Lu's favoured option is called a gravitational tractor. It involves placing a relatively massive spacecraft near enough to an approaching asteroid to shift its trajectory using only the minuscule force of gravity between the two objects. Although the method requires significant lead time and will not work in all cases, it has the advantage of controlling a hazardous object "in one piece", say Lu.It's not nearly a sexy as a thermonuclear cleaver, but it'll have to do.
According to Lu, Apophis is particularly amenable to this form of manoeuvring. Prior to its threatening approach in 2036, the asteroid will sweep past Earth in the spring of 2029. Any change in the asteroid's position before this will be greatly magnified by the 2029 encounter, which could, in turn, eliminate the chance of an impact in 2036.
Such a mission could succeed with a 1-metric-tonne spacecraft arriving at Apophis as late as 2027, says Schweickart, who envisions a protocol that would allow the UN to 'contract' the world's space agencies to remove the threat.
Feb 17, 2007
Apophis given 1 in 45,000 chance
Great. One more thing to worry about while spooning out the morning gruel. An asteroid named Apophis has a .002% chance of striking Earth on Sunday, April 13, 2036, potentially triggering a tsunami that would wipe out the west coast. But don't worry: scientists are on it.