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Orbiting legacy: 25 years of human presence in space
The International Space Station (ISS), humanity's most costly and ambitious orbital outpost, marked a quarter-century of continuous occupation in 2025. Circling Earth at 400 km (250 miles), the station has hosted over 280 astronauts and cosmonauts since its first crew arrived on 2 November 2000-meaning every person born after that date has lived in an era where space has never been uninhabited.
The birth of a global endeavor
The ISS's origins trace to a frigid November morning in 1998, when Russia launched the Zarya module from Kazakhstan's Baikonur Cosmodrome. The project, merging the abandoned U.S. Freedom program with a successor to Russia's Mir, faced skepticism over delays and budget overruns. Yet by late 2000, NASA's Bill Shepherd and Russian cosmonauts Sergei Krikalev and Yuri Gidzenko activated the station's lights, beginning an unbroken chain of human presence in low Earth orbit.
Engineering marvel: Size, assembly, and habitability
Today, the ISS comprises 16-20 pressurized modules, eight solar arrays, and countless interlocking components built across four continents. The U.S. Space Shuttle played a pivotal role in assembly, using its robotic arm to position modules with precision. Despite its sprawling structure-equivalent to a six-bedroom house in volume-microgravity allows astronauts to utilize every surface, though designated floors and ceilings help maintain orientation.
Living quarters are compact: private crew cabins resemble a British phone booth, while sleeping bags tether to walls to prevent drifting. Noise from ventilation fans and frequent sunrises (16 daily) challenge rest, though astronauts personalize their spaces with photos and mementos.
Survival in orbit: Health, hygiene, and sustenance
Space exacts a toll on the human body. Prolonged weightlessness weakens muscles, bones, and eyesight, compelling astronauts to exercise two hours daily using treadmills, cycles, and resistance machines. British astronaut Tim Peake even ran a marathon in 2016, completing 42 km (26.1 miles) in 3 hours and 35 minutes.
Water recycling is critical: the station's system recovers 90% of moisture from urine, sweat, and breath, turning it into potable water. Despite weekly cleanings, 55 microbial species coexist with crews. Food has evolved from pastes to gourmet meals, including espresso and space-grown lettuce, though astronauts still lack permission to eat experimental baked goods like the cookies returned to Earth in 2019.
Science and daily life aboard the ISS
Astronauts dedicate much of their time to experiments, from medical research (e.g., worm studies to combat Earth diseases) to material science. Hobbies range from photography-showcased via the Cupola's panoramic windows-to music. Canadian Chris Hadfield famously recorded Space Oddity, while Don Pettit crafted a didgeridoo from a vacuum cleaner.
Toilets, however, remain a high-stakes challenge. Chris Hadfield once spent hours repairing the U.S. segment's malfunctioning system during a Russian spacewalk, calling it his "proudest day in space."
Risks and records: From debris to endurance
Orbital debris poses a growing threat. The ISS has dodged catastrophic collisions, though impacts-like the chip in a Cupola window photographed by Tim Peake in 2015-highlight the danger. Over 270 spacewalks have been conducted, with the longest lasting nearly nine hours. Luca Parmitano's 2013 EVA nearly ended in disaster when his helmet filled with water.
Endurance records continue to fall. NASA's Frank Rubio holds the ISS record for the longest single mission (371 days), while cosmonaut Valeri Polyakov's 437-day stint on Mir remains unmatched. The oldest ISS resident, Don Pettit, returned to Earth on his 70th birthday.
Costs, commerce, and the future
Operating the ISS costs NASA $3-4 billion annually, with seat prices on SpaceX's Dragon capsule at $55 million and Russia's Soyuz at $80 million. The station has also opened to private visitors, with 13 "spaceflight participants" paying up to $35,000 per night for accommodations.
Recent setbacks, like Boeing's Starliner mission stranding astronauts for months, underscore the complexities of spaceflight. Yet the ISS's legacy endures: a testament to international collaboration, scientific discovery, and human resilience.
What's next?
As the ISS ages, plans for its decommissioning loom. Meanwhile, successor stations and lunar missions are already in development, ensuring humanity's presence beyond Earth will continue.
