Is space debris so dangerous? Where to start cleaning the orbits? What legal problems need to be solved for this? What projects are offered? The correspondent of "RG" is talking about this with Vladimir Agapov, a senior researcher at the Institute of Applied Mathematics. M. V. Keldysh, which is the head organization of the Russian Academy of Sciences on the space debris problem.
So, the leading space powers, from words about the danger of space pollution, finally decided to get down to business. The pioneers will be the Japanese, who will test such a cleaning system in February. But is it really so relevant? After all, the years go by, there is a lot of talk about the danger of garbage, but by and large no serious accidents have happened because of it. Maybe let it fly, and do not need to spend a lot of money?
Vladimir Agapov: Let's first figure out what, in fact, we are talking about. What is space debris? According to experts, more than 650 thousand different objects more than one centimeter in size revolve around the Earth. Of these, only large ones are currently tracked, more than 10 centimeters, of which there are about 22 thousand. The rest of the hundreds of thousands are incognito, "Mr. X". But there are even smaller ones, about a millimeter, their number is estimated at about 3.5 million objects.
The most unpleasant thing is that this armada is constantly growing. Not only because more and more vehicles are sent into space, which, in the end, also become garbage. The trouble is that the "dirt" itself is not passive. After all, the fragments flying with great speed collide with each other, are destroyed, giving rise to hundreds and thousands of new objects for many years. It is no coincidence that the ISS and other spacecraft are being withdrawn from the course of a probable collision with space mud with increasing frequency.
But when they talk about avoiding collisions, then we are talking only about sufficiently large fragments that are constantly tracked by special locators and telescopes. But there is much more small placer in orbit, which no one can track, but which is also extremely dangerous. It is known that after landing in the front windows of a number of spacecraft, microcracks of such a critical size were revealed that a complete depressurization of the spacecraft could just about occur. Realizing all these problems, the space powers have now dramatically intensified their work on combating space debris. Here time must not be wasted, the situation must not be brought to the brink, when the problem is overripe and it will be too late.
But the Japanese are already ready to be the first to start cleaning …
Vladimir Agapov: This is not entirely true. It is only about testing one of the many options. There is no doubt, it is important, but rather still, to draw attention to the problem. In fact, before taking on concrete projects seriously, it is necessary to take an inventory of all space debris. Where and what flies, how dangerous are these objects. At the moment, we do not have a complete picture. In low orbits, up to three thousand kilometers above the Earth's surface, about 80 percent of the debris "dangles", at high, and primarily geostationary, which is about 36 thousand kilometers above the Earth, and in intermediate elliptical orbits - the remaining 20 percent.
It would seem that we urgently need to take up low orbits, where the lion's share of debris has collected. But on the other hand, the geostationary orbit is no less important for us - after all, about 430 vehicles are currently operating on it, each costing tens, or even hundreds of millions of dollars. Thanks to them, we have the Internet, satellite TV and a host of other amenities. And unlike low orbits, there is only one geostationary, and we cannot lose such a unique natural resource.
That is, before you take up the space mop, you need to decide on priorities?
Vladimir Agapov: Of course. And it is not at all necessary to start with coarse dirt. It may turn out that it flies where there are no active devices. It is better not to touch such fragments in the near future, especially if they do not collide with each other. But it is not enough to single out a dangerous grouping, it is already necessary to understand in it what is most dangerous. That is, build a priority tree. And only after that start spending money on cleaning the orbits. Otherwise, the effect of all this cleaning will be scanty.
Or maybe, in parallel, the countries should agree so as not to litter at all? Stop pollution?
Vladimir Agapov: At the initiative of the UN, a number of such measures have been developed, agreed upon by various countries. There are some pretty obvious ideas here. For example, if a satellite or a rocket stage has worked out, then they either need to be taken out of this orbit to a lower one, from where, due to deceleration, they will descend and burn up in the atmosphere. Or even drown in the ocean. This applies to large objects, but there are much more trifles that are separated when the devices are launched and during operation - all kinds of nuts, bolts, etc. The obvious solution is to create designs so that nothing gets separated.
But the main supplier of garbage is explosions in orbit. The reasons are very different. Most often residual fuel explodes. The fact is that after the satellite is put into orbit, fuel components, including self-igniting ones, remain in the rocket stage. As long as the tanks are intact, nothing terrible happens, but if, say, a micrometeorite breaks through the wall, an explosion occurs, and the step shatters into thousands of small pieces. Therefore, after the completion of the flight program, it is recommended to open special valves in order to drain off the remaining fuel in the form of gases.
What projects are being proposed today in order to remove the accumulated garbage? How effective is the method that the Japanese will be testing?
Vladimir Agapov: The Japanese project assumes that a special satellite will launch into orbit and deploy an electrodynamic trawl. This is a metal mesh 300 meters long, 30 centimeters wide, and the thickness of the threads is about 1 millimeter. The trawl will move in orbit, generating a magnetic field and capturing some of the small debris. In a few months, the "seine" with the catch under the influence of the Earth's magnetic field will change its orbit and enter the dense layers of the atmosphere, where it will burn up.
The project is quite obvious, but the question is, will such a trawl collect a lot of garbage? Indeed, in spacecraft, not so many materials are used that are magnetized, mainly non-magnetic aluminum alloys, various dielectric films, and recently composite materials are used. Many other projects are being considered today. For example, it is proposed to use lasers. But this option immediately raises a lot of questions. How to aim the beam at a small object that no one sees? It is not clear. They say we will fight the visible. Let's say, directing a laser beam at it, we will push the object. But where? Who can predict where he will fly if he does not know the shape of the object, its mass, material? As a result of such an impact, the object can become even more dangerous, collide with some kind of working apparatus.
In my opinion, one of the most interesting ideas is the use of different braking systems. For example, after the end of its service life, the satellite throws out a "sail", "parachute" or just a large balloon that is inflated with gas. As a result, the area of the entire structure increases sharply, which greatly inhibits it. The device will quickly lower the flight altitude, enter the dense layers of the atmosphere and burn up.
In science fiction films, various manipulators have been operating in orbits for a long time, which remove and install satellites and other equipment. Are there such projects in the portfolio of scientists?
Vladimir Agapov: Of course. But they are technically perhaps the most difficult. After all, a large garbage object has a mass of up to several tons and rotates in a complex way, it is not controllable. Has tremendous momentum. How to capture it and not destroy either the manipulator or the spacecraft itself, on which the manipulator is installed? Complex technical problems have to be solved here.
3.5 million different space debris revolves around the Earth
But besides purely scientific and technical problems, there are other problems. After all, in this way, you can remove not only garbage, but also other people's spacecraft, even working ones. That is, in essence, these are dual-use systems - civil and military. Therefore, there is an important legal aspect in the fight against space debris. On the one hand, space debris flies in orbit, but on the other, even "dead" objects that have expired are owned by someone. And an attempt by one of the countries, even with the best intentions, to remove someone else's object, can lead to very serious conflicts. This means that such operations must be carried out in a coordinated manner with all participants so that additional risks do not arise. The world community is working on these issues today, because everyone understands that any sudden movement can lead to unpleasant consequences for everyone. By the way, even if we suddenly stop flying into space altogether, the amount of debris will still grow. Estimates show that only due to mutual collisions of already flying fragments in 20-30 years, the increase in debris will exceed its loss as a result of natural processes of deceleration in the upper atmosphere and de-orbiting.
reference
Today, the total mass of space debris in orbit is about 6,700 tons. Its density at altitudes of 800-1000 kilometers has reached a critical level. Due to a collision with it, the probability of losing a spacecraft for a period of 10-15 years is already higher than the probability of losing a spacecraft due to a failure of onboard systems. The probability of collision of two large objects in low orbits is estimated as one event in 15 years. Even 10 years ago, this figure is 4 times lower.
