Kessler Syndrome as seen by an artist
Everything will be bad
The numerical expression of technological progress, the fact that the number of satellites is increasing, also has its dark side. By no means every apparatus, at the end of its active life, goes culturally into a special burial orbit so as not to disturb anyone. Further, when the satellite is separated from the upper stage or the last stage of the launch vehicle, they are both in the target or transfer orbit, and not every upper stage then goes into its disposal orbit. The design features of the rockets also lead to the fact that several objects of space debris may appear on one launched vehicle. As a result, for 2020 the number of tracked objects in orbit approached 21 thousand.
NASA ODPO Image
And the calculations of the amount of space debris are pessimistic - satellites and spent stages sometimes explode (more precisely, they burst when some tank, in which pressure remains, collapses) and, so far rarely, collide with each other. Depending on the settings of the model, the amount of garbage grows slowly or quickly. And it's important to note that these models do not yet account for the deployment of the huge space constellations Starlink, OneWeb, Amazon's Project Kuiper and several possible Chinese counterparts.
NASA calculations in the LEGEND model
Dangerous intersections
With all the seriousness of the threat of an increase in the amount of space debris that threatens us, there are two bright facts that are most evident as the mistakes of the film "Gravity". First, there is no need to fear an instant explosive growth in the amount of space debris. Models show a gradual increase in the number of satellite collisions in orbit. According to calculations by the European Space Agency, a serious collision of objects in orbit occurs at a frequency of approximately every five years. And the frequency of five collisions per year, which makes it almost impossible to launch new satellites, is expected around the 22nd century. Secondly, such collisions will not knock out all satellites in all orbits; there are still relatively safe routes in space, as well as very dangerous intersections.
Concentration of satellites in specific orbits, source
Low Earth Orbit . Its main advantage is that the lower the orbital altitude, the faster the satellite will brake against the remnants of the atmosphere and burn up in its dense layers. For altitudes up to 600 km, depending on the area and mass of the device, the time can vary greatly, but the estimates of the European Space Agency say that in 25 years any debris will disappear without our participation.
Orbital distribution of objects in the MASTER model of the European Space Agency
Polar and sun-synchronous orbits... Orbits with an inclination of 90 ° and an altitude of 800-1200 km are now the most dangerous places in space. First, many satellites have already been launched there - these orbits are very convenient for observing the Earth. Further, the orbits intersect above the poles, where the danger of collision increases many times, and collision is possible at any angle, including head-on, when maximum energy is released, and the debris is scattered on a variety of trajectories. And, finally, debris from the 2009 collision is already flying here, when the long-broken Soviet satellite Kosmos-2251 and the working Iridium-33 collided on intersecting courses and formed 2,296 visible debris. As a matter of fact, this collision took place in the most probable place - near the pole at an altitude of 789 km.The constellations of satellites will make this place even more dangerous - OneWeb will have to operate in a polar orbit with an altitude of 1200 km, and Starlink's plans indicate orbits with heights of 1100, 1325, 1130 and 1275 km, and the company has already been asked to limit itself only to devices at an altitude of 550 km.
Navigation satellites in medium orbits . GLONASS satellites are located in three planes at an altitude of 19400 km, GPS - 20180, Beidou - 21500 and Galileo - 23222. This is enough to form visible density bursts on the graphs, but even taking into account the broken devices, the probability of collision here is very small - There are not so many satellites yet, but there is still enough space.
Geotransition orbits . Density bursts noticeable on the graphs give geostationary transfer orbits, in which the last or penultimate stages of the rockets that bring satellites into geostationary orbits remain. Different required characteristic velocity (delta-V) gives as many as three noticeable groups - from Baikonur, Cape Canaveral and Kourou. There are no living vehicles here, only old debris, and so far the probability of a collision is relatively small.
, NASA
... It is very convenient for the operation of relay satellites and meteorological devices that observe the whole hemisphere, therefore there are relatively many satellites, and the fact that it has been used for a long time means that there is enough old broken debris there. Forces that have a disturbing effect on the orbit and require fuel consumption to maintain it, here, in a peculiar sense, help to "remove debris" - the Moon that is left without fuel or broken devices is gradually dragged into orbit with an inclination of 15 °, and a slight asymmetry of the Earth places debris in the area one of two equilibrium points. But here there are objects in orbit with high eccentricity (elongated, not circular), so collisions with a relative speed of up to 4 km / s are possible. It also has its own burial orbit a little higher,and an increasing proportion of satellites live to the point of running out of fuel, spending its last drops on civilized care in the cemetery. Also, the uniqueness of the geostationary orbit is that a special scavenger satellite can actually work here (for example, in a polar orbit, it could put things in order only in vehicles flying in the same plane).
The fight for cleanliness
As they say, posing and understanding a problem is already half of the solution. The fact that Kessler syndrome will develop slowly means that humanity has a chance to cope with it. It will not be easy - objects already in space will gradually generate more and more debris by themselves, and no one will agree to introduce a moratorium on the launch of new satellites. But the problem is not unsolvable either - in recent years, a variety of space debris removal projects have appeared - from sails and cable systems to extravagant ideas like nets.or recycling garbage into fuel for scavenger flights. There are no standards and mandatory requirements yet, but we can hope that in the foreseeable future, vehicles will begin to receive reliable systems that can de-orbit even broken satellites. if he doesn't want to be left without access to space.