Let's say thanks to Hollywood for the fact that modern films so often demonstrate one of the most popular scenarios of the destruction of the planet - the fall of an asteroid. NASA claims that there are no reasons for panic, but the extinct dinosaurs would have argued with that. Therefore, there are more and more people who insist on the need to create an effective system to protect the planet.
If the threat of an asteroid fall is real, then you need to understand how to save the Earth. You must admit that the presence of a technology for detecting space objects is only the starting point. In case of danger, we cannot do without a system for changing the flight path of a near-Earth object. We need a defender in orbit.
And now get acquainted with a gravitational tractor. This is a theoretical spacecraft designed to deflect an approaching object in outer space. And here physical contact between the ship and the asteroid is excluded, since the gravitational field is used. Yes, the idea seems crazy, but NASA and other space agencies believe it will work.
The concept of a gravity tractor in 2015 was first described by Edward Lou and Stanley Love from the Lyndon Johnson Space Center. Since an asteroid with parameters around 200 m can cause destruction and death of living beings, the researchers insisted on the need to consider realistic ways to protect the planet.
Any option involving contact with an object causes a high risk. Therefore, Lou and Love decided to use gravity to move an object from a trajectory. In fact, the gravity tractor plays the role of a tugboat, using its own gravitational pull, to push the asteroid to another route. The vehicle must maintain a steady direction so that in the course of gravitational interaction the tractor itself will not be influenced.
Now it is important to consider one nuance. The spacecraft created on our planet will demonstrate only a small gravitational pull relative to other space objects. Moreover, the attraction is so insignificant that the spacecraft will have to spend several years to significantly change the course of the asteroid.
This strategy is offered by Lou and Love. That is, you need to send a gravitational tractor to a dangerous asteroid several decades before its arrival in order to tow the space rock to a safe distance. You can even send several gravity tractors to increase the chances of success.
This strategy will work only under two conditions. First, we must find in time a dangerous near-Earth object in order to have enough time to change the trajectory. Now things are not bad, since NASA controls the trajectories of all near-Earth asteroids, checking everyone for the probability of falling to Earth.
The key element is the NEOWISE spacecraft, which tracks comets and asteroids approaching the Earth. In just a few years of work, the project successfully characterized 439 objects, checking in total about 19,000 space bodies.
Now NEOWISE spends on tracking flybys of large objects from several months to several years. But NASA is trying to speed up the process and increase the prediction of the future trajectory in order to catch the threat in time.
Artistic vision of the IKAROS space probe moving with the help of a solar sail
The second problem is displacement. We are still not close to the development of an interstellar travel propulsion system. For the device to be able to move near the asteroid for several years, it will need an engine that does not depend on fuel. Experimental architect Rachel Armstrong believes that the most effective method of movement will be the solar sail, using the wind of our star to move the spacecraft forward. Scientists are already building and testing this technology. But the problem is that the thin material of the solar pair risks collapsing even from the smallest fragments of an asteroid flying near it.
Therefore, you should think more radically. Perhaps you should turn to laser technology or electron beams to move the device.
ARM (Asteroid Redirect Mission) vehicle could test gravity tractor method for planetary defense
NASA is showing an interest in building defenses against the asteroid threat. Therefore, they consider various projects and think through tests in space. It is important to understand whether the gravitational tractor can work in reality. For example, you can run a test model to an artificial small object and follow the gravitational influence on the flight path.
If in the distant future an asteroid will truly become a threat, then a gravity tractor is able to save the planet. It's not as spectacular as the explosions in Hollywood movies, but it's safe.