🛰️ Living in Orbit: How the Space Station Works

What you’ll learn

1. A House in OrbitGrasp what the ISS is: its size, altitude and continuous occupation.The ISS is the largest human-built structure in space, about 400 km up and continuously crewed since 2000 by an international partnership. Everything a crew needs — air, water, the sense of up and down — must be engineered aboard.
2. Why It Falls Around EarthExplain orbit as continuous free fall and the numbers behind it.Astronauts float because the station is in constant free fall around Earth, not because gravity is absent. Moving at nearly 8 km/s, it circles the planet every 90 minutes, giving about 16 sunrises a day.
3. The ModulesDescribe how the station is built from pressurised modules and labs.The ISS is assembled from pressurised modules bolted together, including the Destiny, Columbus and Kibo laboratories from the US, Europe and Japan. In weightlessness crews work on all four walls of each sealed, air-filled module.
4. Power from the SunExplain how solar arrays and batteries power the station.Large sun-tracking solar arrays generate on the order of 100 kW, and batteries carry the station through the dark half of each orbit. Aging arrays are upgraded with newer roll-out panels during spacewalks.
5. Air to BreatheUnderstand how the life-support system supplies oxygen and removes CO₂.In a sealed cabin the station must make its own oxygen — by splitting water through electrolysis — and continuously scrub out exhaled carbon dioxide. It also controls humidity and heat to keep the air breathable indefinitely.
6. Water RecyclingExplain how the station recycles about 90% of its water.Because launching water is costly, the station reclaims roughly 90% of it from humidity, washing water and urine, purifying it cleaner than many taps. Closing this loop is essential for long-duration spaceflight.
7. Life in MicrogravityDescribe daily life in microgravity: sleep, exercise and food.Crews sleep strapped in cabins, eat mostly rehydrated food from pouches, and exercise about two hours a day to counter bone and muscle loss of roughly 1% a month. Weightlessness reshapes every ordinary routine.
8. Getting There and CargoExplain how crews and cargo reach and dock with the station.Rockets such as Soyuz and SpaceX Dragon carry crew, while Dragon, Cygnus and Progress deliver cargo, each matching the station's orbit for a precise rendezvous and docking. Regular resupply keeps the outpost stocked.
9. Working OutsideUnderstand spacewalks and the role of Canadarm2.Some tasks require spacewalks of six or seven hours in spacesuits that act as personal spacecraft, always tethered for safety. Canada's 17-metre Canadarm2 captures cargo, moves equipment and can carry astronauts to a worksite.
10. Science and the FutureAppreciate the station's science and its coming succession.The ISS enables research needing sustained weightlessness and serves as an Earth-observation platform, informing medicine, industry and deep-space plans. It is expected to be retired and deorbited around 2030, with commercial stations to follow.

Questions this course answers

Grounded in trusted sources

• NASA — International Space Station Facts and Figures (nasa.gov)
• NASA — Environmental Control and Life Support System (ECLSS) overview
• NASA — Reference Guide to the International Space Station
• ESA — International Space Station and the Columbus laboratory
• Canadian Space Agency — Canadarm2 and the Mobile Servicing System

Every Wunder lesson is built from real, reputable sources — never invented.

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