From the MIT Technology Review article of a new paper from Gong, et al called "Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection"...
Apophis is a 46 million tonne asteroid that will pass within a hair's breath of Earth in 2029. However, Apophis's trajectory is likely to take it through a region of space near Earth known as a keyhole that will ensure the asteroid returns in 2036.
Nobody knows how close Apophis will come on that pass. But if there's a chance of a collision, we'll have only 7 years to work out how to avoid catastrophe.
Today, Shengping Gong and pals at Tsinghua University in Beijing say they've come up with a plan that will ensure Apophis never returns to Earth on this timescale .
They point out that keyholes are tiny, in this case just 600 metres wide. So deflecting Apophis by only a small amount in the near future will ensure it misses the keyhole and so cannot return to Earth.
There are various ways to deflect an asteroid. Gong and pals say their preference is to use a solar sail to place a small spacecraft into a retrograde orbit and on collision course with Apophis. The retrograde orbit will give it an impact velocity of 90km/s which, if they do this well enough in advance, should lead to a collision large enough to do the trick.
PAPER REFERENCE:
Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection
Authors: Shengping Gong, Junfeng Li, Xiangyuan Zeng
(Submitted on 16 Aug 2011)
Abstract: Near Earth Asteroids have a possibility of impacting with the Earth and always have a thread on the Earth. This paper proposes a way of changing the trajectory of the asteroid to avoid the impaction. Solar sail evolving in a H-reversal trajectory is utilized for 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: the minimum solar distance along the trajectory and lightness number. A larger lightness number and a smaller solar distance lead to a higher impact velocity. Finally, the deflection capability of a solar sail impacting with the asteroid along the H-reversal is discussed. The results show that a 10 kg solar sail with a lead-time of one year can move Apophis out of a 600-m keyhole area in 2029 to eliminate the possibility of its resonant return in 2036.
Cite as: arXiv:1108.3183v1 [astro-ph.IM]
Link: MIT Technology Review Article
Link: Paper (PDF format)
