Momentum enhancement effects and extrapolations, 18-R6318

Background

Given the success of the NASA Double Asteroid Redirection Test (DART) mission as well as testing we performed with our two-stage light gas gun, the question arises of what is still left to know? We’ve now measured β for an impact at 6.14 km/s (based on a Dimorphos mass estimate) and seen Dimorphos’ surface. Things we do not know are:

1. The three primary factors affecting β are absolute size of the impactor, asteroid porosity, and asteroid strength.  We would like to separate out these effects so that we can extrapolate the results of these tests and the DART impact.  We would also like to know if the characteristic rock size in terms of impactor size affects β.
2. A computational code of choice (CTH) is not correctly computing β for Al 2024-T351 targets. Why? Good computations are required to extrapolate to other impact scenarios.
3. What is the slope of the curve for β versus impact speed for targets made of a collection of rocks? This information is needed for extrapolation to other asteroid impact scenarios.

Approach

Perform additional impact experiments (at 2 and 5.5 km/s) and computations.

Accomplishments

A series of impact experiments were performed at 2 km/s and another series between 5 and 5.5 km/s.  These experiments showed some interesting behaviors in momentum enhancement β that we are analyzing.  We have also performed computations of the impact with the hydrocode EPIC as part of our effort to understand the behavior of the impact computations. These experiments and computations have focused on crushed basalt targets. The targets have been held in place with grout both with and without water. (Since the targets are hung vertically in the pendulum, it is necessary to pack them in such a way that the material does not fall out of the target.)