If you take a moment to look up at the night sky, you might spot a bright object gliding steadily through the darkness. It's not a star or an aeroplane; what you're seeing is the International Space Station, or ISS.
The International Space Station (ISS) is located about 250 miles above the Earth. Picture something as large as a football field, filled with solar panels, labs, and living spaces for astronauts. The ISS is the most expensive and complex thing humanity has ever created in space.
For over 25 years, the ISS has been an amazing achievement in engineering, bringing together space agencies from around the world. It has supported thousands of scientific studies that help us learn how humans, materials, and technology behave in the unique conditions of space, especially in microgravity.
And there's something really fascinating about the ISS: it travels at an incredible speed of 17,500 miles per hour! At this pace, the astronauts aboard see 16 sunrises and sunsets every day, completing an orbit around the Earth approximately every 90 minutes.
Let’s explore this extraordinary machine and what makes it so special!
What Is the International Space Station?
The International Space Station, commonly called the ISS, is a large habitable spacecraft and microgravity laboratory orbiting Earth.
It was built through an international partnership involving five major space agencies:
NASA — United States
Roscosmos — Russia
ESA — European Space Agency
JAXA — Japan
CSA — Canadian Space Agency
The station was assembled piece by piece in orbit rather than being launched as one enormous spacecraft.
Construction began in 1998, when the Russian-built Zarya module was launched. The U.S.-built Unity module followed, and astronauts connected the two modules during Space Shuttle mission STS-88.
The first long-duration crew, known as Expedition 1, arrived on November 2, 2000.
Since then, humans have lived continuously aboard the ISS. NASA describes the station as a unique convergence of science, technology and human innovation, while current NASA information records more than 290 visitors from dozens of countries over the station's lifetime.
The ISS is therefore not simply a spacecraft.
It is a permanently occupied research facility in low Earth orbit.
How High Is the International Space Station?
The International Space Station generally orbits at an altitude of roughly 370 to 460 kilometres (230 to 286 miles) above Earth, although its exact altitude changes over time.
NASA commonly describes its operating altitude as approximately 250 miles (400 kilometres).
That might sound extremely high, but compared with the enormous size of Earth, the ISS is actually relatively close to our planet.
The station experiences a very thin atmosphere even at this altitude. Atmospheric drag gradually slows the ISS and causes its orbit to decrease, so periodic reboost manoeuvres are required to raise it again.
In other words, the ISS is constantly falling toward Earth — but it is moving sideways so quickly that it continuously misses the planet.
That is what we call orbit.
How Fast Does the International Space Station Travel?
The ISS travels at approximately 28,000 kilometres per hour (17,500 miles per hour).
At that speed, it takes the station only about 90 minutes to complete one orbit around Earth.
That means astronauts aboard the ISS experience approximately:
16 sunrises and 16 sunsets every 24 hours.
Imagine watching the Sun rise, cross the sky and then disappear — only to see another sunrise roughly 90 minutes later.
NASA notes that the station's exact orbital period varies with altitude, generally falling in the 90–93-minute range.
How Does the ISS Stay Up There? (The Art of Falling Forever)
How Big Is the International Space Station?
The ISS is enormous compared with most spacecraft.
Its overall structure stretches about 109 metres (356 feet) across its major span — roughly comparable to the length of an American football field.
Its solar arrays make the station especially impressive when viewed from a distance.
NASA's current station facts give the ISS a mass of roughly 419,725 kilograms (925,335 pounds), although the actual mass changes as spacecraft arrive and depart.
The station contains approximately:
388 cubic metres of habitable volume
About 1,005 cubic metres of pressurised volume
Eight major solar arrays
A solar-array wingspan of about 109 metres
Six sleeping quarters
Two bathrooms
Exercise equipment
Laboratories
Robotic systems
Multiple docking ports
NASA compares the living and working space to a large six-bedroom house.
Unlike a house on Earth, almost everything inside the ISS must be carefully designed for microgravity.
Who Lives on the International Space Station?
The ISS normally operates with an international crew.
NASA's current station overview lists seven Expedition 74 crew members, although the number can temporarily change during crew handovers and visiting missions.
Astronauts and cosmonauts can spend months aboard the station.
Their daily life combines science, maintenance, exercise, communication with mission control and basic everyday activities such as eating, sleeping and personal hygiene.
But almost every ordinary activity becomes different in microgravity.
There is no normal "up" or "down."
Objects don't simply stay on a table.
Water doesn't pour into a glass in the familiar way.
And astronauts cannot simply walk from one room to another.
They float.
What Is Life Like Inside the ISS?
Life inside the ISS is carefully scheduled.
Astronauts spend a significant portion of their working day conducting scientific experiments and maintaining the station.
They also have to exercise for approximately two hours every day.
Why?
Because living in microgravity causes the human body to lose muscle and bone mass.
On Earth, gravity constantly challenges our muscles and bones. In orbit, that load is dramatically reduced.
Exercise therefore becomes an essential part of keeping astronauts physically healthy during long-duration missions.
Astronauts also have scheduled time for meals, personal activities, communication with family and mission control, and sleep.
Life aboard the ISS provides a fascinating example of how humans adapt to living and working in space.
Sleeping itself is unusual.
Instead of lying on a conventional bed, astronauts use sleeping bags attached to walls or other surfaces inside the station.
Because there is no normal sense of floor or ceiling, almost any orientation can become a sleeping position.
What Do Astronauts Do on the International Space Station?
The ISS is essentially a laboratory in orbit, so science is one of the main reasons astronauts live there.
Researchers use the station to study what happens when gravity is dramatically reduced.
Experiments cover areas including:
Human Health
Scientists investigate how the human body changes during long-duration spaceflight.
Research includes:
Bone and muscle loss
Cardiovascular changes
Vision
Immune-system responses
Human physiology
Disease mechanisms
Medical technologies
Some experiments use specialised biological systems such as tissue chips and protein crystals to study processes that are difficult to investigate under Earth's gravity.
Biology
Plants, cells, microorganisms and other biological systems can behave differently in microgravity.
Researchers use the ISS to understand these changes and investigate whether plants can eventually support future human exploration.
Materials Science
Materials can behave differently when convection and sedimentation are reduced.
This gives scientists opportunities to study processes that are difficult to reproduce on Earth.
Physics
The ISS provides a unique environment for experiments involving fluids, combustion, particles and other physical phenomena.
Microgravity allows scientists to isolate effects that are normally masked by Earth's gravity.
Earth Observation
The station also acts as an observation platform.
Astronauts photograph Earth's atmosphere, oceans, cities, storms, glaciers and natural events from orbit.
Because the ISS moves around Earth roughly every 90 minutes, astronauts can observe an enormous portion of the planet over time.
NASA notes that the station's orbit passes over areas containing the vast majority of the world's population.
Why Is Microgravity Important?
One of the biggest scientific advantages of the ISS is its microgravity environment.
On Earth, gravity affects almost every experiment we conduct.
For example, fluids naturally settle, and heavier materials tend to move downward.
Inside the ISS, those effects are greatly reduced.
This allows scientists to observe processes in a different physical environment.
NASA describes the station's orbital environment as particularly valuable for studying fluid behaviour, materials, biological systems and the effects of space conditions on humans and technology.
The knowledge gained from these experiments isn't only useful for astronauts.
Some ISS research contributes to technologies and medical research that can have applications on Earth.
How Was the International Space Station Built?
The ISS was not constructed on Earth and then launched in one piece.
That would have been practically impossible.
Instead, it was assembled in orbit over many years.
The first major element, Zarya, was launched on November 20, 1998.
Then, during Space Shuttle mission STS-88, astronauts connected Zarya with the U.S.-built Unity module in December 1998.
This marked the beginning of the station's major on-orbit assembly.
More modules, laboratories, truss segments, solar arrays and other systems were added over time.
Astronauts performed hundreds of spacewalks to connect cables, install equipment, repair systems and expand the station.
NASA's current overview records more than 280 spacewalks at the ISS since December 1998.
The station therefore represents not one launch, but decades of launches, robotics, engineering and human labour.
The International Space Station Is an Engineering Marvel
The ISS has to operate in an environment that is extremely hostile to ordinary technology.
It faces:
Extreme temperature changes
Vacuum
Radiation
Micrometeoroids
Orbital debris
Atmospheric drag
Continuous exposure to sunlight and darkness
Yet the station has remained continuously inhabited since November 2000.
Its systems are supported by thousands of components and extensive computer networks.
The station also uses large solar arrays to generate electrical power.
NASA lists the ISS's power-generation capability at approximately 75 to 90 kilowatts, depending on configuration and operating conditions.
What Is the Canadarm2?
One of the most recognisable pieces of ISS technology is Canadarm2.
It is a large robotic arm used to move equipment, support visiting spacecraft operations and assist with station maintenance.
The robotic system is approximately 17 metres (55 feet) long and has multiple joints and end-effectors.
Instead of astronauts having to manually move every large object outside the station, robotic systems can perform tasks with extraordinary precision.
This is an important lesson for future space exploration: humans and robots can work together rather than treating them as competing technologies.
How Many Times Does the ISS Orbit Earth?
The International Space Station completes roughly 16 orbits of Earth per day.
One orbit takes approximately 90 minutes.
That works out to more than 15,000 kilometres per hour? No — the station is actually moving much faster, at roughly 28,000 km/h.
Over the course of a single day, the station travels an enormous distance.
NASA describes the distance travelled by the ISS as roughly equivalent to going from Earth to the Moon and back in about a day.
How Many Countries Built the International Space Station?
The ISS is one of the greatest examples of international cooperation in space.
Five major space agencies are responsible for the partnership:
NASA, Roscosmos, ESA, JAXA and CSA.
The broader partnership involves 15 countries, including the United States, Russia, Japan, Canada and participating European countries through ESA.
The international nature of the project is important because the station's components were developed in different countries and integrated together in orbit.
Engineers, scientists, astronauts and mission-control teams around the world have to coordinate constantly.
The ISS and India's Space Journey
India is not one of the five primary ISS partner agencies, but the ISS is highly relevant when looking at India's growing human-spaceflight ambitions.
India's Gaganyaan mission is designed to develop India's own human spaceflight capability.
For readers interested in India's space programme, you can also read our detailed guide to ISRO's Gaganyaan mission and India's human-spaceflight ambitions.
The experience gained globally from long-duration human spaceflight aboard stations such as the ISS has helped advance understanding of spacecraft systems, astronaut health, life-support technologies and operations in orbit.
What Has the ISS Taught Us About Living in Space?
Perhaps the biggest contribution of the ISS is that it has allowed humans to learn how to live and work in space for long periods.
Going to space for a few hours is one thing.
Living there for months is completely different.
The ISS has provided experience in:
Long-duration human spaceflight
Life-support systems
Water recycling
Space medicine
Exercise in microgravity
Food preparation
Psychological and social challenges
Spacewalking
Robotic operations
Scientific research
Spacecraft docking
Emergency procedures
These lessons matter for future missions to the Moon and eventually Mars. India's Chandrayaan-3 mission demonstrated the country's growing capability in lunar exploration.
For example, a future Mars mission cannot simply depend on astronauts returning to Earth quickly if something goes wrong.
The longer humans stay away from Earth, the more important autonomous systems, medical knowledge, reliable life support and crew cooperation become.
What Happens to the ISS After 2030?
The International Space Station is approaching the later phase of its operational life.
NASA currently plans to transition from the ISS toward commercial space stations in low Earth orbit, with the ISS expected to continue supporting research through around 2030.
The idea is not simply to stop human activity in low Earth orbit.
Instead, NASA's strategy is to encourage commercially operated space stations that can provide research, astronaut training, technology demonstrations and other services.
This could represent a major change in how humans use low Earth orbit.
The ISS was largely developed and operated through government space agencies.
Future stations are expected to involve a greater role for commercial companies.
In that sense, the ISS may eventually become a bridge between the first era of permanent human occupation in low Earth orbit and a more commercially driven space economy.
Can You See the International Space Station From Earth?
Yes.
You don't need a telescope to see the ISS.
Under suitable conditions, it can appear as a bright moving object crossing the night sky.
It does not normally blink like an aeroplane, and it can move noticeably faster across the sky than a typical aircraft.
The best viewing opportunities generally occur around sunrise or sunset, when sunlight reflects from the station while the surrounding sky is relatively dark.
NASA's Spot the Station service can provide location-specific information about upcoming visible passes.
This makes the ISS one of the easiest human-made objects in space for ordinary people to observe directly.
How Will the International Space Station End?
The ISS cannot simply be abandoned in orbit.
Because of its enormous size and mass, a controlled end-of-life process is required.
NASA and its international partners have been planning for a controlled deorbit of the station.
The objective is to guide the station safely into Earth's atmosphere at the end of its operational life, where most of the structure will break apart and burn up.
The remaining debris would be directed toward a remote area of the ocean.
The exact sequence depends on the spacecraft, station conditions and future mission planning, so the final disposal process should not be treated as a single fixed event already completed.
International Space Station: Amazing Facts
Here are some of the most fascinating ISS facts in one place:
1. The ISS has been continuously inhabited since November 2000.
2. It travels at approximately 28,000 km/h.
3. It circles Earth roughly every 90 minutes.
4. Astronauts can experience about 16 sunrises and sunsets every day.
5. The station is about 109 metres across its major span.
6. The ISS has approximately 388 cubic metres of habitable volume.
7. Astronauts exercise for about two hours every day to reduce the effects of microgravity on their bodies.
8. More than 280 spacewalks have taken place at the station.
9. The station has hosted hundreds of visitors from many countries.
10. The ISS can sometimes be seen from Earth without a telescope.
11. The station uses large solar arrays to generate electrical power.
12. The ISS has hosted thousands of scientific investigations over its lifetime.
13. It travels around Earth so quickly that astronauts see a new sunrise roughly every 90 minutes.
14. The station is being used as a testbed for technologies and knowledge needed for future human exploration.
NASA's current station data supports these figures, although some values — especially mass, altitude and crew numbers — naturally change with station operations and visiting spacecraft.
Why the International Space Station Still Matters
After more than 25 years, it might be tempting to think of the ISS as an old spacecraft.
But its importance goes far beyond its age.
The station has demonstrated that humans can maintain a permanent presence in low Earth orbit for decades.
It has shown that countries with different space programmes can build and operate a single complex laboratory.
It has produced scientific data that would be difficult or impossible to obtain under normal Earth gravity.
And perhaps most importantly, it has given humanity practical experience for the next stage of exploration.
The Moon is closer than Mars, but both destinations require technologies and knowledge that can be tested much closer to Earth.
The ISS has therefore become a stepping stone between Earth's surface and the much larger ambitions of human space exploration.
Final Thoughts
The International Space Station is more than a giant spacecraft orbiting Earth.
It is a laboratory, home, engineering platform, observatory and international scientific collaboration all at once.
Every 90 minutes, it races around our planet at roughly 28,000 kilometres per hour.
Inside, astronauts conduct experiments, exercise, repair equipment, communicate with Earth and experience a completely different way of living.
And while the ISS is expected to reach the end of its operational era around 2030, the knowledge developed aboard it will continue influencing human spaceflight long after the station itself is gone.
The next chapter may involve commercial space stations, lunar missions and eventually human journeys to Mars.
In that sense, the ISS isn't simply a destination.
It is one of humanity's most important stepping stones toward becoming a spacefaring civilisation.
Frequently Asked Questions About the International Space Station
What is the International Space Station?
The International Space Station is a permanently occupied spacecraft and microgravity research laboratory orbiting Earth. It is operated through a partnership involving NASA, Roscosmos, ESA, JAXA and CSA.
How fast does the ISS travel?
The ISS travels at approximately 28,000 kilometres per hour (17,500 mph).
How high is the ISS above Earth?
Its orbit generally ranges from roughly 370 to 460 kilometres above Earth, with an average commonly described as about 400 kilometres.
How long does the ISS take to orbit Earth?
It takes approximately 90 minutes to complete one orbit.
How many times does the ISS orbit Earth in a day?
The station makes approximately 16 orbits of Earth every 24 hours.
Can you see the ISS from Earth?
Yes. Under favourable conditions, the ISS can be seen as a bright moving object in the sky without a telescope. NASA's Spot the Station service provides information about visible passes.
How many astronauts live on the ISS?
The regular crew size is generally around seven, although the number can temporarily change during crew rotations and visiting missions.
What do astronauts do on the ISS?
Astronauts conduct scientific experiments, maintain the station, operate equipment, exercise, perform spacewalks when required and support visiting spacecraft operations.
When will the ISS retire?
NASA currently plans for the ISS to operate through around 2030, followed by a transition toward commercial low Earth orbit space stations.
Why is the ISS important?
The ISS provides a unique microgravity environment for scientific research and gives humanity decades of practical experience in living and working in space. That knowledge is important for future missions to the Moon, Mars and beyond.
