Limits on the use of nuclear explosives for asteroid deflection

Recent studies by the US National Research Council identify nuclear explosives as the only current technology able to deflect large asteroids (those exceeding 500 m in diameter) or to mitigate impacts of smaller bodies when the warning time is short. Previous work predicts that either a standoff burst or a very low-yield surface burst is easily capable of deflecting a large (1 km) asteroid without fragmentation. Alternatively, large near-surface or just sub-surface bursts can sufficiently disrupt and disperse smaller bodies (300 m) to ensure that large fractions (in excess of 99.99%) miss the Earth entirely. Even for very short warning times (less than a month), more than 99.5% of a body′s mass can be deflected off of an Earth-bound trajectory. However, successfully deflecting a small body, while avoiding fragmentation, becomes a challenging problem when the required kinetic energy increment is a substantial fraction of the body′s potential. This paper addresses the challenge of preventing the production of substantial low-speed debris while deflecting small bodies with an impulsive method.

► Standoff nuclear bursts can defend against Earth-bound asteroids.
► We modeled the effects of standoff nuclear bursts on Apophis-sized asteroids.
► We examined the effects of porosity on the deflection of asteroids.
► Higher porosity lowered the risk of fragmentation when deflecting via standoff burst.