NASA's plans to create a robust economy in low-Earth orbit where private spaceflight companies can flourish could eventually leave the agency's astronauts stranded on Earth with nowhere to go.Why it matters: NASA hopes to play a lead role in developing a private spaceflight economy, including private sector astronauts. The agency sees this as a way to free it up to focus on farther afield goals like bringing humans back to the Moon and, eventually, to Mars.But if private industry takes over human spaceflight destinations in low-Earth orbit and funding and political support for NASA missions to the Moon or Mars dissipates, there may be no point in having a government-sponsored human spaceflight program at all.Driving the news: On Friday, NASA announced it would create a market for private human spaceflight in low-Earth orbit.The agency wants American companies to fly their astronauts first to the International Space Station starting in 2020 and then later to space stations that companies operate themselves.The catch: By largely giving up control of human spaceflight in orbit, a region of key importance for Earth science and other discoveries, NASA risks that its human spaceflight program might be more heavily impacted by political whims.Today, NASA uses the International Space Station, in part, as a testbed for further exploration of the solar system.With the ISS aging toward obsolescence, NASA may be carrying out that research on private space outposts in the future.But if, at the same time, the deep space missions get delayed or canceled, it's harder to see where NASA astronauts fit into that broader landscape."If the private sector takes over low-Earth orbit, and the political support for exploration dissipates, then what's the rationale for a government program?"John Logsdon, founder of the Space Policy Institute at George Washington University, to AxiosBetween the lines: It's realistic to imagine NASA's exploration goals will shift in the near or long term. The space agency is constantly facing political whiplash when new administrations take over and impose new spaceflight goals.The impetus for getting private companies into the human spaceflight game stems in part from the need to cut NASA's costs of launching to orbit.The agency currently spends about $1.8 billion of its $3 billion to $4 billion space station budget on transportation.If launch costs were reduced, that would free up money for NASA's broader exploration goals.But, but, but: It's not yet clear exactly how much demand there will be in the private sector for human spaceflight to low-Earth orbit. A 2017 report looking at the market for a privately run space station found there isn't an obvious, profit-driven demand for such a facility in orbit, at least not yet.The fading International Space StationFor better or worse, sometime in the next decade, the International Space Station program will likely reach the end of its life, bringing a unique and successful venue for international diplomacy to an end.Where it stands: The ISS has been a source of international collaboration in space since the first module launched in 1998, but when the program ends, there may be no publicly funded replacement on the way.Details: Even if the private space stations NASA is now banking on never become a reality, eventually the ISS’ major components will reach the end of their technical lifespans in orbit."[T]he idea here is to start early so that there could be potentially a private sector space station that serves NASA's needs," NASA associate administrator William Gerstenmaier said during a NASA press conference at Nasdaq headquarters in New York on Friday.The impact: When the space station ends, international collaboration in space could look very different. In fact, it could give way to growing competition instead.U.S. space rival China is planning to have its own space station in orbit by around 2022, but it's unclear exactly what kind of collaboration U.S. companies might be able to have with the nation.The private space stations NASA's betting on might one day play host to astronauts from other countries aside from the U.S. as well, potentially democratizing human spaceflight around the world.NASA still plans to collaborate with other space programs on human spaceflight when the station ends. For example, the agency is working with Europe and Japan on its Artemis program to return astronauts to the Moon.Yes but: Private sector space stations are less likely to play a large role in space diplomacy, since they'll be aiming for profit.The ISS has acted like a peacekeeping force in the past. (In 2014, for example, Russia and the U.S. were at odds on Earth, but the two countries still needed to cooperate in space.)It remains to be seen if a private space station will be able to fill that role as well.Go deeper: NASA looks to private companies to help commercialize low-Earth orbit