Presentation #108.04 in the session Planetary Defense! Part Two.
If a sizeable asteroid is found to be on an Earth-impacting trajectory, a Kinetic Impactor (KI) mission may be considered as the simplest and most direct approach for deflecting the asteroid and preventing the impact. But what are the realistic bounds on the size of asteroid that can be deflected away from impact, as a function of warning time and assuming an existing launch vehicle? This study examines KI mission capabilities statistically, against a set of realistic impacting asteroid orbits and using realistic KI intercept-trajectory mission designs. The median asteroid size that can be deflected away from Earth impact using a single KI mission is plotted as function of warning time and momentum enhancement factor (beta). The risk that a KI mission would disrupt the asteroid, instead of simply deflecting it as a single body, is discussed next, and shown to be a significant limitation for the KI technique. If the canonical disruption threshold rule is enforced, limiting the applied velocity change (delta-v) to less than 10% of the asteroid escape velocity, that delta-v may not be enough to move the asteroid trajectory away from Earth-impacting, even when that deflection is applied decades before impact. In fact, for a large fraction of likely potential impactor orbits, no single KI mission can mitigate the impact without disruption, regardless of asteroid size or beta value, and even with more than 30 years of warning.