It took 12 years to build in space, and people have lived and worked aboard it continuously since Oct. 31, 2000 – 225 visitors, from 18 different countries, so far. Its crewmembers have logged more than 1,000 hours of extravehicular activity on more than 200 spacewalks. More than 3,000 scientific investigators, representing more than 100 countries, have participated in more than 2,400 studies and published more than 1,400 results. It’s as big as a football field, weighs nearly a million pounds, and is the most expensive ($100 billion) object ever built.

The numbers are mind-boggling enough that citing them almost muddies the historic significance of the International Space Station (ISS). It’s hard to boil down everything that’s happened in low-Earth orbit (LEO) over the last 20 years, though many thoughtful scientists and historians have made the effort. The Center for Knowledge Diffusion, a U.S. nonprofit that promotes educational access, has illustrated, with its ISS Map of Science, the interdisciplinary flow of knowledge spurred by research aboard the station. The map shows connections among fields as diverse as the humanities and social sciences; medical and biological sciences; and engineering, math, chemistry, and physics – a scope unequaled by any research platform, anywhere.

The ISS has changed the world’s ideas about what’s possible in space. In the nearly 18 years during which humans have continuously inhabited LEO, the program has demonstrated the ability for people in spacesuits to assemble large structures in space. In recent years it has revolutionized robotic assembly in space, with external payloads installed and removed via ground-controlled robotics. It continues to foster the creation of a commercial marketplace for space-based services, from research logistics to microsatellite deployment. The scientific and technical accomplishments achieved by the ISS program have already begun to yield benefits for humanity, in forms ranging from new medical procedures to remote sensing tools.

Whether it is a customer or benefactor of the ISS in 2025, NASA will have the same primary objectives for work on the space station, outlined in its Transition Report: to prepare for deep space missions, to maintain global leadership in human spaceflight, to enable a commercial market in low-Earth orbit, and to continue to foster research and development efforts that will benefit life on Earth.

The ISS program’s international partners – the United States, Russia, Canada, Japan, and the
12 member nations of the European Space Agency (ESA) – have achieved what may be the station’s most significant legacy: a tradition of working together on peaceful activity in space. The intergovernmental agreements developed to make the ISS happen are remarkable for their simplicity and agility, allowing relationships to grow and change over time, and they’ve also laid the groundwork for new collaborations in space, such as the European Service Module that will provide navigation, propulsion, electricity, water, oxygen, nitrogen, and temperature control for Orion, NASA’s spacecraft for exploring the solar system.

According to Joel Montalbano, NASA’s deputy International Space Station program manager, this decades-long tradition of cooperation in space is sturdier than most treaties negotiated on Earth, where relationships are often roiled by the winds of geopolitics. The ISS operates, literally and figuratively, above such concerns. “For example,” said Montalbano, “you see today the U.S.-Russian relationship, at the political level, is not really the greatest. But in operating with our Russian colleagues on the space station, nothing has changed … the physics is the same, whether you’re in the U.S. or Russia, and there is a job to do where people’s lives are at stake, and we work together with our Russian colleagues.”

 

The Transition Ahead

As NASA and its international partners celebrate the ISS’ remarkable 20-year record of innovation and collaboration, they also face a decision point: There is much the ISS can still accomplish in space – and much research yet to be done aboard the station to lay the groundwork for NASA’s and its partners’ crewed explorations of the solar system. At the same time, NASA now spends a little over $3 billion annually on the ISS program, with a significant amount of the cost for commercial cargo and crew.

In a 2014 report titled “Pathways to Exploration: Rationales and Approaches for a U.S. Program of Human Space Exploration,” the National Research Council concluded that within a few years, continuing to fund the ISS at this rate, without an overall increase in the human spaceflight budget, will negatively affect NASA’s schedule of crewed missions to Mars. Both the legislative and executive branches responded to this report by encouraging development of a commercial marketplace aboard the station, with the goal of shifting most, if not all, of the ISS operating costs onto private companies.

As of summer 2018, the future of the ISS was an unsettled question between the White House and Congress. The White House’s 2019 budget request, released in February 2018, proposed an end to direct federal funding of the station beginning in 2025. A month later, NASA submitted, as required by Congress, its ISS Transition Report, laying out its plan to transition the station to commercial operations. Congress responded by asking the agency to consider other options, including the extension of ISS operations until 2028 or beyond.

Whether it is a customer or benefactor of the ISS in 2025, NASA will have the same primary objectives for work on the space station, outlined in its Transition Report: to prepare for deep space missions, to maintain global leadership in human spaceflight, to enable a commercial market in low-Earth orbit, and to continue to foster research and development efforts that will benefit life on Earth.

For now, the agency is working to understand what “commercialization” of the ISS might mean.