Shape Dependence of the Kinetic Deflection of Asteroids

Hayabusa2 extended mission: New voyage to rendezvous with a small asteroid rotating with a short period

“…Growing efforts have proposed effective procedures for deflecting hazardous objects. Kinetic impactors and explosive processes have been one of common mitigation technologies considered in the communities (Leung et al, 2017;Wie et al, 2017), although the physical properties of target asteroids are key parameters of the deflection efficiency (Bruck Syal et al, 2016;Feldhacker et al, 2017). There have been proposed other deflection techniques using ablation (McMahon and Scheeres, 2017), mass ejection (Brack and McMahon, 2020), tethering (Venditti et al, 2020), and gravitational tractor (Lu and Love, 2005).…”

DART mission determination of momentum transfer: Model of ejecta plume observations

“…In general, the vector momentum transfer ∆𝑀𝒗 is not collinear with the incident momentum vector 𝑚𝑼 because of the ejecta momentum vector, which is not anti-parallel to the incident direction, but is affected by either or both of: 1. the local surface inclination to the incident direction as discussed by (Feldhacker et al 2017), or 2. presence of topography or a blocky surface at the impact site (Owen et al 2017, Stickle et al 2018. For the DART impact, approach imaging will provide information on these impact conditions and target characteristics (Cheng et al 2018), by determining the impact location and the local surface inclination, and identifying few meter scale or larger blocks if present.…”

“…When a kinetic impactor of mass m strikes a target at a velocity U, the momentum transferred to the target of mass M, written as 𝑀∆𝒗, can exceed the incident momentum mU because of momentum carried away in a backward direction by impact ejecta. The momentum transfer efficiency β is defined by (Feldhacker et al, 2017)…”

Ejecta distribution and momentum transfer from oblique impacts on asteroid surfaces

“…The first term on the righthand side is the momentum imparted directly by the impactor P i ; the second term is the component of the momentum imparted by the escaping ejecta that acts normal to the surface; the third term is the component of the momentum imparted by the escaping ejecta that acts parallel to the surface, positive in the downrange direction. If the net momentum imparted to the target by the escaping ejecta can be assumed to act along the surface normal vector (i.e., ψ m = 0) then the third term can be neglected (Feldhacker et al, 2017;Cheng et al, 2020).…”