issue of Nature, might be the better option. Our proposed solar sail GT is based on their general concept but employs a solar sail instead of ion engines, which has the advantage of longer mission lifetimes and no concern of rocket plume impingement on the asteroid surface. A 5-year towing of Apophis using a 2500-kg solar sail GT spacecraft (equipped with a modest 90 m × 90 m, 50-kg solar sail) and an additional 3-year coasting time will be more than sufficient to move Apophis out of a keyhole.
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