One minute you’re fooling around in a couple of short-lived space stations that stumble into the atmosphere and burn up, the next you’ve spent a decade and a half with continuous habitation of a major International Space Station. Time flies when you’re outside the gravity well!

The First Days on the Space Station

December 6, 1998: Attaching Zarya to Unity using space shuttle Endeavour’s Canadarm. Image credit: NASA/IMAX

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The International Space Station is too large for any one rocket to boost off-planet, so it was assembled one piece at a time in orbit. The first component, the Zarya Control Module, launched on November 20, 1998, followed by the Unity node and pressurized mating adapters in December, the Zvezda Service Module service module in July 2000, and the first truss with more mating adapters in October. Finally the next month, the first crew set forth in a Soyuz spacecraft to actually live on the station.

December 2, 2000: The International Space Station was just the Zarya Control Module, Unity Node, Zvezda Service Module and Z1-Truss when Expedition 1 moved in. Image credit: NASA

Expedition 1 docked with the space station on November 2, 2000, opening the hatch at 4:23 am for NASA astronaut William Shepherd and Roscosmos cosmonauts Sergei Krikalev and Yuri Gidzenko to start 136 days in space. Their mission overlapped with the arrival of more astronauts, with each subsequent mission overlapping for fifteen years of uninterrupted human presence in space.

Most astronauts on the station stay nearly six months, split between two six-month expeditions. Image credit: NASA

The Bits and Bolts that Make a Station in Space

June 6, 2014: Solar panels provide the power to keep the space station functioning. Image credit: NASA

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Meanwhile, the space station just keeps on growing in continuous slow construction until the present day, with new docking ports and an inflatable module expected soon. Major structural components were contributed by the United States and Russia, but also by the European Union, Canada, and Japan.

April 24, 2015: Scott Kelly’s living quarters for his Year in Space. Image credit: NASA/Scott Kelly

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The station is now just under 110 meters (357 feet) end-to-end, massing 419,455 kilograms (924,739 pounds). The eight solar arrays hold 262,400 solar cells generate 84 to 120 kiowatts of electricity, enough to power 40 homes. At 915 cubic meters (32,333 cubic feet) pressurized volume and 388 cubic meters (13,696 cubic feet) habitable volume, about the same as a six-bedroom home or the cabin of a Boeing 747. That’s roughly four times the size of Mir, or five times larger than Skylab. That space includes two bathrooms, a gymnasium, and the Cupola, a 360° degree windowed chamber.

September 16, 2007: The International Space Station after the installation of a new set of solar panels. Image credit: NASA

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The International Space Station flies at an average altitude of 400 kilometers (248 miles) above the Earth at 28,000 kilometers per hour (17,500 miles per hour). It circles the planet every 90 minutes for 15 sunrises (and sunsets!) a day. It’s the next-brightest object in the sky after the moon, and can be seen with the naked eye. Use Spot the Station to determine the next time it’ll be visible from your location!

November 2, 2015: Expedition 45 members celebrate 15 years of living on the space station. Image credit: NASA/Scott Kelly

A Truly International Affair

Although started by the American and Russian space programs, the International Space Station is a truly global project. Image credit: NASA

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The number of astronaut-visitors to the station are even more varied than the countries that built it: in 15 years, the station has hosted over 220 people from 17 different countries including Kazakhstan, Brazil, Denmark, and South Africa.

July 21, 2009: Clockwise from bottom-left: Mike Barratt, Roman Romanenko, unidentified crew member, Koichi Wakata, Robert Thirsk, Julie Payette, Frank De Winne, and Christopher Cassidy. Out of frame or not clearly seen: Mark Polansky, Doug Hurley, Dave Wolf, Tim Kopra, Tom Marshburn, and Gennady Padalka.

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Some of the most unusual crew combinations were on April 2010 when four women were in space at the same time (the highest concentration of women in orbit ever), and in July 2009 when 13 astronauts from five nationalities were on the station simultaneously. The crew included astronauts from Belgium, Canada, Japan, Russia, and the United States.

The Challenges of Staying Alive

September 23, 2015: The Japan Aerospace Exploration Agency (JAXA) Kounotori 5 H-II Transfer Vehicle (HTV-5) docked to the station during a night pass over the Nile River. Image credit: NASA

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Keeping astronauts alive is no easy task. They require food, water, air, and heat to survive so far from the comforting environment of Earth. Each six-month expedition of six astronauts requires 6,350 kilograms (7 tons) of supplies carried to the station by a mix of space agency and commercial vehicles.

March 3, 2011: Expedition 26 and STS-133 crew members share a meal in the Unity node. Image credit: NASA

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Like all remote fieldworkers, the quality of the food is always a good topic of discussion. Of the more than 26,500 meals served in space, the regular favourites are shrimp cocktails, tortillas, and macaroni and cheese (although station-grown lettuce may become a new hit!)

Astronaut Kjell Lindgren demonstrates that fresh fruit deliveries are always highly welcome. Image credit: NASA

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The space station isn’t all about people: it takes a lot of computer power to everything operating smoothly. That’s split between space and ground: around 1.8 million lines of flight software code are run by 52 computers on the space station, with another 3.3 million lines of software code on ground support computers. In the American segment of the station, 44 computers communicate via 100 data networks transferring 400,000 signals about pressure, temperature, valve positions, and more. Their hard drive space totals a measly 1.5 gigabites, far smaller than the 500-gigabyte hard drive of a single modern personal computer.

September 1, 2009: Kevin Ford and Robert Thirsk operate the Canadarm2 from the Destiny laboratory of the International Space Station. Image credit: NASA

Stepping Outside for a Spacewalk

December 12, 1998: Astronauts Jerry Ross and Jim Newman connect power and data cables between the Unity and Zarya modules. Image credit: NASA

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Even with all that space, astronauts occasionally duck out of the station to stretch their legs. Between NASA and Roscosmos, 121 people have completed 189 spacewalks. Starting with astronauts Jerry Ross and James Newman on December 7, 1998, people have spent 1,184 hours constructing and maintaining the station. Astronaut Michael Lopez-Alegria and cosmonaut Gennady Padalka share the record for most spacewalks with 10 each totalling 67 hours, 40 minutes and 38 hours, 37 minutes respectively.

Even more spacewalks are scheduled for next week. Image credit: NASA

Science on the Orbital Laboratory

September 2015: Kimiya Yui and Kjell Lindgren remove items from storage rack to make room for new communications hardware. Image credit: NASA

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Each mission gets more ambitious. Expedition 1 started off with an impressive 22 scientific experiments (with an experiment in protein crystal growth starting even before their arrival!), but astronauts now get to spend about 35 hours a week on research. That means over the nearly six months of Expedition 45 and 46, the astronauts will conduct a total of 191 scientific investigations. The experiments are housed in 29 standardized racks with equipment slotted in and removed as needed. Of those 29, 15 are attached external payloads outside the station exposed to the harsh space environment.

September 3, 2009: A suitcase-sized materials experiment on the outside of the space station. Image credit: NASA

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Even the research on the space station is international: the over 1,760 investigations on the orbiting laboratory involve researchers from 83 countries! Continuing in the tradition of Skylab and the space shuttles, the experiments also include student projects, bringing the opportunity to participate in space science to classrooms around the world.

November 28, 2014: Releasing the SpinSat to test a new thrust technique for satellites. Image credit: NASA

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The results are published in more than 1,200 scientific papers over the years. That’s not all thumb-twiddling, either: the very first experiment ever run on the station on growing protein crystals is leading to the development of new medical treatments, including new drugs for treating muscular dystrophy.

The Eye Tracking Device for astronauts was so good we now use it during laser eye surgery on Earth. Image credit: NASA

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Using astronauts as guinea pigs is also leading to direct medical improvements on Earth. Trying to keep astronauts from losing bone mass density as quickly has resulted in dietary and exercise guidelines for older adults, and studying osteoporosis in moustronauts led to the development of Prolia. The need to provide medical services to astronauts through the Advanced Diagnostic Ultrasound in Microgravity (ADUM) project led to greater accessibility of small ultrasound units and tele-medicine for remote regions. The results can be even more direct: the Eye Tracking Device experiment on astronauts was so successful that same equipment is now used in laser eye surgery at home.

Astronaut Samantha Cristoforetti conducts plethysmography and pulmonary function system measurements for the Brain Drain investigation. Image credit: NASA

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Even when astronauts aren’t directly involved as test subjects, we can still get good science: their research into the genetic pathway activating in Salmonella bacteria led to new microbial vaccines, while the Capillary Flow Experiments (CFE) is helping understand fluid behaviour in microgravity, leading to the development of new terrestrial medical devices.

Alex Gerst works on a Capillary Flow Experiments investigating fluid behaviour in microgravity. Image credit: NASA

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Even the hardware is inspiring developments on Earth. The hardcore efforts on the space station to reduce-reuse-recycle ) is improving water purification and processing efforts for the rest of the planet (up to 65% of all water is recaptured and reused on the station!), to improve air quality, and to improve agricultural techniques. The remote-controlled dexterity of Canadarm2 and Dextre have inspired both neuroArm for remotely performing surgery and the Image-Guided Autonomous Robot (IGAR) to work inside MRI machines identifying tumors.

The Canadarm2 is strong enough to fling cargo craft (and even space shuttles) around with abandon. Image credit: NASA

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Equipment on the outside of the station also lends a helping hand. The Hyperspectral Imager for the Coastal Ocean (HICO) is the latest effort to monitor water quality from space, reporting on water clarity, phytoplankton concentrations, light absorption and the distribution of cyanobacteria. The ISS SERVIR Environmental Research and Visualization System (ISERV) takes photos of developing countries impacted by natural disasters to help them coordinate a rapid response to floods, fires, volcanic eruptions, deforestation, harmful algal blooms and other catastrophes.

The Alpha Magnetic Spectrometer-02, a particle detector for low Earth orbit space radiation environment. Image credit: NASA

Living in Space Benefits Everyone

March 16, 2012: Star trails seen in a long exposure from the International Space Station. Image credit: NASA/Don Pettit

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The space station also improves life for the rest of us, directly and indirectly. Along with all the science being done in orbit, we pragmatically benefit from an outpost in space to support commercial industry. The space station support commercial space operations, including cargo runs to supply the station, providing a launch platform for cubesats, and offering up some of their rack space to commercial investigations.

Cubesats launching from the International Space Station. Image credit: NASA

More indirectly, having children grown up who have never known a world where we didn’t live among the stars is an incredible thing for a bunch of hairless apes scrabbling about in the dirt. With fifteen years of uninterrupted habitation, the International Space Station is a mark of global cooperation, of coming together to achieve the impossible, and making science fiction into a reality.

2009: The International Space Station with freshly-installed solar panels.

Top image: NASA astronaut Tracy Caldwell Dyson takes a break to gaze through the Cupola during Expedition 24 in 2010. Credit: NASA


Contact the author at mika.mckinnon@io9.com or follow her at @MikaMcKinnon.

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