How Diffractive Solar Sails Could Stop a Killer Asteroid at 100 km/s

A new technique for deflecting potentially hazardous asteroids has been proposed, using a solar sail to hit the target head-on. The sail, called a diffractive solar sail, uses microstructured optical gratings to diffract light sideways, without the sail itself turning. This allows the sail to keep its whole face towards the Sun, even at perihelion, while still providing a significant thrust to change the asteroid's trajectory. The researchers simulated several configurations and found that reflection-type diffractive sails are the most effective. The sail can be used to deliver a 100 km/s impactor to an asteroid in around 200-300 days from launch time, shaving nearly a year off the mission time of a standard reflective solar sail.

The DART mission, which successfully moved a small asteroid using a kinetic impactor, demonstrated that impactors can be used to deflect asteroids, but it was limited by the direction of approach. The new solar sail technique could potentially deflect an asteroid at 100 km/s, imparting 230 times more energy per kilogram of impactor mass than the DART test. However, the challenge lies in getting the spacecraft moving in the opposite direction, as most spacecraft orbit the Sun in a counter-clockwise direction. Solar sails can potentially reverse this direction, but it requires a lot of energy to achieve. The diffractive solar sail is designed to simplify attitude control and provide the necessary thrust for this maneuver.

The diffractive solar sail is a promising solution for deflecting asteroids, but it requires careful simulation and testing. The researchers simulated different configurations and found that reflection-type diffractive sails are the most effective. The sail can be used to deliver a 100 km/s impactor to an asteroid in around 200-300 days from launch time, shaving nearly a year off the mission time of a standard reflective solar sail. This technique could potentially be used to deflect a dangerous asteroid like Apophis, which will come within 38,000 km of Earth in 2029. The diffractive solar sail could provide a more efficient and effective way to deflect asteroids than traditional methods, offering a new tool in the arsenal of asteroid deflection technologies.

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