What is it and where does it come from?

Space debris is any man-made object in orbit around the Earth that no longer serves a useful purpose. This includes

• derelict spacecraft
• upper stages of launch vehicles
• parts of spacecraft produced by collisions or explosions
• tiny flecks of paint released from the surfaces of spacecraft as they undergo severe temperature changes and therefore expand and contract 

For fifty years, people have been dumping waste in space, from space missions. One astronaut lost a glove, which went into its own orbit. Another one lost a camera. Astronauts in the Mir space station dumped rubbish bags out through a hatch and into empty space.

There are currently over 9,000 tracked objects larger than 10 cm orbiting the Earth. Those between one and 10 cm, which cannot be tracked but are potentially lethal to satellites, number more than 100 000. Most of these circle the Earth at seven to eight kilometres per second and less than 2 000 kilometres above our heads.

At the moment the collision risk is extremely small, but an increase in space debris will present a real threat to operational spacecraft. For example, an object with a mass of 1 g travelling at seven kilometres per second can easily damage a satellite. If the object weighs more than a few grammes, the satellite could be completely destroyed, at enormous cost to the operator.

British National Space Centre (2004), Space debris

Are people at risk from falling space debris?

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