Space Junk - IELTS Reading Answers & Explanations

You should spend about 20 minutes on Questions 15-29, which are based on Reading Passage 2 below

Space Junk

Since the Soviet Union successfully launched the first man-made satellite, Sputnik 1, in 1957, about 5,000 more satellites have been put into orbit around the Earth. About 2,000 of these are active and although the rest are now dead, they remain in orbit, together with parts from all the rockets that carried them there. These remnants are often referred to as space junk, space trash or orbital debris. The debris ranges in size from 1-10 centimetres and there are estimated to be around half a million pieces with an additional 23,000 fragments bigger than 10 centimetres. These larger pieces can be observed and tracked from the ground. The waste is found in all zones of the Earth's orbit: low Earth orbit, which is within 2,000 kilometres of the Earth's surface; medium orbit, which is between 2,000 and 36,000 kilometres from the Earth's surface; and high orbit, which is beyond that. Most satellites are in low Earth orbit, as is the International Space Station (ISS). The problem is that most of the space debris is found there too and this is becoming a huge problem.

Some of the debris in low Earth orbit is eventually captured by the Earth's gravity and burns up when it enters the Earth's atmosphere or reaches its surface. However, most of the space junk stays in low Earth orbit and this can have several unwanted consequences. In 2009, almost 500 miles above Siberia, there was a collision between the obsolete Russian satellite Cosmos 2251 and the working US communication satellite Iridium 33. The satellites collided with each other at a speed of 11.7 kilometres per second and produced more than 2,000 pieces of debris. This was the first time two satellites were actually observed hitting each other in space, and the fragments from that collision could be seen spreading out over a very wide area over the following months.

Even though the area within low Earth orbit is vast, the speed at which pieces of junk travel means that they are deadly at the infrequent times they encounter another object. In 2006 a small piece of space junk hit the ISS and damaged one of its windows. Later, in 2014, the ISS had to make an emergency manoeuvre to avoid a piece of junk from the Russian Cosmos 2251 satellite smashing into it. The potential disaster was only averted because a supply vehicle that was docked with the space station fired its thrusters and raised the ISS by one kilometre out of the path of the space junk. This example illustrates the first problem with the debris: satellites need to carry out important work but are in constant danger of being damaged or destroyed. The ISS was designed to withstand impacts from debris up to one centimetre in size but in order to prevent it being hit by larger objects, scientists have to watch for space junk and try to move the station out of harm's way if necessary; the lives of the people on board could be at risk so it is extremely important to monitor the paths of the pieces of debris. However, it is very difficult to accurately plot the course of a debris fragment and so the ISS is only moved when there is probability of a strike. The junk from Cosmos 2251 was spotted only six hours before it passed within three kilometres of the ISS's position. As debris is broken into smaller and smaller pieces, tracking it becomes increasingly difficult.

The second problem is what happens when we launch satellites and rockets in the future. Some scientists describe space junk as an umbrella or ring around the Earth, which any future launch will need to punch through to go into space. No one really knows how bad the problem has to get before it prevents us putting objects into space or makes it very expensive to do so. The astrophysicist Donald Kessler, who used to work for NASA, calculated that if there is enough junk in orbit, collisions between pieces would create high-velocity smaller pieces of debris that would then hit even more objects, resulting in a chain reaction, producing more and more destructive pieces of debris. The problem is made worse when satellites remain in space after their working lives or when they are destroyed deliberately. An anti-satellite test in 2007 destroyed an obsolete weather satellite, creating 3,000 pieces of space debris, and a missile strike in 2019 scattered thousands more pieces into orbit. The gradual accumulation of space junk caused by debris colliding and creating more junk is called the Kessler syndrome and it will build up over the next 100 years. Eventually, the time between collisions will become shorter and shorter, and it is predicted that a cloud of deadly space junk will circle the planet.

Kessler believes that we need legislation that requires countries to build satellites that re-enter the atmosphere after their mission has ended and impose penalties on countries that do not do this. The problem is that the damage is already done and even if everyone keeps to the rules, collisions are still happening and the amount of debris is growing. This points to a second aspect of the potential solution: clean up the biggest pieces. The larger debris could be tracked and removed; Kessler believes that if we could take just five objects per year out of orbit, the problem would stabilise. Although this sounds simple, satellites travel at great speeds and some are very large. Ideas for dealing with inactive satellites include removing them using harpoons or nets based on the ISS. A satellite service station that would repair satellites and extend their working lives has also been proposed. Whichever solution is brought forward, however, it will need international cooperation and this could be more difficult to achieve than catching the wayward satellites.