Asteroids, flying in outer space, can cause enormous damage to our planet. Imagine that one day scientists sitting in the Observatory, confirmed that flies to the Earth asteroid, and States possessing space capabilities, it is urgent to agree on how to stop him.
The further development of events depends on how much time, according to astronomers, remains before the collision.
But none of the possible solutions will not be easy, and at least in one of the cases, you will need to use nuclear weapons.
Large-scale asteroid impacts are rare. The last of these events that could cause mass casualties was the fall of the Tunguska meteorite in 1908, in a remote corner of Siberia – he is believed to have exploded about ten kilometers above the ground.
Such collisions occur every few centuries. However, Siberia is a pretty desolate place; even today its population is small and scattered over a vast territory.
But if a meteorite landed on four or five hours later, it would be equivalent to that in the sky over St. Petersburg have rocked nuclear explosion in the megaton.
Recently we have seen a recurrence of this terrible scenario on a smaller scale. In 2013, a meteor exploded over Chelyabinsk at an altitude of 30 kilometers.
From the Windows of carved glass, 1,400 people were injured. The power of the explosion was equivalent to about 500 kilotons is about 30 times the power of the atomic bomb dropped on Hiroshima – but it was pretty high above the ground, thus avoiding serious damage.
Such collisions happen much more often – about three times a year. Most of them occur over the ocean or in remote corners of the planet, so usually we do not notice them.
However, the question is not whether there will be a clash, but the question is when it will happen.
Governments around the world treat this issue seriously and are taking the first tentative steps to avoid a dangerous collision.
In January, the National Board of the USA on Aeronautics and space research (NASA) established a coordination unit for the protection of the planet as a single of the person responsible for conducting observations of asteroids.
This Department interacts with other space agencies in the framework of the discussion of possible solutions to the problems associated with the prospect of falling to the Ground of large fragments of rocks flying in space.
According to a NASA specialist on the protection of the planet, now the Department deals mainly with the detection of such asteroids and coordination of the various observing programmes – after all, in order to avoid collision with such objects, it is necessary to know where they are.
“We try to identify any potential threats for a few years, and even decades before they become a reality,” he says.
After the detection of a dangerous asteroid begins to develop plans to prevent the collision.
The simplest method is to use a heavy object, taken with the spacecraft, or the spacecraft as a battering RAM – a kind of cosmic Billiards.
It is hoped that in this way the asteroid will be knocked off course, and he passes the Earth.
Over the next few years will be testing this technology as part of a joint mission of the European space Agency and NASA called the Asteroid Impact and Deflection Assessment (Aida, “Evaluation of the effects of ramming an asteroid and change its path”).
The mission will involve two spacecraft – the Asteroid Impact Monitor (AIM), which will start flying in late 2020, and Double Asteroid Redirection Test (DART), the start of which is scheduled for 2021.
In 2022, they will reach the asteroid called 65803 Didim and his companion Digimon. The diameter of Didim is about 780 meters, and Digimon – about 170 meters.
The least of them goes around more times at 11.9 hours, and the distance between them is only 1100 meters.
The first probe will approach the asteroid to study its composition. The second probe upon arrival, bumps into Digimon, and the first will be to observe how change the orbit of a smaller asteroid in a collision.
The point is to find out exactly how much you can move the asteroid without risking to send him on a dangerous path – the first step to the development of technology in changing the course of the heavenly bodies.
To illustrate the importance of this mission, you can give an example: the famous meteor crater in Arizona USA, probably formed in the fall of an object the size of three times less of Didim, the diameter of the crater reaches is 1.18 km.
If a stone the size of a Didim crashed into the Ground on the lowest possible speed – approximately 15.5 kilometers per second – it would lead to the release of about two megatons of energy – enough to destroy an entire city.
At maximum speed (approximately 34.6 kilometers per second) freed four megatons of energy (four million tons of TNT).
“We’re going to change the orbit of a satellite at which it moves around the asteroid,” explains Patrick Michel, senior researcher at the National research center of France and one of the leaders of the mission – because the orbital speed of the satellite is only 19 centimeters per second”.
He adds that from the Earth it will be possible to measure even small changes, and the period of treatment Didiana should vary by approximately four minutes.
It is also important to assess how effective this technology is. “All of our developed model [RAM the asteroid] is based on the principles of physics collisions, investigated only on the laboratory level – to centimeter-scale targets,” says Michelle.
Could we apply these models to real asteroids remains an open question.
Johnson adds that this technology is most developed – people already have the experience of approaching asteroids, in particular, as part of the launch of NASA’s interplanetary probe Dawn to study the dwarf planet Ceres, and mission of the European space Agency Rosetta to study the comet 67P / Churyumov – Gerasimenko.
In addition to RAM, you can also use a gravitational tug – just to put a relatively large spacecraft into orbit around the asteroid, so under the influence of their mutual gravitational attraction of the asteroid’s course gradually changed.
The advantage of this method is that it requires only to deliver the apparatus on the corresponding orbit, which will be of a “halo” – to approximate the circle with center at the point where acting on the object is the force of attraction of the Sun is equal to the force of gravity of the asteroid.
This method may be tested in the framework of the mission of NASA’s Asteroid Redirect Mission (“Mission to change the trajectory of the asteroid), one of whose tasks will be to move the asteroid back to near-earth space.
However, both of these methods require time; for the organization of flight beyond the earth’s orbit, you need a good four years, and the spacecraft will take another one to two years to get to the corresponding asteroid.
If time left is less, we may have to come up with something else.
Zichen Zhang, a physicist from the University of California at Santa Barbara (USA), opines that as an alternative it would be possible to use laser technology.
The laser will not cause an explosion of the asteroid as a space station “death Star” from “Star wars”, but will turn a small part of its surface in pairs.
Zhang and his colleagues, working under the guidance of cosmologist Philip Lubin, presented a range of orbital models in the framework of the presentation given at the astronomical society of the Pacific.
This method may seem inefficient, but let’s not forget that if you apply it at an early stage, even small effects can cause the deflection of the asteroid from the course of many thousands of kilometers.
According to Zichen Zhang, the advantage of this method is that long-range laser cannon can be placed directly on the earth’s orbit, and did not race with it behind the asteroid.
Laser gun capacity of about one gigawatt, shooting during the month, can deflect asteroid with a diameter of 80 metres – similar to the Tunguska meteorite from the path at a distance twice the radius of the Earth (12 800 km).
This will be just enough to avoid the collision.
And, you can send into space the unit is equipped with less powerful lasers, but in this case he will need to approach the asteroid and follow him at a relatively close distance.
Given the lower power laser is of the order of 20 kilowatts, ” he’d have to work for several years, although the calculations of Zhang, it turns out that an artificial satellite delivered into orbit of the asteroid 15 years before a potential collision, can also change its trajectory sufficiently.
According to Zichen Zhang, in favor of placing the laser in earth orbit says the fact that to follow the asteroid or comet in its orbit is not as easy as it seems, although such experience is already available.
“Initially, the Rosetta spacecraft had to fly to another comet (46R), but since the launch was postponed and the location of the comet was no longer so convenient for the approach, the goal had to change. However, if some comet will fly to the Earth, we will not be able to afford to choose a more convenient target.”
Tracking asteroids is not so difficult, but on approaching him, according to the scientist, still will take about three years.
At the same time, as noted by Johnson, one of the main problems associated with the use of any laser, is that no one has yet managed to put into orbit any object with a diameter of a kilometer, not to mention the sets of laser cannons.
“There is much that seems to me ill-conceived, for example, it is possible to convert solar energy to laser energy with sufficient reliability to provide such a lengthy work.”
In addition, there is the “nuclear option”. Those who watched the American sci-Fi movies “Armageddon” or “deep impact”, it is perfectly logical, but actually it’s much more difficult.
“In this case it is necessary to build up the whole infrastructure,” says Massimiliano creating an alternative, an employee of the University of Strathclyde (UK).
His proposal was to detonate a nuclear bomb at a certain distance from the target. As is the case with the laser, it is assumed to vaporize part of the surface that will create traction and get hit by a asteroid from orbit.
“When ablation [breaking] the advantage is high energy efficiency,” he says.
Despite the fact that lasers and atomic bombs might work in those cases, when the asteroid is close enough already, the efficiency of these methods depends largely on the specific composition of the asteroid, since the temperature of the evaporation from them will be different.
The problem also poses a risk of spread of the fragments, since many of the asteroids represent only a pile of weakly coupled between a rock pieces.
The impact on such facilities may not be very effective. As noted by Johnson, this is the big plus of the method of gravitational tug if you use this way of protection against the asteroid, its composition and grip are not of great significance.
However, any of these methods may face a major obstacle – political considerations.
Signed in 1967, the international the outer space Treaty imposes a ban on the use and testing of nuclear weapons in outer space, and the placement on-orbit laser cannon capacity in gigawatts can make anyone nervous.
Zichen Zhang calculated that if you reduce the power of the orbital laser to 0.7 gigawatts, he will be able to move the asteroid by only a distance equal to about 0.3 of the radius of the Earth is about 1 911 kilometers.
“Asteroids smaller size, can erase from the face of the earth the whole city, are much more common than giant, capable of destroying an entire planet. Now imagine that this asteroid is flying to new York. Depending on circumstances not entirely successful attempt to avoid a collision of an asteroid with the Earth can lead to the fact that instead of new York will suffer, for example, London.”
“If there is substantial risk of such a development, the Europeans are unlikely to be so readily agreed to trust the trajectory of the asteroid to the United States,” notes physicist from the University of Santa Barbara.
However, in practice, such obstacles may not be quite so insurmountable. “In these agreements there are loopholes,” explains Johnson, referring to the outer space Treaty and the Treaty on comprehensive ban of nuclear tests.
For example, the Treaty on outer space there is no ban on launching ballistic missiles pass through outer space and can be carriers of nuclear weapons.
And in light of the need to protect the planet’s dissatisfaction with their use it is possible to repay.
Patrick Michel notes that unlike any other natural disaster such a catastrophe can be prevented.
“This event is a natural risk which is very low compared to the tsunami and similar phenomena. And it is the only one [of natural disasters], in respect of which we are able to do something”.
