NASA will for the first time attempt Monday to deflect the trajectory of an asteroid. This mission, named Dart, will make it possible to test one of the main techniques envisaged in the event of a future threat to the Earth.
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With this demonstration, the idea is to begin to “add instruments to our toolbox,” said Lindley Johnson, planetary defense officer at NASA, during a press conference. But “we need several methods, depending on the circumstances encountered.”
Here is an overview of the different concepts studied.
Kinetic impact
The so-called kinetic impact technique is the one experimented by NASA on Monday.
It consists of hitting an asteroid with a ship, in order to “push” it slightly, and thus deviate its trajectory. A bit like playing pool in space.
This first test will make it possible to understand how the asteroid reacts, and therefore to better calculate the force required in the future.
The size of the ship used will depend on the size of the asteroid threatening to collide with Earth.
It is also possible that several ships will be required, according to Lindley Johnson.
gravity tractor
The so-called gravitational tractor method consists of flying one or more vessels near the targeted asteroid, in order to slowly modify its trajectory by the gravitational attraction generated.
“Such a technique would take longer to implement,” Lindley Johnson warned, and therefore implies that the target would be detected years or even decades before a potential collision.
In addition, this process would be much less effective on large objects, for example asteroids over 500 meters in diameter.
To remedy this problem, NASA engineers proposed in 2017 that the spacecraft used dig the asteroid in order to recover material, and thus increase its effect thanks to this additional mass.
But these ideas will first have to be tested, and would require “decades to be built, launched, and implemented during a mission”, according to NASA.
Nuclear explosion
Another option is more like the one implemented in Hollywood movies: using a nuke to redirect or destroy an asteroid.
“This may be the only effective strategy for the most dangerous asteroids,” those a kilometer or more in diameter, NASA wrote in an article on the subject. This method might also be used “as a last resort”, if other techniques have failed previously.
However, these weapons are controversial.
In 2021, Lori Glaze, a NASA official, said that according to the American agency, the best way would be to produce an explosion near the asteroid, so that it is moved by its blast. Aiming at it directly would indeed risk fragmenting it into several pieces, and thus multiplying the objects posing a potential risk to the Earth.
But in 2018, an article by Russian scientists investigated the hypothesis of a direct impact.
According to them, destroying an asteroid 200 meters in diameter would require a bomb 200 times more powerful than that of Hiroshima. They also felt that digging into the asteroid and then placing the bomb there would be more efficient — just like the scenario in the movie Armageddon.
