Since the start of the space age in the 1950’s, we’ve been sending all sorts out into the darkness. We’ve sent up hundreds of rockets and thousands more satellites, many of which are still there. Space is once more a hot topic, and companies such as SpaceX and even Amazon are hoping to send up thousands more satellites in the coming years. This poses a problem though: Space Junk. With more and more satellites in orbit, the risk of collision has hit a critical level; what new research is there to sweep it all up?
As well as creating a “bit” of a mess down here on Earth, it turns out we’re doing a pretty good job of cluttering up space too… Obviously not all space, but primarily the area around our planet where things can orbit. Space junk (or debris) is created when rockets and satellites are launched or when they’re no longer in use (because who’s picking up litter in space right?). Some debris in a lower orbit (just a couple of hundred kilometres up) can return to earth relatively quickly (a few years or so, and burn up as they reenter the atmosphere, so they never reach the ground). Junk at a higher orbit (around 36,000 kilometres), where communications and weather satellites are positioned, can continue to circle the Earth for hundreds (possibly thousands) of years.
Debris can range from huge satellites to tiny paint flecks which have fallen from a rocket. There are around 2,000 active satellites orbiting earth, ~3,000 “dead” (inactive) satellites, ~34,000 pieces of debris around 10cm in diameter, and millions more smaller pieces, but no matter how tiny, damage can be done. In fact, we’ve reached a critical level of space junk and a potentially disastrous chain reaction could happen. In 1978 a NASA scientist, Donald Kessler, came up with a theory that if there was enough space junk in orbit, colliding with enough satellites, this would produce a chain reaction creating more space junk and making our orbit unusable; this is known as the Kessler Syndrome. Obviously, if two satellites collided there would be a pretty big problem, but why can paint flecks cause an issue for large satellites? All space debris is travelling at 17,500 mph, which is ~10 times faster than a bullet. At such speeds, even a paint fleck sized piece of debris has enough power to completely destroy or greatly damage a satellite. What does this means for us?
Although space exploration beyond our planet is unaffected by our space junk, the satellites which we use every day are not. Satellites have to now perform “collision avoidance manoeuvres” hundreds of times a year to prevent damaging space junk collisions. The International Space Station (ISS) is not exempt, and also has to watch out for such debris and perform these avoidance moves. Currently, collisions to date have been rare with the last satellite destruction from space junk reported in 2009, but that does not mean it is impossible. In the coming years, companies such as Amazon and SpaceX plan to launch vast networks of satellites to beam internet down to Earth. This could lead to an extra 50,000 satellites in orbit. Why are satellites so important? Satellites provide the ability to collect data more quickly than any instrument on the ground as they have a bird’s eye view of the Earth. Satellites give us the ability to make calls across the world, watch TV wherever we are, and accurately track weather systems, to name but a few applications.
So how do we remove space junk and protect our satellites? Astroscale: Space sweepers was founded in 2013 as the world’s first space cleaning start-up. Created by Nobu Okada, he recruited scientists from NASA, Japan’s space agency (Jaxa) and the European Space Agency (Esa) to tackle the space junk issue (employees are called space sweepers). Astroscale is working to attach a docking device on commercial satellites which could locate and remove future debris left behind by companies. The removal satellite will approach debris from behind which is difficult as the debris tumbles and rotates. The satellite has to synchronise with the motion of the debris, before capturing and stabilising it, and finally bringing it down to the atmosphere to burn (disposal). The company has raised $140 million to date, with a planned launch of its first removal satellite mission this year (2020)! You can see a simulation of their work below:
Alongside Astroscale, Esa has its own research into debris removal which, in 2018, even included deploying a big net to catch disused satellites! Satellites are deeply embedded in our daily lives. We may not see them every day, or the space junk which surrounds our planet, but we are at a critical point and will only require debris removal technology more in the future, as space exploration continues. Watch this space…