Predictive theory for onset and rate of bulk cratering mechanisms in lunar rocket landings

Develop a predictive theory that determines both the onset thresholds and the erosion or excavation rates of bulk cratering mechanisms induced by rocket exhaust impinging on lunar regolith, specifically including bearing capacity failure, diffusion-driven shearing, shock impingement fluidization, and diffused gas eruption, to address conditions expected for larger lunar landers thrusting close to the surface.

Background

The paper presents and validates a theory for surface erosion of lunar soil under rocket exhaust using optical measurements from Apollo 16, but explicitly distinguishes this from bulk cratering phenomena that can occur under different landing conditions. These bulk mechanisms, relevant for larger landers or thrusting near the surface, include bearing capacity failure, diffusion-driven shearing, shock impingement fluidization, and diffused gas eruption.

While Apollo landings generally did not exhibit sustained bulk cratering, observations suggest possible brief bulk ejection near touchdown. The authors state that a predictive theoretical framework for when these bulk mechanisms initiate and how rapidly they proceed does not yet exist, marking a clear gap necessary for mission risk assessment and mitigation.