International Space Station (ISS)

FIELDS OF STUDY: Aerospace Engineering; Astronautics; Space Technology

ABSTRACT: The International Space Station (ISS) is an artificial, habitable satellite that orbits Earth at an altitude of about 400 kilometers (250 miles). It has been designed, assembled, operated, and maintained by an international coalition that includes the space agencies of the United States, Russia, Japan, Canada, and Europe. At any time, up to seven astronauts live and work on the space station, maintaining its operations and conducting important research studies that increase scientific knowledge of the solar system. The ISS is hailed as a model for international scientific, technological, and diplomatic cooperation.

An International Undertaking

The International Space Station (ISS) is one of the most complex space projects ever undertaken. It is an enormous artificial, habitable satellite. A coalition of nations that includes the United States, Russia, Europe, Japan, and Canada designed, developed, built, operate, and maintain the station. The ISS was established for the purpose of learning more about space in order to know more about Earth. The coalition's vision refers to the station as "a human outpost in space, bringing nations together for the benefit of life on Earth and beyond."

The ISS is approximately the size of an American football field—about 109 meters (360 feet) long and 48 meters (160 feet) wide. It is so large that no Earth rocket had the power to launch it into space in one piece. Therefore, the ISS was built in parts and assembled in space over a long period of time. The first piece of the station was launched from Earth in 1998. The last piece was added more than forty missions later, in 2011.

The ISS is located in low Earth orbit at an altitude of about 400 kilometers (250 miles). It moves at a speed of about 28,000 kilometers (17,500 miles) per hour and orbits Earth every ninety minutes. Three to seven astronauts live on the space station at any one time. These astronauts come from many different countries and stay on the station for missions that last an average of six months.

Designed as living and working quarters for astronauts, the ISS has been occupied since 2000. It is constructed in a series of clustered modules. These are pressurized chambers that humans can live in. The modular structure has the added benefit of being customizable. Existing modules can be removed and new modules added as technologies improve and missions change.

The modules are grouped together in the center of the station and attached to a main truss (load-bearing support). The truss also supports the giant solar panels, heat radiators, and other exterior equipment that spread outside the station. This equipment provides the heat and power the station needs to support life.

The habitable modules also include a laboratory with a range of scientific equipment. The astronauts spend about thirty-five hours per week conducting experimental research in a range of disciplines, including physics, astronomy, biology, meteorology, and chemistry, among others. They also spend time operating the station's controls, cleaning and maintaining the equipment, and repairing anything that is not working optimally. Sometimes the astronauts take spacewalks outside the ISS to work on the outside of the station or make repairs.

The ISS is a unique project not only because of the complex technology it needs to work, but also because it has been a greatly successful international effort. The main space agencies involved with ISS are the Canadian Space Agency (CSA), the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), the Russian Federal Space Agency (Roscosmos), and the United States' National Aeronautics and Space Administration (NASA). By December 2021, 258 people had visited the ISS, including 158 Americans, fifty-four Russians, and nine Canadians.

Political and Technical Complexities

Representatives from the United States, Russia, Europe, Japan, and Canada set the legal framework for the ISS project in January 1998 by signing the International Space Station Intergovernmental Agreement (IGA). Through the IGA and subsequent agreements, officials created a cooperative partnership with shared responsibilities. These include the design, development, funding, operation, and use of the station. The agreement also established ISS as a peaceful venture in accordance with international laws and customs.

The ISS designers intended the station to serve as a laboratory and observation center in low Earth orbit. It was also appointed as a staging base for possible future missions to space bodies such as the moon, Mars, and asteroids. Later, the coalition agreed that the ISS had other purposes and goals involving commerce, diplomacy, and education.

The ISS operates as a joint station. Russian cosmonauts operate one side of the craft, and American astronauts operate the other. The American side includes modules and equipment from Canadian, Japanese, and European partners. The groups share responsibility for navigation, operations, and station command. They also share living space, meeting for meals, exercise times, and resources. One of the greatest triumphs of the ISS is the cooperation it has fostered among the nations. The various groups work together to plan, coordinate, and monitor the different activities and missions conducted aboard.

The ISS is connected to two main Earth-based mission control centers. These are operated by NASA and Roscosmos. NASA's center is located in Houston, Texas, while Roscosmos's center is located in Moscow, Russia.

Unexpected Partnership

From the late 1940s through the early 1990s, the United States and the Soviet Union were engaged in the Cold War, with each side considering the other its major competitive threat. Part of the Cold War involved the space race. This was a competition between the two countries during which both sought to establish themselves as superior in space technologies.

During this time, both countries developed and launched a series of rockets and probes into space. This rivalry led to the development of both artificial satellites and manned spacecraft. The Soviet Union built the first simple space station by linking two of its craft in space. The United States developed the first reusable spacecraft through its shuttle program. These advances in technology helped scientists to learn more about the nature of Earth and space.

The space race was an important element of the larger competition between the two countries, as advances in space research could be put to military use. For example, space probes and satellites that supplied observational data could be used for spying purposes or to give one country an advantage in armed conflict.

The fall of the Soviet Union in 1991 and subsequent changes in political alliances and boundaries led to talks of an international partnership in space. These talks later came to fruition as the ISS.

Life Onboard

For many years, the main method of transporting astronauts to and from the ISS was via Soyuz TMA vehicles, which are operated by Roscosmos. These small Russian spacecraft launch and land in the Republic of Kazakhstan. However, in May 2020, US aerospace company SpaceX successfully sent two NASA astronauts to the ISS on board its Dragon spacecraft; this marked the first time a private company successfully transported humans to the ISS, as well as the end of NASA's total dependence on Roscosmos for astronaut transport. Historically, it could take astronauts almost two days to reach the ISS, but later trips made the journey in about six hours. Transport craft connect to the ISS via specialized docks that allow the astronauts to enter and leave the space station. On Soyuz spacecraft, the return trip is much faster and takes up to three astronauts about three and a half hours.

The inhabitants of the ISS follow a designated schedule of tasks. Astronauts have compared the experience to life onboard a carefully controlled ship. Almost every day in orbit is planned by mission control. This keeps the astronauts occupied and ensures that the station continues to run in an optimal manner.

Astronauts spend many hours per day working in the laboratory or on research projects. They also complete many housekeeping and maintenance duties to make sure that the station continues to run as designed. Some days the astronauts spend hours removing and loading rubbish and moving fresh supplies into the station. On others the astronauts may spend the better part of the day preparing for brief space walks on the exterior of the station. These walks are conducted when observations or repairs need to be made. To stay safe during these walks, the astronauts wear special space suits that allow them to survive the hostile conditions of space.

Astronauts eat three meals and exercise at least two hours per day. This amount of exercise is needed to combat the effect of living in microgravity. Because of this microgravity, exercise is performed in unique ways. American astronauts ride an exercise bike that has no handles or seat. They can place a laptop anywhere in space around them to watch entertainment or speak to mission control while exercising.

Astronauts sleep in small, private units with sleeping bags attached to the walls. The attached sleeping bags anchor the astronauts to the wall and keep them from floating around during sleep. The bags are designed to help the astronauts feel contained so they can relax.

Legacy

The ISS is an important part of NASA's space program, which is focused on designing and building capabilities to send humans farther into the solar system than ever before. The ISS has made the goal of travel to Mars a real possibility because the station's microgravity environment lets scientists conduct research that would not be possible on Earth. Through its work on the ISS, NASA and other space agencies have developed a much deeper understanding of what it takes for humans to survive in space for long periods of time. Technologies developed for the ISS have helped scientists to craft efficient water systems, advanced life support capabilities, and human-robotic interfaces that minimize the loss of human life. The station has helped scientists build and test technologies such as automatic flight refueling and cargo supply systems.

The ISS has also been crucial in the creation of a sense of cooperation and goodwill among the participating space agencies and their nations. As scientists have teamed up and shared their research and resources, the ISS has become a blueprint for international cooperation among the United States and its many allies.

Despite these positive developments, the great cost of operating the ISS led to ongoing debate over its continued operations and NASA's priorities. In June 2019, NASA announced that the ISS would open to commercial space travel beginning in 2020, something the agency had previously resisted even after Russia offered the first tourist visits to the station in 2001. The move was intended to reduce NASA's financial commitment to the ISS by bringing in tourist revenue, with an ultimate goal of fully turning the ISS over to commercial ownership from which NASA could rent space. Private visitors to the ISS would be responsible for the cost of using the station and its food, water, and life support systems, estimated at $35,000 per person per night. In addition, space tourists would need to pay as much as $58 million for round-trip travel to the ISS, which would be provided by a commercial space travel company such as SpaceX or Boeing. In March 2020, the Bartolomeo platform, a commercial payload hosting platform, was launched to the ISS to be attached to the exterior of the European Columbus module. The following year, the Nauka, also known as the Multipurpose Laboratory Module-Upgrade, was docked on the ISS. Meanwhile, Russia and the private US company SpaceX continued to develop plans to resume tourist missions.

The gradual deterioration of the ISS, along with the eventual need to retire and de-orbit the station, has prompted NASA and other space agencies to begin planning for a future without the ISS. In April 2021, Roscosmos announced that Russia would withdraw from the ISS in 2025, with the hopes of launching its own space station in 2030. In December 2021, NASA extended its operations on the ISS until the end of 2030. After ceasing operations and retiring the station, NASA plans to use visiting spacecraft to push the ISS out of orbit and send it crash-landing into a remote part of the Pacific Ocean.

In 2022, amidst the Russian Invasion of Ukraine that began in February of that year, Russian President Vladimir Putin announced Russia's intention of withdrawing from the ISS program sometime after 2024. The invasion brought into question the operation of the ISS as diplomatic relations between the US and Russia quickly deteriorated following the latter's invasion of Ukraine. Previously in 2022, NASA announced plans to de-orbit the ISS in January 2031.

Principal Terms

• Canadian Space Agency: Canada's government agency established in 1989 to manage Canadian space activities and research.
• European Space Agency: an intergovernmental organization made up of twenty-two European countries in charge of Europe's space program and research since 1975.
• Japan Aerospace Exploration Agency: Japan's government agency formed in 2003 to head the country's civilian space activities and research.
• National Aeronautics and Space Administration: the government agency established in 1958 to run and oversee the United States' space program and research.
• Russian Federal Space Agency: the government agency created in 1992 to officially coordinate Russian space activities and research.
• Soyuz: the Russian spacecraft used to carry astronauts to and from the International Space Station.

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