The scenario where a celestial body threatens to impact the Earth is very popular and many solutions have been proposed to mitigate the associated risk. Some of them can be considered “soft” and consist in landing on or rendez-vous with the incoming asteroid several years in advance of the collision and then altering its trajectory by various means, such as painting it in order to alter its albedo and therefore the radiation pressure or by pushing it gently using a gravitational tractor (Lu and Love 2005). The mechanical device described below could also be used to change the trajectory. All these scenarios need a lot of time, even discounting mission preparation. If the incoming body is not a near-earth object but, for instance, a comet nucleus, more than ten years are likely to be necessary to reach it. Some “hard” solutions do not require a rendez-vous, but an interception, possibly with a large relative velocity. They can be implemented on a much shorter timeframe. Detonating a nuclear device could disperse the incoming body as the gravitational binding energy of an asteroid is surprisingly low. The difficulty might then be the timing: the explosion should take place before the impact but late enough to create a strong absorption of its energy (mainly X rays), which would turn a percentage of the mass of the asteroid into hot gases generating a shock wave that could disperse the asteroid and additionally creating a mean impulse which would alter the trajectory of the centre of gravity of the cloud of debris. In (Massonnet and Meyssignac 2006), a two step procedure is proposed where a smaller asteroid is first captured and “parked” on a L1-L2 Earth-Sun Lagrange orbit, and then sent into a trajectory impacting the incoming threat.
KeywordsDiscrete Element Method Final Mass Lagrange Point Halo Orbit Solar Sail
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