How diffractive solar sails could stop a killer asteroid at 100 km/s

An international team of researchers has proposed a novel method to deflect potentially hazardous asteroids using diffractive solar sails. The technique involves launching an impactor from the opposite direction of the asteroid, thereby increasing the energy transferred to the target body. The researchers simulated several solar sail configurations for an H-reversal trajectory and found that reflection-type diffractive sails were the clear winner. These sails can maintain their entire face toward the sun while directing all thrust into sideways motion, significantly simplifying attitude control and providing the necessary push for the maneuver.

The simulations showed that diffractive sails could deliver a 100 km/s impactor to Apophis, a 340-meter-wide asteroid, in around 200–300 days from launch. This is nearly a year less than the time required for a standard reflective solar sail, which is a significant improvement. The researchers also found that diffractive sails could impart up to 230 times more energy per kilogram of impactor mass than the DART mission, which hit the asteroid at 6 km/s.

The study highlights the potential of diffractive solar sails as a viable alternative to traditional impactors, which require years of orbital maneuvers to get the spacecraft in the right direction. The technique could be used to deflect asteroids like Apophis, which will come within 38,000 kilometers of Earth in 2029. The research is published in the arXiv preprint server and provides a theoretical feasibility study, design strategies, and applications for this innovative approach.

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