The JHUAPL Planetary Impact Lab (PIL): Capabilities and initial results

The Planetary Impact Lab (PIL) at the Johns Hopkins University Applied Physics Laboratory (JHUAPL) includes a single-stage, compressed inert gas gun that can be used for impact experiments. The impact angle can be varied from 15° to 90° with respect to horizontal, a capability which enables oblique impacts into unconsolidated or granular materials (e.g., regolith analogs). The gun currently achieves impact velocities up to 400 m/s, although future enhancements could increase the maximum projectile velocity. Experiments can be done with atmospheric pressures ranging from ambient pressure down to ~75 Pa. The gun uses sabots produced with state-of-the-art additive manufacturing techniques (AM). Several engineering challenges had to be overcome to create a reliable AM sabot; however, AM sabots are ~45% lighter than and provide substantial cost savings over machined sabots. The PIL gun is currently being used to investigate impact processes on sloped coarse-grained surfaces, with application to planetary science and, specifically, rubble-pile asteroids. In contrast to previous studies of impacts onto slopes, we kept the projectile trajectory perpendicular to the target surface, thereby disentangling the effects of oblique impacts from the effects caused by a sloped surface. Initial results show enhanced crater collapse in the sloped target, with most of the collapse occurring in the direction parallel to the surface gradient. Consequently, final craters on sloped targets have smaller volumes and reduced depth-to-diameter ratios.