A Data-Derived Scaling Approach for Plume-Surface Interaction Crater Formation

This work presents a methodology for scaling test-scale plume-surface interaction (PSI) crater formation data to flight-scale. Methods for scaling both crater erosion rate and crater geometry (width and depth) were derived from scaling relationships proposed by previous PSI studies. Two methods for predicting crater width were investigated - one using an empirical scaling law for the crater aspect ratio and another informed by surface shear stress profiles from computational fluid dynamics (CFD). Data from three independent studies were then used to assess the performance of the developed scaling methodology. Results show that data from all three sources agree well with the crater erosion rate scaling methodology, with the caveat that limited data exist in regimes truly relevant to landing on the Moon. The performance of the geometry scaling methodology was more nuanced. The empirical scaling for crater aspect ratio performed well against PSI data obtained under Earth-atmospheric ambient pressure, but did a poor job of predicting the aspect ratio of craters formed from highly underexpanded plumes under vacuum conditions. Data from the Human Landing System (HLS) program’s Plume Surface Interaction Ground Test will be used to further improve the performance of the scaling methodology and to provide flight-scale predictions for PSI effects caused by HLS landers.