Momentum Enhancement from a 3 cm Diameter Aluminum Sphere Striking a Small Boulder Assembly at 5.4 km s⁻¹

Abstract

An impact experiment was performed with a target of relevance to the upcoming DART impact. In this experiment, a collection of stones that is similar to a rubble pile was the target, though it was necessary to hold the stones in place (in this case with cement) since the target was hung vertically to perform the experiment. The stones–cement target has a higher density and a lower porosity than expected for Dimorphos, with the density being 2.92 g cm−3. A 3 cm diameter aluminum sphere was launched at a speed of 5.44 km s−1, which is similar to the anticipated 6.1 km s−1 impact speed of DART. The stones–concrete target was completely disassembled by the impact. The target was mounted on a pendulum. The swing of the pendulum was measured and from it the momentum enhancement β = 3.4 − 1.0 + 0.1 was measured. Due to possible lateral expansion of debris material, this value is a lower bound on the momentum enhancement that would be imparted to an extended target.

Momentum transfer from the DART mission kinetic impact on asteroid Dimorphos

“…Our result for β is consistent with numerical simulations 13 – 23 and laboratory experiments 24 – 29 of kinetic impacts, which have consistently indicated that β is expected to fall between about 1 and 6. However, non-unique combinations of asteroid mechanical properties (for example, cohesive strength, porosity and friction angle) can produce similar values of β in impact simulations 20 .…”

Momentum Transfer from the DART Mission Kinetic Impact on Asteroid Dimorphos

“…Our result for 𝛽 is consistent with numerical simulations [11][12][13][14][15][16][17][18][19][20][21] and laboratory experiments [22][23][24][25][26][27][28] of kinetic impacts, which have consistently indicated that 𝛽 is expected to fall between about 1 and 6. However, non-unique combinations of asteroid mechanical properties (e.g., cohesive 5 strength, porosity, and friction angle) can produce similar values of 𝛽 in impact simulations 18 .…”

Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission

“…The range of β values determined from the DART mission are within the range of pre-impact predictions from simulations, which spanned β values from 1 to 6 Stickle et al 2022). Experiments have also determined a comparable range of β values, including an experiment with a target that was a collection of stones to mimic a rubble pile and resulted in a β value of 3.4 (Walker et al 2022). Section 6.3 provides a more complete reference listing of pre-impact models and experiments.…”

“…As such, it is a complicated problem with many factors and parameters to consider. Pre-impact models (Jutzi & Michel 2014;Stickle et al 2015;Bruck Syal et al 2016;Stickle et al 2017;Raducan et al 2019Raducan et al , 2020Rainey et al 2020;Stickle et al 2020;Raducan et al 2021Raducan et al , 2022aRaducan et al , 2022bKumamoto et al 2022;Luther et al 2022;Owen et al 2022;Stickle et al 2022;Graninger et al 2023;DeCoster et al 2024b) and experiments (Walker et al 2013;Flynn et al 2015;Hoerth et al 2015;Durda et al 2019;Chourey et al 2020;Flynn et al 2020;Ormö et al 2022;Walker et al 2022) showed a range of possible β values and have been crucial for informing the post-impact models and interpretations. Also, despite the wealth of data associated with DARTʼs kinetic impact test, there still remain some key unknown quantities, in particular the mass and material properties of Dimorphos, ranging from the small-scale properties to the global-scale interior structure.…”