Today, 8 March 2016, at a distance of about 22 000 kilometers from Earth (14 000 kilometers below the orbit of geostationary satellites), 2013 TX68 asteroid with a diameter from 25 to 50 meters will pass. He has a unsteady, poorly predictable orbit. Subsequently, he will approach the Earth in 2017, and then in 2046 and 2097. The probability that this asteroid will fall to Earth is vanishingly small, but if this happens, the blast wave will be twice as powerful as the one that the Chelyabinsk meteorite produced in 2013 year.
So, 2013 TX68 is not particularly dangerous, but the asteroid threat to our planet with this relatively small “cobblestone” is not exhausted. In 1998, the US Congress instructed NASA to locate all nearby asteroids that are as large as one kilometer across and capable of threatening Earth. According to the classification of NASA, all small bodies fall into the “nearby” category, including comets that approach the Sun at a distance equal to at least 1 / 3 astronomical unit (AU). Recall that A.e. - This is the distance from Earth to the Sun, 150 millions of kilometers. In other words, in order for the “visitor” not to cause concern to earthlings, the distance between it and the solar orbit of our planet must be no less than 50 million kilometers.
By the year 2008, NASA as a whole had fulfilled this assignment, finding 980 similar flying debris. In 95%, the trajectories were precisely defined. None of these asteroids poses a threat in the foreseeable future. But at the same time, NASA, based on the results of observations obtained using the WISE space telescope, concluded that at least 4700 asteroids with a size of at least 100 meters pass by our planet. Scientists were able to find only 30% of them. And, alas, astronomers were able to detect only 1% of the number of 40-meter asteroids, periodically "walking" near the Earth.
In total, as scientists believe, in the Solar System they "run hither" to 1 a million asteroids located close to Earth, of which only 9600 were reliably detected. If the “cobblestone” size 100 – 150 meters passes at a distance of 0,05 a.e. from our planet (which is approximately 20 of the Earth-Moon distances, that is, 7,5 of millions of kilometers), according to NASA classification, it automatically falls into the category of “potentially dangerous objects”. Those of the American Aerospace Agency currently has about 1600 units.
How big is the danger
The likelihood of the fall of a large celestial "wreck" on the Earth is very small. It is believed that asteroids up to 30 meters across should burn in dense layers of the atmosphere on the way to the surface of the planet or at least collapse into small fragments.
Of course, much will depend on the material from which the space rogue is "made". If this is a “snowball” (a fragment of a comet consisting of ice interspersed with stones, soil, iron), then even with a large mass and size it will most likely “slam” like a Tungus meteorite somewhere high in the air. But if the meteorite consists of stones, iron or iron-stone mixture, then even with a smaller size and mass than the "snow", it will be much more likely to reach the Earth.
As for the celestial bodies across to 50 meters, they are believed by scientists to “visit” our planet no more than once in 700 – 800 years, and if we talk about 100-meter uninvited “guests”, then the frequency of “visits” already from 3000 years and more. However, the 100-meter fragment is guaranteed to sign a sentence to a metropolis like New York, Moscow or Tokyo. Fragments as large as 1 kilometers (guaranteed regional catastrophe, approaching global) and more fall to Earth not more than once every few million years, and giants 5 more than a kilometer and more once every few tens of millions of years.
Good news in this sense, said the Internet resource Universetoday.com. Scientists from universities in Hawaii and Helsinki, observing asteroids for a long time and estimating their number, came to an interesting and comforting conclusion for earthlings: celestial "debris" that spend enough time close to the Sun (at a distance of at least 10 solar diameters) will be destroyed by our luminary.
True, relatively recently, scientists have started talking about the danger posed by the so-called "centaurs" - giant comets, the size of which comes across to 100 kilometers. They cross the orbits of Jupiter, Saturn, Uranus and Neptune, have extremely unpredictable trajectories and can be directed to our planet by the gravitational field of one of these giant planets.
Forewarned is forearmed
Mankind already has technologies of protection against asteroid-comet hazard. But they will be effective only if a celestial fragment threatening the Earth is detected in advance.
At NASA, there is a “Search Program for Nearby Objects to Earth” (it is also called Spaceguard, which translates as “space guard”), which involves all space surveillance tools that are at the agency’s disposal. And in 2013, the Indian launch vehicle PSLV launched the first space telescope developed and built in Canada into near-earth polar orbit, whose mission is to control space. It was named NEOSSat - Near-Earth Object Surveillance Satellite, which translates as "Satellite tracking for objects nearby the Earth." In the 2016 – 2017 years, it is expected that another cosmic “eye” called Sentinel, created by the US-based non-governmental organization В612, will be launched into orbit.
Works in the field of space monitoring and Russia. Almost immediately after the fall of the Chelyabinsk meteorite in February 2013, employees of the Institute of Astronomy of the Russian Academy of Sciences proposed to create a “Russian system for countering space threats. This system would represent only a complex of space observation tools. Its declared value amounted to 58 billion rubles.
And recently it became known that the Central Scientific Research Institute of Mechanical Engineering (TsNIIMash) plans to create a center for warning about space threats in terms of asteroid-comet hazard within the framework of the new Federal Space Program before 2025. The concept of the Nebosvod-S complex suggests placing two spacecraft of observation in geostationary orbit and two more in the orbit of the Earth’s orbit around the Sun.
According to the experts of TsNIIMash, these devices will be able to become a “space barrier” through which practically no dangerous asteroid measuring several tens of meters will pass unnoticed. “This concept has no analogues and can become most effective for detecting dangerous celestial bodies with a lead time of up to 30 days or more before they enter the Earth’s atmosphere,” the press service of TsNIIMash noted.
According to a representative of this service, the institute participated in 2012 – 2015 in the international NEOShield project. As part of the project, Russia was asked to develop a system for rejecting asteroids that could threaten the Earth, using nuclear explosions in space. It was planned in this area and cooperation between Russia and the United States. 16 September 2013 in Vienna, Rosatom CEO Sergey Kiriyenko and US Secretary of Energy Ernst Moniz signed an agreement between the Russian Federation and the United States on cooperation in research and development in the nuclear and energy sectors, which created prerequisites for interaction between the two countries in the fight against asteroid danger. Unfortunately, the sharp aggravation of Russian-American relations, which began in 2014, actually put an end to this interaction.
Push away or blow up
Available to mankind technology provides two basic ways to protect against asteroids. The first can be used if the danger is detected in advance. The task is to send a spacecraft (SC) to the heavenly fragment, which will be fixed on its surface, turn on the engines and lead the “visitor” away from the trajectory leading him to collision with the Earth. Conceptually, this method has already been tested three times in practice.
In 2001, the American spacecraft "Shoemaker" landed on the asteroid Eros, and in 2005, the Japanese Hayabus probe not only sank to the surface of the Iterok asteroid, but also took samples of its substance, after which it returned safely to Earth in June 2010. The European spacecraft Fila, which in November 2014 of the year landed on the comet 67R Churyumov-Gerasimenko, continued the baton. Imagine now that instead of these spacecraft, tugs would be sent to these celestial bodies, the purpose of which would not be to study these objects, but to change the trajectory of their movement. Then all they had to do was to hold on to an asteroid or comet stronger and turn on their propulsion systems.
But what to do in a situation if a dangerous celestial body is discovered too late? One way remains - to blow up. This method has also been tested in practice. In 2005, NASA successfully rammed Comet 9P / Tempel using the Penetrating Spacecraft to conduct a spectral analysis of the cometary substance. Suppose now that instead of a ram a nuclear warhead would be used. This is exactly what Russian scientists are proposing to do, striking the upgraded Aprofis asteroid, which should approach the Earth in 2036. By the way, in 2010, Roscosmos had already planned to use Apophis as a testing ground for a spacecraft tug that was supposed to take the cobblestone aside, but these plans remained unfulfilled.
There is, however, a circumstance that gives specialists grounds to show skepticism about the use of a nuclear charge to destroy an asteroid. This is the absence of such an important damaging factor of a nuclear explosion as an air wave, which markedly reduces the effectiveness of the use of an atomic bomb for an asteroid / comet.
To prevent the nuclear charge from losing its damaging power, the experts decided to use a double strike. The Hypervelocity Asteroid Intercept Vehicle (HAIV), currently being developed at NASA, will beat the Hypervelocity Asteroid Interceptor. And this spacecraft will do this in the following way: first it will reach the "finish line" leading to the asteroid. After that, something like a battering ram separates from the main spacecraft, which will strike the first strike on the asteroid. A crater is formed on the “cobblestone”, into which the main spacecraft with a nuclear charge “leaps”. Thus, thanks to the crater, an explosion will occur not on the surface, but already inside the asteroid. Calculations show that the 300-kiloton bomb, exploded only three meters deep under the surface of a solid, increases its destructive capacity by at least 20 times, thus turning into a 6 megaton nuclear charge.
NASA has already awarded grants to several US universities to develop a prototype of such an "interceptor".
The main American "guru" in the matter of combating asteroid danger with the help of nuclear weapons is a physicist and developer of nuclear weapons at the Livermore National Laboratory, David Dearborn. Currently, he and his colleagues are engaged in bringing the W-87 warheads on high alert. Its power is 375 kilotons. This is about one third of the power of the most destructive warhead currently in service with the US, but 29 is more powerful than the bomb that fell on Hiroshima.
NASA has published a computer graphics capturing an asteroid in space and redirecting it to near-Earth orbit. "Capture" of the asteroid is planned for the sake of scientific purposes. For a successful operation, the celestial body must rotate around the sun, and its size should not exceed nine meters in diameter.
Rehearsal of destruction
The European Space Agency (ESA) will conduct a rehearsal of the destruction. Asteroid 65802 Didim, discovered in 1996 year, was chosen for the role of the “victim”. This is a binary asteroid. The diameter of the main body 800 meters, and that which revolves around it at a distance of 1 kilometer, - 150 meters. In fact, Didim is a very “peaceful” asteroid in the sense that in the foreseeable future there is no threat to the Earth from it. Nevertheless, ESA, together with NASA, intends to ram it with a spacecraft in the 2022 year, when it will be at a distance of 11 millions of kilometers from Earth.
The planned mission received the romantic name AIDA. True, she has nothing to do with the Italian composer Giuseppe Verdi, who wrote the opera of the same name. AIDA is an abbreviation for Asteroid Impact & Deflection Assessment, which translates as "Assessment of a collision with an asteroid and the subsequent change in its trajectory." And the spacecraft itself, which is to ram the asteroid, was named DART. In English, this word means "dart", but, as in the case of AIDA, this word is an abbreviation of the phrase Double Asteroid Redirection Test, or "Experiment to change the direction of motion of a double asteroid." "Dart" must crash into Didim at a speed of 22 kilometers per hour.
The effects of the impact will be observed by another device flying in parallel. It was called AIM, that is, the “target”, but, as in the first two cases, it is an abbreviation: AIM - Asteroid Impact Monitor (“Asteroid collision tracking”). The purpose of the observation is not only to estimate the impact of the impact on the asteroid's trajectory, but also to analyze the asteroid matter knocked out in the spectral range.
But where to place the interceptors of asteroids - on the surface of our planet or in Earth orbit? In orbit, they are in a state of "readiness number one" to repel a threat from space. This eliminates the risk that is always present when a spacecraft is launched into space. After all, it is at the start and launch stage that the probability of failure is highest. Imagine: an interceptor should be urgently sent to the asteroid, but the launch vehicle could not bring it out of the atmosphere. And the asteroid is flying ...
However, it was none other than the orbital location of the nuclear interceptors, but Edward Teller himself, the “father” of the American hydrogen bomb. In his opinion, one cannot simply bring nuclear explosive devices into near-Earth space and calmly watch them spin around the Earth. They will need to constantly maintain, and it will take time and money.
Involuntary obstacles to the creation of nuclear interceptors of asteroids and create international treaties. One of them is the Nuclear Test Ban Treaty in the atmosphere, outer space and under water of the 1963 year. The other is the Outer Space Treaty of 1967, which prohibits the introduction of nuclear weapons into space. But if people have a technological “shield” that can save them from the asteroid-comet apocalypse, then it would be extremely unwise to put political-diplomatic documents in their hands instead.