The International Space Station (ISS) is a permanently crewed, multinational space laboratory in low-Earth orbit. Continuously staffed since 2 November 2000, it is the longest-running space station program of all time.
NASA and its international partners conduct research aboard the ISS that helps us learn about the effects of long-term spaceflight on the human body. They also test technologies that will be needed for human missions beyond low-Earth orbit.
The ISS is the easiest artificial object to see in the night sky. Use NASA’s Spot the Station website to find out when it will fly over your location, and encourage others to do the same.
Why do we need the International Space Station?
If you could drive your car at highway speeds in a straight line off the Earth, you could reach the orbital height of the International Space Station (ISS) in about 4 hours. Not that you’d be able to wave to the crew: the soccer field-sized complex would zip past in the blink of an eye as it performed another 90-minute lap of Earth.
The ISS is a permanently crewed, multinational space laboratory. Continuously staffed since 2 November 2000, it is the longest-running space station program of all time, and consistently cited among the world's most ambitious engineering projects. The station has a pressurized volume equivalent to a Boeing 747, with nearly half of that free for the crew to float around in. With regular resupply missions, the ISS can indefinitely host up to 7 crewmembers.
NASA and its international partners conduct research aboard the ISS that helps us learn more about the physical and mental effects of long-term spaceflight on the human body. As we prepare for new missions to the Moon and Mars, it is crucial to understand how to cope with spaceflight side effects like vision degradation, bone and muscle loss, and more. The ISS also allows us to test technologies that will be needed for human missions beyond low-Earth orbit, such as next-generation life support systems.
Cosmonaut Mikhail Kornienko
Roscosmos cosmonaut Mikhail Kornienko waves through an ISS window during an August 10, 2015 spacewalk.
The ISS shows that multiple countries and private companies can work together for the peaceful exploration of space. Born out of the ashes of the Cold War as a way for the U.S. and Russia to focus on a common goal, the station and its operations have largely remained unaffected by the fluctuations of Earthly politics. It is a complex, expensive project that requires the cooperation of 15 nations working under formal international agreements.
As one of the world’s longest-running spaceflight programs, the ISS holds a special place in popular culture. In the United States, a majority of the public believes astronauts, not just robots, should explore space. Astronauts on the station regularly speak with school children, inspiring new generations of scientists, technologists, engineers, artists, and mathematicians. The station’s positive societal impact, combined with its function as a one-of-a-kind research laboratory for multiple nations, enables it to both directly and indirectly benefit space science and exploration.
The final flyaround
The International Space Station is viewed from Space Shuttle Atlantis on July 19, 2011 during the shuttle program's final flyaround inspection.
How the International Space Station works
The ISS is essentially a series of pressurized and unpressurized modules launched by U.S. and Russian rockets and pieced together in space over the course of 13 years. Though completed in 2011, the station has continued to grow in size, with a commercial demonstration module added in 2016 and more planned in the near-future. The station’s pressurized modules are divided into a Russian and U.S. segments which are managed independently. NASA pays the majority—77%—of the U.S. segment’s annual operations costs, with Japanese, European, and Canadian space agencies contributing the rest.
The station is typically staffed by dual 3-person crews assigned to overlapping 6-month missions, with each unique complement of 6 people composing a numbered Expedition (each 3-person crew will serve on two Expeditions during their stay). NASA and Russia’s space agency Roscosmos have also experimented with longer-duration crew stays, and are expected to continue doing so.
Know Your Crew Vehicles
Only 2 spacecraft have ever transported astronauts to the ISS: The Space Shuttle, which retired in 2011, and Russia’s reliable Soyuz, a small capsule that can hold 3 people. Thanks to NASA’s commercial crew program, that’s about to change: SpaceX’s Dragon 2 will make its first astronaut flight in May 2020, to be followed later by Boeing’s Starliner.
Commercial crew represents a new relationship between NASA and private industry. It will ferry astronauts to and from the International Space Station, but also potentially create an entirely new market for humans in space.
The space station’s official time zone is UTC, a compromise between NASA’s mission control in Houston and Russia’s mission control near Moscow. Astronaut time aboard the ISS is dedicated to a wide variety of activities. To mitigate the effects of prolonged weightlessness, crew members exercise 2 hours per day. They also spend considerable time on maintenance tasks ranging from the mundane (cleaning air filters and disinfecting handrails) to the extreme (replacing external batteries during a spacewalk).
Science and research aboard the ISS generally falls into 4 categories:
Studies on how living in space affects the human body
Technology demonstrations for future human spaceflight equipment, including experience gained from current operational systems
Physical science experiments that benefit from the station’s weightless environment
Earth science and astrophysics instruments that use the station as an orbital platform
Jessica Meir and Christina Koch
Jessica Meir, left, and Christina Koch, right, prepare for the first all-woman spacewalk scheduled for 18 October 2019.
The station’s most distinguishing feature is its 16 dual-sided solar arrays, which together produce up to 120 kilowatts of power—enough to power more than 40 homes. The solar arrays automatically track the Sun, producing a golden glint from both direct sunlight and light reflected off the Earth, making the station at times brighter than any natural object in the night sky except the Moon when seen from the ground.
Four uncrewed cargo vehicles currently service the International Space Station: the SpaceX Dragon, the Northrop Grumman Cygnus, the Russian Progress, and the Japanese H-II Transfer Vehicle (HTV). A fifth cargo spacecraft, the Sierra Nevada Dream Chaser, is expected to come online in the early 2020s.
Sign up for The Downlink, our weekly toolkit that contains news, announcements, and actions you can take to support space science and exploration.
Take our Space Advocacy 101 course to learn the inner works of NASA, how Congress develops space legislation, and how to engage with your elected officials.
Share this page with a friend, spread the word on social media, and tell others about the importance of knowing the cosmos and our place within it.
In accordance with our human spaceflight principles, The Planetary Society believes NASA’s human spaceflight efforts should be dedicated to sending humans beyond low-Earth orbit, with the ultimate goal of landing humans on Mars. The ISS remains an excellent place to conduct research that helps us learn about the mental and physical effects of long-term spaceflight. We can also use the ISS to test technologies that will be needed for human missions beyond low-Earth orbit.
The International Space Station is a triumph of engineering and international cooperation. It also represents a significant annual cost of approximately $4 billion for NASA to operate, supply, and crew. At the moment, NASA and its partners do not currently have the budget to sustain both the ISS and develop a robust human deep space exploration program. As a consequence, NASA has started to investigate how it might transition away from its role as the primary funder of the ISS if more funding is not forthcoming.
Sign up for the Space Advocate newsletter to stay on top of the latest space policy news, and find out when we have specific policy actions you can take.
Let's Change the World
Become a member of The Planetary Society and together we will create the future of space exploration.