Interesting observation about the grouser spacing and the slip. Indeed agreed that slip is non-zero even on level ground as the wheel will initially spin to enable the grousers to get a grip/traction of the surface by shearing the soil in front of the grouser's leading edge. However, the angular velocity of the rover wheel will also affect the slip provided all other factors remain constant.

For eg. keeping all parameters exactly the same as the above test setup, increasing the rover velocity by imparting additional rpms on the wheel, the slip will increase if there is not sufficient traction at the soil-grouser interface. This effect is more defined for grousers of smaller dimensions i.e. lower height, especially on lunar surface where we expect to find loose soil.

On the negative side, i.e. with softer terrain, there are more chances of grousers penetrating the top soil layer and hence creating greater traction, and comparatively higher motion (bulldozing & rolling) resistance due to inherent drag. This is result in higher torque requirement and hence higher power consumption. From experience there is an optimal slip vs. DP area which imparts maximum traction (& DP) on such loose surface within acceptable power consumption margin.

Ricky8midnightmoon
Rover Locomotion Engineer