Sen. Bill Nelson (D-FL) issued a stern warning to Trump Administration officials today that if they attempt to end operations of the International Space Station (ISS) in 2025 “they’ll have a fight on their hands.” Nelson was responding to media reports that the FY2019 budget request may propose just that.

The Trump Administration announced yesterday that release of the FY2019 President’s Budget Request (PBR) will be delayed by a week, from February 5 to February 12, because the 3-day government shutdown disrupted its production. Nonetheless, several media outlets have obtained copies of a draft of the NASA portion. It is only a draft. Changes could be made before it is ultimately presented to Congress.

The Verge broke the story yesterday.

The ISS is a partnership among the United States, Russia, Japan, Canada, and 11 European countries operating through the European Space Agency (ESA). Proposed by President Reagan in his 1984 State of the Union address and authorized by Congress in the FY1985 NASA Authorization Act, Europe, Canada and Japan formally became partners in 1988. After the end of the Cold War and the collapse of the Soviet Union in 1991, Russia joined the partnership. Originally named Space Station Freedom, it was redesigned in the early 1990s and the Freedom name was dropped. Since then it has simply been called the International Space Station.

The issue today is how long to operate ISS in low Earth orbit (LEO), incurring a cost to NASA of $3-4 billion per year, versus shifting NASA’s resources to human exploration of destinations beyond LEO like the Moon and Mars. In a budget-constrained environment, adding $3-4 billion to NASA’s $19-20 billion annual budget to do both would be highly problematical.

The last few years have witnessed considerable discussion of turning LEO over to the private sector so instead of operating a government facility, NASA could purchase whatever services it needs from companies operating their own space stations. The question is how to transition from the NASA-dominant paradigm to a new commercial model.

Concerned about how to make that as painless as possible, the 2017 NASA Transition Authorization Act, passed by Congress and signed by President Trump in March 2017, required NASA to submit an ISS Transition Plan by December 1, 2017. NASA did not meet that deadline. Acting NASA Administrator Robert Lightfoot explained last month that NASA decided to wait pending decisions from the White House on the budget and other matters.

NASA has opened partnership opportunities to some companies to develop commercial space stations. Bigelow Aerospace, for example, has a prototype expandable space module attached to ISS right now. NASA has not, however, initiated a “commercial station” public-private partnership (PPP) analogous to the “commercial cargo” and “commercial crew” programs already underway to resupply ISS with cargo and ferry crews back and forth.

Reagan’s 1984 State of the Union address directed NASA to build a permanently occupied space station within 10 years in cooperation with international partners. NASA estimated the cost at that time as $8 billion. Instead, it was 25 years before construction was complete and the U.S. cost ranges from $60-100 billion (depending in part on whether marginal or average costs are used to calculate the cost of the associated space shuttle launches).

Europe and Japan paid for their own modules and other hardware and services. Canada contributed the robotic Canadarm2. Russia provided some of its hardware. While generally there is no exchange of funds between the partners, NASA paid for the first Russian-built module, Zarya, and has been paying Russia to ferry crews to and from the ISS since the shuttle was terminated. The partnership operates under an Intergovernmental Agreement (IGA) that is a treaty in all the countries except the United States (where it is an Executive Agreement). Representatives of all the partners make decisions through the Multilateral Coordination Board that meets periodically.

How long to operate ISS is not a new question. It was a focal point in NASA budget discussions during the George W. Bush Administration when it was still under construction. Bush directed NASA to return humans to the surface of the Moon by 2020 (the Constellation program) and promised to add $1 billion over 5 years, but that was not nearly enough. He told NASA to terminate the space shuttle as soon as construction of the ISS was completed, even though NASA and its partners had planned on using the shuttle for delivering cargo and crews throughout the station’s lifetime. Space shuttle operations were terminated in 2011, freeing $3-4 billion per year. NASA budget projections showed funding for ISS ending in FY2015 which could have made that money available for Constellation, too.

President Obama extended the U.S. commitment to ISS operations to 2020 and then to 2024. NASA successfully worked to win the support of the other partners, some of whose governments were becoming skeptical about the benefits of the program.

All the partners now are committed to operating ISS “at least” until 2024. It is not a firm end date. ISS advocates argue that the facility only became fully operational in 2010 and more time is needed to utilize it. They view 2028 — 30 years after the first ISS module was launched — as the earliest operations should end.

Nelson is a steadfast advocate for ISS, issuing this statement in reaction to the stories that the Trump Administration may propose ending U.S. operations in 2025.

“If the administration plans to abruptly pull us out of the International Space Station in 2025, they’re going to have a fight on their hands. Such a move would likely decimate Florida’s blossoming commercial space industry, which is one of the reasons why Congress has directed NASA to look at extending the ISS to 2028 and to provide a plan to help scientists and researchers continue experimenting in low-Earth orbit beyond that.”

Crews have lived aboard ISS continuously since November 2000, rotating on 4-6 month shifts. Since construction ended in 2010, they have devoted an increasing number of crew hours to scientific experiments compared to operations and maintenance tasks, which consume much of their time.

ISS advocates consider the facility a symbol of national pride and resist the idea that the only space station orbiting earth 10 years from now might be China’s. They also view it as a one-of-a-kind microgravity scientific laboratory that could produce groundbreaking results if only given time.

Furthermore it is viewed as a key to successful commercialization of LEO. The business success of PPPs created by NASA for the commercial cargo and commercial crew programs with SpaceX, Orbital ATK, and Boeing depend on those companies selling enough services to recoup their investments. The idea was that the companies would find customers other than NASA, but that has not happened yet. Building a base of non-NASA customers to use the U.S. ISS facilities has also been slow, but advocates insist that the tide is turning and commercial use will grow significantly in the coming years. Hence Nelson’s concern about decimating the commercial space industry if ISS operations end 7 years from now.

The annual operations costs to NASA are the sticking point, however. The Trump Administration and many in Congress, not to mention NASA itself, want to move beyond LEO. Should the nation continue to spend $3-4 billion per year on ISS or shift it to human lunar and Mars exploration programs? These questions have bedeviled the program through many administrations and Congresses.

One difference this time is that commercial and international partners want to join in human exploration beyond LEO, but how much they will invest themselves versus relying on NASA for the lion’s share of the costs is unknown.

What is undeniable is that the ISS will not last forever. Degradation of system components and long-term exposure to the radiation and micrometeoroid environment of space will take its toll. At some point decisions will have to be made about what comes next in LEO. The FY2019 budget process may be that point.

Editor’s Note: For anyone interested in the history of the evolution of the space station from 1984-2005, here is a link to testimony I gave to the Senate Commerce Committee in April 2005 when I was a space policy specialist at the Congressional Research Service. A table summarizing key milestones is an appendix.