The International Space Station is a home and laboratory where astronauts live and work while it orbits Earth. Europe's agency supplies its Columbus laboratory. Its principal partners are the space agencies of the United States, Russia, Europe, Japan and Canada. The station's pressurized modules are about 218 feet (67 meters) long. As of November 2026: people have lived on the station without a break since November 2000. As of November 2026, seven people are living on the station (Expedition 75).

Astronauts and everything in the station float, because the station is weightless inside. Astronauts float because they and the station are falling around Earth together, not because there is no gravity. Earth's gravity still pulls on the station. At that height it is only about 10 percent weaker than on the ground. The station circles Earth at about 28,800 kilometers an hour, 400 kilometers up. One circuit takes about 92 minutes.

Water is heavy. It takes a lot of energy to send it up into space. The station cleans and recycles water from sweat and breath, and astronauts drink it. As of November 2026, NASA says the station has shown it can recover about 98 percent of its water.

A rocket lifts astronauts and their spacecraft off the ground. It burns fuel and pushes hot gas out of its engine. When the rocket pushes its exhaust out, the exhaust pushes the rocket the other way. A jet engine needs oxygen from the air to work, but a rocket engine carries everything it needs. Big rockets have stages. They can drop used-up sections and stay as light as possible.

Without gravity pressing down on them, astronauts' bones lose about 1 to 1.5 percent of their mineral density each month. Astronauts also lose muscle mass faster than they would on Earth. Astronauts exercise to keep their muscles and bones strong. As of November 2026, crews on the station exercise about two hours a day, and NASA schedules two and a half hours.

Astronauts wear spacesuits for spacewalks, outside the station, because space is airless. It is dangerous without one. A spacesuit backpack holds oxygen for astronauts to breathe. It removes the carbon dioxide they breathe out. Spacesuits protect astronauts from radiation and from bits of space dust. In the near vacuum of space there is no air to carry heat away, so suits cool astronauts with water in tubes.

Astronauts practice spacewalks in a huge pool. In water, a neutrally buoyant object neither floats nor sinks, which is how a pool imitates weightlessness. A centrifuge is a spinning machine that presses on astronauts with the same g-forces they feel during launch. It teaches them to work under the high forces of launch.

On April 12, 1961, Yuri Gagarin became the first person to orbit Earth, in Vostok 1. Gagarin's flight around Earth lasted 108 minutes. Alan Shepard became the first American in space on May 5, 1961, in a 15-minute flight. It did not go all the way around Earth. Valentina Tereshkova became the first woman in space on June 16, 1963.

Artemis II launched on April 1, 2026, from Kennedy Space Center in Florida. It carried NASA astronauts Reid Wiseman, Victor Glover and Christina Koch. The Orion spacecraft carries astronauts. The SLS rocket gives the power to lift it off Earth and send it into deep space. As of November 2026, NASA plans Artemis III for 2027: four astronauts in the Orion spacecraft on a test flight in low Earth orbit, not to the Moon. As of November 2026, NASA plans for its first crewed Moon landing under the Artemis program to take place in 2028.

As of November 2026, NASA says Mars remains its horizon goal for human exploration. As of November 2026, NASA's goal is to send humans to Mars as early as the 2030s. As of November 2026, getting to Mars could take up to 6 to 9 months, and a round trip with a long wait for the planets to line up could take 3 to 3.5 years. Radio signals take roughly 3 to 25 minutes to travel between Earth and Mars, depending on where the planets are.

Words to know

• centrifuge: spinning machine
• buoyant: able to float
• stages: rocket sections
• exhaust: hot gas out
• orbits: circles around