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Who takes down the trash?
This question arises not only in many households, but also in space travel.
The earth is surrounded by a huge cloud of space debris.
According to estimates by the European Space Agency (Esa), this amounts to a total of 8500 tons of waste.
Esa's radar systems have around 23,000 objects at least ten centimeters in size in their sights, which whiz around our planet at an average speed of 25,000 kilometers per hour.
Among other things, they come from burned-out rocket stages and disused satellites.
Experts assume that there are around a million pieces of scrap from a size of one centimeter in earth orbit.
They could all collide with spaceships or working satellites, causing great damage.
Every journey by astronauts to the space station or later to the moon or Mars inevitably leads through near-Earth space.
At a certain garbage density in orbit, manned space travel would simply no longer be possible.
"Garbage hunters" in space: ClearSpace-1 is to collect space junk in 2025
Source: ClearSpace
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Of course, the many valuable satellites are also threatened.
Of the approximately 6,000 satellites in orbit, around half are still in use, and the number of satellites will increase dramatically in the coming years.
Various private companies are in the process of bringing large swarms of communications satellites into space, which can then, among other things, bring the Internet to the most remote corners of the planet.
OneWeb, Starlink or Planet are the names of these networks.
Similar to climate change, space debris can also have tipping points, after which the problems become dramatically greater.
With junk in orbit, it's easy to explain.
Once two larger pieces of scrap collide, a large number of new, smaller particles are created in this crash.
These in turn pose an additional risk.
In the worst case, it could lead to a cascade of collisions that litter the near-earth space for a long time in such a way that space travel would become a high-risk affair.
For many years experts have been discussing this problem and the urgent need to dispose of space debris.
Now Esa wants to send a "garbage collection" into space for the first time.
The disused upper stage of a Vega rocket launched in 2013 is to be fished out of orbit 700 kilometers above sea level in 2025.
For this purpose, a probe called “ClearSpace-1” weighing around 500 kilograms is first placed in a 500 kilometer high orbit.
From there, the “chaser” (“hunter”) is supposed to locate the target object with the help of several cameras and a radar system and control it independently.
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"ClearSpace-1" will slowly approach the 112 kilogram and two meter tall scrap piece and then clasp it with its four spider-leg-like arms.
Combined in this way to form a cosmic duo, the “Chaser” will push the ensemble deeper into the earth's atmosphere with the thrust of its engine.
There, garbage and garbage hunters will burn up together.
This method of taking down rubbish has the obvious disadvantage of being very complex and therefore expensive.
Esa paid 86 million euros for the garbage hunter built by the Swiss company Clearspace.
In total, the mission costs around 111 million.
Clearspace has to finance the difference itself.
The "ClearSpace-1" mission costs about as much as a new satellite.
If you imagine that a new car would be just as expensive as it would later be scrapped, then it becomes clear that this concept cannot be the last word in wisdom.
A garbage hunter in space should be able to dispose of more than just one old satellite or a piece of junk.
It would be ideal if new satellites were designed and built from the outset in such a way that their later disposal is as simple and inexpensive as possible.
OneWeb is already cooperating with the Japanese company Astroscale to make satellites as suitable for towing as possible.
Astroscale also wants to fish disused satellites out of orbit - but not with gripper arms, but with the help of a magnet.
The first use of the Astroscale garbage collection is planned for 2026.