international cooperation that have kept it flying have been quietly grand in their own ways.
“I think,” says Ehrenfreund, “that the International Space Station has proven itself to be one of the most solid and peaceful international collaboration projects of all time.”
