Jet-induced cratering of a granular surface with application to lunar spaceports

TL;DR

This study experimentally investigates lunar soil erosion caused by rocket exhaust, revealing the significant role of diffusion-driven flow and recirculation in crater formation, challenging existing lunar erosion theories.

Contribution

It identifies diffusion-driven flow as a key erosion mechanism and provides detailed scaling laws for slow regime cratering, filling gaps in lunar erosion models.

Findings

Diffusion-driven flow occurs in both slow and fast cratering regimes.

Recirculation of sand governs slow regime crater growth.

Existing lunar erosion theories omit diffusion-driven flow, which is now recognized as important.

Abstract

The erosion of lunar soil by rocket exhaust plumes is investigated experimentally. This has identified the diffusion-driven flow in the bulk of the sand as an important but previously unrecognized mechanism for erosion dynamics. It has also shown that slow regime cratering is governed by the recirculation of sand in the widening geometry of the crater. Scaling relationships and erosion mechanisms have been characterized in detail for the slow regime. The diffusion-driven flow occurs in both slow and fast regime cratering. Because diffusion-driven flow had been omitted from the lunar erosion theory and from the pressure cratering theory of the Apollo and Viking era, those theories cannot be entirely correct.