The 1971 moon mission Lunar Roving Vehicle (LRV)  used tires that  were  designed to have a load capacity  of about 57 lbs of moon weight. NASA’s  next moon mission is intended to be an ambitious one, which is expected to raise the load capacity requirement  of the tire by  nearly ten-fold. 

Concept designs that would achieve this aggressive target were evaluated by finite element method and the results were presented to NASA. Comparisons with the prototype test data were done wherever appropriate to ascertain accuracy of the predicted structural responses.

Two different and novel numerical approaches to evaluate the lunar tire are described. The first approach involves modeling the wire-meshed tire as rebars embedded in membrane elements and sandwiched between two continuum elements. The membrane approach utilizes the explicit time integration finite element scheme, and the method’s effectiveness is shown by the excellent agreement between the numerical and laboratory results.

The second approach involves modeling the wires explicitly by depicting the two layers of wire mesh as two layers of beam elements interconnected by interlocking joints representing the crimp joints used in manufacturing these tires.  It is demonstrated here that the joint motions can be simulated by utilizing the connector elements capability in ABAQUS and enforcing a limit on the rotation on the joint angles. It was found that the limiting angle configurations can be determined by a simple shear mode experiment of a square grid sample. The validation of the computational approach is shown by demonstrating extremely good correlation to the measured force-deflection curves in vertical, lateral, longitudinal and torsion directions. An extension to the approach is demonstrated by attaching tread plates to the wire carcass. The effects of the tread plate geometry on the tire stiffnesses and footprint are quantified.