The first planetary defense mission, DART, proved that it is possible to change the orbital path of an asteroid via kinetic impact. The effectiveness of the kinetic impact method is quantified in terms of the momentum enhancement factor β, which is known to depend on the structure and properties of the target body at the time of impact. The penultimate image from the DART spacecraft showed the surface of the rubble pile asteroid Dimorphos is covered with large boulders. It is likely that the “strength” of an individual boulder will be greater than the strength of the collective rubble pile, and thus an impact into the boulder rather than the underlying granular bed could result in very different effectiveness of the kinetic impactor. This work seeks to investigate the effects of the strength of the impacted boulder on the momentum enhancement factor, and implications for mission design, by performing hypervelocity impact experiments on a rock sample sitting on a granular bed to simulate a rubble pile target. Spherical aluminum impactors will be launched at 3 km/s to study the ejecta and crater development within the target. Data analysis will include in-situ diagnostics such as high-speed camera imaging at 2-5 million frames per second and ejecta tracking to study the ejecta cloud development. Post-mortem analysis of the sample will include micro-CT scans to understand crater formation. The results of this study will help to improve future planetary mission design by providing insights into the mechanisms associated with momentum enhancement in heterogeneous targets.