Satellites move quickly

Space junk Very fast and very dangerous


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Burned rocket stages, broken satellites, lost screwdrivers and splintered paint particles: the orbit around the earth is full of space junk. The rubbish is dangerous - and now quite widespread.

Status: 01.12.2020

Around 8,500 tons of scrap rush overhead. It occurs, for example, when two satellites collide. Some of these objects are quite large, while others are tiny. Space junk is always dangerous: at a speed of tens of thousands of kilometers per hour, even tiny particles turn into destructive projectiles.

ESA's concept: defective satellites are to be captured with a network and then brought to crash.

"When an aluminum ball just one centimeter in diameter hits a satellite, it has the energy of a mid-range car that drives into it at around fifty kilometers per hour."

Heiner Klinkrad, head of space debris at ESA

The orbits of the two satellites crossed over northern Siberia.

A rather spectacular collision in space occurred in February 2009. The American communications satellite Iridium 33 collided with the Russian reconnaissance satellite Kosmos 2251 at an altitude of almost 800 kilometers. The impact speed was almost twelve kilometers per second.

The energy released in the impact was equivalent to about ten tons of TNT explosives. No wonder there wasn't much left of the satellites: an estimated 100,000 pieces of the debris were an inch or more in size. However, it is not just the number of fragments that is problematic, but also the height of their orbit: the fragments will orbit the earth for around a hundred years before they burn up in the atmosphere.

Satellites between junk

Two years earlier, China deliberately shot a disused satellite with a rocket. The result: more than 3,000 larger fragments in space. The International Space Station (ISS) has to fly evasive maneuvers every year because such debris comes dangerously close to it.

In 1995, the Cerise satellite was hit by space debris.

Even a single piece of space junk can have devastating consequences. In 1985, an Ariane rocket transported a satellite into space. The top stage of the rocket exploded. Ten years later, a fragment of this rocket hit the French Cerise spy satellite at 50,000 kilometers per hour. An important boom to stabilize the position was demolished. Ground control just managed to keep the spinning satellite in orbit.

Since 1957, when the first Sputnik satellite was launched, there have been hundreds of proven explosions and collisions in space. What remained are more than 20,000 objects that are at least ten centimeters in size. Around a million parts are larger than a centimeter. And there are probably more than 150 million very small pieces of scrap that are bigger than a millimeter in size.

Simulation of a collision in geostationary orbit.

The fragments are, however, distributed quite differently: Most of them orbit the earth at a distance of 800 to 1,000 kilometers. Many parts are also at an altitude of 1,400 kilometers. Then there is a big loophole. Numerous objects can again be found in the zone of around 20,000 kilometers from Earth: this is where the navigation satellites are located. After all, there is a large number of debris at an altitude of around 36,000 kilometers. There they endanger satellites that are in a so-called geostationary orbit. That is, viewed from the earth, they appear to be standing still. Satellites of this height are responsible, among other things, for the transmission of television and radio programs as well as telephone calls and data.

When rubble meets rubble - the Kessler effect

Two days after the collision, the rubble is already widely spread.

There is a lot of space in the orbits far out. But the scrap piles up here: The gravity is too weak to ensure that the debris plunges into the atmosphere and burns up. There is therefore a risk of a chain reaction at some point: If two satellites collide, their fragments collide with other satellites and produce even more fragments. Eventually collision objects collide with collision objects and the situation gets completely out of control.
Discontinued satellites are to be sent to a so-called "cemetery railway" according to international regulations. It lies about 300 kilometers above the geostationary orbit. Defective satellites from lower orbits, however, should, according to the will of the UN, return to earth as far as possible - and in such a way that they do not cause damage anywhere.

  • Space junk problem. radioWelt, January 25, 2019 at 6:05 am, Bavaria 2
  • Space debris - a threat to the ISS. nano, 03.09.2018, 5.45 p.m., ARD-alpha.