International Space Station Guide: Orbit, Crew, and Daily Life

The International Space Station is the largest human-made object ever placed in orbit, and it has hosted people continuously since November 2000. It works as a shared laboratory, a test bed for life support, and a proving ground for systems that future deep-space missions will depend on. This guide explains how the station flies, how it was assembled, and what daily life aboard looks like.

What the station is

The station is a modular structure built from pressurized modules, a long metal truss, and large solar arrays. It is not a single spacecraft. It was assembled piece by piece over more than a decade, with components launched on Russian Proton and Soyuz rockets, on the American Space Shuttle, and on several other launch vehicles. Its main job is to host experiments that need microgravity, long exposure to space, or a view of Earth that a short mission cannot provide.

The station was never meant to be a tourist hotel or a factory. Its value comes from continuous operation. Researchers can run experiments for months, return samples to Earth, and engineers can test hardware in the real space environment before committing it to a longer mission.

Orbit and speed

The station flies in low Earth orbit at an altitude that has typically been around 400 to 420 kilometres. At that height the air is still thin enough to create measurable drag, so the station slowly loses altitude and must be raised periodically. It travels at roughly 7.66 kilometres per second, which is about 27,600 kilometres per hour. One complete orbit takes about 93 minutes.

Because of that period, the crew sees about 16 sunrises and 16 sunsets every 24 hours. The light cycle is so fast that lighting and work schedules are shifted to keep sleep patterns stable, a challenge covered in more detail in the human-body article in this section.

Why this orbit

Low Earth orbit is far cheaper to reach than the Moon or Mars. It also keeps the station inside Earth's magnetic field for much of its path, which shields it from some of the most energetic radiation found in deep space. The trade-offs are the regular need for reboost burns and the constant risk from small pieces of orbital debris that can puncture a module.

Structure and modules

The station has two main segments. The United States Orbital Segment is operated mainly by NASA, with contributions from ESA, JAXA, and CSA. The Russian Orbital Segment is operated by Roscosmos. Both segments share power and docking ports, and crews move between them through connecting nodes.

Key American modules include Destiny, the main laboratory, and Unity and Harmony, which are connecting nodes. The European Columbus laboratory and the Japanese Kibo module add research space, and Kibo also includes an external platform for experiments exposed to open space. The Russian segment includes Zvezda, which provides living quarters and a large part of station control, and Zarya, the first module launched.

The Canadian robotic arm, Canadarm2, moves modules, handles cargo, and supports spacewalks. Without that arm, many assembly and maintenance tasks would be far slower.

Assembly history

Assembly began in 1998 with Zarya, followed by Unity later that year. Construction continued through the 2000s and into the early 2010s. American Space Shuttles delivered many of the largest segments until the Shuttle fleet retired in 2011. Expedition 1 arrived in November 2000, and that date marks the start of continuous human occupancy.

Partners and funding

The station is an intergovernmental project. Its five main partner agencies are NASA, Roscosmos, ESA, JAXA, and CSA. Counting the member states of ESA, the program involves about 15 countries. Agreements define how each partner contributes modules, crew time, and transport, and how each partner receives a share of research time.

Costs are spread across the partners, and each agency funds its own modules, crew training, and science program. This shared model is one reason the station grew so large, but it also means that schedule changes in one country can ripple across the whole program.

Life aboard: daily routine

A typical crew has six or seven members. Days follow a schedule planned on the ground and divided into work blocks, exercise, meals, and personal time. Crew members typically spend about two hours a day on exercise, which is required to slow muscle and bone loss in microgravity.

Experiments take up most of the working time. Researchers study materials, fluid physics, combustion, biology, medicine, and Earth observation. Some tasks are routine maintenance, such as replacing air filters, servicing water hardware, and inspecting vents and seals. Crews also talk with flight controllers in Houston, Moscow, and other control centers around the world.

Sleep takes place in small private compartments where crew members zip themselves into sleeping bags attached to a wall. Meals are prepared from packaged food that is rehydrated or heated. Hygiene uses wipes and rinse-free methods because water is precious.

Supply and crew transport

Crews arrive and depart in spacecraft such as the Russian Soyuz capsule and, since 2020, SpaceX Crew Dragon vehicles operated under NASA's Commercial Crew program. Uncrewed cargo arrives on Russian Progress spacecraft, SpaceX Dragon cargo missions, Northrop Grumman Cygnus, and the Japanese H-II Transfer Vehicle, known as HTV or Kounotori. ESA's Automated Transfer Vehicle flew five times between 2008 and 2014 before that program ended.

Cargo vehicles are not only supply trucks. They carry experiments, spare parts, crew provisions, and propellant for reboost burns. Several of them carry trash out of the station and burn up on reentry along with it.

Power, air, and water

Solar arrays on the truss generate electricity that is distributed through the station. The arrays turn to follow the Sun, and batteries carry the station through each eclipse when its orbit passes into Earth's shadow. Peak output is roughly 120 kilowatts under good conditions.

Life support is one of the most critical systems. Electrolysis splits water into hydrogen and oxygen, and the oxygen goes into the cabin air. Scrubbers remove carbon dioxide, and a reactor can convert some of that carbon dioxide back into water. The water recovery system reclaims urine, sweat, and humidity from cabin air. NASA reports recovery rates around 98 percent, which is one of the most important numbers for long missions.

Key figures

Item	Approximate figure
Orbit altitude	400 to 420 km
Orbital speed	about 7.66 km/s
Orbital period	about 93 minutes
Pressurized volume	about 916 cubic metres
Mass	about 420 tonnes
Solar array peak power	about 120 kW
Typical crew size	6 to 7
Water recovery	about 98 percent

Science and research

Research aboard covers protein crystal growth, flame behaviour in microgravity, human physiology, plant growth, and advanced materials. Some results have shaped medicine and industrial processes on Earth. Other experiments test technology for lunar and Mars missions, including air and water recycling, robotic systems, and tools that astronauts can repair on their own.

The station also serves as a platform for Earth observation. Its orbit passes over most of the planet, which lets cameras track weather systems, wildfires, and coastlines from a vantage point that aircraft and satellites in other orbits cannot match at the same cost.

Key takeaways

The International Space Station is a long-running proof that people can live and work in orbit for extended periods. Its orbit, power system, and life support hardware show how a complex habitat must balance energy, air, water, and waste every hour of every day.

Its partnership model shows how five space agencies and about 15 countries can share one expensive research platform. Its schedule shows that daily routines, exercise, and maintenance matter as much as the headline experiments.

For readers who want to understand the station's health risks, the human-body article in this section explains how microgravity and radiation affect the crew. For readers who want to understand how crews leave the station to work outside, the spacesuit article explains the gear that makes spacewalks possible.