Tens of thousands of objects like old spacecrafts and satellites pose a severe problem for space travel. Scientists recently gathered in Germany to discuss the problem.
A layer of space debris surrounds the globe
Gathering in the German city of Darmstadt, more than 220 space experts discuss the problems of space debris this week.
It's a serious challenge for space exploration: Since 2001, space shuttle windows have been replaced 80 times due to sub-millimeter object impacts. Some 330 million objects larger than a millimeter are orbiting around the earth, according to experts.
Sooner or later they will all come down back to earth -- but this could take years or even decades, which is long enough to cause a lot of trouble.
"The relative velocity of objects traveling in space is in the order of ten times the velocity of a fast rifle bullet," said Heiner Klinkrad, a debris specialist at the European Space Operation Center in Darmstadt. "There are objects of up to ten tons up there. If something like that hits your satellite it will completely shatter your satellite."
Dangerous near collisions
International Space Station
Large objects, however, can be detected and are tracked by a number of countries, including Germany, France, Great Britain and the US by using optical telescopes and radar. And if necessary, avoidance maneuvers are carried out. The International Space Station so far has had to avoid a dangerous collision six times.
The really dangerous bits are of medium size, between one and 10 centimeters. They cannot be detected but can still be harmful. Sometimes older rocket bodies that still contain fuel explode. One explosion can lead to another, which leads Klinkard to believe that the situation in outer space might actually get out of control.
"Ultimately the explosion fragments collide with each other and than you may have an escalation effect, a sort of chain reaction," he said. "Then you have a runaway situation which is out of control and some orbit altitudes may not be used for spaceflight anymore."
Call for international agreement
During the Darmstadt conference, the experts agreed that international measures have to be taken to tackle these problems. Experts are asking for a United Nations-backed agreement of all aerospace-nations on avoiding debris, keeping certain orbits free of it, and bringing back larger parts of it to earth while tracking the others.
ESA image of MSG-1 European weather satellite in orbit over Europe and north Africa, artist rendition
Satellites, for example, can be steered onto a higher level where they collapse, eventually re-enter the orbit and evaporate into a kind of spray. But that usually comes with severe monetary consequences. The satellite owner loses about three months of operational time needed to carry out the maneuver. And there is always the risk that the junk such as rocket stages made of stainless steel or titanuim simply will not evaporate.
The conference's results will now be handed over to the politicians. Klinkrad said he hopes that international laws will be implemented in order to reduce the dangers of space debris in outer space and down here on earth.