On Nov. 2, 2025, NASA honored 25 years of continuous human presence aboard the International Space Station. What began as a fragile framework of modules has evolved into a springboard for international cooperation, advanced scientific research and technology demonstrations, the development of a low Earth orbit economy, and NASA's next great leaps in exploration, including crewed missions to the Moon and Mars.
The first expedition
This legacy of achievement in global human endeavors began with the first crew's arrival to the space station on Nov. 2, 2000. Expedition 1 crew members NASA astronaut William M. Shepherd and Russian Aviation and Space Agency, now Roscosmos, cosmonauts Yuri P. Gidzenko and Sergei K. Krikalev launched from the Baikonur Cosmodrome in Kazakhstan two days prior. After a successful docking, the crew transferred aboard the station and began bringing it to life. Their primary tasks during their four-month mission included installing and activating the life support and communications systems and working with three visiting space shuttle crews to continue the station's assembly. The trio returned to Earth in March 2001 aboard space shuttle Discovery, after having turned the station over to the Expedition 2 crew.
(Space)walking into history
Assembly and maintenance of the International Space Station would not be possible without the skilled work of crew members performing intricate tasks, in bulky spacesuits, in the harsh environment of space. In addition to station upkeep, spacewalks provide a platform for testing and improving spacesuits and tools - critical information for future exploration of the Moon and Mars. Other spacewalks have included operations for scientific research. In Jan. 2025, for example, crew members collected samples for an investigation examining whether microorganisms have exited through station vents and can survive in space, to better inform spacecraft design that helps prevent human contamination of Mars and other destinations.
More than 270 spacewalks dedicated to the space station have been accomplished in the last quarter century. Several made station and human spaceflight history:
- May 1999: NASA astronaut Tamara Jernigan became the first woman to complete a spacewalk at the space station, in support of its construction.
- September 2000: Also during space station assembly, NASA astronaut Edward T. "Ed" Lu and Roscosmos cosmonaut Yuri I. Malenchenko conducted the first U.S.-Russian spacewalk.
- March 10, 2001: NASA astronauts James Voss and Susan Helms set the record for longest spacewalk in U.S. history, at 8 hours and 56 minutes.
- First spacewalks by international partners included:
- April 2001 - Canadian Space Agency astronaut Chris Hadfield
- July 2005 - Japan Aerospace Exploration Agency astronaut Soichi Noguchi
- Aug. 2006 - European Space Agency astronaut Thomas Reiter
- Feb. 26, 2004: NASA astronaut Mike Foale and Russian cosmonaut Aleksandr Y. Kaleri complete the first spacewalk with no one inside the station.
- Oct. 18, 2019: The first all-female spacewalk in history, conducted by NASA astronauts Christina Koch and Jessica Meir.
Orbiting laboratory welcomes first commercial crew
The International Space Station welcomed its first commercial crew members on May 31, 2020, when former NASA astronauts Robert Behnken and Douglas Hurley joined Expedition 63 Commander and NASA astronaut Chris Cassidy and Roscosmos cosmonauts Anatoly Ivanishin and Ivan Vagner aboard the orbiting laboratory.
Behnken and Hurley lifted off from Kennedy Space Center in Florida the day before on NASA's SpaceX Demo-2 test flight - the first launch of American astronauts from U.S. soil since the space shuttle's retirement in 2011.
The duo quickly integrated with the rest of the crew and participated in a number of scientific experiments, spacewalks, and public engagement events during their 62 days aboard station. Overall, the pair spent 64 days in orbit, completed 1,024 orbits around Earth, and contributed more than 100 hours of time to supporting the orbiting laboratory's investigations before splashing down on Aug. 2.
Successful completion of the Demo-2 mission paved the way for regular SpaceX flights carrying astronauts to and from the space station. With another certified crew transportation system in place, the International Space Station Program added research time and increased the opportunity for discovery aboard humanity's testbed for exploration, including preparations for human exploration of the Moon and Mars.
Frank Rubio's record-breaking year in space
On Sept. 27, 2023, NASA astronaut Frank Rubio returned to Earth after spending 371 days aboard the International Space Station-the longest single spaceflight by a U.S. astronaut in history. His mission surpassed the previous record of 355 days, set by NASA astronaut Mark Vande Hei, and provided scientists with an unprecedented look at how the human body adapts to more than a year in microgravity.
Rubio's record-setting mission supported six human research studies, including investigations into diet, exercise, and overall physiology and psychology. He was the first astronaut to test whether limited workout equipment could still maintain health and fitness, an important consideration for future spacecraft with tighter living quarters. He also contributed biological samples, surveys, and tests for NASA's Spaceflight Standard Measures, a study that collects health data from astronauts to better understand how the body adapts to space-knowledge that helps prepare crews for the Artemis campaign to the Moon and future trips to Mars.
Alongside his fellow crew members, Rubio participated in dozens of investigations and technology demonstrations, from growing tomato plants with hydroponic and aeroponic techniques to materials science experiments that advance spacecraft design.
Long-duration missions help inform future spaceflight and lay the groundwork for the next era of human exploration.
A global foundation for growing a low Earth orbit economy
The space station is one of the most ambitious international collaborations ever attempted. It brings together international flight crews, multiple launch vehicles, globally distributed launch and flight operations, training, engineering, and development facilities, communications networks, and the international scientific research community for the benefit of all humanity.
An international partnership of space agencies operates the elements of the orbiting laboratory: NASA, Roscosmos, ESA (European Space Agency), JAXA (Japan Aerospace Exploration Agency), and CSA (Canadian Space Agency). Each partner takes primary responsibility for managing and running the station hardware it provides, as well as on-Earth construction, launch support, mission operations, communications, and research and technology facilities that support the station.
At least 290 individuals representing 26 countries, and the five international partners have visited the orbiting laboratory during its 25 years of continuous human presence. Some of those visitors flew to the station on private astronaut missions. These missions contribute to scientific, outreach, and commercial activities. They also help demonstrate the demand for future commercial space stations and are an important component of NASA's strategy for enabling a robust and competitive commercial economy in low Earth orbit.
The results of the international partnership created through the space station and its accomplishments exemplifies how countries can work together to overcome complex challenges and achieve collaborative goals.
