How to Clean Up Space Junk
Space junk in orbit around Earth is increasingly becoming a problem. Collisions can lead to the damage and destruction of satellites and even harm the ISS. Satellite systems expert Dr Joon Wayn Cheong from UNSW explains some possible solutions.
Dr Joon Wayn Cheong, a satellite systems expert from the University of New South Wales, thinks that there should be an international effort to clean up the space junk that is orbiting Earth. Space junk consists of the remains of satellites and other technology that was sent up into orbit, but has since stopped operation, and is now stuck up there.
Since humans have been launching objects into space for decades now, the accumulation of these pieces of debris continues to grow. Space junk can range in size from a few millimetres across (like paint specs) through to defunk satellite and rocket stages, which are the size of buses. However, due to the high velocity of these objects - they are considered a high risk when an impact occurs.
The problem is, that these pieces of space junk collide with each other, and other satellites, and break into smaller and smaller pieces. These pieces of space junk, large and small, can cause major problems for other satellites and technology in orbit.
“Space debris can travel up to 10 kilometres per second which has the same impact of being hit by a small cricket ball at 100 kilometres per hour,” says Dr Cheong.
“The exterior of satellites is often covered in solar panels, which consist of brittle glass. So regardless of how small the debris it collides with, the satellite will be likely damaged, and therefore more debris is created. These satellites are vulnerable - they’re not designed to be smashed.”
Space Junk: an Exponential Real Estate Problem
The European Space Agency estimates that there are 34,000 objects larger than 10 centimetres in orbit around Earth, and up to 128 million between one millimetre and one centimetre. Space junk, even this small, can still cause problems, such as taking up precious orbital real estate.
“Space junk contaminates the orbits it occupies; it uses up the orbital slot that another functional, more useful satellites could occupy,” says Dr Cheong.
“We’re seeing an increasing trend of space agencies and companies sending many satellites into much higher orbits, primarily the upper Low Earth Orbit (LEO), and in some cases the GEO orbit.
“But they get into a situation where they lose control of these satellites, or they stop functioning completely but still continue to occupy the orbit for 10 to 15 years and there’s no way of retrieving them.”
“And as time goes by, their position in space becomes more and more precious because there are fewer orbital paths available to send up new satellites for important purposes such as communications, positioning, earth observation and other technologies.”
Cleaning up Space Junk
Space junk exponentially creating more debris through collisions is called Kessler Syndrome. Dr Cheong suggests that one possible solution to this is to move space junk into a “graveyard orbit” once satellites have reached the end of their mission.
“For the satellites that are further away, they should be moved to a graveyard orbit.”
“Graveyard orbits are at a much higher altitude and do not interfere with common operational orbits,” he says.
For other space junk, he suggests that it should be pulled into the Earth’s atmosphere to burn up.
“For the satellites that are closer to Earth, you can move them to an even lower orbit and let gravity pull them back down to Earth and they decay faster as they move through the gradually thicker atmosphere beneath it,” Dr Cheong said.
The moving of space junk into safer orbits using lasers is currently being explored by researchers.
However, cleaning up space junk like this requires decision making and preparation to be made during the planning stages of a mission.
“The onus is on the spacecraft operators to ensure they have enough fuel at the end of their mission to make a conscious decision about what to do with the satellite – just don’t dump it and further pollute our orbits.”
Decisions would also have to be made as to whether certain pieces of space junk could be kept as space heritage, and whether it should be kept in orbit. This technology can demonstrate history and significance. But, should this be at the risk of exponential collisions and Kessler Syndrome?
“The biggest issue with these objects is that they cannot be tracked or controlled. If we can control them, we can easily ensure they avoid and manoeuvre around nearby objects,” said Dr Cheong.