When a rocket carrying the first module of the International Space Station blasted off from Kazakhstan in November of 1998, NASA officials said the station would serve as an orbiting home for astronauts and cosmonauts for at least 15 years.
It has now been more than 18 years that the station has been continuously occupied by people. The place is impressive, with more living space than a six-bedroom house and with two bathrooms and a large bay window for looking down at Earth.
NASA and its international partners have spent decades and more than $100 billion to make the station a reality. The trouble is, as the agency sets its sights on returning people to the moon, the aging station has become a financial burden. And it's not clear what its future holds.
NASA spends between $3 billion and $4 billion a year operating the station and flying people back and forth. That's about half the agency's budget for human exploration of space.
The United States and other participating nations have pledged to fund the space station until at least 2024, but it will surely last longer than that. Gilles Leclerc, head of space exploration at the Canadian Space Agency, says there's no way that the international partners would come together in five years and decide to just crash the station into the ocean so that resources could be directed to other space goals.
"It would be a waste. We cannot ditch the International Space Station. There's just too much invested," Leclerc says. "It's quite clear, it's unanimous between the partners that we continue to need a space station in low Earth orbit."
So NASA has floated one money-saving idea: Turn the space station over to the private sector. That's why, a few weeks ago, NASA officials held a big press event at the Nasdaq stock market's MarketSite in New York City.
"NASA is opening the International Space Station to commercial opportunities and marketing these opportunities as we've never done before," said the agency's chief financial officer, Jeff DeWit. "The commercialization of low Earth orbit will enable NASA to focus resources to land the first woman and next man on the moon by 2024, as the first phase in creating a sustainable lunar presence to prepare for future missions to Mars."
Astronaut Christina Koch appeared in video beamed down from space. "We are so excited to be part of NASA as our home and laboratory in space transitions into being accessible to expanded commercial and marketing opportunities, as well as to private astronauts," she said.
All this produced a sense of déjà vu in John Logsdon, a space historian with George Washington University. In the 1980s, when Ronald Reagan's administration first proposed building a permanent space station, part of the pitch was "the idea that it could be a place for a wide variety of commercial activities, with billions of dollars of economic payoff," says Logsdon. "So here we are in 2019, finally going to test that hypothesis."
When reporters asked how much revenue could come in from new commercial activities on the station, however, NASA officials wouldn't give any numbers, saying there was too much uncertainty.
"The 12 industry studies NASA commissioned last year estimated revenue projections for future low-Earth orbit destinations across a variety of markets, and those projections varied significantly as a result of uncertainty associated with these future markets," a NASA spokesperson told NPR. "The markets and services that will generate revenue need to be cultivated by the creative and entrepreneurial private sector."
"That is the right answer because they don't know yet," says Tommy Sanford, executive director of the Commercial Spaceflight Federation.
But if the space station became commercially operated or even privately owned, NASA could become just one of many customers.
"You need to be focused on adding as many customers as possible and hoping to reach a tipping point, at some point, where you retain all of them," says Sanford. "Then that eventually lowers your cost, because you are one of many customers. You aren't bearing the entire cost of the infrastructure and transportation."
Some question whether any business could make a go of running a space station without the government still ponying up a ton of money.
"Candidly, the scant commercial interest shown in the station over its nearly 20 years of operation give us pause about the agency's current plans," NASA Inspector General Paul Martin told members of Congress last year.
As all of these discussions go on, the station keeps getting older. Space is a harsh environment. The hardware is wearing out, and major components are certified only until 2028.
"Space station really has up to, say, less than 10 years of lifetime," says Dava Newman, a scientist at MIT and a former NASA deputy administrator.
She loves the station and has flown experiments on it. But she thinks with time running out, there needs to be a strategic plan for its end.
"There might be some elements of space station that the private [sector] might be able to take over, a module or two," she says. "All of that needs to be put into place, probably with government funding."
Eventually, big components of the station will have to crash back down to Earth. Asked when NASA expected to deorbit the station, a spokesperson for the agency said that no specific year is being targeted.
"Transition from the space station will occur once commercial habitable destinations are available and can support NASA's needs as one of many customers," the spokesperson said.