Since the dawn of spaceflight, us humans have been launching things into space. From rockets to satellites, thousands of objects are currently orbiting Earth. This poses a growing risk of collisions as we launch more.
As long as spaceflight has existed, we’ve also been creating a bit of a mess. Many of the thousands of objects orbiting Earth are dead satellites, along with bits of debris from all the rockets that have been launched. This issue is starting to arise—and more quickly than we think.
WHAT IS SPACE DEBRIS?
Space debris (or space junk) is any piece of machinery or debris left by humans in space.
It can refer to big objects such as dead satellites or rocket boosters. It can also refer to smaller things, like bits of debris, paint flecks, or pieces of nuts and bolts that have fallen off a rocket.
Most of it is located in low Earth orbit (LEO), which is within 2,000 km of Earth’s surface, though some debris is also in geostationary orbit 35,786 km above the Equator and everywhere in between.
HOW MUCH OF IT IS THERE?
While there are about 11-12 thousand active satellites orbiting Earth (which alone is a massive amount), there are approximately 3,100 dead satellites as well. What’s more, there are around 54,000 objects larger than 10 cm orbiting Earth and millions of smaller pieces that are undetectable (the estimation is that there are around 900,000 pieces of debris larger than 1 cm altogether), but could nonetheless prove disastrous if they were to hit something else.
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| This is what a 14 gram piece of space junk can do to a solid block of aluminium. |
Now, if there were more and more pieces of space debris (even small ones like the one shown above), could you imagine what this could do to a new piece of machinery launched here?
All (even human) missions would be at risk, as well as the International Space Station, because all it takes is a 14-gram piece of junk floating around and you’ve got yourself a real problem.
Objects in orbit also include spent upper stages from rockets (around 11% of all space debris).
You can see the sheer amount of debris around Earth from sites like “
HOW IS SPACE DEBRIS CREATED?
All space debris is the result of us launching objects from Earth, and it remains in orbit until it re-enters the atmosphere.
Some objects with lower orbits of a few hundred kilometers can return quickly as the drag here is still great enough to pull them in. They often re-enter the atmosphere within a few years of launch and, for the most part, they’ll burn up—so they don’t reach the ground. But satellites placed in geostationary orbits of around 36,000 km can stay in that orbit for hundreds or even thousands of years.
Some space debris is caused by collisions or anti-satellite tests in orbit. When two satellites collide, they break apart into thousands of little pieces, creating lots of new debris.
The worst space-debris event happened on January 11, 2007, when the Chinese military destroyed the Fengyun-1C weather satellite in a test of an anti-satellite system, creating more than 3,000 fragments (more than 20% of all debris at that time). That is, 3,000 traceable fragments—the estimations are that the test created more than 150,000 smaller untraceable fragments.
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| This was the cloud of debris that Fengyun-1C created |
Within two years, the fragments spread from their original positions of creation to all kinds of places all around Earth’s orbit. The debris completely encircled Earth at this point and would not re-enter the atmosphere for decades to come.
WHAT RISK DOES SPACE DEBRIS POSE TO SPACE EXPLORATION?
Fortunately, at the moment, space debris does not pose a huge risk to our exploration efforts. The biggest danger it poses is to other satellites in orbit.
Each year, hundreds of avoidance maneuvers are performed by all kinds of satellites and even the ISS to move out of the way and not be hit by an oncoming piece of debris.
On particularly dangerous occasions, such as in November 2021, when the ISS passed through a debris cloud from a Russian anti-satellite test, astronauts close the station’s hatches and remain sheltered in their spacecraft.
Although, because of the high speeds at which objects orbit Earth (up to 8 km/s), a collision with even a small piece of debris can damage a spacecraft.
For example, windows of the Space Shuttle often had to be replaced due to collisions with objects smaller than 1 mm. This is why in orbit the Space Shuttle flew tail first to protect the forward-facing crew compartment.
THE KESSLER SYNDROME:
This is an idea proposed by NASA scientist Donald Kessler in 1978. He said that if there was too much space debris in orbit, it could result in a chain reaction where more and more objects collide and create new space debris in the process, to the point where Earth’s orbit becomes so littered with space debris (from larger parts to hundreds of thousands of untraceable small parts) that it becomes unusable.
This situation would be extreme, but some experts worry that a variant of this situation could be a problem one day, and steps should be taken to prevent it from happening. This idea was also popularized by the movie “Gravity.”
Some satellites in geostationary orbit that are near the end of their missions are moved to a “graveyard” orbit 300 km higher than GEO itself. Here, some dead satellites are collected so they remain far away from all the live satellites at GEO.
ON WHICH SPACE DEBRIS SHOULD WE FOCUS?
Many experts tried to make lists of the 50 most dangerous pieces of space debris that need immediate removal, but none of the teams agreed on the same ones.
Given the exorbitant cost of removing space debris (tens of millions of dollars per piece), it is tough to find a list of the ones that pose the most threat. There are thousands (if not tens of thousands) of objects that would be better removed from Earth’s orbit, but if each removal costs millions, then who would be willing to do it?
It is certain that with the pace that objects are currently launching into space, we will see some sort of more serious problem arise. It is not that probable yet that the Kessler Syndrome will become reality, but within a few decades, it could well be.
The only reasonable solution to this is that the companies launching and sending objects to space will care the same way about the object’s life after its mission as its launch and start. They need to focus on how to remove space debris, but maybe more importantly, how to decrease the pace at which it is being created.
Nobody wants a future where all of Earth’s orbit is so littered with debris that we cannot physically launch anything or anyone without damaging or completely destroying it as it flies through this cloud of junk.
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