I will crash
The most realistic and also the simplest way to manipulate an asteroid is to simply crash into it, with the help of kinetic energy. This method has proven its fundamental efficiency in practice when using the American DART apparatus. collapsed to the asteroid Dimorph orbiting the larger Didymos. As a result, the orbital duration decreased by 32 minutes to 11 hours 23 minutes and the speed decreased by 2.7 mm/s.
Despite its apparent simplicity, the impact of the collision was complex. The collision of a 500 kg device with a 4.8 billion kg stone cannot be explained within the framework of a school physics problem. The impact released energy equivalent to the explosion of five tons of TNT, which ejected the material into space. This ejection created jet thrust and transferred additional momentum to the asteroid, which was impossible to accurately calculate in advance because this required precise knowledge of the composition and structure of the surface.
A change in speed of a few millimeters per second may seem insignificant, but it is not the drop in speed itself that is important, but its effect on the asteroid’s orbit. Since the diameter of the Earth is 12.7 thousand km and it moves in orbit at a speed of 30 km/s, the asteroid only needs to arrive a few minutes later and it will no longer be able to hit the target. This method should work most effectively when an asteroid is hit at a time when it is at the other end of the solar system, so it is important to detect a hazardous object as early as possible.
nuclear explosion
If the asteroid is very large or discovered too late, a more powerful impact (e.g. nuclear weapons) will be required. At the same time, an atomic explosion occurring in space is nothing like an atmospheric explosion, because there is no gas around to create a powerful explosion wave. The device impacts the asteroid with just a flash of light, x-rays and a stream of neutrons. When encountered with a surface, all three damaging factors will heat the surface and evaporate to a shallow depth. The asteroid’s vaporized rock will work like a rocket engine, pushing the celestial body in the opposite direction of the explosion.
There are many nuances in the nuclear bombardment of an asteroid. For example, it is not clear at what distance the explosion will occur. If a bomb collides with an asteroid at escape velocity, it will simply break apart and not explode. This means that you will either have to detonate it at a significant distance using a rangefinder (at high speeds it is impossible to set the distance with an accuracy of several meters), or you will have to slow down and gently land the bomb on the ground. A celestial body that requires a lot of fuel.
An underground explosion is necessary so that all the energy of the bomb is transferred to the rock and does not evaporate into space. American scientists in 2013 offered This is exactly the concept of deflecting an asteroid, and the crater formed after the first explosion can be used as a jet engine nozzle in subsequent explosions. Modified nuclear bunker destruction munitions that can penetrate the ground when dropped from an aircraft are ideal for this type of operation. However, they would not survive a cosmic speed impact and would either need to be partially braked or hit the asteroid while it was in orbit rather than towards it.
A significant advantage of an atomic projectile over a kinetic attack is its ability to deflect a very loosely held mass of flying debris. A nuclear flash at a distance of several meters can “carefully” vaporize a surface without breaking the object into many pieces with an unpredictable trajectory.
Lasers, excavators and gravity
Impact and nuclear strike are considered by NASA to be realistic measures in case of danger, but scientists also propose many other concepts for anti-asteroid defense. For example, a spacecraft can be placed next to a celestial body to pull it in the desired direction with gravitational force. At the same time, according to the law of gravity, the probe will also be attracted by the asteroid, but it will be able to resist it thanks to the thrust of a solar sail or a high-efficiency ion rocket engine. This method is good because it allows you to pull even a loose pile of crushed stone.
But if a solid object threatened the Earth, a device with a rocket engine could land directly on it, anchor itself and create thrust. There are many variations of this concept. For example, according to the MADMEN project, several drilling rigs or excavators are supposed to land on the asteroid, which will launch stones into space at high speed and create thrust. This will avoid restrictions in the fuel supply to the device.
Destruction of the surface, similar to a nuclear explosion but on a smaller scale, can be caused by a powerful laser beam. It won’t be able to reach the asteroid from Earth, but it could be placed on a spacecraft with large solar panels. Currently in the US Army to go past Military tests of a pre-production model of a combat laser to destroy drones and missiles, so it can be considered that such technologies are already quite mature. Alternatively, the laser could be replaced with a system of large mirrors that reflect sunlight to a single point on the asteroid.
Finally, some scientists offer even more exotic ideas. For example, a solar sail with an area of hundreds of meters or more could get stuck on a dangerous asteroid. According to another project, the orbit can be changed due to the controlled Yarkovsky effect. This is what physicists call the reactive impulse created by photons of infrared radiation from the cooling surface of a cosmic body. If an asteroid is painted with white or black paint in the right places, the forces acting on it will change, but the effect will be very weak and will only play a role if it is used long before the impact.
All these methods, unlike impact and nuclear attack, require long preparation and, perhaps, will only work if you start taking action several years before a possible disaster.