Wherever mankind goes there is always a common footprint which we — humans leave everywhere — debris. Unfortunately, even the space is not an exception.
What Is the Problem?
The satellites which fly around our planet have a speed of around 8 km/s. This speed is eight times the speed of a bullet. Tiniest sand grain at this speed in the space has enough energy to penetrate and damage the spacecraft. A ten grams bolt at speed of 10 km/s is equivalent to an explosion of an anti-tank warhead. Any satellite or spacecraft will be completely destroyed. Therefore, dealing with space debris is a very serious issue.
The “Gravity” movie actually shows the collision of the spacecraft with debris. Therefore, the ISS has included tracking of space debris in the maintenance program and in case of a possible meeting, the ISS changes its orbit in order to prevent collisions.
Today, if you are launching a rocket you have to try to avoid making contact with anything on the way to the orbits. In order to do this special time periods are chosen so that the orbit of the apparatus does not intersect with space debris. Moreover, the duration of these periods is only calculated for the fragments which we know and “control”. While there are around ten thousand objects in the near-Earth orbits which are “in control”, in total there are around six hundred thousand. The rest of the debris is so small that it is impossible to determine their orbits with our technology. There was no need to worry about such things before.
Scientists believe that the accumulated debris might one day lead to a war on Earth. If the orbital debris threaten the military satellites it will be hard to prove that the collision was an accident. This issue became of current interest after the Chinese satellite debris pushed the Russian “Blitz” (which is designed to work with the international system of laser sensing) off the orbit in 2013.
And each such collision creates new litter, which increases the possibility of a new encounter and thus the chances of beginning a chain reaction. This kind of “chain reaction” even has a name — the Kessler syndrome. The major problem of this syndrome is the “domino effect”, as the collision of two large objects creates even more clashes, but this time they are smaller. And each of these fragments is able to run into other debris or a spacecraft which will cause a chain reaction and the birth of more and more debris. After a large encounter (for example a collision between a space station and a satellite) the number of created fragments could make the near-Earth space completely unfit for flights!
What Creates These Fragments?
The spacecraft launches create numerous fragments accompanied by its launch: bolts, caps and last stages of the launch vehicles. From time to time spent rockets explode or collide and, as a result, create a large amount of tiny fragments.
Almost a third of all debris appeared thanks to two events. The first is the fault of China, which conducted an anti-satellite missile test and deliberately shot down its own satellite, creating three thousand fragments.
The second event occurred in 2009, when satellites Iridium 33 and Kosmos-2251 collided. As a result a cloud of debris was formed from the two thousand fragments which led to a threat of collision with the ISS. Fortunately, it was possible to change the dangerous flight trajectory of the station and avoid collision, thanks to the cargo ship Georges Lemaître of ESA. These fragments could bring great harm to the ISS and cause human casualties.
It is necessary to launch the spacecraft so that as little garbage is left in the orbit as possible. So does SpaceX with their multiple stage launch vehicles.
When a space satellite fails it has to leave the orbit which is used by other working satellites. So now there is even a new term: the “graveyard orbit” — an area where all space debris, if possible, is moved and where is kept. It is located 200 km above the geostationary orbit. According to NASA the “graveyard orbit” has more than eight thousand used satellites. This is an international problem, which is being discussed on meetings by space agencies representatives, but space exploration will continue to use rockets since there is no other way at this moment.
The amount of debris is growing and this problem needs to be solved. If waste is not collected it will fly until it collides with something or will not burn in the atmosphere. But it will not happen soon — in a thousand and perhaps in a hundred thousand years.
The amount of space junk has increased substantially in recent decades. The pollution process of the near-Earth orbit over the last sixty years:
The problem has to be solved in several stages. At first, more sensitive telescopes should be created which will allow the observation of these space objects. The next step will be improving the protection of satellites and space stations against shocks and increasing their maneuverability. It is also important to think how to completely avoid creating new junk.
Many ways are offered in cleaning the space: nets and harpoons, space balloons, tugs, laser redirection to Earth, space garbage trucks. But let’s not discuss them as they are either ineffective or very expensive.
But a new project of Japanese scientists from the Riken research institute is quite promising. They suggest to use a powerful laser to shoot down the debris from the orbit.
The first step towards the realization of this idea would be the attempt to install a twenty centimeters telescope and a 100 fiber laser on the ISS. The laser beam should change the flight trajectory of a fragment and then it should enter the Earth’s atmosphere and burn up in it. Scientists claim that the accuracy of such system would be very high as it would shoot down objects as small as one square centimeter!
If the Japanese experiment succeeds, a full-size laser system for the destruction of space debris will be installed on the ISS. Its dimensions will be more than that of the experimental: the telescope will have a diameter of three meters and the laser will consist of ten thousand fibers. With such a laser gun it will be possible to shoot down debris at a distance of up to one hundred kilometers from the ISS.
In the future it is possible to launch a spacecraft, the sole purpose of which would be to clean space debris around the Earth.
What Danger Carries Space Debris to Earth?
If you got the impression that space debris are dangerous only to satellites and spacecrafts, it is not so. Smaller pieces of junk fall into the atmosphere on a daily basis, while larger fall several times a month. The largest objects, which are situated in low-Earth orbits, slow down gradually and enter the atmosphere after a while. According to NASA almost every year some parts of satellites and rockets reach Earth.
In addition to debris created by humans, there are many small objects in the Solar System in general. When a “falling star” is burned in the night sky you are actually seeing these small objects. If the object is larger, then happens what has occurred in Chelyabinsk in 2013 or in 1908 in Tunguska taiga — two catastrophic events. And if the object is much larger then we can recall the extinction of the dinosaurs sixty-five million years ago.
There may be even more fatal consequences when the crust of the planet is destroyed, as probably happened on Venus, where the entire planet is made up of a solid lava field. And there may be even worse as in our Solar System there is an asteroid belt between Mars and Jupiter which is likely to be the fragments of a destroyed planet by an asteroid.
The danger is very serious and a lot of attention is paid to research probable solutions at the highest levels of international cooperation. In particular, there is a special commission at the UN which is working on this issue. There is a group on the study of space risks in the Russian Academy of Sciences in Russia.
The astronomical accuracy is high: we can look very far, we can measure distance to planets, their mass, but this accuracy is not enough to solve this problem.
Today big efforts are made to clean up the littered by mankind space. Let’s hope that in the near future it will be much cleaner there. We hope that when people will finish with the cleaning of space, we will direct our efforts on cleaning our Earth. In the meantime, while waste is not utilized, it is possible to see a rotating visualization of 150 thousand objects around the Earth.