The International Space Station
People have lived on the space station without a break since 2 November 2000.
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A laboratory the size of a football field
The International Space Station is the largest structure people have built in space. NASA gives it as 109 m end to end, one yard short of an American football field including the end zones, with a mass of 419,725 kg. Its eight main solar arrays produce 75 to 90 kilowatts. Inside, the living and working space is larger than a six-bedroom house, with six sleeping quarters, two bathrooms, a gym and a 360-degree window. Five space agencies from 15 countries operate it: NASA, Roscosmos, the European Space Agency, JAXA of Japan and the Canadian Space Agency.
No rocket could lift something that size in one piece, so it was built in orbit like a construction kit. The first module, the Russian-built Zarya, was launched on a Proton rocket from Baikonur on 20 November 1998. NASA counts 42 assembly flights, 37 by the US space shuttles and five by Russian rockets. On 2 November 2000 the first resident crew, NASA's Bill Shepherd with cosmonauts Yuri Gidzenko and Sergei Krikalev, arrived, and the station has had people aboard ever since.
Sixteen sunrises a day
The station flies about 400 km up at roughly 28,000 km/h, NASA's "about 17,500 miles per hour" or five miles a second. It goes round Earth about every 90 minutes, 16 times in 24 hours, so the crew see 16 sunrises and 16 sunsets a day. Life is arranged round microgravity. Water forms floating balls, sleeping bags are tied to the wall, and astronauts exercise at least two hours a day because muscles and bones weaken when they do not have to hold the body up. Long stays are part of the research: NASA's Peggy Whitson set the US record of 665 days in space in total by 2017.
NASA puts the station's speed another way: it covers the distance to the Moon and back in about a day. At 28,000 km/h, 24 hours makes 672,000 km, close to the 768,800 km of a Moon round trip. At 400 km there is still a trace of air, far too thin to breathe but enough to drag on something the size of the station, so it slowly sinks. Engines on the station and on visiting spacecraft fire from time to time to raise it again.
You can see the station with your own eyes. It shines by reflected sunlight, so it is visible only around dawn or dusk, when the ground is dark but the station, high up, is still in sunshine. It looks like a bright, steady star gliding across the sky in a few minutes, with no blinking lights. NASA's Spot the Station service lists passes for your town. In the sky model above, set the time to 18:00 and then 19:00 and watch the Sun's altitude in the card: the useful window is the hour or two after sunset.
| ISS (NASA) | Value |
|---|---|
| Length end to end | 109 m (356 ft) |
| Mass | 419,725 kg |
| Orbits per day | 16 |
| Speed | about 28,000 km/h |
| Crew aboard since | 2 November 2000 |
| Assembly flights | 42 (37 shuttle, 5 Russian) |
| Partners | 5 agencies, 15 countries |
- NASA gives the ISS speed as 17,500 miles per hour. How many km/h is that? (nearest hundred; 1 mile = 1.609 km)
- The ISS makes 16 orbits a day. How many sunrises do the crew see in a week?
- When was the first ISS module, Zarya, launched?
- 20 November 1998
- 2 November 2000
- 12 April 1961
- How many space agencies operate the ISS?
- When can you see the ISS from the ground?
- At noon
- Around dawn or dusk, when the ground is dark but the station is sunlit
- Only at midnight
- Yi So-yeon flew from 8 to 19 April 2008. How many days?
- Why do ISS astronauts exercise at least two hours a day?
- To keep warm
- Muscle and bone weaken in microgravity
- To power the station
- The ISS mass is 419,725 kg. How many tonnes is that? (whole number)
- Of the 42 assembly flights, how many were US space shuttle flights?
- Why was the ISS built in orbit from many pieces?
- No rocket could launch it in one piece
- It was cheaper to build on the Moon
- To keep it secret
- ISS: 109 m, about 420 t, built from 42 assembly flights starting with Zarya (20 Nov 1998).
- Crewed without a break since 2 Nov 2000; 5 agencies, 15 countries.
- About 400 km up, 16 orbits a day, about 28,000 km/h.
- Visible near dawn and dusk when it is sunlit and the ground is dark.
- Yi So-yeon, the first Korean in space, flew 8 to 19 April 2008.
Sources for this course (17)
- Town of Auburn MA, Robert Goddard (auburnma.gov/693/Robert-Goddard)
- History.com This Day in History, 16 March 1926 (Tsiolkovsky 1903 treatise)
- NASA "What Was the Saturn V?" (nasa.gov/learning-resources/for-kids-and-students/what-was-the-saturn-v-grades-5-8)
- NASA Earth Fact Sheet (nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html, GM 0.39860 × 10⁶ km³/s², escape velocity 11.186 km/s, sidereal rotation 23.9345 h)
- NASA History "The Dawn of the Space Age" (nasa.gov/history/dawn-of-the-space-age)
- NASA "April 1961, First Human Entered Space" (nasa.gov/image-article/april-1961-first-human-entered-space)
- GPS.gov Space Segment (gps.gov/space-segment)
- KARI (kari.re.kr: KOMPSAT-1 1999, Chollian, Nuri launch dates, Danuri contents/193, 194, 196 and news release 2022-12-28)
- Korea.kr policy news on the Nuri second launch, 21 June 2022 (korea.kr/news/policyNewsView.do?newsId=148902762)
- Korea AeroSpace Administration (kasa.go.kr, founded 27 May 2024)
- NASA International Space Station Facts and Figures (nasa.gov/international-space-station/space-station-facts-and-figures)
- ISS National Lab on Zarya and Expedition 1 (issnationallab.org/iss360/celebrating-the-20th-anniversary-of-the-first-international-space-station-module)
- Korea Herald and Korea.net on Yi So-yeon, 8 April 2008 (koreaherald.com/article/10711787, korea.net/NewsFocus/HonoraryReporters/view?articleId=264742)
- NASA Apollo pages (nasa.gov/the-apollo-program, nasa.gov/history/apollo-11-mission-overview, nasa.gov/mission/artemis-ii)
- NASA Voyager 1 (science.nasa.gov/mission/voyager/voyager-1) and "What is a light-day" (science.nasa.gov/mission/voyager/voyager-1/voyager-1-what-is-a-light-day)
- NASA Stennis Lagniappe July 2015 on New Horizons at Pluto (nasa.gov/wp-content/uploads/2015/05/julylagniappe.pdf)
- NASA SVS 5534 Parker Solar Probe (svs.gsfc.nasa.gov/5534).
Checked: 2026-10-18