Terramechanics: Testing Wheel Designs for Planetary Surfaces

Abstract

Planetary Exploration Missions have been an ongoing aspect of the NASA tradition since 1957. In an effort to better understand the surfaces, atmospheres, and geographic properties of planets in the solar system, the planetary rover was invented. In 1997, the Pathfinder landed on Martian terrain. The Pathfinder contained an important robotic vehicle, the planetary rover Sojourner. Sojourner, developed by United States scientists and engineers, was the first rover to land on the surface of Mars. On soft, usually sandy, rocky surfaces the planetary rover has engaged in loss of traction and wheel slippage. In order to investigate wheel-surface interaction, an automated test simulation system was designed and built in the Space Systems Laboratory and the Manufacturing building at the University of Maryland. Experiments that tested the draw-bar pull produced at varying weights with multiple wheel designs in a manual test simulation system state were conducted in an effort to confirm previous assumptions. In an effort to measure the force required to pull a weighted cart through the sandy surface, a series of tests were conducted in which the force was measured over a short period of time using the test simulation system. Wheel-slippage occurred in several cases as the weight increased on the more narrow wheels. After the force was measured and recorded with the force gauge and the Logger Pro III software, the depth of the tread was measured. This process of collecting data was repeated for three different wheels and each wheel was tested under four and then six different weight conditions. In a continuation of the current experiment, a second experiment will be conducted in the near future to determine the draw-bar pull produced from varying wheel designs in an automated test simulation system with varying weights. Also, future experiments will test the torque produced from the wheel-surface interaction.