![]() ![]() The 600 kg projectile impacts targets with varying porosities, between 10 and 50%, and cohesions from 1 to 100 kPa, at a velocity of 6 km/s. The first benchmark study focuses on the influence of target properties on the efficiency of the momentum transfer from the DART impact, β, for materials similar to the regolith simulant. Both results agree with the lower bound of the experimental constraints. From our numerical models, we determined ejecta curtain angles 0.5 ms after the impact as 48° (glass beads) and 30° (regolith, Fig. In the case of the regolith simulant, at ~0.5 ms after the impact, the ejecta curtain angle was 30-40°. In the glass beads target laboratory experiment, at ~0.5-1 ms after the impact, the ejecta curtain made an angle of 50-60°. We determine β-values of 2.9 and 1.4, which agree well with experimentally determined values of 2.7 and 1.3, respectively. The regolith simulant used f ~ 0.8 and an initial porosity of 42%. The glass beads target was modelled using a Drucker-Prager criterion with a coefficient of internal friction, f = 0.5 and an initial porosity of 35%. We have simulated the crater formation in glass beads and regolith simulant with iSALE-2D at impact speeds of 2.4 km/s and 2.2 km/s, respectively. ![]() In a second step, we continue the benchmarking work done by the Hera impact working group to detect, assess and remove deviations between two different numerical schemes, iSALE (in 2D and 3D) and Bern SPH at the scale of the DART impact. To validate our shock physics codes, we compare our results against observations from a recent laboratory study, where PVC projectiles with a mass of ~25 mg were accelerated to velocities of 1-2 km/s, impacting glass beads, sand and regolith simulant targets. This approach was used previously for systematic parameter studies and benchmarking studies. For both codes, the ejection behaviour is analysed as described in, and the ejection data is used to determine the momentum transferred to the target for deflection (momentum enhancement factor β = ejecta + impactor momentum / impactor momentum). In this study, we employ the Drucker-Prager and the Lundborg rheology models to describe the strength of the material. Both codes include the simulation of material compaction (iSALE: ε-α model SPH: P-α model) and different strength models. On the other hand, Bern's grid-free Smooth Particle Hydrodynamics (SPH) is most appropriate to study the ejection of material and processes where the entire target body is involved. ISALE-2D/-3D is a grid-based arbitrary Eulerian Lagrangian (ALE) code and is best suited to study crater formation and the propagation of shock waves from a high velocity impact into targets with a variety of different properties. Hence, as a first step, accurate validation tests against laboratory experiments are conducted to improve the reliability of results from numerical modelling. Although all codes solve similar forms of conservation equations and use similar constitutive models, different numerical schemes can produce systematically different results. We model the impact using two different numerical schemes: a continuum approach using iSALE-2D/-3D & a smooth particle approach using Bern SPH. The objective of this study, which is conducted in the context of the NEO-MAPP project, is to model the collision of the kinetic impactor with Dimorphos and to predict the outcome of the impact with respect to parameters that are measurable by spaceborne and in-situ instrumentation provided by the Hera mission. A second, follow-up spacecraft, Hera, will arrive at the system several years after the impact to characterize the system and the impact consequences. The impact will eject asteroid material from the target surface, leading to a measurable change in the orbital period of the binary. In the context of these missions, a spacecraft, DART, will impact the secondary of the 65803 Didymos system, Dimorphos, at the end of October 2022. ![]() ![]() The AIDA international collaboration, which includes the DART (NASA) and Hera (ESA) missions, aims to test the technology of deflection by a kinetic impactor and to enhance our understanding of small bodies in general. ![]()
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