Meeting in the cosmic ocean
The first satellite collision in Earth history occurred on February 10, 2009. The chances of this happening were slim to none; It’s like launching two motorboats into the ocean with an infinite amount of fuel, setting a random route, and waiting for them to meet. In space, the chance of collision is even less due to the presence of an additional coordinate height.
It turned out that the collision between Cosmos 2251 and Iridium 33 was linked to Russia. Kosmos-2251 was the domestic military communications satellite of the old Strela-2M system. It lasted only two years after its launch in 1993 and has remained in orbit as space debris ever since. Iridium 33, on the contrary, was an active civilian communication device of the American provider company of the same name. It was also launched by Russia with a Proton rocket from the Baikonur Cosmodrome in 1997. Satellites collided over the territory of the Russian Federation in the Taimyr Peninsula region.
Both devices were orbiting at an altitude of 700-800 km, inclined at almost 90 degrees relative to each other. And as a result, they flew towards each other at total speeds of over 10 km/h. predictions physicists released energy equivalent to the explosion of one to five tons of TNT.
It was not a shame that Kosmos-2251 was not working, but the loss of Iridium 33 created the risk of communications blackout. stated operator company. It is believed that such a collision should completely destroy both vehicles, but it turned out that this was not the case. Iridium satellites created an artificial astronomical phenomenon: periodic bright flashes appeared in the sky as the Sun reflected from the huge antennas. CCTV camera succeeded to change such a flash from Iridium 33 after the collision, which means that it survived at least partially, although of course it lost its functionality.
Following the incident, neither party sought damages or compensation from the other; The incident was considered an unfortunate accident.
Long term results
The loss of a single spacecraft that could break down on its own is not that significant. A much more serious problem was the cloud of fragments left by the satellites; 1,668 of them were Russians and 628 were Americans. Each fragment retained its original orbital velocity and added random momentum from the collision and explosion. Some began to cross the orbit of the ISS, and in 2012 one of the pieces passed within a hundred meters of the station. It was small and could not destroy all the orbital modules with a single blow, but just in case, the astronauts took up space in the descent module so that they could return to Earth in case of an emergency.
The main problem with parts of destroyed vehicles is that they remain in orbit for a long time. Less than half of the tracks in seven years (until 2016) burned in the atmosphere. Now, according to the website Space-Track.com, 916 and 212 parts remain from the devices.
Therefore, spacecraft operators try to track their future approaches to buy time to avoid them. But not all satellites have exact orbital parameters, and in the event of a collision in 2009, algorithms guessthat they will disperse 500 meters away from each other. In total, Iridium received about 400 warnings a week about possible collisions, but the company’s president evaluated The probability of such an event occurring is 1 in 50 million.
Lasers and capture nets
The number of spacecraft is growing very rapidly every year: for example, the Starlink operator alone currently has more than five thousand satellites in low orbits (altitude of about 550 km), and there will be many more in the future. The more spacecraft there are, the more debris they leave behind and the higher the risk of collision. If this trend continues, near-Earth orbit will be unsuitable for the deployment of satellites, let alone manned stations.
In this context, engineers have proposed many projects to clear orbit. For low-orbit satellites, these are not needed at all: Starlink, for example, already uses plasma engines to prevent crashes. Without their work, the atmosphere will gradually lower the orbit so that the devices will burn up in five to ten years.
However, in higher orbits devices can exist for tens and hundreds of years. If they are disorganized and do not have time to orient themselves in the dense layers of the atmosphere or in grave orbit, then only a “space janitor” can lift them. this name there is Various orbital tug projects capable of docking with a decommissioned satellite and pulling it into safe orbit.
More exotic projects involve the use of a mesh network like this project presented Russian Space Systems engineers. Their devices will capture not only large satellites but also cubesats (miniature and economical satellites)as well as debris and spent rocket stages that are extremely difficult to dock. After that, the “janitor” grinds the caught prey on millstones, turns it into powder and uses it as a fuel component to increase active working time.
There is a proposal to handle space debris in a non-contact manner using an “ion vacuum cleaner”. For example, such a project presented Scientists from Samara University.
“Approaching the selected garbage object from a distance of about ten meters, the cleaning device will direct the ion jet of the engine, called a plasma torch, at it. “The particles of the ion stream colliding with the surface of space debris generate a force that will be used to move the debris in the desired direction,” Alexander Ledkov, one of the authors of this idea, wrote in his monograph “Dynamics of Dynamics.” Control of Spatial Motion and Space Debris During Transport by Ion Flow.
Finally, the orbit of the debris can be changed using a ground-based or space-based laser. With calculations NASA’s current technology would allow the beam to shift its orbit by several meters per day due to photon pressure alone. A significant disadvantage of this method is the risk of destruction of the spacecraft under the influence of the laser, which will lead to the formation of smaller fragments that are more difficult to deal with.
In any case, it will be necessary to find ways to deal with space debris. In the 1970s, scientists predicted Kessler syndrome. According to this hypothesis, a collision of two satellites can create a mass of fragments, and with an overcrowded orbit, due to the domino effect, it can destroy other satellites into fragments, subsequent satellites, etc. becomes completely unfit for human use. Without a “space wiper” of one form or another, implementation of Kessler syndrome is almost inevitable.