When we think about junk, things like garbage bins or landfills come to mind -- but there's another junk problem, one that's hard to see with the naked eye from the Earth. Space junk, researchers warn, is a growing problem, and if we don't address it quickly, it may soon be too much to handle.
There are a total of 6,542 satellites that are currently occupying Earth’s orbit, but only half of them are actually doing something. The other half are inactive -- they're simply junk. To make matters even more problematic, over 1,200 satellites were launched in 2020 -- this marks a record, but generally speaking, we could expect more and more satellites to be plopped into orbit.
Now, imagine one day Earth’s orbit becomes overcrowded and two such large satellites hit each other. Both the satellites would get broken into smaller pieces that would further clash with other satellites and trigger a series of unstoppable collisions and a lot of junk pieces flying around. This has happened a few times already.
Due to these collisions, our planet's orbit gets more and more cluttered with debris, to the extent that eventually, we will end up having no room to launch more rockets and satellites. Such a situation in which Earth’s orbit becomes completely unusable because of large amounts of space junk is referred to as Kessler syndrome -- a phenomenon first envisioned by NASA scientist Donald J. Kessler in 1978.
Fortunately, we're not at that stage yet. For now, space junk does not seem like a big problem but aerospace experts suggest that in the coming years, the number of satellite launches and space missions could increase dramatically, and this is likely to add more junk to space and make Earth’s orbit more crowded than ever. Simply put, if we don't start taking action quickly, it will soon be too late.
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What is space junk and why it’s dangerous?
Space junk is a generic term. Unusable satellite parts, rocket components, and debris of man-made machines in space are called "space junk". Until now, NASA has tracked 27,000 such items that are aimlessly moving in Earth’s orbit. This orbital debris can move at a speed of 24,000 km/h (15,000 mph), and therefore any such fast-moving piece of junk can hit and destroy a functional satellite or a passing by rocket at any time.
We're already seeing some of this damage in action. In March 2021, the 18th Space Control Squadron (18SPCS), a space control unit under the US Space Force confirmed that a small debris piece named Object 48078 hit China’s Yunhai 1-02 satellite. According to Astrophysicist Jonathan McDowell, Object 48078 was a remnant of Zenet-2, a Russian rocket that was launched in the year 1996. McDowell further added that the “Yunhai 1-02 satellite broke up” after the collision.
However, such collisions due to space junk are still rare. Before the Yunhai 1-02 crash, the last collision reported was in 2009. Moreover, such collisions can be prevented by mission controllers by adjusting the position of a satellite. Every year many satellites are manoeuvered multiple times in order to avoid collision with space junk, even the International Space Station (ISS) has performed more than 20 junk avoidance maneuvers since its launch in 1998.
The space junk problem does not seem like a big issue for now but if not dealt with properly, it may lead to chaos in our planet’s orbit in the future -- chaos that will be extremely difficult to address.
A small but growing problem
Before 2010, only around 100 satellites were launched every year but in the year 2020, for the first time, more than 1000 satellites were sent to space. The numbers continue to increase in 2021 as well because so far, 1400 new satellites have already been placed in orbit this year.
Moreover, in the early days of space exploration, there used to be only a few agencies that would send satellites into space -- like NASA, Roscosmos, and the European Space Agency. Nowadays, active private players like SpaceX and Blue Origin have created a boom in the aerospace industry and are launching more and more satellites. These companies are planning to launch mega-constellations (groups of satellites that cover large orbital area) in Earth’s orbit to provide wireless broadband internet services across the globe, in the coming years -- an exciting project that is bound to help millions around the world, but which also poses new threats to the problem of space junk.
These mega-constellations would bring an unprecedented increase in the number of satellites revolving around Earth (a report suggests that the Earth’s orbit may have 100,000 satellites by 2030). With every launch, the amount of space junk will also increase making the orbit more congested. As a result, both the existing and new satellites will have to perform more collision avoidance maneuvers.
Therefore, more fuel and resources would be spent on saving the satellites from space junk. Sooner or later, with an increasing number of space missions, the growing amounts of space junk might raise the frequency of outer space collisions and over the course of time, it could ultimately cause the Kessler syndrome.
Is it possible to free Earth’s orbit of space junk?
Cleaning up space junk is not as easy as it sounds. For starters, imposing a ban doesn't seem like a promising idea.
Rockets are launched to explore space and collect information about other planets in our galaxy, whereas, man-made satellites are placed in Earth's orbit in order to facilitate communication, navigation, military assistance, earth observation, weather forecast, mineral search, and many other activities that hold great importance for humans. Therefore, banning space missions and new satellite launches is obviously not a solution.
Cleaning our planet's orbit is both an expensive and complicated process. However, researchers and space agencies are working on this and they keep coming up with new and interesting methods to remove space junk from Earth’s orbit.
Around 2012, a group of researchers working at EPFL (Swiss Federal Institute of Technology) came up with the idea of a special satellite (called CleanSpaceOne) that could attach itself to a targeted piece of space junk and drag the same back towards earth. The researchers proposed that during its journey to Earth, both the satellite and space junk would be burnt by the atmospheric heat.
This idea sounds promising, but it will also be costly, and bringing down satellites one at a time will be very time-consuming.
In 2016, the Japanese Aerospace Exploration Agency sent an electrodynamic tether in space that could direct space junk towards Earth’s atmosphere by using the planet’s magnetic field. A couple of years later, the Surrey Space Center in the UK launched the RemoveDEBRIS project in April 2018, this project was focused to encourage and demonstrate various space junk removal technologies. Under the RemoveDEBRIS initiative the effectiveness of methods involving net, harpoon, and drag sail for catching space junk was tested.
Researchers at Purdue University also developed a drag sail named Spinnaker3 in 2020. This powerful drag sail is an efficient and cost-effective way to deal with space junk as it does not require any fuel during its operation. Moreover, it can drag even rocket-sized space debris back to Earth’s atmosphere so that they get destroyed in peace. Spinnaker3 is expected to launch in November 2021 on a Firefly rocket.
Astroscale, an orbital junk removal company from Japan, launched the ELSA-d (End-of-Life Services by Astroscale-demonstration) satellite in March 2021. This advanced debris removal system uses magnetic satellite catching technology to pick small inactive satellites from Earth’s orbit. ELSA-d successfully completed its first satellite capturing test on August 25, 2021, and it is now moving on to the next phases of its space junk removing process.
As is generally the case, prevention is better than cure. In the case of space junk, it's not yet a big problem -- but by the time it becomes a big problem, it may be too big to handle efficiently, which is why it's best to act as quickly as possible.
Aerospace experts are following this closely and if their research is supported, we'll likely soon see effective waste-management strategies for space -- and by the time we're ready to go on our first interplanetary picnic, we'll have a clean, green (hopefully), and beautiful orbital view.