Consequences of Asteroid Fragmentation During Impact Hazard Mitigation

Abstract

The consequences of the fragmentation of an Earth threatening asteroid due to an attempted deflection are examined in this paper. The minimum required energy for a successful impulsive deflection of a threatening object is computed and compared to the energy required to break-up a small size asteroid. The results show that the fragmentation of an asteroid that underwent an impulsive deflection, such as a kinetic impact or a nuclear explosion, is a very plausible event. A statistical model is used to approximate the number and size of the fragments as well as the distribution of velocities at the instant after the deflection attempt takes place. This distribution of velocities is a function of the energy provided by the deflection attempt, while the number and size of the asteroidal fragments is a function of the size of the largest fragment. The model takes also into account the gravity forces that could lead to a re-aggregation of the asteroid after fragmentation. The probability distribution of the pieces after the deflection is then propagated forward in time until the encounter with the Earth. A probability damage factor (i.e., expected damage caused by a given size fragment multiplied by its impact probability) is then computed and analyzed for different plausible scenarios, characterized by different levels of deflection energies and lead times.

Gravitational perturbations correlated with the asteroid kinetic impact deflection technique

“…Some studies also discuss the fragmentation which occurs upon a too large impulse being imparted, or by natural impacts. 13 – 15 . They show that too large impulses should be avoided for a kinetic impact.…”

On the deflection of asteroids with mirrors

“…The second best was solar sublimation with all the other methods order of magnitude less effective (according to the proposed comparison criteria). Although nuclear explosions were the most effective, a subsequent study by Sanchez et al (2010) demonstrated that for both nuclear explosions and kinetic impacts, a resulting fragmentation of the asteroid could potentially increase the risk of impact(s) on the Earth.…”

Micrometeoroid Fluence Variation in Critical Orbits due to Asteroid Disruption

“…This type of characterization of the fragment size distribution is presented by Sanchez, Vasile and Radice [27]. They present an accumulative power law distribution to model fragment size distribution.…”

“…Past studies on side effects of disruption have focused on Earth-impact events of ejected fragments [27]. Studies by Kaplinger, Wie, and Dearborn have shown that in some cases, Earth-impacting mass can be reduced by up to 90% through a combination of nuclear disruption and atmospheric burnup [21].…”

“…Vasile and Radice [27]. The cumulative distribution is changed to non-cumulative which yields the total number of particles in each size bin.…”