Modeling Momentum Transfer from Kinetic Impacts: Implications for Redirecting Asteroids

Abstract

Kinetic impactors are one way to deflect a potentially hazardous object headed for Earth. The Asteroid Impact and Deflection Assessment (AIDA) mission is designed to test the effectiveness of this approach and is a joint effort between NASA and ESA. The NASA-led portion is the Double Asteroid Redirect Test (DART) and is composed of a ~300-kg spacecraft designed to impact the moon of the binary system 65803 Didymos. The deflection of the moon will be measured by the ESA-led Asteroid Impact Mission (AIM) (which will characterize the moon) and from ground-based observations. Because the material properties and internal structure of the target are poorly constrained, however, analytical models and numerical simulations must be used to understand the range of potential outcomes. Here, we describe a modeling effort combining analytical models and CTH simulations to determine possible outcomes of the DART impact. We examine a wide parameter space and provide predictions for crater size, ejecta mass, and momentum transfer following the impact into the moon of the Didymos system. For impacts into "realistic" asteroid types, these models produce craters with diameters on the order of 10 m, an imparted Δv of 0.5-2 mm/s and a momentum enhancement of 1.07 to 5 for a highly porous aggregate to a fully dense rock.

The effects of asteroid layering on ejecta mass-velocity distribution and implications for impact momentum transfer

“…The efficiency of momentum transfer has been found to vary significantly depending on the target asteroid's properties and its composition (Holsapple and Housen, 2012;Jutzi and Michel, 2014;Stickle et al, 2015;Bruck Syal et al, 2016). Based on the results of experimental impacts in layered targets (Quaide and Oberbeck, 1968), it is likely that target layering will also affect the mass and velocity of the ejecta, and therefore, β.…”

“…Half space control cases Y 0 = 0.1 kPa Y 0 = kPa Y 0 = 10 kPa Y 0 = 100 kPa Our results are broadly consistent with previous impact simulations where targets with similar cohesive strengths were used. For example, simulations by Bruck Syal et al (2016) suggested a 10 km/s impact into a 1 kPa, 20% porous target would produce a β − 1 ≈ 3, while impacts into much stronger targets, of a few MPa, have been shown to produce β − 1 between 0.1 and 1 (Jutzi and Michel, 2014;Stickle et al, 2015;Cheng et al, 2016)). As discussed in Raducan et al (2019), these results emphasise the importance of cohesion in determining the β value and the outcome of asteroid deflection.…”

European component of the AIDA mission to a binary asteroid: Characterization and interpretation of the impact of the DART mission

“…It is expected that b > 1 because of the momentum returned from the incident direction by impact ejecta. However, b predictions for kinetic impacts on asteroids cover a wide range of values from near unity to well above three (e.g., Walker and Chocron, 2011;Holsapple and Housen, 2012;Jutzi and Michel, 2014;Stickle et al, 2015;Cheng et al, 2016;Bruck Syal et al, 2016). Results of laboratory impact experiments can be scaled up (though the scaling is very uncertain) to predict asteroid deflection by kinetic impacts, using numerical simulations and analytical scaling models (Housen and Holsapple, 2011;Walker et al, 2013;Flynn et al, 2015).…”

The Double Asteroid Redirection test mission

“…Preliminary models of the DART impact suggest a range of 1-6 for , depending on assumptions on the nature of the target body. [9] These models will continue to be improved over the course of the DART development, and the data returned from DART will be used to validate and improve these impact models.…”