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The Space Environment and Earth's Atmosphere

When learning about spacesuits we need to understand the space environment.

The basic laws of physics, such as those regarding pressure and heat exchange, apply just as much in orbit around Earth as they do on it.

But there are differences between the environment above our atmosphere and the environment at ground level, so applying these laws can have surprising effects in space.

Scientists and engineers who create spacesuits and survival systems for astronauts use their knowledge of these differences and the effects they can have on people working in space.

Many complex technologies are used in designing spacesuits, but their objective is simple: to enable people to live and work in an environment that is inherently harmful to them.

We will begin by comparing the space environments to Earth.

Environments

Density of the air around Earth

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You may think that in the upper layers of the atmosphere there is no air. This is not the case. Air is in fact present, although, of course, there is not enough for a person to breathe at, say, the altitude of the International Space Station (ISS), about 400 km above the Earth's surface.

The air density at this height is about 800 million atoms per cubic centimetre. In the exosphere (the outer layer of our atmosphere), more than 600 km from the Earth's surface, air is still present, but at only about 150,000 atoms per cubic centimetre.

Meteorites

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Meteorites are usually stony or metallic fragments of celestial bodies (asteroids, comets, etc.). It is believed that they result from the explosion of these celestial bodies, and their size varies from that of a block of several tonnes to the size of a grain of sand (micrometeorites).

The largest ones can measure up to one hundred metres and weigh approximately sixty tonnes (if a block is much greater in volume, it is usually considered to be an asteroid rather than a meteorite).

Meteorites usually revolve with great velocity around the Sun on specific orbits of great eccentricity. Some, however, only travel through the solar system without a specific trajectory.

Meteorites pose a very real danger for astronauts. Given the speed at which they move, an impact involving one of them, even if it is small, would be fatal. Luckily, the probability of a collision is minute and the spacesuits currently used are reinforced with Dacron and Kevlar, providing effective protection against micrometeorites.

• Some planets have an atmosphere and others do not