Mars landing engine plume impingement ground interaction

A subscale landing site alteration program was conducted in support of future Mars landed Missions to provide site alteration data including soil erosion mechanisms and dependency on throttle level, altitude, and ground slope. A 25% scale Viking Lander Engine was fired into a representative Mars stimulant soil-media test bed. The test facility was operated at ~633 Pa to match the supersonic plume expansion at mars ambient pressure. The test apparatus utilized quarter symmetry with the use of baffle planes. A media that is 1/3 the density of Mars silica was used to match the 1/3 gravity Mars ballistic coefficient and particle trajectories. Key findings include soil bulk shear failure as the primary erosion mechanism, nonlinear dependence of erosion with throttle level and ground slope, and particle size. Another key finding is that we observed significantly larger erosion rates for supersonic jets (underexpanded) at Mars atmospheric pressure as opposed to jets (highly over-expanded) at Earth atmospheric environment. The highest ground pressures were also observed in the Mars atmospheric regime with jet expansion ratios greater than 2.