Results of analytical touchdown dynamics investigations are presented which were conducted to obtain estimates of the probability of stable landing for configurations with various landing gear diameters. Both three-legged and four-legged vehicles are considered in the analysis. Dynamic scaling considerations are taken into account so that the results are applicable to a wide range of vehicle size and mass. A Monte Carlo approach is taken in the determination of initial landing conditions. Results indicate that for a given probability of stable landing, a three-legged vehicle requires a landing gear diameter only slightly larger than the diameter required for a four-legged vehicle. Therefore the three-legged vehicle's landing gear should weigh less.