Space junk increasing problem
Is space debris dangerous?
More than 600 000 objects in Earth orbit
Space debris is made up of macroscopic particles near Earth. ‘Macroscopic’ means that the particles of space debris can be seen at close range with the naked eye. It is estimated that over 600 000 objects larger than half an inch across orbit Earth. They include satellites that are no longer active, burnt out rocket stages or their debris, screws, wires and waste from solid fuel rocket motors. From November 2008 until 3 August 2009, when it re-entered the atmosphere, a tool bag from the Space Shuttle was orbiting Earth.
Natural ‘space debris’ is also a risk to space flight. Micrometeoroids can collide with space vehicles. They move at speeds far in excess of seven miles per second (Earth’s surface escape speed), and hence are traveling much faster than orbital debris.
Space debris is not just a risk to unmanned satellites. Systems with people on board, such as the International Space Station, must be protected against small objects with deflectors and matting – and the ISS must take avoiding action for objects larger than four inches across.
The lifetime of space debris depends on the height of its flight path, because the particles of scrap are slowed down by the residual atmosphere and this is denser near Earth than at greater heights. The lifetime of a particle at a height of 250 miles (the altitude of the ISS) is about one year, whereas at 600 miles it rises to about one thousand years.
Just as on Earth, the simplest way to reduce rubbish in space is to avoid it altogether – rocket stages and old satellites can be actively slowed down and made to burn up in the atmosphere. Gathering up space debris is complex and a spaceship requires a great deal of fuel for it. Other disposal concepts – such as firing laser beams at the junk – are being studied but are not yet ready for deployment.
German Aerospace Center