Scientists at St. Petersburg State University have calculated how to protect the planet from a collision with a dangerous asteroid using a low-thrust engine. To do this, it must be installed either on a space body threatening the Earth, or on a "gravitational tractor" - so far a theoretical apparatus for changing the trajectory of objects with the help of gravitational action.
The material about this was published in the journal Astronomy Reports. The idea of saving the Earth from deadly asteroids excites not only Hollywood filmmakers, but also scientists around the world. Their fears are understandable - provided that the celestial body is relatively small, about 20 meters in diameter, a meeting with it could lead to a repetition of the Chelyabinsk scenario. But if the diameter is the same as that of the Tunguska space body, about 100 meters, the consequences will be equivalent to the explosion of several atomic bombs. If such an asteroid falls into the desert, nothing terrible will happen, but when it hits the city, it will turn it into ruins.
“One of the ways to fight asteroids is to hit a dangerous celestial body with a rocket. As a result, a large impulse should appear that will cause the asteroid to change its orbit. This path is suitable for bodies whose diameter does not exceed 100 meters,”notes the first author of the article, head of the Department of Celestial Mechanics of St. Petersburg State University Konstantin Kolshevnikov.
The most radical method is the explosion of an asteroid with a nuclear bomb. If the diameter of the body does not exceed 100 meters, it can be destroyed. If the dimensions are larger, the explosion will not destroy the entire asteroid, but the reactive force that has arisen will help change the trajectory of the remaining part and secure the planet. However, if the body is already flying to Earth, this method will not work.
The fact is that most asteroids, before hitting the planet, approach it several times. Thus, after the next rapprochement, several years may pass before the body will fly aimingly towards the Earth. At this time, it also needs to be blown up. Only in this way, the expert notes, it will be possible to ensure that the debris will scatter in space and will not threaten humanity. However, the likelihood that the asteroid will fly to Earth "without warning" still exists.
A group of scientists from St. Petersburg State University calculated the possibility of using a peaceful method of dealing with asteroids, which excludes explosions and collisions with rockets. Astronomers believe that it is possible to deflect a cosmic body from the orbit of a collision with the Earth using a low-thrust engine. “The aim of the study was to establish the fundamental possibility of using such a method. According to our calculations, asteroids up to 55 meters in diameter with an engine thrust of 1 newton can be deflected in about one year. If the body is up to 50 meters, then with a thrust of 20 Newtons it can be deflected in a month. If the diameter is up to 150 meters, and the engine thrust is 20 Newtons, it will take a year to complete the operation,”says Konstantin Kolshevnikov.
Scientists have created a model problem, according to which the engine provides constant tangential acceleration.In this case, the impulse is directed tangentially to the trajectory of the asteroid and, if necessary, increases or decreases the speed of the body. As a result, the asteroid is warmed up with the Earth. In order to change the direction of the body's movement more strongly, more powerful motors will be needed. However, according to the expert, the low-thrust engine is the most profitable option, taking into account fuel consumption.
Another question is how to install the engine on a space body. The matter is further complicated by the fact that the asteroid is constantly rotating. This task requires a separate solution and new calculations. However, it can be circumvented with a "gravity tractor". “Using a gravity tractor is like pulling yourself up by your hair. Suppose there is a relatively large asteroid, say, 100 meters in diameter. A spacecraft flies by next to it and stops relative to this body.
As a result of gravitational attraction, it begins to fall on this asteroid. Here you need to turn on the engine so that the device goes to the side. As a result, it pulls this large asteroid with it. It turns out the same thing - low thrust. "Traktor" is also good because the rotation of the asteroid does not matter. If you mount the engine directly on the asteroid, it will rotate with it. But the tractor will not rotate,”explains Konstantin Kolshevnikov.
Moreover, both spacecraft - the "gravitational tractor" and the low-thrust engine, which is supposed to be fixed on the asteroid, exist today only in theories and models. “Humanity may suddenly face an unforeseen danger. Could anyone have predicted the coronavirus pandemic? Or the fall of the Chebarkul meteorite? It is impossible to know in advance what resources will be required to save humanity next time. The advancement of science can help to cope with such threats. Moreover, it is especially important to develop precisely the fundamental science,”says Vladimir Titov, another author of the article, associate professor of the Department of Celestial Mechanics of St. Petersburg State University.
The continuation of the study will require more serious calculations. However, mankind still has time for this, scientists are convinced. Together with Konstantin Kolshevnikov and Vladimir Titov, postgraduate students of the Department of Celestial Mechanics of St. Petersburg State University Danila Milanov and Kristina Oskina worked on the article. The study was supported by a grant from the Russian Science Foundation.