Remember, we recently made fun of the headlines that a bunch of asteroids that are terribly dangerous for our planet are flying towards us! Laughter laughter, but if you seriously delve into this information, then everything turns out to be not as rosy as we would like.
No one disputes the fact that a really dangerous asteroid can change its orbit and begin to threaten the Earth. And what to do? After all, we will not even notice it in time. Here a block with a diameter of 620 meters was noticed just 20 days before arrival. Well, you noticed, and what's next? After reading all sorts of options, you basically catch yourself thinking that something incredibly fantastic like the movie "Asteroid" is being proposed, but no one has any idea how long, by whom and how it will be implemented. Further it gets worse. Few people imagine the consequences of these proposals, because no one has tried anything and everyone operates with the words "probably" and "maybe".
In reality, we have rather limited capabilities, for example:
In theory, anti-missile defense (ABM) systems such as the A-135 / A-235 missiles that defended Moscow can detect and attack a small asteroid at an altitude of 850 kilometers. Some of these missiles have nuclear warheads for transatmospheric areas. In theory, even a weak warhead is enough to initiate the destruction of a body like the Chelyabinsk or Tunguska meteorite. If it disintegrates into fragments less than ten meters, each of them will burn high in the atmosphere. And the resulting blast wave will not even be able to knock out the windows in residential buildings.
However, the peculiarity of meteoroids and asteroids falling to Earth from space is that most of them move at speeds of 17-74 kilometers per second. This is 2-9 times faster than the A-135 / A-235 interceptor missiles. It is impossible to accurately predict the trajectory of an asymmetric body and an unclear mass in advance. Therefore, even the best anti-missile missiles of earthlings are not able to hit the "Chelyabinsk" or "Tungus". Moreover, this problem is unavoidable: chemical-fueled rockets physically cannot provide speeds of 70 kilometers per second or higher. In addition, the likelihood of an asteroid falling precisely on Moscow is minimal, and other large cities in the world are not protected even by such a system. All this makes the standard missile defense system very ineffective for dealing with space threats.
Bodies less than a hundred meters in diameter are generally very difficult to spot before they begin to fall to Earth. They are small, usually of a dark color, which makes them difficult to see against the background of the black depths of space. It will not work to send a spacecraft to them in advance to change their trajectory. If such a celestial body can be seen, it will be done at the last moment, when there is almost no time left to react. So, the August (2016) asteroid was noticed just twenty hours before the approach. It is clear that he “aim” more precisely - and there would be nothing to stop the heavenly guest. Conclusion: we need some other means of "close combat", allowing to intercept targets many times faster than our best ballistic missiles.
Promotional video:
Starting in 2016, we will be able to see most of the bodies over 120 meters in diameter. It was in 2016 that it was planned to commission the Mauna Loa telescope in Hawaii. It will be the second in the University of Hawaii's Asteroid Terrestrial-impact Last Alert System (ATLAS). However, even before its introduction, ATLAS had already seen its first near-Earth asteroid with a diameter of less than 150 meters.
However, even a previously discovered asteroid hundreds of meters in size will not be able to quickly "deploy" in such a way that it avoids collision with the Earth. The problem here is that its kinetic energy is so high that a standard thermonuclear warhead simply cannot provide an explosion on impact. A contact strike at a collision speed of more than 300 meters per second will physically crush the elements of a nuclear warhead even before it has time to explode: after all, the mechanisms that ensure the explosion take time to operate. In addition, according to the calculations of specialists from NASA, even if the warhead miraculously explodes (hitting the asteroid "from behind", on a catch-up course), it will hardly change anything. An object hundreds of meters in diameter has such a curvature of the surface that more than 90 percent of the energy of a thermonuclear explosion will simply dissipate into space,but will not go to the correction of the asteroid's orbit.
There is a method of overcoming asteroid curvature protection and speed protection. After the fall of the Chelyabinsk body, NASA presented the concept of the Hypervelocity Asteroid Intercept Vehicle (HAIV). This is a tandem anti-asteroid system in which the head is a non-nuclear blank. When correcting the orbit of the asteroid, it will hit it first, and at a speed of about ten kilometers per second, leaving behind a small crater. It is into this funnel that the second part of the HAIV is planned to be sent - a warhead with a yield of 300 kilotons to two megatons. Exactly at the moment when the second part of HAIV enters the funnel, but has not yet touched its bottom, the charge will detonate, and the bulk of its energy will be transferred to the victim asteroid.
Here is more about Apophysis and when it will collide with the Earth
Researchers from Tomsk State University recently worked on a similar approach to dealing with medium-sized asteroids on the Skif supercomputer. They simulated the detonation of an Apophis-type asteroid with a megaton nuclear warhead. At the same time, it was possible to find out that the optimal moment of detonation will be the one when the asteroid passes at some distance from the planet even before the last approach to the planet. In this case, the exploded debris will continue its way away from the Earth. Accordingly, the danger of a meteor shower from fragments of a celestial body will be reduced to zero. And this is important: after a nuclear explosion of the required (megaton) power, the debris of the asteroid will carry more radiation threat than Chernobyl.
At first glance, HAIV or its analogs will close all the problems. Bodies less than 300 meters away after such a double blow will fall to pieces. Only about a thousandth of their mass will enter the Earth's atmosphere. Bigger bodies, especially metal asteroids, won't give up so easily. But even in them, the evaporation of matter from the funnel will give a significant impulse, significantly changing the original orbit. According to calculations, one such anti-asteroid "shot" should cost 0.5-1.5 billion dollars - sheer trifles, less than the cost of one rover or B-2 bomber.
One problem is that it is unreasonable to rely on a weapon that has never been tested at least at a test site. And NASA currently receives about one-fortieth of US military spending annually. With such a modest rationing, the agency is simply not in a position to allocate hundreds of millions for testing HAIV. But even if such tests were carried out, there would be little sense from them. The same ATLAS promises to warn about the average size of the asteroid in a month, or even a couple of weeks. It is impossible to build HAIV from scratch in such a time, and keeping it on alert is too expensive for NASA's modest, by American standards, budget.
Mankind's prospects in the fight against large asteroids - especially over a kilometer - look much better at first glance than in the case of small and medium ones. Kilometer objects in most cases can be seen through already deployed telescopes, including space ones. Of course, not always: in 2009, near-Earth asteroids with a diameter of 2-3 kilometers were discovered. The fact that such discoveries are still taking place means that the likelihood of suddenly detecting a large body approaching our planet is even at the current level of development of astronomy. However, it is quite obvious that such objects are decreasing every year and in the foreseeable future they may not remain at all.
Even our country, despite the lack of allocated government funding for the search for asteroid threats, plays a significant role in tracking them. In 2012, the group of Vladimir Lipunov from Moscow State University created a global network of MASTER robotic telescopes, covering both a number of domestic and foreign instruments. In 2014, the MASTER network opened the four-hundred-meter 2014 UR116, potentially capable of colliding with our planet in the foreseeable future.
However, large asteroids have their own unpleasant characteristics. Suppose we learned that the seventy-kilometer 55576 Amic with a potentially unstable orbit is heading towards Earth. It is possible to "process" it with a tandem HAIV with a thermonuclear warhead, but this will create unnecessary risks. What if, in doing so, we provoke the loss of one of its loose parts by the asteroid? In addition, large bodies of this kind have satellites - they themselves are not so small. A nearby explosion is capable of provoking a sharp change in the satellite's orbit, which can lead the disturbed body anywhere - and to our planet too.
Let's give one example. The aforementioned MASTER telescope network a year and a half ago discovered 2014 UR116 less than 13 million kilometers from Earth. Had he headed towards the planet even at a moderate speed of 17 kilometers per second - and in less than ten days, their paths would have crossed. With a convergence speed of 70 kilometers per second, it would have been a matter of days. If a thermonuclear explosion splinters off a series of debris from a multi-kilometer body, one of them can easily slip away from our attention. And when it appears in the field of view of telescopes a few million kilometers from us, it will be too late to start production of another HAIV interceptor.
Certainly, with large bodies, the collision with which is known in advance, you can interact safer and without an explosion. So, the Yarkovsky effect constantly changes the orbit of almost all asteroids, and without the danger of their dramatic destruction or loss of satellites. The effect is that the part of the asteroid heated by the Sun inevitably falls into the unlit night zone during its rotation. There it gives off heat to space through infrared radiation. The photons of the latter impart an impulse to the asteroid in the opposite direction.
It is believed that the effect is easy to use to divert large "dinosaur killers" from a dangerous trajectory of approach to Earth. It is enough to send a small probe to the asteroid carrying a robot with a balloon of white paint. Spraying it on a large surface, you can achieve a sharp change in the Yarkovsky effect acting on the body. Thus, a white surface, for example, emits photons less actively, weakening the force of the effect and changing the direction of the asteroid's motion.
It may seem that the effect is in any case too small to affect anything. For example, for an asteroid Golevka with a mass of 210 million tons, it is approximately 0.3 Newtons. What can such a "force" change in relation to a celestial body? Oddly enough, for many years the effect will be quite serious. From 1991 to 2003, the trajectory of Golevka deviated from the calculated one by 15 kilometers because of it.
There are other ways to slowly remove a large body from a dangerous orbit. On the asteroid, you can install a solar sail from a film or throw a carbon fiber net over it (both options were worked out by NASA). In both cases, the light pressure of the sun's rays on the celestial body will increase, which means that it will gradually move in the direction from the Sun, avoiding collision with us.
Sending a probe with paint, sail or net would mean a long-range space mission that would cost far more than launching a tandem HAIV. But this option is much safer: it will not create unpredictable changes in the orbit of a fired large asteroid. Accordingly, it will not threaten the separation of large fragments from it, capable of falling to Earth in the future.
It is easy to see that such a defense against a large asteroid has its weak points. Today, no one has a finished rocket with a robot painter; it will take many years to prepare it for flight. Plus sometimes space probes break. If the device "glitches" on a distant comet or asteroid, like the Japanese Hayabusa on the asteroid Itokawa in 2005, there may simply not be time left for a second attempt at painting on a cosmic scale. Are there no more reliable methods that exclude unsafe thermonuclear bombardment and sending not always reliable probes? There are, but they are again very incredibly fantastic and it is incomprehensible when realizable.
In Western countries, the situation is aggravated by the fact that no administration plans space programs for more than a few years. Everyone is justifiably afraid that upon the transfer of power, the new administration will immediately close the expensive programs of its predecessors. So there is no point in starting them. In states like the PRC, everything is formally better. The planning horizon there is pushed far into the future. However, in practice, they do not have either technological (China) or financial (Russia) capabilities to deploy tandem systems like HAIV or orbital laser arrays like DE-STAR.
And what about the USA? And last year the USA decided to independently create an anti-meteorite defense. Well, of course! They will be like "Captain America" to defend the Earth from the enemy themselves! Well, like in Hollywood movies, you remember. The result will be "zilch", but the main thing is to loudly declare yourself.
All this means that the above projects will begin their implementation only after a multi-megaton explosion of an unnoticed body over a densely populated area. Such an event - which, in general, is bound to happen sooner or later - will definitely cause human casualties.
Only after that we can confidently await political sanctions for the construction of anti-asteroid defense systems both in the West and, possibly, in Russia.
Well, in the net result - if anything, we are finished. Right?