A 1/6 scale mass model of the lander was prototyped to investigate landing stability. The dynamic similarity of 1/6 scale drop tests on Earth to full scale landing on Moon was validated through previous acceleration data collection in the motion capture.
The tip over stability and the effects of non-trivial variables such as the friction coefficient and bearing strength were analyzed to produce a limit of tip over stability graph. The video below is shows the result of preliminary drop tests.
Tip over experiments were performed on a stiff surface unlike lunar regolith, such that the results could be verified by simulations which model the ground as a rigid surface. The goal is to determine the bounds of stability for a complete range of expected vertical and horizontal velocities, slopes and surface types. GRC-1 was used in few experiments as a lunar simulant, but it doesn’t provide a high fidelity model of the lunar surface for landing which primarily depends on friction and bearing strength.
The surface plot below, generated by simulation results, illustrates the marginal stability limit on flat surfaces with no horizontal velocity, as the x-y axis represent friction coefficient and slope, and z axis as vertical velocity. Left region is stable and the right region outside the surface is unstable.