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How do astronauts stay alive in space?
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How do astronauts stay alive in space?
Last modified: Monday, 6 April 2026, 2:35 PM
How do astronauts stay alive in space?
What do astronauts need to survive in space?
Astronauts survive in space thanks to special equipment and technology that helps them stay safe and healthy.
Space is a very dangerous place but here's how they stay safe.
When astronauts go outside of their spaceship or space station, they wear spacesuits. These suits are like mini-spaceships that protect their bodies.
The temperatures outside in space are extreme. As the ISS travels from sunlight into darkness, the temperature drops from 120°C to -160°C.
The spacesuit gives them air to breathe, keeps them warm or cool, and protects them from space dust and the Sun's strong cosmic rays.
In space, there is no air like on Earth, so astronauts bring their own oxygen. Their spaceship makes air for them to breathe, just like how plants help make air on Earth.
On the International Space Station (ISS), there is a continuous supply of oxygen. It is taken from water.
The spaceship also removes bad air (carbon dioxide) so astronauts don't become sick from breathing it.
Fresh food doesn’t keep for long in space so all meals and snacks are packaged to stay fresh for up to nine months.
Astronauts add water to this freeze-dried food and heat it up. They can even eat their favourite foods like pizza and cookies.
However, no crumbly food is allowed on board the spacecraft as the bits would float around and block air vents and equipment.
The water on the ISS is recycled from the astronauts sweat and even their urine!
Don’t worry though, machines clean the water to make it safe to drink again.
Space is filled with harmful radiation and cosmic rays from the Sun.
Spacecrafts and spacesuits provide some protection.
The walls of spaceships are like shields that help block dangerous radiation from space.
On Earth, the force that keeps us standing on the ground is gravity. However, at 400 km above the Earth, astronauts experience zero gravity or weightlessness.
This means that they float around, and many astronauts report that it makes them feel sick for the first couple of weeks.
When they arrive back down to Earth, many astronauts are a few centimetres taller. This is because the spine is not exposed to the pull of Earth's gravity. This means that the vertebra (the little disks that make up the spine) can expand and relax, allowing astronauts to actually grow taller.
Without gravity in space, astronauts float around, which might seem fun but their muscles and bones become weak because they don't have to hold up the body or walk or run.
It is really important for astronauts to do exercise in space.
To stay strong, astronauts use special equipment to exercise for about two hours every day. This means that they do not lose too much bone or muscle mass, so that when they return to Earth they can still function normally.
Living in space is very different from living on Earth.
Astronauts sleep in sleeping bags that are attached to the walls so they don't float away while they sleep.
Astronauts also have to wear eye masks or cover the windows because the Sun sets and rises every 90 minutes as they orbit the Earth.
Astronauts from around the world spend up to a year in space at one time, living and working on the ISS. Even though there are up to six astronauts at any one time, it can still get lonely.
Astronauts have regular contact with their colleagues, friends and family through special radios and video calls so that they can maintain good mental health.
When astronauts finish their mission, they come back to Earth in their spaceship.
The spaceship uses parachutes and other systems to slow down so that they can land safely.
Accordion content here.
Tim Peake on the importance of spacesuits
You might have dreamed of floating in space: the International Space Station (ISS) glinting in the sunshine beside you and the Earth hanging below. It might sound like a beautiful and calm place, but space comes with a serious health warning.
If you stepped out into space without the proper equipment you’d only last a few seconds. The ISS needs to recreate the conditions of Earth in space. Astronauts need air to breathe, water to drink and a stable environment.
Yet, even within the safety of the ISS, there are invisible dangers that push the human body to its limits.
What’s it like for the men and women who have to live and work on the final frontier?
Spacesuits keep astronauts alive in space
Tim Peake explains how spacesuits keep astronauts alive when they're outside the space station. Archive: NASA
The International Space Station (ISS) is our floating laboratory in space
Fascinating Facts
- Spacesuits are designed to protect astronauts from temperatures as low as −156 °C.
- On 18th March, 1965 Russian cosmonaut Alexei Leonov became the first person to perform a spacewalk.
- It is theorised that astronauts could enter space without a spacesuit, but they would only survive for at most 15 seconds due to the extreme temperatures, pressure and radiation.
- Spacecraft have heatproof tiles on the underside. These protect the astronauts from the high temperatures and prevent the spacecraft from being destroyed on re-entry. Re-entry temperatures can reach as high as 1,650 °C.
- Construction on the ISS began in 1998, but new modules are added regularly to keep it up to date with technology and the latest research.
- NASA has recorded over 170 million pieces of space debris orbiting the Earth, ranging in size from 1mm to much larger satellites.
- All astronauts need to learn to speak and read Russian as it's used on the ISS and in the Soyuz space capsule.
- Astronauts can grow up to 3% taller whilst in space, although they go back to normal when back on the Earth.
Life on the ISS
Explore the gallery below to find out what day-to-day life is like for astronauts on board the International Space Station (ISS).
The International Space Station is a habitable artificial satellite. It travels around the Earth at 17,000 mph.
Living in space, astronauts have a unique opportunity to conduct experiments in weightlessness. They work on almost every area of science you can think of, from material science to medicine, and from microorganisms to meteorology.
All the food eaten by the astronauts on their mission is carefully planned in advance. It is important that they receive enough vitamins and minerals to stay healthy on their voyage. Like camping foods, some are dried and require water before eating.
Like here on Earth, astronauts need to exercise to stay healthy. On the ISS astronauts are weightless, so they need to be strapped in to give their muscles a workout.
Italian astronaut Samantha Cristoforetti spent 199 days and 16 hours in space. Enough time for her to need a haircut. However, this requires a vacuum cleaner to capture the cut hairs before they can float away.
The ISS has a control tower with panoramic views called the cupola. It is not only used to take fantastic photographs, but it also helps the crew when they operate a robotic arm to carry out tasks outside the station.
Putting on a spacesuit is complicated and before heading outside the ISS the astronauts need to be sure they are safe. Preparing for a spacewalk, or what astronauts refer to as extravehicular activity (EVA), requires teamwork.
The ISS is made of many interconnected modules and was built by astronauts in space. EVAs (or spacewalks) are needed from time to time to carry out general maintenance or repairs to the station.
Falling asleep on the ISS requires a sleeping bag that is attached to the walls of the ship. Without the straps, astronauts could float about and hurt themselves. It also gives astronauts the familiar feeling of lying in a bed.s9
Fascinating Facts
The ISS travels at a speed of five miles per second
It completes 16 orbits of Earth every 24 hours.
This means that astronauts can see as many as 16 sunrises every day.
You can see the ISS on a clear night with binoculars or a telescope
What happens to the body in space?
There isn’t an up or down in space, like we’re used to on Earth, so your brain can become confused. Astronauts often complain of feeling sick during the first few weeks on the ISS and their bodies usually take a little time to adjust.
Living in space has been described as being a bit like standing on your head. With less gravity pushing down on you, fluids tend to pool in the upper parts of the body. This gives astronauts a puffy, red face.
On the ISS the pull of gravity isn't as strong as on Earth. Your muscles don’t need to work as hard and your bones weaken. Each crew member has a strict daily exercise routine to make sure they don’t waste away.
Your heart muscle gets weaker as well, as it requires less effort to pump blood around the body in microgravity. Astronauts also typically grow a few centimetres taller in space.
Without the Earth’s atmosphere to protect them, astronauts are constantly bombarded by cosmic rays. These invisible waves zap the body and increase the risk of diseases.
Astronauts on the ISS feel weightlessness, but this can affect their body and health
Fran Scott explores what happens to the body in a vacuum. Archive: ESA, NASA
Did you know?
When astronauts land back on Earth, they are often carried out of the capsule because their leg muscles are too weak from their time in space.
Astronauts on the ISS feel weightlessness, but this can affect their body and health
Important words
Astronauts – A person trained to travel in space. In Russia they are known as cosmonauts.
Cosmic rays – High energy particles that travel through space. They come from our Sun and from outside of our Solar System.
Gravity – A force that pulls things to the ground on Earth. It also holds planets, moons and asteroids in their orbits around the Sun.
International Space Station (ISS) – The largest space station ever built. It orbits the Earth in low orbit. Five international space agencies collaborate to keep it operational.
Radiation – Energy that moves from one place to another in waves or particles.
Spacesuits – A suit that protects astronauts from the harsh environment of space. It keeps the astronaut warm, provides air and water and protects them from cosmic rays.
Weightlessness – In space there is no gravity. Astronauts can float around and are weightless.