About a century before humans had the technology to do anything about it, their longing to slip the bonds of Earth was overpowering enough to inspire some eerily prescient fantasies about living in space. “The Brick Moon,” perhaps the first written mention of a crewed space station, was a novella published serially in The Atlantic by Edward Everett Hale in 1869, four years after Jules Verne’s novel From the Earth to the Moon. Hale’s plot follows the narrator’s scholarly companions as they fashion a 200-foot sphere made of bricks – iron, the narrator explains, would have been too heavy – and accidentally launch it into space with 37 of them aboard. Though the brick moon’s inhabitants never figure out how to return to Earth, they survive by growing crops.

The Apollo Applications Program, formally launched in 1967, was focused on long-duration flights in low-Earth orbit, and led to the design of the American space station known as Skylab, which orbited Earth from 1973 to 1979.

By the 1960s, science (not to mention science fiction) had advanced considerably, to the point where the United States and the Soviet Union were launching manned spacecraft into orbit and were already plotting how to apply their new technologies to support long-duration human spaceflight. With its Salyut program, the Soviet Union launched the first crewed space stations beginning in 1971. NASA research centers had been mulling rudimentary designs for an American space station since the early 1960s, based on a modified Apollo Command/Service Module (CSM) with an attached laboratory. The Apollo Applications Program, formally launched in 1967, was focused on long-duration flights in low-Earth orbit, and led to the design of the American space station known as Skylab, which orbited Earth from 1973 to 1979.

Today’s International Space Station bears imprints of both the Salyut and Skylab programs: A Soyuz capsule remained permanently docked at Salyut stations, to provide a means of emergency escape, while the Apollo CSM served the same function for Skylab. American and Soviet crews conducted experiments inside the modules and performed spacewalks for exterior maintenance. The “second-generation” Salyut stations, Salyut 6 and 7, each had two ports to allow resupply by cargo spacecraft.

The voluminous Skylab, built from a hollowed-out upper stage of NASA’s Saturn V moon rocket, was launched unmanned in May 1973 and visited by three-man astronaut crews who served on missions lasting between 28 and 84 days. The interior of Skylab, divided into tiered decks, was designed with habitability in mind, with a wardroom and private sleeping quarters separate from the laboratory.

In 1969, as the Apollo Moon landing drew near, President Richard Nixon directed the formation of a Space Task Group that would define goals for NASA’s post-Apollo space program. The agency was on the threshold of history, about to do something unthinkable just years earlier, and the president wanted NASA to define how it might build on its ability to visit the Moon.

The group envisioned a number of possibilities, including crewed satellites in Earth or lunar orbit, human travel to Mars, and “space transportation systems that carry their payloads into orbit and then return and land as a conventional jet aircraft.” In their report, the Space Task Group called for a space station to support the goal of landing on Mars.

A budget that would fund both a space station and a reusable Space Transportation System (STS, or Space Shuttle, as it was soon colloquially known) seemed unlikely, so NASA focused first on the shuttle, as the use of expendable rockets to build and supply an orbiting base would exceed the cost of the base itself. A Space Shuttle, with a laboratory within it, would allow capabilities to be studied and harnessed while new technologies were researched. The Space Shuttle Program was already well underway by the time Skylab was launched into orbit.

Two international partners helped NASA meet the Space Shuttle Program’s mission requirements. In 1969, NASA invited Canada to develop a robotic arm for use in deploying, maneuvering, and capturing orbiter payloads. In August 1973, NASA signed a memorandum of understanding with the European Space Research Organization, predecessor to today’s European Space Agency (ESA), to build a scientific laboratory for use on Space Shuttle flights. These 5.4-meter-long by 4.12-meter-diameter cylindrical “Spacelab” modules would fit securely into the payload bays of shuttle orbiters and connect to crew compartments via a narrower “tunnel” cylinder.

One important detail, however, emerged consistently among all eight studies: the modular, incremental approach to assembly. It made sense not only logistically, but also geopolitically: Modular assembly would encourage collaboration by allowing international partners to design their own building blocks to best serve the organization’s needs.

The robotic Canadarm entered orbit aboard the first space-capable orbiter, Columbia, in November 1981, and was first used in March 1982 to deploy and maneuver a Plasma Diagnostics package. The first Spacelab module was launched in Columbia’s payload bay in November 1983. The ten-day mission saw the conduct of 72 scientific experiments, in fields ranging from plasma physics to astrobiology.

While the Space Shuttle Program had been nearing its first launch, a NASA study group was conceptualizing what it called the Space Operations Center, a shuttle-serviced, permanently crewed facility in low-Earth orbit. After the election of Ronald Reagan to the presidency in 1980, the agency formed a Space Station Task Force that commissioned studies from eight aerospace contractors focused on space station needs, attributes, and architectural options.

From the start, NASA envisioned a space station as an international collaboration, and invited prospective partners to an orientation briefing in 1982. Europe, Japan, and Canada became informal observers of the contractor studies, which were released in the spring of 1983. The studies offered a variety of options for how a future space station might be configured and built, but several key details – how building blocks could be optimized for transport in a shuttle payload bay, for example, or how the module interiors should be composed – remained vague.

One important detail, however, emerged consistently among all eight studies: the modular, incremental approach to assembly. It made sense not only logistically, but also geopolitically: Modular assembly would encourage collaboration by allowing international partners to design their own building blocks to best serve the organization’s needs. In December 1983, Reagan directed NASA to continue with the effort to design and build a space station.

 

To the Drawing Board: Space Station Freedom

 

In his State of the Union Address delivered in January 1984, Reagan announced the nation’s commitment to building a space station in collaboration with international partners. “Tonight,” he said, “I am directing NASA to develop a permanently manned space station and to do it within a decade. … We want our friends to help us meet these challenges and share in their benefits. NASA will invite other countries to participate so we can strengthen peace, build prosperity, and expand freedom for all who share our goals.”

Conspicuously absent among the partners whom Reagan believed to share American goals was the Soviet Union, which was already building on the successes of its Salyut program and developing a “third generation” space station: Mir, the world’s first multi-module station, which would be assembled in orbit from 1986 to 1996. The Americans and Soviets had collaborated on the Apollo-Soyuz Test Program in the 1970s, but tensions between the two Cold War adversaries had ratcheted up since the inauguration of Reagan, who branded the Soviet Union an “evil empire” in a 1983 speech.

Shortly after Reagan’s State of the Union Address, NASA administrator James Beggs described the agency’s vision for the station. It would consist of three orbiting facilities: an occupied base, an autonomous co-orbiting platform, and another automated platform in a polar orbit. It would also provide eight capabilities in one package:

• a laboratory in space;
• a permanent observatory for Earth and the universe;
• a transportation node and operations base for vehicles and payloads;
• an assembly facility;
• a servicing facility;
• a factory for space hardware and systems;
• a storage depot;
• and a staging base for lunar or deep-space missions.

It was an ambitious concept, and Beggs immediately set out to find partners to share the work. In 1984, NASA signed agreements with the European Space Agency (ESA) and with Japan’s National Space Development Agency (NASDA) to provide their own laboratory modules for the station. With the support of the president and Congress, NASA established a Space Station Program Office at Johnson Space Center, Houston, and in April 1985, the office awarded several contracts to conduct definition studies and preliminary design.

That same year, the agency launched a pair of experiments, ACCESS and EASE, aboard the shuttle Atlantis. The experiments demonstrated the feasibility of astronauts assembling large structures in space, but also suggested that the favored “Dual Keel” design, featuring a long central truss with earthward and spaceward booms, would be challenging, and expensive, to build. NASA’s projected cost for its modules – a laboratory, centrifuge, and living quarters – was also proving to have been optimistically low.

Over the next several years, as designs were hashed out and details emerged, trade-offs were made between development costs and operating costs. The wisdom of designing a station for assembling and servicing hardware that didn’t exist yet, for programs yet to be funded – spacecraft for deep-space explorations, for example – was questioned, and station designers were forced to make hard choices. For the station to be financially feasible, its purpose would focus, at least initially, on its role as a research laboratory and observatory.

1988 also marked a milestone in the international collaboration of space agencies, as a multilateral agreement was signed by the United States, Japan, Canada, and nine member nations of the ESA.

The United States, NASA, and its space station program suffered a tragic blow on Jan. 28, 1986. The Space Shuttle Challenger, departing for its 10th flight, exploded 73 seconds after liftoff, killing all seven crewmembers aboard. The accident resulted in a two-and-a-half-year grounding of the shuttle fleet, and discussions in the wake of the disaster led to reduced flight schedules, as well as reductions in the amount of cargo allowed aboard each orbiter. The renewed emphasis on safety led to an insistence that an escape craft or “lifeboat” be docked at the station at all times.

Growing costs were one factor in the decision to pare down the Dual Keel design into what was known as the “Revised Baseline Configuration,” featuring a single horizontal truss with modules clustered near the center and solar arrays at the ends. In 1988, as this design moved into full development with main contractors Boeing, McDonnell Douglas, GE-Aerospace, and Rockwell, Reagan gave it a name: Space Station Freedom.

1988 also marked a milestone in the international collaboration of space agencies, as a multilateral agreement was signed by the United States, Japan, Canada, and nine member nations of the ESA. The four space agencies signed memoranda of understanding outlining the contributions each would provide to the space station: Europe and Japan agreed to build laboratory modules, and Canada agreed to build a Mobile Servicing System (MSS), consisting of a robotic arm and a trolley system that would move it along the truss. In return for providing services, such as power and crew and cargo transport, NASA obtained rights to use half the research facilities in the European and Japanese modules.

The first year of President George H.W. Bush’s administration was a rocky start for the new space station venture. While Space Shuttle flights had resumed, the program was still plagued by delays and climbing costs. Bush envisioned the space station as a critical component of NASA’s Space Exploration Initiative (SEI), which would have placed Americans back on the Moon in 1989. The station would have been an assembly point for the lunar missions, but SEI was terminated because of insufficient funding being appropriated. Some of NASA’s budget was being devoted to building shuttle Endeavour to replace the lost Challenger, and the NASA human spaceflight budget was being devoted to the space station. NASA was forced once again to temper its ambitions for the space station.

Ongoing redesigns reduced the length of the U.S. habitation and laboratory modules to 27 feet, in part because the original 45-foot-long modules, when fully outfitted and integrated, would have been too heavy for the shuttle to carry into orbit. Redesigns also reduced both the length and cross-section of the longitudinal truss.

As work continued, in 1991 an event that would have major significance for the future of the space station project was underway. In December of that year, the Soviet Union collapsed and dissolved as a functioning state. Seemingly overnight, the Cold War was over. The Russian space program, however, had been going strong. The Mir space station, its cosmonauts now citizens of a yet-to-be-named country, was still being assembled in low-Earth orbit, though its future, and the future of the Russian space program, were faced with uncertainty.

With the collapse of the Soviet Union, collaborative work with the Russians gained new importance. In 1992, NASA personnel made the first trip to Russia to look into use of the Soyuz as a crew rescue vehicle. This expanded into considering use of a Russian docking module and airlock, and subsequently this effort was broadened to include the Shuttle-Mir mission and later to multiple missions of the shuttle to Mir.

 

Russian Rescue

 

It’s no exaggeration to say that in 1993, when President William J. Clinton took office, the space station was on the brink of elimination; the White House budget director recommended canceling the program outright, and the House of Representatives came within a single vote of zeroing it out in NASA’s budget. NASA, with the support of Vice President Al Gore, ordered yet another redesign.

On Sept. 2, 1993, Gore and Prime Minister Viktor Chernomyrdin signed an accord merging Mir-2 and Space Station Alpha into a single project that would soon be known simply as the International Space Station (ISS).

There were three configurations considered, called Alpha, Beta, and Charlie. Alpha used some 75 percent of the Space Station Freedom hardware, and subsequently most of the hardware that had previously been deleted was added back. While one segment of truss was removed from each side, it was essentially the same as Space Station Freedom in appearance and capability, envisioned as a world-class research laboratory in three fields: microgravity, life sciences, and technology.

Meanwhile, within a month of taking office in April 1992, NASA Administrator Daniel Goldin was contacted by Yuri Koptev, his counterpart at the Russian federal space agency, who suggested the two agencies might combine their resources to build and operate a space station. Russia had already begun building modules for its planned Mir-2 station, but the future of the Russian program, given the new country’s political and fiscal circumstances, was precarious.

The Russian-built but U.S.-funded Functional Cargo Block, named Zarya, was the primary early Russian contribution, along with the Zvezda Service Module (the same as the Core Module or Base Block of the earlier Mir and a direct successor of the earlier Salyut stations).

Shortly after, in June 1992, Boris Yeltsin and Bush signed an expanded space exploration agreement that considered flying Russian cosmonauts on a U.S. Space Shuttle mission, sending a U.S. astronaut to Mir for an extended flight, and pursuing the possibility of docking the Space Shuttle with Mir in 1994 or 1995. This joint effort was called the Shuttle-Mir Program. The advantages to including Russian hardware and expertise in the space station program were clear, for both geopolitical and pragmatic reasons. In terms of the station’s capabilities, NASA claimed Russian participation would allow it to be built a year sooner, cost $2 billion less than the Alpha design, have 25 percent more usable volume, generate 42.5 kilowatts more electrical power, and accommodate six crew members instead of the planned four. The ability to park two Soyuz capsules permanently at the station (one Soyuz would be required for each three crewmembers) took pressure off NASA and its partners to develop their own crew return vehicle. Progress spacecraft, the expendable Russian cargo carriers, could aid in supplying the station.

On Sept. 2, 1993, Gore and Prime Minister Viktor Chernomyrdin signed an accord merging Mir-2 and Space Station Alpha into a single project that would soon be known simply as the International Space Station (ISS). On the American side, NASA’s Johnson Space Center took the lead, and Boeing signed on as the prime contractor.

The existing Shuttle-Mir program was expanded to become Phase 1 of the new ISS program, and added a whole series of shuttle flights to the Mir Orbital Station.

A few months later, in February 1994, cosmonaut Sergei Krikalev – who had been stranded in orbit when the Soviet Union fell and forced to stay an extra six months aboard Mir after a cancelled Soyuz flight – joined the crew of the Space Shuttle Discovery to become the first cosmonaut to fly aboard an American orbiter. About a year later, astronaut Norman Thagard became the first American to serve aboard Mir, joining a three-month expedition whose crewmembers were brought home aboard the Space Shuttle Atlantis. In November 1995, Atlantis delivered a Russian-built docking module to the station, marking a milestone: the first addition of a module to a working space station in orbit.

A major milestone for the International Space Station was finally achieved on May 16, 2011, when the last flight of the Space Shuttle Endeavour delivered one of the station’s most important experimental packages: the Alpha Magnetic Spectrometer (AMS-02), an antimatter detector that will aid scientists in understanding the origins of the universe.

The revamped ISS design had already taken shape. It was based on a modified Space Station Alpha, somewhat bigger, with some of the formerly deleted pieces added back. It comprised a horizontal truss perpendicular to the station’s flight path, and modules clustered near the truss’s centerline, mostly at right angles to the truss. The truss was arranged symmetrically, with four pairs of solar arrays extending from each end. The Russian-built but U.S.-funded Functional Cargo Block, named Zarya, was the primary early Russian contribution, along with the Zvezda Service Module (the same as the Core Module or Base Block of the earlier Mir and a direct successor of the earlier Salyut stations). The main thing to disappear from the U.S.-provided systems was the propulsion system. The station was now totally reliant on Russian-provided propulsion. Early on, Russia would also provide the habitation and life support functions, and the Soyuz would provide the emergency return capability. By 1997, NASA had begun shifting funds from space station evaluations and studies into space station construction.

In January 1998 the ISS partners – the United States, Russia, Japan, Canada, and nine participating ESA nations – signed a new Intergovernmental Agreement on Space Station Cooperation (IGA) and three memoranda of understanding outlining the duties, rights, and responsibilities of each of the members, under the overall leadership of program manager NASA. The Americans and Russians would supply the building blocks – the main living, working, and utility modules – while Europe and Japan would contribute laboratories (Columbus and Kibo, respectively) and other modules. Canada would contribute a robotic arm, Canadarm2, that would help with berthing, assembly, and maintenance. The larger structures would be lifted by Space Shuttle orbiters from Kennedy Space Center, or by Proton rockets from Baikonur Cosmodrome, Kazakhstan. The ESA would contribute logistical and supply launches with Ariane rockets from the Guiana Space Center, Korou, French Guiana, and Japan with HII-A rockets from Tanegashima Space Center in the Osumi Islands.

 

The Utilization Era: On the Threshold of Deep Space

 

With its partnerships formalized, a workable design funded by Congress, and building blocks under construction, the International Space Station was finally ready to take shape in orbit, about 250 miles above Earth. As ISS partners built hardware and planned for the assembly to begin, NASA reminded the American public of its rationale for undertaking one of the most ambitious construction programs in history. The ISS mission – “to enable long-term exploration of space and provide benefits to people on Earth” – included nine objectives:

• To create a permanent orbiting science institute in space capable of performing long-duration research in the materials and life sciences areas in a nearly gravity-free environment.
• To conduct medical research in space.
• To develop new materials and processes in collaboration with industry.
• To accelerate breakthroughs in technology and engineering that would have immediate, practical applications for life on Earth – and will create jobs and economic opportunities today and in the decades to come.
• To maintain U.S. leadership in space and in global competitiveness, and to serve as a driving force for emerging technologies.
• To forge new partnerships with the nations of the world.
• To inspire the nation’s children, foster the next generation of scientists, engineers, and entrepreneurs, and satisfy humanity’s ancient need to explore and achieve.
• To invest for today and tomorrow. Every dollar spent on space programs returns at least $2 in direct and indirect benefits.
• To sustain and strengthen the United States’ strongest export sector – aerospace technology – which in 1995 exceeded $33 billion.

The first two building blocks of the ISS were launched in late 1998. On Nov. 20, the control module Zarya (Russian for “sunrise,” to signal a new era of cooperation between Russia and the United States) was lifted into low-Earth orbit by a Proton rocket from Baikonur. Zarya, also known as the Functional Cargo Block, or FGB, was joined shortly afterward by the first American module, Unity (Node 1).

The assembly of the International Space Station in itself comprises an epic story. It took about 15 years to build the station in orbit, a process that saw further modifications to the overall plan (see “Design and Assembly” article). After the tragic loss of another Space Shuttle orbiter, Columbia, and its crewmembers in 2003, assembly was delayed – and when it resumed 30 months later, it was with an eye to easing the strain on the existing fleet. Two key components – the centrifuge module, an effort that had been taken up by Japan; and a Russian Science Power Platform – were canceled. A major milestone for the International Space Station was finally achieved on May 16, 2011, when the last flight of the Space Shuttle Endeavour delivered one of the station’s most important experimental packages: the Alpha Magnetic Spectrometer (AMS-02), an antimatter detector that will aid scientists in understanding the origins of the universe.

Several modifications to the ISS have been made since 2011, but that date marked the end of the assembly phase of the ISS project and the dawn of another: the utilization phase, the era in which the station would make its contributions to the global commons through a mature and robust research and development program.

The utilization phase is less than a decade old, and its history is still being written – but long before assembly complete, the ISS had already recorded remarkable breakthroughs, achievements, and benefits for humanity. Some of the earliest and most obvious benefits were in the form of technology transfers and adaptation. The system developed by NASA to recycle ISS wastewater into drinkable water, for example, has been adapted all over the globe into filtration systems that can provide drinkable water without the need for electrical power. The first of these ground-based water filtration systems was installed in northern Iraq in 2006, and in the years since, collaborations between aid organizations have demonstrated how aerospace technology can help to solve global problems, with applications including home water purifiers in India, village-wide systems throughout Latin America, and even individual survival kits that can be distributed as first response devices for natural and humanitarian disasters.

Several medical innovations have been spun off from the ISS’s robotic arm, Canadarm2, and Dextre, the robotic handyman that can be mounted at the arm’s end. Among the first was neuroArm, the first surgical robot capable of being guided by a magnetic resonance imaging (MRI) machine. In May 2008, a Canadian surgical team completed the first surgical removal of a brain lesion, a meningioma tumor, with neuroArm.

Throughout the more than 17 years that humans have lived and worked continuously aboard the station, more than 2,400 experiments from researchers in more than 100 countries have been hosted aboard the unique microgravity laboratory.

Some of the technologies aboard the ISS are already directly benefiting lives on Earth. Unlike many Earth-imaging satellites, which typically use polar orbits, the station is close to the planet and offers plentiful opportunities for imaging vegetation and forests in temperate regions. Imaging and remote-sensing technologies aboard the ISS have already proved valuable in helping tropical island communities to understand and manage changing reef ecosystems; in monitoring flooding and providing agricultural information to North American farmers; in collecting data on the depth and clarity of coastal waters and the characteristics of littoral seabeds; in monitoring the lagoon surrounding Venice, Italy; in providing high-resolution images of the flooding caused by Japan’s 2011 tsunami, and more. In 2014, to boost the station’s Earth-sensing capabilities, NASA announced that it would install several new instruments for monitoring ocean winds, clouds and atmospheric particulates, the ozone layer, lightning, forest canopies, and water content in vegetation.

In January 2012, the ISS helped to save a life at sea after the Icelandic fishing trawler Hallgrímur, out of range of coastal tracking stations, capsized and sank in a storm off the coast of Norway. The Earth’s curvature blocked the signal from reaching land, but the ESA, curious to know if a receiver mounted on the ISS could track ships out of terrestrial range, had mounted a test receiver on the station’s exterior. ISS astronauts did receive the Hallgrímur’s distress signal, and relayed it to the Royal Norwegian Air Force, which dispatched a helicopter to the spot. The ship’s sole survivor, who had spent several hours in the water, was found and rescued.

Through various programs such as Teaching from Space, in-flight education downlinks, and others, the ISS has become an invaluable tool for teaching young people around the world about these technologies and encouraging careers in science, technology, engineering, and mathematics (STEM). Space station astronauts and cosmonauts have shared their daily routines with schoolchildren, allowed university students to assume remote control of the station’s imaging cameras, and challenged grade school students to design experiments for the microgravity environment.

Science is now the primary focus of the ISS mission, and the story of the utilization phase is mostly the story of research and development in space. Throughout the more than 17 years that humans have lived and worked continuously aboard the station, more than 2,400 experiments from researchers in more than 100 countries have been hosted aboard the unique microgravity laboratory. NASA’s 2005 authorization designated the U.S. Orbital Segment a National Laboratory, and when it selected the nonprofit Center for Advancement of Science in Space (CASIS) to manage the laboratory in 2011, it was with the explicit focus on space research aimed at improving life on Earth.

The partnership that was formalized among a dozen international partners in 1998 has grown to involve the participation of nearly a hundred more countries, dozens of private contractors, and public and private foundations.

Much of the research activity on the ISS takes the form of fundamental investigations and basic observations, which can take years to unfold and produce tangible results – but some of these investigations have already shown great promise. To mention just a few:

• In the microgravity environment of the ISS, crewmembers experience bone loss at a rate of about 10 times that of people who suffer from osteoporosis. Studies of space-induced bone loss have shown where the greatest loss occurs, and suggested countermeasures – such as energy intake, vitamin D, and strenuous resistance exercises – that can be used to counteract it.
• The ability to grow larger, higher-quality protein crystals in microgravity has enabled the development of a new drug for treating Duchenne Muscular Dystrophy (DMD). Scientists, using crystals grown on the ISS, were able to formulate a drug, TAS-205, targeting a specific location on the protein. Based on terrestrial research in animal subjects, researchers think the drug may be able to double the lifespan of people with DMD, an incurable genetic disorder.
• The Russian-German Plasma Kristall Experiment laboratory has provided the knowledge base for medical spinoffs for the use of cold plasma in medical applications, for the disinfection of wounds, acceleration of healing, and even the inactivation of cancerous tumors.

Much of the research conducted aboard the ISS is aimed at solving the problems of long-term space expeditions. A crewed mission to Mars is likely to take 3 years or more, and researchers aboard the station are helping answer questions about how to enable humans to live, work and remain healthy in space for extended periods. Among the things ISS researchers have learned:

• Plants can be genetically modified to grow better and provide more nutrients when grown in microgravity.
• DNA damage caused by space radiation (specifically, to frozen mouse sperm) does not affect the viability of offspring – and the Japanese Space Pup investigation has revealed that much of this damage is mitigated or repaired after fertilization.
• The ISS Twins Study, which compared identical twin NASA astronauts Mark and Scott Kelly after Scott’s nearly year-long stay aboard the station, revealed that long-term spaceflight is associated with oxygen deprivation stress, increased inflammation, and dramatic shifts in gene expression cause by changes in nutrient uptake.

The nine-part mission articulated by NASA in the late 1990s has been largely fulfilled in part due to the agency’s efforts, since 2005, to promote a commercial market in low-Earth orbit. NASA’s research partners in space now include not only international partners, but also a growing number of private entities. These collaborations have provided the space station with new or updated capabilities while opening new markets to companies. Even small businesses, such as NanoRacks and Space Tango, who offer hardware and launch/flight support for private customers’ ISS-based experiments, have established a presence in space.

The growing number of private-sector partners has had a significant economic impact around the world. The $33 billion in American aerospace exports NASA reported in 1995 has more than quadrupled, reaching $143 billion in 2017. The ESA’s studies of the station’s economic impact have concluded that every 100 jobs in the space sector generate 90 additional jobs in the European economy, and the ISS adds 210,000 jobs annually to the labor market.

In 1962, in his famous speech at Rice University, President John F. Kennedy explained his administration’s rationale for going to the Moon, saying that one of the reasons the United States needed to “set sail on this new sea” was because the new field of space science needed the guidance of American values. “For space science,” he said, “like nuclear science and all technology, has no conscience of its own. Whether it will become a force for good or ill depends on man.” Now that science has taken center stage in the ISS program, with research consuming the intended share of astronaut and cosmonaut working time, the unique space laboratories offered to the world’s scientists have generated what may by the station’s most important overall benefit, if perhaps its most difficult to quantify: the increased access to, and interest in, peaceful cooperation in space.

In 2011, for example, a group of fifth-graders from New York were able to send their experiment, a study of microgravity’s effect on fish eggs, to the ISS by becoming customers of NanoRacks, which helped them package their payload and get it into one of the locker spaces in the Japanese-made Kibo module. The partnership that was formalized among a dozen international partners in 1998 has grown to involve the participation of nearly a hundred more countries, dozens of private contractors, and public and private foundations. It’s an unprecedented pool of talent and knowledge, ready to propel humanity into the next era of spaceflight – the coming “space renaissance,” foreseen by agency heads around the world, that will see humans make their way to Mars, and perhaps beyond – and it will have sprung from the success of one of the most ambitious and challenging international collaborations ever attempted.