Near Earth Asteroids such as the 320m large Apophis that will pass Earth in 2029 and 2036 is constant threath to Earth. A new Chinese paper proposes a way of changing the trajectory of the asteroid to avoid the impaction with a solar-sail.

They use a solar sail evolving in a H-reversal trajectory for their proposed asteroid deflection.

Firstly, the dynamics of solar sail and the characteristics of the H-reversal trajectory are analyzed. Then, the attitude of the solar sail is optimized to guide the sail to impact with the object asteroid along a H-reversal trajectory.

The impact velocity depends on two important parameters:

1. the minimum solar distance along the trajectory and
2. Lightness number. A larger lightness number and a smaller solar distance lead to a higher impact velocity.

The paper discusses the deflection capability of a solar sail impacting with the asteroid along the H-reversal

The results show that a 10kg solar sail with a lead-time of one year can move Apophis out of a 600m keyhole area in 2029 to eliminate the possibility of its resonant return in 2036.

Despite the probability of an impact of less than 1 in a million, this is a real threath against Earth, as the 320m wide Apophis would cause severe regional damage

Source: arXiv