Released in September 2024 by an oversight committee of the US National Aeronautics and Space Administration (NASA), a safety report about the International Space Station (ISS) cited, in addition to 50 other “areas of concern,” a troublesome leak first detected six years ago in one of the station’s modules [
1]. Given the persistent leak, called “a top safety risk” [
2], and the fact that the space sta-tion has outlived its original life expectancy by more than 10 years, the agency’s current plans call for decommissioning the ISS in 2031 by dragging it into the Pacific Ocean [
3]. Meanwhile, however, efforts started in 2021 to have a commercial contractor develop a successor for the ISS have largely stalled [
4], leaving NASA with the potential choice of further extending the life of the aging sta-tion or being without a crewed presence in low-Earth orbit (LEO) for the first time in more than three decades.
“The end of the space station would be the end of a distinct era of NASA’s history,” said Casey Dreier, chief of space policy at the Planetary Society, headquartered in Pasadena, CA, USA. “And with the future of a crewed station in LEO in the hands of companies that are very uncertain and have never been tested in a serious way, many in the agency are feeling nervous.”
While originally expected to be completed by 1994 for 8 billion USD, the ISS took four more years (1998) to first launch into orbit and cost more than 100 billion USD to construct [
4]. The station (
Fig. 1), which additionally costs about 3 billion USD annually to operate and maintain [
4], is managed jointly by NASA, Roscosmos, and an international coalition that includes the European, Japanese, and Canadian space agencies. In recent years, the ISS has accommodated a crew of three to four astronauts at a time to perform basic scientific research in a microgravity environment and study the long-term health impacts of living in space on humans [
4].
“There is a real concern for leaks that develop from cyclic fati-gue; such leaks occur due to the gradual accumulation of micro-scopic damage within the material over time and eventually grow in magnitude at an exponential rate,” said Michael Kezirian, adjunct professor of astronautics practice at the University of Southern California in Los Angeles, CA, USA, and president of the International Space Safety Foundation (Redding, CA, USA). “You might have a hairline coming through, but if it becomes a quarter-inch hole you have very few options.”
ISS crews keep the hatch to PrK closed when the module is not in use, lessening the leak’s impact. If the leak worsens, a long-term solution would be to close the hatch permanently, but that would deprive the station of a docking port used by Progress and Soyuz spacecraft [
6]. In July 2024, prompted by concerns about the leak, NASA awarded a 266 000 USD contract to SpaceX (Starbase, TX, USA) to devise a contingency plan to evacuate American astronauts from the station [
2]. “The leak may not be catastrophic, but it is putting into focus that this is an aging piece of hardware,” Dreier said. “The last thing NASA wants is to lose astronauts on a station by pushing it too long.”
The OIG report also cited other challenges to keeping the ISS operational, including potential supply chain issues—the report identified 588 parts operating beyond their planned operational lifetimes and in need of replacement. Other problems include solar panels losing efficiency over time, ongoing issues with the certifi-cation of Boeing’s CST-100 Starliner to provide a redundant crew transportation capability [
7], and growing risks of collisions with tiny meteors and orbital debris [
8].
In June 2024, NASA awarded SpaceX an 843 million USD con-tract to develop a deorbit vehicle for the ISS based on the com-pany’s Dragon spacecraft [
3]. Typically, 16 Draco engines power the Cargo Dragons that regularly visit the ISS. The deorbit vehicle would carry an additional 30 Draco engines and six times the fuel of a typical Dragon mission to give the uncrewed spacecraft the brawn needed to drag the sprawling station into the Pacific Ocean sometime in 2031. “That beefed-up Dragon would go down with the ISS in an uncrewed suicide mission,” said Laura Forczyk, owner of the space consulting firm Astralytical (Palm Bay, FL, USA).
In 2021, looking ahead to a future without the ISS, NASA awarded contracts valued at between 125 million and 160 million USD to three companies—Blue Origin (Kent, WA, USA), Nanoracks (Houston, TX, USA), and Northrop Grumman (Dulles, VA, USA)— to begin preliminary work on a commercial space station, an effort the agency has named its Commercial LEO Destination (CLD) pro-gram [
9]. A fourth firm, Axiom Space (Houston, TX, USA), had received 140 million USD a year earlier to construct the first hab-itable, commercially built module on the ISS—the company hopes to launch the module in 2026 and then undock it to fly free when the station is decommissioned [
10].
To date, each of the contracted companies has experienced more setbacks than successes. Financially strapped Axiom has repeatedly delayed its timelines for module launches [
11]. In Octo-ber 2023, citing a weak business case, Northrop Grumman dropped its own plans for building a CLD, and instead joined a team led by Voyager Space (Denver, CO, USA) [
12], which had acquired Nanoracks [
4]. And although it has met contractual milestones, particularly in developing its life-support systems [
13], Blue Ori-gin’s partnership with Sierra Space (Louisville, CO, USA) to develop its CLD, called Orbital Reef, could be ending, with both companies seemingly prioritizing other projects—for Blue Origin, its Blue Moon lunar lander; for Sierra Space, its Dream Chaser spaceplane [
14].
In late
2025, NASA plans to award additional contracts to one or more private companies to develop CLDs, with the front runners being Vast Space (Long Beach, CA, USA) and SpaceX [
4]. The latter has proposed turning a variant of its massive Starship spacecraft into a habitable space station [
15]. “SpaceX has a lot on their plate right now, but that has not stopped them in the past from propos-ing these kinds of concepts,” Forczyk said.
Even if SpaceX joins the fray, the race for the United States to avoid a gap in its LEO presence may have already been lost, accord-ing to the OIG. “In our judgment, even if early design maturation is achieved in 2025—a challenging prospect in itself—a commercial platform is not likely to be ready until well after 2030,” the OIG wrote in a 2021 report [
16]. It added that, without a working sta-tion, “the nascent low-Earth orbit commercial space economy would likely collapse, causing cascading impacts to commercial space transportation capabilities, in-space manufacturing, and microgravity research.”
NASA’s CLD program is not the only option for crewed commer-cial opportunities in LEO. The Chinese Manned Space Agency (CMSA) is exploring opening its Tiangong station, which launched into LEO in 2021 and now has three habitable modules, to com-mercial activities, including a low-cost commercial cargo system [
17]. CMSA also plans to expand Tiangong to six modules, includ-ing a co-orbiting Hubble-class space telescope, named Xuntian, that can dock with the space station for maintenance and potential upgrades [
18]. A six-module Tiangong would, however, be just over a third of the mass of the roughly 450 tonnes ISS. In October 2024, CMSA unveiled the design of two new reusable uncrewed shuttles called Qingzhou and Haolong to take cargo to and from Tiangong [
19].
Regardless of what flags current or future space stations fly under, doubts about the long-term prospects for a LEO space econ-omy have been widely raised, including by industry analysts who published an influential report in 2017 [
20]. The major piece miss-ing, the report stated, is a compelling application that makes it profitable for humans to live and work in space. A more recent analysis [
21], published in 2024 by researchers at the International Space University in Illkirch-Graffenstaden, France, suggests multi-ple revenue streams could make a CLD commercially viable, including educational and creative industries, space-based science, in-space manufacturing, and space tourism [
22],[
23]. There is also the possibility that automated research and manufacturing in LEO might eliminate some of the need for humans in space. For example, Varda (El Segunda, CA, USA) has demonstrated the ability to do pharmaceutical research in orbit on the cheap, with its first mission landing in February 2024 after spending eight months in space [
24].
“From my vantage point, there is currently no clear business case for a crewed space station—if there were, we would have them by now,” Dreier said. “A lot of commercial space is faith-based, with the hope that an ecosystem will develop, which is why, at this point, significant government support is needed to get it off the ground.”
So far, however, NASA’s spending on its CLD program appears to reflect a less-than-full commitment. While the development of viable commercial space stations is likely to require billions of USD in funding, the agency has spent 650 million USD over the last five years on the effort [
4].
“The lack of commitment to CLD that we are seeing from NASA may reflect the agency’s focus on the Artemis mission to the Moon and Mars missions after that,” Forczyk said. “Regardless, there is enough interest from other countries like China and India that, looking forward, perhaps well past this decade, I believe we will see a diversification of commercial space stations with specialized uses as what we do as a society here on Earth travels out to LEO and beyond.”
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