How do spacesuits support astronauts?

1. An astronaut floats out of the space station to fix something. Out here there is no air to breathe, and it is baking hot in sunlight and freezing in shadow. What keeps her safe?
2. First the suit fills with air. On Earth, air presses on your body all the time, and your body needs that. The suit holds air around the astronaut like a balloon she can wear.
3. The backpack is a life support machine. Tanks send fresh oxygen to the helmet. A fan pulls the breathed-out air back, and a filter takes out the carbon dioxide so it can be used again.
4. Working inside a sealed suit is hot, and there is no breeze to cool you. So the astronaut wears stretchy underwear threaded with thin tubes. Cool water flows through them and carries her body heat to the backpack.
5. The suit's wall is a sandwich of many layers. An airtight layer holds the air in. Shiny layers reflect the Sun's heat. A tough outer layer stops tiny bits of space dust that fly faster than bullets.
6. Sound needs air to travel, so nobody could hear a shout in space. A cap with earphones and microphones connects to a radio in the backpack. Air, cooling, protection and a radio: a spacecraft you can wear!

This suit has been opened up so you can see inside. Tap each part.

• Helmet and visor. The helmet is a clear, strong bubble full of oxygen. A gold-coated visor slides down like sunglasses to block the Sun's glare.
• Radio cap. A soft cap holds earphones and microphones close to the astronaut's ears and mouth. It connects to a radio and an antenna in the backpack.
• Life support backpack. The backpack holds everything the suit needs to keep working: oxygen tanks, a fan, a filter for used air, cooling water, a battery and the radio.
• Oxygen tanks. These tanks hold oxygen squeezed in very tightly. A valve lets out just enough to breathe and to keep the suit puffed up.
• Cooling garment. Under the suit the astronaut wears stretchy long underwear with thin tubes sewn in. Cool water flows through the tubes and soaks up body heat.
• Suit layers. The wall of the suit has many layers. The inner ones hold the air. The shiny ones block heat. The outer one is tough enough to stop speeding dust.
• Gloves. Gloves are the hardest part to make. They must hold air and still let the fingers bend to grip tools. Tiny heaters in the fingertips keep them warm.

Engineers test suits on a dummy in an airless chamber before anyone wears them. Pump air into the suit and watch the arm try to reach the red pad. Then try the sun lamp.

Experiment: What happens to the suit when you pump in more and more air?

1. Tap the pump until the dial is in the green zone. Can the arm reach the pad?
2. Keep pumping into the red zone. Watch the arm now.
3. Switch on the sun lamp and use the cooling water to keep the inside comfy.

What we found: With a little air the suit is soft. In the green zone it is firm enough to protect a person, and the arm still bends. Pump in too much and the suit goes as stiff as a hard tire, so the arm cannot reach the pad. That is why real suits use quite a low pressure.

Turn on JavaScript to try it yourself.

Get the suit ready for a spacewalk in bright sunlight: all three lights green. Then do it again in Earth's cold shadow.

On Earth, a thick blanket of air surrounds us. We breathe it, and it also presses gently on our bodies all the time. In space there is almost no air at all. There is nothing to breathe and nothing to press on the body, and a body cannot work like that. So an astronaut who goes outside must take a little piece of Earth along. That is what a spacesuit is.

The suit is filled with air like a balloon, so the body feels pressure again. A backpack sends fresh oxygen to the helmet and cleans the air that is breathed out, so it can be used over and over. Because the suit is sealed, body heat cannot escape, so cool water is pumped through thin tubes in the astronaut's underwear to carry the heat away.

The wall of the suit has many layers. One holds the air in. Shiny ones bounce the Sun's heat away. The tough outer one stops tiny grains of space dust that move faster than bullets. A gold-coated visor works like very strong sunglasses, and a radio lets the astronaut talk, because sound cannot travel where there is no air.

There is one tricky problem. Air inside the suit pushes outward and makes it stiff, like a pumped-up tire. With too much air, the astronaut could hardly bend an arm. So the suit uses less air pressure than we have on Earth, and the air is pure oxygen so there is still plenty to breathe. A diving suit is a good comparison, but a diver is squeezed by the water outside, while an astronaut's suit is pushed out from the inside.

Key words

Pressure

How hard air pushes on things. Your body needs air pushing gently on it.

Vacuum

A place with almost no air or other gas in it, like space.

Life support

The machines that supply oxygen, clean the air and control temperature so a person can stay alive.

Carbon dioxide

The gas we breathe out. Too much of it is harmful, so the suit removes it.

Cooling garment

Close-fitting underwear with thin tubes of water that carry body heat away.

Micrometeoroid

A tiny grain of rock or dust flying through space at great speed.

Check your thinking

1. Why does an astronaut need a spacesuit outside the station?

   Show the answer

   Space has no air to breathe and no air pressure on the body. A body needs air to breathe and air pressing on it. The suit brings both.

2. How does the suit stop the astronaut from getting too hot?

   Show the answer

   Cool water flows through tubes in the underwear and carries heat away. A sealed suit traps body heat, so water in thin tubes carries it to the backpack.

3. What happens if too much air is pumped into a spacesuit?

   Show the answer

   It gets so stiff that it is hard to bend. Air pushing out from inside makes the suit stiff, like a pumped-up tire.

4. The station flies from sunlight into Earth's shadow. What should happen to the cooling?

   Show the answer

   Turn it down, because less heat is coming in. In shadow no sunshine heats the suit, so too much cooling would make the astronaut cold.

5. Why can't astronauts just shout to each other outside?

   Show the answer

   Sound needs air to travel, and space has none. Sound is a wobble passed along through air. With no air, radio waves carry the voice instead.